Characteristics and Activity of Steamed Zeolites for Butanol Upgrading to Higher Olefins

The increasing prevalence of renewable alcohols derived from biomass feedstocks make them an ideal platform for developing into transportation fuel. Butanol is a promising bioproduct that can be generated either from direct fermentation or ethanol condensation chemistry, and can be further upgraded to fuels and chemicals in a selective manner. Development in the methanol-to-gasoline (MTG) process has shown zeolite catalysts to be particularly effective for the production of higher olefins, capable of catalyzing both the dehydration and oligomerization reactions in a single step and directly converting butanol to jet or diesel range hydrocarbons. However, changes to the catalyst in the initial startup phase and over time are reflected in the dynamic product distribution, shrinking the optimal reaction window. Dealumination through steaming has been shown to be an effective modification method, impacting the distribution and coordination of aluminum as well as the overall zeolite structure. Tests showed that presteaming ZSM-5 zeolites prior to the reaction of butanol resulted in the immediate stabilization of the reaction product distribution. Catalyst characterization revealed significant differences in the zeolite lattice structure and acid sites from steaming and after reaction. In this presentation, the specific effects of steaming on the catalyst structure and reaction sites will be discussed along with their role in stabilizing the reaction product distribution.