Study Of The Synthesis, Characterization And Activity Of The Functionalized Mesoporous Silica Immobilized Photocatalysts

Polyoxomelatates as catalysts have been widely researched,but as photocatalysts since the early 80s last century.Because of good photocatalytic activity,they have attracted much attention as homogeneous catalysts since then,such as decatungstate. The mesoporous materials,especially the SBA-15 have been paid much attention since the discovery of M41S series.It has large surface area and wide range of pore dimensions(2-50 nm),it is sure that the reactants is easy to access to active sites; more important,it provides a unique inorganic support that can anchor the active components on it,and make them have much potential applications in many research fields.What's more,as they have high hydro-thermo stability and lots of silanols on their surface,therefore they can be modified more easily.All these advantageous make many people choosing the mesoporous materials as supports in synthesis of catalysts.In this thesis,the active specie decatungstate was anchored on the SBA-15 surface,which was successfully modified by organic functional groups,and the functionalized mesoporous materials kept their original morphological structure.In addition,the catalytic activity was widely investigated in alkanes,alkenes and alcohols oxidation to corresponding carbonyl compounds.1.An efficient,environment friendly procedure is developed for ethylbenzene photooxidation to acetophone by using an aminopropyl-functionalized SBA-15 supported decatungstate W₁₀O₃₂^4-catalyst in CH₃CN solution.The heterogenized W₁₀O₃₂^4-catalyst W₁₀/AP-SBA(I)showed a higher activity than it in homogenous for the liquid phase photooxidatin of ethylbenzene under the conditions:a flow of oxygen (1 atm,3 ml·min^-1)at room temperature using CH₃CN as solvent;and gave acetophenone as a main product in high selectivity(＞84%).Effects of various aspects on the catalysts' activity have been investigated,such as solvent,oxidant,the amount of the catalyst etc.Solvent has much effect on the yield,at the same reaction condition,CH₃CN/H₂O(v:v=1:1)as co-solvent gave the highest yield.2.Aminopropyl was successfully functionalized on SBA-15 by one pot synthesis method,decatungstate W₁₀O₃₂^4-was also immobilized on successfully by ion-exchanged method.BET and TEM results showed that the organic-modified SBA-15 supported W₁₀O₃₂^4-——W₁₀/AP-SBA(â…¡)still have one-dimensional hexagonal pore structure and large surface area.The catalyst W₁₀/AP-SBA(â…¡)was a good catalyst in oxidation of alkanes and alcohols.The catalyst whose support was functionalized by co-condensation method showed higher catalytic performance than that prepared by grafting in the same reaction condition.3.Aminopropyl and i-Butyl bi-functionalized SBA-15 was prepared by in-situ method.The catalyst,W₁₀O₃₂^4-was supported on this material by ion-exchanged method,denoted as W₁₀/AP-C₄-SBA(I).BET and TEM results showed that W₁₀/AP-C4-SBA(I)still have pore structure and large surface area but not the one-dimensional hexagonal structure of SBA-15.FT-IR and UV-vis investigation found that the structures of W₁₀O₃₂^4-had been preserved.The catalytic performance of W₁₀/AP-C4-SBA(I)was also investigated in ethylbenzene photooxidation. However,at the same condition,W₁₀/AP-C₄-SBA(I)gave the lowest activity in all of the three catalysts.The hydrophobic increased in the catalysis surface which led to the enhancing of the catalytic activity can't compensate the pore structure destroyed which resulted in the decreasing of the catalytic activity may be a main reason for this consequences.4.Aminopropyl and alkyl group(with different alkyl chain length)were successfully functionalized on SBA-15 by grafted method,and the decatungstate W₁₀O₃₂^4-was immobilized on the support triumphantly by ion-exchanged method. BET and TEM results showed that the catalysts W₁₀/AP-C_n-SBA still have one-dimensional hexagonal pore structure and large surface area.It was found that the structures of W₁₀O₃₂^4-had been preserved by FT-IR and UV-vis investigation.The catalyst W₁₀/AP-C₈-SBA showed the best catalytic performance among all the catalysts in ethylbenzene photooxidation at the same reaction condition.Then we extended our studies to various aryl alkanes' systems using W₁₀/AP-C₈-SBA as a catalyst.It was indicated that the photooxygenation of all alkylbenzenes proceeded efficiently.What's more,the catalyst W₁₀/AP-C₈-SBA can be reused for six times in photooxygenation of ethylbenzene;it demonstrated the catalysts possess high stability and reusability.