Effect of carburization protocols on molybdenum carbide synthesis and study on its performance in CO hydrogenation

Molybdenum carbides were prepared under different carburization conditions. The role of carburization protocol was studied while their CO hydrogenating performances were evaluated in a fixed-bed reactor at 280 degrees C, 3.1 MPa, and H-2/CO = 2.0. The structure of the carbides mainly depended on the type and concentration of carbon source while the crystallite size depended on carbon source and temperature. The surface area, morphology and surface carbon deposition phenomenon of the carbides were sensitive to heating rate and holding time other than the above factors. Though the bulk structure was the same at a carburization temperature range from 630 to 760 degrees C, the carburization degree of the carbides was changing continuously. This diversity led the bond strength of molecular adsorbed CO weaken at a higher carburization temperature while the adsorptive strength of H-2 was hardly changed. Both the adsorptive quantities of CO and H-2 followed the same trend, with the highest amount on the carbide prepared at 630 degrees C. The activities of the catalysts correlated well with their adsorptive quantities of CO and H-2, and the product selectivity was related to their hydrogenation capacity. (C) 2015 Elsevier B.V. All rights reserved.