Selective hydrodeoxygenation of acetone to propene via bifunctional metal-acid catalysis

• Gas-phase acetone-to-propene HDO by bifunctional metal-acid catalysis was investigated. • The process involves acetone hydrogenation to i-PrOH on metal sites, followed by i-PrOH dehydration to propene on acid sites. • Copper chromite paired with Cs 2.5 H 0.5 PW 12 O 40 (1:1 w/w) achieved a 92 % propene yield, surpassing previously reported catalysts. • During the HDO process, Cu(II) in CuCr is reduced to Cu(0), which serves as the active sites for hydrogenation. • The optimal molar ratio of Cu(0) to H + surface sites was determined to be Cu/H + = 5. This study investigated the hydrodeoxygenation (HDO) of acetone to produce propene at a gas-solid interface using bifunctional metal-acid catalysts. The catalysts included various copper compounds (such as copper chromite (CuCr), CuO, Cu/SiO 2 , Cu/TiO 2 and Cu/γ-Al 2 O 3 ) as the metal components along with tungstophosphoric heteropoly compounds (H 3 PW 12 O 40 (HPW) and Cs 2.5 H 0.5 PW 12 O 40 (CsPW)) and zeolites (HZSM-5, H-Mordenite and HY) as the acid components. These components were physically mixed to form bifunctional catalysts. The catalysts were characterised using BET, XRD, H 2 -TPR, DRIFTS and STEM-EDX. The HDO process involved the hydrogenation of acetone to isopropanol on metal sites, followed by dehydration to propene on acid sites. Catalyst activity decreased in the following order: CuCr > CuO, Cu/SiO 2 > Cu/TiO 2 , Cu/Al 2 O 3 and CsPW > HZSM-5 > HPW > HY, H-Mordenite. The combination of CuCr with CsPW (1:1 w/w) produced the best results, with 93% propene selectivity at 99% acetone conversion (92% propene yield) under mild conditions (180 °C and 1 bar pressure), surpassing previously reported catalysts. During the process, Cu(II) in CuCr was reduced to Cu(0), serving as the active sites for hydrogenation. At the optimal CuCr/CsPW ratio of 1:1 w/w, the molar ratio of Cu(0) to H + surface sites was estimated to be Cu/H + = 5 as a first-order estimate. This study demonstrated that Cu-based bifunctional metal-acid catalysis is promising for the selective HDO of ketones to alkenes.