| Cyclohexene due to contain active C=C bond is widely used in various field of chemical industry, it is a kind of important chemical intermediates and raw materials,after the concept of the preparation of cyclohexene in benzene selective hydrogenation since 1934 has been come up for the first time, it has caused extensive concern of scholars from all over the world. compared to traditional production process, preparation of cyclohexene in benzene selective hydrogenation is not only low cost of the raw material, simple process and high economic value of by-products cyclohexane, but also reduces the energy consumption, environment friendly and energy efficient, so it is a very broad application prospect and production potential.But because of the limitation of thermodynamics, the generated cyclohexene will deeply hydrogenated to cyclohexane, so that the yield of cyclohexene is difficult to improve. The Asahi Japan had made the process industrialization and reached about40% of benzene conversion rate and about 80% of cyclohexene selectivity. Because of using the pure ruthenium catalyst in industrialization process, the price is high, the specific surface area is small and easy to sinter deactivation, on the contrary, the supported Ru catalysts performance is stable and the price is low. So how to prepared the supported catalyst which has high catalytic performance and better cyclohexene selectivity has very important significance. This topic mainly studies on the carrier of SBA-15, the preparation of hydrophilic Zr O2-SBA-15 carrier doped with hydrophilic Zr O2 and the preparation and optimization of supported Ru catalyst with La additives, along with the catalytic performance of the catalyst in benzene selective hydrogenation.Firstly, the work has been conducted in the preparation of mesoporous molecular sieve SBA-15 and conditions optimization. SBA-15 with the advantage of the larger specific surface area, uniform structure and narrow pore size distribution is widely used in catalytic hydrogenation process. SBA-15 has been prepared with P123 as the surfactant and TEOs as silicon source under acid condition after crystallization and roasting. By means of optimizing the preparation conditions of acid concentration,the mole ratio of surfactant and silicon source, crystallization time and crystallization temperature, synthetic SBA-15 has a relatively small specific surface area, large pore volume and pore diameter and highly ordered mesoporous structure, the catalyst of Ru-La supported on the SBA-15 by double solvent impregnation method has good catalytic effect in selective hydrogenation of benzene process.Secondly, the preparation conditions of Zr O2-SBA-15 carrier were optimized. Zr O2-SBA-15 that been prepared by hydrothermal synthesis method has low surface area and bigger pore diameter, this structure is helpful for benzene hydrogenation process.By means of the research of Zr O2 modifying content, crystallization time and crystallization temperature of the preparation conditions, ruthenium catalyst has better catalytic activity with the appropriate extended crystallization temperature and crystallization time under the condition of the lower amount of Zr O2. Combined with XRD, N2 physical adsorption, TEM, we found synthetic Zr O2-SBA-15 contained more tetragonal zirconia, thus it had more surface hydroxyl and hydrophilic enhancement, it made the generated cyclohexene strip from the catalyst surface more easily, thus Ru catalyst structure is more neat, the yield of cyclohexene also increased. Ru-La/Zr O2-SBA-15 catalyst prepared with Zr O2-SBA-15 optimal preparation condition can get 64.0% of benzene conversion, 63.9% of cyclohexene selectivity and 40.9% of the yield of cyclohexene.Finally, the influence of the active component Ru and the additive La and reaction conditions in benzene selective hydrogenation was performed. From the different loading amounts of Ru and La/Ru ratio, it can be seen that the yield of cyclohexene increases with the increase of La/Ru ratio, but more La content leads to lower yield of cyclohexene. We found through the results obtained under different reaction conditions: the reaction time, reaction temperature, stirring rate, hydrogen pressure etc. all have certain influence to the selective hydrogenation of benzene. |
PDF Full Text Request