Studies On The Novel Catalysts In The Selective Oxidation Of C-5with H₂O₂

With the rapid development of petrochemical industry, the industry output of cyclopentadiene, the main composition of C5fraction, is also increasing. Cyclopentene (CPE) can be obtained by selective catalytic hydrogenation of cyclopentadiene. The comprehensive utilization of resource-rich and inexpensive CPE has industrial significance.There are a variety of reaction paths of the oxidation of CPE under different reaction conditions, and the main products are cyclopentene oxide (CPO), glutaraldehyde (GA) and glutaric acid (GAC). The strong oxidants, such as strong acid, peracetic acid and alkyl hydrogen peroxide, and the toxic solvents and catalyst are essential. Neither of these methods meets the development requirements of today’s green chemistry. The high price, complex process route and low atom utilization limit its industrial applications. The way of the gradual oxidation of CPE to CPO, GA and GAC with hydrogen peroxide solution is environment-friendly, and it will open up new way for the comprehensive utilization of CPE. There is still few studies on the step-by-step oxidation of CPE up till now. Therefore, the main purpose of this dissertation is to investigate and explore the new catalyst with high performance and stability in the gradual oxidation of CPE, and provide guidance for the comprehensive utilization of CPE.1. Investigation on the catalytic performance of MCM-41modified with phosphotungstic acid (HPA) in the selective epoxidation of CPEHPA was controllably immobilized on the external or internal surface of MCM-41by the inter-reaction between HPA and organoamino-groups which is selectively grafted on the external and internal surface of MCM-41. In the selective epoxidation of CPE, the homogeneous HPA catalysts show a high CPE conversion but a low CPO selectivity (0%). After immobilization, although the conversion is lower than that of HPA, the selectivity to CPO achieves100%. This also proves that the method of surface modification successfully anchored HPA on the surface of MCM-41and the obtained HPA-MCM-41catalyst does not contain bulk HPA. Affected by the mass transfer rate, the external surface modified catalyst shows a higher activity than the internal modification.2. Studies on the catalytic oxidation of GA from CPO with H2O2As homogeneous catalyst, tungstic acid was used to catalyze the oxidation of CPO to prepare GA, and the anion and cation of tungstic acid were altered to explore the unique catalytic activity of tungstic acid. The optimal reaction conditions were:35℃, n(W):n(CPO)=7%,76wt%aqueous hydrogen peroxide as oxidant, n(H2O2):n(CPO)=1.3, reaction time5min, solvent TBP7.5ml. The high CPO conversion of100%and GA selectivity of95%were obtained. The catalyst with various ions didn’t show as good performance an tungstic acid. Tungstic acid was loaded on the HMS to get the heterogeneous catalytic material. When the loading amount was10%, the highest conversion of99.6%was obtained and the highest selectivity of GA reached93.6%.Selective oxidation of CPO to GA over WS2also has been carried out with aqueous hydrogen peroxide. Both the conversion of CPO and the selectivity of GA over WS2are better than the use of WO3and WC catalyst. The green ultrasound method was used to load WS2on the HMS. The physic-chemical properties were characterized by SEM, TEM and XRD. The structures of WS2and HMS gives different change and there is a layer of WS2covered on the surface of HMS. While the loading amount is20%, the highest catalytic performance was obtained, and the GA selectivity increased to95.3%from73.5%of non-loaded WS2. The activity results can be comparable with homogeneous tungstic acid and supported tungsten oxide catalysts. In the stability test, the activity is not significantly reduced after four runs. The good performance of WS2/HMS is in relation to the coating structure.3. Excellent catalytic performance of graphite oxide in the selective oxidation of GA by aqueous hydrogen peroxide Selective oxidation of GA to GAC over graphite oxide (GO) catalyst has been carried out with aqueous hydrogen peroxide. In order to explore the properties of catalyst and the catalytic mechanism, the physico-chemical properties were characterized by SEM, TEM, XRD and XPS. Without any modification, GO was directly used to catalyze the oxidation of GA and showed a good performance which is comparable with tungstic acid. From the results of XPS and FTIR, we found that the surface functional groups of GO gave different change after treating with H2O2or KBH4. The catalytic activity has a slight increase when the GO was treated with50%aqueous H2O2solution and decreased evidently when the GO was treated with KBH4, which could be attributed to the increase of the amount of C-O and C=O after oxidation treatement or the decrease of the amount after reduction treatement. The oxygen-containing functional groups on graphite oxide surface play an important role in the catalytic process. The catalysts have also been used in the oxidation of glutaric acid reaction for the investigation of catalytic stability. And it is of significance to mention that GO shows excellent reusability in the reaction. After three cycles, the catalyst shows nearly the same catalytic activities (conversion of glutaraldehyde and selectivity to glutaric acid), suggesting that it’s a real heterogeneous carbon catalyst.