咪唑改性MCM-22分子筛的制备及甲烷无氧芳构化性能
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摘要
以硅溶胶为硅源,环己亚胺为模板剂,在动态条件下利用水热合成法合成了MCM-22分子筛,并在该体系下以咪唑为添加剂合成了咪唑改性MCM-22-I分子筛,考察了咪唑对MCM-22-I分子筛合成的影响,利用FTIR、XRD、SEM、ICP、BET、NH_3-TPD、H_2-TPR和TG/DTG等手段分别对咪唑改性前后分子筛的物化性质进行了表征。结果表明,咪唑改性能够增大MCM-22的比表面积、孔容和酸性,同时可有效降低模板剂HMI的用量。采用等体积浸渍法制备了6Mo/MCM-22和6Mo/MCM-22-I双功能催化剂,在连续流动固定床反应器上,反应温度700℃、反应压力1.01×105Pa(1atm)、空速1500mL/(g-cat·h)的反应条件下,考察了催化剂催化甲烷无氧芳构化合成苯的催化剂性能。结果表明,与6Mo/MCM-22催化剂相比,咪唑改性的6Mo/MCM-22-I催化剂具有更高的择形性能和催化活性,甲烷的平均转化率提高了24.1%,苯的平均生成速率和选择性分别提高了24.3%和10.0%。
Imidazole modified MCM-22 molecular sieves(MCM-22-I) were synthesized by hydrothermal synthesis method under dynamic conditions using imidazole as additives. The effect of imidazole on the synthesis of MCM-22 zeolites was investigated. The physicochemical properties of the molecular sieve samples were characterized by FTIR,XRD,SEM,ICP,BET,NH_3-TPD,H_2-TPR,and TG/DTG. The results showed that MCM-22-I displayed large specific surface area, abundant pore structure and enhanced acidity and the modification by imidazole can reduce the amount of the template agent HMI used. The6 Mo/MCM-22-I and 6 Mo/MCM-22 catalysts were prepared by incipient-wetness impregnation method.The catalytic performance evaluation of the catalysts for methane dehydroaromatization were carried out in a fixed bed reactor under the reaction conditions of 700℃, P = 1 atm and space velocity of 1500 mL/(g-cat·h). The results showed that methane conversion increased by 24.1%, the formation rate and the selectivity of benzene by using imidazole modified 6 Mo/MCM-22-I catalyst increased by 24.3% and 10%,respectively, compared with conventional 6 Mo/MCM-22 catalyst.
Imidazole modified MCM-22 molecular sieves(MCM-22-I) were synthesized by hydrothermal synthesis method under dynamic conditions using imidazole as additives. The effect of imidazole on the synthesis of MCM-22 zeolites was investigated. The physicochemical properties of the molecular sieve samples were characterized by FTIR,XRD,SEM,ICP,BET,NH_3-TPD,H_2-TPR,and TG/DTG. The results showed that MCM-22-I displayed large specific surface area, abundant pore structure and enhanced acidity and the modification by imidazole can reduce the amount of the template agent HMI used. The6 Mo/MCM-22-I and 6 Mo/MCM-22 catalysts were prepared by incipient-wetness impregnation method.The catalytic performance evaluation of the catalysts for methane dehydroaromatization were carried out in a fixed bed reactor under the reaction conditions of 700℃, P = 1 atm and space velocity of 1500 mL/(g-cat·h). The results showed that methane conversion increased by 24.1%, the formation rate and the selectivity of benzene by using imidazole modified 6 Mo/MCM-22-I catalyst increased by 24.3% and 10%,respectively, compared with conventional 6 Mo/MCM-22 catalyst.
引文
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[26]RAVISHANKAR R,BHATTACHARYA D,JACOB N E,et al.Characterization and catalytic properties of zeolite MCM-22[J].Microporous Materials,1995(4):83-93.
[27]ZHANG H Y,SHAO S S,XIAO R,et al.Characterization of coke deposition in the catalytic fast pyrolysis of biomass derivates[J].Energy&Fuels,2014,28(1):52-57.
[28]LIU H M,SU L L,WANG H X,et al.The chemical nature of carbonaceous deposits and their role in methane dehydroaromatization on Mo/MCM-22 catalysts[J].Applied Catalysis A:General,2002,236(1/2):263-280.
[29]MA D,WANG D Z,SU L L,et al.Carbonaceous deposition on Mo/HMCM-22 catalysts for methane aromatization:a TP technique investigation[J].Journal of Catalysis,2002,208(2):260-269.
[2]能源供需趋势[J].中外能源,2017,3(22):101-102.Energy supply and demand trends[J].Sino-Global Energy,2017,3(22):101-102.
[3]WANG L S,TAO L X,XIE M S,et al.Dehydrogenation and aromatization of methane under non-oxidizing conditions[J].Catalysis Letters,1993(21):35-41.
[4]CHENG X,YAN P,ZHANG X Z,et al.Enhanced methane dehydroaromatization in the presence of CO2over Fe-and Mgmodified Mo/ZSM-5[J].Molecular Catalysis,2017(437):114-120.
[5]胥月兵,陆江银,王吉德,等.Mo基分子筛催化剂及甲烷无氧芳构化[J].化学进展,2011,23(1):90-106.XU Y B,LU J Y,WANG J D,et al.Mo based zeolite catalysts and oxygen free methane aromatization[J].Progress in Chemistry,2011,23(1):90-106.
[6]MA S Q,GUO X G,ZHAO L X,et al.Recent progress in methane dehydroaromatization:from laboratory curiosities to promising technology[J].Journal of Energy Chemistry,2013,22(1):1-20.
[7]MARIA B,DANIELA M,FRANCE S,et al.A study of the nature,strength,and accessibility of acid sites of H-MCM-22 zeolite[J].Journal of Physical Chemistry C,2008,112(24):9023-9033.
[8]CHU N B,WANG J Q,ZHANG Y,et al.Nestlike hollow hierarchical MCM-22 microspheres:synthesis and exceptional catalytic properties[J].Chemistry of Materials,2010,22(9):2757-2763.
[9]YIN X Y,CHU N B,YANG J H,et al.Synthesis of the nanosized MCM-22 zeolite and its catalytic performance in methane dehydroaromatization reaction[J].Catalysis Communication,2014,43:218-222.
[10]SHU Y Y,OHNISHI R,ICHIKAWA M,et al.Stable and selective dehydrocondensation of methane towards benzene on modified Mo/HMCM-22 catalyst by the dealumination treatment[J].Catalysis Letters,2002,81(1/2):9-17.
[11]HU J,WU S,LI Z F,et al.Nano-MoO3-modified MCM-22 for methane dehydroaromatization[J].Applied Organometallic Chemistry,2015,29(9):638-645.
[12]TIAN H F,ZHANG Z Z,CHANG H,et al.Catalytic performance of imidazole modified HZSM-5 for methanol to aromatics reaction[J].Journal of Energy Chemistry,2017,26(3):574-583.
[13]ZHANG G Q,BAI T,CHEN T F,et al.Conversion of methanol to light aromatics on Zn-modified nano-HZSM-5 zeolite catalysts[J].Industrial&Engineering Chemistry Research,2014,53(39):14932-14940.
[14]STEPHEN L L,ANTHONY S F,GORDON J K,et al.Zeolite MCM-49:a three-dimensional MCM-22 analogue synthesized by in situ crystallization[J].Journal of Physical Chemistry,1996,100(9):3788-3798.
[15]WIESLAW J R,JIRI C.Two dimensional zeolites:dream or reality?[J].Catalysis Science&Technology,2011(1):43-53.
[16]CORMA A,CORELL C,FORNES V,et al.Infrared spectroscopy,thermoprogrammed desorption,and nuclear magnetic resonance study of the acidity,structure,and stability of zeolite MCM-22[J].Zeolites,1995,15(7):576-582.
[17]CORMA A,CORELL C,PARIENTE J P.Synthesis and characterization of the MCM-22 zeolite[J].Zeolites,1995,15(1):2-8.
[18]SCHEINER S,YI M Y.Proton transfer properties of imidazole[J].Journal of Physical Chemistry,1996,100:9235-9241.
[19]RICHARD W B,YOUNG H K,ANNE H,et al.Structure and density of Mo and acid sites in Mo-exchanged H-ZSM5 catalysts for nonoxidative methane conversion[J].Journal of Physical Chemistry B,1999,103(28):5787-5796.
[20]杨平,辛靖,李明丰,等.负载Mo、W氧化物对Y型分子筛结构及酸性的影响[J].石油学报,2011,27(5):668-673.YANG P,XIN J,LI M F,et al.Effects of molybdenum/tungsten oxides loading on the structure and acidity of the zeolites[J].Acta Petrolei Sinica,2011,27(5):668-673.
[21]SHEILA G F,FATIMA M Z,LUCIA R R,et al.Influence of support acidity of NiMoS catalysts in the activity for hydrogenation and hydrocracking of tetralin[J].Applied Catalysis A:General,2010,384(1/2):51-57.
[22]ARRIBAS M A,MARTINEZ A.The influence of zeolite acidity for the coupled hydrogenation and ring opening of 1-methylnaphthalene on Pt_USY catalysts[J].Applied Catalysis A:General,2002,230(1/2):203-217.
[23]ARNOLDY P,JONGE J C M D,MOULIJN J A.Temperatureprogrammed reduction of MoO3and MoO2[J].Journal of Physical Chemistry,1985,89(21):4517-4526.
[24]MA D,SHU Y Y,BAO X H,et al.Methane dehydroaromatization under nonoxidative conditions over Mo/HZSM-5 catalysts:EPR study of the Mo species on/in the HZSM-5 zeolite[J].Journal of Catalysis,2000,189(2):314-325.
[25]刘红梅,徐奕德.甲烷无氧芳构化反应催化剂Mo/HZSM-5的H2-TPR研究[J].催化学报,2006,27(4):319-323.LIU H M,XU Y D.H2-TPR study on Mo/HZSM-5 catalyst for CH4dehydroaromatization[J].Chinese Journal of Catalysis,2006,27(4):319-323.
[26]RAVISHANKAR R,BHATTACHARYA D,JACOB N E,et al.Characterization and catalytic properties of zeolite MCM-22[J].Microporous Materials,1995(4):83-93.
[27]ZHANG H Y,SHAO S S,XIAO R,et al.Characterization of coke deposition in the catalytic fast pyrolysis of biomass derivates[J].Energy&Fuels,2014,28(1):52-57.
[28]LIU H M,SU L L,WANG H X,et al.The chemical nature of carbonaceous deposits and their role in methane dehydroaromatization on Mo/MCM-22 catalysts[J].Applied Catalysis A:General,2002,236(1/2):263-280.
[29]MA D,WANG D Z,SU L L,et al.Carbonaceous deposition on Mo/HMCM-22 catalysts for methane aromatization:a TP technique investigation[J].Journal of Catalysis,2002,208(2):260-269.