Synthesis And Catalytic Performance In Oxidative Desulfurization Of Hierarchical Porous TS-1 Molecular Sieves

Concerning the increasing environmental problems,non-sulfuration of gasoline and diesel has become a trend.Oxidative desulfurization?ODS?using Titanium silicalite-1?TS-1?as catalyst can remove thiophene and methyl-thiophene selectedly and efficiently in mild reaction condition which are hard to remove by hydrocatalytic oxidation.This technology has attracted much attention for its excellent catalytic performances However,TS-1 suffers from obvious diffusion limitation arising from its small micropores,and this limitation is very pronounced for the reactions with bulky reactants and products.The mesoporous or macroporous is beneficial to reduce the diffusion of bulky reactants,increase the contact of reactants with active center.In this paper,sodium hydroxide was employed to synthesize low-cost titanium silicon molecular sieve?TS-1?under hydrothermal conditions.The chemicophysical properties of the catalyst were characterized by XRD,XRF,TEM,UV-Vis and N₂ adsorption.Hierarchical zeolite was prepared by hydrothermal post-treatment.The effects of treatment methods,treatment solution concentration,treatment time and temperature were examined in detail.The results indicate that alkali treatment can contribute to the generation of mesoporous structure without degradation of TS-1framework.With the increase of alkali treatment concentration,it increases that the amount of dissolving framework silicon and the number of mesopores.However,the alkali-treated desilicication of TS-1 would lead to the leak of framework titanium with increasing content of Na OH.However alkali-acid-alternating treatment can remove sodium ions and non-framework titanium remarkably.The content of active titanium species,framework titanium,increases,which improves the catalytic activity dramatically.On the removal of bulky benzothiophene,the removal rate rises from 49%to 71%.In the oxidation system with TS-1 zeolite as catalyst,this paper further evaluated the effect of solvent,amounts of oxidants,reaction temperature and reaction time.The results showed that:UHP is preferred as oxidant.n?O?/n?S?=6 was the appropriate oxidant amount.Methanol is a better catalytic oxidation solvent.The removal rate of thiophene increases gradually,and thiophene is completely removed after 3 hours of reaction.