The Clean And High-efficient Conversion Route Of Methane

With the development of the global economy, the requirements of energy and resources are increasing greatly. The shortage of hydrocarbons resources of coal and petroleum will inevitably hinder economic development. The technologies in the chemical industry have to be changed with the change of hydrocarbons resources structure. It is necessary to investigate new method for chemical conversion of hydrocarbons resources containing methane, which is very more abundant in nature.The indirect and direct method for conversion of methane was reported. Due to the properties of methane, high methane conversion and products selectivity can not be obtained at the same time, because there is a mutual restraint relationship between them. So far, the operative technology of methane direct conversion has not yet formed.At present, methane indirect conversion is an applied method. Methane conversion via syngas is a traditional indirect way. The method has suffer the disadvantages such as high consumption of energy, low hydrocarbons utilization rate, huge equipment investments. With the exhaustion of the coal and petroleum resources and low-carbon development concept gradually being accepted by the community. The disadvantages of syngas method attract much attention nowadays. So the clean and efficient alternative processes should be required.In order to clean and efficient converse methane into high value-added chemicals, the methane conversion method via photochemical brominating was improved in this thesis. Firstly, methane is conversed into bromomethane and dibromomethane via bromination reaction by photochemical method. Secondly, some valuable derivatives of bromomethane or dibromomethane can be prepared.The processes of methane converse into bromomethane and dibromomethane via photochemical brominating was studied in more detail. The results indicate that bromomethane and dibromomethane can be obtained with high selectivity through suitably controlling reaction conditions. It is found that diffusion rate of bromine, intensity of light source and reaction time are the main influencing factors of the process. Moreover, the matching regulation between the product distribution and characteristic wavelength of light source was explored. The products (bromomethane and dibromomethane) were synthesized with high selectivety (91.3%) and99%conversion based on bromine at the optimum conditions.The development of dibromomethane down-stream product was studied in detail. High concentration mehtanal solution was obtained using dibromomethane and hexanol as starting material by condensation and hydrolysis reaction. In the continuous hydrolytic equipment designed in the thesis, the reaction equilibrium can be moved by removing the hexanol produced in the hydrolysis reaction. The concentration of methanal solution reached to18.9%in the present of catalyst HZSM-5.The synthesis of dimethyl carbonate (DMC) from selective oxidation of dimethoxymethane (DMM) with dioxygen was investigated. The by-product is water in the reaction. Comparing to conventional synthesis of DMC, the synthesis process of DMC from selective oxidation of DMM is simple, high atom-economic and eco-friendly. The highest the DMM conversion(94.9%) and the DMC selectivity (86.2%) was obtained over the0.3g Cu-MCM41-2catalysts under2.0MPa O2pressure at160℃for2h in presence of the initiator NHPI(lmmol). In the five-time recycling operations, no deactivation was observed, which shown catalyst of Cu-MCM41-2is steady in the reaction system and is in favor of the large-scale production of DMC from DMM with dioxygen in chemical industry.In addition, the urea was synthesized through reaction between dibromomethane and ammonia, Modified polyphenylene oxide resin was obtained by the reaction between dibromomethane and benzenediol.The recycle of HBr was carried out by the method designed in the thesis. The advantages of the method are clean and relatively cheap oxidant, high recycle ratio and simple process.Through these studies suggest that the method of methane conversion via photochemical brominating was feasible and has a number of obvious advantages over the traditional method.