The Optimization Of Cu-Mn Based Catalyst For DME Direct Synthesis And Kinetics

Success in the economical synthesis of dimethyl ether (DME) has a great significance for the diversification and purification of energy sources in our country. In contrast of conventional "two-step" DME synthesis process, direct synthesis of DME from syngas, which has an inherent advantage in technology and economy, comes to become the research topic recently. Based on the new Cu-Mn-Zn/Y bi-functional catalyst developed by our groups, the composition of catalyst is optimized as well as reaction conditions, and then the kinetics of direct DME synthesis over this well optimized catalyst is studied.In Chapter 2, the effect of the loading of metallic components, the content of Cu, and Mn on the catalytic performance of Cu-Mn-Zn/Y bi-functional catalyst in DME direct synthesis from syngas is studied. Under the condition that the loading of metallic components is 30 mmol/g-Y, the mole ratio of Cu/(Cu+Mn+Zn) is 0.6 and Mn/(Cu+Mn+Zn) equals to 0.3, the catalyst performs prominent activity. The results of X-ray diffractometry (XRD), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD) showed that the presence of the excess CuO phase in conjunction with the mixed oxide Cu_1+xMn_2-xO₄ and ZnMn₂O₄, which is conducive to the adsorption of CO, is responsible for higher catalytic activity.In Chapter 3, the effect of operating conditions (temperature, pressure, space velocity, and mole ratio of H2/CO) on the conversion of CO, selectivity to DME, yield of DME and product distribution is researched. CO conversion is up to 85% at 260℃ and 2.0 MPa, with a selectivity to DME of 67% and a yield of DME of 57%, for space velocity of 1500h_-1 and for a feed made up of H₂/CO=1.5.In Chapter 4, several kinetics models for DME direct synthesis based on the methanol synthesis model and methanol dehydration model via every reaction pathways are derived from literatures Experiment datas obtained from isothermal integral reactor, subsequently used for the estimation of the parameters in the proposed models. Combining a set of statistically significant and physicallymeaningful parameter groups, the best kinetics is as follows:pp+ 'cco1 ^co2 + (^//jPh2) 2\'-VIt accurately predicts the experimentally obtained results.