Partial Hydrogen Research Articles

Hydrogen loss from pyroxene within granulite xenoliths at Damaping, North China craton

The preservation of original water contents within nominally anhydrous minerals is essential for understanding the deep Earth’s water budget. Here we present a comprehensive analysis of mineral chemistry and Fourier transform infrared spectroscopy on 15 lower-crustal granulite xenoliths collected from Damaping in the North China craton. Our analyses reveal that the orthopyroxene grains from two samples exhibit hydrogen-deficient rims, suggestive of hydrogen loss. Drawing upon experimentally determined hydrogen diffusivity in pyroxene, we propose that clinopyroxene, despite the absence of evident hydrogen zoning, may have likewise undergone partial hydrogen depletion. Our findings call into question the conventional belief that hydrogen concentrations in pyroxene are faithful proxies for the original water content in the continental lower crust. We attribute the loss of hydrogen in pyroxene to magmatic outgassing, most likely occurring during the surface flow stage. Such a process could partially explain the relatively lower water contents documented in the granulite xenoliths when compared to those found in the Precambrian granulite terranes from the North China craton. Considering recent studies on mantle xenoliths, it becomes evident that both basalt-hosted mantle and lower-crustal xenoliths may have experienced partial loss of their original water contents within the deep Earth.

Influence of PVA resin and cross-linking agent on the structure and properties of semi-refined carrageenan-based packaging films

For the high content of carrageenan in some seaweed and the low cost and easy availability of semi refined carrageenan (SRC), SRC resin powder was selected as our research object. Due to its water solubility, a solution casting method was adopted to form film, hoping to prepare food packaging materials that partially replace petroleum based resin. The pure SRC resin casting film is very brittle and cannot be formed. Therefore, 40wt% glycerol was added to the formula to plasticize and improve the flexibility and demoulding ability of SRC. The plasticized SRC film still has limitations. Soluble petroleum based polymer poly(vinyl alcohol) (PVA) resin was used as a blending modifier, cinnamaldehyde (CIN) as a crosslinking agent for acetal reaction with hydroxyl groups, boric acid (BA) as a provider of acidic environment and an auxiliary agent for generating partial hydrogen bonds with hydroxyl groups. Eight experimental research formulas were designed and FTIR, XRD, thermodynamic properties and mechanical properties of the modified films were analyzed. Both microscopic and macroscopic analyses have shown that under the acidic conditions of BA, CIN undergoes an acetal reaction with SRC and PVA, therefore mass ratio of the formula that SRC/glycerol/PVA/CIN/BA is 100/40/33.3/10/10, the film has the best tensile strength of 34.85Mpa, higher than that of other films. It has been proven that CIN does indeed act as a crosslinking agent in the formula, forming a network structure that enhances it.

Manufacturing Process of Low‐Contamination Titanium Foam as Implant Material for Cranioplasty Based on Replica Technique

The article investigates the development of a manufacturing route for highly porous titanium foams suitable for craniofacial surgery applications, particularly in cranioplasties. The study focuses on the polyurethane replication method for foam production and emphasizes reducing residual gas content, as it significantly affects the mechanical properties and suitability for approval of the foams. Various factors such as starting materials, solvent debinding, heating schedules, and hydrogen atmosphere are analyzed for their impact on residual gas content. It is shown that significant reductions in residual gas content can only be achieved by reworking each step of the process. A combination of initial solvent debinding of the PU template with dimethyl sulphoxide, reduction of suspension additives, use of coarser Gd. 1 powders, and an integrated debinding and sintering process under partial hydrogen atmosphere achieves a significant reduction in residual gas content. This way, the potential for producing titanium foams that comply with relevant standards for craniofacial implants is demonstrated.

Effects of Hybrid POSS Nanoparticles on the Properties of Thermoplastic Elastomer-Toughened Polyamide 6.

In this study, polyamide 6 (PA6)/thermoplastic elastomer (TPE) blends were prepared to decrease the notch sensitivity of PA6 for automotive applications, and the morphological, rheological, mechanical, and thermal properties of PA6/TPE blends, which are partially miscible or immiscible depending on the TPE ratio, were significantly improved in the existence of polyhedral oligomeric silsesquioxane (POSS) nanoparticles with multiple reactive epoxy groups as compatibilizers. An unstable phase morphology was obtained with the addition of TPE into PA6 without POSS nanoparticles, whereas interfacial interactions between phases in the presence of POSS were enhanced as a result of a significant decrease in the average particle size from 1.39 to 0.41 μm. The complex viscosity value of the 70PA6/30TPE blend, which was 20 kPa/s-1 at 0.1 rad/s angular frequency, reached 380 kPa/s-1 with the addition of POSS due to the formation of long chains by the generation of graft and/or block copolymers, which resulted in a 65% increase in Young's modulus value. Most notably, the Izod impact strength of pure PA6, which was 10 kJ/m2, increased by 290% with the incorporation of POSS. It was confirmed by FTIR analysis that the reactive multiple epoxy groups of MultEpPOSS and EPPOSS nanoparticles react with the proper groups of PA6 and/or TPE, and also, a partial hydrogen bonding interaction occurs between PA6-TPE from the shifting of N-H and carbonyl peaks. In conclusion, it can be suggested that POSS nanoparticles can serve as highly effective compatibilizers for PA6/TPE blends and have potential commercial applications, especially in the automotive sector.

Application of MOFs in Hydrogen Storage

This research analyzes the current energy problems and environmental problems and proposes to use hydrogen energy as a clean alternative energy source, which has high energy density and less pollution. After comparing the advantages and disadvantages of various hydrogen storage solutions, metal-organic frameworks (MOFs) are selected as the storage and transportation medium because of its large capacity, favourable reversibility, appropriate reaction conditions and relatively low density. The hydrogen storage mechanism of MOFs and the factors affecting its hydrogen storage capacity are introduced and discuss some methods to improve the storage features of MOFs. Three promising, MOFs, MOF-5, MIL-101 and NU-1501, are listed and their storage performance and specific structure are introduced. The current problems in the application and processing of partial hydrogen storage MOFs are proposed, and some feasible solutions and processing methods are introduced. Finally, the application prospects of MOFs are prospected and suitable development directions are proposed, which will be helpful for future research.

Enhanced hydrogen embrittlement of steel by the premature hydrogen dissociation with the increasing inert gas pressure in hydrogen-containing mixtures

Regarding hydrogen embrittlement (HE) in the mixtures of hydrogen and inert gas, the results were understood mainly based on the partial hydrogen gas pressure. On the other hand, the effect of the total gas pressure has not been fully investigated. In this study, fatigue crack growth rate (FCGR) tests were conducted in high-purity hydrogen gas at different gas pressures. Also, the FCGR tests were conducted in hydrogen and nitrogen mixtures at different total gas pressures. The hydrogen partial pressure in the mixture was the same as the high-purity hydrogen. This was the first time that acceleration of the FCGR in the mixtures compared to that in the high-purity hydrogen was observed. To elucidate the mechanism of the enhanced HE in the mixtures, hydrogen permeation and hydrogen desorption experiments were carried out. Based on the results of these tests, the acceleration of the FCGR in the mixtures could be interpreted by the fast hydrogen entry rate, which may result in a higher local hydrogen concentration near the crack tip during a limited time. Density functional theory (DFT) calculations were performed to consider the total gas pressure effect on an atomic scale. The thrust force of other gas molecules in the mixtures made the hydrogen molecules enter the potential field of the iron surface sooner, advancing the dissociation of the hydrogen. This will increase the surface concentration of the hydrogen atoms.

Deciphering Reversible Homogeneous Catalysis of the Electrochemical H2 Evolution and Oxidation: Role of Proton Relays and Local Concentration Effects**

AbstractNickel bisdiphosphine complexes bearing pendant amines form a unique series of catalysts (so‐called DuBois’ catalysts) capable of bidirectional/reversible electrocatalytic oxidation and production of dihydrogen. This unique behaviour is directly linked to the presence of proton relays installed close to the metal center. We report here for the arginine derivative [Ni(P2CyN2Arg)2]6+ on a mechanistic model and its kinetic treatment that may apply to all DuBois’ catalysts and show that it allows for a good fit of experimental data measured at different pH values, catalyst concentrations and partial hydrogen pressures. The bidirectionality of catalysis results from balanced equilibria related to hydrogen uptake/evolution on one side and (metal)‐hydride installation/capture on the other side, both controlled by concentration effects resulting from the presence of proton relays and connected by two square schemes corresponding to proton‐coupled electron transfer processes. We show that the catalytic bias is controlled by the kinetic of the H2 uptake/evolution step. Reversibility does not require that the energy landscape be flat, with redox transitions occurring at potentials up to 250 mV away for the equilibrium potential, although such large deviations from a flat energy landscape can negatively impacts the rate of catalysis when coupled with slow interfacial electron transfer kinetics.

Deciphering Reversible Homogeneous Catalysis of the Electrochemical H2 Evolution and Oxidation: Role of Proton Relays and Local Concentration Effects.

Nickel bisdiphosphine complexes bearing pendant amines form a unique series of catalysts (so-called DuBois' catalysts) capable of bidirectional/reversible electrocatalytic oxidation and production of dihydrogen. This unique behaviour is directly linked to the presence of proton relays installed close to the metal center. We report here for the arginine derivative [Ni(P2 Cy N2 Arg )2 ]6+ on a mechanistic model and its kinetic treatment that may apply to all DuBois' catalysts and show that it allows for a good fit of experimental data measured at different pH values, catalyst concentrations and partial hydrogen pressures. The bidirectionality of catalysis results from balanced equilibria related to hydrogen uptake/evolution on one side and (metal)-hydride installation/capture on the other side, both controlled by concentration effects resulting from the presence of proton relays and connected by two square schemes corresponding to proton-coupled electron transfer processes. We show that the catalytic bias is controlled by the kinetic of the H2 uptake/evolution step. Reversibility does not require that the energy landscape be flat, with redox transitions occurring at potentials up to 250 mV away for the equilibrium potential, although such large deviations from a flat energy landscape can negatively impacts the rate of catalysis when coupled with slow interfacial electron transfer kinetics.

Crucial role of Ce particles during initial hydrogen absorption of AB-type hydrogen storage alloys

The hydrogen storage behavior and the microstructural features of AB-type Ti50Fe48V2 hydrogen storage alloys containing a small amount of cerium (Ce) were investigated to understand the effect of Ce addition during initial hydrogen absorption. The initial hydrogen absorption kinetics of the alloys improved significantly at room temperature with Ce addition, which exhibited no significant influence on the pressure-composition isotherms for hydrogen absorption and desorption. Fine spherical particles containing Ce, which were determined to be γ-Ce mixed with cerium oxide, were dispersed in the ordered body-centered cubic TiFe matrix. During the early stage of hydrogen absorption, small cracks were initiated around the Ce particles, likely caused by the volume expansion owing to the formation of ε-CeH2. Subsequently, many large cracks, believed to have formed owing to the hydrogenation of the TiFe matrix, propagated during further hydrogen absorption. Therefore, these Ce particles appear to play a crucial role by providing starting points for the initial hydrogenation, with this mechanism explaining the significant increase in the primary hydrogen absorption kinetics after Ce addition. Notably, some small pits were observed after partial hydrogen absorption, possibly attributed to the hydrogenation of Ce particles underneath the alloy surfaces.

Towards Quantum-Chemical Level Calculations of SARS-CoV-2 Spike Protein Variants of Concern by First Principles Density Functional Theory.

The spike protein (S-protein) is a crucial part of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with its many domains responsible for binding, fusion, and host cell entry. In this review we use the density functional theory (DFT) calculations to analyze the atomic-scale interactions and investigate the consequences of mutations in S-protein domains. We specifically describe the key amino acids and functions of each domain, which are essential for structural stability as well as recognition and fusion processes with the host cell; in addition, we speculate on how mutations affect these properties. Such unprecedented large-scale ab initio calculations, with up to 5000 atoms in the system, are based on the novel concept of amino acid-amino acid-bond pair unit (AABPU) that allows for an alternative description of proteins, providing valuable information on partial charge, interatomic bonding and hydrogen bond (HB) formation. In general, our results show that the S-protein mutations for different variants foster an increased positive partial charge, alter the interatomic interactions, and disrupt the HB networks. We conclude by outlining a roadmap for future computational research of biomolecular virus-related systems.

Measurements of breakdown voltage and critical current density in a water electrolysis varying area and shape of working electrode

This work investigated the influence of the working electrode on the partial contact glow discharge electrolysis (CGDE) using disk and rectangle shaped cathodes in a water electrolysis. The breakdown voltage and the critical current density (CCD), which are due to the initial formation of partial hydrogen film were measured together with in situ observation of hydrogen bubble behaviors. As the cathode area increased, the breakdown voltage increased regardless of shape of the cathode as the active area increased. By contrast, the CCD decreased at different rates depending on the cathode shape. The formation of the hydrogen bubble layer adjacent to the cathode surface elucidates this result. In case of the disk, the thickness of the bubble layer remarkably increased with increased cathode area, resulting in the CCD decrease since the partial hydrogen film was readily formed, while a trivial change of the bubble layer was observed in case of the rectangle. Thus, a milder decreasing trend of CCD was measured in case of rectangle cases than that of disk cases. The wetted perimeter per area (P/A) was introduced as a more generalized parameter affecting the CCD.

Hyphenated liquid chromatography - diode array detection - charged aerosol detection - high resolution - multistage mass spectrometry with online hydrogen/deuterium exchange: One stop solution for pharmaceutical impurity profiling

Hyphenation of different analytical techniques has always been advantageous in structural characterization as it saves time, money and resources. In the pharmaceutical sector, chromatography-based impurity profiling, including identification, characterization, and quantification in drug substances or finished products, is of utmost importance to comply with quality, patient safety and regulatory requirements. These impurities are monitored using LC-UV/DAD and identified and/or characterized using HRMS and MS/MS. LC analysis usually yields the area percent purity of the targeted peak, however, this is not sufficient for pharmaceutical purposes; where the regulatory requirement is to report impurities in percent weight by weight. Unfortunately, the non-availability of impurity standards and relative response factors at an early stage of drug development, risks the product quality due to the inability of the method to differentiate percent purity, and percent weight by weight. Hence, there is a need for a distinctive way of determining the relative response factor. In the current study, a unique hyphenation has been employed by integrating LC with DAD, CAD, and HRMSn with hydrogen-deuterium exchange. The LC flow, post-DAD detection has been diverted to CAD with an inverse gradient for relative response factor determination and MS Orbitrap for exact mass, and MSn fragmentation. A separate infusion pump has been incorporated to infuse D2O on a need basis, which can perform partial hydrogen deuterium exchange for determining the number of labile hydrogens in the impurity structure. This hyphenation has been validated with four model compounds and a total of nineteen chromatographic peaks. The technique provides ample information for their qualitative analysis along with percent weight-by-weight values, which fulfils the regulatory requirements and can be used as one-stop solution for impurity profiling.

Evaluation of the difference in adsorption of sodium alginate as an efficient and non-toxic arsenopyrite depressant on the surface of arsenopyrite and chalcopyrite

In this study, sodium alginate (SA) was used as a selective depressant, combined with potassium permanganate oxidizing pretreatment, which will benefit the separation of chalcopyrite and arsenopyrite. Flotation experiments were conducted with chalcopyrite and arsenopyrite after treatment with SA and/or potassium permanganate, and the possible complexes formed by SA on the mineral surface were theoretically analyzed. SA was more easily adsorbed on the arsenopyrite surface after potassium permanganate pretreatment. The maximum depressant effect of arsenopyrite was observed following treatment with 62.5 mg/L of potassium permanganate and 1000 mg/L of SA with flotation at pH 11. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that the adsorption of SA on the chalcopyrite and arsenopyrite surfaces was dominated by chemisorption. Theoretical analyses confirmed that the adsorption strength of SA on the arsenopyrite surface was higher than that on chalcopyrite. Furthermore, the intermolecular interactions between SA and the possible complexes formed were investigated using interaction region indicator function tools. The results of this investigation revealed that SA adsorption on chalcopyrite and arsenopyrite surfaces is controlled by partial covalent hydrogen bonds and other weak interactions. Therefore, SA can be used as a promising green depressant for the separation of arsenopyrite during chalcopyrite flotation.

A partial element stage cut electrochemical hydrogen pump model for hydrogen separation and compression

In this work, a partial element stage cut electrochemical hydrogen pump (EHP) model for the separation of multiple H2-contaning gases and hydrogen compression was proposed to realize fast prediction of the EHP’s performance (nearly 10 s for one IEHP–E point). Three real factors, namely, anode impurity diffusion, hydrogen back-diffusion and anode catalyst deactivation, were embedded into the model. The model accuracy was verified for four aspects (current density distribution, polarization curve, hydrogen recovery and purity) under four feedstock systems (H2/N2, H2/CH4, H2/He and H2/CO2) and a wide cathode pressure range of 0.1–1.0 MPa. The model had good accuracy (R2≥0.90). Benefiting from the embedding of the real factor of the hydrogen back-diffusion, hydrogen back-diffusion ratio was simulated accurately under a wide cathode pressure range of 0.13–20 MPa. By considering the dual- effect on current density caused by PEM proton conduction and GDL mass transformation resistance, optimal region of hydrogen recovery rate, energy efficiency and hydrogen purity can be simulated. About 64 % and 53 % for hydrogen recovery rate and energy efficiency can be achieved under low hydrogen feedstock of 20 mol%. In summary, it is promising to realize the “hydrogen economy” in the future under the utilization of EHP.

Analysis of TihxOy Films Produced by Physical Vapor Deposition Method

For decades, partially oxidized hydrides were commonly considered as undesirably contaminated phases and were avoided by scientists. Nevertheless, more recently, it was realized that in some hydrides and oxides, partial substitution of dissimilar H− and O2− anions allows one to obtain unique optical and electrical properties that might have appealing applications in commercial products. It was determined that specific properties of so called oxyhydride materials strongly depend on the used synthesis methods; therefore, there is a great interest in exploring various variants of oxyhydride formation. In the current study, TiHxOy films were deposited by a reactive magnetron sputtering process in Ar-O2-H2 gas mixtures. Color, transparency and crystal phase composition of the films coherently reacted to the Ar:O2:H2 gas ratio. Namely, the rise in partial hydrogen pressure promoted the formation of anatase phase TiO2 structure and darkening of the films. Interestingly, this had only minimal impact on the band gap values, but had a relatively strong negative effect on the photocatalytic activity of the films. The unaccustomed results stressed the difference between the partially reduced TiO2 with a significant amount of oxygen vacancies and synthesized TiHxOy films where some O2− ions are implicitly substituted by H− ions.

Facile fabrication of self-healing silicone-based poly(urea-thiourea)/tannic acid composite for anti-biofouling

• A novel composite of silicone-based poly(urea-thiourea) and tannic acid is prepared by a facile method. • The composite presents a tough and highly stretchable performance. • The composite exhibits a fast self-healing property at room temperature in both air and artificial sea water. • The coating based on the composite shows a strong adhesion strength to substrates. • The coating exhibits a good antibacterial property and favorable anti-diatom performance. A novel silicone-based poly(urea-thiourea)/tannic acid composite (PDMS-P(Ua-TUa)-TA) with excellent mechanical, self-healing and antifouling properties is developed. The multiple dynamic hydrogen bonds formed by thiourea groups, urea groups, and tannic acid (TA) molecules ensured a tough elastomer (ultimate strength: 2.47 MPa) with high stretchability (∼1000%). TA molecules as partial hydrogen bonding cross-linking sites interacted rapidly with urea and thiourea groups before the migration of polymer chains, resulting in fast and efficient self-healing. Scratches on the film completely disappeared within 12 min, and the repair efficiency of strength was up to 98.4% within 3 h under ambient condition. Self-healing behavior was also evaluated in artificial seawater and the healing efficiency (HE) was 95.1%. Furthermore, TA uniformly dispersed in the polymer matrix provides good antibacterial and anti-diatom properties, as well as strong adhesion to the substrate (∼2.2 MPa). Laboratory bioassays against marine bacteria adhesion (∼96%, ∼95% and ∼93% reduction for P. sp., E. coli , and S. aureus , respectively) and diatom attachment (∼84% reduction) demonstrated an outstanding antifouling property of the PDMS-P(Ua-TUa)-TA. This work provides a promising pathway towards the development of high-performance silicone-based coatings for marine anti-biofouling.

Using carbonized hybrid FeNPs@ZIF-8 for the sustained release of doxorubicin hydrochloride

Controlling the slow release of drugs in carriers and reducing environmental pollution and damage from antibiotics is important and challenging research. In this paper, a novel composite material of carbonized FeNPs@ZIF-8 (C-Fe3O4 @ZIF-8) was used to load and release doxorubicin hydrochloride (DOX). Compared with conventional ZIFs materials, greatly enhancing the magnetic properties, drug loading capacity and controlled drug release of the carrier agent. Interestingly, by establishing a dual stimulus response system with environmental factors of pH and temperature, results showed release rate of 61.6 % at a pH of 3 and a temperature of 37 °C. In addition, the SEM-EDS results showed that the surface of C-Fe3O4 @ZIF-8 was partially broken but maintained a stable morphology before and after release. Meanwhile the nitrogen absorption desorption curve (BET) and hysteresis loop reveal that C-Fe3O4 @ZIF-8 can maintain a large specific surface area and a magnetization intensity of 12.4 emu g−1 after release. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), on the other hand, reveal the presence of partial ligand and hydrogen bond breaks during the release of DOX from DOX-loaded C-Fe3O4 @ZIF-8. Finally, the release of DOX from C-Fe3O4 @ZIF-8 at different pH and temperature is consistent with the Higuch and Bhaskas models, where the latter dominates and proposes a release mechanism. Therefore, the magnetic composite C-Fe3O4 @ZIF-8 in this study has great potential for DOX to effectively control drug release and targeted cancer therapy.

Vacancy defect assisted enhanced nitrogen fixation in boron nitride nanomaterials

In this investigation, the possibility of employing hexagonal boron nitride nanomaterials (h-BN) as catalysts for nitrogen reduction has been studied using electronic structure calculations. Specifically the role played by the vacancy defects in the h-BN has been studied for the activation of N2 and synthesis of ammonia. The basic hypothesis considered in this investigation is that the coordinatively unsaturated defective sites are highly reactive due to termination of bonds and they can activate N2 efficiently. Both the charge transfer from h-BN flake to N2 molecule and the elongation of NN bond have been chosen as criteria for the evaluation of nitrogen activation. Results show that the N-vacancy defects with coordinatively unsaturated B-atoms facilitate nitrogen activation. Further, findings have revealed that the high reactivity of the vicinal B-atom (open) of vacancy defect is responsible for the undesirable reduction at BN surface. Hence, partial hydrogenation strategy has been adopted to tune the reactivity of the vacancy defects. Results elucidate that, partial hydrogen efficiently controls the activation process of nitrogen, which in turn reduces the overpotential of NRR from 1.80 to 0.24 V. Comprehensive observations from this study demonstrate that experimental development of h-BN catalysts has immense potential for the activation of N2 and ammonia synthesis.

Characterization of the Adsorption Mechanism of Cadmium(II) and Methylene Blue upon Corncobs Activated Carbon

A promising new activated carbon (AC) was produced from corncobs (CCs) by boric acid-based chemical activation to remove methylene blue (MB) as an organic pollutant and cadmium ions (Cd2+) as an inorganic pollutant from aqueous solutions. After the produced activated carbon (CCs-AC) was characterized, the adsorption mechanism of CCs-AC, which is one of the most interesting topics in the literature, was the primarily focus. The possible adsorption mechanisms of Cd2+ and MB on CCs-AC from aqueous solutions are discussed with respect to pH, thermodynamic values, and regeneration parameters. The results show that the adsorption of Cd2+ on CCs-AC was favorable at pH values higher than 4. In contrast, the adsorption process was almost pH-independent for MB. Variation of pH showed that the adsorption of Cd2+ on CCs-AC primarily occurs by electrostatic interaction. However, MB adsorption may also involve π-π dispersion forces and partial hydrogen bonding. The Cd2+ adsorbed on CCs-AC was quantitatively desorbed by HCl, whereas MB was not desorbed quantitatively by any solution. While a temperature increase has a positive effect on the adsorption of both methylene blue and Cd2+, the thermodynamic results show that MB adsorption is primarily chemisorption (ΔH of 24.28 kJ/mole), while Cd2+ adsorption is mostly physisorption (ΔH of 7.20 kJ/mole). Using Langmuir adsorption isotherms, the MB adsorption capacity of CCs-AC, which primarily has a microporous structure, was 0.88 mmol/g, while the Cd2+ adsorption capacity was 1.28 mmol/g.

Characteristics of Co–Ca catalyzed coal hydrogasification in a mixture of H2 and CO2 atmosphere

Coal catalytic hydrogasification (CCHG) is a promising approach for producing substituted natural gas by using pure hydrogen as a gasifying agent. If pure hydrogen could be replaced by cheaper crude gas from the coal gasifier, the economy of CCHG would be significantly improved. However, the composition of crude gas is complicated because in addition to H2, CO, CO2 and H2O are contained in it. To preliminarily investigate the influence of CO2 in the feed gas on CCHG, a mixture of H2 and CO2 with a CO2 concentration of 10% (denoted as H2 + CO2) was used for Co–Ca catalyzed coal hydrogasification at 850 °C and 3 MPa in a fluidized bed reactor. The results showed that the concurrence of coal hydrogasification with CO2 methanation produced CH4 efficiently. The CH4 yield (based on the carbon in coal) increased from 77.4% for pure H2 to 188% for H2 + CO2 within 120 min. More than 90% CO2 in situ conversion and 72.3% coal conversion were achieved. The catalytic effect of the Co–Ca loaded coal considerably improved the CH4 selectivity of CO2 methanation from 43.5% to 82.7%. The forms of Co and Ca in H2 + CO2 were consistent with those in pure hydrogen. The slow coal hydrogasification rate in H2 + CO2 was mainly attributed to the two-fold effects of CO2 methanation: the decrease in the partial hydrogen pressure and the competitive adsorption behavior of H2 and CO (a by-product of CO2 methanation) molecules on the cobalt active surface. This work provides a unique approach for simultaneously realizing the conversion of coal and the utilization of CO2.