This article was downloaded by: [New York University] On: 10 October 2014, At: 05:19 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste ab
ab
c
S. Vichaphund , D. Aht-Ong , V. Sricharoenchaikul & D. Atong
d
a
Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand b
Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand c
Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand d
Ceramic Technology Research Unit, National Metal and Materials Technology Center, Pathumthani 12120, Thailand Published online: 29 Mar 2014.
To cite this article: S. Vichaphund, D. Aht-Ong, V. Sricharoenchaikul & D. Atong (2014) Characteristic of fly ash derivedzeolite and its catalytic performance for fast pyrolysis of Jatropha waste, Environmental Technology, 35:17, 2254-2261, DOI: 10.1080/09593330.2014.900118 To link to this article: http://dx.doi.org/10.1080/09593330.2014.900118
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 17, 2254–2261, http://dx.doi.org/10.1080/09593330.2014.900118
Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste S. Vichaphunda,b , D. Aht-Onga,b , V. Sricharoenchaikulc and D. Atongd∗ of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand; b Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand; c Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand; d Ceramic Technology Research Unit, National Metal and Materials Technology Center, Pathumthani 12120, Thailand
a Department
Downloaded by [New York University] at 05:19 10 October 2014
(Received 11 December 2013; accepted 27 February 2014 ) Fly ash from pulp and paper industries was used as a raw material for synthesizing zeolite catalyst. Main compositions of fly ash consisted of 41 wt%SiO2 , 20 wt%Al2 O3 , 14 wt%CaO, and 8 wt% Fe2 O3 . High content of silica and alumina indicated that this fly ash has potential uses for zeolite synthesis. Fly ash was mixed with 1–3 M NaOH solution. Sodium silicate acting as silica source was added into the solution to obtain the initial SiO2 /Al2 O3 molar ratio of 23.9. The mixtures were then crystallized at 160◦ C for 24 and 72 h. Zeolites synthesized after a long synthesis time of 72 h showed superior properties in terms of high crystallinity, less impurity, and small particle size. The catalytic activities of fly ash-derived zeolites were investigated via fast pyrolysis of Jatropha wastes using analytical pyrolysis-gas chromatograph/mass spectrometer (GC/MS). Pyrolysis temperature was set at 500◦ C with Jatropha wastes to catalyst ratio of 1:1, 1:5, and 1:10. Results showed that higher amounts of catalyst have a positive effect on enhancing aromatic hydrocarbons as well as decreasing in the oxygenated and N-containing compounds. Zeolite Socony Mobil-5 (ZSM-5) treated with 3 M NaOH at 72 h showed the highest hydrocarbon yield of 97.4%. The formation of hydrocarbon led to the high heating value of bio-oils. In addition, the presence of ZSM-5 derived from fly ash contributed to reduce the undesirable oxygenated compounds such as aldehydes, acids, and ketones which cause poor quality of bio-oil to only 0.8% while suppressed N-compounds to 1.7%. Overall, the ZSM-5 synthesized from fly ash proved to be an effective catalyst for catalytic fast pyrolysis application. Keywords: fly ash; synthesis; zeolite; catalyst; fast pyrolysis
1. Introduction A large amount of fly ash has been generated from coalbased thermal power plants in several kinds of industries. In general, these wastes were disposed in landfill causing environmental problems. Therefore, the idea to utilize fly ash as a value-added product has attracted much attention. Because of being rich in SiO2 and Al2 O3 , fly ash is widely used in many applications such as soil amendment, adsorbents for gas and water cleaning, nuclear waste stabilization, building materials, and particularly, zeolite synthesis. The utilization of fly ash as a starting material to synthesize zeolite has been greatly focused because this process can reduce the fly ash disposal cost, minimize environmental impact, and importantly increase high-valued products. Several zeolites such as zeolite X, zeolite Na-P1, anacime, hydroxyl sodalite, zeolite Y, faujasite, and Zeolite Socony Mobil-5 (ZSM-5) were successfully synthesized from fly ash by alkaline hydrothermal methods. Zeolite derived from fly ash was expected to be of use in several applications including ion-exchange, gas absorber, detergent, molecular sieves, and catalysts.[1–3] However, there have only been ∗ Corresponding
author. Email: [email protected]
© 2014 Taylor & Francis
few reports focusing on the zeolite derived from fly ash in catalyst applications.[1,2] Moreover, there has been no report involving catalytic fast pyrolysis of biomass wastes using fly ash-derived zeolite catalysts. Generally, products obtained from pyrolysis of biomass are liquid bio-oil, solid char, and non-condensable gases. Bio-oils contained high oxygen contents of approximately 35–45 wt% due to their oxygen-rich compounds such as water, acids, alcohols, aldehydes, ketones, furans, phenolic compounds, and sugar derivatives. These components cause poor properties of bio-oil including low heating value, incompatibility with petroleum fuel, high viscosity, chemical instability, and acidity.[4,5] Therefore, the elimination of oxygen in bio-oil is required in order to improve fuel property and to use bio-oil in conventional transport fuel. Two types of upgrading methods which have been applied to reject oxygen from organic compounds are hydrotreating and catalytic cracking. The former process needs hydrogen to react with oxygen to form water as by-product. In the case of the latter process, catalytic cracking can convert oxygenated compounds produced during biomass pyrolysis
Downloaded by [New York University] at 05:19 10 October 2014
Environmental Technology directly to hydrocarbons which can improve bio-oil quality. In contrast to hydrotreating, catalytic vapour cracking can proceed at atmospheric pressure without the requirement of high hydrogen pressure which result in the reduction of operating cost.[4,6,7] Among zeolite catalysts, ZSM-5 (structure type mordenite framework inverted) with three-dimensional pore system consisting of sinusoidal (5.3 × 5.6 Å) and straight (5.2 × 5.7 Å) channels exhibits superior capability on promoting catalytic cracking reaction because of its superior properties such as high surface area, pore structure, molecular sieve characteristics, active site, and high thermal resistance.[8–10] The improved properties of bio-oil obtained through the pyrolysis of biomass over zeolite are realized through deoxygenation reactions by reducing oxygenated compounds and enhancing aromatic selectivity. In addition, a few researchers suggested that ZSM-5 catalyst has the advantage of long life time and can be regenerated. Aho et al. [11] proved that the spent zeolites including H-Beta, H-Y, H-ZSM5, and H-MOR were successfully regenerated at 450◦ C for 2 h without the changing structure of zeolites. Carlson et al. [7] studied the life time and regeneration of ZSM-5. They found that the catalyst could be applied in pyrolysis process for 10 timesregeneration cycles and was regenerated at 600◦ C in air atmosphere for 3 h. After characterization, the ZSM-5 structure after 10 reaction/regeneration cycles showed a slight change in the intensity of X-ray diffraction (XRD) peak at a small angle, 2θ = 8. In this research, fly ash collected from pulp and paper industries in Thailand was used as the raw material for synthesizing ZSM-5 catalyst. After synthesis, the catalytic activity of fly ash-derived zeolites was investigated via fast pyrolysis of Jatropha wastes in order to upgrade the pyrolysis vapours using analytical pyrolysis-GC/MS (PyGC/MS) technique. The catalytic cracking using ZSM-5 catalyst was intended to convert oxygenated compounds produced during Jatropha pyrolysis directly to hydrocarbons which can improve bio-oil quality. Jatropha wastes which are by-products from bio-fuel extraction process found abundantly in many local plants in Thailand were selected as a biomass feedstock. The pyrolysis of this waste can help extract additional values from Jatropha and also reduce environmental problems from waste disposal. The pyrolysis temperature was set at 500◦ C for 30 s with the Jatropha wastes to catalyst ratio of 1:1, 1:5, and 1:10. Jatropha pyrolysis products and catalyst selectivity were then discussed.
2. Material and methods 2.1. Fly ash characterization Fly ash collected from pulp and paper industries in Thailand was used as a raw material for synthesizing zeolite catalyst. Chemical composition and phase analysis of as-received fly
2255
ash were examined by X-ray Fluorescence (XRF: Philips PW 2404) and XRD (Socony PANalytical, X’ Pert Pro). 2.2. Synthesis of ZSM-5 synthesis from fly ash Initially, 3 g of fly ash was mixed with 25 ml of 1–3 M NaOH solution at 90◦ C for 3 h under stirring condition in order to form appropriate silicate and aluminate salts for further zeolitization. Then, the sodium metasilicate pentahydrate (≥ 97%, Fluka) as an additional silica source was mixed into the fly ash solution to obtain the initial SiO2 /Al2 O3 molar ratio of 24. After that, tetrapropylammonium bromide (TPABr, 98%, Aldrich) acting as an organic template was added to the solution. After homogeneous mixing, the slurry was transferred into a Teflon-lined stainless steel autoclave in order to perform crystallization at 160◦ C for 24 and 72 h. After crystallization, the solid cake was filtered and washed by deionized water. The sample powders were dried at 100◦ C overnight and calcined at 540◦ C for 5 h in air atmosphere to remove the organic templatefrom zeolite network. To obtain HZSM-5, the powder was converted to H-form by ion-exchange with 1 M NH4 Cl solution at 80◦ C for 8 h. The sample was then washed with deionized water to remove chloride ions, dried at 100◦ C overnight, and calcined at 540◦ C for 5 h in air atmosphere. Phase analysis of synthesized powder was performed by X-ray powder diffraction (XRD; PANalytical, X’ Pert Pro) with 40 kV, 45 mA, CuKα radiation. The sample was scanned at 2θ from 5◦ to 60◦ with a step size of 0.02. Microstructure was characterized by scanning electron microscope (SEM; JEOL, JSM-5410). For elemental analysis, energy dispersive Xray spectroscope (EDX; model Oxford Inca 300) with X-ray dot mapping was used. The particle size and distribution were measured using laser diffraction by Mastersizer 2000 (Version 5.54 Serial Number: MAL 1021434, Malvern Instrument Ltd). The specific surface area was determined by nitrogen adsorption using Autosorb-1 (Quantachrome instruments). The samples were degassed for 8 h at 300◦ C prior to the analysis. The acidity of synthesized ZSM-5 catalysts was determined by the temperature-programmed desorption (NH3 -TPD) using BELCAT instrument. Prior to the measurement, the catalyst (approximately 0.1 g) was pre-treated at 500◦ C for 1 h under a helium atmosphere to remove water. After cooling to 100◦ C, ammonia gas adsorption was carried out for 1 h and subsequently, helium gas was purging at the same temperature for 30 min to eliminate the physisorbed ammonia. Next, the sample was heated from 100◦ C to 800◦ C with the heating rate of 10◦ C/min. The desorbed ammonia was detected by using a thermal conductivity detector. 2.3. Catalytic performance of ZSM-5 from fly ash Jatropha wastes left after extraction of oil from biodiesel production process from local plants in Thailand were used as a biomass feedstock. Prior to the test, this waste was
S. Vichaphund et al.
dried at 60◦ C for 24 h, crushed with a grinder, and then sieved to fine powder with the particle size equal to or less than 125 μm (100 mesh). Component analysis of Jatropha wastes consisted of 57.0% cellulose, 17.6% hemicelluloses, and 25.4% lignin. The volatile matter and fixed carbon contents are 73.8% and 13.6%, respectively, while ash contents of 5.8% are higher than approximately 1.0% of typical wood. Carbon is the main element (49.2%) with small amounts of 6.4% hydrogen, 4.5% nitrogen, and 1.1% sulphur. The oxygen content of 39.6% is considerably high which could be a precursor to oxygenated compounds. Pyrolysis was performed using a Pyroprobe pyrolyser (multifuntional pyrolyzer, PY-2020iD, Frontier Lab) with an auto-shot sampler AS-1020E interfaced to a GC-Mas spectrometer (GCMS-QP2010, Shimudzu). Approximately 0.4 mg Jatropha wastes were used in each experiment. In order to investigate the effect of Jatropha waste to catalyst ratios, catalysts were placed above the biomass layer at the Jatropha wastes to catalyst ratio of 1:1, 1:5 and 1:10. The sample was pyrolysed with the Pyroprobe set at 500◦ C for 30 s. Previous study showed that high liquid yield was achieved from pyrolysis of Jatropha waste at this moderate temperature.[12] The GC column employed was a 30 m × 0.25 mm Ultra alloy 5 (i.d., 0.25 μm film thickness). Helium (99.999%) was used as a carrier gas with a column flow of 1.3 ml/min and the split injector ratio was 1:50. During the analysis of the pyrolytic products, the oven temperature was started from 50◦ C (3 min) to 200◦ C (heating rate of 5◦ C/min) then to 350◦ C (heating rate of 10◦ C/min and hold for 10 min). The injector and detector temperatures were kept at 280◦ C, and the mass spectrometer was operated in electron ionization mode at 70 eV. The mass spectra were obtained from m/z 20 to 800 with the scan speed of 625 amu/s. Identification of chromatographic peaks was achieved according to the National Institute of Standards Table 1.
and Technology and Wiley mass spectrum libraries. Product quantification is based on percentages of relative peak area of each compound to the total peak areas obtained from the chromatogram. These relative peak areas are then added up according to their associated categories and selectivity of particular group of compounds is then realized. Noncatalytic fast pyrolysis of Jatropha waste was also tested for comparison to the catalytic runs in terms of product yields and composition of pyrolysis vapour. 3. Results and discussion 3.1. Fly ash characterization The chemical composition of fly ash characterized by XRF mainly consisted of 41.4 wt%SiO2 , 20.0 wt%Al2 O3 , 14.1 wt%CaO, and 8.4 wt% Fe2 O3 with small amounts of SO3 , MgO, K2 O, TiO2 , Na2 O, and P2 O5 as listed in Table 1. Due to the high content of CaO of more than 8 wt%, this fly ash was classified as class C according to ASTM C618.[1] Additionally, the high content of silica and alumina indicated that this fly ash has potential for zeolite synthesis. From XRD result as displayed in Figure 1(a), fly ash showed high crystallinity of quartz (SiO2 ) as a main phase with minor phases of anhydrite (CaSO4 ) and calcite (CaCO3 ). These minerals were generally found in fly ash particles.[1,13] The morphology monitored by SEM showed that the fly ash particles were large and quite irregular in appearance (Figure 1(b)). 3.2. Synthesized zeolites from fly ash The XRD patterns of ZSM-5 synthesized with 1–3 M NaOH for 24 and 72 h were shown in Figure 2. It can be seen that the alkaline solution contributed to the increase in silicate and aluminate solutions via fly ash dissolution.[13–15]
Chemical composition of fly ash.
Oxides
SiO2
Al2 O3
CaO
Fe2 O3
SO3
MgO
K2 O
TiO2
Na2 O
P2 O5
Others∗
L.O.I.
Particle size (μm)
(wt%)
41.4
20.0
14.1
8.4
4.9
2.3
2.0
0.6
0.4
0.4
0.5
4.8
26.08
(a)
(b) Quartz Anhydrite Calcite
Intensity (a.u.)
Downloaded by [New York University] at 05:19 10 October 2014
2256
10
Figure 1.
20
30
40 50 2Theta (deg)
60
70
80
Physical appearance of as-received Fly ash: (a) XRD pattern and (b) SEM micrograph.
Environmental Technology (a)
ZSM-5, Quartz,
2257
(b)
Anhydrite Calcite
ZSM-5,
Anhydrite
Quartz,
Calcite Fly ash
1 M NaOH
5
15
25
35
Intensity (a.u.)
Intensity (a.u.)
Fly ash
1 M NaOH
2 M NaOH
2 M NaOH
3 M NaOH
3 M NaOH
45
55
5
2q q (degrees)
Figure 2. (b) 72 h.
Downloaded by [New York University] at 05:19 10 October 2014
Table 2.
25
35
45
55
2q q (degrees)
XRD pattern of ZSM-5 synthesized from fly ash at 160◦ C with 1–3 M NaOH concentration with reaction times for (a) 24 h and Properties of ZSM-5 synthesized from fly ash at 160◦ C. Synthesis time
NaOH
Particle size
Surface area
Pore size
Pore volume
(Å)
(cm3 /g)
Si
Al
Ca
Fe
33.30 36.95 37.10 31.78 32.94 33.10
0.22 0.24 0.20 0.20 0.20 0.24
50.0 51.3 49.3 54.8 53.9 55.2
5.0 3.9 3.9 2.8 3.5 3.6
1.8 2.5 1.0 1.4 2.4 1.4
4.8 2.1 0.8 n.d.∗ n.d.∗ 2.1
Samples
(h)
(M)
(μm)
(m2 /g)
ZSM-5
24
1 2 3 1 2 3
20.20 20.84 17.00 18.00 19.65 18.30
424 407 345 406 380 453
72
∗ Not
15
Element (wt%)
determined.
This assumption was supported by the reduction of quartz intensity after synthesis process. After the dissolution step, silicate and aluminate species reacted together with the presence of TPABr as an organic template, further condensed, and crystallized to form ZSM-5 crystals. At short synthesis time of 24 h (Figure 2(a)), the formation of ZSM-5 was detected as a major phase with the characteristic diffraction peaks occurring at 2θ of 7–9◦ and 23–25◦ .[16] Meanwhile the intensity of quartz decreased significantly compared to the as-received fly ash. With increasing synthesis time from 24 to 72 h (Figure 2(b)), the high-crystallinity ZSM-5 was obtained with small amount of quartz and analcime phases. In terms of NaOH concentration, the change of alkaline concentration from 1 to 3 M did not significantly affect the crystallinity as there was no observed change in intensity of the diffraction peaks. The elemental analysis of samples was determined by EDX as shown in Table 2. The alkali treatment could remove Ca and Fe from fly ash to form insoluble hydroxides. However, it was possible that there were calcium and iron species remaining in zeolite structure. The result was confirmed by small amounts of Ca and Fe elements detected in ZSM-5 structure after synthesis. This finding is consistent with that of other studies.[3,17–19] Calcium ion in solution might react with CO2 in the atmosphere leading to very small amounts of CaCO3 ,[18] while iron could incorporate into the framework in trace amounts.[19]
The particle size, surface area, pore size, and pore volume of ZSM-5 from fly ash treated by 1–3 M NaOH synthesized at 160◦ C for 24 and 72 h is illustrated in Table 2. The particle size of synthesized zeolite revealed the agglomerates in size with the mean diameters in the range 17.0–20.8 μm. From these results, synthesized ZSM-5 treated with 3 M NaOH for 72 h yielded the highest surface area of 453 m2 /g with a pore size of 33.1 Å. The pore size of zeolite catalysts were classified as mesoporous materials (the pore size ∼20–500 Å).[16] The SEM micrographs of zeolites derived from fly ash under different synthesis conditions were exhibited in Figure 3. It can be seen that both parameters, NaOH concentration and synthesis time, had an effect on the formation of ZSM-5 crystals. With an increase in NaOH concentration from 1 to 3 M (Figure 3(a)–3(c)), particles changed from irregular and round-shaped to be more cubic-like crystal. From previous studies, the alkalinity is one of the important factors for zeolitization. When the NaOH concentration in the mixture was increased, OH− promoted the dissolution of fly ash to silicate and aluminate species while Na+ accelerated the crystallization step which included nucleation and crystal growth.[14,15] Therefore, the morphology of zeolite treated by high alkali concentration was shown to be more cubic in shape. Moreover, zeolite particles obtained from 72 h long crystallization time had a tendency to increase the rate of crystal growth as shown in Figure 3(d)–3(f).[20]
S. Vichaphund et al.
ZSM-5 particles with 3 M NaOH and a crystallization time of 72 h (Figure 3(f)) were agglomerated (18.30 μm) and consisted of many single cubic particles with size less than 5 μm.
Downloaded by [New York University] at 05:19 10 October 2014
3.3.
Catalytic activity of ZSM-5 derived from fly ash using Py-GC/MS In this experiment, zeolites synthesized with 1–3 M NaOH after a long synthesis time of 72 h were selected for examining the catalytic performance on fast pyrolysis of Jatropha by using Py-GC/MS. The pyrolysis temperature was set at 500◦ C. From previous study, the result showed that high liquid yield was achieved from the pyrolysis of Jatropha waste at this moderate temperature.[12] In addition, biomass liquids are known to have an acidic structure. Large amounts of acids can cause corrosion problem in engines.[6,9,10] Kaewpengkrow et al. [21] studied the pyrolysis of Jatropha waste with Py-GC/MS at 400–600◦ C and reported that the lowest acid yield was obtained after pyrolysis at 500◦ C. According to Huber et al., who wrote a review on synthesis of transportation fuel from biomass, the operating conditions for upgrading bio-oil using zeolite are temperatures from 350 to 500◦ C to reduce oxygen content.[22] Aho et al. [11] investigated the influence of zeolites on the catalytic pyrolysis of pinewood in a fluidized bed reactor at 500◦ C. Furthermore, French and Czernik reported good deoxygenation activity of ZSM-5 for the catalytic cracking of hardwood at 500◦ C.[6] Figure 4 shows the product yields including gas, liquid, and solid from fast pyrolysis of Jatropha waste with and without synthesized ZSM-5 catalysts at 500◦ C. Gas and liquid yields were determined by relative percentages of peak area directly obtained from the chromatogram of GC after normalization of the corresponding total product yields, whereas solid residues were calculated by the weight difference of samples before and after pyrolysis. It was found that the liquid and gas products were observed in the range 45.9–61.4% and 14.8–30.6%, respectively. From the analysis, most of the gas product was carbon dioxide with small amounts of carbon monoxide, propane, and butane. The presence of ZSM-5 catalysts increased the gas formation. High content of catalysts resulted in superior secondary cracking and decomposition reactions of liquid product leading to higher gas yields at those conditions. Solid residues were in the range 19.0– 31.8%, which were comparable to the values obtained in other studies.[6,23] Jatropha waste as biomass wastes was initially pyrolysed at 500◦ C in order to investigate the non-catalytic pyrolytic products. Pyrolysis vapours usually contained both volatile and non-volatile compounds. However, GC/MS was able to detect only the organic volatile compounds. The ion chromatograms displayed more than 100 peaks and the perfect separation of all peaks was not
Gas
100
Liquid
Solid
90 80 Product yields (%)
2258
70 60 50 40 30 20 10 0 1
2
3
4 5 6 7 Types of catalysts
8
9
10
Figure 4. Product yields (%) from Py-GC/MS of Jatropha waste using ZSM-5 catalysts synthesized from fly ash at 160◦ C for 72 h with 1–3 M NaOH concentrations and Jatropha to catalyst ratios: (1) No catalyst, (2) ZSM-5/1 M NaOH, (3) ZSM-5/2 M NaOH, (4) ZSM-5/3 M NaOH ((2)–(4) referred the Jatropha to catalyst ratios = 1 : 1); (5) ZSM-5/1 M NaOH, (6) ZSM-5/2 M NaOH, (7) ZSM-5/3 M NaOH, ((5)–(7) referred the Jatropha to catalyst ratios = 1 : 5); (8) ZSM-5/1 M NaOH, (9) ZSM-5/2 M NaOH, (10) ZSM-5/3 M NaOH ((8)–(10) referred the Jatropha to catalyst ratios = 1 : 10).
possible due to the complex composition of the pyrolysis vapours. A total of 50 peaks from the chromatogram was then identified and classified as 11 organic compounds based on their major chemical functional groups such as aromatic hydrocarbons, aliphatic hydrocarbons, phenols, ketones, aldehydes, acids, N-containing compounds, sugars, and others (alcohols, ethers, and esters). The overall pyrolytic products from fast pyrolysis of Jatropha waste with and without zeolite catalysts were shown in Figure 5. The selectivity of pyrolytic products was represented by the peak area (%). Each percentage of peak area was based on the peak areas of selected characteristic molecular or fragment ion chromatograms. Without zeolite catalyst, non-catalytic pyrolytic products (Figure 5(1)) contained mainly acid compounds (50.7%), which was mostly linoleic acid (C18:2) (37.0%), commonly detected in Jatropha oils.[24] Nitrogen element in Jatropha is generally higher than other woody biomass. Therefore, N-containing compounds in pyrolytic vapours were found in high content (20.3%). Other oxygenated compounds consisted of ketones (7.5%), alcohols (3.0%), esters (2.0%), ethers (3.7%), and phenols (2.8%). The heavy compounds such as sugar products were found in small content, 3.7%. Unfortunately, the pyrolytic products contained small amounts of hydrocarbon (4.0%). Before catalytic testing, the acidity of selected catalysts was also analysed as shown in Table 3. The ammonia TPD results of synthesized zeolites consisted of two desorption peaks. The first peak at 100–300◦ C was weak acid sites and the second peak (300–600◦ C) was strong acid sites.[10] From the results, the total acidity decreased insignificantly
2259
Figure 3. SEM micrograph of ZSM-5 from fly ash at 160◦ C (a) 1 M NaOH, 24 h,(b) 2 M NaOH, 24 h, (c) 3 M NaOH, 24 h, (d) 1 M NaOH, 72 h, (e) 2 M NaOH, 72 h, and (f) 3 M NaOH, 72 h. Aromatic HC
Aliphatic HC
Phenol
Ketone
Aldehyde
Acid
Others
N-comp.
Sugar
Table 3. Acidity of ZSM-5 synthesized from fly ash at 160◦ C, for 72 h. Acidic site determined by NH3 -TPD (mmol NH3 g−1 )
100% 90%
First peak Second peak NaOH (T desorption (300◦ C < T ◦ Samples (M) < 300 C) desorption < 600◦ C) Total
80% Product selectivity (%)
Downloaded by [New York University] at 05:19 10 October 2014
Environmental Technology
70% 60%
ZSM-5
50% 40%
1 2 3
0.562 0.512 0.525
0.457 0.505 0.454
1.019 1.017 0.979
30% 20% 10% 0%
1
2
3
4
5
6
7
8
9
10
Types of catalysts
Figure 5. Product selectivity (%) detected from Py-GC/MS of Jatropha waste using ZSM-5 catalysts synthesized from fly ash at 160◦ C for 72 h with 1–3 M NaOH concentrations and Jatropha to catalyst ratios: (1) no catalyst, (2) ZSM-5/1 M NaOH, (3) ZSM-5/2 M NaOH, (4) ZSM-5/3 M NaOH ((2)–(4) referred the Jatropha to catalyst ratios = 1 : 1); (5) ZSM-5/1 M NaOH, (6) ZSM-5/2 M NaOH, (7) ZSM-5/3 M NaOH, ((5)–(7) referred the Jatropha to catalyst ratios = 1 : 5); (8) ZSM-5/1 M NaOH, (9) ZSM-5/2 M NaOH, (10) ZSM-5/3 M NaOH ((8)–(10) referred the Jatropha to catalyst ratios = 1 : 10).
in the order of ZSM-5 treated by NaOH 1 M > 2 M > 3 M, respectively. The slight decrease in acidity was observed as the concentration of NaOH increased. The silicate species from fly ash can be easily dissolved in the mixture in the presence of high NaOH concentration; thus ZSM-5 treated by 3 M NaOH exhibited high Si/Al molar ratio and lower acidity. The presence of ZSM-5 synthesized from fly ash showed a good performance for cracking pyrolysis vapours. The unfavourable oxygenated compounds such as acids, ketones, and aldehydes were effectively reduced via several
reaction path ways including dehydration, decarboxylation, decarbonylation, and oligimerization.[6,7,9] At lowest zeolite content (Jatropha:catalyst ratio of 1:1) (Figure 5 (2)– (4)), synthesized ZSM-5 increased hydrocarbon yields from 4% in the case of Jatropha pyrolysis to 26% in the current case. It was noticed that ZSM-5 treated by 1 M NaOH showed higher hydrocarbon selectivity compared to others because of its higher acidity. Nevertheless, the amount of solid residue formed after pyrolysis using this catalyst was higher (Figure 4 (2)). The increase in hydrocarbon contributed to enhance heating values of bio-oil.[25,26] However, in the presence of low zeolite content, it was noticed that the acid selectivity was considerably high due to the increased rate of sugar decomposition. High acid selectivity caused bio-oils to be more acidic. In addition, high yields of other oxygenated compounds were still detected. The presence of ketones and aldehydes are responsible for aging reaction and instability of bio-oils. With an increase in the amount of catalyst used (Jatropha:catalyst ratio of 1:5) (Figure 5 (5)–(7)), it was clear that ZSM-5 synthesized from fly ash completely eliminated sugars, acids and diminished other oxygenated compounds to less than 1%. As a result, the high aromatic selectivity was achieved in the range 77.6–83.5%. The selectivity of ZSM-5
Downloaded by [New York University] at 05:19 10 October 2014
2260
S. Vichaphund et al.
with respect to hydrocarbons was in the following order of ZSM-5 treated by NaOH 3 M > 2 M > 1 M. It was thought that high yields of solid residue that occurred after pyrolysis using ZSM-5 treated by 1 M NaOH limited the hydrocarbon selectivity. This aromatic selectivity was comparable to the results tested by Murata et al. [10] who investigated the fast pyrolysis of Jatropha waste using GC/MS. In the presence of commercial ZSM-5, the aromatic selectivity was above 90% using the catalyst to biomass ratio of 6.25. As for the aliphatic hydrocarbon, lower selectivity was obtained as the catalyst content increased. This might be due to further aromatization of light hydrocarbon or olefin to produce aromatic compounds.[7,25] Furthermore, N-containing compounds decreased distinctly to 8.5–12.0%. The result suggested that the high amount of zeolite was required to remove nitrogen content. Several researches reported that the pyrolysis of biomass and coal containing nitrogen compounds generated intermediate nitrogenous species such as HCN, HNCO, and NH3 depending on the nitrogen functionalities. In the presence of catalysts, nitrogenous species might react with oxygenated compounds to form NOx as well as partly convert into nitrogen gas.[27–29] Therefore a sudden decrease in nitrogencontaining compounds was noticed. The ability of ZSM-5 to eliminate nitrogen-containing compounds in pyrolysis process was confirmed by Thangalazhy-Gopakumar et al. [30] The result showed that although deoxygenation happened for low catalyst content, denitrogenation by zeolite started only at high catalyst loading (biomass:catalyst ratio of 1:4). At the highest zeolite content (Jatropha:catalyst ratio of 1:10) (Figure 5 (8)–(10)), catalytic fast pyrolysis with ZSM5 produced the highest selectivity of aromatic compounds, above 93%. This result agreed with that of other studies using commercial zeolite catalysts. Calson et al. studied the catalytic fast pyrolysis of glucose using fixed-bed with a variety of catalyst to biomass ratios of 1.5, 2.3, 4.0, 9.0, and 19.0, respectively. The highest catalyst to feed ratio of 19.0 generated high aromatic selectivity.[26] ThangalagalazhyGopakumar et al. reported that the increase in biomass to commercial ZSM-5 catalyst ratios from 1:4 to 1:9 raised the aromatic yields from pyrolysis products.[31] The major aromatic hydrocarbon products found in this work were toluene (C7 ), xylene (C8 ), benzene (C6 ), and naphthalene compounds (C10 –C12 ) as well as small amounts of ethylbenzene (C8 ) and indene compounds (C9 –C11 ). This suggested that the formation of monocyclic aromatics could possibly occur within ZSM-5 pores due to their specific molecular dimensions.[16,26] The main aromatic compounds produced from ZSM-5 were in the range of gasoline (C5 –C12 ) and were in agreement with the literature.[32] In contrast, the aliphatic yields tended to decrease as the amount of catalyst increased due to the aromatization of light hydrocarbon as discussed previously. High catalyst content considerably influenced the decrease in oxygenated and N-containing compounds which was beneficial for improving poor properties of bio-oils. Among all catalysts tested, ZSM-5 treated
by 3 M NaOH and synthesized at 72 h had highest surface area and demonstrated the highest hydrocarbon yield of 97.4% and suppressed oxygenated and N-containing yields to only 0.8% and 1.7%, respectively. In addition, from Figure 4, the result showed that this catalyst resulted in an increase in the production of liquid yield and decrease in solid and gas fractions compared to ZSM-5 treated by 1 and 2 M NaOH. The decrease in char was mainly attributed to the larger pore diameter in ZSM-5 structure as exhibited in Table 2. This result agreed well with previous research from Mochizuki et al.[33] They reported that the reduction of solid residues was observed by using catalysts with a larger pore size. From these results, it can be concluded that the biomass to catalyst ratio has an effect on the increase in aromatic hydrocarbons yields as well as the decrease in the oxygenated and N-containing compounds. Furthermore, it was indicated that ZSM-5 synthesized from fly ash seemed to be effective catalysts for catalytic fast pyrolysis application. ZSM-5 treated with 3 M NaOH synthesized for 72 h showed superior performance among others thus it will be further applied in a continuous feed fixed bed pyrolyzer in the future work. The catalyst life time and regeneration will also be investigated. 4. Conclusions ZSM-5 catalyst was successfully synthesized from fly ash by using 1–3 M NaOH at 160◦ C for 24 and 72 h. ZSM5 synthesized with 1–3 M NaOH after a long synthesis time of 72 h showed superior properties of catalyst such as high crystallinity, less impurity, and small particle size. Therefore, these zeolites were selected for further catalytic activity assessment. The results indicated that ZSM-5 synthesized from fly ash had a great potential as catalyst for catalytic fast pyrolysis application. In addition, it was found that high catalyst content had the positive effect on the increase in aromatic hydrocarbons yields as well as the decrease in the oxygenated and N-containing compounds. Among all catalysts tested, ZSM-5 synthesized with 3 M NaOH at 72 h showed the highest hydrocarbon yield of 97.4% and suppressed oxygenated and N-containing yields to only 0.8% and 1.7%, respectively. The formation of hydrocarbon led to the high heating values of bio-oils. In addition, the presence of ZSM-5 derived from fly ash contributed to reduce the undesirable oxygenated compounds such as aldehydes, acids, ketones which cause poor quality of bio-oil. A few percentages of N-containing components suggested that further denitrogenation may be required prior to utilization of the obtained liquid fuel. Funding This research is granted by the National Metal and Materials Technology Center, Thailand [Project No.MT-B-53-END-07082-C]. The Py-GC/MS was supported by JST/JICA, Science and Technology Research Partnership for Sustainable Development
Environmental Technology (SATREPS), Japan. S.Vichaphund would like to acknowledge Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok, Thailand for financial support. The authors are grateful to the Ratchadaphiseksomphot Endowment Fund of Chulalongkorn University [RES560530188EN] for partially funding of this work.
Downloaded by [New York University] at 05:19 10 October 2014
References [1] Wang S. Application of solid ash based catalysts in heterogeneous catalysis. Environ Sci Technol. 2008;42: 7055–7063. [2] Chareonpanich M, Namto T, Kongkachuichay P, Limtrakul J. Synthesis of ZSM-5 zeolite from lignite fly ash and rice husk ash. Fuel Process Technol. 2004;85:1623–1634. [3] Amrhein C, Haghnia GH, Kim TS, Mosher PA, Gagajena RC, Amanios T, Torre LDL. Synthesis and properties of zeolites from coal fly ash. Environ Sci Technol. 1996;30:735–742. [4] Czernik S, Bridgwater AV. Overview of applications of biomass fast pyrolysis oil. Energ Fuel. 2004;18:590–598. [5] Oasmaa A, Elliott DC, Korchonen J. Acidity of biomass fast pyrolysis bio-oils. Energ Fuel. 2010;24:6548–6554. [6] French R, Czernik S. Catalytic pyrolysis of biomass for biofuels production. Fuel Process Technol. 2010;91: 25–32. [7] Carlson TR, Chenge Y-T, Jae J, Huber GW. Production of green aromatics and olefins by catalytic fast pyrolysis of wood sawdust. Energ Environ Sci. 2011;4:145–161. [8] Pattiya A, Titiloye JO, Bridgwater AV. Fast pyrolysis of cassava rhizome in the presence of catalysts. J Anal Appl Pyrolysis. 2007;81:72–79. [9] Mihalcik DJ, Mullen CA, Boateng AA. Screening acidic zeolites for catalytic fast pyrolysis of biomass and its components. J Anal Appl Pyrolysis. 2011;92:224–232. [10] Murata K, Liu Y, Inaba M, Takahara I. Catalytic fast pyrolysis of Jatropha waste. J Anal Appl Pyrolysis. 2012;94:75–82. [11] Aho A, Kumar N, Eranen K, Salmi T, Hupa M, Murzin DY. Catalytic pyrolysis of woody biomass in a fluidized bed reactor: influence of the zeolite structure. Fuel. 2008;87: 2493–2501. [12] Sricharoenchaikul V, Atong D. Thermal decomposition study on Jatropha curcus L waste using TGA and fixed bed reactor. J Anal Appl Pyrolysis. 2009;85:155–162. [13] Querol X, Alastuey A, Lopez-Soler A, Plana F. A fast method for recycling fly ash: microwave-assisted zeolite synthesis. Environ Sci Technol. 1997;31:2527–2533. [14] Murayama N, Yamamoto H, Shibata J. Mechanism of zeolite synthesis from coal fly ash by alkali hydrothermal reaction. Int J Miner Process. 2002;64:1–17. [15] Ojha K, Pradhan NC, Samanta AN. Zeolite from fly ash: synthesis and characterization. Bull Mater Sci. 2004;27: 555–564. [16] Szostak R. Molecular sieves-principles of synthesis and identification. London: Blackie Academic& Professional, Thomson Science; 1998. [17] Kim DJ, Chung HS. Synthesis and characterization of ZSM5 zeolite from serpentine. Appl Clay Sci. 2003;24:69–77.
2261
[18] Inada M, Eguchi Y, Enomoto N, Hojo J. Synthesis of zeolite from coal fly ashes with different silica-alumina composition. Fuel. 2005;84:299–304. [19] Anuwattana R, Balkus Jr. KJ, Asavapisit S, Khummongkol P. Conventional and microwave hydrothermal synthesis of zeolite ZSM-5 from the cupola slag. Micropor Mesopor Mat. 2008;111:260–266. [20] Mohamed RM, Fouad OA, Ismail AA, Ibrahim IA. Influence of crystallization time on the synthesis of nanosized ZSM-5. Mater Lett. 2005;59:3441–3444. [21] Kaewpengkrow P, Atong D, Sricharoenchaikul V. Effect of Pd Ru Ni and ceramic supports on selective deoxygenation and hydrogenation of fast pyrolysis Jatropha residue vapors. Renew Energy. 2014;65:92–101. [22] Huber GW, Iborra S, Corma A. Synthesis of transportation fuels from biomass chemistry catalysts and engineering. Chem Rev. 2006;106:4044–4098. [23] Mochizuki T, Chen S-Y, Toba M, Yoshimura Y. PyrolyzerGC/MS system-based analysis of the effects of zeolite catalysts on the fast pyrolysis of Jatropha husk. Appl Catal A-Gen. 2013;456:174–181. [24] Achten WMJ, Verhot L, Franken YJ, Mathijs E, Singh VP, Aerts R, Muys B. Jatropha bio-diesel production and use. Biomass Bioenerg. 2008;32:1063–1084. [25] Thangalazhy-Gopakumar S, Adhikari S, Gupta RB. Catalytic pyrolysis of biomass over HZSM-5 under hydrogen pressure. Energ Fuel. 2012;26:5300–5306. [26] Carlson TR, Tompsett GA, Conner WC, Huber GW. Aromatic production from catalytic fast pyrolysis of biomass-derived feedstocks. Top Catal. 2009;52: 241–252. [27] Wu Z, Sugimoto Y, Kawashima H. Catalytic nitrogen release during a fixed-bed pyrolysis of model coals containing pyrrolic or pyridinic nitrogen. Fuel. 2001;80:251–254. [28] Hansson K-M, Samuelsson J, Tullin C, Amand L-E. Formation of HNCO HCN and NH3 from the pyrolysis of bark and nitrogen-containging model compounds. Combust Flame. 2004;137:265–277. [29] Li L, Takarada T. Conversion of nitrogen compounds and tars obtained from pre-composted pig manure pyrolysis, over nickel loaded brown coal char. Biomass Bioenerg. 2013;56:456–463. [30] Thangalazhy-Gopakumar S, Adhikari S, Chattanathan SA, Gupta RB. Catalytic pyrolysi of green algae for hydrocarbon production using HZSM-5 catalyst. Bioresour Technol. 2012;118:150–157. [31] Thangalazhy-Gopakumar S, Adhikari S, Gupta RB, Tu M, Taylor S. Production of hydrocarbon fuels from biomass using catalytic pyrolysis under helium and hydrogen environments. Bioresour Technol. 2011;102:6742–6749. [32] Escola JM, Aguado J, Serrano DP, Briones L, Diaz de tuesta JL, Calvo R, Fernandez E. Conversion of polyethylene into transportation fuels by the combination of thermal cracking and catalytic hydroreforming over Ni-supported hierarchical beta zeolite. Energ Fuel. 2012;26:3187–3195. [33] Mochizuki T, Atong D, Chen S-Y, Toba M, Yoshimura Y. Effect of SiO2 pore size on catalytic fast pyrilysis of Jatropha residues by using pyrolyzer-GC/MS. Catal Commun. 2013;36:1–4.
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste ab
ab
c
S. Vichaphund , D. Aht-Ong , V. Sricharoenchaikul & D. Atong
d
a
Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand b
Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand c
Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand d
Ceramic Technology Research Unit, National Metal and Materials Technology Center, Pathumthani 12120, Thailand Published online: 29 Mar 2014.
To cite this article: S. Vichaphund, D. Aht-Ong, V. Sricharoenchaikul & D. Atong (2014) Characteristic of fly ash derivedzeolite and its catalytic performance for fast pyrolysis of Jatropha waste, Environmental Technology, 35:17, 2254-2261, DOI: 10.1080/09593330.2014.900118 To link to this article: http://dx.doi.org/10.1080/09593330.2014.900118
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 17, 2254–2261, http://dx.doi.org/10.1080/09593330.2014.900118
Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste S. Vichaphunda,b , D. Aht-Onga,b , V. Sricharoenchaikulc and D. Atongd∗ of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand; b Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand; c Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand; d Ceramic Technology Research Unit, National Metal and Materials Technology Center, Pathumthani 12120, Thailand
a Department
Downloaded by [New York University] at 05:19 10 October 2014
(Received 11 December 2013; accepted 27 February 2014 ) Fly ash from pulp and paper industries was used as a raw material for synthesizing zeolite catalyst. Main compositions of fly ash consisted of 41 wt%SiO2 , 20 wt%Al2 O3 , 14 wt%CaO, and 8 wt% Fe2 O3 . High content of silica and alumina indicated that this fly ash has potential uses for zeolite synthesis. Fly ash was mixed with 1–3 M NaOH solution. Sodium silicate acting as silica source was added into the solution to obtain the initial SiO2 /Al2 O3 molar ratio of 23.9. The mixtures were then crystallized at 160◦ C for 24 and 72 h. Zeolites synthesized after a long synthesis time of 72 h showed superior properties in terms of high crystallinity, less impurity, and small particle size. The catalytic activities of fly ash-derived zeolites were investigated via fast pyrolysis of Jatropha wastes using analytical pyrolysis-gas chromatograph/mass spectrometer (GC/MS). Pyrolysis temperature was set at 500◦ C with Jatropha wastes to catalyst ratio of 1:1, 1:5, and 1:10. Results showed that higher amounts of catalyst have a positive effect on enhancing aromatic hydrocarbons as well as decreasing in the oxygenated and N-containing compounds. Zeolite Socony Mobil-5 (ZSM-5) treated with 3 M NaOH at 72 h showed the highest hydrocarbon yield of 97.4%. The formation of hydrocarbon led to the high heating value of bio-oils. In addition, the presence of ZSM-5 derived from fly ash contributed to reduce the undesirable oxygenated compounds such as aldehydes, acids, and ketones which cause poor quality of bio-oil to only 0.8% while suppressed N-compounds to 1.7%. Overall, the ZSM-5 synthesized from fly ash proved to be an effective catalyst for catalytic fast pyrolysis application. Keywords: fly ash; synthesis; zeolite; catalyst; fast pyrolysis
1. Introduction A large amount of fly ash has been generated from coalbased thermal power plants in several kinds of industries. In general, these wastes were disposed in landfill causing environmental problems. Therefore, the idea to utilize fly ash as a value-added product has attracted much attention. Because of being rich in SiO2 and Al2 O3 , fly ash is widely used in many applications such as soil amendment, adsorbents for gas and water cleaning, nuclear waste stabilization, building materials, and particularly, zeolite synthesis. The utilization of fly ash as a starting material to synthesize zeolite has been greatly focused because this process can reduce the fly ash disposal cost, minimize environmental impact, and importantly increase high-valued products. Several zeolites such as zeolite X, zeolite Na-P1, anacime, hydroxyl sodalite, zeolite Y, faujasite, and Zeolite Socony Mobil-5 (ZSM-5) were successfully synthesized from fly ash by alkaline hydrothermal methods. Zeolite derived from fly ash was expected to be of use in several applications including ion-exchange, gas absorber, detergent, molecular sieves, and catalysts.[1–3] However, there have only been ∗ Corresponding
author. Email: [email protected]
© 2014 Taylor & Francis
few reports focusing on the zeolite derived from fly ash in catalyst applications.[1,2] Moreover, there has been no report involving catalytic fast pyrolysis of biomass wastes using fly ash-derived zeolite catalysts. Generally, products obtained from pyrolysis of biomass are liquid bio-oil, solid char, and non-condensable gases. Bio-oils contained high oxygen contents of approximately 35–45 wt% due to their oxygen-rich compounds such as water, acids, alcohols, aldehydes, ketones, furans, phenolic compounds, and sugar derivatives. These components cause poor properties of bio-oil including low heating value, incompatibility with petroleum fuel, high viscosity, chemical instability, and acidity.[4,5] Therefore, the elimination of oxygen in bio-oil is required in order to improve fuel property and to use bio-oil in conventional transport fuel. Two types of upgrading methods which have been applied to reject oxygen from organic compounds are hydrotreating and catalytic cracking. The former process needs hydrogen to react with oxygen to form water as by-product. In the case of the latter process, catalytic cracking can convert oxygenated compounds produced during biomass pyrolysis
Downloaded by [New York University] at 05:19 10 October 2014
Environmental Technology directly to hydrocarbons which can improve bio-oil quality. In contrast to hydrotreating, catalytic vapour cracking can proceed at atmospheric pressure without the requirement of high hydrogen pressure which result in the reduction of operating cost.[4,6,7] Among zeolite catalysts, ZSM-5 (structure type mordenite framework inverted) with three-dimensional pore system consisting of sinusoidal (5.3 × 5.6 Å) and straight (5.2 × 5.7 Å) channels exhibits superior capability on promoting catalytic cracking reaction because of its superior properties such as high surface area, pore structure, molecular sieve characteristics, active site, and high thermal resistance.[8–10] The improved properties of bio-oil obtained through the pyrolysis of biomass over zeolite are realized through deoxygenation reactions by reducing oxygenated compounds and enhancing aromatic selectivity. In addition, a few researchers suggested that ZSM-5 catalyst has the advantage of long life time and can be regenerated. Aho et al. [11] proved that the spent zeolites including H-Beta, H-Y, H-ZSM5, and H-MOR were successfully regenerated at 450◦ C for 2 h without the changing structure of zeolites. Carlson et al. [7] studied the life time and regeneration of ZSM-5. They found that the catalyst could be applied in pyrolysis process for 10 timesregeneration cycles and was regenerated at 600◦ C in air atmosphere for 3 h. After characterization, the ZSM-5 structure after 10 reaction/regeneration cycles showed a slight change in the intensity of X-ray diffraction (XRD) peak at a small angle, 2θ = 8. In this research, fly ash collected from pulp and paper industries in Thailand was used as the raw material for synthesizing ZSM-5 catalyst. After synthesis, the catalytic activity of fly ash-derived zeolites was investigated via fast pyrolysis of Jatropha wastes in order to upgrade the pyrolysis vapours using analytical pyrolysis-GC/MS (PyGC/MS) technique. The catalytic cracking using ZSM-5 catalyst was intended to convert oxygenated compounds produced during Jatropha pyrolysis directly to hydrocarbons which can improve bio-oil quality. Jatropha wastes which are by-products from bio-fuel extraction process found abundantly in many local plants in Thailand were selected as a biomass feedstock. The pyrolysis of this waste can help extract additional values from Jatropha and also reduce environmental problems from waste disposal. The pyrolysis temperature was set at 500◦ C for 30 s with the Jatropha wastes to catalyst ratio of 1:1, 1:5, and 1:10. Jatropha pyrolysis products and catalyst selectivity were then discussed.
2. Material and methods 2.1. Fly ash characterization Fly ash collected from pulp and paper industries in Thailand was used as a raw material for synthesizing zeolite catalyst. Chemical composition and phase analysis of as-received fly
2255
ash were examined by X-ray Fluorescence (XRF: Philips PW 2404) and XRD (Socony PANalytical, X’ Pert Pro). 2.2. Synthesis of ZSM-5 synthesis from fly ash Initially, 3 g of fly ash was mixed with 25 ml of 1–3 M NaOH solution at 90◦ C for 3 h under stirring condition in order to form appropriate silicate and aluminate salts for further zeolitization. Then, the sodium metasilicate pentahydrate (≥ 97%, Fluka) as an additional silica source was mixed into the fly ash solution to obtain the initial SiO2 /Al2 O3 molar ratio of 24. After that, tetrapropylammonium bromide (TPABr, 98%, Aldrich) acting as an organic template was added to the solution. After homogeneous mixing, the slurry was transferred into a Teflon-lined stainless steel autoclave in order to perform crystallization at 160◦ C for 24 and 72 h. After crystallization, the solid cake was filtered and washed by deionized water. The sample powders were dried at 100◦ C overnight and calcined at 540◦ C for 5 h in air atmosphere to remove the organic templatefrom zeolite network. To obtain HZSM-5, the powder was converted to H-form by ion-exchange with 1 M NH4 Cl solution at 80◦ C for 8 h. The sample was then washed with deionized water to remove chloride ions, dried at 100◦ C overnight, and calcined at 540◦ C for 5 h in air atmosphere. Phase analysis of synthesized powder was performed by X-ray powder diffraction (XRD; PANalytical, X’ Pert Pro) with 40 kV, 45 mA, CuKα radiation. The sample was scanned at 2θ from 5◦ to 60◦ with a step size of 0.02. Microstructure was characterized by scanning electron microscope (SEM; JEOL, JSM-5410). For elemental analysis, energy dispersive Xray spectroscope (EDX; model Oxford Inca 300) with X-ray dot mapping was used. The particle size and distribution were measured using laser diffraction by Mastersizer 2000 (Version 5.54 Serial Number: MAL 1021434, Malvern Instrument Ltd). The specific surface area was determined by nitrogen adsorption using Autosorb-1 (Quantachrome instruments). The samples were degassed for 8 h at 300◦ C prior to the analysis. The acidity of synthesized ZSM-5 catalysts was determined by the temperature-programmed desorption (NH3 -TPD) using BELCAT instrument. Prior to the measurement, the catalyst (approximately 0.1 g) was pre-treated at 500◦ C for 1 h under a helium atmosphere to remove water. After cooling to 100◦ C, ammonia gas adsorption was carried out for 1 h and subsequently, helium gas was purging at the same temperature for 30 min to eliminate the physisorbed ammonia. Next, the sample was heated from 100◦ C to 800◦ C with the heating rate of 10◦ C/min. The desorbed ammonia was detected by using a thermal conductivity detector. 2.3. Catalytic performance of ZSM-5 from fly ash Jatropha wastes left after extraction of oil from biodiesel production process from local plants in Thailand were used as a biomass feedstock. Prior to the test, this waste was
S. Vichaphund et al.
dried at 60◦ C for 24 h, crushed with a grinder, and then sieved to fine powder with the particle size equal to or less than 125 μm (100 mesh). Component analysis of Jatropha wastes consisted of 57.0% cellulose, 17.6% hemicelluloses, and 25.4% lignin. The volatile matter and fixed carbon contents are 73.8% and 13.6%, respectively, while ash contents of 5.8% are higher than approximately 1.0% of typical wood. Carbon is the main element (49.2%) with small amounts of 6.4% hydrogen, 4.5% nitrogen, and 1.1% sulphur. The oxygen content of 39.6% is considerably high which could be a precursor to oxygenated compounds. Pyrolysis was performed using a Pyroprobe pyrolyser (multifuntional pyrolyzer, PY-2020iD, Frontier Lab) with an auto-shot sampler AS-1020E interfaced to a GC-Mas spectrometer (GCMS-QP2010, Shimudzu). Approximately 0.4 mg Jatropha wastes were used in each experiment. In order to investigate the effect of Jatropha waste to catalyst ratios, catalysts were placed above the biomass layer at the Jatropha wastes to catalyst ratio of 1:1, 1:5 and 1:10. The sample was pyrolysed with the Pyroprobe set at 500◦ C for 30 s. Previous study showed that high liquid yield was achieved from pyrolysis of Jatropha waste at this moderate temperature.[12] The GC column employed was a 30 m × 0.25 mm Ultra alloy 5 (i.d., 0.25 μm film thickness). Helium (99.999%) was used as a carrier gas with a column flow of 1.3 ml/min and the split injector ratio was 1:50. During the analysis of the pyrolytic products, the oven temperature was started from 50◦ C (3 min) to 200◦ C (heating rate of 5◦ C/min) then to 350◦ C (heating rate of 10◦ C/min and hold for 10 min). The injector and detector temperatures were kept at 280◦ C, and the mass spectrometer was operated in electron ionization mode at 70 eV. The mass spectra were obtained from m/z 20 to 800 with the scan speed of 625 amu/s. Identification of chromatographic peaks was achieved according to the National Institute of Standards Table 1.
and Technology and Wiley mass spectrum libraries. Product quantification is based on percentages of relative peak area of each compound to the total peak areas obtained from the chromatogram. These relative peak areas are then added up according to their associated categories and selectivity of particular group of compounds is then realized. Noncatalytic fast pyrolysis of Jatropha waste was also tested for comparison to the catalytic runs in terms of product yields and composition of pyrolysis vapour. 3. Results and discussion 3.1. Fly ash characterization The chemical composition of fly ash characterized by XRF mainly consisted of 41.4 wt%SiO2 , 20.0 wt%Al2 O3 , 14.1 wt%CaO, and 8.4 wt% Fe2 O3 with small amounts of SO3 , MgO, K2 O, TiO2 , Na2 O, and P2 O5 as listed in Table 1. Due to the high content of CaO of more than 8 wt%, this fly ash was classified as class C according to ASTM C618.[1] Additionally, the high content of silica and alumina indicated that this fly ash has potential for zeolite synthesis. From XRD result as displayed in Figure 1(a), fly ash showed high crystallinity of quartz (SiO2 ) as a main phase with minor phases of anhydrite (CaSO4 ) and calcite (CaCO3 ). These minerals were generally found in fly ash particles.[1,13] The morphology monitored by SEM showed that the fly ash particles were large and quite irregular in appearance (Figure 1(b)). 3.2. Synthesized zeolites from fly ash The XRD patterns of ZSM-5 synthesized with 1–3 M NaOH for 24 and 72 h were shown in Figure 2. It can be seen that the alkaline solution contributed to the increase in silicate and aluminate solutions via fly ash dissolution.[13–15]
Chemical composition of fly ash.
Oxides
SiO2
Al2 O3
CaO
Fe2 O3
SO3
MgO
K2 O
TiO2
Na2 O
P2 O5
Others∗
L.O.I.
Particle size (μm)
(wt%)
41.4
20.0
14.1
8.4
4.9
2.3
2.0
0.6
0.4
0.4
0.5
4.8
26.08
(a)
(b) Quartz Anhydrite Calcite
Intensity (a.u.)
Downloaded by [New York University] at 05:19 10 October 2014
2256
10
Figure 1.
20
30
40 50 2Theta (deg)
60
70
80
Physical appearance of as-received Fly ash: (a) XRD pattern and (b) SEM micrograph.
Environmental Technology (a)
ZSM-5, Quartz,
2257
(b)
Anhydrite Calcite
ZSM-5,
Anhydrite
Quartz,
Calcite Fly ash
1 M NaOH
5
15
25
35
Intensity (a.u.)
Intensity (a.u.)
Fly ash
1 M NaOH
2 M NaOH
2 M NaOH
3 M NaOH
3 M NaOH
45
55
5
2q q (degrees)
Figure 2. (b) 72 h.
Downloaded by [New York University] at 05:19 10 October 2014
Table 2.
25
35
45
55
2q q (degrees)
XRD pattern of ZSM-5 synthesized from fly ash at 160◦ C with 1–3 M NaOH concentration with reaction times for (a) 24 h and Properties of ZSM-5 synthesized from fly ash at 160◦ C. Synthesis time
NaOH
Particle size
Surface area
Pore size
Pore volume
(Å)
(cm3 /g)
Si
Al
Ca
Fe
33.30 36.95 37.10 31.78 32.94 33.10
0.22 0.24 0.20 0.20 0.20 0.24
50.0 51.3 49.3 54.8 53.9 55.2
5.0 3.9 3.9 2.8 3.5 3.6
1.8 2.5 1.0 1.4 2.4 1.4
4.8 2.1 0.8 n.d.∗ n.d.∗ 2.1
Samples
(h)
(M)
(μm)
(m2 /g)
ZSM-5
24
1 2 3 1 2 3
20.20 20.84 17.00 18.00 19.65 18.30
424 407 345 406 380 453
72
∗ Not
15
Element (wt%)
determined.
This assumption was supported by the reduction of quartz intensity after synthesis process. After the dissolution step, silicate and aluminate species reacted together with the presence of TPABr as an organic template, further condensed, and crystallized to form ZSM-5 crystals. At short synthesis time of 24 h (Figure 2(a)), the formation of ZSM-5 was detected as a major phase with the characteristic diffraction peaks occurring at 2θ of 7–9◦ and 23–25◦ .[16] Meanwhile the intensity of quartz decreased significantly compared to the as-received fly ash. With increasing synthesis time from 24 to 72 h (Figure 2(b)), the high-crystallinity ZSM-5 was obtained with small amount of quartz and analcime phases. In terms of NaOH concentration, the change of alkaline concentration from 1 to 3 M did not significantly affect the crystallinity as there was no observed change in intensity of the diffraction peaks. The elemental analysis of samples was determined by EDX as shown in Table 2. The alkali treatment could remove Ca and Fe from fly ash to form insoluble hydroxides. However, it was possible that there were calcium and iron species remaining in zeolite structure. The result was confirmed by small amounts of Ca and Fe elements detected in ZSM-5 structure after synthesis. This finding is consistent with that of other studies.[3,17–19] Calcium ion in solution might react with CO2 in the atmosphere leading to very small amounts of CaCO3 ,[18] while iron could incorporate into the framework in trace amounts.[19]
The particle size, surface area, pore size, and pore volume of ZSM-5 from fly ash treated by 1–3 M NaOH synthesized at 160◦ C for 24 and 72 h is illustrated in Table 2. The particle size of synthesized zeolite revealed the agglomerates in size with the mean diameters in the range 17.0–20.8 μm. From these results, synthesized ZSM-5 treated with 3 M NaOH for 72 h yielded the highest surface area of 453 m2 /g with a pore size of 33.1 Å. The pore size of zeolite catalysts were classified as mesoporous materials (the pore size ∼20–500 Å).[16] The SEM micrographs of zeolites derived from fly ash under different synthesis conditions were exhibited in Figure 3. It can be seen that both parameters, NaOH concentration and synthesis time, had an effect on the formation of ZSM-5 crystals. With an increase in NaOH concentration from 1 to 3 M (Figure 3(a)–3(c)), particles changed from irregular and round-shaped to be more cubic-like crystal. From previous studies, the alkalinity is one of the important factors for zeolitization. When the NaOH concentration in the mixture was increased, OH− promoted the dissolution of fly ash to silicate and aluminate species while Na+ accelerated the crystallization step which included nucleation and crystal growth.[14,15] Therefore, the morphology of zeolite treated by high alkali concentration was shown to be more cubic in shape. Moreover, zeolite particles obtained from 72 h long crystallization time had a tendency to increase the rate of crystal growth as shown in Figure 3(d)–3(f).[20]
S. Vichaphund et al.
ZSM-5 particles with 3 M NaOH and a crystallization time of 72 h (Figure 3(f)) were agglomerated (18.30 μm) and consisted of many single cubic particles with size less than 5 μm.
Downloaded by [New York University] at 05:19 10 October 2014
3.3.
Catalytic activity of ZSM-5 derived from fly ash using Py-GC/MS In this experiment, zeolites synthesized with 1–3 M NaOH after a long synthesis time of 72 h were selected for examining the catalytic performance on fast pyrolysis of Jatropha by using Py-GC/MS. The pyrolysis temperature was set at 500◦ C. From previous study, the result showed that high liquid yield was achieved from the pyrolysis of Jatropha waste at this moderate temperature.[12] In addition, biomass liquids are known to have an acidic structure. Large amounts of acids can cause corrosion problem in engines.[6,9,10] Kaewpengkrow et al. [21] studied the pyrolysis of Jatropha waste with Py-GC/MS at 400–600◦ C and reported that the lowest acid yield was obtained after pyrolysis at 500◦ C. According to Huber et al., who wrote a review on synthesis of transportation fuel from biomass, the operating conditions for upgrading bio-oil using zeolite are temperatures from 350 to 500◦ C to reduce oxygen content.[22] Aho et al. [11] investigated the influence of zeolites on the catalytic pyrolysis of pinewood in a fluidized bed reactor at 500◦ C. Furthermore, French and Czernik reported good deoxygenation activity of ZSM-5 for the catalytic cracking of hardwood at 500◦ C.[6] Figure 4 shows the product yields including gas, liquid, and solid from fast pyrolysis of Jatropha waste with and without synthesized ZSM-5 catalysts at 500◦ C. Gas and liquid yields were determined by relative percentages of peak area directly obtained from the chromatogram of GC after normalization of the corresponding total product yields, whereas solid residues were calculated by the weight difference of samples before and after pyrolysis. It was found that the liquid and gas products were observed in the range 45.9–61.4% and 14.8–30.6%, respectively. From the analysis, most of the gas product was carbon dioxide with small amounts of carbon monoxide, propane, and butane. The presence of ZSM-5 catalysts increased the gas formation. High content of catalysts resulted in superior secondary cracking and decomposition reactions of liquid product leading to higher gas yields at those conditions. Solid residues were in the range 19.0– 31.8%, which were comparable to the values obtained in other studies.[6,23] Jatropha waste as biomass wastes was initially pyrolysed at 500◦ C in order to investigate the non-catalytic pyrolytic products. Pyrolysis vapours usually contained both volatile and non-volatile compounds. However, GC/MS was able to detect only the organic volatile compounds. The ion chromatograms displayed more than 100 peaks and the perfect separation of all peaks was not
Gas
100
Liquid
Solid
90 80 Product yields (%)
2258
70 60 50 40 30 20 10 0 1
2
3
4 5 6 7 Types of catalysts
8
9
10
Figure 4. Product yields (%) from Py-GC/MS of Jatropha waste using ZSM-5 catalysts synthesized from fly ash at 160◦ C for 72 h with 1–3 M NaOH concentrations and Jatropha to catalyst ratios: (1) No catalyst, (2) ZSM-5/1 M NaOH, (3) ZSM-5/2 M NaOH, (4) ZSM-5/3 M NaOH ((2)–(4) referred the Jatropha to catalyst ratios = 1 : 1); (5) ZSM-5/1 M NaOH, (6) ZSM-5/2 M NaOH, (7) ZSM-5/3 M NaOH, ((5)–(7) referred the Jatropha to catalyst ratios = 1 : 5); (8) ZSM-5/1 M NaOH, (9) ZSM-5/2 M NaOH, (10) ZSM-5/3 M NaOH ((8)–(10) referred the Jatropha to catalyst ratios = 1 : 10).
possible due to the complex composition of the pyrolysis vapours. A total of 50 peaks from the chromatogram was then identified and classified as 11 organic compounds based on their major chemical functional groups such as aromatic hydrocarbons, aliphatic hydrocarbons, phenols, ketones, aldehydes, acids, N-containing compounds, sugars, and others (alcohols, ethers, and esters). The overall pyrolytic products from fast pyrolysis of Jatropha waste with and without zeolite catalysts were shown in Figure 5. The selectivity of pyrolytic products was represented by the peak area (%). Each percentage of peak area was based on the peak areas of selected characteristic molecular or fragment ion chromatograms. Without zeolite catalyst, non-catalytic pyrolytic products (Figure 5(1)) contained mainly acid compounds (50.7%), which was mostly linoleic acid (C18:2) (37.0%), commonly detected in Jatropha oils.[24] Nitrogen element in Jatropha is generally higher than other woody biomass. Therefore, N-containing compounds in pyrolytic vapours were found in high content (20.3%). Other oxygenated compounds consisted of ketones (7.5%), alcohols (3.0%), esters (2.0%), ethers (3.7%), and phenols (2.8%). The heavy compounds such as sugar products were found in small content, 3.7%. Unfortunately, the pyrolytic products contained small amounts of hydrocarbon (4.0%). Before catalytic testing, the acidity of selected catalysts was also analysed as shown in Table 3. The ammonia TPD results of synthesized zeolites consisted of two desorption peaks. The first peak at 100–300◦ C was weak acid sites and the second peak (300–600◦ C) was strong acid sites.[10] From the results, the total acidity decreased insignificantly
2259
Figure 3. SEM micrograph of ZSM-5 from fly ash at 160◦ C (a) 1 M NaOH, 24 h,(b) 2 M NaOH, 24 h, (c) 3 M NaOH, 24 h, (d) 1 M NaOH, 72 h, (e) 2 M NaOH, 72 h, and (f) 3 M NaOH, 72 h. Aromatic HC
Aliphatic HC
Phenol
Ketone
Aldehyde
Acid
Others
N-comp.
Sugar
Table 3. Acidity of ZSM-5 synthesized from fly ash at 160◦ C, for 72 h. Acidic site determined by NH3 -TPD (mmol NH3 g−1 )
100% 90%
First peak Second peak NaOH (T desorption (300◦ C < T ◦ Samples (M) < 300 C) desorption < 600◦ C) Total
80% Product selectivity (%)
Downloaded by [New York University] at 05:19 10 October 2014
Environmental Technology
70% 60%
ZSM-5
50% 40%
1 2 3
0.562 0.512 0.525
0.457 0.505 0.454
1.019 1.017 0.979
30% 20% 10% 0%
1
2
3
4
5
6
7
8
9
10
Types of catalysts
Figure 5. Product selectivity (%) detected from Py-GC/MS of Jatropha waste using ZSM-5 catalysts synthesized from fly ash at 160◦ C for 72 h with 1–3 M NaOH concentrations and Jatropha to catalyst ratios: (1) no catalyst, (2) ZSM-5/1 M NaOH, (3) ZSM-5/2 M NaOH, (4) ZSM-5/3 M NaOH ((2)–(4) referred the Jatropha to catalyst ratios = 1 : 1); (5) ZSM-5/1 M NaOH, (6) ZSM-5/2 M NaOH, (7) ZSM-5/3 M NaOH, ((5)–(7) referred the Jatropha to catalyst ratios = 1 : 5); (8) ZSM-5/1 M NaOH, (9) ZSM-5/2 M NaOH, (10) ZSM-5/3 M NaOH ((8)–(10) referred the Jatropha to catalyst ratios = 1 : 10).
in the order of ZSM-5 treated by NaOH 1 M > 2 M > 3 M, respectively. The slight decrease in acidity was observed as the concentration of NaOH increased. The silicate species from fly ash can be easily dissolved in the mixture in the presence of high NaOH concentration; thus ZSM-5 treated by 3 M NaOH exhibited high Si/Al molar ratio and lower acidity. The presence of ZSM-5 synthesized from fly ash showed a good performance for cracking pyrolysis vapours. The unfavourable oxygenated compounds such as acids, ketones, and aldehydes were effectively reduced via several
reaction path ways including dehydration, decarboxylation, decarbonylation, and oligimerization.[6,7,9] At lowest zeolite content (Jatropha:catalyst ratio of 1:1) (Figure 5 (2)– (4)), synthesized ZSM-5 increased hydrocarbon yields from 4% in the case of Jatropha pyrolysis to 26% in the current case. It was noticed that ZSM-5 treated by 1 M NaOH showed higher hydrocarbon selectivity compared to others because of its higher acidity. Nevertheless, the amount of solid residue formed after pyrolysis using this catalyst was higher (Figure 4 (2)). The increase in hydrocarbon contributed to enhance heating values of bio-oil.[25,26] However, in the presence of low zeolite content, it was noticed that the acid selectivity was considerably high due to the increased rate of sugar decomposition. High acid selectivity caused bio-oils to be more acidic. In addition, high yields of other oxygenated compounds were still detected. The presence of ketones and aldehydes are responsible for aging reaction and instability of bio-oils. With an increase in the amount of catalyst used (Jatropha:catalyst ratio of 1:5) (Figure 5 (5)–(7)), it was clear that ZSM-5 synthesized from fly ash completely eliminated sugars, acids and diminished other oxygenated compounds to less than 1%. As a result, the high aromatic selectivity was achieved in the range 77.6–83.5%. The selectivity of ZSM-5
Downloaded by [New York University] at 05:19 10 October 2014
2260
S. Vichaphund et al.
with respect to hydrocarbons was in the following order of ZSM-5 treated by NaOH 3 M > 2 M > 1 M. It was thought that high yields of solid residue that occurred after pyrolysis using ZSM-5 treated by 1 M NaOH limited the hydrocarbon selectivity. This aromatic selectivity was comparable to the results tested by Murata et al. [10] who investigated the fast pyrolysis of Jatropha waste using GC/MS. In the presence of commercial ZSM-5, the aromatic selectivity was above 90% using the catalyst to biomass ratio of 6.25. As for the aliphatic hydrocarbon, lower selectivity was obtained as the catalyst content increased. This might be due to further aromatization of light hydrocarbon or olefin to produce aromatic compounds.[7,25] Furthermore, N-containing compounds decreased distinctly to 8.5–12.0%. The result suggested that the high amount of zeolite was required to remove nitrogen content. Several researches reported that the pyrolysis of biomass and coal containing nitrogen compounds generated intermediate nitrogenous species such as HCN, HNCO, and NH3 depending on the nitrogen functionalities. In the presence of catalysts, nitrogenous species might react with oxygenated compounds to form NOx as well as partly convert into nitrogen gas.[27–29] Therefore a sudden decrease in nitrogencontaining compounds was noticed. The ability of ZSM-5 to eliminate nitrogen-containing compounds in pyrolysis process was confirmed by Thangalazhy-Gopakumar et al. [30] The result showed that although deoxygenation happened for low catalyst content, denitrogenation by zeolite started only at high catalyst loading (biomass:catalyst ratio of 1:4). At the highest zeolite content (Jatropha:catalyst ratio of 1:10) (Figure 5 (8)–(10)), catalytic fast pyrolysis with ZSM5 produced the highest selectivity of aromatic compounds, above 93%. This result agreed with that of other studies using commercial zeolite catalysts. Calson et al. studied the catalytic fast pyrolysis of glucose using fixed-bed with a variety of catalyst to biomass ratios of 1.5, 2.3, 4.0, 9.0, and 19.0, respectively. The highest catalyst to feed ratio of 19.0 generated high aromatic selectivity.[26] ThangalagalazhyGopakumar et al. reported that the increase in biomass to commercial ZSM-5 catalyst ratios from 1:4 to 1:9 raised the aromatic yields from pyrolysis products.[31] The major aromatic hydrocarbon products found in this work were toluene (C7 ), xylene (C8 ), benzene (C6 ), and naphthalene compounds (C10 –C12 ) as well as small amounts of ethylbenzene (C8 ) and indene compounds (C9 –C11 ). This suggested that the formation of monocyclic aromatics could possibly occur within ZSM-5 pores due to their specific molecular dimensions.[16,26] The main aromatic compounds produced from ZSM-5 were in the range of gasoline (C5 –C12 ) and were in agreement with the literature.[32] In contrast, the aliphatic yields tended to decrease as the amount of catalyst increased due to the aromatization of light hydrocarbon as discussed previously. High catalyst content considerably influenced the decrease in oxygenated and N-containing compounds which was beneficial for improving poor properties of bio-oils. Among all catalysts tested, ZSM-5 treated
by 3 M NaOH and synthesized at 72 h had highest surface area and demonstrated the highest hydrocarbon yield of 97.4% and suppressed oxygenated and N-containing yields to only 0.8% and 1.7%, respectively. In addition, from Figure 4, the result showed that this catalyst resulted in an increase in the production of liquid yield and decrease in solid and gas fractions compared to ZSM-5 treated by 1 and 2 M NaOH. The decrease in char was mainly attributed to the larger pore diameter in ZSM-5 structure as exhibited in Table 2. This result agreed well with previous research from Mochizuki et al.[33] They reported that the reduction of solid residues was observed by using catalysts with a larger pore size. From these results, it can be concluded that the biomass to catalyst ratio has an effect on the increase in aromatic hydrocarbons yields as well as the decrease in the oxygenated and N-containing compounds. Furthermore, it was indicated that ZSM-5 synthesized from fly ash seemed to be effective catalysts for catalytic fast pyrolysis application. ZSM-5 treated with 3 M NaOH synthesized for 72 h showed superior performance among others thus it will be further applied in a continuous feed fixed bed pyrolyzer in the future work. The catalyst life time and regeneration will also be investigated. 4. Conclusions ZSM-5 catalyst was successfully synthesized from fly ash by using 1–3 M NaOH at 160◦ C for 24 and 72 h. ZSM5 synthesized with 1–3 M NaOH after a long synthesis time of 72 h showed superior properties of catalyst such as high crystallinity, less impurity, and small particle size. Therefore, these zeolites were selected for further catalytic activity assessment. The results indicated that ZSM-5 synthesized from fly ash had a great potential as catalyst for catalytic fast pyrolysis application. In addition, it was found that high catalyst content had the positive effect on the increase in aromatic hydrocarbons yields as well as the decrease in the oxygenated and N-containing compounds. Among all catalysts tested, ZSM-5 synthesized with 3 M NaOH at 72 h showed the highest hydrocarbon yield of 97.4% and suppressed oxygenated and N-containing yields to only 0.8% and 1.7%, respectively. The formation of hydrocarbon led to the high heating values of bio-oils. In addition, the presence of ZSM-5 derived from fly ash contributed to reduce the undesirable oxygenated compounds such as aldehydes, acids, ketones which cause poor quality of bio-oil. A few percentages of N-containing components suggested that further denitrogenation may be required prior to utilization of the obtained liquid fuel. Funding This research is granted by the National Metal and Materials Technology Center, Thailand [Project No.MT-B-53-END-07082-C]. The Py-GC/MS was supported by JST/JICA, Science and Technology Research Partnership for Sustainable Development
Environmental Technology (SATREPS), Japan. S.Vichaphund would like to acknowledge Center of Excellence on Petrochemical and Materials Technology, Chulalongkorn University, Bangkok, Thailand for financial support. The authors are grateful to the Ratchadaphiseksomphot Endowment Fund of Chulalongkorn University [RES560530188EN] for partially funding of this work.
Downloaded by [New York University] at 05:19 10 October 2014
References [1] Wang S. Application of solid ash based catalysts in heterogeneous catalysis. Environ Sci Technol. 2008;42: 7055–7063. [2] Chareonpanich M, Namto T, Kongkachuichay P, Limtrakul J. Synthesis of ZSM-5 zeolite from lignite fly ash and rice husk ash. Fuel Process Technol. 2004;85:1623–1634. [3] Amrhein C, Haghnia GH, Kim TS, Mosher PA, Gagajena RC, Amanios T, Torre LDL. Synthesis and properties of zeolites from coal fly ash. Environ Sci Technol. 1996;30:735–742. [4] Czernik S, Bridgwater AV. Overview of applications of biomass fast pyrolysis oil. Energ Fuel. 2004;18:590–598. [5] Oasmaa A, Elliott DC, Korchonen J. Acidity of biomass fast pyrolysis bio-oils. Energ Fuel. 2010;24:6548–6554. [6] French R, Czernik S. Catalytic pyrolysis of biomass for biofuels production. Fuel Process Technol. 2010;91: 25–32. [7] Carlson TR, Chenge Y-T, Jae J, Huber GW. Production of green aromatics and olefins by catalytic fast pyrolysis of wood sawdust. Energ Environ Sci. 2011;4:145–161. [8] Pattiya A, Titiloye JO, Bridgwater AV. Fast pyrolysis of cassava rhizome in the presence of catalysts. J Anal Appl Pyrolysis. 2007;81:72–79. [9] Mihalcik DJ, Mullen CA, Boateng AA. Screening acidic zeolites for catalytic fast pyrolysis of biomass and its components. J Anal Appl Pyrolysis. 2011;92:224–232. [10] Murata K, Liu Y, Inaba M, Takahara I. Catalytic fast pyrolysis of Jatropha waste. J Anal Appl Pyrolysis. 2012;94:75–82. [11] Aho A, Kumar N, Eranen K, Salmi T, Hupa M, Murzin DY. Catalytic pyrolysis of woody biomass in a fluidized bed reactor: influence of the zeolite structure. Fuel. 2008;87: 2493–2501. [12] Sricharoenchaikul V, Atong D. Thermal decomposition study on Jatropha curcus L waste using TGA and fixed bed reactor. J Anal Appl Pyrolysis. 2009;85:155–162. [13] Querol X, Alastuey A, Lopez-Soler A, Plana F. A fast method for recycling fly ash: microwave-assisted zeolite synthesis. Environ Sci Technol. 1997;31:2527–2533. [14] Murayama N, Yamamoto H, Shibata J. Mechanism of zeolite synthesis from coal fly ash by alkali hydrothermal reaction. Int J Miner Process. 2002;64:1–17. [15] Ojha K, Pradhan NC, Samanta AN. Zeolite from fly ash: synthesis and characterization. Bull Mater Sci. 2004;27: 555–564. [16] Szostak R. Molecular sieves-principles of synthesis and identification. London: Blackie Academic& Professional, Thomson Science; 1998. [17] Kim DJ, Chung HS. Synthesis and characterization of ZSM5 zeolite from serpentine. Appl Clay Sci. 2003;24:69–77.
2261
[18] Inada M, Eguchi Y, Enomoto N, Hojo J. Synthesis of zeolite from coal fly ashes with different silica-alumina composition. Fuel. 2005;84:299–304. [19] Anuwattana R, Balkus Jr. KJ, Asavapisit S, Khummongkol P. Conventional and microwave hydrothermal synthesis of zeolite ZSM-5 from the cupola slag. Micropor Mesopor Mat. 2008;111:260–266. [20] Mohamed RM, Fouad OA, Ismail AA, Ibrahim IA. Influence of crystallization time on the synthesis of nanosized ZSM-5. Mater Lett. 2005;59:3441–3444. [21] Kaewpengkrow P, Atong D, Sricharoenchaikul V. Effect of Pd Ru Ni and ceramic supports on selective deoxygenation and hydrogenation of fast pyrolysis Jatropha residue vapors. Renew Energy. 2014;65:92–101. [22] Huber GW, Iborra S, Corma A. Synthesis of transportation fuels from biomass chemistry catalysts and engineering. Chem Rev. 2006;106:4044–4098. [23] Mochizuki T, Chen S-Y, Toba M, Yoshimura Y. PyrolyzerGC/MS system-based analysis of the effects of zeolite catalysts on the fast pyrolysis of Jatropha husk. Appl Catal A-Gen. 2013;456:174–181. [24] Achten WMJ, Verhot L, Franken YJ, Mathijs E, Singh VP, Aerts R, Muys B. Jatropha bio-diesel production and use. Biomass Bioenerg. 2008;32:1063–1084. [25] Thangalazhy-Gopakumar S, Adhikari S, Gupta RB. Catalytic pyrolysis of biomass over HZSM-5 under hydrogen pressure. Energ Fuel. 2012;26:5300–5306. [26] Carlson TR, Tompsett GA, Conner WC, Huber GW. Aromatic production from catalytic fast pyrolysis of biomass-derived feedstocks. Top Catal. 2009;52: 241–252. [27] Wu Z, Sugimoto Y, Kawashima H. Catalytic nitrogen release during a fixed-bed pyrolysis of model coals containing pyrrolic or pyridinic nitrogen. Fuel. 2001;80:251–254. [28] Hansson K-M, Samuelsson J, Tullin C, Amand L-E. Formation of HNCO HCN and NH3 from the pyrolysis of bark and nitrogen-containging model compounds. Combust Flame. 2004;137:265–277. [29] Li L, Takarada T. Conversion of nitrogen compounds and tars obtained from pre-composted pig manure pyrolysis, over nickel loaded brown coal char. Biomass Bioenerg. 2013;56:456–463. [30] Thangalazhy-Gopakumar S, Adhikari S, Chattanathan SA, Gupta RB. Catalytic pyrolysi of green algae for hydrocarbon production using HZSM-5 catalyst. Bioresour Technol. 2012;118:150–157. [31] Thangalazhy-Gopakumar S, Adhikari S, Gupta RB, Tu M, Taylor S. Production of hydrocarbon fuels from biomass using catalytic pyrolysis under helium and hydrogen environments. Bioresour Technol. 2011;102:6742–6749. [32] Escola JM, Aguado J, Serrano DP, Briones L, Diaz de tuesta JL, Calvo R, Fernandez E. Conversion of polyethylene into transportation fuels by the combination of thermal cracking and catalytic hydroreforming over Ni-supported hierarchical beta zeolite. Energ Fuel. 2012;26:3187–3195. [33] Mochizuki T, Atong D, Chen S-Y, Toba M, Yoshimura Y. Effect of SiO2 pore size on catalytic fast pyrilysis of Jatropha residues by using pyrolyzer-GC/MS. Catal Commun. 2013;36:1–4.
