| Maleic anhydride can be produced by the oxidation of benzene or butane. It is the third-largest anhydride in the world except phthalic anhydride and acetic anhydride. Lots of valuable chemical raw materials such as succinic anhydride、 γ-butyrolactone、 tetrahydrofuran and 1,4-butanediol can be produced by the selective hydrogenation of maleic anhydride. Up to now, lots of researches are focused on how to prepare a catalyst with high activity and selectivity to direct synthesize the product of maleic anhydride hydrogenation.The catalysts used in maleic anhydride hydrogenation include noble metal Pd, Pt and non-noble metal Cu and Ni based catalysts. The hydrogenation products varies with the hydrogenation condition and catalyst used. The morphology size, and electronic configuration of active component can make a significant impact on hydrogenation performance of catalysts. In the open study, the hydrogenation performance of catalysts are improved by altering preparation method and introducing addition agent. Little research was focused on investigating the effect of support. The reported research about the influence of support on the performance of catalyst in the hydrogenation of maleic anhydride have indicated that the support can affect the hydrogenation performance of catalyst by affecting the interaction between metal and support. But whether the support can affect performance of catalyst in the hydrogenation of maleic anhydride by interacting with the reactants and changing its adsorption state on the catalyst surface, haven’t reported yet.Based on the preliminary work of our research group about the study of TiO2-SiO2 mixed oxides supported Ni-based catalyst, N2 adsorption, XRD, H2-TPR, XPS and H2-TPD characterization methods were used to study the effect of support calcination temprature, polymorphs of TiO2 and catalysts reduction conditions on catalyst texture, surface properties and catalytic performance of Ni/TiO2 catalyst in hydrogenation of maleic anhydride.The main results and conclusions are as follows:1. The effect of support calcination temperature on the performance of Ni/TiO2 catalyst in hydrogenation of maleic anhydride is studied. With the increasing of TiO2 calcination temprature, the selective to y-butyrolactone first increased and then decreased. The highest selectivity to y-butyrolactone of 60.0% was obtained over Ni/TiO2 catalyst when the support was calcined at 720 ℃. The higher y-butyrolactone was ascribed to the formation of more high energy surface when the support calcination temprature was increased. Then, higher concentration of TiOx (x< 2) species and oxygen vacancies were obtained over Ni/TiO2 catalyst. The oxygen vacancies can promote the hydrogenation of C=O group by accepting lone pair of electrons of oxygen in C=O group. When the TiO2 calcination temprature is 810 ℃, anatase TiO2 transformed to rutile TiO2, and TiO2 support is difficult to be reduced and the selective of y-butyrolactone decrease.2. The effect of TiO2 polymorphs on the catalytic performance of Ni/TiO2 catalysts for hydrogenation reaction of maleic anhydride were investigated. The results of the study showed that the hydrogenation activity of C=O of catalyst with anatase TiO2 as support was significantly higher than that with rutile TiO2 as support. The higher activity of C=O hydrogenation can be attributed to a higher concentration of the oxygen vacancies produced during the reduction process. Oxygen vacancies could promote the hydrogenation of C=O group by accepting lone pair of electrons of oxygen in C=O group.3. The catalytic performance of Ni/TiO2 catalyst which is reduced directly without calcination was studied. The resault revealed that the TiO2 in the Ni/TiO2 catalyst reduced directly without calcination was easy to be reduced. Compared to the one that reduced after calcination, TiO2 in the Ni/TiO2 catalyst reduced directly without calcination can produce more oxygen vacancies which can promote the hydrogenation of C=O group. |
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