Efficient catalysts for simultaneous dehydration of light alcohols in gas phase

Abstract

We report the simultaneous dehydration of light alcohols over rare earth phosphate catalysts. Catalytic reactions were carried out in a gas-phase fixed-bed reactor at temperatures ranging from 490 to 643 K. The catalyst samples were synthesized and characterized using various techniques, and their acid properties compared by monitoring the desorption of 2,6-dimethylpyridine by means of FTIR spectroscopy. The catalysts were found to be very efficient for the simultaneous dehydration of ethanol and 1-butanol to ethylene and 2-butene. This catalytic dehydration should involve the moderately strong Brønsted and Lewis acid sites revealed on the catalysts' surface, whose strength distribution was sufficiently broad to minimize the competition between dehydration of the two alcohols. The catalysts were also very efficient in the direct dehydration of alcohol mixtures produced by bacterial fermentation (PBE: propanol–1-butanol–ethanol and ABE: acetone–1-butanol–ethanol). This outcome makes it possible to consider a metathesis-based industrial process for the production of propylene, in which the first step involves the dehydration of alcohol mixtures produced by biomass degradation. These catalysts are shown to present further advantages such as their insensitivity to the addition of water in the gas feeds, relative stability with time on stream, and straightforward regeneration.