The impact of support surface area on the SMSI decoration effect and catalytic performance for Fischer-Tropsch synthesis of Co-Ru/TiO2-anatase catalysts

[EN] A series of Co-Ru/TiO2 catalysts (10 wt% Co, 0.5 wt% Ru, nominal loadings) were prepared by impregnation of TiO2-anatase supports synthesized with different specific surface areas (Ti-L: 53 m2 /g, Ti-M: 117 m2 /g, and Ti-H: 148 m2 /g) by tuning the conditions of the hydrothermal synthesis and/or the calcination treatments. The most relevant physicochemical properties of supports and catalysts were determined by a set of techniques including ICP-OES, XRD, N2 physisorption, electron microscopy (FESEM, HAADF-STEM, HR-TEM), H2-TPR, H2 chemisorption, and IR-CO. Oxidized precursors were reduced in-reactor under flowing pure H2 at 400 °C for 10 h and evaluated for Fischer-Tropsch synthesis (FTS) in a fixed bed reactor at 220 °C, 2.0 MPa, and H2/CO molar ratio of 2. These catalysts exhibited the well-known strong metal-support interaction (SMSI) effect reported for TiO2 materials by which partially reduced TiOx species formed during the catalyst reduction step migrate and decorate the surface of the supported metal phases. The extent to which the SMSI effect occurred was found to increase with the surface area of the TiO2-anatase carrier, as supported by H2 chemisorption, TEM, and IR-CO surface titration experiments. As a consequence, the activity per total mass of cobalt or cobalt-time-yield (CTY) of the Co-Ru/TiO2 catalysts gradually declined with the increase in support surface area: Co-Ru/Ti-L > Co-Ru/ Ti-M > Co-Ru/Ti-H. The catalysts, however, displayed similar initial TOFs, implying a negligible influence of the SMSI effect on the initial intrinsic activity of the surface Co0 sites. The high surface area Co-Ru/Ti-H catalyst exhibiting the most pronounced SMSI also presented the lowest C5+ selectivity. This behavior was explained by considering the contribution of two effects: the lower resistance to the intraparticle diffusion of ¿-olefins when increasing the support surface area, as inferred from the olefin-to-paraffin ratios and the values of the diffusionrelated parameter ¿, and the reduction in size of the cobalt ensembles on the terraces of Co0 nanoparticles, connected to the extent of SMSI, on which chain growth events are favored.Financial support by the MINECO of Spain through the Severo Ochoa (SEV 2012-0267) and ENE2014-5761-R projects is gratefully acknowledged. The authors also thank the Microscopy Service of the Universitat Politecnica de Valencia for its assistance in microscopy characterization. F. Bertella (Science without Frontiers - Process no. 13705/13-0) thanks CAPES for a predoctoral fellowship.Bertella, F.; Concepción Heydorn, P.; Martinez Feliu, A. (2017). The impact of support surface area on the SMSI decoration effect and catalytic performance for Fischer-Tropsch synthesis of Co-Ru/TiO2-anatase catalysts. Catalysis Today. 296:170-180. https://doi.org/10.1016/j.cattod.2017.05.001S17018029

Modulating the catalytic behavior of non-noble metal nanoparticles by inter-particle interaction for chemoselective hydrogenation of nitroarenes into corresponding azoxy or azo compounds

[EN] Aromatic azoxy compounds have wide applications and they can be prepared by stoichiometric or catalytic reactions with H2O2 or N2H4 starting from anilines or nitroarenes. In this work, we will present the direct chemoselective hydrogenation of nitroarenes with H-2 to give aromatic azoxy compounds under base-free mild conditions, with a bifunctional catalytic system formed by Ni nanoparticles covered by a few layers of carbon (Ni@C NPs) and CeO2 nanoparticles. The catalytic performance of Ni@C-CeO2 catalyst surpasses the state-of-art Au/CeO2 catalyst for the direct production of azoxybenzene from nitrobenzene. By means of kinetic and spectroscopic results, a bifunctional mechanism is proposed in which, the hydrogenation of nitrobenzene can be stopped at the formation of azoxybenzene with >95% conversion and >93% selectivity, or can be further driven to the formation of azobenzene with >85% selectivity. By making a bifunctional catalyst with a non-noble metal, one can achieve chemoselective hydrogenation of nitroarenes not only to anilines, but also to corresponding azoxy and azo compounds. (C) 2018 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).This work has been supported by the European Union through the SynCatMatch project (ERC-AdG-2014-671093). Financial supports by the Spanish Government-MINECO through the program "Severo Ochoa" (SEV-2016-0683) are gratefully acknowledged. The authors also thank the Microscopy Service of UPV for kind help with TEM and STEM measurements.Liu, L.; Concepción Heydorn, P.; Corma Canós, A. (2019). Modulating the catalytic behavior of non-noble metal nanoparticles by inter-particle interaction for chemoselective hydrogenation of nitroarenes into corresponding azoxy or azo compounds. Journal of Catalysis. 369:312-323. https://doi.org/10.1016/j.jcat.2018.11.011S31232336

TiO2 polymorph dependent SMSI effect in Co-Ru/TiO2 catalysts and its relevance to Fischer-Tropsch synthesis

[EN] Pure anatase and rutile TiO2 samples were synthesized by thermal treatment of reverse microemulsions and applied as supports for preparing Ru-promoted Co catalysts (0.5 wt% Ru, 10 wt% Co). The catalysts were characterized by ICP-OES,XRD,Raman spectroscopy, N2 physisorption, H2-TPR, electronmicroscopy (FESEM, HAADF-STEM), H2 chemisorption,XPS, and in situ IR-CO after H2 reduction and reaction with syngas, and their catalytic performance for Fischer-Tropsch synthesis (FTS) studied at industrial conditions (220 ¿C, 2.0 MPa, H2/CO = 2). The two catalysts exhibited comparable mean Co particle sizes (5¿6 nm) as well as high and alike degrees of cobalt reduction (ca. 90%). The SMSI decoration effect arising during H2 reduction was much more pronounced for the anatase-supported catalyst resulting in lower cobalt-timeyield (CTY) compared to that supported on TiO2-rutile. In situ IR-CO under syngas conversion conditions showed equivalent cobalt surface reconstruction and nature of the surface Co0 sites for both catalysts in their working state, and revealed a partial reversibility of the SMSI effect during FTS by which a significant fraction of the decorated Co0 centers in the anatase-based catalyst was uncovered and became available for reaction. The implication of this effect on TOFs is discussed. The C5+ selectivity was higher for the rutile-based catalyst, although a clear impact of the SMSI effect on selectivities was not inferred from our results.Financial support by the MINECO of Spain through the Severo Ochoa project (SEV 2012-0267) is gratefully ackonowledged. The authors also thank the Microscopy Service of the Universitat Politecnica de Valencia for its assistance in microscopy characterization. F. Bertella (Science without Frontiers - Process no. 13705/13-0) thanks CAPES for a predoctoral fellowship.Bertella, F.; Concepción Heydorn, P.; Martinez Feliu, A. (2017). TiO2 polymorph dependent SMSI effect in Co-Ru/TiO2 catalysts and its relevance to Fischer-Tropsch synthesis. Catalysis Today. 289:181-191. https://doi.org/10.1016/j.cattod.2016.08.008S18119128

Synthesis of borasiloxanes by oxidative hydrolysis of silanes and pinacolborane using Cu3(BTC)2 as a solid catalyst

[EN] A convenient method for the synthesis of borasiloxanes from silanes and pinacolboranes using Cu-3(BTC)(2) as a heterogeneous catalyst in acetonitrile at 70 degrees C is reported. This procedure is more convenient than Ru and Pd based homogeneous catalysts because it avoids the use of noble metals, easy handling of starting materials and the catalyst can be reused.AD thanks the University Grants Commission (UGC), New Delhi, for the award of an Assistant Professorship under its Faculty Recharge Programme. AD also thanks the Department of Science and Technology, India, for the financial support through Extra Mural Research Funding (EMR/2016/006500). Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2015-69153-CO2-1) is gratefully acknowledged.Dhakshinamoorthy, A.; Asiri, AM.; Concepción Heydorn, P.; García Gómez, H. (2017). Synthesis of borasiloxanes by oxidative hydrolysis of silanes and pinacolborane using Cu3(BTC)2 as a solid catalyst. Chemical Communications. 53(72):9998-10001. https://doi.org/10.1039/c7cc05221aS9998100015372Liu, W., Pink, M., & Lee, D. (2009). Conjugated Polymer Sensors Built on π-Extended Borasiloxane Cages. Journal of the American Chemical Society, 131(24), 8703-8707. doi:10.1021/ja902333pKhelevina, O. G., & Malyasova, A. S. (2014). Cross-linking of borosiloxane oligomers and properties of materials with vulcanized borosiloxane coating. Russian Journal of Applied Chemistry, 87(4), 480-484. doi:10.1134/s10704272140400144Puneet, P., Vedarajan, R., & Matsumi, N. (2016). Alternating Poly(borosiloxane) for Solid State Ultrasensitivity Toward Fluoride Ions in Aqueous Media. ACS Sensors, 1(10), 1198-1202. doi:10.1021/acssensors.6b00346Han, Y.-K., Yoo, J., & Yim, T. (2016). Distinct Reaction Characteristics of Electrolyte Additives for High-Voltage Lithium-Ion Batteries: Tris(trimethylsilyl) Phosphite, Borate, and Phosphate. Electrochimica Acta, 215, 455-465. doi:10.1016/j.electacta.2016.08.131Makarova, E. A., Shimizu, S., Matsuda, A., Luk’yanets, E. A., & Kobayashi, N. (2008). meso-Aryl tribenzosubporphyrin—a totally substituted subporphyrin species. Chemical Communications, (18), 2109. doi:10.1039/b801712cNeville, L. A., Spalding, T. R., & Ferguson, G. (2000). A Novel Borosilicate Cage Compound with an Incomplete B4Si4 Cube Structure: [(tBuSi)4(CH2=CHC6H4B)4O10]. Angewandte Chemie, 39(20), 3598-3601. doi:10.1002/1521-3773(20001016)39:203.0.co;2-aMingotaud, A.-F., Héroguez, V., & Soum, A. (1998). Synthesis of difunctional borasiloxanes and their behavior in metathesis reactions. Journal of Organometallic Chemistry, 560(1-2), 109-115. doi:10.1016/s0022-328x(98)00498-7Beckett, M. A., Rugen-Hankey, M. P., & Sukumar Varma, K. (2003). Synthesis and characterisation of cyclo-boratetrasiloxane, (RBO)(Me2SiO)3 (R=nBu, Ar), derivatives. Polyhedron, 22(25-26), 3333-3337. doi:10.1016/s0277-5387(03)00478-9Schiavon, M. A., Armelin, N. A., & Yoshida, I. V. P. (2008). Novel poly(borosiloxane) precursors to amorphous SiBCO ceramics. Materials Chemistry and Physics, 112(3), 1047-1054. doi:10.1016/j.matchemphys.2008.07.041Brisdon, B. J., Mahon, M. F., Molloy, K. C., & Schofield, P. J. (1992). Synthesis and structural characterization of cycloborasiloxanes: The X-ray crystal structures of cyclo-1,3,3,5,5-pentaphenyl-1-bora-3,5-disiloxane and cyclo-1,3,3,5,7,7-hexaphenyl-1,5-dibora-3,7-disiloxane. Journal of Organometallic Chemistry, 436(1), 11-22. doi:10.1016/0022-328x(92)85022-oMurphy, D., Sheehan, J. P., Spalding, T. R., Ferguson, G., Lough, A. J., & Gallagher, J. F. (1993). Compounds containing B–O–X bonds (X = Si, Ge, Sn, Pb). Part 4.—Crystal structures of B(OSiPh3)3, PhB(OSiPh3)2and PhB(OGePh3)2. J. Mater. Chem., 3(12), 1275-1283. doi:10.1039/jm9930301275Zhao, Z., Cammidge, A. N., & Cook, M. J. (2009). Towards black chromophores: μ-oxo linked phthalocyanine–porphyrin dyads and phthalocyanine–subphthalocyanine dyad and triad arrays. Chemical Communications, (48), 7530. doi:10.1039/b916649aFujdala, K. L., Oliver, A. G., Hollander, F. J., & Tilley, T. D. (2003). Tris(tert-butoxy)siloxy Derivatives of Boron, Including the Boronous Acid HOB[OSi(OtBu)3]2and the Metal (Siloxy)boryloxide Complex Cp2Zr(Me)OB[OSi(OtBu)3]2:  A Remarkable Crystal Structure with 18 Independent Molecules in Its Asymmetric Unit. Inorganic Chemistry, 42(4), 1140-1150. doi:10.1021/ic0205482Kleeberg, C., Cheung, M. S., Lin, Z., & Marder, T. B. (2011). Copper-Mediated Reduction of CO2with pinB-SiMe2Ph via CO2Insertion into a Copper–Silicon Bond. Journal of the American Chemical Society, 133(47), 19060-19063. doi:10.1021/ja208969dMetcalfe, R. A., Kreller, D. I., Tian, J., Kim, H., Taylor, N. J., Corrigan, J. F., & Collins, S. (2002). Organoborane-Modified Silica Supports for Olefin Polymerization:  Soluble Models for Metallocene Catalyst Deactivation. Organometallics, 21(8), 1719-1726. doi:10.1021/om010284bKijima, I., Yamamoto, T., & Abe, Y. (1971). Alkoxysilanes. VIII. The Preparation of Alkoxysiloxy Derivatives of Aluminum and Boron. Bulletin of the Chemical Society of Japan, 44(11), 3193-3194. doi:10.1246/bcsj.44.3193Marciniec, B., & Walkowiak, J. (2008). New catalytic route to borasiloxanes. Chemical Communications, (23), 2695. doi:10.1039/b801013gOhmura, T., Torigoe, T., & Suginome, M. (2012). Catalytic Functionalization of Methyl Group on Silicon: Iridium-Catalyzed C(sp3)–H Borylation of Methylchlorosilanes. Journal of the American Chemical Society, 134(42), 17416-17419. doi:10.1021/ja307956wYoshimura, A., Yoshinaga, M., Yamashita, H., Igarashi, M., Shimada, S., & Sato, K. (2017). A convenient and clean synthetic method for borasiloxanes by Pd-catalysed reaction of silanols with diborons. Chemical Communications, 53(43), 5822-5825. doi:10.1039/c7cc02420gIto, M., Itazaki, M., & Nakazawa, H. (2014). Selective Boryl Silyl Ether Formation in the Photoreaction of Bisboryloxide/Boroxine with Hydrosilane Catalyzed by a Transition-Metal Carbonyl Complex. Journal of the American Chemical Society, 136(17), 6183-6186. doi:10.1021/ja500465xChatterjee, B., & Gunanathan, C. (2017). Ruthenium-catalysed multicomponent synthesis of borasiloxanes. Chemical Communications, 53(16), 2515-2518. doi:10.1039/c7cc00787fHuang, Y.-B., Liang, J., Wang, X.-S., & Cao, R. (2017). Multifunctional metal–organic framework catalysts: synergistic catalysis and tandem reactions. Chemical Society Reviews, 46(1), 126-157. doi:10.1039/c6cs00250aDhakshinamoorthy, A., Asiri, A. M., & Garcia, H. (2016). Mixed-metal or mixed-linker metal organic frameworks as heterogeneous catalysts. Catalysis Science & Technology, 6(14), 5238-5261. doi:10.1039/c6cy00695gDhakshinamoorthy, A., Alvaro, M., & Garcia, H. (2010). Aerobic Oxidation of Benzylic Alcohols Catalyzed by Metal−Organic Frameworks Assisted by TEMPO. ACS Catalysis, 1(1), 48-53. doi:10.1021/cs1000703Schlichte, K., Kratzke, T., & Kaskel, S. (2004). Improved synthesis, thermal stability and catalytic properties of the metal-organic framework compound Cu3(BTC)2. Microporous and Mesoporous Materials, 73(1-2), 81-88. doi:10.1016/j.micromeso.2003.12.027Dhakshinamoorthy, A., Alvaro, M., & Garcia, H. (2010). Metal-Organic Frameworks as Efficient Heterogeneous Catalysts for the Regioselective Ring Opening of Epoxides. Chemistry - A European Journal, 16(28), 8530-8536. doi:10.1002/chem.201000588Dhakshinamoorthy, A., Alvaro, M., & Garcia, H. (2009). Metal organic frameworks as efficient heterogeneous catalysts for the oxidation of benzylic compounds with t-butylhydroperoxide. Journal of Catalysis, 267(1), 1-4. doi:10.1016/j.jcat.2009.08.001Opanasenko, M., Dhakshinamoorthy, A., Shamzhy, M., Nachtigall, P., Horáček, M., Garcia, H., & Čejka, J. 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Non-noble metal catalysts for hydrogenation: A facile method for preparing Co nanoparticles covered with thin layered carbon

Metallic cobalt nanoparticles with surface CoOx patches covered by thin layered carbon (named Co@C) have been directly synthesized by thermal decomposition of Co-EDTA complex. Raman spectra and HRTEM images suggest that discontinuities can be found in the disordered layered carbon. XPS shows that the CoOx patches in the Co@C nanoparticles can reduced to metallic Co by H-2 under reaction conditions (7 bar at 120 degrees C), and H-2-D-2 exchange experiments show that the reduced metallic Co nanoparticles covered by carbon layers can dissociate H-2. The Co@C nanoparticles show excellent activity and selectivity during chemoselective hydrogenation of nitroarenes for a wide scope of substrates under mild reaction conditions. Based on the results from DRIFTS adsorption experiments, we propose that metallic Co in the Co@C nanoparticles is the active phase. The role of the carbon layers is to protect the Co from overoxidation by air, leading to the chemoselective hydrogenation of nitroarenes. (C) 2016 Elsevier Inc. All rights reserved.L.L. thanks ITQ for a contract. The European Union is also acknowledged by ERC-AdG-2014-671093-SynCatMatch. The authors also thank the Microscopy Service of UVP for kind help with TEM and STEM measurements.Liu, L.; Concepción Heydorn, P.; Corma Canós, A. (2016). Non-noble metal catalysts for hydrogenation: A facile method for preparing Co nanoparticles covered with thin layered carbon. Journal of Catalysis. 340:1-9. doi:10.1016/j.jcat.2016.04.006S1934

Methanol to olefins: activity and stability of nanosized SAPO-34 molecular sieves and control of selectivity by silicon distribution

[EN] Nano-SAPO-34 molecular sieves synthesized in a microwave environment with 20 nm crystal size showed a longer lifetime than SAPO-34 prepared by the conventional hydrothermal method in the reaction of methanol to olefins. It has been found that silicon distribution strongly affects the lifetime and selectivity. Thus, silicon at the border of the silicon islands gives a higher lifetime and lower C2/C3 ratio. This change in activity and selectivity is better explained in terms of different silicon distribution than by preferential diffusion of ethene through the 8MR pores and agrees with transition-state selectivity. The effects of equilibrium of olefins and deactivation by coke were isolated, showing that after full formation of the hydrocarbon pool, selectivity is independent of deactivation by coke.Financial support by the Spanish MINECO (MAT2012-37160, CSD2009-00050-CONSOLIDER/INGENIO 2010), and Generalitat Valenciana by the PROMETEO program is acknowledged. Z. Li acknowledges China Scholarship Council (CSC) for a fellowship. J. Yu thanks the support by the State Basic Research Project of China (Grant no. 2011CB808703) and the National Natural Science Foundation of China.Li, Z.; Martínez Triguero, LJ.; Concepción Heydorn, P.; Yu, J.; Corma Canós, A. (2013). Methanol to olefins: activity and stability of nanosized SAPO-34 molecular sieves and control of selectivity by silicon distribution. Physical Chemistry Chemical Physics. 15(35):14670-14680. https://doi.org/10.1039/c3cp52247dS14670146801535Bjørgen, M., Joensen, F., Spangsberg Holm, M., Olsbye, U., Lillerud, K.-P., & Svelle, S. (2008). Methanol to gasoline over zeolite H-ZSM-5: Improved catalyst performance by treatment with NaOH. Applied Catalysis A: General, 345(1), 43-50. doi:10.1016/j.apcata.2008.04.020Vennestrøm, P. N. R., Grill, M., Kustova, M., Egeblad, K., Lundegaard, L. F., Joensen, F., … Beato, P. (2011). Hierarchical ZSM-5 prepared by guanidinium base treatment: Understanding microstructural characteristics and impact on MTG and NH3-SCR catalytic reactions. Catalysis Today, 168(1), 71-79. doi:10.1016/j.cattod.2011.03.045Barbera, K., Bonino, F., Bordiga, S., Janssens, T. V. W., & Beato, P. (2011). Structure–deactivation relationship for ZSM-5 catalysts governed by framework defects. Journal of Catalysis, 280(2), 196-205. doi:10.1016/j.jcat.2011.03.016Na, K., Choi, M., & Ryoo, R. (2013). Recent advances in the synthesis of hierarchically nanoporous zeolites. Microporous and Mesoporous Materials, 166, 3-19. doi:10.1016/j.micromeso.2012.03.054Jacobsen, C. J. H., Madsen, C., Houzvicka, J., Schmidt, I., & Carlsson, A. (2000). Mesoporous Zeolite Single Crystals. Journal of the American Chemical Society, 122(29), 7116-7117. doi:10.1021/ja000744cKim, J., Choi, M., & Ryoo, R. (2010). Effect of mesoporosity against the deactivation of MFI zeolite catalyst during the methanol-to-hydrocarbon conversion process. Journal of Catalysis, 269(1), 219-228. doi:10.1016/j.jcat.2009.11.009Firoozi, M., Baghalha, M., & Asadi, M. (2009). The effect of micro and nano particle sizes of H-ZSM-5 on the selectivity of MTP reaction. Catalysis Communications, 10(12), 1582-1585. doi:10.1016/j.catcom.2009.04.021Rownaghi, A. A., & Hedlund, J. (2011). Methanol to Gasoline-Range Hydrocarbons: Influence of Nanocrystal Size and Mesoporosity on Catalytic Performance and Product Distribution of ZSM-5. Industrial & Engineering Chemistry Research, 50(21), 11872-11878. doi:10.1021/ie201549jSommer, L., Mores, D., Svelle, S., Stöcker, M., Weckhuysen, B. M., & Olsbye, U. (2010). Mesopore formation in zeolite H-SSZ-13 by desilication with NaOH. Microporous and Mesoporous Materials, 132(3), 384-394. doi:10.1016/j.micromeso.2010.03.017Wu, L., Degirmenci, V., Magusin, P. C. M. M., Szyja, B. M., & Hensen, E. J. M. (2012). Dual template synthesis of a highly mesoporous SSZ-13 zeolite with improved stability in the methanol-to-olefins reaction. Chemical Communications, 48(76), 9492. doi:10.1039/c2cc33994cWu, L., Degirmenci, V., Magusin, P. C. M. M., Lousberg, N. J. H. G. M., & Hensen, E. J. M. (2013). Mesoporous SSZ-13 zeolite prepared by a dual-template method with improved performance in the methanol-to-olefins reaction. Journal of Catalysis, 298, 27-40. doi:10.1016/j.jcat.2012.10.029Schmidt, F., Paasch, S., Brunner, E., & Kaskel, S. (2012). Carbon templated SAPO-34 with improved adsorption kinetics and catalytic performance in the MTO-reaction. Microporous and Mesoporous Materials, 164, 214-221. doi:10.1016/j.micromeso.2012.04.045Hirota, Y., Murata, K., Tanaka, S., Nishiyama, N., Egashira, Y., & Ueyama, K. (2010). Dry gel conversion synthesis of SAPO-34 nanocrystals. Materials Chemistry and Physics, 123(2-3), 507-509. doi:10.1016/j.matchemphys.2010.05.005Lee, K. Y., Chae, H.-J., Jeong, S.-Y., & Seo, G. (2009). Effect of crystallite size of SAPO-34 catalysts on their induction period and deactivation in methanol-to-olefin reactions. Applied Catalysis A: General, 369(1-2), 60-66. doi:10.1016/j.apcata.2009.08.033Lee, Y.-J., Baek, S.-C., & Jun, K.-W. (2007). Methanol conversion on SAPO-34 catalysts prepared by mixed template method. Applied Catalysis A: General, 329, 130-136. doi:10.1016/j.apcata.2007.06.034Wang, P., Lv, A., Hu, J., Xu, J., & Lu, G. (2012). The synthesis of SAPO-34 with mixed template and its catalytic performance for methanol to olefins reaction. Microporous and Mesoporous Materials, 152, 178-184. doi:10.1016/j.micromeso.2011.11.037Álvaro-Muñoz, T., Márquez-Álvarez, C., & Sastre, E. (2012). Use of different templates on SAPO-34 synthesis: Effect on the acidity and catalytic activity in the MTO reaction. Catalysis Today, 179(1), 27-34. doi:10.1016/j.cattod.2011.07.038Lin, S., Li, J., Sharma, R. P., Yu, J., & Xu, R. (2010). 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Thermal stability and dehydroxylation of Brønsted acid sites in silicoaluminophosphates H-SAPO-11, H-SAPO-18, H-SAPO-31, and H-SAPO-34 investigated by multi-nuclear solid-state NMR spectroscopy. Microporous and Mesoporous Materials, 56(3), 267-278. doi:10.1016/s1387-1811(02)00491-2Blackwell, C. S., & Patton, R. L. (1988). Solid-state NMR of silicoaluminophosphate molecular sieves and aluminophosphate materials. The Journal of Physical Chemistry, 92(13), 3965-3970. doi:10.1021/j100324a055Lok, B. M., Messina, C. A., Patton, R. L., Gajek, R. T., Cannan, T. R., & Flanigen, E. M. (1984). Silicoaluminophosphate molecular sieves: another new class of microporous crystalline inorganic solids. Journal of the American Chemical Society, 106(20), 6092-6093. doi:10.1021/ja00332a063Vomscheid, R., Briend, M., Peltre, M. J., Man, P. P., & Barthomeuf, D. (1994). The Role of the Template in Directing the Si Distribution in SAPO Zeolites. 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The Journal of Physical Chemistry B, 108(10), 3107-3113. doi:10.1021/jp030249dWatanabe, Y., Koiwai, A., Takeuchi, H., Hyodo, S. A., & Noda, S. (1993). Multinuclear NMR Studies on the Thermal Stability of SAPO-34. Journal of Catalysis, 143(2), 430-436. doi:10.1006/jcat.1993.1287BUSCA, G. (1991). FT-113 study of the surface properties of the spinels NiAl2O4 and CoAl2O4 in relation to those of transitional aluminas. Journal of Catalysis, 131(1), 167-177. doi:10.1016/0021-9517(91)90333-yBusca, G., Lorenzelli, V., Ramis, G., & Willey, R. J. (1993). Surface sites on spinel-type and corundum-type metal oxide powders. Langmuir, 9(6), 1492-1499. doi:10.1021/la00030a012Eilertsen, E. A., Arstad, B., Svelle, S., & Lillerud, K. P. (2012). Single parameter synthesis of high silica CHA zeolites from fluoride media. Microporous and Mesoporous Materials, 153, 94-99. doi:10.1016/j.micromeso.2011.12.026Bordiga, S., Regli, L., Cocina, D., Lamberti, C., Bjørgen, M., & Lillerud, K. P. (2005). 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Journal of Catalysis, 264(1), 77-87. doi:10.1016/j.jcat.2009.03.009Song, W., Fu, H., & Haw, J. F. (2001). Supramolecular Origins of Product Selectivity for Methanol-to-Olefin Catalysis on HSAPO-34. Journal of the American Chemical Society, 123(20), 4749-4754. doi:10.1021/ja0041167Arstad, B., Nicholas, J. B., & Haw, J. F. (2004). Theoretical Study of the Methylbenzene Side-Chain Hydrocarbon Pool Mechanism in Methanol to Olefin Catalysis. Journal of the American Chemical Society, 126(9), 2991-3001. doi:10.1021/ja035923jZhou, H., Wang, Y., Wei, F., Wang, D., & Wang, Z. (2008). Kinetics of the reactions of the light alkenes over SAPO-34. Applied Catalysis A: General, 348(1), 135-141. doi:10.1016/j.apcata.2008.06.033Chen, D., Moljord, K., & Holmen, A. (2012). A methanol to olefins review: Diffusion, coke formation and deactivation on SAPO type catalysts. Microporous and Mesoporous Materials, 164, 239-250. doi:10.1016/j.micromeso.2012.06.046Wang, C.-M., Wang, Y.-D., & Xie, Z.-K. (2013). 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Identification of Distinct Copper Species in Cu-CHA Samples Using NO as Probe Molecule. A Combined IR Spectroscopic and DFT Study

[EN] Combining IR spectroscopy of NO adsorption on copper exchanged molecular sieves with the chabazite structure, i.e. Cu-SAPO-34 and Cu-SSZ-13, and theoretical calculations, different types of copper species have been identified. On one hand, [Cu¿OH]+ species can be accurately distinguished, characterized by a ¿NO frequency at 1788¿ 1798 cm¿1 depending on their location in the chabazite structure (6R vs. 8R) and composition (Cu-SAPO-34 vs. Cu-SSZ-13). On the other hand, dimeric copper oxo [Cu¿O¿ Cu]2+ species have been properly identified by means of DFT modelling, that proposes a ¿NO stretching frequency of 1887 cm¿1, which has been confirmed experimentally in the Cu-SAPO-34 sample. Finally the location of isolated Cu2+ ions either in the 6R units or in the 8R positions of the chabazite cavity could be accurately defined according to DFT data, and validated in the experimental IR spectra with IR bands between 1907 and 1950 cm¿1. Regarding to Cu+ species, IR spectroscopy of CO reveals different types of Cu+ species as evidenced by their ability to form mono, di and try carbonyls. The unambiguous differentiation of different types of copper species is of great interest in further identification of active sites for the NH3- SCR reaction.This work has been supported by the Spanish Government through "Severo Ochoa Program" (SEV 2012-0267), and MAT2015-71261-R, the European Union through ERC-AdG-2014-671093 (SynCatMatch); and the Generalitat Valenciana through the Prometeo program (PROMETEOII/2013/011). R.M. acknowledges "La Caixa - Severo Ochoa" International PhD Fellowships (call 2015).Concepción Heydorn, P.; Boronat Zaragoza, M.; Millan, R.; Moliner Marin, M.; Corma Canós, A. (2017). Identification of Distinct Copper Species in Cu-CHA Samples Using NO as Probe Molecule. A Combined IR Spectroscopic and DFT Study. 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Nature of Active Nickel Sites and Initiation Mechanism for Ethylene Oligomerization on Heterogeneous Ni-beta Catalysts

[EN] Higher olefins produced via ethylene oligomerization are versatile commodity chemicals serving a vast range of industries with large global economic impact. Nickel aluminosilicates are promising candidates to replace the homogeneous catalysts employed in industrial ethylene oligomerization processes. The current poor understanding of the true nature of the active nickel centers and the nickel-mediated oligomerization mechanism in these materials, however, hampers the rational design of improved catalysts. Here we applied in situ time- and temperature-resolved FTIR spectroscopy with simultaneous MS analysis of products to disentangle these fundamental issues using nanocrystalline Ni-beta zeolite as catalyst. We elucidate that isolated Ni2+ cations grafted on acidic silanols are the most likely active species in the working catalysts rather than the generally accepted ion-exchanged nickel cations. On the basis of our results, a plausible initiation mechanism involving a nickel vinyl hydride intermediate from which chain propagation proceeds similarly to the Cossee-Arlman pathway is proposed.This work was supported by the MINECO of Spain through the Severo Ochoa Program for Centers of Excellence (SEV 2016-0683) and ENE2014-5761-R project. The authors extend their acknowledgement to the EU project OCMOL ("Oxidative Coupling of Methane followed by Oligomerization to Liquids", 7th Framework Programme, GA no. 228953)Moussa, S.; Concepción Heydorn, P.; Arribas Viana, MDLD.; Martinez Feliu, A. (2018). Nature of Active Nickel Sites and Initiation Mechanism for Ethylene Oligomerization on Heterogeneous Ni-beta Catalysts. ACS Catalysis. 8(5):3903-3912. https://doi.org/10.1021/acscatal.7b03970S390339128

Enhanced Stability of Cu Clusters of Low Atomicity against Oxidation. Effect on the Catalytic Redox Process

[EN] By a combination of theoretical modeling and XPS and SERS spectroscopic studies, it has been found that it is possible to stabilize metallic copper species under oxidizing reaction conditions by adjusting the atomicity of subnanometer copper clusters. Small Cu-5 clusters display low reactivity toward O-2 dissociation, being less susceptible to oxidation than larger Cu-8 or Cu-20 systems. However, in the presence of water this reactivity is strongly enhanced, leading to oxidized Cu-5 clusters. In that case, the interaction of Cu-5 with atomic O oxygen is weak, favoring recombination and O-2 desorption, suggesting an easier transfer of O atoms to other reactant molecules. In contrast, copper clusters of higher atomicity or nanoparticles, such as Cu-5 and Cu-20, are easily oxidized in the presence of O-2, leading to very stable reactive O atoms, resulting in low reactivity and selectivity in many oxidation reactions. Altogether, Cu-5, clusters are proposed as promising catalysts for catalytic applications where stabilization of metallic copper species is strongly required.The authors thank the MINECO (Consolider Ingenio 2010-MULTICAT CSD2009-00050 and Severo Ochoa program SEV-2012-0267), Generalitat Valenciana (PROMETEOII/2013/011 Project), and European Union (ERC-AdG-2014-671093-SynCatMatch) for financial support. E.F. and S.G.-G. thank the MINECO for their fellowship SVP-2013-068146 and financial support through project MAT2011-28009, respectively.Concepción Heydorn, P.; Boronat Zaragoza, M.; García García, S.; Fernández-Villanueva, E.; Corma Canós, A. (2017). Enhanced Stability of Cu Clusters of Low Atomicity against Oxidation. Effect on the Catalytic Redox Process. ACS Catalysis. 7(5):3560-3568. https://doi.org/10.1021/acscatal.7b00778S356035687

In-Situ-Generated Active Hf-hydride in Zeolites for the Tandem N-Alkylation of Amines with Benzyl Alcohol

[EN] In this work, we have studied the catalytic activity of different silicates (MFI, MCM-41, and Beta) containing Lewis acid sites (including Sn, Ti, Zr, and Hf) for the tandem N-alkylation reaction of aniline with benzyl alcohol. The Hf- and Zr-Beta were the most active catalysts for this transformation, showing in both cases selectivities toward the corresponding N-benzylaniline higher than 97%. FTIR and DFT analyses confirm that the active sites in the Hf-Beta catalyst for this process are the open sites where one of the four Hf-O bonds is hydrolyzed. Moreover, the amount of these active species could be notoriously increased with previous thermal treatment of the Lewis acid zeolite with benzyl alcohol. Isotopically labeled experiments and theoretical mechanistic studies reveal that the N-alkylation reaction occurs through a hydrogen borrowing pathway, in which in situ Hf-hydride species were generated. Finally, the Hf-Beta zeolite was reused several times in the N-alkylation reaction without any appreciable deactivation detected. This catalytic system could be expanded to a variety of amines, including aliphatic and biomass-derived amines.This work has been supported by the Spanish Government through "severo Ochoa" (SEV-2016-0683, MINECO), MAT2017-82288-C2-1-P (AEI/FEDER, UE), and RTI2018101033-B-I00 (MCIU/AEI/FEDER, UE). Dr. Susana Valencia is acknowledged for the preparation of the Ti-Beta sample. The Electron Microscopy Service of the UPV is also acknowledged for their help in sample characterization. Part of the computations were performed on the Tirant III cluster of the Servei d'Informa`tica of the University of Valencia.Rojas-Buzo, S.; Concepción Heydorn, P.; Corma Canós, A.; Moliner Marin, M.; Boronat Zaragoza, M. (2021). In-Situ-Generated Active Hf-hydride in Zeolites for the Tandem N-Alkylation of Amines with Benzyl Alcohol. ACS Catalysis. 11(13):8049-8061. https://doi.org/10.1021/acscatal.1c01739S80498061111