Single-step conversion of ethanol into n-butene-rich olefins over metal catalysts supported on ZrO2-SiO2 mixed oxides

With airlines committed to drastically reduce their carbon footprint by 2050, producing jet fuel from renewable ethanol is of particular interest. Recently, we reported on an Ag/ZrO2/SBA-16 catalyst that is very effective for directly converting ethanol into to n-butene-rich olefins jet fuel precursors (i.e., 88% at full conversion). Here, we report on a Cu/ZrO2/SBA-16 catalyst that presents remarkable olefins selectivity (i.e., 89% at 96% conversion) and enhanced stability as compared to Ag/ZrO2/SBA-16 catalyst. Under severe operating conditions a conversion loss < 10% was observed with the Cu/ZrO2/SBA-16 catalyst as compared to a 50% loss of conversion with the Ag/ZrO2/SBA-16 catalyst. Combined experimental and computational tools revealed that replacing Ag with Cu shifts the reaction pathway of crotonaldehyde hydrogenation from 1,3-butadiene (i.e., coke precursor) production to butyraldehyde formation. Experiments conducted with 4%Cu/4%ZrO2 supported on SBA-16, dealuminated zeolite Beta, and aluminum silicate revealed the performance and stability advantage of the SBA-16-supported catalyst.