A Study On Direct Synthesis Of Acetic Acid From CBM And CO₂ By Two-Step Reaction Sequence In The Way Of "Short Contact" And In The Presence Of Water

Activition and convertion of both coal-bed methane(CBM) and CO2 are one of the most challenging subjects in the field of catalysis now, which put resources, energy and environmentprotection in interity. This project made the synthesis of acetic acidfrom CH4 and CO2 in heterogeneous catalysts possible, through atwo-step reaction overcoming the thermodynamic limitations. Based on the previous work, this dissertation put forward "short contact" reaction way to strength the two-step reaction, which is realized by feeding diluting gas in the feed interval. And as to restrain the decomposion of acetic acid and improve the desorption of acetic acid, the way joining water steam to the reaction gases has been applied. Three kinds of CoPd/TiO2, CoPd/SiO2 and CuCo/TiO2 catalysts have been evaluated by a micro-reactor apparatus, characterized by means of XRD, FTIR, TEM, SEM and XPS techniques, related to their reactivity. Main conclusionsachieved are showed as following:(1) The "short contact" reaction can effectively restrain the formation of by-products and improve the selectivity to the aimed products in the two-step reaction convertion of CH4-CO2. And the "short contact" reaction applied to hydrogenation of CO2 or CO can also raise the formation rate and the selectivity of the aimed alcohol.(2) The way joining water steam to the reaction gases can increase the formation rate and selectivity of acetic acid and make the formation rate of acetic acid stable.(3) The best flow velocity of water is 0.4ml/min.(4) The formation of methanol is retrained to a large extent and the formation of ethanol and acetic acid are improved to a certain degree in the first step of the reaction with water.(5) The average activity of CoPd/TiO2 catalyst is highest, then CuCo/TiO2, and the activity of CoPd/SiO2 is the lowest in the three catalysts.(6) The best feed way of the three kinds of catalysts is all the way of CH4+H2+H2O/CO2+H2+H2O.(7) The characterization of FTIR demonstrates that the acetic acid species is adsorbed in the catalyst surface after reaction, especially the reaction with water.(8) Metal Cu is not the main factor for the formation of acetic acid, which mainly prompt the formation of methanol. Active metal Cu is oxygenated in the reaction with water, which prevents the hydrogenation of catalyst.(9) The metal on the support-TiO2 is even than the support-SiC^, in accordance to the reaction activity. In comparison to Cu and Co, Pd has more stronger interaction with support-TiO2.(10)The reunion of catalyst is restrained by water to a certain extent.