Hierarchically porous materials: synthesis strategies and structure design

Chemical Society Reviews, Journal Year: 2016, Volume and Issue: 46(2), P. 481 - 558

Published: Dec. 1, 2016

This review addresses recent advances in synthesis strategies of hierarchically porous materials and their structural design from micro-, meso- to macro-length scale.

Language: Английский

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Dynamic multinuclear sites formed by mobilized copper ions in NO _x selective catalytic reduction

Science, Journal Year: 2017, Volume and Issue: 357(6354), P. 898 - 903

Published: Aug. 18, 2017

Copper ions exchanged into zeolites are active for the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia (NH3), but low-temperature rate dependence on copper (Cu) volumetric density is inconsistent reaction at single sites. We combine steady-state and transient kinetic measurements, x-ray absorption spectroscopy, first-principles calculations to demonstrate that under conditions, mobilized Cu can travel through zeolite windows form ion pairs participate in an oxygen (O2)-mediated CuI→CuII redox step integral SCR. Electrostatic tethering framework aluminum centers limits volume each explore thus its capacity pair. The dynamic, reversible formation multinuclear sites from atoms represents a distinct phenomenon falls outside conventional boundaries heterogeneous or homogeneous catalyst.

Language: Английский

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Selective anaerobic oxidation of methane enables direct synthesis of methanol

Science, Journal Year: 2017, Volume and Issue: 356(6337), P. 523 - 527

Published: May 4, 2017

Direct functionalization of methane in natural gas remains a key challenge. We present direct stepwise method for converting into methanol with high selectivity (~97%) over copper-containing zeolite, based on partial oxidation water. The activation helium at 673 kelvin (K), followed by consecutive catalyst exposures to 7 bars and then water 473 K, consistently produced 0.204 mole CH3OH per copper zeolite. Isotopic labeling confirmed as the source oxygen regenerate zeolite active centers renders desorption energetically favorable. On basis situ x-ray absorption spectroscopy, infrared density functional theory calculations, we propose mechanism involving CuII oxide centers, CuI reoxidation concurrent formation hydrogen.

Language: Английский

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The Direct Catalytic Oxidation of Methane to Methanol—A Critical Assessment

Angewandte Chemie International Edition, Journal Year: 2017, Volume and Issue: 56(52), P. 16464 - 16483

Published: June 23, 2017

Despite the large number of disparate approaches for direct selective partial oxidation methane, none them has translated into an industrial process. The methane to methanol is a difficult, but intriguing and rewarding, task as it potential eliminate prevalent natural gas flaring by providing novel routes its valorization. This Review considers synthesis derivatives from homogeneous heterogeneous pathways. By establishing severe limitations related catalytic we highlight vastly superior performance systems which produce or incorporate specific measures, such use multicomponent catalysts stabilize methanol. We thereby identify protection being indispensable future research on catalysis.

Language: Английский

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Small-Pore Zeolites: Synthesis and Catalysis

Chemical Reviews, Journal Year: 2018, Volume and Issue: 118(11), P. 5265 - 5329

Published: May 10, 2018

In the past decade or so, small-pore zeolites have received greater attention than large- and medium-pore molecular sieves that historically dominated literature. This is primarily due to commercialization of two major catalytic processes, NOx exhaust removal methanol conversion light olefins, take advantage properties these materials with smaller apertures. Small-pore possess pores are constructed eight tetrahedral atoms (Si4+ Al3+), each time linked by a shared oxygen These eight-member ring (8MR) provide small molecules access intracrystalline void space, e.g., during car cleaning (NOx removal) en route its into while restricting larger molecule entrance departure critical overall catalyst performance. total, there forty-four structurally different zeolites. Forty-one can be synthesized, first synthetic zeolite (KFI, 1948) was in fact material. Although field 8MR chemistry has expanded many directions, progress synthesis framework-specific, leaving insights generalizations difficult realize. review focuses on relevant details all provides some generalized findings related insights. Next, applications where either been commercialized investigations presented, aim providing structure-activity relationships. The ends summary discusses (i) both progress, (ii) list opportunities field, (iii) brief future outlook.

Language: Английский

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Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity

Chemical Reviews, Journal Year: 2017, Volume and Issue: 117(3), P. 2059 - 2107

Published: Jan. 19, 2017

A longstanding research goal has been to understand the nature and role of copper–oxygen intermediates within copper-containing enzymes abiological catalysts. Synthetic chemistry played a pivotal in highlighting viability proposed expanding library known cores. In addition number new complexes that have synthesized since previous reviews on this topic journal (Mirica, L. M.; Ottenwaelder, X.; Stack, T. D. P. Chem. Rev. 2004, 104, 1013–1046 Lewis, E. A.; Tolman, W. B. 1047–1076), field seen significant expansion (1) range cores characterized, (2) amount mechanistic work performed, particularly area organic substrate oxidation, (3) use computational methods for both corroboration prediction intermediates. The scope review limited well-characterized examples species but seeks provide thorough picture spectroscopic characteristics reactivity trends discussed.

Language: Английский

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Strategies for the Direct Catalytic Valorization of Methane Using Heterogeneous Catalysis: Challenges and Opportunities

ACS Catalysis, Journal Year: 2016, Volume and Issue: 6(5), P. 2965 - 2981

Published: March 31, 2016

In this Perspective, we highlight the main challenges to be addressed in development of heterogeneous catalysts for direct functionalization methane. Along with our personal view on current developments field, outline mechanistic, engineering, and catalyst design issues that have hampered implementation new technologies possible paths overcome these problems.

Language: Английский

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New trends in tailoring active sites in zeolite-based catalysts

Chemical Society Reviews, Journal Year: 2019, Volume and Issue: 48(4), P. 1095 - 1149

Published: Jan. 1, 2019

This review discusses approaches for tailoring active sites in extra-large pore, nanocrystalline, and hierarchical zeolites their performance emerging catalytic applications.

Language: Английский

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Catalytic Oxidation of Methane into Methanol over Copper-Exchanged Zeolites with Oxygen at Low Temperature

ACS Central Science, Journal Year: 2016, Volume and Issue: 2(6), P. 424 - 429

Published: June 13, 2016

The direct catalytic conversion of methane to liquid oxygenated compounds, such as methanol or dimethyl ether, at low temperature using molecular oxygen is a grand challenge in C-H activation that has never been met with synthetic, heterogeneous catalysts. We report the first demonstration direct, oxidation into over copper-exchanged zeolites reaction temperatures (483-498 K). Reaction kinetics studies show sustained activity and high selectivity for variety commercially available zeolite topologies under mild conditions (e.g., 483 K atmospheric pressure). Transient steady state measurements isotopically labeled molecules confirm turnover. rates apparent energies are affected by topology, caged-based Cu-SSZ-13) showing highest rates. Although low, discovery sites will accelerate development strategies directly oxidize conditions.

Language: Английский

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Methane Oxidation to Methanol Catalyzed by Cu-Oxo Clusters Stabilized in NU-1000 Metal–Organic Framework

Journal of the American Chemical Society, Journal Year: 2017, Volume and Issue: 139(30), P. 10294 - 10301

Published: June 14, 2017

Copper oxide clusters synthesized via atomic layer deposition on the nodes of metal–organic framework (MOF) NU-1000 are active for oxidation methane to methanol under mild reaction conditions. Analysis chemical reactivity, in situ X-ray absorption spectroscopy, and density functional theory calculations used determine structure/activity relations Cu-NU-1000 catalytic system. The Cu-loaded MOF contained Cu-oxo a few Cu atoms. was present ambient conditions as mixture ∼15% Cu+ ∼85% Cu2+. accompanied by reduction 9% catalyst from Cu2+ Cu+. products, methanol, dimethyl ether, CO2, were desorbed with passage 10% water/He at 135 °C, giving carbon selectivity 45–60%. oxo stabilized provide an active, first generation MOF-based, selective catalyst.

Language: Английский

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