Optimization and kinetic study of ultrasonic assisted esterification process from rubber seed oil

Optimization and Purification of Terpenyl Flavor Esters Catalyzed by Black Cumin (Nigella sativa) Seedling Lipase in Organic Media

Geranyl butyrate and citronellyl butyrate esters are industrially important fruity flavors that are being used in food and as a fragrance in cosmetics. Previously terpenyl fruity flavors have been successfully synthesized in organic solvents using crude seedlings enzymes. The purpose of the current study was to standardize reaction parameters for the optimal synthesis of geranyl butyrate using the best chosen black cumin seedling lipase in an organic medium through direct esterification reactions. Geranyl butyrate and citronellyl butyrate esters were identified, quantified through gas chromatography, confirmed through GC-MS, and partiallypurified through the distillation process. Effect of organic solvents (acetonitrile, n-hexane, pentane, heptane, and toluene), alcohol and acid concentrations (0.125–0.3 M), temperature (20–50°C), incubation time (1–72 h), and enzyme concentrations (0.05–0.3 g) were studied on the synthesis of geranyl butyrate using black cumin seedling lipase. The highest conversion yields of ester (96%) were obtained when 0.25 M of geraniol and butyric acid were reacted at 37°C for 48 h in the presence of 0.25 g of crude seedling lipase enzyme in n-hexane. It was concluded that the germinated black cumin seedling lipase proved to be the best among the selected biocatalysts for the synthesis of geranyl butyrate in n-hexane.

Continuous Double-Step Esterification Production of Palm Fatty Acid Distillate Methyl Ester Using Ultrasonic Tubular Reactor

Double-step esterification to produce biodiesel from palm fatty acid distillate (PFAD) was performed by utilizing an ultrasound clamp reactor. Six pairs of ultrasonic clamps were attached to the left and right sides of the stainless-steel tube, and each pair was separated 100 mm apart from each other. Therefore, a total of 12 units of ultrasound clamps distributed 4800 W maximum power (12 × 400 W) throughout the continuous reactor by an ultrasonic generator. To optimize each step of the continuous esterification process for producing methyl ester from PFAD, a response surface methodology was used. The final 93.32 wt % methyl ester purity was attained under a double-step esterification process. For the first step, a 3.75:1 molar ratio of methanol to PFAD (46.4 vol % methanol), 6.6 vol % sulfuric acid, and 400 mm length of ultrasound clamp at 25 L/h PFAD flow rate for converting the PFAD to 60.24 wt % methyl ester were recommended. For the second step, the esterification was repeated under a molar ratio of methanol to the first esterified oil of 2.87:1 (61.6 vol % methanol), 5.6 vol % of sulfuric acid, and 400 mm length of ultrasound clamp at 25 L/h esterified oil flow rate. The ultrasonic clamp reactor achieved high yields of esterified oil and the crude biodiesel in a relatively short residence period of 32 s. To determine the product yields of a double-step esterification process, the maximum yields were 103.9 wt % first esterified oil, 107.6% crude biodiesel, and 98 wt % purified biodiesel when calculated on the basis of 100 vol % initial PFAD. The average energy consumed in the production of double-step esterification biodiesel was 0.05796 kWh/L. Therefore, this current approach has a high potential for producing biodiesel with less energy and requires less time to convert the PFAD to a high purity of methyl ester.

Biodiesel production enhanced by ultrasound-assisted esterification and transesterification of inedible olive oil

In the first phase of this study, inedible olive oil with different initial free fatty acid concentrations (2.5, 5.0, and 10.0%) was processed through acid-catalyzed esterification. Various heating methods were used for this purpose. The ultrasound-assisted esterification and traditional magnetic stirrer-assisted esterification methods were similar to each other in terms of their effects on free fatty acid reduction. However, the ultrasound reaction time was significantly shorter than that of the traditional magnetic stirrer. In the second phase of this study, biodiesel production was carried out through the ultrasound-assisted transesterification of inedible olive oil. Independent variables were, namely, ultrasound power level (30, 90, and 150 W), methanol/oil mole ratio (3, 9, and 15), catalyst concentration (0.5, 1.0, and 1.5%), ultrasound time (15, 30, and 45 min), and reaction temperature (45, 55, and 65 °C), which affected the yield indices and physicochemical constants of the produced biodiesel. The purest biodiesel (98.95%) and the highest amount of yield (92.69%) were observed when using an ultrasound power level of 90 W, a methanol/oil mole ratio of 9, a catalyst concentration of 1.0%, an ultrasound time of 30 min, and a reaction temperature of 55 °C. Optimizing the reaction conditions of the ultrasound operation can effectively increase the biodiesel yield (92.69%), while reducing the energy consumption (4.775 kWh/kg) and shortening the reaction time (30 min), compared to the traditional magnetic stirrer (77.28%, 2.17 kWh/kg, and 120 min, respectively). Therefore, ultrasound-assisted transesterification can serve as an effective alternative because of its fast and economic operation for making biodiesel out of inedible olive oil.

Continuous Ultrasound-Assisted Esterification and Transesterification of Palm Fatty Acid Distillate for Ethyl Ester Production

Ethyl ester production from palm fatty acid distillate (PFAD) with ethanol in the presence of sulfuric acid and potassium hydroxide was performed in a continuous three-step process using the ultrasound clamps and an ultrasonic probe. The ultimate goal was to produce biodiesel from the PFAD. In the first and second esterification steps, 16 units of a 400 W ultrasound clamp (20 kHz) were attached 100-m apart along each tubular reactor. In the third transesterification step, a 1000-W ultrasonic homogenizer (18 kHz) was used in a 100-mL continuous reactor. A composite central design of experiments and the response surface methodology (RSM) were used to develop predictive models and identify the optimal conditions of each step based on the purities of ethyl ester. The optimal conditions in the first step were 46.1 vol.% ethanol, 1.4 vol.% sulfuric acid, and purity 66.68 wt.% ethyl ester. In the second step, the optimized conditions were 57 vol.% ethanol, and 2.1 vol.% sulfuric acid, purity 95.32 wt.% ethyl ester. The final transesterification step was carried out with 14.6 vol.% ethanol and 3.9 gKOH L−1. As a result, a final ethyl ester purity of 98.15 wt.% was achieved in the biodiesel using the three-step process.

A novel charge derivatization-direct infusion mass spectrometry method for the quantitative analysis of C1-C8 fatty acids in rubber seed oil-based biodiesel

The free fatty acids that contain one to eight carbons (C₁-C₈) in biodiesel would affect the quality of biodiesel. It is still a matter of challenge to simultaneously determine the composition of C₁-C₈ fatty acids in seed oil and seed oil-based biodiesel. Herein, a novel method of charge derivatization coupling with direct infusion mass spectrometry (CD-DIMS) was developed for the determination of the C₁-C₈ fatty acids in biodiesels. A fixed-charge derivatization reagent, 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide (CMCT), was used to convert fatty acids into their cationic derivatives, which significantly improved the sensitivity and selectivity of detection. Good linearity was observed with the limits of detection (LODs) in the range of 0.0002-0.001 μg mL^-1 for the investigated fatty acids. The recovery was in the range of 85.1%-101.9% and the matrix effect was within the range of 75.5-93.2%. The developed method was carried out to analyze C₁-C₈ fatty acids in rubber seed oil (RSO) and RSO-based biodiesels produced by different catalysts, including NaOH, TiO₂, and carbodiimide. It was also applied to the dynamic monitoring of C₁-C₈ fatty acids in RSO and produced RSO biodiesels during the oxidation process. As results, formic acid, acetic acid, and propionic acid were detected in aged RSO and biodiesel samples. The contents of formic acid, acetic acid, and propionic acid all increased in aged RSO and biodiesels, but with different growth rates. These results demonstrated that the developed CD-DIMS method can provide a quick, accurate, and sensitive analysis of C₁-C₈ fatty acids in seed oil and biodiesel samples.

Effects of enzymatic free fatty acid reduction process on the composition and phytochemicals of rice bran oil

The effects of enzymatic free fatty acid reduction process (EFFARP) on the composition and phytochemicals of dewaxed and degummed rice bran oil (DDRBO) were investigated and compared with the effects observed using internal acyl acceptors. The acid value of DDRBO was effectively decreased from 16.99 mg KOH/g to approximately 0.36 mg KOH/g by EFFARP. EFFARP significantly decreased the moisture content and peroxide value of DDRBO and increased the induction period. The Sn-2 fatty acid comoposition of DDRBO after EFFARP was very reaching the total fatty acid composition. EFFARP significantly increased the triacylglycerol content compared to the control, while the oryzanol content was not obviously affected. The contents of free sterol, and total tocopherol and tocotrienol were increased slightly by EFFARP compared to the control. When conducted under vacuum with added nitrogen, EFFARP shows great application potential in the edible oil industry.

Esterification of Glycerol With Oleic Acid Over Hydrophobic Zirconia-Silica Acid Catalyst and Commercial Acid Catalyst: Optimization and Influence of Catalyst Acidity

Catalytic esterification of glycerol with oleic acid (OA) was optimized over hydrophobic mesoporous zirconia-silica heterogeneous acid catalyst (ZrO₂-SiO₂-Me&Et-PhSO₃H) and benchmarked with commercial catalysts (Aquivion and Amberlyst 15) in order to examine the effect of catalyst acidity on conversion, yield and product selectivity. The process optimisation results showed an 80% conversion with a 59.4% glycerol mono-oleate (GMO) and 34.6% glycerol dioleate (GDO) selectivities corresponding to a combined GMO and GDO selectivity of 94.8% at equimolar OA-to-glycerol ratio, 160°C reaction temperature, 5 wt% catalyst concentration with respect to the OA weight and 4 h reaction time. This work reveals that the hydrophobic and mild acidic ZrO₂-SiO₂-Me&Et-PhSO₃H catalyst outperformed Amberlyst 15 and Aquivion with a yield of 82% and GMO selectivity of 60%. It is found that catalyst acidity is a key parameter for catalytic activity and conversion rate. Nevertheless, high acidity/acid strength reduced the product yield in the glycerol esterification of OA.

Synthesis and Optimization of Methyl Laurate Using Sulfonated Pyrrolidonium Ionic Liquid as a Catalyst

Methyl laurate was synthesized from lauric acid and methanol using Brønsted acid ionic liquids as catalysts, by an esterification reaction. The efficiencies of four different catalysts, 1-methylimidazolium hydrogen sulfate ([Hmim]HSO4), 2-pyrrolidonium hydrogen sulfate ([Hnhp]HSO4), 1-(3-sulfonic acid) propyl-2-pyrrolidonium hydrogen sulfate ([C3SO3Hnhp]HSO4) and H2SO4 were compared. The effect of the methanol/lauric acid molar ratio, reaction temperature, reaction time, and catalyst dosage on the lauric acid conversion was investigated by single-factor experiments. On the basis of single-factor experiments, the esterification of lauric acid and methanol was optimized using response surface methodology (RSM) based on central composite design (CCD). The results showed that the most effective catalyst was the ionic liquid [C3SO3Hnhp]HSO4. The optimal conditions were as follows: [C3SO3Hnhp]HSO4 dosage of 10 % (based on the mass of lauric acid), methanol/lauric acid molar ratio of 9:1, reaction time of 1 h and reaction temperature of 70 °C. Under these conditions, the lauric acid conversion reached 95.33 %. The catalytic activity of [C3SO3Hnhp]HSO4 still remained high after 5 cycles.

Optimization and kinetic study of methyl laurate synthesis using ionic liquid [Hnmp]HSO4 as a catalyst

Methyl laurate was synthesized from lauric acid (LA) and methanol via an esterification reaction using ionic liquids (ILs) as catalysts. The efficiencies of three different catalysts, 1-methylimidazole hydrogen sulfate ([Hmim]HSO4), 1-methyl-2-pyrrolidonium hydrogen sulfate ([Hnmp]HSO4) and H2SO4, were compared. The effect of the methanol/LA molar ratio, reaction temperature, reaction time and catalyst dosage on the esterification rate of LA was investigated by single-factor experiments. Based on the single-factor experiments, the esterification of LA and methanol was optimized using response surface methodology. The results showed that the most effective catalyst was the IL [Hnmp]HSO4. The optimal conditions were as follows: [Hnmp]HSO4 dosage of 5.23%, methanol/LA molar ratio of 7.68 : 1, reaction time of 2.27 h and reaction temperature of 70°C. Under these conditions, the LA conversion of the esterification reached 98.58%. A kinetic study indicated that the esterification was a second-order reaction with an activation energy and a frequency factor of 68.45 kJ mol-1 and 1.9189 × 109 min-1, respectively. The catalytic activity of [Hnmp]HSO4 remained high after five cycles.

Lipase-catalyzed transesterification of epoxidized soybean oil to prepare epoxy methyl esters

Epoxidized soybean oil methyl esters could be efficiently prepared with the transesterification of epoxidized soybean oil (ESBO) with a lower dosage of methanol using lipase Novozym 435 as catalyst. The optimum parameters were as follows: the molar ratio of 5:1 (methanol to ESBO), 5% Novozym 435 as catalyst, at 45 °C for 14 h, with a stirring speed of 600rpm, under which the epoxidized soybean oil methyl esters (ESBOME) could be obtained at a 95.7% yield. During the enzymatic transesterification process, the oxirane oxygen values were kept unchangeable, which indicated that excellent functional group tolerance could be achieved under such mild reaction conditions. In addition, the recyclability of the immobilized enzyme Novozym 435 in this transesterification process was examined and the results showed that the biocatalyst could be reused ten times without losing any reaction activity or selectivity. And the final products of ESBOME were also identified by IR and NMR analysis. The kinetic data obtained followed the Ping-Pong Bi mechanism model (Vmax = 6.132 mol·L-1min-1, Km,S = 0,0001 mol·L-1, Km, A = 796.148 mol·L-1, Ki, A = 0,0004 mol·L-1) with competitive inhibition by methanol.