(532df) Metal Incorporation into Zeolites Via Acid-Base Mediated Ion Exchange for Methane Dehydroaromatization

Currently, about 15% of domestic use of benzene, carrying the value of nearly $1B/year, is imported to the US from other countries. Given the economic and environmental impact of this situation, we are pursuing a feasible and greener alternative to benzene production from abundant domestic shale gas.

We report syntheses of precursors of molybdenum zeolite ZSM-5 catalysts for methane dehydroaromatization (MDA) utilizing the acid-base properties of the metal salts and the zeolites to influence the characteristics of the precursor. Slurry of zeolite at either acid or base pH and solution of metal precursor on the opposite side of neutrality are simultaneously added to a reactor at a constant pH chosen to optimize the deposition of metal to the zeolite. For instance, addition of high pH ammonium molybdate solution and low pH zeolite slurry results in precursors with good metal loading. Examples with other metals and differing conditions will be shown. This approach is thought to favor the deposition of the metal directly at the protic (Al) sites of the zeolite which are believed to be involved in the catalytic process of forming benzene from methane. Characterization by chemical analyses (ICP-MS and -OES), SEM imaging, EDS spectroscopy, powder XRD, thermal analysis, and other techniques will be presented. Catalytic activity results from the activated precursors prepared in this way are presented and compared to activated precursors obtained by other routes such as incipient wetness impregnation and hydrothermal ion exchange.