Direct synthesis of dimethyl ether from CO2 hydrogenation over a highly active, selective and stable catalyst containing Cu-ZnO-Al2O3/Al-Zr(1:1)-SBA-15

Aluminum and zirconium doped SBA-15 (Al-Zr(1 : 1)-SBA-15) mesoporous catalysts were prepared by an in situ hydrothermal method and physically mixed (1 : 1 ratio) with the Cu-ZnO-Al2O3 (CZA) catalyst for direct DME synthesis from CO2 hydrogenation. The high metal incorporation in the SBA-15 (Si/M = 10; where M = Al + Zr) framework enhances the surface area and porosity. The other physiochemical properties and catalytic activity of the Al-Zr(1 : 1)-SBA-15 catalyst were analyzed by SAXS, WAXD, N-2 adsorption-desorption, TEM, SEM, EDX, XPS, CO2-TPD, NH3-TPD, FTIR, and ICP-OES. The optimum reaction conditions of DME synthesis from CO2 are as follows: 240 degrees C, 3 MPa pressure, H-2/CO2 = 3 and GHSV of 1500 mL g(cat)(-1) h(-1). The catalyst was found to be stable during a 100 h TOS study and the CO2 conversion and DME selectivity were only reduced to 19.06 from 22.5% and 69.56 from 73.07%, respectively, and the space time yield of DME (STYDME) achieved was 160.25 g(DME) h(-1) kg(cat)(-1). It was found that methanol dehydration to DME synthesis followed both the Langmuir-Hinshelwood and Eley-Rideal mechanisms. The pathway is solely dependent on the availability of acidic and basic sites on the catalyst surface.

Automated summary

Aluminum and zirconium doped SBA-15 catalysts were prepared and physically mixed with Cu-ZnO-Al2O3 catalyst for direct synthesis of DME from CO2. The incorporation of metals in SBA-15 framework enhanced surface area and porosity. The optimum reaction conditions for DME synthesis were determined. The catalyst showed good stability and high selectivity for DME production.