Methyl Ester Yield Research Articles

Synthesis of Biodiesel from Refined Waste Cooking Oil with Active Natural Zeolite

This research evaluates refining waste cooking oil with active natural zeolite, utilizes it for biodiesel synthesis, and characterizes the synthesized methyl ester. This experimental laboratory research was carried out: (1) activation of natural zeolite, (2) refining waste cooking oil with active natural zeolite, (3) determination of free fatty acid (FFA) content of the oil, (4) transesterification with KOH catalyst, (5) characterization of the synthesized methyl esters according to the SNI 7182:2015, and (6) identification of the methyl ester component by GC-MS. The results showed that the FFA content of the refined waste cooking oil using active natural zeolite with concentrations of 10%, 20%, and 30% per mass of oil were 2.97, 2.0, and 1.56%, respectively. The yield of methyl ester transesterified with various concentrations of KOH (0.8, 1.0, and 2% per mass of oil), respectively, were 80.13, 85.34, and 74.98%. The synthesized methyl ester resulted in the characteristics: 0.867 g/mL of density; 5.72 cSt of viscosity; 1.449 of refractive index; 1.46 g KOH/g of acid number; and 0.023% of water content. Identification of GC-MS obtained the synthesized methyl esters, which include: 46.10% of methyl hexadecanoic, 41.68% of methyl 9-octadecanoic, 6.42% of methyl octadecanoic, and 5.80% of methyl eicosanoic.

Enzymatic In Situ Interesterification of Rapeseed Oil with Methyl Formate in Diesel Fuel Medium

The purpose of this research was to evaluate the process of enzymatic biodiesel synthesis by directly using rapeseed as a raw material, extracting the oil contained within and interesterifying with a mixture of methyl formate and mineral diesel, choosing the amount of mineral diesel so that the ratio between it and the rapeseed oil in the seeds was 9:1. As the final product of the interesterification process, a mixture of mineral diesel and biodiesel was obtained directly, which is conventionally produced by mixing the mineral diesel and biodiesel. The tests were performed using enzymatic catalysis using the lipase Lipozyme TL TIM. Process optimization was performed using the response surface methodology. A model describing the interaction of three independent variables and their influence on the yield of rapeseed oil methyl esters was developed. The physical and chemical indicators of the product obtained under optimal interesterification conditions were evaluated.

Biodiesel Production from Jatropha Curcas Oil Using Li/Pumice as Catalyst in a Fixed-Bed Reactor

A packed-bed catalytic configuration reactor using pumice granules loaded with lithium (Li/Pumice) as a heterogeneous catalyst was developed for the continuous biodiesel production. For this purpose, Jatropha curcas oil was used as an alternative feedstock to edible oils and diethyl ether was used as a cosolvent to improve the mass transfer between the phases present in the transesterification reaction. The solid catalyst was characterized, and its catalytic activity was evaluated for the biodiesel production. Fatty acid methyl esters (FAME) yield of 100% was achieved under the conditions of 1.4 mL min-1, 20.0 methanol/oil molar ratio, 0.57:1 cosolvent/methanol molar ratio and 40ºC. Moreover, Li/Pumice catalyst shows high stability for the continuous biodiesel production.

Potential Heterogenous Catalyst from Pineapple waste for Biodiesel Production

Biodiesel is a viable alternative to petroleum-based fuels due to its potential to lower greenhouse gas emissions. Recently, the utilization of waste biomass materials for the production of fuels and other energy products has been explored. In this current study, a potential heterogeneous solid catalyst was obtained from pineapple waste peels and graphite oxide (GO). Its potential for transesterification in biodiesel production was investigated using the impregnation mass ratio of 1 GO: 3 pineapple waste. The methanol to coconut oil molar ratio of 18:1, impregnation temperature of 80 °C and H3PO4 activating agent were found to yield the highest fatty acid methyl ester (FAME) yield of 53.71%.

Resource Utilization of Waste Cooking Oil Catalyzed by Na2CO3/ZSM-5.

A catalyst with a simple synthetic process and good catalytic performance was prepared using Na2CO3 as the active component and ZSM-5 as the carrier for the resource utilization of waste cooking oil. The structure of Na2CO3/ZSM-5 was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, and the effects of parameters such as Na2CO3 loading, catalyst percentage, and reaction time on the yield of fatty acid methyl esters were investigated. The results showed that the conversion of waste cooking oil to fatty acid methyl esters yielded up to 96.89% when the Na2CO3 loading was 35%, the reaction temperature was 65 °C, the reaction time was 2 h, and the catalyst percentage was 1 wt %. The Na2CO3/ZSM-5 catalyst could be used to replace H2SO4 or NaOCH3 in the industrial treatment of waste cooking oil for its resource utilization.

Preparation of Brönsted-Lewis dual acidic catalyst Ce-HPW-F and its simultaneous catalytic esterification and transesterification of oleic acid and castor oil with methanol to synthesize biodiesel

A series of Brönsted-Lewis dual acidic catalyst Ce(x)-HPW-F(x = 1/3, 2/3, 1, 4/3, x is the molar ratio of Ce to HPW) were synthesized by introducing Ce3+ and F- into 12-tungstophosphoric acid (H3PW12O40, HPW) with Keggin structure. The structure, morphology, valence state, elemental composition, acid site density and type of Ce-HPW-F catalyst were analyzed by FT-IR, XRD, BET, SEM, XPS, NH3-TPD, and Py-IR. The catalytic activities and stabilities of the obtained catalysts were studied in the esterification and transesterification reactions of oleic acid and castor oil (Simulated acidified oil, SAO). The Ce(1/3)-HPW-F has presented optimum catalytic activity. A yield of fatty acid methyl esters (FAME) 93.0 % was obtained at the 18:1 methanol to SAO molar ratio, 4 wt% catalyst, 110°C reaction temperature and reaction time of 90 min. The high catalytic activity of Ce(1/3)-HPW-F could be attributed to the strong Brönsted and Lewis acidity. The Lewis acidity was generated from the partial exchange of Ce3+ with the proton (H+) in HPW and increased through the formation of Ce-F bond between the strongly electronegative F- and Ce3+. Meanwhile, in the highly polar medium (methanol), the binding force between O and H+ was reduced due to the negative charge dispersion of the outer oxygen in the phosphotungstic acid anion and the polarization of W=Od formed by the terminal O and W. This may lead to the stepwise dissociation of H+ in HPW that had not been exchanged by Ce3+. However, F- could form the hydrogen bond with H+ to avoid the occurrence of the above phenomenon. After reusing Ce(1/3)-HPW-F catalyst for four times, the total yield of FAME could still achieve more than 75 %.

Assessing and optimizing the efficacy of synthesized CaO-based nano-catalysts for biodiesel production

ABSTRACT The current research proposed the work on the consumption of waste cooking oil (WCO) as a valuable resource for the production of biodiesel. This study focuses on maximizing output yield by employing composite heterogeneous catalysts, namely calcinated calcium oxide with aluminum oxide (CaO/Al2O3) and calcium oxide with titanium oxide (CaO/TiO2). The calcination process was adopted for the catalysts at 600°C for 5 h to improve catalytic activities and to increase surface area. XRD and TGA were implemented to analyze the crystal structure and thermal stability of these heterogeneous catalysts. Experimentation was planned by implementing the response surface methodology (RSM) approach in combination with the Box-Behnken design. The optimum yield of fatty acid methyl esters (FAMEs) was experimentally observed at 96.56%, using CaO/Al2O3 at methanol to oil (m/o) molar ratio of 11.9:1, 3.19% catalyst loading, 53.79°C and 76.86 minutes (min). The maximum experimental yield with CaO/TiO2 was observed at 98.15% with the optimized operating conditions of independent process variables viz. m/o molar ratio 11:99, 2.53 wt.% catalyst loading and 68.14 min at 59.79°C. The research recommends the potential use of WCO and both the heterogeneous catalysts for optimal biodiesel yield; however, CaO/TiO2 exhibits superior performance over CaO/Al2O3, which is also confirmed by the XRD and TGA results.

Application of Response Surface Methodology (RSM) in the statistical evaluation of biodiesel production from the neutral lipids of the Coelastrella-Nannochloropsis consortium

The paramount challenge in economically workable microalgal biodiesel production is the selection of a competent catalyst to improve the fatty acid methyl ester yield with desirable fatty acid composition. Though countless researchers have explored different homogeneous and heterogeneous catalysts to improve the transesterification efficacy, achieving greater biodiesel production from the neutral lipids of the microalgal consortium using a statistical tool, response surface methodology is scarce. Thus, the present study applied Response surface methodology to statistically analyze the biodiesel production from the neutral lipids of the indigenous Coelastrella-Nannochloropsis consortium (CNC) on the way to commercial feasibility. Onset of the study, the neutral lipids and acid value of the CNC were determined to be 18.74% and 2.73%, respectively. The transesterification of the neutral lipids of CNC was optimized through the coded factors in the RSM for various reaction parameters as combined influence viz., (i) Catalyst dose: methanol volume, (ii) Catalyst dose: reaction time; (iii) Catalyst dose: reaction temperature, (iv) Time: temperature, (v) time: methanol volume, (vi) temperature: methanol volume. Based on the ANOVA, coefficient determination, 2% KOH, 2 h time, 70 °C temperature, and 9 mL methanol volume were ascertained to be optimal values to accomplish 92% biodiesel production. Further, the biodiesel has desirable palmitic, palmitoleic, stearic, oleic, linoleic, and linolenic acids, with palmitic acid as the prevalent fatty acid contributing 16–18%. In addition, the tested fuel properties of CNC biodiesel satisfy international biodiesel standards.

Process optimization of one-step direct transesterification and dual-step extraction-transesterification of the Chlorococcum-Nannochloropsis consortium for biodiesel production

In the present study, the efficacy of one-step direct transesterification (OSDT) and Dual-step extraction-transesterification (DSET) of Chlorococcum sp., Nannochloropsis sp., and their consortium was evaluated for fatty acid methyl ester (FAME) yield. Initially, the biomass yield and lipid content of the two strains and their consortium were estimated. Of the biomasses, the consortium showed a higher biomass yield of 1.41 g/L and lipid content of 30.2%, which is higher than the monocultures irrespective of the different biomass drying methods used. With regards to the FAME yield, OSDT and DSET have yielded almost similar quantities about 21 g/100g dried biomass. Of the different reaction conditions of OSDT tested, a higher FAME yield at 70–71% (based on lipid weight) was obtained at 75 °C reaction temperature, 3 h reaction time with a 2g sample size. Eventually, the fatty acid composition of consortium biomass revealed higher levels of saturated and monounsaturated fatty acids in the vicinity of 46 and 25%, respectively. Based on the results, it is concluded that OSDT is a promising method due to its low energy consumption, cost-effective and time-saving attributes for quality biodiesel production from the Chlorococcum-Nannochloropsis consortium.

S2O82−/CeO2 Solid Superacid Catalyst Prepared by Radio-Frequency Plasma-Assisted Hydrothermal Method

CeO2 was prepared using a hydrothermal method, modified by radio-frequency plasma in the form of glow discharge, and then the solid superacid S2O82−/CeO2 was prepared by the impregnation method. A series of properties such as pore structure was characterized by N2 adsorption–desorption experiments, surface morphology was characterized by TEM, crystal phase was characterized by XRD, and surface acidity of the catalyst was characterized by Py-IR and Hammett titration. The methyl esterification reaction of tryptophan was used to evaluate the activity of the solid superacid. The results showed that the catalyst modified by radio-frequency plasma had a larger specific surface area, more surface oxygen vacancies, smaller particle size, and higher total acid content. The yield of tryptophan methyl ester reached a higher level of 94.5% (150 °C, 1 MPa, 2 h), catalyzed by the modified S2O82−/CeO2. This work verified the feasibility of plasma technology in the field of catalytic activity enhancement of solid superacid.

Effect of different inocula on the granulation process, reactor performance and biodiesel production of algal-bacterial granular sludge (ABGS) under low aeration conditions

The algal-bacterial granular sludge (ABGS) system is a prospective wastewater treatment technology, but few studies focused on the effects of different inoculum types on the establishment of the ABGS system under low aeration conditions (step-decrease superficial gas velocity from 1.4 to 0.5 cm/s). Results from this study indicated that compared with other inocula, the ABGS formed by co-inoculating aerobic granular sludge (AGS) and targeted algae (Chlorella) exhibited a shorter granulation period (shortened by 15 days), higher total nitrogen (89.4%) and PO43--P (95.0%) removal efficiencies, and a greater yield of fatty acid methyl esters (FAMEs) (9.04 mg/g MLSS). This was possibly attributed to that the functional bacteria (e.g. Thauera, Gemmobacter and Rhodobacter) in the inoculated AGS facilitated the ABGS granulation. The inoculated algae promoted their effective enrichment under illumination conditions and enhanced the production of extracellular polymeric substances, thus improving the stability of ABGS. The enriched algae were attached to the outer layer of the granules, which could provide sufficient oxygen for bacterial metabolism, revealing the inherent mechanisms for the good stability of ABGS under low aeration intensity. Overall, the rapid granulation of ABGS can be achieved by inoculating optimal inocula under low aeration conditions, which is convenient and economically feasible, and motivates the application of algal-bacterial consortia.

Application of efficient soft computing approaches for modeling methyl ester yield from Azadirachta Indica (Neem) seed oil: A comparative study of RSM, ANN and ANFIS

This work centers on methyl ester yield modeling; by Azadirachta Indica seed oil (AISO) transesterification, using Adaptive Neuro-fuzzy Inference System (ANFIS), Artificial Neural Network (ANN) and Response Surface Methodology (RSM). AISO was obtained from the seeds of Azadirachta Indica tree. The oils were extracted from the seeds using solvent extraction method. The physicochemical properties of AISO and Azadirachta Indica seed oil methyl ester (MAISOt) were determined using standard methods. Fatty acid composition was determined using, Gas Chromatography (GC). Statistical evaluations of these models show their efficacy in the order RSM < ANN < ANFIS, with ANFIS as the best; as indicated by its very high R2 value of 0.9999 and low RMS error value of 0.0011. The ANFIS predicted minimum and maximum values for % methyl ester yields were 54.66 and 90.25 %, respectively, while the other models predicted similar methyl ester yields. The physicochemical characterization results of AISO and MAISOt samples, show that their respective viscosity, dielectric strength (DS), pour and flash points values were (8.83 and 3.47 mm 2s−1), (33.42 and 48.93 KV), (9 and -6 °C), and (162 and 174 °C). These results indicated the MAISOt sample’s potential use as a transformer fluid. GC result indicated that MAISOt was unsaturated. Finally, on the basis of the gotten model results, ANFIS was adjudged as the best predictive model, followed by ANN and RSM, in that order.

Production of 2,5-Furandicarboxylic Acid Methyl Esters from Pectin-Based Aldaric Acid: from Laboratory to Bench Scale.

2,5-Furandicarboxylic acid (FDCA) is one of the most attractive emerging renewable monomers, which has gained interest especially in polyester applications, such as the production of polyethylene furanoate (PEF). Recently, the attention has shifted towards FDCA esters due to their better solubility as well as the easier purification and polymerisation compared to FDCA. In our previous work, we reported the synthesis of FDCA butyl esters by dehydration of aldaric acids as stable intermediates. Here, we present the synthesis of FDCA methyl esters in high yields from pectin-based galactaric acid using a solid acid catalyst. The process enables high substrate concentrations (up to 20 wt %) giving up to 50 mol % FDCA methyl esters with total furancarboxylates yields of up to 90 mol %. The synthesis was successfully scaled up from gram-scale to kilogram-scale in batch reactors showing the feasibility of the process. The stability of the catalyst was tested in re-use experiments. Purification of the crude product by vacuum distillation and precipitation gave furan-2,5-dimethylcarboxylate with a 98 % purity.

Green Production of Biodiesel from High Acid Value Oil via Glycerol Esterification and Transesterification Catalyzed by Nano Hydrated Eggshell-Derived CaO

Biodiesel is a widely recognized and favored liquid biofuel, primarily attributed to its biodegradability and non-toxicity. However, the development of biodiesel is hindered by its high production costs. Here, we developed a method that combines glycerol esterification and transesterification reaction catalyzed using nano-hydrated CaO for the green production of biodiesel from high acid value oil. Waste eggshell was chosen as the calcium source to examine the effect of hydration temperature and duration. The catalysts were optimized using a synthesis process involving under calcination for 3 h at 875 °C, followed by hydration at 60 °C for 6 h and subsequent dehydration at 725 °C. The catalyst loading, alcohol-to-oil mass ratio, reaction temperature, and duration were optimized to 2.5 wt%, 35%, 60 °C, and 2 h, respectively. Under the optimized conditions, the yield of fatty acid methyl ester reached 94.44%. The catalyst was successfully reused eight cycles while maintaining a yield of fatty acid methyl ester at 80.52%. In addition, a comprehensive overview was summarized to compare the catalyst preparation methods, reaction conditions, biodiesel yield, and reusability in the production of biodiesel using eggshell-derived CaO.

A liquefied ammonia method for extracting lipids from Nannochloropsis oculata without drying and cell disruption

Lipid extraction technology that avoids energy-consuming processes, such as drying and cell disruption, is needed for efficient biofuel production. Here, we propose a novel technique for lipid extraction directly from wet Nannochloropsis oculata using liquefied NH3, eliminating energy-consuming drying and cell-disruption steps. An experimental apparatus to distribute liquefied NH3 to the sample at 20 °C and 0.85 MPa was developed. At an NH3/sample ratio of 45 (wt./wt.), approximately 48.5 wt% of the sample was separated as a crude extract, with the removal of over 99 wt% of the water content. The elemental composition of the feedstock and crude extract did not indicate any increase in N levels. The total fatty acid methyl ester yields (10.5 % of dry-weight biomass) were comparable to those obtained using conventional methods. The crude extract contained valuable C12–C20 fatty acids, indicating that liquefied NH3 extraction is attractive for producing bioproducts from wet microalgae.

Polyoxometalate-Modified Amphiphilic Polystyrene-block-poly(2-(dimethylamino)ethyl methacrylate) Membranes for Heterogeneous Glucose to Formic Acid Methyl Ester Oxidation.

Herein, we present a new heterogeneous catalyst active toward glucose to formic acid methyl ester oxidation. The catalyst was fabricated via electrostatic immobilization of the inorganic polyoxometalate HPA-5 catalyst H8[PMo7V5O40] onto the pore surface of amphiphilic block copolymer membranes prepared via non-solvent-induced phase separation (NIPS). The catalyst immobilization was achieved via wet impregnation due to strong coulombic interactions between protonated tertiary amino groups of the polar poly(2-(dimethylamino)ethyl methacrylate) block and the anionic catalyst. Overall, three sets of five consecutive catalytic cycles were performed in an autoclave under 90 °С and 11.5 bar air pressure in methanol, and the corresponding yields of formic acid methyl ester were quantified via head-space gas chromatography. The obtained results demonstrate that the membrane maintains its catalytic activity over multiple cycles, resulting in high to moderate yields in comparison to a homogeneous catalytic system. Nevertheless, presumably due to leaching, the catalytic activity declines over five catalytic cycles. The morphological and chemical changes of the membrane during the prolonged catalysis under harsh conditions were examined in detail using different analytic tools, and it seems that the underlying block copolymer is not affected by the catalytic process.

Upgrading catalytic properties of green synthesized TiO2 for green fuel production from apricot seeds oil

The ongoing energy crisis and global warming issues have pushed the research community to search for sustainable energy supplies such as biodiesel (methyl esters). In this regard, inedible oils which are not consumed by humans could be potential sources for methyl esters production. Herein, the methyl esters were produced by trans-esterifying the apricot seeds oil (ASO) employing series of green synthesized (mediated by banana peel extract) TiO2 based NiO-TiO2 heterogeneous nano-catalysts with varying loadings of NiO (5, 10 and 15 by wt%). The as-prepared catalysts were characterized using advanced techniques like FT-IR, XRD, SEM and FE-SEM. These studies established the successful impregnation of NiO with TiO2 NPs. The efficiency of NiO-TiO2 with 10 wt% of NiO loading calcined at 500 °C was superior due to the highest biodiesel yield compared to other nano-catalysts. The parametric study of transesterification reaction to yield methyl esters adapting this catalyst revealed the maximum yield (93.4 %) with MeOH: oil and catalyst loading of 20:1 and 2 wt% correspondingly in 1 h at 55 °C. GC–MS analysis was executed for investigating and confirming the composition of obtained methyl esters at optimized conditions. Furthermore, the heterogeneous catalyst was reusable for five cycles for transesterification of ASO. The kinetic investigations showed that transesterification of ASO was compatible with pseudo-first order model. In addition, fuel characteristics such as calorific and acid value were measured by using titrations and bomb calorimeter respectively and compared with ASTM6751 and EN14214 standards.

Biodiesel Production from Seed Oil Obtained from Pongamia pinnata L.

At the present time biodiesel are the most promising source of energy as it is renewable and can accomplished the rising energy demand. Pongamia pinnata L. (commonly known as Karanj) is an evergreen tree of family Fabaceae sub family Papilioneaceae, has been recognized as a potential source of biodiesel prepared from the oil obtained from its seeds. In the present work, biodiesel fuel was prepared by alkaline-catalyzed esterification of high free fatty acids present in Karanj oil. The transestrification reaction was performed by varying practical parameters such as NaOH percentage (0.50%, 0.75%, 1%), methanol to oil ratio ( 3:1, 6:1, 9:1), and reaction temperature and time (40°C for 2h, 60°C for 2h, room temperature for 24h) at constant stirring at 150 rpm. Optimum alkaline-catalyzed transesterification was achieved using 1% NaOH as a solid alkaline catalyst with a methanol-to-oil ratio of 1:6, temperature at 600C. The yield of methyl esters from Karanja oil under the optimal condition was 92%. The biodiesel and oil contents were analysed using Gas Chromatography and Mass Spectroscopy (GC-MS) analyser. Fuel properties of the biodiesel obtained by transesterification were tested and found to meet the ASTM (American Society for Testing and Material) specifications.

Immobilization of Candida catenulata cells by surface-loading of an amino-functionalized Fe3O4 nanoparticles and its application as the sustainable whole-cell biocatalyst for enzymatic biodiesel production

In this study, the intracellular lipases of Candida catenulata were examined as a whole-cell biocatalyst (WCB) of soybean oil transesterification and obtained a fatty acid methyl ester (FAME) yield of 79.1%. To facilitate the biocatalyst recovery and improve its stability, the WCB was attached to magnetic Fe3O4 nanoparticles activated by a linear structure of polyethyleneimine (PEI) as the multi-amino-functionalized arm. The preparation procedure of the magnetic whole-cell biocatalysts (MWCBs) was optimized by considering the pH during immobilization (X1), the weight ratio of nanoparticles-to-cell (X2), and PEI concentration (X3) using the response surface methodology. The best optimal setting of the variables was determined at X1 of 6.1, X2 of 0.6, and X3 of 0.7 w% with the transesterification activity of 7.6 × 105 IU gbiocatalyst−1 gained a FAME yield of 78.4% after 3 h. The MWCBs showed an improvement in thermal stability where the optimal temperature was shifted from 34C to 38 °C and the deactivation energy was increased from 183.9 kJ mol−1 and 223.6 kJ mol−1 after the immobilization. The MWCBs displayed satisfactory sustainability in the repeated transesterification experiments and maintained 87.3% of the original activity after 10 cycles which was higher than the bare-WCB system with a recovery of 57.4%.

Kaolinite and Illite Based Clay Supporting Nickel: its Synthesis, Characterization, and Catalytic Optimazion in a Lab-Scale Fatty Acid Methyl Ester Production

The increasing world energy needs are not matched by the limited availability of fossil fuels thus the development of clean and sustainable fuels is the right solution. Biodiesel is one of these fuels and can be produced through transesterification reactions of vegetable oils in the presence of a catalyst. Acidic natural clay can be an option because of its large abundance, especially in the Indonesia and is heterogeneous in the solution it catalyzes. In this study, clay samples were obtained from an area in Bukittinggi City, West Sumatra Province, and then combined by wet impregnation with nickel as a catalyst in the transesterification reaction of used cooking oil to produce fatty acid methyl esters. Based on X-Ray diffraction (XRD) analysis, the presence of nickel ions does not affect the diffraction pattern of clay minerals contained in the soil consisting of kaolinite and illite. Measurements with X-Ray fluorescence (XRF) showed that the silicon-aluminum mole ratio also did not show a significant change where before mixing the value was 2.0 and after that it only decreased about 5 % to 1.9. The pore diameter of the catalyst was 3.03 nm known by Surface Area Analyzer (SAA). Several variations have been carried out to optimize the catalytic performance of the nickel supported clay and the best conditions were obtained when the catalyst concentration was 3 wt %, the methanol-oil mole ratio was 6:1, the reaction temperature was 70 °C and the reaction carried out for 3 hours. Under these conditions, the yield of methyl ester produced was 63 %