Study On Preparation And Properties Of Hydrodeoxygenation Catalysts

Boi-oil,a renewable carbon resource,could be produced via a fast pyrolysis process.These liquid fuels contained many oxygenates,including phenols,furans,esters,alcohols,ketones and aldehydes etctera,which contributed to its high oxygen content and then lowered its heating value.Furthermore,these oxygenates caused to some adverse properties such as high viscosity,corrosiveness,immiscibility with hydrocarbon fuels and thermal instability and so on.Hence,an available process for the removal of oxygen atoms from the pyrolysis liquid fuels was required.Hydrodeoxygenation?HDO?is an attractive and efficient technology.Sufide has a percet catalytic,widely used in HDO reaction reach.In this paper,firstly,Co-Mo-S catalysts were synthesized by a facile hydrothermal synthesis and their activities were tested with p-cresol and benzothiophene as model compounds.When Co/Mo mole ratio in Co-Mo-S was adjusted to 0.3,the catalyst presented a flower-like morphology and exhibited highest activity,which was attributed to its specific structure and the synergy effect between CoS₂ and MoS₂.In the HDO of p-cresol,direct deoxygenation?DDO?was the main reaction route and toluene selectivity reached to 97.5%.The hydrogen consumption was markedly cut down.By adding small amount of benzothiophene,p-cresol conversion was enhanced because the produced H2 S from the hydrodesufurization?HDS?of benzothiophene slowed down the catalyst deactivation.In simultaneous HDO of p-cresol and HDS of benzothiophene,because of the competitive adsorption of reactants on the active sites,both the toluene selectivity and desulfurization degree were lowered compared with the single component reactions.Secondly,associated with the carbonization of glucose in the hydrothermal process,MoS₂/amorphous carbon composites were synthesized by one-step hydrothermal method and characterized by various technologies.Introducing carbon into MoS₂ increased its surface area and enlarged the edge-to-corner ratio of the MoS₂ slab of MoS₂ phase,which contributed to a high deoxygenation degree in the HDO of p-cresol,but excessive carbon covered some MoS₂ edges that acted as active sites for HDO reaction and lowered the conversion.The presence of water modified the surface structure of MoS₂ and had a great effect on the HDO activity and product distribution.During the HDO reaction,sulfur-oxygen exchange at the edges of MoS₂ resulted in the loss of S atoms and the intensity decrease of?002?diffraction peak for MoS₂ phase,which was accelerated by increasing the added water amount.Carbon in MoS₂ only acted as a support and had no preventing effect to water.When the added water was 0.2 g,i.e.,water/p–cresol molar ratio was 0.5:1,after reaction at 275 °C for8 h,toluene selectivity and deoxygenation degree increased to 91.3% and 94.2%respectively.