Citral hydrogenation over Pt loaded micro- and mesoporous supports : the interplay between steric limitations and acidity

The effect of pore morphology and acidity on the selectivity in the hydrogenation of citral was investigated on a series of bifunctional catalysts: Pt-H-SAPO-5, Pt-H-Y zeolite, and Pt-H-MCM-41. The reaction was studied in a batch reactor at 70oC with 10 bar total pressure. The highest selectivity to the unsaturated alcohols of 57% was obtained on the Pt-H-SAPO-5 catalyst at a conversion of 46%. The interplay among a monodimensional pore channel of the H-SAPO-5 support, weak Br?nsted acidity of this silicoaluminophosphate, and large platinum nanoparticles contributed to a high selectivity. The corresponding turn over frequency was 0.036 s-1. Pt-H-MCM-41 showed the highest selectivity to menthol as by product, while Pt-H-Y zeolite demonstrated the highest dehydration rate

Effect of the Preparation of Pt-Modified Zeolite Beta-Bentonite Extrudates on Their Catalytic Behavior in n-Hexane Hydroisomerization

Four different types of shaped catalysts with controlled deposition of platinum and the same composition were prepared by extrusion of beta zeolite agglomerated with bentonite as an aluminosilicate clay binder. The catalysts were characterized using mechanical strength tests; scanning electron microscopy for morphology; transmission electron microscopy for porosity and periodicity; nitrogen physisorption for surface area, pore volume, and pore size distribution; and Fourier transform infrared spectroscopy using pyridine as a probe molecule to elucidate the presence, strength, and amount of Bronsted and Lewis acid sites. Elemental analysis was carried out using energy-dispersive X-ray microanalysis. Activity and selectivity of catalysts in the isomerization of n-hexane were evaluated using a fixed bed reactor at 200-350 degrees C. At low temperature, the performance of metal/acid bifunctional shaped catalysis was strongly affected by the metal-to-acid site ratio. This ratio and the total acidity were strongly influenced by the preparation method of the shaped catalysts, while the textural properties were comparable. The highest conversion of n-hexane and selectivity to C-6 isomers (comprising all branched isomers, such as methyl pentane and dimethylbutane) was obtained with extrudates prepared via in situ synthesis with platinum located on the zeolite. The extrudates prepared in this way have the highest metal-to-acid site ratio and their closest proximity, albeit the lowest mechanical strength

Reductive Amination of Ketones with Benzylamine Over Gold Supported on Different Oxides

Reductive amination of cyclohexanone with benzylamine was investigated at 100 °C under 30 bar hydrogen in toluene with five different gold catalysts prepared by deposition–precipitation method and supported on TiO2, La2O3/TiO2, CeO2/TiO2, La2O3 and CeO2. Size of metallic gold varied in the range of 2.6–3.6 nm. The best catalysts in reductive amination of cyclohexanone with benzylamine were 4 wt% Au/TiO2 and 4 wt% Au/CeO2/TiO2 giving 72% and 79% yield of the desired amine. The most acidic and basic catalysts were also unselective and exhibited low activity towards imine hydrogenation. The best catalyst 4 wt% Au/CeO2/TiO2 gave in reductive amination of propiophenone 56% selectivity to the corresponding amine at 20% conversion in 5 h.</p

Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at root s=13 TeV

Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at root s = 13TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb(-1). Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12 +/- 0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations.Peer reviewe

Measurement of the top quark mass using events with a single reconstructed top quark in pp collisions at root s=13 TeV

Abstract:A measurement of the top quark mass is performed using a data sample en-riched with single top quark events produced in thetchannel. The study is based on proton-proton collision data, corresponding to an integrated luminosity of 35.9 fb−1, recorded at√s= 13TeV by the CMS experiment at the LHC in 2016. Candidate events are selectedby requiring an isolated high-momentum lepton (muon or electron) and exactly two jets,of which one is identified as originating from a bottom quark. Multivariate discriminantsare designed to separate the signal from the background. Optimized thresholds are placedon the discriminant outputs to obtain an event sample with high signal purity. The topquark mass is found to be172.13+0.76−0.77GeV, where the uncertainty includes both the sta-tistical and systematic components, reaching sub-GeV precision for the first time in thisevent topology. The masses of the top quark and antiquark are also determined separatelyusing the lepton charge in the final state, from which the mass ratio and difference aredetermined to be0.9952+0.0079−0.0104and0.83+1.79−1.35GeV, respectively. The results are consistentwithCPTinvariance

Influence of reaction parameters on the hydrogenolysis of hydroxymatairesinol over carbon nanofibre supported palladium catalysts

The influence of catalyst particle size, stirring rate, catalyst mass (0.2–0.6 g), reaction temperature (60–70 C), and reactant concentration (1.3–4 mmol/L, with constant reactant/catalyst ratio) on the hydrogenolysis of the lignan hydroxymatairesinol (HMR) to matairesinol (MAT) was studied under hydrogen atmosphere using a carbon nanofibre supported palladium catalyst. When the temperature or HMR concentration was increased, the reaction rate increased as expected. However, the reaction rate was inversely dependent on the stirring rate, e.g., was influenced by external mass transfer, which was explained by the fact that the reaction rate decreases at higher hydrogen concentrations

Reductive Amination of Ketones with Benzylamine Over Gold Supported on Different Oxides

[EN] Reductive amination of cyclohexanone with benzylamine was investigated at 100 °C under 30 bar hydrogen in toluene with five different gold catalysts prepared by deposition–precipitation method and supported on TiO, LaO/TiO, CeO/TiO, LaO and CeO. Size of metallic gold varied in the range of 2.6–3.6 nm. The best catalysts in reductive amination of cyclohexanone with benzylamine were 4 wt% Au/TiO and 4 wt% Au/CeO/TiO giving 72% and 79% yield of the desired amine. The most acidic and basic catalysts were also unselective and exhibited low activity towards imine hydrogenation. The best catalyst 4 wt% Au/CeO/TiO gave in reductive amination of propiophenone 56% selectivity to the corresponding amine at 20% conversion in 5 h. Graphical Abstract: [Figure not available: see fulltext.]Open access funding provided by Abo Akademi University (ABO). The research is funded from Tomsk Polytechnic University Competitiveness Enhancement Program project VIU-RSCBMT-65/2019