TiO_2/MCM-22催化合成对二甲苯的研究
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摘要
以钛酸四丁酯为前驱体,乙醇为溶剂,通过浸渍法制备了一系列TiO_2改性MCM-22微孔分子筛择形催化剂,在连续流动固定床反应器上考察了甲苯与碳酸二甲酯烷基化合成对二甲苯的择型催化性能。通过XRD、FT-IR、N2吸附-脱附、NH_3-TPD、XPS、吡啶吸附FT-IR、UV-Vis等手段对催化剂进行表征,并考察了反应温度、空速对甲苯烷基化反应的影响。结果表明,制备的TiO_2改性MCM-22催化剂在甲苯与碳酸二甲酯烷基化合成对二甲苯过程中不仅表现出优异的择型性能,而且还保持了较高的催化活性。这是由于钛酸四丁酯具有较大的分子尺寸,在浸渍过程中仅微孔分子筛外表面酸性位被有效覆盖,而分子筛孔内的酸性位并未受到影响。
A series of TiO_2 modified MCM-22 catalysts are prepared by impregnation method with tetrabutyl titanate as the precursor and ethanol as the solvent. The shape-selective catalytic performances of the TiO_2 modified MCM-22 catalysts in the synthesis of p-xylene via alkylation of toluene with dimethyl carbonate are investigated on a fixed bed reactor.The catalysts are characterized by means of XRD,FT-IR,N_2 adsorption-desorption,NH_3-TPD,XPS,FT-IR with pyridine adsorption and UV-Vis. Influences of temperature and velocity on the toluene alkylation are also studied. The results indicate that the TiO_2 modified MCM-22 catalysts prepared by using tetrabutyl titanate as the precursor and ethanol as the solvent exhibit an excellent shape-selectivity along with a high catalytic activity in the synthesis of PX,which achieves a well coverage of the acid sites on the external surface of MCM-22 zeolite and preserve the acid sites in the pores of MCM-22 simultaneously because of the big molecular size of tetrabutyl titanate.
A series of TiO_2 modified MCM-22 catalysts are prepared by impregnation method with tetrabutyl titanate as the precursor and ethanol as the solvent. The shape-selective catalytic performances of the TiO_2 modified MCM-22 catalysts in the synthesis of p-xylene via alkylation of toluene with dimethyl carbonate are investigated on a fixed bed reactor.The catalysts are characterized by means of XRD,FT-IR,N_2 adsorption-desorption,NH_3-TPD,XPS,FT-IR with pyridine adsorption and UV-Vis. Influences of temperature and velocity on the toluene alkylation are also studied. The results indicate that the TiO_2 modified MCM-22 catalysts prepared by using tetrabutyl titanate as the precursor and ethanol as the solvent exhibit an excellent shape-selectivity along with a high catalytic activity in the synthesis of PX,which achieves a well coverage of the acid sites on the external surface of MCM-22 zeolite and preserve the acid sites in the pores of MCM-22 simultaneously because of the big molecular size of tetrabutyl titanate.
引文
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[23]廖有贵,薛金召,肖雪洋,等.固定床渣油加氢处理技术应用现状及进展[J].石油化工,2018,47(9):1020-1030.
[24]Chang C C,Jin F,Jang L Y,et al.Effect of the grafting agent on the structure and catalytic performance of Ti-MCM-22[J]. Catalysis Science&Technology,2016,6(20):7631-7642.
[25]陆轶群.TS-1分子筛的合成及其催化性能[D].上海:华东师范大学,2016.
[2]孔德金,杨为民.芳烃生产技术进展[J].化工进展,2011,30(1):16-25.
[3]裴力.对二甲苯的发展现状和市场分析[J].现代化工,2015,(12):4-5.
[4]Tsai T C,Liu S B,Wang I. Disproportionation and transalkylation ofalkylbenzenes over zeolite catalysts[J].Applied Catalysis A General,1999,181(2):355-398.
[5]李永昕,吴润泽,薛冰.HMCM-22/MCM-41的制备及其在甲苯碳酸二甲酯烷基化中的催化性能[J].化工进展,2010,29(5):875-879.
[6]牛俊峰,梁战桥.二甲苯异构化工业过程中副反应的控制[J].石油化工,2015,44(1):89-94.
[7]Sotelo J L,Uguina M A,Valverde J L,et al.Deactivation kinetics of toluene alkylation with methanol over magnesium-modified ZSM-5[J].Industrial&Engineering Chemistry Research,1993,35(4):2548-2554.
[8]Inagaki S,Kamino K,Kikuchi E,et al.Shape selectivity of MWWtype aluminosilicate zeolites in the alkylation of toluene with methanol[J].Applied Catalysis A General,2007,318(7):22-27.
[9]Zhu Z,Chen Q,Xie Z,et al.The roles of acidity and structure of zeolite for catalyzing toluene alkylation with methanol to xylene[J].Microporous&Mesoporous Materials,2006,88(1):16-21.
[10]Zhao Y,Tan W,Wu H,et al.Effect of Pt on stability of nano-scale ZSM-5 catalyst for toluene alkylation with methanol into p-xylene[J].Catalysis Today,2011,160(1):179-183.
[11]韩文雯,王清涛,张群峰,等.MCM-22分子筛催化烷基化反应的研究进[J].现代化工,2017,37(10):20-24.
[12]闻振浩,杨大强,朱学栋.苯和甲醇烷基化反应机理及催化剂研究进展[J].现代化工,2017,(1):41-44.
[13]Kim J H,Ishida A,Okajima M,et al. Modification of HZSM-5 by CVD of various silicon compounds and generation of para-selectivity[J].Journal of Catalysis,1996,161(1):387-392.
[14]Zhu Z,Chen Q,Xie Z,et al. Shape-selective disproportionation of ethylbenzene to para-diethylbenzene over ZSM-5 modified by chemical liquid deposition and Mg O[J].Journal of Molecular Catalysis A Chemical,2006,248(1-2):152-158.
[15]Bauer F,Chen W H,Bilz E,et al.Surface modification of nano-sized HZSM-5 and HFER by pre-coking and silanization[J]. Journal of Catalysis,2007,251(2):258-270.
[16]李永昕,邓丽君,薛冰.甲苯与碳酸二甲酯择形烷基化合成对二甲苯[J].化工进展,2010,29(4):665-669.
[17]王永飞,薛冰,许杰,等.乙酸镁改性ZSM-5分子筛上甲苯与碳酸二甲酯的择形烷基化[J].化工进展,2011,30(7):1498-1502.
[18]韩蕾,欧阳颖,罗一斌,等.不同元素改性ZSM-5分子筛在轻烃催化裂解中的应用[J].石油学报(石油加工),2018,34(2):419-429.
[19]Uguina M A,Sotelo J L,Serrano D P,et al.Magnesium and silicon as ZSM-5 modifier agents for selective toluene disproportionation[J].Industrial&Engineering Chemistry Research,1992,31(8):1875-1880.
[20]Liu N,Zhu X,Hua S,et al.A facile strategy for preparation of phosphorus modified HZSM-5 shape-selective catalysts and its performances in disproportionation of toluene[J]. Catalysis Communications,2016,77:60-64.
[21]薛冰,吴浩,文琳智,等.硼酸改性MCM-22分子筛催化甲苯烷基化合成对二甲苯[J].化工进展,2017,36(6):2177-2182.
[22]王振东,张云贤,张斌,等.不同形貌MCM-22分子筛的合成及其催化性能[J].石油学报(石油加工),2014,30(2):110-114.
[23]廖有贵,薛金召,肖雪洋,等.固定床渣油加氢处理技术应用现状及进展[J].石油化工,2018,47(9):1020-1030.
[24]Chang C C,Jin F,Jang L Y,et al.Effect of the grafting agent on the structure and catalytic performance of Ti-MCM-22[J]. Catalysis Science&Technology,2016,6(20):7631-7642.
[25]陆轶群.TS-1分子筛的合成及其催化性能[D].上海:华东师范大学,2016.