Catalytic Decomposition Of Methane Research Articles

Fe catalysts for methane decomposition to produce hydrogen and carbon nano materials

Conducting catalytic methane decomposition over Fe catalysts is a green and economic route to produce H2 without CO/CO2 contamination. Fused 65wt% and impregnated 20wt% Fe catalysts were synthesized with different additives to investigate their activity, whereas showing Fe-Al2O3 combination as the best catalyst. Al2O3 is speculated to expose more Fe0 for the selective deposition of carbon nano tubes (CNTs). A fused Fe (65wt%)-Al2O3 sample was further investigated by means of H2-TPR, in-situ XRD, HRTEM and XAS to conclude 750°C is the optimized temperature for H2 pre-reduction and reaction to obtain a high activity. Based on density functional theory (DFT) study, a reaction mechanism over Fe catalysts was proposed to explain the formation of graphite from unstable supersaturated iron carbides decomposition. A carbon deposition model was further proposed which explains the formation of different carbon nano materials.

The effects of autohydrolysis pretreatment on the structural characteristics, adsorptive and catalytic properties of the activated carbon prepared from Eucommia ulmoides Oliver based on a biorefinery process

Eucommia ulmoides Oliver (EU) wood was consecutively treated by autohydrolysis pretreatment and chemical carbonization post-treatment based on a biorefinery process. Results showed that the optimal condition of the autohydrolysis pretreatment and carbonization process yielded 10.37kg xylooligosaccharides (XOS), 1.39kg degraded hemicellulosic products, 17.29kg other degraded products from hemicelluloses and 40.72kg activated carbon (SBET of 1534.06m2/g) from the 100kg raw materials. Simultaneously, 29.14kg gas products generated from the optimum integrated process was significantly lower than that from the direct carbonization process (68.84kg). Besides, the optimal activated carbon (AC170–1.0) also showed a moderate catalytic activity and high stability for hydrogen production by catalytic methane decomposition. Overall, the data presented indicated that the integrated process is an eco-friendly and efficient process to produce XOS and activated carbon, which is beneficial for value-added and industrial application of EU wood.

Unzipping of multi-wall carbon nanotubes with different diameter distributions: Effect on few-layer graphene oxide obtention

Few-layer graphene oxide (FLGO) was obtained by chemical unzipping of multi-wall carbon nanotubes (MWCNT) of different diameter distributions. MWCNT were synthesized by catalytic decomposition of methane using Fe‐Mo/MgO catalysts. The variation in the Fe/Mo ratio (1, 2 and 5) was very influential in MWCNT diameter distribution and type of MWCNT obtained, including textural, chemical, structural and morphological characteristics. MWCNT diameter distribution and surface defects content had a profound impact on the characteristics of the resulting FLGO. Thus, MWCNT obtained with the catalyst with a Fe/Mo: 5 and presenting a narrow diameter distribution centered at 8.6±3.3nm led to FLGO maintaining non-oxidized graphite stacking (according to XRD analysis), lower specific surface area and higher thermostability as compared to FLGO obtained from MWCNT showing wider diameter distributions. The presence of more oxygen-containing functionalities and structural defects in large diameter nanotubes promotes the intercalation of species towards the inner layers of the nanotube, resulting in an enhanced MWCNT oxidation and opening into FLGO, what improves both micro- and mesoporosity.

Evaluation of activated carbons based on olive stones as catalysts during hydrogen production by thermocatalytic decomposition of methane

Catalytic decomposition of methane over carbon materials has been intensively studied as an environmental approach for CO2-free hydrogen production without further by-products except hydrogen and valuable carbon. In this work, we will investigate the catalytic activity of activated carbons based on olive stones prepared by two different processes. Additionally, the effect of three major operational parameters: temperature, weight of catalyst and flow rate of methane, was determined. Therefore, a series of experiments were conducted in a horizontal-flow fixed bed reactor. The outflow gases were analysed using a mass spectrometer. The textural, structural and surface chemistry properties of both fresh and used activated carbons were determined respectively by N2 gas adsorption, X-Ray Diffraction and Raman and Temperature Programmed Desorption. The results reveal that methane decomposition rate increases with temperature and methane flow however it decreases with catalyst weight. The two carbon samples exhibit a high initial activity followed by a rapid decay. Textural characterization of the deactivated carbon presents a dramatic drop of surface area, pore and micropore volumes against an increase of average pore diameter confirming that methane decomposition occurs mainly in micropores. XRD characterization shows a turbostratic structure of fresh samples with more graphitization in deposed carbon explaining the lowest activity at the end of reaction. Raman spectra reveal the domination of the two bands G and D which varying intensities affirm that the different carbons tend to organise in aromatic rings. Finally the surface chemistry qualitatively changes greatly after methane dissociation for CAGOC unlike CAGOP but quantitatively a small difference is observed which indicates that these functionalities may have a role in this heterogeneous reaction but cannot be totally responsible. Among the two catalysts tested, CAGOC has the highest initial methane decomposition rate but CAGOP is the most stable one.

Preparation of Modified Red Mud-Supported Fe Catalysts for Hydrogen Production by Catalytic Methane Decomposition

A modified red mud- (MRM-) supported Fe catalyst (xFe/MRM) was prepared using the homogeneous precipitation method and applied to methane decomposition to produce hydrogen. The TEM and SEM-EDX results suggested that the particle sizes of the xFe/MRM catalysts were much smaller than that of raw red mud (RM), and the active metal Fe was evenly distributed over the catalyst structure. Moreover, BET results indicated that the surface areas and pore volumes of the catalysts were significantly improved, and the pore sizes of xFe/MRM were distributed from 5 to 12 nm, which is typical for a mesoporous material. The activities of those catalysts for the catalytic decomposition of methane were studied at atmospheric pressure at a moderate temperature of 650°C; the results showed that the xFe/MRM catalysts were more active than RM and MRM. The methane conversion curves of xFe/MRM catalysts exhibited similar variation tendencies (three-step) during the reaction despite different Fe contents, and the loading amount of Fe clearly affected the activity of the catalysts.

Hydrogen Production from Methane Decomposition Using Nano Metal Oxides

Nanotechnology is like an umbrella, under this maximum all the fields, branches are developing, like a green-house effect for plant. Nanotechnology can provide new concepts for the energy department which can utilise and provide new sources for all energy challenges, like generation, renewable and storage with less energy consumption, that provide an economy to the development to country. This can be achieved with the help of hydrogen for energy application; thermo catalytic decomposition of methane is a simple process to produces carbon free hydrogen. Mono metallic NiO, Co3O4, ZrO2 and ZnO catalyst were synthesised by a solution combustion process. The methane decomposition and catalyst activity test is done at fixed bed reactor with a methane flow rate of 54 SCCM with an operation condition of 850°C temperature under atmospheric pressure respectively. The catalyst is characterised by BET, XRD and PSA. The complete observation and catalyst performance shows that catalyst activity is high at the initial time of reaction and decreases with deposition (time) of carbon over the catalyst. As resultant the methane decomposition showed activity nearly 3h for all the catalyst. Comparison study shows that hydrogen yield and deposited carbon occurs (catalyst activity) is completely based on particle size, Surface area and Pore volume of material used.

Catalytic decomposition of methane over Ni/SiO2: influence of Cu addition

The influence of Cu addition to Ni/SiO2 catalysts was studied in the catalytic decomposition of methane. Samples were prepared by impregnation and characterized by SBET, TPR, TPO, XRD and Raman spectroscopy. The activity tests were performed at temperatures ranging from 500 to 700 °C in a fixed bed reactor with in-line gas chromatography analysis. The presence of copper had an effect on the SBET of calcined samples, improving the dispersion and decreasing the reduction temperature of NiO particles. The addition of small amounts of copper facilitates the activation of NiO with methane and allows obtaining small crystallites of Ni°, which prevents the catalyst deactivation by sintering in temperatures above 500 °C. The characterization of carbon deposited on Cu-containing samples indicated the formation of multi-walled carbon nanotubes. The sample containing 1 wt% of Cu has the best performance for the production of hydrogen from methane decomposition.

Nano size Hβ zeolite as an effective support for Ni and Ni[sbnd]Cu for COx free hydrogen production by catalytic decomposition of methane

Mono and bimetallic catalysts of Ni and Cu on Hβ zeolite supports were tested for the COx free hydrogen production by decomposition of methane. The effect of Cu addition and the support particle size were investigated. XRD analysis of the reduced samples demonstrated that for catalysts based on nano-sized Hβ zeolite particles (nano-Hβ), the Ni and Cu were only present in the form of a NiCu alloy, whereas when commercial Hβ zeolite (Hβ) was used; segregated Cu0 and Ni0 species were also observed. Addition of Cu was found to dramatically improve the H2 yield by the formation of surface NiCu alloys. The particle size of the Hβ zeolite has a pronounced effect on the Ni and NiCu dispersion, and consequently on the methane decomposition activity. The surface area of NiCu on the nano-Hβsurface was estimated by a combination of H2 pulse chemisorption and N2O titration methods. The Cu species in close proximity to Ni sites inhibited carbon deposition at the Ni sites, resulting in higher rates of H2 formation. Consistent with this finding, NiCu/nano-Hβ was the most active of the catalysts tested. The physicochemical characteristics of the commercial and nano-Hβ supported Ni and/or NiCu catalysts are rationalized by TEM, H2-TPR, XPS and Raman spectroscopy in conjunction with H2 production rates.

Hydrogen production by catalytic methane decomposition over Ni, Co, and Ni-Co/Al2O3 catalyst

ABSTRACTHydrogen is a chief source of energy. Catalytic decomposition produces hydrogen and carbon. In this work, x%M/Al2O3 (where M is Ni, Co and combined Ni-Co, and x is 10%, 15%, and 30%) has been successfully employed as a catalyst. The effect of activation temperature and active metal type and loading on catalyst perfomance was investigated. The catalysts were characterized with BET, XRD, TPO, TPR, TEM, XPS, and Raman. The results displayed that the 30%Co/Al2O3 catalyst activated at 500°C provided the greatest catalytic performance toward methane conversion. 30%Co/Al2O3 catalyst activated at 500°C formed amorphous carbon.

Production of hydrogen by catalytic methane decomposition over alumina supported mono-, bi- and tri-metallic catalysts

Hydrogen, an environmentally benign source of energy, has significantly attracted the attention of researchers in recent decades. This article discusses hydrogen production by methane decomposition over alumina supported iron-nickel-cobalt based mono-, bi- and tri-metallic catalysts. The catalysts were prepared by using wet-impregnation strategy. The fresh catalysts were characterized using different techniques such as BET, H2-TPR, and XRD. Likewise, a morphological study of selected spent catalyst was complemented by employing TEM as well as TPO. The catalytic activity results revealed that bimetallic catalysts consisting of 30 wt.% Fe and 15 wt.% Co exhibited excellent performance among all the tested catalysts. In addition, the results of sensitivity analysis revealed that an activation span of 90 min, GHSV of 5000 mL/h gcat at 700 °C as a reaction temperature were found to be the optimum process conditions. Significantly, it can be seen that in a an extended run of 1400 min involving 12 regeneration cycles, high methane conversion (>55%) can be maintained.

Methane decomposition over high-loaded Ni-Cu-SiO2 catalysts

The performance of Ni-SiO2 and Ni-Cu-SiO2 during repeated catalytic decomposition of methane (CDM) reactions and subsequent regeneration of the deactivated catalysts with air has been studied. The catalytic activity of the 75%Ni-25%SiO2 catalyst in the second and third CDM was lower than that during the first, while the lifetime of the catalyst did not change significantly. Both the lifetime and the catalytic activity of 65%Ni-10%Cu-25%SiO2 in the second and third CDM reactions decreased significantly. 55%Ni-20%Cu-25%SiO2 showed better performance than the other two catalysts, and its activity and lifetime did not change significantly until the third CDM reaction. The hydrogen yields of 55%Ni-20%Cu-25%SiO2 were 56.8gH2/gcat., 42.8gH2/gcat., and 2.4gH2/gcat. for the first, second, and third CDM reactions, respectively. Spherical carbon structures were observed on the catalysts following all three CDM reactions over 75%Ni-25%SiO2. However, similar carbon structures were only observed following the second and third CDM over 65%Ni-10%Cu-25%SiO2, and only following the third cycle with 55%Ni-20%Cu-25%SiO2. The formation of spherical carbon during the repeated CDM reactions strongly influenced the performance of the catalysts.

Hydrogen production via catalytic methane decomposition over alumina supported iron catalyst

In this paper, iron-based catalysts, calcined at different temperatures (300–800°C), supported over alumina, were investigated for hydrogen production via catalytic methane decomposition. The catalysts were prepared by using different methods such as impregnation and co-precipitation. The fresh and spent catalysts were characterized using different techniques such as Brunauer, Emmett and Teller (BET), temperature-programmed reduction by hydrogen (H2-TPR), X-ray powder diffraction (XRD), thermogravimetry analysis (TGA), Field Emission Scanning Electron Microscope (FESEM) and transmission electron microscopy (TEM). Results revealed that for both impregnated and co-precipitated catalysts, calcination temperature of 500°C is optimal. Type of precursor iron oxide on the alumina support has a strong influence on its performance for methane decomposition.

CNT Production through the Catalytic Decomposition of Methane on Ni-Cu/γ-Al2O3 at Varying Ni-Cu Ratios: An Ab Initio and Empirical Investigation

CNT Production through the Catalytic Decomposition of Methane on Ni-Cu/γ-Al2O3 at Varying Ni-Cu Ratios: An Ab Initio and Empirical Investigation

Methane-induced Activation Mechanism of Fused Ferric Oxide-Alumina Catalysts during Methane Decomposition.

Activation of Fe2 O3 -Al2 O3 with CH4 (instead of H2 ) is a meaningful method to achieve catalytic methane decomposition (CMD). This reaction of CMD is more economic and simple against commercial methane steam reforming (MSR) as it produces COx -free H2 . In this study, for the first time, structure changes of the catalyst were screened during CH4 reduction with time on stream. The aim was to optimize the pretreatment conditions through understanding the activation mechanism. Based on results from various characterization techniques, reduction of Fe2 O3 by CH4 proceeds in three steps: Fe2 O3 →Fe3 O4 →FeO→Fe0. Once Fe0 is formed, it decomposes CH4 with formation of Fe3 C, which is the crucial initiation step in the CMD process to initiate formation of multiwall carbon nanotubes.

High-loaded Ni[sbnd]Cu[sbnd]SiO2 catalysts for methane decomposition to prepare hydrogen and carbon filaments

NiSiO2 and NiCuSiO2 catalysts were prepared by a hetero-phase sol–gel method. Two types of kinetic experiments (routes I, II) were designed to test the catalytic performance of the NiCuSiO2 catalysts, and the textural properties of the carbon filaments were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Compared to traditional method of catalytic decomposition of methane (CDM) reaction, where the reduction process and the decomposition of methane occurred at the same temperature (route I), the NiCuSiO2 catalysts exhibited superior catalytic performance at a reaction temperature of 750 °C using route II. This finding was attributable to the introduction of methane into the reactor at lower temperatures, which can prevent the NiCu particles from sintering into larger clusters during the thermal treatment processes, and the carbon filament by-product could play the role of a growing support to enhance the dispersion of the metal particles. However, when the catalyst decomposition occurred at 750 °C, NiCu alloy particles broke down, and a phase separation was observed, which might be related to the loss in catalytic activity. Due to the disordered carbon formed over the NiCuSiO2 catalysts during the CDM reaction, the generated carbon filaments might begin to crack methane at a higher temperature.

Surface composition changes of CuNi-ZrO2 during methane decomposition: An operando NAP-XPS and density functional study

Bimetallic CuNi nanoparticles of various nominal compositions (1:3, 1:1, 3:1) supported on ZrO2 were employed for operando spectroscopy and theoretical studies of stable surface compositions under reaction conditions of catalytic methane decomposition up to 500°C. The addition of Cu was intended to increase the coke resistance of the catalyst. After synthesis and (in situ) reduction the CuNi nanoparticles were characterized by HR-TEM/EDX, XRD, FTIR (using CO as probe molecule) and NAP-XPS, all indicating a Cu rich surface, even when the overall nanoparticle composition was rich in Ni. Density functional (DF) theory modelling, applying a recently developed computational protocol based on the construction of topological energy expressions, confirmed that in any studied composition Cu segregation on surface positions is an energetically favourable process, with Cu preferentially occupying corner and edge sites. Ni is present on terraces only when not enough Cu atoms are available to occupy all surface sites.When the catalysts were applied for methane decomposition they were inactive at low temperature but became active above 425°C. Synchrotron-based operando NAP-XPS indicated segregation of Ni on the nanoparticle surface when reactivity set in for CuNi-ZrO2. Under these conditions C 1s core level spectra revealed the presence of various carbonaceous species at the surface. DF calculations indicated that both the increase in temperature and especially the adsorption of CHx groups (x=0-3) induce the segregation of Ni atoms on the surface, with CH3 providing the lowest and C the highest driving force.Combined operando and theoretical studies clearly indicate that, independent of the initial surface composition after synthesis and reduction, the CuNi-ZrO2 catalyst adopts a specific Ni rich surface under reaction conditions. Based on these findings we provide an explanation why Cu rich bimetallic systems show improved coke resistance.

Catalytic Methane Decomposition over Fe‐Al2O3

The presence of a Fe-FeAl2 O4 structure over an Fe-Al2 O3 catalysts is demonstrated to be vital for the catalytic methane decomposition (CMD) activity. After H2 reduction at 750 °C, Fe-Al2 O3 prepared by means of a fusion method, containing 86.5 wt % FeAl2 O4 and 13.5 wt % Fe(0) , showed a stable CMD activity at 750 °C for as long as 10 h.

Decomposition of methane over alumina supported Fe and Ni–Fe bimetallic catalyst: Effect of preparation procedure and calcination temperature

Catalytic decomposition of methane has been studied extensively as the production of hydrogen and formation of carbon nanotube is proven crucial from the scientific and technological point of view. In that context, variation of catalyst preparation procedure, calcination temperature and use of promoters could significantly alter the methane conversion, hydrogen yield and morphology of carbon nanotubes formed after the reaction. In this work, Ni promoted and unpromoted Fe/Al2O3 catalysts have been prepared by impregnation, sol–gel and co-precipitation method with calcination at two different temperatures. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, temperature programmed reduction (TPR) and thermogravimetric analysis (TGA) techniques. The catalytic activity was tested for methane decomposition reaction. The catalytic activity was high when calcined at 500°C temperature irrespective of the preparation method. However while calcined at high temperature the catalyst prepared by impregnation method showed a high activity. It is found from XRD and TPR characterization that disordered iron oxides supported on alumina play an important role for dissociative chemisorptions of methane generating molecular hydrogen. The transmission electron microscope technique results of the spent catalysts showed the formation of carbon nanotube which is having length of 32–34nm. The Fe nanoparticles are present on the tip of the carbon nanotube and nanotube grows by contraction–elongation mechanism. Among three different methodologies impregnation method was more effective to generate adequate active sites in the catalyst surface. The Ni promotion enhances the reducibility of Fe/Al2O3 oxides showing a higher catalytic activity. The catalyst is stable up to six hours on stream as observed in the activity results.

Triple-layer catalytic hollow fiber membrane reactor for hydrogen production

Triple-layer hollow fiber catalytic membrane reactor (T-HFCMR) consisting of: (1) Ni-based catalyst (outer) layer; (2) porous inorganic support (middle) layer; and (3) ultrathin Pd-based membrane (inner) layer, has been successfully developed and used as a catalytic membrane reactor for hydrogen production. A 0.16molm−2s−1 of H2 gas can be produced from the T-HFCMR via catalytic decomposition of methane (as a model reaction) at 600°C and 2bar. Due to high H2 permeability of the ultrathin (ca. 1.2µm) Pd-based membrane, up to 84% of the total H2 produced (H2 recovery) can be extracted from the reaction side. Moreover, a constant permeation of H2 from the reaction side also remarkably increases the reaction conversion. Furthermore, mechanical damages (e.g. scratching) of Pd–Ag membrane can also be prevented as the membrane is not exposed directly to the external surface, making it more flexible for practical applications.

Carbon produced by the catalytic decomposition of methane on nickel: Carbon yields and carbon structure as a function of catalyst properties

The interplay of carbon quantity, carbon type, methane decomposition activity and catalyst deactivation by deposited carbon are all important aspects to be considered in assessing the practical use of the catalytic methane decomposition route, using nickel/titania catalysts.Increasing the nickel loading from 7% to 20% in Ni/TiO2 increased methane decomposition conversion but the activities and carbon yields per unit Ni fell as the nickel content increased. The carbon produced on high Ni-loaded samples is more graphitic in nature. Filaments of carbon are the main products and the diameter increases as the Ni particle size on the catalyst increases, which, in turn, increasing at higher Ni loadings. Studies of binary supports on the activity of nickel demonstrated that not all systems led to improved catalyst performance. But, in these systems, factors such as metal-support interaction are also important. Introduction of copper to the supported nickel system exerts an effect on the morphology of the carbon nanostructures produced but other aspects are little affected.