Applications Of Microwave In Methane Conversion

For the abundant reserves of methane and the theoretical and actual importance of studies on conversion of which, we utilized microwave technique in the process of methane conversion and did some explorations on two aspects of microwave heating oxidative coupling of methane and atmospheric pressure microwave discharge in the thesis.During experiments we found a new catalyst of LiCl/SiCh which presented a unique reaction performance of oxidative coupling of methane under microwave heating mode, a large amount of acetylene was found in the products, and the selectivity of which could be higher than that of ethylene, while the major product of the same reactions under conventional electric furnace heating mode was ethylene. Furthermore, during experiments the highest total C2 yield of 15.1% could be obtained under microwave heating mode, which were much higher than that of conventional electric furnace heating mode (10.9%) at the same composition of feed gas and space velocity. Our researches were focus on this catalyst, and the microwave hot-spot effect was proved existed on the catalyst under microwave irradiation by means of mass spectra on-line, XRD, physical adsorption and high sensitive infrared pyrometer. As a result, it was brought forward that the microwave hot-spot effect on the catalyst was the main reason for the differences between microwave heating and conventional electric furnace heating oxidative coupling of methane reactions.Usually methane conversion under continuous microwave discharge was conducted at low pressure (<1atm). We designed an atmospheric pressure microwave discharge reactor, which could maintain a stable continuous microwave discharge under atmospheric pressure so that methane conversion could be conducted under atmospheric pressure microwave discharge. The process of methane conversions in this reactor was investigated. The results of experiments showed that the principalproducts of methane conversion under microwave discharge were acetylene when pure methane or methane and hydrogen mixtures were used as the feed gas. Hydrogen could suppress the coke formation during methane conversion and enhance methane conversion. The C2 hydrocarbons yield of 54.2% could be obtained, while with the presence of SiOa catalyst the C2 yield could reach 70.6%. The main product of methane conversion of microwave discharge was CO and H2 when methane and CO2 or methane and C>2 mixtures were used as the feed gas, the catalysts could enhanced the conversion of methane and CC>2. We gave some discussions about the process and mechanism of the reactions under atmospheric pressure microwave discharge when pure methane, methane and hydrogen mixtures, methane and CO2 mixtures, methane and 62 mixtures were used as feed gas respectively by means of mass spectra on-line. Furthermore, a new approach of atmospheric pressure microwave discharge enhanced chemical vapor deposition for synthesizing carbon nanotubes from methane was investigated preliminarily.