Catalytic cracking of 1, 3, 5-triisopropylbenzene over silicoaluminophosphate with hierarchical pore structure
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In order to prepare a highly active catalyst for the catalytic cracking of larger molecules, a novel micro-mesoporous silicoaluminophosphate composite (define as mesoporous SAPO-5) with hierarchical tri-modal pore size distributions has been firstly synthesized via post-synthetic method in acidic condition and subsequently characterized. Morphology control of the composite is attempted by adjusting pH value of the synthetic system. Three different morphologies of composite, including sphere-, rod- and net-like, are obtained in the different conditions. Possible mechanism for the formation of mesoporous SAPO-5 has been proposed. The mesoporous SAPO-5 exhibits higher cracking activity than conventional microporous SAPO-5 for cracking of 1, 3, 5-triisopropylbenzene (1, 3, 5-TIPB) under the same reaction conditions. The result indicates that the mesoporous SAPO-5 with hierarchical pore structure is favorable for catalytic cracking of large molecule. When the cumene as the reaction molecule, the microporous SAPO-5 catalyst exhibits higher conversion in catalytic cracking of cumene compared to the mesoporous SAPO-5, and the result may be attributed to that microporous SAPO-5 has much stronger acidity and specific selectivity than mesoporous SAPO-5 catalyst in catalytic cracking of cumene. Meanwhile, corresponding carbenium ion mechanism can account for the products formed during the whole reaction process.
KeywordsCatalytic cracking Hierarchical pore structure Silicoaluminophosphate
This work was supported by the 973 Program under Grant (No. 2003CB615802), the Foundation for State Key Laboratory of Multiphase Complex Systems (No. MPCS-2014-A-04 Y425016124 J. Q.), National Natural Science Foundation of China (No.51302266 Q. J.) and Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (Q. J.).
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