Study On Direct Dehydrogenation Of C₃H₈ To C₃H₆ And H₂ By Microwave Catalysis And Its Microwave Catalyst Effect

In recent years,because the traditional process of producing propylene has faced problems such as lack of oil resources and limited co-production rations,the direct catalytic dehydrogenation of propane（C₃H₈）to value-added propylene（C₃H₆）has attracted much attention.Moreover,there is a large extent by the price difference between propane and propylene,which makes the process has become the fastest growing and most promising new technology.Direct dehydrogenation of propane to propylene is a strongly endothermic reaction(（?）₂₉₈=124 k J/mol)restricted by thermodynamic equilibrium.According to Le Chatelier,a high propane conversion depends largely on a high temperature of～550-700°C.Unfortunately,C-C bond is more reactive than C-H bond at high temperature,which will lead to unnecessary side reactions,and even result in coke deposition and sinter.Moreover,the costly Pt-based and detrimental Cr-based catalysts it uses also have the inevitable problems of carbon deposition and deactivation.In this paper,we develop a novel approach for direct propane dehydrogenation reaction under microwave catalytic reaction mode（MCRM）,and develop a series of high-efficiency microwave catalysts,and carrie out characterizations of the catalysts.The specific research content is as follows:（1）We investigated the direct dehydrogenation of C₃H₈ to C₃H₆ by microwave catalysis at low temperature（450°C）on Co-Sn/NC catalyst.We found the Co-Sn/NC microwave catalyst can efficiently catalyze the direct dehydrogenation of C₃H₈ to C₃H₆ in the MCRM.When the temperature is as low as 450°C,the C₃H₈ conversion and the C₃H₆ selectivity are 15%and 80%,respectively.Which greatly surpass the corresponding C₃H₈ conversion and C₃H₆ selectivity in the conventional reaction mode（CRM）.（2）We investigated the direct dehydrogenation of C₃H₈ to C₃H₆ on V/Si Beta+Si C mixed catalyst in the MCRM.Moreover,the comparison of the activity of V/H-Beta and V/Si Beta catalysts under the same conditions was also investigated.It is found that when the temperature is 550°C,the C₃H₈ conversion and the C₃H₆selectivity are 20%and 80%,respectively.Which greatly surpass the corresponding C₃H₈ conversion and C₃H₆ selectivity in the conventional reaction mode（CRM）.（3）We investigated the direct dehydrogenation of C₃H₈ to C₃H₆ on Co-Y/Si Beta+Si C mixed catalyst in the MCRM.It is found that when the temperature is 550°C,the C₃H₈ conversion and the C₃H₆ selectivity are 30%and 85%,respectively.Which greatly surpass the corresponding C₃H₈ conversion and C₃H₆ selectivity in the conventional reaction mode（CRM）.（4）Microwave irradiation has a selective effect.That is,the C₃H₆ selectivity under microwave catalytic reaction mode is higher than that under the conventional reaction mode,which displays a microwave selective catalytic effect.Moreover,microwave irradiation can reduce the apparent activation energy,which suggests a significant microwave direct catalytic effect.