The Preparation Of Woody-biomass Hydro-liquefaction Mo-based Catalysts And Catalytic Performance

Nowadays,with the rapid development of human society,the demand for fossil energy is increasing,but the contamination of the environment makes people have to find clean and green renewable energy to replace traditional fossil fuels such as oil and natural gas.Biomass resources are abundant,renewable and carbon neutral,and have gradually become the research focus of the scientists all over the world.The hydroliquefaction of biomass is a kind of promising method which can transform biomass into fuels efficiently.The key point of this technology is to find a type of catalyst which can convert biomass into bio-oil with high calorific value.The mesoporous material SBA-15 has large pore size,large specific surface area and good hydrothermal stability.It can inhibit coking reaction and reduce the formation of coke in the process of woody-biomass hydroliquefaction,allowing larger biomass macromolecule intermediates enter the pore of catalyst and be cracked into small molecules.The meso-microporous molecular sieve ZSM-5-SBA-15 combines the advantages of mesoporous and microporous supports,such as the strong acidity of microporous H-ZSM-5 and the large pore size of mesoporous material SBA-15.It can not only accelerate the breaking of C-C bonds andβ-O-4 bonds which have high stability,but also slow down the deactivation rate of active centers,reducing the phenomenon of coke deposition,prolonging the using time of catalysts and further improve the yield of bio-oil.In this paper,MoS₂/Al-SBA-15 and MoS₂/ZSM-5-SBA-15 catalysts were prepared and tested by the experiments of hydroliquefaction of sawdust.The acidity and pore structure of the Al-SBA-15 supports were adjusted by changing the synthesis conditions,such as the ratio of silicon to aluminium,the reaction temperature of the precursor solution,and p H.The proportion of different pore structures and the types of acidity sites of ZSM-5-SBA-15 were adjusted by changing the additive amount of H-ZSM-5 to the meso-microporous molecular sieve ZSM-5-SBA-15.It was found that a relative higher bio-oil yield（52.3%）can be obtained when the hydroliquefaction reaction was catalyzed by MoS₂/Al-SBA-15 which was prepared at the synthesis conditions of p H=1.5,n _Si/Al=10,and the reaction temperature of precursor solution is 40 C.In terms of MoS₂/ZSM-5-SBA-15,when the mass ratio of ZSM-5 to SBA-15 is 0.8 g,the highest oil yield（65.67%）can be achieved.The effects of reaction conditions such as temperature,time,hydrogen pressure and catalyst dosage during the process of hydroliquefaction reactions were also investigated,it could be clearly seen that the highest oil yield（65.67%）could be obtained at 340℃,under an initial H₂ pressure（8 MPa）,reaction time was 30 min and catalyst dosage was 0.08 g.The characterization results of bio-oil obtained from the reaction evaluation of the optimum catalysts showed that both catalysts significantly reduced the contents of oxygen in bio-oil,and the content of hydrocarbons increased significantly,indicating that the hydrodeoxygenation effect of the MoS₂/ZSM-5-SBA-15 and MoS₂/Al-SBA-15 catalysts were better.