Influence of Domain Size and Support Composition on the Reducibility of SiO and TiO Supported Tungsten Oxide Clusters.

Supported tungsten oxides are widely used in a variety of catalytic reactions. Depending on the support, the cluster size, oxidation state, reducibility and speciation of the tungsten oxides can widely differ. When promoted with a platinum group metal, the resulting spillover of hydrogen may facilitate the reduction of supported tungsten oxide species, depending on the support.

Selective deconstruction of mixed plastics by a tailored organocatalyst.

Plastic represents an essential material in our society; however, a major imbalance between their high production and end-of-life management is leading to unrecovered energy, economic hardship, and a high carbon footprint. The adoption of plastic recycling has been limited, mainly due to the difficulty of recycling mixed plastics. Here, we report a versatile organocatalyst for selective glycolysis of diverse consumer plastics and their mixed waste streams into valuable chemicals.

Surfactants Used in Colloidal Synthesis Modulate Ni Nanoparticle Surface Evolution for Selective CO Hydrogenation.

Colloidal chemistry holds promise to prepare uniform and size-controllable pre-catalysts; however, it remains a challenge to unveil the atomic-level transition from pre-catalysts to active catalytic surfaces under the reaction conditions to enable the mechanistic design of catalysts. Here, we report an ambient-pressure X-ray photoelectron spectroscopy study, coupled with in situ environmental transmission electron microscopy, infrared spectroscopy, and theoretical calculations, to elucidate the surface catalytic sites of colloidal Ni nanoparticles for CO hydrogenation. We show that Ni nanoparticles with phosphine ligands exhibit a distinct surface evolution compared with amine-capped ones, owing to the diffusion of P under oxidative (air) or reductive (CO + H) gaseous environments at elevated temperatures.

Incidence of Recurrent Exertional Heat Stroke in a Warm-Weather Road Race.

Exertional heat stroke (EHS) survivors may be more susceptible to subsequent EHS; however, the occurrence of survivors with subsequent EHS episodes is limited. Therefore, the purpose of this study was to evaluate the incidence of participants with repeated EHS (EHS-2+) cases in a warm-weather road race across participation years compared to those who experienced 1 EHS (EHS-1). A retrospective observational case series design was utilized.

Person Ability Scores as an Alternative to Norm-Referenced Scores as Outcome Measures in Studies of Neurodevelopmental Disorders.

Although norm-referenced scores are essential to the identification of disability, they possess several features which affect their sensitivity to change. Norm-referenced scores often decrease over time among people with neurodevelopmental disorders who exhibit slower-than-average increases in ability. Further, the reliability of norm-referenced scores is lower at the tails of the distribution, resulting in floor effects and increased measurement error for people with neurodevelopmental disorders.

High-throughput operando-ready X-ray absorption spectroscopy flow reactor cell for powder samples.

A high-throughput, operando-ready X-ray absorption spectroscopy catalytic reaction cell consisting of 4 parallel reactors was designed to collect X-ray absorption near edge structure and extended fine structure spectra under reaction conditions. The cell is capable of operating at temperatures from ambient conditions up to 773 K and pressures from ambient to 2 MPa in a variety of gas environments. The cell design is mechanically simple, and programmable operation at beamline 8-ID (NSLS-II, Brookhaven National Laboratory) makes it straightforward to use.

Early Indicators of Creatine Transporter Deficiency.

Early identification is a goal for creatine transporter deficiency and will be critical for future treatment. Before their first birthday, one-half of this sample showed both a significant feeding/weight gain issue and delayed sitting or crawling. Combined, these early indicators could have alerted providers to conduct a urine screen.

Exertional heat illness incidence and on-site medical team preparedness in warm weather.

To investigate the influence of estimated wet bulb globe temperature (WBGT) and the International Institute of Race Medicine (IIRM) activity modification guidelines on the incidence of exertional heat stroke (EHS) and heat exhaustion (HEx) and the ability of an on-site medical team to treat those afflicted. Medical records of EHS and HEx patients over a 17-year period from the New Balance Falmouth Road Race were examined. Climatologic data from nearby weather stations were obtained to calculate WBGT with the Australian Bureau of Meteorology (WBGT) and Liljegren (WBGT) models.

Mechanistic Studies of Single-Step Styrene Production Using a Rhodium(I) Catalyst.

The direct and single-step conversion of benzene, ethylene, and a Cu(II) oxidant to styrene using the Rh(I) catalyst (DAB)Rh(TFA)(η-CH) [DAB = N,N'-bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA = trifluoroacetate] has been reported to give quantitative yields (with Cu(II) as the limiting reagent) and selectivity combined with turnover numbers >800. This report details mechanistic studies of this catalytic process using a combined experimental and computational approach. Examining catalysis with the complex (DAB)Rh(OAc)(η-CH) shows that the reaction rate has a dependence on catalyst concentration between first- and half-order that varies with both temperature and ethylene concentration, a first-order dependence on ethylene concentration with saturation at higher concentrations of ethylene, and a zero-order dependence on the concentration of Cu(II) oxidant.

Selective Aerobic Oxidation of Alcohols over Atomically-Dispersed Non-Precious Metal Catalysts.

Catalytic oxidation of alcohols often requires the presence of expensive transition metals. Herein, it is shown that earth-abundant Fe atoms dispersed throughout a nitrogen-containing carbon matrix catalyze the oxidation of benzyl alcohol and 5-hydroxymethylfurfural by O in the aqueous phase. The activity of the catalyst can be regenerated by a mild treatment in H .

The important role of hydroxyl on oxidation catalysis by gold nanoparticles.

Although gold is generally considered to be a relatively inert metal, supported gold nanoparticles have demonstrated exceptionally high catalytic activity for the oxidation of carbon monoxide and alcohols at modest temperatures. In both cases, the presence of hydroxyl groups substantially promotes the reaction rate, presumably by participating in the reaction. Direct comparisons of CO oxidation to alcohol oxidation over gold catalysts have been difficult for scientists to explain.

Selective hydrogenolysis of polyols and cyclic ethers over bifunctional surface sites on rhodium-rhenium catalysts.

A ReO(x)-promoted Rh/C catalyst is shown to be selective in the hydrogenolysis of secondary C-O bonds for a broad range of cyclic ethers and polyols, these being important classes of compounds in biomass-derived feedstocks. Experimentally observed reactivity trends, NH(3) temperature-programmed desorption (TPD) profiles, and results from theoretical calculations based on density functional theory (DFT) are consistent with the hypothesis of a bifunctional catalyst that facilitates selective hydrogenolysis of C-O bonds by acid-catalyzed ring-opening and dehydration reactions coupled with metal-catalyzed hydrogenation. The presence of surface acid sites on 4 wt % Rh-ReO(x)/C (1:0.

Reactivity of the gold/water interface during selective oxidation catalysis.

The selective oxidation of alcohols in aqueous phase over supported metal catalysts is facilitated by high-pH conditions. We have studied the mechanism of ethanol and glycerol oxidation to acids over various supported gold and platinum catalysts. Labeling experiments with (18)O(2) and H(2)(18)O demonstrate that oxygen atoms originating from hydroxide ions instead of molecular oxygen are incorporated into the alcohol during the oxidation reaction.

Intercalation of ethylene glycol into yttrium hydroxide layered materials.

Intercalation of ethylene glycol into layered yttrium hydroxide containing nitrate counterions was accomplished by heating the reagents in a methanol solution of sodium methoxide under autogenous pressure at 413 K for 20 h. The resulting crystalline material had an expanded interlayer distance of 10.96 A, confirming the intercalation of an ethylene glycol derived species.

Surface Raman spectroscopy of the interface of tris-(8-hydroxyquinoline) aluminum with Mg.

Surface Raman spectroscopy in ultrahigh vacuum is used to interrogate interfaces formed between tris-(8-hydroxyquinoline) aluminum (Alq(3)) and vapor-deposited Mg. The Raman spectral results for deposition of Mg mass thicknesses between 5 and 20 A indicate formation of a complex interfacial region composed primarily of Mg-Alq(3) adducts and small-grained amorphous or nanocrystalline graphite, the presence of which may have a significant effect on the electronic properties of this metal-organic interface. The observed shifts in nu(ring), nu(C-N), nu(Al-N), and nu(Al-O) modes along with the appearance of nu(Mg-C) and nu(Mg-O) modes suggest a structure for the Mg-Alq(3) adduct in which Mg is bound to the O and C atoms of Alq(3).

Surface Raman spectroscopy of chemistry at the tris(8-hydroxyquinoline) aluminum/Ca interface.

Surface Raman spectroscopy in ultrahigh vacuum is used to interrogate interfaces formed between tris(8-hydroxyquinoline) aluminum (Alq(3)) and vapor-deposited Ca. Vapor deposition of Ca onto Alq(3) films results in the appearance of new vibrational modes consistent with the formation of a Ca-Alq(3) adduct in which Ca is bound through the O of Alq(3.) In addition, the graphitic carbon is observed to form with the deposition of Ca onto Alq(3) films.

Importance of counterion reactivity on the deactivation of Co-salen catalysts in the hydrolytic kinetic resolution of epichlorohydrin.

Possible modes of deactivation of Jacobsen's Co-salen catalyst during the hydrolytic kinetic resolution (HKR) of epichlorohydrin were explored by UV-vis spectroscopy, X-ray absorption spectroscopy, and electrospray ionization mass spectrometry, combined with recycling studies. Although an active Co(III)-salen catalyst deactivated substantially after multiple cycles without regeneration, the catalyst maintained its +3 oxidation state throughout the runs. Thus, deactivation of Co-salen during HKR was not the result of Co reduction.

Oxidation of H2 and CO over ion-exchanged X and Y zeolites.

Zeolites X and Y exchanged with Group IA cations were synthesized by aqueous ion exchange of NaX and NaY and used as catalysts in the oxidation of H2 and CO at temperatures ranging from 473 to 573 K. The CsX zeolite was the most active material of the series for both reactions whereas HX was the least active. Moreover, the oxidation of CO in H2 was very selective (approximately 80%) over the alkali-metal exchanged materials.

Investigation of Pd leaching from supported Pd catalysts during the Heck reaction.

Palladium supported on amorphous silica, mercapto-functionalized silica, amine functionalized silica, and zeolite Y has been studied as a catalyst in the Heck reaction of iodobenzene with butyl acrylate in the presence of triethylamine base and dimethylformamide solvent. Trapping of soluble Pd with poly(4-vinylpyridine), hot filtration tests during the batchwise Heck reaction, and reaction tests of effluents from a fixed bed continuous reactor support the conclusion that leached Pd is the active phase in the Heck reaction for all of the catalysts tested. Two different paths of Pd leaching that depend on the chemical state of the Pd were elucidated in this study.

Raman spectroscopy and dioxygen adsorption on Cs-loaded zeolite catalysts for butene isomerization.

Cesium-exchanged zeolite X was impregnated with cesium acetate (Cs(Ac)/CsX) or cesium carbonate (Cs(2)CO(3)/CsX) and subsequently calcined to yield a basic catalyst. The Raman spectra of calcined Cs(Ac)/CsX and Cs(2)CO(3)/CsX exhibited a new peak at 1036 cm(-1) associated with the occluded species. No evidence for cesium peroxide or superoxide was observed.

Investigation of alumina-supported Au catalyst for CO oxidation by isotopic transient analysis and X-ray absorption spectroscopy.

Alumina-supported Au particles (1.16 wt %) were prepared by a deposition-precipitation method involving a HAuCl4 precursor. X-ray absorption spectroscopy at the Au L(III) edge was used to monitor the evolution of the Au oxidation state and atomic structure during pretreatment in He up to 623 K.

Metal particle growth during glucose hydrogenation over Ru/SiO2 evaluated by X-ray absorption spectroscopy and electron microscopy.

Biorenewable resources such as carbohydrates are considered alternative feedstocks for oxygenated chemicals. This work investigates the stability of silica-supported Ru catalysts in the aqueous phase conversion of glucose to sorbitol. In situ X-ray absorption spectroscopy at the Ru K edge revealed that air-exposed silica-supported Ru was in an oxidized state but was subsequently reduced in aqueous solutions saturated with 40 bar H(2) at 373 K.

A quantum chemical study of the decomposition of Keggin-structured heteropolyacids.

Heterpolyacids (HPAs) demonstrate catalytic activity for oxidative and acid-catalyzed hydrocarbon conversion processes. Deactivation and thermal instability, however, have prevented their widespread use. Herein, ab initio density functional theory is used to study the thermal decomposition of the Keggin molecular HPA structure through the desorption of constitutional water molecules.

Location, acid strength, and mobility of the acidic protons in Keggin 12-H3PW12O40: a combined solid-state NMR spectroscopy and DFT quantum chemical calculation study.

Solid-state 13C NMR experiments and quantum chemical Density Functional Theory (DFT) calculations of acetone adsorption were used to study the location of protons in anhydrous 12-tungstophosphoric acid (HPW), the mobility of the isolated and hydrated acidic protons, and the acid strength heterogeneity of the anhydrous hydroxyl groups. This study presents the first direct NMR experimental evidence that there are two types of isolated protons with different acid strengths in the anhydrous Keggin HPW. Rotational Echo DOuble Resonance (REDOR) NMR experiments combined with quantum chemical DFT calculations demonstrated that acidic protons in anhydrous HPW are localized on both bridging (Oc) and terminal (Od) atoms of the Keggin unit.