Review on the Catalytic Hydrogenation of Bromate in Water Phase

[EN] The presence of bromate in water sources generates environmental concern due to its toxicity for humans. Diverse technologies, like membranes, ion exchange, chemical reduction, etc., can be employed to treat bromate-polluted water but they produce waste that must be treated. An alternative to these technologies can be the catalytic reduction of bromate to bromide using hydrogen as a reducing agent. In this review, we analyze the research published about this catalytic technology. Specifically, we summarize and discuss about the state of knowledge related to (1) the different metals used as catalysts for the reaction; (2) the influence of the support on the catalytic activity; (3) the characterization of the catalysts; (4) the reaction mechanisms; and (5) the influence of the water composition in the catalytic activity and in the catalyst stability. Based on published papers, we analyze the strength and weaknesses of this technique and the possibilities of using this reaction for the treatment of bromate-polluted water as a sustainable process.This research was funded by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER), projects RTI2018-101784-B-I00.Cerrillo, JL.; Palomares Gimeno, AE. (2021). Review on the Catalytic Hydrogenation of Bromate in Water Phase. Catalysts. 11(3):1-18. https://doi.org/10.3390/catal11030365S11811

NOx selective catalytic reduction at high temperatures with mixed oxides derived from layered double hydroxides

[EN] Mixed oxides derived from layered double hydroxides (LDHs) have been investigated as potential catalysts for the NOx removal at high temperatures. The best results were obtained with Co–Al mixed oxides derived from LDHs that are active at 750 ◦C in the presence of oxygen and water. These catalysts could reduce or/and decompose the NOx formed in the dense phase of the FCC regenerator, being deactivated at oxygen concentrations higher than 1.5%. Nevertheless this deactivation is not permanent and they would be regenerated after reduction with hydrogen at 530 ◦C. The influence of the layered double hydroxides (LDHs) preparation method on the catalyst activity was studied, observing that the activity of the catalyst depends on its chemical composition but it does not depend on the initial LDHs crystallinity, obtaining similar results independently of the synthesis method.A.E. Palomares and C. Franch thank the Spanish Government (projects MAT2009-14528-C02-01 and CONSOLIDER INGENIO 2010) and the European Union (European Community's Seventh Framework Programme FP7/2007-2013 under Grant Agreement No. 226347 Project) for financial support. A. Ribera and G. Abellan acknowledge financial support from the Spanish Ministerio de Ciencia e Innovacion with FEDER co-financing (CTQ-2011-26507) and the Generalitat Valenciana (Prometeo Program).Palomares Gimeno, AE.; Franch Martí, C.; Ribera, A.; Abellán, G. (2012). NOx selective catalytic reduction at high temperatures with mixed oxides derived from layered double hydroxides. Catalysis Today. 191(1):47-51. https://doi.org/10.1016/j.cattod.2012.01.023S4751191

The Influence of the Support on the Activity of Mn-Fe Catalysts Used for the Selective Catalytic Reduction of NOx with Ammonia

[EN] Mono and bimetallic Mn-Fe catalysts supported on different materials were prepared and their catalytic performance in the NH3-SCR of NOx was investigated. It was shown that Mn and Fe have a synergic effect that enhances the activity at low temperature. Nevertheless, the activity of the bimetallic catalysts depends very much on the support selected. The influence of the support on the catalyst activity has been studied using materials with different textural and acid-base properties. Microporous (BEA-zeolite), mesoporous (SBA15 and MCM41) and bulk (metallic oxides) materials with different acidity have been used as supports for the Mn-Fe catalysts. It has been shown that the activity depends on the acidity of the support and on the surface area. Acid sites are necessary for ammonia adsorption and high surface area produces a better dispersion of the active sites resulting in improved redox properties. The best results have been obtained with the catalysts supported on alumina and on beta zeolite. The first one is the most active at low temperatures but it presents some reversible deactivation in the presence of water. The Mn-Fe catalyst supported on beta zeolite is the most active at temperatures higher than 350 degrees C, without any deactivation in the presence of water and with a 100% selectivity towards nitrogen.This research was funded by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER), projects RTI2018-101784-B-I00 and RTI2018-101033-B-100 and by Generalitat Valenciana and European Social Fund, the pre doctoral grant ACIF2017.López-Hernández, I.; Mengual Cuquerella, J.; Palomares Gimeno, AE. (2020). The Influence of the Support on the Activity of Mn-Fe Catalysts Used for the Selective Catalytic Reduction of NOx with Ammonia. Catalysts. 10(1):1-12. https://doi.org/10.3390/catal10010063S112101Gao, F., Tang, X., Yi, H., Zhao, S., Li, C., Li, J., … Meng, X. (2017). A Review on Selective Catalytic Reduction of NOx by NH3 over Mn–Based Catalysts at Low Temperatures: Catalysts, Mechanisms, Kinetics and DFT Calculations. Catalysts, 7(7), 199. doi:10.3390/catal7070199Yu, J. J., Cheng, J., Ma, C. Y., Wang, H. L., Li, L. D., Hao, Z. P., & Xu, Z. P. (2009). NOx decomposition, storage and reduction over novel mixed oxide catalysts derived from hydrotalcite-like compounds. Journal of Colloid and Interface Science, 333(2), 423-430. doi:10.1016/j.jcis.2009.02.022Forzatti, P. (2001). Present status and perspectives in de-NOx SCR catalysis. Applied Catalysis A: General, 222(1-2), 221-236. doi:10.1016/s0926-860x(01)00832-8Rutkowska, M., Díaz, U., Palomares, A. E., & Chmielarz, L. (2015). Cu and Fe modified derivatives of 2D MWW-type zeolites (MCM-22, ITQ-2 and MCM-36) as new catalysts for DeNO x process. Applied Catalysis B: Environmental, 168-169, 531-539. doi:10.1016/j.apcatb.2015.01.016PALOMARES, A., PRATO, J., IMBERT, F., & CORMA, A. (2007). Catalysts based on tin and beta zeolite for the reduction of NOx under lean conditions in the presence of water. Applied Catalysis B: Environmental, 75(1-2), 88-94. doi:10.1016/j.apcatb.2007.03.013Palomares, A. E., Franch, C., & Corma, A. (2011). Determining the characteristics of a Co-zeolite to be active for the selective catalytic reduction of NOx with hydrocarbons. Catalysis Today, 176(1), 239-241. doi:10.1016/j.cattod.2010.11.092Palomares, A. E., Prato, J. G., & Corma, A. (2003). Co-Exchanged IM5, a Stable Zeolite for the Selective Catalytic Reduction of NO in the Presence of Water and SO2. Industrial & Engineering Chemistry Research, 42(8), 1538-1542. doi:10.1021/ie020345lWang, R., Wu, X., Zou, C., Li, X., & Du, Y. (2018). NOx Removal by Selective Catalytic Reduction with Ammonia over a Hydrotalcite-Derived NiFe Mixed Oxide. Catalysts, 8(9), 384. doi:10.3390/catal8090384Qi, G., & Yang, R. T. (2003). Low-temperature selective catalytic reduction of NO with NH3 over iron and manganese oxides supported on titania. Applied Catalysis B: Environmental, 44(3), 217-225. doi:10.1016/s0926-3373(03)00100-0Forzatti, P., Nova, I., & Tronconi, E. (2009). Enhanced NH3 Selective Catalytic Reduction for NOx Abatement. Angewandte Chemie International Edition, 48(44), 8366-8368. doi:10.1002/anie.200903857Gillot, S., Tricot, G., Vezin, H., Dacquin, J.-P., Dujardin, C., & Granger, P. (2018). Induced effect of tungsten incorporation on the catalytic properties of CeVO4 systems for the selective reduction of NOx by ammonia. Applied Catalysis B: Environmental, 234, 318-328. doi:10.1016/j.apcatb.2018.04.059Krishnan, A. T., & Boehman, A. L. (1998). Selective catalytic reduction of nitric oxide with ammonia at low temperatures. Applied Catalysis B: Environmental, 18(3-4), 189-198. doi:10.1016/s0926-3373(98)00036-8Li, J., Chang, H., Ma, L., Hao, J., & Yang, R. T. (2011). Low-temperature selective catalytic reduction of NOx with NH3 over metal oxide and zeolite catalysts—A review. Catalysis Today, 175(1), 147-156. doi:10.1016/j.cattod.2011.03.034Boningari, T., & Smirniotis, P. G. (2016). Impact of nitrogen oxides on the environment and human health: Mn-based materials for the NO x abatement. Current Opinion in Chemical Engineering, 13, 133-141. doi:10.1016/j.coche.2016.09.004Putluru, S. S. R., Schill, L., Jensen, A. D., Siret, B., Tabaries, F., & Fehrmann, R. (2015). Mn/TiO2 and Mn–Fe/TiO2 catalysts synthesized by deposition precipitation—promising for selective catalytic reduction of NO with NH3 at low temperatures. Applied Catalysis B: Environmental, 165, 628-635. doi:10.1016/j.apcatb.2014.10.060Chmielarz, L., Kuśtrowski, P., Dziembaj, R., Cool, P., & Vansant, E. F. (2006). Catalytic performance of various mesoporous silicas modified with copper or iron oxides introduced by different ways in the selective reduction of NO by ammonia. Applied Catalysis B: Environmental, 62(3-4), 369-380. doi:10.1016/j.apcatb.2005.09.004Chmielarz, L., Dziembaj, R., Grzybek, T., Klinik, J., Łojewski, T., Olszewska, D., & Papp, H. (2000). Catalysis Letters, 68(1/2), 95-100. doi:10.1023/a:1019094327927Gao, Y., Luan, T., Zhang, S., Jiang, W., Feng, W., & Jiang, H. (2019). Comprehensive Comparison between Nanocatalysts of Mn−Co/TiO2 and Mn−Fe/TiO2 for NO Catalytic Conversion: An Insight from Nanostructure, Performance, Kinetics, and Thermodynamics. Catalysts, 9(2), 175. doi:10.3390/catal9020175Song, C., Zhang, L., Li, Z., Lu, Y., & Li, K. (2019). Co-Exchange of Mn: A Simple Method to Improve Both the Hydrothermal Stability and Activity of Cu–SSZ-13 NH3–SCR Catalysts. Catalysts, 9(5), 455. doi:10.3390/catal9050455Paolucci, C., Di Iorio, J. R., Ribeiro, F. H., Gounder, R., & Schneider, W. F. (2016). Catalysis Science of NOx Selective Catalytic Reduction With Ammonia Over Cu-SSZ-13 and Cu-SAPO-34. Advances in Catalysis, 1-107. doi:10.1016/bs.acat.2016.10.002Wu, Z., Jiang, B., & Liu, Y. (2008). Effect of transition metals addition on the catalyst of manganese/titania for low-temperature selective catalytic reduction of nitric oxide with ammonia. Applied Catalysis B: Environmental, 79(4), 347-355. doi:10.1016/j.apcatb.2007.09.039Putluru, S. S. R., Schill, L., Jensen, A. D., & Fehrmann, R. S. N. (2018). Selective Catalytic Reduction of NOx with NH3 on Cu-, Fe-, and Mn-Zeolites Prepared by Impregnation: Comparison of Activity and Hydrothermal Stability. Journal of Chemistry, 2018, 1-11. doi:10.1155/2018/8614747Thirupathi, B., & Smirniotis, P. G. (2012). Nickel-doped Mn/TiO2 as an efficient catalyst for the low-temperature SCR of NO with NH3: Catalytic evaluation and characterizations. Journal of Catalysis, 288, 74-83. doi:10.1016/j.jcat.2012.01.003Peña, D. A., Uphade, B. S., & Smirniotis, P. G. (2004). TiO2-supported metal oxide catalysts for low-temperature selective catalytic reduction of NO with NH3I. Evaluation and characterization of first row transition metals. Journal of Catalysis, 221(2), 421-431. doi:10.1016/j.jcat.2003.09.003Qi, G., Yang, R. T., & Chang, R. (2004). MnOx-CeO2 mixed oxides prepared by co-precipitation for selective catalytic reduction of NO with NH3 at low temperatures. Applied Catalysis B: Environmental, 51(2), 93-106. doi:10.1016/j.apcatb.2004.01.023Roy, S., Viswanath, B., Hegde, M. S., & Madras, G. (2008). Low-Temperature Selective Catalytic Reduction of NO with NH3 over Ti0.9M0.1O2-δ (M = Cr, Mn, Fe, Co, Cu). The Journal of Physical Chemistry C, 112(15), 6002-6012. doi:10.1021/jp7117086Shi, J., Zhang, Z., Chen, M., Zhang, Z., & Shangguan, W. (2017). Promotion effect of tungsten and iron co-addition on the catalytic performance of MnOx/TiO2 for NH3-SCR of NOx. Fuel, 210, 783-789. doi:10.1016/j.fuel.2017.09.035Husnain, N., Wang, E., Li, K., Anwar, M. T., Mehmood, A., Gul, M., … Mao, J. (2018). Iron oxide-based catalysts for low-temperature selective catalytic reduction of NO x with NH3. Reviews in Chemical Engineering, 35(2), 239-264. doi:10.1515/revce-2017-0064Wang, X., Wu, S., Zou, W., Yu, S., Gui, K., & Dong, L. (2016). Fe-Mn/Al 2 O 3 catalysts for low temperature selective catalytic reduction of NO with NH 3. Chinese Journal of Catalysis, 37(8), 1314-1323. doi:10.1016/s1872-2067(15)61115-9Thirupathi, B., & Smirniotis, P. G. (2011). Co-doping a metal (Cr, Fe, Co, Ni, Cu, Zn, Ce, and Zr) on Mn/TiO2 catalyst and its effect on the selective reduction of NO with NH3 at low-temperatures. Applied Catalysis B: Environmental, 110, 195-206. doi:10.1016/j.apcatb.2011.09.001Kim, Y. J., Kwon, H. J., Heo, I., Nam, I.-S., Cho, B. K., Choung, J. W., … Yeo, G. K. (2012). Mn–Fe/ZSM5 as a low-temperature SCR catalyst to remove NOx from diesel engine exhaust. Applied Catalysis B: Environmental, 126, 9-21. doi:10.1016/j.apcatb.2012.06.010Huang, J., Tong, Z., Huang, Y., & Zhang, J. (2008). Selective catalytic reduction of NO with NH3 at low temperatures over iron and manganese oxides supported on mesoporous silica. Applied Catalysis B: Environmental, 78(3-4), 309-314. doi:10.1016/j.apcatb.2007.09.031Li, J., Yang, C., Zhang, Q., Li, Z., & Huang, W. (2015). Effects of Fe addition on the structure and catalytic performance of mesoporous Mn/Al–SBA-15 catalysts for the reduction of NO with ammonia. Catalysis Communications, 62, 24-28. doi:10.1016/j.catcom.2015.01.003Chen, Z., Wang, F., Li, H., Yang, Q., Wang, L., & Li, X. (2011). Low-Temperature Selective Catalytic Reduction of NOx with NH3 over Fe–Mn Mixed-Oxide Catalysts Containing Fe3Mn3O8 Phase. Industrial & Engineering Chemistry Research, 51(1), 202-212. doi:10.1021/ie201894cPalomares, A. E., Prato, J. ., & Corma, A. (2002). A new active zeolite structure for the selective catalytic reduction (SCR) of nitrogen oxides: ITQ7 zeolite. Catalysis Today, 75(1-4), 367-371. doi:10.1016/s0920-5861(02)00066-4Jeong, N. C., Lee, J. S., Tae, E. L., Lee, Y. J., & Yoon, K. B. (2008). Acidity Scale for Metal Oxides and Sanderson’s Electronegativities of Lanthanide Elements. Angewandte Chemie International Edition, 47(52), 10128-10132. doi:10.1002/anie.200803837Sun, M., Lan, B., Yu, L., Ye, F., Song, W., He, J., … Zheng, Y. (2012). Manganese oxides with different crystalline structures: Facile hydrothermal synthesis and catalytic activities. Materials Letters, 86, 18-20. doi:10.1016/j.matlet.2012.07.011Deng, S., Zhuang, K., Xu, B., Ding, Y., Yu, L., & Fan, Y. (2016). Promotional effect of iron oxide on the catalytic properties of Fe–MnOx/TiO2 (anatase) catalysts for the SCR reaction at low temperatures. 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A short review about NOx storage/reduction catalysts based on metal oxides and hydrotalcite-type anionic clays

[EN] The increasing problem of atmospheric pollution by NOx has resulted in stricter regulations on their emissions. NOx storage/reduction (NSR) is considered as efficient catalytic technology to abate lean-burn NOx. A wide variety of catalysts have been extensively examined for this purpose. The use of metal oxides, hydrotalcites and their derivatives as NOx storage/reduction catalysts has been reviewed. Suitable combination particularly the catalytic redox component and the storage component can lead to improved activity in NOx decomposition and capturing under the lean-rich conditionsJablonska, M.; Palomares Gimeno, AE.; Wegrzyn, A.; Chmielarz, L. (2014). A short review about NOx storage/reduction catalysts based on metal oxides and hydrotalcite-type anionic clays. Acta Geodynamica et Geomaterialia. 11(2):175-186. doi:10.13168/AGG.2013.0063S17518611

Cu and Fe modified derivatives of 2D MWW-type zeolites (MCM-22, ITQ-2 and MCM-36) as new catalysts for DeNOx process

Zeolites with MWW topology (MCM-22, ITQ-2, and MCM-36) exchanged with copper and iron were studied as catalysts for selective catalytic reduction of NO with ammonia. It was shown that delamination and pillaring of layered MCM-22 zeolite resulted in the formation of ITQ-2 and MCM-36, respectively. Both these materials were characterized by MWW topology and significant contribution of mesopores. In a series of the zeolite based catalyst the most promising results in a process of selective catalytic reduction of NO with ammonia were obtained for the copper doped samples (Cu-MCM-22 and Cu-ITQ-2), however catalytic performance of the studied catalytic systems strongly depends on type, content and form of deposited transition metal species. Moreover, both these catalysts were found to be catalytically stable in the DeNOx process after hydrothermal treatment.U.D. and A.E.P. thank for the financial support to Spanish Government by Consolider-Ingenio MULTICAT CSD2009-00050, MAT2011-29020-0O2-01 and Severo Ochoa Excellence Program SEV-2012-0267.Rutkowska, M.; Díaz Morales, UM.; Palomares Gimeno, AE.; Chmielarz, L. (2015). Cu and Fe modified derivatives of 2D MWW-type zeolites (MCM-22, ITQ-2 and MCM-36) as new catalysts for DeNOx process. Applied Catalysis B: Environmental. 168:531-539. https://doi.org/10.1016/j.apcatb.2015.01.016S53153916

Influence of the synthesis method on the catalytic activity of mayenite for the oxidation of gas-phase trichloroethylene

[EN] Catalytic oxidation of trichloroethylene (TCE) in heterogeneous phase (gas-solid) is an effective strategy for the conversion of this pollutant in less harmful compounds, namely CO2, CO and HCl. In this work, we have studied the use of mayenite, a cost-effective material, as an active catalyst for the TCE conversion. In particular, we have assessed the influence of the mayenite synthesis method (hydrothermal, sol-gel and ceramic) on the reaction performance. The materials have been characterized by different techniques, such as XRD, N-2-sorption (BET), TPR, Raman spectroscopy, FESEM-EDX and TEM. The analysis of the light-off curves and product distribution, has shown that the use of the hydrothermal method for the mayenite synthesis results in the most active and selective catalyst. This has been related with a higher surface area and with a higher concentration of oxygen anions in the mayenite prepared by this method. It has been found that the presence of water in the stream do not influence the catalytic performance of the material. A mechanism for the reaction and for the partial deactivation of the catalyst has been proposed.This work was supported by the grants ORSA167988 and ORSA174250 funded by the University of Salerno. AI gratefully acknowledges the Erasmus+ traineeship program. AEP and JMT thanks the Spanish Ministry of Economy and Competitiveness and the Fondo Europeo de Desarrollo Regional through MAT2015-71842-P and CTQ2015-68951-C3-1-R (MINECO/FEDER)Intiso, A.; Martínez-Triguero, J.; Cucciniello, R.; Rossi, F.; Palomares Gimeno, AE. (2019). Influence of the synthesis method on the catalytic activity of mayenite for the oxidation of gas-phase trichloroethylene. Scientific Reports. 9:1-9. https://doi.org/10.1038/s41598-018-36708-2S199Greene, H. L., Prakash, D. S. & Athota, K. V. Combined sorbent/catalyst media for destruction of halogenated VOCs. Appl. Catal. 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A Novel Synthetic Route to Prepare High Surface Area Mayenite Catalyst for TCE Oxidation

[EN] Mayenite (Ca12Al14O33) was synthesized by a novel route based on the use of polymethyl methacrylate (PMMA) as a soft templating agent. The material was tested for the total oxidation of trichloroethylene in the gas phase and the catalytic performance was analysed when using different initial amounts of PMMA in the catalyst synthesis. The results were compared with those obtained with a mayenite synthetized by a classical hydrothermal method. The highest activity in terms of TCE conversion was achieved in the presence of mayenite prepared using 10% w/w of PMMA; its activity was also higher than that of the hydrothermal mayenite. The surface area and the number of superoxide anions (O-2(-)) seem to be the main properties determining the catalytic activity of the material.This research was funded by University of Salerno, grant number ORSA167988 and ORSA174250.Intiso, A.; Martínez-Triguero, J.; Cucciniello, R.; Proto, A.; Palomares Gimeno, AE.; Rossi, F. (2019). A Novel Synthetic Route to Prepare High Surface Area Mayenite Catalyst for TCE Oxidation. Catalysts. 9(1):1-8. https://doi.org/10.3390/catal9010027S1891Yang, S., Kondo, J. N., Hayashi, K., Hirano, M., Domen, K., & Hosono, H. (2004). Formation and Desorption of Oxygen Species in Nanoporous Crystal 12CaO·7Al2O3. Chemistry of Materials, 16(1), 104-110. doi:10.1021/cm034755rCucciniello, R., Intiso, A., Castiglione, S., Genga, A., Proto, A., & Rossi, F. (2017). Total oxidation of trichloroethylene over mayenite (Ca12Al14O33) catalyst. Applied Catalysis B: Environmental, 204, 167-172. doi:10.1016/j.apcatb.2016.11.03

Multifunctional catalyst for maximizing NOx oxidation/storage/reduction: The role of the different active sites

A multifunctional catalyst/storage material has been prepared to maximize NOx removal. This material is based on mixed oxides derived from modified layered double hydrotalcites (LDH). A cobalt catalytic function oxidizes the NO to NO2. The NO2 is stored as nitrate in the basic sites of the material. The basic properties of the Co/Mg/Al mixed oxide derived from LDH were enhanced by doping with sodium, improving the storage capacity of the catalyst. Finally, the introduction of vanadium sites, enables the reduction¿decomposition of the nitrates. This multisite catalyst/storage material results in a well equilibrate formulation that maximizes catalyst conversion and regenerabilityFinancial support from the Spanish Ministry of Economy and Competitiveness through the Severo Ochoa program (SEV-2012-0267) as well as operating grants Consolider Ingenio Multicat (CSD-2009-00050) and MAT-2012-3856-C02-01 is gratefully acknowledged. Authors want to thank Maria Orti for her collaboration in the experiments.Palomares Gimeno, AE.; Uzcategui Paredes, A.; Franch Martí, C.; Corma Canós, A. (2013). Multifunctional catalyst for maximizing NOx oxidation/storage/reduction: The role of the different active sites. Applied Catalysis B: Environmental. 142-143:795-800. https://doi.org/10.1016/j.apcatb.2013.06.015S795800142-14

The Influence of the Support Nature and the Metal Precursor in the Activity of Pd-based Catalysts for the Bromate Reduction Reaction

This is the peer reviewed version of the following article: J. L. Cerrillo, C. W. Lopes, F. Rey, A. E. Palomares, ChemCatChem 2021, 13, 1230, which has been published in final form at https://doi.org/10.1002/cctc.202001797. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] Palladium catalysts supported on different materials (alumina, activated carbon and mixed oxide derived from hydrotalcite) and prepared with different metal precursors (nitrate, chloride and acetate) have been characterized and tested for the bromate reduction reaction. The catalytic behavior depends on the support nature and on the metallic precursor used for the catalyst preparation. Pd catalyst supported on a mixed oxide has a low activity due to the high affinity of the reconstructed support for the Br- formed, preventing the reactants to approximate the active Pd sites. Pd catalyst supported on activated carbon has a surface negative charge and a microporous structure, making difficult the interaction of the active sites with the reactants. The best results are obtained with the catalyst supported on alumina due to its physical-chemical properties, i. e. mesoporosity, positive surface charge and reversible adsorption of reactants and products. These characteristics make easy bromate and H-2 adsorption on the active sites and subsequent reaction, thus resulting in a better activity. The Pd precursor salt also influences the catalytic activity as it has an effect on the Pd nanocrystal size. The best results are obtained with the metal precursor that produces homogeneous and large Pd metallic crystallites.Authors thank the Spanish Ministry of Economy and Competitiveness through RTI2018-101784-B-I00 (MINECO/FEDER) and SEV2016-0683 projects for the financial support. We gratefully acknowledge ALBA synchrotron for allocating beamtime and CLAESS beamline staff for their technical support during our experiment. C.W. Lopes (Science without Frontiers -Process no. 13191/13-6) thanks CAPES for a predoctoral fellowship. J.L. Cerrillo is grateful to MINECO for the Severo Ochoa contract for PhD formation (SVP-2014-068600).The authors also wish to thank Elena Crespo and Adrian Pla for their collaboration in the experimental part of the paper.Cerrillo, JL.; Lopes, CW.; Rey Garcia, F.; Palomares Gimeno, AE. (2021). The Influence of the Support Nature and the Metal Precursor in the Activity of Pd-based Catalysts for the Bromate Reduction Reaction. ChemCatChem. 13(4):1230-1238. https://doi.org/10.1002/cctc.202001797S1230123813

An in situ XAS study of the activation of precursor-dependent Pd nanoparticles

[EN] The activation of precursor-dependent Pd nanoparticles was comprehensively followed by in situ X-ray absorption spectroscopy on two inorganic supports for rationalizing the final catalytic activity. Two series of Pd-based catalysts (7 wt% Pd) were prepared by impregnation of gamma-Al2O3 and activated carbon supports varying the metal precursor (Pd(NO3)(2), PdCl2 and Pd(OAc)(2)). The most relevant physicochemical properties of the studied catalysts were determined by several techniques including ICP-OES, XRD, N-2 adsorption and XAS. The results indicate that the thermal stability of the metal precursor plays an important role in the size and speciation of the formed Pd nanoparticles after the activation process. The Cl-based precursor, which presents high thermal stability, passes through a PdOxCly mixed phase when submitted to calcination on Pd/Al2O3 and leaves Cl-species after metal reduction on Pd/C (which can be detrimental to catalytic reactions). Differently, Pd(OAc)(2) and Pd(NO3)(2) promote the formation of larger species due to different precursor decomposition pathways. Ordered PdO is observed even before calcination when Pd(NO3)(2) was used as a metallic source, which translates into large nanoparticles after reduction in H-2. By using the average coordination numbers of Pd species obtained from EXAFS data of the as-reduced catalysts, a correlation was observed comparing the three precursors: PdCl2 generates smaller nanoparticles than Pd(OAc)(2), which in turn generates smaller nanoparticles than Pd(NO3)(2), regardless of the support used for catalyst preparation.The authors thank the Spanish Ministry of Economy and Competitiveness through MAT2015-71842-P (MINECO/FEDER) and SEV-2016-0683 projects for the financial support. We gratefully acknowledge ALBA synchrotron for allocating beamtime (proposal 2015091414), Carlo Marini and CLAESS beamline staff for their help and technical support during our experiment. C. W. Lopes (Science without Frontiers - Process no. 13191/13-6) thanks CAPES for a predoctoral fellowship. J.L. Cerrillo wishes to thank MINECO for the Severo Ochoa contract for PhD formation (SVP-2014-068600).Wittee Lopes, C.; Cerrillo, JL.; Palomares Gimeno, AE.; Rey Garcia, F.; Agostini, G. (2018). An in situ XAS study of the activation of precursor-dependent Pd nanoparticles. Physical Chemistry Chemical Physics. 20(18):12700-12709. https://doi.org/10.1039/C8CP00517FS12700127092018Chen, X., Huo, X., Liu, J., Wang, Y., Werth, C. J., & Strathmann, T. J. (2017). Exploring beyond palladium: Catalytic reduction of aqueous oxyanion pollutants with alternative platinum group metals and new mechanistic implications. Chemical Engineering Journal, 313, 745-752. doi:10.1016/j.cej.2016.12.058Lu, C., Wang, M., Feng, Z., Qi, Y., Feng, F., Ma, L., … Li, X. (2017). 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