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TL;DR: In this paper, a controlled reduction in the effective dimensions of the catalyst pore openings, and/or channels, along with deactivation of acidic surface sites, has been proposed as a mechanism for the selective production of p-xylene.
513 citations
TL;DR: In this article, data were presented for para-selective and nonselective formation of xylenes from alkylation of toluene with methanol and disproportionation over ZSM-5 class zeolite catalysts.
381 citations
TL;DR: In this paper, a mechanism was proposed where oxides of these elements, present in the zeolites, reduce the dimensions of pore openings and channels sufficiently to favor formation and outward diffusion of p-xylene, the isomer with the smallest minimum dimension.
266 citations
Patent•
03 May 1977TL;DR: In this article, a process for the selective production of para-xylene by methylation of toluene in the presence of a catalyst comprising a crystalline aluminosilicate zeolite was described.
Abstract: Process for the selective production of para-xylene by methylation of toluene in the presence of a catalyst comprising a crystalline aluminosilicate zeolite, said zeolite having a silica to alumina ratio of at least about 12 and a constraint index, as hereinafter defined, within the approximate range of 1 to 12 which catalyst has undergone prior treatment with steam to reduce the alpha value thereof to less than about 500 and preferably within the range of less than about 20 but greater than zero.
118 citations
Patent•
08 Oct 1980TL;DR: In this article, a method for decreasing catalyst coking and extending the usable catalyst life by pre-treatment of the catalyst with steam and/or a phosphorus-containing compound was proposed.
Abstract: There is disclosed a method for decreasing catalyst coking and extending the usable catalyst life by pre-treatment of the catalyst with steam and/or a phosphorus-containing compound. Catalysts benefiting from such pre-treatment comprise crystalline zeolites characterized by a silica to alumina mole ratio of at least 12 and a constraint index, as herein defined, within the approximate range of 1 to 12.
83 citations
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961 citations
TL;DR: A broad classification and survey of organic chemistry over zeolites is presented in this paper, which reflects, for the most part, a mechanistic rather than a process or applications frame of reference.
564 citations
TL;DR: The shape-selective catalysis as discussed by the authors was proposed to increase the selectivity of a desired product and reduce the coke formation in zeolite catalysts by reducing the number of catalytic sites inside the pore structure.
556 citations
TL;DR: The application of zeolite-based catalysts in the production of chemicals and fine chemicals is an emerging field, and will greatly depend on the discovery of new or known structures by alternative, lower cost, synthesis routes, and the fine tuning of their textural properties as mentioned in this paper.
549 citations
TL;DR: This review considers the mixed molecular-nanostructure approach that can be used to develop more demanding catalytic sites, by derivatizing the surface of solids or tethering or immobilizing homogeneous catalysts or other chemical functionalities.
Abstract: In this review, a brief survey is offered on the main nanotechnology synthetic approaches available to heterogeneous catalysis, and a few examples are provided of their usefulness for such applications. We start by discussing the use of colloidal, reverse micelle, and dendrimer chemistry in the production of active metal and metal oxide nanoparticles with well-defined sizes, shapes, and compositions, as a way to control the surface atomic ensembles available for selective catalysis. Next we introduce the use of sol–gel and atomic layer deposition chemistry for the production and modification of high-surface-area supports and active phases. Reference is then made to the more complex active sites that can be created or carved on such supports by using organic structure-directing agents. We follow with an examination of the ability to achieve multiple functionality in catalysis via the design of dumbbells, core@shell, and other complex nanostructures. Finally, we consider the mixed molecular-nanostructure approach that can be used to develop more demanding catalytic sites, by derivatizing the surface of solids or tethering or immobilizing homogeneous catalysts or other chemical functionalities. We conclude with a personal and critical perspective on the importance of fully exploiting the synergies between nanotechnology and surface science to optimize the search for new catalysts and catalytic processes.
535 citations