Efficient solvent-free hydrodeoxygenation of bio-lipids over bifunctional NiW catalyst: Manipulations of surface-active sites by thermal pretreatment

The effect of thermal pretreatment on the bifunctional NiW catalyst and its hydrodeoxygenation (HDO) performance on oleic acid were investigated. Increasing the calcination temperature (CT) not only led to the growth of NiW particles, but caused the migration of Ni to the surface that resulted in the segregation of W. The reduction temperature (RT) was also able to tune the catalyst surface composition. A lower RT (600 degrees C) led to a W-rich surface, while a higher one (700 degrees C) interestingly resulted in a Ni-rich surface. To this end, the ratio of surface-active sites, i.e., the partially reduced W species (W delta+) to Ni0 ones (W delta+/Ni0), was manipulated. The highest W delta+/Ni0 ratio of 2.6 was reached at the CT and RT of 550 degrees C and 700 degrees C, respectively, which contributed to an impressively high solvent-free deoxygenation of 95.1% at only 300 degrees C. The deoxygenation rate (rdeoxy.) was much higher than that of the reported non-precious catalysts, even comparable to the precious ones. Additionally, a high catalyst durability was found on non-acid feedstocks like triglycerides, long-chain alcohols, etc., but an acidic substrate like oleic acid tended to leach the loaded metals that eventually lessened the HDO activity.

Automated summary

The effect of thermal pretreatment on the bifunctional NiW catalyst and its hydrodeoxygenation (HDO) performance on oleic acid were studied. It was found that increasing the calcination temperature led to particle growth and segregation of W on the catalyst surface, while the reduction temperature could tune the catalyst surface composition. The highest W delta+/Ni0 ratio was achieved at 550 degrees C and 700 degrees C for CT and RT, respectively, resulting in an impressive deoxygenation rate of 95.1% at 300 degrees C. The catalyst showed higher activity than non-precious catalysts and even comparable to precious ones. However, the HDO activity was decreased when using an acidic substrate like oleic acid due to metal leaching.