Stability and Regeneration of Copper-on-Silica-Magnesia for Acrylamide Synthesis in the Liquid-Phase Fixed-Bed Operation

Abstract

Catalytic conversion of acrylonitrile to acrylamide over copper-on-silica-magnesia was carried out in the liquid phase fixed-bed flow system at 80°C. Selective formation of amide with consatnt conversion of nitrile was observed over 70 h on stream. Kinetic data showed strong adsorption of amide, resulting in deviation from first-order kinetics. The catalyst was sensitive to oxygen, a slight amount of oxygen might decrease the catalytic activity. Oxygen. dissolved in the solvent water, whose concentration might be limited to a lower level in practical cases, changed the color of the catalyst bed gradually. By using oxygen-saturated and air-saturated water, during 360 h on stream, brownish yellow and dull black bands developed from the top to the end of the bed. Up to 200 h, the brownish yellow band (presumably Cu₂O ⋅n H₂O) was spread over the entire bed, and the conversion of nitrile increas ed without a decrease in selectivity to amide. In further 160 h, the catalytic activity degenrated, and it might be attributed to the growth of a black band (presumably CuO) from the top of the bed. Regeneration of deactivated catalyst was successful by hydrogen reduction at 200∼300°C.