Glycerol valorization by etherification to polyglycerols by using metal oxides derived from MgFe hydrotalcites

• The MgFe hydrotalcites have been synthesized by coprecipitation method.
• The MgFeOx mixed oxides have been tested in the etherification of glycerol.
• The MgFeO4 shows the best catalytic performance.
• The maximum conversion achieved was of 41.1% after 24 h of reaction.
• The catalysts do not show lixiviation neither Fe nor Mg to the reaction media.

This work investigates the use of MgFe mixed oxides, derived from layered double hydroxides (LDH) with Mg/Fe molar ratio ranging from 1 to 4, as base catalysts for the etherification of glycerol. LDH precursors and catalysts were characterized by XRD, XPS, CO2-TPD, NH3-TPD, N2 adsorption and DTA–TG analysis. The MgFe mixed oxides exhibit excellent textural properties, with specific surface areas close to 200 m2 g−1 and average pore diameters in the mesoporous range. This family of catalysts has shown to be active in the formation of polyglycerols from glycerol without solvent, at 220 °C, in a batch reactor. The highest conversion (41%) is found for the MgFeO4 catalyst prepared with a Mg/Fe molar ratio of 4, whereas full selectivity to diglycerols is only reached for the MgFeO1 catalyst. Only diglycerols (DGs) and triglycerols (TGs) have been detected after 24 h of reaction.

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