CARBON DIOXIDE CAPTURE AND HYDROGENATION TO METHANOL USING CU-BASED DUAL FUNCTIONAL MATERIALS

Abstract

The industrial revolution and energy demand have significantly increased greenhouse gas emissions, among them carbon dioxide (CO2), which is responsible for severe environmental concerns such as climate change. To this end, various CO2 mitigation systems have been investigated, with more research focused on integrating CO2 capture and its conversion into value-added products. Recently, dual functional materials (DFMs) that couple the co-existence of adsorbing material for CO2 capture and catalytic material for its conversion into valuable products has gained a great deal of attention. Moreover, it considers a cost-effective and promising eco-friendly solution with the utilization of renewable sources for energy needs such as solar energy. Several research works covering the progress in applying DFMs to produce methane and comparing it with conventional technologies are available in the literature. However, utilizing DFMs to synthesize methanol or higher hydrocarbons is very scarce. This study aims to develop novel DFMs (Cu/Na2O/Al2O3 and Cu/CaO/Al2O3) that couple different adsorbents properties, and active catalyst metal specie to capture and convert CO2 to methanol and other useful chemicals or fuels. The most promising DFM was promoted with Rhodium (Rh) to enhance its activity. The developed materials were prepared via incipient wetness impregnation method and characterized using BET, BJH, XRD, TEM, SEM, EDX, XPS, and H2-TPR analysis techniques. This research examines the adsorption capacity of the DFMs using a mass suspension balance (MSB) under fixed isothermal experimental conditions and different pressures. The experiment findings showed that the DFMs attained a CO2 uptake in the range of 65.4-111.2 mg/gDFM. The catalytic performances of the synthesized DFMs were investigated in a packed bed reactor testing the effects of adsorbent types and compositions, Cu compositions, and promoter on the catalytic activity of the materials. The DFMs exhibited good CO2 conversion (11%-27%) and methanol selectivity (12.7-30%). Rh-promoted DFM showed higher selectivity towards methanol (30%). Moreover, Rh-promoted DFM was further investigated continuously for about 120 hours under varied temperature, pressure, and space velocity conditions. The highest CO2 conversion and methanol yield were attained under operation conditions of 350 oC, 80 bars and 5000 h-1.