Biofuel Additives Research Articles

Kinetic study of synthesis of bio-fuel additives from glycerol using a hetropolyacid

Concerns about the ever increasing quantities of glycerol produced as a by-product of the process of manufactureof bio-diesel serve as a fuel for research about the alternative uses of glycerol. The esterificationof glycerol with acetic acid over Cesium supported heteropolyacid (CsPWA) serving as the catalyst wascarried out. The products obtained were mono, di and tri acetins which have wide application as biofuels.A series of experiments were carried out with CsPWA as catalyst and parameters considered for studieswere temperature, molar ratio of reactants (acetic acid:glycerol) and the catalyst loading weight percent.Each parameter was varied keeping the other two constant and the results were recorded. Temperaturewas varied from 80 °C to 110 °C; molar ratio of glycerol to acetic acid is between 3:1 and 9:1 and catalystloading of 3%w/w to 7%w/w. The yield and conversion varied for different conditions, but in general, theyield of diacetin and triacetin increased with time. Optimum parameters were adjudged to be 110 °C witha molar ratio of 9:1 of the reactants and catalyst loading being 5% weight of reaction mixture wheremaximum glycerol conversion of 98% was obtained. The results obtained indicate that the esterificationof glycerol with acetic acid is a consecutive reaction and the kinetic model was developed based on homogeneousfirst order reaction series by optimization method using MATLAB, and rate constants (k 1 , k 2and k 3 ) were determined. From the rate constants at different temperatures, using Arrhenius equationthe activation energies (E 1 , E 2 and E 3 ) were also determined.

Direct catalytic conversion of carbohydrates to methyl levulinate: Synergy of solid Brønsted acid and Lewis acid

Conversion of biomass derived carbohydrates to alkyl levulinates is an important process due to the wide application of alkyl levulinates as chemicals and biofuel additives. Efficient conversion of cheap and abundant glucose to alkyl levulinates over easily separated and regenerated solid catalyst is highly desirable. Here, the transformation of glucose to methyl levulinate (MLE) was studied over dual solid acid catalysts. The synergistic effect of solid Brønsted (B) acid and solid Lewis (L) acid was observed. A combined catalyst system consisting of both B acid and L acid was found to be more efficient for the production of MLE from glucose. 62% yield of MLE was given over the combined catalyst of SO42−/ZrO2 and Sn-Beta prepared by postsynthesis method at 170°C for 24h. The roles of L acid sites of SO42−/ZrO2 and Sn-Beta, and B acid sites of SO42−/ZrO2 were discussed in detail. Alternative biomass-derived carbohydrates also gave moderate to good yields of MLE. Recyclability studies indicated that the combined catalyst system can be reused without significant change in the yield of MLE, proving its easy recovery and thermal stability during regeneration.

Efficient Catalytic Upgrading of Levulinic Acid into Alkyl Levulinates by Resin-Supported Acids and Flow Reactors

Biomass-derived levulinic acid (LA) is an excellent substrate to obtain high-value esters that can be used as second-generation biofuels and biofuel additives. The present study focuses on the identification and definition of the key parameters crucial for the development of chemically and environmentally efficient protocols operating in continuous-flow for the preparation of structurally diverse alkyl levulinates via the esterification of LA. We have focused on the use of solid acid catalysts consisting of sulfonated cation exchange resins and considered different aliphatic alcohols to prepare levulinates 3 and 11–17 regioselectively, and in good to high yields (50–92%). Direct correlations between several reaction parameters and catalyst activity have been investigated and discussed to set proper flow reactors that allow minimal waste production during the workup procedure, enabling Environmental factor (E-factor) values as low as ca. 0.3, full recoverability and reusability of the catalysts, and the production of levulinates up to ca. 5 gxh−1 scale.

Facile Synthesis of Ethyl-4-ethoxy Pentanoate as a Novel Biofuel Additive Derived from γ-Valerolactone

The synthesis of new biomass-derived ethers is of great interest for the development of biofuels and biofuel additives. In this study, we report the facile synthesis of a novel bioether ethyl-4-ethoxy pentanoate (EEP) from γ-valerolactone (GVL), a well-known biomass platform compound. The formation of EEP involves the etherification of ethyl-4-hydroxyl pentanoate (EHP) formed by GVL ring opening catalyzed by H-β-zeolite in ethanol. When operated at 140 °C for 2 h under autogenous pressure, the highest EEP yield of 55% was achieved at 62% GVL conversion and 89% EEP selectivity. The EEP yield was significantly improved to 86% by increasing the reaction temperature to 160 °C, where the EEP selectivity reached ∼97%. The extraordinarily high selectivity to EEP over H-β is likely correlated to its unique structure, which has strong Lewis acid sites as well as an optimal pore size.

Artificial neural network based predictions of cetane number for furanic biofuel additives

The next generation of alternative fuels is being investigated through advanced chemical and biological production techniques for the purpose of finding suitable replacements for diesel and gasoline while lowering production costs and increasing process yields. Chemical conversion of biomass to fuels provides a plethora of pathways with a variety of fuel molecules, both novel and traditional, which may be targeted. In the search for new fuels, an initial, intuition-driven evaluation of fuel compounds with desired properties is required. Due to the high cost and significant production time needed to synthesize these materials at a scale sufficient for exhaustive testing, a predictive model would allow chemists to preemptively screen fuel properties of potentially desirable fuel candidates. Recent work has shown that predictive models, in this case artificial neural networks (ANN’s) analyzing quantitative structure property relationships (QSPR’s), can predict the cetane number (CN) of a proposed fuel molecule with relatively small error. A fuel’s CN is a measure of its ignition quality, typically defined using prescribed ASTM standards and a cetane testing engine. Alternatively, the analogous derived cetane number (DCN), obtained using an Ignition Quality Tester (IQT), is a direct measurement alternative to the CN that uses an empirical inverse relationship to the ignition delay found in the constant volume combustion chamber apparatus. DCN data points acquired using an IQT were utilized for model validation and expansion of the experimental database used in this study. The present work improves on an existing model by optimizing the model architecture along with the key learning variables of the ANN and by making the model more generalizable to a wider variety of fuel candidate types, specifically the class of furans and furan derivatives, by including specific molecules for the model to incorporate. The new molecules considered include tetrahydrofuran, 2-methylfuran, 2-methyltetrahydrofuran, 5,5′-(furan-2-ylmethylene)bis(2-methylfuran), 5,5′-((tetrahydrofuran-2-yl)methylene)bis(2-methyltetrahydrofuran), tris(5-methylfuran-2-yl)methane, and tris(5-methyltetrahydrofuran-2-yl)methane. Model architecture adjustments improved the overall root-mean-square error (RMSE) of the base database predictions by 5.54%. Additionally, through the targeted database expansion, it is shown that the predicted cetane number of the furan-based molecules improves on average by 49.21% (3.74 CN units) and significantly for a few of the individual molecules. This indicates that a selected subset of representative molecules can be used to extend the model’s predictive accuracy to new molecular classes. The approach, bolstered by the improvements presented in this paper, enables chemists to focus on promising molecules by eliminating less favorable candidates in relation to their ignition quality.

Kinetic study of synthesis of bio-fuel additives from glycerol using a hetropolyacid

Abstract Concerns about the ever increasing quantities of glycerol produced as a by-product of the process of manufacture of bio-diesel serve as a fuel for research about the alternative uses of glycerol. The esterification of glycerol with acetic acid over Cesium supported heteropolyacid (CsPWA) serving as the catalyst was carried out. The products obtained were mono, di and tri acetins which have wide application as biofuels. A series of experiments were carried out with CsPWA as catalyst and parameters considered for studies were temperature, molar ratio of reactants (acetic acid:glycerol) and the catalyst loading weight percent. Each parameter was varied keeping the other two constant and the results were recorded. Temperature was varied from 80°C to 110°C; molar ratio of glycerol to acetic acid is between 3:1 and 9:1 and catalyst loading of 3%w/w to 7%w/w. The yield and conversion varied for different conditions, but in general, the yield of diacetin and triacetin increased with time. Optimum parameters were adjudged to be 110°C with a molar ratio of 9:1 of the reactants and catalyst loading being 5% weight of reaction mixture where maximum glycerol conversion of 98% was obtained. The results obtained indicate that the esterification of glycerol with acetic acid is a consecutive reaction and the kinetic model was developed based on homogeneous first order reaction series by optimization method using MATLAB, and rate constants (k 1 , k 2 and k 3 ) were determined. From the rate constants at different temperatures, using Arrhenius equation the activation energies (E 1 , E 2 and E 3 ) were also determined.

Biobased Furanics: Kinetic Studies on the Acid Catalyzed Decomposition of 2-Hydroxyacetyl Furan in Water Using Brönsted Acid Catalysts

Biobased furanics like 5-hydroxymethylfurfural (5-HMF) are interesting platform chemicals for the synthesis of biofuel additives and polymer precursors. 5-HMF is typically prepared from C6 ketoses like fructose, psicose, sorbose and tagatose. A known byproduct is 2-hydroxyacetylfuran (2-HAF), particularly when using sorbose and psicose as the reactants. We here report an experimental and kinetic modeling study on the rate of decomposition of 2-HAF in a typical reaction medium for 5-HMF synthesis (water, Brönsted acid), with the incentive to gain insights in the stability of 2-HAF. A total of 12 experiments were performed (batch setup) in water with sulfuric acid as the catalyst (100–170 °C, CH2SO4 ranging between 0.033 and 1.37 M and an initial 2-HAF concentration between 0.04 and 0.26 M). Analysis of the reaction mixtures showed a multitude of products, of which levulinic acid (LA) and formic acid (FA) were the most prominent (Ymax,FA = 24 mol %, Ymax,LA = 10 mol %) when using HCl. In contrast, both LA and FA were formed in minor amounts when using H2SO4 as the catalyst. The decomposition reaction of 2-HAF using sulfuric acid was successfully modeled (R2 = 0.9957) using a first-order approach in 2-HAF and acid. The activation energy was found to be 98.7 (±2.2) kJ mol–1.

Optimized whole cell biocatalyst from acetoin to 2,3‐butanediol through coexpression of acetoin reductase with NADH regeneration systems in engineered Bacillus subtilis

AbstractBACKGROUND2,3‐Butanediol (2,3‐BD) has a wide range of applications in chiral molecular synthesis, biofuel additives, and in food flavor additive manufacturing. Fermentation is a favorable method for 2,3‐BD production. However, it requires much time and produces several NADH related byproducts which compete with 2,3‐BD production. Bacillus subtilis has an excellent ability for 2,3‐BD production by biocatalysis. However, its production is limited by low intracellular NADH and the reversible property of acetoin reductase (AR/2,3‐BDH). The whole cell biocatalyst process with two different NADH regeneration systems was designed for efficient production of 2,3‐BD in B. subtilis 168.RESULTSFormate dehydrogenase and glucose dehydrogenase for NADH regeneration were successfully co‐expressed with acetoin reductase in B. subtilis 168. After optimization of biocatalyst bioconversion conditions, B. subtilis 168/pMA5‐bdhA‐HpaII‐fdh yielded 74.5 g L−1 of 2, 3‐BD with 9.3 g L−1 h−1 productivity by fed batch and 115.4 g of 2,3‐BD was achieved using same batch bacterium by three repeated batch bioconversions. On the other hand, 63.7 g L−1 of 2, 3‐BD was produced with 7.92 g L−1 h−1 productivity by B. subtilis 168/pMA5‐bdhA‐HpaII‐gdh. To our knowledge, the volume productivity obtained here is the highest ever reported for biocatalysis.CONCLUSIONA higher productivity of 2,3‐BD from acetoin was achieved by whole cell biocatalysis with NADH regeneration systems in B. subtilis 168. This approach can be applied for NADH related bio‐based chemicals production to improve titer, yield and productivity. © 2017 Society of Chemical Industry

Solvent-free microwave-assisted synthesis of solketal from glycerol using transition metal ions promoted mordenite solid acid catalysts

The present study demonstrates a clean and green approach for the production of bio-fuel additives from renewable glycerol acetalization using microwave irradiation as heating method. Various transition metal ion (M=Fe-, Co-, Ni-, Cu- & Zn-) promoted mordenite solid acid catalysts were prepared by wet impregnation method and examined for the acetalization of glycerol with acetone. Investigation of the structural and chemical properties of the catalysts was achieved using XRD, FT-IR, TGA-TPD, SEM/EDX and XPS techniques. Comparative studies using conventional heating were performed in order to study the efficiency of microwave-assisted acetalization reactions. The effect of various operating parameters on the catalytic activity studies was examined. Amongst the metal-promoted mordenite catalysts tested, Cu-Mor had the best performance due to the presence of a large amount of acidic sites and the synergetic effects of metal particles interacting with mordenite. Microwave-assisted acetalization of glycerol into Solketal was found to be an energy efficient route for glycerol valorization achieving 98% selectivity to solketal at 95% glycerol conversion during a reaction time of 15min over Cu-Mor catalyst and acetone/glycerol at a molar ratio of 3:1. Reuse of spent catalyst showed good repeatability for up to four reaction cycles with a marginal decrease in conversion.

Porous Ti/Zr Microspheres for Efficient Transfer Hydrogenation of Biobased Ethyl Levulinate to γ-Valerolactone.

γ-Valerolactone (GVL) is one of the versatile platform molecules and biofuel additives derived from the lignocellulosic biomass. Herein, the efficient synthesis of GVL from biobased ethyl levulinate (EL) using alcohol as both H-donor and solvent without an external hydrogen source has been achieved over porous Ti/Zr microspheres. The catalysts (TixZry) with different Ti/Zr molar ratios were synthesized using hexadecylamine (HDA) as a structure-directing agent via a sol–gel process combined with solvothermal treatment and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis, NH3/CO2-TPD, N2 adsorption–desorption, and pyridine-IR. A high GVL yield of 90.1% at 100% EL conversion was obtained at 180 °C for 6 h over Ti2Zr8 in 2-propanol. The microspheric and porous structure, enhanced surface areas, and acid/base contents by the proper introduction of Ti species into Zr oxide were demonstrated to be responsible for the pronounced performance. The microspheric Ti2Zr8 porous catalyst could be reused at least six times with no decrease in catalytic activity.

Exploiting H-transfer as a tool for the catalytic reduction of bio-based building blocks: the gas-phase production of 2-methylfurfural using a FeVO4 catalyst

A new reductive process in the field of biomass valorisation for the sustainable production of bio-fuel additives and chemicals.

PROGRESS ON POTENTIAL TECHNOLOGIES FOR GLYCEROL VALORIZATION INTO OXYGENATED FUEL ADDITIVES: A REVIEW

Glycerol has tremendous potential to be transformed into highvalue derivatives /functional chemicals. Demand for renewable sources, surplus availability, low cost and lower environmental impact have led to numerous selective processes for glycerol conversion into products for sustainability of bio-diesel industry. Bio-fuel derived platform molecules are in great demand as there is shift from petro-based chemicals to green chemicals and one of the main interests in the recent years is in the production of bio-fuel additives. This paper reviews different techniques and relevant catalysts used for the production of bio-fuel additives from different pathways such as esterification, etherification, acetalization and acetylation.

Late post-injection of biofuel blends in an optical diesel engine: Experimental and theoretical discussion on the inevitable wall-wetting effects on oil dilution

In a diesel engine, diesel particulate filter is used to reduce particle matter emissions. Diesel particulate filter requires periodic regenerations under high-temperature conditions in the exhaust pipe in order to oxidize the accumulated soot. A common strategy to produce high exhaust gas temperature is to inject late post-injections after the main injection. However, this practice may dilute the engine oil, causing engine wear. Biofuel addition to petroleum diesel may increase oil dilution even more. This is related to the fuel spray characteristics, the post-injection control and the vaporization process of fuel in engine oil. In this study, spray properties of late post-injection were studied with petroleum diesel and two types of transport biofuel blends containing 30% either fatty acid methyl ester or hydro-treated vegetable oil. Three different late post-injection timings were investigated. Image sequences of the main spray flame as well as the non-combusting late post-injection spray were extracted. In order to verify oil dilution during regeneration cycle and late post-injection, oil samples from six-cylinder test engine were analyzed. According to the present experiments, differences in the spray characteristics are not significant with the tested fuels. However, higher oil dilution rates were observed with fuel blend composed of 30% fatty acid methyl ester. All the studied late post-injection timings were noted to lead to the unwanted cylinder spray/wall interaction and wall-wetting consequently diluting the engine oil. The spray/wall interaction is thoroughly explained by introducing a theoretical/computational framework which characterizes any spray/wall interaction in terms of a phase diagram for any considered operation conditions. The novelty of this study arises from (1) first comparison of fatty acid methyl ester and hydro-treated vegetable oil blends in an optical engine, (2) strong evidence on the phenomena related to post-injection phase in six-cylinder and single-cylinder optical engine configurations and (3) the development of a single-droplet model showing inevitable wall-wetting.

Design of a Highly Efficient Indium-Exchanged Heteropolytungstic Acid for Glycerol Esterification with Acetic Acid

A series of highly active, selective, and stable solid indium-exchanged tungstophosphoric acid catalysts had been prepared, characterized and evaluated for bio-derived glycerol esterification with acetic acid to produce valuable biofuel additives. It was found that the Inx/3H3−xPW with nanotube structure owns Lewis acidity and Bronsted acidity in one, which favors for the efficient esterification of glycerol into monoglycerides with higher selectivity. Among all, In0.8H0.6PW presented exceptionally high activity with 88 % conversion and 96 % selectivity to MAG within 30 min of reaction time at 120 °C using 4:1 molar ratio. The better performance came from its remarkable stability, due to the unique Keggin structure, high acidity as well as nanotube structure. In addition, this In0.8H0.6PW catalyst did not suffer from deactivation of water in the six consecutive reaction tests.

Acetylation of glycerol over bimetallic Ag–Cu doped rice husk silica based biomass catalyst for bio-fuel additives application

Acetylation of glycerol with acetic acid was carried out over bimetallic silver and copper deposited rice husk silica-alumina like ecofriendly green catalyst. Bio-additive like mono, di and tri acetyl glycerol synthesis from raw glycerol (one of the main product of biodiesel), which are gaining attention as additives for improving petroleum fuel properties towards biofuel additive development applications. Advantage of using bimetallic catalyst for glycerol acetylation due to possible synergistic effect between the metals and it enhances the catalytic conversion and selectivity compared to single metal catalyst. The prepared catalysts were characterised by XRD, FT-IR and TEM. Silver and copper incorporated RHS (rice husk silica)-alumina catalysts are shown higher activity and selectivity towards diacetin (di acetyl glycerol) and triacetins (tri acetyl glycerol) formation by catalytic acetylation of glycerol. Higher conversion (98 %) and good selectivity (51 %) is achieved.

Production of biofuel additives by esterification and acetalization of bioglycerol

The current transition from petrochemical resources to biomass-derived platform molecules is in great demand for the development of synergies, scientific innovations and breakthroughs, and steep changes in the infrastructure of chemical industries. This article is focused on new opportunities for the production of biofuel additives from bioglycerol, which is obtained as waste and/or by-product from the current biodiesel industries. Here, we summarize the recent relevant processes for the production of biofuel additives from bioglycerol over various acid catalysts in two different pathways: (i) the esterification of bioglycerol with acetic acid, levulinic acid and other acids, and (ii) the acetalization of bioglycerol with acetone, furfural, benzaldehyde and other carbonyl compounds. It is evident that the synthesis of biofuel additives through esterfication and acetalization of bioglycerol is an important research area with imperative prospects for industrial applications.

Cesium exchanged tungstophosphoric acid supported on tin oxide: An efficient solid acid catalyst for etherification of glycerol with tert-butanol to synthesize biofuel additives

Cesium exchanged tungstophosphoric acid (CsTPA) supported on tin oxide catalysts were prepared and their physio-chemical properties were derived from X-ray diffraction, FT-IR, laser Raman spectroscopy and temperature programmed desorption of NH3. The catalysts activity was evaluated for etherification of glycerol with tert-butanol. The characterization results of the catalysts revealed that the primary Keggin structure remained intact during the exchange of TPA protons with Cs+ ions. The activity results showed that etherification activity depended on the amount of the CsTPA over SnO2 and the catalyst with 20wt% CsTPA supported on SnO2 showed high catalytic activity with 90% glycerol conversion with 44% selectivity toward higher ethers. The activity of the catalyst depends on amount of surface acidic sites and dispersion amount of CsTPA over SnO2. The etherification reaction was carried at different reaction parameters and optimum reaction conditions were established. The catalysts were recyclable and showed constant activity up on reuse.

Synthesis of Bio-fuel Additives From Glycerol Over Poly(Vinyl Alcohol) With Sulfonic Acid Groups

Condensation of glycerol with acetone was carried out over poly(vinyl alcohol) with sulfonic acid groups at 70°C. The main product of glycerol acetalization is solketal. Catalysts with different amounts of sulfonic acid groups were prepared. It was observed that the catalytic activity increases with the crosslinking degree, due to the increases of the amount of sulfonic acid groups on poly(vinyl alcohol). Further, the influence of various reaction parameters, such as catalyst loading, molar ratio glycerol to acetone, and temperature, on the acetalization of glycerol over PVA40 was studied. It was found that at 70°C, with 0.2 g of catalyst loading and with a molar ratio of glycerol to acetone 1:6, a glycerol conversion of about 94% after 3 h can be obtained. The PVA40 catalyst was recycled and reused with negligible loss in the activity, after the fifth use.

Glycerol Valorization as Biofuel Additives by Employing a Carbon-Based Solid Acid Catalyst Derived from Glycerol

A two-step process was developed for the preparation of triacetylglycerol (TAG), a biofuel additive employing a solid acid catalyst derived from glycerol. The first step involves esterification of glycerol with acetic acid (1:4 mol) at 115 °C for 1 h in the presence of catalyst (5 wt %) to obtain 100% conversion of glycerol with 22, 67, and 11% MAG, DAG, and TAG, respectively. In the second step, the esterified product mixture after removal of excess acetic acid and moisture was acetylated with acetic anhydride (1 mol with respect to glycerol) at 115 °C for 30 min to obtain 100% TAG. The recovered catalyst was reused for five cycles without any significant loss of its initial activity. The protocol is cost-effective due to the use of highly stable and recyclable SO3H-carbon catalyst for the production of TAG with minimum moles of acetic acid and acetic anhydride in shorter reaction time.

Characterization-Based Molecular Design of Bio-Fuel Additives Using Chemometric and Property Clustering Techniques

In this work, multivariate characterization data such as infrared (IR) spectroscopy was used as a source of descriptor data involving information on molecular architecture for designing structured molecules with tailored properties. Application of multivariate statistical techniques such as principal component analysis (PCA) allowed capturing important features of the molecular architecture from complex data to build appropriate latent variable models. Combining the property clustering techniques and group contribution methods (GCM) based on characterization data in a reverse problem formulation enabled identifying candidate components by combining or mixing molecular fragments until the resulting properties match the targets. The developed methodology is demonstrated using molecular design of biodiesel additive which when mixed with off-spec biodiesel produces biodiesel that meets the desired fuel specifications. The contribution of this work is that the complex structures and orientations of the molecule can be included in the design, thereby allowing enumeration of all feasible candidate molecules that matched the identified target but were not part of original training set of molecules.