Studying the Effect of Promotion with Copper on the Activity of the Ni/Al2O3 Catalyst in the Process of Ester Hydrotreatment

Resumo

A study is made of the effect of the composition of the active component of copper-doped nickel catalysts on their activity and selectivity in the hydrodeoxygenation (HDO) of model compounds of vegetable oils (esters) to remove oxygen atoms from them with the formation of alkanes. It is shown that the Ni/Al₂O₃ and Ni–Cu/Al₂O₃ catalysts are active in this process. With them, the hydrodeoxygenation of methyl ester of hexadecanoic acid mixed with ethyl ester of decanoic acid results in the formation of С₆−С₁₆ alkanes and oxygen-containing products, while methane and ethane can be found in the gas phase. When the Ni : Cu ratio in the catalysts is lowered, the conversion of esters and the capability of these catalysts for C–C bond hydrogenolysis are reduced. This means the introduction of copper can promote retention of the carbon skeleton of alkanes obtained as a result of hydrodeoxygenation, along with the amount of methane. According to X-ray diffraction data, introducing copper into the Ni/Al₂O₃ catalyst results in the formation of Ni_1 – xCu_x solid solutions. According to X-ray photoelectron spectroscopy data, lowering the content of copper in the Ni–Cu/Al₂O₃ catalyst raises the Ni : Cu ratio on a sample’s surface.