Transesterifications using a hydrocalumite synthesized from waste slag: an economical and ecological route for biofuel production

Abstract

Blast furnace slag (BFS), a high volume byproduct resulting from iron-making processes, was used as a low-cost and abundant precursor for preparing a hydrocalumite, and the thus prepared slag-made hydrocalumite and its derivatives were applied for transesterifications of esters including triglycerides. In the transesterification of n-ethyl butyrate, calcined samples provided higher catalytic activities than those of the as-synthesized hydrocalumite due to the interfusion of slag-derived impurity elements, such as Fe and Mn, which act as catalyst promoters. Furthermore, the catalyst calcined at 800 °C in air worked as an efficient catalyst for the transesterification of soybean oil with methanol, affording up to 97% yield of fatty acid methyl esters (FAME) after 6 h under relatively moderate reaction conditions (i.e., methanol/soybean oil = 12, reaction temperature = 60 °C, use of 1 wt% catalyst), and its catalytic performance was reproduced even after air-exposure for 1 day. It is believed that the slag-made hydrocalumite can replace existing solid base catalysts as a low-cost alternative for biodiesel production and potentially contribute to the sustainable chemical processes in an economical and ecological way.