Transesterification double step process modification for ethyl ester biodiesel production from vegetable and waste oils

In this study, the transesterification double step process (TDSP) was modified to enable the usage of ethanol as a transesterification agent in the production of biodiesel from vegetable and waste oils. The TDSP comprises a two-step transesterification procedure, which is initiated by a homogeneous basic catalysis step and followed by an acidic catalysis step. To optimize the transesterification parameters, different reaction mixtures and conditions were tested. Compared with methanol transesterification, larger ethanol and catalyst amounts as well as higher reaction times and temperatures were required. However, the results were consistent with those usually reported for ethanol transesterification. The obtained biodiesels (i.e., fatty acid ethyl esters (FAEEs)) were analyzed by standard physico-chemical techniques in addition to ¹H NMR, ¹³C NMR and FTIR spectroscopies, indicating high quality and purity biodiesel products. The obtained conversions were evaluated by ¹H NMR spectroscopy. For the optimized process, the triglyceride conversion to biodiesel was ?97% for all oils used. The overall process yields are considerably high when compared to the single basic catalysis yields.     

Biodiesel production from high FFA rubber seed oil

Currently, most of the biodiesel is produced from the refined/edible type oils using methanol and an alkaline catalyst. However, large amount of non-edible type oils and fats are available. The difficulty with alkaline-esterification of these oils is that they often contain large amounts of free fatty acids (FFA). These free fatty acids quickly react with the alkaline catalyst to produce soaps that inhibit the separation of the ester and glycerin. A two-step transesterification process is developed to convert the high FFA oils to its mono-esters. The first step, acid catalyzed esterification reduces the FFA content of the oil to less than 2%. The second step, alkaline catalyzed transesterification process converts the products of the first step to its mono-esters and glycerol. The major factors affect the conversion efficiency of the process such as molar ratio, amount of catalyst, reaction temperature and reaction duration is analyzed. The two-step esterification procedure converts rubber seed oil to its methyl esters. The viscosity of biodiesel oil is nearer to that of diesel and the calorific value is about 14% less than that of diesel. The important properties of biodiesel such as specific gravity, flash point, cloud point and pour point are found out and compared with that of diesel. This study supports the production of biodiesel from unrefined rubber seed oil as a viable alternative to the diesel fuel.     

A Transesterification Double Step Process — TDSP for biodiesel preparation from fatty acids triglycerides

This study introduces a two consecutive steps basic–acid transesterification process, (denominated Transesterification Double Step Process — TDSP) for biodiesel production from vegetable oils. The process involves homogeneous consecutive basic–acid catalysis steps and is characterized by formation of well-defined phases, easy separation procedures, high reaction velocity and high conversion efficiency. The proposed TDSP is different in relation to other traditional two-step procedures which normally include acid esterification followed by basic transesterification, or enzymatic or even supercritical transesterification conditions. The biodiesel (fatty acid methyl esters) was analyzed by standard biodiesel techniques in addition to ¹H-NMR, indicating high quality and purity biodiesel products. The transesterification of sunflower and linseed oils resulted in oil conversions higher than 97% corresponding to yields of 85%. A probable reaction mechanism responsible for the process is presented.     

利用菜籽油脱臭馏出物制备生物柴油新工艺

以菜籽油脱臭馏出物为原料,首先以D002阳离子交换树脂作催化剂,进行酯化反应,降低原料酸值;然后以氢氧化钾作催化剂进行醇解反应来制备生物柴油的二步法新工艺路线。结果表明:D002阳离子交换树脂具有很强的催化活性,游离脂肪酸最高转化率达97.7%,连续使用4次后,催化活性仍然很高,达96%以上;碱催化过程中甘油酯的最高转化率达97.4%。产品品质大都符合美国ASTMD6751-03生物柴油标准。由此可见,先用树脂催化处理高酸值废油,然后进行碱催化制备生物柴油二步法工艺是一种切实可行的方法。     

Production of ethyl ester from crude palm oil by two-step reaction with a microwave system

The production of ethyl esters of fatty acids from a feed material of crude palm oil (CPO) with a high free fatty acid (FFA) content under microwave assistance has been investigated. Parametric studies have been carried out to investigate the optimum conditions for the esterification process (amount of ethanol, amount of catalyst, reaction time, and microwave power). As a result, a molar ratio of FFA to ethanol of 1:24 with 4% wt./wt. of H₂SO₄/FFA, a microwave power of 70 W, and a reaction time of 60 min have been identified as optimum reaction parameters for the esterification process aided by microwave heating. At the end of the esterification process, the amount of FFA had been reduced from 7.5 wt.% to less than 2 wt.%. Similar results were obtained following conventional heating at 70 °C, but only after a reaction time of 240 min. Transesterification of the esterified palm oil has been accomplished with a molar ratio of CPO to ethanol of 1:4, 1.5 wt.% KOH as a catalyst, a microwave power of 70 W, and a reaction time of 5 min. This two-step esterification and transesterification process provided a yield of 80 wt.% with an ester content of 97.4 wt.%. The final ethyl ester product met with the specifications stipulated by ASTM D6751-02.     

Reduction of high content of free fatty acid in sludge palm oil via acid catalyst for biodiesel production

In this study, sulphuric acid (H₂SO₄) was used in the pretreatment of sludge palm oil for biodiesel production by an esterification process, followed by the basic catalyzed transesterification process. The purpose of the pretreatment process was to reduce the free fatty acids (FFA) content from high content FFA (> 23%) of sludge palm oil (SPO) to a minimum level for biodiesel production (> 2%). An acid catalyzed esterification process was carried out to evaluate the low content of FFA in the treated SPO with the effects of other parameters such as molar ratio of methanol to SPO (6:1-14:1), temperature (40-80 °C), reaction time (30-120 min) and stirrer speed (200-800 rpm). The results showed that the FFA of SPO was reduced from 23.2% to less than 2% FFA using 0.75% wt/wt of sulphuric acid with the molar ratio of methanol to oil of 8:1 for 60 min reaction time at 60 °C. The results on the transesterification with esterified SPO showed that the yield (ester) of biodiesel was 83.72% with the process conditions of molar ratio of methanol to SPO 10:1, reaction temperature 60 °C, reaction time 60 min, stirrer speed 400 rpm and KOH 1% (wt/wt). The biodiesel produced from the SPO was favorable as compared to the EN 14214 and ASTM D 6751 standard.     

Optimization of biodiesel production from edible and non-edible vegetable oils

The non-edible vegetable oils such as Jatropha curcas and Pongamia glabra (karanja) and edible oils such as corn and canola were found to be good viable sources for producing biodiesel. Biodiesel production from different edible and non-edible vegetable oils was compared in order to optimize the biodiesel production process. The analysis of different oil properties, fuel properties and process parameter optimization of non-edible and edible vegetable oils were investigated in detail. A two-step and single-step transesterification process was used to produce biodiesel from high free fatty acid (FFA) non-edible oils and edible vegetable oils, respectively. This process gives yields of about 90-95% for J. curcas, 80-85% for P. glabra, 80-95% for canola, and 85-96% for corn using potassium hydroxide (KOH) as a catalyst. The fuel properties of biodiesel produced were compared with ASTM standards for biodiesel.     

Optimization of Two-Step Biodiesel Production from Beef Tallow with Microwave Heating

Animal fats are by-products from slaughterhouses that may be utilized as renewable energy source. This study was about biodiesel production from high free fatty acid beef tallow waste using two-step process with microwave heating. Sulfuric acid and NaOH were used as catalysts with methanol for the first esterification and second transesterification step, respectively. Catalyst loadings were between 0.25% and 2.5%, with applied microwave power of 340?W, operation time of 10–50?min, and oil-to-methanol molar ratio between 1:3 and 1:15. These process parameters were optimized using the design of experiments. The yields and properties of the biodiesel were assessed. The results indicated that the two-step process were successful in converting the beef tallow to biodiesel. Statistical analysis of the results showed that significant contributions were from the linear and quadratic terms of these three variables. The optimum conditions for esterification and transesterification were reported. Validity of the predicted models was confirmed by the experimental verification.     

Kinetic model for the esterification of free fatty acids from palm oil with methanol using sulfuric acid as catalyst and sensitivity analysis in tubular reactors

Industrial biodiesel production from crude palm oil (CPO) by homogeneous transesterification requires some conditioning stages. One is deodorization, where free fatty acids (FFA) are stripped out from the CPO. The FFA from the deodorizer is esterified using a homogeneous acid catalyst to produce more biodiesel and improve process profitability. This work studied the sulfuric acid-catalyzed esterification of FFA with methanol. The factors evaluated were temperature (between 40 and 60°C) and catalyst concentration (between 0.15 and 1.5 wt% based on the mixture). The parameters of a reversible second-order kinetic model were adjusted from experimental data using a genetic algorithm. The kinetic model, which adequately represents the esterification reaction, according to the Fisher–Snedecor test, was used to perform a sensitivity analysis in isothermal, adiabatic, and non-isolated continuous tubular esterification reactors using ASPEN HYSYS V10. The results showed that the highest conversion (~96%) was predicted using an isothermal reactor. However, its installation and operational costs could also be the highest. An adiabatic reactor was preferred, which optimal conversion of 94.5% was predicted at temperature, catalyst concentration, residence time, and methanol-to-FFA molar ratio of 140°C, 0.3 wt%, 47 min, and 6.7, respectively, its predicted operational cost was 0.63 dollars per biodiesel kilogram. Therefore, the adjusted and validated model has a relevant importance in the biofuel sector, not only in Colombia, but also worldwide.     

酯化-酯交换两步法制备生物柴油的动力学

以潲水油（WCO）为原料,探讨了酯化-酯交换两步法制备生物柴油的反应动力学。以活性炭负载硫酸铁［Fe₂(SO₄)₃/AC］为负载型催化剂,通过测定不同反应温度、不同甲醇/脂肪酸（FFA）摩尔比条件下WCO中游离脂肪酸的转化率,以此确定酯化反应的动力学控制步骤及动力学方程中的待定参数,从而建立了在实验温度范围内酯化反应的动力学方程,并根据碱催化酯交换反应机理,在简化的动力学模型基础上,推导出了WCO中甘油三酯（TG）与甲醇发生酯交换反应的宏观动力学方程。结果表明,酯化反应和酯交换反应的动力学方程在实验条件范围内都能较好地描述各自的反应过程。     

餐饮废油制生物柴油研究进展

简述了餐饮废油（ WCO）转化为生物柴油的反应原理,比较了利用WCO转化制备生物柴油的各种方法,主要有均相转化法（包括酸催化法、碱催化法和酸碱两步催化法）、非均相转化法（包括固体碱催化法、固体酸催化法）、酶催化法、超临界转化法等,分析了不同方法的特点。     

Optimization of biodiesel production from crude palm oil using ultrasonic irradiation assistance and response surface methodology

BACKGROUND: Production of biodiesel from crude palm oil (CPO) with 6 wt% of free fatty acid (FFA) using a low‐frequency ultrasonic irradiation (40 kHz) technique was investigated in the present work. The objective of this study was to determine the relationship between various important parameters of the alkaline catalyzed transesterification process to obtain a high conversion to biodiesel. Response surface methodology (RSM) was used to statistically analyze and optimize the operating parameters of the process. A central composite design (CCD) was adopted to study the effects of the methanol to oil molar ratio, the catalyst concentration, reaction temperature, and irradiation time on conversion to biodiesel. RESULTS: The result from the RSM analysis indicated that the methanol to oil molar ratio, catalyst concentration and irradiation time have the most significant effects on the conversion to biodiesel. Moreover, a coefficient of determination (R²) value of 0.93 shows the fitness of a second‐order model for the present study. Based on this second‐order model, the optimum conditions for alkaline catalyzed transesterification of CPO were found to be a methanol to oil molar ratio of 6.44:1, catalyst concentration 1.25 wt%, reaction temperature 38.44 °C and irradiation time 25.96 min. At the calculated optimum condition, the conversion to biodiesel reached 97.85%. Under these same conditions, the experimental value was 98.02 ± 0.6%. CONCLUSIONS: The mathematical model developed has been proven to adequately describe the range of the experimental parameters studied and provide a statistically accurate prediction of the optimum conversion to biodiesel. Copyright © 2011 Society of Chemical Industry     

Non-Evaporative Solvent Recovery Step in Deacidification of Used Frying Oil as Biodiesel Feedstock by Methanol Extraction

An alternative deacidification process combining a liquid–liquid extraction with a non-evaporative solvent recovery step was proposed for preparing used frying oil (UFO) as biodiesel feedstock. The liquid–liquid extraction step using methanol was simulated for obtaining refined UFO with a final residual free fatty acids (FFA) content ≤ 1%. Solvent recovery step of the process, which is based on the precipitation of FFA with Ca(OH)₂ as insoluble calcium soaps, was investigated experimentally. With the aim of maximizing the FFA removal from the methanol extract, the influence of process variables such as FFA concentration in the extract phase, Ca(OH)₂ amount, stirring rate and temperature were investigated by using model extract phases. Complete removal of FFA was achieved in 30, 20, and 15 min, from the extract phases containing 3.86, 7.78, and 11.58 wt% FFA, respectively, when the precipitation was carried out at a temperature of 65 °C, stirring rate of 250 rpm and by using 18 times the stoichiometric Ca(OH)₂ amount. The precipitate quickly settled down due to the agglomeration, thereby provided an efficient and easy separation of the methanol from the solids. Provided the final residual content of FFA in methanol was too low, recovered methanol can be recycled for more FFA extraction. Although the suggested process offers a feasible method for preparing UFO as biodiesel feedstock, the effect of other decomposition products in UFO must be investigated in depth for using such a process on an industrial scale.     

Conversion of waste cooking oil to biodiesel using ferric sulfate and supercritical methanol processes

In this comparative study, conversion of waste cooking oil to methyl esters was carried out using the ferric sulfate and the supercritical methanol processes. A two-step transesterification process was used to remove the high free fatty acid contents in the waste cooking oil (WCO). This process resulted in a feedstock to biodiesel conversion yield of about 85-96% using a ferric sulfate catalyst. In the supercritical methanol transesterification method, the yield of biodiesel was about 50-65% in only 15 min of reaction time. The test results revealed that supercritical process method is probably a promising alternative method to the traditional two-step transesterification process using a ferric sulfate catalyst for waste cooking oil conversion. The important variables affecting the methyl ester yield during the transesterification reaction are the molar ratio of alcohol to oil, the catalyst amount and the reaction temperature. The analysis of oil properties, fuel properties and process parameter optimization for the waste cooking oil conversion are also presented.     

Optimization of pretreatment reaction for methyl ester production from chicken fat

In biodiesel production, to use low cost feedstock such as rendered animal fats may reduce the biodiesel cost. One of the low cost animal fats is the chicken fat for biodiesel production. It is extracted from feather meal which is prepared from chicken wastes such as chicken feathers, blood, offal and trims after rendering process. However, chicken fats often contain significant amounts of FFA which cannot be converted to biodiesel using an alkaline catalyst due to the formation of soap. Therefore, the FFA level should be reduced to desired level (below 1%) by using acid catalyst before transesterification. For this aim, sulfuric, hydrochloric and sulfamic (amidosulfonic) acids were used for pretreatment reactions and the variables affecting the FFA level including alcohol molar ratio, acid catalyst amount and reaction time were investigated by using the chicken fat with 13.45% FFA. The optimum pretreatment condition was found to be 20% sulfuric acid and 40:1 methanol molar ratio based on the amount of FFA in the chicken fat for 80 min at 60 °C. After transesterification, the methyl ester yield was 87.4% and the measured fuel properties of the chicken fat methyl ester met EN 14214 and ASTM D6751 biodiesel specifications.     

A Density Functional Theory Study on the Acid-Catalyzed Transesterification Mechanism for Biodiesel Production from Waste Cooking Oils

The acid-catalyzed transesterification reaction has been one of the most effective methods to produce biodiesel, especially from waste cooking oils (WCO) with high contents of water and free fatty acids (FFA). However, in the acid-catalyzed processes, the H⁺ action mechanism and the controlling step of the reaction rate have been ambiguous. To clearly understand the reaction process, the DMol3 module based on the density functional theory (DFT) was employed to investigate the acid (H⁺-)-catalyzed transesterification mechanism of methanol and oleic acid monoacylglycerol (OAM). The one step transesterification without a catalyst and the feasible paths of SN2 (substitution nucleophilic bimolecular) and SN1 (substitution nucleophilic unimolecular) reaction mechanisms with H⁺-based catalysts were built as Path 1, Path 2, and Path 3, respectively. The calculated structures, thermodynamic, and kinetic data revealed that the H⁺-based catalysts could effectively reduce the activation energy for the transesterification reaction, and the Path 2 based on the SN2 reaction mechanism was the optimal reaction path. A tetrahedral intermediate (IM2-2) could be generated with the highest active energy of 15.383 kcal mol⁻¹, implying that there was the most stable structure of IM2-2 as the key species in the transesterification process. Hence, the increasing decomposition rate of IM2-2 accelerated the forward reaction in H⁺-based biodiesel processes. The calculated active energy of 15.383 kcal mol⁻¹ was in good agreement with the kinetic data for the monoacylglycerol transesterification of 15.067 kcal mol⁻¹. Our calculations should provide basic and reliable theoretical data for further understanding the mechanism of transesterification of WCO to biodiesel products in the future work.     

Biodiesel production from vegetable oil using heterogenous acid and alkali catalyst

Zanthoxylum bungeanum seed oil (ZSO) with high free fatty acids (FFA) can be used for biodiesel production by ferric sulfate-catalyzed esterification followed by transesterification using calcium oxide (CaO) as an alkaline catalyst. Acid value of ZSO with high FFA can be reduced to less than 2 mg KOH/g by one-step esterification with methanol-to-FFA molar ratio 40.91:1, ferric sulfate 9.75% (based on the weight of FFA), reaction temperature 95 °C and reaction time 2 h, which satisfies transesterification using an alkaline catalyst. The response surface methodology (RSM) was used to optimize the conditions for ZSO biodiesel production using CaO as a catalyst. A quadratic polynomial equation was obtained for biodiesel conversion by multiple regression analysis and verification experiments confirmed the validity of the predicted model. The optimum combination for transesterification was methanol-to-oil molar ratio 11.69:1, catalyst amount 2.52%, and reaction time 2.45 h. At this optimum condition, the conversion to biodiesel reached above 96%. This study provided a practical method to biodiesel production from raw feedstocks with high FFA with high reaction rate, less corrosion, less toxicity, and less environmental problems.     

Two-step biodiesel production from Jatropha curcas crude oil using SiO2·HF solid catalyst for FFA esterification step

A high quality biodiesel was produced from Mexican Jatropha curcas crude oil (JCCO) by a two step catalyzed process. The free fatty acids (FFA) were first esterified with methanol, catalyzed by a solid catalyst: SiO₂ pretreated with HF. The catalyst showed a high number of Lewis acid surface sites, and no CO₂ or H₂O adsorption activity. This catalyst showed a high FFA esterification activity and high stability. After 30 esterification runs, the catalyst activity remained unchanged. During the second step, the triglycerides present in the JCCO were transesterified with methanol catalyzed by NaOH. The chromatographic analysis of the biodiesel obtained, revealed that the process proposed in this investigation led to a very high quality biodiesel, meeting the international requirements for its utilization as a fuel. The combustion gas emissions of the JCCO biodiesel were studied by FTIR spectroscopy using a laboratory combustor. These preliminary results showed low amounts of aromatic and sulfur containing compounds. However, halogenated compounds and dicyclopentadiene were also detected at the combustor exhaust.     

The use of a modified TDSP for biodiesel production from soybean, linseed and waste cooking oil

In this study, the Transesterification Double Step Process (TDSP) for the production of biodiesel from vegetable oil was modified to yield a shorter reaction time and products with improved quality. TDSP consists in a two step transesterification procedure which starts with a basic catalysis, followed by an acidic catalysis. The process modifications included a reduction in the concentration of catalysts, a reduction in the reaction time of the first step and the direct mixing of methanol/acid solution, without cooling the system between the first and second step. A comparison between washed and unwashed biodiesel demonstrates that the final washing and drying procedure is necessary for satisfactory results. The products were analyzed by ¹H-NMR and nineteen different biodiesel analyses specific for international quality certification. The modified procedure resulted in a high conversion index (97% for waste cooking oil and soybean oil and 98% for linseed oil) and high yield (87 ± 5% for waste cooking oil, 92 ± 3% for soybean and 93 ± 3% for linseed oil). The biodiesel produced by the modified TDSP met ASTM, EN ISO and ABNT standards before the addition of stabilizer.     

Synthesis and characterization of mono‐acylglycerols through the glycerolysis of methyl esters obtained from linseed oil

Here we investigate the production and characterization of mono‐acylglycerols through the glycerolysis of biodiesel, a methyl ester mixture, obtained from linseed oil. The biodiesel employed was derived from linseed oil through transesterification according to transesterification double step process 1 . The efficiency of H₂SO₄, CaO, and NaOH as catalysts was evaluated for the production of mono‐acylglycerols. The glycerolysis reactions were performed by varying the molar ratio of the reagents (biodiesel:glycerol), the type and amount of catalyst, reaction time and temperature. Systematic evaluation of reaction yield is shown as a function of these parameters. Reaction products were characterized through IR spectroscopy, hydrogen NMR, and the GC techniques. The study of three different catalysts indicated that the most efficient was 5% NaOH in a 1:5 biodiesel–glycerol molar ratio with 10 h reaction time. The reaction reached a maximum of 85% biodiesel conversion with a mono‐acylglycerol yield of 72% at 130°C.