Course Of Hydrogenation Research Articles

Computer Modeling of the Deformation of Structural Elements Under the Conditions of Creep in the Course of Hydrogenation of the Metal Under Complex Loading

Computer Modeling of the Deformation of Structural Elements Under the Conditions of Creep in the Course of Hydrogenation of the Metal Under Complex Loading

Ir-Catalyzed Double Asymmetric Hydrogenation of 3,6-Dialkylidene-2,5-diketopiperazines for Enantioselective Synthesis of Cyclic Dipeptides.

An Ir/spiro[4,4]-1,6-nonadiene-based phosphine-oxazoline ligand (SpinPHOX) complex-catalyzed double asymmetric hydrogenation of 3,6-dialkylidene-1,4-dimethylpiperazine-2,5-diones has been developed, providing efficient and practical access to a wide variety of chiral 3,6-disubstituted-2,5-diketopiperazines in high yields with exclusive cis-diastereo- and excellent enantioselectivities (>99% de, up to 98% ee). The synthetic utilities of the protocol have been demonstrated in a gram scale synthesis of 6a and efficient construction of chiral products 8, 14, and 17 as well as a 2-butenyl-bridged bicyclic diketopiperazine 10 and hydroxydiketopiperazine 11. With an analogous achiral Ir catalyst, the hydrogenation of enantiopure monohydrogenated intermediate 7a gave cis-6a as the only product, indicating that the second-step hydrogenation of the titled transformation is a chiral substrate controlled process. The reaction profile study for asymmetric hydrogenation (AH) of 5a revealed that the concentration of the monohydrogenation intermediate 7a remained at a low level (<8%) during the course of hydrogenation. The hydrogenation of 5a to 6a proceeded significantly faster than that of its half-hydrogenated intermediate ( S)-7a, indicating that the titled reaction involves primarily a processive mechanism, in which a single catalyst molecule performs consecutive hydrogenation of the two C═C double bonds in substrate 5a without dissociation of the partially reduced 7a. The present protocol represents a rare example of asymmetric catalytic consecutive hydrogenation of heterocycles and provides an alternative way for efficient construction of cyclic dipeptides.

Concentration-Dependent Transformation Plasticity Effect During Hydrogenation of Technically Pure Titanium Irradiated with an Electron Beam

Using the methods of X-ray diffraction analysis, the concentration-dependent transformation plasticity effect +TPE) is investigated during hydrogenation of the technically pure titanium (VT1-0) irradiated on one side with a low-energy high-current electron beam in a SOLO facility using three 50 μs pulses at the pulse repetition frequency 0.3 s–1 and the beam energy density W = 18 J/cm2. Its irradiation is performed in an argon atmosphere at the residual pressure 0.02 Pa. It is found out that the concentration-dependent TPE in the course of hydrogenation is due to the low stability state of the α-Ti crystal lattice formed in the specimen surface layer upon its e-beam irradiation. Relaxation of the elastic plane macrostresses occurs as a result of the development of concentration inhomogeneity of hydrogen or formation of α″-Ti and ω-Ti martensitic phases.

Asymmetric Transfer Hydrogenation of 1‐Aryl‐3,4‐Dihydroisoquinolines Using a Cp*Ir(TsDPEN) Complex

We report herein a simple alternative method for the asymmetric transfer hydrogenation (ATH) of 1‐aryl‐3,4‐dihydroisoquinolines (1‐Ar‐DHIQs) that are known to be challenging substrates owing to their poor reactivity. The hydrogenation protocol employs the readily available Cp*Ir(TsDPEN) {where Cp* = pentamethylcyclopentadienyl and TsDPEN = (S,S)‐HNCHPhCHPhNTs2–} catalytic complex, 2‐propanol and HCOOH/triethylamine mixture as the solvent and hydrogen donor, and anhydrous phosphoric acid as an inexpensive additive. The series of examined substrates shows a favorable tolerance to various functional groups. Unlike 1‐alkyl‐DHIQs, where the enantiomeric excess (ee) starkly changes during the course of hydrogenation, 1‐Ar‐DHIQs exhibit a constant ee value, which makes the method practical and useful for the production of fine chemicals containing the 1,2,3,4‐tetrahydroisoquinoline motif.

Acoustic Investigations of the Strained State of Hydrogenated 09G2S Steel

We study the acoustic properties of inhomogeneous plastically deformed specimens made of 09G2S steel. The specimens with residual strains were successively subjected to heat treatment and hydrogenation from the gas phase. After each procedure, we measured the space distributions of the velocity of longitudinal acoustic waves. We also analyzed the mechanisms of changes in the velocity in the course of hydrogenation in the region of the specimen with residual strains.

Hydrogen Permeability of the Surface Nanocrystalline Structures of Carbon Steel

We studied the hydrogen permeability of the surface nanocrystalline structures formed by the mechanical-pulse treatment on 45 steel with the use of various technological media. It is shown that these structures are characterized by a much lower hydrogen permeability as compared with the untreated steel, thus revealing the formation of a large number of hydrogen traps in the course of treatment. The hardened surface layer is more susceptible to the development of dissipated damage in the course of hydrogenation but may also serve as a barrier for the penetration of hydrogen into the matrix material.

Synthesis and research of the nickel catalysts of liquid-phase hydrogenation of benzene promoted by ferroalloys

This work develops the technique and technology of modification by ferroalloys of floatable nickel catalysts of hydrogenation of benzene. It in detail studies the influence of the nature of metal of the catalyst, the modifying additives, the size of particles, technological parameters. They worked up reliable data on phase, granulometric and chemical structures, porous structure explaining activity, selectivity and stability of catalysts. The synthesized nickel catalysts are tested in the course of hydrogenation of benzene to cyclohexane in the liquid phase.

Degradation Reactions in Anthraquinone Process of Hydrogen Peroxide Synthesis

Present research concentrates on the process of anthraquinone degradation in the course of hydrogenation carried out in the presence of palladium catalyst. Hydrogenation experiments were carried out using agitated glass laboratory batch type reactor at atmospheric pressure of hydrogen and temperature of 55 °C. Catalytic tests were performed using solutions composed of 2-ethyl-9,10-anthraquinone (eAQ) and a mixture of eAQ and 2-ethyloxanthrone (OXO) with various proportions. Degradation of anthraquinone was studied and in particular, the role of reduced forms of quinone namely hydroquinone and its tautomer OXO is discussed. A difference in the course of reactions pathways: hydrogenation of aromatic rings to give 2-ethyl-5,6,7,8-tetrahydro-9,10-anthraquinone (active quinone) and hydrogenolysis reactions yielding degradation products was observed. Present research concentrates on the process of 2-ethyl-9,10-anthraquinone degradation on palladium catalyst. The role of reduced forms, hydroquinone-enol form and its keto-tautomer is discussed.

Experimental study of the influence of hydrogenation on synthesis of carbon nanostructures in a reactor with activated hydrogen

The role of backward pyrolysis of carbon during hydrogenation of unstructured carbon black and nanotube growth in a reactor with hydrogen activated by diffusion through a heated metallic wall is studied. If the wall is heated nonuniformly, the amorphous unstructured carbon deposit “climbs” in the course of hydrogenation by active hydrogen and deposits again when falling on the heated metal surface, self-organizing into more ordered nanofibers and nanotubes as a result of forward pyrolysis. It is shown that this effect can be used for raising the concentration of carbon nanotubes growing on catalyst particles in the deposited layer.

Hydrogenation of nitrobenzonitriles using Raney nickel catalyst

2-, 3-, 4-Nitrobenzonitriles were hydrogenated using Raney nickel catalyst in the environment of two different solvents (methanol and dioxane). The position of the nitro group relative to the nitrile group plays the dominant role in the course of hydrogenation. The nearer the substituent to the nitrile group is, the larger is its effect. 3- and 4-nitrobenzonitriles were hydrogenated to their primary amines, in contrast to 2-nitrobenzonitrile, which was transformedvia intramolecular oxidation to 2-aminobenzamide. During hydrogenation, numerous intermediates were formed. The choice of the solvent is another significant parameter affecting the course of hydrogenation.

Synthesis, structure, and catalytic properties of polymer-immobilized rhodium clusters

Immobilized Rh6 clusters (cyclohexene hydrogenation catalysts) were prepared by the polymer-analogous transformations or copolymerization of cluster-containing monomers and characterized. Intermediates formed in the course of a catalytic reaction were studied using IR spectroscopy, XPS, and atomic force microscopy. It was found that the relative intensity of a low-energy line in the Rh3d 5/2 spectrum of the initial polymer-immobilized cluster in the XPS spectrum of Rh6 increased in the course of hydrogenation. The catalytic activity of the immobilized complex changed symbatically with both the number of Rh atoms bound to the H(CO) group and the number of Rh atoms, the charge on which was greater than that in the parent cluster. Some experimental evidence was obtained in favor of the hypothesis of cluster fragmentation in the course of hydrogenation with the formation of highly active, most likely, nanosized particles, which are true catalysts, in low concentrations. The surface of macrocomplex particles after hydrogenation became more homogeneous and hydrophilic; this fact is also indicative of an increase in the concentration of polar functional groups in surface layers. This was likely due to Rh-Rh bond cleavage in the polymer-immobilized cluster.

연료전지의 수소저장용 마그네슘계 합금의 표면제어에 의한 전기화학적 수소화 거동 연구

Mg₂Ni계 합금 입자의 수소저장 특성에 대한 표면처리 효과가 마이크로 전극 측정법에 의해 검토되었다. 카본-섬유로 된 마이크로 전극을 KOH 수용액 속에서 조정자를 사용하여 수소 단일입자에 접촉시켰다. 상온에서 Mg₂Ni 합금의 수소저장 특성은 니켈 도금용액에 의한 표면 처리에 의해 크게 개선되었다. 니켈 도금용액 속에 있는 함유된 나트륨염(sodium phosphate 및 sodium dihydrogen citrate)이 합금을 아몰퍼스와 같은 형태로 만들었으며, 그 결과 상온에서 수소 흡장/방출 용량이 최초의 17[mAh/g]에서 150[mAh/g]로 향상되었다. 합금 입자 내에서 수소원자의 겉보기 화학적 확산계수를 계산하기 위하여 Potential-step 실험을 실시하였으며 데이터 해석을 위해 구형확산 모델을 적용하였다. 실험결과로서 겉보기 확산계수(DSUBapp/SUB)는 수소 흡장 및 방출되는 전 과정에서 10??～10??[㎠/s] 수준인 것으로 확인되었다.

Effect of hydrogen on phase and structural transformations in titanium alloys of different classes

We study the laws of phase and structural transformations in titanium alloys under the action of dissolved hydrogen and in the course of subsequent degassing. We show the possibility to control structure formation in them with the help of alloying with hydrogen and to obtain structures that cannot be obtained by conventional technological methods. It has been established that the alloying system determines the character of interaction of these alloys with hydrogen in the course of hydrogenation. After additional alloying with hydrogen, intermediate hydrides are formed in titanium alloys with β-isomorphic stabilizers (V, Nb), Ti Cr2 intermetallic compound appears in alloys with β-eutectoid stabilizer (Cr), and Ti3Al compound is formed in alloys with high aluminum content. After vacuum annealing of hydrogen-containing specimens at 600°C, a composite heterophase (α + β + α2) or (α + β + TiCr2) structure is formed, and intermetallic particles in it have an incoherent boundary.

마이크로 전극에 의한 2차 전지용 활물질 단일 입자의 전기화학적 평가

마이크로전극을 사용하여 니켈-수소 전지의 전극 활물질인 수소저장합금<TEX>$(MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3})$</TEX>과 수산화니켈의 단일입자에 대하여 전기화학적 특성을 평가하였다. 즉 마이크로 전극을 활물질 입자 한 개 위에 전기적인 접촉을 이루도록 조정하고 전위 주사(Cyclic Voltammograms) 및 포텐셜 스텝(Potential Step)으로 실험을 실시하였다. 그 결과 수소저장 합금 입자의 경우 -0.9, -0.75, -0.65V 부근에서 3개의 산화 피크 및 -0.98V에서 수소발생 전위, 그리고 수산화니켈 입자의 경우 프로톤 산화 환원 반응(0.45V, 0.32V)과 산소 발생 반응 전위를 보다 명확하게 확인 할 수 있었다. 그리고 수소흡장합금 입자 내에서의 수소 흡장 및 방출 전 과정에 대해 수소 확산계수 <TEX>$(D_{app})\;(10^{-9}\sim10^{-10}cm^2/s)$</TEX>가 얻어졌다. Electrochemical properties were studied for a single particle of active material of hydrogen storage alloy <TEX>$(MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3})$</TEX> and nickel hydroxides <TEX>$(NiOH)_2$</TEX> for the secondary Nickel Metal Hydride (Ni-MH) batteries using the microelectrode, which was manipulated to make electrical contact with an active material particle for cyclic voltammograms (CV) and potential-step experiments. As a result of CV test, it was found that three kinds of hydrogen oxidation peaks at -0.9, -0.75 and -0.65 V and hydrogen evolution peak at -0.98 V for hydrogen storage alloy were separately observed and two kinds of peaks of proton oxidation/reduction at 0.45 and 0.32 V and oxygen evolution reaction (OER) at 0.6 V for nickel hydroxides were also more clearly observed. Furthermore hydrogen diffusion coefficient within a single particle was also found to vary the order between <TEX>$10^{-9}\;and\;10^{-10}cm^2/s$</TEX> over the course of hydrogenation and dehydrogenation process for potential-step experiments.

연료전지의 수소저장용 합금에 대한 수소확산반응의 속도론적 해석

본 논문은 마이크로 전극 시스템에 의하여 연료전지 및 Ni-MH 전지로의 응용을 가정한 AB?계 수소저장합금인 MmNi<SUB>3.55</SUB>Co<SUB>0.75</SUB>Mn<SUB>0.4</SUB>Al<SUB>0.3</SUB>의 단일 입자에 대하여 전기화학적인 평가를 수행하였다. 즉 Carbon fiber 마이크로 전극을 합금 입자 한개 위에 전기적인 접촉을 이루도록 조정하고, 합금 입자 내에서 수소원자의 겉보기 화학적 확산계수를 계산하기 위하여 Potential-Step 실험을 실시하였다. 여기에서 사용되는 합금입자는 치밀하고 전도성이 있는 구형이므로 데이터 해석을 위해 구형확산 모델을 적용하였다. 실험결과로서 겉보기 확산계수(D<SUB>app</SUB>)는 수소 흡장 및 방출되는 전 과정에서 10??과 10?¹?[㎠/s] 수준인 것으로 확인되었다. 마이크로 전극 측정 시스템에 의한 단일 입자의 전기화학적 평가는 기존의 Composite Film 전극에 비해 수소저장합금에 대해 보다 상세하고 정확한 정보를 쉽게 얻을 수 있었다.

Comparison of hydrogen storage characteristics between as-cast and melt-spun TiCr1.1V0.5Fe0.1Mn0.1 alloys

Abstract Hydrogen storage characteristics of as-cast and melt-spun TiCr 1.1 V 0.5 Fe 0.1 Mn 0.1 alloys were investigated by pressure–composition–temperature (PCT) tests, X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD showed that both the as-cast and the melt-spun alloys were similarly consisted of V based BCC phase and Ti 1.07 Cr 1.93 phase. However, PCT tests showed that the melt-spun alloy, with larger hysteresis between hydrogen absorption and desorption, had higher hydrogen storage capacity than the as-cast alloy. More interestingly, the phase compositions of the two fully hydrogenated alloys were entirely different. The as-cast and the melt-spun alloys should have different atomic motion mechanisms during the course of hydrogenation.

Hydrogenation of 2-Ethylanthraquinone over Pd/SiO2and Pd/Al2O3in the Fixed-Bed Reactor. The Effect of the Type of Support

The effects of the type of support and Pd concentration profile in alumina and silica supported egg-shell catalysts and their performance in the hydrogenation of 2-ethylanthraquinone (eAQ) were studied in 'Anthra' (AQ) and 'All-Tetra' systems. The activity and deactivation of catalysts were determined in the fixed-bed reactor. Solution saturated with hydrogen, (concentration of active quinones 60g/dm3, eAQ in the AQ system, 30% of eAQ and 70% of H4eAQ–2-ethlytetrahydroanthraquinone, in the All-Tetra system) was circulated through the catalyst bed at temperature 50°C and pressure 5bar. The contents of eAQ, active quinones, H4eAQ and degradation products were determined in the course of hydrogenation by GC method. The egg-shell palladium catalysts (1–2wt% Pd) prepared by the precipitation of palladium hydroxide onto alumina and silica supports pre-impregnated with various alkaline (NaHCO3, NaH2PO4, Na2SiO3) solutions were used in the hydrogenation experiments. Pd concentration profile inside the grains of catalysts was characterized by scanning electron microscopy. A difference between alumina and silica carriers with respect to the course of side reactions producing degradation products was found. Degradation of quinones in the hydrogenolytic reactions predominated on alumina supported catalysts, while the catalysts with silica favoured the hydrogenation of aromatic rings resulting in H4eAQ-active quinone. As a crucial factor for the decrease in the activity during the hydrogenation run, the reactivity of catalyst in the hydrogenolytic reactions was established. Alumina supported catalysts exhibited much higher deactivation than those of silica supported ones. Silica carrier as well as silica species introduced onto alumina under pre-impregnation with Na2SiO3 exhibited an advantageous role in the catalyst performance, in terms of activity and deactivation.

Nature of chemical bond and phase stability of hydrogen storage compounds

Our recent investigations on the nature of the chemical bond and phase stability of hydrogen storage compounds and their hydrides are reviewed in search of a new method for materials design. A series of electronic structure calculations has been performed using the DV-Xα molecular orbital method. It is found that hydrogen interacts more strongly with hydride non-forming elements, B, (e.g. Ni, Mn, Fe) than hydride forming elements, A, (e.g. La, Zr, Ti, Mg) in every hydrogen storage compound, despite that there is a larger affinity of A element for hydrogen than B element in the binary metal-hydrogen system. The stability of hydrides can be elucidated in terms of the nature of the chemical bond between atoms in a small polyhedron where hydrogen is stored and also of the crystal structural evolution in the course of hydrogenation. In addition, it is shown that the A/B compositional ratio of hydrogen storage compounds is predictable using a simple parameter, 2×Bo(AB)/[Bo(AA)+Bo(BB)], where Bo(AB), Bo(AA) and Bo(BB) are the bond orders between atoms given in the parentheses.

Hydrogenation on granular palladium-containing catalysts: II. Hydrogenation of nitroheterocyclic compounds

Nitroheterocyclic compounds were reduced in a classical reactor with an agitator equipped with a cell for fixed bed of catalyst. As catalysts were applied granular palladium catalysts (0.5% of Pd on γ-Al2O3 and 2% of Pd on granulated carbon). Anilines and 3-amino-2(1H)-pyridones were obtained in high yield at reduction of the appropriate nitro compounds, and the activity of the catalyst samples only slightly decreased. Yet aminopyrazoles and aminoimidazoles obtained by hydrogenation on palladium were very sensitive to the presence of air even as hydrochlorides. In the course of hydrogenation of nitropyrazoles and nitroimidazoles the activity of the catalyst markedly decreased.

Influence of Cyclic Preloading on the Hydrogen Degradation of Materials

We present the results of numerical analysis of the influence of the mode of preliminary cyclic loading on hydrogen-induced crack growth in high-strength steel with regard for the stress-strain state and diffusion of hydrogen. The elastoplastic stress-strain state at the crack tip under cyclic loading followed by monotonic loading is simulated for the case of high strains. The diffusion of hydrogen at the crack tip is modeled by taking into account the evolution of the stress-strain state from postcyclic compression to tension in the course of hydrogenation. It is shown that the accumulation of hydrogen in the process zone depends on the distribution of residual stresses induced by cyclic preloading.