Catalytic Hydrodeoxygenation of Renewable Oils to Diesel-Range Hydrocarbons Using Ir-ReOx/SiO2 Catalyst

Hydrodeoxygenation (HDO) of renewable plant and waste
cooking oils to long-chain alkanes is a sustainable and promising
process for the production of carbon neutral diesel products. We found that an Ir-ReOx/SiO2 catalyst is effective for the HDO of such
oils for conversion to long-chain alkanes under
very mild conditions . Near
quantitative carbon yields (>80 wt%) in alkanes is obtained from various
renewable oils (palm oil, soybean oil, rapeseed oil, sunflower oil and
waste cooking oil) at 180 °C and 2 MPa H2. A reaction pathway for the HDO
of renewable oils is proposed. The first step is the hydrogenation of
C=C double bonds to form saturated triglycerides. Then the saturated
triglycerides undergo hydrogenolysis to form a mixture of esters, acids and
propane. The hydrogenation of the carboxylic group via aldehyde
produces a fatty alcohol, which undergoes a sequential direct hydrogenolysis to
long-chain alkanes with high carbon efficiency and selectivity over the Ir-ReOx/SiO2
catalyst. Partial decarbonylation of the aldehyde
intermediates to alkanes with a single carbon loss is also observed, but minimized.