Preparation of alumina-supported molybdenum carbide

Abstract

Molybdenum carbide on alumina was studied by XPS, XRD, and temperature-programmed surface reaction (TPSR) with hydrogen. The molybdenum carbide was prepared by nitridation of 12.5 wt% MoO3/Al2O3 in NH3 flow at 700°C, followed by carburization in mixture of 20% CH4/H2 at 700°C for 3 h. The CH4 formation spectrum during TPSR was deconvolved into three peaks at 490, 690, and 810°C. The peak at 490°C was assigned to reduction of carbidic carbon, and peaks at 690°C and 810°C were assigned to reduction of free carbon by the results of XPS and XRD measurements. Therefore, TPSR measurements revealed that molybdenum carbide was formed on alumina by carburization at 700°C in the same manner as with unsupported sample. The pre-nitridation before carburization resulted in the formation of carbide with a larger surface area and less free carbon than by direct carburization.