| Propylene oxide (PO) is a very important organic chemical material, and is one of the 35 most produced chemicals on the planet. As a result, whether the production technique route is good or not has a great impact on the world economy and environment. An ideal process of direct epoxidation of propylene in the presence of hydrogen and oxygen has been discovered. It has the advantages of simple process, no by-products, no pollution, cheap raw materials and so on. However, the industrialization of this process is one of the most challenging subjects in the field of catalysis. On the other hand, allyl alcohol is one of the rich downstream products of PO. The production of allyl alcohol through isomerization of PO over lithium phosphate catalyst is generally used in industry.In this thesis, we studied the two reactions of PO isomerization and propylene epoxidation over supported gold catalysts, respectively. First, we deposited nano-gold onto the surface of Li3PO4 to prepare Au/Li3PO4 catalyst and prepared a series of LI3PO4 at different pH to study their performance of PO isomerization. The results showed that the deposition of Au and the decrease of pH couldn’t change the crystal structure of Li3PO4. But the results of IR and CO2-TPD indicated that the surface of the Li3PO4 exists not only strong basic sites, but also weak basic site. Moreover, the deposition of Au strengthened the basicity of the strong basic site. From the analysis of reaction kinetics, we conclude that the formation of allyl alcohol on Li3PO4 needs the synergism of both basic site and acid site, but the formation of propanal needs only the acid site.Second, we deposited gold on the CTS-1 with different sizes which was prepared by classical method. We discovered that as the crystal size became large, the content of gold at the exterior surface of CTS-1 decreased, and the Au content in the micropores increased. When the size of the support> 900 nm, the gold efficiency and the stability of Au/CTS-1 were enhanced. The results of TG and HAADF showed that the main reason of deactivation is the agglomeration of gold nanoparticles at the exterior surface.Then we deposited gold on the TTS-1 which was prepared by two-step hydrolysis. This method could greatly reduce the usage of the extremely expensive template TPAOH, so that the cost of the preparation of the support could be cut down. After the gold deposition, we could obtain high gold efficiency (> 200 gOP·h-1·gAu-1 catalyst and high hydrogen efficiency (85%) catalyst when the gold content was low.At last we synthesized a support named as HTS-1 with hollow structure through dissolution-crystallization. The XRD and TEM results showed that the process changed the crystal form of TS-1 from monoclinic to orthorhombic, which represents the formation of S-l. However, no matter what the TPAOH concentration or the hydrothermal temperature is, all the samples of HTS-1 contain the extra-framework TiO2, which is disadvantage to the catalytic performance. Finally, we concluded that the HTS-1 support is not suitable for the Au-Ti catalyt system. |
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