Dehydration of butanol towards butenes over MFI, FAU and MOR: influence of zeolite topology

Abstract

The effect zeolite topologies have on different types of reactions is one of the fundamental aspects that has made zeolite catalysts immensely popular at an industrial level. Yet, the influence of zeolite topology on catalysis is still not fully understood. The influence of three distinctly different zeolite topologies, MFI, FAU and MOR on the kinetics, product selectivity and catalyst stability for the dehydration of butanol isomers has been investigated. Experimental results showed H-MFI as the most active and most stable catalyst under dehydration conditions. The activity of both other catalysts, H-FAU and H-MOR, is lower and decreased significantly over 48 hours. Comparing the different catalysts and their product distribution under identical conditions indicated large similarities particularly between H-FAU and H-MFI. In contrast, for H-MOR the formation of dibutyl ether is lower than for the other zeolites. The suppression of ether formation in H-MOR is commonly found for the dehydration of smaller alcohols such as ethanol, but it is typically accompanied by a strong increase in activity, which is lacking for butanol dehydration. The experimental results observed for H-MOR could be simulated using a H-MFI based microkinetic model, adjusted for H-MOR. The good performance of the model, achieved with limited adjustments, indicates the possibility to use a common reaction network for the dehydration of alcohols over all three studied zeolites. These findings and the interpretation allow for the design of processes using specific zeolite catalysts tailored to the reactant and intermediates to convert green oxygenated feedstocks to classic petrochemical products.