Structure-reactivity relationship in isolated Zr sites present in Zr-zeolite and ZrO2 for the Meerwein-Ponndorf-Verley reaction

[EN] The influence of the crystallographic phase of ZrO2 on its catalytic performance in the MPV reduction of cyclohexanone with propan-2-ol has been systematically investigated by combining accurate synthesis procedures, XRD and HRTEM characterization, kinetic measurements and DFT calculations, and compared to that of Zr-beta zeolite. The higher intrinsic activity of monoclinic zirconia as compared to other ZrO2 phases is not due to a lower activation energy for the rate-determining step, but to an adequate distribution of reactant fragments on the catalyst surface, indicating a structure-activity relationship for this reaction when catalyzed by ZrO2 and also by Zr-beta zeolite. Inexpensive and stable ZrO2 catalysts for the MPV reaction have been obtained by controlling the crystallographic phase of the synthesized material.This work has been supported by the Spanish Government through the "Severo Ochoa Program" (SEV 2012-0267). The Electron Microscopy Service of the UPV is acknowledged for their help in sample characterization. The Red Espanola de Supercomputacion (RES) and Centre de Calcul de la Universitat de Valencia are gratefully acknowledged for computational facilities and technical assistance. F. Gonell is grateful to Ministerio de Educacion, Cultura y Deporte for a PhD grant (AP2010-2748).Gonell-Gómez, F.; Boronat Zaragoza, M.; Corma Canós, A. (2017). Structure-reactivity relationship in isolated Zr sites present in Zr-zeolite and ZrO2 for the Meerwein-Ponndorf-Verley reaction. Catalysis Science & Technology. 7(13):2865-2873. https://doi.org/10.1039/c7cy00567aS2865287371

Effect of the C-alpha substitution on the ketonic decarboxylation of carboxylic acids over m-ZrO2: the role of entropy

[EN] The kinetics of the ketonic decarboxylation of linear and branched carboxylic acids over m-ZrO2 as a catalyst has been investigated. The same apparent activation energy is experimentally determined for the ketonic decarboxylation of both linear pentanoic and branched 2-methyl butanoic acids, while the change in entropy for the rate-determining step differs by nearly 50 kJ mol(-1). These results show that the difference in reactivity between linear and branched acids is due to entropic effects, and is related to the probability of finding the reactant molecules adsorbed and activated in a suitable way on the catalyst surface.The authors thank MINECO (Consolider Ingenio 2010-MULTICAT, CSD2009-00050 and Severo Ochoa program, SEV-2012-0267), Generalitat Valenciana (PROMETEOII/2013/011 Project), and the Spanish National Research Council (CSIC, Es 2010RU0108) for financial support. Red Espanola de Supercomputacion (RES) and Centre de Calcul de la Universitat de Valencia are gratefully acknowledged for computational facilities and technical assistance. A. P., F. G. and B. O.-T. thank MINECO (Juan de la Cierva and FPU Programme) and CSIC (JAE Programme) for their fellowships, respectively. M. R. is grateful to the Generalitat Valenciana for a BEST 2015 fellowship.Oliver-Tomás, B.; Gonell-Gómez, F.; Pulido, A.; Renz, M.; Boronat Zaragoza, M. (2016). Effect of the C-alpha substitution on the ketonic decarboxylation of carboxylic acids over m-ZrO2: the role of entropy. Catalysis Science and Technology. 6(14):5561-5566. https://doi.org/10.1039/c6cy00395hS55615566614Friedel, C. (1858). Ueber s. g. gemischte Acetone. Annalen der Chemie und Pharmacie, 108(1), 122-125. doi:10.1002/jlac.18581080124W. L. Howard , in Encyclopedia of Chemical Technology (Kirk-Othmer), Wiley-Interscience, New York, 4th edn, 1998, vol. 1, pp. 176–194H. Siegel and M.Eggersdorfer, Ullmann's Encyclopedia of Industrial Chemistry, VCH, Weinheim, 1990Huber, G. W., Iborra, S., & Corma, A. (2006). Synthesis of Transportation Fuels from Biomass:  Chemistry, Catalysts, and Engineering. Chemical Reviews, 106(9), 4044-4098. doi:10.1021/cr068360dCorma, A., Iborra, S., & Velty, A. (2007). Chemical Routes for the Transformation of Biomass into Chemicals. Chemical Reviews, 107(6), 2411-2502. doi:10.1021/cr050989dChheda, J. N., Huber, G. W., & Dumesic, J. A. (2007). Liquid-Phase Catalytic Processing of Biomass-Derived Oxygenated Hydrocarbons to Fuels and Chemicals. Angewandte Chemie International Edition, 46(38), 7164-7183. doi:10.1002/anie.200604274Renz, M. (2005). Ketonization of Carboxylic Acids by Decarboxylation: Mechanism and Scope. European Journal of Organic Chemistry, 2005(6), 979-988. doi:10.1002/ejoc.200400546Corma, A., Renz, M., & Schaverien, C. (2008). Coupling Fatty Acids by Ketonic Decarboxylation Using Solid Catalysts for the Direct Production of Diesel, Lubricants, and Chemicals. ChemSusChem, 1(8-9), 739-741. doi:10.1002/cssc.200800103Pham, T. N., Sooknoi, T., Crossley, S. P., & Resasco, D. E. (2013). Ketonization of Carboxylic Acids: Mechanisms, Catalysts, and Implications for Biomass Conversion. ACS Catalysis, 3(11), 2456-2473. doi:10.1021/cs400501hSerrano-Ruiz, J. C., Wang, D., & Dumesic, J. A. (2010). Catalytic upgrading of levulinic acid to 5-nonanone. Green Chemistry, 12(4), 574. doi:10.1039/b923907cAlonso, D. M., Bond, J. Q., & Dumesic, J. A. (2010). Catalytic conversion of biomass to biofuels. Green Chemistry, 12(9), 1493. doi:10.1039/c004654jCorma, A., Oliver-Tomas, B., Renz, M., & Simakova, I. L. (2014). Conversion of levulinic acid derived valeric acid into a liquid transportation fuel of the kerosene type. Journal of Molecular Catalysis A: Chemical, 388-389, 116-122. doi:10.1016/j.molcata.2013.11.015Rajadurai, S. (1994). Pathways for Carboxylic Acid Decomposition on Transition Metal Oxides. Catalysis Reviews, 36(3), 385-403. doi:10.1080/01614949408009466Gliński, M., Kijeński, J., & Jakubowski, A. (1995). Ketones from monocarboxylic acids: Catalytic ketonization over oxide systems. Applied Catalysis A: General, 128(2), 209-217. doi:10.1016/0926-860x(95)00082-8Pestman, R., Koster, R. M., van Duijne, A., Pieterse, J. A. Z., & Ponec, V. (1997). Reactions of Carboxylic Acids on Oxides. Journal of Catalysis, 168(2), 265-272. doi:10.1006/jcat.1997.1624Parida, K., & Mishra, H. K. (1999). Catalytic ketonisation of acetic acid over modified zirconia. Journal of Molecular Catalysis A: Chemical, 139(1), 73-80. doi:10.1016/s1381-1169(98)00184-8Hendren, T. S., & Dooley, K. M. (2003). Kinetics of catalyzed acid/acid and acid/aldehyde condensation reactions to non-symmetric ketones. Catalysis Today, 85(2-4), 333-351. doi:10.1016/s0920-5861(03)00399-7Martinez, R. (2004). Ketonization of acetic acid on titania-functionalized silica monoliths. Journal of Catalysis, 222(2), 404-409. doi:10.1016/j.jcat.2003.12.002Pulido, A., Oliver-Tomas, B., Renz, M., Boronat, M., & Corma, A. (2012). Ketonic Decarboxylation Reaction Mechanism: A Combined Experimental and DFT Study. ChemSusChem, 6(1), 141-151. doi:10.1002/cssc.201200419Ignatchenko, A. V., DeRaddo, J. S., Marino, V. J., & Mercado, A. (2015). Cross-selectivity in the catalytic ketonization of carboxylic acids. Applied Catalysis A: General, 498, 10-24. doi:10.1016/j.apcata.2015.03.017Ignatchenko, A. V., & Kozliak, E. I. (2012). Distinguishing Enolic and Carbonyl Components in the Mechanism of Carboxylic Acid Ketonization on Monoclinic Zirconia. ACS Catalysis, 2(8), 1555-1562. doi:10.1021/cs3002989Ignatchenko, A. V. (2011). Density Functional Theory Study of Carboxylic Acids Adsorption and Enolization on Monoclinic Zirconia Surfaces. The Journal of Physical Chemistry C, 115(32), 16012-16018. doi:10.1021/jp203381hJackson, M. A., & Cermak, S. C. (2012). Cross ketonization of Cuphea sp. oil with acetic acid over a composite oxide of Fe, Ce, and Al. Applied Catalysis A: General, 431-432, 157-163. doi:10.1016/j.apcata.2012.04.034Plint, N. ., Coville, N. ., Lack, D., Nattrass, G. ., & Vallay, T. (2001). The catalysed synthesis of symmetrical ketones from alcohols. Journal of Molecular Catalysis A: Chemical, 165(1-2), 275-281. doi:10.1016/s1381-1169(00)00445-3Randery, S. (2002). Cerium oxide-based catalysts for production of ketones by acid condensation. Applied Catalysis A: General, 226(1-2), 265-280. doi:10.1016/s0926-860x(01)00912-

Copper-doped titania photocatalysts for simultaneous reduction of CO2 and production of H-2 from aqueous sulfide

Copper-doped titanium dioxide materials with anatase phase (Cu-TiO2, atomic Cu contents ranging from 0 to 3% relative to the sum of Cu and Ti), and particle sizes of 12-15 nm, were synthesised by a solvo-thermal method using ethanol as the solvent and small amounts of water to promote the hydrolysiscondensation processes. Diffuse reflectance UV-vis spectroscopy show that the edges of absorption of the titania materials are somewhat shifted to higher wavelengths due to the presence of Cu. X-ray photoelectron spectroscopy (XPS) indicate that Cu(II) is predominant. Photocatalytic CO2 reduction experiments were performed in aqueous Cu-TiO2 suspensions under UV-rich light and in the presence of different solutes. Sulfide was found to promote the efficient production of H-2 from water and formic acid from CO2. The effect of the Cu content on the photoactivity of Cu-TiO2 was also studied, showing that copper plays a role on the photocatalytic reduction of CO2.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2012-32315) is gratefully acknowledged. F.G. and B.J.-L. are thankful for financial support from Spanish Government (AP2010-2748 PhD grant and MAT2011-27008 project) and Jaume I University (P1 1B2014-21 project). SCIC from Jaume I University and Servicio de Microscopia Electronica at Universitat Politecnica de Valencia are also acknowledged for instrumental facilities. A.V.P. is grateful to both the Consejo Superior de Investigaciones Cientifficas (CSIC) and the European Social Fund (ESF) for a JAE-Doc postdoctoral grant. Lichen Liu is gratefully acknowledged for assistance in recording HRTEM images.Gonell-Gómez, F.; Puga Vaca, A.; Julián López, B.; García Gómez, H.; Corma Canós, A. (2016). Copper-doped titania photocatalysts for simultaneous reduction of CO2 and production of H-2 from aqueous sulfide. Applied Catalysis B: Environmental. 180:263-270. https://doi.org/10.1016/j.apcatb.2015.06.019S26327018

Structure–activity relationship in Ti phosphate-derived photocatalysts for H2 evolution

[EN] Photocatalytic H2 production has emerged as one of the most clean and promising renewable energy sources. In spite of the efforts to obtain efficient photocatalysts able to produce H2 from Sun light and water, there is still the need to prepare cheaper and environmental friendlier photocatalysts. Phosphate-based materials could be good candidates to fulfill these requirements. In this manuscript we have prepared a set of mixed Ti3+/Ti4+ valence, open-framework titanium phosphates (of-TiPO4) and mixed titanium oxide/phosphate derivatives (cr-TiP), correlating their structure and composition with the photocatalytic activity for H2 production. We determined that mixed titanium oxide/phosphate crystalline phases produced enhanced H2 evolution under Sun simulated light irradiation than mixed Ti3+/Ti4+ valence, open-framework titanium phosphates and titanium oxide phases.Financial support by the Spanish Ministry of Economy and competitiveness (CIQ2015-69153-C2-1-R) is gratefully acknowledged.Mateo-Mateo, D.; Gonell-Gómez, F.; Albero-Sancho, J.; Corma Canós, A.; García Gómez, H. (2017). Structure–activity relationship in Ti phosphate-derived photocatalysts for H2 evolution. Journal of Energy Chemistry. 26(2):295-301. https://doi.org/10.1016/j.jechem.2016.09.016S29530126

Isolated Fe(III)-O Sites Catalyze the Hydrogenation of Acetylene in Ethylene Flows under Front-End Industrial Conditions

[EN] The search for simple, earth-abundant, cheap, and nontoxic metal catalysts able to perform industrial hydrogenations is a topic of interest, transversal to many catalytic processes. Here, we show that isolated FeIII¿O sites on solids are able to dissociate and chemoselectively transfer H2 to acetylene in an industrial process. For that, a novel, robust, and highly crystalline metal¿organic framework (MOF), embedding FeIII¿OH2 single sites within its pores, was prepared in multigram scale and used as an efficient catalyst for the hydrogenation of 1% acetylene in ethylene streams under front-end conditions. Cutting-edge X-ray crystallography allowed the resolution of the crystal structure and snapshotted the single-atom nature of the catalytic FeIII¿O site. Translation of the active site concept to even more robust and inexpensive titania and zirconia supports enabled the industrially relevant hydrogenation of acetylene with similar activity to the Pd-catalyzed process.This work was supported by the MINECO (Spain) (Projects CTQ2016-75671-P, CTQ2014-56312-P, CTQ2014-55178-R, and Excellence Units "Severo Ochoa" and "Maria de Maeztu" SEV-2016-0683 and MDM-2015-0538) and the Ministero dell'Istruzione, dell'Universita e della Ricerca (Italy) (FFABR 2017). M.M. thanks the mineco for a predoctoral contract. Thanks are also extended to the Ramon y Cajal Program (E.P.) and the "Suprograma atraccio de talent-contractes postdoctorals de la Universitat de Valencia" (J.F.-S.). A.L.-P. and J.F.S. also thank fBBVA for the concession of a young investigator grants.Tejeda-Serrano, M.; Mon, M.; Ross, B.; Gonell-Gómez, F.; Ferrando-Soria, J.; Corma Canós, A.; Leyva Perez, A.... (2018). Isolated Fe(III)-O Sites Catalyze the Hydrogenation of Acetylene in Ethylene Flows under Front-End Industrial Conditions. Journal of the American Chemical Society. 140(28):8827-8832. https://doi.org/10.1021/jacs.8b04669S882788321402

Design of new nanomaterials for their use in catalysis and photochemistry

Durante el trabajo realizado en la presente tesis doctoral, se han diseñado y desarrollado nuevos nanomateriales para su uso en catálisis, fotocatálisis y fotoquímica. El capítulo 2, se ha centrado en la síntesis y caracterización de nanomateriales basados en ZrO2 y WOx-ZrO2 obtenidos mediante síntesis microondas. Además se han evaluado sus propiedades catalíticas en diferentes reacciones. El capítulo 3, trata sobre el diseño de nanocatalizadores para hidrogenaciones selectivas, cuyo contenido es confidencial. En el capítulo 4 se han desarrollado nanomateriales basado en Cu-TiO2 para la fotoreducción de CO2 y purificación de agua. Además se han introducido partículas de Er,Yb:Y2O3 conversoras de energía en fotoánodos para mejor aprovechamiento del espectro solar y producción de H2. Finalmente en el capítulo 4, se han introducido nanopartículas conversoras de energía basadas en Er,Yb:ZrO2 y ErTm,Yb:NaYF4 en nanocompuestos híbridos de diureasil y PDMS, respectivamente, y sus propiedades estructurales y ópticas fueron estudiadas en profundidad.The present PhD Thesis deals about the design and development of new nanomaterials for their use in catalysis, photocatalysis and photochemistry. Chapter 2 has devoted to the synthesis and characterization of ZrO2 and WOx-ZrO2 obtained by microwave synthesis. Moreover their catalytic properties have been tested in several reactions. Chapter 3 is focused on nanocatalysts design for selective hydrogenations, whose content is confidential. Chapter 4 deals about the synthesis of Cu-TiO2 for the simultaneous CO2 photoreduction and sulfide abatement. Moreover, upconverting particles based on Er,Yb:Y2O3 have been introduced in fotoanodes for a better solar spectrum profit. Finally, in chapter 4 Er,Yb:ZrO2 y ErTm,Yb:NaYF4 based upconversion nanoparticles were introduced in hybrid nanocomposites made of diureasil and PDMS, respectively, and their optical and structural properties were further studied.Programa de Doctorat en Cièncie

Hydroxyapatites as Versatile Inorganic Hosts of Unusual Pentavalent Manganese Cations

Contrary to molecular species, only very few solids are reported to host manganese (V) species. Herein, we report three new compounds with a hydroxyapatite structural backbone built on the MnVO4 3− anion: Sr5[(Mn1−xSix)O4]3(OH)1−3x (x = 0 and 0.053), Sr5(MnO4)3(OH)1−yFy (y = 0.90), and Sr5[(Mn1−xSix)- O4]3F1−3x (x = 0.058). These solids are fully characterized using powder X-ray and neutron powder diffraction, scanning transmission electron microscopy, electron energy loss spectroscopy (EELS), thermogravimetric analysis, and magnetic measurements. Especially, we report for the first time EELS Mn−L2,3 spectra of manganese with the oxidation state (V). Contrary to other Mn(V) oxides, these solids and the nominal compound Sr5(MnO4)3OH do not comprise Ba2+ cations but rely only on Sr2+ cations, showing that barium is not a required element to stabilize Mn(V) species in inorganic solids. We show that by tuning soft chemistry conditions on the one hand and post-treatment topological transformation conditions on the other hand, Mn(V) and hydroxyl groups can be substituted by Si(IV) and fluoride ions, respectively. Hence, we deliver solids with a potentially wide composition range. These compounds show significant oxygen anionic conduction, thus suggesting the emergence of new functional materials built from high-oxidation state manganese cations.Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEpu