One-step methyl isobutyl ketone (MIBK) synthesis from 2-propanol: Catalyst and reaction condition optimization

Abstract

The one-pot gas-phase synthesis of methyl isobutyl ketone (MIBK) from 2-propanol is studied using bifunctional catalysts under mild conditions. The effect of the catalyst copper content and acid–base properties as well as that of the operational conditions on the MIBK yield is investigated. Copper loadings of 2–6 wt% and moderate catalyst Lewis acidity and Brönsted basicity are required to obtain MIBK yields of 27%, values comparable with the current commercial process from acetone (DMK) at high pressures. A gas-phase process for methyl isobutyl ketone (MIBK) synthesis from 2-propanol in one-pot is studied as an alternative to the conventional technology for producing MIBK from acetone (DMK). Bifunctional copper/acid–base catalysts able to operate at mild temperatures and atmospheric pressure were prepared and characterized by measuring the acid and base properties as well as the metal dispersion. It was found that a Cu-Mg-Al mixed oxide catalyst gives high MIBK yields. In this catalyst, the metal fraction in loadings of 2–6 wt% promotes the hydro-dehydrogenation steps at high rates whereas the surface acid–base sites of moderate acid and base properties favor the aldol condensation reaction. The effect of different operational conditions such as reaction temperature and reactant partial pressure was also investigated. The MIBK formation rate was enhanced by increasing 2-propanol partial pressure in a wide range, consistently with a positive 2-propanol reaction order in the overall kinetics whereas the presence of hydrogen in the reactant mixture inhibited MIBK synthesis due to a negative order with respect to H 2 . An increase of the reaction temperature and the use of inert atmosphere improved the MIBK yield. By operation at 533 K in N 2 the Cu-Mg-Al catalyst with 6.4 wt% Cu, yields 27% MIBK in comparison to the 30% typically obtained in current commercial liquid-phase high-pressure processes from DMK.