Low Hydrogen Pressure Research Articles

Hydrogen storage and heat transfer properties for large-capacity double thin-layered annulus ZrCo bed with secondary containment cavity

Fast heat and mass delivery with high cycling stability of the core component, hydrogen storage bed, in SDS are essential for the operation of the future tritium factory in ITER project. However, the aforementioned properties are still perplexing in large-capacity ZrCo bed, especially for that with secondary containment structure required by the actual tritium operation in the future. Herein, the performance including heating, cycling and cooling with two different size ZrCo beds (loading of ZrCo are 200 g and 2000 g respectively) were systematically studied. The experimental data shows that the maximum heating ability of the middle-size/full-scale storage bed are both about 10 °C/min, and the maximum hydrogen absorption capacity of these ZrCo beds are 44.6 L/405.5 L, respectively. Besides, hydrogen pressure and hydrogen retention during the following desorption can affect the cycling performance of the ZrCo bed. The use of transfer pump can reduce the pressure of the bed during the hydrogen desorption process (operated at 500 °C), which inhibits the disproportionation reaction of the ZrCo alloy. However, the degree of hydrogen pressure reduction in two the types of ZrCo bed are different. As a result, the cycling capacity of the middle-size bed (93.4%, lower hydrogen pressure) is higher than the full-scale bed (68.7%, higher hydrogen pressure) after 10 cycles. When the transfer pump was not used and operated at lower temperature (350 °C), the beds cannot release hydrogen completely, and partial hydrogen atoms are retained in the ZrCo alloy. The middle-size bed still maintains a hydrogen storage capacity of 94.5% after 10 cycles, while 75.9% of the hydrogen storage capacity remained for the full-scale bed. Therefore, the increase of hydrogen surplus in ZrCo alloy is helpful to improve its cycling stability. At last, the cooling performances of the beds under 10 different cooling methods were studied. Among the cooling methods, the best cooling rate was achieved by filling nitrogen in the secondary containment cavity and flowing water passing through the cooling circuit of the bed. This work will provide a crucial reference for the design and optimization of the subsequent operation technology of SDS in ITER. • Thin double-layered annulus ZrCo bed with secondary containment cavity is manufactured. • Real-time pumping transfer helps to improve the circulation stability of the ZrCo bed. • Keep remaining H in the ZrCo is benefits to improve its cycling stability.

Borophane Polymorphs

Hydrogenated borophenes─borophanes─have recently been synthesized as a new platform for studying low-dimensional borides, but most of their lattice structures remain unknown. Here, we determine the structures of borophane polymorphs on Ag(111) by performing extensive structural search using the cluster expansion method augmented with first-principles calculations. Our results reveal rich borophane polymorphs whose stability depends on hydrogen pressure. At relatively low hydrogen pressures, borophane structures with rhombic patterns of two-center-two-electron B-H bonds are energetically preferred, in excellent agreement with two experimentally observed phases. In a wider range of hydrogen pressures, the structure with a combination of two-center-two-electron B-H and three-center-two-electron B-H-B bonds is a deep global minimum, rationalizing its experimental prevalence. For all these borophane polymorphs, their hydrogen "skin" raises the energy barriers for oxidation above 1.1 eV, while their work functions can be reduced by more than 0.5 eV through varying the hydrogen coverage.

Catalytic production of low-carbon footprint sustainable natural gas

Natural gas is one of the foremost basic energy sources on earth. Although biological process appears as promising valorization routes to transfer biomass to sustainable methane, the recalcitrance of lignocellulosic biomass is the major limitation for the production of mixing gas to meet the natural gas composition of pipeline transportation. Here we develop a catalytic-drive approach to directly transfer solid biomass to bio-natural gas which can be suitable for the current infrastructure. A catalyst with Ni2Al3 alloy phase enables nearly complete conversion of various agricultural and forestry residues, the total carbon yield of gas products reaches up to 93% after several hours at relative low-temperature (300 degrees Celsius). And the catalyst shows powerful processing capability for the production of natural gas during thirty cycles. A low-carbon footprint is estimated by a preliminary life cycle assessment, especially for the low hydrogen pressure and non-fossil hydrogen, and technical economic analysis predicts that this process is an economically competitive production process.

Co-Cxny Embedded in N-Doped Carbon as Robust Catalysts for the Synthesis of Γ-Valerolactone from the Hydrogenation of Levulinic Acid Under Low Hydrogen Pressure

Co-Cxny Embedded in N-Doped Carbon as Robust Catalysts for the Synthesis of Γ-Valerolactone from the Hydrogenation of Levulinic Acid Under Low Hydrogen Pressure

Experimental evidence for the suitability of the hydrogen decomposition process for the recycling of Nd-Fe-B sintered magnets

An effective and complete processing route for the recycling of sintered Nd-Fe-B scrap magnets was proposed. Sintered Nd-Fe-B magnets were subjected to the Hydrogen Decrepitation (HD) process at various temperatures in the range of 50–300 °C, at two different pressures, 50 kPa and 200 kPa, followed by vacuum dehydrogenation in the range of 720–820 °C. The structure refinement efficiency and magnetic properties of the powders obtained were characterized. Low hydrogen pressure (50 kPa) was found to increase the magnetic properties at each temperature for all powder fractions. It was also shown that particle refinement occurs at low (50 °C, 100 °C) temperatures for low (50 kPa) pressure and higher temperatures (200 °C, 300 °C) for high pressure (200 kPa), respectively. High pressure also accelerates the initialization of the HD process at each temperature. No correlation was found between hydrogenation temperature and magnetic properties of the powders, except for the small increase in coercivity increase with growing temperature. The coarse fraction (400–500 µm) was found to have the highest magnetic properties for almost each HD process. The best magnetic properties Hci = 497 kA/m, Br = 1.1 T, and (BH)max = 121 kJ/m3 were obtained for hydrogenation at a temperature of 50 °C, pressure 50 kPa and dehydrogenation at 780 °C.

Two-phase anaerobic digestion of food waste: Effect of semi-continuous feeding on acidogenesis and methane production

In present investigation, effect of diverting acidogenic off-gas from leached bed reactor (LBR) to up-flow anaerobic sludge blanket (UASB) reactor during semi-continuous food waste (FW) anaerobic digestion was evaluated. In test LBR headspace pressure (3.3 psi) was maintained with intermittent headspace gas transfer into UASB. In control, same headspace pressure was maintained without gas transfer. The semi-continuous FW addition affected the characteristics and production of leachate in control and test LBR. The cumulative COD, total soluble products and methane yields were 1.26, 1.37 and 3 times higher in the test LBR than the control. The acetate and methane yields from test LBR were 697.8 g·kgVSadded−1 and 167.55 mL·gCOD−1feeding. Acidogenic gas transfer maintained low partial pressure of hydrogen and the hydrogen to carbon-di-oxide ratio in the headspace of LBR, which were thermodynamically favorable for microbial metabolism and concomitant high-rate production of acetate-rich volatile fatty acid and methane-rich biogas from FW.

Inverter-based modeling and energy efficiency analysis of off-grid hybrid power system in distributed generation

Distributed Generation systems are made up of different power generation systems, which are wind turbines, solar panels, fuel cells, energy storage units, micro turbines, and combined heat cycle plants. An inverter is one of the most critical components of Distributed Generation systems. This paper focuses on inverter-based modeling and energy efficiency analysis of the off-grid hybrid system in Distributed Generation. The proposed system is created and simulated using MATLAB/Simulink platform. The obtained results show that the efficiency of the inverter varies between 49.671% and 93.794% under different loads. Model results comply with the inverter efficiency curve specified by the European Commission and U.S. Department of Energy procedures. In the model, the inverter energy efficiency of the hybrid system is compared according to temperature, wind speed, solar radiation, and hydrogen pressure. The inverter exhibits superior performance at low hydrogen pressures. Besides, the efficiency of the inverter is analyzed under load changes.

Model-based comparison of batch and flow syntheses of an active pharmaceutical ingredient using heterogeneous hydrogenation

This work presents a model-based comparison of the batch and flow syntheses for doripenem, which is an antibiotic active pharmaceutical ingredient. The targeted reaction is heterogeneous hydrogenation, the most widely used method for reduction reaction in drug syntheses. We developed rigorous physical models considering the decrease in catalyst activity and the leaching of catalyst as the critical factors in the actual operation. Experiments were performed to estimate model parameters for reaction and catalyst poisoning. Conditions of leaching were observed, and an indicator for estimating leaching possibility was developed. A multiobjective evaluation regarding yield and leaching possibility indicated that the flow synthesis gives the optimal solution. However, the flow synthesis exhibited a significant weakness at low hydrogen pressure due to poor mass transfer of hydrogen in the reaction system. This result suggests the importance of careful selection and control of the operational conditions in flow synthesis before implementation.

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.

Production of jet fuel by hydrorefining of Fischer-Tropsch wax over Pt/Al-TUD-1 bifunctional catalyst

TUD-1 supported bifunctional platinum catalysts were prepared and characterized for structural and textural properties, acidity, and platinum dispersion. The acidity of TUD-1 was varied by isomorphous substitution of Al and Ti in the framework. The TUD-1 supports possess a three-dimensional amorphous structure as shown by XRD. BET-N2 adsorption and pyridine FTIR studies revealed that the incorporation of Al in the TUD-1 framework enhances the surface area and generates Brønsted acidity. The catalysts were screened for hydrorefining of Fischer-Tropsch wax with C8-C44 n-paraffins. The catalysts prepared with Si-TUD-1 and Ti-TUD-1 supports were not active for hydrocracking and hydroisomerization due to the absence of Brønsted acid sites, which was verified by pyridine FTIR. Increasing the amount of Al in the framework gradually increased the Brønsted acid sites and thus promoted hydrocracking and hydroisomerization of F-T wax. Pt/Al-TUD-1 catalyst with a Si/Al ratio of 10 produced more jet fuel range hydrocarbons. Hydrorefining of F-T wax was evaluated over an optimal Pt/Al-TUD-1 (Si/Al = 10) catalyst at different pressures and temperatures. Hydroisomerization was favored at low hydrogen pressure. Increasing the temperature shifted the hydrocarbon distribution more towards gasoline due to severe cracking. The temperature of 330 °C and a hydrogen pressure of 5 MPa were found to be optimum to produce jet fuel range hydrocarbons that meet the ASTM specification of cold flow properties. This study proves the feasibility of the production of renewable jet fuel that is directly compatible with fossil-based aviation engines, through hydrorefining of F-T waxes using a mesoporous bifunctional catalyst.

Quantitative assessment of the hydrogen induced cracking for 2.25Cr-1Mo-0.25V steel under electrochemical charging conditions

Hydrogen induced cracking (HIC) sensitivity of a vanadium-modified high strength steel at room temperature was studied by hydrogen concentration measurement, post-failure analysis, and interface characterization. It was found that the HIC sensitivity was relatively low as indicated by the small number of surface blisters and the random occurrence of internal cracks. This is partially attributed to the low hydrogen pressure in the defects, resulting from the high hydrogen solubility of the material. The immune inclusions with no cracks were identified after severe charging condition featuring more intact interface, indicating that the integrity of the interface and the size of voids may control the crack initiation.

Highly Dispersed Rh/NbOx Invoking High Catalytic Performances for the Valorization of Lignin Monophenols and Lignin Oil into Aromatics

As fossil fuels are constantly depleted, valorization of lignocellulosic biomass into valuable aromatic compounds is of great significance but exceedingly challenging. In this work, the structure and catalytic performance of various Rh/Nb₂O₅ catalysts were studied in detail via the catalytic hydrodeoxygenation of a representative lignin monophenol compound 2-methoxy-4-propylphenol. The best catalytic performance was obtained over Rh/Nb₂O₅-400 (Nb₂O₅ calcined at 400 °C) with an exceptional 98% yield of propylbenzene under 0.5 MPa H₂, which was mainly due to the cooperation between highly dispersed Rh metals and NbOₓ species, in which Rh was responsible for dissociation of H₂ and NbOₓ for breaking of C–O bonds at the metal–support interface. Besides, the lignin oil obtained in depolymerization of raw pine wood was directly used as the substrate in the catalytic hydrodeoxygenation reaction over the Rh/Nb₂O₅-400 catalyst under 0.5 MPa H₂. Encouragingly, the liquid products were identified and found that lignin oil was completely converted into C₆–C₁₀ hydrocarbons (>99% selectivity) with an 80.1 mol % yield of aromatics. The results achieved in this work highlighted that high-value utilization of lignocellulosic biomass feedstocks to produce aromatic chemicals and liquid fuels could be achieved over Rh/Nb₂O₅ under a low hydrogen pressure.

Understanding the promoter effect of bifunctional (Pt, Ni, Cu)-MoO3-x/TiO2 catalysts for the hydrodeoxygenation of p-cresol: A combined DFT and experimental study

The effect of Pt, Ni, and Cu promoters on the partial reduced MoO3-x/TiO2 catalysts for the hydrodeoxygenation (HDO) reaction of p-cresol was investigated through experiments and density functional theory (DFT) calculations. The MoO3-x/TiO2 was firstly prepared and then Pt, Ni, or Cu precursor was introduced. The mixed Mo4+, Mo5+, and Mo6+ states were identified by XPS. The HR-TEM and TEM-EDX images suggest that the MoO3-x becomes amorphous and is well-dispersed on TiO2 supports leading to direct contact of the metal on MoO3-x/TiO2. The HDO of p-cresol under a low hydrogen pressure (5 bar) at 300 °C showed the %conversion as the following order: Pt-MoO3-x > Ni-MoO3-x > Cu-MoO3-x > MoO3-x. DFT results explained the differences of catalytic performance of the catalysts and the role of the promoters in enhancing the H2 activation. The high electronegativity and density of state near the Fermi level are responsible for the high catalytic performance of Pt-MoO3-x/TiO2, which shows barrierless for H2 dissociation and allows this catalyst to be active under a milder reaction temperature and pressure. These results deepen the fundamental understanding of the role of the promoters toward the key reaction step in HDO, which is beneficial for guiding the development of catalysts for biomass conversion.

Stress concentration affecting hydrogen-assisted crack in API X70 pipeline base and weld steel under hydrogen/natural gas mixture

A sudden change in the geometrical parameters of a material, such as bends, T-branches, and welded joints may increase the stress concentration, which in turn may enhance the diffusible hydrogen concentration. In this study, quantitative evaluations of the effect of stress concentration factors on hydrogen environmental embrittlement (HEE) will be studied based on the mechanical performance of notched tensile specimens with variations in the stress concentration factors (Kt) of the X70 pipeline base and weld metal. To highlight the role of stress concentration, the tests are performed under a 10 MPa gas mixture condition with a low partial hydrogen pressure. The maximum strengths of the notched specimens were nearly consistent across all Kt values. The degree of HEE susceptibility of the base metal increased with increasing Kt value. However, in the weld metal, prominent reductions in the RA occurred at all Kt values. The complex HEE susceptibility of the weld metal can be attributed to the synergistic action of the microstructure heterogeneity and Kt values.

Study on hydrogen absorption and surface properties of TiZrVNbCr high entropy alloy

In this study, we examined the microstructure, hydrogen absorption behavior, and native oxide layer of 20Ti–20Zr–20V–20Nb–20Cr high entropy alloy. It was revealed that the alloy consisted of two phases with the chemical composition of 31.1Ti-19.6Zr-16.6V-26.0Nb-6.7Cr (bright phase) and 9.1Ti-20.3Zr-23.4V-14.1Nb-33.1Cr (dark phase). Even though an oxide layer was formed on the surface of the alloy due to the exposure to an air atmosphere for 10 days, it could absorb hydrogen at a low hydrogen pressure without any thermal activation process. After the hydrogen absorption experiment, not only the hydrogen absorption as high as 1.77 wt% was achieved, but the phase transformation occurred; the bright phase transformed to dihydride and the dark one did monohydride. To clarify which phase mainly contributed to the hydrogen absorption behavior, ingots with chemical composition of the dark and bright phases were prepared separately. The hydrogen absorption occurred only for the dark phase ingot, not for the bright phase ingot, suggesting that only the oxide layer on the dark phase seems to have a reactivity with hydrogen. XPS results revealed that while the Cr element was not detected in the oxide film on the bright phase, the oxide film on the dark phase possessed the Cr element. Based on the results, the presence of the Cr element in the oxide would be ascribed to the high reactivity with hydrogen.

Study of boron doped amorphous silicon lightly hydrogenated prepared by DC magnetron sputtering for infrared detectors applications

The objective of this study is to investigate the effect of boron doping concentration on the bolometric properties of lightly hydrogenated amorphous silicon doped with boron (a-Si: H(B)) films. Thin film a-Si: H(B) samples with different boron concentrations are prepared by co-sputtering of boron and silicon at relatively low hydrogen pressure. FTIR analyses show that the intensity of the characteristic peak of the substitutional boron gradually increases with the addition of boron. Increasing in boron concentration affects the bolometric properties of the lightly hydrogenated a-Si: H (B) films, including conductivity at room temperature (σRT) and thermal resistance coefficient (TCR). Indeed, when the boron concentration increases from 1.5 to 43%, σRT increases from 1.4 10−6 to 2 10−3 Ω−1 cm−1 while the absolute value of TCR decreases from 3% to 8% K−1, respectively. In addition, lightly hydrogenated a-Si: H (B) films exhibit good thermal stability. We have showed in this study that lightly hydrogenated a-Si: H(B) can be considered as a potential candidate for low-cost, high-performance uncooled micro bolometers.

Rate-Controlling Steps for the Hydriding Reaction of the Intermetallic Compound Mg₂Ni.

Mg₂Ni samples were prepared by sintering a pelletized mixture under an argon atmosphere in a stainless steel crucible at 823 K. The XRD pattern of the prepared Mg₂Ni sample showed a well crystallized Mg₂Ni phase. The hydriding and dehydriding properties of the prepared samples were examined at 518-593 K under relatively low hydrogen pressures of 3-7 bar H₂. At 573 K under 7 bar H₂, the activation of the Mg₂Ni sample was completed at the number of cycles of six (n = 6). At n = 7, the hydrided fractions of the sample were 0.53 (1.99 wt% H) at 4.97 min, 0.72 (2.71 wt% H) at 9.52 min, 0.81 (3.05 wt% H) at 31.15 min, and 0.81 (3.05 wt% H) at 60.07 min. The particle sizes of the prepared Mg₂Ni were not homogeneous and the particles had irregular shapes. We analyzed the rate-controlling steps for the hydriding reaction of the intermetallic compound Mg₂Ni by examining the dependences of hydriding rates on hydrogen pressure and temperature in the same reacted fraction ranges. The analyses in the same reacted fraction ranges were done in order to eliminate the influence of the interfacial area on the hydriding rate. When the driving force, which is the difference between the applied hydrogen pressure Po and equilibrium plateau pressure Peq at a given temperature, was low, the nucleation of Mg₂Ni hydride controlled the hydriding rate of Mg₂Ni. After the nucleation of the Mg₂Ni hydride, the rate-controlling step of the hydriding reaction of Mg₂Ni was analyzed to be the forced flow of hydrogen molecules through pores, inter-particle channels, or cracks.

Atomically-ordered active sites in NiMo intermetallic compound toward low-pressure hydrodeoxygenation of furfural

Activation of oxygen-containing functional groups plays a key role in sustainable biomass upgrading and conversion. In this work, a NiMo intermetallic compound (IMC) catalyst was prepared based on layered double hydroxides (LDHs) precursors, which displayed prominent catalytic performance for furfural hydrodeoxygenation (HDO) to 2-methylfuran (2-MF) (yield: 99 %) at a rather low hydrogen pressure (0.1 MPa), significantly superior to NiMo alloy, monometallic Ni and other Ni-based catalysts ever reported. CO-IR, STEM, EXAFS and XANES give direct evidences that the atomically-ordered Ni/Mo sites in NiMo IMC determine the uniform bridging-type adsorption mode of CO bond in furfural whilst adsorption of furan ring is extremely suppressed. In situ FT-IR and DFT calculation further substantiate that ordered Ni-Mo bimetallic sites of IMC, in contrast to the random atomic sequence in NiMo alloy, facilitate the activation and cleavage of COH bond in the intermediate (furfuryl alcohol, FOL), accounting for the production of 2-MF. This work demonstrates the decisive effect of atomically-ordered active sites in IMC catalyst on activation of oxygen-containing functional groups and product selectivity, which can be extended to catalytic upgrading of biomass-derived platform molecules.

Hydrodebromination of Aromatic Bromides Catalyzed by Unsupported Nanoporous Gold: Heterolytic Cleavage of Hydrogen Molecule

AbstractUnsupported nanoporous gold (AuNPore) is a highly efficient, practically applicable, and recyclable catalyst for hydrodebromination of aromatic bromides. The AuNPore‐catalyzed hydrodebromination of aromatic bromides proceeded smoothly at relatively low hydrogen pressure and temperature to achieve good to excellent yields of the corresponding non‐bromine variants. The selective hydrodebromination reaction occurred exclusively in the coexistence of chlorine atom. For the first time, a mechanistic study revealed that the H−H bond splits in a heterolysis manner on the surface of AuNPore to generate Au−H hydride species.

General regularities of thermal decomposition of transition metal dihydrides in a medium with low hydrogen partial pressure

The results of the calorimetric studies of thermal dissociation of titanium, zirconium, magnesium, and palladium hydrides performed in recent years are presented. The multiplet character of thermal dissociation characteristic of all these hydrides is shown. A good correlation between the course of differential scanning calorimetry curves and the results of thermogravimetry has been demonstrated.The discrete nature of the decomposition processes is established. A sequence of mechanisms occurring during the heating of transition metal dihydrides in a medium with a low partial pressure of hydrogen has been proposed: rearrangement in the hydride phase; destruction of metal - hydrogen bonds to form a solid solution supersaturated with hydrogen; diffusion of hydrogen to the interface of solid phase - environment; molization of hydrogen at the exit from the solid phase.