MPa Hydrogen Pressure Research Articles

Hydrogen Storage Properties and Reactive Mechanism of LiBH4/Mg10YNi-H Composite

The Mg10YNi alloy was hydrogenated and then coupled with LiBH4 to form LiBH4/Mg10YNi-H reactive hydride composite. The results indicate that thermal dehydrogenation stability of LiBH4 can be remarkably reduced by combining with Mg10YNi hydride. The starting and ending temperatures for hydrogen desorption from the LiBH4/Mg10YNi-H composite are approximately 275 and 430 oC, respectively. Dehydrogenation of the LiBH4/Mg10YNi-H composite proceeds mainly in two steps with a total reaction of 12LiBH4 + 2.5Mg10YNiH20 → 24Mg + MgNi2.5B2 + 2.5YB4 + 12LiH + 43H2. After rehydrogenation at 450 oC under 9 MPa hydrogen pressure, the LiBH4/Mg10YNi-H composite starts to release hydrogen around 260 oC, and as much as approximately 5.2 wt.% of hydrogen can be desorbed during the second dehydrogenation process.

A rare earth hydride supported ruthenium catalyst for the hydrogenation of N-heterocycles: boosting the activity via a new hydrogen transfer path and controlling the stereoselectivity.

Hydrogenation of N-heterocycles is of great significance for their wide range of applications such as building blocks in drug and agrochemical syntheses and liquid organic hydrogen carriers (LOHCs). Pursuing a better hydrogenation performance and stereoselectivity, we successfully developed a rare earth hydride supported ruthenium catalyst Ru/YH3 for the hydrogenation of N-heterocycles, especially N-ethylcarbazole (NEC), the most promising LOHC. Full hydrogenation of NEC on Ru/YH3 can be achieved at 363 K and 1 MPa hydrogen pressure, which is currently the lowest compared to previous reported catalysts. Furthermore, Ru/YH3 shows the highest turnover number, namely the highest catalytic activity among the existing catalysts for hydrogenation of NEC. Most importantly, Ru/YH3 shows remarkable stereoselectivity for all-cis products, which is very favorable for the subsequent dehydrogenation. The excellent performance of Ru/YH3 originates from the new hydrogen transfer path from H2 to NEC via YH3. Ru/LaH3 and Ru/GdH3 also reveal good activity for hydrogenation of NEC and Ru/YH3 also possesses good activity for hydrogenation of 2-methylindole, indicating that the use of rare earth hydride supported catalysts is a highly effective strategy for developing better hydrogenation catalysts for N-heterocycles.

Improved hydrogen storage properties of MgH2 by the addition of TiCN and its catalytic mechanism

The hydrogen storage properties of MgH2–x wt%TiCN (x = 5, 10, 15) composites were systematically investigated and the results show that the addition of TiCN can effectively improve the de/rehydrogenation kinetics of MgH2. Taken the onset dehydrogenation temperature and isothermal de/rehydrogenation kinetics into consideration, the MgH2–10 wt% TiCN composite was shown to have the best performance. It was found that the MgH2–10 wt% TiCN composite could release 4 wt% H2 in 17.3 min at 300 °C while the as-synthesized MgH2 could not release any hydrogen under the same condition. Besides, the MgH2–10 wt% TiCN composite could absorb 4.63 wt% H2 under 3.2 MPa hydrogen pressure at 300 °C within 20 s. Compared with as-synthesized MgH2, the activation energy of the MgH2–10 wt% TiCN composite was significantly decreased from 183.76 ± 10 to 106.82 ± 5 kJ/mol. X-ray diffraction analysis revealed that the TiCN remained stable during the ball milling and the following de/rehydrogenation cycle. The catalytic mechanism was also proposed that the TiCN particles absorbed on MgH2 not only served as charge transfer centers and accelerated the hydrogen incorporation and dissociation rate but also provided more diffusion channels for hydrogen, which contributed to the good de/rehydrogenation properties of MgH2.

Isolation and radiocarbon analysis of elemental carbon in atmospheric aerosols using hydropyrolysis

Radiocarbon (14C) analysis is a powerful tool that can unambiguously distinguish fossil and non-fossil sources of carbonaceous particles. However, one of the big challenges of this method is to isolate elemental carbon (EC) or black carbon (BC) for 14C analysis. Hydropyrolysis (hypy) has proven to be an effective method for separating BC in environmental matrices. The potential of hypy for isolation of EC from atmospheric aerosols is evaluated using typical combustion products from non-fossil (biomass), fossil fuel (coal and petroleum), and ambient aerosol samples collected in Beijing and Guangzhou. Using solid state nuclear magnetic resonance (NMR) along with measurement of carbon content and 14C, hypy conditions of 15 MPa hydrogen pressure and 550 °C temperature was confirmed to effectively separate EC from aerosol samples. Consequently, a comparison study of EC 14C in aerosol samples separated using the two-step heating method (CTO-375), thermal-optical method and hypy was conducted. The results show that hypy is an effective and stable approach for matrix-independent 14C quantification of EC in aerosols.

Upgrading of Scenedesmus obliquus oil to high-quality liquid-phase biofuel by nickel-impregnated biochar catalyst

This work investigated the optimization of process parameters in the upgrading of the oil extracted from Scenedesmus obliquus microalgae using a novel nickel-impregnated biochar catalyst. The effects of temperature, dodecane-to-oil mass ratio and pressure on the upgraded liquid-phase biofuel yield were evaluated and optimized by central composite design of the response surface methodology (RSM). The model equation generated from RSM showed that dodecane-to-oil mass ratio and pressure, as well as the quadratic effects of all the three factors, were significant model terms in predicting the yield of upgraded liquid-phase biofuel. Maximum liquid biofuel yield was attained at 246.89 °C, 3.72 (w/w) dodecane-to-oil mass ratio, 3.84 MPa hydrogen pressure and 6 h processing time. Validation runs resulted in an upgraded biofuel yield of 69.4%, which was in close agreement with predicted values generated by RSM. The upgraded biofuel comprised of 100% green liquid hydrocarbons containing 94% alkanes and 6% alkenes. Its main fuel properties, such as heating value (43.78 MJ kg−1), elemental composition, density, and viscosity, exceeded those of the fatty acid methyl ester standard and were found comparable to those of petroleum diesel. More importantly, the results of the ultimate analysis and confirmed by the findings from Fourier transform infrared and gas chromatography – mass spectroscopy analyses, showed significantly low oxygen and nitrogen content and absence of sulfur in the upgraded biofuel.

Antioxidant and Fluorescence Properties of Hydrogenolyzised Polymeric Proanthocyanidins Prepared Using SO₄2-/ZrO₂ Solid Superacids Catalyst.

Larix bark oligomeric proanthocyanidins (LOPC) were prepared from larix bark polymeric proanthocyanidins (LPPC) by catalytic hydrogenolysis using SO42−/ZrO2 solid superacid as the catalyst. The catalyst to polymeric proanthocyanidins ratio was 0.2:1 (m/m). The LOPC, obtained after hydrogenolysis at 100 °C for 4 h under 3 MPa hydrogen pressure, retained the structural characteristics of proanthocyanidins. The average degree of polymerization was reduced from 9.50% to 4.76% and the depolymerization yield was 53.85%. LOPC has good antioxidant properties and, at the same concentration, the reducing ability of LOPC was much higher than that of LPPC. The IC50 values of LOPC for scavenging DPPH• and ABTS•+ radicals were 0.046 mg/mL and 0.051 mg/mL, respectively. LOPC is biocompatible and has fluorescent properties that are affected by external factors, such as solvent polarity, pH and the presence of different metal ions. These features indicate that LOPC could be developed as a new biological fluorescent marker. The depolymerization of low-value polymeric proanthocyanidins to provide high-value oligomeric proanthocyanidins and the development of new applications for proanthocyanidins represent significant advances.

The Influence of Temperature on the Degree of Bio-Oil Hydroupgrading over High-Loaded NiCu-SiO2 Catalyst at Low Hydrogen Content

The process of upgrading of pyrolysis bio-oil via hydrodeoxygenation was studied at 0.6 MPa hydrogen pressure and 150–350 °C in the presence of the NiCu-SiO2catalyst prepared by the sol-gel method. The catalyst resistance to agglomeration of the active component and to the carbon deposition on its surface was examined. The oxygen content in the liquid products of lignocellulose pyrolysis was shown to decrease from 37 to 15 wt.% as the process temperature rose. A CHNS-O analyzer was used to establish that the coke quantity on the catalyst surface at 350 °C decreased to one fourth of that at 150 °C. XPS studies revealed that the elevation of the process temperature led to progressive agglomeration of the particles followed by a decrease in their size at high temperature due to dissolution of the active components of the catalyst in the reaction medium.

Depolymerization of Lignin to Produce Monophenols and Oligomers Using a Novel Ni/Ce-CNT Catalyst

A novel composite catalyst consisting of nickel, cerium, and carbon nanotube (CNT) was developed for native lignin and industrial lignin depolymerization. It was found that Ni and Ce had synergistic effects on the depolymerization. Native lignin was depolymerized to monophenols with a yield of 21.4% at 300 °C for 2 h under 2 MPa hydrogen pressure with serious coke formation. A milder condition set at 280 °C for 2 h under 2 MPa hydrogen pressure provided a monophenols yield of 13.5% with 78.6% lignin removal, but much less coke formation and better catalyst reusability. Even after running the trial four times, the catalyst presented high efficiency. Industrial lignin was depolymerized to oligomers, which are a series of aromatic micromolecules that could be extracted by specific organic solvents such as ethyl acetate. Those oligomers could be used as high calorific value bio-oil. After being depolymerized at 260 °C for 1 h under 2 MPa hydrogen pressure, the yields of oligomers were 56.0% and 11.6% extracted by ethyl acetate (EA) and petroleum ether (PE), respectively. After recycling four times, the catalyst still exhibited high activity. It was clear that the Ni/Ce-CNT was an effective catalyst in lignin depolymerization.

From the Laves Phase CaRh2 to the Perovskite CaRhH3–in Situ Investigation of Hydrogenation Intermediates CaRh2Hx

The hydrogenation properties of the cubic Laves phase CaRh2 and the formation of the perovskite CaRhH3 were studied by in situ thermal analysis (differential scanning calorimetry), sorption experiments, and in situ neutron powder diffraction. Three Laves phase hydrides are formed successively at room temperature and hydrogen gas pressures up to 5 MPa. Cubic α-CaRh2H0.05 is a stuffed cubic Laves phase with statistically distributed hydrogen atoms in tetrahedral [Ca2Rh2] voids (ZrCr2H3.08 type, Fd3̅ m, a = 7.5308(12) Å). Orthorhombic β-CaRh2D3.93(5) (own structure type, Pnma, a = 6.0028(3) Å, b = 5.6065(3) Å, c = 8.1589(5) Å) and γ-CaRh2D3.20(10) (β-CaRh2H3.9 type, Pnma, a = 5.9601(10) Å, b = 5.4912(2) Å, c = 8.0730(11) Å) are low-symmetry variants thereof with hydrogen occupying distorted tetrahedral [Ca2Rh2] and trigonal bipyramidal [Ca3Rh2] voids. Hydrogen sorption experiments show the hydrogenation to take place already at 0.1 MPa and to yield β-CaRh2H3.8(2). At 560 K and 5 MPa hydrogen pressure the Laves phase hydride decomposes kinetically controlled to nanocrystalline rhodium and CaRhD2.93(2) (CaTiO3 type, Pm3̅ m, a = 3.6512(2) Å). The hydrogenation of CaRh2 provides a synthesis route to otherwise not accessible perovskite-type CaRhH3.

Low-cost Sieverts-type apparatus for the study of hydriding/dehydriding reactions

Abstract The design and construction of a low-cost equipment for the study of hydriding/dehydriding reactions of different materials are presented. This is a Sieverts-type apparatus where a small amount (0.2–1 g) of solid hydrogen storage materials can be characterized. The apparatus combines the features of double lines (sample and reference) to eliminate small thermal effects on the reservoir and sample-holder volumes, with a Δp = Δpsample − Δpreference approach to eliminate the need of a differential pressure transducer and to reduce costs. This apparatus can work from vacuum to 10 MPa hydrogen pressure and from room temperature to 673 K. Pressure, temperature and volume data are transformed by a real gases equation state and mass balance into hydrogen uptake or release in wt%. Characterization of typical hydrogen storage materials such as LiAlH4 and Mg is presented to validate the performance of the apparatus.

Acid catalysis dominated suppression of xylose hydrogenation with increasing yield of 1,2-pentanediol in the acid-metal dual catalyst system

One-pot conversion of xylose to 1,2-pentanediol was investigated in a dual catalyst system composed of Ru/C and niobium phosphate as hydrogenation and acid catalysts, respectively. A series of niobium phosphate catalysts well-characterized by XRD, N2 physisorption, FT-IR, NH3-TPD, Py-IR and XPS were tested regarding the effect of their acid properties on product selectivity for the studied process. A systematic study was reported on the effect of reaction conditions. The combined yield of 21–27% to 1,2-pentanediol and its precursor 1-hydroxyl-2-pentanone was accomplished at 423 K under 3.0 Mpa hydrogen pressure in water-γ-valerolactone/cyclohexane biphasic system. At optimized conditions, the correlation between the product yield and the surface Lewis/Brønsted ratio were analyzed. The results revealed that the lower apparent activation energy of xylose dehydration reaction catalyzed by Lewis acid site accounted for the high product selectivity for sugar intermediate and furfural hydrogenation processes, especially for the combined selectivity to 1,2-pentanediol and 1-hydroxyl-2-pentanone. This study lays the grounds for further design of improved solid acid catalysts with high selectivity of 1, 2-pentanediol.

Effect of organic nitrogen compounds on deep hydrodesulfurization of middle distillate

An effect of organic nitrogen compounds on deep hydrodesulfurization catalyst (CoMo/Al2O3) has been carried out using micro-flow reactor at 5 MPa hydrogen pressure, 1.5 h−1 liquid hours space velocity, and 330 to 380 °C temperature. The experiments were conducted in two steps; at first, prepare nitrogen free Kuwaiti straight run gas oil (SRGO) while in the second step is to test hydrotreating (HDT) catalytic activities using synthetic diesel feed to achieve ultra-low sulfur diesel (ULSD). Hence the role of nitrogen compounds and their effect on HDS activity was studied with nitrogen-free SRGO and spiked (added indole and quinoline), which indicated an apparent tendency of strong inhibition effect by basic nitrogen on deep HDS process.Indeed, inhibition and deep HDS conversion are also dependent on the H2 partial pressure and its dissociative species (i.e., Hδ+ and Hδ−). It is expected that basic nitrogen compounds can easily consume Hδ+ ions during hydrotreating which is assumed to be the rationale behind the stronger inhibition of the hydrogenation function. It was found that quinoline has a more noticeable adverse effect than indole, particularly at a lower temperature. HDS activity results indicated that the adsorbed nitrogen species showed more acceptable behavior at a lower temperature while at high-temperature inhibition effect is not very significant, which could be because of the adsorption nature of nitrogen species.

High Catalytic Behavior of Activated Carbon‐Supported K‐Fe‐Ni Based Catalysts for 1,6‐Hexanedinitrile Hydrogenation under Mild Conditions

AbstractActivated carbon supported potassium and iron doped nickel‐based catalysts were prepared and characterized by XRD, chemisorption of H2, H2‐TPR, XPS, N2 adsorption‐desorption analysis, NH3‐TPD, SEM, TEM, HRTEM and HAADF‐STEM. The catalytic behaviors were conducted on the hydrogenation of 1,6‐Hexanedinitrile to 6‐aminohexanenitrile and 1,6‐hexanediamine under 338 K‐358 K and 2 MPa hydrogen pressure. It can be deduced that the reducibility of the nickel oxide, the surface of the Ni0+ content and the dispersibility of nickel nanoparticles can be significantly enhanced by doping a certain amount of iron as the results of the synergetic effect between nickel and iron. Moreover, the introduction of potassium not only can effectively increase the alkaline site of the catalyst so as to inhibit the formation of by‐products, but also improve the dispersion of nickel nanoparticles by suppressing the sintering effect. However, the addition of excessive potassium is unfavorable to the nickel oxide reduction. It can be seen that activated carbon supported potassium and iron doped nickel‐based catalyst gives better catalytic performance of 91.32% conversion of 1,6‐Hexanedinitrile and 91.82% selectivity to 6‐aminohexanenitrile and 1,6‐hexanediamine under mild conditions of 348 K and 2 MPa.

Destabilization of LiBH4 by SrF2 for reversible hydrogen storage

The de-/rehydrogenation features of the 6LiBH4/SrF2 reactive hydride system have been systematically investigated. It was found that the thermal stability of LiBH4 can be reduced markedly by combining it with SrF2. Dehydrogenation of the 6LiBH4/SrF2 system proceeds via the 6LiBH4 + SrF2 → SrB6 + 2LiF + 4LiH + 10H2 reaction, which involves SrH2 as the intermediate product. The dehydrogenation enthalpy change was experimentally determined to be 52 kJ/mol H2 based on the P–C isotherm analysis. For rehydrogenation, LiBH4 and SrF2 were regenerated along with LiSrH3 at 450 °C under ∼8 MPa hydrogen pressure; thus, approximately 5.2 wt% of hydrogen can be released during the second dehydrogenation process.

Reversible hydrogenation of the Zintl phases BaGe and BaSn studied by in situ diffraction

Abstract Hydrogenation products of the Zintl phases AeTt (Ae = alkaline earth; Tt = tetrel) exhibit hydride anions on interstitial sites as well as hydrogen covalently bound to Tt which leads to a reversible hydrogenation at mild conditions. In situ thermal analysis, synchrotron and neutron powder diffraction under hydrogen (deuterium for neutrons) pressure was applied to BaTt (Tt=Ge, Sn). BaTtHy (1<y<1.67, γ-phases) were formed at 5 MPa hydrogen pressure and elevated temperatures (400–450 K). Further heating (500–550 K) leads to a hydrogen release forming the new phases β-BaGeH0.5 (Pnma, a=1319.5(2) pm, b=421.46(2) pm, c=991.54(7) pm) and α-BaSnH0.19 (Cmcm, a=522.72(6) pm, b=1293.6(2) pm, c=463.97(6) pm). Upon cooling the hydrogen rich phases are reformed. Thermal decomposition of γ-BaGeHy under vacuum leads to β-BaGeH0.5 and α-BaGeH0.13 [Cmcm, a=503.09(3) pm, b=1221.5(2) pm, c=427.38(4) pm]. At 500 K the reversible reaction α-BaGeH0.23 (vacuum)⇄β-BaGeH0.5 (0.2 MPa deuterium pressure) is fast and was observed with 10 s time resolution by in situ neutron diffraction. The phases α-BaTtHy show a pronounced phase width (at least 0.09<y<0.36). β-BaGeH0.5 and the γ-phases appear to be line phases. The hydrogen poor (α- and β-) phases show a partial occupation of Ba4 tetrahedra by hydride anions leading to a partial oxidation of polyanions and shortening of Tt–Tt bonds.

Hydrogen storage studies in Pd/Ti/Mg films

This paper describes investigations (a) on the efficacy of Ti layer as a barrier against the intermixing of Pd and Mg in Pd/Ti/Mg films and (b) the hydrogen storage characteristics of the tri-layered films and the related bulk composites. The Mg film was prepared by resistive evaporation while the Pd and Ti films were deposited by e-beam evaporation. The analysis by Rutherford backscattering spectrometry (RBS) and glancing-incidence X-ray diffraction (GI-XRD) of the Pd/Ti/Mg/Si(substrate) films annealed in vacuum in 348–573 K temperature range revealed that Ti effectively prevents the intermixing of Pd and Mg up to ∼523 K. However, mixing across Pd/Ti, Ti/Mg and Mg/Si interfaces commences around 523 K that progresses with the temperature of annealing though PdMg phases are not formed even at 573 K. The as-deposited Pd/Ti/Mg films are hydrogenated to ∼7 wt % (62 at%) at 323–423 K at 0.15 MPa hydrogen pressure and dehydrogenated completely at ∼ 473 K. The extent of (de)hydrogenation of the films was determined non-destructively by the 1H(19F,αγ)16O nuclear reaction. The powder composites derived from the films, on the other hand, reversibly stored ∼2.2 wt% hydrogen up to 18 cycles in 323–473 K temperature range. The superior cyclic stability is attributed to the inhibition of mixing between Pd and Mg and, as a result, the formation of PdMg inter-metallics by titanium.

Interaction of Ground SmCo4.8Zr0.2 Alloy with Hydrogen

The hydrogen pressure and reaction time were studied during disproportionation of the ground SmCo4.8Zr0.2 alloy. The alloy ground at ν = 100 rpm for τ = 24 h disproportionates at 0.5 MPa hydrogen pressure within 15–30 min, the alloy ground at ν = 200 rpm for τ = 6 and 12 h disproportionates at 0.5 MPa hydrogen pressure, and the alloy ground at ν = 300 rpm for τ = 6 h disproportionates into SmHx and ht-Co below 0.1 MPa hydrogen pressure. Residues of the CaCu5–type ferromagnetic phase were found among the disproportionation products.

Formation of aluminium hydride (AlH3) via the decomposition of organoaluminium and hydrogen storage properties

Aluminium hydride (AlH3) is a promising hydrogen storage material due to its competitive hydrogen storage density and moderate decomposition temperature. However, there is no convenient way to prepare/regenerate AlH3 from (spent) Al by direct hydrogenation. Herein, we report on a novel approach to generate AlH3 from the decomposition of triethylaluminium (Et3Al) under mild hydrogen pressures (10 MPa) with the use of surfactants. With tetraoctylammonium bromide (TOAB), the synthesis led to the formation of nanosized AlH3 with the known α phase, and these nanoparticles released hydrogen from 40 °C instead of the 125 °C observed with bulk α-AlH3. However, when tetrabutylammonium bromide (TBAB) was used instead of TOAB, larger nanoparticles believed to be related to the formation of β-AlH3 were obtained, and these decomposed through a single exothermic process. Despite the possibility to form α-AlH3 under low conditions of temperature (180 °C) and pressure (10 MPa), TOAB stabilised AlH3 was found to be irreversible when subjected to hydrogen cycling at 150 °C and 7 MPa hydrogen pressure.

Vacancy ordering in Pd11Bi2Se2 - Crystal structure and properties

The crystal structure of Pd11Bi2Se2 was determined and refined from X-ray single crystal data (space group Fd3¯m, a = 12.4879(14) Å, Z = 8). In contrast to the earlier reported Pd3(Bi0.6Se0.4), the title compound crystallizes in a 2 × 2 × 2 superstructure of the BiF3 type with ordered bismuth and selenium distribution and an ordered vacancy according to Pd11□Bi2Se2. The vacancy is located at the center of a palladium tetrahedron capped with a bismuth tetrahedron (stella quadrangula). Pd11Bi2Se2 is isopointal to Li13In3 but shows different ordering of the minority components. Pd11Bi2Se2 is inert to water, organic solvents and concentrated hydrochloric acid and its melting point is 905(1) K. It exhibits a very small effective magnetic moment of μeff = 0.0114(2) μB per palladium atom. Pd11Bi2Se2 does not take up hydrogen up to 7.2(2) MPa hydrogen pressure and temperatures up to 703 K. In the electronic structure, the region near the Fermi level is dominated by almost filled Pd 4d-states. Low yet non-zero density of states and a pseudo-gap at the Fermi level might indicate Pd11Bi2Se2 to be a poor metal.

An evaluation of high temperature hydrogen attack resistance and a possible new microstructure development based remnant life assessment method of a clean ASME Gr.91 thick section steel plate

A thick section plate specimen of a completely refined Gr.91 steel plate met the requirements of ASME code concerning the toughness and creep strengths due to exact control of the chemical composition and lowering of impurities. Low impurities also resulted in almost the same HTHA (High Temperature Hydrogen Attack) resistance as that of 2.25Cr-1Mo steel at 500ºC at 20 MPa hydrogen pressure. The long-term creep strength of Gr.91 steel is reduced by the presence of weld heat-affected-zones. The weakening phenomenon is due to the formation of ‘Type IV damage’. In this study, a crystal misorientation diagram transition analysis method using electron-back-scattering-diffraction analysis, EBSD, is applied to predict the remnant creep life of the HAZ. The trial prediction agrees with the actual rupture time.