The Synthesis Of Higher Hydrocarbons Through Oxidative Bromination Of Propane

Propane has never been used effectively and always been used as fuels. While the energy resource is becoming short, the current way using the propane is not an efficient one. To improve the value of utilization of propane, converting it to the high value chemicals is of great scientific and practical importance. This is what we want to do in this paper. In this paper, we create a new process which includes two steps to convert propane to higher hydrocarbons:in the first step, the propane is converted to alkyl bromides through the bromination of propane, and in the second step, alkyl bromides are converted to higher hydrocarbons through the dehydrogen bromide reaction. By this method, propane could be efficiently and easily converted to higher hydrocarbons. This process could be taken in a mild condition and only consumes some oxygen, which is an energy-saving and environmental protection way.In this paper, the main work of our research is the first step—The synthesis of alkyl bromides through the bromination of propane. In our research, we used propane, oxygen and hydrogen bromide as reactants and chose the excellent catalyst for this reaction. Different catalysts were tested for the reaction, and we had found an effective catalyst which has good performance for high conversion of propane and the selectivity of alkyl bromides. Then, the effect of the calcined temperature of catalyst, the load of the metal on SiO2, and the reaction conditions such as reaction temperature, hydrogen bromide fluent and the flux ratio of propane to oxygen were investigated for the conversion of propane, selectivity of alkyl bromide, and the selectivity of CH4, CO and CO2. In these experiments, we got a good result while we used the 9%V/SiO2 as the catalyst. We could obtain the good conversion of propane and high yield of alkyl bromides (11.0% and 10.7%, respectively) at 310℃and the flow rate of C3H8, O2 and N2 was 18.0,4.0 and 5.0mL/min, respectively, and the flow rate of HBr was 4.0mL/h. In addition, we had done some research for the second step. We had investigated different ratio of Si/Al of HZSM-5 which supported ZnO as the catalyst and the different load of ZnO on the best Si/Al of HZSM-5 we had found. At last, we found the best one—6%ZnO/HZSM-5 (Si/Al=360), which performed a high catalytic function. On this catalyst, the conversion of alkyl bromides and the selectivity of aromatics was 100% and 75%, respectively, and the catalyst would never be inactive until it had reacted in 18.8 hours.The characteristics of the catalysts were also discussed on the results of BET, TPD, TG/DSC and XRD characterization. The catalytic factors and the reasons of inactivation of catalyst were discussed. What’s more, we designed some reactions to discuss the preliminary mechanism of oxidative bromination of propane. The result showed that it was a radical reaction, and it happened while Br was generated from O2 and HBr. And we could speculate that CO, CH4 and CO2 mainly came from the oxidation of alkyl bromide.