Synthesis and Characterization of Massive Molybdenum Carbides and Supported Carbide-Containing Catalysts Mo_2C/C Prepared through Mechanical Activation

摘要

Procedures for the synthesis of massive molybdenum carbide by the mechanical activation of a mixture of MoO_3, commercial carbon, and Zn in air and the synthesis of the supported carbide-containing catalyst Mo_2C/C by the mechanical activation of commercial carbon impregnated with a 16% aqueous solu- tion of ammonium paramolybdate in an inert atmosphere were developed for the first time. With the use of a set of physicochemical methods, the metal contents, particle sizes, specific surface areas, and phase compo- sitions of the mechanically activated composites were determined. The structure of the carbide-containing supported catalyst was studied by electron microscopy, and its acidic properties were studied by the temper- ature-programmed desorption of ammonia; catalytic tests in the model reactions of dibenzothiophene (DBT) and alkane aromatization were performed. It was found that the Mo_2C/C catalyst exhibited high activity in these reactions: the conversion of DBT at a contact time of 3–6 h was 80–85%. The conversion of n-heptane at a contact time of 2 h was 31.2%, and 100% toluene was the reaction product. An increase in the contact time to 6 h led to a decrease in the conversion of n-heptane to 1.3%, and to 47% C_6–C_7 cycloalkanes were present in the reaction products. The results of this work are indicative of the high catalytic activity of the Mo_2C/C catalyst obtained by mechanical activation.