Biofuel Additives Research Articles

Biofuel Additives: Thermodynamic Studies of Glycerol Ethers

Glycerol offers vast potential for the design of new “green” solvents and molecular building blocks from naturally derived resources. Etherification of glycerol at one or more of the three alcohols yields large decreases in viscosity and makes the resulting products attractive “green” solvent candidates. Our prior works have demonstrated efficient synthesis of 1,3-diether-2-alcohol, 1,3-diether-2-ketone, and 1,2,3-triether compounds with glycerol skeletons with a variety of functional groups in both symmetric and asymmetric patterns. As the potential applications for these compounds become more widely explored, there is a need to understand their properties so that they may be properly evaluated for use in existing and new process technologies. In this work, the thermodynamic properties of four glycerol ethers with systematically varied functional groups are measured and evaluated. Data reported will not only help supplement the library of glycerol derivative properties, but also provide guidance for the development of novel biofuel additives.

Metal-exchanged phosphotungstate nanoparticles with improved acidity as the catalyst for esterification of glycerol with acetic acid

Abstract A series of metal-exchanged phosphotungstate salts, Fe-TPA, Cr-TPA, Cu-TPA, and Ni-TPA were synthesized by sonication and tested for glycerol esterification with acetic acid to obtain biofuel additives. A systematic, chemical, structural, and morphological characterization and determination of acidity were used by various analytical techniques. XRD and FT-IR studies confirmed the Keggin structure of all metal exchanged phosphotungstate salts with no impurities coming from metal nitrate salts. The incorporation of metal cations in phosphotungstic acid leads to decreased crystallite size as seen from XRD diffractograms. N2 adsorption-desorption analysis showed that the Type II isotherms were obtained for all metal exchanged phophostungstate salts, characteristic of non-porous or macroporous materials. SEM images of metal exchanged phosphotungstate salts displayed well-shaped crystalline particles. SEM-EDX analysis showed that the calculated tungsten metal ratios are in good agreement with the theoretical ratios of those for all the metal exchanged salts, verified by XRF results. The exchange of protons by the metal cations improved the thermal stability observed in the TGA analysis. The acidity strengths, from NH3-TPD analysis, were found in the following order; TPA > Fe-TPA > Cr-TPA > Cu-TPA. Additionally, pyridine-FTIR gives that the exchanging of transition metal into the phosphotungstic acid decreased the Brønsted acidity while increasing the Lewis acidity and this mostly affects the efficiency of the esterification reaction. The activity of metal exchanged salts was in the given order; Fe-TPA > Cr-TPA > Cu-TPA > Ni-TPA. Among these Fe-TPA salt, having a good ratio of Brønsted and Lewis acidity, have the selectivity for di- and triacetin (68 and 10%), with the highest conversion (96%). The iron phosphotungstate salts are a promising catalyst with sustainable Bronsted acidity during the reaction, high desired product selectivity at low temperature, easy synthesizability, inexpensive, and environmentally friendly.

Use of biobased crude glycerol, obtained biocatalytically, to obtain biofuel additives by catalytic acetalization of furfural using SAPO catalysts

High-pure crude glycerol, obtained from the transesterification of coconut oil with ethanol using lipase enzyme-type as biocatalyst, has been used for the acetalization of furfural with several SAPO 5 and SAPO 34 catalysts. SAPOs were prepared using microwaves and conventional heating for comparison, and were characterized by X-ray diffraction, nitrogen physisorption, elemental analysis, thermogravimetry of adsorbed cyclohexylamine and scanning electron microscopy techniques. The use of microwaves allowed us the incorporation of slightly higher amounts of silicon into the aluminophosphate structure, and the preparation of the materials in much shorter preparation times, with the subsequent energy saving. Additionally, the SAPOs prepared with microwaves showed lower crystallinity but higher surface area than those prepared by conventional heating. Comparable catalytic results were obtained when these catalysts were tested for the acetalization of furfural with commercial or with the crude glycerol obtained by biocatalytic transesterification of coconut oil, leading to very high selectivity values to the desired mixture dioxane + dioxolane (93–100 %), which can be used as biofuel additives, for conversion values between 60 and 73 %, as determined by gas chromatography. This confirmed the high purity of the glycerol obtained by the biocatalytical process, as previously observed by 1H NMR. SAPO 34 catalysts showed higher conversion than SAPO 5 catalysts due to their higher amount of more accessible Brønsted acid sites, related to their structure. Interestingly, catalysts prepared with microwaves resulted in slightly higher conversion values than those prepared by conventional heating. This can be explained by the incorporation of higher amounts of silicon in the framework, probably due to the higher homogeneity of the microwaves heating, which results in a higher amount of protons, as confirmed by TGA of adsorbed cyclohexylamine, responsible for the catalysis.

Sustainable Upgrade of Bioderived Glycerol to Solketal through Acetalization over Metal-Free Mordenite Catalysts

In the current work, acetalization of crude glycerol to produce valuable solketal, a renewable fuel additive, is studied over metal-free mordenite-based catalysts. The perfect combination of the appropriate acidity and suitable porosity is required to achieve optimum solketal yield from glycerol. The property–activity correlation was established through various physicochemical characterizations, and reaction parameters were optimized to maximize the solketal yield. The modified mordenite catalyst showed exceptionally high catalytic activity toward the acetalization of crude glycerol and as high as 99% yield of solketal was achieved under mild reaction conditions, i.e., a reaction temperature of 60 °C, a time of 4 h, and atmospheric pressure. The catalyst showed tolerance for water and other impurities present in crude glycerol in addition to excellent recyclability up to three cycles without any regeneration treatment. The economical, easy-to-prepare, recyclable, metal-free, moisture-tolerant nature of the catalyst makes it a promising catalyst candidate to be used at a larger scale. The catalytic process has the potential to utilize crude glycerol obtained from biodiesel plants for the synthesis of biofuel additives solketal. This highlights the industrial and environmental significance of this work.

Variation in sooting characteristics and cetane number of diesel with the addition of a monoterpene biofuel, α-pinene

Diesel fuel combustion generates soot particles, which are harmful for human health and the environment. To reduce soot emission, various solutions are proposed in the literature such as the use of metal-additives in fuels, fuel blending with biofuels, and the use of diesel particulate filters. This study analyses the effect of the addition of a bicyclic monoterpene hydrocarbon biofuel, α-pinene to diesel in different proportions on the fuel cetane number, sooting propensity, and the physicochemical properties of soot nanoparticles. The addition of 10% α-pinene to diesel exhibited a synergistic effect on sooting tendency and reduced the threshold sooting index of diesel by 21%, even though α-pinene is an unsaturated hydrocarbon, and had a minimal impact on cetane number, which reduced from 63.5 for diesel to 61.5 for the blended fuel. The influence of α-pinene addition to diesel on soot nanostructural characteristics and reactivity is determined through different characterization approaches including HRTEM, TGA, XRD, SEM-EDX, and EELS. The results indicate that α-pinene addition to diesel imposes curvatures in soot nanostructure, creates relatively smaller fringes (PAHs) in soot, and reduces soot aromatic content to improve soot oxidation rate.

Photoionization of Two Potential Biofuel Additives: γ-Valerolactone and Methyl Butyrate.

The photoionization of two potential biofuel additives, γ-valerolactone (GVL, C5H8O2) and methyl butyrate (MB, C5H10O2) has been studied by imaging photoelectron photoion coincidence spectroscopy (iPEPICO) at the VUV beamline of the Swiss Light Source (SLS). The vibrational fine structure in the photoelectron spectrum is compared with a Franck-Condon simulation for the electronic ground-state band of the GVL cation. In the lowest energy dissociative photoionization channel of GVL, CO2 is lost, resulting in a 1-butene fragment ion with a 0 K appearance energy of E0 = 10.35 ± 0.01 eV. A newly calculated 1-butene ionization energy of 9.595 ± 0.015 eV establishes the reverse barrier height to CO2 loss as 66.6 ± 4.3 kJ mol-1. Methyl butyrate cations undergo McLafferty rearrangement, which explains the missing ion signal at the computed adiabatic ionization energy of 9.25 eV. After H transfer, ethylene is lost in the lowest energy dissociation channel to yield the methyl acetate enol ion at E0 = 10.24 ± 0.04 eV. This value connects the energetics of methyl butyrate with that of methyl acetate enol ion, which is established at ΔfHo0K[CH2C(OH)OCH3+] = 502 ± 6 kJ mol-1. Parallel to ethylene loss, methyl loss is also observed from the enol tautomer of the parent ion. Both samples exhibit low-energy nonstatistical dissociative ionization channels. In GVL, the methyl-loss abundance rises quickly but levels off suddenly in the energy range of the first electronically excited states, indicating nonstatistical competition between CH3 and CO2 loss. In MB, the major parallel dissociation channel is the loss of a methoxy radical. Calculations indicate that McLafferty rearrangement is inhibited on the excited-state surface. Indeed, breakdown curve modeling of this and a sequential CO-loss channel confirms a second statistical regime in dissociative photoionization, decoupled from ethylene loss.

Current Trends and Future Prospects of Nanotechnology in Biofuel Production

Biofuel is one of the best alternatives to petroleum-derived fuels globally especially in the current scenario, where fossil fuels are continuously depleting. Fossil-based fuels cause severe threats to the environment and human health by releasing greenhouse gases on their burning. With the several limitations in currently available technologies and associated higher expenses, producing biofuels on an industrial scale is a time-consuming operation. Moreover, processes adopted for the conversion of various feedstock to the desired product are different depending upon the various techniques and materials utilized. Nanoparticles (NPs) are one of the best solutions to the current challenges on utilization of biomass in terms of their selectivity, energy efficiency, and time management, with reduced cost involvement. Many of these methods have recently been adopted, and several NPs such as metal, magnetic, and metal oxide are now being used in enhancement of biofuel production. The unique properties of NPs, such as their design, stability, greater surface area to volume ratio, catalytic activity, and reusability, make them effective biofuel additives. In addition, nanomaterials such as carbon nanotubes, carbon nanofibers, and nanosheets have been found to be cost effective as well as stable catalysts for enzyme immobilization, thus improving biofuel synthesis. The current study gives a comprehensive overview of the use of various nanomaterials in biofuel production, as well as the major challenges and future opportunities.

Production of Furfural-Diethyl-Acetal as Biofuel Additives for Gasoline by Metal Free Porphyrin Photocatalyst Under Visible Light

Production of Furfural-Diethyl-Acetal as Biofuel Additives for Gasoline by Metal Free Porphyrin Photocatalyst Under Visible Light

Production of Biofuel Additives from Glycerol Etherification Using Zirconia Supported Phosphotungstic Acid

Production of Biofuel Additives from Glycerol Etherification Using Zirconia Supported Phosphotungstic Acid

Structure–Activity Relationships of WOx-Promoted TiO2–ZrO2 Solid Acid Catalyst for Acetalization and Ketalization of Glycerol towards Biofuel Additives

Structure–Activity Relationships of WOx-Promoted TiO2–ZrO2 Solid Acid Catalyst for Acetalization and Ketalization of Glycerol towards Biofuel Additives

Solid acid carbon catalysts for sustainable production of biofuel enhancers via transesterification of glycerol with ethyl acetate

SO3H-bearing carbons prepared from sugars or glycerol were used as catalysts for the production of acetins via a transesterification route. Two methods of preparation of functionalized carbon catalysts were compared: a) an energy-efficient, one-pot synthesis including partial carbonization of precursors with H2SO4 coupled with simultaneous in-situ functionalization and b) a two-step method including template synthesis of carbon followed by functionalization of the obtained product with sulfuric acid or diazonium salt. The synthesized carbons were used in an eco-friendly process of glycerol transesterification with ethyl acetate under different reaction conditions. All the prepared samples were found to effectively catalyze the reaction, producing a mixture of mono-, di- and triacetins (MA, DA and TA, respectively); however, the efficient production of the target compounds, namely DA and TA, which are valuable biofuel additives, was found to be strongly dependent on the content of sulfonic groups on the surface of these catalysts. A direct correlation between –SO3H concentration and glycerol conversion, as well as the yield of higher esters was established. Moreover, the applied method of one-pot combined partial carbonization and functionalization with H2SO4 was shown to be a convenient way to obtain carbonaceous solid acid catalysts that can be used as promising alternatives to modified carbons produced by conventional two-step techniques.

Impact of microalgae biofuel on microgas turbine aviation engine: A combustion and emission study

This paper investigates the authenticity of the biofuels as an alternative to Jet A fuel. Owing to the fact of reduced CO2 emission quality, biofuels can be used in the field of aviation to substantially reduce the CO2 emission and improve the performance. In this analysis, microalgae Spirulina biofuel was added with Jet-A fuel at different proportions such as 20%, 40%, 60%, 80% and 100%. The proportions used are B20% (20% biofuel with 80% jet-A fuel), B40% (40% biofuel with 60% Jet-A fuel), B60% (60% biofuel with 40% Jet-A fuel), B80% (80% biofuel with 20% Jet-A fuel) and B100% biofuel. All the test results were compared with the neat jet A fuel. The experiments were conducted at different engine speeds. A small experimental jet engine was used to conduct all the experimental tests. Engine performance characteristics and emission characteristics were found for different fuel blends. It is concluded that the biofuel at a lower proportion level with the Jet–A fuel comparatively produced a good result. In terms of thrust and engine speed, the lower level of addition of biofuel is fruitful. The emission level of CO, CO2, and NOx was reduced owing to the presence of excess oxygen content in the blends. However, when the addition percentage was increased, the results produced by them were not positive because of its low energy.

Characterizing and using a new bi-functional catalyst to sustainably synthesize methyl levulinate from biomass carbohydrates

In recent years, significant attention has been dedicated to converting biomass carbohydrates into alkyl levulinates (biofuel additives) in alcoholic media, in search of various cheap and active solid catalysts through relatively easy pathways and from non-dangerous precursors. The synthesis of methyl levulinate (ML) using a new Brønsted/Lewis acid sites catalyst was investigated, emphasizing the influence of three parameters (catalyst loading, the molar concentration of fructose in methanol, and reaction temperature) on the process. The synthetized catalyst, SO42−/TiO2–La2O3 coating Fe3O4, was characterized by different techniques (FT-IR, XRD, TGA, TEM-EDX, ICP-OES). The design of the ML synthesis experiment was carried out using the Box-Behnken technique, while the response surface methodology was applied to obtain the optimized process conditions. A mathematical model of the catalytic synthesis was built, based upon first principles, and the experimental time variation of the reaction mixture concentrations was used to find, through regression, the values of the constants of a newly proposed kinetic model.

Corn distillers dried grains with solubles: Production, properties, and potential uses

AbstractBackground and objectivesThe grain‐based ethanol production has been increasing as the demand for biofuel additives increased, and the fossil fuel sources decreased. Distillers dried grains with solubles (DDGS) are a primary coproduct of bioethanol plants of the conventional corn dry‐grind process. With increasing corn‐based ethanol production, DDGS production is increased, and it has become a global commodity. Despite the high nutritional value of DDGS, however, its uses are still not fully explored. This review aims to provide a comprehensive summary of the DDGS production process, chemical and physical properties, nutritional value, and the potential of using DDGS in cattle, fish, poultry feed, and human foods. The challenges of using DDGS in animal feed and human food are discussed.FindingsDistillers dried grains with solubles has been identified as a protein substitute that is both readily available and competitively priced (per unit protein) compared to other conventional alternative protein sources. Researchers have discovered measures to boost DDGS quality and safety. Several approaches have been proposed to improve the DDGS digestibility and nutritional value. Although the benefits and risks associated with the DDGS uses are identified, more research is required to regulate the quality and safety standards for DDGS.ConclusionsVersatile applications of DDGS will valorize this coproduct. The development of DDGS utilization enhances health and functional benefits to animals and humans; it also assists bioethanol plants economically.Significance and noveltyThe information will not only provide knowledge of DDGS in terms of its production process, nutritional value, and applications but, more importantly, explore the opportunities of developing new uses of this under‐utilized commodity.

The Synergy of Two Biofuel Additives on Combustion Process to Simultaneously Reduce NOx and PM Emissions

The article presents the results of research on the influence of two fuel additives that selectively affect the combustion process in a diesel engine cylinder. The addition of NitrON® reduces the concentration of nitrogen oxides (NOx), due to a reduction in the kinetic combustion rate, at the cost of a slight increase in the concentration of particulate matter (PM) in the engine exhaust gas. The Reduxco® additive reduces PM emissions by increasing the diffusion combustion rate, while slightly increasing the NOx concentration in the engine exhaust gas. Research conducted by the authors confirmed that the simultaneous use of both of these additives in the fuel not only reduced both NOx and PM emissions in the exhaust gas but additionally the reduction of NOx and PM emissions was greater than the sum of the effects of these additives—the synergy effect. Findings indicated that the waveforms of the heat release rate (dQ/dα) responsible for the emission of NOx and PM in the exhaust gas differed for the four tested fuels in relation to the maximum value (selectively and independently in the kinetic and diffusion stage), and they were also phase shifted. Due to this, the heat release process Q(α) was characterized by a lower amount of heat released in the kinetic phase compared to fuel with NitrON® only and a greater amount of heat released in the diffusion phase compared to fuel with Reduxco® alone, which explained the lowest NOx and PM emissions in the exhaust gas at that time. For example for the NOx concentration in the engine exhaust: the Nitrocet® fuel additive (in the used amount of 1500 ppm) reduces the NOx concentration in the exhaust gas by 18% compared to the base fuel. The addition of a Reduxco® catalyst to the fuel (1500 ppm) unfortunately increases the NOx concentration by up to 20%. On the other hand, the combustion of the complete tested fuel, containing both additives simultaneously, is characterized, thanks to the synergy effect, by the lowest NOx concentration (reduction by 22% in relation to the base). For example for PM emissions: the Nitrocet® fuel additive does not significantly affect the PM emissions in the engine exhaust (up to a few per cent compared to the base fuel). The addition of a Reduxco® catalyst to the fuel greatly reduces PM emissions in the engine exhaust, up to 35% compared to the base fuel. On the other hand, the combustion of the complete tested fuel containing both additives simultaneously is characterized by the synergy effect with the lowest PM emission (reduction of 39% compared to the base fuel).

Acetalization of glycerol and benzaldehyde to synthesize biofuel additives using SO42-/CeO2–ZrO2 catalyst

Synthesis of 1,3- dioxane and 1,3-dioxolane, using sulfated CeO2–ZrO2 catalyst for acetalization of glycerol with benzaldehyde, is the focus of present work. SO42-/CeO2–ZrO2 catalyst was synthesized using combustion method. Experiments were carried out to analyze the effect of various solvents (n-hexane, toluene, tert-butyl alcohol, pentanol), molar ratios (1:3, 1:5, 1:7), catalyst loadings (3 wt%, 5 wt%, 9 wt %) and temperatures (80 °C, 90 °C, 100 °C) on glycerol conversion and selectivity of the products. Selectivity of 87.20% dioxolane and 12.80% dioxane was obtained at molar ratio of 1:3, 9 wt% catalyst loading and temperature of 100 °C.Strong NH3 desorption peak from NH3-TPD study indicated the high acidic strength of sulphated catalyst. Strong surface acidity and surface porosity (observed from TEM and SEM analysis) contributed to an enhanced activity of the catalyst for glycerol acetalization reaction. The kinetics of the reaction was studied using an elementary kinetic law. A correlation coefficient of 0.98 from the selected kinetic model proved that the rate of acetalization reaction was dependent on glycerol concentration and acetal formation was instantaneous. The study demonstrated the application of an environmentally benign, inexpensive, thermally stable, active SO42-/CeO2–ZrO2 catalyst for glycerol acetalization reaction to synthesize 1,3-dioxolane as the desired product.

A reusable magnetic nanocatalyst for bio-fuel additives: the ultrasound-assisted synthesis of solketal

We report an efficient ultrasound-assisted room temperature synthesis of solketal by acetalization of glycerol with acetone.

Catalytic hydrogenation and etherification of 5-Hydroxymethylfurfural into 2-(alkoxymethyl)-5-methylfuran and 2,5-bis(alkoxymethyl)furan as potential biofuel additives

In this study, 5-hydroxymethylfurfural (HMF) was converted into several biofuel additives such as alkoxymethylfurans (AMFs) and 2,5-bis(alkoxymethyl)furans (BAMFs) through two-step sequential hydrogenation and etherification reactions. In the first step, zinc‑iron magnetic nanocatalyst supported on activated carbon (ZnO-Fe3O4/AC) was prepared for the selective hydrogenation of HMF into BHMF and 5-MFA via Meerwein-Ponndorf-Verley (MPV) reaction in three different hydrogen donor alcohols (ethanol, 1-propanol, and 1-butanol). The important physical properties of the catalyst such as crystallinity, chemical composition, morphology, reduction behavior, and surface area were studied by using several analytical techniques. The effect of hydrogenation parameters such as catalyst concentration, temperature, and time on the selectivity of (BHMF and 5-MFA), and HMF conversion were studied. The best hydrogenation results were obtained with 0.2 mmole HMF and 100 mg of catalyst at 200 °C for 12 h. In the second step, three commercial Brønsted acid catalysts were used to convert the hydrogenated products into alkoxymethylfurans (AMFs) and 2,5-bis(alkoxymethyl)furans (BAMFs). At the optimum etherification conditions (65 °C and 10 h), a spectrum of mono-, di-, and tri- ether compounds were obtained. The hydrogenation catalyst (ZnO-Fe3O4/AC) was recycled and used for five times without a remarkable reduction in its catalytic activity.

Catalytic acetalization of glycerol to biofuel additives over NiO and Co3O4 supported oxide catalysts: experimental results and theoretical calculations

A series of NiO and Co3O4 supported oxide catalysts was synthesized and investigated in the acetalization of glycerol with butyraldehyde to biofuels production. The catalysts were characterized by XRD, N2 sorption, FTIR and Raman spectroscopy, SEM-EDS and HRTEM techniques. The influence of the catalysts mass, glycerol to butyraldehyde molar ratios, reaction temperature and presence of solvent were deeply investigated. The dispersion of Ni and Co oxides gave distinct effects on the catalytic performances of the solids with AlTi and CeMn being actives in all conditions tested. The mechanistic aspect of the reaction was investigated by density functional theory (DFT). Among the catalysts, the high acidity of the Co/CeMn and Ni/CeMn promoted the acetalization of glycerol more efficiently to produce 4-methanol-2-propyl-1,3-dioxolane, in spite of the glycerol oligomers formation. The correlation of the structure, acidity, morphology and texture of the solids with the catalytic performance was illustrated for solventless acetalization of glycerol with butyraldehyde reaction. The theoretical calculations by DFT studies revealed a more favorable route to 1,3-dioxolane production.

Synthesis of furfural from Acacia mangium wood sawdust‐derived xylose by continuous distillation method using sulfonated carbonaceous catalyst from the same source

AbstractIn this study, the hydrolysate containing ~15 g/L of xylose, which was obtained from Acacia mangium wood sawdust was used for the synthesis of xylose by a continuous distillation method. The synthesis was conducted at 150 °C for 7 h using a carbon‐based sulfonated catalyst (CBSC) from the same biomass source with an acid density of about 4.0 mmol/g. The CBSC showed its efficient catalytic activity in the dehydration of xylose to furfural. Under the optimal catalyst dosage of 20 wt% over xylose, the yield of furfural was 20.4 mol% and 34 wt% of xylose was transformed to furfural. The results presented a successful utilization of a wood‐derived solid acid catalyst for production of furfural from the same biomass source as a sustainable production of furans for biofuel additives.