The Combination of Calcium Oxide and Cu/ZrO2 Catalyst and their Selective Products for CO2 Hydrogenation

The catalytic activities of Cu/ZrO 2 _CaO catalysts were investigated on CO 2 hydrogenation. The CO 2 hydrogenations were carried out over combination of calcium oxide and Cu/ZrO 2 catalyst. Two calcination temperatures were chosen at 300 and 650 o C according to thermal decomposition results. The catalysts were characterized by means of N 2 adsorption-desorption, H 2 temperature programmed reduction and X-ray diffraction. The CO 2 hydrogenation under atmospheric pressure and at 250 o C was carried out over copper-based catalysts combined with calcium oxide namely i.e. Cu/ZrO 2 _CaO300, Cu/ZrO 2 _CaO650, Cu/ZrO 2 _Cu/CaO and Cu/ZrO 2 +CaO. The catalytic activities over all catalysts were consistent for 4 hours. The catalytic reaction rates over copper-based catalysts were in the range of 2.2 - 4.7 × 10 -4 μmol L -1 s -1 g cat -1 . The modification of calcium oxide can improve the catalytic activity of copper-based catalysts to 4.7 × 10-4 μmol L -1 s -1 g cat -1 . The calcination temperature can cause a difference in active species that impact on product selectivity. The CaO consisting in copper-based catalysts, i.e. Cu/ZrO 2 _CaO650, facilitate the growth of long chain hydrocarbon, whereas Cu/ZrO 2 _CaO300 favors the formation of carbon monoxide plausibly arising from reverse water gas shift reaction. Directly combined calcium oxide with Cu/ZrO 2 via physically mixing, i.e. Cu/ZrO 2 +CaO, can improve the rate of methanol production.