Co–Ni Catalysts Derived from Hydrotalcite-Like Materials for Hydrogen Production by Ethanol Steam Reforming

A series of Co–Ni catalysts, prepared from hydrotalcite (HT)-like materials by co-precipitation, has been studied for the hydrogen production by ethanol steam reforming. The total metal loading was fixed at 40% and the Co–Ni composition was varied (40–0, 30–10, 20–20, 10–30 and 0–40). The catalysts were characterized using X-ray diffraction, N₂ physisorption, H₂ chemisorption, temperature-programmed reduction, scanning transmission electron microscope and energy dispersive spectroscopy. The results demonstrated that the particle size and reducibility of the Co–Ni catalysts are influenced by the degree of formation of a HT-like structure, increasing with Co content. All the catalysts were active and stable at 575 °C during the course of ethanol steam reforming with a molar ratio of H₂O:ethanol = 3:1. The activity decreased in the order 30Co–10Ni > 40Co ~ 20Ni–20Co ~ 10Co–30Ni > 40Ni. The 40Ni catalyst displayed the strongest resistance to deactivation, while all the Co-containing catalysts exhibited much higher activity than the 40Ni catalyst. The hydrogen selectivities were high and similar among the catalysts, the highest yield of hydrogen was found over the 30Co–10Ni catalyst. In general, the best catalytic performance is obtained with the 30Co–10Ni catalyst, in which Co and Ni are intimately mixed and dispersed in the HT-derived support, as indicated by the STEM micrograph and complementary mapping of Co, Ni, Al, Mg and O.     

H2 adsorption and H/D exchange on Au/TS-1 and Au/S-1 catalysts

We report a combined quantum-mechanics/molecular-mechanics (QM/MM) analysis of H₂ dissociation and hydrogen–deuterium (H/D) exchange on four potential active sites inside the TS-1 pores: (1) Au₃/T6–Ti-non-defect, (2) Au₃/T6–Si-non-defect, (3) Au₃/T6–Ti-defect, and (4) Au₃/T6–Si-defect. We provide full kinetic and thermodynamic data calculated at standard conditions (298.15 K, 1 atm) for Eley–Rideal mechanisms on these sites. The H/D exchange on Au₃/TS-1 occurs in two steps: (1) first H₂ dissociation on Au₃/TS-1 to form H–Au₃–H species and (2) D₂ (or second H₂) attack on these H–Au₃–H species to form HD. The energetics of the first H₂ dissociation step is site-sensitive (with respect to Au sites), while that of the D₂ (or second H₂) addition step is not site-sensitive. We found that two different mechanisms for the second step are both kinetically and thermodynamically favorable. The most favorable mechanism (ΔE _act ~ 28 kcal/mol) involves an attack of D₂ on both the H atoms in the H–Au₃–H intermediate, and two HD molecules are formed simultaneously. The first H₂ dissociation step is almost thermoneutral and the D₂ (or second H₂) addition step is somewhat exothermic. A comparison of the pure QM and QM/MM calculations on Au₃/TS-1 suggests that the formation of the H–Au₃–H species inside the TS-1 pores becomes thermodynamically more favorable due to the long-range interactions. The activation energies for the first H₂ dissociation step (19–24 kcal/mol) are lower than those for the D₂ (or second H₂) addition step (28–31 kcal/mol). Therefore, the increase in the HD formation rate with temperature is likely to be stronger than the increase in the H–Au₃–H formation rate. On the basis of the calculated activation energies and the reaction thermochemistry, we predict a viable Eley–Rideal H/D exchange pathway that may operate at or above 573 K. We also found potential H/D exchange channels on bare TS-1 (without Au₃) where gas-phase D₂ (or second H₂) attacks the Ti–OH or Si–OH groups (of defect sites) and exchanges one of the D atoms to form HD and Ti–OD or Si–OD groups.     

Synthesis of Poly(propargyl esters) with Rhodium Catalysts and Their Characterization

Summary Propargyl esters (HC≡CCH₂OC(=O)R; 1: R = n-C₅H₁₁, 2: R = CH₃, 3: R = CHBrCH₃, 4: R = C₆H₅, 5: R = C(C₆H₅)₃) were polymerized by using (nbd)Rh⁺(η⁶-Ph-B^-Ph₃) (nbd = 2,5-norbornadiene) to produce poly(1)–poly(5) with molecular weights in the range of M_n = 4,900–40,000. Poly(1), poly(3) and poly(4) were readily soluble in common organic solvents such as toluene, THF and CHCl₃, and poly(2) showed similar solubility behavior except that it was insoluble in THF. Poly(5) did not dissolve in any organic solvent. Poly(1) was yellow oil, while poly(2)–poly(5) were yellow solids. Poly(1)–poly(4) exhibited UV-vis absorptions in a range of 300–425 nm, which are attributed to the conjugation of the main chain. All the polymers were thermally stable up to 150–200 °C.     

Direct liquid‐phase side‐chain oxidation of alkylbenzenes over 2 catalyst

Only the side‐chain oxidation of alkylbenzenes (R–C₆H₃–R′–R″ R=H, Me, Et, Prⁱ R′=H, Me; and R″=H, Me) by oxygen (35–50 atm, 200)C° is promoted in the presence of [Pd(phen)(OAc)₂]. This revised version was published online in July 2006 with corrections to the Cover Date.     

Liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit

The liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit (800°C; 1 h; activator, KOH) were studied by thermal analysis, IR spectroscopy, and ¹H and ¹³C NMR spectroscopy. They were formed in ∼30% yield; they consisted of pyrogenic water (∼50%) and a resinous mixture of organic substances with increased hydrogen and oxygen contents and decreased carbon and sulfur contents. On heating, potassium hydroxide completely decomposed the quinoid structures of coal, decreased the concentration of aromatic components in resin, and increased the concentrations of CH₃-, -CH₂-, and OH-groups. This is consistent with the well-known thermally initiated reactions of alkaline degradation and dehydrogenation at high temperatures (400–800°C). The thermal lability of resinous products was evaluated, and the heats of combustion (32.4–32.7 MJ/kg) were determined; the latter values indicate that these products can be used as fuel.     

Phase transformation in CeO2–Co3O4 binary oxide under reduction and calcination pretreatments

The CeO₂–Co₃O₄ binary oxide was prepared by impregnation of the high surface area Co₃O₄ support (S.A. = 100m² g⁻¹) with cerium nitrate (20 wt% cerium loading on Co₃O₄). Pretreatment of CeO₂–Co₃O₄ binary oxide was divided both methods: reduction (under 200 and 400 °C, assigned as CeO₂–Co₃O₄–R200 and CeO₂–Co₃O₄–R400 and calcination (under 350 and 550 °C, assigned as CeO₂–Co₃O₄–C350 and CeO₂–Co₃O₄–C550). The binary oxides were investigated by means of X-ray diffraction (XRD), nitrogen adsorption at −196 °C, infrared (IR), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and temperature programmed reduction (TPR). The results showed that the binary oxides pretreatment under low-temperatures possessed larger surface area. The cobalt phase of binary oxides also was transferred upon the treating temperature, i.e., the CeO₂–Co₃O₄–R200 binary oxide exhibited higher surface area (S.A. = 109m² g⁻¹) and the main phase was CeO₂,Co₃O₄ and CoO. While, the CeO₂–Co₃O₄–R400 binary oxide exhibited lower surface area (S.A. = 40m² g⁻¹) and the main phase was CeO₂, CoO and Co. Apparently, the optimized pretreatment of CeO₂–Co₃O₄ binary oxide can control both the phases and surface area.     

Degradation of 2-chlorophenol by Fenton and photo-Fenton processes

The photodegradation of a specific organic pollutant using the Fenton and the photo-Fenton processes has been examined in aqueous solution. The applications of the Fenton process and the photo-Fenton process to the degradation of 2-chlorophenol (2-CP) were investigated. The dependence on the following experimental conditions had been evaluated: initial pH (1.0–9.0), hydrogen peroxide (0.67–2 mM), ferrous ions (0.1–2 mM), initial concentration of 2-CP (0.1–2 mM). The optimal experimental conditions were 1 mM H₂O₂, 1 mM ferrous ion and pH 3.0. Under the optimal conditions, the degradation efficiency of 2-CP in the photo-Fenton process was enhanced 4% more than that of the Fenton process. Experimental results about the degradation of 2-CP show that UV irradiation improves the degradation efficiency of the Fenton process. The major intermediate formed during the degradation of 2-CP was p-benzoquinone.     

Silicon and Chlorine Substituted Unsaturated Polymers: ROMP of (bicyclo[2,2,1]hept-5-en-2-yl)ethylchlorodimethylsilane via Mo-based catalyst

Ring opening metathesis polymerization (ROMP) of a norbornene derivative that contains silicon and chlorine, (bicyclo[2,2,1]hept-5-en-2-yl)ethylchlorodimethylsilane, by using electrochemically produced active catalyst species (MoCl₅–e⁻–Al–CH₂Cl₂) was investigated. Silicon and chlorine containing unsaturated polymer was characterized by ¹H, ¹³C, and ²⁹Si-NMR and FTIR spectroscopy. The thermal behavior of the polymer was determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).     

Study of geometrical and electronic effects induced by hydrogen chemisorption on supported Pt particles. Analysis of Pt–H EXAFS and Pt–H anti-bonding state shape resonances

Geometrical and electronic effects induced by hydrogen chemisorption on supported Pt particles are studied by analysing the Pt–H anti-bonding shape resonance. The fundamental principles of a new analysis method of the L₂ and L₃ X-ray absorption edges are summarised. The method is used for studying the Pt–H bonding properties of weakly and strongly bonded hydrogen on surfaces of supported metal catalysts. Also the interaction of hydrogen with a Pt/CeO₂ catalyst as a function of the reduction temperature is investigated. The new analysis method makes it possible to follow the changes in the electronic structure of a Pt/Al₂O₃ catalyst as a function of the metal particle size. This revised version was published online in June 2006 with corrections to the Cover Date.     

Oxyethylated sulfonamides as nonionic soil wetting agents

Various N-alkylbenzenesulfonamides of the type RφSO₂NHR′, where R is t-butyl, or hydrogen and R′ is decyl, octyl, t-octyl, 2-ethylhexyl, hexyl, and butyl, were treated with ethylene oxide (EO) to yield polydisperse adducts RφSO₂ N(R′)(EO)_xH where x is any integer from 2 to 20. Each series of adducts exhibited a range of properties and water solubility. Wetting ability, surface tension, cloud point, and hydrophilic-lipophilic balance (HLB) were related to structure and EO content to determine the most efficient wetting agent for peat moss and cotton skeins. Optimum wetting properties were found for adducts containing 5–10 EO units and in particular with t-C₄ H₉φSO₂N(t-C₈H₁₇)(EO)_xH. This EO chain-length region corresponded to cloud points of 25°, minimal surface tensions, and HLB values 10–12. Agricultural Research Service, U.S.D.A.     

Preparation of supported palladium membrane and separation of hydrogen

Palladium acetate was sublimed at a reduced pressure at 400°C., carried into the macropores of the porous wall of an α-alumina support tube and was decomposed there. A thin palladium membrane which was thus formed showed a hydrogen permeance of 10⁶ mol·m²·s¹.-Pa¹ and a hydrogen/nitrogen permselectivity higher than 1000. The membrane was stable against hydrogen embrittlement even when the permeation temperature was varied between 100 and 300°C., and it was stable to sulfur or chlorine. To test the ability of this system for the separation of hydrogen and deuterium, a palladium disk was used instead of the prepared membrane since a definite membrane thickness was necessary for calculation. When H₂ and D₂ permeated through the membrane independently, the H/D permselectivity was approximately 7 at 150–200°C under a feed side pressure of 0.4 MPa and a permeate side pressure of 0.1 MPa. When a mixture of H₂ and D₂ was fed, the H/D permselectivity was reduced to 1.2–1.6.     

The thermal activation of propyl groups on Pt(111)

The thermal chemistry of 1‐ and 2‐propyl moieties on Pt(111) was studied by using temperature‐programmed desorption (TPD) and reflection–absorption infrared spectroscopy (RAIRS). The propyl intermediates were prepared via thermal activation of the C–I bond of 1‐ and 2‐iodopropane adsorbed precursors, respectively. It was determined that the subsequent thermal activation of those propyl groups results in a competition between reductive elimination to propane, β‐hydride elimination to propene, and complete decomposition to propylidyne (and eventually to hydrogen and surface carbon). It was found that while the 2‐propyl intermediate favors propene production, 1‐propyl also yields significant amounts of propane. The formation of propene via β‐hydride elimination was identified by isotopic labeling TPD experiments, and directly about 200 K by RAIRS. Coadsorption experiments with hydrogen and deuterium were used to characterize hydrogenation and H–D reactions. All possible propene and propane isotopomers are formed from both 1‐ or 2‐iodopropane on the D/Pt(111) surface, indicating that exchange is likely to occur via a cyclic propyl–propene–propyl mechanism involving the formation of both 1‐ and 2‐propyl intermediates. Relative rates for 1‐ versus 2‐propyl conversion were estimated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Kinetic Study of the Prooxidant Effect of α-Tocopherol. Hydrogen Abstraction from Lipids by α-Tocopheroxyl Radical

A kinetic study of the prooxidant effect of α-tocopherol was performed. The rates of allylic hydrogen abstraction from various unsaturated fatty acid esters (ethyl stearate 1, ethyl oleate 2, ethyl linoleate 3, ethyl linolenate 4, and ethyl arachidonate 5) by α-tocopheroxyl radical in toluene were determined, using a double-mixing stopped-flow spectrophotometer. The second-order rate constants (k _p) obtained are <1 × 10⁻² M⁻¹ s⁻¹ for 1, 1.90 × 10⁻² M⁻¹ s⁻¹ for 2, 8.33 × 10⁻² M⁻¹ s⁻¹ for 3, 1.92 × 10⁻¹ M⁻¹ s⁻¹ for 4, and 2.43 × 10⁻¹ M⁻¹ s⁻¹ for 5 at 25.0 °C. Fatty acid esters 3, 4, and 5 contain two, four, and six –CH₂– hydrogen atoms activated by two π-electron systems (–C=C–CH₂–C=C–). On the other hand, fatty acid ester 2 has four –CH₂– hydrogen atoms activated by a single π-electron system (–CH₂–C=C–CH₂–). Thus, the rate constants, k _abstr/H, given on an available hydrogen basis are k _p/4 = 4.75 × 10⁻³ M⁻¹ s⁻¹ for 2, k _p/2 = 4.16 × 10⁻² M⁻¹ s⁻¹ for 3, k _p/4 = 4.79 × 10⁻² M⁻¹ s⁻¹ for 4, and k _p/6 = 4.05 × 10⁻² M⁻¹ s⁻¹ for 5. The k _abstr/H values obtained for 3, 4, and 5 are similar to each other, and are by about one order of magnitude higher than that for 2. From these results, it is suggested that the prooxidant effect of α-tocopherol in edible oils, fats, and low-density lipoproteins may be induced by the above hydrogen abstraction reaction.     

The First Case of Competitive Heterogeneously Catalyzed Hydrogenation using Continuous-Flow Fixed-Bed Reactor System: Hydrogenation of Binary Mixtures of Activated Ketones on Pt-Alumina and on Pt-Alumina-Cinchonidine Catalysts

Abstract  

Under the experimental conditions of the Orito reaction the competitive hydrogenations of four binary mixtures of ethyl pyruvate (EP), methyl benzoylformate (MBF), pyruvic aldehyde dimethyl acetal (PA) and 2,2-diethoxyacetophenone (DAP) on unmodified Pt/Al₂O₃ (racemic hydrogenation) and catalyst modified by cinchonidine (chiral hydrogenation) were studied using continuous-flow fixed-bed reactor system (CFBR). Conversions of chiral and racemic hydrogenations were determined under 4 MPa H₂ pressure, at 293 K using toluene/acetic acid 9/1 as solvent. In the competitive chiral hydrogenation of MBF + EP and DAP + PA binary mixtures (S1 + S2) a new phenomenon was observed: namely the EP and PA are hydrogenated faster than MBF and DAP, whereas in racemic one the MBF and DAP are hydrogenated faster than the former ketones. The phenomenon verified for the first time in CFBR is dependent on the adsorption mode of the surface complexes of various compositions (S1–Pt, S2–Pt, S1–CD–Pt, S2–CD–Pt, CD = cinchonidine). In the chiral hydrogenation of DAP a rate decrease, i.e., “ligand deceleration” was observed instead of rate enhancement.     

Highly electrophilic metallocenes and their role in alkene polymerizations

This summary explores three main topics: (1) zwitterionic alternatives to cationic metallocene alkyl complexes as olefin polymerization catalysts, based on borato (–BR ₃ ^- ) and boryl (–BR₂) substituted cyclopentadienyl ligands (R = C₆F₅); including zwitterionic zirconium allyl complexes of the type CpZr(η³-allyl){η³-allyl–CH₂B(C₆F₅)₃}; (2) reactions which contribute to catalyst deactivation, notably aluminum alkyl mediated C₆F₅ transfer reactions as well as C–H activation reactions including an unusual case of catalyst self-reactivation; (3) the role of highly electrophilic metallocene complexes of aluminum, zirconium and yttrium in combination with weakly coordinating anions as initiators for the carbocationic polymerization of isobutene and isobutene–isoprene copolymerizations is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Non-isothermal degradation kinetics of poly (2,2′-dihydroxybiphenyl)

Catalytic oxidative polymerization of 2,2′-dihydroxybiphenyl (DHBP) was performed by using Schiff base polymer-Cu (II) complex and hydrogen peroxide as catalyst and oxidant, respectively. According to size exclusion chromatography (SEC) analysis, the number-average molecular weight (M _n), weight-average molecular weight (M _w) and polydispersity index (PDI) values of poly (2,2′-dihydroxybiphenyl) (PDHBP) were found to be 37,500, 90,000 g mol⁻¹ and 2.4, respectively. The thermal degradation kinetics was investigated by thermogravimetric analysis in dynamic nitrogen atmosphere at four different heating rates: 5, 10, 15 and 20 °C min⁻¹. The derivative thermogravimetry curves of PDHBP showed that its thermal degradation process had one weight-loss step. The apparent activation energies of thermal decomposition for PDHBP as determined by Tang, Flynn–Wall–Ozawa (FWO), Kissenger–Akahira–Sunose (KAS), Coats–Redfern (CR) and Invariant kinetic parameter (IKP) methods were 109.1, 109.0, 110.0, 108.4 and 109.8 kJ mol⁻¹, respectively. The mechanism function and pre-exponential factor were determined by master plots and Criado–Malek–Ortega method. The most likely decomposition process was a D _n Deceleration type in terms of the CR, master plots and Criado–Malek–Ortega results.     

Unique adsorption and catalytic behavior of H2 and CO over hollow Silica-Rh, -Ir, and -Ru nanocomposites prepared by Reversed Micelle Technique

Hollow silica nano spheres containing Rh, Ir or Ru metal particles were synthesized by Rh(NH₃)₆Cl₃ aq, Ir(NH₃)₃Cl₃ aq or Ru(NH₃)₆Cl₃ aq/NP-6/cyclohexane reversed micelle system. Hydrolysis of TEOS surrounding metal ammine complex crystals inside the micelle caused the formation of the hollow, which contained small metal particles inside and tiny metal clusters in the silica network. The amounts of H₂ adsorption over Rh and Ir nanocomposites were two to three times more in the cases of hollow-SiO₂ catalysts compared with those of non-hollow ones, suggesting the occlusion of hydrogen inside the hollows of Rh–SiO₂ or Ir–SiO₂. CO molecules could also permeate into the silica wall and be adsorbed on the metal clusters in the silica wall after 573 K pretreatment. Especially in the case of Ru nanocomposite the amount of adsorbed CO was much more than that of H₂, suggesting some unique character of Ru metal nanoparticles. After 773 K pretreatment, however, the amount of CO(a) decreased drastically to less than 1/10 of H(a), indicating the densification of Si–O–Si bonds and the formation of ultra-micropores in the silica wall where only H₂ can selectively permeate. Selective formation of methane was observed in the CO–H₂ reaction over these nanocomposite catalysts, provably because of the higher concentration of hydrogen inside the hollow and silica network.     

Promotion and inhibition of oxidation of rich hydrogen-air mixtures by nitric oxides (NO and NO<Subscript>2</Subscript>) during adiabatic self-ignition

The tracer method was used to numerically study the effect of nitric oxides (NO and NO₂) on the oxidation of rich hydrogen-air mixtures during adiabatic self-ignition at low and high initial temperatures and a pressure of 0.1 MPa. At low temperatures, the added NO interacts with HO₂ to form NO₂, and NO₂ then interacts with H to form NO. When NO₂ is added at the same temperatures, a two-stage mechanism takes place: NO formed by the reaction NO₂ + H is not involved in the reaction until NO₂ is almost completely consumed. In the temperature range 900–1200 K, NO₂ inhibits self-ignition through participation in the reaction with H, leading to the replacement of part of the completely branched chain H → (O, OH) → 3H by the unbranched chain H → OH → H. At low initial temperatures, NO effectively promotes hydrogen oxidation due to replacement of the unbranched chain H → HO₂ → H₂O₂ → OH → H by a chain with branching.     

Essential fatty acid-supplemented diet decreases renal excretion of immunoreactive arginine-vasopressin in essential fatty acid-deficient rats

Essential fatty acid (EFA)-deficient rats have been reported to have very concentrated urine and low urinary prostaglandin E₂ (PGE₂) excretion. Both parameters were normalized by feeding an EFA-supplemented diet (H.S. Hansen [1981] Lipids 16, 849–854). The urinary excretion rate of immunoreactive arginine-vasopressin (iAVP) has been determined in these rats. The iAVP excretion rate was high: ca. 4.8 mU/24 hr, during the EFA-deficient period compared to the controls, 0.7–1.3 mU/24 hr. One day after the dietary change, iAVP excretion rate was still high, but it decreased significantly (p<0.05) at the second measurement 7 days later. It is suggested that the water-conserving effect of vasopressin 1 day after the dietary change was suppressed by the very high PGE₂ production, resulting in normal renal water excretion. PGE₂ and water excretion data were published in the paper just cited.     

IR-spektroskopische Untersuchung zur Lösungsmittelwechselwirkung von 1-Benzylidenpyrazolid-3-on-betainen

Investigation of Solvent-Solute Interactions of 1-Benzylidenepyrazolidone (3) -betaines by I.R. Spectroscopy The infrared spectra of eight 1-benzylidenepyrazolidone(3)-betaines ( 1–7 and 3 m ) have been measured in 22 solvents of different polarity. The carbonyl band of these compounds indicates specific and non-specific solvent-solute interactions, which are qualitatively characterized by the electrophilic properties of the solvent (E-value, acceptor number AN). Intermolecular hydrogen bonds have been detected in protic solvents. The thermodynamic quantities of the associate equilibrium, K,Δ_RH,Δ_RS were determined in chloroform and deuterochloroform, respectively, by the i.r. intensity method.