ARTICLE pubs.acs.org/EF
Catalytic Hydropyrolysis of Five Chinese Coals Zhichao Ma,†,‡,§ Xiaoxun Ma,*,†,‡,§ Jincheng Luo,†,‡,§ Long Xu,†,‡,§ and Fan Yang|| †
School of Chemical Engineering, Northwest University, Xi’an, Shaanxi 710069, People’s Republic of China Chemical Engineering Research Center of the Ministry of Education for Advanced Use Technology of Shanbei Energy, Xi’an, Shaanxi 710069, People’s Republic of China § Shaanxi Research Center of Engineering Technology for Clean Coal Conversion, Xi’an, Shaanxi 710069, People’s Republic of China China Huanqiu Contracting and Engineering Corporation, Beijing 100029, People’s Republic of China
)
‡
ABSTRACT: Five Chinese coals were subjected to pyrolysis by thermogravimetry (TG). The investigated pyrolysis conditions included pyrolysis atmospheres (N2 and 10% H2/N2) and catalysts (MoS2 and ZnCl2) with different amounts (0.5, 1.0, 2.0, 5.0, and 10%). The existence of hydrogen improved the final conversion and reduced the reaction temperature by different degrees. With the addition of catalysts, the maximal reaction rate in the hydropyrolysis process was increased for all coals, except Shaotong coal. The optimal catalytic amount for each coal was determined by the final conversion. MoS2 was more effective on the increase of the total conversion than ZnCl2, while ZnCl2 was more effective on reducing the peak temperature of secondary devolatilization. Finally, the kinetics results showed that the activation energy would be lower in the catalytic hydropyrolysis process than that in the non-catalytic run. Tongchuan coal was subjected to pyrolysis in a fixed bed. The results showed that ZnCl2 and MoS2 improved the conversion in different ways. ZnCl2 increased the yield of liquid but has little effects on the yield of benzene, toluene, and xylene (BTX), while MoS2 increased the yield of BTX obviously in hydropyrolysis.
1. INTRODUCTION Coal occupies nearly 30% of the total energy consumption in the whole world and about 75% of the total energy consumption in China. Coal gasification is considered as one of the key technologies to achieve clean, efficient, and comprehensive use of coal.1,2 From this process, coal can be converted into fuel gas or raw materials of chemical synthesis (syngas). However, the high-value chemicals abundant in feedstock for coal gasification, such as aromatic chemicals, will be completely destroyed during such a process.3 At present time, the shortage of petroleum resources is increasingly serious. In the face of the serious energy security, it is more important to develop an efficient process to use chemical structures contained in coal, which is rich in volatiles. Therefore, how to extract the high-value chemicals from coal has attracted more and more researchers. High-value-added chemicals, such as benzene, toluene, and xylene (BTX), and high-heat-value energy can be produced from coal with a suitable process.4 The hydropyrolysis process to produce liquids was first studied by Dent et al. as early as 1937, and after that, extensive studies had been carried out.59 In pyrolysis, the existence of hydrogen can stabilize the intermediate species once formed, which favors the pyrolysis process. The coal pyrolysis conditions, such as atmospheres, catalysts, and the type of coal, affect the coal conversion greatly. The chemical bonds are broken by the combined action of heat and pressure in coal pyrolysis. However, some stronger links cannot be broken by thermal action and need the presence of a suitable catalyst and/or the addition of atomic hydrogen. Our previous research on Tongchuan coal pyrolysis has been performed by He et al.10 It is found that the addition of hydrogen and catalysts is effective to improve the coal pyrolysis conversion. The product distribution of catalytic hydrocracking of coal-related model compounds r 2011 American Chemical Society
(e.g., PEBN) suggested that selective conversion of coals is possible under selected reaction conditions with the presence of proper catalysts.11 Many studies show that the addition of translation metal (Ni or Mo) can improve the yields of light aromatic hydrocarbons remarkably. During coal pyrolysis, the rupture of cross-links can produce a lot of radicals.12 The conversion would be increased, if the radicals are stabilized by hydrogen radicals. Sulfide molybdenum is a typical hydrogenation catalyst.13 The catalytic effect of the impregnated molybdenum catalyst on the hydropyrolysis of bitumous and sub-bitumous coals was studied by many researchers and obtained a high tar yield with a high pressure.14,15 However, from the results of Maldonaldo-Hodar et al., the most active catalyst form is MoS2, which is produced by hydrogenation under the severest conditions.16 ZnCl2 has attracted considerable attention because of its obvious catalytic activity. Jolly et al. studied the slow pyrolysis of a bituminous coal under helium and found that the hydrogen evolution was enhanced in the presence of ZnCl2.17 The flash pyrolysis of ZnCl2-impregnated bituminous coal was observed by Kandiyoti et al.18 The results showed that the yield of tar was increased from 22 to 35%. Nursen et al. studied the effect of ZnCl2 on the pyrolysis of Turkish coal and found that there was a synergetic effect between the inherent minerals and ZnCl2 added as a catalyst.19 Zou et al. researched the effect of ZnCl2 on the pyrolysis of Huolinhe coal and found that the final conversion was increased too.20 All of them were performed in an inert atmosphere. Filomena et al. researched the hydropyrolysis of Received: August 29, 2011 Revised: November 17, 2011 Published: November 18, 2011 511
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Table 1. Proximate and Ultimate Analyses of Coal Samples Used proximate analyses (wt %)
a
ultimate analyses (wt %)
volatile matterdaf
fixed carbondafa
Cdaf
Hdaf
Ndaf
Odafa
Sdaf
2.90
35.87
64.13
81.62
5.30
1.42
11.42
0.238
10.61
35.87
64.13
80.28
4.55
0.88
13.84
0.45
13.73
41.06
58.94
76.04
4.46
1.57
17.00
0.81
10.77
7.36
46.34
53.66
73.99
4.45
1.37
19.76
0.43
12.74
17.88
59.91
40.09
67.19
5.40
0.98
26.33
0.88
sample
moisturead
SFSBC
5.36
TSBC
5.03
WSBC
7.66
HL SL
ashad
By difference.
South African coal in an autoclave and found that the highest conversion was obtained by adding ZnCl2 as a catalyst.21 In the foregoing work, bituminous or sub-bituminous coals were always used as the research objects. The coalification rank and composition of the coal have determining influence on its catalytic pyrolysis.22 Thus, in this work, five typical Chinese coals (Shenmu-Fugu, Tongchuan, Wulumuqi, Huolinhe, and Shaotong coals, with different contents of volatiles, from 35.87 to 59.91%) were subjected to pyrolysis by thermogravimetry (TG). The investigated pyrolysis conditions included pyrolysis atmospheres and catalysts (MoS2 and ZnCl2) with different amounts. The dynamics had also been calculated in this research. A fixed bed was used to research the effects of the atmosphere and catalysts on the product distribution.
where W0 is the initial weight of the coal (air-dried basis), Acoal is the amount of ash (air-dried basis), W is the weight of the coal of any time in pyrolysis, c is the mass fraction of catalyst loadings, Wc0 is the initial weight of the catalysts, and Wc is the weight of the catalyst at any time in the pyrolysis. A good reproducibility was obtained in all of the TG experiments to ensure the accuracy of the results. 2.3. Fixed bed Reactor and Product Analysis. The pyrolysis experiment of TSBC was performed on a horizontal fixed bed apparatus, which was similar to the system used elsewhere.24 The fixed bed with an inner diameter of 25 mm and a total length of 600 mm was heated using a silicon electric heater. In experiments, the coal sample of about 1 g was placed at the center of the reactor and then pyrolyzed at a linear heating rate of 10 °C/min within the temperature range from 50 to 900 °C, at a steady reactant gas flow of 100 mL/min (N2 or H2), and the holding time at 900 °C was 20 min. Briefly, the reactive gas flows through the reactor and carried out the volatile produced by coal pyrolysis into a cool trap and condensed at 80 °C. The char was obtained in the reactor. The tar was obtained in the cool trap after the removal of water. A gas chromatograph (GC) equipped with KB-Wax columns and a flame ionization detector was used to analyze BTX. The flow rate of gases after the cool trap was measured by a wet gas flow meter. The yield of gases (CO, CO2, and C1C3) was analyzed online by an Agilent 3000 micro GC at an interval of 2 min. The yield of tar (Ytar, wt %), gas (Ygas, wt %), and conversion (x, wt %) with a dry and ash-free (daf) basis were calculated with
2. EXPERIMENTAL SECTION 2.1. Materials. Shenmu-Fugu sub-bituminous coal (SFSBC), Tongchuan sub-bituminous coal (TSBC), Wulumuqi sub-bituminous coal (WSBC), Shaotong lignite (SL), and Huolinhe lignite (HL) were subjected in this research. The particle size was less than 150 μm. The proximate and ultimate analyses of the coals were shown in Table 1. MoS2 used in this experiment was synthesized by the sodium sulfide precipitation method.23 It was used in fine powder, which favored its mixture with coal. ZnCl2 (analytical reagent) was bought from the Tianjin Kermel Chemical Reagent Co., Ltd. MoS2 was mechanically mixed with coals. ZnCl2 was dispersed onto the coals by incipient wetness impregnation from the aqueous solution, and the impregnated or raw coal samples were dried in a vacuum oven at 80 °C for 4 h before use. 2.2. Thermogravimetric Apparatus. The thermogravimetric analysis (TGA) system (TGA/SDTA851e) was used for pyrolysis experiments. About 10 mg of coal sample was placed in a 70 mL ceramic crucible and pyrolyzed under 80 mL/min reactant gas flow from 100 to 900 °C at a heating rate of 30 °C/min. The apparatus requires that the concentration of hydrogen cannot be more than 10%; therefore, hydropyrolysis experiments performed by TG were in an atmosphere of 10% hydrogen (volume ratio, with the remaining 90% for nitrogen). Pyrolysis conversion is defined as the weight loss of coal in the process of pyrolysis. The conversion (x) without catalysts was calculated by the following equation: x¼
W0 W 100% W0 ð1 Acoal Þ
x¼
mcoal mchar 100% mcoal ð1 Mcoal Acoal Þ
Ytar ¼
mtar 100% mcoal ð1 Mcoal Acoal Þ Z
Mi Ygas ¼
∑i
ð3Þ
ð4Þ
t
VCi dt 0
mcoal ð1 Mcoal Acoal Þ 22:4
ð5Þ
where Mcoal is the content of water in coal (wt %, air-dried basis), Acoal is the content of ash in coal (wt %, air-dried basis), mchar, mtar, and mcoal are the masses of the produced pyrolysis char, tar, and coal fed into the reactor (g), respectively, t is the time that the pyrolysis lasts (s), Ci is the concentration of gas species i (vol %), V is the flow rate of the gas exit from the reactor (L/min), and Mi is the molecular weight of gas species i.
ð1Þ
The TGA of the catalyst was made under the same conditions as coal pyrolysis. The coal-based weight loss curve can be obtained after calculating and deducting the weight loss of the catalyst by the following equation: " # W0 W Wc0 Wc c ð1 þ cÞ 100% x¼ W0 ð1 Acoal Þ 1 þ c Wc0
3. RESULTS AND DISCUSION 3.1. Raw Coal Pyrolysis in Nitrogen and Hydrogen. The weight loss curves (TG) and weight loss rate curves [differential thermogravimetry (DTG)] of SFSBC, TSBC, and WSBC in the atmospheres of nitrogen and 10% hydrogen are shown in Figures 13.
ð2Þ 512
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Figure 4. Variations of the weight loss and weight loss rate of HL with atmosphere.
Figure 1. Variations of the weight loss and weight loss rate of SFSBC with atmosphere.
Figure 5. Variations of the weight loss and weight loss rate of SL with atmosphere.
Figure 2. Variations of the weight loss and weight loss rate of TSBC with atmosphere.
range of 600750 °C is attributed to the secondary devolatilization. In comparison to nitrogen, the existence of hydrogen was effective to improve pyrolysis conversion. The final weight loss of coals was increased, except SFSBC. The most prominent is WSBC coal, with a relative increase of 7%. From DTG curves, in the stage of primary devolatilization reactions, the maximal weight loss rate has been reduced with different degrees. The maximal weight loss rate in the stage of secondary devolatilization in hydrogen was higher than that in N2. According to the radical pyrolysis mechanism, the existence of hydrogen can stabilize the coal fragments produced in primary devolatilization reactions.25,26 By this way, the fractions were stable in the lowtemperature range; therefore, the maximal loss rate in the first stage of pyrolysis was decreased. The hydrogen radicals formed and attacked the chemical bond of the coal more easily at high temperatures. Therefore, the hydrocracking of condensed aromatics in the coal structure was enhanced. At the same time, hydrogen could reduce the polycondensation reactions of pyrolysis, which resulted in the increase of the maximal weight loss rate in secondary devolatilization. The TG and DTG of HL and SL are shown in Figures 4 and 5. The addition of hydrogen improved the final conversion by relatively 4.15 and 2.16%, respectively. It is found that the volatile matter released from 250 to 600 °C was more remarkable than
Figure 3. Variations of the weight loss and weight loss rate of WSBC with atmosphere.
There were two peaks in the DTG of all three coals. The first peak in the temperature range of 300600 °C is attributed to the primary devolatilization, and the second peak in the temperature 513
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Figure 6. Changes in conversion of SFSBC with different addition amounts of catalysts.
Figure 8. Changes in conversion of WSBC with different addition amounts of catalysts.
Figure 7. Changes in conversion of TSBC with different addition amounts of catalysts.
Figure 9. Changes in conversion of HL with different addition amounts of catalysts.
that of the other three coals. For SL, there was a significant pyrolysis peak around 336 °C. The low-rank coals contain more carboxylic groups, which will be removed at around 250 °C.27 With a higher temperature range (300400 °C), the coals loss more lower molecular-weight organic species, mainly aliphatic compounds, which arise from groups that are “loosely bound” to the more thermally stable part of the coal structure. 3.2. Effect of Catalysts on Hydropyrolysis. The ZnCl2 and MoS2 amounts of 0.5, 1.0, 2.0, 5.0, and 10% (wt % in the coal sample) were selected in the experiments. The relationship between the addition amount and the final conversion for each coal pyrolysis is shown in Figures 610. It is shown that there is an optimal addition amount for each coal, which is determined by final conversion. With the decrease in the coal rank, the difference between the effects of the two catalysts became small and there is almost no catalytic effect on the hydropyrolysis of SL. With an increase of the addition amount, the catalytic effect of ZnCl2 declined more remarkably than that of MoS2. An excessive addition amount of ZnCl2 will block the micropore in the coal structure when it melts during pyrolysis, which makes the mass transfer depress sharply. Thus, the recondensation reactions among radicals once produced in primary devolatilization reactions would happen in the coal internal structure, and the conversion was decreased. SL, which was the lowest rank coal among the five coals, should have high activity and release volatile matter easily at a relatively lower temperature during pyrolysis.
Figure 10. Changes in conversion of SL with different addition amounts of catalysts.
Hence, the effect of catalysts on improving the activity of SL components was not remarkable. The DTG curves of catalytic hydropyrolysis for each coal, which were obtained with the optimal catalytic amounts, are shown in Figures 1114, and the comparison between the catalytic effects of ZnCl2 and MoS2 is shown in Table 2. As shown from Figures 1114, the maximal weight loss rate in 514
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Figure 11. DTG curves of SFSBC catalytic hydropyrolysis.
Figure 14. DTG curves of HL catalytic hydropyrolysis.
Table 2. Comparison between the Catalytic Effects of ZnCl2 and MoS2 sample SFSBC TSBC WSBC DE-WSBC HL
Figure 12. DTG curves of TSBC catalytic hydropyrolysis.
SL
increase of
decrease
catalyst
conversion (%)
of Tma (°C)
0.5% MoS2
8.8
0
0.5% ZnCl2 1.0% MoS2
1 10.1
28 0
0.5% ZnCl2
2
40
2.0% MoS2
9.8
0
2.0% ZnCl2
11
47
2.0% ZnCl2
2b
20b
1.0% MoS2
7.5
0
1.0% ZnCl2
5.6
0
1.0% MoS2 1.0% ZnCl2
0 0
0 0
a Tm = peak temperature in the second stage of pyrolysis. b The results are compared to the pyrolysis of DE-WSBC without a catalyst.
easily.25,30 At the same time, hydrogen can be adsorbed and dissociated on the proper surface of MoS2, and more coal fragment radicals will be stablized by hydrogenation.31,32 Therefore, the final conversion can be increased. ZnCl2 can melt during the coal pyrolysis and penetrate into the internal coal structure. Therefore, the heat transfer is enhanced, and the chemical bond, which will be broken at a higher temperature, would be broken at a relatively lower temperature. Therefore, the peak temperature in secondary devolatilization was decreased.21 The ash content of WSBC was the highest among the four coals. The remarkable catalytic effect of ZnCl2 on WSBC may be due to the synergistic effect between the inherent minerals present in WSBC and ZnCl2. Therefore, the WSBC sample was demineralized with HCl and HF by the standard methods.19 A demineralized WSBC (DE-WSBC) and the ZnCl2 impregnated sample were hydropyrolyzed in the same conditions, and the increase of conversion compared to the DE-WSBC was shown in Table 2. The results are similar to those of Nursen et al.; therefore, the suitable internal mineral matter in WSBC can improve the catalytic effect of ZnCl2. 3.3. Kinetic Calculation. There are two different approaches for kinetic calculation: the modeling of coal pyrolysis in terms of total volatile yield (overall weight loss) or an approach based on
Figure 13. DTG curves of WSBC catalytic hydropyrolysis.
primary devolatilzation was increased for all coals with the addition of MoS2. As seen from Table 2, MoS2 was more effective on the increase of the total conversion than ZnCl2, except WSBC, while the addition of ZnCl2 reduced the peak temperature of secondary devolatilization in the hydropyrolysis of all coals, except HL, which had no remarkable peak in the DTG curve. Metal sulfide is always used as the catalyst for hydrogenation and hydrocracking of coals.28,29 The existence of MoS2 makes the chemical bonds in the coal structure break more 515
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Table 3. Kinetic Parameters of the TSBC Pyrolysis Process correlation
pyrolysis
temperature
process
range (°C)
E (kJ mol1)
k0 (s1)
coefficient
400450
119.7
1.58 106
650720 400450 650700
N2 10% H2/N2 1% MoS2 0.5% ZnCl2
Table 4. Results of TSBC Pyrolysis in a Fixed-Bed Reactor (wt %) process
tar
CO2 CO CH4 C2
C3 BTX
0.9986
raw coalN2
20.71
9.36 2.77 3.15 1.70 1.16 0.54 0.57
213.94
1.74 10
9
0.9962
117.43
1.13 106
0.9980
raw coalH2 0.5% ZnCl2H2
23.69 28.83
11.13 1.63 2.95 1.91 1.32 0.59 0.81 12.57 1.76 2.99 2.78 1.87 0.75 0.97
186.99
1.26 108
0.9888
1.0% MoS2H2
29.98
11.89 0.58 2.03 6.73 1.41 1.13 1.42
400450
116.77
9.71 10
0.9970
650700
175.92
3.28 107
108.57 153.78
71.08 10 1.58 102
400450 600650
5
explanation for the decrease of the peak temperature in the secondary devolatilization. 3.4. Pyrolysis of TSBC in a Fixed-Bed Reactor. TSBC was subjected to pyrolysis in a fixed bed to investigate the effects of atmosphere and catalysts on conversion and distribution of the products. The effects of hydrogen and catalysts on the conversion and yields of tar, gases, and BTX were shown in Table 4. The conversion in a fixed bed is a little lower than that in TG. This is because the mass and heat transfer in TG are better than those in a fixed bed. With the addition of hydrogen, the conversion was increased about 3%, which is similar to the results obtained by TG, and the tar yield was increased 1.77%. The yield of CO2 was decreased, while other gases were not affected significantly. The yield of BTX changed from 0.57 to 0.81%, which is identical to other studies.5,810,37 In hydropyrolysis of coal, there will be more hydrogen radicals. Thus, the coal fragment radicals produced in coal pyrolysis can be stabilized more easily than those in N2, which reduces the polycondensation reactions in coal pyrolysis and increases the conversion. With the presence of H2, more oxygen in the coal structure is eliminated as H2O rather than carbon oxide. Both ZnCl2 and MoS2 improved the conversion by different degrees, 8.12 and 9.27%, respectively. However, the effects on the distribution of products are different. ZnCl2 is more effective on the increase of the tar yield, while MoS2 is more effective on the increase of the BTX yield. For CH4, it is about 4 times higher than the yield of coal pyrolysis in N2 after the addition of MoS2. In comparison to the TG results, the increase of conversion was improved after the addition of ZnCl2. That may be due to the concentration of hydrogen. ZnCl2 can melt and penetrate into the coal structure to enhance the heat transfer and lead to the breaking of more internal links. With the presence of enough hydrogen, the fragments could transform into stable species by abstracting hydrogen and, at the same time, the cyclodehydrogenation reactions catalyzed by ZnCl2 could also be suppressed. Therefore, the conversion was further improved. However, the internal action would favor the formation of heavier molecular products. MoS2 is favorable to the adsorption and dissociation of hydrogen and has good catalytic activity to enhance the hydrogenation reaction. Therefore, the radicals formed in primary devolatilization reactions will be stabilized by hydrogen radicals. At the same time, the hydrogen radicals would attack the coal matrix to produce more hydrocarbon gases, such as CH4. With the presence of more contents of CH4, the reaction H• + CH3 T CH4 may be suppressed and the H radicals have to react with other radicals and form more stable materials, such as BTX.38
0.9916 2
0.9981 0.9933
the description of individual species that evolve.33 This study focuses on the approach for total volatile yield. The single reaction model was selected for the kinetics in the pyrolysis process.34,35 Assuming first-order kinetics (n = 1), then the model is shown as the following equation: dx ¼ k0 expðE=RTÞð1 xÞ dt
ð6Þ
where k0 is the pre-exponential factor (s1), E is the activation energy (kJ mol1), R is the gas constant (8.314 103 kJ mol1 K1), T is the temperature of the coal sample, t is the time, and x is the pyrolysis conversion, which can be calculated by x¼
conversion
M0 Mt M0 Mf
ð7Þ
where M0 is the initial weight of the coal sample, Mf is the final weight of the coal sample, and Mt is the weight of the coal sample at time t. During pyrolysis, the heating rate (k) is constant, k = dT/dt. After rearranging and taking the logarithm of both sides dx=dT k0 E 1 ln ¼ ln ð8Þ 1x R T k The plot of ln[(dx/dt)/(1 x)] versus 1/T gives a straight line if the process can be assumed as a first-order reaction. Activation energy (E) can be determined from the slope, and the preexponential factor (k0) can be determined from the intercept. It is found that different coals have different reaction stages. The kinetic parameters of TSBC pyrolysis were calculated, which are shown in Table 3. The pyrolysis process of TSBC was divided into two stages for kinetic calculation. The temperature range of the two linear regions is corresponding to that of the two stages of pyrolysis (i.e., 400450 °C and 650720 °C). The reaction with a high activation energy needs a high temperature or long reaction time.36 The activation energy of pyrolysis in 10% H2/N2 (117.43 and 186.99 kJ mol1) is lower than that in nitrogen (119.7 and 213.94 kJ mol1). This suggests that pyrolysis is easier to be carried out in 10% H2/N2 than in nitrogen. This is consistent with the experimental phenomenon that the peak temperature in the second stage of pyrolysis is decreased with the presence of hydrogen. The addition of catalysts makes activation energy in every stage decrease further, which shows that the catalysts are effective. Especially after the addition of 2% ZnCl2, the activation energy is decreased from 213.94 to 153.78 kJ mol1 and the second linear region is decreased to 600650 °C. This is a good
4. CONCLUSION Five Chinese coals were pyrolyzed with different conditions (atmospheres and catalysts) by TG. Hydropyrolysis of coal improved the final conversion and reduced the reaction temperature to different degrees. The addition of catalysts further 516
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improved conversion of coal hydropyrolysis, except SL. MoS2 was more effective than ZnCl2 on improving final conversion, while ZnCl2 reduced the temperature of the secondary gas-phase reaction. There was an optimal catalytic amount for each coal, which was determined by final conversion. The dynamics had also been calculated. The pyrolysis process can be described by a two-step independent first-order kinetic model. The addition of catalysts will make the activation energy of coal pyrolysis decrease and the characteristic temperature change. TSBC was subjected to pyrolysis in a fixed bed. The addition of hydrogen increased the yield of BTX. MoS2 and ZnCl2 increased final conversion in different ways. ZnCl2 is more effective in increasing the yield of BTX, while MoS2 improved the yield of gases and BTX obviously.
(21) Filomena, P.; Gulyurtlu, I.; Lobo, L. S. Fuel 1999, 78, 761–768. (22) Wu, B. Pyrolysis performances of Shendong and Pingshuo coals in different reactor. Doctoral Dissertation, Dalian University of Technology, Dalian, China, 2009; p 18. (23) Hu, X. G.; Wo, H. Z.; Hu, K. H. Mater. Mech. Eng. 2004, 28, 32–34. (24) Fan, J. J.; Zhang, Z. X.; Jin, J.; Zhang, J. M. Energy Fuels 2007, 21, 2805–2808. (25) Jin, H. H.; Zhu, Z. B. CIESC J. 1992, 43, 726–732. (26) Zhu, X. D.; Zhu, Z. B. J. Chem. Eng. Chin. Univ. 1999, 13, 223–226. (27) Watanabe, I.; Sakanishi, K.; Mochida, I. Energy Fuels 2002, 16, 18–22. (28) Wei, X. Y.; Ogata, E.; Zong, Z. M.; Niki, E. Energy Fuels 1992, 6, 868–869. (29) Ni, H. Z.; Zong, Z. M.; Zhang, L. F.; Zhou, S. L.; Xiong, Y. C.; Wang, X. H.; Wei, X. Y. Energy Fuels 2002, 16, 1154–1159. (30) Yokoyama, S.; Yamamoto, M.; Yoishida, R. Fuel 1991, 70, 163–167. (31) Wen, X. D.; Zeng, T.; Teng, B. T.; Zhang, F. Q.; Li, Y. W.; Wang, J. G.; Jiao, H. J. J. Mol. Catal. A: Chem. 2006, 191–200. (32) Wang, N.; Li, W.; Li, B. Q. J. Fuel Chem. Technol. 1999, 23, 1–4. (33) Anja, H.; Rosemary, B.; Marek, A. Proc. Combust. Inst. 2005, 30, 2177–2185. (34) Mustafa, V. K.; Esber, O.; Ozgen, K.; Cahit, H. J. Anal. Appl. Pyrolysis 1998, 45, 103–110. (35) Liu, Q. R.; Hu, H. Q.; Zhou, Q.; Zhu, S. W.; Chen, G. H. Fuel 2004, 83, 713–718. (36) Lazaro, M. J.; Moliner, R.; Suelves, I. J. Anal. Appl. Pyrolysis 1998, 47, 111–125. (37) Kuichi, M. Fuel Process. Technol. 2000, 62, 119–135. (38) Liao, H. Q.; Li, B. Q.; Zhang, B. J. Fuel 1998, 77, 847–851.
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*E-mail:
[email protected].
’ ACKNOWLEDGMENT This work was supported by the Shaanxi Important Innovative Projects in Science and Technology of China (2009ZKC04-06), the National Key Technology R&D Program of China (2009BAA20B02), the Key Science and Technology Program of Shaanxi Province of China (2010K01-082), the National Science Foundation of China (NSFC 21006078 and 2011JY006), and the Research and Development of Science and Technology of Shaanxi Province (2007K07-13). ’ REFERENCES (1) Wu, L. J.; Zhou, J.; Liu, L. Clean Coal Technol. 2002, 8, 31–34. (2) Ye, Y. L.; Li, T. W. Lutianhua Keji 2005, 3, 248–250. (3) Zhang, X. F. Study on coal gasification and pyrolysis based on decoupling conversion. Master’s Dissertation, Beijing University of Chemical Technology, Beijing, China, 2008; p 19. (4) Guo, S. C. Coal Chemical Technology; Chemical Industry Press: Beijing, China, 1992; pp 4245. (5) Xu, W. C.; Matsuoka, K.; Akiho, H.; Kumagai, M.; Tomita, A. Fuel 2003, 82, 677–685. (6) Nelson, P. F.; Tyler, R. J. Energy Fuels 1989, 3, 488–494. (7) Takayuki, T.; Yoshiyuki, O.; Kenji, T. Catal. Today 1997, 39, 127–136. (8) Chareonpanich, M.; Zhang, Z. G.; Nishijima, A. Coal Sci. Technol. 1995, 24, 1483–1486. (9) Steven, M. C.; Douglas, P. H. Fuel 1982, 61, 1149–1154. (10) He, T.; Ma, X. X.; Luo, J. C. Coal Convers. 2008, 31, 4–7. (11) Wei, X. Y.; Ni, H. Z.; Zong, Z. M.; Zhou, S. L.; Xiong, Y. C.; Wang, X. H. Energy Fuels 2003, 17, 652–657. (12) Belen, L.; Roberto, G.; Sabino, R. M. Energy Fuels 1997, 11, 411–415. (13) Song, C.; Saini, A. K.; Yoneyama, Y. Fuel 2000, 79, 249–261. (14) Snape, C. E.; Bolton, C.; Dosch, R. G.; Stephens, H. P. Energy Fuels 1989, 3, 421–425. (15) Rocha, J. D.; Brown, S. D.; Love, G. D.; Snape, C. E. J. Anal. Appl. Pyrolysis 1997, 91–103. (16) Maldonaldo-Hodar, F. J.; Rivera-Utrilla, J.; Mastral, A. M.; Teresa Izquierdo, M. Fuel 1995, 74, 1709–1715. (17) Jolly, R.; Charcosset, H.; Boudou, J. P. Fuel Process. Technol. 1988, 20, 51–60. (18) Kandiyoti, R.; Lazaridis, J. I.; Dyrvold, B. Fuel 1984, 63, 1583–1587. (19) Nursen, A. Z.; Yuda, Y. Energy Fuels 2000, 14, 820–827. (20) Zou, X. W.; Yao, J. Z.; Yang, X. M. Energy Fuels 2007, 21, 619–624. 517
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