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Green Chemistry with Zeolite Catalysts It is difficult to spend any time in the chemical process industry without hearing about zeolite catalysts. "Zeolite" is the broad term used to describe a family of minerals called tectosilicates. These minerals contain small pores which provide a generous surface area. Zeolites are constructed of tetrahedral AlO4-5 and SiO4-4 molecules bound by oxygen atoms. Currently, there are 40 known natural zeolites and in excess of 140 synthetic zeolites. Zeolites can be custom made by manipulating the structure, silica-alumina ratio, pore size, and density. Other metals can also be incorporated into zeolites to obtain specific catalytic properties. The motivations for using zeolite catalysts are primarily profit and environmental regulation compliance. Zeolites can help produce products at more mild temperatures and pressures which lowers operating costs. They also are used for their superior control of reaction selectivity which saves on feed costs and by reducing waste streams, saves on treatment costs. Specific Zeolite Accomplishments 1. NOx emission reductions by selective catalytic reduction (SCR) References: Marcus, Bonnie K. and Cormier, William E.,
"Going Green with Zeolites", Chemical Engineering Progress, June 1999 |
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