Comparative Ethoxylation and Process Optimization of Palm Kernel Oil and Jatropha Oil Derivatives as Bio-Based Surfactants
Ojile Dale Ojo
Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria.
Ekpunobi Uche Eunice
Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria.
Okeke Abuchi Princewill *
Department of Chemistry, Shanahan University, Onitsha, Anambra State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Responding to the growing demand for sustainable industrial chemicals, research is advancing towards the sustainable supply of novel feedstocks for surfactant production. This study evaluated the ethoxylation and optimisation of Palm Kernel Oil (PKO) and Jatropha oil as bio-based feedstocks for bio-innocent surfactants. Both oils were processed to ensure low free fatty acid content (less than 0.25%) and low moisture content (less than 0.07%) for efficient chemical conversion. Fatty alcohols were prepared by transesterification and catalytic hydrogenation, followed by ethoxylation using ethylene oxide gas in a high-pressure autoclave. Three process variables, namely reaction temperature, catalyst concentration, and the ethylene oxide-to-oil molar ratio, were optimised using Response Surface Methodology (RSM) with a face-centred Central Composite Design (CCD). Yields of 94.2% for PKO and 91.8% for Jatropha were achieved under the optimum conditions of an EO:oil ratio of 11:1 (mol/mol), 0.8 wt% KOH catalyst, and a reaction temperature of 160°C. Successful ethoxylation was confirmed by FTIR spectroscopy through the hydroxyl (–OH) and ether (C–O–C) functional groups. The Hydrophilic-Lipophilic Balance (HLB) values of the synthesised surfactants were 11.0 and 10.8 for the PKO and Jatropha derivatives, respectively, classifying both as oil-in-water emulsifiers. Surface tension was 28 mN/m, comparable to that of petroleum-based nonylphenol ethoxylates. The surfactants also exhibited favourable green chemistry indicators, with E-factors of 0.08 and 0.11 kg/kg for the PKO and Jatropha derivatives, respectively. The results indicate that both PKO and Jatropha oil have potential as renewable feedstocks for the synthesis of high-performance, ecologically compatible surfactants for industrial formulations.
Keywords: Palm kernel oil, Jatropha oil, bio-based surfactants, fatty alcohol ethoxylation, nonionic surfactants, response surface methodology, central composite design, hydrophilic-lipophilic balance, critical micelle concentration, surface tension, green chemistry