Synthesis Of Transition Metal Doped MOS₂ And Its Application In Catalytic Hydrogenation Liquefactio Of Alkali Ligin

Alkali lignin is a by-product of pulp and paper industry, mostly existing in pulping waste liquor. It is a kind of natural renewable aromatic compounds. It is very important to make full use of alkali ligni by liquification, degradation and other methods, which is of great significance for the world to solve the energy crisis and achieve sustainable development. Moreover, H2, as a raw material, can be converted into fuels in hydrogenation liquefaction process. It is safer and more efficient than burning H2 directly. In addition, MoS2 has different kinds of properties such as metallic, a narrow energy band and good stability. If MoS2/SrTiO3 composites were synthesized, the degradation rate of organic dye can be more effective than traditional perovskite photocatalyst. Therefore, it is important for people to solve environmental pollution problems.In this research, MoS2 with doping transiton metal (Ni, Co, Ag) catalyst has been synthesized by hydrothermal method and the synthesized catalyst can be applied to the hydrogenation of alkali lignin. The effects of reaction temperature, time, pressure of H2 and kinds of catalyst have been investigated during hydrogenation liquefaction of alkali lignin through single factor method, with the yields of bio-oil, degraded lignin, solid residue, gas and analyzing compouds of bio-oil as the indexes.The results show that MoS2、Ni-MoS2、Co-MoS2 and Ag-MoS2 catalysts synthesized by hydrothermal method has layer nanoflowers structure and the edge of stacking layers is wedge sharped which provides a number of hydrogenation centers. After doping with Ni and Co, the layer stucture of MoS2 becomes more curved and the degree of stacking is reduced, leading to the higher hydrogenation activity. The maximum yield of bio-oil and conversion of alkali lignin were 78.02% and 88.27%, respectively, at optimal condition of 290℃,1 h, and 2.5 MPa H2 with MoS2 catalyst. The yield of bio-oil and conversion of alkali lignin can be improved by transtion metal Ni and Co. However, it seems that Ag is not helpful for the improvement of the yield of bio-oil. Even, excessive content of Ag results in the unsatisfactory hydrogened performance. Bio-oil is composed primarily of phenol, esters, acids, sulfide, and nitride compounds. Products are more selective by using MoS2、Ni-MoS2、 Co-MoS2 and Ag-MoS2 catalysts. Hydrodesulfurization and hydrodenitrification are easily reacted by droping with transtion metal, leading to bio-oil with good quality.In addition, MoS2/SrTiO3 has been successfully prepared via a two-step simple hydrothermal method. The effect of loading M0S2 and the photocatalytic mechanism have been investigated by degradation of MO organic dyes under UV-light irradiation. The results show that the effect of balanced loading M0S2 can efficiently suppress recombination of electron-hole pairs and improve interfacial charge transfer, leading to high photocatalytic degradation activity. MO organic dyes with concentration of 30 mg L-1 can be completely degraded in 60 min under UV light with 0.05 wt%MoS2/SrTiO3 photocatalyst.