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1.
Chempluschem ; 89(1): e202300313, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37902603

RESUMO

The direct hydrogenation of CO2 into alcohols is an attractive but challenging catalytic reaction. Herein, it was shown that Cu nanoparticles supported on MFI and BEA zeolites have high catalytic activity and selectivity for converting CO2 into ethanol and isopropanol. Furthermore, we investigated the effect of introducing mesopores via carbon templating and encapsulating the Cu nanoparticles via subsequent recrystallization. All the catalysts were characterized by N2 physisorption, XRD, SEM, TEM, NH3 TPD, XPS, and XRF, before we tested them in a high-pressure water-filled autoclave with a constant partial pressure of CO2 (1 MPa) and an increasing partial pressure of H2 (3-5 MPa). In general, the mesoporous zeolite catalysts resulted in a higher CO2 conversion and selectivity toward ethanol than their non-mesoporous equivalents, while the recrystallized catalyst with encapsulated Cu nanoparticles had a higher selectivity towards isopropanol. For example, Cu@m-S1 showed the highest isopropanol productivity among the recrystallized mesoporous zeolites, corresponding to 20.51 mmol g-1 h-1 under the given reaction conditions. These findings highlight the importance of mesopores in zeolite catalysts for CO2 hydrogenation to alcohols and point a new direction for further research and development.

2.
Chem Commun (Camb) ; 56(40): 5378-5381, 2020 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-32285881

RESUMO

In this work, we investigated the catalytic effect of adding sulfur on Zn/ZSM-5 catalyst for direct conversion of ethane to aromatics. We show that the continuous addition of hydrogen sulfide (H2S) effectively stabilizes zinc, prevents coking and results in a highly selective and stable catalyst. Considering the high content of sulfur in shale gas resources, these results highlight the importance of investigating catalysts under realistic operating conditions.

3.
ACS Nano ; 13(2): 2463-2472, 2019 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-30649849

RESUMO

Nanostructured carbons with different pore geometries are prepared with a liquid-free nanocasting method. The method uses gases instead of liquid to disperse carbon precursors, leach templates, and remove impurities, minimizing synthetic procedures and the use of chemicals. The method is universal and demonstrated by the synthesis of 12 different porous carbons with various template sources. The effects of pore geometries in catalysis can be isolated and investigated. Two of the resulted materials with different pore geometries are studied as supports for Ru clusters in the hydrogenolysis of 5-hydroxymethylfurfural (HMF) and electrochemical hydrogen evolution (HER). The porous carbon-supported Ru catalysts outperform commercial ones in both reactions. It was found that Ru on bottleneck pore carbon shows a highest yield in hydrogenolysis of HMF to 2,5-dimethylfuran (DMF) due to a better confinement effect. A wide temperature operation window from 110 to 140 °C, with over 75% yield and 98% selectivity of DMF, has been achieved. Tubular pores enable fast charge transfer in electrochemical HER, requiring only 16 mV overpotential to reach current density of 10 mA·cm-2.

4.
Angew Chem Int Ed Engl ; 53(46): 12513-6, 2014 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-25196739

RESUMO

With the ongoing developments in biomass conversion, the oxidation of bioethanol to acetaldehyde may become a favorable and green alternative to the preparation from ethylene. Here, a simple and effective method to encapsulate gold nanoparticles in zeolite silicalite-1 is reported and their high activity and selectivity for the catalytic gas-phase oxidation of ethanol are demonstrated. The zeolites are modified by a recrystallization process, which creates intraparticle voids and mesopores that facilitate the formation of small and disperse nanoparticles upon simple impregnation. The individual zeolite crystals comprise a broad range of mesopores and contain up to several hundred gold nanoparticles with a diameter of 2-3 nm that are distributed inside the zeolites rather than on the outer surface. The encapsulated nanoparticles have good stability and result in 50 % conversion of ethanol with 98 % selectivity toward acetaldehyde at 200 °C, which (under the given reaction conditions) corresponds to 606 mol acetaldehyde/mol Au hour(-1) .


Assuntos
Biocombustíveis , Etanol/química , Ouro/química , Nanopartículas/química , Zeolitas/química , Acetaldeído/química , Biocombustíveis/análise , Catálise , Oxirredução
5.
Angew Chem Int Ed Engl ; 53(33): 8645-8, 2014 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-25044615

RESUMO

We describe a solid polyphenylene support that serves as an excellent platform for metal-catalyzed reactions that are normally carried out under homogeneous conditions. The catalyst is synthesized by palladium-catalyzed Suzuki coupling which directly results in formation of palladium nanoparticles confined to a porous polyphenylene network. The composite solid is in turn highly active for further Suzuki coupling reactions, including non-activated substrates that are challenging even for molecular catalysts.

6.
Chem Commun (Camb) ; 48(18): 2427-9, 2012 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-22274843

RESUMO

Synthesis of amides by aerobic oxidative coupling of alcohols or aldehydes with amines via intermediate formation of methyl esters is highly efficient and selective when using a catalytic system comprised of supported gold nanoparticles and added base in methanol.


Assuntos
Álcoois/química , Aldeídos/química , Amidas/química , Amidas/síntese química , Aminas/química , Técnicas de Química Sintética/métodos , Ouro/química , Catálise , Oxirredução , Especificidade por Substrato
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