Carbon-Supported Nickel Catalysts—Comparison in Alpha-Pinene Oxidation Activity

Abstract

In this work, carbon-supported nickel catalysts with different Ni content (1, 2.5, 5, 10, and 20 wt%) were tested in the oxidation of alpha-pinene in solvent-free reaction conditions. The process of catalyst preparation consisted of two stages. In the first stage, the activated carbon from spent coffee grounds was obtained. In the second stage, the active phase in the form of nickel compounds was applied using two methods: (1) the impregnation of the material with the nickel salt solution, and next reduction in H2, and (2) the hydrothermal method in the autoclave using the reductor and the reaction stabilizer. The obtained catalysts were subjected to the following instrumental studies: FT-IR, XRD, SEM, and N2 adsorption at −196 °C. The performed catalytic tests showed that the catalysts containing 5 wt% of Ni (porous material obtained by the impregnation method) and 1 wt% of Ni (porous material obtained by the hydrothermal method) were the most active in the oxidation of alpha-pinene, and the main oxidation products were alpha-pinene oxide, verbenol, and verbenone. Ultimately, the hydrothermal method of catalyst preparation turned out to be more advantageous because it allows one to obtain higher selectivities of the epoxide compound, probably due to the greater stability of this organic compound in pores.