Studies On Catalysts And Intrinsic Kinetics For Synthesis Of Dimethyl Ether From Carbon Dioxide Hydrogenation

Carbon dioxide, the richest carbon source in the world, is a greenhouse gas, which influences the global environment in a significant manner. Direct synthesis of methanol from CO₂ hydrogenation has been recognized as one of the most promising immobilization technologies for emitted CO₂. Although the catalytic performance of methanol synthesis catalysts has been recently improved, the conversion of CO₂ and the selectivity of methanol still maintains at low level due to the constrains of thermodynamic equilibrium. In consideration of the above-mentioned problems, some researchers paid their attentions to the downstream product of methanol, such as the synthesis of dimethyl ether (DME). Catalytic hydrogenation of the emitted CO₂ into DME is a new kind of synthetic technology, which not only can relieve the contamination of CO₂, but also can obtain the valuable chemicals and fuels—DME. This new synthetic technology will surely bring a remarkable environmental and economic efficiency, especially to those petrochemical plants producing a large number of by-products CO₂ and H2. More than 100,000 t high-purity CO₂ (purityï¹¥99%) was directly discharged into the air every year during the production of epoxyethane in Alkene Factory, Yangzi petrochemical company, Ltd., China. In order to relieve the contamination of CO₂, an extensive study concerning the catalysts and the kinetics for DME synthesis from the exhausted CO₂ had been carried out as a result of co-work between Nanjing university of technology and Yangzi petrochemical company, Ltd. from the year 2001 to 2004, and the works of this dissertation is the main of this project.The direct synthesis of DME from CO₂ was supposed to be composed of three reaction steps: methanol synthesis, methanol dehydration and reverse water gas shift (RWGS) reaction, it was necessary to discuss the effect of technological conditions on the chemical equilibrium of this complex reaction system from the viewpoint of thermodynamics. At the beginning of the dissertation, effects of reaction temperature, pressure, H2/CO₂ mole ratio and the added water vapor, CO and inert gas to the feed gas on chemical equilibrium were calculated respectively using Peng-Robinson state equation. It was found that decreasing reaction temperature and increasing pressure and H2/CO₂ molar ratio were favor of the equilibrium conversion of CO₂...