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From a technical and economic point of view, our aim is to provide viable solutions for the replacement of fossil fuels which are currently used in internal combustion diesel engines. In this research, two new biofuels composed of second-generation vegetable oils (SVO),used oil sunflower (SO) or castor oil (CO), and the ABE blend (acetone/butanol/ethanol) were evaluated. ABE is an intermediate product from the fermentation of carbohydrates to obtain bio-butanol. Besides, the ABE blend exhibits suitable properties as biofuel, such asvery low kinematic viscosity, reasonable energy density, low autoignition temperature, and broad flammability limits. Diesel/ABE/SVO triple blends were prepared, characterized and then, tested on a diesel engine, evaluating power output, consumption, and exhaust emissions. The power output was slightly reduced due to the low heating values of ABE blend. Also, engine consumed more fuel with the triple blends than with diesel under low engine loads whereas, at medium and high loads, the fuel consumption was very similar to that of diesel. Regarding exhaust gas emissions, soot wasnotably reduced, and nitrogen oxides (NOx) and carbon monoxide (CO2) emissions were lower or comparable to that of diesel, while the CO emissions increased. The use of these biofuels allows the replacement of high percentagesof diesel without compromising engine power and achievinga significant reduction in pollution emissions. Furthermore, a notable improvement in cold flow properties of the fuel blends is obtained, in comparison with diesel.

Embargado hasta 01/12/2024 Sulfonic and propylsulfonic silica-based catalysts were synthesized, characterized and tested in the acetalization of glycerol (G) by a sustainable, solvent-free and fast procedure, under microwave irradiation, to produce solketal (S). The catalysts were prepared by different grafting procedures and their surface and structural properties were investigated by means of N2 adsorption isotherms, Thermogravimetric Analysis (TGA), X-ray Photoelectron Spectroscopy (XPS) and X-Ray Fluorescence Spectroscopy (XRF). Under the optimized reaction conditions (Temperature 40 °C, microwave power ˂100 W, time 2 min and 1:12 glycerol/acetone molar ratio) the sulfonic materials, produced by the hydrothermal grafting, showed excellent performance in terms of activity, selectivity and stability, with no leaching of sulfonic groups after several cycles. By the correlation of the structure properties of the materials and their activity, the performance of the catalysts was shown strictly correlated both to the acidity and the surface density of the active sites.

The catalytic hydrogenation of captured CO2 by different industrial processes allows obtaining liquid biofuels and some chemical products that not only present the interest of being obtained from a very low-cost raw material (CO2) that indeed constitutes an environmental pollution problem but also constitute an energy vector, which can facilitate the storage and transport of very diverse renewable energies. Thus, the combined use of green H2 and captured CO2 to obtain chemical products and biofuels has become attractive for different processes such as power-to-liquids (P2L) and power-to-gas (P2G), which use any renewable power to convert carbon dioxide and water into value-added, synthetic renewable E-fuels and renewable platform molecules, also contributing in an important way to CO2 mitigation. In this regard, there has been an extraordinary increase in the study of supported metal catalysts capable of converting CO2 into synthetic natural gas, according to the Sabatier reaction, or in dimethyl ether, as in power-to-gas processes, as well as in liquid hydrocarbons by the Fischer-Tropsch process, and especially in producing methanol by P2L processes. As a result, the current review aims to provide an overall picture of the most recent research, focusing on the last five years, when research in this field has increased dramatically.

Resumen de la publicación de una participación en formato µVídeo en en el congreso Divulga NextGen (1ª edición) que se celebrará online, de manera gratuita y en las redes sociales los días 26, 27 y 28 de mayo de 2021., {"references":["[1] F. Creutzig, P. Jochem, O.Y. Edelenbosch, L. Mattauch, D.P. van Vuuren, D. McCollum, Minx, J. Transport: A roadblock to climate change mitigation? Urban mobility solutions foster climate mitigation. sciencemag.org Science, Energy and Environment, 2015, 350 issue 6263, 911-912","[2] M. Lopes, L. Serrano, I. Ribeiro, P. Cascão, N. Pires, S. Rafael, L.Tarelho, A. Monteiro, T. Nunes, M. Evtyugina, Emissions characterization from EURO 5 diesel/biodiesel passenger car operating under the new European driving cycle. Atmospheric environment 2014, 84, 339-348","[3] J. Calero, D. Luna, E.D. Sancho, C. Luna, F.M. Bautista, A.A. Romero, A. Posadillo, J. Berbel, C. Verdugo-Escamilla. An overview on glycerol-free processes for the production of renewable liquid biofuels, applicable in diesel engines. Renewable and Sustainable Energy Reviews 2015, 42, 1437-1452."]}

Embargado hasta 31/08/2023 Background: Biomass is the only renewable alternative to fossil fuels to produce chemicals. In this sense, glycerol is an important biomass-derived platform chemical obtained as a by-product during biodiesel generation. This paper reports for the first time the photocatalytic acetalization of glycerol with acetone to produce cyclic ketals, interesting chemicals with several applications such as solvents or (bio)fuel additives. Methods: Commercial TiO2 (Aeroxide® Evonik P25) was used as the photocatalyst and very mild reaction conditions (30 °C, solar-simulated light) were utilized. The effect of glycerol/acetone ratio and catalyst concentration on both glycerol conversion and five-membered/six-membered ring acetal ratio was studied through factorial design of experiments. P25 concentration was in the 1–3 g/L range whereas acetone/glycerol molar ratio varied between 6 and 20.Findings: All in all, the maximum conversion (89.6%) corresponded to 1.86 g/L and acetone/glycerol ratio of 10.96. Selectivity to the 5-membered ring ketal (solketal) was over 92% in all cases. This procedure would constitute the fourth-generation synthesis of solketal by glycerol acetalization with acetone.

Dimethyl carbonate (DMC) is an interesting blending component for diesel fuel (D) owing to the high oxygen content (53 wt.%) and the absence of C–C bonds in its structure. Moreover, DMC can be produced from CO2 and methanol, which provides a renewable way to reduce anthropogenic CO2. This research has been addressed to assess the use of DMC as a solvent of sunflower oil (SO) and castor oil (CO), with the purpose of obtaining biofuels that can replace fossil diesel as much as possible. The blending of DMC with straight vegetable oils (SVOs) reduces their high viscosity, allowing their usage as drop-in biofuels without chemical treatments. Based on viscosity requirements of European Standard EN 590, the optimal DMC/SVO double blends have been tested as direct biofuels by themselves or mixed with fossil diesel in D/DMC/SVO triple blends. Relevant physico-chemical properties of fuels have been analyzed. Engine parameters such as power output, brake-specific fuel consumption (BSFC) and soot emissions have been studied to determine the effect of new biofuels on efficiency of a diesel engine. An outstanding engine efficiency is shown by the studied D/DMC/SVO triple blends, either with SO or CO as an SVO. The low calorific value of DMC is the main reason for reduction in power and BSFC, as the amount of diesel in the triple blends is reduced. Experimental results demonstrate that the use of these biofuels allows the replacement of up to 40% of fossil diesel, without compromising the power and BSFC of the engine, and accomplishing optimal cold flow properties and a marked drop in exhaust emissions.

Glycerol is the main by-product of biodiesel production. For this reason, its valorization into value-added products, by using green procedures, represents an important goal. Different sulfonic acid silica- or titania-based catalysts were prepared, characterized and tested in the glycerol etherification process, assisted by microwaves, in order to obtain biodiesel additives. The surface and structural properties of the catalysts were investigated by means of N2 adsorption isotherms, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and acid capacity measurements by X-Ray Fluorescence Spectroscopy (XRF). The best performance in terms of activity was achieved in the presence of the sulfonic function directly linked to the amorphous silica. By the correlation of the structure properties of the materials and their activity, the performance of the catalysts was shown to be influenced mainly by the surface area, pore volume and acidity. Recycling experiments performed over the most active systems showed that the sulfonic silica-based materials maintained their performance during several cycles.

The gas-phase glycerol (Gly) transformation in the presence of oxygen has been studied on cobalt oxide systems (10 and 20 wt% Co) supported on a synthetic mesoporous aluminium phosphate (AlPO4) calcined at 350 °C, as well as on a binary Co-Al phosphate with a Co content of 10 wt%. Synthetic binary phosphate of Al-M (M = Fe, V) have also been tested. The acidity (number and nature of acid sites) of the solids was determined by pyridine adsorption, whereas the reducibility was determined by H2 TPR. The propene oxidation was employed as a test reaction. The influence of the amount of oxidant agent and the reaction temperature on both the glycerol conversion and the yield to reaction products was studied. The formation of acrylic acid; acetic acid and carbon dioxide was favoured for values of O2/Gly ≥ 2 molar ratio and of temperatures beyond 250 °C. The Co oxide species in the supported systems that were the easiest to reduce (lower H2 desorption temperature) exhibited the highest activity to produce acrylic acid. The formation of acetic acid and carbon dioxide was also promoted, suggesting the participation of the acid sites in addition to redox sites. Among the metals investigated here, Co would form part of the required catalyst for the formation of acrylic acid from glycerol. Based on the identified products in this study, some possible reactions involved in the glycerol transformation into oxidized compounds, have been suggested.

This research is supported by MINECO-ENE2016-81013-R (AEI/FEDER, EU), MICIIN (Project ref. PID2019-104953RB-100), Consejería de Transformación Económica, Industria, Conocimiento y Universidades de la Junta de Andalucía (UCO-FEDER Project CATOLIVAL, ref. 1264113-R, 2018, and Project ref. P18-RT-4822) and FEDER Funds for financial support. The Government of Ireland Postdoctoral Fellowship Programme-2015 (GOIPD/2015/287) is thankfully acknowledge by V.G.-P., This research article is part of the doctoral thesis of C.L., directed by professors D.L., F.M.B. and C.V.-E., who in a general way conceived and designed the experiments and wrote the paper. V.G.-P. collaborated in a decisive way contributing everything concerning the investigated inorganic supports. R.E., F.J.L.-T., J.C. and L.A.-D. have made also substantive intellectual contributions to this study, substantial input to conception and design, as well as to the acquisition, analysis and interpretation of data. A.A.R. and R.E. were also involved in drafting and revising the manuscript, so that everyone gave final approval to the current version to be published in Catalysts journal. All authors have read and agreed to the published version of the manuscript., The synthesis of two biocatalysts based on a commercial Candida antarctica lipase B, CALB enzyme (E), physically immobilized on two silica supports, was carried out. The first support was a periodic mesoporous organosilica (PMO) and the second one was a commercial silica modified with octyl groups (octyl-MS3030). The maximum enzyme load was 122 mg enzyme/g support on PMO and 288 mg enzyme/g support on octyl-MS3030. In addition, the biocatalytic efficiency was corroborated by two reaction tests based on the hydrolysis of p-nitrophenylacetate (p-NPA) and tributyrin (TB). The transesterification of sunflower oil with ethanol was carried out over the bio-catalysts synthesized at the following reaction conditions: 6 mL sunflower oil, 1.75 mL EtOH, 30 °C, 25 μL NaOH 10 N and 300 rpm, attaining conversion values over 80% after 3 h of reaction time. According to the results obtained, we can confirm that these biocatalytic systems are viable candi-dates to develop, optimize and improve a new methodology to achieve the integration of glycerol in different monoacylglycerol molecules together with fatty acid ethyl esters (FAEE) molecules to obtain Ecodiesel., Consejería de Transformación Económica, Industria, Conocimiento y Universidades de la Junta de Andalucía, MICIIN PID2019-104953RB-100, MINECO-ENE2016-81013-R, UCO-FEDER 1264113-R, GOIPD/2015/287, P18-RT-4822, European Commission, European Regional Development Fund, Agencia Estatal de Investigación

The synthesis of organosilica-aluminum phosphates by a simple and cheap sol-gel method was carried out with varying amounts of two different silica precursors, 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (C) and (3-mercaptopropyl)trimethoxysilane (MPTMS); and several Al/P molar ratios. The solids were calcined in air, at different temperatures. The etherification of glycerol with tert-butyl alcohol was carried out in the liquid-phase under microwave irradiation and also by conventional heating. The incorporation of organosilica in the final solids took place in a 50–60%, as verified by TGA, ICP-MS, XPS and 1H–29Si CP MAS NMR. The highest yield to h-GTBE (21%) was obtained at autogenous pressure, 85 °C and 15 min of reaction time under microwave, on the solid prepared with 10 mmol of C; Al/P = 1.5 and calcined at 250 °C. This material, with a balanced percentage of mesopores and macropores, also exhibited the highest number of acid sites determined by acid-base titration, as well as by results from TGA and by elemental analysis. The acidity and the hydrophilic character of the solids have been found to be key parameters for the catalytic activity, whereas porosity seems to be advantageous for the reusability of the solids, avoiding deactivation.

Today, biofuels are indispensable in the implementation of fossil fuels replacement processes. This study evaluates ethyl acetate (EA) as a solvent of two straight vegetable oils (SVOs), castor oil (CO), and sunflower oil (SO), in order to obtain EA/SVO double blends that can be used directly as biofuels, or along with fossil diesel (D), in the current compression-ignition (C.I.) engines. The interest of EA as oxygenated additive lies not only in its low price and renewable character, but also in its very attractive properties such as low kinematic viscosity, reasonable energy density, high oxygen content, and rich cold flow properties. Revelant fuel properties of EA/SVO double and D/EA/SVO triple blends have been object of study including kinematic viscosity, pour point (PP), cloud point (CP), calorific value (CV), and cetane number (CN). The suitability of using these blends as fuels has been tested by running them on a diesel engine electric generator, analyzing their effect on engine power output, fuel consumption, and smoke emissions. Results obtained indicate that the D/EA/SO and D/EA/CO triple blends, composed by up to 24% and 36% EA, respectively, allow a fossil diesel substitution up to 60–80% providing power values very similar to conventional diesel.In addition, in exchange of a slight fuel consumption, a very notable lessening in the emission of pollutants as well as a better behavior at low temperatures, as compared to diesel, are achieved.

The present paper investigates the feasibility of using acetone (ACE) in triple blends with fossil diesel (D) and straight vegetable oils (SVOs) as alternative fuel for diesel engines. In this respect, ACE is selected as an oxygenated additivedue to its favorable propertiesto be mixed with vegetable oils and fossil diesel. In fact, the very low kinematic viscosity allows reduces the high viscosity of SVOs. ACE&rsquo, s oxygen content, low autoignition temperature, and very low cloud point and pour point values highlight its possibilities as an additive in D/ACE/SVO triple blends. Moreover, ACE can be produced through a renewable biotechnological process, an acetone&ndash, butanol&ndash, ethanol (ABE) fermentation from cellulosic biomass. The SVOs tested were castor oil (CO), which is not suitable for human consumption, and sunflower oil (SO), used as a standard reference for waste cooking oil. The viscosity measurement of the ACE/SVO double blend was considered crucial to choose the optimum proportion, which better fulfilled the specifications established by European standard EN 590. Moreover, some of the most significant physicochemical properties of D/ACE/SVO triple blends, such as kinematic viscosity, cloud point, pour point, and calorific value, were determined to assess their suitability as fuels. The blends were evaluated in a conventional diesel generator through the study of the following parameters: engine power, smoke emissions, and fuel consumption. Despite the low calorific value of ACE limits its ratio in the mixtures due to engine knocking problems, the experimental results reveal an excellent performance for the blends containing up to 16-18% of ACE and 22-24% of SVO. These blends produce similar engine power as to fossil diesel, but with slightly higher fuel consumption. Considerable reductions in emissions of air pollutants, as well as excellent cold flow properties are also obtained with these triple blends. In summary, the use of these biofuels could achieve a substitution of fossil diesel up to 40%, independently on the SVO employed.

In this work, the experimental conditions for the transesterification reaction of sunflower oil, over commercial calcium oxide (CaO) as heterogeneous catalysts, have been optimized employing a multi-factorial design based on the response surface methodology (RSM). Hence, the effects of temperature, methanol/oil molar ratio and have been considered. The partial transesterification of sunflower oil produces one mol of monoglyceride (MG) and two moles of fatty acids methyl esters (FAME). This blend constitutes a new type of biofuel called Ecodiesel which can be applicable to diesel engines. This Ecodiesel integrates the glycerol as MG removing by-products and increasing the lubricity of the biofuel. Thus, the reaction conditions, obtained by Response surface methodology (RSM), that promote the highest values of selectivity to Ecodiesel are 65 °C of reaction temperature, 0.7 g of CaO and methanol/oil molar ratio of 5.3. On the other hand, in order to get a biofuel with lower viscosity, 65 °C and 0.7 g of CaO were also employed, although a lower methanol/oil molar ratio of 2 was employed. Operating under these selected experimental conditions, a high conversion value (70 %), a selectivity value to Ecodiesel of 35 % and a viscosity value around 15 cSt can be achieved. The biofuel thus obtained can be used in blends with diesel because in order to accomplish the viscosity limits stablished in the EN 14214. Consequently, this methodology could represent an advance in the technical and economic feasibility in the process of replacing fossil fuels by renewable fuels.

The main objective of this work is to contribute to a gradual replacement process of fossil diesel (D) with biofuels composed by diethyl carbonate (DEC) and either sunflower or castor oil, as straight vegetable oils (SVOs). DEC is a very interesting candidate as an oxygenated additive not only because of its low price and renewable nature, but also its favorable fuel properties, such as very low kinematic viscosity, high cetane number, high oxygen content, rich cold flow properties and good miscibility with fossil diesel and vegetable oils. In this work, the more suitable DEC/SVO biofuels are chosen based on kinematic viscosity, according to the European normative. Additionally, the most relevant physical–chemical properties of (bio)fuels such as density, calorific value, cloud point, pour point and cetane number are determined. The influence of DEC on engine performance and exhaust emissions is analyzed by fueling a conventional Diesel engine with the different D/DEC/SVO triple and DEC/SVO double mixtures. The tests results are also compared with commercial diesel. From the results, it is concluded that Diesel engine fueled with the blends studied exhibits an excellent performance in terms of power output, very similar to diesel. Additionally, the use of these blends can remarkably decrease smoke emissions down to 98%, with respect to fossil diesel. The addition of DEC shows a significant improvement in cold flow properties of fuel mixtures in the exchange of a slightly higher brake specific fuel consumption (BSFC) than diesel. Interestingly, the pure biofuels composed by DEC and SVO allow for a suitable engine operation and achieve the lowest emissions, which means these blends can be successfully employed in current engines without adding fossil diesel, i.e., their use entail a 100% renewability.

The etherification of glycerol with tert -butyl alcohol has been carried out in the liquid-phase on different sulfonic acid functionalized hybrid silicas obtained by oxidative cleavage of tetrasulfide bridges. These materials exhibited different textural properties and acidities ranging from 0.5 to 2.3 mmol g −1 . First of all, different experimental variables, including the reactant ratio and temperature have been tested and all catalysts were essayed under optimal conditions. The best catalytic behavior of the hybrid silicas was obtained on S 50 TS 50 O (Y h-GTBE = 28%) at 75 °C and autogenous pressure. In fact, the glycerol conversion obtained on S 50 TS 50 O, clearly surpassed that obtained on A-15 (74 and 51%, respectively). The acidity and the hydrophilic character of the sulfonated hybrid silicas solids have been found to be key parameters for their catalytic activity whereas the surface area and porosity do not seem to be advantageous for this reaction. All catalysts were reused and subjected to an extensive characterization.

The catalytic behaviour of mesoporous simple (M = Al, Fe, Co, Mn) and binary (Al/M; M = Fe,V,Ca; molar ratio Al/Fe = 50; Al/V = 2; Al/Ca = 1) metal phosphates, synthesized by an economical gelation method, in the gas-phase glycerol reaction at temperatures between 220 °C and 280 °C, has been investigated. The morphology, textural properties and the acidity by pyridine TPD, of the phosphates were also determined. The activity of the phosphates in the formation of the main reaction product (acrolein) depended not only on their acidity (mainly acid sites of weak-medium strength) but also on the redox sites and morphology exhibited. Thus, the aluminium-vanadium phosphate showed the highest value of yield to acrolein, 62% (equivalent to a productivity of 0.88 g A C R g c a t ⋅ h ) at 280 °C, whereas the amorphous FePO4 and AlPO4 were appreciably more active than the rest of the simple phosphates, exhibiting a high crystalline character. The apparent activation energy values obtained for the acrolein formation ranged between 18 and 91 kJ/mol. Based on the identified products in this study, some possible reactions involved in the glycerol transformation have been suggested.

The synthesis of vanadium oxide systems with V 2 O 5 loadings below, above or corresponding to the theoretical monolayer (1–34 wt.% of V 2 O 5 ) obtained by impregnation with vanadyl oxalate or vanadyl acetylacetonate of a mesoporous amorphous aluminum phosphate, AlPO 4 , calcined at different temperatures (from 350 °C to 650 °C), has been carried out. Materials were characterized by XRD, Raman, DR UV–vis, 51 V, 27 Al and 31 P MAS NMR and nitrogen adsorption. Their acidity and reducibility were evaluated through pyridine TPD and hydrogen TPR, respectively, and their catalytic behavior in the 2-propanol reaction. The vanadium salt promoted the crystallization and loss of porosity of AlPO 4 , to a greater degree when acetylacetonate of vanadyl was the vanadium source and the vanadium loading increased. Similarly, the highest vanadia dispersion was obtained on AlPO 4 calcined at 350 °C and impregnated with vanadyl oxalate. The vanadium systems were more active than their respective supports in the 2-propanol reaction. Furthermore, the weak-medium acid sites that predominate in AlPO 4 and vanadia species are the active sites for the propene formation. The formation of propanone required redox sites, the most active being those of the vanadia species in close contact with AlPO 4 , which were also more easily reducible. Both parallel reactions would proceed though concerted mechanisms.

Sulfonated carbons have been prepared from an important waste in Andalusia, the olive stones. The sulfonic acid groups incorporation has been made by sulfuric acid treatment and different conditions have been tested, i.e., temperature, carbon/sulfuric acid weight ratio, sulfonation time, as well as two ways of heating, either conventional heating or microwave irradiation. The morphology of the solids has been characterized by XRD and Raman Spectroscopy and their textural properties evaluated by N2 adsorption- desorption of nitrogen at 77 K. The incorporation of sulfur in the carbons has been verified by elemental analysis, TGA, XPS and ATR-IR. The acidity of the solids was evaluated by elemental analysis (sulfur content) and compared with the results obtained from acid-base titration. The sulfonation time needed to attain an identical sulfur incorporation percentage was considerably reduced under microwave irradiation in comparison to conventional heating (30 min vs. 2 h). The highest yield obtained in the microwave-assisted etherification of glycerol with tert-butyl alcohol at autogenous pressure, 75 °C and 15 min of reaction (∼21 %) is comparable to those reported on other sulfonated carbons but using higher temperatures (100−120 °C) and reaction times (6 h). Furthermore, the sulfonated carbons exhibited high stability, maintaining their activity after being used in several consecutive reactions.

This research evaluates the possibility of using straight oils such as castor oil, which is not suitable for food use, and sunflower oil, used as a standard reference for waste cooking oils, in blends with gasoline as second-generation biofuels. To this end, a study of the rheological properties of biofuels obtained from these double blends has been carried out. The aim is to take advantage of the different properties of gasoline, i.e., its low viscosity and its high energy density to obtain blends whose rheological properties allow the substitution of fossil diesel in high extent. The incorporation of fossil diesel to these gasoline/oil mixtures produces diesel/gasoline/oil triple blends, which exhibited the suitable rheological properties to be able to operate in conventional diesel engines. Therefore, the behavior of these blends has been evaluated in a conventional diesel engine, operating as an electricity generator. The triple blends allow the substitution of fossil diesel up to 40% with sunflower oil, and up to 25% with castor oil, with excellent power results achieved for blends in which diesel is substituted up to 40%, and also in fuel consumption at high demand in comparison to conventional fossil diesel. Besides, a significant reduction in the emission of pollutants has also been obtained with these triple blends.

Two inorganic solids have been evaluated as supports of Lipozyme RM IM, a Rhizomucor miehei lipase immobilized on a macroporous anion exchange resin, in order to improve its application as a biocatalyst in the synthesis of biofuels. The experimental conditions have been optimized to get the selective transesterification of sunflower oil, by using a multi-factorial design based on the response surface methodology (RSM). In this way, the effects of several reaction parameters on the selective ethanolysis of triglycerides to produce Ecodiesel, a biodiesel-like biofuel constitute by one mole of monoglyceride (MG) and two moles of fatty acid ethyl ester (FAEE), have been evaluated. Thus, it was obtained that a 6:1 oil/ethanol molar ratio, 0.215 g of biocatalyst supported in silica-gel (0.015 g Lipase/0.2 g silica-gel), 50 µL of 10 N NaOH, together with previous optimized reaction parameters, 35 °C reaction temperature and 120 min of reaction time, gave the best results (conversions around 70%; selectivity around 65%; kinematic viscosities about 9.3 mm2/s) in the reaction studied. Besides, Lipozyme RM IM, supported on silica-gel, biocatalyst exhibited a very good stability, remaining its activity even after 15 cycles.

This research aims to promote the use of second-generation biofuels based mainly on Castor oil, which is not adequate for food use, and Sunflower oil as a standard reference for recycled oils. They have been applied in the production of Ecodiesel, a biofuel that integrates glycerol as monoglyceride, employing sodium methoxide as homogeneous catalyst and ethanol as solvent, but operating in milder conditions than in the synthesis of conventional biodiesel in order to obtain a kinetic control of the selective transesterification. The behavior of biofuels has been evaluated in a conventional diesel engine, operating as an electricity generator. The contamination degree was also evaluated from the opacity values of the generated smokes. The different biofuels here studied have practically no differences in the behavior with respect to the power generated, although a small increase in the fuel consumption was obtained in some cases. However, with the biofuels employed, a significant reduction, up to 40%, in the emission of pollutants is obtained, mainly with the blend diesel/castor oil/alcohol. Besides, it is found that pure Castor oil can be employed directly as biofuel in triple blends diesel/biofuel/alcohol, exhibiting results that are very close to those obtained using biodiesel or Ecodiesel.

In this study, the evaluation of the catalytic behavior of several wild bacterial strains in the 1,3-selective ethanolysis of triglycerides with ethanol to produce a new type of biodiesel (Ecodiesel) that integrates glycerol as monoacylglycerols was carried out. The Ecodiesel production not only avoids the elimination of glycerol, which is largely generated as a by-product in the biodiesel industry, but also results in an increase in the biofuel yield. The wild microbial strain samples were obtained from several lipophilic organisms. In addition to evaluate the enzymatic extracts, the minimum grade of purification of the strains, necessary to obtain similar results to those attained with commercial lipases was studied. This purification treatment included a dialysis followed by a lyophilization process. Such extracts were directly used as biocatalysts in the transesterification reaction of sunflower oil with ethanol, attaining much better results (yield close to 100%) than those obtained with strains which were not submitted to the purification process (yields lower than 10%). Furthermore, the results here obtained are similar to those obtained with commercial lipases but were achieved under mild conditions and lower reaction time (2 h). In addition, the stability of the enzymatic extracts was corroborated by subsequent reactions, showing no loss of activity. Thus, this study brings to light that enzymatic extracts obtained by a very simple purification process can be economically competitive with the conventional biodiesel production methods.

Research has been carried out on the liquid phase dehydration of glycerol to acrolein on mesoporous amorphous aluminum phosphates obtained by a simple ammonia sol–gel method and calcined at 450 °C and 650 °C as well as on commercial zeolites with different SiO2/Al2O3 ratio and structures (H-ZSM-5 and HY). The acidity of the solids was evaluated by pyridine adsorption (TPD and DRIFT) and also by the 2-propanol reaction test. The AlPO4-650 exhibited the highest yield to acrolein 23% (3.1 mmolACR/gcat h) at 270 °C and 1 bar pressure. The activity of the solids in the dehydration of glycerol to acrolein was not only affected by their acidity (nature and strength of the acid sites) but also by the volume and diameter of pore.

Biodiesel is a biofuel obtained from vegetable oils or animal fats by transesterification with methanol, so that it offers a very promising alternative respect to diesel fuel, since it is able to provide a suitable substitute for the fossil diesel in unmodified internal combustion engines, pure or in blends. However, a major barrier exists to consolidate this conventional biodiesel, as the more suitable biofuel for the replacement of fossil fuel. This drawback is related to the significant amount of glycerol obtained as a byproduct in the transesterification process, which exceeds at least 10% by weight of oil used as raw material. Thus, future widespread use of biofuels depends on developing new process technologies to produce high quality transportation fuels from biologically derived feedstocks, which avoid this key handicap. These new biofuels, like the biodiesel, need to be also compatible with the fossil fuel as well as with existing transportation infrastructures to be economically feasible. In this respect, various alternative methods are currently under development to convert vegetable oils into a high quality diesel fuel, fully compatible with petroleum derived diesel fuel but avoiding the existing glycerol glut. The present review aims to explore the current state of available technologies and recent information in research, production practices and engineering developed to produce alternative high-quality diesel fuel from vegetable oils, by hydrotreating of triglycerides in conventional oil refineries (green diesel) as well as those novel biofuels that integrate glycerol into their composition ( Gliperol®, DMC-Biod® and Ecodiesel®) and the respective technologies for their productions. These very recent biofuels obtained from oils and fats, seek to achieve greater atom efficiency (ideally 100%) because nor glycerol neither other byproduct is generated, avoiding any purification treatment, so that the overall production process of the biofuel is in large extension simplified.

The obtaining of Ecodiesel, a biofuel applicable to diesel engines which keeps the glycerin as monoglyceride (MG), was achieved through a selective ethanolysis process of sunflower oil, by application of Lipozyme RM IM, a Rhizomucor miehei lipase immobilized on macroporous anion exchange resins. This biocatalyst that was already described in the synthesis of conventional biodiesel has also shown its efficiency in the present selective enzymatic process, after optimization of the influence of various reaction parameters. Thus, an adequate activity is obtained that is maintained throughout five successive reuses. Quantitative conversions of triglycerides (TG) with high yields to fatty acid ethyl esters (FAEE) were obtained under mild reaction conditions that correspond to the transformation of TG in a mixture of two moles of FAEE and a mole of MG, thus avoiding the glycerol production. Thus, the selective transesterification reaction of sunflower oil with absolute ethanol can be carried out under standard conditions with oil/ethanol volume ratio 12/3.5 (mL), at constant pH obtained by the addition of 50 μl of aqueous solution of 10 N NaOH, reaction temperature of 40 °C and 40 mg of Lipozyme RM IM. Under these experimental conditions six successive reactions can be efficiently carried out.

In this research have been achieved the optimized experimental conditions to obtain the partial transesterification of sunflower oil with methanol, using CaO as an alkaline heterogeneous catalyst, to produce one mole of monoglicride (MG) and two moles of fatty acids methyl esters (FAME). This blend constitutes a new type of biofuel (Ecodiesel), applicable to diesel engines, which integrates the glycerine as monoglyceride (MG). Thus, similar results to those previously described by enzymatic partial alcoholysis of triglycerides are obtained through the kinetic control of the chemical reaction, so that the same type of biodiesel is obtained by using CaO, instead of the more expensive lipases. In order to obtain an improvement in conversion and kinematic viscosity, the influence on catalytic performance of several kinetic parameters was separately evaluated. It was obtained that a 6:1 molar ratio of methanol to oil, 7 wt% CaO catalyst, 65 °C reaction temperature, 60 min time reaction and 0.3% water content respect to oil, gave the best results. Besides, CaO catalyst maintained sustained activity after being repeatedly used for 20 cycles.

It is currently a much debated topic the potential economic benefits of biomass use for biodiesel production in arid lands. In this respect, the main focus has been directed to determine which different plant species are highly adapted and capable to produce significant amounts of triglycerides to be used in the biodiesel industry under arid conditions. However, very few studies have addressed the technological changes that will be needed to convert triglycerides into biofuels without making a large consumption of scarce water, as it is demanded by current technology. Beside, with current conventional transesterification technology, the production of glycerine as a byproduct is also a serious problem because of the large water requirements needed for its removal from biodiesel, before it can be used in motor engines. The main methods commonly employed to reduce the viscosity of vegetable oil in order to be used in diesel engines are its high dilution with petrodiesel (