Carbon dioxide reduction to synthetic fuel on zirconia supported copper-based catalysts and gibbs free energy minimization: Methanol and dimethyl ether synthesis

Abstract

Thermodynamic equilibria of carbon dioxide recycling via CO2 hydrogenation were predicted by minimization of Gibbs free energy at given conditions, where all existing components were in the gaseous state, for comparison with experimental results obtained with zirconia supported copper-based catalysts. Carbon dioxide hydrogenated to synthetic fuel, i.e. methanol, was investigated at 10 bar and 150–400 °C. The CuZnZrO2 catalyst was highly selective towards methanol at low temperatures (up to 99% selectivity), offering the highest yield of 12.6 g CH3OH kg-catalyst−1 h−1. However, carbon monoxide was the product with higher selectivity at temperatures above > 210 °C. Physically mixing CuZnZrO2 with potassium-modified HZSM5 zeolite increased the CO2 conversion. The synergetic effect between potassium-modified HZSM5 zeolite improved the production of methanol which can be subsequently transformed into dimethyl ether. The bi-functional catalyst allowed the synthesis of valuable products at 50.3 g kg-catalyst−1 h−1 (CH3OH, dimethyl ether, and hydrocarbon), while mixing pure HZSM5 with CuZnZrO2 was inherently selective towards hydrocarbons (up to 80%) and allowed the synthesis of valuable products at 14.6 g kg-catalyst−1 h−1.