Preparation Of Molybdenum Carbide-based Catalysts With Molybdenum-rich Vacancies Induced By Defect Engineering And Their Desulfurization Performance

The goal of the thesis is to prepare SiO2 nanospheres with different diameters by the classical Stober method,and these SiO2 nanospheres serve as hard templates,low-cost chitosan and ammonium molybdate tetrahydrate(AHM)which were carbon source and molybdenum source.Mixed-baking-etching,a series of Mo-vacancies(defective)-based molybdenum carbide-based catalysts(MoxC@N-CS)with different pore sizes were synthesized,and the active component MoxC particles were uniformly in-situ anchored in the three-dimensional macroporous carbon network structure,which can be used as targeted catalyst to test the performance of adsorbed/oxidized thiophene-based sulfur compounds.In the adsorption desulfurization:The adsorption performance of MoxC@N-CS in three different loading ratios,is investigated,and MoxC@N-CS(l)is optimized as the best adsorbent.Exploring the effects of other experimental factors on the adsorption of DBT.The optimal adsorption desulfurization conditions are as follows:when T=60 min,t=40?,and m=0.01g,the maximum capacity to adsorb DBT is 152 mg/g(the adsorption removal rate of DBT can reach 53%).After five cycles of experiments,the amount of DBT adsorbed decreased from 152 mg/g to 123.42 mg/g,(decrease 19%)which demonstrates its excellent cycle stability.Finally,based on the adsorption kinetics and properties of the target catalysts,the adsorption performance of four different pore size catalysts was investigated.The structure and morphology of the synthesized catalysts were characterized by SEM and TEM,and their kinetic also was studied.The results clear that the four pore size catalysts MoxC@N-CS(l)exhibit a three-dimensional macroporous network structure with uniform pore size and regular morphology.The pseudo-secondary kinetic model more accurately describes the adsorption process of four different pore sizes catalysts.This process involves all adsorption processes.Furthermore,both the langmuir and Freundlich models work well to study adsorbent adsorption of DBT behavior.Therefore,the adsorption behavior of the adsorbent on DBT is a combination of physical adsorption and chemical adsorption.Finally,the above analysis is to demonstrate that proper pore size is critical for the diffusion and adsorption properties of the adsorbate in its pores.In terms of oxidative desulfurization:MoxC@N-CS,a heterogeneous nanocatalyst,is used for the oxidative removal(ODS)of dibenzothiophene in model fuels.When hydrogen peroxide(H2O2)works as the oxidant,the desulfurization efficiency of MoxC@N-CS(2)sample reaches 100%under the experimental conditions:50 ?,60 min,O/S=5:1,MoxC@N-CS(2)shows rapid kinetics and low active energy in the oxidative removal of dibenzothiophene since the stable three-dimensional macroporous network structure is helpful to facilitate rapidly mass transfer and the created Mo vacancies increase the number of intrinsic active sites.In addition,MoxC@N-CS(2)exhibited excellent recyclability after 5 cycles,while the catalytic activity of the ODS reaction did not decrease greatly.