Thermally Stable Cu-Ni-Zn Alloy Catalysts for the Efficient Synthesis of Morpholine from Diethylene Glycol

Abstract

Cu-based catalysts exhibit high activity in catalyzing the conversion of alcohols to amines, but they are prone to sintering under high-temperature conditions. Alloying has long been considered a promising approach to improving the catalytic performance of metal materials. Therefore, this paper proposes a novel improvement strategy. Firstly, Al2O3-supported multimetallic catalysts prepared by the co-precipitation method were subjected to hydrothermal treatment, successfully constructing ternary alloy catalysts. Secondly, the formation of the catalyst surface structure was controlled by adjusting the metal ratios. The study shows that Zn plays a linking role in the formation of CuZn and CuNiZn alloys, and the formation of these ternary alloys increases the number of acidic groups and the specific surface area of the catalyst. The combined effect of Zn and Ni makes the CuNiZn/Al2O3 catalysts more active than monometallic and bimetallic catalysts in catalyzing the synthesis of morpholine from diethylene glycol, with the Cu2.0Ni2.0Zn1.0/Al2O3 catalyst achieving the highest morpholine yield of 93%. Additionally, the Cu2.0Ni2.0Zn1.0/Al2O3 catalyst exhibits excellent thermal stability, with less than a 2% decrease in the initial diethylene glycol conversion after 50 hours of continuous reaction. This thermally stable CuNiZn/Al2O3 catalyst has strong potential for commercial morpholine synthesis from diethylene glycol.

Keywords: Cu-based catalyst, DEG Synthesis of MPH, CuNiZn Alloying, Thermal stability