Development of Carbon–Silica Composite Materials and Their Studying and Testing for Preparing Heterogeneous Biocatalysts for the Low-Temperature Synthesis of Esters

• Published in: Kinetics and catalysis Vol. 64; no. 2; pp. 201 - 214
• Main Authors: Kovalenko, G. A., Perminova, L. V., Goidin, V. V., Zavorin, A. V., Moseenkov, S. I., Kuznetsov, V. L.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.04.2023; Springer Nature B.V
• Subjects: Biocatalysts; Butanol; Carbon; Catalysis; Chemical composition; Chemistry; Chemistry and Materials Science; Composite materials; Diameters; Enzyme activity; Esterification; Esters; Heat treatment; Low temperature; Moisture effects; Multi wall carbon nanotubes; Physical Chemistry; Silicon dioxide; Synthesis; Tetraethyl orthosilicate; Thermogravimetric analysis; X ray fluorescence analysis; lipase adsorption; multiwalled carbon nanotubes; biocatalysts; esterification; carbon–silica composit
• ISSN: 0023-1584; 1608-3210
• DOI: 10.1134/S0023158423020039

Carbon–silica composite materials (CSCMs) containing different amounts of silica and carbon components are obtained using two silica precursors (silica sol and silane) and multiwalled carbon nanotubes (MWNTs). At the initial stage of obtaining CSCMs by method 1, a fine MWNT powder is subjected to impregnation by moisture capacity with silica sol; in accordance with method 2, MWNTs are treated with tetraethoxysilane and then subjected to hydrolysis and polycondensation. The silica (SiO 2 ) content in the composites is varied in a range of 3–60 wt %. After drying and an appropriate heat treatment at 250–350°C, the composite materials are studied by various physicochemical methods, namely, nitrogen porosimetry, electron microscopy, X-ray fluorescence analysis, and thermogravimetric analysis. It is found that the parameters, including texrural characteristics, significantly differ depending on the chemical composition of the CSCMs. Thus, with an increase in the SiO 2 content, the specific surface area of the composite materials increases (by a factor of 2) and the pore diameter distribution curves exhibit maxima (at 20–40 nm). The composite materials are studied as adsorbing supports for preparing heterogeneous biocatalysts (BCs) for the low-temperature synthesis of esters, in which the active component is lipase immobilized exclusively on the carbon surface of the nanotubes. With a decrease in the MWNT content in the composite materials, the enzyme activity and operational stability of the BCs, which are measured in the esterification of heptanoic acid (С 7 ) with butanol (С 4 ), monotonically decrease; at the maximum SiO 2 content (58 wt %), the activity decreases by a factor of 2–8.