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[Display omitted] • Physicochemical property of a sustainable aviation fuel and its blends with RP-3 are compared. • The sustainable aviation fuel is mainly composed of large iso-alkanes and lack of aromatics. • Ignition delay times of the sustainable aviation fuel and its blends with RP-3 are close. • Chemical structural effect on the ignition of the sustainable aviation fuel is analyzed. Sustainable aviation fuel (SAF) is an alternative jet fuel that represents the most viable near-term solution to decarbonize the aviation industry. The airworthiness certification of SAF requires a basic understanding of its physicochemical property and combustion property. Herein, this work reports an experimental and kinetic modeling study on the physicochemical property and ignition characteristics of a SAF from Hydroprocessing Esters & Fatty acids (HEFA) and its blends with traditional RP-3 jet fuel. The physicochemical properties are analyzed, and a shock tube (ST) facility is adopted to measure the ignition delay times (IDTs) of the HEFA and its blends with RP-3. The complete group-type to component-by-component analysis of the two fuels are analyzed via two-dimensional gas chromatography (GC×GC) technique, and the results are then used to construct surrogate models. Detailed and lumped kinetic mechanisms are used to predict the measured IDTs based on the surrogate models. Finally, sensitivity analysis and rate-of-production (ROP) analysis are employed to uncover the chemical compositions on the ignition kinetics of the HEFA and its blends with RP-3. The present work should be valuable to understand the combustion chemistry of SAF and also to promote the airworthiness certification process for the large-scale usage of the studied HEFA. [ABSTRACT FROM AUTHOR]

• RuRe/ZSM-5(18) was an efficient catalyst for production of biofuels from fatty esters/acids. • n -C 12 H 26 was produced with a 95.2 % yield in the hydrodeoxygenation of C 11 H 23 COOCH 3. • The synergy of ReO x and Brønsted acid induced metallic Ru to be electron-deficient. • The electron-deficient Ru inhibited decarbonylation but facilitated hydrogenation. • ReO x facilitated the adsorption of carboxyl while Brønsted acid promoted dehydration. The hydrodeoxygenation of fatty acids and esters is a critical pathway to produce biofuels. We report an efficient RuRe/ZSM-5(18) catalyst for hydrodeoxygenation of methyl laurate, the selectivity of n -C 12 H 26 reached up to 95.2 % at complete conversion under the reaction conditions of 200 °C, 3 MPa H 2 , 3 h. The contribution of ReO x and acid sites was discussed from the perspective of dynamics and thermodynamics. ReO x was available for the adsorption of substrate and intermediates, the acidity from ReO x species and ZSM-5 are conducive to the cleavage of C O bond. The synergistic effects of ReO x and Brønsted acid sites induced Ru0 species to be electron-deficient, which preferred to adsorb aldehyde group in a linear adsorption configuration and facilitated for the hydrogenation of the aldehyde intermediate to alcohol, followed by dehydration to produce hydrocarbons. Thus, RuRe/ZSM-5(18) catalyst presented superior activity and chemoselectivity in the hydrodeoxygenation of methyl laurate as well as a series of fatty acids and esters without loss in carbon numbers in reactant. [ABSTRACT FROM AUTHOR]

[Display omitted] • Palm fatty acid distillate (PFAD) was used as a hydroprocessing feedstock. • Byproducts were formed by side reactions of free fatty acids (FFA) intermediates. • Fatty alcohols, wax esters, and ketones were the FFA-derived oxygenated byproducts. • Increasing the PFAD content in the feed accelerated the side reactions. • The side reactions resulted from higher concentration of strongly-adsorbed FFA. As the hydroprocessed esters and fatty acids (HEFA) process is being commercialized to manufacture sustainable aviation fuel, the feedstock is shifted from edible oils to low-purity residues. As a hydroprocessing feedstock, this study focused on a byproduct in palm processing, palm fatty acid distillate (PFAD) mainly composed of free fatty acids (FFA) that is virtually the hydrodeoxygenation intermediate because the rates of involved reactions largely depend on the PFAD concentration in the feed, thereby altering product distribution including saturated C 15–18 hydrocarbon products. As a result of hydroprocessing the mixtures of refined palm oil (RBDPO) with PFAD over Pt/Al 2 O 3 , side reactions derived from FFA intermediate (hydrogenation to fatty alcohols, esterification to wax esters, ketonization, and ester/ketone hydrodeoxygenation) were found to take place, which was accelerated as the PFAD was more present in the feed. Furthermore, the activity results obtained by tuning reaction variables such as time, H 2 pressure, temperature, and catalyst amount identified that the higher concentration of PFAD with strong adsorption on the catalyst was responsible for the side reactions. Therefore, it could be suggested to add the PFAD of 40 wt% or less into refined glyceride feedstock when the reaction conditions used in this work are employed. If the addition of more PFAD is desired, it would be necessary to develop a hydroprocessing catalyst to prefer the adsorption of hydrogen to that of FFA intermediate. Consequently, this work can serve as a guideline for utilizing FFA-containing raw materials for the HEFA process. [ABSTRACT FROM AUTHOR]

• Continuous mode supercritical biodiesel production offers less energy consumption. • Microwave transesterification should be monitored to keep uniform temperature profile. • Hydrodynamic cavitation provides high efficiency by decreasing the reaction times. • For hydrodynamic cavitation optimum hole to pipe diameter ratio should be taken as 20. • For ultrasonic transesterification amplitude and cycle rate influence the yield. Biodiesel is a mixture of fatty acid esters formed by transesterification of vegetable oil, animal fat, algae oil or waste oil with an alcohol like methanol (CH 3 OH), ethanol (C 2 H 5 OH) or higher alcohols. There are many important catalytic variables like catalyst type and composition, support type and pretreatment conditions (i.e. calcination temperature and time) which are utilized to achieve high yields for the transesterification reaction. In addition, operational conditions such as reaction temperature, alcohol type, alcohol to oil molar ratio and stirring speed have also quite high significance. Moreover, all these variables can be optimized under supercritical conditions by novel techniques like ultrasonic and microwave irradiation or hydrodynamic cavitation. In this work, significant catalytic and operational variables for biodiesel production are reviewed. In addition, dominant parameters together with their limitations during the application of advanced technologies are investigated in detail. Then, it has been concluded that, for better control and higher yields of biodiesel production, future research works should focus on addition of co-solvents, use of longer chain alcohols, bulky structures or ionic liquids, adjustment of mode of irradiation and modification of the instrumentation or the equipment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Catalyst type and E/F ratio significantly affected the yield and composition of the CBD. • SnCl 2 showed the best performance in terms of the CBD yield and its esters content. • Temperature and time had no significant effect on the yield and quality of the CBD. • The CBDs had extremely low N and S contents and were abundant in esters. • Ethyl oleate and ethyl palmitate were the two main fatty acid esters in CBDs. Abstract Lewis acid-catalyzed in situ transesterification/esterification of tigernut (Cyperus esculentus) was conducted in sub/supercritical ethanol. An L 16 (44) orthogonal design with four factors at four levels was employed to investigate the influence of the process variables on the product distribution and the composition of crude biodiesel (CBD). The four factors were temperature (230–290 °C), time (0–90 min), ethanol to feedstock ratio (E/F) (4/3–16/3 mL/g), and catalyst type (ZnCl 2 , FeCl 3 , SnCl 2 , and H 3 PO 4). The results showed that the catalyst type and E/F ratio were the two most influential variables affecting the yield and composition of the CBD. Of the Lewis acids tested, SnCl 2 showed the highest performance in terms of the CBD yield and its esters content. Increasing the E/F ratio essentially led to a higher CBD yield and higher ester content of the CBD. A higher temperature and longer reaction time resulted in an obvious increase in the gas yield but had no significant effect on the yield and quality of the CBD. The produced CBDs had extremely low N and S contents (0.2–0.6 wt% and less than 0.1 wt%, respectively) and were abundant in fatty acid esters (∼70%), mainly ethyl oleate and ethyl palmitate, making it more suitable for subsequent biofuel production. [ABSTRACT FROM AUTHOR]

Highlights • Combustion and emissions of date pit methyl esters in a modern diesel engine. • Tested unblended and as B20 relative to soybean and rapeseed methyl esters. • Similar ignition delay for all esters despite differences in fatty acid profile. • Date pit esters showed higher peak heat release but lower NOx emissions. • All methyl esters emitted lower particulates levels than reference fossil diesel. Abstract Current biofuels for diesel engines are largely derived from food crops and there is significant concern, recognised by legislation, that such fuels do not result in net reductions of greenhouse gas emissions when considering the entirety of the production to usage lifecycle. A potential alternative approach is to utilise the lipid content of organic waste streams arising from food crop cultivation for the manufacture of sustainable diesel fuels. This paper therefore presents experimental studies carried out on a modern direct injection diesel engine supplied with a biodiesel (fatty acid methyl esters) produced from waste date pits to determine the combustion and emissions characteristics of an alternative fuel produced from a food residue. Date pit methyl esters were tested relative to both rapeseed and soybean methyl esters, unblended and as blends with a reference fossil diesel, alongside reference fossil diesel and a commercially available fossil diesel from Oman, at constant injection timing and constant ignition timing at a constant engine speed of 1200 rpm. Gas chromatograph analysis of the methyl esters fatty acid composition found a significantly shorter mean alkyl moiety chain length and lower number of double bonds in the case of the date pit esters than either the rapeseed or soybean biodiesel. All of the methyl esters exhibited a similar duration of ignition delay less than that displayed by a reference fossil diesel, but with a higher premixed burn fraction and peak heat release rate in the case of date pit methyl esters relative to those of rapeseed and soybean. Exhaust emissions of NOx were found to be lowest for the unblended date pit methyl esters, suggesting a greater influence of adiabatic flame temperature on rates of thermal NOx production than global in-cylinder temperatures in the case of the unblended methyl esters. Relative to the reference fossil diesel and Oman diesel, all of the methyl esters tested resulted in low particulate matter emissions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Viscosity prediction of fatty acid esters and biodiesels. • Development of two models based on different approaches for predictive purposes. • Semi-theoretical method based on rough-hard-sphere-chain model. • ANN modeling of viscosity data of FAEs and biodiesels. Abstract This work addresses the prediction of dynamic viscosities of several fatty acid esters and biodiesel fuels using a semi-theoretical model and artificial neural network as well. The semi-theoretical model used rough hard-sphere theory for the correlation and prediction of dynamic viscosities. In this respect, a smooth hard-sphere-chain expression and a coupling parameter of translational-rotational motions were employed to develop the rough hard-sphere-chain scheme. The three molecular parameters as well as the liquid densities required in this model were taken from previously developed perturbed Yukawa-chain equation of state (Fluid Phase Equilibria, 372 (2014) 105–112). Artificial neural network modeling employed a multilayer perceptron comprising one hidden layer and 21 neurons, managed according to the constructive approach. The performance of both semi-theoretical and ANN model have been checked by predicting dynamic viscosities over the temperature range within 283–393 K and pressures up to 140 MPa with the average absolute relative deviation of 3.10% (for 648 data points) and 0.91% (for 796 data points), respectively. The ANN model developed herein, has been trained, validated and tested for the set of data gathered, pointing that the efficiency of the neural network model was found excellent on the entire dataset. [ABSTRACT FROM AUTHOR]

Vegetable oils (VOs) comprise 90%–98% triglycerides (three fatty acids esters and glycerol), with trace amounts of mono-glycerides and di-glycerides. The content of glycerides in VOs can vary depending on the specific type of oil, the processing methods used, and other factors such as the cultivar and harvest date. VOs have been examined for usage in different applications due to their physicochemical properties, including stationary engines, big ships, and Diesel engines of low and medium speed. There are around 350 VOs that have the potential to be used as fuel sources, the vast majority of which have yet to have their physicochemical properties investigated. Regression models based purely on VOs fatty acid content are beneficial in this context. This study conducts a regression analysis of VOs density (DE), kinematic viscosity (KV), flash point (FP), and low and high heating values (LHV and HHV) as a function of their fatty acids. Several experimental databases were selected, including the values of VOs fatty acid composition and physico-chemical properties. Optimal non-linear polynomials were chosen for the regression procedure. Scheffé polynomials offer different fitting alternatives to adjust the VOs experimental databases using their five main fatty acids: from simple linear polynomials (including five terms) to full cubic polynomials (including 35 terms). The polynomials are validated by showing how well their results correspond with the experimental databases. The standard error values for the proposed full polynomials concerning the databases for DE, KV, FP, LHV, and HHV are 0.70%, 7.79%, 7.86%, 1.66%, and 0.19%, respectively. • Non-linear regression of vegetable oils properties from their fatty acids is conducted. • Scheffé polynomials from simple linear to full cubic polynomials are analyzed. • Density, kinematic viscosity, flash point, and low and high heating values are evaluated. • Errors of full models for these properties are 0.70%, 7.79%, 7.86%, 1.66%, and 0.19%. [ABSTRACT FROM AUTHOR]

• Speed of sound was measured in two biodiesels at high pressure (up to 200 MPa). • Density was measured in two biodiesels at high pressure (up to 200 MPa). • Derivative volumetric and acoustic properties were determined up to 200 MPa. • Thermophysical properties were predicted up to 200 MPa with a good accuracy. This work presents experimental data on sound velocities and densities for two biodiesel fuels, namely sunflower methyl ester and a blend of Palm, Rapeseed, and Soybean methyl esters at pressures ranging from atmospheric to 200 MPa and temperatures from 293.15 to 393.15 K. Speed of sound data were obtained up to 200 MPa using a pulsed echo method. Density was determined by measuring the period of a vibrating tube up to 100 MPa and by integrating the sound velocity between 100 and 200 MPa. These measurements were coupled to determine other properties, such as isothermal compressibility, isentropic compressibility, and acoustic impedance, which strongly influence the injection process in diesel engines. The experimental data were compared with a set of models previously developed to predict the density and sound velocity of biodiesels under high pressure based on their fatty acid ester composition. [ABSTRACT FROM AUTHOR]

In this study, turkey rendering fat biodiesel (TRFB) was produced by two-step reactions (esterification and transesterification). Fatty acid ester content and yield in methyl ester were found 96.7% and 88.5% respectively. TRFB was blended with diesel fuel (DF) at 10%, 20%, and 50% (v/v) proportion to obtain fuel blends named TRFB10, TRFB20 and TRFB50, respectively. The effects of TRFB blends on the combustion, performance and exhaust emissions of a direct injection single cylinder diesel engine were systematically investigated under different engine loads, at the constant engine speed of 2000 rpm. The results show that the maximum cylinder pressure (CP max ) and maximum heat release rate (HRR max ) values of the TRFB blends were higher than those of DF for all engine loads because of the low cetane number of the TRFB and the rapid burning of the fuel accumulated in the combustion chamber during the long ignition delay. It was observed that the DF has a higher exhaust gas temperature than the biodiesel blends at high loads because of the longer combustion duration of the DF. The brake thermal efficiency (BTE) values of the TRFB blends were found to be lower than those of DF at all loads. Since the heating value of the biodiesel is lower than that of DF, it was observed that the brake specific fuel consumption (BSFC) values of TRFB blends are higher compared to those of DF. In addition, TRFB10, TRFB20 and TRFB50 blends reduce smoke opacity approximately 20%, 25% and, 40%, respectively, and cause a slight increase in nitrogen oxide (NO x ) emissions. [ABSTRACT FROM AUTHOR]

In the present investigation, Date ( Phoenix dactylifera L.) stones were utilized in the production of different types of biodiesel in addition to bio-oil. The oil was extracted from the date stones with a yield of 10.50 wt% and is used in the production of fatty acid methyl, ethyl and mixed methyl/ethyl esters via KOH- catalyzed transesterification process with methanol, ethanol and mixed methanol and ethanol, respectively. Properties of the obtained biodiesels, such as the density, kinematic viscosity, flash point, acid value, cloud and pour points, total and free glycerin contents and the refractive index were evaluated and found comparable to those of ASTM D 6751 biodiesel. The FTIR spectroscopy confirmed conversion of date stone oil to biodiesel. The date stones were also tested as new non-edible feedstock for bio-oil production by pyrolysis process in a semi batch reactor. The influence of the pyrolysis temperature, pyrolysis time and precursor particles size on the bio- oil yield was investigated. Maximum bio- oil yield (52.67% ± 1.50) was obtained at 500 °C pyrolysis temperature with a pyrolysis time of 60 min and feed particle size of 0.25 mm. The ultimate analysis, FTIR spectroscopy and adsorption column chromatography were determined to characterize the chemical composition of the obtained bio- oil. Furthermore, several important fuel properties, like the density, kinematic viscosity, flash point, pour point and the acidity index of date stones bio- oil were also determined following ASTM standard test methods and found comparable to those documented for other bio- oils in literature. The chemical composition of the bio- oil produced through pyrolysis of date stones showed the potential of date stones as an important source of alternative fuel and chemicals as well. [ABSTRACT FROM AUTHOR]

The droplet suspension technology was used under the condition of atmospheric pressure and 873 K. The n -butanol concentration ranged from 0% to 75% to investigate the effect of n -butanol concentration on the puffing characteristics of a n -butanol-fatty acid methyl esters (FAME) droplet. Experimental results showed that BUT25, BUT50 and BUT75 (BUT’XX’ represented XX% n -butanol by mass fraction in the n -butanol-FAME blend) underwent three phases, namely the transient heating phase, fluctuation evaporation phase and equilibrium evaporation phase. The temperatures of BUT25, BUT50 and BUT75 were similar at the start and end of the transient heating phase. The duration of BUT75’s transient heating phase was much longer than that of BUT25 and BUT50. Therefore, the evaporation cooling of BUT75 was the most prominent because the temperature growth rate of BUT75 was significantly less than that of BUT25 and BUT50. Furthermore, the fluctuation evaporation phase could be divided into the strong and weak fluctuation stages. The violent fluctuation was only observed in the strong fluctuation stage. The weak fluctuation stage was similar as the stable evaporation. The active rupture was found in the strong fluctuation stage and the passive rupture was found in the weak fluctuation stage. The active and passive ruptures were caused by the fast bubble expansion and surface evaporation respectively. In addition, many periodic processes were contained in the strong fluctuation stage. The similarity degree of the periodic process showed a slump and a gradual increase, which were caused by bubble expansion and droplet recovery respectively. The bubble expansion of BUT50 was greater than that of BUT75. Significant bubble expansion led to the violent deformation after bubble rupture. The recovery time of BUT50 was longer than that of BUT75. Therefore, the similarity degree of BUT50 exhibited a wavy structure and BUT75 displayed a comb-like structure in the strong fluctuation stage. [ABSTRACT FROM AUTHOR]

The composition of biodiesel is significantly influenced by the feedstock sources. This variation in biodiesel composition may cause changes in fuel physiochemical properties and further affect the engine operation processes such as the fuel injection and spray processes. In this study, the macroscopic and microscopic spray parameters of diesel fuel and three biodiesel components (methyl laurate, methyl oleate and ethyl oleate) on a diesel common rail injection system are investigated at conditions of different injection pressures and ambient pressures. The macroscopic spray parameters, including the tip penetration distance, projected spray area, spray front velocity, spray cone angle, and the maximum spray width, of different fatty acid esters are characterized and compared to those of diesel fuel. Further, the images of fuel spray development obtained by the high speed camera are converted to grayscale ones, and the grayscale values within the spray contours are extracted to evaluate the light intensity level and distribution characteristics for different fuels. Finally, the microscopic spray characteristics of test fuels measured using a split laser particle size analyzer indicated that fuel properties also play an important role in the droplet sizes, and the droplets of methyl laurate and diesel have smaller SMD than methyl oleate and ethyl oleate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Review of 48 different fatty acid esters, which are the main components of biodiesel. • Discussion of density and viscosity models for pure fatty acid esters. • Experimental data at low and high temperatures as well as high pressure are lacking. Biodiesel fuels consist of a mixture of different fatty acid esters. The thermophysical properties of the fatty acid esters are decisive for combustion and storage. Especially density and viscosity influence, e.g., energy density, spray quality and lubrication in a diesel engine. For some of the fatty acid esters, several studies on thermophysical properties can be found in the literature in a wide pressure and a reasonably wide temperature range. However, for several of the esters, data at high pressures as well as low and high temperatures are missing; for some of them, even data at atmospheric pressure are missing. To develop thermophysical property models, comprehensive sets of experimental density and viscosity data are required. Therefore, this work reviews the available experimental data on density and viscosity of fatty acid methyl, fatty acid ethyl and fatty acid butyl esters. Data gaps present in the literature are illuminated. 16 different esters are considered for each of the three ester families. The homologous series of saturated esters from hexanoate (C6:0) to octadecenoate (C18:0) as well as the unsaturated esters oleate (C18:1), linoleate (C18:2), and linolenate (C18:3) are included. In addition, an overview of generalised models for the description of density and viscosity at elevated pressure is given. [ABSTRACT FROM AUTHOR]

[Display omitted] • Measurements of VLE data with modified Othmer ebulliometer at sub and atmospheric pressure. • Analysis of the fluid phase behavior of alcohol + palmitate ester systems. • Thermodynamic modelling with the GC-VT-PR and PC-SAFT models. • Group contribution and volume translation in a cubic equation of state. • Thermodynamic consistency of VLE using the L-W test. Fossil sources of energy become focus of many debates due to the pollution caused by them. In this scenario, renewable fuels, as biodiesel, are studied to improve their production efficiency and become more competitive with fossil fuels and even substitute them. Biodiesel, produced by the transesterification reaction, is constituted by a mixture of fatty acid esters and needs to be separated from its reactional solution in order to be commercialized. To improve the separation processes, the thermodynamic behavior of the mixtures involving components of the biodiesel needs to be known. Aiming this, the vapor–liquid equilibrium (VLE) of the methanol + methyl palmitate and ethanol + ethyl palmitate systems was analyzed at 50.3 and 101.3 kPa and the experimental data were submitted to a thermodynamic consistency test and thermodynamic modeling with the Peng-Robinson (PR), Group Contribution Volume Translated Peng-Robinson (GC-VT-PR) and the Perturbed Chain - Statistical Associating Fluid Theory (PC-SAFT) equations of state. Experimental data were considered thermodynamically consistent, and the modeling showed good results in terms of the lowest relative deviations of temperature and vapor mole fraction obtained with the GC-VT-PR and PC-SAFT models. [ABSTRACT FROM AUTHOR]

[Display omitted] • Integrated process (extraction and reaction) to produce esters. • Pressurized ethyl acetate resulted in greater process selectivity. • Higher content of esters were obtained from the interesterification reaction. • Temperature influenced the production of esters. • The addition of water increased the production of esters and reduced decomposition. This work investigated the production of fatty acid ethyl esters (FAEE) from forage radish seeds using a sequential process with pressurized ethanol and ethyl acetate as solvents and acyl acceptors. First, the effect of the solvent on the extraction was determined and subsequently, the sequential reaction was carried out with the material from the pressurized liquid extraction (PLE) where the effects of temperature, residence time and water concentration were investigated. Conventional extraction was carried out for comparative purposes with regards to the oil quality of the PLE and its efficiency in the reaction. The use of ethanol resulted in a high mass yield, which was attributed to the high non-lipid fraction in the extracted material, and ethyl acetate retained proteins, phenolic compounds and sugars in the defatted meal. The main fatty acids in the oil were oleic and erucic acids and high levels of minority compounds were observed in the PLE oil. In the sequential reaction, supercritical ethyl acetate at 300 °C provided the highest FAEE content (42 wt% in 25 min). The addition of water in the acyl acceptor increased the production of FAEE, reduced the thermal degradation of the esters and provided a product with low levels of acylglycerols. Oils from PLE and conventional extraction showed similar performance in the synthesis of esters. Ethyl linolenate and ethyl linoleate were the esters that showed the highest level of degradation. The highest content of FAEE (53 wt%) was reached at 300 °C with 20% (v/v) of water, resulting in a triacetin content of 0.92 wt%. [ABSTRACT FROM AUTHOR]

[Display omitted] • HEFA is a well-established technology for biofuel production. • Lignocellulose feedstocks are superior for bio jet production. • Second-generation biofuels are economic and environmentally friendly. • FT techniques has highest GHGs saving technique but higher capital cost. Given how quickly the aviation sector is growing, it is crucial to find sustainable ways to supply the demand. Modern technological developments and the creation of alternative jet fuels are crucial elements that could help eliminate greenhouse gases (GHGs) like CO 2 emissions. Traditional jet fuel produces a sizable amount of GHG emissions, which has raised concern on a global scale. Compared to conventional jet fuel, biofuel is thought to be more renewable and less polluting. Biojet fuels might work as an effective substitute. The varieties of bio jet fuel, manufacturing procedures (including alcohol-to-jet, oil-to-jet, syngas-to-jet, and sugar-to-jet ways), existing regulations, and the effects of bio jet fuels on the environment and the economy are all covered in length in this overview. These are the techniques that are most frequently used to create bio-jet fuel from both edible and inedible feedstock. The main conclusions of this review indicate that the most popular method for producing biofuel is hydrogenated esters and fatty acids (HEFA). The Fischer-Tropsch (FT) approaches cost more to install even though they produce fewer GHGs. Environmentally beneficial and technologically advanced, second-generation biofuels are a great choice. It has been revealed that jatropha is a crop that produces a lot of energy. The price of feedstock and the lack of bio-jet fuel are the two biggest obstacles to substituting conventional fuel. To increase the power and quality of energy, further in-depth research on optimal feedstocks is necessary. In order to address the needs of both commercial and military aircraft, biomass jet fuel has a lot of potential to replace conventional jet fuel. High yield should be one of the properties of the feedstock without affecting food production. [ABSTRACT FROM AUTHOR]

[Display omitted] The present study evaluated the total energy output and economic feasibility of biodiesel production coupled with value-added nitrogen-containing compounds (NCCs) through co-pyrolysis of low- and high-protein biowaste. Corn straw (CS) and human hair waste (HW) were used at different blend ratios of 0%, 25%, 50%, 75%, and 100%, w/w. Individual pyrolysis of HW showed 20.7% higher bio-oil yield than CS due to higher volatiles in HW, while co-pyrolysis resulted in synergistic action which enhanced both bio-oil yield with higher fatty acids/esters proportion. The highest recorded bio-oil yield was 46.3% using 75% HW blend ratio, which showed insignificant difference with that of HW. In addition, co-pyrolysis resulted in reduction of NCCs by 13.7% comparing to HW, with simultaneous enhancement of fatty acids and esters contents by 67.8% and 13.2%, respectively. Therefore, transesterification of co-pyrolyzed bio-oil showed the highest biodiesel proportion of 20.7%, representing 4.7-times and 61.7% higher than CS and HW, respectively. In addition, transesterified co-pyrolyzed bio-oil showed 27.0% NCCs, which was 8.2-times higher than that of CS. Due to the higher calorific value of biodiesel compared to bio-oil, biodiesel of the co-pyrolyzed bio-oil showed the highest total energy output in the biorefinery route (3753 MJ/ton biomass), which was higher than the total energy output from the conventional route of bio-oil production from CS (3738 MJ/ton biomass). However, additional revenue of 39,860 US$/ton biomass was estimated in the biorefinery route due to NCCs fraction, which provides a new insight towards future industrial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The WCO was directly used as collector for CGFS flotation. • Co-disposal of WCO and CGFS is achieved by efficient way. • More than 90 wt % of the unburned carbon in CGFS was recovered. • The loss-on ignition of the tailings is 4.15 wt %. Waste cooking oil (WCO) and coal gasification fine slag (CGFS) are both wastes and harmful to human health and environment without proper disposal. In this work, co-dispose of the two wastes was investigated, i.e. the WCO was directly used as a flotation collector for carbon ash separation of the CGFS. The WCO contains numbers of long-chain fatty acids and esters, thereby is a potential flotation collector for carbon ash separation of the CGFS. As a result, the recovery of unburned carbon increased with the WCO dosage increased, but the loss-on ignition (LOI) of tailings gradually decreased. The optimum flotation condition is 6 ∼ 7 kg/t of WCO with 3 kg/t of frother. In this condition, the recovery of unburned carbon increases to 89.59 ∼ 90.34 wt %, while the LOI of tailings decreases to 4.48 ∼ 4.15 wt %. Therefore, the WCO is a feasible and efficient flotation collector for carbon ash separation of the CGFS. It also has potential industrial application, because this approach is also economical and eco-friendly for co-dispose of the two wastes. [ABSTRACT FROM AUTHOR]

The two-stage injection processes of three fatty acid esters, methyl laurate, methyl oleate and ethyl oleate, were investigated and compared with that of fossil diesel using a high-pressure diesel engine common rail injection system. The injection characteristics studied included injector inlet pressure characteristics, and rate and quantity of fuel mass injected per cycle. The effects of fuel properties and injection dwell time between the pilot and main injection events were also considered. Differences in the fuel properties of diesel and fatty acid esters caused modest changes in the main injection quantities and fuel pressure fluctuation characteristics after the end of injection, and the changes were affected by different injection pressures. The injection dwell time was also found to influence the injector inlet pressure characteristics at the start of the main injection event and thus the amount of fuel injected during main injection was slightly changed. [ABSTRACT FROM AUTHOR]

• Synthetic aromatic kerosene (SAK) is characterized with measurements and GCxGC-VUV. • VUV spectroscopy identifies 26 structural isomers (93.6 % mass) in the SAK. • 9 properties are reported for a HEFA/SAK blend, including swelling and dielectric constant. • A two-dimensional VUV deconvolution methodology identifies co-eluting species. • Property predictions uncertainties are reduced with VUV identification. This research explores an advanced method of fuel composition determination and builds upon typical hydrocarbon group type analyses performed with two-dimensional gas chromatography (GCxGC). In this study, structural information of individual species within Virent's Synthetic Aromatic Kerosene (SAK) is identified by vacuum ultraviolet (VUV) spectroscopy. By mass, 71.3% of the components elute within six peaks of the chromatogram, from which 12 unique species are identified through a novel deconvolution method. Overall, the identification of 93.6%m across 26 structural isomers is made by the methods described in this work. With 93.6%m ascribed to specific isomers, the precision of fuel property predictions improves dramatically. For example, the absolute error of the viscosity prediction is reduced by 90% because of this advancement in diagnostic capability, and its 95-percentile confidence interval (precision only) is reduced by 93%. Additionally, the properties of SAK, blended with hydro processed esters fatty acids (HEFA), are demonstrated to have blended properties consistent with conventional jet fuel. [ABSTRACT FROM AUTHOR]

Diesel from direct coal liquefaction (DDCL) is a product obtained from direct coal liquefaction (DCL). Compared with petrodiesel, DDCL contains almost no sulfur element. Other than this feature, several other properties of DDCL are similar to those of petrodiesel. Therefore, DDCL is applicable to automobile diesel fuel. However, the cetane number (CN) of DDCL is only 44. In this article, fatty acid esters are investigated as potential CN improvers for DDCL. According to the recent standard GB 19147-2013, 1 vol% fatty acid esters can be added to diesel fuel. The performance of different fatty acid esters and the other properties of ester blending are also investigated. Several fatty acid esters can be considered potential CN improvers to enhance DDCL for automobile diesel fuel. The structures of fatty acid esters, such as chain length, double bonds, and different alkyl head group on the fatty acid alkyl esters, can affect the performance of CN improvers. Moreover, the obtained wear results showed that 1% of fatty acid esters can improve fuel lubricity from 630 μm to 514 μm. The other properties of DDCL are changed a little after fatty acid esters are added. [ABSTRACT FROM AUTHOR]

In this contribution, we confirmed that aviation fuels could be synthesized directly from microalgae lipids in water over a Pt/C catalyst without additional hydrogen. After decarboxylation at 330 and 370 °C for 120 min, the oxygen content in the microalgae lipids was significantly reduced and the heating value of produced aviation fuels was greatly increased. The reaction mechanism of direct decarboxylation of microalgae lipids to aviation fuels was further investigated using each of the representative compounds in microalgae lipids, such as methyl laurate, methyl eicosanoate, methyl stearate, ethyl stearate, and tristearin as the starting material in separate reactions under the same conditions. Those reaction conditions, solvent, water loading, catalyst loading and reactant loading, were optimized. It was concluded that among the tested solvents, water was the most favorable for the selective decarboxylation of methyl stearate, that the catalytic decarboxylation rate of fatty acid esters with larger carbon numbers in water was faster than those with smaller carbon numbers, and that the Pt/C catalyst retained its activity through its third use. These results provide new insights for the direct decarboxylation of microalgae lipids to aviation fuels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Higher yield of bio-crude obtained by holding for 3 min with flash heating HTL. • The addition of ethanol results in the highest C, H, energy recovery from bio-crude. • Bio-crude with ethanol-water has the highest content of fatty acids and esters. • The bio-crude produced by the two-step process has a low nitrogen content. • Bio-crude produced with air as the medium has a high level of bioactive substances. Reducing carbon emissions has become the current focus of attention all over the world. Alternative biofuels are an important means to achieve the carbon reduction. Among them, hydrothermal liquefaction (HTL) of algae-based biomass has been widely studied because of its environmental friendliness and mild conditions. In this paper, the effect of different conditions on microalgae bio-crude enhancement was investigated, using innovative experimental methods, including flash heating HTL with two step or by co-solvent. It showed that recovery of carbon, hydrogen and energy could reach 0.53, 0.48 and 0.58 respectively at 250 °C for 30 min with ethanol-water co-solvent as the medium. The highest total content of fatty acids and fatty acid esters were found in the bio-crude with methanol/ethanol-water co-solvent as the medium. The nitrogen content of the bio-crude obtained by the two-step method is lower than that of the one-step method. The content of cholesterol and vitamin E as indicators of bioactive substances performed well with ethanol-water co-solvent as the liquid phase medium, containing 16.1% in bio-crude at 240 °C for 3 min, and also advantageously with air as the gas phase medium. [ABSTRACT FROM AUTHOR]

• Butyl caprate and butyl laurate were investigated. • Speed of sound was measured at high pressure. • Density-temperature curves of butyl caprate intersect those of butyl laurate. • Different isentropic compressibility of esters can be compensated by temperature. • The isentropic compressibility of butyl laurate and methyl laurate is close to those of diesel fuel. The butyl-based fatty acid esters can be considered as fully biorenewable components of biodiesel fuel due to the possibility of synthesis from biobutanol and vegetable or animal oils. For this reason in this work high pressure thermophysical properties of butyl caprate (butyl decanoate) and butyl laurate (butyl dodecanoate) used for optimization spray characteristics in diesel injection systems are studied. The speed of sound was measured at temperatures from 293 to 318 K and pressures from 0.1 to 101 MPa. The speed of sound, density, isobaric heat capacity, viscosity, surface tension were measured under atmospheric pressure and at the temperatures from the range of 273 to 363 K. The effect of temperature and pressure on density, isentropic and isobaric compressibilities, isobaric heat capacity, and isobaric thermal expansion was determined by the acoustic method. The results obtained show that differences between density and isentropic compressibility of esters can be compensated by temperature and/or pressure. Comparison of thermophysical properties of butyl caprate and butyl laurate with characteristics for diesel, biodiesel composed of fatty acids methyl esters of rapeseed oil, neat methyl and ethyl esters shows that they can be considered as promising fuel additives in this regard. [ABSTRACT FROM AUTHOR]

After a careful reconsideration of the article (S. M. Hosseini, M. Pierantozzi, J. Moghadasi, Fuel 235 (2019) 1083–1091), several typo have appeared in the key equations of this article which would not allow the readers to utilize the underlying molecular semi-theoretical model for the calculation of dynamic viscosity of pure fatty acid esters and biodiesels without any problem. Regarding this, an Erratum is presented to fix this issue. [ABSTRACT FROM AUTHOR]

Highlights: [•] Injection of methyl oleate, ethyl oleate, and methyl laurate are investigated. [•] Difference in injection delay is found among test fuels. [•] Pressure oscillation damps more rapidly for methyl oleate and ethyl oleate. [•] Fatty acid esters have lower volume but higher mass injection quantity than diesel. [ABSTRACT FROM AUTHOR]

Highlights: [•] First study of lipase-catalyzed ethanolysis of castor oil in a solvent-free system. [•] Over 90% conversion of castor oil to fatty acid ethyl esters was obtained in 6h. [•] Results are comparable with published results obtained using n-hexane as solvent. [Copyright &y& Elsevier]

[Display omitted] • Densities and viscosities of ethyl laurate + ethanol were measured and modeled. • Association effects on properties of ethyl laurate + ethanol were studied. • Excess volumes and viscosity deviations of different fatty acid ester + alcohol mixtures were compared and analyzed. The mixtures of fatty acid ester + alcohol are promising substitution fuels in engines. Due to their strong self- and cross-hydrogen bonds, the properties of these kinds of mixtures may show different characteristics from the fossil fuels composed of non-associating substances. In this work, the association effects on density and viscosity of fatty acid ester + alcohol are investigated from both experimental and theoretical aspects. The ethyl laurate + ethanol mixtures with 9 M fraction compositions are chosen, and the two properties are measured using a capillary viscometer system at temperatures from 313 K to 343 K and pressures up to 15 MPa. The positive excess volume and viscosity deviation of the mixtures are obtained, and the former is negligible compared to the experimental uncertainty. The Cubic-Plus-Association equation of state (CPA EoS) and the friction theory model are used to model the mixtures of ethyl laurate + ethanol. The relations of their self- and cross-associations to density, viscosity, and two excess properties (excess volume and viscosity deviation) are summarized. Different saturated fatty acid ester + 1-alcohol mixtures are also modeled with the CPA EoS. The variation characteristics of their viscosity deviations are analyzed and explained by their different association strength and the mole number of associated molecules. [ABSTRACT FROM AUTHOR]

Abstract: The transesterification reaction of sunflower oil with ethanol to produce fatty acid ethyl esters (FAEEs) was studied by using calcined calcium zincate as solid base catalyst. The effect of experimental parameters, such as catalyst loading, ethanol:oil molar ratio, free fatty acid and water contents, and stability in the ethanolysis of sunflower oil in the presence of calcium zincate thermally treated at temperatures as low as 400°C are reported. Thus, by using a 3wt.% of catalyst at 78°C, FAEE yields higher than 95wt.% after 3h of reaction time, can be reached. The addition of FFA (until 1.1° of acidity) does not affect the catalytic activity, with yields values higher than 95wt.%, but water brings about a negative effect. However, the catalyst has demonstrated to be less resistant to the reutilization in the ethanolysis process due to the leaching of calcium species, but addition of sodium carbonate to the catalyst before the catalytic process allows obtaining, after washing with water, a biodiesel with concentrations of Ca and Na lower than 5ppm. [Copyright &y& Elsevier]

Abstract: This study optimized the conversion of animal fat wastes into ethylic biodiesel by alkali-catalyzed process under mild conditions. A mix of chicken and swine fat residues was used as feedstock for biodiesel production. A full 33 factorial design was used to optimize process parameters for maximum fatty acid ethyl esters yield. Factors were evaluated at three different levels: temperature (30;50;70°C), ethanol:fat molar ratio (6:1;7:1;8:1) and catalyst concentration (0.44;0.88;1.32 wt.%). Effects of the process variables were analyzed using response surface methodology. Moreover, optimum conditions were applied in a bench-scale reactor and biofuel produced was characterized. It was observed that at high temperatures (50 and 70°C), phase separation between biodiesel and glycerol was impaired. Although high conversion was achieved (96.2%) at 70°C, this condition is not recommended because no spontaneous phase separation was verified. On the other hand, 30°C was identified as the best temperature for biodiesel ethanolysis, using 0.96 wt.% catalyst and 7:1 ethanol:fat molar ratio. With these conditions, it is possible to achieve around 83% conversion. Despite the oxidative stability and total glycerin, biodiesel measured properties agreed with quality requirements established by Official Regulations (ASTM 6751 and EN 14214). [Copyright &y& Elsevier]

Abstract: In the present work, the sodium hydroxide-catalyzed synthesis of fatty acid ethyl esters (FAEE) from sunflower oil and ethanol was optimized using a 33 full factorial design of experiments with two replications and the response surface methodology (RSM). The effects of temperature, ethanol-to-oil molar ratio and catalyst loading on the FAEE were studied. The ANOVA results shows that at the 95% confidence level all three factors and the 2-way interactions of reaction temperature with ethanol-to-oil molar ratio and catalyst loading significantly affect the FAEE formation. A second-order polynomial equation is developed to relate the FAEE purity and the operational variables (temperature, ethanol-to-oil molar ratio and catalyst loading). The fitted model shows a good agreement between predicted and actual FAEE purities (R 2 =0.937; mean relative percentage deviation ±1%), demonstrating the validity of the regression analysis in the process optimization. The optimal process conditions were: ethanol-to-oil molar ratio of 12:1, reaction temperature of 75°C and catalysts loading of 1.25%. The RSM is proved to be suitable method for optimizing the operating conditions in order to maximize the FAEE purity. [Copyright &y& Elsevier]

Abstract: Bio-diesel is a mixture of fatty acid methyl esters, and is produced by trans-esterification of renewable feed-stock. This study develops an economically attractive and environmentally acceptable bio-diesel production process using multi-objective optimization. It considers bio-diesel production using waste cooking oil as the feed-stock, which can reduce bio-diesel cost. Both the pre-treatment and trans-esterification sections of this process are simulated in a process simulator followed by optimization for multiple objectives using multi-objective differential evolution with taboo list. Profit, fixed capital investment and organic waste from the biodiesel process are considered as objectives for optimization. Effect of variation in feed flow rate on process performance is also studied. The results show that the amount of organic waste can change significantly with only small variations in the economic objectives, and they provide alternative process designs with different environmental impacts, for implementation. [Copyright &y& Elsevier]

Abstract: Biodiesel is a fuel composed by fatty acid esters, usually methyl esters (FAME), have common structural features, as allylic hydrogens, bis-allylic hydrogens and secondary hydroxyl, that determinate its oxidative stability. In this study, the oxidation temperature (OT) of biodiesels formulated from a mixture design of methyl stearate, methyl oleate, methyl linoleate and methyl ricinoleate was determined by pressurized differential scanning calorimetry (PDSC). The generic representation for the mixtures was developed and their coefficients were used as parameters to describe the OT. A non-linear dependence of OT with the descriptors of allylic hydrogen , bis-allylic hydrogen and secondary hydroxyls were observed in the empirical domain D exp ={(a; c, d, f) ; 0⩽ c ⩽4 and 0⩽ d ⩽2 and 0⩽ f ⩽1 and a =19}, where the Ca parameter for chain length was kept fixed. [Copyright &y& Elsevier]

[Display omitted] • LBC and LTL at equal proportions: best results of biodiesel. • High conversions (98%) at a space–time of 16 h: over 21 days. • Ester content of the products according to EN 14214. • The two-stage continuous process reduced MAG content in about 63%. • Two-stage continuous process: undetectable amounts of DAG on biodiesel. Technically and economically viable production processes are frequently reported, but products often fail to meet EN 14214 specifications. This study aimed to investigate the transesterification of palm kernel oil catalyzed by a combination of lipases from different sources and produce biodiesel in accordance with current quality standards. Transesterification reactions were first carried out in a stirred batch reactor at 45 °C using an oil:alcohol molar ratio of 1:8. In batch runs, a 50:50 mixture of Burkholderia cepacia lipase and Thermomyces lanuginosus lipase immobilized onto a silica hydroxyethylcellulose matrix resulted in the highest fatty acid ethyl ester yield (98%) and a decrease in kinematic viscosity from 30.35 to 4.00 mm2 s−1. The product had undetectable levels of DAG and low content of MAG (1.68 wt%). The enzymes were then packed separately in a continuous two-stage reactor operating at different space times (16 and 14 h) and oil/alcohol molar ratios (1:12, 1:10, and 1:8). The highest volumetric productivity (415.3 μmol g cat −1 h−1) was achieved using an oil/alcohol molar ratio of 1:8 and space–time of 16 h. The biodiesel had an alkyl ester content above 98%, a MAG content of less than 0.7 wt%, undetectable DAG content, and kinematic viscosity of 4.22 ± 0.25 mm2 s−1, thereby complying with EN 14214. [ABSTRACT FROM AUTHOR]

• Flammability assessment of jet fuel surrogates through flash point measurement. • Novel flash point data on 25 solutions containing biofuels and dodecane. • Binary interaction parameters optimized and validated from flash point data. • Predictive and semi-empirical models were accurate for flash point calculation. As interest in biofuel blends has grown through the years, especially in terms of jet fuel blend development, it has become more and more important to be aware of their physical chemical properties. One of them is the Flash Point (FP), which is intimately related to the flammability of the blend. With this in mind, the aim of this study was to determine experimentally and also mathematically new FP data on binary and ternary solutions containing ethanol, fatty acid ethyl esters (FAEE), and dodecane, as a way of providing data for flammability evaluation of jet fuels based on surrogates. Therefore, FPs of seventeen binary systems and eight ternary systems were measured. A vapor pressure approach was employed to FP prediction with NRTL and original UNIFAC activity coefficient models in order to further analyze flammability in terms of solution behavior, while providing guidance for FP prediction of these systems, needed for fuel development. NRTL binary interaction parameters were adjusted from FP data, as these parameters are not available in the literature for FAEE multicomponent systems. It was observed that addition of ethanol to dodecane or FAEEs steeply decreases FP. On the other hand, addition of FAEEs to dodecane does not affect FP as drastically, which implies an almost ideal behavior for these systems. Both the original UNIFAC and NRTL models were able to improve FP prediction in comparison to the ideal model for all ternary systems with RMSDs ranging from 4.6 K to 0.5 K and 1.3 K to 0.3 K respectively, which points to the validity of the adjusted NRTL parameters. [ABSTRACT FROM AUTHOR]

• Review on transformations of vegetable oils and fatty acids to jet fuel. • Fatty acid and ester hydrocracking 255–260 °C over Ni gives above 50% yield of the aviation type fuel components. • The desired catalyst should possess weak and medium strong acidity, small metal particle sizes and mesoporosity. • Reaction kinetics, mechanism and kinetic modelling are also summarized. The review covers transformations of vegetable oils and fatty acids to jet fuel intensively studied during the recent years. A special emphasis is put on the liquid product yields and the product distribution with the latter one affecting the fuel properties. In addition, the desired catalyst properties have been summarized. One of the best results was reported for Jatropha oil processing, giving above 80 wt% yield of the liquid phase products over Ni supported on H 3 PW 12 O 40 /hydroxyapatite at ca. 400 °C under 30 bar hydrogen. Palm oil hydroconversion was performed in a two-step process over Pt/Al 2 O 3 followed by Pt/HY, at 395 °C and 245 °C, respectively giving 54% jet fuel components. Typically also other products such as diesel range hydrocarbons are formed. Fatty acid and ester hydroconversion proceeds at lower temperatures, 255–260 °C over Ni supported catalysts producing above 50% yield of the aviation type fuel components. The desired catalyst contains acid sites with weak and medium strength, small metal particle sizes and mesoporosity, which facilitate diffusion of branched alkanes. Reaction kinetics, mechanism and kinetic modelling are also summarized. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ecofriendly natural materials are transformed to bifunctional solid catalyst. • Highly acidic waste cooking oil was converted to biodiesel at a yield of 97%. • Developed composite catalyzes simultaneous esterification-transesterification. • Full Factorial Design was efficient for optimizing catalyst preparation (error < 4%). • The optimum catalyst is stable, not leachable and can be reused up to 25 times. A bi-functional catalyst based on natural components was designed and optimized via full factorial design for catalyzing the simultaneous esterification-transesterification process. The factors affecting the catalyst synthesis were as follows: crosslinking time (0.5–2 h), CaCl 2 concentration (1–5 w/v%), sodium alginate to k-carrageenan mass ratio (1.5:1–3:1 w/w), and sodium bentonite to k-carrageenan mass ratio (1:1–4:1 w/w). The free fatty acids conversion into esters and total esters yield were the indicative responses. The results from this study showed that the maximum total esters yield of 97% was obtained at a crosslinking time of 0.5 h, CaCl 2 concentration of 1 w/v%, sodium alginate to k-carrageenan mass ratio of 1.5:1, and sodium bentonite to k-carrageenan mass ratio of 4:1. The reaction conditions were 21:1 methanol to oil molar ratio, 3 wt% catalyst loading, and 10 min sonication time using a 750 W rod-sonicator. The impulse ratio was 45:30, and the sonication amplitude was 50%. This catalyst was reused 25 times, in some cases, without a decline in its catalytic activity. Furthermore, the catalyst does not leach or dissolve in the reaction medium and the physical characteristics of the methyl esters matched the ASTM standards for biodiesel. [ABSTRACT FROM AUTHOR]

[Display omitted] • New VLE (PTxyz) measurements for biolubricants, biofuels, bioplasticizers industries. • Data pressure and temperature ranges: 4394–26790 Pa, 306–423 K. • Ternary systems studied: [Ethanol + 2-Ethyl-1-hexanol or 1-Octanol + 1-Dodecanol]. • Multicomponent system studied: [the ternaries + Balanites aegyptiaca ethyl esters]. • Excellent predictive performance of Dortmund modified UNIFAC model for these VLE. The aim of this paper is to bring valuable phase equilibria information for the design and operation of biolubricant and related biofuel product processes. As a result, Vapor-Liquid Equilibrium (VLE) measurements, at different temperatures, pressures and global compositions, for the ternary systems [Ethanol + 2-Ethyl-1-hexanol + 1-Dodecanol] and [Ethanol + 1-Octanol + 1-Dodecanol], as well as a multicomponent system containing these alcohols together with Balanites aegyptiaca fatty acid ethyl esters are reported for the first time (data pressure and temperature ranges: 4394–26790 Pa, 306–423 K). The Dortmund modified UNIFAC model showed very high accuracy in the prediction of these VLE, with overall average absolute deviations on the liquid and vapor molar compositions of 0.007 and 0.0003 for the ternary systems, 0.003 and 0.006 for the multicomponent system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lipids can be extracted from primary sludge using green solvents. • Thermodynamic data from lipids extraction was used to obtain ternary diagrams. • Calcium soaps were efficiently recovered (~96%) by using ethyl butyrate. • Extraction performance can be easily predicted using ANN with R2 = 0.98. • Calcium soaps can be used as biolubricant or as source of biodiesel (yield > 85%). This work focuses on the recovery of resources from urban sewage sludge. Sewage sludge is generated by water treatment plants and contains a significant amount of lipids that can be used in a number of applications in fine chemistry. This study reports the extraction of lipids from sewage sludge using ethyl esters of volatile fatty acids as solvents. A thermodynamic study was first performed using synthetic primary sludge in order to identify the best operating conditions to apply on real samples of urban primary sludge. Ethyl butyrate showed the best separation performance. It was capable of efficiently recovering the lipid component from primary sewage sludge, which typically resulted in 13–23% of total solids. Highly pure calcium soaps can be extracted in high amounts (yield up to 93%), while the exhausted residual aqueous phase resulted as not significantly contaminated by the solvent and could be anaerobically digested easily. Finally, calcium soaps can be directly used as biolubricant or efficiently converted into biodiesel using aluminum chloride hexahydrate as a catalyst (yield 85%). [ABSTRACT FROM AUTHOR]

• First depiction of ultrasound assisted intensification of biodiesel from mahua oil. • Two stage processing required for high acid value non-edible oil. • Understanding into effect of operating conditions for intensified biodiesel production. • Ultrasonic horn gives best results for intensification with almost twice yields. • Much higher yield (93%) for biodiesel using ultrasonic horn. Sustainable production of biodiesel as second-generation fuel from mahua oil, applied as a green feedstock based on the non-edible nature, was investigated using the two step approach of esterification followed by transesterification reaction with intensification studies using ultrasound. Comparison with the conventional method based on only stirring allowed highlighting the intensification benefits due to ultrasound. Experiments were performed using the ultrasonic horn and ultrasonic bath for comparing the efficacy of the type of ultrasonic reactor for intensification. Effect of various reaction parameters like reaction temperature, the molar ratio of reactants and catalyst loading on the yield has also been analyzed. The results indicated that, maximum intensification was achieved using the ultrasonic horn and optimized parameters established for maximum yield were 45 °C as the temperature, 45 min as the reaction time, 1:9 as the molar ratio of oil to alcohol, 0.5 wt% as the KOH catalyst loading with 120 W as the ultrasonic power and 50% as the duty cycle. Under optimized conditions, the obtained yields for the conventional method was 39%, while the corresponding yield obtained under similar conditions for ultrasonic horn and bath was 93 and 55% respectively. It was clearly demonstrated that ultrasound allowed obtaining higher yields at lower temperature and reaction times directing lower cost of production. Overall, the work clearly demonstrated the process intensification benefits due to the use of ultrasonic horn with better effectiveness compared to the design of ultrasonic bath. [ABSTRACT FROM AUTHOR]

• Glycerol enriched non-calcined calcium oxide was used as catalyst in butanolysis of Jatropha oil. • Influences of temperature and butanol molar ratio on conversion and ester yield were evaluated. • From main factors and their interaction, temperature was found to highly affect both responses. • As curvatures for both responses were significant, quadratic models were used for optimization. • Maximum oil conversion and butyl ester yield to be obtained at optimum conditions were determined. The butanolysis of Jatropha oil using glycerol enriched non-calcined calcium oxide as heterogenous catalyst was carried out to investigate the influences of reaction temperature and butanol: oil molar ratio on Jatropha oil conversion (X JOB) and the yield of fatty acid butyl esters (Y FABEs). The central composite design involved two factors (reaction temperature and butanol: oil molar ratio) and two levels factorial (22) was used to determine the impacts of the factors on X JOB and Y FABEs and to optimize the reaction process. From the main factors and their interaction, temperature was found to highly affect both the X JOB and Y FABEs. As curvatures are statistically significant (p ≤ 0.05), the second order models (quadratic models) were found to be more suitable to optimize the butanolysis process. Based on the regression models and the response surface methodology, the maximum X JOB (98.16%) and Y FABEs (95.79%) were predicted to be obtained at the optimum temperatures of 87.35 and 90.48 oC and butanol: oil molar ratios of 9.13:1 and 13.24:1, respectively. The maximum Y FABEs of 95.64% was also experimentally obtained at the optimum conditions predicted for the Y FABEs. From the results obtained for the experimental ranges investigated, the present study suggested that glycerol enriched non-calcined calcium oxide can be used as a good alternative catalyst for biodiesel production using butanol. More studies are also suggested for upscaling the reaction process of the current experiments by using more integrated reaction factors. [ABSTRACT FROM AUTHOR]

• Increasing fuel hydrogen content systematically reduced nvPM number, mass, and size. • Measured nvPM emissions were loss corrected using particle size distributions. • Particle loss correction factors are impacted by fuel composition and APU condition. • APU exit nvPM emissions were inversely correlated with fuel hydrogen content. Replacement of conventional petroleum jet fuel with sustainable aviation fuels (SAFs) can significantly reduce non-volatile Particulate Matter (nvPM) emissions from aircraft main engines and auxiliary power units (APUs). As part of the Initiative Towards sustAinable Kerosene for Aviation (ITAKA) project, the impact of fuel hydrogen content on nvPM number and mass emissions and particle size distributions were investigated using a GTCP85 APU burning blends of conventional (Jet A-1) and Hydrotreated Esters and Fatty Acids (HEFA)-derived (Used Cooking Oil and Camelina) aviation fuels. The measurements were conducted during two separate test campaigns performed three years apart, each employing a different regulatory compliant sampling and measurement reference system for aircraft engine nvPM emissions. The objective was to investigate the correlation of fuel hydrogen content with nvPM number and mass emissions at the engine exit plane (EEP) independent of fuel composition, measurement system, and ambient conditions. The nvPM number and mass emissions and size distributions systematically decreased with increasing fuel hydrogen content regardless of the fuel composition or APU operating condition. The measured nvPM emissions were particle loss-corrected to the EEP and normalised to a common fuel hydrogen content. Similar rates of nvPM reductions were observed for both test campaigns at all investigated APU operating conditions, confirming that engine exit nvPM reductions correlate with fuel hydrogen content for fuels of relatively similar compositions. This analysis method can be applied to emissions data from other engine types to compare the reduction in nvPM emissions for sustainable aviation fuels and blends. [ABSTRACT FROM AUTHOR]

• An artificial intelligence method has been used to predict surface tension of biodiesels. • The accuracy of utilized databank has been evaluated. • The results have been compared with Kay, Dalton, and UNIFAC outputs. • A comprehensive sensitivity analysis has been done on effective parameters. Recently, increasing demands for energy accelerates the study on renewable energy resources so biodiesels become one of interesting topics for the researchers. Due to wide and user-friend applications of artificial intelligence methods, in this study, an artificial intelligence method based on support vector machine algorithm optimized by Grey wolf optimization algorithm is suggested to estimate the surface tension of biodiesels. To this end, the experimental surface tension dataset has been collected and divided into two datasets of 59 and 19 points for training and testing randomly. After various comparisons with the real surface tension dataset for the proposed artificial intelligence method, three existing models including UNIFAC, Kay and Dalton models have been participated in the comparisons. The determined R-squared values for Kay, Dalton, UNIFAC, and support vector machine are 0.627, 0.6462, 0.8483, and 0.9905, respectively. According to these results, developed model is the best predictive tool for calculation of surface tension of biodiesels. Additionally, the accuracy of biodiesel surface tension databank has been investigated. On the other hand, the impacts of contributed variables in the models on surface tension of biodiesel fuels have been investigated as an another novel point. It explains that the heaviest fractions have been known as the most effective variables on determination of surface tension of biodiesels. Therefore, this study involves a novel and accurate tool for prediction of surface tension of biodiesels and also sensitivity analysis on effective parameters to help researchers in production of cleaner fuels. [ABSTRACT FROM AUTHOR]

The purpose of the current study is to propose a procedure to predict the effect of pressure on biodiesel density based on fatty acid alkyl ester profiles and density values at atmospheric pressure. Based on a Murnaghan equation of state to describe the effects of pressure on density and a group-contribution method to factor in the diversity of fatty acid alkyl ester components in biodiesels, the method is applicable up to 200 MPa in a wide temperature range from 280 to 400 K. Comparison of results with experimental data show that the method provides reliable high pressure predictions for biodiesels and biodiesel blends. Typical deviations calculated between the proposed method and experimental data are 0.05% for Fatty Acid Methyl Esters and 0.04% for Fatty Acid Ethyl Esters in terms of Average Absolute Deviation, with maximum deviations of the same order of magnitude as those of experimental uncertainties. [ABSTRACT FROM AUTHOR]

In order to guarantee safe handling of a combustible liquid, such as biodiesel, it is important to be aware of its Flash Point (FP). Thus, the present study focused on FP experimental measurement and thermodynamic correlation of binary and ternary mixtures of saturated or unsaturated fatty acid ethyl esters (FAEEs) as surrogates for biodiesel. FP of different types of ethylic biodiesel in terms of feedstock (canola, corn, cotton and soy oils) were also measured and compared with the predicted values. Experiments were carried out in agreement with the standard closed cup procedure ASTM D6450. Liaw's model was applied to FP prediction, with liquid phase non-ideality description accounted for by UNIFAC group contribution models (Original UNIFAC, UNIFAC-Dortmund and UNIFAC-Bessa with revised parameters for fats). FP prediction accounting for non-ideality proved to be accurate, with some difference between the UNIFAC type models and Root Mean Square Deviations (RMSD) varying from 0.27 K to 3.95 K for binary and ternary mixtures. [ABSTRACT FROM AUTHOR]

The study of an anion-exchange resin (Amberlyst A26 (OH)) catalyzed transesterification of Jatropha (Jatropha curcas L.) oil was conducted to determine the effects of three variables: reaction temperature, ethanol: oil molar ratio and catalyst amount, on Jatropha oil conversion (X JO) and fatty acid ethyl esters yield's (Y FAEEs). The modified central composite design that involved three independent factors (temperature, ethanol: oil molar ratio and the catalyst present) with two levels, but not included the non-linear stage, was employed to optimize the process. From the main factors and their interactions, the ethanol: oil molar ratio was found to highly affect the X JO and Y FAEEs. In this study, the statistical analysis showed that curvature is not significant (p ≤ 0.05), and thus, from the model regression equations, linear model was found to be more suitable to optimize the responses. By using the regression analysis and the response surface plots, the optimum X JO and Y FAEEs of 37.63% and 36.31%, respectively were predicted to be obtained at the optimum temperature of 55 °C, ethanol: oil molar ratio of 35:1 and catalyst amount of 15%. Employing higher amount of catalyst reduced the X JO and Y FAEEs , particularly, when the variable interacted with the reaction temperature. [ABSTRACT FROM AUTHOR]

• Biodiesel was synthesized from microalgae. • Non-catalytic transesterification was performed with two supercritical fluids. • Rate constants were determined based on pseudo first order kinetic model. • Activation energies were obtained from temperature dependence of the rate constants. • Reaction rates were faster in ethanol compared to ethyl acetate. The decline of fossil fuel reserves and the problems of climate change due to emission of greenhouse gases necessitates the need for alternative sustainable green biofuels. Biodiesel is one such green biofuel which is a mixtures of mono-alkyl esters. In the present study, fatty acid ethyl esters were synthesized from dry microalgae in supercritical ethanol and ethyl acetate. The temperature was varied from 523 to 653 K while keeping pressure at 20 MPa and the ratio of algae to ethylating agent (wt./vol.) at 1:10. The duration of the transesterification reaction was between 20 and 60 min and 20 to 80 min for the ethanol and ethyl acetate systems, respectively. For the ethanol system, >95% of conversions were obtained in 50 min at 593 K whereas with the ethyl acetate system, >60% of conversions were obtained in 50 min at 653 K. The rate constants and activation energies were evaluated by pseudo first order kinetics and Arrhenius equation, respectively. The activation energies were 67.1 and 78.5 kJ/mol for ethanol and ethyl acetate systems, respectively. The reaction rates were higher for ethanol compared to ethyl acetate system. [ABSTRACT FROM AUTHOR]

This work aimed at the enzymatic synthesis of fatty acid esters with potential application as biolubricants from microalgae oil and fusel oil using Burkholderia cepacia lipase immobilized on Nb 2 O 5. The lipid-bearing Dunaliella salina biomass was grown in bubble column photobioreactors, yielding 100 g of biomass and 20 g of oil containing high content of saturated (37.8%) and monounsaturated fatty acids (41.2%) and a low content of polyunsaturated fatty acids (20.9%). The reaction assays were carried out in 50 mL glass reactor containing 10 g of medium composed by microbial oil and fusel oil components (ethyl, butyl, or isoamyl alcohols) and fusel oil as acyl acceptors at a fixed molar ratio of 1:8 (oil to alcohol) using iso-octane as solvent. Batch runs were performed at 45 °C under constant magnetic stirring (150 rpm) for a maximum of 120 h. Macaw palm oil was used as a control under the same reaction conditions. The biocatalyst was found to be efficient in converting the microalgal oil fatty acids into their corresponding alkyl esters attained yields ranging from 70.8 to 89.0% at 120 h reaction, depending on size of the alcohol chain. The kinematic viscosities of the esters produced confirmed the high transesterification yields, considering the viscosity of microalgae oil decreased from 60.1 to a range of 8.9–11.3 m2 s−1 (40 °C) after the enzymatic modification. [ABSTRACT FROM AUTHOR]

• High biodiesel yield was produced from wet microalgae biomass. • Moisture inhibition was contributed by reverse reaction due to the present of water. • Increased methanol concentration and adding co-solvent can reduce moisture inhibition. • n -Butanol and tetrahydrofuran had opposite selectivity towards fatty acid esters. In the present study, the effect of co-solvent and different reaction parameters on fatty acid ester yield composition produced from in-situ transesterification of wet Chlorella vulgaris was investigated. The result showed that under wet microalgae condition (75 wt% of moisture content), increasing of methanol concentration resulted in more significant improvement of fatty acid ester yield as compared to H 2 SO 4 concentration. This was due to the equilibrium shifting to the FAME product direction under high methanol concentration condition. The highest fatty acid ester yield attained under wet microalgae condition was 96.0 wt% of esterifiable lipid with 650 mol/mol and 10000 mol/mol of H 2 SO 4 and methanol concentration, respectively. Besides, by introducing small amount of n -butanol or tetrahydrofuran (THF) (0.1 mol/mol of methanol) as co-solvent resulted to remarkable enhancement in fatty acid ester yield (100 wt% and 98.7 wt% of esterifiable lipid corresponding to n -butanol and THF, respectively) and 33% reduction of methanol usage. This was due to the synergetic effect of co-solvent in the lipid extraction process and enhancement of solubility between lipid and methanol phase to accelerate the transesterification reaction. Moreover, n -butanol or THF also lead to different selectivity of fatty acid esters, whereby high concentration of long-chain fatty acid esters (e.g. C18) were attained with n -butanol while short-chain fatty acid esters (e.g. C10 and C16) were obtained by adding THF. Overall, the results from the present study revealed the possibility to obtain high fatty acid ester yield from wet microalgae paste that could be useful for scale-up study. [ABSTRACT FROM AUTHOR]