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Robert K Grasselli - One of the best experts on this subject based on the ideXlab platform.
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active centers catalytic behavior symbiosis and redox properties of mov nb ta teo Ammoxidation catalysts
Topics in Catalysis, 2006Co-Authors: Johan Holmberg, Robert K Grasselli, Arne Andersson, D J Buttrey, James D Burrington, Wataru Ueda, Jun Kubo, Claus G Lugmair, Anthony F VolpeAbstract:Selective as well as waste forming active centers were defined for MoVNbTeO and MoVTaTeO catalysts in the Ammoxidation of propane to acrylonitrile and all catalytic functionalities were assigned to specific elements at the respective active centers. Symbiosis between M1 and M2 phases of these catalysts was observed, with phase cooperation being more extensive in the Nb than Ta containing compositions. The difference in catalytic effectiveness arises most likely because contact and surface area exposure of the two respective, cooperating phase pairs are not equal. The M1 phase of the catalysts is reducible by propane and ammonia in the absence of dioxygen and is regenerable to its original, fully oxidized state by dioxygen (air). No structural collapse is observed even after 120 C3H8 + NH3 reduction pulses. The so induced reduction of the catalyst extends up to 70 layers deep. The product distribution over the first few pulses is very similar to that under catalytic conditions, supporting the concept that lattice oxygen is involved in the catalytic Ammoxidation process. Therefore, the Ammoxidation of paraffins is a redox process, as is of course the well-known olefin Ammoxidation process. (Less)
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catalytic behaviour of m1 m2 and m1 m2 physical mixtures of the mo v nb te oxide system in propane and propene Ammoxidation
Applied Catalysis A-general, 2004Co-Authors: Johan Holmberg, Robert K Grasselli, Arne AnderssonAbstract:Essentially pure orthorhombic M1 and pseudo-hexagonal M2 phases were prepared using the precursor method. Consistent with literature the M1 phase was shown to be effective for propane Ammoxidation to acrylonitrile while the M2 phase was essentially inert for propane activation. Both phases convert propene efficiently to acrylonitrile. Both phases show a significant selectivity dependence on the ammonia and oxygen concentrations in the feed, revealing thereby additional insights into the reaction mechanism. Physical mixtures of the two separately prepared phases exhibited symbiosis in the Ammoxidation of propane when finally divided (similar to5 mum), thoroughly mixed and brought into intimate contact with each other. Acrylonitrile yields significantly higher than those obtained with the M1 phase alone were demonstrated with a 50 wt.% M1/50 wt.% M2 physical mixture having a corresponding Surface area ratio of about 4:1. The phase cooperation effect is particularly large at high propane conversions and non-existent when the particle size of the phases is too large (e.g. >250 mum) and the inter-particle contact is poor. Published by Elsevier B.V. (Less)
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structural aspects of the m1 and m2 phases in movnbteo propane Ammoxidation catalysts
Zeitschrift Fur Kristallographie, 2004Co-Authors: Peter Desanto, Robert K Grasselli, D J Buttrey, Claus G Lugmair, Anthony F Volpe, Brian H Toby, Thomas VogtAbstract:The structures of Ml and M2 in MoVNbTeO propane Ammoxidation catalysts have been solved using a combination of TEM, neutron powder diffraction, and synchrotron X-ray powder diffraction. The unit cell of M1 is Pba2 (No. 32) with a = 21.134(2) A, b = 26.658(2) A, c = 4.0146(3) A and Z = 4. The formula unit is Mo 7.8 V 1.2 NbTe 0.937 O 28.9 . The unit cell of M2 is Pmm2 (No. 25) with a = 12.6294(6)A, b = 7.29156(30) A, c = 4.02010(7) A and Z = 4. The formula unit is Mo 4.31 V 1.36 Te 1.81 Nb 0.33 O 19.81 . Tellurium sites in hexagonal channels of both phases are displaced toward vanadium-occupied framework sites, whereas Te in the heptagonal channel of Ml is near the channel center. The chemical topology resulting from oxidation states and Madelung site potentials presents active moieties for the Ammoxidation of propane in Ml and propene in M2. EPR confirmed the presence of V 4+ and possibly Mo 5+ in Ml and V 4+ in M2.
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structural characterization of the orthorhombic phase m1 in movnbteo propane Ammoxidation catalyst
Topics in Catalysis, 2003Co-Authors: Peter Desanto, Robert K Grasselli, D J Buttrey, Claus G Lugmair, Anthony F Volpe, Brian H Toby, Thomas VogtAbstract:The structure of the orthorhombic phase in the MoVNbTeO propane Ammoxidation catalyst system has been characterized and refined using a combination of TEM, synchrotron X-ray powder diffraction (S-XPD), and neutron powder diffraction (NPD). This phase, designated as M1 by Ushikubo et al. [1], crystallizes in the orthorhombic space group Pba2 (No. 32) with a = 21.134(2) A, b = 26.658(2) A, and c = 4.0146(3) A. The formula unit is Mo7.5V1.5NbTeO29. Bond valence sum calculations indicate the presence of d 1 metal sites neighbored by d 0 metal sites. The d 1 sites are occupied by a distribution of Mo5+ and V4+, whereas the d 0 sites are occupied by a distribution of Mo6+ and V5+. Out-of-center distortions in d 0 octahedra are consistent with the second-order Jahn–Teller effect and lattice effects. We argue that the V5+–O–V4+/Mo5+ moieties adjacent to Te4+ and Mo6+ sites in the [001] terminal plane provide a spatially isolated active site at which the selective Ammoxidation of propane occurs.
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surface characterization and reactivity in Ammoxidation reactions of vanadium antimonate catalysts
Applied Catalysis A-general, 1994Co-Authors: Arne Andersson, Robert K Grasselli, S L T Andersson, Gabriele Centi, Mehri Sanati, Ferruccio TrifiroAbstract:Unsupported vanadium antimonate catalysts with Sb/V ratios of 1 and 5 and samples with the latter ratio supported on alumina were studied in toluene and propane Ammoxidation to benzonitrile and acrylonitrile, respectively, and were characterized by X-ray photoelectron spectroscopy (XPS) analysis before and after catalytic tests. Activity data for toluene Ammoxidation suggest that excess antimony with respect to the stoichiometric amount required for forming the VSbO4 rutile phase affects the dispersion of the latter phase giving smaller particles. Vanadium sites are involved both in the activation of toluene and in the insertion of nitrogen in this reaction, whereas antimony does not play a specific role in the reaction mechanism. In propane Ammoxidation, on the other hand, due to a higher reaction temperature with respect to toluene (500°C vs. 370°C), free vanadia on the surface of the catalyst has a negative influence on the selectivity because it promotes the conversion of ammonia to nitrogen, decreasing the surface nitrogenous species required for the selective formation of acrylonitrile. Excess antimony is thus necessary for completing the reaction between antimony and vanadium oxides, but antimony also participates in the reaction mechanism. In propane Ammoxidation, in fact, XPS data show that both vanadium and antimony sites are reduced. Tentatively, vanadium sites are involved in the activation of propane, while antimony sites insert nitrogen. The differences between the toluene and propane Ammoxidation mechanisms are interpreted to be primarily related to the different reaction temperatures.
Arne Andersson - One of the best experts on this subject based on the ideXlab platform.
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active centers catalytic behavior symbiosis and redox properties of mov nb ta teo Ammoxidation catalysts
Topics in Catalysis, 2006Co-Authors: Johan Holmberg, Robert K Grasselli, Arne Andersson, D J Buttrey, James D Burrington, Wataru Ueda, Jun Kubo, Claus G Lugmair, Anthony F VolpeAbstract:Selective as well as waste forming active centers were defined for MoVNbTeO and MoVTaTeO catalysts in the Ammoxidation of propane to acrylonitrile and all catalytic functionalities were assigned to specific elements at the respective active centers. Symbiosis between M1 and M2 phases of these catalysts was observed, with phase cooperation being more extensive in the Nb than Ta containing compositions. The difference in catalytic effectiveness arises most likely because contact and surface area exposure of the two respective, cooperating phase pairs are not equal. The M1 phase of the catalysts is reducible by propane and ammonia in the absence of dioxygen and is regenerable to its original, fully oxidized state by dioxygen (air). No structural collapse is observed even after 120 C3H8 + NH3 reduction pulses. The so induced reduction of the catalyst extends up to 70 layers deep. The product distribution over the first few pulses is very similar to that under catalytic conditions, supporting the concept that lattice oxygen is involved in the catalytic Ammoxidation process. Therefore, the Ammoxidation of paraffins is a redox process, as is of course the well-known olefin Ammoxidation process. (Less)
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catalytic behaviour of m1 m2 and m1 m2 physical mixtures of the mo v nb te oxide system in propane and propene Ammoxidation
Applied Catalysis A-general, 2004Co-Authors: Johan Holmberg, Robert K Grasselli, Arne AnderssonAbstract:Essentially pure orthorhombic M1 and pseudo-hexagonal M2 phases were prepared using the precursor method. Consistent with literature the M1 phase was shown to be effective for propane Ammoxidation to acrylonitrile while the M2 phase was essentially inert for propane activation. Both phases convert propene efficiently to acrylonitrile. Both phases show a significant selectivity dependence on the ammonia and oxygen concentrations in the feed, revealing thereby additional insights into the reaction mechanism. Physical mixtures of the two separately prepared phases exhibited symbiosis in the Ammoxidation of propane when finally divided (similar to5 mum), thoroughly mixed and brought into intimate contact with each other. Acrylonitrile yields significantly higher than those obtained with the M1 phase alone were demonstrated with a 50 wt.% M1/50 wt.% M2 physical mixture having a corresponding Surface area ratio of about 4:1. The phase cooperation effect is particularly large at high propane conversions and non-existent when the particle size of the phases is too large (e.g. >250 mum) and the inter-particle contact is poor. Published by Elsevier B.V. (Less)
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Ammoxidation of propane over antimony vanadium oxide catalysts
Journal of Catalysis, 1994Co-Authors: Roland Nilsson, Thomas Lindblad, Arne AnderssonAbstract:Catalysts belonging to the Sb-V-O system were prepared with various Sb/V ratios and were used for propane Ammoxidation to acrylonitrile. XRD patterns of freshly prepared samples show those with excess vanadia to consist of V2O5 and SbVO4, while SbVO4 and α-Sb2O4 are constituents in the samples with a Sb/V ratio above unity. High rate and selectivity for propylene formation at low conversion are characteristic for samples with excess vanadia and considering XRD, Raman, infrared, and XPS results, this is explained by formation of amorphous vanadia spread over the surface of SbVO4. Catalysts with both α-Sb2O4 and SbVO4 phases are the most selective for acrylonitrile formation, a function that is linked to their ability to selectively transform intermediate propylene. XPS data suggest this function to be associated with the formation of suprasurface antimony sites on SbVO4 as a result of migration of antimony from α-Sb2O4 during the catalytic process. Raman and infrared spectral features revealed that compared with SbVO4, the samples with both α-Sb2O4 and SbVO4 are more efficiently reoxidised during propane Ammoxidation. Rate dependences on the partial pressures of reactants over a sample with excess α-Sb2O4 show that the adsorption of propane is the rate limiting step for propylene formation, and that acrylonitrile and carbon oxides are predominantly formed from the intermediate propylene in routes comprising nonequilibrated steps. Addition of water vapour results in an increase of rate and selectivity for acrylonitrile formation. The kinetic dependences indicate that for acrylonitrile formation it is advantageous to have a feed rich in propane and to use recirculation for obtaining high productivity.
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surface characterization and reactivity in Ammoxidation reactions of vanadium antimonate catalysts
Applied Catalysis A-general, 1994Co-Authors: Arne Andersson, Robert K Grasselli, S L T Andersson, Gabriele Centi, Mehri Sanati, Ferruccio TrifiroAbstract:Unsupported vanadium antimonate catalysts with Sb/V ratios of 1 and 5 and samples with the latter ratio supported on alumina were studied in toluene and propane Ammoxidation to benzonitrile and acrylonitrile, respectively, and were characterized by X-ray photoelectron spectroscopy (XPS) analysis before and after catalytic tests. Activity data for toluene Ammoxidation suggest that excess antimony with respect to the stoichiometric amount required for forming the VSbO4 rutile phase affects the dispersion of the latter phase giving smaller particles. Vanadium sites are involved both in the activation of toluene and in the insertion of nitrogen in this reaction, whereas antimony does not play a specific role in the reaction mechanism. In propane Ammoxidation, on the other hand, due to a higher reaction temperature with respect to toluene (500°C vs. 370°C), free vanadia on the surface of the catalyst has a negative influence on the selectivity because it promotes the conversion of ammonia to nitrogen, decreasing the surface nitrogenous species required for the selective formation of acrylonitrile. Excess antimony is thus necessary for completing the reaction between antimony and vanadium oxides, but antimony also participates in the reaction mechanism. In propane Ammoxidation, in fact, XPS data show that both vanadium and antimony sites are reduced. Tentatively, vanadium sites are involved in the activation of propane, while antimony sites insert nitrogen. The differences between the toluene and propane Ammoxidation mechanisms are interpreted to be primarily related to the different reaction temperatures.
Vadim V Guliants - One of the best experts on this subject based on the ideXlab platform.
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m1 to m2 phase transformation and phase cooperation in bulk mixed metal mo v m o m te nb catalysts for selective Ammoxidation of propane
Topics in Catalysis, 2008Co-Authors: P Korovchenko, N R Shiju, Alan Dozier, Uschi M Graham, M O Guerreroperez, Vadim V GuliantsAbstract:In the present study we systematically explored hydrothermal synthesis of bulk mixed metal Mo–V–(Te–Nb)–O catalysts and investigated the bulk characteristics of the resulting M1 and M2 phases as well as their roles in the selective Ammoxidation of propane. It was found that unlike Mo–V–Te–Nb–O M1 phases, the Mo–V–Te–O M1 phases may be quantitatively transformed into M2 phases of the same chemical composition indicating that Nb stabilizes the M1 structure. The stabilizing role of Nb and Te was further observed in high resolution TEM studies of Mo–V–(Te–Nb)–O catalysts which indicated that structural order and the M1 phase domain size progressively decreased in this order: Mo–V–Te–Nb–O > Mo–V–Te–O > Mo–V–O. The cooperation between the M1 and M2 phases in propane Ammoxidation to acrylonitrile was observed only at low propane conversions suggesting that the M1 phase is the only crystalline phase required for the activity and selectivity of the Mo–V–Te–Nb–O catalysts in propane Ammoxidation to acrylonitrile at practical propane conversions.
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the role of surface basal planes of layered mixed metal oxides in selective transformation of lower alkanes propane Ammoxidation over surface ab planes of mo v te nb o m1 phase
Journal of the American Chemical Society, 2008Co-Authors: Raveendran N Shiju, Xinhua Liang, Alan W Weimer, Chengdu Liang, Sheng Dai, Vadim V GuliantsAbstract:The surface ab planes of the M1 phase exposed selectively after atomic layer deposition (ALD) of alumina followed by crushing showed significantly improved selectivity to acrylonitrile during propane Ammoxidation. The results demonstrated the importance of surface ab planes for the activity and selectivity of the M1 phase in propane Ammoxidation and general utility of surface modification by ALD in studies of catalytic behavior of surface planes in layered mixed metal oxides.
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13c isotope labeling study of propane Ammoxidation over m1 phase mo v te nb o mixed oxide catalyst
Journal of Physical Chemistry C, 2007Co-Authors: Raveendran N Shiju, Ramesh R Kale, Suri S Iyer, Vadim V GuliantsAbstract:Direct Ammoxidation of propane to acrylonitrile has been investigated recently as an alternate method for the current process based on propene. The Mo−V−Te−Nb−O mixed oxide is the most promising catalyst at present for this reaction. The reaction mechanism of propane Ammoxidation over this catalyst is still not investigated experimentally. In this work, we have tested the presence of C6 intermediates during the course of the reaction using 13C-labeled propane. The results show that a direct pathway for the Ammoxidation of propane to acrylonitrile without skeletal rearrangement of the carbon backbone operates under realistic, steady-state conditions.
Xiuquan Jia - One of the best experts on this subject based on the ideXlab platform.
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Carboxylic acid-modified metal oxide catalyst for selectivity-tunable aerobic Ammoxidation
Nature Publishing Group, 2018Co-Authors: Xiuquan Jia, Fei Xia, Jin GaoAbstract:Precisely controlling the surface properties of base-metal oxide catalysts to tune the reaction selectivity remains a challenge. Here, the authors show that a green modification of manganese oxide surface with carboxylates can be used to tune the Ammoxidation selectivity toward the desired products
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Al-Doping Promoted Aerobic Amidation of 5‑Hydroxymethylfurfural to 2,5-Furandicarboxamide over Cryptomelane
2018Co-Authors: Xiuquan Jia, Fei Xia, Yizheng HuangAbstract:Liquid-phase Ammoxidation of biomass-derived platform compound 5-hydroxymethylfurfural (HMF) provides a sustainable route for the synthesis nitrogen-containing chemicals from renewable resources. A series of metal-cation-doped (In3+, Cr3+, Co2+, Ni2+, Cu2+, Zn2+, Al3+) cryptomelanes ([M]-K-OMS-2) were prepared and used as catalyst for the aerobic Ammoxidation-hydration tandem reaction of HMF to 2,5-furandicarboxamide. Al-doped K-OMS-2 prepared with the refluxing method showed enhanced catalytic performance in comparison with K-OMS-2. Kinetic experiments indicated that the efficient synthesis of 2,5-furandicarboxamide over 0.15[Al]-K-OMS-2 catalyst was attributed to its higher activity on slow steps of alcohol oxidation and nitrile hydration during the amidation reaction of HMF. The results of XPS, O2-TPD-MS, and NH3-TPD-MS indicated that the Al-doping increased the lattice oxygen reactivity and the strength of strong acid sites, which were responsible for the enhanced efficiency of 0.15[Al]-K-OMS-2
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alkali α mno2 naxmno2 collaboratively catalyzed Ammoxidation pinner tandem reaction of aldehydes
Catalysis Science & Technology, 2016Co-Authors: Xiuquan Jia, Min Wang, Jin GaoAbstract:The tandem reaction is a growing field to yield important advances toward green and sustainable chemistry. Herein, we report a bifunctional manganese oxide catalyst with an interface binding redox phase (α-MnO2) and a basic phase (NaxMnO2). The molar ratio of NaOH/Mn plays a great role in the formation of α-MnO2/NaxMnO2. The sodium cation is essential for the formation of a basic NaxMnO2 phase while the potassium cation promotes the formation of a redox-active α-MnO2 phase. The interface structure of α-MnO2/NaxMnO2 geometrically favors the Ammoxidation–Pinner tandem reaction to synthesize imidates in a 58–96% yield from aldehydes. Thus a phase collaborative effect is observed. In the Ammoxidation process, the redox cycle of MnIV/MnIII is involved and the lattice oxygen in the α-MnO2 phase acts as an active oxygen species. The O–H in methanol is activated and dissociated on the basic sites of NaxMnO2 to the adsorbed methoxyl species to facilitate the Pinner synthesis. This approach bypasses the conventional synthesis of imidates, which suffer from harsh reaction conditions and the requirement for multiple steps.
Alexis T Bell - One of the best experts on this subject based on the ideXlab platform.
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insights into the mechanism and kinetics of propene oxidation and Ammoxidation over bismuth molybdate catalysts derived from experiments and theory
Journal of Catalysis, 2021Co-Authors: Alexis T BellAbstract:Abstract Robert K. Grasselli was a pioneer in the development and commercialization of catalysts for propene oxidation to acrolein and Ammoxidation to acrylonitrile, products that today are produced at the level of over 10 billion pounds per year. The catalysts used for both processes are contain bismuth molybdates augmented by up to seven additional elements used to attain high activity, selectivity, and stability. The importance of propene oxidation and Ammoxidation has stimulated considerable interest in understanding the mechanism and kinetics of these processes and the particular role of catalyst composition and structure in defining catalyst activity and selectivity. Virtually all of this work has been carried out using bismuth molybdates, primarily α-Bi2Mo3O12. The objective of this paper is to review the findings of experimental studies and illustrate how theoretical studies based on density functional theory provide additional insights that support deductions drawn from experiments and, more importantly, provide information that cannot be accessed experimentally.
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a dft investigation of the mechanism of propene Ammoxidation over α bismuth molybdate
ACS Catalysis, 2017Co-Authors: Rachel B Licht, Alexis T BellAbstract:The mechanisms and energetics for the propene oxidation and Ammoxidation occurring on the (010) surface of Bi2Mo3O12 were investigated using density functional theory (DFT). An energetically feasible sequence of elementary steps for propene oxidation to acrolein, propene Ammoxidation to acrylonitrile, and acrolein Ammoxidation to acrylonitrile is proposed. Consistent with experimental findings, the rate-limiting step for both propene oxidation and Ammoxidation is the initial hydrogen abstraction from the methyl group of propene, which is calculated to have an apparent activation energy of 27.3 kcal/mol. The allyl species produced in this reaction is stabilized as an allyl alkoxide, which can then undergo hydrogen abstraction to form acrolein or react with ammonia adsorbed on under-coordinated surface Bi3+ cations to form allylamine. Dehydrogenation of allylamine is shown to produce acrylonitrile, whereas reaction with additional adsorbed ammonia leads to the formation of acetonitrile and hydrogen cyanide....
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the mechanism and kinetics of propene Ammoxidation over α bismuth molybdate
Journal of Catalysis, 2016Co-Authors: Rachel B Licht, Alexis T Bell, Diana VogtAbstract:Abstract Propene Ammoxidation over Bi2Mo3O12 was investigated to elucidate product (acrylonitrile, acetonitrile, HCN, acrolein, N2, etc.) formation pathways. Propene consumption rate is first order in propene and zero order in ammonia (for NH3/C3H6 = 0–2) and oxygen (for O2/C3H6 ⩾ 1.5) partial pressures, with an activation energy (Ea = 22 kcal/mol) comparable to that for propene oxidation, suggesting the same rate-limiting step for both reactions. We propose two N-containing species are relevant at Ammoxidation conditions: adsorbed NH3 on surface Bi3+ ions that reacts with a propene derivative to form products with C N bonds, and a few metastable M-NHx (M = Mo, Bi; x = 1, 2) groups that are very sensitive to destruction by water, but that are responsible for NH3 oxidation to N2. A proposed reaction mechanism and model that captures the experimental trends in product distribution as a function of partial pressures and temperature are presented.