Fatty Acid Methyl Ester Content Research Articles

Biodiesel production from microbial oil provided by oleaginous yeasts from olive oil mill wastewater growing on industrial glycerol

This study focuses on the potential of four lipogenic yeasts to produce lipids using glycerol as carbon substrate; Candida molendinolei MH267796, Meyerozyma caribbica MH267795 and Rhodotorula minuta MH267794 were isolated from olive oil mill wastewater, while Cryptococcus curvatus ATCC20509 was used as control strain. Lipid production with crude glycerol was higher than that provided with pure glycerol. Fed-batch bioreactor cultures with M. caribbica MH267795 led to the production of 42.12 g L−1 of total dry weight with a microbial oil content of 48.14% (w w−1). In general terms, tested biodiesel properties meet all the limits set by European biodiesel standard UNE 14214:2013, excepting fatty acid methyl ester content. In addition, M. caribbica MH267795 oil biodiesel depicts a fatty acid methyl ester content (90.2% (w w−1)) higher than that of the most intensively studied C. curvatus oil biodiesel. Re-use of crude glycerol as raw material in biodiesel industry has been proven through fermentation, increasing potential full-scale application of such alternative.

Characteristics of direct transesterification using ultrasound on oil extracted from spent coffee grounds

Spent coffee grounds (SCG), the residue after brewing coffee beverage, is a promising biodiesel feedstock due to its high oil contents (15‒20%). However, SCG should be pretreated to reduce the high free fatty acid content, which hampers transesterification reaction. To overcome this, we explored a direct transesterification reaction of SCG using ultrasound irradiation and identified the optimal sonication parameters. A high fatty acid methyl ester (FAME) content, up to 97.2%, could be achieved with ultrasound amplitude of 99.2 <i>μ</i>m, irradiation time of 10 min, and methanol to oil ratio of 7:1 in the presence of potassium hydroxide concentration of 1.25 wt.%. In addition, we demonstrated that ultrasound irradiation is an efficient method to produce biodiesel from untreated SCG in a short time with less energy than the conventional mechanical stirring method. The physical and chemical properties of the SCG biodiesel met the requirements for an alternative fuel to the current commercial biodiesel.

Classification of ANFO samples based on their fuel composition by GC–MS and FTIR combined with chemometrics

Ammonium nitrate fuel oil (ANFO) is one of the most favorite explosives used in terrorist attacks. This explosive is a complex mixture of 95–96% ammonium nitrate (AN) and 4–5% liquid hydrocarbons (fuel oil). In this study, we analyze a variety of ANFO explosive mixtures in order to classify their different sources of origin by observing the difference in fuel components. The study was performed by mixing ammonium nitrate with eight different diesel brands collected in Lincoln, UK in two seasons (winter and summer). The samples were extracted using appropriate solvent and extracts were subsequently analyzed in sextuplicate by gas chromatography―mass spectrometry (GC–MS) and Fourier transform infrared spectroscopy (FTIR). A classification model was performed using principal component analysis (PCA) and Lineal Discriminant Analysis (LDA). In this study, four fatty acid methyl ester (FAME) contents were observed by GC–MS in all summer samples but found lack in some winter sample resulting in seasonal variation effect. The classification of pre-blast ANFO samples was achieved using GC–MS and FTIR in a combination with PCA/LDA. The results significantly showed the variation of specific diesel components and providing different classification performance among ANFO samples with high classification performance. Therefore, this study can be beneficial in forensic investigation that the use of diesel components are able to classify among different ANFO samples.

Optimization of biodiesel production by in situ transesterification from dry biomass of Choricystis minor var. minor via response surface methodology

The development of low-cost and cost-effective technologies to produce biodiesel from microalgae is a challenge being addressed by many researchers. This work optimized direct transesterification of dry biomass of Choricystis minor var. minor using H3PO4 and KOH as catalysts. The acid reaction conditions were optimized by Box–Behnken design and the base catalysis by 32 factorial design with replication. The fatty acid methyl ester (FAME) yield was investigated by response surface methodology. The H3PO4 catalyst was able to convert more than 50% of the triacylglyceride into FAME. Applying an analysis of variance, the temperature variable was the most significant factor, followed by reaction time. The interaction between time and temperature also positively influenced the model. The optimum conditions for acid catalysis were H3PO4 solution 10 mL, 60 °C, and 3 h. In base catalysis, the model presented a lower statistical significance, with no significant differences in FAME content. The base catalysis conditions determined were temperature of 30 °C for 1 h. The qualitative and quantitative profile of FAMEs was similar for both designs evaluated. The statistical tool made it possible to optimize the biodiesel production by dry microalgae biomass at lower cost, with less labor and in less time.

Fatty acid profile of peel and pulp of Spanish jujube (Ziziphus jujuba Mill.) fruit

The fatty acid methyl esters (FAMEs) profiles of fruit peel and pulp of 4 Spanish cultivars of Ziziphus jujuba were studied. The FAMEs profile of the cultivar ‘GAL’ was studied under two farming practices, (i) organic, ‘GAL-E’ and conventional, ‘GAL-T’. Eleven FAMEs were identified, the predominant ones were cis-palmitoleic acid (pulp) and oleic and palmitic acid (peel). When comparing the FAMEs profiles between organic and conventional ‘GAL’ peel jujube fruits, the ‘GAL-E’ (organic) presented a higher unsaturated/saturated ratio than the ‘GAL-T’ cultivar (conventional), while this relationship in the pulp was the opposite. The ‘DAT’ cultivar was interesting for its high palmitoleic acid content while the ‘GAL-E’ and ‘GAL-T’ cultivars had high contents of oleic, palmitic and linoleic acids. The LDA (linear discriminant analysis) model showed that the FAMEs contents could be used to discriminate the studied cultivars, and the agricultural practice, because all groups were clearly separated with no overlaps.

Potential Protein and Biodiesel Sources from Black Soldier Fly Larvae: Insights of Larval Harvesting Instar and Fermented Feeding Medium

Primarily produced via transesterification of lipid sources, fatty acid methyl ester (FAME) of biodiesel derived from insect larvae has gained momentum in a great deal of research done over other types of feedstock. From the self-harvesting nature of black soldier fly larvae (BSFL), research had, however, only concentrated on the harvest of BSFL on sixth instar. Through rearing BSFL on coconut endosperm waste (CEW), 100 BSFL were harvested at the fifth and sixth instar, then modification on CEW with mixed-bacteria powder was carried out. It was found that the fifth instar BSFL had 34% lipid content, which was 8% more than the sixth instar. Both instars had similar corrected protein contents around 35–38%. The sixth instar BSFL contained around 19% of chitin, which was about 11% more than the fifth instar. Biodiesel products from both instars showed no differences in terms of FAME content. With modification on CEW, at 0.5 wt% of mixed-bacteria powder concentration, the maximum waste-to-biomass conversion (WBC) and protein conversion (PC) were achieved at 9% and 60%, respectively. Moreover, even with the shorter fermentation time frame of CEW, it did not affect the development of BSFL in terms of its WBC and PC when fed with 14 and 21 days fermented medium. FAME from all groups set, which predominantly constituted about C12:0 at around 60%, followed by C14:0 at around 15%, C16:0, and C18:1 both at 10% on average. Lastly, the FAME yield from BSFL was improved from 25% (sixth instar) to 33% (fifth instar) and showed its highest at 38.5% with modification on raw CEW with 0.5 wt% mixed-bacteria powder and fermented for 21 days. Thus, harvesting BSFL at earlier instar is more beneficial and practical, as it improves the FAME yield from the BSFL biomass.

Bench-scale production of sewage sludge derived-biodiesel (SSD-BD) and upgrade of its quality

Even if sewage sludge gain acceptance as a potential feedstock for biodiesel (BD) production, water content and contaminants in sewage sludge still remain as obstacles for the production and quality of biodiesel, respectively. Crude BD was produced from a feedstock of wet sewage sludge with 85% water content via in-situ wet-transesterification in a bench-scale (10 L) reactor, and then further treated for enhancing the BD quality to a transportation grade through a series of refining processes. The wet-transesterification was optimized in terms of crude BD yield by varying methanol dosage, methanol/co-solvent (xylene) ratio and reaction time. The maximum crude BD yield and the fatty acid methyl ester (FAME) content were 11.05 and 67.41%, respectively, when methanol dosage, methanol/co-solvent and reaction time were 15 mL/g, 0.5 and 12 h, respectively. The refining process consisting of vacuum distillation, degumming and neutralization, which satisfied the BD standards (EN14214) and visually improved color and transparency. Based on GC-FID analysis, the FAME content in the refined BD highly increased by eliminating the residual impurities. Applicability of the refined BD as a transportation fuel was confirmed by comparing the quality of the BD blended with the commercial petroleum-diesel (PD) at 3% (BD3) with the standard specification.

Synthesis and catalytic evaluation of hematite (α-Fe2O3) magnetic nanoparticles from iron sand for waste cooking oil conversion to produce biodiesel through esterification-transesterification method

Indonesia’s catalyst needs to reach 2000 tons/year with active period of 1 up to 2 years. The catalyst requirement is largely filled with import catalysts. Iron sand has a potential to be used as a catalyst mainly because of the hematite magnetic mineral content (α-Fe2O3). α-Fe2O3 can be synthesized from iron sand using coprecipitation and calcination method. Performance of these synthesized catalyst evaluated through the production of biodiesel from waste cooking oil by esterification-transesterification method. The catalyst preparation by chemical coprecipitation method followed with calcination. Catalyst was characterized by using XRD, SEM-EDX, BET, and PSA and tested for biodiesel production. α-Fe2O3 phase was obtained at calcination temperature 650°C, 700°C, 750°C and 800°C. The best character is given at temperature 700°C. Biodiesel obtained meets SNI (Standar Nasional Indonesia) based on density, viscosity, and acid number. Yield of biodiesel obtained by using α-Fe2O3 calcined at 700°C reaches 86.781% while Fatty Acid Methyl Ester (FAME) content obtained reaches 87.880%.

Optimization and kinetic modeling of waste lard methanolysis in a continuous reciprocating plate reactor

Abstract Continuous biodiesel production from a waste pig-roasting lard, methanol and KOH was carried out in a reciprocating plate reactor (RPR) using a factorial design containing three process factors, namely methanol/lard molar ratio, catalyst loading, and normalized height of the reactor. The main goals were to optimize the influential process factors with respect to biodiesel purity using the response surface methodology and to model the kinetics of the transesterification reaction in order to describe the change of triacylglycerols (TAG) and fatty acid methyl esters (FAME) concentrations along the RPR height. The first-order rate law was proved for both the reaction and the mass transfer. The model of the changing reaction mechanism and mass transfer of TAG was also applicable. Both kinetic models agreed with the experimental concentrations of TAG and FAME determined along the RPR height.

Contributions of the microbial community to algal biomass and biofuel productivity in a wastewater treatment lagoon system

The vast majority of research on algal biofuel production has been conducted on single species as monocultures in small, closed systems. Growth of algae in wastewater has potential to help overcome shortages of water, nitrogen, and phosphorus availability; however, cultivation in open wastewater systems presents several unique challenges that include colonization by a variety of bacteria, archaea, viruses, and other eukaryotic species. Here, we monitored the microbial community, water chemistry, and fatty acid methyl ester (FAME) content of 5 connected wastewater treatment lagoons over the course of a year. DNA was sequenced from all three Domains in addition to viral DNA specific to eukaryotic algae. Each lagoon demonstrated a unique community profile even when taxa were classified at the coarsest level. Significant correlations were observed between community members, chemical variables, and FAME concentrations. In contrast to previous findings that correlated elevated FAME with nutrient deprivation, we observed high levels of FAME (up to 48% w/w) in some nutrient replete lagoons. High FAME concentrations (%w/w) were significantly correlated to ammonia, nitrite, total Kjeldahl nitrogen (TKN), pH, phosphate, and total phosphorus (R2 = 0.74). FAME quantified by volume (g L−1) correlated with higher biomass concentrations (R2 = 0.78) whereas high FAME as %w/w coincided with lower algal cell densities. Under these uncontrolled conditions, high biomass concentrations provided for a higher overall biofuel content (g L−1), rather than high lipid content with low biomass concentration. High FAME (>19% w/w) also correlated to the abundance of particular bacteria and the major capsid protein (MCP) specific to dsDNA viruses that can infect eukaryotic algae (Phycodnaviridae). Our findings inform the potential of algal biofuel production using wastewater lagoons and estimates of interactions within the diverse microbial community. The resulting data can provide significant insight into biomass and/or lipid accumulation in a large open system.

Wastewater-leachate treatment by microalgae: Biomass, carbohydrate and lipid production

Increases in wastewater discharges and the generation of municipal solid wastes have resulted in deleterious effects on the environment, causing eutrophication and pollution of water bodies. It is therefore necessary to investigate sustainable bioremediation alternatives. Wastewater treatment using consortia of microalgae-bacteria is an attractive alternative because it allows the removal and recycling of nutrients, with the additional advantage of biomass production and its subsequent conversion into valuable by-products. The present study aims to integrate wastewater and landfill leachate treatment with the production of microalgal biomass, considering not only its valorization in terms of lipid and carbohydrate content but also the effect of nutrient limitation on biomass formation. The effect of treating a mixture of raw wastewater with different leachate ratios (0%, 7%, 10% and 15%) was investigated using a microalgae-bacteria consortium. Two microalgae (Desmodesmus spp. and Scenedesmus obliquus) were used. Nutrient removal, biomass concentration, carbohydrate, lipid and Fatty Acid Methyl Ester (FAMEs) content and morphological changes were evaluated. Removals of 82% of NH4+ and 43% of orthophosphate from a wastewater-leachate mixture (containing 167 mg/L NH4+ and 23 mg/L PO43-) were achieved. The highest final yield was obtained using Desmodesmus spp. (1.95 ± 0.3 g/L). The microalgae were observed to accumulate high lipid (20%) and carbohydrate (41%) contents under nutrient limiting conditions. The concentration of Polyunsaturated Fatty Acids (PUFAs) also increased. Morphological changes including the disintegration of coenobia were observed. By using a mixture of wastewater-leachate it is possible to remove nutrients, since microalgae tolerate high ammonia concentrations, and simultaneously increase the algal biomass concentration containing precursors to allow biofuel production.

Chemical composition and protective role of Pulicaria undulata (L.) C.A. Mey. subsp. undulata against gastric ulcer induced by ethanol in rats

Pulicaria undulata subsp. undulata (Family; Asteraceae) is a medicinal plant used to treat inflammation. The objective of this study is to explore the protective effect of the ethanol extract of P. undulata subsp. undulata aerial parts against ethanol induced gastric ulcer in rats. The chemical composition of plant extract, the unsaponifiable matter and the fatty acid methyl esters were analyzed. The biological evaluation was carried out through measuring ulcer indices, oxidative stress markers, certain marker enzymes, inflammatory index and the histopathological assessment of the stomach in rats. The total unsaponifiable matter (94.29%) and the fatty acid methyl ester (82.96%) content were identified. Gastric ulcer recorded significant increase in gastric volume and lesion counts (p < 0.0001). Drastic changes in all biochemical parameters under investigation were observed. Protection with plant extract reversed the action of ethanol by variable degrees of improvement in comparison with the reference drug. The presence of carbohydrates and proteins that acted as a mucilage lining the stomach inner wall give its protective action. In conclusion, P. undulata subsp. undulata succeeded to have anti-ulcerative protective effect. The measured biomarkers served as a good mirror to predict gastric ulcer and the presence of carbohydrates, protein and fibers present in the plant extract acted as a mucilage lining the inner intestinal wall and protect against ethanol induced gastric ulcer. Future study will be carried out to identify the biologically active compounds responsible for plant protection against the gastric ulcer.

A review of optimum conditions of transesterification process for biodiesel production from various feedstocks

Development of low-cost, sustainable and environmentally friendly biodiesel is a key focus in the energy industry worldwide. It is known that selecting suitable raw feedstock materials and optimising an efficient transesterification process are crucial in biodiesel production. Effective and realistic strategies are imperative in order to boost the quantity and quality of biodiesel production. In fact, scientists and researchers have put great effort to improve the market value of their biodiesel products. In recent years, the feasibilities of several raw materials as feedstocks to produce biodiesel have been assessed by researchers. These materials were reported able to produce biodiesel that met international standards, namely the American Society for Test and Materials D6751 and European Standard 14214. Although these biodiesel products have met the quality criteria, their fatty acid methyl ester (FAME) contents differ. This review focuses on optimum conditions (methanol/oil molar ratio, amount of catalyst, reaction temperature and reaction time) of transesterification process for biodiesel production from various feedstocks. The influence of these factors on FAME composition is also discussed. This review is beneficial to scientists working on biodiesel production particularly for the evolution of eco-friendly and low-cost biodiesel.

Multi-objective optimization of integrated biodiesel production and separation system

Biodiesel is a mixture of fatty acid methyl esters (FAME), which can be produced by the transesterification reaction of vegetable oils with methanol. The production of biodiesel is comprised of a series of stages such as reaction, methanol separation, water washing, decantation, and unreacted oil separation followed by the biodiesel purification. Each of these stages involves certain performance measures which need to be optimized for making the overall process cost-effective and productive. Therefore, a commercial base catalyzed batch transesterification process is optimized first with an objective: maximization of the fatty acid methyl esters concentration in final batch time. Dynamic optimization is used with the hot water flow rate passing through the reactor jacket as the decision variable. Orthogonal collocation on finite elements (OCFE) method is employed to convert the dynamic optimization problem into a non-linear programming (NLP) problem. The integrated reaction-separation steps of the biodiesel production process is modeled and simulated in Aspen Plus. Total two multi-objective optimization (MOOP) problems are formulated and solved to capture the trade-offs among the performance indices of the reactor and separation units collectively. Compared to the dynamic optimization problem result, MOOP-1 produced an optimal biodiesel concentration of 0.97 kmol/m3 at an optimal reactor energy cost of 0.12 $/l FAME produced. MOOP-2 determined that the energy expenditure in the reactor jacket is 1.064 times the total energy usage of all the reboilers of the distillation columns. In comparison to MOOP-1, the Pareto-fronts of MOOP-2 produced more cost-effective results in terms of comprehensive trade-offs among the objective functions used.

Preparation of α-Fe2O3-Al2O3 Catalysts and Catalytic Testing for Biodiesel Production

The objective of this research was for preparation and characterization of α-Fe2O3−Al2O3 catalyst α-Fe2O3 was syntheses by using precipitation and calcination in 700 oC. α-Fe2O3 was impregnated in Al2O3 with wet methods and followed calcination processing. The catalyst was characterized for morphology, crystalinity and specific surface area. The catalysts performance was evaluated by producing biodiesel from waste cooking oil through esterification-transesterification. Biodiesels obtained meet SNI based on density, viscosity, and acid number. Yield of biodiesel and Fatty Acid Methyl Ester (FAME) content of biodiesel obtained by using α-Fe2O3- Al2O3 catalyst where yield reaches 86.78% and FAME content reaches 87.88%.

Optimization of Phototrophic Growth and LipidProduction of a Newly Isolated Microalga, Desmodesmus sp. KAERI-NJ5

In this study, a novel microalgal strain, Desmodesmus sp. KAERI-NJ5, was isolated, identified, and evaluated as a candidate for biodiesel feedstock. In a preliminary study, the effects of four general microalgal growth factors, including temperature, pH, light intensity, and concentration of nitrogen source (KNO3), on the microalgal photoautotrophic growth were evaluated. With the exception of light intensity, the growth factors needed to be optimized for the microalgal biomass production. Optimization was done using response surface methodology. The optimal conditions for biomass production were pH 6.54, 27.66℃, and 0.52 g/l KNO3. The biomass production at the optimal conditions was 1.55 g/l, which correlated well with the predicted value of 1.5 g/l. The total lipid and fatty acid methyl ester contents of the cells grown at the optimal conditions were 49% and 21.2% of cell dry weight, respectively. To increase the lipid content of the biomass, microalgae were challenged by nitrogen starvation. Enhancement of total lipid and fatty acid content up to 52.02% and 49%, respectively, were observed. Lipid analysis of the nitrogen-starved cells revealed that C16 and C18 species accounted for 95.9% of the total fatty acids. Among them, palmitic acid (46.17%) and oleic acid (39.43%) dominantly constituted the algal fatty acids. These results suggest Desmodesmus sp. KAERI-NJ5 as a promising feedstock for biodiesel production.

Lipolytic bacterial strains mediated transesterification of non-edible plant oils for generation of high quality biodiesel

Biodiesel is one of the best alternative to depleting fossil fuels for transport sector. However, biodiesel production via lipase mediated transesterification has limitation of high costing microbial enzymes. In order to overcome this limitation, a process of sequential treatment of oil industry wastewater using isolated lipolytic bacterial strains and biodiesel production from non-edible plant oils was studied. In this study, efficient lipase producing bacteria were isolated and evaluated for production of biodiesel from mustard, soybean, jatropha and taramira oils utilizing methanol for the transesterification of oils and bioremediation. Selected strains were then identified, using 16s rRNA sequencing. Further, Bacillus subtilis strain Q1 KX712301 was optimized for biodiesel production from non-edible taramira oil via Plackett-Burman and central composite design. Highest volumetric yield of biodiesel obtained was 102% at optimized parameters. Finally, a sequential bioremediation of vegetable oil contaminated wastewater and then microbial production of biodiesel from non-edible taramira oil was carried out using efficient lipase producer B.subtilis strain Q1 at optimized conditions. During sequential process, complete chemical oxigen demand reduction of oil containing wastewater and theoretical volumetric yield of biodiesel was achieved. Gas chromatography/mass spectrometry chromatogram revealed that the total fatty acid methyl ester content of the produced biodiesel was >98% which is in accordance with the biodiesel quality standards specified by both ASTM and EU-14103.

Direct Analysis of Synthetic Phenolic Antioxidants, and Fatty Acid Methyl Ester Stability in Biodiesel by Liquid Chromatography and High-Resolution Mass Spectrometry

Methods to identify and quantify synthetic phenolic antioxidants, 3-tert-butyl-4-hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butyl-hydroquinone (TBHQ) and propyl gallate (PG), in biodiesel samples by using reversed-phase liquid chromatography (LC) were developed. Using a C18 phase with LC and UV detection showed co-elution between BHT and fatty acid methyl esters (FAME) in the biodiesel sample, whereas an alkyl phenyl modified stationary phase resulted in good separation of all antioxidants from the fatty acid matrix, and allowed more accurate quantification of antioxidants in biodiesel samples. The latter column was applied for further study. Calibration curves for the four antioxidants were constructed, and the limit of detection estimated. Good calibration linearity was observed over the investigated concentration range of 10–80 ppm, with correlation coefficients (R2) ranging from 0.9986 to 0.9995 for all antioxidants. LOD values of 0.010, 0.015, 0.0125 and 0.030 ppm, and recoveries of 70 ± 2, 85 ± 2, 103 ± 2 and 92 ± 4% for PG, TBHQ, BHA and BHT at injected concentrations of 35 ppm were established, respectively. The method was applied for quantification of antioxidants in biodiesel without addition of spiked antioxidants, then for biodiesel spiked with the four antioxidants, and a commercial source of biodiesel with BHT addition. Identification of FAME in the biodiesel samples was performed by using an instrument capable of ultra-high performance LC hyphenated with an electrospray Orbitrap mass spectrometer (UHPLC–ESI-OrbitrapMS). The stability of antioxidants and FAME in different samples was then investigated. Total FAME C18 content decreased to 52 ± 4% w/w after 1 week, and 29 ± 6% w/w after 8 weeks in the test sample without antioxidants; FAME content and antioxidant composition were stable in the samples with antioxidants added, even after 8 weeks exposure to sunlight.

Optimization and kinetic study of biodiesel production through esterification of oleic acid applying ionic liquids as catalysts

In this study, 1-methylimidazolium hydrogen sulfate, [HMIM]HSO4, ionic liquid, was successfully applied as a catalyst in the biodiesel production through the esterification reaction of oleic acid with methanol. A response surface methodology (RSM) known as Box-Behnken Design (BBD) was applied to optimize the main experimental reaction conditions, using a set of 27 experiments. This optimization was based on the maximization of both the conversion of oleic acid and the Fatty Acid Methyl Esters (FAME) content of the obtained biodiesel samples. It was concluded that the two most relevant parameters for both the conversion and the FAME content were the molar ratio between oleic acid and methanol and the catalyst dosage. Accordingly to the model, the optimum condition for the maximum conversion was determined as being 8 h, 110 ± 2 °C, 15:1 M ratio methanol/oleic acid and a catalyst dosage of 15 wt%, resulting in a 95% conversion and for the maximum FAME content were 8 h, 110 ± 2 °C, 14:1 M ratio and a catalyst dosage of 14 wt%, leading to a FAME content of 90%. The kinetics of the esterification reaction was also evaluated, and the experimental results were well described using a third-order reaction model. The kinetic parameters were experimentally determined, and the value of the activation energy was 6.8 kJ/mol and the pre-exponential factor was 0.0765 L2.mol−2.min−1 confirming that the ionic liquid, [HMIM]HSO4, is a good alternative for replacing traditional catalysts for biodiesel production through esterification reaction.

Development of high microwave-absorptive bifunctional graphene oxide-based catalyst for biodiesel production

A novel heterogeneous bi-functional catalyst namely silicon carbide/sodium hydroxide-graphene oxide (SiC/NaOH-GO) was successfully developed and characterized using fourier transform infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA), scanning electron microscope (SEM), energy disperse X-ray analysis (EDX), Brunauer–Emmett–Teller analysis (BET), X-ray diffraction (XRD), carbon dioxide temperature programmed-desorption of carbon dioxide (CO2-TPD) and ammonia temperature programmed-desorption (NH3-TPD). The catalyst was applied in microwave-assisted transesterification and esterification of binary model feedstock (rapeseed oil and oleic acid) containing 20% free fatty acid (FFA) and optimized using respond surface methodology (RSM) based on centre composite design. The study revealed that the optimum reaction conditions were 13:1 wt ratio of SiC/NaOH to GO, 5 wt% of catalyst loading, reaction temperature of 65 °C and 6 min reaction time to attain 96% of yield of transesterification and 92% of yield of esterification. Then, the optimized catalyst (13:1 wt ratio of SiC/NaOH) was applied in Chlorella vulgaris lipid with high free fatty acid content (26%) to further confirmed the ability of converting triglycerides and free fatty acid (FFA) to biodiesel simultaneously. The study revealed that 92% of FFA of microalgae lipid was converted and 81% of fatty acid methyl ester content (FAME) was attained under the optimum conditions of methanol to lipid molar ratio of 48, 5 min reaction time, 4 wt% catalyst and reaction temperature of 85 °C.