Amination of allyl alcohol to propionitrile over a Zn30Cr4.5/γ-Al2O3 bimetallic catalyst via coupled dehydrogenation–hydrogenation reactions

Abstract

A Zn30Cr4.5/γ-Al2O3 bimetallic catalyst that can perform coupled dehydrogenation and hydrogenation reactions was prepared for the amination of allyl alcohol to propionitrile. During the catalysis, the hydrogen derived from the dehydrogenation of the alcohol and imine acted as an in situ source for the hydrogenation of the carbon-carbon double bond. The catalyst exhibited good performance for the reaction at atmospheric ammonia pressure. The parameters that affect the catalyst performance were studied thoroughly, and an optimized process for synthesizing propionitrile from allyl alcohol and ammonia over the catalyst was obtained. Under the optimized conditions, the propionitrile yield was greater than 65%. The characterization results indicated that the dehydrogenation reaction mainly occurred on the Lewis acid sites and revealed that ZnAl2O4 is the active species for the coupled dehydrogenation–hydrogenation reactions. Chromium doping of the γ-Al2O3-supported zinc catalyst Zn30/γ-Al2O3 resulted in a decrease in the size of the ZnAl2O4 crystallites, which was favorable for the dehydrogenation–hydrogenation reactions. The characterization results also revealed that the catalyst deactivation was due to carbon deposition on the catalyst during the catalytic run. The catalyst could be reactivated by blowing air into the reactor at a high temperature.