High Hydrogen Partial Pressure Research Articles

Re-evaluating the impact of feeding shock on anaerobic co-digestion of food waste and waste activated sludge: Trade-off between efficiency and stability

To optimize the feeding strategy of anaerobic digestion (AD) treating food waste and waste activated sludge, the impact of relative feeding shock (RFS) on the trade-off between efficiency and stability was re-evaluated at six feeding conditions from 1/96 (approximate continuous feeding) to 1. The results showed that increasing the RFS from 1/96 to 1/3 increased the CH4 yield from 293.23 mL CH4/g-total solid (TS) to the maximum value of 345.11 mL CH4/g-TS, which was due to the highest specific microbial growth rates (μmax) of acetate (1.05d-1) and propionate (0.48d-1) and a balanced reaction rate between acidogenesis and methanogenesis. However, when the RFS increased to 1, the total volatile fatty acids (TVFA) concentration increased from 0.51 to 5.90 g-COD/L, with the predominant VFAs changing from acetate to propionate, limiting methanogenesis. Meanwhile, the stability coefficient decreased to 0.37, leading to decreased CH4 yield and μmax. In addition, the high hydrogen partial pressure caused by high RFS increased the Gibbs free energy by 17 %, aggravating the thermodynamic disadvantages. The abundant methanogens shifted from Methanosaeta to Methanosarcina, which cooperated with a syntrophic partner-Syntrophomonas to ensure the smooth VFAs degradation at RFS of 1/3. These findings provide prima facie insights into the optimization of operational conditions for AD treating organic wastes.

Numerical analysis on the effect of diluted hydrogen fuel by a fixed amount of supplied hydrogen using a quasi-three-dimensional solid oxide fuel cell model

Solid oxide fuel cell (SOFC) has excellent fuel flexibility for various fuels. Despite some drawbacks like storage and transportation, hydrogen stands up as the best fuel for SOFC. Hydrogen fuel is diluted non-reactive gas species before it is supplied to the SOFC. In this study, a quasi-three-dimensional SOFC model with real microstructure is used to analyse the effect of the diluted fuel mixture. The hydrogen fuel is diluted with nitrogen and a small amount of steam. The mole amount of hydrogen within fuel mixtures is kept constant. On the other hand, the air that is supplied to the air channel of the SOFC remains unchanged. It is found that the cell that is supplied with the highest concentration of hydrogen has the highest performance due to its high partial pressure of hydrogen within the fuel mixture. Such a high partial pressure promotes a low anode concentration loss. Also, the cell that is supplied with a low hydrogen concentration is unable to benefit from its high average cell temperature as its performance is drained by the low partial pressure of hydrogen within the fuel mixture.

Feasibility of successive hydrogen and methane production in a single-reactor configuration of batch anaerobic digestion through bioaugmentation and stimulation of hydrogenase activity and direct interspecies electron transfer

Two-stage anaerobic digestion is a promising way to increase the efficiency of decomposition of organic waste. However, spatial separation of stages makes this technology less economically attractive. In this work, we studied a model of two-stage anaerobic digestion with stages separated in time in one reactor. To implement this model, we used a combination of (1) bioaugmentation with a hydrogen-producing Thermoanaerobacterium thermosaccharolyticum SP-H2, resistant to low pH, (2) setting a low initial pH (5.5) to reduce the activity of hydrogenotrophic methanogens, (3) supplementing additives in the form of soluble iron (II) and granular activated carbon (GAC) to stimulate hydrogenase activity and direct interspecies electron transfer (DIET), respectively. For comparison, two methanogenic inoculums with different dominant microbial groups and initial iron concentrations were used. With the simultaneous addition of GAC and iron (II), sequential production of hydrogen and methane was observed for both methanogenic inoculums. Without the addition of GAC, methane formation was practically not observed, which, apparently, indicated the impossibility of syntrophic degradation of acidogenesis products due to the high partial pressure of hydrogen and the absence of conductive material for activation of DIET. Significant differences in hydrogenase activity and the kinetics of hydrogen and methane formation according to the modified Gompertz equation depending on the iron content in the system may indicate the importance of this additive. Further studies should be aimed at determining the optimal initial pH, concentrations of stimulating additives, bioaugmentation and methanogenic cultures, as well as confirming the stability of the proposed single-reactor two-stage anaerobic digestion system in semi-continuous mode.

Thermophilic Water Gas Shift Reaction at High Carbon Monoxide and Hydrogen Partial Pressures in Parageobacillus thermoglucosidasius KP1013

The facultatively anaerobic Parageobacillus thermoglucosidasius oxidizes carbon monoxide to produce hydrogen via the water gas shift (WGS) reaction. In the current work, we examined the influence of carbon monoxide (CO) and hydrogen (H2) on the WGS reaction in the thermophilic P. thermoglucosidasius by cultivating two hydrogenogenic strains under varying CO and H2 compositions. Microbial growth and dynamics of the WGS reaction were monitored by evaluating parameters such as pressure, headspace composition, metabolic intermediates, pH, and optical density. Our analyses revealed that compared to the previously studied P. thermoglucosidasius strains, the strain KP1013 demonstrated higher CO tolerance and improved WGS reaction kinetics. Under anaerobic conditions, the lag phase before the WGS reaction shortened to 8 h, with KP1013 showing no hydrogen-induced product inhibition at hydrogen partial pressures up to 1.25 bar. The observed lack of product inhibition and the reduced lag phase of the WGS reaction support the possibility of establishing an industrial process for biohydrogen production with P. thermoglucosidasius.

High pressure synthesis, physical properties and electronic structure of monovalent iron compound LaFePH

Using high pressure synthesis under high hydrogen partial pressure condition, we synthesized a new analogue of iron-based superconductors LaFePH with a formal iron charge of 1+ and new oxyhydrides LaFePO1−xHx with x ranging 0 ​< ​x ​< ​1. In contrast to the analogous arsenides LaFeAsO1−xHx and isoelectronic Co-oxyphosphide LaCoPO, neither superconducting, magnetic nor structural transitions were observed in LaFePO1−xHx except the already known superconducting transition in x ​= ​0. DFT calculations reveal that the hydride ion substitution for the oxygen site dopes electrons into the Fe-3d and raises the Fermi level, leading to a partial electron transfer from the Fe-3d to La-5d. We attribute the absence of magnetism in LaFePH to the reduced onsite Coulomb interaction in the Fe-3d orbitals due to the expansion of the 3d orbital and the shielding effect of La-5d electrons.

Computational Design of Alloy Nanostructures for Optical Sensing of Hydrogen

Pd nanoalloys show great potential as hysteresis-free, reliable hydrogen sensors. Here, a multiscale modeling approach is employed to determine optimal conditions for optical hydrogen sensing using the Pd–Au–H system. Changes in hydrogen pressure translate to changes in hydrogen content and eventually the optical spectrum. At the single particle level, the shift of the plasmon peak position with hydrogen concentration (i.e., the “optical” sensitivity) is approximately constant at 180 nm/cH for nanodisk diameters of ≳100 nm. For smaller particles, the optical sensitivity is negative and increases with decreasing diameter, due to the emergence of a second peak originating from coupling between a localized surface plasmon and interband transitions. In addition to tracking peak position, the onset of extinction as well as extinction at fixed wavelengths is considered. We carefully compare the simulation results with experimental data and assess the potential sources for discrepancies. Invariably, the results suggest that there is an upper bound for the optical sensitivity that cannot be overcome by engineering composition and/or geometry. While the alloy composition has a limited impact on optical sensitivity, it can strongly affect H uptake and consequently the “thermodynamic” sensitivity and the detection limit. Here, it is shown how the latter can be improved by compositional engineering and even substantially enhanced via the formation of an ordered phase that can be synthesized at higher hydrogen partial pressures.

Comparative Analysis of Brucepastera parasyntrophica gen. nov., sp. nov. and Teretinema zuelzerae gen. nov., comb. nov. (Treponemataceae) Reveals the Importance of Interspecies Hydrogen Transfer in the Energy Metabolism of Spirochetes.

Most members of the family Treponemataceae (Spirochaetales) are associated with vertebrate hosts. However, a diverse clade of uncultured, putatively free-living treponemes comprising several genus-level lineages is present in other anoxic environments. The only cultivated representative to date is Treponema zuelzerae, isolated from freshwater mud. Here, we describe the isolation of strain RmG11 from the intestinal tract of cockroaches. The strain represents a novel genus-level lineage of Treponemataceae and is metabolically distinct from T. zuelzerae. While T. zuelzerae grows well on various sugars, forming acetate and H2 as major fermentation products, strain RmG11 grew poorly on glucose, maltose, and starch, forming mainly ethanol and only small amounts of acetate and H2. In contrast to the growth of T. zuelzerae, that of strain RmG11 was strongly inhibited at high H2 partial pressures but improved considerably when H2 was removed from the headspace. Cocultures of strain RmG11 with the H2-consuming Methanospirillum hungatei produced acetate and methane but no ethanol. Comparative genomic analysis revealed that strain RmG11 possesses only a single, electron-confurcating hydrogenase that forms H2 from NADH and reduced ferredoxin, whereas T. zuelzerae also possesses a second, ferredoxin-dependent hydrogenase that allows the thermodynamically more favorable formation of H2 from ferredoxin via the Rnf complex. In addition, we found that T. zuelzerae utilizes xylan and possesses the genomic potential to degrade other plant polysaccharides. Based on phenotypic and phylogenomic evidence, we describe strain RmG11 as Brucepastera parasyntrophica gen. nov., sp. nov. and Treponema zuelzerae as Teretinema zuelzerae gen. nov., comb. nov. IMPORTANCE Spirochetes are widely distributed in various anoxic environments and commonly form molecular hydrogen as a major fermentation product. Here, we show that two closely related members of the family Treponemataceae differ strongly in their sensitivity to high hydrogen partial pressure, and we explain the metabolic mechanisms that cause these differences by comparative genome analysis. We demonstrate a strong boost in the growth of the hydrogen-sensitive strain and a shift in its fermentation products to acetate during cocultivation with a H2-utilizing methanogen. Our results add a hitherto unrecognized facet to the fermentative metabolism of spirochetes and also underscore the importance of interspecies hydrogen transfer in not-obligately-syntrophic interactions among fermentative and hydrogenotrophic guilds in anoxic environments.

New insights into the mechanisms underlying biochar-assisted sustained high-efficient co-digestion: Reducing thermodynamic constraints and enhancing extracellular electron transfer flux

To clarify the roles of biochar in the anaerobic co-digestion of waste activated sludge (WAS) and food waste (FW), batch tests were conducted coupled with thermodynamics, extracellular electron transfer flux and microbial community analysis. Compared with the control group, biochar significantly facilitated the co-digestion at three periods, but its sustainable facilitation was mainly in the syntrophic methanogenesis of volatile fatty acids (VFAs). The thermodynamic analysis confirmed that biochar could alleviate limitations imposed by high hydrogen partial pressure during interspecies hydrogen transfer (IHT), the thermodynamic windows was expanded 137% and 92% in the syntrophic methanogenesis of acetate and propionate, respectively. Meanwhile, due to the redox capacity of biochar (4.85 and 0.35 μmol e−/g biochar), the equivalent current of direct interspecies electron transfer (DIET) flux for syntrophic methanogenesis of acetate and propionate obtained were 1.0 × 10−4 A and 0.9 × 10−4 A, which were 108 times than that of IHT. It should be noticed that the functional microorganisms like Methanosarcina which could participate DIET were only enriched on the surface of biochar, the dominant Methanothermobacter in suspended sludge probably indicate IHT was still the main pathway for syntrophic methanogenesis. Nevertheless, the DIET triggered by the redox-active moieties on the surface of biochar and the enhanced IHT by alleviating thermodynamic restrictions, promoted the syntrophic methanogenesis synergistically.

Nickel Foam Promotes Syntrophic Metabolism of Propionate and Butyrate in Anaerobic Digestion.

Enhanced interspecies electron transfer (IET) among symbiotic microorganisms is an effective method to increase the rate of methane (CH4) production in anaerobic digestion. Direct interspecies electron transfer (DIET), which does not involve dissolved redox media, is considered an alternative and superior method to enhance methane production by interspecific hydrogen (H2) transfer (IHT). In this study, nickel foam was built into a semicontinuous anaerobic reactor to investigate its effect on the metabolism of propionate and butyrate. Both increased the average yield of CH4 in anaerobic digestion by 18.1 and 15.9%, respectively. Analysis of bacterial and archaeal communities showed that the addition of nickel foam could increase the relative abundance of microbial communities involved in DIET and could increase the diversity of microorganisms in the reactor. Moreover, the anaerobic digestion performance of the nickel foam reactor was good at high hydrogen partial pressure.

Efficient water splitting through solid oxide electrolysis cells with a new hydrogen electrode derived from A-site cation-deficient La0.4Sr0.55Co0.2Fe0.6Nb0.2O3-δ perovskite

Steam splitting using solid oxide electrolysis cells (SOECs) is highly attractive for mass production of high-purity hydrogen, while its economic competitiveness strongly relies on the availability of low-cost, active and stable hydrogen electrodes. Here, we report an A-site cation-deficient La0.4Sr0.55Co0.2Fe0.6Nb0.2O3-δ (LSCFN55) perovskite is such a hydrogen electrode for SOEC, exhibiting a high electrolysis current density of 0.956 A/cm2 with an applied voltage of 1.3 V at 850 °C and good stability in a high humidity and hydrogen partial pressure environment. The introduction of A-site cation deficiency into the perovskite oxide lattice of LSCFN55 promotes the exsolution of partial cobalt and iron from the oxide bulk with the formation of Co2Fe alloy nanoparticles that decorate the surface of perovskite main phase, simultaneously SrO is segregated to form nanocomposites with the alloy. The outstanding electro-catalytic activity of alloy nanoparticles, the favorable water adsorption capability of SrO, the high oxygen-ion conductivity of the perovskite main phase, and the improved electronic conductivity of the material, cooperatively contribute to the superior performance of the electrode. The strong interaction between the alloy nanoparticles and the perovskite substrate effectively suppresses the sintering of the nanoparticles while the SrO phase protects the alloy nanoparticles from oxidation, both then contribute to the high operating stability of the electrode.

Insight into hydrostatic pressure effects on diffusible hydrogen content in wet welding joints using in-situ X-ray imaging method

In this study, a special phenomenon of gas evolution in the metal droplet and melt pool during underwater wet welding was investigated by in-situ imaging method in a simulated deep-water environment. In general, the dissolved hydrogen escaped from molten droplet and molten pool in the form of bubbles during molten metal solidification. As the increase of hydrostatic pressure, the gas cannot expand enough to burst the droplet and release gas, but instead of entering into molten pool again. The combinations of the internal pressure in the bubble and hydrogen-rich atmosphere induced by welding arc resulted in that the melt pool has been subjected to dual influences. The diffusible hydrogen content in the deposited metal significantly increased from 23.3 to 66.3 ml/100 g with increasing the water depth to 150 m, which was related to the high hydrogen partial pressure and the rapid solidification rate of molten metal.

Isolation of an Obligate Mixotrophic Methanogen That Represents the Major Population in Thermophilic Fixed-Bed Anaerobic Digesters.

Methanothermobacter Met2 is a metagenome-assembled genome (MAG) that encodes a putative mixotrophic methanogen constituting the major populations in thermophilic fixed-bed anaerobic digesters. In order to characterize its physiology, the present work isolated an archaeon (strain Met2-1) that represents Met2-type methanogens by using a combination of enrichments under a nitrogen atmosphere, colony formation on solid media and limiting dilution under high partial pressures of hydrogen. Strain Met2-1 utilizes hydrogen and carbon dioxide for methanogenesis, while the growth is observed only when culture media are additionally supplemented with acetate. It does not grow on acetate in the absence of hydrogen. The results demonstrate that Methanothermobacter sp. strain Met2-1 is a novel methanogen that exhibits obligate mixotrophy.

Biohydrogen production from winery effluents: control of the homoacetogenesis through the headspace gas recirculation

AbstractBACKGROUNDFermentative hydrogen production has an inherent limitation caused by hydrogen‐consuming metabolic pathways such as homoacetogenesis related to high hydrogen partial pressures. In this study, a strategy based on recirculating the headspace gas was applied to increase the hydrogen release from the liquid to the gas phase in an upflow anaerobic sludge blanket(UASB) reactor fed with winery effluents. The influence of the gas upflow recirculation velocity on hydrogen production, hydrogen consumption by homoacetogenesis, and microbial community structure was evaluated.RESULTSUnder the control condition (only liquid recirculation), the hydrogen productivity was as much as 22 mL H2 L−1 h−1. Conversely, the hydrogen productivity increased up to 62 mL H2 L−1 h−1 when the reactor was operated with an upflow gas recirculation velocity of 28.6 m d−1. The increase in mass transfer, due to the gas recirculation, produces a decrease (up to 70%) in the hydrogen consumption rate associated with homoacetogenesis. High‐throughput 16s rDNA sequencing characterization showed that the gas recirculation strategy promoted the development of hydrogen‐producing microorganisms related to Megasphaera elsdenii and decreased the abundance of hydrogen‐consuming bacteria related to Clostridium carboxidivorans and C. ljungdahlii.CONCLUSIONThe results indicated that headspace recirculation at gas upflow velocities higher than 17.8 m d−1 increased the hydrogen production rate concomitantly with the reduction of both the homoacetogenic activity and the abundance of H2‐consuming bacteria. The study demonstrated that headspace recirculation could be a promising way to control homoacetogenesis, and therefore, to increase the biohydrogen productivity from complex substrates such as winery effluents. © 2019 Society of Chemical Industry

Effective low-temperature hydrogenolysis of lignin using carbon-supported ruthenium and formic acid as reducing agent

Herein, we report that re-condensation of lignin fragments after high temperature and hydrogen partial pressure treatment of lignin could be effectively avoided if the Cα-OH in the lignin are pre-oxidized to Cα = O. The pre-oxidized lignin was depolymerized into bio-oil through formylation-elimination-hydrogenolysis using carbon-supported ruthenium as a catalyst, and formic acid (FA) as an in-situ hydrogen source in methanol. Bio-oil of 41 wt% with a low average molecular weight of 690 Da, including 8.24 wt% monomers, was obtained at 110 °C after 24 h of reaction. In contrast to lignin, the hydrogen content in the obtained bio-oil significant increased and the oxygen content reduced, leading to a higher heating value (HHV) of 31 MJ/kg.

Reversibility of hydrolysis inhibition at high hydrogen partial pressure in dry anaerobic digestion processes fed with wheat straw and inoculated with anaerobic granular sludge

In dry anaerobic digestion (AD), methanogenic performances are lowered by high solid contents. Low performances are often caused by a decrease of the gas-liquid transfer kinetics leading to local accumulation of inhibitory by-products. Hydrogen was previously identified as an inhibitor of hydrolytic and acetogenic microbial activities in dry AD. CO2 is also generated but its impact on the microbial activity remains unknown. In this study, the reversibility of dry AD inhibition at high H2 partial pressure (PH2 of 1 bar) was investigated by adding CO2 (400 mbars) after 11 and 18 days of methanogenesis inhibition, in an AD process operated at 25% TS, using wheat straw as substrate and inoculated with anaerobic granular sludge. As soon as CO2 was added, the methanogenic activity rapidly recovered within 3 days, from 0.41 ± 0.1 to 3.77 ± 0.8 and then 2.25 ± 0.3, likely through the hydrogenotrophic pathway followed by the acetoclastic pathway, respectively. This result was confirmed by the high abundance of Methanomicrobiales (83%) and the emergence of Methanosarcinales sp (up to 17%) within the methanogenic community. Furthermore, the recovery kinetics were impacted by the duration of the inhibition period suggesting a different impact of the high PH2 on hydrogenotrophic and acetoclastic methanogens.

Y2O3-Inserted Co-Pd/zeolite catalysts for reductive amination of polypropylene glycol

Cobalt-based catalysts having different base strengths were prepared by controlling the amount of yttrium oxide (Y2O3). These catalysts were used for the facile one-pot synthesis of polyetheramine (PEA) from polypropylene glycol (PPG) through reductive amination. It is noticed that high hydrogen partial pressures up to 40 bar inhibit the formation of cobalt nitride and lead to a high PEA yield although it has been known that dehydrogenation from alcohol to ketone is the rate-determining step. The Y2O3-inserted Co-Pd/Molecular sieve13X catalyst also showed high activity toward PEA even at low hydrogen partial pressure. Y2O3 played a crucial role in giving basicity to the catalyst, which not only prevents the formation of cobalt nitride but also promotes hydrogenation of imine to amine at a wide range of H2 pressure. Thus Y2O3 inserted Co-Pd/Molecular sieve 13X provides unique performance toward enhancing the PEA yield while suppressing the catalyst deactivation caused by the cobalt nitride formation.

Theoretical Study on the Hydrogenation Mechanisms of Model Compounds of Heavy Oil in a Plasma-Driven Catalytic System

Heavy oil will likely dominate the future energy market. Nevertheless, processing heavy oils using conventional technologies has to face the problems of high hydrogen partial pressure and catalyst deactivation. Our previous work reported a novel method to upgrade heavy oil using hydrogen non-thermal plasma under atmospheric pressure without a catalyst. However, the plasma-driven catalytic hydrogenation mechanism is still ambiguous. In this work, we investigated the intrinsic mechanism of hydrogenating heavy oil in a plasma-driven catalytic system based on density functional theory (DFT) calculations. Two model compounds, toluene and 4-ethyltoluene have been chosen to represent heavy oil, respectively; a hydrogen atom and ethyl radical have been chosen to represent the high reactivity species generated by plasma, respectively. DFT study results indicate that toluene is easily hydrogenated by hydrogen atoms, but hard to hydrocrack into benzene and methane; small radicals, like ethyl radicals, are prone to attach to the carbon atoms in aromatic rings, which is interpreted as the reason for the increased substitution index of trap oil. The present work investigated the hydrogenation mechanism of heavy oil in a plasma-driven catalytic system, both thermodynamically and kinetically.

Geochemical Effects of Millimolar Hydrogen Concentrations in Groundwater: An Experimental Study in the Context of Subsurface Hydrogen Storage.

Hydrogen storage in geological formations is one of the most promising technologies for balancing major fluctuations between energy supply from renewable energy plants and energy demand of customers. If hydrogen gas is stored in a porous medium or if it leaks into a shallow aquifer, redox reactions can oxidize hydrogen and reduce electron acceptors such as nitrate, FeIII and MnIV (hydro)oxides, sulfate, and carbonate. These reactions are of key significance, because they can cause unintentional losses in hydrogen stored in porous media and they also can cause unwanted changes in the composition of protected potable groundwater. To represent an aquifer environment enclosing a hydrogen plume, laboratory experiments using sediment-filled columns were constructed and percolated by groundwater in equilibrium with high (2-15 bar) hydrogen partial pressures. Here, we show that hydrogen is consumed rapidly in these experiments via sulfate reduction (18 ± 5 μM h-1) and acetate production (0.030 ± 0.006 h-1), while no methanogenesis took place. The observed reaction rates were independent from the partial pressure of hydrogen and hydrogen consumption only stopped in supplemental microcosm experiments where salinity was increased above 35 g L-1. The outcomes presented here are implemented for planning the sustainable use of the subsurface space within the ANGUS+ project.

Tritium permeability measurement in hydrogen-tritium system

Understanding of thermodynamic equilibria of multi-components hydrogen isotopes is required to accurately measure tritium permeability at the expected low tritium partial pressure and non-negligible high hydrogen partial pressure in a fusion blanket system. A gas-driven tritium permeation system that is capable of independently controlling hydrogen and tritium partial pressures was developed at Idaho National Laboratory to accurately measure low partial pressure tritium permeability. The thermodynamic equilibria for hydrogen (H) – tritium (T) permeation through metal are discussed to accurately measure tritium permeability, and the experimental conditions required for evaluating tritium permeability in H-T system are presented.

A High-Performance Nanoreactor for Carbon–Oxygen Bond Hydrogenation Reactions Achieved by the Morphology of Nanotube-Assembled Hollow Spheres

Hydrogenation of carbon–oxygen bonds is extensively used in organic synthesis. However, a high partial pressure of hydrogen or the presence of excess hydrogen is usually essential to achieve favorable conversions. In addition, because most hydrogenations are consecutive reactions, the selectivity is difficult to manipulate, leading to an unsatisfactory distribution of products. Herein, a copper silicate nanoreactor with a nanotube-assembled hollow sphere (NAHS) hierarchical structure is proposed as a solution to these problems. In the case of dimethyl oxalate (DMO) hydrogenation, the NAHS nanoreactor achieves remarkable catalytic activity (the yield of ethylene glycol is 95%) and stability (>300 h) when the H2/DMO molar ratio is as low as 20 (in comparison to typical values of 80–200). For further investigation, nanotubes and lamellar-shaped Cu/SiO2 catalysts with similar surface areas of active sites of NAHSs were investigated as contrasts. By a combination of high-pressure hydrogen adsorption and Monte ...