Study On The Desulfurization Performance Of Porous Carbon-based Composites Derived From Biomas

With the global over-exploitation and use of petroleum energy,the quality of crude oil is deteriorating and the sulphur content in crude oil is increasing year by year.The emission of sulphur and oxygen compounds,which cause environmental pollution and ecological damage,has caused worldwide concern.Hydrodesulphurisation(HDS),the main catalytic reaction for the removal of sulphur compounds from oil,has been used industrially.Currently common HDS catalysts are mainly nickel/cobalt promoted molybdenum based catalysts,which have been widely used in various HDS systems due to their excellent performance.The marginal sulphur vacancies are the active sites of HDS,so the controlled synthesis of molybdenum-based catalysts with more active sites and smaller sizes is important for promoting HDS performance.However,the small size active phase is prone to aggregation,so finding a suitable carrier is currently the key to improving the catalytic performance of HDS.Conventional HDS catalysts use alumina as the carrier,but the strong interaction between alumina and metal results in low active metal sulphation,which is no longer sufficient for deep HDS,so the development of cheap and easily available excellent carriers is imminent.The preparation of carbon carriers from waste biomass has become a new carrier material due to its high specific surface area,controlled surface composition and low cost.In this thesis,a series of composites using waste biomass-derived porous carbon as a carrier and loaded with(Zn)NiMoSx active phase were prepared by a facile synthetic method to achieve deep HDS.The main studies in this thesis are as follows:A porous carbon material with high specific surface area and high graphitization was successfully prepared by introducing a graphitization catalyst(FeCl3)and an activator(ZnCl2)into biomass Coconut shell at the same time and calcining it under nitrogen protection at 900℃.The graphitization degree and specific surface area of the porous carbon material were adjusted by varying the concentration of the graphitization catalyst and calcination temperature.The degree of graphitization and specific surface area of the porous carbon material were adjusted by varying the concentration and calcination temperature of the graphitization catalyst.The HDS performance tests showed that the graphitisation of the different carbon carriers had a small effect on the HDS activity,while the specific surface area had a more significant effect.The optimum catalyst NiMoSx/GPC-3-900 achieved 94.7%conversion of dibenzothiophene at a WHSV of 120 h-1,93.18%selectivity for direct desulphurisation and a kHDS of 23.73 x 10-7 mol/(g·s).The activator ZnCl2 was used to modulate the porous structure of the derived carbon carriers to obtain biomass-derived porous carbon materials with a large specific surface area(1581.1 m2/g).The ZnNiMoSx active phase was highly dispersed on the carrier surface and MoS2 on the porous carbon C-3 showed fewer layers(2-4 layers)and shorter lengths(4-5 nm),which leads to the formation of more marginal active sites in the material.In addition,the introduction of Zn species increases the degree of sulphation of the molybdenum-based catalyst,which leads to higher HDS activity.The synthesised optimal catalyst ZnNiMoSx/C-3 still achieves 99.7%conversion of dibenzothiophene at a WHSV of 120 h-1,with a direct desulfurisation selectivity of 94.5%and a high kHDS of 39.42 × 10-7 mol/(g·s)for dibenzothiophene.Finally,Starting from biomass straw,the specifi c surface area and lamella thickness of straw-derived biomass carbon were successfully adjusted by introducing the activator ZnCl2.It was found that the specific surface area of the straw increased and then decreased with increasing ZnCl2 mass,which was due to excessive dehydration of the carbon material caused by excessive ZnCl2,destruction of the pore structure and reduction of the specific surface area.The optimum catalyst ZnNiMoSx/PC-3 obtained after loading with ZnNiMoSx active phase showed a conversion of 90.1%for dibenzothiophene at a WHSV of 120 h-1,a direct desulphurisation selectivity of 85.02%and a kHDS of 22.66× 10-7 mol/(g·s).