Vanadium Supported on Alumina and/or Zirconia Catalysts for the Selective Transformation of Ethane and Methanol

[EN] Vanadium supported on pure (Al2O3, ZrO2) or mixed zirconia-alumina (with Al/(Al + Zr) ratio of 0.75 or 0.25) catalysts have been prepared by wet impregnation, using homemade prepared supports. The catalysts have been characterized and tested in the oxidative dehydrogenation (ODH) of ethane and in the methanol aerobic transformation. The catalytic performance strongly depends on the nature of the metal oxide support. Thus, activity decreases in the order: VOx/ZrO2 > VOx/(Al,Zr-oxides) > VOx/Al2O3. On the other hand, at low and medium ethane conversions, the selectivity to ethylene presents an opposite trend: VOx/Al2O3 > VOx/(Al,Zr-oxides) > VOx/ZrO2. The different selectivity to ethylene at high conversion is due to the lower/higher initial ethylene formation and to the extent of the ethylene decomposition. Interestingly, VOx/(Al,Zr-oxides) with low Zr-loading present the lowest ethylene decomposition. The catalytic results obtained mainly depend on the nature of the supports whereas the role of the dispersion of vanadium species is unclear. In methanol oxidation, the catalysts tested present similar catalytic activity regardless of the support (Al2O3, ZrO2 or mixed Al2O3-ZrO2) but strong differences in the selectivity to the reaction products. Thus, dimethyl ether was mainly observed on alumina-supported vanadium oxide catalysts (which is associated to the presence of acidic sites on the surface of the catalyst, as determined by TPD-NH3). Formaldehyde was the main reaction product on catalysts supported on Zr-containing oxides (which can be related to a low presence of acid sites). In this article, the importance of the presence of acid sites in ethane ODH, which can be estimated using the methanol transformation reaction, is also discussed.The authors would like to acknowledge the DGICYT (CTQ2015-68951-C3-1-R and MAT2017-84118-C2-1-R projects), the Secretary of State for International Cooperation in Spain (Project AP/040992/11) and FEDER for financial support. B.S. also thanks the University of Valencia (UV-INV-AE16-484416).Benomar, S.; Masso Ramírez, A.; Solsona Espriu, BE.; Isaadi, R.; López Nieto, JM. (2018). Vanadium Supported on Alumina and/or Zirconia Catalysts for the Selective Transformation of Ethane and Methanol. Catalysts. 8(4):1-18. https://doi.org/10.3390/catal8040126S11884Chieregato, A., López Nieto, J. M., & Cavani, F. (2015). Mixed-oxide catalysts with vanadium as the key element for gas-phase reactions. Coordination Chemistry Reviews, 301-302, 3-23. doi:10.1016/j.ccr.2014.12.003Nieto, J. M. L. (2006). 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Study on the structure, acidic properties of V–Zr nanocrystal catalysts in oxidative dehydrogenation of propane. Applied Surface Science, 289, 316-325. doi:10.1016/j.apsusc.2013.10.158Elbadawi, A. H., Ba-Shammakh, M. S., Al-Ghamdi, S., Razzak, S. A., & Hossain, M. M. (2016). Reduction kinetics and catalytic activity of VO x /γ-Al 2 O 3 -ZrO 2 for gas phase oxygen free ODH of ethane. Chemical Engineering Journal, 284, 448-457. doi:10.1016/j.cej.2015.08.048Rostom, S., & de Lasa, H. I. (2017). Propane Oxidative Dehydrogenation Using Consecutive Feed Injections and Fluidizable VOx/γAl2O3 and VOx/ZrO2–γAl2O3 Catalysts. Industrial & Engineering Chemistry Research, 56(45), 13109-13124. doi:10.1021/acs.iecr.7b01369HERACLEOUS, E., & LEMONIDOU, A. (2006). Ni–Nb–O mixed oxides as highly active and selective catalysts for ethene production via ethane oxidative dehydrogenation. Part I: Characterization and catalytic performance. 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Nickel oxide supported on porous clay heterostructures as selective catalysts for the oxidative dehydrogenation of ethane. Catalysis Science & Technology, 6(10), 3419-3429. doi:10.1039/c5cy01811kGärtner, C. A., van Veen, A. C., & Lercher, J. A. (2014). Oxidative Dehydrogenation of Ethane on Dynamically Rearranging Supported Chloride Catalysts. Journal of the American Chemical Society, 136(36), 12691-12701. doi:10.1021/ja505411sTatibouët, J. M. (1997). Methanol oxidation as a catalytic surface probe. Applied Catalysis A: General, 148(2), 213-252. doi:10.1016/s0926-860x(96)00236-0Forzatti, P., Tronconi, E., Elmi, A. S., & Busca, G. (1997). Methanol oxidation over vanadia-based catalysts. Applied Catalysis A: General, 157(1-2), 387-408. doi:10.1016/s0926-860x(97)00026-4Wachs, I. E., Chen, Y., Jehng, J.-M., Briand, L. E., & Tanaka, T. (2003). Molecular structure and reactivity of the Group V metal oxides. Catalysis Today, 78(1-4), 13-24. doi:10.1016/s0920-5861(02)00337-1Shah, P. 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Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane

[EN] NiO and metal-promoted NiO catalysts (M-NiO, with a M/(M+Ni) atomic ratio of 0.08, with M = Nb, Sn, or La) have been prepared, tested in the oxidative dehydrogenation (ODH) of ethane, and characterized by means of XRD, TPR, HRTEM, Raman, XPS, and in situ XAS (using H-2/He, air or C2H6/He mixtures). The selectivity to ethylene during the ODH of ethane decreases according to the following trend: Nb NiO Sn NiO > La NiO > NiO, whereas the catalyst reducibility (determined by both TPR and XAS using H-2/He mixtures) shows the opposite trend. However, different reducibility and catalytic behavior in the absence of oxygen (ethane/He mixtures) have been observed, especially when comparing Nb- and Sn-promoted NiO samples. These differences can be ascribed mainly to a different phase distribution of the promoter. The results presented here are discussed in terms of the nature of active and selective sites for ODH of ethane in selective and unselective catalysts, but also the role of promoters and the importance of their phase distribution.The authors would like to acknowledge the DGICYT in Spain CTQ2012-37925-C03-2, CTQ2015-68951-C3-1-R, and CTQ2015-68951-C3-3-R. Authors thank European Synchrotron Radiation Facility, ESRF (Project CH-4512; BM25-SpLine Beamlime). Authors from ITQ also thank Project SEV-2016-0683 for financial support. D.D. thanks MINECO and Severo Ochoa Excellence Program for his fellowship (SVP-2014-068669). B.S. also thanks UV-INV-AE16-484416. Finally, the authors thank the Electron Microscopy Service of Universitat Politecnica de Valencia for their support.Delgado-Muñoz, D.; Solsona Espriu, BE.; Ykrelef, A.; Rodriguez-Gomez, A.; Caballero, A.; Rodríguez-Aguado, E.; Rodriguez-Castellón, E.... (2017). Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane. The Journal of Physical Chemistry C. 121(45):25132-25142. https://doi.org/10.1021/acs.jpcc.7b07066S25132251421214

Porous clays heterostructures as supports of iron oxide for environmental catalysis

[EN] Porous Clays Heterostructures (PCH) from natural pillared clays (bentonite with a high proportion of montmorillonite) have been used as supports of iron oxide for two reactions of environmental interest: i) the elimination of toluene (a representative compound of one of the most toxic subsets of volatile organic compounds, aromatics) by total oxidation and ii) the selective oxidation of H2S to elemental sulfur. For both reactions these catalysts have resulted to be remarkably more efficient than similar catalysts prepared using conventional silica as a support. Thus, in the total oxidation of toluene it has been observed that the catalytic activity obtained using siliceous PCH is two orders of magnitude higher than that with conventional silica. The catalytic activity has shown to be dependant of the capacity of the support for dispersing iron oxide in a way that the higher the dispersion of iron oxide on the surface of the support, the higher is the activity. In the case of the selective oxidation of H2S to S both higher catalytic activity and higher selectivity to S have been observed using siliceous porous clays heterostructures than using conventional silica. Highly dispersed FeOx species have been shown as highly selective towards elemental sulfur whereas more aggregated FeOx species favour the formation of sulphur oxides decreasing the selectivity to S. Analyses of the surface by XPS have shown the predominance of sulfate species in the catalysts presenting low selectivity to elemental sulfur.The authors would like to acknowledge the DGICYT in Spain (CTQ2015-68951-C3-1-R, CTQ2015-68951-C3-3-R, CTQ2012-37925-C03-2, CTQ2012-37925-C03-3 and CTQ2012-37984-C02-01) and FEDER for financial support. We also thank the University of Valencia for funding (UV-INV-AE-16-484416) and SCSIE-UV for assistance.Sanchis Martinez, R.; Cecilia, J.; Soriano Rodríguez, MD.; Vazquez, I.; Dejoz, A.; López Nieto, JM.; Rodriguez-Castellon, E.... (2008). Porous clays heterostructures as supports of iron oxide for environmental catalysis. Chemical Engineering Journal. 334:1159-1168. https://doi.org/10.1016/j.cej.2017.11.060S1159116833

Total oxidation of VOCs on mesoporous iron oxide catalysts: soft chemistry route versus hard template method

[EN] A comparative study on the total oxidation of volatile organic compounds, VOCs, on mesoporous iron oxide catalysts prepared by soft chemistry route versus those achieved by hard template methodThe authors would like to acknowledge the DGICYT in Spain (CTQ2012-37925-C03-1, CTQ2012-37925-C03-2, CTQ2012-37925-C03-3 and CTQ2012-37984-C02-01) and FEDER for financial support. We also thank the University of Valencia and SCSIE-UV for assistance.Solsona Espriu, BE.; Garcia, T.; Sanchis Martinez, R.; Soriano Rodríguez, MD.; Moreno, M.; Rodríguez-Castellon, E.; Agouram, S.... (2016). Total oxidation of VOCs on mesoporous iron oxide catalysts: soft chemistry route versus hard template method. The Chemical Engineering Journal and the Biochemical Engineering Journal. 290:273-281. https://doi.org/10.1016/j.cej.2015.12.109S27328129

Oxidative dehydrogenation of ethane over NiO-CeO2 mixed oxides catalysts

[EN] In this paper we present the synthesis, characterization and catalytic behaviour in the oxidative dehydrogenation of ethane of NiO-CeO2 mixed oxides. The addition of cerium oxide to NiO strongly modifies its catalytic performance, although the changes in the catalytic behaviour depend on the catalyst composition. The incorporation of low amounts of cerium oxide to NiO multiplies the productivity to ethylene in the oxidative dehydrogenation of ethane by a factor of ca. 7, which is the result of an increase in both catalytic activity and selectivity to ethylene. The enhanced activity has been related to the remarkable increase of the surface area of catalyst and the low crystal sizes of NiO that takes place when a tiny amount of cerium oxide is incorporated to the NiO. The higher selectivity to ethylene has been related to the modification of the nature of Ni-O species, which implies a lower production of carbon oxides. On the other hand, high activity and selectivity is also observed over catalysts rich in cerium ( with Ni/ Ce ratios between 0.2 and 3). In this case, a different mechanism can be proposed in which the high capacity of CeO2 to bomb oxygen from bulk to surface and the partial formation of NiO and Ce1-xNixO2 facilitates a faster reoxidation of active Ni-sites by a synergic effect improving catalytic activity. (C) 2011 Elsevier B.V. All rights reserved.The authors would like to thank the DGICYT in Spain (Project CTQ2009-14495) for financial support. SH thanks a fellowship from DGICYT.Solsona Espriu, BE.; Concepción Heydorn, P.; Hernández Morejudo, S.; Demicol, B.; López Nieto, JM. (2012). Oxidative dehydrogenation of ethane over NiO-CeO2 mixed oxides catalysts. Catalysis Today. 180(1):51-58. https://doi.org/10.1016/j.cattod.2011.03.056S5158180

Influence of gel composition in the synthesis of MoVTeNb catalysts over their catalytic performance in partial propane and propylene oxidation

[EN] MoVTeNb mixed oxides catalysts have been prepared by a slurry method with different molar compositions (Mo/Te ratio from 2 to 6 and Nb/(V + Nb) ratio from 0 to 0.7) in the synthesis gel leading to different crystalline phases distribution and catalytic behaviour in the partial oxidation of both propane and propylene to acrylic acid. Chemical analysis indicates that the composition of samples before and after the heat-treatment changes, especially the Te-content, since a significant amount of Te is lost during the heat-treatment step when the amount of oxalate (from niobium oxalate) increases in the synthesis gel. Thus, the nature of the crystalline phases and the catalytic performance of heat-treated materials will be related to the final chemical composition. On the other hand, only the catalysts presenting Te(2)M(20)O(57) (M = Mo, V, Nb) crystalline structure, the so-called M1 phase, were active and selective in the partial oxidation of propane to acrylic acid. Moreover, all catalysts were active and relatively selective to the formation of O-containing products, i.e. acrolein and/or acrylic acid, during the partial propylene oxidation although the more active ones were those presenting M1 phase. (C) 2009 Elsevier B.V. All rights reserved.Financial support from DGICYT in Spain (Project CTQ2006- 09358/BQU) and the European Union through the FP6 Integrated Project (TOPCOMBI, NMP2-CT2005-515792) is gratefully acknowledgedIvars Barceló, F.; Solsona Espriu, BE.; Hernández Morejudo, S.; López Nieto, JM. (2010). Influence of gel composition in the synthesis of MoVTeNb catalysts over their catalytic performance in partial propane and propylene oxidation. Catalysis Today. 149(3-4):260-266. doi:10.1016/j.cattod.2009.09.018S2602661493-

Selective propane oxidation over MoVSbO catalysts. On the preparation, characterization and catalytic behavior of M1 phase

Nb-free (SbO)(2)M(20)O(56) catalysts (M = Mo, V) presenting pure M1 phase have been prepared by a post-synthesis treatment with hydrogen peroxide of a heat-treated MoVSbO mixed metal oxide catalyst previously prepared by hydrothermal method. The characterization of catalysts and their results for propane oxidation suggest that the optimization in the preparation of the M1 phase depends strongly on the washing procedure. The optimal removing of Sb species formed during post-synthesis treatment can explain the improvement in the catalytic activity; while the better selectivity to acrylic acid of the catalysts obtained by post-synthesis treatment can be explained by the elimination of M2 phase and the modification of the M1 phase crystals surface. The importance of M1 phase in the catalytic performance during the selective propane oxidation over Nb-free Mo-V-Sb based catalysts is also discussed. (C) 2008 Elsevier Inc. All rights reserved.The authors thank the Spanish CICYT for financial support (Projects NAN2004-09267-CO3-02 and CTQ2006-09358/BQU) and the technical support of the Microscopy Department of Universidad Politecnica de Valencia (Spain).Ivars Barceló, F.; Solsona Espriu, BE.; Rodriguez-Castellon, E.; López Nieto, JM. (2009). Selective propane oxidation over MoVSbO catalysts. On the preparation, characterization and catalytic behavior of M1 phase. Journal of Catalysis. 262(1):35-43. https://doi.org/10.1016/j.jcat.2008.11.021S3543262

Promoted NiO catalysts for the oxidative dehydrogenation of ethane

Metal oxide promoted NiO catalysts with a Ni/(Me + Ni) atomic ratio 0.92 have been investigated for the oxidative dehydrogenation of ethane. These materials have been characterized by several techniques (N-2-adsorption, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transformed infrared spectroscopy of adsorbed CO and ethylene). The nature of surface sites is strongly influenced by the valence and the acid/base characteristics of the metal oxide promoters, which have a great impact on the selectivity to ethylene. Accordingly, a clear correlation between selectivity to ethylene and the valence of the promoter has been observed in the present work. Additionally, the acidity of the catalyst also enhances the selectivity to ethylene.The Spanish authors would like to thank the DGICYT in Spain (Project CTQ2012-37925-C03-1 and CTQ2012-37925-C03-2) for financial support.López Nieto, JM.; Solsona Espriu, BE.; Grasselli, RK.; Concepción Heydorn, P. (2014). Promoted NiO catalysts for the oxidative dehydrogenation of ethane. Topics in Catalysis. 57(14-16):1248-1255. doi:10.1007/s11244-014-0288-2S124812555714-1

Influence of the Nature of the Promoter in NiO Catalysts on the Selectivity to Olefin During the Oxidative Dehydrogenation of Propane and Ethane

[EN] A comparative study of the catalytic properties for the oxidation of C2-C3 alkanes and olefins has been carried out over unpromoted and M-promoted NiO catalysts (Me¿=¿K, La, Ce, al, Zr, Sn, Nb). The catalysts have been characterized by several physico-chemical techniques (UV Raman, Visible Raman, FTIR of adsorbed CO and XPS). The characteristics of promoter elements are of paramount importance, since they are able to modify both the nature of the active nickel and the concentration of electrophilic O2¿/O¿ oxygen species. Thus, a relatively high acidity and valence of the promoter oxide (with oxidation state higher than¿+¿3) are necessary to achieve high selectivity to olefins during the oxidative dehydrogenation (ODH) of C2¿C3 alkanes. In addition, an inverse correlation between the selectivity to the corresponding olefin and the concentration of electrophilic oxygen species has been observed, although the selectivity to propene during propane ODH is lower than the selectivity to ethylene achieved during ethane ODH. On the other hand, a very low influence of alkane conversion on the selectivity to the corresponding olefins is observed. This behaviour can be explained by considering that the reaction rate for olefin combustion is lower than the reaction rate for alkane oxidation. However, the comparative study of the oxidation of alkanes and olefins suggest that the differences observed between the ODH of propane and ethane are not related to the reactivity of olefins, but to the different number and reactivity of C¿H bonds in both alkanes. A discussion on the importance of the concentration of active sites and the characteristics of the alkanes fed on the selectivity to olefin during the alkane ODH is also presented.The authors would like to acknowledge the Ministerio de Ciencia, Innovacion y Universidades of Spain (RTl2018-099668-B-C21 and MAT2017-84118-C2-1-R projects) and FEDER. Authors from ITQ also thank Project SEV-2016-0683 for supporting this research. D.D. thanks MINECO and Severo Ochoa Excellence Program for his fellowship (SVP-2014-068669).Delgado Muñoz, D.; Sanchis, R.; Solsona Espriu, BE.; Concepción Heydorn, P.; López Nieto, JM. (2020). Influence of the Nature of the Promoter in NiO Catalysts on the Selectivity to Olefin During the Oxidative Dehydrogenation of Propane and Ethane. Topics in Catalysis. 63(19-20):1731-1742. https://doi.org/10.1007/s11244-020-01329-5173117426319-2

Selective oxidation of propane over alkali-doped Mo-V-Sb-O catalysts

[EN] Alkali metal-doped MoVSbO catalysts have been prepared by impregnation of a MoVSbO-mixed oxide (prepared previously by a hydrothermal synthesis) and finally activated at 500 or 600 degrees C in N-2. The catalysts have been characterized and tested for the selective oxidation of propane and propylene. Alkali-doped catalysts improved in general the catalytic performance of MoVSbO, resulting more selective to acrylic acid and less selective to acetic acid than the corresponding alkali-free MoVSbO catalysts. However, the specific behaviour strongly depends on both the alkali metal added and/or the final activation temperature. At isoconversion conditions, catalysts activated at 600 degrees C present selectivity to acrylic acid higher than that achieved on those activated at 500 degrees C, both K-doped catalysts presenting the highest yield to acrylic acid. The changes in the number of acid sites as well as the nature of crystalline phases can explain the catalytic behaviour of alkali-doped MoVSbO catalysts. (C) 2008 Elsevier B.V. All rights reserved.Financial support from DGICYT in Spain through Project CTQ2006-09358/BQU is gratefully acknowledged.Ivars Barceló, F.; Solsona Espriu, BE.; Botella Asuncion, P.; Soriano Rodríguez, MD.; López Nieto, JM. (2009). Selective oxidation of propane over alkali-doped Mo-V-Sb-O catalysts. Catalysis Today. 141(3-4):294-299. doi:10.1016/j.cattod.2008.07.002S2942991413-