MPa Hydrogen Research Articles

An in situ tribometer for measuring friction and wear of polymers in a high pressure hydrogen environment.

High pressure hydrogen effects on the friction and wear of polymers are of importance to myriad applications. Of special concern are those used in the infrastructure for hydrogen vehicle refueling stations, including compressor sliding seals, valves, and actuators. While much is known about potentially damaging embrittlement effects of hydrogen on metals, relatively little is known about the effects of high pressure hydrogen on polymers. However, based on the limited results that are published in the literature, polymers also apparently exhibit compatibility issues with hydrogen. An additional study is needed to elucidate these effects to avoid incompatibilities either through design or material selection. As part of this effort, we present here in situ high pressure hydrogen studies of the friction and wear on example polymers. To this end, we have built and demonstrated a custom-built pin-on-flat linear reciprocating tribometer and demonstrated its use with in situ studies of friction and wear behavior of nitrile butadiene rubber polymer samples in 28 MPa hydrogen. Tribology results indicate that friction and wear is increased in high pressure hydrogen as compared both with values measured in high pressure argon and ambient air conditions.

Water-soluble palladium nanoparticles as an active catalyst for highly selective hydrogenation of nitrobenzene to aniline

Palladium (Pd) nanoparticles (NPs) stabilized by tri-block copolymer polyoxyethylene–polyoxypropylene–polyoxyethylene (P123) micelles were synthesized in water using a hydrogenation reduction method. Well-dispersed P123 micelles in the aqueous phase favored the stabilization of Pd NPs. The P123–Pd micellar catalyst was first applied in the liquid phase hydrogenation of nitrobenzene (NB), showing excellent catalytic activity, and the only reaction product detected was aniline (AN). Using water as the reaction medium and under mild conditions, both the preparation of catalysts and NB hydrogenation were convenient and environmentally friendly. Under the optimal conditions, the isolated catalyst phase could be recycled at least five times, and the catalytic activity and selectivity remained unchanged. A reaction scheme was suggested. First-order kinetics was determined at 3.0 MPa hydrogen pressure and temperature 30–75 °C, and the activation energy was 40.18 kJ mol−1. This work provides an environmentally benign and effective method for the hydrogenation of NB to AN.

Efficient Furfuryl Alcohol Synthesis from Furfural over Magnetically Recoverable Catalysts: Does the Catalyst Stabilizing Medium Matter?

AbstractWe report hydrogenation of furfural (FF) to furfuryl alcohol (FA) with novel Pt‐and Pd‐containing magnetite nanoparticles (NPs) stabilized by polyphenylquinoxaline (PPQ) and hyperbranched pyridylphenylene polymer (PPP). FF is one of the major ingredients of biooil produced by biomass pyrolysis, while FA is a source of value‐added chemicals, thus, creating a sustainable path from biomass to important compounds. We demonstrate that catalytic NPs (Pt0 or Pd0) of approximately 3 nm in diameter form in the polymer shells of magnetite NPs and the catalysts are magnetically recoverable. The search for optimal reaction conditions of the FF hydrogenation revealed that the highest selectivity is obtained at 120 °C and 6 MPa hydrogen pressure in i‐propanol as solvent. The solvent effect is due to combination of good FF solubility and accessibility of catalytic NPs for the FF adsorption. A comparison of the catalytic activities of the Pd‐containing magnetite NPs stabilized by PPQ and PPP validates the advantages of the open and rigid structure of the hyperbranched PPP vs. linear PPQ. For Pd‐containing magnetite NPs stabilized by PPP, the high selectivity to FA of 99.3% at nearly 100% FF conversion was achieved at a remarkable activity of 871 min−1 and high catalyst stability.

Enhanced hydriding kinetics of Mg-10 at% Al composite by forming Al 12 Mg 17 during hydriding combustion synthesis

Abstract Mg-based alloys are widely considered as promising materials for hydrogen storage. However, owing to the high chemical activity of Mg, the surface of Mg powder is always covered with a layer of close packed MgO, which can retard the hydrogenation of Mg. In this paper, 10 at% Al was added to accelerate the hydriding kinetics of Mg through tabletting and grinding treatments. After heating to 420 °C and subsequent holding at 340 °C for 120 min under 1.5 MPa hydrogen pressure, the Mg-10 at% Al composite could absorb 6.34 wt% H2 in the process of hydriding combustion synthesis (HCS) while the same treated pure Mg powder was barely hydrided. Upon heating from room temperature to 420 °C, Al alloyed with Mg to form an Al12Mg17 phase on the surface of Mg particles and the newly formed alloy was oxide-free, which would react with H2 when the temperature decreased to 340 °C. Then hydrogen was able to get into the inner part of the Mg particle from the former Al12Mg17 sites where the MgO shell had been broken in the alloying period to further react with unhydrided Mg.

Hydrogen-enhanced fatigue life analysis of Cr–Mo steel high-pressure vessels

Cr–Mo steel high-pressure vessel made of 4130X is a promising economical candidate for hydrogen storage and transport in hydrogen refueling stations. However, the mechanical properties of 4130X in hydrogen gas and the hydrogen-enhanced fatigue life of a 4130X vessel with a design pressure higher than 45 MPa are not completely understood. In this work, the tensile and fatigue properties of 4130X at different positions of a manufactured vessel in 92 MPa hydrogen gas were studied. The fatigue life prediction for the 4130X vessel was performed using fracture mechanics method. The influences of initial crack size and outside diameter on the fatigue life were also investigated. Results indicate that the 4130X from the shoulder area attains a lower relative reduction of area (RRA) and higher fatigue-crack growth rate (FCGR) in hydrogen gas than those of the specimens from the cylinder and juncture. The FCGR measured in hydrogen increases with increasing hydrogen pressure, and the FCGR in 92 MPa hydrogen gas is 30–50 times of the FCGR in air. As the initial crack size increases, not only the fatigue life of the hydrogen storage vessel decreases, but also the hydrogen-induced fatigue life loss is aggravated. Furthermore, the influence of outside diameter on the fatigue life of the hydrogen storage vessel is minimal.

Threshold stress intensity factor for hydrogen-assisted cracking of CR-MO steel used as stationary storage buffer of a hydrogen refueling station

In order to determine appropriate value for threshold stress intensity factor for hydrogen-assisted cracking (KIH), constant-displacement and rising-load tests were conducted in high-pressure hydrogen gas for JIS-SCM435 low alloy steel (Cr-Mo steel) used as stationary storage buffer of a hydrogen refuelling station with 0.2% proof strength and ultimate tensile strength equal to 772 MPa and 948 MPa respectively. Thresholds for crack arrest under constant displacement and for crack initiation under rising load were identified. The crack arrest threshold under constant displacement was 44.3 MPa m1/2 to 44.5 MPa m1/2 when small-scale yielding and plane-strain criteria were satisfied and the crack initiation threshold under rising load was 33.1 MPa m1/2 to 41.1 MPa m1/2 in 115 MPa hydrogen gas. The crack arrest threshold was roughly equivalent to the crack initiation threshold although the crack initiation threshold showed slightly more conservative values. It was considered that both test methods could be suitable to determine appropriate value for KIH for this material.

Application of silica-supported Fe–Cu nanoparticles in the selective hydrogenation of p-dinitrobenzene to p-phenylenediamine

Supported bimetallic Fe–Cu/SiO2 materials are synthesized, and their catalytic activity in hydrogenation of dinitrobenzene to phenylenediamine at 145–180°С and 1.3 MPa hydrogen pressure is studied for the first time. The best results (89% selectivity toward p-phenylenediamine at complete conversion of p-dinitrobenzene) are obtained for the sample synthesized via co-deposition with subsequent calcination at 300°С. The sample contains 7% iron and 3% copper. The formation of separate phases of metal oxides (for the catalysts prepared by impregnation) and mixed bimetallic oxide phases (in case of co-deposition procedure) in calcined samples is revealed via thermoprogrammed reduction with hydrogen.

The Influence of the Composition of Molybdenum Modified NiCu-Containing Catalysts on the Activity and Selectivity to Hydrogenation of Furfural to Produce Valuable Chemicals

The influence of the composition of molybdenum modified NiCu-containing catalysts on the activity and selectivity to hydrogenation of furfural – a product of acid hydrolysis of hemicellulose biomass – was studied. The initial NiCu catalyst was prepared by the sol-gel method and stabilized with 10 wt % SiO 2 by impregnating the calcined sol-gel with ethyl silicate. Molybdenum was introduced in the form of oxide Mo(VI) on the stage of blending of oxide precursors of the metals. Selective hydrogenation of furfural was achieved using a batch reactor at 100–200 °C and 6 MPa of hydrogen. It was established that the rise of the process temperature led to an increase in the yields of 2-methylfurane and complete hydrogenation products. At low process temperatures, 2-methylfurane practically was not formed but furfuryl and tetrahydrofurfuryl alcohols were the main products. In comparison to the NiCu systems, the modified NiCuMo-SiO 2 catalysts were more active to hydrogenation of furfural and more selective to 2-methylfurane; this may be accounted for by the formation of solid NiMo(Cu) solutions and by the formation of Mo x+ on the catalyst surface.

115MPa水素ガス中での低合金鋼SCM435とSNCM439の各種強度特性および設計指針の提案

115MPa水素ガス中での低合金鋼SCM435とSNCM439の各種強度特性および設計指針の提案

Enhanced hydrogen adsorption on graphene by manganese and manganese vanadium alloy decoration.

In this work, two kinds of novel manganese decorated (G + Mn) and manganese-vanadium co-decorated (G + MnV) graphene composites are synthesized by in situ wet chemical reduction, and their hydrogen storage properties and microstructures are characterized by Sievert-type adsorption apparatus, BET, SEM, TEM/STEM, EDX and EELS. Compared with pristine graphene, Mn decoration marginally increases the hydrogen adsorption capacity of graphene at room temperature and 4 MPa hydrogen pressure from 0.25 wt% to 0.36 wt%. On the other hand, the co-decoration of Mn and V increases the room temperature hydrogen storage capacity of graphene significantly to 1.81 wt% under 4 MPa hydrogen pressure, which is 1.56 wt% higher than the capacity of pristine graphene. The microstructures and valence states of the decorated Mn and Mn-V nanoparticles are investigated by TEM, EDX and EELS analyses, and strong interactions between the decorated nanoparticles and graphene are observed. Based on the results from structural analyses, potential enhancement mechanisms are suggested in terms of the catalytic effects of nanoparticles on graphene hydrogen adsorption. Given the relatively low cost of Mn and V metals compared to noble metals such as Pd, Pt and Au, these results demonstrate a low cost and effective way to significantly enhance the room temperature hydrogen adsorption properties of graphene for potential hydrogen storage applications.

70MPa水素ステーション実証試験で使用されたプレクーラー冷却パイプの事例解析

70MPa水素ステーション実証試験で使用されたプレクーラー冷却パイプの事例解析

Lessons learned from leaching of dry milled high burnup UO2 fuel under H2 atmosphere

AbstractA trend in the operation of nuclear power reactors is the increase in discharge burnup of the fuel. Intrusion of groundwater in a failed canister of a future deep repository is expected to occur in the presence of hydrogen, produced by the anoxic corrosion of iron and by radiolysis of water. Compelling evidence now exists that hydrogen inhibits oxidative dissolution of irradiated nuclear fuel or alpha doped UO2, however the number of studies involving high burnup fuel are limited. In the experiment PWR UO2 fuel with a burnup of ∼75 MWd/kgU was leached in simulated groundwater (10 mM NaCl, 2 mM NaHCO3) at room temperature under 5 MPa of hydrogen. Since the main objective was to investigate the fuel matrix dissolution, a fuel fraction that had previously been leached for over one year was reused. The U-238 and Tc-99 concentration was found to vary in the samples taken over 1100 days of leaching, depending on the degree of centrifugation. The erratic behavior of this autoclave experiment is tentatively attributed to a high surface area, with sub-micrometer sized fuel particles adhering to larger fuel fragments (evidenced by electron microscopy), caused by the fuel milling at the start of the experiment. This likely promoted an increased amount of pre-oxidation of the fuel as well as the potential for reductive precipitation and subsequent release of colloids from the autoclave. As a comparison, initial results from an ongoing autoclave experiment with coarser fuel fragments are also given.

Hydrogen accelerated fatigue crack growth of friction stir welded X52 steel pipe

Friction stir welded steel pipelines were tested in high pressure hydrogen gas to examine the effects of hydrogen accelerated fatigue crack growth. Fatigue crack growth rate (da/dN) vs. stress-intensity factor range (ΔK) relationships were measured for an X52 friction stir welded pipe tested in 21 MPa hydrogen gas at a frequency of 1 Hz and R = 0.5. Tests were performed on three regions: base metal (BM), center of friction stir weld (FSW), and 15 mm off-center of the weld. For all three material regions, tests in hydrogen exhibited accelerated fatigue crack growth rates that exceeded an order of magnitude compared to companion tests in air. Among tests in hydrogen, fatigue crack growth rates were modestly higher in the FSW than the BM and 15 mm off-center tests. Select regions of the fracture surfaces associated with specified ΔK levels were examined which revealed intergranular fracture in the BM and 15 mm off-center specimens but an absence of intergranular features in the FSW specimens. The X52 friction stir weld and base metal tested in hydrogen exhibited fatigue crack growth rate relationships that are comparable to those for conventional arc welded steel pipeline of similar strength found in the literature.

Hydrocracking of Vacuum Gas Oil on Bimetallic Ni-Mo Sulfide Catalysts Based on Mesoporous Aluminosilicate Al-HMS

The activity and selectivity of a bimetallic Ni-Mo sulfide catalyst based on mesoporous aluminosilicate Al-HMS with Si/Al ratio of 10 in the vacuum gas oil hydrocracking process in a reactor with a fixed catalyst bed was studied. The dependence of the activity and selectivity of the NiS-MoS2/Al-HMS (Si/Al = 10) catalyst on the process parameters (temperature, hydrogen pressure, volume stock feed rate, etc.) was investigated. It was shown that in the 380-450°C range at 5 MPa hydrogen pressure the catalyst ensures conversion of the heavy part of the hydrocarbon stock into fuel fractions with high selectivity in the middle distillates and makes it possible to reduce the sulfur content of the liquid hydrocracking products.

Graphite encapsulated molybdenum carbide core/shell nanocomposite for highly selective conversion of guaiacol to phenolic compounds in methanol

Graphite encapsulated molybdenum carbides (Mo2C@C) were synthesized via the hydrothermal carbonization of a solution of glucose and ammonium molybdate followed by temperature programmed reduction. Characterization and structural analyses revealed that the synthesized Mo2C@C nanoparticles had a molybdenum core/carbon shell structure with a particle size ranging from 50nm to 100nm and a core size range of 5–45nm. The catalytic performance of the graphite encapsulated molybdenum carbides was evaluated on conversion of guaiacol to phenolic compounds in methanol. At 340°C under 2.8MPa hydrogen pressure, a 76.3% guaiacol conversion was obtained with selectivities of 68.6% for phenol and 93.5% for phenolic compounds. Thus, Mo2C@C showed high selectivity for phenolic compounds in methanol.

Transient temperature and pressure behavior of high-pressure 100 MPa hydrogen during discharge through orifices

High-pressure hydrogen at a maximum of 100 MPa in a 1-L-volume vessel is discharged through 0.1-mm- and 0.2-mm-diameter orifices that imitate cracks, and the transient temperature and pressure behavior of the hydrogen in the vessel is presented. The hydrogen at the initial pressure of 100 MPa during its discharge through the ϕ 0.2-mm orifice reaches half of the initial pressure after 16 s, while it takes approximately nine times longer for the ϕ 0.1-mm orifice to reach half of the initial pressure. We theoretically calculate the transient temperature and pressure according to the fundamental equations based on the mass and energy conservations using an accurate equation of state for hydrogen. The actual flow rate through an orifice is generally smaller than the theoretically calculated flow rate because of the contraction flow. Therefore, in this study, we adopt the effective diameters of the orifices instead of the actual diameters, and from comparisons with the experimental pressure, we estimate them to be 0.6 and 0.9 of the actual diameters for the ϕ 0.1-mm and ϕ 0.2-mm orifices, respectively. We use a functional form with a time constant for the heat transfer coefficient to represent the transient temperature behavior, and we describe the time dependence of the heat transfer coefficient. The results show that the calculated temperature and pressure are in good agreement with the experimental values obtained.

Direct and reversible hydrogen storage of lithium hydride (LiH) nanoconfined in high surface area graphite

LiH has great potential as a high capacity hydrogen storage material (12 wt.%), however its thermodynamic stability has so far precluded practical application. Temperatures near 700 °C are required for hydrogen release and uptake. Herein, we report on a novel method to realise hydrogen uptake and release under milder temperature conditions without using any catalyst or alloying. Through nanoconfinement within the pores (2–20 nm) of high surface area graphite (HSAG) LiH displayed remarkable hydrogen storage properties and was able to release 1.9 wt.% of hydrogen from 200 °C. Reversibility was also achieved under the moderate conditions of 300 °C and 6 MPa hydrogen pressure. This demonstrates that the properties of LiH are particle size dependent and thus leads to new possibilities to realise the potential of LiH as a practical high capacity hydrogen storage material.

Furfural Hydrogenation to Furfuryl Alcohol over Bimetallic Ni–Cu Sol–Gel Catalyst: A Model Reaction for Conversion of Oxygenates in Pyrolysis Liquids

High metal loading NiCu-based catalyst of Picula™ series produced by sol–gel technique was applied to furfural hydrogenation in the presence of hydrogen. This reaction represents the stabilization of pyrolysis oil that involves the selective reduction of aldehydes and ketones to alcohols and unsaturated C–C double bonds of pyrolysis oils components. The catalysts were pre-reduced at 250 and 300 °C. According to XRD analysis results, copper is mainly in the metallic state, and Ni is mostly in the form of oxide and silicate. XPS measurements reveal that hydrogen treatment at 250 °C leads to the partial reduction of Ni to the metallic state (6 %) while further reduction at 300 °C leads to an increase in this proportion up to 39 %. A 100 % selectivity towards furfuryl alcohol was achieved at 130 °C and 5 MPa of hydrogen in a batch reactor using decyl alcohol as a solvent. In the experiments with i-propanol as a solvent at 110–170 °C the main product was furfuryl alcohol, but minor components traced back were tetrahydrofurfuryl alcohol, 2-methylfuran and isopropyl furfuryl ether. The lower catalyst reduction temperature promotes the formation of isopropyl ester, while a higher reduction temperature favors further furfuryl alcohol hydrogenation.

Molecular hydrogen attenuates radiation-induced nucleobase damage to DNA in aerated aqueous solutions

Purpose: The main aim of the present study is to gain mechanistic insights into the modulating effect of molecular hydrogen on the γ-radiation-induced alteration pathways of DNA nucleobases.Materials and methods: Aerated aqueous solutions of calf thymus DNA were exposed to a 60Co source at doses ranging from 0 to 55 Gy under normoxic conditions, in the presence or not of 0.7 MPa hydrogen or helium. The measurement of several modified bases was performed using HPLC associated with electrospray ionization tandem pass spectrometry (HPLC-ESI-MS/MS). Bleaching of aqueous solutions of p-nitrosodimethylaniline (p-NDA) solutions was also used to allow the quantification of hydroxyl radical (•OH) formation.Results: pNDA bleaching was significantly reduced in the presence of hyperbaric hydrogen. This is undoubtedly due to •OH scavenging by H2 since, under the same conditions, He had no effect. Similarly, base alterations were significantly reduced in the presence of hydrogen, as compared to controls under normal atmosphere or in the presence of helium. The relative proportions of modified nucleobases were not changed, showing that the only effect of H2 is to scavenge •OH without exhibiting reducing properties.Conclusions: Our findings demonstrate that H2 exerts a significant protection against radiation-induced DNA base damage in aqueous solutions, •OH scavenging being the only mechanism involved.

Study on the synthesis and hydrogen storage properties of Mg2CuH3

In this study, Mg2CuH3 was prepared using the replacement-diffusion method, and its structure was confirmed by X-ray photoelectron spectroscopy. The hydrogen storage properties of Mg2CuH3, such as dehydrogenation temperature and hydrogen content, were subsequently characterized. Results indicate that Mg2CuH3 is a multiphase material and that the main phase is composed of MgCu2 and MgH2. The optimum reaction conditions for the synthesis of Mg2CuH3 are as follows: 6 MPa hydrogen, hydriding reaction temperature of 350 °C, and reaction time of 5 h. The onset dehydrogenation temperature of Mg2CuH3 is about 420 °C, which is lower than that of MgH2 (440 °C). The dehydrogenation peak temperature of Mg2CuH3 is close to that of MgH2. The hydrogen contents of Mg2CuH3 and MgH2 as measured by simultaneous thermal analysis DSC–TG are about 2.36% and 7.4%, respectively, which are near the results measured by elementary analysis and lower than the theoretical values probably because of the existence of some impurities.