Relationships among the Catalytic Performance, Redox Activity, and Structure of Cu-CHA Catalysts for the Direct Oxidation of Methane to Methanol Investigated Using In Situ XAFS and UV–Vis Spectroscopies DOI
Junya Ohyama,

Yuka Tsuchimura,

Airi Hirayama

и другие.

ACS Catalysis, Год журнала: 2022, Номер 12(4), С. 2454 - 2462

Опубликована: Фев. 3, 2022

Catalytic reaction systems for the direct conversion of methane to methanol have been previously developed using Cu zeolites. Among these materials, Cu-CHA has reported show relatively high catalytic performance during CH4–O2–H2O mixtures, although this activity varies with composition. In present study, four catalysts having different compositions and levels were prepared, redox properties local structures specimens analyzed in situ X-ray absorption fine structure UV–vis diffuse reflectance spectroscopies conjunction a mixture. The relationships between rates materials activities (as reflected turnover frequency (TOF) CH4 oxidation) assessed, analysis showed that reduction rate was highly correlated activity. data also suggested Cu2+ is associated activation C–H bonds CH4, which rate-determining step overall reaction. effects on selectivity CH3OH, TOF value, studied. Those samples proportions ions coordinated six-membered rings (Z2Cu) CHA framework exhibited higher than [CuOH]+ eight-membered (ZCuOH), values former not those latter because slower species. catalyses can be attributed difference Cu2Ox active formed Z2Cu-rich ZCuOH-rich samples.

Язык: Английский

In Situ Spectroscopic Studies on the Redox Cycle of NH3−SCR over Cu−CHA Zeolites DOI
Chong Liu,

Hiroe Kubota,

Takehiro Amada

и другие.

ChemCatChem, Год журнала: 2020, Номер 12(11), С. 3050 - 3059

Опубликована: Фев. 25, 2020

Abstract The selective catalytic reduction of NO with ammonia (NH 3 −SCR) catalyzed by Cu−CHA zeolites is thoroughly investigated using in situ spectroscopic experiments combined on‐line mass spectroscopy (MS) under steady‐state NH −SCR conditions and transient for Cu(II)/Cu(I) redox cycles. Quantitative analysis the XANES spectra show that ‐coordinated Cu(II) species dominant Cu at low temperatures (100–150 °C). At higher temperatures, [Cu(NH ) 2 ] + complex coexist, possibly because rate Cu(II)→Cu(I) step comparable to Cu(I)→Cu(II) oxidation step. In XANES, IR/MS, UV‐vis/MS on half cycle demonstrate occurs via reaction ‐liganded yield N H O. For cycle, Cu(I) 10 % O 200 °C indicate an increased density CHA zeolite exhibits a rate. UV‐vis reoxidation different mixtures oxidant feed gas key role cycle. It suggested only as oxidant, high promotes SCR activity enhancing oxidative activation during

Язык: Английский

Процитировано

75
Viologen‐Immobilized 2D Polymer Film Enabling Highly Efficient Electrochromic Device for Solar‐Powered Smart Window DOI Creative Commons
Zhiyong Wang, Xiangkun Jia, Panpan Zhang

и другие.

Advanced Materials, Год журнала: 2021, Номер 34(1)

Опубликована: Окт. 8, 2021

Electrochromic devices (ECDs) have emerged as a unique class of optoelectronic for the development smart windows. However, current ECDs typically suffer from low coloration efficiency (CE) and high energy consumption, which thus hindered their practical applications, especially components in solar-powered EC Here, high-performance with fully crystalline viologen-immobilized 2D polymer (V2DP) thin film color-switching layer is demonstrated. The density vertically oriented pore channels (pore size ≈ 4.5 nm; 5.8 × 1016 m-2 ) synthetic V2DP enables utilization redox-active viologen moieties benefits Li+ ion diffusion/transport. As result, as-fabricated achieve rapid switching speed (coloration, 2.8 s; bleaching, 1.2 s), CE (989 cm2 C-1 ), consumption (21.1 µW cm-2 ). Moreover, it managed to fabricate transmission-tunable, self-sustainable window prototypes by integrating transparent solar cells. This work sheds light on designing electroactive polymers molecular precision optoelectronics paves route toward developing self-powered windows offset electricity buildings.

Язык: Английский

Процитировано

68
Spectroscopic Definition of a Highly Reactive Site in Cu-CHA for Selective Methane Oxidation: Tuning a Mono-μ-Oxo Dicopper(II) Active Site for Reactivity DOI
Hannah M. Rhoda, Dieter Plessers, Alexander J. Heyer

и другие.

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(19), С. 7531 - 7540

Опубликована: Май 10, 2021

Using UV-vis and resonance Raman spectroscopy, we identify a [Cu2O]2+ active site in O2 N2O activated Cu-CHA that reacts with methane to form methanol at low temperature. The Cu-O-Cu angle (120°) is smaller than for the core on Cu-MFI (140°), its coordination geometry zeolite lattice different. Site-selective kinetics obtained by operando show more reactive Cu-MFI. From DFT calculations, find increased reactivity of direct reflection strong [Cu2OH]2+ bond formed along H atom abstraction reaction coordinate. A systematic evaluation these cores reveals higher O-H strength due relative orientation two planes coordinating bidentate O-Al-O T-sites connect lattice. This work our earlier study ( J. Am. Chem. Soc, 2018, 140, 9236-9243) elucidates how constraints can influence reactivity.

Язык: Английский

Процитировано

64
Dynamic Evolution of Zeolite Framework and Metal-Zeolite Interface DOI

Zhong‐Pan Hu,

Jingfeng Han, Yingxu Wei

и другие.

ACS Catalysis, Год журнала: 2022, Номер 12(9), С. 5060 - 5076

Опубликована: Апрель 14, 2022

Zeolites and metal-zeolites are a class of porous materials that have been widely utilized in industry. So far, several fundamental questions relating to the dynamic evolution zeolite framework metal-zeolite interface remain unanswered. Contrary classical view zeolites as static, rigid, changeless material, atoms foreign metals can dynamically interconvert under pretreatment or reaction conditions, making it difficult identify real active centers mechanisms. With development characterization techniques theoretical calculations, more profound understanding at atomic scale has achieved. This critical Review will feature recent progress metal-zeolites, mainly focusing on T–O–T bonds breaking formation, metal valence state transformation, phase evolution, migration. We compare these proposed mechanisms analyze their suitability distinct experimental conditions. highlight identification sites catalytic mechanism should be cautious consider Finally, we summarize usages limitations different characteristic techniques, propose some future research directions about hope bridge gaps between knowledge achieved characterizations nature guide zeolite-based synthesis, modification, application.

Язык: Английский

Процитировано

55
Mechanisms and site requirements for NO and NH3 oxidation on Cu/SSZ-13 DOI
Yilin Wang, Runze Zhao, Kenneth G. Rappé

и другие.

Applied Catalysis B Environment and Energy, Год журнала: 2024, Номер 346, С. 123726 - 123726

Опубликована: Янв. 15, 2024

Язык: Английский

Процитировано

11
Exploring the Impact of Active Site Structure on the Conversion of Methane to Methanol in Cu‐Exchanged Zeolites DOI Creative Commons
Florian Göltl, Saurabh Bhandari, Edgard A. Lebrón‐Rodríguez

и другие.

Angewandte Chemie International Edition, Год журнала: 2024, Номер 63(23)

Опубликована: Апрель 4, 2024

Abstract In the past, Cu‐oxo or ‐hydroxy clusters hosted in zeolites have been suggested to enable selective conversion of methane methanol, but impact active site's stoichiometry and structure on methanol production is still poorly understood. Herein, we apply theoretical modeling conjunction with experiments study these two factors partial oxidation Cu‐exchanged zeolite SSZ‐13. Phase diagrams developed from first‐principles suggest that Cu‐hydroxy dimers are stabilized when O 2 N used activate catalyst, respectively. We confirm predictions experimentally determine a stepwise process, can convert twice as much compared Cu‐hydroxyl dimers. Our models rationalize how Cu‐di‐oxo up molecules while Cu‐di‐hydroxyl only one molecule per catalytic cycle. These findings imply Cu clusters, at least oxo group hydroxyl groups needed This simple structure–activity relationship allows intuitively understand potential small oxygenated hydroxylated transition metal methanol.

Язык: Английский

Процитировано

11
Formation of HCHO, CO and H2 by methane oxidation with O2 over Cu catalysts stabilized in silicoaluminophosphates DOI Creative Commons
Mana Shimakawa,

Rieko Nagase,

Ryoya Kugo

и другие.

Catalysis Science & Technology, Год журнала: 2025, Номер unknown

Опубликована: Янв. 1, 2025

The catalytic performance of Cu catalysts supported on SAPO34 (denoted as Cu/SAPO) for methane oxidation with O 2 has been investigated in detail.

Язык: Английский

Процитировано

1
Dynamic CuII/CuI speciation in Cu-CHA catalysts by in situ Diffuse Reflectance UV–vis-NIR spectroscopy DOI
Chiara Negri, Matteo Signorile, Natale G. Porcaro

и другие.

Applied Catalysis A General, Год журнала: 2019, Номер 578, С. 1 - 9

Опубликована: Март 25, 2019

Язык: Английский

Процитировано

68
Excellent selective catalytic reduction of NOx by NH3 over Cu/SAPO-34 with hierarchical pore structure DOI
Rui Li, Peiqiang Wang,

Shibo Ma

и другие.

Chemical Engineering Journal, Год журнала: 2019, Номер 379, С. 122376 - 122376

Опубликована: Июль 30, 2019

Язык: Английский

Процитировано

65
Spectroscopic Evidence of Efficient Generation of Dicopper Intermediate in Selective Catalytic Reduction of NO over Cu-Ion-Exchanged Zeolites DOI
Akira Oda,

Hitomi Shionoya,

Yuusuke Hotta

и другие.

ACS Catalysis, Год журнала: 2020, Номер 10(20), С. 12333 - 12339

Опубликована: Окт. 8, 2020

The key reactive sites in the selective catalytic reduction (SCR) of NO using ammonia (NH3–SCR) are Cu(II)/Cu(I) ammine complexes encapsulated within zeolite catalysts. reaction intermediate important CuI → CuII reoxidation step has been proposed as dicopper species. However, obtaining definitive spectroscopic probe for under NH3–SCR remains a quite challenging subject. Here we report evidence efficient generation over Cu-ion-exchanged zeolites. state Cu ion condition was analyzed fiber-optic UV–vis–NIR spectroscopy; distinct fingerprint (μ–η2:η2-peroxo)dicopper(II) detected. Our assignment rationalized by density functional theory calculations. intensity fingerprints dimeric copper much higher than expected from previous reports, and it also found that such is observable only conditions. This finding strongly supports previously suggested dynamic contributions to catalysis.

Язык: Английский

Процитировано

62