Synthesis of Nanostructured Carbon on Ni Deposited on Mesoporous Aluminum, and Titanium Oxides. Investigation of Biocatalytic Properties of Lipase Adsorbed on Carbon–Mineral Supports

Abstract

This work is a continuation of the studies devoted to the synthesis of nanostructured carbon (NSC) as a result of the pyrolysis of a mixture of H₂ + C₃–C₄ alkanes on supported Ni catalysts. Mesoporous alumina (γ-Al₂O₃) and titania (TiO₂), on which Ni(II) compounds are deposited by impregnation or homogeneous precipitation, are studied as carriers. Using the methods of thermogravimetric analysis and scanning electron microscopy, it is shown that the activity of Ni catalysts (carbon yield) and the morphology of synthesized NSC are largely determined by the chemical nature of the support. It is found that the synthesis of NSC in the form of carbon nanofibers with a pronounced filamentary structure proceeds only on a Ni catalyst supported on titanium dioxide. The mesoporous carbon–mineral supports obtained after catalytic pyrolysis were studied in the adsorptive immobilization of the enzyme such as Thermomyces lanuginosus lipase. The adsorption properties of the supports, as well as the enzymatic activity and stability of the prepared biocatalysts in the esterification of saturated fatty acids (capric, C10: 0) with aliphatic alcohols (isopentanol, C₅) in the non-aqueous media of organic solvents (hexane and diethyl ether) at ambient temperature, are studied. Biocatalysts prepared by lipase adsorption on NSC/TiO₂ show the maximum esterification activity of 100 EA/g, which is 20–45 times higher than the activity of lipase adsorbed on NSC/Al₂O₃.