H-MCM-22 zeolitic catalysts modified by chemical liquid deposition for shape-selective disproportionation of toluene
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Catalysts were prepared by dealumination of H-MCM-22 zeolite with oxalic acid leaching, followed by shaping and liquid phase modification with siloxane. The catalytic performance was measured with selective disproportionation of toluene in a fixed-bed reactor. The unmodified H-MCM-22 zeolite exhibited much higher initial activity than H-ZSM-5 with a thermodynamic equilibrium distribution of xylene products. The oxalic acid treatment of H-MCM-22 improved the selectivity for para-xylene by 10–18%. The modification by siloxane of the oxalic acid treated H-MCM-22 turned out to be highly selective for para-xylene, however, with the expense of the conversion. It is proposed that the high para-selectivity was closely associated with the contraction of micropore windows and the elimination of acid sites at the external surface by the deposited silica. Therefore, the modified H-MCM-22 is a potential catalyst for the selective disproportionation of toluene with a high para-selectivity.
KeywordsMCM-22 Disproportionation of toluene Para-xylene Dealumination Chemical liquid deposition
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- 4.W.O. Haag and D.H. Olson. USP 4,097, 543 (1978).Google Scholar
- 9.Y. Qin, Y.H. Yue, and Z. Gao, Chem. J. Chinese U. 19, 1479 (1998).Google Scholar
- 12.M.K. Rubin and P. Chu. US Patent No. 4,954, 325 (1990).Google Scholar
- 37.J.H. Liang, X.Q. Ren, and J. Wang, Petrochem. Tech. (Chinese) 33-S1, 1010 (2004).Google Scholar