The Combination of Calcium Oxide and Cu/ZrO<sub>2</sub> Catalyst and their Selective Products for CO<sub>2</sub> Hydrogenation
Keywords:Calcium oxide, copper-based catalyst, CO2 hydrogenation.
The catalytic activities of Cu/ZrO2_CaO catalysts were investigated on CO2 hydrogenation. The CO2 hydrogenations were carried out over combination of calcium oxide and Cu/ZrO2 catalyst. Two calcination temperatures were chosen at 300 and 650oC according to thermal decomposition results. The catalysts were characterized by means of N2 adsorption-desorption, H2 temperature programmed reduction and X-ray diffraction. The CO2 hydrogenation under atmospheric pressure and at 250oC was carried out over copper-based catalysts combined with calcium oxide namely i.e. Cu/ZrO2_CaO300, Cu/ZrO2_CaO650, Cu/ZrO2_Cu/CaO and Cu/ZrO2+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 21.8 – 47.4 μmol L-1 s-1 g cat-1. The modification of calcium oxide can improve the catalytic activity of copper-based catalysts to 47.4 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/ZrO2_CaO650, facilitate the growth of long chain hydrocarbon, whereas Cu/ZrO2_CaO300 favors the formation of carbon monoxide plausibly arising from reverse water gas shift reaction. Directly combined calcium oxide with Cu/ZrO2 via physically mixing, i.e. Cu/ZrO2+CaO, can improve the rate of methanol production.
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