Partial Hydrogen Research Articles

Liquid-Phase Hydrogenation of Aromatic Mononitro Compounds on Supported Porous Catalysts at Partial Hydrogen Pressures Lower than 0.1 MPa

The influence of the hydrogen partial pressure varied in the interval (4.3–100) × 103 Pa on the kinetics of liquid-phase catalytic hydrogenation of aromatic mononitro compounds in the presence of platinum and iridium supported on activated carbon in various percent ratios (Pt/C-2.5% and Ir/C-5%) was studied for 3,4-dichloronitrobenzene as example. A decrease in the hydrogen partial pressure leads to a significant decrease in the rate of the nitro compound consumption and in the yield of the intermediate arylhydroxylamine. A kinetic mechanism of hydrogenation of the nitro compound, satisfactorily describing the experimental data, was suggested.

Hydrogen and Nitrogen Modification of Anodized TiO2 Nanotube Arrays for Photoelectrochemical Oxidation of Water

TiO2 nanotube arrays (NTs) made by electrochemical anodization exhibit significant potential as a photoanode in low cost, sustainable photoelectrochemical cells for solar water oxidation.1 The wide bandgap (3.2eV, λ < 387 nm) of these materials, however, limits the photocurrent, and the low mean free path of charge carriers further limits performance. Formation of substoichiometric phases or generation of suitable defects have been proven to enhance photoresponse.2 Thermal treatment of TiO2 under reducing atmosphere, for example, generates high-conductivity, oxygen deficient TiO2-xmaterials, including the Magneli phases. Similarly, nitrogen doping may decreases the band gap, enabling increased light absorption. In this work, anodized TiO2 nanotubes were modified via hydrogen or ammonia gas treatments to generate various substoichiometric phases, characterized by reduced bandgap and higher conductivity. In particular, annealing in partial hydrogen pressure (5 at%) leads to a gradual phase transformation of anatase to rutile and various Magneli phases, yielding an enhanced photoelectrochemical response up to 2.2-fold at 1.23VRHE. Annealing in ammonia and argon flow on the other hand results in oxygen loss with barely detectable N incorporation, resulting in a 4-5 fold photocurrent enhancement at 1.23VRHE with a significant cathodic shift (~100 mV) of the onset potential. The fraction of the photogenerated charges utilized for water splitting was estimated by comparing photoelectrochemical performance with or without hole scavenger species.3 All modified samples displayed higher water oxidation efficiency (above 80%) compared with unmodified TiO2(~65%). In order to evaluate the surface disorder introduced by the modification, electrochemical impedance spectroscopy (EIS) was carried out, showing higher charge carrier density. Overall, this work demonstrates that hydrogen or ammonia annealing treatments enhance significantly photoelectrochemical performance.

Computational Investigation into the Interactions of Traditional Chinese Medicine Molecules of WenQingYin with GluR2.

Docking and molecular dynamics simulations have been carried out to investigate the interaction of a traditional Chinese medicine, WenQingYin, with the glutamate receptor 2 (GluR2) subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor. Four representative drug components of WenQingYin, namely 2-(3,4-dihydroxyphenyl)-5,6,7-trihydroxy-4H-chromen-4-one (PHF), 4-hydroxy-3-methoxybenzoic acid (HMB), 4-(2,3-dihydroxy-3-methylbutoxy)-7H-furo[3,2-g]chromen-7-one (DHMBP) and methyl 7-formylcyclopenta[c]pyran-4-carboxylate (cerbinal), and their complexes with GluR2 were simulated. Our results show that PHF, HMB, and DHMBP formed a partial hydrogen bond with GluR2 in its ligand-binding domain. However, cerbinal was not stable in the ligand-binding domain of GluR2 and induced a significant change in the structure of GluR2. Three-dimensional plots represent the contact and movement situation of the traditional Chinese medicine molecules in the ligand-binding domain. The combined results of the docking and molecular dynamics simulations provide insight into the interaction between these traditional Chinese medicine molecules and proteins.

Electronic structure and chemical hydrogen storage of a porous sp3 tetragonal BC2N compound

By means of first-principles calculations, we predict an all-sp3 hybridized tetragonal BC2N compound (tet-BC2N) which is suggested to be obtained by transversely compressing (4,0) carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) arrays. Accompanied by the transition from sp2-hybridized nanotubes to sp3-hybridized tet-BC2N, not only the bond length and diameter of tubes but also the electronic bandgap increases. Strikingly, the bandgap of the tet-BC2N can be mediated by controlling the ratio of BNNTs to total nanotubes from 1/2 to 1. However, it is almost a constant for the ratio changing from 0 to 1/2. In addition, this study shows that the tet-BC2N is a potential material for chemical hydrogen storage. While the weight percentage of hydrogen storage is up to 3.9 wt%, the adsorbed hydrogen still exists in the form of molecules. Even if the weight percentage of hydrogen storage increases to 7.6 wt%, the tet-BC2N is still intact but partial hydrogen molecules split into atoms.

Hydrogen generation by laser irradiation of colloids of iron and beryllium in water

The hydrogen generation under irradiation of aqueous colloids of iron and beryllium nanoparticles by 10-ns pulses of the first harmonic of a Nd : YAG laser with an energy density of about 80 J cm−2 in the solution is experimentally investigated. The partial hydrogen content in the atmosphere above the colloidal solutions of nanoparticles first increases with increasing irradiation time and then reaches a stationary level (400 − 500 Torr). The hydrogen generation rate, being nonzero in the case of irradiation of pure water, passes through a maximum with an increase in the nanoparticle concentration. The results obtained are discussed in terms of the dissociation of water molecules under a direct electron impact from the optical breakdown plasma formed in the liquid.

Synthesis and Characterization of Carbon Fiber Based Porous CNTs-RGO/BDD for Application as Microelectrodes

ABSTRACTMicroelectrodes have attracted great interest for electroanalysis because of their unique properties, such as nonlinear diffusion, increased rate of mass transport and reduced capacitance, which allows a fast response. In this work, we created a porous nanocomposite of boron doped diamond (BDD) deposited on carbon nanotubes – reduced graphene oxide (CNTs – RGO) by Hot Filament Chemical Vapor Deposition (HFCVD) technique. The resulting material yielded porous BDD microelectrodes. On the first step, we have grown the CNTs on carbon fiber (CF) surface by Thermal CVD in a tubular reactor. Camphor solution and Fe-Co were carbon and catalyst source, respectively. For exfoliation, CNTs were treated by hydrogen plasma and oxygen plasma. We applied a seeding solution containing nanodiamond dispersed in KCl aqueous solution. Diamond nanoparticles interact with oxygen-containing groups on CNTs, promoting an efficient seeding. We deposited BDD films in an HFCVD reactor using methane/hydrogen gas mixtures. For doping, a partial hydrogen flow bubbled in a closed vessel containing a solution of boron oxide dissolved in methanol. The microelectrodes were characterized by Raman Scattering Spectroscopy, Scanning Electron Microscopy with Field Emission Gun and Cyclic Voltammetry. The crystalline quality of CNTs and BDD doping level were studied by Raman analysis. SEM micrographs showed that nanocomposite presented high porosity. Electrochemical analysis showed that the deposition of BDD on CNTs-RGO increased the electrochemical response of the microelectrode. Besides, this electrode presented a low capacitive current in comparison with BDD grown on flat substrates. Further, the porous BDD nanocomposite showed itself to be promising in electroanalysis.

Hydrocracking of vacuum residue with solid and dispersed phase catalyst: Modeling of sediment formation and hydrodesulfurization

Effect of dispersed Mo based catalyst on residual hydrocracking was investigated in this paper. The study was performed in an industrial scale hydrocracking unit with the average reactor temperature of 399–419°C and pressure of 18MPa. Vacuum residue from Ural crude oil was fed to the reactor. A sediment formation model was proposed with parameters sets for the regime with classical supported Ni-Mo/Al2O3 catalyst and for that with a combined system of supported and dispersed catalyst. Four process parameters were incorporated in the model equation: reaction temperature, hydrogen partial pressure, exothermic gain and hydrogen makeup to feed mass ratio. A decrease of the sediment formation with the application of dispersed Mo catalyst was observed, which results in higher Mo concentration in the liquid phase and thus in higher hydrogenation activity and stabilization of coke precursors. Hydrodesulfurization was also investigated and a sulfur distribution model was created with parameters for both regimes. The model contains three lumps with significant sulfur content: sulfur contained in the vacuum residue, sulfur contained in the vacuum gas oil and hydrogen sulfide. Application of the catalyst and increase of reaction temperature from 399–414°C to 414–419°C resulted in increase of average sulfur conversion in vacuum residue from 86.5% to 87.9%.

On Lewis acidity/basicity and hydrogen bonding in the equation-of-state approach

The central objective of this work is to revisit the development of the widely used Lewis acidity/basicity scales and seek possibilities for their eventual unification. The primary focus is on hydrogen bonding interactions which are dealt with the estimation of hydrogen-bond-donor (HBD) and hydrogen-bond-acceptor (HBA) capacity of the compounds. The developments are made by having in mind their implementation in a thermodynamic equation-of-state framework for the reliable estimation of all basic thermodynamic quantities of compounds over a broad range of external conditions. Gutmann’s donor and acceptor numbers, the Hard–Soft Acid and Base principle, Drago’s electrostatic and covalent interaction parameters E and C, the LFER/LSER acidity and basicity, α and β (A and B), parameters, the Hansen partial hydrogen – bonding solubility parameters and Klamt’s quantum-chemically derived hydrogen – bonding cosmoments are all combined with the recent partial solvation parameter (PSP) approach in an effort to develop a unified hydrogen bonding scale. The challenges and the perspectives of this unification are critically discussed.

Tailoring the Electronic Structure of Covalently Functionalized Germanane via the Interplay of Ligand Strain and Electronegativity

The covalent functionalization of 2D crystals is an emerging route for tailoring the electronic structure and generating novel phenomena. Understanding the influence of ligand chemistry will enable the rational tailoring of their properties. Through the synthesis of numerous ligand-functionalized germanane crystals, we establish the role of ligand size and electronegativity on functionalization density, framework structure, and electronic structure. Nearly uniform termination only occurs with small ligands. Ligands that are too sterically bulky will lead to partial hydrogen termination of the framework. With a homogeneous distribution of different ligands, the band gaps and Raman shifts are dictated by their relative stoichiometry in a pseudolinear fashion similar to Vegard’s law. Larger and more electronegative ligands expand the germanane framework, thereby lowering the band gap and Raman shift. Simply by changing the identity of the organic ligand, the band gap can be tuned by ∼15%, highlighting the po...

Efficacy assessment of independent severe accident mitigation measures in OPR1000 using MELCOR code

ABSTRACTIn-vessel and ex-vessel mitigation strategies have been revisited to improve the severe accident management (SAM) for operating nuclear power plants. Because independent mitigation measures tend to produce positive and adverse effects simultaneously, it is necessary to investigate the efficacy of individual measures by means of proper quantification. Thus, in the present study we investigated the overall efficacy of existing SA mitigation strategies prepared for the Optimized Power Reactor 1000 MWe (OPR1000) by means of MELCOR 1.8.6 code. The numerical evaluation showed that the Mitigation-01, feeding water into the steam generators, is the most effective among the other mitigations. In addition, Mitigation-02, reactor coolant system depressurization, could not mitigate the SA sufficiently when applied individually. Among the four ex-vessel mitigation strategies, execution of containment spray was effective in removing most of the aerosol fission product but also intensified hydrogen combustion by increasing the partial hydrogen pressure owing to steam condensation. Mitigation-07, operation of passive autocatalytic recombiners (PARs), could reduce the hydrogen concentration, though the catalytic reaction was predicted to increase the containment pressure. In conclusion, this study suggests that mitigation measures should be carefully selected, and that counteracting measures should be prepared to minimize potential adverse effects.

Important role of the ethylenedioxy group bound to the thienyl-di-vinylene π-conjugation unit of tricyanofuran-based donor-acceptor electro-optic chromophores

We report the design, synthesis and characterization of a series of electro-optic chromophores comprised of amino-benzene with a benzyloxy group as the donor units, thienyl-di-vinylene with ethylenedioxy as the π-conjugation bridge, and tricyanofuran derivatives as the acceptor units. The improvement of linear and nonlinear optical properties was found in electro-optic chromophores with ethylenedioxy compared with the chromophores without ethylenedioxy. The data obtained from hyper-Rayleigh scattering, absorption spectrum, and 1H-NMR measurements indicate the improved structural stability of π-conjugation unit, which may be induced by the steric effect and partial intra-molecular hydrogen bonding related to ethylenedioxy.

Separation performance of foils from Pd—In(6%)—Ru(0.5%), Pd—Ru(6%), and Pd—Ru(10%) alloys and influence of CO2, CH4, and water vapor on the H2 flow rate through the test membranes

The H2 flow rate through the 30-μm thick foil from Pd—Ru(6%) and Pd—Ru(10%) alloys at 673 and 773 K was found to be controlled by the diffusion of H atoms in the foil bulk. The interrelation between hydrogen permeability through the Pd—In(6%)—Ru(0.5%), Pd—Ru(10%), Pd—Ru(6%), and Pd—Ag(23%) membranes and the permeability pre-exponential factors in the Sieverts equation in the 573—773 K temperature interval indicated that the hydrogen permeability depended on the structural characteristics of palladium alloys. The influence of the CO2, CH4, and water vapor impurities on the H2 flow rate through the studied membranes depended on the driving force nature (the sweep gas or transmembrane pressure) used for the development of the partial hydrogen pressure difference across the membrane. The negative influence of CH4 and CO2 was observed only when using a transmembrane pressure and at the impurity content of 20% or more. This effect increased with increasing temperature in the 573—773 K range, with the influence of CO2 being more pronounced due to its reaction with hydrogen leading to the formation of CO. The influence of water vapor was studied at its 11—23% content in hydrogen and at 573 and 773 K of temperature. The negative influence of water vapor was found to subside as its content in the hydrogen mixture decreased and the temperature increased. It was shown that water vapor can be used as a sweep gas and at T = 773 K its influence on the H2 flow rate through the membrane was almost the same as that of N2.

Industrial catalyst market worth $22.0 bn by 2020

A catalytic Pd76Ag19Cu5 alloy membrane reactor packed with 5% Ni/Ce0.6Zr0.4O2 catalyst was adopted in this study to investigate hydrogen production performance from the dry reforming reaction of methane and carbon dioxide. The 1:1 CH4/CO2 feed was introduced to the reactor with 60 mg of the catalyst at a flow rate of 20 ml/min at 550 °C. The effluent gas compositions were examined using an online gas chromatographer (GC). Compared to a conventional reactor without the membrane, the CH4 and CO2 conversions were significantly increased by 3.5-fold and 1.5-fold, respectively. Correspondingly, the overall H2 yield was greatly improved from about 10–35%. Additionally, the hydrogen selectivity increased from 47 to 53%. It is theorized that the in-situ partial hydrogen withdrawal by the membrane mainly caused the dry reforming reaction equilibrium to shift forward and created a hydrogen-deprived environment unfavorable for the competing reversible water-gas shift reaction to take place.

Improved hydrogen production from dry reforming reaction using a catalytic packed-bed membrane reactor with Ni-based catalyst and dense PdAgCu alloy membrane

A catalytic Pd76Ag19Cu5 alloy membrane reactor packed with 5% Ni/Ce0.6Zr0.4O2 catalyst was adopted in this study to investigate hydrogen production performance from the dry reforming reaction of methane and carbon dioxide. The 1:1 CH4/CO2 feed was introduced to the reactor with 60 mg of the catalyst at a flow rate of 20 ml/min at 550 °C. The effluent gas compositions were examined using an online gas chromatographer (GC). Compared to a conventional reactor without the membrane, the CH4 and CO2 conversions were significantly increased by 3.5-fold and 1.5-fold, respectively. Correspondingly, the overall H2 yield was greatly improved from about 10–35%. Additionally, the hydrogen selectivity increased from 47 to 53%. It is theorized that the in-situ partial hydrogen withdrawal by the membrane mainly caused the dry reforming reaction equilibrium to shift forward and created a hydrogen-deprived environment unfavorable for the competing reversible water-gas shift reaction to take place.

Mechanochemistry and hydrogen storage properties of 2Li3N+Mg mixture

The Li–Mg–N–H hydrogen storage system is a promising hydrogen storage material due to its moderate operation temperature, good reversibility, and relatively high capacity. In this work, the Li–Mg–N–H composite was directly synthesized by reactive ball milling (RBM) of Li3N and Mg powder mixture with a molar ratio of 2:1 under hydrogen pressure of 9 MPa. More than 8.8 wt% hydrogen was absorbed during the RBM process. The phases and structural evolution during the in situ hydrogenation process were analyzed by means of in situ solid–gas absorption and ex situ X-ray diffraction (XRD) measurements. It is determined that the hydrogenation can be divided into two steps, leading to mainly the formation of a lithium magnesium imide phase and a poorly crystallized amide phase, respectively. The H-cycling properties of the as-milled composite were determined by temperature-programmed dehydrogenation (TPD) method in a closed system. The onset dehydrogenation temperature was detected at 125 °C, and it can reversibly desorb 3.1 wt% hydrogen under a hydrogen back pressure of 0.2 MPa. The structural evolution during dehydrogenation was further investigated by in situ XRD measurement. It is found that Mg(NH2)2 phase disappears at about 200 °C, and Li2Mg2N3H3, LiNH2, and Li2MgN2H2 phases coexist at even 300 °C, revealing that the dehydrogenation process is step-wised and only partial hydrogen can be desorbed.

Aromatic Alcohols as Model Molecules for Studying Hydrogenolysis Reactions Promoted by Palladium Catalysts

The hydrogenolysis reaction of aromatic alcohols (benzyl alcohol, 1-phenylethanol and diphenylmethanol), promoted by supported palladium catalysts, such as Pd/TiO2, Pd/SiO2 and Pd/Co3O4, has been investigated at 0.1 MPa H2 and 323 K. The catalysts have been characterized by BET, TPR, XRD, TEM and XPS. A different kinetic behaviour was observed: in presence of Pd/TiO2 and Pd/SiO2 catalysts, prepared by impregnation, the hydrogenolysis activity follows the order benzyl alcohol > 1-phenylethanol ≥ diphenylmethanol, whereas it is totally reversed on Pd/Co3O4, prepared by co-precipitation. All results indicate that the reactivity of supported Pd catalysts, in the hydrogenolysis reaction, depends on the support nature, the preparation method of catalysts and the aromatic alcohols structure. Kinetic experiments carried out at different partial hydrogen pressure allow to elucidate the pathway of the C–OH bond scission, involving a radical substitution of the carbon bonded OH group by a hydrogen atom coming from the metal surface “via” associative and dissociative paths.

ChemInform Abstract: The Non‐innocent Role of Cerium Oxide in Heterogeneous Catalysis: A Theoretical Perspective

AbstractReview: 125 refs.

Nano-film modification of collagen hydrogels for controlled growth factor release

We demonstrate the fabrication of nano-modified collagen hydrogels that afford controlled growth factor release for induced pluripotent stem (iPS) cell culture. Specifically, we focused on the preparation and characterization of graphene oxide (GO) sheets incorporated into collagen-based hydrogels for controlled growth factor release. Fibroblast growth factor-2 (FGF-2) bound to collagen via electrostatic interactions and partial hydrogen bonding. Various GO sheet quantities were incorporated and evenly distributed in collagen hydrogels. Taking advantage of the low permeability of GO sheets, FGF-2 release was regulated in a controlled manner. In this manuscript, three different GO sheet concentrations were applied to obtain different release profiles over a period of 400h in the presence of serum. The incorporation of GO sheets into collagen hydrogels offers a new approach to control the release of biologically active macromolecules (e.g., growth factors).

Fabrication of a Ni/MgO Nanocomposite Catalyst by Exolution

A Ni(NixMg1-x)O nanocomposite catalyst was fabricated by exsolution technique from a (NixMg1-x)O solid solution powder. On reduction, Ni2+ ion close to the surface exsolved as nano particles, which were homogeneously distributed in the matrix powder surface. TEM observation suggested that the exsolution occurred preferentially at the edge surface of the matrix powder. The methane partial oxidation and hydrogen selectivity over the nanocomposite catalysts were evaluated over the temperature range, 300 to 900ºC.

The non-innocent role of cerium oxide in heterogeneous catalysis: A theoretical perspective

Ceria (CeO2) is the most significant of the oxides of rare-earth elements in industrial catalysis with its reducibility being essential to its functionality in catalytic applications. The complexity of real (powder) catalysts hinders the fundamental understanding of how they work. Specifically, the role of ceria in the catalytic activity of ceria-based systems is still not fully understood. To elucidate it, well-defined ceria-based model catalysts are prepared experimentally or created theoretically and studied. The purpose of this brief review is to discuss recent results on model ceria-based catalysts using CeO2(111), VOx/CeO2(111), and Ni/CeO2(111) as examples of catalysts for partial alkyne hydrogenation, oxidative dehydrogenation, and hydrogen production, respectively. The emphasis is here put on theoretical studies and special attention is given to the effects of ceria as catalyst support.