PETR 24 |
| The catalytic activity of zeolites often is limited by the diffusion of reagents and reaction products through the framework pore network, thus compromising their effectiveness for environmentally relevant processes such as polymer reclamation and condensed phase conversions. Recently, several efforts have been made to reduce the diffusion path length in zeolites by confining crystal growth to a nanometer length scale or by providing intracrystal mesopores during synthesis. More recently, we report a method to prepare templated zeolites with small intracrystal mesopores (average pore size 2-5 nm) and narrow pore size distributions.[1] In this method a silane-functionalized polymer is used as a porogen for the formation of intracrystal mesopores of ZSM-5, denoted MSU-MFI. Here we report on the improved catalytic properties of MSU-MFI zeolites. Remarkable catalytic activity has been observed for the thermal pyrolysis (cracking) of high density polyethylene (HDPE) and the condensed phase esterification of various organic acids. In the pyrolysis of HDPE, the catalyst considerably reduces the temperature needed for polymer decomposition in comparison to a conventional ZSM-5. Moreover, the liquid phase esterification of high molecular weight acids was at least twice as efficient over mesoporous MSU-MFI (Si/Al=50) in comparison to a conventional ZSM-5 (Si/Al=40, Zeolyst Inc.) under equivalent reaction conditions, indicating the benefits of improved active site accessibility provided by the presence of intracrystal mesopores. [1] H. Wang,; T. J. Pinnavaia, Angew. Chem. Int. Ed. 2006, 4(45), 7603-7606. |
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Zeolite Catalysis for Green Chemistry in Synthesis of Chemicals and Fuels
1:20 PM-5:30 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 209, Oral
Division of Petroleum Chemistry |