Influence of reaction conditions and kinetic analysis of the selective hydrogenation of oleic acid toward fatty alcohols on Ru-Sn-B/Al₂O₃ in the flow reactor

The hydrogenation of oleic acid (cis-9-octadecenoic acid) into oleyl alcohol (methyl-9-octadecen-1-ol) was studied in the presence of a bimetallic RuSn supported over alumina catalyst in the flow reactor. It was shown that the process should be performed at the temperature range of 280–330 °C, hydrogen pressure of 3.5–5.3 MPa and contact time less than 0.2 h in order to obtain the highest possible yield of desired products (fatty alcohols and waxes). The study by physicochemical methods (XRD, BET, TPR, XPS, TEM) revealed that modification of the catalyst with boron promotes additional simultaneous reduction of the major part of tin and ruthenium oxides, most of which are reduced below 310 °C. Crystalline Ru_xSn_y structures with variable composition, which seem to be the active component of the selective hydrogenation catalyst, were found to be formed after the reaction at temperatures higher than 300 °C. Our work demonstarted that a scheme of oleic acid transformations includes formation of waxes by recombination of carboxyl and alkanes intermediates, acid decarboxylation and hydrocracking of waxes to alkanes. Mathematic simulation methods allowed us to estimate rate constants of the process stages and the main kinetic parameters (Ea, k₀).