Tunable copper-hydrotalcite derived mixed oxides for sustainable ethanol condensation to n-butanol in liquid phase

• Published in: Journal of cleaner production 2019-02, Vol.209, p.1614-1623
• Main Authors: Benito, Patricia, Vaccari, Angelo, Antonetti, Claudia, Licursi, Domenico, Schiarioli, Nicola, Rodriguez-Castellón, Enrique, Raspolli Galletti, Anna Maria
• Format: Article
• Language: English
• Subjects: Alcohol coupling; Copper-hydrotalcite; Ethanol condensation; Guerbet reaction; n-Butanol
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2018.11.150

Improvement of processes starting from renewable feedstocks to produce chemicals and biofuels up to now derived from fossil carbon feedstocks is paramount to creating environmentally sustainable industrial processes. Guerbet condensation of ethanol to give n-butanol represents a turning point not only respect to the traditional petrochemical “oxo” process, but also to the bio-chemical path (Acetone Butanol Ethanol “ABE” process). In this work, different Cu/Mg/Al hydrotalcite-derived mixed oxides catalysts, with Cu atomic content in the range 7.6–1.0%, were synthetised, characterized, and tested for the Guerbet reaction. The adopted catalysts are easy to produce, and based on available, cheap and non-toxic metals. Tailoring Cu-content in hydrotalcite-derived Cu/Mg/Al mixed oxides allowed us to selectively address this reaction towards n-butanol formation, highlighting how a low Cu-content favours the condensation to n-butanol and higher alcohols, in particular n-hexanol, decreasing the ester formation. The Guerbet selective co-production of [n-butanol + n-hexanol] is economically even more attractive than that of the sole n-butanol, being both saleable products. Good catalytic performances to n-butanol and n-hexanol were achieved, in a batch process carried out under subcritical conditions. These catalysts have required a simple procedure of recovery, showing good recyclability, in term of catalytic performances to give the target products, thus opening the way to applicative perspectives. [Display omitted] •BuOH was synthesized by condensation of ethanol in liquid phase.•Different Cu/Mg/Al hydrotalcite-derived mixed oxides were employed as catalysts.•Tailoring Cu-content allows us to address the reaction toward BuOH formation.•Characterization of catalysts enables to establish structure-performance trends.•Conversion up to 32.0 mol % with selectivity to BuOH of 53 mol% were ascertained.