Song Tan

Hydrothermal synthesis of bimodal mesoporous MoS2 nanosheets and their hydrodeoxygenation properties

In this study, bimodal mesoporous MoS2 nanosheets were successfully synthesized by a hydrothermal method. The effect of pH value, pressure, time and temperature in the preparation process of MoS2 on its structure property and catalytic activity were studied in detail. Low pH value and pressure were beneficial for the preparation of a MoS2 nanosheet with a large surface area and narrow bimodal pore distribution, which exposed more effective active sites on the surface and provided suitable space for reactants and products to diffuse in less resistance. But the acceleration hydrolysis of CS(NH2)2 at the low pH value enhanced the formation rate of MoS2 and then weakened the nanosheet structure. In the HDO of p-cresol, MoS2 exhibited high catalytic activity, and the dominant route was direct deoxygenation. After 4 h, both the conversion and deoxygenation degree reached 99.9% at 300 °C, and toluene selectivity was 66.2%. The HDO reaction mechanism could be well explained by the Rim-Edge model. The higher conversion in the HDO of p-cresol on MoS2 depended on the larger surface area and greater number of big pores of the catalyst, while the higher direct deoxygenation activity of MoS2 depended on the greater number of layers in its stacks.

Preparation of hydrophobic reduced graphene oxide supported Ni-B-P-O and Co-B-P-O catalysts and their high hydrodeoxygenation activities

Hydrophobic reduced graphene oxide supported Ni-B-P-O and Co-B-P-O catalysts were synthesized by a chemical reduction method and these dispersed relatively well in a non-polar solvent, prevented contact with water, and consequently protected the active phases and exhibited high catalytic activity in the liquid-phase p-cresol hydrodeoxygenation reaction: both the conversion and deoxygenation degree were higher than 99% at 225 °C for 1 h.

Highly selective catalytic conversion of phenols to aromatic hydrocarbons on CoS2/MoS2 synthesized using a two step hydrothermal method

CoS2/MoS2 catalysts were prepared using a two-step hydrothermal procedure for the first time, i.e., MoS2 was synthesized and then CoS2 was prepared and deposited on the surface of the MoS2. The characterization results presented that CoS2 and MoS2 are separated in the resultant catalysts and the surface area of CoS2/MoS2 was much higher than that of Co–Mo–S prepared using a one step method. In the hydrodeoxygenation (HDO) of p-cresol, the presence of CoS2 enhanced the conversion, but excessive CoS2 on the surface of the MoS2 reduced its activity. With an appropriate amount of CoS2, the catalyst presented an unprecedented HDO activity and direct deoxygenation (DDO) selectivity: 98% deoxygenation degree with a selectivity of 99% toluene at 250 °C for 1 h. This CoS2/MoS2 catalyst also exhibited high DDO activity for other phenolic monomers, which minimized hydrogen consumption and improved the economic efficiency.

Microwave-assisted hydrothermal synthesis of amorphous MoS2 catalysts and their activities in the hydrodeoxygenation of p-cresol

Based on the normal hydrothermal method, MoS2 amorphous catalysts were synthesized by using molybdenum(V) chloride to replace molybdate under microwave conditions. The catalysts with different structures and morphologies were obtained by changing the synthesis conditions such as pH value, reaction time, temperature and S/Mo molar ratio and their activities were tested in the hydrodeoxygenation (HDO) of p-cresol. The results showed that the structure of MoS2 and its catalytic activity were mainly influenced by the pH value in the synthesis procedure. The surface area decreased with the reduction of pH value. MoS2 possessed a sheet-like shape when the pH was adjusted to an appropriate value. The catalyst synthesis conditions for MoS2 had little effect on the product distribution but affected the conversion in the HDO of p-cresol. The HDO activity of MoS2 depended on the sheet-like shape and slab length. High reaction temperature was beneficial to enhance the deoxygenation degree. The prepared MoS2 had good stability during the reaction, and also presented high activity in the HDO of other phenols such as phenol, o-cresol and 4-ethylphenol. This facile process was easy to operate and the synthesis time for MoS2 was shortened to 0.5 h, which demonstrated its superiority and efficiency.

SDBS-assisted hydrothermal synthesis of flower-like Ni–Mo–S catalysts and their enhanced hydrodeoxygenation activity

Ni–Mo–S catalysts were prepared by sodium dodecyl benzene sulfonate (SDBS) assisted hydrothermal synthesis. The presence of SDBS increased the NiS2 crystallite size, enlarged the interlayer distance of MoS2 plane and formed loose flower-like architecture, which contributed to the enhanced HDO activity. Compared with Ni–Mo–S synthesized in the absence of SDBS, p-cresol conversion, methylcyclohexane selectivity and deoxygenation degree was increased by 24%, 25.1% and 26.3%, respectively.