The Nature of the Catalytic Sites in HZSM-5- Activity Enhancement
1986; Elsevier BV; Linguagem: Inglês
10.1016/s0167-2991(09)60934-4
ISSN2542-6613
AutoresR.M. Lago, W.O. Haag, R.J. Mikovsky, David H. Olson, Stuart D. Hellring, Kirk D. Schmitt, George T. Kerr,
Tópico(s)Ammonia Synthesis and Nitrogen Reduction
ResumoThe catalytic activity of HZSM-5, when carefully prepared in the absence of water vapor, is strictly proportional to its tetrahedral Al content. All sites have equal activity, which includes sites having zero (single) and one (paired) next nearest neighbor Al atoms. While severe steaming reduces the catalytic activity, mild steaming produces catalysts of higher activity. New catalytic sites are generated with a specific activity 45-75 times greater than that of the normal sites. The resulting zeolite has a combination of enhanced activity sites and normal activity sites. Paired Al framework atoms appear to be required for the formation of enhanced acidic centers. A kinetic model encompassing rates of enhanced site generation, their decomposition and dealumination has been developed.
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