Guerbet upgrading of ethanol to n-butanol using Ru(iii) catalysts under air

Mahitha, PM and Nakul, S and Kulkarni, NV and Jagirdar, BR and Jones, WD (2023) Guerbet upgrading of ethanol to n-butanol using Ru(iii) catalysts under air. In: New Journal of Chemistry, 47 (16). pp. 7470-7475.

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Abstract

A series of in situ prepared Ru(iii) complexes supported by easily accessible N-donor organic pincer ligands were used as catalysts in the Guerbet upgrading reaction of ethanol under aerobic conditions. Tridentate bis(benzimidazole) ligand systems containing amino-dimethyl (L1) and pyridine (L2) backbones were found to make more efficient catalyst systems as compared to the bidentate bis(benzimidazole) ligand systems containing phenyl (L3) and ethene (L4) backbones. Potassium t-butoxide was found to be the most compatible base for this catalyst system. Reaction with 0.1 mol% of the catalyst and 10 mol% of potassium t-butoxide yielded 27% of n-butanol at 71% selectivity (150 °C, 24 h). Increase in the catalyst or base loading mostly resulted in increased reactivity but selectivity towards the key product n-butanol was found to decrease. On the other hand, reducing the reaction period to 12 h resulted in slightly decreased reactivity but the reaction provides n-butanol with high selectivity (76%). Contrarily, increased reaction period resulted in enhanced conversion of ethanol to higher alcohols. Under moderate and aerobic reaction conditions, the catalytic system was found to efficiently upgrade ethanol to higher alcohols. The decrease in the catalytic activity of the system over time was speculated to be due to the gradual deactivation of the base upon reaction with water (by-product of the Guerbet reaction). Poor solubility of the catalytic system in aqueous solutions makes it unsuitable for direct Guerbet reaction of fermentation broth.

Item Type:	Journal Article
Publication:	New Journal of Chemistry
Publisher:	Royal Society of Chemistry
Additional Information:	The copyright for this article belongs to Royal Society of Chemistry.
Keywords:	Catalyst activity; Catalyst selectivity; Ethylene; Ligands; Potassium compounds; Ruthenium compounds, Bis(benzimidazole) ligand; Catalyst system; Catalytic system; Higher alcohols; Ligand system; N-butanol; Organics; Pincer ligands; Reaction period; ]+ catalyst, Ethanol
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	25 May 2023 07:54
Last Modified:	25 May 2023 07:54
URI:	https://eprints.iisc.ac.in/id/eprint/81520

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