Oxidative Desulfurization Catalyzed By Subnano MoO₃/mesoporous SiO₂ Nanocomposites

Subnano metal clusters perform better catalytic activity than traditional metal nanoparticles due to its size.Metal oxides subnanoclusters just sprout recently.Due to the environmental pollution,most countries in the world pay great attention to the desulphurization of oil.Oxidative desulfurization attracts wide public concern because of the advantages.Subnano-MoO3 supported on ultrasmall mesoporous silica has been successfully synthesized by reverse microemulsion.The formation mechanism of mesoporous silica as well as the reaction conditions for oxidative desulfurization were investigated.The particle size of the nanocomposite and MoO3 could be easily controlled by the amount of ammonium molybdate and ammonia.The subnano-MoO3/mesoporous silica nanocomposite was 14.2 ± 4.9 nm and MoO3 was less than 1 nm.The obtained subnano-MoO3/mesoporous SiO2 was used to catalyze the oxidative desulfurization of DBT.It was more active due to its better dispersion and more exposed active sites.Beside,we performed the oxidative desulfurization under various reaction conditions,such as T(temperature),t(time),the ratio of oxidant to sulfur compound([O]/[S])and the ratio of catalyst to sulfur compound([cat.]/[S]).The optimum reaction condition was established.When O/S was 6 at 70 oC for 15 min,the DBT conversion was up to 100%.However,the subnano-MoO3/mesoporous SiO2 has less stability because MoO3 subnanoclusters tend to leach during the reaction owing to its tiny size.In order to promote the stability of subnano-MoO3 further,we put the subnano-MoO3 on amino functionalized silica.The coordination between MoO3 and –NH2 inhibited the leaching of MoO3.As a result,the subnano-MoO3/amino functionalized mesoporous SiO2 has better stability.When used for oxidative desulfurization reaction,the DBT conversion was only reduced from 96% to 92% after 5 run times.In addition,the formation mechnism of amino functionalized silica was explored.The amino functionalized silica was prepared by the cohydrolysis and cocondensation of TEOS and APTES.