Hydrodeoxygenation of p-cresol on MoS2: the effect of adding hexadecyl trimethyl ammonium bromide during the catalyst synthesis

Abstract

This study prepared unsupported MoS2 catalysts by a one-step hydrothermal method using ammonium heptamolybdate and thiocarbamide as materials. The morphology and microstructure of MoS2 catalysts were changed by adding different amounts of hexadecyl trimethyl ammonium bromide (CTAB). The resultant catalysts were characterized by X-ray diffraction, nitrogen physisorption and transmission electron microscopy. The surface area and pore volume of MoS2 increased first and then decreased with the addition amount of CTAB. The structural difference between these catalysts lies in the number of layers in stacks and slab length of MoS2 structure. The structure–activity correlation was studied by using the hydrodeoxygenation (HDO) of p-cresol as the probe reaction. In the HDO of p-cresol, the end products were toluene, 4-methylcyclohexene and methylcyclohexane, and the possible HDO reaction routes were proposed. The effects of addition of CTAB during the synthesis of MoS2 and HDO reaction temperature on conversion and products distribution were analyzed. The changes of product distribution were explained based on the Rim-Edge model. The direct deoxygenation (DDO) route occurs on the edge active sites while the hydrogenation–dehydration (HYD) route occurs on brim sites of multi-stacks MoS2 particles. Thus, the slab length and slab stacking layers had a great effect on the catalytic activity of MoS2 and products distribution.