Silica-supported Z-selective Ru olefin metathesis catalysts

Under embargo until: 2022-01-17Recently reported thiolate-coordinated ruthenium alkylidene complexes show promise in Z-selective and stereoretentive olefin metathesis reactions. Herein we describe the immobilization of three Ru complexes containing a bulky aryl thiolate on mesostructured silica via surface organometallic chemistry. The applied methodology gives isolated catalytic sites homogeneously distributed on the silica surface. The catalytic results with two model substrates show comparable Z-selectivities to those of the homogeneous counterparts.acceptedVersio

Microsoft Access as a Support System in New Student Reception SMA Negeri 1 Curug Tanggerang

The rapid computer developments lately almost cover all areas of life one of them is a computer or computer USAge in educational institutions. The development of personal computers (PCs) are becoming more sophisticated and faster process but with a smaller form than the initial findings so that price is becoming more affordable and easily obtainable.Suggested advantage is that it can save time, effort and accuracy of the data more reliable, but still there are still perceived shortage is the lack of experts who understand the software that is used is when there hamabatn obstacles and interference

Tandem Hydrogenation/Hydrogenolysis of Furfural to 2-Methylfuran over a Fe/Mg/O Catalyst: Structure–Activity Relationship

The hydrodeoxygenation of furfural (FU) was investigated over Fe-containing MgO catalysts, on a continuous gas flow reactor, using methanol as a hydrogen donor. Catalysts were prepared either by coprecipitation or impregnation methods, with different Fe/Mg atomic ratios. The main product was 2-methylfuran (MFU), an important highly added value chemical, up to 92% selectivity. The catalyst design helped our understanding of the impact of acid/base properties and the nature of iron species in terms of catalytic performance. In particular, the addition of iron on the surface of the basic oxide led to (i) the increase of Lewis acid sites, (ii) the increase of the dehydrogenation capacity of the presented catalytic system, and (iii) to the significant enhancement of the FU conversion to MFU. FTIR studies, using methanol as the chosen probe molecule, indicated that, at the low temperature regime, the process follows the typical hydrogen transfer reduction, but at the high temperature regime, methanol dehydrogenation and methanol disproportionation were both presented, whereas iron oxide promoted methanol transfer. FTIR studies were performed using furfural and furfuryl alcohol as probe molecules. These studies indicated that furfuryl alcohol activation is the rate-determining step for methyl furan formation. Our experimental results clearly demonstrate that the nature of iron oxide is critical in the efficient hydrodeoxygenation of furfural to methyl furan and provides insights toward the rational design of catalysts toward C–O bonds' hydrodeoxygenation in the production of fuel components

Synthèse de matériaux hybrides mésostructurés en présence de tensioactifs non-ioniques - Contrôle de la chimie dans les pores et dans les murs

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

SH-Functionalized Cubic Mesostructured Silica as Support for Small Gold Nanoparticles

International audienceGold nanoparticles supported on cubic mesostructured silica have been synthesized leading to a highly selective catalyst for aerobic oxidation of trans-stilbene

A Solid Iridium Catalyst for Diastereoselective Hydrogenation

International audienceAn Ir(NHC) supported catalyst is used in the selective hydrogenation of terpinen-4-ol to cis p-menthan-4-ol. Its activity, selectivity and stability are compared to those of a homogeneous homologue [IrCl(COD)MesImPr] and to a commercial Pd/C. The solid Ir catalyst is much more selective than the Pd catalyst (92 vs. 42% at 80°C) but also more active, more selective and more stable than the iridium complex in solution. For the first time, a supported catalyst shows an enhanced activity with respect to a complex in a diastereoselective hydrogenation reaction

Development of Pd supported catalysts using thiol-functionalized mesoporous silica frameworks: application to the chemo-and regio-selective C-3 arylation of free-indole

International audienceWe report here the development of Pd-supported catalysts for the selective C-3 arylation of free-indole using thiol-functionalized silica supports to anchor the palladium centers. The palladium (II) complex, Pd(OAc)2, was efficiently loaded into various thiol-functionalized mesostructured silicas at room temperature. These materials exhibit different contents of surface SH groups (0.3 to 1.8 SH/nm2) and various SH/Pd molar ratios from 6 to 65. It was found that the catalysts containing the most isolated surface SH groups (0.3 SH/nm2) and the highest loading of Pd were the most active, reaching 70% of conversion, 1400 as turnover numbers and 100% selectivity in the C-3 arylated product using only 0.05 mol% of Pd. However, a leaching of active Pd species (1.7 ppm) was detected. The best compromise was found for a specific solid containing isolated surface thiol groups (0.3 SH/nm2) and a very low loading of Pd (SH/Pd = 65). It exhibited a high TON (608) with a very low Pd leaching of 0.5 ppm in the course of the catalytic reaction. These results thus illustrate that both surface SH site isolation and concentration, as well as the SH/Pd ratio are key parameters to access high catalytic performances and very low leaching of metal during catalysis

Highly dispersed silica-supported iridium and iridium-aluminium catalysts for methane activation prepared via surface organometallic chemistry

The grafting of an iridium–aluminium precursor onto silica followed by thermal treatment under H2 yields small (<2 nm), narrowly distributed nanoparticles used as catalysts for methane H/D exchange. This Ir–Al/SiO2 catalyst demonstrated enhanced catalytic performances in comparison with the monometallic Ir/SiO2 analogue (TOFs of 339 h−1versus 117 h−1 respectively), highlighting the promoting effect of aluminium. TON up to 900 is obtained after 9 hours, without evidence of catalyst deactivation, and identical performances are achieved after air exposure, underlining the good robustness of both Ir–Al/SiO2 and Ir/SiO2 catalytic materials.ISSN:1359-7345ISSN:1364-548

Alkene hydrosilylation with supported and unsupported Ni nanoparticles: strong influence of the Ni environment on activity and selectivity

International audienc

Dissolution dynamic nuclear using materials obtained by incorporation of radicals by covalent bonding on existing porous solids

Priority Data: PCT/IB2015/002441 - 17.11.2015- IBThe present invention concerns a process for polarizing 1H, 13C, 15N or another nucleus of an analyte by dissolution dynamic nuclear polarization (D- DNP), said process comprising the successive steps of: i) providing a liquid sample containing the analyte to be polarized; ii) impregnating a porous material carrying radicals with the liquid sample containing the analyte, iii) cooling the impregnated material, at a temperature in the range from 0.5 K to 300 K, iv) submitting the impregnated material in the cooled state obtained in step, iii) to D-DNP conditions to polarize, directly or indirectly, the selected nuclear spin of the analyte, v) warming the impregnated material obtained after step iv) and passing a solution through the material which will carry the polarized analyte with it, wherein the material carrying radicals which is impregnated in step ii) was obtained by incorporating radicals through covaient bonding on an initial existing porous solid, this initial existing porous solid being exclusively inorganic or being a carbon based solid with a content of carbon representing at least 97% of the mass of the initial existing porous solid.La présente invention concerne un processus de polarisation de 1H, de 13C, de 15N ou d'un autre noyau d'un analyte par polarisation nucléaire dynamique par dissolution (D-DNP), les étapes dudit processus consistant successivement : i) à réaliser un échantillon liquide contenant l'analyte à polariser; ii) à imprégner un matériau poreux portant des radicaux avec l'échantillon liquide contenant l'analyte, iii) à refroidir le matériau imprégné, à une température comprise entre 0,5 K et 300 K, iv) à soumettre le matériau imprégné à l'état refroidi obtenu à l'étape iii) à des conditions de D-DNP pour polariser, directement ou indirectement, le spin nucléaire sélectionné de l'analyte, v) à réchauffer le matériau imprégné obtenu après l'étape iv) et à passer une solution à travers le matériau qui emportera l'analyte polarisé avec elle, le matériau portant des radicaux qui est imprégné dans l'étape ii) ayant été obtenu par incorporation de radicaux à travers une liaison covalente sur un solide poreux initial existant, ce solide poreux initial existant étant exclusivement inorganique ou étant un solide à base de carbone dont la teneur en carbone représente au moins 97 % de la masse du solide poreux existant initial