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摘要: 采用石英管固定床反应器, 考察了1123K, CH4/N2=1:4的状态下, 煤焦表面官能团对甲烷裂解的影响。煤焦表面主要含有羟基、羰基和醚键等官能团, 分别通过氢氧化钡、苯肼和碘化氢溶液对煤焦表面进行化学处理, 除去煤焦表面相应的官能团, 研究处理后煤焦的催化活性, 得出煤焦中官能团对甲烷裂解的影响。氢氧化钡处理煤焦后, 煤焦中部分羟基被氢氧化钡消耗, 甲烷初始转化率和氢气初始收率分别为90.5%和65.2%, 说明煤焦中的羟基不利于甲烷的裂解。通过苯肼处理煤焦中羰基并使之转化, 甲烷初始转化率和氢气初始收率分别为55.4%和42.9%, 说明煤焦中的羰基对甲烷裂解有利。碘化氢处理煤焦后, 煤焦中的醚键转化成羟基, 甲烷的转化率和氢气收率都明显下降, 说明醚键的存在对甲烷裂解同样有利。随着反应时间的延长, 甲烷的转化率和氢气的收率降低, 催化剂逐渐失活。反应前后煤焦电镜扫描照片表明, 甲烷裂解生成的积炭沉积在煤焦表面, 堵塞煤焦的孔道, 煤焦的比表面积减小, 催化活性降低。Abstract: Methane cracking was studied over a set of Xiaolongtan lignite chars in a fixed bed reactor at 1123K and atmospheric pressure with a mixture of CH4/N2 (1:4). The chars were obtained by pyrolysis of raw Xiaolongtan coal in nitrogen at 1173K for 30min in a fixed bed reactor. The main functional groups in coal char were hydroxyl group, carbonyl group and ether bond and so on, which can be protected by dipping the char into solutions of barium hydroxide, phenyl hydrazine and hydrogen iodide, respectively. The catalytic activity of coal chars treated by barium hydroxide was lower than the raw chars, while that of the chars treated by phenyl hydrazine or hydrogen iodide were higher. Hydroxy in the coal char was expended by Ba (OH)2. The initial methane conversion was achieved at about 90.5% for the Ba (OH)2 -treated char with equivalent-volume impregnation. The corresponding hydrogen yield was at about 65.2%. The carbonyl group of the coal char was reduced by phenyl hydrazine, with the methane conversion and hydrogen yield about 55.4% and 42.9%, respectively. The methane conversion and hydrogen yield decreased, while the ether bond turned into hydroxy. It was speculated that hydroxyl group in coal char restrain the methane cracking, while carbonyl group and ether bond accelerate it. The methane conversion and hydrogen yield on the different coal chars decreased with increasing reaction duration. The char became deactivated at 123min following its exposure to methane. The main reason was that the carbon from methane cracking was deposited on the char, which is supported by scanning electron microscopy analysis.
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Key words:
- lignite char /
- hydrogen /
- methane cracking /
- function group /
- catalysis
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图 1 实验装置示意图
Figure 1 Schematic diagram of the experimental system
①: gas; ②: pressure relief valve; ③: mass flow controllers; ④: mixing chamber; ⑤: temperature controller; ⑥: quartz tube reactor; ⑦: electrically heated furnace
图 2 1123K甲烷在不同煤焦上裂解的氢平衡
Figure 2 Hydrogen balance over different coal chars
◇: Xiaolongtan liginite char; ○: char washed by barium hydroxide of equivatent-volume impregnation; ●: char washed by barium hydroxide of exceeding volume dipping; □: char washed by phenyl hydrazine of equivatent-volume impregnation; ■: char washed by phenyl hydrazine of exceeding volume dipping; △: char washed by hydrogen iodide of equivatent-volume impregnation; ▲: char washed by hydrogen iodide of exceeding volume dipping
图 3 小龙潭煤焦以及处理煤焦的红外光谱谱图
Figure 3 Infrared spectra of Xiaolongtan coal char and the treated chars
a: Xiaolongtan liginite char; b: char washed by barium hydroxide; c: char washed by phenyl hydrazine; d: char washed by hydrogen iodide
图 4 甲烷在氢氧化钡处理煤焦上裂解的转化率和氢气收率
Figure 4 Methane conversions and hydrogen yields over different chars
(a): conversions of methane cracking; (b): hydrogen yields of methane cracking ◇: Xiaolongtan liginite char; ○: char washed by barium hydroxide of equivatent-volume impregnation; ●: char washed by barium hydroxide of exceeding volume dipping
图 5 甲烷在苯肼处理煤焦上裂解的转化率和氢气收率
Figure 5 Methane conversions and hydrogen yields over different chars
(a): conversions of methane cracking; (b): hydrogen yields of methane cracking ◇: Xiaolongtan liginite char; □: char washed by phenyl hydrazine of equivatent-volume impregnation; ■: char washed by phenyl hydrazine of exceeding volume dipping
图 6 甲烷在碘化氢处理煤焦上裂解的转化率和氢气收率
Figure 6 Methane conversions and hydrogen yields over different chars
(a): conversions of methane cracking; (b): hydrogen yields of methane cracking ◇: Xiaolongtan liginite char; △: char washed by hydrogen iodide of equivatent-volume impregnation; ▲: char washed by hydrogen iodide of exceeding volume dipping
图 7 不同煤焦反应前后的SEM照片
Figure 7 SEM images of chars washed by different solution before (a, b, c, d) and after (a', b', c', d') being subjected to methane cracking
(a and a': Xiaolongtan coal char, b and b': coal char washed by Ba (OH)2, c and c': coal char washed by phenyl hydrazine, d and d': coal char washed by HI)
表 1 原煤和煤焦的工业分析和元素分析
Table 1 Proximate and ultimate analyses of the parent coal and its char
Sample Proximate analysis wad/% > Ultimate analysis wad/% M A V S C H O N Coal 24.8 16.3 38.8 1.3 39.7 1.8 15.2 1.0 Char 0.7 23.5 3.0 2.0 68.6 1.4 3.1 0.8 
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[1] 许珊, 王晓来, 赵睿.甲烷催化制氢气的研究进展[J].化学进展, 2003, 15(2):141-150. http://www.cnki.com.cn/Article/CJFDTOTAL-NYYJ200502005.htmXU Shan, WANG Xiao-lai, ZHAO Rui. Study on the production of hydrogen from methane[J]. Prog Chem, 2003, 15(2):141-150.) http://www.cnki.com.cn/Article/CJFDTOTAL-NYYJ200502005.htm [2] 白宗庆, 陈皓侃, 李文, 李保庆.甲烷在活性炭上裂解制氢研究[J].燃料化学学报, 2006, 34(1):66-70. http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract16950.shtmlBAI Zong-qing, CHEN Hao-kan, LI Wen, LI Bao-qing. Hydrogen production from methane pyrolytic decomposition over activated carbons[J]. J Fuel Chem Technol, 2006, 34(1):66-70.) http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract16950.shtml [3] 白宗庆, 陈皓侃, 李文, 李保庆.流化床中甲烷在活性炭上裂解制氢研究[J].天然气化工, 2006, 31(1):1-4. http://www.cnki.com.cn/Article/CJFDTOTAL-TRQH200601000.htmBAI Zong-qing, CHEN Hao-kan, LI Wen, LI Bao-qing. Hydrogen production by methane decomposition over activated carbon in a fluidized-bed reactor[J]. Nat Gas Chem Ind, 2006, 31(1):1-4.) http://www.cnki.com.cn/Article/CJFDTOTAL-TRQH200601000.htm [4] STEINBERG M. The Hy-C process (thermal decomposition of natural gas) potentially the lowest cost source of hydrogen with the least CO2 emission[J]. Energy Convers Manage, 1995, 36(6/9):791-796. https://www.researchgate.net/publication/222758081_The_Hy-C_process_thermal_decomposition_of_natural_gas_potentially_the_lowest_cost_source_of_hydrogen_with_the_least_CO2_emission [5] POIRIER M G, SAPUNDZHIEV C. Catalytic decomposition of natural gas to hydrogen for fuel cell applications[J]. Int J Hydrogen Energy, 1997, 22(4):429-433. doi: 10.1016/S0360-3199(96)00101-2 [6] CHOUDHARY T V, SIVADINARAYANA C, CHUSUEI C C, KLINGHOFFER A, GOODMAN D W. Hydrogen production via catalytic decomposition of methane[J]. J Catal, 2001, 199(1):9-18. doi: 10.1006/jcat.2000.3142 [7] 潘智勇, 沈师孔. Ni/SiO2催化剂上甲烷催化裂解制氢[J].燃料化学学报, 2003, 31(5):466-470. http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract16847.shtmlPAN Zhi-yong, SHEN Shi-kong. Hydrogen production via direct cracking of methane over Ni/SiO2 catalysts[J]. J Fuel Chem Technol, 2003, 31(5):466-470.) http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract16847.shtml [8] SERBAN M, LEWIS M A, MARSHALL C L, DOCTOR R D. Hydrogen production by direct contact pyrolysis of natural gas[J]. Energy Fuels, 2003, 17(3):705-713. doi: 10.1021/ef020271q [9] CHEN J L, LI Y D, LI Z Q, ZHANG X X. Production of COx-free hydrogen and nanocarbon by direct decomposition of undiluted methane on Ni-Cu-alumina catalysts[J]. App Catal A:Gen, 2004, 269(1/2):179-186. https://www.researchgate.net/publication/272409643_Direct_decomposition_of_methane_over_SBA-15_supported_Ni_Co_and_Fe_based_bimetallic_catalysts [10] 白宗庆, 陈皓侃, 李文, 李保庆.热重-质谱联用研究焦炭在甲烷气氛下的热行为[J].燃料化学学报, 2005, 33(4):426-430. http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract16589.shtmlBAI Zong-qing, CHEN Hao-kan, LI Wen, LI Bao-qing. Study on the thermal performance of metallurgical coke under methane by TG-MS[J]. J Fuel Chem Technol, 2005, 33(4):426-430.) http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract16589.shtml [11] MURADOV N. CO2-free production of hydrogen by catalytic pyrolysis of hydrocarbon fuel[J]. Energy Fuels, 1998, 12(1):41-48. doi: 10.1021/ef9701145 [12] MURADOV N. Hydrocarbon-based systems for CO2-free production of hydrogen//Proceeding of 13th World Hydrogen Energy Conference. Beijing, 2000:428-433. [13] MURADOV N. Catalysis of methane decomposition over elemental carbon[J]. Catal Commun, 2001, 2(3/4):89-94. https://www.researchgate.net/publication/222971069_Catalysis_of_methane_decomposition_over_elemental_carbon [14] MURADOV N. Hydrogen via methane decomposition:An application for decarbonization of fossil fuels[J]. Int J Hydrogen Energy, 2001, 26(11):1165-1175. doi: 10.1016/S0360-3199(01)00073-8 [15] MURADOV N, VEZIROGLU T N. From hydrogen to hydrogen-carbon to hydrogen economy[J]. Int J Hydrogen Energy, 2005, 30(3):225-237. doi: 10.1016/j.ijhydene.2004.03.033 [16] BAI Z Q, CHEN H K, LI W, LI B Q. Hydrogen production by methane decomposition over coal char[J]. Int J Hydrogen Energy, 2006, 31(7):899-905. doi: 10.1016/j.ijhydene.2005.08.001 [17] SUN Z Q, WU J H, HAGHIGHI M, BROMLY J, NG E, WEE H L, WANG Y, ZHANG D K. Methane cracking over a bituminous coal char[J]. Energy Fuels, 2007, 21(3):1601-1605. doi: 10.1021/ef060616v [18] ZHANG Y, WU J H, ZHANG D K. Cracking of simulated oil refinery off-gas over a coal char, petroleum coke, and quartz[J]. Energy Fuels, 2008, 22(2):1142-1147. doi: 10.1021/ef700680d [19] 徐泽夕, 吴晋沪, 王洋, 张东柯.甲烷在褐煤煤焦上的裂解反应研究[J].燃料化学学报, 2009, 37(3):277-281. http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract17443.shtmlXU Ze-xi, WU Jin-hu, WANG Yang, ZHANG Dong-ke. Methane craking over lignite char[J]. J Fuel Chem Technol, 2009, 37(3):277-281.) http://rlhxxb.sxicc.ac.cn/CN/abstract/abstract17443.shtml [20] WEI L, TAN Y S, HAN Y Z, ZHAO J T, WU J H, ZHANG D K. Hydrogen production by methane cracking over different coal chars[J]. Fuel, 2011, 90(11):3473-3479. doi: 10.1016/j.fuel.2011.06.053 [21] 魏玲, 谭猗生, 韩怡卓, 赵建涛.煤焦中灰成分对甲烷裂解的影响[J].化工学报, 2015, 66(9):3733-3738. http://www.cnki.com.cn/Article/CJFDTOTAL-HGSZ201509062.htmWEI Ling, TAN Yi-sheng, HAN Yi-zhuo, ZHAO Jian-tao. Influence of coal char on methane cracking[J]. CIESC J, 2015, 66(9):3733-3738.) http://www.cnki.com.cn/Article/CJFDTOTAL-HGSZ201509062.htm [22] 朱之培, 高晋生.煤化学[M].上海:上海科学技术出版社, 1984, 122-129.ZHU Zhi-pei, GAO Jin-sheng. Coal Chemistry[M]. Shanghai:Shanghai Scientific & Technical Publishers, 1984, 122-129.) [23] 李庆钊, 林柏泉, 赵长遂, 武卫芳.基于傅里叶红外光谱的高温煤焦表面化学结构特性分析[J].中国电机工程学报, 2011, 31(32):46-52. http://www.cnki.com.cn/Article/CJFDTOTAL-ZGDC201132007.htmLI Qing-zhao, LIN Bai-quan, ZHAO Chang-sui, WU Wei-fang. Chemical structure analysis of coal char surface based on Fourier-Transform infrared spectrometer[J]. Proc CSEE, 2011, 31(32):46-52.) http://www.cnki.com.cn/Article/CJFDTOTAL-ZGDC201132007.htm [24] FIGUEIREDO J L, PEREIRA M F R, FREITAS M M A, ORFAO J J M. Modification of the surface chemistry of activated carbons[J]. Carbon, 1999, 37:1379-1389. doi: 10.1016/S0008-6223(98)00333-9 [25] 孟华平.煤焦表面含氧官能团对甲烷分解反应的催化作用.太原:太原理工大学, 2008.MENG Hua-ping. The catalytic effect of oxygen-containing group in coal char surface on methane decomposition reaction. Taiyuan:Taiyuan University of Technology, 2008.) [26] 单晓梅, 朱书全, 张文辉, 李书荣, 李淑琴.氧化法改性煤基活性炭和椰壳活性炭的研究[J].中国矿业大学学报, 2003, 32(6):729-733. http://www.cnki.com.cn/Article/CJFDTOTAL-ZGKD200306032.htmSHAN Xiao-mei, ZHU Shu-quan, ZHANG Wen-hui, LI Shu-rong, LI Shu-qin. Modification surface properties of coal based and coconut shell activated carbons by oxidation[J]. J China Univ Min Technol, 2003, 32(6):729-733.) http://www.cnki.com.cn/Article/CJFDTOTAL-ZGKD200306032.htm -
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