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Electroreduction allows for the transformation of a chemically inert molecule such as CO2 into a wide variety of useful carbon products. Unlike other approaches operating at higher temperatures, electrochemical reduction holds great promise since it achieves reduction under ambient conditions, thereby providing more control over the reaction selectivity. By controlling basic parameters such as the potential and the composition of the electrode, CO2 can be transformed into a variety of products including carbon monoxide, syngas (CO/H2), methane, and methanol. This reduction process takes place without external hydrogen, since water can be used as a source of both electrons and protons. Furthermore, this technology, when combined with renewable wind- or solar-derived electricity, has the potential to serve as a storage system for excess electricity. Despite these advantages, a number of challenges need to be overcome before reaching commercialization. New (and cheaper) electrocatalyst formulations with high faradaic selectivities are required. Impressive progress has been made on carbon-doped materials, which, in certain cases, have outperformed expensive noble metal-based materials. Research is also needed on new electrochemical reactor configurations able to overcome kinetic/mass transport limitations, which are crucial to reduce overpotentials. Fine control over the nature of the active sites and the reaction conditions is important to avoid parasitic reactions such as the hydrogen evolution reaction (HER), and therefore increases the faradaic efficiency towards the desired products.

The design of new insulating envelopes is a direct route towards energy efficient buildings. The combinations of novel materials, such as phase-change (PCM), and advanced manufacturing techniques, such as additive manufacturing, may harness important changes in the designing of building envelopes. In this work we propose a novel methodology for the design of cement-based building envelopes. Namely, we combined the use of a multiscale, multiphysical simulation framework with advanced synthesis techniques, such as the use of phase-change materials and additive manufacturing for the design of concrete envelopes with enhanced insulation properties. At the material scale, microencapsulated PCMs are added to a cementitious matrix to increase heat storage. Next, at the component level, we create novel designs for the blocks, here defined as HEXCEM, by means of additive manufacturing. The material and component design process is strongly supported on heat transfer simulations with the use of the finite element method. Effective thermal properties of the mixes can be obtained and subsequently used in macroscale simulations to account for the effect of the volume fraction of PCMs. From the experimental and numerical tests, we report an increase in the the thermal inertia, which results in thermal comfort indoors.

The preparation of MOFs including a metal with an easily exchangeable oxidation state, while maintaining the same crystal structure and stability, is of paramount importance for myriad applications. In this work, a new synthesis method is reported that can be used to prepare Ce/Zr‐MOFs (UiO‐66 structure) having only Ce(III), a mixed‐valence Ce(IV)/Ce(III), or only Ce(IV) cations, as desired. The materials are characterized using a large number of techniques, including X‐ray absorption and X‐ray photoelectron spectroscopies. Authors acknowledge financial support by MINECO (Spain) through projects, MAT2017-86992-R and MAT2016-80285-P. EVRF acknowledges MINECO for his Ramón y Cajal fellow RYC-2012-11427. The authors also would like to thank Diamond Light Source (I20-Scanning beamline) for the beamtime given at the proposal SP19114.

The effect of the addition of three oxophilic co-metals (Sn, Mo and Re) on the electrochemical performance of Pd in the ethanol oxidation reaction (EOR) was investigated by performing half-cell and membrane-less electrolysis cell experiments. While the additions of Sn and Re were found to improve significantly the EOR performance of Pd, Mo produced no significant promotional effect. When added in significant amounts (50:50 ratio), Sn and Re produced a 3–4 fold increase in the mass-normalized oxidation peak current as compared to the monometallic Pd/C material. Both the electrochemical surface area and the onset potential also improved upon addition of Sn and Re, although this effect was more evident for Sn. Cyclic voltammetry (CV) measurements revealed a higher ability of Sn for accommodating OH- species as compared to Re, which could explain these results. Additional tests were carried out in a membrane-less electrolysis system. Pd50Re50/C and Pd50Sn50/C both showed higher activity than Pd/C in this system. Chronopotentiometric measurements at constant current were carried out to test the stability of both catalysts in the absence of a membrane. Pd50Sn50/C was significantly more stable than Pd50Re50/C, which showed a rapid increase in the potential with time. Despite operating in the absence of a membrane, both catalysts generated a high-purity (e.g., 99.99%) hydrogen stream at high intensities and low voltages. These conditions could lead to significant energy consumption savings compared to commercial water electrolyzer, Se investigó el efecto de la adición de tres cometales oxófilos (Sn, Mo y Re) en el rendimiento electroquímico de Pd en la reacción de oxidación de etanol (EOR) realizando experimentos de celdas de electrólisis sin membrana y de media celda. Si bien se encontró que las adiciones de Sn y Re mejoraban significativamente el rendimiento EOR de Pd, Mo no produjo un efecto promocional significativo. Cuando se agregaron en cantidades significativas (proporción 50:50), Sn y Re produjeron un aumento de 3 a 4 veces en la corriente máxima de oxidación de masa normalizada en comparación con el material monometálico Pd/C. Tanto el área de superficie electroquímica como el potencial de inicio también mejoraron con la adición de Sn y Re, aunque este efecto fue más evidente para Sn. Las mediciones de voltamperometría cíclica (CV) revelaron una mayor capacidad de Sn para acomodar especies de OH- en comparación con Re, lo que podría explicar estos resultados. Se llevaron a cabo pruebas adicionales en un sistema de electrólisis sin membrana. PD50 Re 50 /C y Pd 50 Sn 50 /C mostraron una mayor actividad que Pd/C en este sistema. Se realizaron medidas cronopotenciométricas a corriente constante para probar la estabilidad de ambos catalizadores en ausencia de membrana. El Pd 50 Sn 50 /C fue significativamente más estable que el Pd 50 Re 50 /C, que mostró un rápido aumento del potencial con el tiempo. A pesar de operar en ausencia de una membrana, ambos catalizadores generaron una corriente de hidrógeno de alta pureza (por ejemplo, 99,99%) a intensidades altas y voltajes bajos. Estas condiciones podrían conducir a un ahorro significativo en el consumo de energía en comparación con los electrolizadores de agua comerciales

The hydrogenation of nitroarenes to produce the corresponding amines using dihydrogen as reducing agent has an important industrial role, since it allows to obtain important added-value products. This reaction needs the help of a catalyst to proceed. Many catalysts have been already tested and studied. Most of them are based on noble metals supported on metal oxides. These catalysts perform well, but they are expensive and thus, alternative systems are needed. In this context, cobalt-based catalysts have emerged as adequate alternatives, despite cobalt nanoparticles per se are not very active for this reaction. A way to improve the catalytic activity of cobalt nanoparticles is by supporting them on a support with functional groups that are able to change their intrinsic properties and to enhance their catalytic properties. In this sense, N-containing carbons are promising candidates to be used as support, since nitrogen functionalities may modify the catalytic properties of cobalt. In this work, cobalt nanoparticles supported on N-doped activated carbons have been prepared and studied as catalysts for the hydrogenation of 1-chloro-4-nitrobencene to the corresponding chloro-aniline. It is demonstrated that the catalytic activity is enhanced by the presence of nitrogen species in the support. When the temperature of the catalyst activation treatment (reduction under flowing hydrogen) is increased, the catalytic activity increases drastically in the presence of nitrogen functionalities on the support. The catalysts have been characterised by transmission electron microscopy (TEM), temperature-programmed reduction (TPR), X-ray diffraction, X-ray photoelectron spectroscopi (XPS) and N2 adsorption at 77 K. It has been found that the enhanced catalytic activity was due to two different factors, namely the interaction of the cobalt particles with the nitrogen functional groups (forming Co4N), and the development of mesopores in the support during the activation process that increases the accessibility of reactants to the active sites. Authors acknowledge financial support by MINECO (Spain) through the projects MAT2017-86992-R and MAT2016-80285-P and the European Union for the project “eForFuel”, grant agreement 763911. J. C. S. R. would like to thank the Spanish Ministry of Science and Innovation for financial support through the Ramón y Cajal Program, Grant: RYC-2015-19230 J. C. S. R. would also like to thank Junta de Andalucía for financial support through the projects PY18-RE-0012 and IE18_0047_FUNDACIÓN LOYOLA.

Ever-growing anthropogenic activity has increased global energy demands, resulting in growing concentrations of greenhouse gases such as CO2 in the atmosphere. The electroreduction of CO2 has been proposed as a potential solution for reducing anthropogenic CO2 emissions. Despite the promising results obtained so far, some limitations hinder large-scale applications, especially those associated with the activity and selectivity of electrocatalysts. A good number of metal catalysts have been studied to overcome this limitation, but the high cost and low earth abundance of some of these materials are important barriers. In this sense, carbon materials doped with heteroatoms such as N, B, S, and F have been proposed as cheaper and widely available alternatives to metal catalysts. This review summarizes the latest advances in the utilization of carbon-doped materials for the electroreduction of CO2, with a particular emphasis on the synthesis procedures and the electrochemical performance of the resulting materials.

This chapter describes the different approaches that have been developed to synthesize metal organic frameworks (MOFs) with catalytic centres. In general, MOFs are materials composed of an organic and inorganic part, giving them great potential for catalysis. However, many of the stable MOF structures do not have active centres, and these have to be induced. The hybrid nature of these materials makes them unique for the design and synthesis of catalytic materials for desired applications. In this chapter, we describe the methods that can be used to design MOF with catalytic centres.

A series of Cu catalysts supported on SiO2, Al2O3-SiO2, TiO2 rutile, and Cu/TiO2 anatase metal oxides has been studied for methanol reforming in the vapor phase. The highest activity was obtained on Cu/SiO2 catalysts (5493 µmol H2 min-1·gcat -1) followed by Cu/TiO2 rutile, Cu/ Al2O3-SiO2, and anatase. XRD and HRTEM characterization after reaction revealed that on Cu/SiO2 significant sintering occurred during reaction. In contrast, the particle size growth on Cu/TiO2 rutile and anatase was less pronounced, which could be associated with the interaction between Cu clusters and TiO2. Characterization by TGA showed that on Cu/Al2O3-SiO2 the main cause of deactivation was coke deposition.

A novel gas-phase electrocatalytic cell containing a low-temperature proton exchange membrane (PEM) was developed to electrochemically convert CO2 into organic compounds. Two different Cu-based cathode catalysts (Cu and Cu–C) were prepared by physical vapor deposition method (sputtering) and subsequently employed for the gas-phase electroreduction of CO2 at different temperatures (70–90 °C). The prepared electrodes Cu and Cu–C were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM). As revealed, Cu is partially oxidized on the surface of the samples and the Cu and Cu–C cathodic catalysts were comprised of a porous, continuous, and homogeneous film with nanocrystalline Cu with a grain size of 16 and 8 nm, respectively. The influence of the applied current and temperature on the electro-catalytic activity and selectivity of these materials was investigated. Among the two investigated electrodes, the pure Cu catalyst film showed the highest CO2 specific electrocatalytic reduction rates and higher selectivity to methanol formation compared to the Cu–C electrode, which was attributed to the higher particle size of the former and lower CuO/Cu ratio. The obtained results show potential interest for the possible use of electrical renewable energy for the transformation of CO2 into valuable products using low metal loading Cu based electrodes (0.5 mg Cu cm−2) prepared by sputtering, Se desarrolló una nueva celda electrocatalítica en fase gaseosa que contiene una membrana de intercambio de protones (PEM) de baja temperatura para convertir electroquímicamente el CO 2 en compuestos orgánicos. Se prepararon dos catalizadores de cátodo basados ​​en Cu diferentes (Cu y Cu–C) mediante el método de deposición física de vapor (pulverización) y posteriormente se emplearon para la electrorreducción de CO 2 en fase gaseosa a diferentes temperaturas (70–90 °C). Los electrodos Cu y Cu–C preparados se caracterizaron por difracción de rayos X (XRD), fotoemisión de rayos Xespectroscopía (XPS) y microscopía electrónica de barrido (SEM). Como se reveló, el Cu está parcialmente oxidado en la superficie de las muestras y los catalizadores catódicos de Cu y Cu-C estaban compuestos por una película porosa, continua y homogénea con Cu nanocristalino con un tamaño de grano de 16 y 8 nm, respectivamente. Se investigó la influencia de la corriente y la temperatura aplicadas sobre la actividad electrocatalítica y la selectividad de estos materiales. Entre los dos electrodos investigados, la película de catalizador de Cu puro mostró la mayor cantidad de CO 2tasas específicas de reducción electrocatalítica y mayor selectividad para la formación de metanol en comparación con el electrodo de Cu-C, lo que se atribuyó al mayor tamaño de partícula del primero y a la menor relación CuO/Cu. Los resultados obtenidos muestran un potencial interés para el posible uso de energía eléctrica renovable para la transformación de CO 2 en productos valiosos utilizando electrodos basados ​​en Cu de baja carga de metal (0,5 mg Cu cm −2 ) preparados por pulverización catódica.

A novel electrocatalytic system based on a low temperature proton exchange membrane (Sterion) was developed for the gas phase electrocatalytic conversion of CO 2 . This configuration allows the introduction of renewable energy in the chemical production chain via fuels production from direct CO 2 electro-reduction at atmospheric pressure and low temperatures (below 90 °C). For that purpose, three different Membrane Electrode Assemblies (MEAs) based on three different Cu based cathodic-catalysts were prepared and characterized: Cu-G/Sterion/IrO 2 , Cu-AC/Sterion/IrO 2 and Cu-CNF/Sterion/IrO 2 ; graphite (G), activated carbon (AC) and carbon nanofibers (CNF). Thus, H 2 O was fed and electrolyzed on the IrO 2 anode of the cell, thereby supplying H + across the membrane to react with CO 2 in the cathodic-catalyst and leading to the production of a mixture of syn-fuels (syn-gas, methanol, methane…). Remarkably, the nature of the cathodic-catalyst carbon support had a strong influence on the electrocatalytic activity and selectivity of the system. Hence, the Cu-AC-based cathodic-catalyst showed the highest CO 2 electrocatalytic activity, due to the highest surface area of the AC support and the larger metal dispersion of the Cu particles leading to acetaldehyde and methanol as the main reaction products. Besides the lower conductivity of the AC support, the lowest energy consumption values for CO 2 conversion and methanol and acetaldehyde production was also achieved with the MEA based on Cu-AC cathodic catalyst due to its higher electrocatalytic activity.

A novel gas-phase electrocatalytic system based on a low-temperature proton exchange membrane (Sterion) was developed for the gas-phase electrocatalytic conversion of CO2 to liquid fuels. This system achieved gas-phase electrocatalytic reduction of CO2 at low temperatures (below 90 &deg, C) over a Cu cathode by using water electrolysis-derived protons generated in-situ on an IrO2 anode. Three Cu-based cathodes with varying metal particle sizes were prepared by supporting this metal on an activated carbon at three loadings (50, 20, and 10 wt %, 50% Cu-AC, 20% Cu-AC, and 10% Cu-AC, respectively). The cathodes were characterized by N2 adsorption&ndash, desorption, temperature-programmed reduction (TPR), and X-ray diffraction (XRD) and their performance towards the electrocatalytic conversion of CO2 was subsequently studied. The membrane electrode assembly (MEA) containing the cathode with the largest Cu particle size (50% Cu-AC, 40 nm) showed the highest CO2 electrocatalytic activity per mole of Cu, with methyl formate being the main product. This higher electrocatalytic activity was attributed to the lower Cu&ndash, CO bonding strength over large Cu particles. Different product distributions were obtained over 20% Cu-AC and 10% Cu-AC, with acetaldehyde and methanol being the main reaction products, respectively. The CO2 consumption rate increased with the applied current and reaction temperature.

Three different kind of Ni-based catalysts were prepared on a K-β″Al2O3 solid electrolyte by combining the annealing of an organometallic paste and the addition of a catalyst powder. The different catalysts films were tested in the CO2 hydrogenation reaction under electrochemical promotion by K+ ions, and were characterized by XRD and SEM. The catalyst film derived from the addition of an α-Al2O3 powder to the Ni catalyst ink presented the highest catalytic activity as a result of the increase in Ni catalyst film porosity. The influence of the applied potential and other operation variables were evaluated on the Ni catalytic activity and selectivity. Hence, the CO production rate was enhanced either by decreasing the applied potential (with the consequent supply of K+ ions to the catalyst surface) or by increasing the CO2 (electron acceptor) feed concentration. On the other hand, CH4 production rate was favoured at positive potentials (removing K+ from the catalyst surface) or by increasing the H2 (electron donor) feed concentration. The global CO2 consumption rate increased upon negative polarization in all experiments and the electrochemical promotion of catalysis effect showed to be reversible and reproducible. Hence, the electrochemical promotion phenomena demonstrated to be a very useful technique to in situ modify and control the catalytic activity and selectivity of a non-noble metal such as Ni for the production of CH4 or syngas via CO2 valorization.

The development of novel configurations for the production of synthesis gas (syn-gas) of flexible H2/CO ratio is of great importance to reduce the cost for the synthesis of synfuels and high-value chemicals. In this work, we propose a radically novel approach to the direct production of syn-gas with flexible H2/CO ratio based on the solid electrolyte membrane reactor (SEMR). For that purpose, a single-chamber solid electrolyte membrane reactor based on yttria-stabilized zirconia (YSZ) has been developed (Pt/YSZ/Pt), where both active Pt catalysts–electrodes were exposed to the same reaction atmosphere (C2H5OH/H2O = 0.7 %/2 %). The application of different polarizations at temperature range (600–700 °C) allows to control the H2/CO ratio of the obtained syn-gas, i.e., the ratio was varied between 1.5 and 12 under polarization conditions. Unlike conventional catalytic partial oxidation processes, the H2/CO adjustment was managed without the requirement of external O2 feeding to the reactor. An increase in the applied current or potential caused the H2/CO ratio to increase vs. the open-circuit conditions where ethanol reforming occurred on the Pt catalyst–electrodes which is due to an increase in the rate of the electro-catalytic processes. On the other hand, a decrease in the H2/CO ratio at a fixed potential was achieved at higher temperatures due to the further reaction of the produced H2 with the rest of the species present in the gas phase, leading to a decrease in the faradaic efficiency. The proposed configuration may be of great interest especially for biorefinery applications where H2, syn-gas and electricity may be produced from bioethanol.

We have developed a novel gas-phase electrocatalytic system for the conversion of CO2 into added-value chemicals. The system is based on a high-temperature proton-exchange membrane reactor containing a Cu cathodic catalyst supported on carbon nanofibers (CNFs) and an H3PO4-doped polybenzimidazole polymer electrolyte membrane (PBI). The resulting Cu–CNFs/PBI/IrO2 membrane electrode assembly (MEA) allowed the utilization of higher temperatures (110 °C) than has been previously reported. The application of a low current density (− 0.8 mA/cm2) permitted the direct transformation of CO2 into various organic compounds in the C1–C3 range, acetaldehyde being the most common product (85% selectivity). The application of a higher current density (− 1.6 mA/cm2) increased the overall electrocatalytic activity of the system, producing lighter and more saturated compounds. The novel electrochemical cell proposed in this work allows the conversion of CO2 into valuable products under mild conditions (i.e., room pressure, 110 °C) with no requirement for H2 and using electrical energy that could potentially be obtained from renewable energy sources., Hemos desarrollado un novedoso sistema electrocatalítico en fase gas para la conversión de CO 2 en productos químicos de valor añadido. El sistema se basa en un reactor de membrana de intercambio de protones de alta temperatura que contiene un catalizador catódico de Cu soportado en nanofibras de carbono (CNF) y una membrana de electrolito de polímero de polibencimidazol dopado con H 3 PO 4 (PBI). El conjunto de electrodos de membrana (MEA) de Cu–CNFs/PBI/IrO 2 resultante permitió la utilización de temperaturas más altas (110 °C) de lo que se informó anteriormente. La aplicación de una baja densidad de corriente (− 0,8 mA/cm 2 ) permitió la transformación directa de CO 2 en varios compuestos orgánicos en el rango C 1 -C 3 , siendo el acetaldehído el producto más común (85% de selectividad). La aplicación de una mayor densidad de corriente ( −1,6 mA/cm 2 ) aumentó la actividad electrocatalítica global del sistema, produciendo compuestos más ligeros y saturados. La novedosa celda electroquímica propuesta en este trabajo permite la conversión de CO 2 en productos valiosos en condiciones moderadas (es decir, presión ambiental, 110 °C) sin necesidad de H 2 y utilizando energía eléctrica que podría obtenerse potencialmente de fuentes de energía renovables .

Diminishing fossil fuel reserves and global warming issues are driving society toward the search for new renewable sources of energy . Lignocellulosic can significantly displace petroleum in the production of fuels . Oxygenated fuels such as ethanol and biodiesel currently dominate the fuel market although they have important limitations. The production of liquid hydrocarbon fuels from biomass is a paradigmatic transformation allowing the production of fuels chemically identical to those currently used in the transportation sector. The present chapter describes some of the catalytic strategies used to transform biomass-derived molecules into liquid hydrocarbon fuels. These strategies are first focused on decreasing the oxygen content of the original molecule such that its reactivity can be more easily controlled. In a subsequent step, the less oxygenated intermediates are upgraded via C–C coupling reactions to increase the length chain to produce a final product suitable for diesel and jet fuel applications. The present chapter offers a number of examples on biomass-derived acids such as lactic and levulinic acids and biomass sugars such as glucose catalytically transformed into liquid hydrocarbon fuels.

This study reports the production of H2 via catalytic methane decomposition on Pt supported on yttria-stabilized zirconia together with its electrochemical regeneration in a solid electrolyte membrane reactor. Hence, a Pt-YSZporous/YSZ/Pt double-chamber solid electrolyte cell was prepared and tested under two reaction regimes. In the first regime, under open-circuit conditions, hydrogen and carbon are produced on the catalytically active Pt-YSZ porous catalyst via methane decomposition reaction (CH4 (g) → C (s) + 2H2 (g)). In the second regime, under polarization conditions, steam is electrolyzed at the Pt cathode of the cell (H2O + 2e− → H2 + O2−) and the produced O2− ions were simultaneously electrochemically pumped to the Pt/YSZ porous catalyst (anode), thereby allowing removal of the previously deposited carbon (C (s) + O2− → CO2 (g)) and finally regenerating the Pt/YSZ porous catalyst film. We demonstrated that the carbon generated in the methane decomposition step serves as a depolarizating agent in the steam electrolysis process, thus decreasing the electrical energy input required for electrochemically producing pure H2. In addition, during the regeneration step, C2 hydrocarbons (e.g., ethane and ethylene) were obtained as a result of the electrocatalytic methane oxidative coupling on the Pt/YSZ porous catalyst film. The performance and durability of the system was also verified for long operation times in view of the possible practical application of this novel reactor configuration, which combines gas-phase catalysis and electrocatalysis for hydrogen production.

Biomass can efficiently replace petroleum in the production of fuels for the transportation sector. One effective strategy for the processing of complex biomass feedstocks involves previous conversion into simpler compounds (platform molecules) which are more easily transformed in subsequent upgrading reactions. Lactic acid and levulinic acid are two of these relevant biomass derivatives which can easily be derived from biomass sources by means of microbial and/or chemical routes. The present paper intends to cover the most relevant catalytic strategies designed today for the conversion of these molecules into advanced biofuels (e.g. higher alcohols, liquid hydrocarbon fuels) which are fully compatible with the existing hydrocarbons-based transportation infrastructure. The routes described herein involve: (i) deoxygenation reactions which are required for controlling reactivity and for increasing energy density of highly functionalized lactic and levulinic acid combined with (ii) C C coupling reactions for increasing molecular weight of less-oxygenated reactive intermediates.

Nd-doped titania materials prepared using a mild microwave-assisted protocol have been found to possess excelling activities in the photodegradation of water contaminants including phenol and Rhodamine B. These materials were characterized by a number of techniques including N 2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The prepared materials showed high surface area, with the highest value for the catalyst containing a Nd/Ti ratio of 0.03 (341 m 2 /g). The dopant agent was found to be as Nd 3+ ions located on the surface and in the inter-planar space of titanium oxide crystals. Effects of the surface area together with the Nd content and the adsorption ability of the material seem to be involved in the optimum photocatalytic activity found for 0.5%Nd (Nd0.005/TiO 2 ) and 6%Nd (Nd0.06/TiO 2 ) containing materials.

Ni-based catalysts supported on Zn-modified alumina were investigated in the ethanol steam reforming reaction. A commercial γ-alumina was impregnated with different amounts of zinc nitrate (0, 2, 5, 10, 15, 20 wt.% on Zn basis), calcined, and then impregnated with nickel nitrate aqueous solutions. The samples were characterized by a number of techniques: N(2) adsorption at 77 K, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), and temperature-programmed reduction (TPR). Their catalytic behavior in the ethanol steam reforming reaction was studied at 873 K, with a H(2)O/ethanol ratio of 5:1. Two effects of the presence of Zn were detected. On the one hand, zinc modifies the surface structure and the surface chemistry of the catalysts by formation of zinc aluminates, and on the other hand, zinc oxide can be reduced to metallic zinc under reaction conditions, thus modifying the catalytic properties of the active phase. The presence of Zn increases the ethanol conversion to gaseous compounds as compared with the catalyst supported on the Zn-free commercial alumina. The addition of a small amount of Pt (1 wt.%) causes a beneficial effect in the reaction. When Ni catalysts were used without a previous reduction treatment, ethylene was formed in high amounts; however, the Pt-Ni catalysts need no reduction pre-treatment to achieve high H(2) yields (close to 70%) and showed a high stability versus time on stream because of the control of the production of ethylene, a coke precursor.

Helical mesoporous silicas containing aluminium or cerium into their framework have been synthesized via hydrothermal method. The synthesized materials were extensively characterized to understand their physico–chemical properties in view of their future catalytic applications. Low-angle powder XRD patterns of calcined samples showed a hexagonally ordered mesopore structure. NMR spectra of aluminium materials exhibited two signals at 50 and 0 ppm assigned to tetracoordinated and octahedrally coordinated Al 3+ . DR-UV–vis and XPS spectrum of cerium content materials show that cerium was incorporated as Ce 3+ and Ce 4+ into the helical mesoporous material. Materials with molar ratios Si/Al = 95 and Si/Ce = 500 were found to be catalytically active in acid (oxathioacetalisations and alkylations) or redox (epoxidation of cyclohexene) catalyzed processes, respectively.

Continuous flow chemical processes offer several advantages as compared to batch chemistries. These are particularly relevant in the case of heterogeneously catalyzed transformations of biomass-derived platform molecules into valuable chemicals and fuels. This work is aimed to provide an overview of key continuous flow processes developed to date dealing with a series of transformations of platform chemicals including alcohols, furanics, organic acids and polyols using a wide range of heterogeneous catalysts based on supported metals, solid acids and bifunctional (metal + acidic) materials.

Low-load iron oxide nanoparticles on Al-SBA-15 prepared using a novel dry milling approach exhibited excelling activities in the microwave-assisted akylation of toluene with benzyl chloride (Lewis acids promoted reaction) and benzyl alcohol (Bronsted acids promoted reaction) as compared to the parent Al-SBA-15 and similar iron oxide nanoparticles supported on Al-MCM-41 materials. Materials prepared using the milling protocol possessed remarkably low iron loadings (

Several catalysts of cerium oxide highly dispersed on activated carbon were prepared varying the cerium precursor, the solvent and the chemical surface properties of the support, and characterized by several techniques. Afterwards, these materials were investigated as ozonation catalysts for the mineralization of two organic compounds (oxalic acid and aniline). The ozonation results were compared with those obtained in the absence of catalyst and in the presence of the parent activated carbons used for the preparation of these materials. The prepared catalysts have better performances than the parent activated carbons, denoting a clear synergic effect between activated carbon and cerium oxide. The efficiency of the catalysts is mainly affected by the amount of Ce 3+ species on the surface. However, in the ozonation of oxalic acid, the specific surface area and metal oxide particle diameter also played an important role. The use of activated carbon as support favors the removal of both organic compounds studied. Highly dispersed cerium oxide on activated carbon shows better catalytic performance than a composite with the same composition.

A site energy distribution function is proposed that can rapidly generate the binding energy distribution of any adsorbent for any target molecules using only the Sips isotherm parameters, the advantages of which are discussed. The proposed model is successfully applied to determine the site energy distribution of a series of activated carbons, activated carbon fiber, and single-wall carbon nanotubes (SWCNT) for the adsorption of several gas molecules. The proposed model revealed the fact that the sorption capacity of the activated carbons for the target molecule depends on the shape and the size of the binding site energies. The proposed model is very simple to use and does not need any complicated or sophisticated computer programs to determine the distribution of binding energies on the adsorbent surface.

Techno-economic studies of processes for production of dimethyl-furan (DMF) and hydroxymethyl-furfural (HMF) from fructose are performed based on published laboratory results. The early stage of technology development necessitates use of simplified process models to analyze a conceptual bio-refinery producing fuel and chemical intermediates. HMF and DMF production processes are divided into four and six processing areas respectively that include synthesis and purification sections. The HMF process employs a biphasic (aqueous–organic phases) continuously stirred tank reactor (CSTR), and the DMF process has an additional 3-train fixed bed catalytic plug flow tubular reactor (PFTR). The processing capacities are 300 metric ton/day of fructose and the plants will operate for 20 years. Installed equipment costs are estimated (US$2007) as $102.4 million for the HMF and $121.9 million for the DMF process, respectively. The DMF process uses a copper–ruthenium–carbon (Cu–Ru/C) catalyst. Catalyst cost is estimated as $36.4 million for the first charge with replacement cost of $258,500/2-years. Cost analysis is performed following the discounted cash flow method. The minimum selling prices for HMF and DMF are estimated as $1.33/l ($5.03/gal) and $2.02/l ($7.63/gal), respectively. Sensitivity analyses are performed to assess the relative importance of key assumptions on minimum HMF and DMF selling prices. The most significant parameters are feedstock cost, product yields, by-product prices, catalyst cost and total purchased equipment costs. Process and economic uncertainties can be reduced by incorporating better performance (through laboratory and pilot trials) and cost data.

Aqueous-phase reactions at elevated temperatures can cause significant loss of surface area in oxide supports. Addition of a second component can help improve the hydrothermal stability of the support and retain a more open, porous structure. Here we show that small amounts of silica (5 wt%) help improve the activity and stability of Pd/niobia–silica catalysts used for pentanoic acid formation from γ-valerolactone. At the end of the run, the Pd/Nb–Si oxide catalysts showed significantly higher activity than catalysts where the Pd was deposited on commercial niobia (HY-340). Loss of surface area occurred for all of the catalysts; however, surface area loss occurred to lesser extents for the Pd/Nb–Si oxide catalysts. In these samples, the regions that contained more silica retained their porous structure and maintained smaller Pd crystallite sizes after reaction while those areas with depleted silica content transformed into crystalline niobia along with significant metal particle growth. We conclude that addition of silica to niobia not only improves the stability of the support but also helps retain smaller crystallite sizes for the Pd phase, resulting in improved catalytic performance in the bi-functional aqueous-phase conversion of γ-valerolactone into pentanoic acid.

Concerns about diminishing fossil fuel reserves along with global warming effects caused by increasing levels of CO2 in the atmosphere are driving society toward the search for new renewable sources of energy that can substitute for coal, natural gas and petroleum in the current energy system. Lignocellulosic biomass is abundant, and it has the potential to significantly displace petroleum in the production of fuels for the transportation sector. Ethanol, the main biomass-derived fuel used today, has benefited from production by a well-established technology and by partial compatibility with the current transportation infrastructure, leading to the domination of the world biofuel market. However, ethanol suffers from important limitations as a fuel (e.g., low energy density, high solubility in water) than can be overcome by designing strategies to convert non-edible lignocellulosic biomass into liquid hydrocarbon fuels (LHF) chemically similar to those currently used in internal combustion engines. The present review describes the main routes available to carry out such deep chemical transformation (e.g., gasification, pyrolysis, and aqueous-phase catalytic processing), with particular emphasis on those pathways involving aqueous-phase catalytic reactions. These latter catalytic routes achieve the required transformations in biomass-derived molecules with controlled chemistry and high yields, but require pretreatment/hydrolysis steps to overcome the recalcitrance of lignocellulose. To be economically viable, these aqueous-phase routes should be carried out with a small number of reactors and with minimum utilization of external fossil fuel-based hydrogen sources, as illustrated in the examples presented here.

We report a catalytic process to convert cellulose into liquid hydrocarbon fuels (diesel and gasoline), using a cascade strategy to achieve the progressive removal of oxygen from biomass, allowing the control of reactivity and facilitating the separation of products. The process starts with the deconstruction of solid cellulose in an aqueous solution of sulfuric acid yielding an equi-molar mixture of levulinic acid and formic acid. The formic acid in this mixture can then be used (upon decomposition to H2 and CO2) to reduce levulinic acid to γ-valerolactone (GVL) in the sulfuric acid solution over a Ru/C catalyst. The formation of GVL allows strategies for the separation and recycling of the sulfuric acid used in the cellulose deconstruction step. This GVL product, with residual amounts of sulfur, can be upgraded to 5-nonanone with high yields (90%) in a single reactor by using a dual catalyst bed of Pd/Nb2O5 plus ceria-zirconia. The 5-nonanone product is hydrophobic and separates spontaneously from water, yet possesses a functional group that can be used to control the structure and molecular weight of hydrocarbon fuel components formed in downstream catalytic upgrading treatments.

Carboxylic acids and esters are common intermediate products formed in biomass conversion processes. Reaction kinetics studies for upgrading mixtures containing carboxylic acids and esters by ketonization reactions (to achieve C−C coupling) over a ceria−zirconia catalyst have been carried out using butanoic acid, pentanoic acid, and hexanoic acid at temperatures of 548, 573, 598, and 623 K. The results from these experimental studies have been consolidated and described using kinetic models. For the ketonization of hexanoic acid, a kinetic model, previously developed for hexanoic acid, has been modified and extended to describe a wider and more applicable concentration range, between 2.5 and 75 mol %. Furthermore, the homo- and the cross-ketonization of butanoic acid, pentanoic acid, and hexanoic acid have been studied, showing that the rate of cross-ketonization is faster than the rate of homo-ketonization. Because esters are common side products of biomass conversion processes, formed by the esterificat...

We analyze a process for production of 5-nonanone (dibutyl ketone, DBK) from levulinic acid (LA) which is a biobased platform chemical that can be produced in large quantities from a variety of lignocellulosic biomass sources. The techno-economic analysis is based on a catalytic pathway developed in lab scale. The final product (DBK) has applications as an industrial solvent and serves as a platform chemical for the production of liquid hydrocarbon fuels in the diesel and gasoline ranges. A detailed process model has been created for two different product purity levels (90% and 99%). Process economics have been studied in a discounted cash flow analysis to analyze the viability of production and relative product purification costs. The modeled process utilizes 480 metric ton/day of LA feedstock to produce 194 metric ton/day of DBK along with other by-products. Sensitivity analysis is used to identify the impact of key parameters on the minimum selling price of product. Thus, the price of the feedstock (LA) and the DBK final yield were found to be the most sensitive parameters affecting the final price of the product. With the current LA market price ($3.2 per kg) and the experimental yield of 66%, the minimum selling price estimated for a high purity DBK was $8.5 per kg, comparable to the current DBK purchase price ($9.07 per kg) but still quite high compared to the price of a typical petroleum-derived solvent such as methyl ethyl ketone ($0.77 per kg). Further improvements on the lab scale to increase the yield of DBK, and the use of inexpensive LA from the patented Biofine process, would allow the production of DBK at competitive prices for chemical and fuel applications.

Carboxylic acids, common intermediate products in biomass conversion processes, can be converted into ketones via ketonization reactions over a ceria–zirconia catalyst. Reaction kinetics studies were carried out using hexanoic acid, as a representative carboxylic acid, in the presence of 1-pentanol and 2-butanone, as representative biomass-derived alcohol and ketone species. Studies were carried out at temperatures from 448 to 623 K, and employing a range of hexanoic acid partial pressures from 0.05 to 0.3 atm. Two different reactions were observed to take place at these reaction conditions: esterification and ketonization, both consuming hexanoic acid. Product inhibition by water and carbon dioxide was observed and studied by co-feeding these components to the reactor. Hexanoic acid adsorption on the catalyst surface is an important step in the reaction, and the rate of ketonization shifts from second order to zero order as the partial pressure of acid increases. The measured activation energy for the ketonization of hexanoic acid (132 kJ/mol) is higher than the esterification reaction (40 kJ/mol), such that the irreversible ketonization reaction is favored at higher temperatures (>573 K) compared to the reversible esterification reaction. Direct ketonization of esters does not take place in the presence of acids, and instead takes place by hydrolysis with water followed by ketonization of the corresponding acid. The results of this study can be described by a simple kinetic model including site blocking by adsorbed hexanoic acid, carbon dioxide, and water.

Dilute aqueous solutions of lactic acid (30 %wt.) can be catalytically processed at 573 K and 57 bar over a low-metal-content Pt(0.1 %)/Nb(2)O(5) catalyst in a spontaneously separating organic phase rich in valuable products such as C(4)-C(7) ketones. An increase in the lactic acid concentration to 60 wt % allows conversion of approximately 50 % of the carbon feed in this organic layer, while maintaining good stability of the catalyst. Experiments at low conversion showed that lactic acid reacts first over Pt(0.1 %)/Nb(2)O(5) to produce acetaldehyde and propanoic acid (along with CO and CO(2) in the gas phase). These compounds (less oxygenated than lactic acid but still reactive) are the key intermediates in the overall process, and they react differently depending on the nature of the catalyst support. In particular, reaction kinetics studies with propanoic acid as feed showed that Pt(0.1 %)/Nb(2)O(5) favored the formation of pentanones by ketonization reactions, whereas a monofunctional Pt(0.1 %)/carbon catalyst produced ethane and CO(x) by decomposition reactions. In the same manner, acetaldehyde was preferentially hydrogenated to ethanol over Pt(0.1 %)/carbon, whereas the presence of niobia allowed this intermediate to react (by successive aldol condensations) to form C(4)-C(7) condensation products stored in the organic phase. Finally, reaction pathways are proposed to explain the catalytic processing of lactic acid over bifunctional Pt(0.1 %)/Nb(2)O(5). In this scheme, metal sites catalyze hydrogenation reactions and niobia promotes C--C coupling processes (ketonization and aldol condensation), in contrast to C--C cleavage reactions which take place preferentially over Pt(0.1 %)/carbon and lead to loss of carbon in the gas effluent as CO, CO(2), and methane.

The effect of Zn location and reduction temperature have been studied on pure and Zn-modified MCM-41 supported Pt catalysts. Experimental results show that incorporation of Zn into the siliceous framework of the MCM-41 material introduces structural oxidized Zn centres with a high stability towards a reduction treatment even at high temperatures. XP spectra confirm the high stability of these Zn species although, at the highest reduction temperature (723 K), a high mobility of the doping cations from structural positions to the inner wall of the mesopores is observed. Catalytic studies in the chemoselective hydrogenation of crotonaldehyde show that the presence of Zn produces an important decrease in the catalytic activity of the Pt nanoparticles, in accordance with Pt dispersion measurements. However, the presence of Zn improves the selectivity towards the formation of crotyl alcohol. Compared with a conventional impregnated PtZn/MCM-41 catalyst, structural Zn centres in the doped Pt/ZnMCM-41 catalysts exhibit a higher polarizing/activation of the carbonyl double bond giving rise to a higher yield to crotyl alcohol, the product of interest. Additionally, these Zn-modified MCM-41-based Pt catalysts show an excellent behaviour in an important industrial reaction such as the dehydrogenation of iso-butane to iso-butene, with a selectivity of 100%, which remains stable with time on stream.

A new material constituted by cerium dioxide highly dispersed on activated carbon (CeO 2 /AC) was prepared by an impregnation method using cerium(III) nitrate as CeO 2 precursor. In order to evaluate the degree of ceria dispersion on the carbon support, CeO 2 /AC was characterized by a number of techniques: thermogravimetry coupled with a mass spectrometer (TG-MS), N 2 adsorption at 77 K, temperature-programmed desorption (TPD), temperature-programmed reduction (TPR) and transmission electron microscopy (TEM). The analysis of the decomposition process under inert atmosphere indicated that cerium nitrate decomposes at 440–460 K, with the evolution of NO. Furthermore, this process produces an additional oxidation of the carbon surface (with evolution of N 2 O) and the subsequent onset of new oxygen surface groups, detected by means of temperature-programmed desorption. The ceria deposition process takes place with a decrease in the N 2 adsorption capacity of the starting carbon support, and the analysis of the pore size distribution showed that the majority of ceria particles are situated at the most internal part of the carbon porosity. The temperature-programmed reduction profile of CeO 2 /AC was very different to that shown by unsupported CeO 2 , with only one continuous reduction process at low temperatures (800–900 K). Finally, TEM pictures gave direct evidence that ceria is highly dispersed on the carbon surface, with a narrow CeO 2 particle distribution centred around 3 nm.