Biodiesel production by transesterification of waste cooking oil in the presence of graphitic carbon nitride supported molybdenum catalyst

Development of the active metal species with high utilization and accessibility of oil macromoleculars is one of the critical factors affecting heterogeneous metal-based catalysts for production of biodiesel. Here, we synthesized two-dimensional graphitic carbon nitride supported molybdenum (xMo/g-C3N4) catalysts for the facile transesterification of waste cooking soybean oil. Various characterization results of these catalysts show the crystal structure of g-C3N4 is not destroyed, however, Mo oxides phase, containing Mo6+ and Mo5+ state, is detected on the surface of the Mo/g-C3N4 with much Mo-loading, and the ratio of Mo6+/Mo5+ increases significantly with the increasing Mo loading. As expected, compared with the neat g-C3N4 catalyst, the g-C3N4 supported Mo catalyst exhibits a better catalytic performance; especially the 10%Mo/g-C3N4 catalyst has the optimal waste cooking soybean oil conversion of 71.1% and biodiesel selectivity of 99.5%. Furthermore, the experimental parameters and catalytic reusability for the transesterification reaction over 10%Mo/g-C3N4 catalyst are investigated. Moreover, the possible deactivation mechanism and regeneration method of asprepared catalyst are also proposed. This work provides a valuable tactics for the production of clean and low-cost biodiesel from waste cooking soybean oil in the presence of efficient solid catalyst.