Reducing Internal Mass-Transport Limitations of One-dimensional Nanoporous Zeolites from Different Perspectives
Rui Li and Jeffrey D. Rimer
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Road, Houston, TX, 77204, firstname.lastname@example.org
Zeolites possess well-defined pores that provide desired shape selectivity for chemical reactions, which is one essential advantage of their use as catalysts in commercial applications. The ability to tune the geometry and dimensions of internal pores can influence diffusion, adsorption, and catalytic performance. Here, we will discuss methods of tailoring the synthesis of one-dimensional (1D) zeolites, which impose significant mass transfer limitations for internal diffusion. Several 1D zeolites are promising catalysts for reactions such as methanol-to-hydrocarbons,1,2 isomerization, and cracking; however, large internal diffusion pathlengths attributed to poorly engineered crystal size and habit often lead to rapid coking, which imposes restraints for commercial applications. We will present methods to rationally design 1D zeolites with tailored size and morphology. To this end, we examine pathways of crystal nucleation and growth, which predominantly involve non-classical mechanisms associated with precursors (e.g., primary particles and/or bulk amorphous phases). These pathways can be altered through the judicious selection of synthesis parameters. Moreover, we have shown that zeolite growth modifiers (ZGMs)3 are an effective method to selectively alter the properties of zeolite crystals. The advantages of ZGMs are their versatility and low cost, which make them an attractive method of catalyst preparation. Here, we will also discuss how a synergistic combination of synthesis parameters and ZGMs can be used to improve the mass transport properties of 1D zeolites for energy conversion and the production of chemicals.4
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