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Addition effect of 2nd metal to Ru catalysts in hydrogenolysis of squalane was investigated. Addition of V gave lower methane selectivity and higher C14-C16 selectivity and the effect was the most remarkable over SiO 2 support. However, addition of V decreased the catalyst activity and increased the deposited amount of carbonaceous species. From hydrogenolysis of n -hexadecane, addition of V suppressed the formation of methane via terminal C C bond dissociation, but the formation via fragmentation was not suppressed. Ru and V valences in Ru-VO x /SiO 2 (V/Ru = 0.25) after reduction were 0 and +III, respectively. The size of Ru particles was about 4 nm from XRD even in changing V/Ru ratio. H 2 chemisorption showed that V covered the Ru particles and reduced the size of Ru ensemble. In reuse test, it was difficult to retain the catalyst performance for hydrogenolysis of squalane even with various treatments of the recovered catalyst such as washing with n -hexane, heating in N 2 flow or calcination in air. From XAS analysis, the contact of Ru particles with air caused the aggregation of Ru metal especially when calcined in air. [ABSTRACT FROM AUTHOR]

Hydrogenolysis of cork has been examined using a range of precious metal catalysts studying the effect of the support, added base and solvent used. The addition of a catalyst and a base resulted in a bio-oil increase of 9.3–158% compared to when no catalyst was used along with an increase in the lipid yield of 113–258%. The change in the solvent to 2-methyl tetrahydrofuran from the original dioxane solvent system allowed for a change to a “greener” solvent as well as an increased bio-oil yield from 11.5 wt% to 42.6 wt%, in the absence of a base. [ABSTRACT FROM AUTHOR]

Bimetallic Au-Pd nanoparticles supported on TiO 2 show excellent catalytic activity and selectivity to benzaldehyde in the solvent-free transformation of benzyl alcohol to benzaldehyde, where toluene is the main observed by-product, together with smaller amounts of benzoic acid, benzyl benzoate and dibenzyl ether. However, despite the industrial relevance of this reaction and importance of tuning the selectivity to the desired benzaldehyde, only a few attempts have been made in the literature on modeling the reaction kinetics for a quantitative description of this reaction system. A kinetic model for the oxidation of benzyl alcohol over Au-Pd is proposed in this paper. The model assumes that hydrogenolysis, disproportionation and dehydrogenation reactions may occur in parallel, and it has been found satisfactory after a model discrimination procedure was applied to a number of simplified candidate models developed from microkinetic studies. Despite its relative simplicity, the proposed model is capable of representing the reactant conversion and distribution of products observed in experiments carried out at different temperature, pressure and catalyst mass in a stirred batch reactor. Major findings include the quantitative evaluation of the impact of hydrogenolysis and disproportionation pathways on benzaldehyde production. At low temperature the disproportionation reaction is the dominant route to toluene formation, while hydrogenolysis dominates at high temperature. [ABSTRACT FROM AUTHOR]

Kinetics of the liquid phase hydrogenolysis of glycerol was investigated over 35 wt % Cu/MgO catalyst in a slurry batch reactor. The power law and Langmuir-Hinshelwood-Hougen-Watson (LHHW) models were tried to fit the experimental data. To develop the kinetic model, a new reaction mechanism is proposed. To simulate the experimental concentration-time data, the set of differential equations were developed and solved numerically by using ode23 stiff system coupled with the genetic algorithm optimization technique. Kinetic parameters were estimated by minimizing the residual sum of squares between the predicted and experimental concentrations of glycerol, 1,2-propanediol (1,2-PDO), and ethylene glycol (EG). Power law showed that hydrogenolysis of glycerol over 35 wt % Cu/MgO catalyst followed the overall reaction order of 1.2 with respect to glycerol with an activation energy of 84.9 kJ/mol. The LHHW model satisfactorily correlated the rate data, and this model showed good fit between the experimental and calculated concentration of glycerol as well as products. [ABSTRACT FROM AUTHOR]

A novel three-step tandem hydroformylation-acetalization-hydrogenolysis was first proposed to produce alcohols (derivatives) from olefins, and the developed unique Ru(III)-complex [Ru(III)-L2] ligated by the ionic diphosphine (L2) proved efficient toward this tandem reaction. In Ru(III)-L2, the strong π-acceptor nature of L2 guaranteed Ru-center remaining in +3 valence state without redox reaction. Hence, Ru(III)-L2 was able to behave as a bifunctional catalyst merging RuIII-P complex and RuIII Lewis acid, which acted not only as a transition metal catalyst responsible for hydroformylation of olefins and hydrogenolysis of (hemi)acetals but also as a Ru3+ Lewis acid in charge of acetalization of aldehydes [to form (hemi)acetals]. The easily performed acetalization served as a bridge step to get through the pathway from aldehydes to alcohols instead of the direct hydrogenation. [ABSTRACT FROM AUTHOR]

Acesulfame has attracted much attention due to its wide application, environmental persistence and potential safety risk of transformation products (TPs). Little information is known on acesulfame transformation in the presence of oxidants/disinfectants. The acesulfame oxidation by permanganate (Mn(VII)) in water under environmentally relevant conditions was systematically evaluated. The pH of water showed negligible influence in acesulfame oxidation. Inorganic ligand (pyrophosphate) exhibited insignificant effect whereas organic ligands (oxalate, ethylene diamine tetraacetic acid, and humic acid) exerted obvious suppression on acesulfame oxidation. Natural organic matter in real water had important influence in acesulfame oxidation by Mn(VII). Acesulfame transformation pathways were initiated by the attack of Mn(VII) on double bond of ring via [3 + 2] addition electrocyclic reaction and rich electron of N moiety through electrophilic reaction, followed by oxidation and hydrolysis reactions to produce TPs. Among them, five TPs were for the first time identified. The ecotoxicity tests uncover higher toxicity of the TPs than acesulfame itself. The study on oxidative transformation of acesulfame by Mn(VII) would illumine comprehensive evaluation of this emerging contaminant. Water treatment plants need to consider cautiously to protect the safety of downstream system when using Mn(VII) to dispose the water resource containing acesulfame or other artificial sweeteners. [ABSTRACT FROM AUTHOR]

Ketones, derived via the selective ring-opening hydrogenation of biomass-derived furanic compounds, are useful synthons for the production of fuels and lubricant. In this study, 2,5-dimethylfuran (DMF) was used as a model to investigate the liquid-phase hydrogenation of substituted furans over noble metals. The activity and selectivity of carbon-supported Pt, Pd, Rh, and Ru were compared under identical conditions. Pt/C exhibited the highest activity and selectivity for C O bond hydrogenolysis, whereas all other catalysts exhibited a high selectivity for ring hydrogenation to form 2,5-dimethyltetrahydrofuran. The reaction kinetics were measured in detail for liquid-phase hydrogenation of DMF over Pt/C, under conditions that excluded the effects of internal or external mass transfer (333 K–363 K, p H2 = 0.41–0.69 MPa). A reaction mechanism is proposed to explain the parallel formation of 2,5-dimethyltetrahydrofuran, 2-hexanone, and 2-hexanol. This mechanism is consistent with what is known about the adsorption of DMF on Pt, and explains why ring opening occurs directly from adsorbed DMF and not via secondary reaction of 2,5-dimethyltetrahydrofuran. The kinetics of DMF hydrogenation are well represented by the mechanism and the assumption of non-competitive adsorption of organic species and hydrogen atoms. The step involving C O bond cleavage of the aromatic ring had the highest activation energy, 45.4 kJ/mol, and is favored over the steps involving C C bond hydrogenation of the furan ring at elevated temperatures and low p H2 . The reaction kinetics reveal that DMF hydrogenation can be tuned to produce 2-hexanone with 92% selectivity at 100% conversion under relatively mild liquid phase conditions (0.41 MPa, 393 K). [ABSTRACT FROM AUTHOR]

Catalytic hydroprocessing of 4-methylanisole as a representative of lignin-derived bio-oils was catalyzed by a commercial sulphided CoMo/γ-Al2O3 catalyst in a fixed-bed flow reactor at various space velocities, temperatures, pressures, and feed compositions. An approximate reaction network is presented that accounts for the major products, and approximate kinetics are also presented. The kinetically significant reactions are 4-methylanisole conversion to (a) 4-methylphenol via hydrogenolysis, (b) toluene and benzene via hydrodeoxygenation, (c) cyclohexanone and methylcyclohexanone via hydrogenation, and (d) methylphenol derivatives via alkylation and transalkylation. The formation of toluene and benzene along with water and methanol from 4-methylanisole is inferred to result from direct scission of the Caromatic-O bond. Cleavage of the Cmethyl-O bond is faster than cleavage of the Caromatic-O bond. The main pathway to toluene formation is the hydrogenolysis of the Caromatic-O bond of the intermediate 4-methylphenol. [ABSTRACT FROM AUTHOR]

New biomass utilization technologies and concepts are needed to suffice future increasing energy demand. This paper contributes to the understanding of liquid phase pyrolysis (LPP) oil upgrading, which significantly differs from fast pyrolysis (FP) oil upgrading processes. A two-step hydrodeoxygenation (HDO) process was established to convert the LPP oil into a biofuel with diesel fuel-like properties. In the first HDO step (250 °C, 85 bar), the bulk of the water and most of the highly-oxygenated water-soluble carbonaceous constituents were removed, to lower hydrogen consumption in the second HDO step. In addition, the highly reactive compounds were stabilized in the first step. In the second HDO step (400 °C, 150/170 bar), the product specification was improved. This paper shows a proof-of-principle for a two-step HDO process for converting LPP oil to a diesel-like biofuel. [ABSTRACT FROM AUTHOR]

In order to find an effective method for treating urea wastewater, the experiments on the hydrolysis of urea in wastewater were conducted in a fixed bed reactor with different aluminas (α-AlO, γ-AlO, and η-AlO) as catalysts respectively in contrast with inert ceramic particle. The results indicate that the three alumina catalysts show obvious catalytic activity for urea hydrolysis at 125 °C. The order of activity is η-AlO > γ-AlO > α-AlO, and the activity difference increases with increasing temperature. According to the characterization results, surface acidity has little impact on the activity of catalyst. However, it was found that surface basicity of alumina catalyst plays an important role in catalytic hydrolysis of urea, and the activity of catalyst may be also influenced by the basic strength. With η-AlO as catalyst, the urea concentration in wastewater is reduced to 4.96 mg/L at a temperature of 165 °C. Moreover, the η-AlO shows a good stability for urea hydrolysis. The hydrolysis of urea over η-AlO catalyst can evidently reduce the reaction temperature and is promising to replace industrial thermal hydrolysis process. [ABSTRACT FROM AUTHOR]

GTP hydrolysis by elongation factor Tu (EF-Tu), a translational GTPase that delivers aminoacyl-tRNAs to the ribosome, plays a crucial role in decoding and translational fidelity. The basic reaction mechanism and the way the ribosome contributes to catalysis are a matter of debate. Here we use mutational analysis in combination with measurements of rate/pH profiles, kinetic solvent isotope effects, and ion dependence of GTP hydrolysis by EF-Tu off and on the ribosome to dissect the reaction mechanism. Our data suggest that--contrary to current models--the reaction in free EF-Tu follows a pathway that does not involve the critical residue H84 in the switch II region. Binding to the ribosome without a cognate codon in the A site has little effect on the GTPase mechanism. In contrast, upon cognate codon recognition, the ribosome induces a rearrangement of EF-Tu that renders GTP hydrolysis sensitive to mutations of Asp21 and His84 and insensitive to K+ ions. We suggest that Asp21 and His84 provide a network of interactions that stabilize the positions of the γ-phosphate and the nucleophilic water, respectively, and thus play an indirect catalytic role in the GTPase mechanism on the ribosome [ABSTRACT FROM AUTHOR]

Highlights: [•] Kinetic data and DFT used to study C–C rupture on Ir clusters. [•] C2-intermediates formed by quasi-equilibrated adsorption and dehydrogenation. [•] Close agreement between measured kinetic barrier and DFT-derived barriers. [•] C–C cleavage occurs via *CHCH* >107 times faster than for other intermediates. [Copyright &y& Elsevier]

The synthesis of 2,5-dimethylfuran (DMF) from 5-hydroxymethylfurfural (HMF) is a highly attractive route to a renewable fuel. However, achieving high yields in this reaction is a substantial challenge. Here it is described how PtCo bimetallic nanoparticles with diameters of 3.6 ± 0.7 nm can solve this problem. Over PtCo catalysts the conversion of HMF was 100% within 10 min and the yield to DMF reached 98% after 2 h, which substantially exceeds the best results reported in the literature. Moreover, the synthetic method can be generalized to other bimetallic nanoparticles encapsulated in hollow carbon spheres. [ABSTRACT FROM AUTHOR]

Alles unter Kontrolle: Eine stereokonvergente formale Hydrogenolyse von N ‐ Sulfonylaminoalkoholen mit einem chiralen Pd ‐ Katalysator und Trifluoressigsäure (TFA) lieferte chirale Amine mit zwei benachbarten Stereozentren (siehe Schema; TFE=Trifluorethanol, Ts= p ‐ Tosyl). Die Reaktion verläuft über eine säurekatalysierte Dehydratation zum Ensulfamid, Enamin/Imin ‐ Isomerisierung und Pd ‐ katalysierte asymmetrische Hydrierung und ergibt die Produkte mit bis zu 94 % ee. [ABSTRACT FROM AUTHOR]

A model of the kinetics underlying the hydrogenolysis of nitriles and amines, catalysed by Pd/C, has been derived. Benzonitrile and benzylamine were used as archetypical compounds to better understand the various reaction pathways involved in these processes. The reaction order under mild conditions (80 °C, 1 bar H2) for the hydrogenolysis of benzylamine was zero order in benzylamine, indicating strong adsorption of benzylamine to the catalyst, whereas the hydrogenation of benzonitrile was found to be first order in benzonitrile, owing to mass transport limitations, explaining the observed selectivities toward hydrogenolysis versus hydrogenation. Significantly, benzylamine itself was found to reversibly poison the hydrogenolysis function of the catalyst, preventing high yields of hydrogenolysis products at low catalyst loadings. [ABSTRACT FROM AUTHOR]

The interaction of a de novo synthesised ester with single crystal metal surfaces has been investigated as a model system for the heterogeneous hydrogenolysis of esters. Scanning tunnelling microscopy measurements show dissociative adsorption at room temperature on Cu(110) but no significant reaction on Au(111). The dissociative pathway has been identified by comparing with possible fragment species, demonstrating that the ester cleavage occurs along the RCH(CH3)–OC(O)R bond. [ABSTRACT FROM AUTHOR]

Review: 61 refs. [ABSTRACT FROM AUTHOR]