Ultrasound-assisted Transesterification Research Articles

Ultrasound-assisted transesterification of waste cooking oil to biodiesel utilizing banana peel derived heterogeneous catalyst

Scientists are considering substitute energies as a consequence of the increasing global demand for energy. An eco-friendly and high flash point biofuel, biodiesel, can be obtained from different types of animal fats, vegetable oils, and algal oils through transesterification with methanol with the support of a catalyst. The current study focused on exploring a bio-based heterogeneous catalyst, Nendran banana peel (NBP), for biodiesel production from promising feedstocks like waste cooking oil (WCO) using ultrasound-based transesterification. Catalyst morphological characterization showed a microporous structure and shows the minerals like potassium and calcium present in it which help to catalyze the reaction. The resultant biodiesel yield calculated using 1H NMR showed 72.25% conversion. The outcomes of this study showed that the Nendran banana peel can act as a potent catalyst for the biodiesel manufacturing process.Graphical

Enhancing efficiency of ultrasound-assisted biodiesel production catalyzed by Eversa® Transform 2.0 at low lipase concentration: Enzyme characterization and process optimization

This study focused on the ultrasound-assisted transesterification of simulated low-quality feedstocks using a low-cost liquid lipase Eversa® Transform 2.0 (ET2). Enzyme characterization was also performed to investigate the effect of ultrasound parameters on enzyme structure. The optimal ultrasound parameters, 40 % amplitude, and 5 % duty cycle effectively enhanced the reaction rate compared to the conventional stirring method while retaining 95 % of the enzyme activity. Analysis of circular dichroism (CD) spectra revealed the preservation of the secondary structure of ET2 under the optimal ultrasound intensities, while fluorescence spectra indicated a slight change in its tertiary structure. The implementation of a two-stage methanol dosing strategy in the ultrasound-assisted reaction effectively mitigated lipase inhibition, yielding a remarkable fatty acid methyl ester (FAME) content of 92.2 % achieved within a 12-h reaction time. Notable, this high FAME content was achieved with only a 4:1 methanol-to-oil molar ratio and a 0.5 wt% enzyme concentration. Under these optimized conditions, the ultrasound-assisted reaction also demonstrated a 15 % improvement in the final FAME content compared to the conventional stirring method. These promising results hold significant potential for advancing the field of biodiesel production via ultrasound technology, contributing substantively to sustainable energy sources.

Production of biodiesel from waste fish fat through ultrasound-assisted transesterification using petro-diesel as cosolvent and optimization of process parameters using response surface methodology

Biodiesel is a highly promising and viable alternative to fossil-based diesel that also addresses the urgent need for effective waste management. It can be synthesized by the chemical modification of triglycerides sourced from vegetable origin, animal fat, or algal oil. The transesterification reaction is the preferred method of producing biodiesel. However, the non-miscibility of alcohol and oil layer causes excessive utilization of alcohol, catalyst, and a substantial reacting time and temperature. In the current investigation, transesterification of waste fish oil was performed with petro-diesel as cosolvent, under the influence of ultrasound energy. The combination of both techniques is a unique and efficient way to minimize the mass transfer limitations considerably and hence reduces the parameters of the reaction. It is also a sincere effort to comply with the principles of green chemistry. The optimum reaction conditions were obtained using response surface methodology (RSM) that were as follows: molar ratio of methanol to oil 9.09:1, catalyst concentration of 0.97 wt%, cosolvent concentration of 29.1 wt%, temperature 60.1℃, and a reacting time 30 min. Under these listed conditions, 98.1% biodiesel was achievable, which was in close agreement with the expected result. In addition, the cosolvent removal step from the crude biodiesel was also eliminated as it could be employed as a blended fuel in CI engines.

A computational approach in automating the continuous sonicated biodiesel production

Ultrasound-assisted transesterification is an advantageous method of biodiesel synthesis. In an effort to advance the production of high-quality biofuels, this study presents and evaluates a theoretical feedback control technique applicable to a continuous flow transesterification reactor. In this innovative continuous reactor, biodiesel is produced by reacting triglyceride with methoxide under ultrasound mixing. Early development of a dynamic model incorporates concentration changes of biodiesel as well as kinetics modifications under varying ultrasound intensities. After model fitting, a proportional feedback control method is fine-tuned, theoretically implemented, and examined carefully with respect to i) thecontrol of the biodiesel mole fraction, ii) the combination of manipulating various inputs, and iii) the mitigation of unexpectedly emerging biodiesel demand. By manipulating both ultrasound intensity and methoxide flow rate, the system is flexible in achieving high set-points in the biodiesel mole fraction, reaching 60%. As was determined, this controlling strategy can be readily adapted to different ultrasonically operated continuous biofuel reactors of various sizes and shapes. Throughout all simulations, the biodiesel mixture quality was high.

Ultrasound-assisted production of biodiesel from field pennycress (Thlaspi arvense L.) seeds: Process optimization and quality evaluation

Biodiesel has been used more and more widely as it is environmentally friendly and sustainable. However, the traditional method of producing biodiesel often suffers from the low yield and high energy consumption. In order to improve the production efficiency of biodiesel, the ultrasound-assisted method was successfully applied to field pennycress (Thlaspi arvense L.) seed oil extraction and biodiesel transesterification in this study. The Box–Behnken design based on response surface methodology was used to optimize the multivariate processes of ultrasound-assisted extraction and transesterification. The optimal extraction conditions were: liquid to solid ratio of 25:1 mL/g, sonication time of 13 min, sonication amplitude of 90%, and extraction temperature of 45 ℃, with the maximal oil yield of 23.31 ± 0.51%. The optimal transesterification conditions were: methanol to oil ratio of 9.50:1 g/g, sonication amplitude of 90%, temperature of 60 °C, catalyst concentration of 1.36 wt%, and sonication time of 2.50 h, with the maximal biodiesel yield of 95.91 ± 0.28%. The seed oil obtained by ultrasound-assisted method and Soxhlet extraction method showed similar yield, fatty acid composition, and thermal stability, but the former had lower acid value, peroxide value, and free fatty acid content, which could be used as a raw material for the production of biodiesel more suitably. Almost all properties of biodiesel produced by ultrasound-assisted transesterification were compatible with those of biodiesel standards. Moreover, the energy consumption of ultrasound-assisted oil extraction and biodiesel production decreased by 94.84% and 55.50%, compared with that of the corresponding traditional procedures, respectively. Overall, ultrasound-assisted extraction of field pennycress seed oil and transesterification to produce biodiesel are efficient and environmentally friendly.

Statistical optimization of ultrasound‐assisted biodiesel production from Moringa oleifera oil – waste cooking oil mixture using modified conch shell catalyst

AbstractBiodiesel is a potential alternative fuel that offers several environmental benefits and can be used in conventional engines. However, high feedstock cost poses a challenge for its commercial viability. This study focuses on producing biodiesel using waste cooking oil (WCO) and Moringa oleifera oil (MOO) as feedstock, with a specific emphasis on the use of modified conch shell as solid catalyst under ultrasonic conditions. Different mixtures of WCO and MOO were evaluated for their suitability in a two‐stage esterification transesterification process, and the acid value of the WCO‐MOO blend was reduced through an ultrasound‐assisted esterification process. Additionally, a calcium oxide‐based catalyst was developed from conch shells (CS) through calcination for 3 h at 900°C and further modified using water and methanol. The characterization studies confirm the successful development and modification of the CS catalyst and also demonstrates excellent catalytic activity. The ultrasound assisted transesterification process parameters were optimized using response surface methodology (RSM) based Box–Behnken design (BBD). By employing a catalyst loading of 5.8 wt%, methanol to esterified oil volumetric ratio of 0.37:1, and an ultrasonication time of 57 min, a maximum predicted methyl ester conversion of 94.7% was achieved. Therefore, this work provides valuable insights into the use of modified conch shell catalyst for biodiesel production from WCO and MOO mixtures thereby contributing to the advancement of cost‐effective and environmentally friendly biodiesel production methods.

Optimization of ultrasound-assisted oil extraction from Carica candamarcensis; A potential Oleaginous tropical seed oil for biodiesel production

This study focuses on the optimization of ultrasound-assisted oil extraction from Carica candamarcensis seed using response surface methodology. The process parameters considered were extraction time (30–60 min), ultrasound amplitude level (20–40%), and solvent to seed ratio (10–20 mL/g). These were varied as suggested by Box-Behnken experimental model. Optimum values of these process parameters were given by the regression model, with the corresponding extraction yield. The model was validated experimentally to ensure its reliability. Physicochemical properties and fatty acid compositions of the extracted oil were evaluated accordingly. Furthermore, the extracted oil was then converted into biodiesel via ultrasound-assisted transesterification, using potassium hydroxide as the catalyst. FAME contents of the produced biodiesel were measured using gas chromatography. In addition, physicochemical properties of the biodiesel were also determined accordingly. Hence, findings from this study would be beneficial in further exploration on the usage of Carica candamarcensis as a potential feedstock for biodiesel production.

Biodiesel production from a novel renewable source through the ultrasound-assisted transesterification process, using energy efficient nanocatalyst developed from waste material

The depletion of fossil fuels created a thrust for an alternative renewable energy source, which could involve sustainable energy formation and cost-reducing catalysts. The catalyst derived from the waste material, specifically a heterogenous nanocatalyst, could economically add value to the process. In this study, a novel microbial strain, Rhodotorula mucilaginosa strain SML (RM-SML), was used as a source of oil for biodiesel production. The nanocatalyst developed from the Central Avian Research Institute – Broiler (CARIB) breed eggshell was used as a catalyst for transesterification, increasing the sustainability and economic viability of the process. RM-SML yielded 68.79 % of oil to its total dry cell biomass. The calcium carbonate-rich CARIB breed eggshell was calcinated in this study to synthesize a highly dynamic heterogeneous CARIB breed eggshell nanocatalyst (CBESNC). The calcination process parameters involved in the nanocatalyst synthesis were optimized using response surface methodology, yielding a maximum calcium oxide of 38.827 %. The synthesized CBESNC was characterized for its size by scanning electron microscopy imaging and its crystallographic nature by X-ray diffraction analysis. CBESNC was used as a heterogeneous catalyst in the ultrasonic-assisted transesterification of RM-SML bio-oil. The effect of the CBESNC in RM-SML bio-oil transesterification was studied and optimized using the response surface methodology, which yielded a maximum biodiesel conversion of 98.33 %. The prediction model in optimization studies was found to fit with the process and was validated experimentally. RM-SML biodiesel was studied for its physicochemical properties and found to meet American Society for Testing and Materials biodiesel standards. It was further confirmed with Gas Chromatography-Mass Spectrum analysis. The energy analysis results proved the commercialization feasibility of the study.

Feasibility of the Production of Argemone pleiacantha Ultrasound-Assisted Biodiesel for Temperate and Tropical Marginal Areas

The present work studies biofuel production using an American native species that belongs to the Argemone genus. It is considered a weed, and its presence extends from the southern United States to some areas of South America; the species Argemone pleiacantha, together with other species of the same genus, is known as “chicalote”. Oil physical and chemical properties confirm that chicalote oil is an effective raw material for biofuel production, presenting a fatty acid composition similar to that of soybean oil. A biodiesel production study was carried out using two methods of synthesis, conventional and ultrasound-assisted transesterification, employing the same molar ratio and amount of catalyst in both cases. Reaction time and supplied energy during synthesis were compared in batch mode. The results revealed that ultrasound-assisted transesterification has significant advantages over the conventional one in terms of reaction time and energy savings during chicalote oil synthesis to produce fatty acid methyl esters.

Ultrasound-assisted biodiesel generation from waste edible oil using CoFe2O4@GO as a superior and reclaimable nanocatalyst: Optimization of two-step transesterification by RSM

In current study, CoFe2O4@graphene oxide (GO) and CoFe2O4 heterogeneous nanocatalysts were successfully synthesized using the ultrasonic method and then used to generate biodiesel from waste edible oil (WEO) in a two-step transesterification process. To do so, the catalysts surface was characterized using CO2-TPD, SEM, EDX/Map, XRD, VSM, BET, FTIR, and DLS analyses. Also, central composite design (CCD) was utilized to optimize the impact of various factors on biodiesel generation. With the help of ultrasonication, the highest biodiesel yield using CoFe2O4 (91.64%) and CoFe2O4@GO (98.17%) was achieved at time of 55.75 min, temperature of 64.75 °C, methanol/oil ratio of 16.05:1 and catalyst concentration of 5.22 wt%. Also, the highest biodiesel yield without ultrasonication using CoFe2O4 and CoFe2O4@GO were gained as 58.96 and 67.13%, respectively. Moreover, the highest predicted biodiesel yield in the presence of CoFe2O4@GO by the RSM-CCD method is 98.95%, which is the maximum biodiesel yield ever achieved from WEO. The outcomes show that ultrasound-assisted transesterification is an efficient method for biodiesel generation, which can reduce costs and production time. After 5 reuse cycles, the CoFe2O4@GO nanocatalyst showed a yield of about 90%, which is due to its desirable magnetic attributes and easy separation. According to international standards and using FT-IR and HNMR analyses, the biodiesel produced can be used in diesel engines without further modification. Besides, kinetic and thermodynamics studies indicated that the generation reaction of biodiesel using both nanocatalysts is endothermic and non-spontaneous.

Response Surface Methodology and Artificial Neural Networks-Based Yield Optimization of Biodiesel Sourced from Mixture of Palm and Cotton Seed Oil

In this present study, cold flow properties of biodiesel produced from palm oil were improved by adding cotton seed oil into palm oil. Three different mixtures of palm and cotton oil were prepared as P50C50, P60C40, and P70C30. Among three oil mixtures, P60C40 was selected for biodiesel production via ultrasound assisted transesterification process. Physiochemical characteristics—including density, viscosity, calorific value, acid value, and oxidation stability—were measured and the free fatty acid composition was determined via GCMS. Response surface methodology (RSM) and artificial neural network (ANN) techniques were utilized for the sake of relation development among operating parameters (reaction time, methanol-to-oil ratio, and catalyst concentration) ultimately optimizing yield of palm–cotton oil sourced biodiesel. Maximum yield of P60C40 biodiesel estimated via RSM and ANN was 96.41% and 96.67% respectively, under operating parameters of reaction time (35 min), M:O molar ratio (47.5 v/v %), and catalyst concentration (1 wt %), but the actual biodiesel yield obtained experimentally was observed 96.32%. The quality of the RSM model was examined by analysis of variance (ANOVA). ANN model statistics exhibit contented values of mean square error (MSE) of 0.0001, mean absolute error (MAE) of 2.1374, and mean absolute deviation (MAD) of 2.5088. RSM and ANN models provided a coefficient of determination (R2) of 0.9560 and a correlation coefficient (R) of 0.9777 respectively.

Ultrasound-assisted transesterification of tropical goat fat – Palm oil blend for biodiesel synthesis

• Goat fat and palm oil mixture is proven as a promising raw material for biodiesel. • Ultrasound considerably speeds up transesterification of oil in biodiesel synthesis. • Catalyst loading, temperature, and methanol-to-oil molar ratio affect biodiesel yield. • Ultrasound-assisted transesterification obeys the pseudo-first order reaction. • A maximum biodiesel yield of 78.50 % with 98.69 % purity was obtained from goat fat. The increasing trend of global energy demand has encouraged the development of renewable energies, especially those derived from biomass and agricultural residues. This work aimed to study the effect of catalyst loading, temperature, and methanol-to-oil molar ratio on the yield and the reaction kinetics of ultrasound-assisted transesterification of tropical goat fats for biodiesel synthesis. Prior to trans -esterification, the oil extracted from the tropical goat fat was mixed with an equal volume of tropical palm oil to prevent its solidification tendency. To reduce the free fatty acids content of the mixed oil, it was esterified using a methanol-to-oil molar ratio of 9 employing 1 wt% sulfuric acid as the catalyst at 65 °C and 400 rpm agitation speed for 60 min. Then, the esterified oil was further subjected to an ultrasound-assisted transesterification system with sodium hydroxide catalyst for the reaction kinetics and biodiesel synthesis studies. The biodiesel properties were evaluated by both laboratory tests and BiodieselAnalyzer® software, which employs the fatty acid methyl ester composition obtained from GC–MS analysis. The highest conversion (78.50%) was achieved at 65 °C, 2.5 wt% of NaOH, and 8:1 methanol/oil blend molar ratio for 60 min. The pseudo-first order reaction fitted all the experimental data very well by giving the R 2 values higher than 0.98 and an apparent reaction rate constant of 2.15×10 −2 min −1 at the optimum condition. Furthermore, all the examined biodiesel physicochemical properties fulfilled the ASTM D6751 standard suggesting the promising potential of goat fats as the raw material for biodiesel manufacture.

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.

Vegetable Oil Based Compressor Oil-optimising of Tribological Characteristics

ABSTRACT This study explored the use of vegetable oil-based polyolester of rapeseed oil as a potential biolubricant for reciprocating air compressor. Rapeseed oil-based pentaerythritol ester (PE) was formulated via ultrasound-assisted transesterification process. Response surface methodology (RSM) based D-optimal design of experiments was used to analyse the tribological parameters, such as disc rotational speed, load and compressor oils on various tribological behaviours, namely, coefficient of friction (COF) and specific wear rate (SWR) using a pin-on-disc tribometer. The least specific wear rate of 1.85 × 10−5 mm3/Nmand COF of 0.0393 was recorded at optimal conditions. The surface morphology analysis of the tested pin using SEM/EDX and tribo-film formation analysis of disc surface using XPS technique disclosed that blended compressor oil (PE75), i.e., 75% by volume of PE and 25% by volume of synthetic compressor oil (SAE30) has numerous capabilities as environmental friendly compressor oil.

Analysis of RSM Based BBD and CCD Techniques Applied for Biodiesel Production from Waste Cotton-Seed Cooking Oil via Ultrasound Method

Biodiesel was produced from the waste cotton-seed cooking oil with methanol in presence of the calcium oxide catalyst by the ultrasound-assisted transesterification method. The ultrasonication approach was used for biodiesel production as it significantly lower reaction time and is highly energy-efficient. This paper-work focused on the optimization of biodiesel production parameters methanol: oil molar ratio (A), CaO amount (B), process temperature (C) using the two different response surface methodology (RSM) such as box-behnken design and central composite design (CCD). Also a comparison of the results of the box-behnken design (BBD) and central composite design (CCD) has been carried out. Quadratic polynomial equations are obtained by investigating the experimental yield of the transesterification process. The impact of process parameters on biodiesel yield is discussed by various plots. It was found that the foremost influential parameter on biodiesel production was the CaO amount based on both BBD and CCD methods. A critical relationship with experimental results in BBD method R2 value is 97.73%, while within the case of the CCD method R2 value is 99.90%. The Optimized process parameters for the CaO catalyst were determined as Methanol: oil molar ratio: 12:1; CaO amount (w/w)%: 1%; reaction temperature: 50°C; and the corresponding yield: 96.45% for BBD and CCD methods, respectively.

Effect of biodiesel-dimethyl carbonate blends on engine performance, combustion and emission characteristics

Present study investigates the effect of palm biodiesel blends with and without oxygenated alcohol dimethyl carbonate (DMC) on compression ignition engine. H2SO4 was used to treat the crude palm oil. Furthermore, acid treated palm oil was converted into palm biodiesel via ultrasound-assisted transesterification process at operating conditions of catalyst (KOH) concentration of 0.75 wt%, methanol to oil ratio of 60 V/V %, reaction time of 38 min, reaction temperature of 60 °C and 59% duty cycle. The antioxidant used in biodiesel blends was dimethyl carbonate. These samples were prepared by adding DMC 10% by volume into biodiesel blends at stirring speed of 2000 rpm for 30 min in order to make a homogenous blend. The key fuel properties of the six fuel samples before being engine tested were measured including kinematic viscosity, dynamic viscosity, density, flash point, acid value and calorific value. Engine performance, emission and combustion characteristics were investigated by operating engine at full load condition and varying engine speeds from 1100 rpm to 2100 rpm. Major findings were average increase of 1.70%, 1.22% and 0.95% in BP; average decrease of 1.31%, 2.93% and 1.08% in BSFC; average increase of 4.30%, 4.77% and 4.90% in BTE; average decrease of 2.63%, 2.80% and 4.54% in EGT; significant reduction of 19.04%, 25% and 26.47% in CO emissions; average reduction of 12.76%, 19.35% and 33.33% in HC emissions observed for B10 + DMC, B20 + DMC and B30 + DMC as compared to biodiesel blends without antioxidant.

Optimized conventional and ultrasound-assisted ethyl transesterification of jatropha (Jatropha curcas) and palm (Elaeis guineensis) oil mixtures

While biodiesel from jatropha oil is oxidation-sensitive and fluid, palm oil-biodiesel is more stable, but with sub-optimal fluid dynamics. Mixing these oils before reaction could be advantageous for reducing steps in production while generating biodiesel with desired cold-flow and stability properties. Here, we performed central composite designs to optimize the transesterification of jatropha and palm oil mixtures via conventional alkaline (CT) and ultrasound-assisted transesterification (UT), assessing the physicochemical properties of the biodiesel. Acid esterification of oil mixtures was followed by transesterification with NaOH and ethanol. The two-step conversion of jatropha and palm oil binary mixtures was successful. UT resulted in 93%-time reduction (4 min) in comparison to CT (60 min). The increased presence of jatropha oil improved the fluid dynamics of biodiesel. UT is a promising technology for synthesizing biodiesel in less time. The transesterification of binary mixtures is a direct and simple approach for reducing steps in biodiesel production.

Ultrasound-assisted transesterification of soybean oil using low power and high frequency and no external heating source

In this work, high frequency and low power ultrasound without external heating source and mechanical stirring in biodiesel production were studied. Transesterification of soybean oil with methanol and catalyzed by KOH was investigated using ultrasound equipment and ultrasonic transducer. The effect of ultrasonic output power (3 W–9 W), ultrasonic frequency (1 MHz and 3 MHz), and alcohol to oil molar ratio (6:1 and 8:1) have been investigated. The increase in ultrasonic power provided higher conversion rates. In addition, higher conversion rates were obtained by increasing the ultrasonic frequency from 1 MHz to 3 MHz (48.7% to 79.5%) for the same reaction time. Results also indicate that the speed of sound can be used to evaluate the produced biodiesel qualitatively. Further, the ultrasound system presented electric consumption (46.2W∙h) four times lower than achieved using the conventional method (211.7W∙h and 212.3W∙h). Thus, biodiesel production using low power ultrasound in the MHz frequency range is a promising technology that could contribute to biodiesel production processes.

Development of empirical correlations for density and viscosity estimation of ternary biodiesel blends

This study aims to investigate the density and viscosity of ternary biodiesel blends. Fuel density and viscosity play an important role in the fuel injection system, flame propagation, and combustion process in compression ignition engine. The density and viscosity of biodiesel are higher than high-speed diesel which is an implication in the commercialization of biodiesel. In the present study, palm oil has been used for the production of biodiesel through the ultrasound-assisted transesterification process. Three different types of fuel additives including butanol, dimethyl carbonate, and plastic oil have been used for the preparation of nine ternary biodiesel blends. The density and viscosity of individual fuels and ternary biodiesel were measured experimentally in a temperature range of 281.51 K–348.15 K. For the prediction of density and viscosity of ternary biodiesel blends, four density and viscosity models were developed. The prediction accuracy of these developed models was assessed by a statistical tool absolute percentage error (APE). Newly proposed exponential regression models predicted well compared to experimental data for density and viscosity values with high regression coefficient 0.9995 and 0.9841 and lower mean absolute percentage of error 0.012 % and – 0.516 % at (348.15 K) temperature respectively. These correlations are significant for the automobile industry in developing fuel pipeline and transport equipment where additives would be present in diesel-biodiesel fuel blends.

Two-Stage Biodiesel Synthesis from Used Cooking Oil with a High Acid Value via an Ultrasound-Assisted Method

In this study, ultrasound was used to accelerate two-stage (esterification–transesterification) catalytic synthesis of biodiesel from used cooking oil, which originally had a high acid value (4.35 mg KOH/g). In the first stage, acid-catalyzed esterification reaction conditions were developed with a 9:1 methanol/oil molar ratio, sulfuric acid dosage at 2 wt %, and a reaction temperature of 60 °C. Under ultrasound irradiation for 40 min, the acid value was effectively decreased from 4.35 to 1.67 mg KOH/g, which was decreased to a sufficient level (<2 mg KOH/g) to avoid the saponification problem for the subsequent transesterification reaction. In the following stage, base-catalyzed transesterification reactions were carried out with a 12:1 methanol/oil molar ratio, a sodium hydroxide dosage of 1 wt %, and a reaction temperature of 65 °C. Under ultrasound-assisted transesterification for 40 min, the conversion rate of biodiesel reached 97.05%, which met the requirement of EN 14214 standard, i.e., 96.5% minimum. In order to evaluate and explore the improvement of the ultrasound-assisted two-stage (esterification–transesterification) process in shortening the reaction time, additional two-stage biodiesel synthesis experiments using the traditional mechanical stirring method under the optimal conditions were further carried out in this study. It was found that, under the same optimal conditions, using the ultrasound-assisted two-stage process, the total reaction time was significantly reduced to only 80 min, which was much shorter than the total time required by the conventional method of 140 min. It is worth noting that compared with the traditional method without ultrasound, the intensification of the ultrasound-assisted two-stage process significantly shortened the total time from 140 min to 80 min, which is a reduction of 42.9%. It was concluded that the ultrasound-assisted two-stage (esterification–transesterification) catalytic process is an effective and time-saving method for synthesizing biodiesel from used cooking oil with a high acid value.