Study of the heterogeneous acid catalysts for obtaining oxygenated additives from biomass and their application in combustion engines

La presente Tesis Doctoral abarca la síntesis y caracterización de catalizadores de naturaleza ácida con diferentes propiedades estructurales y texturales, y su aplicación en la reacción de eterificación de glicerol con tert-butanol, para obtener los di- y tri-éteres (high ethers) que son empleados como aditivos oxigenados para combustibles. Además, se ha evaluado el carbonato de dimetilo como un disolvente renovable para reducir la alta viscosidad del aceite de ricino y del aceite de girasol (representando al aceite usado) y obtener, así, biocombustibles de segunda generación aptos para los motores diésel actuales. En el artículo “Sulfonated carbons from olive stones as catalysts in the microwave-assisted etherification of glycerol with tert-butyl alcohol” se han sintetizado materiales basados en carbón, utilizando como materia prima el hueso de aceituna, que es un importante residuo en Andalucía, región productora por excelencia de aceite de oliva del mundo. El carbón ha sido tratado con H2SO4 con el fin de incorporar grupos sulfónico en su estructura, empleando calefacción convencional y microondas, a diferentes temperaturas (100 y 150 ᵒC) y tiempos de reacción (0.5, 2 y 5 h). Los sólidos han sido exhaustivamente caracterizados y testados en la reacción de eterificación de glicerol con tert-butanol bajo irradiación microondas. A modo comparativo, se ha empleado también calefacción convencional. En el artículo “Sulfonated organosilica-aluminum phosphates as useful catalysts for acid-catalyzed reactions: Insights into the effect of synthesis parameters on the final catalyst” se ha llevado a cabo la optimización de la síntesis, mediante un método sol-gel, de silicoaluminofosfatos con grupos sulfónico en su estructura, variando la relación Al/P (3-10), el pH final de síntesis (3-9) y el tipo de compuesto organosilano. Se han empleado tres organosilanos diferentes, uno de ellos contiene el grupo sulfónico en su estructura y los otros dos grupos tiol y tetrasulfuro, respectivamente, que deben ser oxidados posteriormente a grupos sulfónico. El objetivo es mejorar la incorporación de grupos sulfónico, a través de la interacción de las especies de Si y Al, y preparar materiales con diferente porosidad, a fin de lograr mejores resultados que los obtenidos previamente por nuestro Grupo de Investigación. Los sólidos sintetizados han sido empleados en la reacción de eterificación de glicerol con tert-butanol bajo irradiación microondas. En el artículo “Evaluation of dimethyl carbonate as alternative biofuel. Performance and smoke emissions of a diesel engine fueled with diesel/dimethyl carbonate/straight vegetable oil triple blends” se ha evaluado el carbonato de dimetilo (DMC) como biodisolvente de dos aceites vegetales, aceite de ricino y aceite de girasol (representando al aceite usado), en la obtención de nuevos biocombustibles de segunda generación, que puedan ser empleados en los vehículos actuales sin necesidad de modificaciones de los motores. Para ello, los diferentes biocombustibles (mezcla DMC/aceite vegetal) han sido añadidos al diésel en diferentes proporciones del 20% al 80% en volumen. Se han determinado propiedades físico-químicas de los combustibles que influyen directamente en el rendimiento de un motor de combustión interna, como la viscosidad, la densidad, las propiedades de flujo en frío, el número de cetano y el valor calorífico. La eficacia de los diferentes biocombustibles se ha evaluado en base a la potencia generada por un motor diésel, las emisiones de hollín generadas y el consumo de combustible. Además de lo indicado anteriormente, durante una estancia de 3 meses realizada en el “Istituto per lo studio dei Materiali Nanostrutturati (ISMN) del Dipartimento di scienze chimiche e tecnologie dei materiali (DSCTM) del Consiglio Nazionale delle Ricerche (CNR)” situado en Palermo (Italia), se sintetizaron materiales basados en sílice funcionalizados con grupos ácidos y/o básicos. Estos materiales serán testados en reacciones de transformación de la biomasa, que requieren de dichos centros, para obtener productos de interés en Química Fina e Industrial como aditivos oxigenados para combustibles, entre otros.The Doctoral Thesis covers the synthesis and characterization of acidic catalysts with different structural and textural properties, and their application in the etherification reaction of glycerol with tert-butyl alcohol, in order to obtain the di- and tri-ethers (high ethers), which are used as oxygenated additives for fuels. In addition, dimethyl carbonate has been evaluated as a renewable solvent to reduce the high viscosity of castor oil and sunflower oil (as a reference for waste cooking oils) and obtain, thus, suitable second-generation biofuels for use in current diesel engines In the article "Sulfonated carbons from olive stones as catalysts in the microwave-assisted etherification of glycerol with tert-butyl alcohol" carbon-based materials have been prepared from olive stones, which are an important waste in Andalusia, the world's leading olive oil-producing region. The carbon has been treated with H2SO4 in order to incorporate sulfonic groups in its structure, using either conventional heating or microwave irradiation, at different temperatures (100 and 150 ᵒC) and reaction times (0.5, 2 and 5 h). The solids have been exhaustively characterized and tested in the etherification reaction of glycerol with tert-butyl alcohol using microwave as way of heating. For comparison, conventional heating has also been employed. In the article "Sulfonated organosilica-aluminum phosphates as useful catalysts for acid-catalyzed reactions: Insights into the effect of synthesis parameters on the final catalyst" the optimization of the synthesis, by a sol-gel method, of organosilica-aluminum phosphates with sulfonic groups in their structure, varying the Al/P ratio (3-10), the final synthesis pH (3-9) and the type of organosilane compound, has been carried out. Three different organosilanes have been employed, one of them containing the sulfonic group in its structure and the other two thiol and tetrasulfide groups, respectively, which are subsequently oxidized to sulfonic groups. The goal is to enhance the incorporation of sulfonic groups, through the interaction between the species of Si and Al, and to prepare materials with tunable porosity, in order to attain better results than those previously obtained by our Research Group. The synthesized solids have been tested in the etherification reaction of glycerol with tert-butyl alcohol under microwave irradiation. In the article “Evaluation of dimethyl carbonate as alternative biofuel. Performance and smoke emissions of a diesel engine fueled with diesel/dimethyl carbonate/straight vegetable oil triple blends” dimethyl carbonate (DMC) has been evaluated as a bio-solvent of both vegetable oils castor oil and sunflower oil (as a reference for waste cooking oils), for obtaining new second-generation biofuels that can be used in current vehicles without engine modifications. Thus, different volumetric proportions of biofuel (DMC/vegetable oil blend), from 20% to 80%, have been added to diesel. Several important fuel properties for the performance of an internal combustion engine, such as viscosity, density, cold flow properties, cetane number and calorific value, have been determined. The efficiency of the different biofuels has been evaluated based on the power generated by a diesel engine; the soot emissions generated and the fuel consumption. In addition to the aforementioned, silica-based materials functionalized with acid and/or basic groups were synthesized during a 3-month stay at the "Istituto per lo study dei Materiali Nanostrutturati (ISMN) del Dipartimento di scienze chimiche e tecnologie dei materiali (DSCTM) del Consiglio Nazionale delle Ricerche (CNR)" located in Palermo (Italy). These materials will be tested in biomass transformation reactions, which require these centers, to obtain value-added chemicals for Fine and Industrial Chemistry, such as oxygenated additives for fuels, among them

An Overview of the Production of Oxygenated Fuel Additives by Glycerol Etherification, Either with Isobutene or tert-Butyl Alcohol, over Heterogeneous Catalysts

Biodiesel production has considerably increased in recent decades, generating a surplus of crude glycerol, which is the main drawback for the economy of the process. To overcome this, many scientists have directed their efforts to transform glycerol, which has great potential as a platform molecule, into value-added products. A promising option is the preparation of oxygenate additives for fuel, in particular those obtained by the etherification reaction of glycerol with alcohols or olefins, mainly using heterogeneous catalysis. This review collects up-to-date research findings in the etherification of glycerol, either with isobutene (IB) or tert-Butyl alcohol (TBA), highlighting the best catalytic performances reported. Furthermore, the experimental sets employed for these reactions have been included in the present manuscript. Likewise, the characteristics of the glycerol ethers–(bio)fuel blends as well as their performances (e.g., quality of emissions, technical advantages or disadvantages, etc.) have been also compiled and discussed

Grains de beauté

El proyecto titulado Grains de beauté es una instalación artística compuesta por un conjunto de fotografías en las que se relacionan un conjunto de figuras a pequeña escala y mi propio cuerpo como mapa o territorio que los alberga. Las analogías entre estos objetos y determinados elementos de mi cuerpo como los lunares, permiten establecer un juego de relaciones que generan una poética, producida por la combinación de ambos. He considerado la fotografía como el soporte más apropiado para representar este juego ya que me permite generar imágenes de apariencia real, que se ven implementadas por la aportación de los objetos, permitiéndome además indagar y analizar diversas posibilidades de carácter plástico y visual en mi proyecto. Este proyecto surge de la necesidad de tamizar las diversas ideas que he ido adquiriendo a lo largo de la carrera y que me han permitido conocerme más, así como la necesidad de plasmar la relación con el mundo que me rodea. He generado una transformación de pequeños elementos cotidianos que pueden pasar desapercibidos para la mayoría, al formato artístico para ensalzarlos como elementos significativos. El resultado ha sido una simbiosis entre elementos de distinta procedencia (lunares y objetos), aparentemente, pero sin embargo enlazados como un tejido. En conclusión, se trata de un proyecto autobiográfico, un retrato entre el cuerpo, lo propio y lo que me rodea, lo externo

Sulfonated carbons from olive stones as catalysts in the microwave-assisted etherification of glycerol with tert-butyl alcohol

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

Advanced Biofuels from ABE (Acetone/Butanol/Ethanol) and Vegetable Oils (Castor or Sunflower Oil) for Using in Triple Blends with Diesel: Evaluation on a Diesel Engine

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

A Review on Green Hydrogen Valorization by Heterogeneous Catalytic Hydrogenation of Captured CO2 into Value-Added Products

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

Biodiesel at the Crossroads: A Critical Review

The delay in the energy transition, focused in the replacement of fossil diesel with biodiesel, is mainly caused by the need of reducing the costs associated to the transesterification reaction of vegetable oils with methanol. This reaction, on an industrial scale, presents several problems associated with the glycerol generated during the process. The costs to eliminate this glycerol have to be added to the implicit cost of using seed oil as raw material. Recently, several alternative methods to convert vegetable oils into high quality diesel fuels, which avoid the glycerol generation, are being under development, such as Gliperol, DMC-Biod, or Ecodiesel. Besides, there are renewable diesel fuels known as “green diesel”, obtained by several catalytic processes (cracking or pyrolysis, hydrodeoxygenation and hydrotreating) of vegetable oils and which exhibit a lot of similarities with fossil fuels. Likewise, it has also been addressed as a novel strategy, the use of straight vegetable oils in blends with various plant-based sources such as alcohols, vegetable oils, and several organic compounds that are renewable and biodegradable. These plant-based sources are capable of achieving the effective reduction of the viscosity of the blends, allowing their use in combustion ignition engines. The aim of this review is to evaluate the real possibilities that conventional biodiesel has in order to success as the main biofuel for the energy transition, as well as the use of alternative biofuels that can take part in the energy transition in a successful way

Hydrogenation of α,β-Unsaturated Carbonyl Compounds over Covalently Heterogenized Ru(II) Diphosphine Complexes on AlPO4-Sepiolite Supports

In this work, the covalent immobilization of two ruthenium(II) complexes, i.e., [RuIICl (bpea){(S)(-)(BINAP)}](BF4), 1, and [RuIICl(bpea)(DPPE)](BF4), 2, where BINAP = 2,2’-bis(diphenylphosphino)-1,1’-binaphthyl and DPPE = 1,2-bis(diphenylphosphino)ethane, have been obtained (AlPO4-Sepiolite@1 and AlPO4-Sepiolite@2) by using a N-tridentate ligand N,N-bis-(2-pyridylmethyl)ethylamine (bpea), linked to an amorphous AlPO4-Sepiolite (20/80) inorganic support. This AlPO4-sepiolite support is able to immobilize the double amount of ruthenium complex (1.65%) than the amorphous AlPO4 (0.89%). Both heterogenized complexes have been assessed as catalysts in the liquid phase hydrogenation of several substrates with carbonyl and/or olefinic double bonds using methanol as solvent, attaining good catalytic activity and high enantioselectivity (99%). The highest Turn Over Number (TON) value (748.6) was obtained over the [RuII Cl (bpea)(DPPE)](BF4) 2 catalyst, although the [RuIICl(bpea){(S)(-)(BINAP)}](BF4) 1 exhibits better reusability. In fact, the [RuIICl(bpea){(S)(-)(BINAP)}](BF4) immobilized on AlPO4-Sepiolite maintained the activity throughout 14 successive runs. Furthermore, some findings on hydrogenation mechanisms of the α,β-unsaturated carbonyl compounds over Ru catalysts have been also obtained

Acetone Prospect as an Additive to Allow the Use of Castor and Sunflower Oils as Drop-In Biofuels in Diesel/Acetone/Vegetable Oil Triple Blends for Application in Diesel Engines

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’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–butanol–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

Biofuels from Diethyl Carbonate and Vegetable Oils for Use in Triple Blends with Diesel Fuel: Effect on Performance and Smoke Emissions of a Diesel Engine

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