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Selective Poisoning of ZSM-5 by Nitrogen Heterocyclics

1991; Elsevier BV; Linguagem: Inglês

10.1016/s0167-2991(08)62714-7

2542-6613

Louis D. Rollmann,

Catalysis and Hydrodesulfurization Studies

Abstract Experiments were conducted to explore the ability of bulky nitrogen compounds to induce para-selectivity in toluene alkylation with ethylene over ZSM-5 catalysts. The experiments showed that: * Injection of a slug of o-phenanthroline into the feed, corresponding to only 10–15% of the zeolitic aluminum in a ZSM-5 catalyst, increased selectivity from 54% para- and 0.3% ortho-ethyltoluene to over 96% para and no detectable ortho-isomer. Toluene (theoretical) and ethylene conversions and selectivities to ethyltoluenes exceeded 90%. * Continued low-level addition of heterocycle was required to maintain para-selectivity. In an example case at 404°C, using an alumina-binder containing catalyst, about 15 ppm N (as o-phenanthroline) was required to maintain 96–97% para-selectivity. Less is required at lower temperature; less is required with binder-free catalyst. The results are explained in terms of N-heterocycle adsorption on external zeolite crystal and binder surface acid catalyst sites.