Toward a comparative description between transition metal and zeolite catalysts for methanol conversion.

ABSTRACT

Transition metals and zeolites are extremely different catalysts used for methanol conversion. Zeolites are able to catalyze methanol conversion to hydrocarbons like gasoline and olefins, while transition metals show the selectivity of syngas. It is quite important to establish a general description from a catalysis point of view for a variety of catalysts. In this work, we have employed density functional theory calculations to correlate adsorption energies for all intermediates over a set of transition metals and zeolites. We have successfully unveiled the difference in chemical reactivity and catalytic activity for zeolites and transition metals; a comparative description has been finally established between the acidity (and porous effects) of zeolites and electronic (and geometrical) effects over transition metals. The hydrogen adsorption strength was suggested to be a general descriptor for both transition metal and zeolite catalysts. In addition, it was found that some zeolites with the same ammonia adsorption strength, which was always used to describe the acidity in experimental studies, are likely to have different theoretical acidity (hydrogen bonding strength). This eventually opens one more dimension for rational selection and design of zeolites for catalysis application.