Low pressure conversion of CO2 to methanol over Cu/Zn/Al catalysts. The effect of Mg, Ca and Sr as basic promoters

Carbon dioxide concentration level is reaching a non-returning point. Carbon capture technologies are immature and short-term actions are necessary. The conversion of CO2 into methanol is a technical challenge. Commercial copper-zinc-alumina catalysts convert maximum 7% carbon dioxide in syngas at high pressures (5 MPa to 10 MPa) and moderate temperatures (473 K to 573 K) into methanol. However, there are not records on the synthesis of methanol at low pressure (P < 2.5 MPa) and without a large excess of hydrogen in the feed. Here, we tested three new catalysts prepared by co-precipitation of copper, zinc and aluminum nitrates (CZA), with strontium, magnesium or calcium as basic promoters to enhance CO2 conversion to methanol. We discussed the microstructure of the catalysts according to the supersaturation of the relative carbonates formed during the coprecipitation synthesis. Compared to the benchmark, the sample doped with Ca showed higher carbon conversion with all the feed compositions tested (syngas, synthetic biosyngas and CO2 with H-2). CZA doped with Sr is inactive in this reaction.