Kinetic study of fuel bio-additive synthesis from glycerol esterification with acetic acid over acid polymeric resin as catalyst

The increase of remnant of glycerol from biodiesel production results in the need to develop valorization strategies for this low-cost by-product. In this context, bio-additives synthesis from glycerol such as acetylglycerides has emerged as an economically viable alternative. In this work, a kinetic study of glycerol esterification with acetic acid over Dowex 650C ion exchange resin as catalyst to obtain fuel bio-additives was performed. The experimental study was carried out in a batch reactor at 353-393 K temperature range using acetic acid to glycerol molar ratio from 3:1 to 9:1 and catalyst loading between 4 and 8 wt%. Furthermore, different kinetic models based on the Langmuir-Hinshelwood-Hougen-Watson (LHHW), Eley-Rideal (ER) and Power Law (PL) approaches were proposed in order to correlate the experimental data. In addition, it was determined that the intraparticle and extraparticle mass and heat transfer resistances in the polymeric resin are negligible. The obtained results from kinetics modeling evidence that the best model to describe the studied reaction was the Eley-Rideal. In this model, it was considered that the catalytic surface reaction was the controlling reaction stage, which involves the reaction between adsorbed acetic acid and glycerol as well as mono- and diglycerides from the bulk liquid phase, generating the corresponding acylglycerides and water. Moreover, it was found that glycerol and water adsorption on the catalytic surface is stronger than that for acetic acid and acetylglycerides.