Increasing Hydrogen Pressure Research Articles

Green Diesel Production Through Deoxygenation Reaction with Natural Zeolite-supported Nickel and Copper Catalyst

The depletion of fossil fuels and their environmental impact necessitate sustainable alternatives. Green diesel, a biofuel with a chemical structure similar to conventional diesel, has gained traction as a viable alternative. This study explores the development of a cost-effective catalyst for green diesel production using deoxygenation. Deoxygenation refers to a broad class of chemical reactions where oxygen atoms are stripped from a molecule. This research employed abundant Indonesian natural zeolite (NZ) as a catalyst support, impregnated with non-noble metals, nickel (Ni), and copper (Cu). The investigation revealed that the NiCu/NZ catalyst achieved the highest oleic acid conversion (90.40%) and green diesel yield. The product distribution, ranging from C15 to C18 hydrocarbons, reflects the moderate acidity of the catalyst, promoting diverse cracking patterns compared to highly acidic catalysts. Additionally, the high specific surface area of NZ facilitates the conversion and good product distribution. Furthermore, the optimization process demonstrated that increasing hydrogen pressure during deoxygenation enhances both conversion rate and green diesel production.

Hydrogenolysis of Poly(Ethylene-co-Vinyl Alcohol) and Related Polymer Blends over Ruthenium Heterogeneous Catalysts.

The hydrogenolysis of polymers is emerging as a promising approach to deconstruct plastic waste into valuable chemicals. Yet, the complexity of plastic waste, including multilayer packaging, is a significant barrier to handling realistic waste streams. Herein, we reveal fundamental insights into a new chemical route for transforming a previously unaddressed fraction of plastic waste - poly(ethylene-co-vinyl alcohol) (EVOH) and related polymer blends - into alkane products. We report that Ru/ZrO2 is active for the concurrent hydrogenolysis, hydrogenation, and hydrodeoxygenation of EVOH and its thermal degradation products into alkanes (C1-C35) and water. Detailed reaction data, product analysis, and catalyst characterization reveal that the in-situ thermal degradation of EVOH forms aromatic intermediates that are detrimental to catalytic activity. Increased hydrogen pressure promotes hydrogenation of these aromatics, preventing catalyst deactivation and improving alkane product yields. Calculated apparent rates of C-C scission reveal that the hydrogenolysis of EVOH is slower than low-density polyethylene. We apply these findings to achieve hydrogenolysis of EVOH/polyethylene blends and elucidate the sensitivity of hydrogenolysis catalysts to such blends. Overall, we demonstrate progress towards efficient catalytic processes for the hydroconversion of waste multilayer film plastic packaging into valuable products.

Effects of hydrogen pressure on hydrogen-assisted fatigue crack growth of Cr-Mo steel

The fatigue crack growth rates (FCGRs) of 4130X steel in 45, 70, 87.5 and 100 MPa hydrogen were measured, and the hydrogen concentrations at the crack tip of test specimens were analyzed by establishing a hydrogen transport model. This model can describe the hydrogen behaviors in the process of environmental embrittlement. Results show that the FCGR increases with the increase in hydrogen pressure. However, the acceleration reaches the threshold under 87.5 MPa. Hydrogen pressure has the same influence on hydrogen concentration, and the threshold of the effect is probably related to the fact that the hydrogen absorption on the material surface reaches the limit.

Incorporation of indium into GaN layers in the context of MOVPE thermodynamics and growth – Ab initio studies

Indium incorporation on the GaN surface (0001) has been analyzed in the context of InGaN growth by Metal Organic Vapor Phase Epitaxy (MOVPE). To understand phenomena at the atomic level, calculations based on Density Functional Theory (DFT) and thermodynamic analysis of the surface processes have been performed. The considerations are limited to the terrace on GaN (0001) surface, covered fully by NH3/NH2 species. The ab initio results indicate that the adsorption energy strongly depends on the electronic properties of the surface. The adsorption energy varies from EadsDFT=-10.0eV for fully NH2 covered to EadsDFT=-3.0eV for mixed 0.69 NH2 + 0.31 NH3 covered surface. This change is related to Fermi level position moved from within valence band, across the bandgap, up to within conduction band. The shift in Fermi energy impacts the energy gained during adsorption due to electron occupation of surface states. Furthermore, a comprehensive thermodynamic analysis was conducted, revealing an additional, albeit smaller, contribution from the vibrational degrees of freedom to free energy. The combined effect of these factors leads to an increase in the equilibrium pressures of indium related to the increase in hydrogen pressure, which correlates with high coverage by ammonia molecules. The results demonstrate that the significant reduction in indium incorporation into InGaN layers during MOVPE growth under conditions of low hydrogen concentration in the vapor can be attributed to the influence of hydrogen on In adsorption processes.

Effect of hydrogen pressure on pore growth and microstructure of GASAR porous Mg–Ag eutectic alloys

In order to study the effect of hydrogen, as a third non-metallic component, on the macroscopic pore growth and eutectic solidification structure in the directional solidification process, GASAR porous Mg–Ag eutectic alloy ingots were prepared by mould casting technology at different hydrogen pressures. The results show that with an increasing hydrogen pressure, the increased temperature gradient promotes the nucleation and growth of pores; for the microstructure, the increased temperature gradient cause an increasing driving force for solidification structure growth, which leads to the instability of the eutectic cells, and the eutectic structure transitions from lamellar to rod-like.

Hydrogenation of calcium carbonate to carbon monoxide and methane

The current cement, steel, refractory and calcium carbide industries rely on thermal decomposition of calcium carbonate (CaCO3) that forms calcium oxide (CaO) and carbon dioxide (CO2). Hydrogenation of CaCO3 may reduce or eliminate CO2 in CaO generation and simultaneously generate carbon monoxide (CO) and/or methane (CH4). This work mainly investigates CaCO3 hydrogenation conditions for CO and CH4 and establishes the kinetics for these reactions. It is found that CH4 forms at temperatures lower than that of CO2 but higher than that of CO. The rates of CO and CH4 formation increase with increasing hydrogen pressure (PH2) but that of CO peaks at PH2 of 0.05–0.10 MPa. The CO2, CO and CH4 yields are 17.7%, 81.4% and 0.9% at the PH2 of 0.10 MPa while 1.2%, 20.0% and 78.8% at the PH2 of 6.00 MPa. The kinetics of CaCO3 conversion and CO and CH4 formation can be better modeled by the shrinking core model (SCM) than the volume reaction model (VRM) and the gas reaction model (GRM). The activation energy (Ea) for CaCO3 conversion and CO and CH4 formation by SCM is 165.8, 156.4 and 211.9 kJ·mol−1, respectively, with the order of PH2 of 0.108, 0.005 and 0.673, respectively.

Hydrogen embrittlement of 20# seamless steel in medium and low pressure gaseous hydrogen

Tubular tensile specimens containing gaseous pure hydrogen inside were used to study the hydrogen embrittlement (HE) of 20# seamless steel by using slow strain rate tensile test. Obvious HE phenomenon was found when containing hydrogen compared to the one containing nitrogen and the percentage elongation and percentage reduction of area after fracture were used to evaluate the HE sensitivity. In addition, as hydrogen pressure increases, the HE sensitivity becomes larger. It is concluded that tubular tensile specimen is suitable for studying the HE sensitivity for materials exposed to gaseous hydrogen.

Structural, Electrical and Optical Properties of Mg-Ni Thin Films for Hydrogen Storage Applications

Using the magnetron sputtering technique, Mg-Ni (150nm) bilayer thin films were deposited onto the simple, and ITO coated glass substrates. To obtain proper mixing and inter diffusion of thin film structure, annealing of the prepared thin films was made at constant temperature 523 K. The surface morphology of thin films confirms the uniform deposition of the Mg-Ni thin films on substrates. The Raman spectroscopy of thin films shows that the intensity of Raman peaks is decreased as the hydrogen pressure increases and variation in the intensity peak confirms the existence of hydrogen in the prepared film. The d.c. conductivity of thin films were observed at different hydrogen pressure (10 - 40 psi) for both the as-deposited and annealed thin films and the variation in the conductivity after hydrogenation was found out. In Uv-Vis spectroscopy, it was found that the optical bandgap of thin films increases with the increase of hydrogen pressure. The deviations in the structural, electrical and optical properties after hydrogenation indicate that Mg-Ni thin films may be used for solid state hydrogen storage applications. HIGHLIGHTS Preparation of Mg-Ni bilayer thin films using magnetron sputtering technique Finding the opportunity to use Mg-Ni bilayer thin film as solid-state hydrogen storage materials Raman spectroscopy for confirming the presence of hydrogen in Mg-Ni bilayer thin films Effect of hydrogen on conductivity and optical energy bandgap of Mg-Ni bilayer thin films GRAPHICAL ABSTRACT

Study on Hydriding Kinetics, Structural Properties and Electrical Conductivity of D.C. Magnetron Sputtered Mg/Al Thin Films

Mg/Al bilayer thin films were successfully deposited by using D.C. magnetron sputtering technique. To study the effect of hydrogenation on structural, optical and electrical properties of Mg/Al thin films, the hydrogenation of the annealed thin films was done under different hydrogen pressure (15, 30 & 30psi). The structural properties of the films were investigated by Raman spectroscopy and decrease in intensity of Raman peaks with increasing hydrogen pressure was observed; this typically confirms the existence of hydrogen in Mg/Al thin films. The thin film is of semiconducting nature and it was found that the electrical conductivity of the film decreases with increasing hydrogen pressure applied. In the hydriding kinetics of the films, it was seen that the resistivity increased along with hydrogen absorption time. Eventually, it attains the equilibrium stage indicating the hydrogen absorption in the thin films. The rate of absorption of hydrogen increases with the pressure of hydrogen over different time ranges and decreases with the absorption of hydrogen over time.

Effect of hydrogen pressure on hydrogenation and pulverization behavior of Sm(CoFeCuZr)z ingot and strip casting flake

Effect of hydrogen pressure on hydrogenation and pulverization behavior of Sm(CoFeCuZr)7.6 alloy prepared by plate mold (PM) and strip casting (SC) has been systematically investigated. Increasing hydrogen pressure can improve the hydrogenation ability. Both the PM and SC have the similar hydrogen absorption process, which can be divided into two stages. The first stage follows the Sieverts’ law (1–5 MPa) while the second one deviates from the Sieverts’ law (5–10 MPa). Rietveld refinement shows that the hydrogen absorption causes different lattice distortion of different phases without changing the phase structure. The internal stress caused by such lattice distortion is the primary reason that accelerates the pulverization of the alloys, and increasing hydrogen pressure can lead to the decrease of particle size of the PM and SC alloys. The hydrogen decrepitation (HD) process are studied in detail based on these results. The hydrogen absorption mechanism of Sm(CoFeCuZr)7.6 alloy can be regarded as a hydrogen dissolution process without phase transformation. In addition, the existence of a large amount of fine grains in the SC has an adverse effect on the alignment, which can be optimized by taking effective methods to reduce the overcooling rate. This work proves that the SC, HD and jet milling process can be a promising new approach to powder preparation for high-performance Sm(CoFeCuZr)z sintered magnets.

Catalytic hydropyrolysis of lignin using NiMo-doped catalysts: Catalyst evaluation and mechanism analysis

NiMo-doped catalysts were investigated for the conversion of lignin to drop-in fuel through catalytic hydropyrolysis. The influence of NiMo-doped catalysts with different carriers and Ni/Mo molar ratios on the hydropyrolysis product distribution were studied using both lignin and lignin model compounds. Two coefficients were proposed to qualitatively evaluate the catalytic performance of NiMo-doped catalysts. Low yield of methane (13.04c%) and high yield of condensable hydrocarbons products (25.82c%) with low selectivity of polyaromatics (4.37%) were obtained at 1.0 MPa H2 and 400 °C catalytic temperature during lignin catalytic hydropyrolysis over Ni1Mo/ZrO2. The hydrodeoxygenation activity of NixMo/ZrO2 depends on Ni0, Mo4+, and Mo3+. The synergistic effect of Ni and Mo promotes the removal of the phenolic methoxy group. The increase in hydrogen pressure tends to make hydrogen to be consumed through hydrocracking and hydrogenation reactions. The influence of Ni1Mo/ZrO2 on evolution of lignin hydropyrolysis volatiles was revealed. Ni shows strong activity in the removal of phenolic hydroxyl groups and benzene ring hydrogenation, while Mo tends to remove phenolic methoxy groups.

Characteristic and kinetics of hydrogen absorption during the heat preservation stage and the cooling stage of TC21 alloy

TC21 alloy is hydrogenated under different initial hydrogen pressures at hydrogenation temperatures in the range of 450 °C–850 °C. Hydrogen absorption characteristic and kinetics during the heat preservation stage and cooling stage, hydrogen content and activation energy are investigated. The hydrogen absorption reaches equilibrium first at higher hydrogenation temperature and initial hydrogen pressure during the heat preservation stage. The hydrogen absorption reaches equilibrium first at lower hydrogenation temperature and initial hydrogen pressure during the cooling stage. Mechanisms of hydrogen absorption are analyzed during the heat preservation stage and the cooling stage. Phase compositions of the hydrogenated TC21 alloys are analyzed by XRD. Hydrogen content increases first and then decreases, then increases slightly, and finally decreases with the increase of hydrogenation temperature. Hydrogen content increases gradually with the increase of initial hydrogen pressure. The activation energy of hydrogen absorption in TC21 alloy is about 18.304 kJ/mol. • H absorption mechanisms were diverse between heat preservation and cooling stage. • H content was affected by hydrogenation temperature and initial hydrogen pressure. • The activation energy of H absorption was about 18.304 kJ/mol.

Understanding cellulose pyrolysis under hydrogen atmosphere

The product distributions of cellulose pyrolysis under different pressures, temperatures, and atmospheres were investigated using a high-pressure micropyrolyzer to clarify the pyrolysis reaction mechanism of cellulose decomposition with hydrogen. EGA-MS results shows that the increase in hydrogen pressure prolonged the second stage of cellulose pyrolysis, which was dominated by decarboxylation. Pyrolysis products of cellulose under helium mainly included levoglucosan, furfural, and acids, while cellulose hydropyrolysis mainly produced C5-C7 ketones, besides small amount of alcohols, aromatics and aliphatic hydrocarbons, and even small amount of phenolics. Carbon yield of ketones was as high as 27.2% from cellulose hydropyrolysis under 2.5 MPa hydrogen and 500 °C. The yield of liquid products and non–condensable hydrocarbons increased with elevated hydrogen pressure. The formation mechanisms of aromatics, phenolics, aliphatic hydrocarbons, aldehydes, ketones, and alcohols under hydrogen atmosphere were discussed. Acetaldehyde was produced by acids through a HDO reaction. C5-C7 chain ketones and cyclic ketones were generated by furfural through HDO and hydrocracking reactions. The Diels–Alder reaction to generate aromatics was enhanced by increasing pyrolysis temperature under hydrogen atmosphere. The reaction network of cellulose hydropyrolysis was also proposed.

Preparing high ratio of trans/trans 2,2-bis(4-hydroxycyclohexyl)propane isomer by one-dimensional nickel-palladium catalyst

Background: 4,4′-isopropylidenediphenol (BPA) hydrogenated to 2,2-bis(4-hydroxycyclohexyl) propane (HBPA) is a simple way to reduce its toxicity and environmental impact. In addition, the higher trans/trans HBPA moiety in polymer will has better mechanical properties. Therefore, how to prepare trans/trans HBPA via hydrogenation is an important issue.Method: One-dimensional nickel-palladium catalyst was successfully synthesized via reduction by an external magnetic field. The high ratio of trans/trans HBPA was characterized by FTIR, GC/MS, and NMR, respectively. The adsorption behavior of BPA and its half-hydrogenated intermediates was studied by Material Studio software.Significant findings: The pd nanoparticles immobilized on the magnetization of 1-D Ni catalyst with high amount of Ni(111) plane is the novelty of this research. The conversion of BPA was high to 100% and the ratio of trans/trans HBPA was over than 75% at 180 °C and 70 kgf/cm2 in isopropanol medium. The trans/trans ratio of HBPA was slightly increasing as increasing hydrogen pressure and decreasing reaction temperature. Reaction intermediate was selected with the aid of molecular simulation. Moreover, the reaction path of BPA hydrogenated by one-dimensional nickel-palladium catalyst was proposed that BPA was firstly hydrogenated to tetrahydro intermediate and followed roll-over mechanism to obtain trans/trans HBPA product.

Thermodynamic Optimization of a High Temperature Proton Exchange Membrane Fuel Cell for Fuel Cell Vehicle Applications

In this paper, a finite time thermodynamic model of high temperature proton exchange membrane fuel cell (HT-PEMFC) is established, in which the irreversible losses of polarization and leakage current during the cell operation are considered. The influences of operating temperature, membrane thickness, phosphoric acid doping level, hydrogen and oxygen intake pressure on the maximum output power density Pmax and the maximum output efficiency ηmax are studied. As the temperature rises, Pmax and ηmax will increase. The decrease of membrane thickness will increase Pmax, but has little influence on the ηmax. The increase of phosphoric acid doping level can increase Pmax, but it has little effect on the ηmax. With the increase of hydrogen and oxygen intake pressure, Pmax and ηmax will be improved. This article also obtains the optimization relationship between power density and thermodynamic efficiency, and the optimization range interval of HT-PEMFC which will provide guidance for applicable use of HT-PEMFCs.

Effects of hydrogen pressure and prior austenite grain size on the hydrogen embrittlement characteristics of a press-hardened martensitic steel

The effects of hydrogen gas pressure and prior austenite grain size (PAGS) on the susceptibility of a 22MnB5 press-hardened martensitic steel (PHS) to hydrogen embrittlement were studied. The hydrogen test apparatus at NIST-Boulder was modified for tensile testing of plate-type and sheet-type specimens in gaseous hydrogen. This modification made it possible to evaluate the slow strain rate tensile (SSRT) properties of the PHS with three different PAGS at various hydrogen pressures (0.21 MPa–5.5 MPa). SSRT testing in gaseous hydrogen resulted in significant reductions of both the tensile strength and ductility, as compared to those measured in air. In addition, the presence of gaseous hydrogen resulted in a transition in fracture morphology from the near-45° slant fracture to a more brittle fracture along a plane perpendicular to the tensile axis. The hydrogen-affected fracture zones were connected to the sheet specimen free surfaces, signifying the effect of external hydrogen. The fracture surfaces of the hydrogen-embrittled specimens contained relatively flat, “cleavage-like” facets, the size of which depended on the PAGS or packet size. The PHS having the largest PAGS represented generally larger secondary cracks and straighter crack paths in addition to a greater area fraction of the “cleavage-like” facets, likely indicative of a lower frequency of crack deflections. Compared to the largest PAGS condition, the two PHS with smaller PAGS were more resistant to the hydrogen-induced fracture especially at relatively low hydrogen gas pressures (<0.52 MPa). In contrast, with an increase in hydrogen pressure, all PHS specimens exhibited significant decreases in tensile strength and ductility. The positive effect of refining martensitic microstructure, at the low hydrogen pressures, is likely associated with improved toughness of the smaller grain-sized specimens.

Hydrogen solubility, interfacial tension, and density of the liquid organic hydrogen carrier system diphenylmethane/dicyclohexylmethane

In the present study, physico-chemical properties of the liquid organic hydrogen carrier (LOHC) system diphenylmethane/dicyclohexylmethane in the presence of dissolved hydrogen are presented for temperatures up to 523 K and pressures up to 10 MPa. Solubility of hydrogen, interfacial tension, and liquid density were measured by the isochoric saturation method, the pendant-drop method, and vibrating-tube method, respectively, which are realized in two experimental setups. The solubility of hydrogen increases with increasing temperature and pressure. For the fully hydrogenated dicyclohexylmethane, it is about 50% higher than for the non-hydrogenated diphenylmethane and similar to that of a mixture from a deliberately stopped hydrogenation process containing also partially hydrogenated cyclohexylphenylmethane. While the interfacial tension decreases slightly with increasing hydrogen pressure at constant temperature, the density remains approximately constant. The latter properties obtained for different mixtures with similar degree of hydrogenation show that the influence of the presence of cyclohexylphenylmethane is small.

Optical, electrical and structural study of Mg/Ti bilayer thin film for hydrogen storage applications

Bilayer Mg/Ti (200 nm) thin films were successfully prepared by using D.C. magnetron sputtering unit. These films were vacuum annealed at 573 K temperature for one hour to obtain homogeneous and intermixed structure of bilayer. Hydrogenation of these thin film structures was made at different hydrogen pressure (15, 30 & 45 psi) for 30 min to visualize the effect of hydrogen on film structure. The UV–Vis absorption spectra, I-V characteristics and Raman spectroscopy were carried out to study the effect of hydrogen on optical, electrical and structural properties of Mg/Ti bilayer thin films. The annealed thin film represents the semiconductor nature with the conductivity of the order of 10-5 Ώ−1-m−1 and it decreases as hydrogen pressure increases. The nonlinear dependence of resistivity on hydrogen pressure reveals inhomogeneous distribution of hydrogen in the thin film. Raman spectroscopy confirmed the presence of hydrogen in thin film where the intensity of peaks was found to be decreased with hydrogen pressure.

Effect of hydrogen-storage pressure on the detonation characteristics of emulsion explosives sensitized by glass microballoons

In this study, hydrogen-storage glass microballoons were introduced into emulsion explosives to improve the detonation performance of the explosives. The effect of hydrogen-storage pressure on the detonation characteristics of emulsion explosives was systematically investigated. Detonation velocity experiments shows that the change of sensitizing gas and the increase of hydrogen pressure have different effects on the detonation velocity. The experimental parameters of underwater explosion increase first and then decreases with the increase of hydrogen pressure. The decrease of these parameters indicates that the strength of glass microballoons is the limiting factor to improve the detonation performance of hydrogen-storage emulsion explosives. Compared with the traditional emulsion explosives, the maximum peak pressure of shock wave of hydrogen-storage emulsion explosives increases by 10.6% at 1.0 m and 10.2% at 1.2 m, the maximum values of shock impulse increase by 5.7% at 1.0 m and 19.4% at 1.2 m. The stored hydrogen has dual effects of sensitizers and energetic additives, which can improve the energy output of emulsion explosives.

Hydrogen crossover in proton exchange membrane electrolysers: The effect of current density, pressure, temperature, and compression

In this paper, the hydrogen crossover through the membrane, which is a major concern from the safety, durability, and efficiency viewpoints, in proton exchange membrane (PEM) electrolysers, is investigated. It is well-documented that hydrogen crossover rate increases by pressure, temperature, and current density. However, how current density affects the hydrogen crossover rate is yet to be fully understood. The effect of current density on hydrogen crossover is usually attributed to hydrogen supersaturation and enhanced hydrogen pressure on the membrane due to the pressure drop through the catalyst layer and liquid/gas diffusion layer (LGDL). However, other parameters, as suggested by recent research studies, can have an important role to play. Here, by developing an analytical model, the effects of several parameters are investigated. The findings from this study suggest that hydrogen crossover is affected by the increase in the membrane temperature, hydrogen supersaturation, and compression of the LGDL. The effect of membrane temperature increase with current density on hydrogen crossover was found to be pronounced at current densities above 2 A cm−2. The increase in hydrogen supersaturation with current density was found to be the main cause of hydrogen crossover during electrolysis. Stack compression increases the hydrogen crossover rate mainly by reducing the mass transfer coefficient and hence the hydrogen supersaturation. The effect of increased hydrogen pressure on the membrane is more noticeable at low operating pressures; however, in general, does not have a major impact on the hydrogen crossover. It is also suggested that the hydrogen length of the diffusion path should also include the ionomer of the CL in addition to the membrane thickness. The findings of this research help with a better understanding of the hydrogen crossover during PEM electrolysis that can be considered during material selection and design of the cell components. This helps with reducing the crossover rate to improve efficiency and durability and ensure safe operations.