Synthesis Of C₂₊ Oxygenates From CH₄ And Syngas By A Continuous Step-wise Reactor

From the perspective of energy-saving emission reduction, clean environment and the utilization of CH4-synthesis gas, the direct synthesis of C2+ oxygenates from the CH4 and synthesis gas is one of the most useful and worthy subject in the catalysis field. After a long period of research, our research group has developed a new technology by which CH4 and CO2 can be converted to acetic acid directly under mild conditions, passing the restrictions of thermodynamics. Then we has designed the fixed bed reaction device with a continuous, stepwise reactor; studied the catalytic system:Cu-Co bimetallc as the active component and TiO2 as catalyst carrier. On the basis of previous research, we studied the direct synthesis of C2+ oxygenates from the CH4 and synthesis gas by the lights of the new technology, and focused on the catalysts improvement to enhance the catalytic property in this dissertation. Cu-Co Catalysts were prepared by equivoluminal impregnation method. The activity of all the catalysts was evaluated in the fixed bed reaction device with a continuous, stepwise reactor. Then these catalysts were characterized by the techniques of XRD、NH3-TPD. H2-TPR and BET, binding their activity data and a variety of characterization results to analyse the catalyst performances. The main conclusions were as follows:(1) The suitable medium acidity and acid strength is beneficial to improving catalytic activity of the catalysts for the synthesis of C2+ oxygenate with CH4 and synthesis gas.(2) It is concluded that the interaction between the TiO2 and the active metal Co-Cu and the good dispersion of Co-Cu/TiO2 in the catalysts improve the catalytic activity.(3) The highly dispersed CuO fragmented crystallite particles is conducive to catalytic hydrogenation and dehydrogenation reaction, and plays an important role in promoting the conversion of CH4 and syngas.(4) On the Cu-Co bimetallic catalysts with various carriers, the order of C2+ oxygenates yield and selectivity is Cu-Co/TiO2> Cu-Co/Al2O3> Cu-Co/SiO2.(5) The catalyst sample impregnated first with Cu has the highest activity, the yield of C2+ oxygenate is 19.92 mg·gcat.-1-h-1 and the selectivity is 67.76%.(6) The impregnation sequence influences the acidity of the catalyst. The way impregnated first with Cu then Co is beneficial to the formation of medium acid and the medium acid is beneficial to the conversion of CH4 and syngas. Then that co-impregnated with Cu and Co is conducive to the formation of strong acid, but the strong acid restrains the conversion.(7) The impregnation sequence influences the existing state of Cu, The way impregnated first with Cu then Co is conducive to the formation of highly dispersed CuO fragmented crystallite particles or clusters.(8) The catalyst sample with 2:1 Cu/Co ratios and 18% Cu-Co contents has the highest activity, the yield of C2+ oxygenate is 19.92 mg-gcat.-1·h-1 and the selectivity is 67.76%.(9) Afer impregnated Cu and Co, the specific surface area, pore volume and the pore diameter are reduced. The smaller average pore size has the higher catalyst activity.