Synthesis of highly active carbon-encapsulated Ni2P catalysts by one-step pyrolysis–phosphidation for hydrodeoxygenation of phenolic compounds†

Abstract

Hydrodeoxygenation (HDO) of phenolic compounds is a promising technology to convert biomass materials to value-added chemicals and fuels. However, the development of highly efficient catalysts remains a great challenge. In this work, a facile one-step pyrolysis–phosphidation strategy for the synthesis of carbon-encapsulated nanostructured Ni₂P@C(x) catalysts (x is the initial mass ratio of NaH₂PO₂ to Ni-MOF-74) under a N₂ atmosphere from a metal–organic framework (Ni-MOF-74) was proposed and the prepared catalysts were used for HDO of phenol. The effects of different values of x and reaction conditions on the phenol HDO performance as well as product distribution were investigated. The results showed that as compared to the Ni@C catalyst (4.2%), the de-oxygenated product selectivity was enhanced 22.8 times by the introduction of the P species due to the promoted dehydration of cyclohexanol over Ni₂P@C(x) catalysts. Ni₂P@C(3) exhibited the best catalytic performance at the temperature of 250 °C, pressure of 2 MPa, and reaction time of 2 h; the conversion of phenol was 100%, and the total yield of deoxygenated products reached 100%. The HDO of phenol over the Ni₂P@C(x) catalyst mainly proceeded via the HYD pathway (hydrogenation of the aromatic ring to cyclohexanol, and dehydration of cyclohexanol to give rise to cyclohexene followed by hydrogenation to cyclohexane).