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Palm Oil-based Biodiesel Fuels
Published in Ozcan Konur, Biodiesel Fuels Based on Edible and Nonedible Feedstocks, Wastes, and Algae, 2021
Al-Zuhair et al. (2007) study the kinetic mechanism of the production of biodiesel from palm oil using lipase in a paper with 146 citations. The reaction took place in an n-hexane organic medium and the lipase used was from Mucor miehei. At a constant methanol concentration of 300 molm-3, they observed that initially, as the palm oil concentration increased, the reaction rate increased. However, the initial rate dropped sharply at substrate concentrations larger than 1,250 molm−3. They observed similar behavior for the methanol concentration effect, where, at a constant substrate concentration of 1,000 molm-3, the initial rate of reaction dropped at methanol concentrations larger than 3,000 molm−3. They adopted a ‘Ping Pong Bi mechanism’ with inhibition by both reactants and developed a mathematical model from a proposed kinetic mechanism and used it to identify the regions where the effect of inhibition by both substrates had arisen. The proposed model equation was essential for predicting the rate of the methanolysis of palm oil in a batch or a continuous reactor and for determining the optimal conditions for the biodiesel product.
Biofuel production from spent coffee grounds via lipase catalysis
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2018
Sanjib Kumar Karmee, Wian Swanepoel, Sanette Marx
In this study, conversion of spent coffee oil to biodiesel was done via lipase catalysis. All experiments were conducted in laboratory scale using a double-necked round-bottomed flask equipped with a condenser and heating cum stirring plate. Along this line, as an initial step, several lipases were screened for biodiesel production, namely lipases from Mucor miehei, Pseudomonas cepacia, Rhizopus delemar, Geotrichum candidum, Candida rugosa, Porcine pancreas-II, Pseudomonas fluorescence, and Candida antarctica lipase-B (Novozyme-435). The reactions were carried out by adding methanol (135 μl) to the reaction mixture according to the stoichiometry (1:3). The reactions were performed at a constant temperature (40ºC) for 6 h. The efficiency of each lipase as a biocatalyst in the transesterification of spent coffee oil conversion to biodiesel is accessed (Figure 2). The results reveal that Novozyme-435 delivered highest spent coffee oil-to-biodiesel conversion (48%), outperforming all other lipases that were used during screening experiments. Novozyme-435 was found to be an efficient catalyst for biodiesel production and used in all further experiments unless otherwise stated.
Improving the reusability of an immobilized lipase-ionic liquid system for biodiesel production
Published in Biofuels, 2019
Yusuf Abdi, Reem Shomal, Hanifa Taher, Sulaiman Al-Zuhair
Among the several lipases that were investigated in biodiesel production, immobilized lipase B from Candida antarctica, known as Novozyme®435, is the most commonly used. For the process to be economic, using the immobilized lipase repeatedly is a must. However, enzymes generally encounter activity losses. In biodiesel production, lipase is inhibited by excess methanol, which strips off essential water molecules from the enzyme's surface [9–13]. To minimize the effect of methanol inhibition, organic solvents, such as n-hexane, have been proposed. The addition of an organic solvent can also reduce the medium viscosity and hence enhance the mass transfer [14–18]. Without a suitable solvent, both the activity and the stability of immobilized enzyme would be reduced significantly, and therefore organic solvents such as n-hexane have been used in most work done on enzymatic biodiesel production. For example, it was reported that with n-hexane, the biodiesel production yield using Mucor miehei lipase increased by five-fold compared to a solvent free system under the same conditions [19]. Having said that, the use of these volatile organic solvents is not recommended, because they are toxic and require an additional solvent recovery unit. As an alternative, ionic liquids (ILs) are currently being proposed due to their negligible vapor pressure and tunable physical properties. The low vapor pressure of the ILs makes them safer than volatile organic solvents, and if the selected IL has a low product solubility, this would allow easy separation of the products. The main disadvantage of ILs is their high cost, compared to the conventional organic solvents, and therefore they are only feasible if they are repeatedly reused, while maintaining high stability of the immobilized enzyme. Most organic solvents are toxic and volatile, and require an additional recovery unit, which further increases the overall production cost [20–22]. Therefore, efforts have been recently devoted to finding alternatives, such as ILs, which are non-volatile and do not need a recovery unit, and at the same time could enhance the reusability of immobilized lipase.