Catalysts For Methane Decomposition Research Articles

Balancing act: influence of Cu content in NiCu/C catalysts for methane decomposition.

Thermal catalytic decomposition of methane is an innovative pathway to produce CO2-free hydrogen from natural gas. We investigated the role of Cu content in carbon-supported bimetallic NiCu catalysts. A graphitic carbon material was used as a model support, and we combined operando methane decomposition experiments in a thermogravimetric analyzer with in situ electron microscopy measurements. The carbon yield was maximum with around 30% Cu in the nanoparticles. Adding more Cu drastically lowered the carbon solubility in the metal nanoparticles, which lowered the initial reaction rate and overall carbon yield. In situ TEM measurements showed that the addition of Cu to the catalysts strongly influenced the metal nanoparticle shape and size during carbon growth, and the growth mode. NiCu particles were larger, remained spherical and facilitated steady CNF growth. In contrast, pure Ni nanoparticles fluctuated in shape, sometimes fragmented, and showed stuttering CNF growth. This was ascribed to fluctuating coverage of part of the Ni nanoparticle surface with amorphous carbon, which increased the chance of total encapsulation and hence deactivation of the individual Ni nanoparticles. This supports a picture where balancing the carbon supply, transport, and nucleation of amorphous and crystalline carbon is crucial. Our results also highlight the importance of combining statistically relevant measurements with microscopic information on individual nanoparticles to understand overall catalytic trends from the combined behavior of individual catalyst nanoparticles.

Promoting Effects of Copper and Iron on Ni/MSN Catalysts for Methane Decomposition

Copper and iron-based bimetallic nickel catalysts supported on Mesostructured Silica Nanoparticles (MSNs) with compositions of 50% Ni–5% Cu/MSN and 50% Ni–5% Fe/MSN were prepared using an impregnation method, and they were compared with a monometallic 50% Ni–MSN catalyst for their activity and stability in methane decomposition reaction. The influence of promoters, such as Cu and Fe, at different reaction temperatures (700 °C, 800 °C and 900 °C) was investigated. The results revealed that the Cu and Fe-promoted catalysts significantly increased the hydrogen yield in methane decomposition compared with the unpromoted catalyst. This could be attributed to the formation of Ni–Cu and Ni–Fe bimetallic alloys in the catalysts, respectively, and this favored the stability of the catalysts. With increasing reaction temperature, the hydrogen yield also increased. However, the hydrogen yield and the lifetime of the nickel catalyst were enhanced upon the addition of iron compared to copper at all the reaction temperatures. The analysis conducted over the spent catalysts validated the formation of multi-walled carbon nanotubes with a bamboo-like internal channel over the catalysts along with a high crystallinity and graphitization degree of the carbon produced.

Solution Combustion Synthesis of Ni/Al2O3 Catalyst for Methane Decomposition: Effect of Fuel

The synthesis of a 90% Ni/Al2O3 catalyst via solution combustion synthesis with various fuels was studied in this work. Catalysts with a high content of the active component (i.e., nickel) were obtained as a result of the combustion of Ni(NO3)2·6H2O and Al(NO3)3·9H2O mixtures with fuel. The fuels, such as hexamethylenetetramine, glycine, urea, starch, citric acid, and oxalic acid, were investigated. The synthesis was carried out in a furnace, with the temperature being raised from room temperature to 450 °C at a rate of 1 °C per min. The paper evaluates the efficiency of fuels and their effect on the structure and properties of catalysts, as well as their catalytic activity. The catalyst was used for the synthesis of hydrogen and carbon nanofibers by methane decomposition at 1 bar and 550 °C. The catalysts were tested in a vertical flow reactor without preliminary reduction. The obtained samples of catalysts and carbon nanomaterials were studied by transmission electron microscopy, low-temperature nitrogen adsorption, and X-ray diffraction. The highest activity of the catalyst was obtained when citric acid was used as a fuel. The specific yields of hydrogen and carbon nanofibers were 17.1 mol/gcat and 171.3 g/gcat, respectively. Catalytic decomposition of methane led to the formation of cup-stacked carbon nanofibers.

Nickel-iron catalyst for decomposition of methane to hydrogen and filamentous carbon: Effect of calcination and reaction temperatures

Nickel-ferrite Ni-Fe (molar ratio 1:2) were synthesised and calcined at different temperatures. The catalytic performances of Ni-Fe for methane decomposition and production of hydrogen and carbon nanostructures were evaluated at various calcination (350–800 °C) and reaction temperatures (700–800 °C). Fresh and spent catalysts were characterized using scanning electron microscopy (SEM), BET surface area, X-ray diffraction (XRD), TGA and Raman spectroscopy. XRD results revealed the formation of highly crystalline NiFe2O4 in calcined samples, while Ni-Fe alloys were observed in the spent catalysts. The NiFe2O4 catalyst has a mesoporous structure with monomodal pore distribution. The surface area decreased from 107.0 to 3.8 m2/g with increasing calcination temperature from 350 to 800 °C. Methane conversion, 48.50%, and hydrogen formation rate, 97.70 × 10-5 mol H2 g−1 min−1 was obtained at reaction temperature of 800 °C. The catalyst activity slightly improved by increasing calcination temperature. The SEM images of spent catalysts revealed the formation of some filamentous carbon over all spent catalysts except for that operated at reaction temperature of 700 °C. TGA studies revealed that the deposited carbon increased with increase in reaction and calcination temperatures and achieved 42.50 and 59.32 wt%, respectively. The graphitization and crystalline of the deposited carbon slightly decreases as calcination temperature increased.

Catalytic decomposition of methane over enteromorpha prolifera-based hierarchical porous biochar

Biochar is a potential catalyst for methane decomposition (CMD) owing to its environmental-friendly and application prospects. In this work, the hierarchical porous biochar was prepared by carbonization and H3PO4 activation using Enteromorpha prolifera (EP) as precursor, respectively. The results show that when the ratio of H3PO4/EP is 1.5, the maximum CH4 conversion is 46%, along with hydrogen output of 396 mmol/gcat, which is 5.8 times as that of the unactivated biochar. The characterization results by XPS, Raman, SEM and HRTEM indicate that P element is inserted in carbon layer in the form of C–O–P, resulting in lattice distortion of carbon layer and larger defect density, and C–O–P plays a dominant role in initial CH4 conversion. The mesopores formed by H3PO4 activation alleviate the influence of the deposited carbon on the catalyst and decrease the deactivation rate, thereby exhibiting better performance in CMD.

CO x ‐free catalytic decomposition of methane over solution combustion synthesis derived catalyst: Synthesis of hydrogen and carbon nanofibers

The catalyst for decomposition of methane to carbon nanofibers and hydrogen was prepared using the solution combustion technique. Dynamics of change of temperature of solution (gel) during the passing of redox reaction of synthesis of catalyst was found experimentally. Testing of catalyst was carried out in a flow through installation. Catalyst with high content of active component 90Ni-10Al2O3 (wt%) was tested in a reaction of methane decomposition in a temperature range 535°С to 675°С and pressures 1 to 5 atm. The samples of carbon nanofibers were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The optimal parameters of catalytic reaction (550°С, 3 atm) providing the high specific yield of hydrogen (287.7 mol/g) were established. The increase of pressure above 1 atm led to prolonged operation of the catalyst. The negative role of temperature rise on the yield of CNFs was found.

Facile Synthesis of Co-Rh Bimetallic Catalysts for Methane Decomposition: Effect of Support Morphology

Facile Synthesis of Co-Rh Bimetallic Catalysts for Methane Decomposition: Effect of Support Morphology

Highly-defective graphene as a metal-free catalyst for chemical vapor deposition growth of graphene glass

Direct synthesis of graphene on insulating substrates is highly desirable for practical applications. Herein, we present a new fabrication method for graphene on quartz which enables the direct growth of high-quality and large-scale graphene films with no metal involved. The growth rate of graphene on insulating substrates was typically extremely slow due to the low catalytic activity and the slow diffusion speed of carbon species on them. Thus, an extra catalyst is required. Instead of metal elements, such as Cu, Ni, and Ga, highly-defective graphene films were applied as the catalyst for methane decomposition. The key feature of our approach is that carbon itself was used as the catalyst for graphene fabrication, which completely avoided the contamination of other elements. As a result, the growth rate of graphene films increased significantly compared to the conventional CVD method. The excellent quality of graphene glass was verified by a series of experimental characterization and the fabrication of a transparent heating device without any transfer process. In addition, the energy barrier of the decomposition of methane was explored using the first principles calculation, which further confirmed the catalytic behavior of highly-defective graphene films.

Numerical Study on Optics and Heat Transfer of Solar Reactor for Methane Thermal Decomposition

This study aims to reduce greenhouse gas emissions to the atmosphere and effectively utilize wasted resources by converting methane, the main component of biogas, into hydrogen. Therefore, a reactor was developed to decompose methane into carbon and hydrogen using solar thermal sources instead of traditional energy sources, such as coal and petroleum. The optical distributions were analyzed using TracePro, a Monte Carlo ray-tracing-based program. In addition, Fluent, a computational fluid dynamics program, was used for the heat and mass transfer, and chemical reaction. The cylindrical indirect heating reactor rotates at a constant speed to prevent damage by the heat source concentrated at the solar furnace. The inside of the reactor was filled with a porous catalyst for methane decomposition, and the outside was surrounded by insulation to reduce heat loss. The performance of the reactor, according to the cavity model, was calculated when solar heat was concentrated on the reactor surface and methane was supplied into the reactor in an environment with a solar irradiance of 700 W/m2, wind speed of 1 m/s, and outdoor temperature of 25 °C. As a result, temperature, methane mass fraction distribution, and heat loss amounts for the two cavities were obtained, and it was found that the effect on the conversion rate was largely dependent on a temperature over 1000 °C in the reactor. Moreover, the heat loss of the full-cavity model decreased by 12.5% and the methane conversion rate increased by 33.5%, compared to the semi-cavity model. In conclusion, the high-temperature environment of the reactor has a significant effect on the increase in conversion rate, with an additional effect of reducing heat loss.

Methane decomposition to produce hydrogen and carbon nanomaterials over costless, iron-containing catalysts

In this work, a series of iron-containing materials (not laboratory-synthesized but from natural, industrial raw materials, by-products or wastes), such as iron concentrate powder, fine/coarse ash and steel slag from steel plants and volcanic mud powder, were investigated as catalysts for methane decomposition. These catalysts exhibited relatively good methane conversion under the following conditions: 2.0 g of catalyst, 50 mL/min CH4, 900 °C for 5 h, even without hydrogen pre-reduction. Fe2O3 species on these samples were found to be gradually reduced by methane to Fe3O4, FeO and then finally into Fe0 active species. When methane decomposed onto the Fe0 active sites, Fe3C species would form to deposit graphite around themselves to finally form carbon nanomaterials, showing possible application in the oxygen evolution reaction and in Li-ion batteries as anode electrodes. Furthermore, using the best catalyst, iron concentrate powder, the effect of temperature and gas hourly space velocity was studied, where 900 °C and 3 L/gcat·h were determined as the optimized reaction conditions to reach the highest carbon/hydrogen yield.

Ni-\u03b3-AL2O3 catalysts for obtaining nanocarbon by decomposition of natural gas

γ-Al2O3 was synthesized by the Sol–gel method, Ni (NO3)2 was placed in the pores by the impregnation method, and Ni-γ-Al2O3 was obtained by pyrolysis in a hydrogen stream in a CVD device. By the method of chemical vapors phase deposition (CVD) on Ni-Al2O3 catalytic converter with decomposition of methane in the natural gas produced carbon nanotubes (CNT) (Chunduri et al. in Mater Express 4(3):235–241, 2014; Zhou et al. in Appl Catal B 208:44–59, 2017). The catalytic activity of the catalysts in methane decomposition was examined from 650 °C to 900 °C by the method of chemical vapors phase deposition (CVD), the yield of CNTs tends to increase with the growth at the ratio of natural gas supply to hydrogen. The specific surface increases with an increase of nickel content and can reach 265.5 m2/g for a sample of 2% Ni-A12O3 at 850 °C. Growth at the temperature of methane decomposition leads to reduction in its specific surface. It has been established that the use of the Ni-Cu/γ-Al2O3 catalytic system, in which copper acts as a stabilizing additive, makes it possible to double the maximum yield of the carbon product during the decomposition of natural gas.

Catalytic decomposition of methane on Ni-containing catalysts prepared by heterophase sol-gel method

The most promising catalysts for the catalytic decomposition of methane are nickel-containing systems, since nickel has high activity, thermal stability, thermal conductivity, and relatively low cost. In this work, catalysts were prepared by the heterophase sol-gel method and investigated using catalytic equipment. The catalysts showed high stability and lifetime during the catalytic decomposition of methane at temperatures ranging from 535 to 675°C.

Formation of the Active Surface of the FeCrAl Catalyst under Electric Current Heating Conditions

An effect of heat treatment conditions (convective, resistive heating) was considered on the composition and surface properties of FeCrAl wire used as a catalyst for methane decomposition. It was shown that resistive heating is a more effective method for activating the FeCrAl wire catalyst, which promotes the dispersion of iron-enriched particles over the surface and an increase in the number of catalytically active sites. The use of resistive heating allows reducing the catalyst pretreatment time to 10 min.

Molten salt-promoted Ni–Fe/Al2O3 catalyst for methane decomposition

Bimetallic Ni–Fe/Al2O3 catalysts were prepared by the molten salt method, and the catalytic performance of the Ni–Fe/Al2O3 catalysts with the KCl–NiCl2 melt for methane decomposition was evaluated at 800 °C. The catalysts and carbon products were characterized by XRD, SEM/EDS, XRF and Raman spectroscopy techniques. The results show that molten salt-promoted Ni–Fe/Al2O3 catalysts exhibit high activity and long-term stability up to 1000 min time on stream without any deactivation. The carbon products over the molten salt-promoted Ni–Fe/Al2O3 catalysts are in the form of small granular particles instead of filamentous carbon for the catalyst without molten salt. The promotional effect of the molten salt may attribute to the higher wettability of the Fe–Ni alloy by molten salt, which can prevent the catalysts from deactivation due to carbon encapsulation.

Influence of group VIB metals on activity of the Ni/MgO catalysts for methane decomposition

Mesoporous 55 wt.% Ni/MgO and group VIB metal (Cr, Mo or W)-doped catalysts were prepared using the facile "one-pot" evaporation-induced self-assembly in ethanol and wetness impregnation methods, respectively. Physicochemical properties of the as-prepared catalysts were characterized by means of the BET, XRD, SEM, TEM, HAADF, XPS, H2-TPR, TPO, and Raman techniques. The doping of Cr to 55 wt% Ni/MgO improved catalytic activity and stability for the decomposition of methane under harsh reaction conditions. The maximal initial methane conversions of 80, 87, and 75% were achieved over the 55 wt.% Ni−xCr/MgO (denoted as 55Ni−xCr/MgO; x = 5, 10, and 15 wt.%) at 675 oC and GHSV = 48,000 mL/(g h), respectively. It is concluded that the high catalytic efficiency of the Cr-doped sample in methane decomposition was associated with its high surface area, high oxygen adspecies concentration, and good low-temperature reducibility. In addition, multi-walled carbon filaments with metal-encapsulated carbon particles were deposited on the Cr-doped catalysts, and the ordered carbon filaments with different diameters and good crystallinity were produced on the surface of the 55Ni−10Cr/MgO catalyst.

Handy synthesis of robust Ni/carbon catalysts for methane decomposition by selective gasification of pine sawdust

Hydrogen is a clean fuel and potential alternative for fossil fuels, and many efforts have been devoted to low-carbon hydrogen production. Highly dispersed and robust Ni/carbon catalysts can be handily prepared in situ for catalytic methane decomposition (CMD) by selective steam gasification of pine sawdust. Effect of the gasification conditions (temperature, mass ratio of PS:Ni, steam flow rate and gasification reaction time) was investigated on the nickel species, activity and stability of the Ni/carbon catalyst in CMD. Besides hydrogen-rich gas released from the gasification process, co-production of hydrogen and carbon fibers can be obtained on the optimized catalyst with high and stable methane conversion (up to higher than 90% at 850 °C) in the 600-min CMD reaction. The implementation of such selective biomass gasification and CMD could be one promising approach towards process intensification for highly cost-effective hydrogen production, and enables it possible to yield a high metal efficiency as well.

Iron catalyst for decomposition of methane: Influence of Al/Si ratio support

20% iron catalysts supported on combined alumina and silica through different proportions (Al2O3:SiO2: 100:0.00, 90.0:10.0, 80.0:20.0 and 0.0:100.0) were tested for the catalytic decomposition of methane to produce H2 and carbon. The catalysts were prepared via impregnation technique. The physicochemical properties of the catalysts were characterized with TGA, XRD, H2-TPR, and TEM techniques. The results specified no reaction for all temperatures when the catalysts were supported with bare silica. Indeed, the 20%Fe/(Si-80)-800 catalyst with 20% silica support operated at 800 °C produced CH4 conversion profile that rapidly descended from 64% to 5% due to the high content of silica. Plain alumina supported catalyst demonstrated the best conversion and stability operated at 800 °C. The CH4 conversion started from 83.4% and lasts at 82.2% after 300 min on stream.

One-pot sol–gel synthesis of Ni/TiO2 catalysts for methane decomposition into COx free hydrogen and multiwalled carbon nanotubes

A series of mesoporous Ni/TiO2 catalysts with different loadings of nickel from 10 to 50 wt% was successfully prepared via a facile one-pot sol–gel route; characterized for its structural, textural and redox properties; and tested for the non-oxidative thermocatalytic decomposition of undiluted methane for the first time. The characterization results reveal the presence of both NiO and NiTiO3 and metallic nickel as active metal phase in the fresh and reduced catalysts, respectively. Spherical catalyst particles were found to be highly inter-aggregated and to provide a porous texture to the catalyst. All of the prepared catalysts exhibited high catalytic activity and stability for methane decomposition. It is due to the fine dispersion of active nickel nanoparticles on the surface of the TiO2 support with proper metal-support interaction. Moreover, with increasing nickel loading and reaction temperature, the yields of hydrogen and nanocarbon were found to be significantly increased. A maximum hydrogen yield of 56% and a final carbon yield of 1544% were obtained for the 50% Ni/TiO2 catalyst at 700 °C with an undiluted methane feed of 150 ml/min for 360 min of time on stream. The catalyst showed high catalyst stability, for a period of 960 min of time on stream and ∼24% hydrogen yield was observed at the end of long-term run using the 50% Ni/TiO2 catalyst. Moreover, irrespective of the nickel loading involved, bulk amount of multiwalled carbon nanotubes were deposited on the surface of the catalyst. XRD and Raman analyses of the spent catalysts showed that the crystallinity of nanocarbon increased with increasing nickel loadings, whereas the graphitization degree remained unaffected, with an ID/IG value of 0.88.

Development of a Noble-structured Catalyst for Methane Decomposition to Produce Pure Hydrogen

The aim of this study is to develop a noble-structured catalyst for methane decomposition to produce pure hydrogen. The Ni/Al2O3 structured catalyst, which was prepared by electroless plating with NaBH4 as the reducing agent, showed a higher activity and stability, indicating the advantage for ensuring the flow path. After a steam treatment to remove the deposited carbon, the decomposition performance of the structured catalyst was regenerated.

Effect of support on methane decomposition for hydrogen production over cobalt catalysts

Cobalt catalysts were tested in methane decomposition reaction at 450 °C to evaluate their catalytic properties in non-oxidative methane conversion for hydrogen production via accumulation of carbon. Silica, alumina and niobia supported cobalt catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), H2 chemisorption and BET surface area measurements. The nature of the support strongly influenced this process. The high initial activity of Co/Al2O3 catalyst reduced at 500 °C lead to a large formation of carbon deposits and consequent catalysts deactivation. For Co/SiO2, the activity increased with reaction time due to reduction of cobalt oxide particles that were not reduced during the reduction pretreatment, and this effect was more pronounced for the reduction at 300 °C. Co/SiO2 reduced at 500 °C was the best catalysts for methane decomposition. For Co/Nb2O5, the Nb2OX species partially covered cobalt particles even for reduced catalysts at low temperature (300 °C) and this effect completely inhibited the reaction after high-temperature reduction (500 °C).