Kinetics of hydroxide‐catalyzed methanolysis of crude sunflower oil for the production of fuel‐grade methyl esters

Methyl esters from crude sunflower oil were produced via methanolysis reaction using sodium hydroxide catalyst. Methanolysis was carried out at different agitation speeds (200–600 rpm), temperatures (25–60 °C), catalyst loadings (0.25–1.00% by weight of oil), and methanol:oil mole ratios (6:1–20:1). Mass‐transfer limitation was effectively minimized at agitation speeds of 400–600 rpm with no apparent lag period. Lowering the temperature resulted in a fall in the rate of reaction prolonging the reaction time necessary to achieve maximum production of methyl ester. Using 0.50% hydroxide catalyst was found to be adequate, resulting in 97–98% conversion without compromising recovery due to soap formation. Increasing the methanol:oil mole ratio beyond the usual amount of 6:1 tended to speed up the initial rate of methanolysis and was found to lower the bonded glycerol content, especially the amount of diglyceride in the sample. Kinetic rate constants were derived from experimental results using second‐order rate expressions, and values of activation energy for glyceride methanolysis have been established. Copyright © 2007 Society of Chemical Industry     

Membrane degumming of crude rice bran oil: Pilot plant study

The procedure for the classical chemical refining of vegetable oils consists of degumming, alkali neutralization, bleaching, and deodorization. Conventional refining of rice bran oil using alkali gives oil of acceptable quality, but the refining losses are very high. A critical work has been carried out to study the application of membrane technology in the pretreatment of crude rice bran oil. Oils intended for physical refining should have a low phosphorus content, and this is not readily achievable by the conventional acid/water degumming process. The application of membrane technology for the pretreatment of rice bran oil has been investigated. The process has already been successfully applied to other vegetable oils. Ceramic membranes, which are important from the commercial point of view, were examined for this purpose. The results showed that the membrane‐filtered oils met the requirements of physical refining, with a substantial reduction in color. It was observed that most of the waxy material was also rejected. Experiments were carried out to establish the relationship between permeate flux and rejection with membrane pore size, trans‐membrane pressure and micellar solute concentration.     

Deacidification of high-acid rice bran oil by reesterification with monoglyceride

Autocatalytic esterification of free fatty acids (FFA) in rice bran oil (RBO) containing high FFA (9.5 to 35.0% w/w) was examined at a high temperature (210°C) and under low pressure (10 mm Hg). The study was conducted to determine the effectiveness of monoglyceride in esterifying the FFA of RBO. The study showed that monoglycerides can reduce the FFA level of degummed, dewaxed, and bleached RBO to an acceptable level (0.5±0.10 to 3.5±0.19% w/w) depending on the FFA content of the crude oil. This allows RBO to be alkali refined, bleached, and deodorized or simply deodorized after monoglyceride treatment to obtain a good quality oil. The color of the refined oil is dependent upon the color of the crude oil used.     

Synthesis of biodiesel from sunflower oil with silica‐supported NaOH catalysts

BACKGROUND: A series of NaOH catalysts supported on commercial silica have been prepared by conventional incipient wetness impregnation and their activity tested in the reaction of transesterification of refined sunflower oil with methanol at 323 K and atmospheric pressure. The effects of the molar methanol/oil ratio, catalyst concentration, NaOH loading and calcination of the supported catalysts have been investigated. RESULTS: It has been found that the transesterification rate largely depends on the catalyst/methanol ratio and that calcination of the NaOH catalysts supported on silica, even at moderate temperatures, had a very negative effect on their activity. Selectivity, on the other hand, is more affected by the methanol/oil ratio. Selectivity for methyl esters (biodiesel) improved with the methanol/oil ratio due to an increased transesterification rate of diglycerides, whereas the selectivity for monoglycerides was not affected. CONCLUSION: The NaOH/silica catalysts suffered from a significant lack of chemical stability under reaction conditions as evidenced by measurements of sodium extracted during the reaction progress; therefore, their performance was affected by the presence of Na dissolved in the methanol phase. Copyright © 2008 Society of Chemical Industry     

Rapid equilibrium extraction of rice bran oil at ambient temperature

Rapid equilibrium extraction of soybean flour has been effective in obtaining an oil with reduced phospholipid content. This technique was examined to obtain a low phospholipid and low free fatty acid rice bran oil (RBO). The amount of RBO extracted with hexane from 1 g of rice bran at 22°C was measured over a 10-min period. The amount of oil extracted from variable amounts of bran with a fixed volume of solvent was also studied. Ninety percent of the oil was extracted in one minute, with 93% of the total RBO being extracted after ten minutes. This compares with the 98% yield obtained from soy flour, but increasing the amount of bran used did not reduce the extraction rate. This extraction method produced a good quality RBO with low phospholipid, low free fatty acid and low peroxide values.     

A novel process for physically refining rice bran oil through simultaneous degumming and dewaxing

A new process for the physical refining of rice bran oil through combined degumming and dewaxing was developed on a laboratory scale and then demonstrated on a commercial scale. The simultaneous degumming and dewaxing of the crude oil with a solution of water and CaCl₂, followed by crystallization at a low temperature (20°C), facilitated precipitation of the hydratable and nonhydratable phosphatides along with the wax, which enabled its separation and reduction to a greater extent. Bleaching and subsequent winterization (20°C) of this oil further reduced the phosphorus content to less than 5 ppm. Thus, these pretreatment steps enabled the physically refined rice bran oil to meet commercially acceptable levels for color, FFA content, and cloud point values (10–12 Lovibond units in a 1-in, cell, <0.25%, and 4–5°C, respectively) with very low neutral oil loss; this has not been observed hitherto. Rice bran oil is known for its high levels of bioactive phytochemicals, such as oryzanol, tocols, and sterols. The process reported here could retain more than 80% of these micronutrients in the end product. This paper was previously presented at the 95th AOCS Annual Meeting and Expo, Cincinnati, Ohio, May 9–12, 2004     

Enzyme‐assisted water‐extraction of oil and protein from rice bran

Enzymatic water‐extraction of oil and proteins from rice bran was studied in a laboratory‐scale set‐up. The effects of the following enzymes – Celluclast 1.5L, hemicellulase, Pectinex Ultra SP‐L, Viscozyme L, Alcalase 0.6L and papain – on oil and protein extraction yields, and the level of reducing sugars in the extract were investigated. The results showed that Alcalase was most effective in enhancing oil and protein extraction yields. Papain was found to be superior to all carbohydrase enzymes but it gave lower yields than Alcalase. Celluclast 1.5L, hemicellulase, Pectinex Ultra SP‐L and Viscozyme L did not affect yields significantly but increased the level of reducing sugars in the extract. © 2002 Society of Chemical Industry     

In situ esterification of rice bran oil with methanol and ethanol

In situ esterifications of high-acidity rice bran oil with methanol and ethanol and with sulfuric acid as catalyst were investigated. In the esterification with methanol, all free fatty acids (FFA) dissolved in methanol were interesterified within 15 min, and it was possible to obtain nearly pure methyl esters. The amount of methyl esters obtained from a given rice bran was dependent on the FFA content of the rice bran oil. In the esterification with ethanol, it was not possible to obtain pure esters as in methanol esterification, because the solubilities of oil components in ethanol were much higher than those in methanol.     

Extraction and purification of oryzanol from rice bran oil and rice bran oil soapstock

Oryzanol is an important value-added co-product of the rice and rice bran-refining processes. The beneficial effects of oryzanol on human health have generated global interest in developing facile methods for its separation from rice bran oil soapstock, a by-product of the chemical refining of rice bran oil. In this article we discuss the isolation of oryzanol and the effect that impurities have on its extraction and purification. Presented are the principles behind the extraction (solid-liquid or liquid-liquid extraction, and other methods) of these unit operations covered in selected patents. Methods other than extraction such as crystallization or precipitation-based or a combination of these unit operations also are reviewed. The problems encountered and the ways to solve them during oryzanol extraction, such as prior processing and compositional variation in soapstock, resistance to mass transfer, moisture content and the presence of surface active components, which cause emulsion formation, are examined. Engineering inputs required for solving problems such as saponification, increasing mass transfer area, and drying methods are emphasized. Based on an analysis of existing processes, those having potential to work in large-scale extraction processes are presented.     

Lipase‐mediated methanolysis of soybean oils for biodiesel production

BACKGROUND: Biodiesel is increasingly perceived as an important component of solutions to the important current issues of fossil fuel shortages and environmental pollution. Biocatalysis of soybean oils using soluble lipase offers an alternative approach to lipase‐catalyzed biodiesel production using immobilized enzyme or whole‐cell catalysis. The central composite design (CCD) of response surface methodology (RSM) was used here to evaluate the effects of enzyme concentration, temperature, molar ratio of methanol to oil and stirring rate on the yield of fatty methyl ester. RESULTS: Lipase NS81006 from a genetically modified Aspergillus oryzae was utilized as the catalyst for the transesterification of soybean oil for biodiesel production. The experimental data showed that enzyme concentration, molar ratio of methanol to oil and stirring rate had the most significant impact on the yield of fatty methyl ester; a quadratic polynomial equation was obtained for methyl ester yield by multiple regression analysis. The predicted biodiesel yield was 0.928 (w/w) under the optimal conditions and the subsequent verification experiments with biodiesel yield of 0.936 ± 0.014 (w/w) confirmed the validity of the predicted model. CONCLUSION: RSM and CCD were suitable techniques to optimize the transesterification of soybean oil for biodiesel production by soluble lipase NS81006. The related lipase NS81006 reuse stability, chemical or genetic modification, and transesterification mechanism should be taken into consideration. Copyright © 2007 Society of Chemical Industry     

Physical refining of rice bran oil in relation to degumming and dewaxing

Physical refining of rice bran oil (RBO) with acidity between 4.0 and 12.4% has been investigated in relation to degumming and dewaxing pretretments. It appears that physical refining after combined low-temperature (10°C) degumming-dewaxing produces good-quality RBO with respect to color, free fatty acid, oryzanol, and tocopherol content.     

新型生物柴油技术研究进展

综述了生物柴油的特性及生产方法,介绍了酯交换法制备生物柴油的反应机理及生产工艺,对各种工艺的优缺点进行了剖析,指出了生物柴油技术发展现在面临的问题及研究方向。     

Degumming rice bran oil using phospholipase‐A1

The efficacy of enzymatic degumming was assessed using the third generation phospholipase‐A₁, Lecitase®‐Ultra (EC 3.1.1.3) from Thermomyces lanuginosa/Fusarium oxysporum with different qualities of crude rice bran oil. The phosphorus content in the oil reduced to ～10 mg/kg from an initial level of 390 mg/kg after 2 h of incubation period at 50°C. However, in the solvent‐phase degumming, there was practically no phospholipid reduction at lower water content (2%) due to the poor contact between the highly nonpolar solvent and the aqueous phase (citric acid, NaOH, and enzyme solutions). Increasing the water content to 20% reduced the phosphorus level in the degummed‐oil to 71 mg/kg but did not match the performance of oil‐phase degumming. The degumming efficiency of Lecitase®‐Ultra was effective in oil‐phase and suitable for practical application. Solvent‐phase enzymatic degumming offers more benefits but needs greater efforts to overcome the challenges.     

Kinetics and mechanism of the KOH — catalyzed methanolysis of rapeseed oil for biodiesel production

The reaction of rapeseed oil with methanol catalyzed by KOH is described by a model consisting of two sequences of consecutive competitive reactions. The first sequence expresses the methanolysis of rapeseed oil to methyl esters (biodiesel) whereas the second sequence describes the always present side reaction‐saponification of glycerides and methyl esters by KOH. The proposed chemical model is described (after rational simplifications) by a system of differential kinetic equations which are solved numerically by two independent computing methods. The thus obtained theoretical kinetic and equilibrium results are compared numerically and/or graphically with the experimental parameters. The latter were obtained by the determination of the relevant components in the actual reaction mixture by analytical methods. According to the experimental results, the proposed reaction scheme is fulfilled with the probability of ca. 78%. The optimal average rate constants and equilibrium constants of individual reaction steps of the discussed scheme are introduced. The limitations of the proposed reaction model are discussed.     

FA monoalkylesters from rice bran oil by <Emphasis Type="Italic">in situ</Emphasis> esterification

Extraction and in situ esterification of rice bran oil with ethanol were investigated by studying the effects of rice bran oil FFA content and water content of ethanol. Ethyl ester formation in the ethanol phase increased as FFA content increased. Neutral oil solubility in this phase fell considerably, resulting in a high ethyl ester content. The decrease of the water content in ethanol led to an increase in neutral oil solubility in ethanol and promoted the equilibrium of reaction to ethyl-ester formation, resulting in lower FFA content of the product. The main factor that affected yield and monoester content when using high-acidity bran and various monohydroxy alcohols was the solubility of neutral oil in alcohol. The highest monoester content was obtained with methanol.     

Deacidifying rice bran oil by solvent extraction and membrane technology

Crude rice bran oil containing 16.5% free fatty acids (FFA) was deacidified by extracting with methanol. At the optimal ratio of 1.8:1 methanol/oil by weight, the concentration of FFA in the crude rice bran oil was reduced to 3.7%. A second extraction at 1:1 ratio reduced FFA in the oil to 0.33%. The FFA in the methanol extract was recovered by nanofiltration using commercial membranes. The DS-5 membrane from Osmonics/Desal and the BW-30 membrane from Dow/Film Tec gave average FFA rejection of 93–96% and an average flux of 41 L/m²·h (LMH) to concentrate the FFA from 4.69% to 20%. The permeate, containing 0.4–0.7% FFA, can be nanofiltered again to recover more FFA with flux of 67–75 LMH. Design estimates indicate a two-stage membrane system can recover 97.8% of the FFA and can result in a final retentate stream with 20% FFA or more and a permeate stream with negligible FFA (0.13%) that can be recycled for FFA extraction. The capital cost of the membrane plant would be about $48/kg oil processed/h and annual operating cost would be about $15/ton FFA recovered. The process has several advantages in that it does not require alkali for neutralization, no soapstock nor wastewater is produced, and effluent discharges are minimized.     

Use of rice bran oil and epoxidized rice bran oil in carbon black–filled natural rubber–polychloroprene blends

In the present study we report the results obtained on the use of rice bran oil (RBO), a naturally occurring nontoxic oil, and its epoxidized variety (epoxidized RBO, or ERBO) in the compounding and vulcanization of different natural rubber–chloroprene rubber (NR–CR) blends. The processability, cure characteristics, and physical properties of the blends prepared with these oils were compared with those of control mixes prepared with aromatic oil. The optimum cure time and scorch time values of the different blends prepared with these oils were found to be lower than those of the respective control blends prepared with aromatic oil. Evaluation of physical properties of the different experimental blends showed that replacement of aromatic oil with these oils did not adversely affect their physical properties. Because RBO contains a good amount of free fatty acids it was tried as a coactivator in addition to its role as a processing aid. The level of these oils required for the blend preparation was optimized in a Brabender plasticorder. Physical properties such as tensile strength, elongation at break, tear strength, swelling index, and abrasion loss, for example, were evaluated for both experimental and control mixes. Comparison of cure characteristics and physical properties of the blends prepared with aromatic oil and with these oils showed that these oils could be used in place of aromatic oil in the above blends. It is also to be noted that aromatic oil is of petroleum origin and is reported to be carcinogenic. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4084–4092, 2003     

离子液体催化大豆油制备生物柴油

制备了对水稳定性好、带—SO₃H官能团的咪唑丙烷磺酸硫酸氢盐离子液体，并以其作为催化剂进行了大豆油酯交换反应制备生物柴油的研究。考察了离子液体的用量、醇与油物质的量比、反应温度和反应时间对酯交换反应的影响及离子液体的稳定性。实验结果表明，在n(甲醇)∶n(大豆油) =12∶1、反应温度120 ℃、反应时间8 h和催化剂用量为原料油质量的4.0%条件下,产物中脂肪酸甲酯收率可达96.5%,且离子液体的稳定性好,可循环使用。