Increasing energy demand necessitates the production of sustainable fuels, which can be in the form of bio-fuels. One of such bio-fuels is biodiesel, which is typically produced via transesterification. The development of homogeneous catalyst that is relatively easy to synthesize, cheap, reusable, and environmentally friendly, is a major issue in transesterification reaction. The use of Deep eutectic solvent (DES) as catalyst, is believed to be a significant step in the direction of attaining a sustainable bio-economy. In this study, deep eutectic solvent was synthesized from different mole ratios of K2CO3/glycerol. The synthesized DES was used as catalyst in the transesterification reaction to produce biodiesel from Jatropha curcas oil. Box-Behnken design (BBD) was used to determine the factors that significantly affect the biodiesel yield. Optimum fatty acid methyl ester (FAME) yield of 98.2845% was achieved at optimum conditions of 1:32.58 mole ratio of K2CO3/glycerol, 8.96% w/w concentration of DES, and 69.58 minutes. GC-MS analysis revealed that the produced biodiesel contained 98.87% ester content. The properties of the biodiesel produced were characterized and found to agree with those of ASTM D6751-12 standard. Thus, suggesting the synthesized DES is a promising catalyst in the transesterification reaction to produce biodiesel from Jatropha curcas oil.

Deep eutectic solvent (DES) is used as a green solvent in science due to its benefits over ionic liquids, such as biocompatibility and biodegradability, chemical stability with water, ease of preparation, and non-toxicity.DES 1 was successfully synthesized in a 1:2 molar ratio of Tetrabutylammonium bromide (TBAB) and polyethylene glycol 400 (PEG 400), while the novel DES 2 and DES 3 were synthesized in a 1:6 molar ratio of TBAB/ dimethyl sulfoxide (DMSO), and TBAB/N,N-dimethyl formamide (DMF) respectively. The performance(s) of the three DESs in the enhancement of heavy Nigerian crude oil recovery at ambient temperature was investigated. DES 1 recovered additional 16.07 % oil from core flooding using Berea sandstone core sample, resulting in an overall recovery of 53.44 %. DES 1 also resulted in an incremental recovery of 35.94 % from Niger-Delta sandstone, with a high ultimate recovery of 85.94 %. The presence of DES 2 and DES 3 were also shown to result in additional oil recovery. A drastic IFT reduction from 5.19 to 2.46mN/m was observed between the oil and the DES2 phase. Thus the study confirms that the presence of TBAB-based DES promotes reduction in the viscosity of the heavy oil and results in more oil recovery. Keywords: Deep eutectic solvents (DES), enhanced oil recovery, interfacial tension, tetrabutylammoniumbromide (TBAB)