A novel ammonium based eutectic solvent for the treatment of free fatty acid and synthesis of biodiesel fuel

In this work, low grade crude palm oil (LGCPO) with high free fatty acids (FFA) content is introduced as a possible biodiesel production feedstock alternative. The pre-treatment of LGCPO was conducted using ammonium-based deep eutectic solvent which consisted of hydrogen bond donor (i.e. p-toluenesulfonic acid monohydrate) (PTSA) and salt (i.e. N,N-diethylenethanol ammonium chloride) as a novel recyclable catalyst (DEAC-DES). The DEAC-DES was used in different dosages to reduce the level of FFA to the acceptable limit for biodiesel production. The esterification reaction was carried out to evaluate the effect of varying reaction operating conditions on the reduction of FFA content. The FFA content of LGCPO was reduced from 9.5% to less than 1% using optimum conditions. Four recycling runs of the DEAC-DES were achieved. The conversion of PTSA to deep eutectic solvent improved the recyclability of the acid and the physical properties such as the elimination of acid hygroscopicity. The LGCPO biodiesel fulfilled the international standards. This study demonstrates a potential route for biodiesel production from abundance LGCPO using DEAC-DES and an alkaline catalyst.