Electrocatalytic hydrogenation of soybean oil in a radial flow-through Raney nickel powder reactor

Abstract

Soybean oil has been hydrogenated electrocatalytically on Raney nickel powder catalyst at atmospheric pressure and moderate temperatures in a novel undivided packed bed radial flow-through reactor. The reactor consisted of a single anode/cathode tubular element, where Raney nickel catalyst powder was contained in the annular space between two concentric porous ceramic tubes and the flow of the reaction medium (a dispersion of oil in a water/t-butanol/tetraethylammonium p-toluenesulfonate electrolyte) was either in the inward or outward radial direction. The innovative design of this reactor allows for a thin nickel bed and a high anode/cathode interfacial area without the normal problems associated with electrolyte flow distribution. The total size of the reactor can be increased without changing the relative anode/cathode position and the electrolyte flow pattern by simply increasing the length and/or number of anode/cathode elements in a single common shell (similar to a shell-and-tube heat exchanger). For the brush hydrogenation of soybean oil, current efficiencies of 90–100% were achieved with a single element reactor when the electrolyte oil content was 10 or 25 wt/vol %, the apparent current density was 10 or 15 mA cm−2, the temperature was 75 °C, and the electrolyte flowed in the inward radial direction. The electrohydrogenated oil product was characterized by a high stearic acid content and low concentrations of linolenic acid and trans fatty acid isomers, as compared to the traditional high temperature chemical catalytic oil hydrogenation route with hydrogen gas.