Sustainable heterogeneously catalyzed single-step and two-step amide derivatives of non-edible natural triglycerides as dual-functional diesel fuel additives

In the present study, the 2.5-Li@CaO-Ca(OH)₂-450 nanocatalyst (a mixture of Bronsted base Ca(OH)₂ and Lewis base CaO) of 30−50 nm size nanoparticles was prepared by a simple wet-chemical method and utilized as a heterogeneous solid catalyst for the one-step and two-step amidation of non-edible high free fatty acids containing triglycerides (TGR) such as waste cooking oil (CO), Karanja oil (KO) and jatropha oil (JO). The 2.5-Li@CaO-Ca(OH)₂-450 nanocatalyst took 45 min, 75 min, and 120 min for the complete one-step amidation (99 % yield) of CO, KO, and JO, respectively. In two-step amidation, the prepared nanocatalyst took 30 min and 45 min in the first step to prepare fatty acid methyl ester (FAME) and fatty acid ethyl ester (FAEE) from CO and then took 20 min and 30 min for complete amidation of FAME and FAEE. The first-order rate constants for the amidation of TGR, FAEE, and FAME were calculated as 0.10 min⁻¹, 0.151 min⁻¹, and 0.225 min⁻¹, respectively. The 2.5-Li@CaO-Ca(OH)₂-450 nanocatalyst was recycled and reused for ten reaction cycles for amidation and also found to complete amidation at room temperature (25−30 °C). The prepared amide derivative acted as a dual functional diesel fuel additive and found to improve the cetane number from 52.6 to 56.1 and lubricity from 460 to 247 μm of diesel fuel.