Methanol synthesis via hydrogenation of mixed CO/CO2 over Mn modified CU/ZNO/AL2O3 catalyst

Abstract

The purposes of this study are to investigate the methanol synthesis by using mixed CO/CO2 hydrogenation on Mn modified Cu/ZnO/Al2O3 catalyst which is prepared by the co-precipitation method and to investigate the overall energy consumption of methanol synthesis based on experimental results through the simulation process using Aspen Plus V.9. The improvement of catalytic activity is performed by a continuous fixed bed microreactor at 250°C under atmospheric pressure for 5 hours on the stream through hydrogenation of different feed composition of CO2/H2, CO/H2, and CO/CO2/H2, and 24000 ml/gcat∙h of GHSV. The physical and chemical properties of the catalysts are measured by various catalyst characterization techniques including N2 adsorption, CO-Chemisorption, SEM-EDX, ICP-MS, XRD, XPS, H2-TPR, NH3-TPD, and CO2-TPD. The experimental results indicate that CZA-Mn catalyst has better catalytic activity than CZA catalyst that can be observed from the increase of methanol space time yield that is corresponding with the results of catalyst characterization. Manganese added on the catalyst indicates that active sites have well-dispersion that help to increase the dissociation rate of hydrogen molecules and to improve spillover. Moreover, the addition of manganese on the catalyst not only facilitate the reduction of CuO, but also enhance the number of total basic sites and the strong adsorption of CO2 due to the shift of moderate basic site to strong basic site and increases the weak acid sites that help to improve the selectivity of methanol. For the overall energy consumption in methanol synthesis investigation, it is found that the amount of CO2 in the reactant is significant to the overall energy consumption and energy consumption of 1 mol-methanol synthesis. Thus, the results indicate CO/CO2/H2 feed with 1:1:2 composition can increase the energy consumption of 1 mol-methanol synthesis to 3.6 and 5.1 times of CO hydrogenation.