Valorization of biofuel industry sub products applying supercritical technology

A. VELEZ; MAYRA FALCO; PAULA SAPPIA; L. ROVETTO

Eindhoven

Simposio; 27th European Symposium on Applied Thermodynamics (ESAT 2014); 2014

Eindhoven University of Technology

Biodiesel is a promising alternative for transportation fuel. Its production increased rapidly over the last years becoming a major player at the current renewable energy scenario. The generation of biodiesel is based on trans-esterification of vegetable oils and fats through the addition of methanol (or other alcohols) and a catalyst, giving glycerol as the principle co-product (10% w/w) in the manufacturing process. As the biodiesel industry is rapidly expanding, a glut of crude glycerol is being created, not just dropping the market value of such product, but more important becoming a disposal problem with environmental impact for the main biodiesel producers [1]. While high purity glycerol is mainly used in food, pharmaceutical, or cosmetics industries, and its market has not been affected by the biodiesel production growth, the excessive generation of crude glycerol flooded the market rising up the need of new applications of this product. Overall, the effective utilization of glycerol will contribute to the viability of biodiesel production. Crude glycerol use, at industrial scale, is mainly restricted to combustion [1], although there are some attempts in using it for composting and animal-feeding. Converting crude glycerol into valued-added products (1,3-propanediol, dihydroxyacetone, ethanol, succinate etc.) through thermo-chemical or biological methods [2]  is an alternative that many researchers are focused on. However, the main drawback in applying those techniques is that the chemical composition of crude glycerol varies significantly with the production process and used feedstock to produce biodiesel; impurities in crude glycerol can greatly influence conversion, production rates and yields of glycerol into other products. Although there are many potential opportunities of using crude glycerol, and some promising results have been achieved [1], it is imperative to point out that there are still technical obstacles to overcome for developing practical processes to directly use crude glycerol from biodiesel production on a large scale. Crude glycerol obtained from biodiesel plants can vary its glycerol content from 62 to 76% (w/w), depending on the feedstock, is usually dark brown color with a high pH (11-12); the two major impurities contained in crude glycerol are methanol and free fatty acids (soaps), but there are also a variety of elements such as calcium, magnesium, phosphorous, or sulfur [3]. Because, traditional glycerol purification processes are expensive and composed by several stages depending on the feedstock [4], in this work the use of supercritical CO2 applied to glycerol purification is evaluated. For this purpose, equilibrium data of the system glycerol + FAME + methanol + scCO2 is obtained in a semibatch type stainless steel extractor using the dynamic method. The efficiency of the separation process is evaluated taking into account the influence of the composition of the mixture, temperature between 323 and 353 K and pressures up to 15 MPa.