Presence Of H2 Gas Research Articles

Efficient conversion of used palm cooking oil into biogasoline over hydrothermally prepared sulfated mesoporous silica loaded with NiMo catalyst

Fossil-based fuels remain a primary global energy source, but their finite and non-renewable nature raises concerns about long-term sustainability. These issues underscore the urgent need for renewable and eco-friendly alternatives such as converting vegetable oil into biofuel. The present work reported biogasoline production from used palm cooking oil catalyzed by sulfated mesoporous silica impregnated with nickel-molybdenum bimetal using the hydrothermal method for both steps. We evaluated the effect of sulfuric acid concentration and metal loading amount on the acidity of the resulting catalysts. Catalysts' performance was assessed through the catalytic cracking and hydrocracking processes with a catalyst-to-feed ratio of 1% at 550°C and an atmospheric pressure. In comparison to mesoporous silica (MS) and sulfated mesoporous silica (SMS-2), along with an increase in acidity, NiMo-impregnated mesoporous silica (NiMo 1/SMS-2) exhibited superior catalytic performance in biogasoline production in the presence of H2 gas, achieving liquid product conversion and gasoline selectivity of 55.9% and 52.37%, respectively. These results are an excellent step for developing biogasoline in a safer process and confirm the capability of mesoporous silica-based catalysts in biofuel production.

High performing chemochromic hydrogen gas sensing using PVP encapsulated Pd: WO3 nanocomposites

This paper reports on a high performing hydrogen (H2) sensing technique that has a great importance in safe operation of H2 including production and storage. The developed H2 sensing nanocomposite is made of polyvinylpyrrolidone (PVP) encapsulated Pd:WO3. The optimized amount of palladium (Pd) nanoparticles expedites achieving eye-readable chemochromic responses in presence of H2 gas, whereas the quasi-reversible property is obtained by the air passivation of PVP. The developed nanocomposite exhibits a high sensitivity and excellent selectivity toward H2 gas. As a result, it shows a rapid color change from brown to bluish-gray with a maximum ΔE value of 40.34 (at 100% H2) in 10 s. The changed color remains visible even after removal of H2 and keeping the samples in air for more than 24 h. More importantly, this quasi-reversible performance with rapid response (10 s) and elongated recovery (> 24 h) is repeatable for multiple cycles, which is achieved for the first time using Pd:WO3. The nanocomposite exhibits long-term stability over 30 days (at ambient condition), as well as performs efficiently at different temperature and humidity conditions. Moreover, the developed nanocomposite can be used as powders, inks, paints, or coatings on different substrates that highlights its efficacy for making multimodal H2 sensing platforms.

Development of High Performance CNTs-Based Sensor for Electrochemical Applications

This work reports the development of a new robust electrode composed of carbon nanotubes (CNTs) for redox potentiometry to determine ascorbic acid. The electrode was fabricated via catalytic chemical vapor deposition (CVD) of ethylene on Ag substrate in the presence of H2 gas at 800 °C. The C2H2:H2 ratio was 75:90 ml/min respectively. The prepared electrode was characterized with SEM, TEM, XRD, XPS, and Raman spectrometry. SEM showed the formation of aligned CNTs. XRD and Raman spectrometry proved the formation of CNTs with a good degree of graphitization and high crystallinity. XPS analysis results showed 80% of SP2 C–C with a small presence of carbonyls and carboxylates, indicating the high perfection of the CNTs formed. CNT/Ag electrode was applied, for the first time, to zero-current potentiometry and was successfully used to determine ascorbic acid in both pure form and in pharmaceutical formula. Ascorbic acid concentrations down to 0.5 mmol/L was determined. Sigmoidal potentiometric curves were obtained and the results were comparable to those obtained from Pt electrode. The CNT/Ag electrode attained fast equilibrium and exhibited good sensitivity and reproducibility. The enhanced sensing efficiency is attributed to the rapid heterogeneous electron transfer and high electrode surface area offered by CNTs grown via CVD. Additionally, the CVD method produced CNT/Ag electrode with strong adhesion of the CNTs layer to the substrate compared to other CNT-based electrodes prepared by casting the CNTs or mixing them with Nafion. This in turn improves the performance and durability. Moreover, unlike the Pt electrode, the CNT on the surface of this electrode may easily be functionalized by immobilizing the desired moieties via various types of strategies to suit different selective routine applications. Figure 1

Hydroformylation-like Reactions Enable Electrochemical Pathways from CO2 to Extended Carbon Chains

Atomically precise active sites on electrode surfaces promise new chemical transformations that simultaneously exploit both the potent physical handle of applied voltage and the highly-tailored reactivity of well-defined active sites. Often, these catalysts have off-electrode analogs in biology or organometallic chemistry, and effectively leveraging these analogies requires an understanding of how catalysis at the active site is perturbed by the complex interplay of electrolyte species and electric fields at electrode interfaces. In this work, we dissect and design two atomically precise catalysts that leverage off-electrode analogies and enable an electrochemical pathway that converts CO2 to extended carbon chains.We show that a new electrified hydroformylation reaction can be used to achieve electrochemical C-C coupling. Hydroformylation is a well-studied thermochemical reaction that performs C-C coupling by appending CO to an olefin in the presence of H2 gas. We mimic homogeneous HFN catalysts on electrode surfaces using single atom-decorated nanoparticles. We show that electrochemistry can be used to circumvent the need to supply H2 as a reactant. Instead, protons, electrons, and CO can be used to hydroformylate a model substrate. Additionally, we study the electrochemical generation of CO, a necessary reactant for hydroformylation, via immobilized cobalt phthalocyanine (CoPc) catalysts. Through collecting kinetic data over a wide range of operating conditions and quantitatively comparing candidate mechanisms, we are able to demonstrate unexpected roles of both the electrolyte and applied potential on the reaction pathway.These studies build towards a more rigorous and quantitative understanding of how the many components of an electrode interface interact with and influence catalysis on atomically precise active sites. It is crucial to carve out this complexity if we wish to effectively import catalysts or design principles from other catalytic contexts onto electrified interfaces.

Pulsed chemical vapor deposition of cobalt and cobalt carbide thin films

Cobalt and cobalt carbide films were successfully fabricated via a simple pulsed chemical vapor deposition (PCVD) technique. The PCVD process employs bis(1,4-di-tert-butyl-1,3-diazadienyl) cobalt as a cobalt precursor. The effect of the reducing agent, H2 gas or H2 plasma, on the chemical composition of the resulting films has been carefully investigated. In the presence of H2 gas, polycrystalline hexagonal close-packed Co was obtained through the thermal decomposition of the Co precursor. When H2 plasma was used as a coreactant, the cobalt carbide was successfully deposited instead. The crystal structure of the deposited film is orthorhombic Co2C. X-ray photoelectron spectroscopy and Raman spectroscopy results show that all the carbon contained in the films were in form of Co–C. The dependence of deposition temperature on cobalt and cobalt carbide characteristics has also been investigated.

Process Steps for High Quality Si-Based Epitaxial Growth at Low Temperature via RPCVD.

The key process steps for growing high-quality Si-based epitaxial films via reduced pressure chemical vapor deposition (RPCVD) are investigated herein. The quality of the epitaxial films is largely affected by the following steps in the epitaxy process: ex-situ cleaning, in-situ bake, and loading conditions such as the temperature and gaseous environment. With respect to ex-situ cleaning, dry cleaning is found to be more effective than wet cleaning in 1:200 dilute hydrofluoric acid (DHF), while wet cleaning in 1:30 DHF is the least effective. However, the best results of all are obtained via a combination of wet and dry cleaning. With respect to in-situ hydrogen bake in the presence of H2 gas, the level of impurities is gradually decreased as the temperature increases from 700 °C to a maximum of 850 °C, at which no peaks of O and F are observed. Further, the addition of a hydrogen chloride (HCl) bake step after the H2 bake results in effective in-situ bake even at temperatures as low as 700 °C. In addition, the effects of temperature and environment (vacuum or gas) at the time of loading the wafers into the process chamber are compared. Better quality epitaxial films are obtained when the samples are loaded into the process chamber at low temperature in a gaseous environment. These results indicate that the epitaxial conditions must be carefully tuned and controlled in order to achieve high-quality epitaxial growth.

Chemoselective synthesis of imine and secondary amine from nitrobenzene and benzaldehyde by Ni3Sn2 alloy catalyst supported on TiO2

Ni3Sn2/TiO2 alloy catalyst prepared by hydrothermal method was applied for the direct one-pot reductive imination of benzaldehyde with nitrobenzene in the presence of H2 gas as a reducing agent. A desired imine, benzylideneaniline, was produced in an excellent yield of 90% without the formation of any by-products. This is due to the chemoselective molecular recognition of Ni3Sn2 alloy nanoparticles supported on TiO2 for the nitro group over the carbonyl group. By prolonging the reaction time, the desired imine was converted into the corresponding secondary amine, N-phenylbenzylamine, with a remarkably high yield of 80% through the catalytic hydrogenation of the CN bond. Finally, we demonstrated that it was easy to reuse the catalyst up to five times.

Hydrocracking of C5-Deasphalted Oil:\t\t\tEffects of H2 and Dispersed Catalysts

Thermal cracking of C5-deasphalted oil\t\t\t\t\t\t(C5-DAO) was performed in a batch reactor at 410°C in\t\t\t\t\tthe absence and presence of H2 gas and catalysts. Coke\t\t\t\t\twas formed during the thermal cracking of C5-DAO even\t\t\t\t\tthough the feed contained no asphaltenes. Although H2\t\t\t\t\tsuppressed asphaltene formation and decreased the coke yield, coke was still\t\t\t\t\tformed in the absence of a catalyst. A slurry-phase dispersed catalyst inhibited\t\t\t\t\tthe transformation of resins into heavier fractions and facilitated <1 wt %\t\t\t\t\tasphaltene yield with no coke formation even under high conversion conditions.\t\t\t\t\tThe main function of the catalyst was the facilitation of hydrogenation\t\t\t\t\treactions and the stabilization of free radicals, leading to liquid production\t\t\t\t\tby inhibiting coke formation. Consequently, the product quality, in terms of\t\t\t\t\thydrogen to carbon ratio and microcarbon residue and S contents, was enhanced by\t\t\t\t\tcatalytic hydrocracking.

Chemo-Mechanically Operating Palladium-Polymer Nanograting Film for a Self-Powered H2 Gas Sensor.

This study proposes a reliable and self-powered hydrogen (H2) gas sensor composed of a chemo-mechanically operating nanostructured film and photovoltaic cell. Specifically, the nanostructured film has a configuration in which an asymmetrically coated palladium (Pd) film is coated on a periodic polyurethane acrylate (PUA) nanograting. The asymmetric Pd nanostructures, optimized by a finite element method simulation, swell upon reacting with H2 and thereby bend the PUA nanograting, changing the amount of transmitted light and the current output of the photovoltaic cell. Since the degree of warping is determined by the concentration of H2 gas, a wide concentration range of H2 (0.1-4.0%) can be detected by measuring the self-generated electrical current of the photovoltaic cell without external power. The normalized output current changes are ∼1.5%, ∼2.8%, ∼3.5%, ∼5.0%, ∼21.5%, and 25.3% when the concentrations of H2 gas are 0.1%, 0.5%, 1.0%, 1.6%, 2%, and 4%, respectively. Moreover, because Pd is highly chemically reactive to H2 and also because there is no electrical current applied through Pd, the proposed sensor can avoid device failure due to the breakage of the Pd sensing material, resulting in high reliability, and can show high selectivity against various gases such as carbon monoxide, hydrogen sulfide, nitrogen dioxide, and water vapor. Finally, using only ambient visible light, the sensor was modularized to produce an alarm in the presence of H2 gas, verifying a potential always-on H2 gas monitoring application.

Tertiary Amine-Ethylene Glycol Based Tandem CO2 Capture and Hydrogenation to Methanol: Direct Utilization of Post-Combustion CO2.

Carbon dioxide capture using tertiary amines in ethylene glycol solvent was performed under ambient conditions. Subsequently, the CO2 captured as alkyl carbonate salts was successfully hydrogenated to methanol, in the presence of H2 gas and Ru-Macho-BH catalyst. A comprehensive series of tertiary amines were selected for the integrated capture and conversion process. While most of these amines were effective for CO2 capture, tetramethylethylenediamine (TMEDA) and tetramethylbutanediamine (TMBDA) provided the best CH3 OH yields. Deactivation of the base due to side reactions was significantly minimized and substantial base regeneration was observed. The proposed system was also highly efficient for CO2 capture from a gas mixture containing 10 % CO2 , as found in flue gases, followed by tandem conversion to CH3 OH. We postulate that such high boiling tertiary amine-glycol systems as dual capture and hydrogenation solvents are promising for the realization of a sustainable and carbon-neutral methanol economy in a scalable process.

Hybrid Physical Chemical Vapour Deposition (HPCVD) of Superconducting MgB2 Thin Films on three Dimensional Copper Substrates

The present work reports the design, development and application of a novel Hybrid Physical Chemical Vapour Deposition (HPCVD) technique for depositing MgB2 thin films, with potential superconductivity, directly on three dimensional (3D) surfaces. A novel solenoid magnetron based set up was used for depositing MgB2 thin films on 3D surfaces of Cu tube. Mg rod was used as the sputter target and source of Mg while high purity BBr3 was used as a novel boron precursor, which was injected into the system using Argon as carrier gas. The plasma mediated decomposition of BBr3 in presence of H2 gas was followed by chemical reaction between Mg and B atoms to deposit MgB2 film on the substrate. Samples were characterized by SEM, EDX, XRD and SQUID techniques. SEM-EDX confirmed deposition of a homogeneous, pore free and dense MgB2 film, while XRD analysis revealed the film to be polycrystalline and multiphasic rather than being purely c-axis oriented. Superconductivity analysis carried out using SQUID measurements indicated a sharp transition with Tc value of 39 K. From the M-H hysteresis loop, the lower critical field Hc1 and critical current density Jc at 4.2 K were calculated to be 700 Oe and 3.5 x 10 7 A/cm 2 , respectively.

Growth Mechanism of Alternating Defect Domains in Hexagonal WS2 via Inhomogeneous W-Precursor Accumulation.

While a hexagonal WS2 monolayer, grown by chemical vapor deposition, exhibits distinctive patterns in photoluminescence mapping, segmented with alternating S-vacancy (SV) and W-vacancy (WV) domains in a single crystal, the formation mechanism for native alternating defect domains remains unresolved to date. Here, the formation mechanism of alternating defect domains in hexagonal WS2 via the precursor accumulation model is experimentally elucidated. A triangular WS2 seed is initially formed, followed by a hexagonal flake. Alternating W-rich (SV) and W-deficient (WV) domains are constructed in hexagonal WS2 flake, which is confirmed by confocal photoluminescence mapping and secondary ion mass spectroscopy. This is explained by the accumulation or scarcity of W-precursors at the edge of the WS2 flake. The W-precursors accumulate near the edges of the initial triangular WS2 seed over time, while they are deficient near the corners of the triangular WS2 , eventually forming WV domains in the truncated hexagonal domains. The heterogeneous accumulation becomes more prominent in the presence of H2 gas through desorption of the W-precursors.

Electrical conduction and dielectric relaxation mechanisms in the KNN-based ceramics

Multilayer ceramic actuators with a base metal internal electrode are in great demand because of their high voltage-driven displacement. Thus, the piezoelectric materials should be sintered in low oxygen partial pressure. The (Li, Ta, Sb)-doped (K,Na)NbO3 (KNN)-based ceramics are heat-treated in O2, air, N2, and 99 vol. % N2/1 vol. % H2 mixture gas at 300 °C in this study to identify the predominant charge carriers by defect chemistry. By analyzing electrical conduction and dielectric relaxation mechanisms, the dominant charge carriers in the ceramics are electrons and oxygen vacancies at low (&amp;lt;450 °C) and high temperature (&amp;gt;500 °C), respectively. In addition, the defect concentration in the ceramics increases with the decreasing oxygen partial pressures, and the change is more evident in the presence of H2 gas. Correspondingly, the electrical properties slightly degrade with the decreasing oxygen partial pressure and severely degrade in the N2/H2 mixture gas. Therefore, the (Li, Ta, Sb)-doped KNN-based ceramics with an n-type conduction mechanism are difficult to sinter in a reducing atmosphere. In order to cofire with base metal electrodes, the p-type conduction should be designed by doping the KNN ceramic in the future for industrial application.

Development of tungsten doped Ni-Zn nano-ferrites with fast response and recovery time for hydrogen gas sensing application

This paper reports on the study of series of tungsten doped Ni0.5Zn0.5WxFe2−xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) ferrites synthesized by a co-precipitation scheme. The crystallite size varies from 62 to 49 nm and the scanning electron microscope (SEM) images show the spinel cubic structure of the powder sample. Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) confirms the presence of Ni, Zn, W and Fe elements in the prepared samples. The specific surface areas of the Ni0.5Zn0.5W0.2Fe1.8O4, Ni0.5Zn0.5W0.4Fe1.6O4 and Ni0.5Zn0.5W0.6Fe1.4O4 samples calculated from Brunauer-Emmett-Teller (BET) method are 18.9 m2/g, 21.5 m2/g and 24.6 m2/g, respectively. The metal oxide pellet type resistive sensor was made for gas sensor application. These sensors are selective for hydrogen (H2) gas. The performance of these sensors for sensing hydrogen gas at a concentration of 1000 ppm in the temperature range 80–300 °C has been investigated. Platinum electrodes were deposited on all the pellets by RF sputtering technique. The subsequent decomposition of platinum oxides on the metal oxide pellet surface results in an increase in surface roughness and electrical resistivity. The sensor shows a change in resistance from 1.21 × 105 Ω to 7.83 × 104 Ω in the presence of H2 gas even at alow temperature. The composition with x = 0.2 at an optimum temperature of 180 °C showed a fast response (14 s) and recovery time (20 s). High sensitivity, low cost, long term stability, high selectivity and fast response at low temperature makes this sensor useful for industrial applications.

Effect of phosphomolybdic acid on the catalytic behavior of bifunctional Pt‐Cr/nanocrystalline Y zeolite in hydroisomerization of n‐octane

AbstractIn this study, Y zeolite nanocrystals were synthesized without an organic template and were used as a support for bifunctional nanocatalysts in the hydroisomerization of n‐octane. Different types of catalysts were synthesized by loading Pt, Cr, and phosphomolybdic acid (HPMo) on Y zeolite nanocrystal supports and were characterized by X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), field emission scanning electron microscope (FE‐SEM), and transmission electron microscope (TEM) analysis. The Cr‐Pt/HPMo‐Y nanocatalyst with a surface area of approx. 600 m2/g showed the best performance in the hydroisomerization of n‐octane. The optimization of n‐octane hydroisomerization over bifunctional nanocatalysts supported on nanocrystalline Y zeolite, in the presence of H2 gas, was applied based on the response surface methodology (RSM) and Box–Behnken design (BBD) template. The effect of three different process variables on the yield of iso‐alkanes as the purpose process was determined. Experiments were carried out using a fixed‐bed microreactor under different ranges of weight hourly space velocity (WHSV) (A = 0.5–1.5 hr−1), H2 to n‐C8 molar ratio (B = 1:1–3:1), and reaction temperature (C = 200–300°C). The RSM proved that the temperature variable had the greatest impact on the hydroisomerization reaction yield.

Platinum Nanoparticle Inclusion into a Carbonized Polymer of Intrinsic Microporosity: Electrochemical Characteristics of a Catalyst for Electroless Hydrogen Peroxide Production.

The one-step vacuum carbonization synthesis of a platinum nano-catalyst embedded in a microporous heterocarbon (Pt@cPIM) is demonstrated. A nitrogen-rich polymer of an intrinsic microporosity (PIM) precursor is impregnated with PtCl62− to give (after vacuum carbonization at 700 °C) a nitrogen-containing heterocarbon with embedded Pt nanoparticles of typically 1–4 nm diameter (with some particles up to 20 nm diameter). The Brunauer-Emmett-Teller (BET) surface area of this hybrid material is 518 m2 g−1 (with a cumulative pore volume of 1.1 cm3 g−1) consistent with the surface area of the corresponding platinum-free heterocarbon. In electrochemical experiments, the heterocarbon-embedded nano-platinum is observed as reactive towards hydrogen oxidation, but essentially non-reactive towards bigger molecules during methanol oxidation or during oxygen reduction. Therefore, oxygen reduction under electrochemical conditions is suggested to occur mainly via a 2-electron pathway on the outer carbon shell to give H2O2. Kinetic selectivity is confirmed in exploratory catalysis experiments in the presence of H2 gas (which is oxidized on Pt) and O2 gas (which is reduced on the heterocarbon surface) to result in the direct formation of H2O2.

Amine-Functionalized Polylactide–PEG Copolymers

The formation of halogenated carboxylic acid intermediate followed by a ring-closing reaction led to amino-functionalized asymmetrical lactide monomer. PEG-based functional diblock and triblock polylactides were synthesized via a controlled ring-opening polymerization in a solvent-free medium with high conversions (up to 96%), low polydispersities as low as 1.06, monomodal GPC traces, and short reaction time (only 1 h). No polymerization of symmetrical monomer, synthesized via condensation of (S)-(+)-CBZ-4-amino-2-hydroxybutyric acid, proved that the preferred site in the mechanism of ring-opening polymerization was found as a methyl site in asymmetrical lactide monomer. A highly efficient deprotection of copolymers was carried out in the presence of H2 gas and Pd/C catalyst without any degradation to obtain the corresponding free amine-functionalized aliphatic poly(α-hydroxy acid)s. These biodegradable thermosensitive polymers, suitable for any local therapy applications, were injectable around 42 °C (so...

Rh nanoparticles grafted on mesoporous silica support as a high-efficiency catalyst for Anthracene hydrogenation

An active, efficient and easy-to-recycle rhodium catalyst was developed, characterized and applied in the hydrogenation of polyaromatic hydrocarbons (PAHs) under mild reaction conditions (40°C, H2 pressure = 4bar, t < 10min). Rhodium nanoparticles were in situ produced by the reduction of Rh3+ ions and deposited onto a previous prepared mesoporous silica support. Rh3+ reduction was carried out using molecular hydrogen (4bar) and temperature (75°C). XPS analysis reveals that the rhodium nanoparticles are present as oxidized species (Rh+1 and Rh3+) and they are reduced to the active species (Rh°) in the presence of H2 gas. After the reaction was completed the catalyst could be rapidly isolated magnetically using a Nd magnet placed on the reactor wall. Recycling studies showed that a single portion of the catalyst could be used for six successive times with no apparent loss of activity. Important features such as the reduction of the catalyst active species using H2 instead of unfriendly environmental chemicals, mild reaction temperature and pressure employed, and the possibility of multiple runs using a single portion of the catalyst are in good agreement with important green chemistry principles such as atom economy and design for energy efficiency.

Electrochemical Performance of Infiltrated Cu-GDC and Cu-PDC Cathode for CO2 Electrolysis in a Solid Oxide Cell

Solid oxide cells are fabricated by utilizing infiltration technique to impregnate: Cu-gadolinium doped ceria (GDC) and Cu-praseodymium doped ceria (PDC) electrodes in yittria stabilized zirconia (YSZ) scaffold. Electrochemical performance of the cell is measured for CO2 electrolysis in presence of H2 gas. The polarization resistances of the cell with Cu-PDC cathode are measured to be of relatively lower value 17.9 Ω cm2 and 5.1 Ω cm2 as compared to the corresponding 23.8 Ω cm2 and 7.5 Ω cm2 on Cu-GDC electrode for CO2/H2 ratio of 92/08 and 28/82 respectively. Similarly, CO2 electrolysis current on Cu-PDC cathode are measured relatively higher to the values of -0.056 A cm-2 at CO2/H2 = 76/24, -0.069 A cm-2 at CO2/H2 = 56/44 and -0.075 A cm-2 at CO2/H2 = 38/62. Impedance spectra of Cu-PDC cell at varying potential, indicated a significant decrease in polarization resistance from 17.9 Ω cm2 to 6.3 Ω cm2 as the applied potential increased from OCV (-0.89 V) to -1.6 V at CO2/H2=92/08. Thus, the experimental results suggested an improved electrocatalytic activity of Cu-PDC cathode as compared to Cu-GDC electrode, which is further improved on increasing the H2 concentration in the feed.

Effect of hydrogen gas addition on combustion characteristics of pulverized coal

A promising approach to decrease CO2 emissions from blast furnaces during ironmaking is to blow a reducing gas containing hydrogen into blast furnaces from their tuyeres. However, the combustion behavior of pulverized coal in the presence of a hydrogen-containing gas has not been elucidated. In this work, the combustion experiments of pulverized coal using a drop tube furnace were carried out to investigate the effect of H2 gas addition on the combustibility of pulverized coal. The combustion ratio of char particles in the presence of H2 gas (when introduced at a flow rate of 0.10L/min) was larger than that in the absence of H2 gas. This is because of the enhanced release of volatile matter from coal and the combustion of char due to an increase in the temperature of the coal particles, which was caused by the drastic combustion of H2 gas. The combustion ratio of char particles when H2 gas was added at flow rates higher than 0.21L/min was considerably smaller than that obtained when H2 gas was not added. It was found that the combustibility of coal was enhanced when an optimum H2 gas flow rate was used.