Interesterification of grease trap waste lipids using methyl acetate under supercritical conditions

Interesterification of Glyceryl Trioctanoate Catalyzed by Sulfonic Silica-Based Materials: Insight into the Role of Catalysts on the Reaction Mechanism

In the present work, the acid-catalyzed interesterification of glyceryl trioctanoate (GTO) with ethyl acetate was investigated as a model reaction for the one-step production of biofuel and its additives. The activity of heterogeneous acid catalysts, such as silica-based propyl-sulfonic ones, was evaluated. Propyl-sulfonic groups were grafted on both amorphous and mesoporous silica oxide (SBA-15, KIT-6) using different functionalization processes and characterized by N₂ adsorpion-desorption isotherm (BET), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and potentiometric titration. During the optimization of the reaction conditions with the most active catalyst (Am-Pr-SO₃H), it was shown that the addition of ethanol allowed a total conversion of GTO together with 89% and 56% yield of ethyl octanoate and triacetin, respectively. The catalytic performance is strictly correlated to the catalyst features, in terms of both the acid capacity and the porous structure. Moreover, the catalytic performance is also affected by a synergistic mechanism between silanols and Pr-SO₃H groups towards the 'silanolysis' of ethyl acetate. The overall results show that the presence of ethanol, the reaction time, and the amount of catalyst shifts the reaction towards the formation of the biofuel mixture composed by ethyl octanoate and triacetin.

Biodiesel Is Dead: Long Life to Advanced Biofuels—A Comprehensive Critical Review

Many countries are immersed in several strategies to reduce the carbon dioxide (CO2) emissions of internal combustion engines. One option is the substitution of these engines by electric and/or hydrogen engines. However, apart from the strategic and logistical difficulties associated with this change, the application of electric or hydrogen engines in heavy transport, e.g., trucks, shipping, and aircrafts, also presents technological difficulties in the short-medium term. In addition, the replacement of the current car fleet will take decades. This is why the use of biofuels is presented as the only viable alternative to diminishing CO2 emissions in the very near future. Nowadays, it is assumed that vegetable oils will be the main raw material for replacing fossil fuels in diesel engines. In this context, it has also been assumed that the reduction in the viscosity of straight vegetable oils (SVO) must be performed through a transesterification reaction with methanol in order to obtain the mixture of fatty acid methyl esters (FAMEs) that constitute biodiesel. Nevertheless, the complexity in the industrial production of this biofuel, mainly due to the costs of eliminating the glycerol produced, has caused a significant delay in the energy transition. For this reason, several advanced biofuels that avoid the glycerol production and exhibit similar properties to fossil diesel have been developed. In this way, “green diesels” have emerged as products of different processes, such as the cracking or pyrolysis of vegetable oil, as well as catalytic (hydro)cracking. In addition, some biodiesel-like biofuels, such as Gliperol (DMC-Biod) or Ecodiesel, as well as straight vegetable oils, in blends with plant-based sources with low viscosity have been described as renewable biofuels capable of performing in combustion ignition engines. After evaluating the research carried out in the last decades, it can be concluded that green diesel and biodiesel-like biofuels could constitute the main alternative to addressing the energy transition, although green diesel will be the principal option in aviation fuel.

Production of Biodiesel from Brown Grease

Among the renewable energy sources is biodiesel. This fuel is usually produced by catalytic transesterification of vegetable oils and animal fats under heating and pressure. Brown grease is a mixture of oils, fats, solids and detergents from food industry wastes that is captured in grease traps. Brown grease is classified as waste and must be treated and disposed of appropriately. It contains oils and fats that can be converted into biodiesel. However, the high concentration of free fatty acids in brown grease does not enable the use of conventional biodiesel production schemes. This study proposes a new scheme for biodiesel production from brown grease. In addition, conditions for the effective separation of a fat phase from brown grease were tested, and the composition of a fatty phase was determined for several grease traps. Esterification and transesterification of brown grease lipids were carried out with methanol, where the Lewis acids BF3 and AlCl3 were used as catalysts and the reaction was activated by ultrasound. The results show that biodiesel can be obtained from brown grease by esterification and transesterification within several minutes under ultrasonic activation at room temperature. These results open prospects for the development of efficient, low-cost and environmentally friendly biodiesel production.