混合模板剂合成高硅铝比纳米HZSM-5分子筛及其MTP反应性能
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摘要
以四丙基氢氧化铵与乙二胺作为混合模板剂,采用水热合成法制备高硅铝比纳米HZSM-5分子筛,对分子筛进行了XRD、FE-SEM、N_2低温吸附、NH_3-TPD等表征,考察了分子筛在MTP反应中的催化性能。结果表明,适量引入乙二胺作为模板剂可以调节分子筛晶粒尺寸、酸强度及酸量。当四丙基氢氧化铵与乙二胺等摩尔混合时,粒径为180nm,酸强度减弱,酸量减少,此时分子筛表现出最优催化性能,丙烯选择性达到45.72%。
Tetrapropylammonium hydroxide(TPAOH) and ethylenediamine(EDA) were mixed as template to hydrothermally synthesize nano-sized HZSM-5 zeolites with high SiO_2/Al_2O_3 molar ratios. The samples were characterized by XRD, FE-SEM, N_2 adsorption, and NH_3-TPD. The catalytic performance of the nano-sized HZSM-5 zeolites in MTP reaction was evaluated in a fixed-bed reactor. The results showed that the zeolite sample grain size and acid strength and amount can be adjusted by the introduction of EDA. Mixing TPAOH and EDA equimolarly, the prepared zeolite had a grain size of 180 nm with decreasing acid strength and amount, and exhibited the optimal catalytic performance with the highest propylene selectivity of 45.72%.
Tetrapropylammonium hydroxide(TPAOH) and ethylenediamine(EDA) were mixed as template to hydrothermally synthesize nano-sized HZSM-5 zeolites with high SiO_2/Al_2O_3 molar ratios. The samples were characterized by XRD, FE-SEM, N_2 adsorption, and NH_3-TPD. The catalytic performance of the nano-sized HZSM-5 zeolites in MTP reaction was evaluated in a fixed-bed reactor. The results showed that the zeolite sample grain size and acid strength and amount can be adjusted by the introduction of EDA. Mixing TPAOH and EDA equimolarly, the prepared zeolite had a grain size of 180 nm with decreasing acid strength and amount, and exhibited the optimal catalytic performance with the highest propylene selectivity of 45.72%.
引文
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[15]Bjorgen M,Svelle S,Joensen F,et al.Conversion of methanol to hydrocarbons over zeolite H-ZSM-5:On the origin of the olefinic species[J].J Catal,2007,249:195-207.
[2]Alipour S M,Halladj R,Askari S.Effects of the different synthetic parameters on the crystal size of nanosized ZSM-5 zeolite[J].Rev Chem Eng,2014,30:289-322.
[3]Galadima A,Muraza O.Recent developments on silicoaluminates and silicoalumino phosphates in the methanol-to-propylene reaction:a mini review[J].Ind Eng Chem Res,2015,54:4891-4905.
[4]Rahimi N,Karimzadeh R.Catalytic cracking of hydrocarbons over modified ZSM-5 zeolites to produce light olefins:A review[J].Appl Catal A,2011,398:1-17.
[5]Song W,Justice R E,Jones C A,et al.Synthesis,characterization,and adsorption properties of nanocrystalline ZSM-5[J].Langmuir,2004,20:8301-8306.
[6]Mohamed R M,Fouad O A,Ismail A A,et al.Influence of crystallization times on the synthesis of nanosized ZSM-5[J].Mater Lett,2005,59(27):3441-3444.
[7]Noack M,Schneider M,Dittmar A,et al.The change of the unit cell dimension of different zeolite types by heating and its influence on supported membrane layers[J].Micropor Mesopor Mater,2009,117:10-21.
[8]Ghorbanpour A,Rimer J D,Grabow L C.Computational assessment of the dominant factors governing the mechanism of methanol dehydration over HZSM5with heterogeneous aluminum distribution[J].ACS Catal,2016,6:2287-2298.
[9]Li J,Ma H,Sun Q,et al.Effect of iron and phosphorus on HZSM-5 in catalytic cracking of 1-butene[J].Fuel Process Technol,2015,134:32-38.
[10]Milovanovic J,StensrΦd R E,Myhrvold E M,et al.Modification of natural clinoptilolite and ZSM-5 with different oxides and a study of the obtained products in lignin pyrolysis[J].J Serb Chem Soc,2014,80(5):717-729.
[11]Inaba M,Murata K,Takahara I,et al.Production of C3+olefins and propylene from ethanol by Zr-modified H-ZSM-5 zeolite catalysts[J].Adv Mater Sci Eng,2012,29:1-7.
[12]Sonnemans M H W,Heijer C,Crocker M.Studies on the acidity of mordenite and ZSM 5-2 loss of broensted acidity by dehydroxylation and dealumination[J].J Phys Chem,1993,97:440-445.
[13]Kissin Y V.Chemical mechanisms of catalytic cracking over solid acid catalysts:alkanes and alkenes[J].Catal Rev,2001,43:85-146.
[14]Svelle S,Olsbye U,Joensen F,et al.Conversion of methanol to alkenes over medium-and large-pore acidic zeolites:steric manipulation of the reaction intermediates governs the ethene/propene product selectivity[J].J Phys Chem C,2007,111:17981-17984.
[15]Bjorgen M,Svelle S,Joensen F,et al.Conversion of methanol to hydrocarbons over zeolite H-ZSM-5:On the origin of the olefinic species[J].J Catal,2007,249:195-207.
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