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1.
ChemSusChem ; 12(14): 3278-3285, 2019 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-31034754

RESUMO

Methyl formate was produced in one pot through the hydrogenation of CO2 to formic acid/formate followed by an esterification step. The route offers the possibility to integrate renewable energy into the fossil-based chemical value chain. In this work, a phosphine-polymer-anchored Ru complex was shown to be an efficient solid catalyst for the direct hydrogenation of CO2 to methyl formate. The 1,2-bis(diphenylphosphino)ethane-like polymer presented the highest activity with a turnover number (TON) of up to 3401 at 160 °C. The reaction parameters were systemically investigated to optimize the reaction towards the formation of methyl formate. This catalyst could be reused seven times without a significant decrease in activity. Evolution of the catalytic Ru center during the reaction was revealed, and a possible reaction mechanism was proposed.

2.
ChemSusChem ; 11(11): 1857-1865, 2018 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-29694717

RESUMO

Formic acid is a promising hydrogen storage medium and can be produced by catalytic hydrogenation of CO2 . Molecular ruthenium complexes immobilized on phosphine polymers have been found to exhibit excellent productivity and selectivity in the catalytic hydrogenation of CO2 under mild conditions. The polymeric analog of 1,2-bis(diphenylphosphino)ethane exhibited the highest activity and turnover numbers up to 13 170 were obtained in a single run. This catalyst was already active at 40 °C and with a catalyst loading of only 0.0006 mol %. Recycling experiments revealed a loss of activity after the first run, followed by a gradual decrease during the subsequent runs. This is attributed to a change in the catalytically active complex during the hydrogenation reaction. High selectivity towards formate and low leaching were maintained in the absence of CO formation. Based on the catalyst characterization, a mechanism for the CO2 hydrogenation is proposed.

4.
Gesnerus ; 72(2): 269-88, 2015.
Artigo em Alemão | MEDLINE | ID: mdl-26902058

RESUMO

Military statistics and medical research were closely related over the 19th century. The army not only made use of these new forms of knowledge, but also provided an important institutional setting through the military medicine, which was of crucial importance to medical research in the 19th century. Besides that, Swiss military also played a crucial role in new geographical and geological research, resulting in a series of new mapping projects. This article looks on the ways, in which military context gained influence on scientific research practices in the second half of the 19th century, by analyzing the case of Heinrich Bircher's work on military recruiting statistics and the endemic goiter. New mapping projects and statistical practices were linked, transforming big parts of the country into pathological spaces. Coming from this point, the article discusses in how far the military context lead to politicizing medical discourses and, furthermore, linked them to discourses of an anthropological crisis, common in many European countries.


Assuntos
Geologia/história , Bócio Endêmico/história , Medicina Militar/história , Militares/história , Bócio Endêmico/epidemiologia , Bócio Endêmico/etiologia , Bócio Endêmico/patologia , História do Século XIX , Militares/estatística & dados numéricos , Suíça/epidemiologia
5.
Chemphyschem ; 14(16): 3801-5, 2013 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-24039117

RESUMO

We demonstrate that the (local) adsorbed carbon monoxide, COad , coverage on the Pt-free areas of bimetallic Pt/Ru(0001) surfaces (a Ru(0001) substrate partly covered by Pt monolayer islands) can be increased to ∼0.80 monolayers (ML), well above the established saturation COad coverage of 0.68 ML, even under ultrahigh vacuum conditions by using spill-over of CO adsorbed on the Pt islands to the Ru areas as an highly effective adsorption channel. The apparent COad saturation coverage of 0.68 ML on pure Ru(0001) is identified as due to kinetic limitations, hindering further uptake from the gas phase, rather than being caused by thermodynamic reasons. This spill-over mechanism is proposed to be a general phenomenon for adsorption on bimetallic surfaces.

6.
Phys Chem Chem Phys ; 12(25): 6864-74, 2010 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-20461242

RESUMO

The stability of three ultrathin TiO(x)/Pt(111) films with different stoichiometry and defectivity and the corresponding Au/TiO(x)/Pt(111) model catalysts in CO or a CO-O(2) (1 : 1) gas mixture up to a pressure of 100 mbar has been investigated. According to previous studies, the ultrathin films proved to be effective substrates to deposit in UHV Au nanoparticles with specific morphologies and lateral sizes ranging between 1 and 6 nm. The films have been characterized before and after the exposure using X-ray photoemission spectroscopy (XPS), low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM). Additional in situ measurements of the CO chemisorption behavior were performed using polarization-modulation infrared reflection-absorption spectroscopy (PM-IRAS). A fully oxidized film is stable in CO and CO-O(2) (1 : 1) ambient, while the reduced films undergo an oxidative dewetting process at RT in the latter atmosphere. This process ultimately produces a nano-composite surface, where very tiny (from 0.5 to 3 nm lateral sizes) titania nanograins are mixed with open, uncovered areas of the Pt substrate. IRAS measurements on the corresponding Au/TiO(x)/Pt(111) model catalysts demonstrated that the CO chemisorption strongly depends on the Au nanoparticle size and morphology, while the actual Ti oxidation state of the oxide support does not seem to play a significant role.

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