Heteropolyacid Incorporated Bifunctional Core-Shell Catalysts for Dimethyl Ether Synthesis from Carbon Dioxide/Syngas

Core-shell-type catalysts, which are synthesized by encapsulating the Cu-ZnO-Alumina type methanol synthesis catalyst (CZA) by silicotungstic acid (STA)-incorporated mesoporous alumina, were prepared following a hydrothermal route and tested in DME synthesis from syngas and CO2. Activity tests, which were performed in the pressure range of 30-50 bar, and the temperature range of 200-300 degrees C, with different feed compositions (CO2/CO/H-2: 50/-/50, 40/10/50, 25/25/50, 10/40/50) showed that the best-operating conditions for the highest DME yield were 275 degrees C and 50 bar. Results proved that the presence of CO2 in the syngas had a positive effect on the DME yield. The total conversion of CO + CO2 increased with an increase in CO2/CO ratio. An overall conversion of CO + CO2 and DME selectivity values were obtained as 65.6% and 73.2%, respectively, with a feed composition of H-2/CO2/CO = 50/40/10. Synthesis of methanol using the CZA catalyst from the CO2-containing gas mixtures was also investigated, and the total conversion of CO + CO2 and methanol selectivity values of 32.0% and 83.6%, respectively, were obtained with the H-2/CO2/CO = 50/40/10 gas mixture. Results proved that the new STA incorporated core-shell-type bifunctional catalysts were highly promising for the conversion of CO(2-)containing syngas to DME.