51
|
Lwin S, Wachs IE. Catalyst Activation and Kinetics for Propylene Metathesis by Supported WOx/SiO2 Catalysts. ACS Catal 2016. [DOI: 10.1021/acscatal.6b03097] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
52
|
|
53
|
Keturakis CJ, Zhu M, Gibson EK, Daturi M, Tao F, Frenkel AI, Wachs IE. Dynamics of CrO3–Fe2O3 Catalysts during the High-Temperature Water-Gas Shift Reaction: Molecular Structures and Reactivity. ACS Catal 2016. [DOI: 10.1021/acscatal.6b01281] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
54
|
Zhu M, Rocha TCR, Lunkenbein T, Knop-Gericke A, Schlögl R, Wachs IE. Promotion Mechanisms of Iron Oxide-Based High Temperature Water–Gas Shift Catalysts by Chromium and Copper. ACS Catal 2016. [DOI: 10.1021/acscatal.6b00698] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
55
|
Lwin S, Li Y, Frenkel AI, Wachs IE. Nature of WOx Sites on SiO2 and Their Molecular Structure–Reactivity/Selectivity Relationships for Propylene Metathesis. ACS Catal 2016. [DOI: 10.1021/acscatal.6b00389] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
56
|
Zhu M, Wachs IE. Resolving the Reaction Mechanism for H2 Formation from High-Temperature Water–Gas Shift by Chromium–Iron Oxide Catalysts. ACS Catal 2016. [DOI: 10.1021/acscatal.6b00659] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
57
|
Chakrabarti A, Gierada M, Handzlik J, Wachs IE. Operando Molecular Spectroscopy During Ethylene Polymerization by Supported CrO x /SiO2 Catalysts: Active Sites, Reaction Intermediates, and Structure-Activity Relationship. Top Catal 2016. [DOI: 10.1007/s11244-016-0546-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
58
|
Zhu M, Wachs IE. Determining Number of Active Sites and TOF for the High-Temperature Water Gas Shift Reaction by Iron Oxide-Based Catalysts. ACS Catal 2016. [DOI: 10.1021/acscatal.5b02961] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
59
|
Zhu M, Wachs IE. Iron-Based Catalysts for the High-Temperature Water–Gas Shift (HT-WGS) Reaction: A Review. ACS Catal 2015. [DOI: 10.1021/acscatal.5b02594] [Citation(s) in RCA: 200] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
60
|
Lwin S, Wachs IE. Reaction Mechanism and Kinetics of Olefin Metathesis by Supported ReOx/Al2O3 Catalysts. ACS Catal 2015. [DOI: 10.1021/acscatal.5b02233] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
61
|
Lwin S, Wachs IE. Determination of Number of Activated Sites Present during Olefin Metathesis by Supported ReOx/Al2O3 Catalysts. ACS Catal 2015. [DOI: 10.1021/acscatal.5b01597] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
62
|
Lwin S, Li Y, Frenkel AI, Wachs IE. Activation of Surface ReOx Sites on Al2O3 Catalysts for Olefin Metathesis. ACS Catal 2015. [DOI: 10.1021/acscatal.5b01944] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
63
|
Gao J, Zheng Y, Tang Y, Jehng JM, Grybos R, Handzlik J, Wachs IE, Podkolzin SG. Spectroscopic and Computational Study of Cr Oxide Structures and Their Anchoring Sites on ZSM-5 Zeolites. ACS Catal 2015. [DOI: 10.1021/acscatal.5b00333] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
64
|
Gao J, Zheng Y, Jehng JM, Tang Y, Wachs IE, Podkolzin SG. Catalysis. Identification of molybdenum oxide nanostructures on zeolites for natural gas conversion. Science 2015; 348:686-90. [PMID: 25858978 DOI: 10.1126/science.aaa7048] [Citation(s) in RCA: 199] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 03/26/2015] [Indexed: 11/02/2022]
Abstract
Direct methane conversion into aromatic hydrocarbons over catalysts with molybdenum (Mo) nanostructures supported on shape-selective zeolites is a promising technology for natural gas liquefaction. We determined the identity and anchoring sites of the initial Mo structures in such catalysts as isolated oxide species with a single Mo atom on aluminum sites in the zeolite framework and on silicon sites on the zeolite external surface. During the reaction, the initial isolated Mo oxide species agglomerate and convert into carbided Mo nanoparticles. This process is reversible, and the initial isolated Mo oxide species can be restored by a treatment with gas-phase oxygen. Furthermore, the distribution of the Mo nanostructures can be controlled and catalytic performance can be fully restored, even enhanced, by adjusting the oxygen treatment.
Collapse
|
65
|
Lwin S, Keturakis C, Handzlik J, Sautet P, Li Y, Frenkel AI, Wachs IE. Surface ReOx Sites on Al2O3 and Their Molecular Structure–Reactivity Relationships for Olefin Metathesis. ACS Catal 2015. [DOI: 10.1021/cs5016518] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
66
|
Keturakis CJ, Ni F, Spicer M, Beaver MG, Caram HS, Wachs IE. Monitoring solid oxide CO2 capture sorbents in action. CHEMSUSCHEM 2014; 7:3459-3466. [PMID: 25333791 DOI: 10.1002/cssc.201402474] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 08/22/2014] [Indexed: 06/04/2023]
Abstract
The separation, capture, and storage of CO2 , the major greenhouse gas, from industrial gas streams has received considerable attention in recent years because of concerns about environmental effects of increasing CO2 concentration in the atmosphere. An emerging area of research utilizes reversible CO2 sorbents to increase conversion and rate of forward reactions for equilibrium-controlled reactions (sorption-enhanced reactions). Little fundamental information, however, is known about the nature of the sorbent surface sites, sorbent surface-CO2 complexes, and the CO2 adsorption/desorption mechanisms. The present study directly spectroscopically monitors Na2 O/Al2 O3 sorbent-CO2 surface complexes during adsorption/desorption with simultaneous analysis of desorbed CO2 gas, allowing establishment of molecular level structure-sorption relationships between individual surface carbonate complexes and the CO2 working capacity of sorbents at different temperatures.
Collapse
|
67
|
|
68
|
Amakawa K, Sun L, Guo C, Hävecker M, Kube P, Wachs IE, Lwin S, Frenkel AI, Patlolla A, Hermann K, Schlögl R, Trunschke A. Der Einfluss von strukturellen Spannungen auf die Reaktivität von getragenen Metalloxidkatalysatoren. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201306620] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
69
|
Amakawa K, Sun L, Guo C, Hävecker M, Kube P, Wachs IE, Lwin S, Frenkel AI, Patlolla A, Hermann K, Schlögl R, Trunschke A. How strain affects the reactivity of surface metal oxide catalysts. Angew Chem Int Ed Engl 2013; 52:13553-7. [PMID: 24259425 DOI: 10.1002/anie.201306620] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Indexed: 10/26/2022]
Abstract
Highly dispersed molybdenum oxide supported on mesoporous silica SBA-15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2-2.5 Mo atoms nm(-2) ). X-ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO4 units are the major surface species at all loadings. Higher reducibility at loadings close to the monolayer measured by temperature-programmed reduction and a steep increase in the catalytic activity observed in metathesis of propene and oxidative dehydrogenation of propane at 8 % of Mo loading are attributed to frustration of Mo oxide surface species and lateral interactions. Based on DFT calculations, NEXAFS spectra at the O-K-edge at high Mo loadings are explained by distorted MoO4 complexes. Limited availability of anchor silanol groups at high loadings forces the MoO4 groups to form more strained configurations. The occurrence of strain is linked to the increase in reactivity.
Collapse
|
70
|
Phivilay SP, Puretzky AA, Domen K, Wachs IE. Nature of Catalytic Active Sites Present on the Surface of Advanced Bulk Tantalum Mixed Oxide Photocatalysts. ACS Catal 2013. [DOI: 10.1021/cs400662m] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
71
|
Wachs IE, Phivilay SP, Roberts CA. Reporting of Reactivity for Heterogeneous Photocatalysis. ACS Catal 2013. [DOI: 10.1021/cs4005979] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
72
|
|
73
|
Carrero CA, Keturakis CJ, Orrego A, Schomäcker R, Wachs IE. Anomalous reactivity of supported V2O5 nanoparticles for propane oxidative dehydrogenation: influence of the vanadium oxide precursor. Dalton Trans 2013; 42:12644-53. [DOI: 10.1039/c3dt50611h] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
74
|
Landon J, Demeter E, İnoğlu N, Keturakis C, Wachs IE, Vasić R, Frenkel AI, Kitchin JR. Spectroscopic Characterization of Mixed Fe–Ni Oxide Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Electrolytes. ACS Catal 2012. [DOI: 10.1021/cs3002644] [Citation(s) in RCA: 376] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
|
75
|
|