Improved O2-assisted styrene synthesis by double-function purification of SWCNT catalyst

The catalytic performance of SWCNT was notably improved in the oxidative dehydrogenation of ethylbenzene (EB) to styrene (ST) upon a double-function purification in one step of the raw SWCNT. This consists of lowering the MeOx concentration and generating surface C=O groups after processing it in nitric acid at controlled conditions, while preserving the structure. The textural improvement was ascribed to the cutting of the tubes/bundles by oxidation and to MeOx removal itself (dilution effect). Both EB conversion and ST selectivity increased with a parallel lowering of the undesired COx selectivity. The conversion was interpreted by the enhancement of the intrinsic properties (i.e., more surface ketonic groups) but also to the higher load of SWCNT in the bed upon purification; both factors contribute to a higher number of active sites (C=O) in the bed for styrene formation. The most purified catalyst underperformed in conversion once the purification altered the SWCNT structure notably. Thus, preserving the structure is an important condition to achieve high conversion and yield. The better selectivity was explained in two ways; more styrene-forming sites (C=O) or less COx-forming sites (uncoated MeOx) in the bed, or both. The styrene yield per catalyst volume was improved by an average of ca. 240 % in comparison to the non-purified SWCNT. Deactivation is critical in maximizing the purification effect on the intrinsic and volumetric yields. In practical terms, the purification method proved to enhance the reaction; the selectivity towards the unwanted COx was significantly lowered with a gain towards styrene, achieving comparable selectivity values as in the conventional process, but operated at much lower temperature

Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution

We propose the treatment of barley straw with 1-ethyl-3-methylimidazolium acetate [EMIMAcO] ionic liquids (ILs) and subsequent precipitation with antisolvent mixtures, thus allowing the separation of the sugar-rich fractions (cellulose and hemicellulose) from the lignin fraction. For this purpose, different concentration ranges of acetone:water antisolvent mixtures were studied. In all cases, a high recovery percentage and a high and effective separation of fractions was achieved for 1:1 acetone:water. The fractionated lignocellulosic compounds were studied by using infrared spectroscopy, scanning electron microscopy and 1H nuclear magnetic resonance characterization techniques. This method allows the possibility of reusing IL, confirming the versatility of the established method. The fraction rich in cellulose and hemicellulose was subjected to acid hydrolysis (0.2 mol/L H2SO4) for 5 h at 140 °C, obtaining a yield of total reducing sugars of approximately 80%, much higher than those obtained in non-pretreated samples.This research was funded by Comunidad de Madrid (Spain) and ERDF (European Regional Development Fund), grant numbers S2013/MAE-2882 (RESTOENE-2-CM), S2018/EMT-4344 (BIOTRES-CM) and CSIC (201880E029). M.L.-S. acknowledges the support of the European Social Fund and Community of Madrid for her contracPeer reviewe

Modulating charge carrier density and mobility in doped graphene by covalent functionalization

[EN] Covalent B-functionalization of B-doped graphene has been performed for the first time. The electronic properties and Hall effect of functionalized N- and B-doped graphene can be tuned by tailoring the electron-donating/-withdrawing properties of the organic addend.The authors appreciate support from the Ministerio de Economia y Competitividad (MINECO) of Spain (projects CTQ2015-69153-CO2-1, CTQ2016-79189-R and MAT2015-69669-P) and the Junta de Comunidades de Castilla-La Mancha (project SBPLY/17/180501/000254). L. M. A. thanks MINECO (CTQ2016-79189-R) for a doctoral FPI grant.Arellano, LM.; Yue, S.; Atienzar Corvillo, PE.; Gómez-Escalonilla, MJ.; Ortega Higueruelo, FJ.; Fierro, JLG.; García Gómez, H.... (2019). Modulating charge carrier density and mobility in doped graphene by covalent functionalization. Chemical Communications. 55(67):9999-10002. https://doi.org/10.1039/c9cc04571fS9999100025567Wang, X., Sun, G., Routh, P., Kim, D.-H., Huang, W., & Chen, P. (2014). Heteroatom-doped graphene materials: syntheses, properties and applications. Chem. Soc. Rev., 43(20), 7067-7098. doi:10.1039/c4cs00141aLavorato, C., Primo, A., Molinari, R., & Garcia, H. (2013). N-Doped Graphene Derived from Biomass as a Visible-Light Photocatalyst for Hydrogen Generation from Water/Methanol Mixtures. Chemistry - A European Journal, 20(1), 187-194. doi:10.1002/chem.201303689Latorre-Sánchez, M., Primo, A., & García, H. (2013). P-Doped Graphene Obtained by Pyrolysis of Modified Alginate as a Photocatalyst for Hydrogen Generation from Water-Methanol Mixtures. Angewandte Chemie International Edition, 52(45), 11813-11816. doi:10.1002/anie.201304505Duan, J., Chen, S., Jaroniec, M., & Qiao, S. Z. (2015). Heteroatom-Doped Graphene-Based Materials for Energy-Relevant Electrocatalytic Processes. ACS Catalysis, 5(9), 5207-5234. doi:10.1021/acscatal.5b00991Putri, L. K., Ong, W.-J., Chang, W. S., & Chai, S.-P. (2015). Heteroatom doped graphene in photocatalysis: A review. Applied Surface Science, 358, 2-14. doi:10.1016/j.apsusc.2015.08.177Niu, L., Li, Z., Hong, W., Sun, J., Wang, Z., Ma, L., … Yang, S. (2013). Pyrolytic synthesis of boron-doped graphene and its application as electrode material for supercapacitors. Electrochimica Acta, 108, 666-673. doi:10.1016/j.electacta.2013.07.025Sahoo, M., Sreena, K. P., Vinayan, B. P., & Ramaprabhu, S. (2015). Green synthesis of boron doped graphene and its application as high performance anode material in Li ion battery. Materials Research Bulletin, 61, 383-390. doi:10.1016/j.materresbull.2014.10.049Khai, T. V., Na, H. G., Kwak, D. S., Kwon, Y. J., Ham, H., Shim, K. B., & Kim, H. W. (2012). Comparison study of structural and optical properties of boron-doped and undoped graphene oxide films. Chemical Engineering Journal, 211-212, 369-377. doi:10.1016/j.cej.2012.09.081Osumi, S., Saito, S., Dou, C., Matsuo, K., Kume, K., Yoshikawa, H., … Yamaguchi, S. (2016). Boron-doped nanographene: Lewis acidity, redox properties, and battery electrode performance. Chemical Science, 7(1), 219-227. doi:10.1039/c5sc02246kXu, Q., Jiang, X., Zhu, W., Chen, C., Hu, G., & Li, Q. (2016). Synthesis, preliminary biological evaluation and 3D-QSAR study of novel 1,5-disubstituted-2(1H)-pyridone derivatives as potential anti-lung cancer agents. Arabian Journal of Chemistry, 9(5), 721-735. doi:10.1016/j.arabjc.2015.08.001Pimenta, M. A., Dresselhaus, G., Dresselhaus, M. S., Cançado, L. G., Jorio, A., & Saito, R. (2007). Studying disorder in graphite-based systems by Raman spectroscopy. Phys. Chem. Chem. Phys., 9(11), 1276-1290. doi:10.1039/b613962kVoggu, R., Rout, C. S., Franklin, A. D., Fisher, T. S., & Rao, C. N. R. (2008). Extraordinary Sensitivity of the Electronic Structure and Properties of Single-Walled Carbon Nanotubes to Molecular Charge-Transfer. The Journal of Physical Chemistry C, 112(34), 13053-13056. doi:10.1021/jp805136eBiswal, M., Zhang, X., Schilter, D., Lee, T. K., Hwang, D. Y., Saxena, M., … Ruoff, R. S. (2017). Sodide and Organic Halides Effect Covalent Functionalization of Single-Layer and Bilayer Graphene. Journal of the American Chemical Society, 139(11), 4202-4210. doi:10.1021/jacs.7b00932Vizuete, M., Gómez-Escalonilla, M. J., Fierro, J. L. G., Ohkubo, K., Fukuzumi, S., Yudasaka, M., … Langa, F. (2014). Photoinduced electron transfer in a carbon nanohorn–C60 conjugate. Chemical Science, 5(5), 2072. doi:10.1039/c3sc53342eAllongue, P., Delamar, M., Desbat, B., Fagebaume, O., Hitmi, R., Pinson, J., & Savéant, J.-M. (1997). Covalent Modification of Carbon Surfaces by Aryl Radicals Generated from the Electrochemical Reduction of Diazonium Salts. Journal of the American Chemical Society, 119(1), 201-207. doi:10.1021/ja963354sBarrejón, M., Gómez-Escalonilla, M. J., Fierro, J. L. G., Prieto, P., Carrillo, J. R., Rodríguez, A. M., … Langa, F. (2016). Modulation of the exfoliated graphene work function through cycloaddition of nitrile imines. Physical Chemistry Chemical Physics, 18(42), 29582-29590. doi:10.1039/c6cp05285aBarrejón, M., Primo, A., Gómez-Escalonilla, M. J., Fierro, J. L. G., García, H., & Langa, F. (2015). Covalent functionalization of N-doped graphene by N-alkylation. Chemical Communications, 51(95), 16916-16919. doi:10.1039/c5cc06285cSu, C.-Y., Xu, Y., Zhang, W., Zhao, J., Tang, X., Tsai, C.-H., & Li, L.-J. (2009). Electrical and Spectroscopic Characterizations of Ultra-Large Reduced Graphene Oxide Monolayers. Chemistry of Materials, 21(23), 5674-5680. doi:10.1021/cm902182

H2 oxidation versus organic substrate oxidation in non-heme iron mediated reactions with H2O2

Herein we show that species generated upon reaction of α-[Fe(CF3SO3)2(BPMCN)] (BPMCN = N,N′-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane) with H2O2 (putatively [FeV(O)(OH)(BPMCN)]) is able to efficiently oxidize H2 to H2O even in the presence of organic substrates, while species formed in the presence of acetic acid (putatively [FeV(O)(OAc)(BPMCN)]) prefer organic substrate oxidation over H2 activation. Mechanistic implications have been analysed with the aid of computational methodsThis work was supported by Spanish Ministerio de Economia y Competitividad (CTQ2012-37420-C02-02 and 01) European Research Council (StG 239910), and Generalitat de Catalunya (2014 SGR 862 and ICREA Academia award to MC). J.Ll.-F. thanks the CELLEX foundation for the starting career program for financial suppor

El pirocloro (H3O)NbWO6-nH2O como catalizador para la deshidratación de Fructosa a 5-hidroximetilfurfural (HMF)

5-hidroximetilfurfural (HMF) es una importante molécula plataforma en la síntesis de diversos productos químicos. En este trabajo, informamos la deshidratación de fructosa a HMF en un sistema bifásico que contiene H2O y MIBK-2-ButOH como fase orgánica y (H3O)NbWO6-nH2O con estructura pirocloro como catalizador. El pirocloro se preparó por química del estado sólido a partir del precursor KNbWO6, seguido de un intercambio iónico en ácido sulfúrico. Este sólido exhibió una alta acidez, demostrando ser activo como catalizador ácido en la deshidratación de fructosa a (HMF). El catalizador es muy estable, ya que no se observó lixiviación de especies de niobio y wolframio a la fase líquida. Los resultados mostraron que el catalizador tiene un efecto catalítico sinérgico positivo en la conversión de fructosa a HMF. El rendimiento más alto de HMF del 33 % se logró a 150 ° C durante 90 min.Fil: Mayer, Sergio Federico. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación en Nanociencia y Nanotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Falcon, Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Poncio, Carlos Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Ribotta, Pablo Daniel. Universidad Nacional de Córdoba. Secretaría de Ciencia y Tecnología. Instituto Superior de Investigación, Desarrollo y Servicio de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Perez, Susana. Instituto de Ciencia de Materiales de Madrid; EspañaFil: Morales delaRosa, Silvia. Instituto de Ciencia de Materiales de Madrid; EspañaFil: Campos Martín, José M.. Instituto de Ciencia de Materiales de Madrid; EspañaFil: Alonso, José Antonio. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; EspañaFil: Fierro, José Luis G.. Instituto de Ciencia de Materiales de Madrid; EspañaXXI Congreso Argentino de Catálisis y X Congreso de Catálisis del MercosurSanta FeArgentinaSociedad Argentina de CatálisisInstituto de Investigaciones en Catálisis y PetroquímicaInstituto de Desarrollo Tecnológico para la Industria Químic

Spatially heterogeneous ages in glassy dynamics

We construct a framework for the study of fluctuations in the nonequilibrium relaxation of glassy systems with and without quenched disorder. We study two types of two-time local correlators with the aim of characterizing the heterogeneous evolution: in one case we average the local correlators over histories of the thermal noise, in the other case we simply coarse-grain the local correlators. We explain why the former describe the fingerprint of quenched disorder when it exists, while the latter are linked to noise-induced mesoscopic fluctuations. We predict constraints on the pdfs of the fluctuations of the coarse-grained quantities. We show that locally defined correlations and responses are connected by a generalized local out-of-equilibrium fluctuation-dissipation relation. We argue that large-size heterogeneities in the age of the system survive in the long-time limit. The invariance of the theory under reparametrizations of time underlies these results. We relate the pdfs of local coarse-grained quantities and the theory of dynamic random manifolds. We define a two-time dependent correlation length from the spatial decay of the fluctuations in the two-time local functions. We present numerical tests performed on disordered spin models in finite and infinite dimensions. Finally, we explain how these ideas can be applied to the analysis of the dynamics of other glassy systems that can be either spin models without disorder or atomic and molecular glassy systems.Comment: 47 pages, 60 Fig

Energías renovables: tecnologías de producción, almacenamiento y uso

Trabajo presentado en el Ciclo de conferencias del 75 Aniversario del CSIC, celebrado en Madrid (España) el 20 de noviembre de 2014.Se describe la génesis de la investigación sobre energías renovables en el CSIC desde el año 2000. Particularmente se hace énfasis en los desarrollos alcanzados por distintos grupos de investigación en la generación de hidrógeno a partir de precursores renovablesPeer Reviewe

Direct synthesis of hydrogen peroxide without the use of acids or halide promoters in dissolution

[EN] We show the first catalyst family able to produce hydrogen peroxide at concentrations higher than 5 wt% in the absence of any promoter or stabilizing agent in dissolution. The catalysts are composed of palladium supported on bifunctionalized silica or resin with acidic groups and bromide.The authors acknowledge financial support from Solvay (Brussels, Belgium). We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe