Optimizing glycerol application for heterogeneous catalyst preparation and further use in biodiesel synthesis

JOANA MAIA DIAS; GABRIEL ORLANDO FERRERO; MARIA DA CONCEIÇÃO MACHADO ALVIM-FERRAZ; MANUEL FONSECA ALMEIDA

Rio de Janeiro

Congreso; 5th International Conference on Engineering for Waste and Biomass Valorisation; 2014

WasteEng

The majority of biodiesel today is produced by an homogeneous alkali-catalysed transesterification with methanol, which enables a relatively short reaction time but requires very good quality raw materials and alcohol to enable high product yield and quality in agreement with current standards [1]. In addition, the high catalyst consumption and the costly purification of biodiesel and glycerol have drawn to the need to develop heterogeneous catalysts for the transesterification reaction, which can be reused, more easily separated from the reaction mixture and enable a better quality of biodiesel and glycerol [2]. The heterogeneous catalysts developed so far still; however, present great limitations such as high temperature of reaction, high catalyst concentration, long reaction time and low yield of esters [3]. The possibility to use glycerol for catalyst preparation presents two major advantages: i) production of a more efficient and active catalyst; and ii) recycling glycerol, a by-product of the reaction, often with great management problems, due to the amounts produced by biodiesel industry (glycerol produced represents approximately 10 wt.% of the raw material). In the present work, a Ca-glyceroxide heterogeneous catalyst was prepared and used for the production of high quality biodiesel using soybean oil as raw material. The process was developed under ambient air conditions and the catalyst preparation conditions, considering the glycerol load on catalyst (40 ? 1000 mg) as well as the transesterification reaction parameters, focusing on catalyst concentration (0.2 ? 1 wt.% relative to oil weight) were optimized aiming to improve FAME yield and quality. All catalysts presented increased activity compared with CaO alone and the most active catalyst was produced using 160 mg of glycerol and 100 mg CaO (50 g of oil were used for the reaction). The optimized reaction conditions were very promising (0.4 wt.% catalyst, 14:1 methanol to oil molar ratio, 2 h, 333 K) with a very low optimized catalyst concentration. The obtained product presented very good quality (97 wt.% purity), fulfilling the selected key quality parameters according to EN 14214 (purity, acid value, water content and calcium content). The catalyst could be re-used during four cycles without loss of activity.