Hydrodeoxygenation Properties Of Unsupported Sulfided Catalyst Prepared By Hydrothermal Method

China’s economy is in a stage of rapid development, where requires more and more energy. However, the traditional fossil energy resources were declining, and their utilization brought many environmental problems. It was extremely urgency to explore a new renewable, green and environmental-friendly fuel. Bio-oil is a liquid fuel from the fast pyrolysis of biomass(wood, straw, etc.) under the conditions of isolated from oxygen and medium temperature, which has attracted a lot of attentions because of the abundance and renewability of raw material and its high energy density. Unfortunately, this bio-oil contains many oxygenic compounds such as phenols, furans, aldehydes, ketones, etc., contributing to its oxygen content(higher than 50%), which leads to a low heating value and thermal instability and then hinders its extensive application as a supplement fuel. Hence, it is necessary to remove the oxygen from bio-oil by hydrodeoxygenation(HDO) process to improve its quality.Firstly, unsupported Ni-Mo-S catalysts with different Ni/(Ni+Mo) molar ratio were prepared by one-step hydrothermal method and characterized by X-ray diffraction, transmission electron microscopy and nitrogen physisorption, and their HDO activities were measured using p-cresol as a model compound. The results indicated that the addition of Ni promoter caused to a reduction in the surface area. The peaks attributed to NiS2 on catalyst surface became noticeable as the Ni content increased in the catalyst. The catalyst with an optimal Ni/(Ni+Mo) molar ratio(0.3) exhibited the highest activity(99.8% deoxgenation degree at 300 °C and 4.0 MPa hydrogen pressure for 6 h). The HDO of p-cresol on these prepared Ni-Mo-S catalysts proceeded with two parallel routes: hydrogenation-dehydration(HYD) and direct deoxygenation(DDO), and HYD/DDO closely related to the Ni/(Ni+Mo) molar ratio of the catalyst, the HDO reaction temperature and H2 pressure.Secondly, bimodal mesoporous MoS2 nanosheets were successfully synthesized by 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 p H value and pressure were beneficial for the preparation of MoS2 nanosheet with a large surface area and narrow bimodal pore distribution. But the accelerated 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 4h, both the conversion and deoxygenation degree reached to 99.9% at 300°C, and toluene selectivity was 66.2%. The HDO reaction mechanism could be well explained by Rim-Edge model. The higher conversion in the HDO of p-cresol on MoS2 depended on the larger surface area and more big pores of the catalyst, while the higher direct deoxygenation activity of MoS2 depended on the more layers in its stacks.