Ultrasound assisted enzymatic conversion of non edible oil to methyl esters

Conventional and ultrasound-assisted hydrolysis and subsequent esterification of Nagchampa oil under mild operating conditions have been investigated with an objective of intensification of methyl esters production using a sustainable approach. The effect of ratio of reactants, temperature, enzyme loading, pretreatment of enzyme (using ultrasonic irradiations) on the hydrolysis and esterification reaction has been studied. Optimum conditions for hydrolysis were observed to be 1:1 weight ratio of oil: water for Lip Z and 1:3 for Lip 2 enzymes, enzyme loading of 400 units for Lip Z and 800 mg for Lip 2 enzymes and reaction time of 6 h. In the case of esterification reaction, optimum conditions obtained were oil to methanol molar ratio of 1:2, enzyme loading of 1000 mg and reaction time of 20 h. Use of pretreated enzyme (using ultrasonic irradiations) was found to increase the extent of esterification reaction from 75% to 92.5%. It was observed that use of ultrasound in the reaction significantly intensified the esterification reaction with time requirement reducing from 20 h for conventional stirring based approach to only about 7.5 h in the presence of ultrasound. The extent of esterification obtained with sonicated enzyme also increased to 96% from 75% with unsonicated enzyme.     

Fast, easy ethanomethanolysis of Jatropha curcus oil for biodiesel production due to the better solubility of oil with ethanol in reaction mixture assisted by ultrasonication

Biodiesel was obtained by transesterification of Jatropha curcus oil with anhydrous methanol, ethanol, and various mixtures of methanol/ethanol system. The present research work ultrasonic assisted transesterification of J. curcus oil was carried out in the presence of various mixtures of methanol/ethanol system and potassium hydroxide (KOH) as a catalyst, keeping the molar ratio of oil to alcohol 1:6. The methodology allows for the reaction to be run under atmospheric conditions. The ethanomethanolysis and ultrasonic mixing promote the rate of transesterification reaction due to the better solubility of oil with ethanol in reaction mixture and obtained methyl esters as well as ethyl esters.     

Application and mechanism of ultrasonic static mixer in heavy oil viscosity reduction

In the present study, heavy oil viscosity reduction in Daqing oil field was investigated by using an ultrasonic static mixer. The influence of the ultrasonic power on the viscosity reduction rate was investigated and the optimal technological conditions were determined for the ultrasonic treatment. The mechanism for ultrasonic viscosity reduction was analyzed. The flow characteristics of heavy oil in the mixer under the effect of cavitation were investigated using numerical modeling, and energy consumptions were calculated during the ultrasonic treatment and vis-breaking processes. The experimental results indicated that the ultrasonic power made the largest impact on the viscosity reduction rate, followed by the reaction time and temperature. The highest viscosity reduction rate was 57.34%. Vacuole was migrated from the axis to the wall along the fluid, accelerating the two-phase transmission and enhancing the radial flow of the fluid, which significantly improved the ultrasonic viscosity reduction. Compared to the vis-breaking process, the energy consumption of ultrasonic treatment process was 43.03% lower when dealing with the same quality heavy oil. The optimal process conditions were found to be as follows: ultrasonic power of 1.8 kW, reaction time of 45 min and reaction temperature of 360 °C. The dissociation of the molecules of heavy oil after ultrasonication has been checked. After being kept at room temperature 12 days, some light components were produced by the cavitation cracking, so the viscosity of the residual oil could not return to that of the original residual oil, which meant that the “cage effect” was not reformed.     

Enzymatic transesterification of Jatropha curcas oil assisted by ultrasonication

Ultrasonication used for the production of fatty acid methyl ester from non-edible vegetable oil using immobilized lipase (Chromobacterium viscosum) as a catalyst from Enterobacter aerogenes to make the process fully ecologically and environmental friendly. The optimal conditions for biodiesel production is the molar ratio oil to methanol 1:4, catalyst concentration 5 wt.% of oil, reaction time 30 min, ultrasonic amplitude 50% (100 W/m(3)) and cycle 0.7s. ultrasonication reduce the reaction time comparing to the conventional batch process. The purity and conversion of the biodiesel was 84.5±0.5 analyzed by reversed phase HPLC.     

Biodiesel production from palm oil using combined mechanical stirred and ultrasonic reactor

This paper investigates the production of biodiesel from palm oil using a combined mechanical stirred and ultrasonic reactor (MS–US). The incorporation of mechanical stirring into the ultrasonic reactor explored the further improvement the transesterification of palm oil. Initial reaction rate values were 54.1, 142.9 and 164.2 mmol/L min for the mechanical-stirred (MS), ultrasonic (US) and MS–US reactors, respectively. Suitable methanol to oil molar ratio and the catalyst loading values were found to be 6 and 1 of oil, respectively. The effect of ultrasonic operating parameters; i.e. frequency, location, and number of transducer, has been investigated. Based on the conversion yield at the reactor outlet after 1 h, the number of transducers showed a relevant role in the reaction rate. Frequency and transducer location would appear to have no significant effect. The properties of the obtained biodiesel (density, viscosity, pour point, and flash point) satisfy the ASTM standard. The combined MS–US reactors improved the reaction rate affording the methyl esters in higher yield.     

Ultrasound assisted intensification of biodiesel production using enzymatic interesterification

Ultrasound assisted intensification of synthesis of biodiesel from waste cooking oil using methyl acetate and immobilized lipase obtained from Thermomyces lanuginosus (Lipozyme TLIM) as a catalyst has been investigated in the present work. The reaction has also been investigated using the conventional approach based on stirring so as to establish the beneficial effects obtained due to the use of ultrasound. Effect of operating conditions such as reactant molar ratio (oil and methyl acetate), temperature and enzyme loading on the yield of biodiesel has been investigated. Optimum conditions for the conventional approach (without ultrasound) were established as reactant molar ratio of 1:12 (oil:methyl acetate), enzyme loading of 6% (w/v), temperature of 40 °C and reaction time of 24 h and under these conditions, 90.1% biodiesel yield was obtained. The optimum conditions for the ultrasound assisted approach were oil to methyl acetate molar ratio of 1:9, enzyme loading of 3% (w/v), and reaction time of 3 h and the biodiesel yield obtained under these conditions was 96.1%. Use of ultrasound resulted in significant reduction in the reaction time with higher yields and lower requirement of the enzyme loading. The obtained results have clearly established that ultrasound assisted interesterification was a fast and efficient approach for biodiesel production giving significant benefits, which can help in reducing the costs of production. Reusability studies for the enzyme were also performed but it was observed that reuse of the catalyst under the optimum experimental condition resulted in reduced enzyme activity and biodiesel yield.     

Ultrasound-assisted oxidation of dibenzothiophene with phosphotungstic acid supported on activated carbon

Phosphotungstic acid (HPW) supported on activated carbon (AC) was applied to catalyze deep oxidation desulfurization of fuel oil with the assist of ultrasound. The sulfur-conversion rate was evaluated by measuring the concentration of dibenzothiophene (DBT) in n-octane before and after the oxidation. Supporting HPW on AC has been verified to play a positive role in UAOD process by a series of contrast tests, where only HPW, AC or a mixture of free HPW and AC was used. The influences of catalyst dose, ultrasound power, reaction temperature, H₂O₂:oil volume ratio and the reuse of catalyst on the catalytic oxidation desulfurization kinetics were investigated. The DBT conversion rate of the reaction catalyzed by supported HPW under ultrasound irradiation was higher than the summation of the reactions with HPW only and AC only as catalyst. With the increase of loading amount of HPW on AC, ultrasound power, H₂O₂:oil volume ratio and reaction temperature, the catalytic oxidation reactivity of DBT would be enhanced. The optimum loading amount of HPW was 10%, exceed which DBT conversion would no longer increase obviously. DBT could be completely converted under the optimized conditions (volume ratio of H₂O₂ to model oil: 1:10, mass ratio of the supported HPW to model oil: 1.25%, temperature: 70 °C) after 9 min of ultrasound irradiation.     

Ultrasonic-assisted transesterification of Jatropha curcus oil using solid catalyst,Na/SiO2

The production of biodiesel from non-edible vegetable oil using ultrasonication, calls for an efficient solid catalyst to make the process fully ecologically and economically friendly. The methodology allows for the reaction to be run under atmospheric conditions. Solid catalyst and ultrasonication reduced the reaction time comparing to the conventional batch processes and we found 98.53% biodiesel yield. The optimal conditions for biodiesel production is the molar ratio oil to methanol 1:9, Catalyst conc. 3 wt.% of oil and 15 min reaction time.     

Fatty acids methyl esters from vegetable oil by means of ultrasonic energy

The transesterification of vegetable oil with short-chain alcohols, in the presence of base-catalyst, by means of low frequency ultrasound (28 and 40 kHz) in order to obtain biodiesel fuel was studied. By using ultrasounds the reaction time is much shorter (10-40 min) than for mechanical stirring. The quantity of required catalyst is 2 or 3 times lower. The molar ratio of alcohol/oil used is only 6:1. Normal chain alcohols react fast, while secondary and tertiary alcohols show some or no conversion after 60 min of reaction. Surprisingly, 40 kHz ultrasounds are much more effective in the reduction of the reaction time (10-20 min). Twenty eight kilohertz give slightly better yields (98-99%), but longer reaction time, while higher frequencies are not useful at all for the transesterification of fatty acids.     

Ultrasound assisted two-stage biodiesel synthesis from non-edible Schleichera triguga oil using heterogeneous catalyst: Kinetics and thermodynamic analysis

Present work deals with the ultrasound-assisted biodiesel production from low cost, substantial acid value kusum (Schleichera triguga) oil using a two-step method of esterification in presence of acid (H₂SO₄) catalyst followed by transesterification using a basic heterogeneous barium hydroxide (Ba(OH)₂) catalyst. The initial acid value of kusum oil was reduced from 21.65 to 0.84 mg of KOH/g of oil, by acid catalyzed esterification with 4:1 methanol to oil molar ratio, catalyst concentration 1% (v/v), ultrasonic irradiation time 20 min at 40 °C. Then, Ba(OH)₂ concentration of 3% (w/w), methanol to oil molar ratio of 9:1, ultrasonic irradiation time of 80 min, and temperature of 50 °C was found to be the optimum conditions for transesterification step and triglyceride conversion of 96.8% (wt) was achieved. This paper also examined the kinetics as well as the evaluation of thermodynamic parameters for both esterification and transesterification reactions. The lower value of activation energy and higher values of kinetic constants indicated a fast rate of reaction, which could be attributed to the physical effect of emulsification, in which the microturbulence generated due to radial motion of bubbles, creates an intimate mixing of the immiscible reactants causing the increase in the interfacial area, giving faster reaction kinetics. The positive values of Gibbs-free energy (ΔG), enthalpy (ΔH) and negative value of entropy (ΔS) revealed that both the esterification and transesterification were non-spontaneous, endothermic and endergonic reactions. Therefore, the present work has not only established the escalation obtained due to ultrasonication but also exemplified the two-step approach for synthesis of biodiesel from non-edible kusum oil based on the use of heterogeneous catalyst for the transesterification step.     

大豆油酯交换法制备生物柴油及气相色谱分析

为获得最佳条件,在单因素试验的基础上,采用正交试验法对大豆油碱催化酯交换法制各生物柴油的工艺参数进行了优化试验,结果表明,制取生物柴油的最佳工艺参数是：醇油摩尔比6：1,催化剂用量为油量的0.8%,反应温度为45℃,反应时间60m in,并且在最优工艺参数下进行了验证试验,得到生物柴油的转化率为97.05%。气相色谱分析结果表明,脂肪酸甲酯含量很高。     

基于铜网置换反应的微纳结构SERS基底制备和应用

电力能源发展与国家经济发展关系密切,因此电网稳定、安全地运行是人民稳定生活的保障。而与稳定可靠的电网的运行有关的是变压器的绝缘水平,因此始终注意电气设备的状况和运行非常重要。而仅由纸绝缘产生的糠醛是目前用于评估电力变压器老化状况最常用的指标之一,所以准确测量变压器油中糠醛含量具有重大意义。拉曼光谱法可以实现对待测物的快速、无损检测,但受限于拉曼散射信号弱,对油中老化特征物这种微量物质检测难度大。表面增强拉曼光谱可以解决痕量物质检测的灵敏性问题,使溶解在变压器油中的老化特征物得到快速、无损地检测。故将SERS应用到变压器油中糠醛的检测对于变压器运行状况的评估具有重要的意义。围绕着变压器油中糠醛作为痕量物质检测灵敏度低的问题,基于置换反应在TEM铜网上制备了微纳米结构的SERS基底,以检测变压器油中的糠醛,为高效,准确地检测变压器油的老化水平提供一种快速、有效的新技术。选择了特定的实验材料,在控制特定的实验条件下基于置换反应制备出微纳结构SERS基底,经过电镜扫描对其表面形貌进行表征;在不同位置进行拉曼检测得到特征拉曼峰峰强的变异系数仅为3.55％,表明该基底的“热点”分布均匀和检测可重复性高;定性分析了一定浓度梯度的变压器油中糠醛和背景噪声的拉曼光谱。选择了1 702 cm-1的拉曼峰作为油中糠醛的特征拉曼峰。定量分析中,建立内标峰和1 702 cm-1处峰强比与变压器油中糠醛浓度的线性函数,得到良好的线性关系。使用3δ准则计算变压器油中糠醛在微纳结构SERS基底上的检测下限约为0.51 mg·L-1。研究说明基于铜网置换反应的微纳结构SERS基底对于变压器油中糠醛具有更灵敏的检测。这对于诊断电力变压器绝缘状况和维护电网稳定非常重要。     

活性炭负载四氯化锡催化豆油制备生物柴油及光谱性质

以活性炭负载四氯化锡为催化剂,用甲醇和大豆油为原料,合成了生物柴油。考察了反应时间、反应温度、催化剂用量和原料配比对生物柴油产率的影响。当反应时间为5.0h,反应温度75℃,催化剂用量为反应物总质量的4.0%,醇油摩尔比7∶1时,生物柴油产率达94.6%。多次使用后,负载催化剂仍表现出较强的催化活性。并利用XRD、FT IR光谱表征了催化剂的物相和产品结构,用气相色谱-质谱联用法对产品进行了定性和定量分析。     

Kinetics of ultrasound-assisted lipase-catalyzed glycerolysis of olive oil in solvent-free system

This work reports experimental kinetic data of solvent-free glycerolysis of olive oil using a commercial immobilized lipase (Novozym 435) under the influence of ultrasound irradiation. The experiments were performed in a mechanically stirred reactor under ultrasound irradiation, evaluating the effects of temperature (50-70 °C), enzyme concentration (2.5-10 wt%) and glycerol to oil molar ratio (0.8:1-3:1). Results show that ultrasound-assisted lipase-catalyzed glycerolysis might be a potential alternative route to conventional methods, as high contents of reaction products, especially monoglycerides, were achieved at mild irradiation power supply (∼130 W) and temperature, in a relatively short reaction time (2 h) and low enzyme content (7.5 wt%). To completeness, two simplified kinetic modeling approaches, based on the ordered-sequential bi bi mechanism and reaction stoichiometry, were employed to represent the experimental data, thus allowing a better understanding of the reaction kinetics.     

Modeling of process intensification of biodiesel production from Aegle Marmelos Correa seed oil using microreactor assisted with ultrasonic mixing

Conventionally, the batch type reactors were used for the production of biodiesel. However, in recent years, the usage of microreactors has started emerging as a significant substitute for biodiesel production due to its higher conversion rate at a short duration. These microreactors have a significantly high surface to volume ratio and high heat-mass transfer rate. The disadvantage of this type of reactors is its low mixing rate of the reagents. This can be overcome with the assistance of ultrasonic mixing. The main objective of this paper is to study the interlaced effect of a continuous flow microreactor and ultrasonic mixing on trans-esterification of Aegle Marmelos Correa seed oil using sodium methoxide catalyst. Results of microreactors with 0.3 mm and 0.8 mm diameter were compared. The effects of process parameters namely, flow rate (2–10 mL/min), reaction temperature (45–65 °C), catalyst amount (0.5–2.5 wt%), oil to methanol molar ratio (1:6–1:18) and ultrasonic mixing time (30–150 s) were studied using response surface methodology (RSM). The biodiesel yield of 98% and 91.8% were obtained for 0.3 mm and 0.8 mm microreactors, respectively. The maximum biodiesel yield observed in 0.3 mm reactor under following optimum conditions: 6.8 mL/min flow rate, 48 °C reaction temperature, 1.3 wt% catalyst, 1:9 oil to methanol molar ratio and 83 s ultrasonic mixing time. The predictive and generalization abilities of RSM and artificial neural network (ANN) models were evaluated and compared. The study showed that ANN and RSM models could predict the yield with an R² value of 0.9955 and 0.9900 respectively. However, the ANN model predicted the yield with the least mean square error value of 0.00001294, which is much lower than RSM.     

Phase-transfer catalysis and ultrasonic waves II: saponification of vegetable oil.

Saponification of oils which is a commercially important heterogeneous reaction, can be speeded up by the application of ultrasound in the presence of phase-transfer catalyst (PTC). This paper focuses on the ability of ultrasound to cause efficient mixing of this liquid-liquid heterogeneous reaction. Castor oil was taken as a model oil and the kinetic of the reaction was followed by the extent of saponification. The hydrolysis of castor oil was carried out with different PTC such as cetyl trimethyl ammonium bromide (CTAB), benzyl triethyl ammonium chloride (BTAC) and tetrabutyl ammonium bromide (TBAB) in aqueous alkaline solution. As hydroxyl anion moves very slowly from aqueous to oil phase, the presence of a PTC is of prime importance. For this purpose, cationic surfactants are selected. The sonication of biphasic system were performed by 20 kHz (simple horn and cup horn) and 900 kHz. It was found that CTAB was better than the two others and this could be related to the molecular structure of the PTCs. The effect of temperature was also studied on the saponification process. By increasing the temperature, the yield was also increased and this could be explained by intermolecular forces, interfacial tension and mass transfer. Saponification of three different vegetable oils shows that the almond oil is saponified easier than the two others and this could be related to their properties such as surface tension, viscosity and density.     

Transesterification of soybean oil by using the synergistic microwave-ultrasonic irradiation

Microwave and ultrasound have been demonstrated to be outstanding process intensification techniques for transesterification of oil. According to their mechanisms, simultaneous effects can surely bring about better enhancement than sole microwave or ultrasound. Therefore, this study aimed to investigate the important factors and their suitable levels in the KOH-catalyzed transesterification of soybean oil with methanol by using synergistic assistance of microwave-ultrasound (CAMU). The feasibility of application of CAMU in transesterification of oil was demonstrated. When the dosage of methanol, soybean oil and KOH were 15.4 g, 34.7 g (with methanol-to-oil molar ratio of 12:1) and 1 g, respectively, and the microwave power, ultrasonic power, ultrasonic mode, reaction temperature and reaction time were 700 W, 800 W, 1:0, 65 °C and 6 min, respectively, the transesterification reached 98.0% of yield, being the highest yield among all the results obtained; while by using 600 W of microwave plus stirring instead of CAMU, only 57.4% of yield could be obtained. Compared with other reaction techniques, the transesterification by applying novel CAMU was found to have remarkable advantages. Furthermore, by monitoring the variation of real-time temperature and microwave power during transesterification reactions with different microwave operation time and by taking comparison of the corresponding yield, it was demonstrated that the main reason for the acceleration of microwave-assisted transesterification was the polarization and further activation of reactants caused by microwave irradiation, but not the factor of fast heating.     

Palm oil hydrolysis catalyzed by lipases under ultrasound irradiation--the use of experimental design as a tool for variables evaluation

Diacylglycerol oil has been increasingly recognized by its good nutritional properties and therefore, different technologies have been developed for obtaining it. The present work focuses on the diacylglycerol production by hydrolysis reaction of the palm oil using the PS IM and TL IM commercial lipases as biocatalysts under ultrasound irradiation. An experimental design (central composite rotatable design - CCRD) adopting surface response was applied as a tool to evaluate the optimal reaction conditions beyond a restrict number of experiments. Reactions were performed in an ultrasound equipment and different variables were investigated, such as temperature (30-55 °C), enzyme content (1-2 wt.% of oil mass), mechanical stirring (300-700 rpm) and reaction time. Both, PS IM and TL IM enzymes showed the best results after 1 h and 30 min of reaction under 30 °C and, applying 300 rpm as stirring. On these conditions, the diacylglycerol yield was around 34% and 39%, respectively; considering that 1% PS IM was applied for the first one and, 2% TL IM for the second one. Therefore, it was obtained good yield of a diacylglycerol-rich oil in shorter reaction times under sonication and soft conditions. The mathematic model proposed suggested a satisfactorily representation of the process and good correlation among the experimental results and the theoretical values predicted by the model equation were achieved.     

Intensification of biodiesel production from soybean oil and waste cooking oil in the presence of heterogeneous catalyst using high speed homogenizer

In the present work, high speed homogenizer has been used for the intensification of biodiesel synthesis from soybean oil and waste cooking oil (WCO) used as a sustainable feedstock. High acid value waste cooking oil (27 mg of KOH/g of oil) was first esterified with methanol using sulphuric acid as catalyst in two stages to bring the acid value to desired value of 1.5 mg of KOH/g of oil. Transesterification of soybean oil (directly due to lower acid value) and esterified waste cooking oil was performed in the presence of heterogeneous catalyst (CaO) for the production of biodiesel. Various experiments were performed for understanding the effect of operating parameters viz. molar ratio, catalyst loading, reaction temperature and speed of rotation of the homogenizer. For soybean oil, the maximum biodiesel yield as 84% was obtained with catalyst loading of 3 wt% and molar ratio of oil to methanol of 1:10 at 50 °C with 12,000 rpm as the speed of rotation in 30 min. Similarly biodiesel yield of 88% was obtained from waste cooking oil under identical operating conditions except for the catalyst loading which was 1 wt%. Significant increase in the rate of biodiesel production with yields from soybean oil as 84% (in 30 min) and from WCO as 88% (30 min) was established due to the use of high speed homogenizer as compared to the conventional stirring method (requiring 2–3 h for obtaining similar biodiesel yield). The observed intensification was attributed to the turbulence caused at microscale and generation of fine emulsions due to the cavitational effects. Overall it can be concluded from this study that high speed homogenizer can be used as an alternate cavitating device to efficiently produce biodiesel in the presence of heterogeneous catalysts.     

Time reducing process for biofuel production from non edible oil assisted by ultrasonication

Limited resources of conventional fuels such as petrodiesel have led to the search for alternative fuels. Various convention batch/continuous processes for the biodiesel production have been developed before the recent year. All processes are time consuming with high labor cost. Thus, we need a new process for biodiesel production which reduces the reaction time and production cost as well as save the energy. In this work, ultrasonic assisted transesterification of Jatropha curcas oil is carried out in the presence of methanol and potassium hydroxide (KOH) as catalyst, keeping the molar ratio of oil to alcohol 1:5, catalyst concentration 0.75 wt% of oil, ultrasonic amplitude 50% and pulse 0.3 cycle, 7 min reaction time under atmospheric condition. Ultrasonic mixing has increased the rate of transesterification reaction as compare to the mechanical mixing.