Biodiesel Production from Castor oil by Two-Step Catalytic Transesterification: Optimization of the Process and Economic Assessment

Abstract

The use of biodiesel and the requirement of improving its production in a more efficient and sustainable way are becoming more and more important. In this research work, castor oil was demonstrated to be an alternative feedstock for obtaining biodiesel. The production of biodiesel was optimized by the use of a two-step process. In this process, methanol and KOH (as a catalyst) were added in each step, and the glycerol produced during the first stage was removed before the second reaction. The reaction conditions were optimized, considering catalyst concentration and methanol/oil molar ratio for both steps. A mathematical model was obtained to predict the final ester content of the biodiesel. Optimal conditions (0.08 mol·L −1 and 0.01 mol·L −1 as catalyst concentration, 5.25:1 and 3:1 as methanol/oil molar ratio for first and second step, respectively) were established, taking into account the biodiesel quality and an economic analysis. This type of process allowed cost saving, since the amounts of methanol and catalyst were significantly reduced. An estimation of the final manufacturing cost of biodiesel production was carried out.Biodiesel production from castor oil was studied in mixtures with soybean oil. Nevertheless, nonsignificant substrate preference was observed [9]. On the other hand, the use of co-solvents was an additional method for improving castor oil biodiesel yield [10]. In this case, hexane was used as a co-solvent and biodiesel yield was not significantly affected by the presence of this compound. A high alcohol/oil molar ratio, 20:1, was also necessary. The transesterification of castor oil using methanol was done with ultrasound; the highest ester content was 93.3% [11]. Solid catalysis was also tested in castor oil transesterification [12]. The catalyst was composed of Ag salts and 29:1 methanol/oil molar ratio, 60 • C, and a reaction time of 3 h were necessary to reach 90% biodiesel yield. As seen in previous works, the effort to enhance the results of the conventional method did not lead to completely satisfactory conclusions. The highest ester content, 97%, was obtained with homogeneous basic catalysis and conventional heating. However, 18.8:1 methanol/oil molar ratio was necessary [8].The transesterification is a reversible reaction. When enough catalyst is present in the reaction medium, chemical equilibrium is reached. Methanol is usually added in higher ratios than the stoichiometric ratio (3:1) in order to shift the equilibrium position of the reaction towards the product side. However, this fact strongly increases the final cost of the process due to the fact that methanol expenses are higher. Therefore, the optimization of the process is vital to reduce environmental impacts and costs [13]. In this research work, a process with two steps was proposed to obtain castor oil biodiesel with high methyl ester content and decrease costs. In this way, two reactions were carried out and, before the second one, the glycerol produced in the first reaction was removed. The removal of this produ...

Fatty Acid Methyl Esters from the Herbal Industry Wastes as a Potential Feedstock for Biodiesel Production

“…According to the literature data, among the vegetable oils and fats, the higher contents of SFAs were found in palm kernel oil (76.0%) and coconut oil (90.5%) with a dominant presence of C12:0 and C14:0 methyl esters, while lower in linseed oil (9.65%), sunflower oil (8.8%), and safflower oil (7.2%) [46]. The total content of C16:0 in analyzed herbal samples is higher than in castor [47], rapeseed, and sunflower oils [48].Presented findings are coherent with previous research on other plant species, where MUFAs were also athigher levels than SFAs (Figures 2-4). Interestingly, MUFA was the main part of FAME compositions in oils, such as sesame (42.0%), rice brain (44.0%), almond (67.9%), olive(68.2%), peanut (71.1%), and rapeseed (72.8%).…”

Production of fatty alcohols from non-edible oils by enzymatic cascade reactions

“…1 Here, especially castor oil takes a prominent position and is currently evaluated as starting material for ricinoleate-based biodiesels. 2,3 To the best of our knowledge, however, the methods of the state-of-the-art almost exclusively centre around the transesterication of castor oil or the esteri-cation of ricinoleic acid. All these methods share the intrinsic disadvantage of being reversible reactions thereby necessitating large molar surpluses of the alcohol to attain signicant conversion into the desired biodiesel fatty acid methyl ester (FAME) (Scheme 1).…”

Herbal Industry Wastes as Potential Materials for Biofuel Production

“…Among them, C16:0 and C18:1 are the most ideal components of biodiesel. The total content of C16:0 in analyzed samples is greater than in castor [12], rapeseed and sunflower oils [13] (Table 1). The results also showed that the unsaturated fatty acid amount was greater than that of saturated fatty acids.…”