Hydrothermal carbonization of biomass as a route for the sequestration of CO2: Chemical and structural properties of the carbonized products

A highly functionalized carbonaceous material (hydrochar) was obtained by means of the hydrothermal carbonization (250 °C) of two representative types of biomass, i.e. eucalyptus sawdust and barley straw. This product has a brown colour; it contains around 50–60% of the carbon originally present in the biomass and it is composed of particles that retain the cellular appearance of the raw material. These particles are covered by microspheres (1–10 μm) which were probably formed as a consequence of the transformation of the cellulose fraction. From a chemical point of view, the hydrochar products have a high degree of aromatization and they contain a large amount of oxygen-containing groups (i.e. carbonyl, carboxylic, hydroxyl, quinone, ester, etc) as was confirmed by Raman, IR and XPS spectroscopic techniques. The presence of these oxygen functionalities on the surface of the hydrochar particles explains their high water affinity (hydrophilic properties). On the basis of the highly condensed chemical nature of the hydrochar products, we postulated that this material has a recalcitrant nature that could lead to a significant increase in carbon turnover time in relation to the biomass. This suggests an important route for the sequestration of CO2 present in the atmosphere.The financial support for this research work provided by the Spanish MCyT (MAT2008-00407) is gratefully acknowledged. M. S. and J. A. M.-A. acknowledge the assistance of the Spanish MCyT for the award of a Postdoctoral Mobility contract and a Juan de la Cierva contract, respectively.Peer reviewe

Synthesis of high surface area TiO2 nanoparticles by mild acid treatment with HCl or HI for photocatalytic propene oxidation

Nanostructured TiO2 photocatalysts with small crystalline sizes have been synthesized by sol-gel using the amphiphilic triblock copolymer Pluronic P123 as template. A new synthesis route, based on the treatment of TiO2 xerogels with acid-ethanol mixtures in two different steps, synthesis and extraction-crystallization, has been investigated, analyzing two acids, hydrochloric and hydriodic acid. As reference, samples have also been prepared by extraction-crystallization in ethanol, being these TiO2 materials amorphous and presenting higher porosities. The prepared materials present different degrees of crystallinity depending on the experimental conditions used. In general, these materials exhibit high surface areas, with an important contribution of microporosity and mesoporosity, and with very small size anatase crystals, ranging from 5 to 7 nm. The activity of the obtained photocatalysts has been assessed in the oxidation of propene in gas phase at low concentration (100 ppmv) under a UVA lamp with 365 nm wavelength. In the conditions studied, these photocatalysts show different activities in the oxidation of propene which do not depend on their surface areas, but on their crystallinity and band gap energies, being sample prepared with HCl both during synthesis and in extraction-crystallizations steps, the most active one, with superior performance than Evonik P25.M. Ouzzine thanks MAEC-AECID for a predoctoral fellowship. J.A. Maciá-Agulló acknowledges the assistance of the Spanish MCyT for their award of a Postdoctoral Juan de la Cierva contract. The authors thank Generalitat Valenciana (GVPRE/2008/004, PROMETEO/2009/047), FEDER, MINECO (MAT2010-15273) and Office of the Vice President for Research, Development and Innovation of University of Alicante (UAUSTI10-08) for financial support

Gold-copper nanoalloys supported on TiO2 as photocatalysts for CO2 reduction by water

Commercial P25 modified by AuCu alloy nanoparticles as thin film exhibits, for CO2 reduction by water under sun simulated light, a rate of methane production above 2000 mu mol (g of photocatalyst)(-1) h(1). Although evolution of hydrogen is observed and O-2 and ethane detected, the selectivity of conduction band electrons for methane formation is almost complete, about 97%. This photocatalytic behavior is completely different from that measured for Au/P25 (hydrogen evolution) and Cu/P25 (lower activity, but similar methane selectivity). Characterization by TEM, XPS, and UVvis spectroscopy shows that Au and Cu are alloyed in the nanoparticles. FT-IR spectroscopy and chemical analysis have allowed one to detect on the photocatalyst surface the presence of CO2 center dot-, CuCO, and elemental C. Accordingly, a mechanism in which the role of Au is to respond under visible light and Cu binds to CO and directs the reduction pathway is proposed.This work has been supported by the Marie Curie project PIEF-GA-2011-298740. Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa CTQ 2012-32315) and the Generalidad Valenciana (Prometeo 2012/2013) is gratefully acknowledged. J.A.M.-A. acknowledges the assistance of the CSIC for their award of a Postdoctoral JAE-Doc contract.Neatu, S.; Maciá Agulló, JA.; Concepción Heydorn, P.; García Gómez, H. (2014). Gold-copper nanoalloys supported on TiO2 as photocatalysts for CO2 reduction by water. Journal of the American Chemical Society. 136(45):15969-15976. doi:10.1021/ja506433kS15969159761364

Comparative study of the micropore development on physical activation of carbon fibers from coal tar and petroleum pitches

Activated carbon fibres (ACFs) have been successfully prepared with a remarkable development of porosity from four isotropic coal tar pitches and four isotropic petroleum pitches. Special care has been put to make the activation process at similar activation rate in order to have a better comparison of the different precursors used. The micropore volumes of petroleum pitches-derived ACFs are higher than those obtained from coal tar pitches under similar activation yields. The resultant ACFs present interesting textural properties: they are essentially microporous materials, with a high adsorption capacity which increases linearly with the burn-off. It has been observed, independently of the pitch precursor used, that the micropore volume is a function of the degree of activation, being, in all the cases, quite similar for a given activation degree if a comprehensive weight loss is considered (carbonization lost and degree of activation).MEC and FEDER (CTQ2006-08958) and GV (GV/2007/144 and ARVIV/2007/063)

Microwave synthesis of microstructured and nanostructured metal chalcogenides from elemental precursors in phosphonium ionic liquids.

We describe a general approach for the synthesis of micro-/nanostructured metal chalcogenides from elemental precursors. The excellent solubility of sulfur, selenium, and tellurium in phosphonium ionic liquids promotes fast reactions between chalcogens and various metal powders upon microwave heating, giving crystalline products. This approach is green, universal, and scalable

Nanopigments in offset printing inks

Comunicación presentada en 36th IARIGAI International Research Conference, Stockholm, September 2009.Nanopigments are a new type of pigment. They are hybrid materials consisting of organic dyes and layered silicate nanoparticles. Nanopigments are already applied to make polymeric coatings and they had shown improvement in mechanical, thermal and stability properties of the substrate and dyes (Batenburg and Fischer, 2001). In this work, nanopigments had been synthesized to be applied in the manufacture of offset printing inks. Therefore, four different nanopigments are pursuit: cyan (C), magenta (M), yellow (Y), and black (K), in order to obtain primary colour for a four-colour-process system

Constructing Hierarchical Porous Zeolites via Kinetic Regulation

Zeolites are crystalline inorganic solids with microporous structures, having widespread applications in the fields of catalysis, separation, adsorption, microelectronics, and medical diagnosis. A major drawback of zeolites is the mass transfer limitation due to the small size of the micropores (less than 1 nm). Numerous efforts have been dedicated to integrating mesopores with the microporous zeolite structures by using templating and/or destructive approaches. Here we provide a new strategy for hierarchical pore size zeolite synthesis, without using supramolecular or hard templates. The branching epitaxial growth behavior, as a result of aluminum-zoning, contributes to the formation of the hierarchical porous zeolite structures

Contribution to characterisation of biochar to estimate the labile fraction of carbon

Different analytical techniques were used to find the most reliable and economic method for determining the labile fraction of C in biochar. Biochar was produced from pine, poplar and willow (PI, PO and WI, respectively) at two temperatures (400 and 550°C) and characterised using spectroscopic techniques [solid state 13C nuclear magnetic resonance spectroscopy (NMR)], molecular markers [pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS)], thermogravimetry (TG), elemental composition and wet oxidation (potassium permanganate and potassium dichromate). Short term incubation (110h) of an A horizon from an Umbrisol amended with the biochar samples at two doses (7.5 and 15tha-1) was also carried out to provide supplementary information on the influence of biochar-soil interaction on CO2 evolution. Spectroscopic analysis demonstrated that the degree of biochar carbonisation was influenced by the type of feedstock and heating conditions and followed the order WI-400<PI-400~WI-550~PO-400<PO-550<PI-550. The thermo-labile fraction of the biochar samples, estimated from TG, ranged between 21% and 49%. The fraction of total C oxidised with potassium permanganate (Cper/Ctotal) was <50gkg-1 in all cases, whereas potassium dichromate (Cdichro/Ctotal) oxidation efficiency ranged between 180 and 545gkg-1. For each type of feedstock, the highest values of either chemically or thermally degradable C corresponded to the biochar produced at low temperature. Results indicate that low cost methodologies, such as dichromate oxidation and TG, reflected the degree of biochar carbonisation, and could therefore be used to estimate the labile fraction of C in biochar. © 2011 Elsevier Ltd.The authors acknowledge financial support from the Ministry of Agriculture and Forestry of New Zealand. They would like to thank the staff of the Departmento Edafología y Química Agrícola, USC – Campus de Lugo, for the pressure plate measurements, and F. Jackson (Nutrition Laboratory, Massey University) for cellulose, hemicellulose and lignin content determination. R.C.P. was partly funded by the NZAGRC. J.A.M.-A. thanks the Spanish MCyT via the award of a Juan de la Cierva contract.Peer Reviewe

Desarrollo de tintas offset basadas en nanopigmentos: síntesis, formulación, ensayo y caracterización de propiedades

El presente proyecto, se ha centrado en el estudio de nuevas tintas de impresión para tecnología de impresión offset, en cuyas formulaciones se han incorporado nanopigmentos novedosos y ecológicos, y en la evaluación de su idoneidad para implementarlas industrialmente en un futuro cercano.Esta investigación ha sido financiada por el Instituto de la Mediana y Pequeña Empresa Valenciana, IMPIVA y cofinanciada por los Fondos europeos de Desarrollo Regional, FEDER