ZSM-22分子筛催化性能及失活行为探究
|
摘要
通过水热合成法制备了ZSM-22分子筛并详细考察了其甲醇制烯烃(MTO)催化性能以及失活行为。结果表明:过低的反应温度不利于甲醇活化;升高温度可以明显提高甲醇转化率,同时也加强了烯烃循环的贡献,从而提高丙烯、丁烯的选择性,而乙烯选择性变化不大;过高的温度会导致甲醇大量裂化成甲烷。甲醇转化率与失活后催化剂的失重量存在明显的折线型关系,说明不同反应时间ZSM-22的失活机理不同。反应初期主要发生孔道内积炭,导致孔道快速堵塞,催化剂迅速失活,而随反应时间延长,积炭主要在外表面生成,催化剂失活速率减缓。
ZSM-22 zeolite was prepared by hydrothermal synthesis and its catalytic performance and deactivation behavior in methanol to olefin(MTO)were explored.The results suggest that low temperature is unfavorable to the activation of methanol,whereas the methanol conversion can be significantly increased with the increase of reaction temperature.Meanwhile,the elevation of reaction temperature can enhance the contribution of alkene cycle,leading to the improvement of the selectivity of propene and butene,while it has less influence on the formation of ethene.However,methanol largely cracks into methane at excessively high temperature.It can be found that there is an obviously fold line relationship between methanol conversion and the amount of coke,illustrating that ZSM-22 has different deactivation behavior with the time on steam.The results verify that the deactivation of ZSM-22 is mainly resulted from the pore blocking at initial period,while the coke species dominantly generate on the external surface of zeolite with the increase of reaction time.
ZSM-22 zeolite was prepared by hydrothermal synthesis and its catalytic performance and deactivation behavior in methanol to olefin(MTO)were explored.The results suggest that low temperature is unfavorable to the activation of methanol,whereas the methanol conversion can be significantly increased with the increase of reaction temperature.Meanwhile,the elevation of reaction temperature can enhance the contribution of alkene cycle,leading to the improvement of the selectivity of propene and butene,while it has less influence on the formation of ethene.However,methanol largely cracks into methane at excessively high temperature.It can be found that there is an obviously fold line relationship between methanol conversion and the amount of coke,illustrating that ZSM-22 has different deactivation behavior with the time on steam.The results verify that the deactivation of ZSM-22 is mainly resulted from the pore blocking at initial period,while the coke species dominantly generate on the external surface of zeolite with the increase of reaction time.
引文
[1]李立新,倪进方,李延生.甲醇制烯烃分离技术进展及评述[J].化工进展,2008,27(9):1332-1335.LI Lixin,NI Jinfang,LI Yansheng.Progress of separation technologies for methanol to olefins[J].Chemical Industry and Engineering Progress,2008,27(9):1332-1335.
[2]OLSBYE U,SVELLE S,BJRGEN M,et al.Conversion of methanol to hydrocarbons:how zeolite cavity and pore size controls product selectivity[J].Angew Chem Int Ed Engl,2012,51(24):5810-5831.
[3]ILIAS S,BHAN A.Mechanism of the catalytic conversion of methanol to hydrocarbons[J].ACS Catalysis,2013,3(1):18-31.
[4]ILIAS S,KHARE R,MALEK A,et al.A descriptor for the relative propagation of the aromatic-and olefin-based cycles in methanol-to-hydrocarbons conversion on H-ZSM-5[J].Journal of Catalysis,2013,303:135-140.
[5]SONG W G,HAW J F,NICHOLAS J B,et al.Methylbenzenes are the organic reaction centers for methanol-to-olefin catalysis on HSAPO-34[J].Journal of the American Chemical Society,2000,122(43):10726-10727.
[6]ARSTAD B,KOLBOE S.The reactivity of molecules trapped within the SAPO-34cavities in the methanol-to-hydrocarbon reaction[J].Journal of the American Chemical Society,2001,123(33):8137-8138.
[7]耿蕊,董梅,王浩,等.十元环分子筛在甲醇芳构化反应中催化性能的研究[J].燃料化学学报,2014,42(9):1119-1127.GENG Rui,DONG Mei,WANG Hao.An investigation on the catalytic performance of 10mr zeolites in methanol aromatization reaction[J].Journal of Fuel Chemistry and Technology,2014,42(9):1119-1127.
[8]CUI Z M,LIU Q,SONG W G,et al.Insights into the mechanism of methanol to olefin conversion at zeolites with systematically selected framework structures[J].Angew Chem Int Ed Engl,2006,45(39):6512-6515.
[9]WANG Q,CUI Z M,CAO C Y,et al.0.3A°makes the difference:dramatic changes in methanol-to-olefin activities between H-ZSM-12and H-ZSM-22zeolites[J].The Journal of Physical Chemistry C,2011,115(50):24987-24992.
[10]TEKETEL S,SVELLE S,LILLERUD K P,et al.Shape-selective conversion of methanol to hydrocarbons over 10-ring unidirectional-channel acidic H-ZSM-22[J].Chem Cat Chem,2009,1(1):78-81.
[11]LI J Z,WEI Y X,QI Y,et al.Conversion of methanol over H-ZSM-22:The reaction mechanism and deactivation[J].Catalysis Today,2011,164(1):288-292.
[12]VERBOEKEND D,CHABANEIX A M,THOMAS K,et al.Mesoporous ZSM-22zeolite obtained by desilication:peculiarities associated with crystal morphology and aluminium distribution[J].Cryst Eng Comm,2011,13(10):3408-3416.
[13]CUI ZM,LIU Q,MA Z,et al.Direct observation of olefin homologations on zeolite ZSM-22and its implications to methanol to olefin conversion[J].Journal of Catalysis,2008,258(1):83-86.
[14]TEKETEL S,SKISTAD W,BENARD S,et al.Shape selectivity in the conversion of methanol to hydrocarbons:the catalytic performance of one dimensional 10-ring zeolites:ZSM-22,ZSM-23,ZSM-48,and EU-1[J].ACS Catalysis,2012,2(1):26-37.
[15]KUMAR N,LINDFORS L E,BYGGNINGSBACKA R.Synthesis and characterization of H-ZSM-22,Zn-H-ZSM-22and GaH-ZSM-22zeolite catalysts and their catalytic activity in the aromatization of n-butane[J].Applied Catalysis A:General,1996,139(1):189-199.
[16]FAN W B,LI R F,FAN B B,et al.Effects of introduction of different alkali metal halides on crystallization and characteristics of ZSM-48in a solid reaction mixture system-Effects of alkali metal chlorides[J].Applied Catalysis A:General,1996,143(2):299-308.
[17]BAERLOCHER C,MCCUSKER L B.Practical aspects of powder diffraction data analysis[J].Advanced Zeolite Science and Applications,1994:391-428.
[2]OLSBYE U,SVELLE S,BJRGEN M,et al.Conversion of methanol to hydrocarbons:how zeolite cavity and pore size controls product selectivity[J].Angew Chem Int Ed Engl,2012,51(24):5810-5831.
[3]ILIAS S,BHAN A.Mechanism of the catalytic conversion of methanol to hydrocarbons[J].ACS Catalysis,2013,3(1):18-31.
[4]ILIAS S,KHARE R,MALEK A,et al.A descriptor for the relative propagation of the aromatic-and olefin-based cycles in methanol-to-hydrocarbons conversion on H-ZSM-5[J].Journal of Catalysis,2013,303:135-140.
[5]SONG W G,HAW J F,NICHOLAS J B,et al.Methylbenzenes are the organic reaction centers for methanol-to-olefin catalysis on HSAPO-34[J].Journal of the American Chemical Society,2000,122(43):10726-10727.
[6]ARSTAD B,KOLBOE S.The reactivity of molecules trapped within the SAPO-34cavities in the methanol-to-hydrocarbon reaction[J].Journal of the American Chemical Society,2001,123(33):8137-8138.
[7]耿蕊,董梅,王浩,等.十元环分子筛在甲醇芳构化反应中催化性能的研究[J].燃料化学学报,2014,42(9):1119-1127.GENG Rui,DONG Mei,WANG Hao.An investigation on the catalytic performance of 10mr zeolites in methanol aromatization reaction[J].Journal of Fuel Chemistry and Technology,2014,42(9):1119-1127.
[8]CUI Z M,LIU Q,SONG W G,et al.Insights into the mechanism of methanol to olefin conversion at zeolites with systematically selected framework structures[J].Angew Chem Int Ed Engl,2006,45(39):6512-6515.
[9]WANG Q,CUI Z M,CAO C Y,et al.0.3A°makes the difference:dramatic changes in methanol-to-olefin activities between H-ZSM-12and H-ZSM-22zeolites[J].The Journal of Physical Chemistry C,2011,115(50):24987-24992.
[10]TEKETEL S,SVELLE S,LILLERUD K P,et al.Shape-selective conversion of methanol to hydrocarbons over 10-ring unidirectional-channel acidic H-ZSM-22[J].Chem Cat Chem,2009,1(1):78-81.
[11]LI J Z,WEI Y X,QI Y,et al.Conversion of methanol over H-ZSM-22:The reaction mechanism and deactivation[J].Catalysis Today,2011,164(1):288-292.
[12]VERBOEKEND D,CHABANEIX A M,THOMAS K,et al.Mesoporous ZSM-22zeolite obtained by desilication:peculiarities associated with crystal morphology and aluminium distribution[J].Cryst Eng Comm,2011,13(10):3408-3416.
[13]CUI ZM,LIU Q,MA Z,et al.Direct observation of olefin homologations on zeolite ZSM-22and its implications to methanol to olefin conversion[J].Journal of Catalysis,2008,258(1):83-86.
[14]TEKETEL S,SKISTAD W,BENARD S,et al.Shape selectivity in the conversion of methanol to hydrocarbons:the catalytic performance of one dimensional 10-ring zeolites:ZSM-22,ZSM-23,ZSM-48,and EU-1[J].ACS Catalysis,2012,2(1):26-37.
[15]KUMAR N,LINDFORS L E,BYGGNINGSBACKA R.Synthesis and characterization of H-ZSM-22,Zn-H-ZSM-22and GaH-ZSM-22zeolite catalysts and their catalytic activity in the aromatization of n-butane[J].Applied Catalysis A:General,1996,139(1):189-199.
[16]FAN W B,LI R F,FAN B B,et al.Effects of introduction of different alkali metal halides on crystallization and characteristics of ZSM-48in a solid reaction mixture system-Effects of alkali metal chlorides[J].Applied Catalysis A:General,1996,143(2):299-308.
[17]BAERLOCHER C,MCCUSKER L B.Practical aspects of powder diffraction data analysis[J].Advanced Zeolite Science and Applications,1994:391-428.