Catalytic Decomposition Of Natural Gas Research Articles

La2O3 supported bimetallic catalysts for the production of hydrogen and carbon nanomaterials from methane

The production of hydrogen and carbon nanomaterials was investigated via catalytic decomposition of natural gas. Bimetallic catalysts, containing Ni and Co, supported over La2O3 were tested for decomposition reaction. The variation in metal loading, gas hourly space velocity (GHSV) and reaction temperature were studied to assess the influence of these important parameters on the catalytic performance. The catalytic testing and characterization results revealed that among all the tested catalysts, the catalyst containing 12.5 wt% Ni and 12.5 wt% Co supported over La2O3 showed higher methane conversion as well as carbon nanomaterials yield. Different characterization techniques such as Inductively coupling plasma atomic absorption spectroscopy (ICP-AES), Brunauer–Emmett–Teller (BET), temperature-programmed reduction (TPR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM) were employed to study the morphological nature of the catalysts before and after reaction.

Production of hydrogen and carbon nanofibers from methane over Ni–Co–Al catalysts

Catalytic decomposition of natural gas has been opted as an alternative route for hydrogen production. Nickel- and Cobalt-based bimetallic catalysts over alumina support were prepared by the co-precipitation method for the investigation of hydrogen production via catalytic decomposition of methane. The effect of different important parameters such as reaction temperature, gas hourly space velocity (GHSV) and metal loading were studied. The catalytic activity and stability results revealed that the catalyst having 25 wt.% each of Ni and Co (25NCA) exhibited the best performance among all tested catalysts. The textural and morphological nature of the calcined and spent catalysts were examined using different characterization techniques including BET, temperature-programmed reduction (TPR), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM).

Catalytic Decomposition of Natural Gas to CO/CO2-Free Hydrogen Production and Carbon Nanomaterials Using MgO-Supported Monometallic Iron Family Catalysts

Monometallic Fe, Co, and Ni/MgO catalysts with 50 wt.% metal loadings were prepared and examined for natural gas decomposition to nanocarbonaceous materials, particularly multiwalled carbon nanotubes (MWCNTs) and co-valuable hydrogen. The catalytic testing was carried out in a fixed-bed horizontal reactor at 700°C under atmospheric pressure. The fresh and/or used catalysts were characterized using XRD, TPR, HRTEM, SEM, TG/DTA, Raman spectroscopy, and BET surface measurements. The resulting data showed that the 50%Co/MgO catalyst displayed higher catalytic decomposition activity of natural gas to COx-free hydrogen production (∼88%), higher yield of MWCNTs, and excellent stability up to 10 h time-on-stream. On the other hand, the Ni-containing catalyst showed lower catalytic activity toward hydrogen and CNTs production, principally due to the formation of rock-salt MgxNi(1-x)O solid solution as observed from XRD and TPR data. Accordingly, the concentration of Ni particles required for natural gas feed was extremely low. The d orbital of Ni was presumed to be occupied during the formation of the solid solution, which inhibits the solublization or adsorption of hydrocarbons on Ni particles. The MWCNTs obtained over Ni-based catalyst had narrow and homogeneous diameters (∼11–13 nm). However, the Fe/MgO catalyst exhibited intermediate activity between those of Ni and Co˭MgO catalysts toward hydrogen production (∼44%). This catalyst produced mixtures of carbon nanofibers and nanotubes.

Effect of progressive Co loading on commercial Co–Mo/Al2O3 catalyst for natural gas decomposition to COx-free hydrogen production and carbon nanotubes

Successive cobalt increments from 3.1% up to 40.0% in a commercial hydrotreating catalyst containing originally 3.1%Co and 10.5%Mo on γ-Al2O3 was investigated at a reaction temperature of 700°C and atmospheric pressure for the catalytic decomposition of natural gas to CO/CO2 free hydrogen and carbon nanomaterials. The fresh and used catalysts were characterized by XRD, BET, TEM and TG-DTA analysis. The catalytic performance data showed that the increase of cobalt concentration improved the catalytic dissociation activity and longevity toward hydrogen production. All surface properties declined with successive addition of cobalt in the catalysts. XRD results showed that the crystallinity was remarkably enhanced and Co3O4 phases predominate upon addition of the cobalt precursor. The catalytic activity was found to be primarily dependent on the extent and degree of isolation of Co3O4 phases on the catalyst surface which reflects that the current reaction is a metal catalyzed one. The influence of metal content on the total carbon yield and the degree of graphitization of the resulting CNTs was investigated by TGA, XRD, Raman spectroscopy and TEM analysis.

H2 production by methane decomposition: Catalytic and technological aspects

Abstract Ni and Co supported on SiO 2 and Al 2 O 3 silica cloth thin layer catalysts have been investigated in the catalytic decomposition of natural gas (CDNG) reaction. The influence of carrier nature and reaction temperature was evaluated with the aim to individuate the key factors affecting coke formation. Both Ni and Co silica supported catalysts, due to the low metal support interaction (MSI), promote s the formation of carbon filament with particles at tip. On the contrary, in case alumina was used as support, metals strongly interact with surface thus depressing both the metal sintering and the detachment of particles from catalyst surface. In such cases, carbon grows on metal particle with a “base mechanism” while particles remain well anchored on the catalyst surface. This allowed to realize a cyclic dual-step process based on methane decomposition and catalyst oxygen regeneration without deactivation of catalyst. Technological considerations have led to conclude that the implement of a process based on decomposition and regeneration of catalyst by oxidation requires the development of a robust catalytic system characterized by both a strong MSI and a well defined particle size distribution. In particular, the catalyst should be able to operate at high temperature, necessary to reach high methane conversion values (> 90%), avoiding at the same time the formation of both the carbon filaments with metal at tip or the encapsulating carbon which drastically deactivate the catalyst.

CH 4 decomposition on Ni and Co thin layer catalysts to produce H 2 for fuel cell

Ni and Co supported on SiO 2 and Al 2O 3 Silica Cloth Thin Layer Catalysts (TLC) were investigated in the Catalytic Decomposition of Natural Gas (CDNG) reaction using a Multilayer Catalytic Reactor (MCR). The influence of support and reaction temperature was evaluated with the aim to design a novel catalyst suitable to develop a dual-step process to produce pure hydrogen for fuel cell. Ni and Co silica supported catalyst, due to the low metal supported interaction (MSI) characterizing such systems, were not found suitable to efficiently perform CDNG reaction. On the contrary in case alumina was used as support both metals strongly interact with surface becoming so more resistant to sintering. In addition in case the metals (both Ni and Co) strongly interact with support surface, the formation of encapsulating carbon is depressed and only filamentous carbon forms. Using Ni and Co TLC supported on Al 2O 3 samples it has been possible to realize a cyclic dual-step process based on reaction and regeneration in oxygen stream without any catalyst detriment. A deactivation modelling to discriminate the role of sintering and coking on the deactivation pattern is proposed.

Methane decomposition over Co thin layer supported catalysts to produce hydrogen for fuel cell

Co/Al 2O 3/Silica Cloth Thin Layer Catalysts (CoAS) for Catalytic Decomposition of Natural Gas (CDNG) were investigated using a new Multilayer Catalytic Reactor (MCR). The influence of Co loading and reaction temperature was evaluated. Irrespective of Co loading, initial CH 4 conversion rises with T R, while for lifetime and carbon capacity (C/Ni, number of CH 4 molecules decomposed for Ni atom until complete deactivation) it is not possible to find a direct relationship with other operating parameters or catalyst characteristics. However, Co loading significantly affects the catalytic activity: Co loading as high as 20 wt.% ensures both long lifetime and high H 2 productivity. On the contrary of what occurs using Ni-based catalysts and irrespective of reaction temperature investigated, filamentous coke forms with a “base” reaction mechanism and Co catalyst can be regenerated in oxygen without any problem, thus allowing to realize a dual-step process for the production of “CO x-free” hydrogen stream.

CFD analysis of multi-phase turbulent flow in a solar reactor for emission-free generation of hydrogen

There have been studies dedicated to finding environmentally friendly solution to impending shortage of fossil fuels by using concentrated solar energy, but the catalytic decomposition of methane using concentrated solar energy has attracted researchers in recent years for its potential to lead to the development of CO2 free hydrogen production process [1-6]. Using concentrated solar energy as process heat, catalytic decomposition of natural gas can be achieved via steam reforming [7] or without introducing water into the media [8]. This study focuses on the latter technique, referred to as “solar cracking” of natural gas, which is illustrated in Figure 1.

Doped Ni Thin Layer Catalysts for Catalytic Decomposition of Natural Gas to produce hydrogen

Doped Ni-based Thin Layer Catalysts (Ni-TLCs) for Catalytic Decomposition of Natural Gas (CDNG) were investigated using a new Multilayer Catalytic Reactor (MCR). The influence of K, La, Mg and Cl on activity–stability patterns of a Ni-TLC catalyst was evaluated. An inverse straight-line relationship between carbon capacity (C/Ni, number of CH 4 molecules decomposed for Ni atom until complete deactivation) and reaction temperature was found independently of the dopant used. However, dopants significantly affect Ni specific activity (TOF, s −1), acting as either an electronic promoter or inhibiting Ni sintering phenomena. Reaction temperature is a key parameter in determining the evolution of coke. At low reaction temperature (<823 K), carbon whiskers form prevalently on “bare” and Mg, La, and Cl doped samples, whereas only the encapsulating carbon type formed on a K doped system. High hydrogen productivity was obtained on an Mg doped catalyst which, furthermore, proved to be the most stable system.

The graphitization of carbon nanofibers produced by the catalytic decomposition of natural gas

Fishbone carbon nanofibers (CNFs) were produced by methane decomposition in a fluidized bed reactor using nickel–copper based catalysts that were prepared with different promoters (SiO 2, Al 2O 3, TiO 2, MgO). The CNFs were subjected to heat treatment (HT) in the temperature range 2400–2800 °C to explore their ability to graphitize. The influence of treatment temperature and CNF metal content on the structural and textural parameters of the resulting heat treated carbon nanofibers was studied. More-ordering was achieved in CNFs containing Si and Ti because of the catalytic effect of these metals. Since titanium carbide appeared after the HT, the formation of graphitic material by carbide decomposition seems to be a plausible mechanism to explain the catalytic graphitization of the CNFs. A parallel evolution of the structural and textural properties of the nanofibers during HT was found, suggesting that a decrease of the specific surface area is caused by the removal of structural defects and an increase of crystallite size.

Catalytic decomposition of natural gas for COx-free hydrogen production in a structured multilayer reactor

Abstract Using a new structured multilayer reactor (MLR) that houses Ni based thin layer catalysts, catalytic decomposition of natural gas (CDNG) for making “COx-free” hydrogen in a TR range of 773–873 K was investigated. The influence of Ni loading (5–50 wt%), Ni particle size, TR, and GHSV (h−1) on the reaction pattern was evaluated. A volcano shape relationship between H2 space time yield ( ST Y H 2 , s t p d m H 2 3 / k g Ni / h ) and Ni loading with a maximum range of 20–25 wt% was found. H2 productivity and catalyst lifetime are controlled by the nature of the coke formed on Ni active species. As such, TR and GHSV significantly affect both the kinetics and the mechanism of coking. At TR 2000 h−1) encapsulating carbon is formed, causing a sudden decline in catalytic activity. A preliminary attempt to find optimal operating conditions ensuring the highest values of H2 productivity is presented. The features of the MLR that allowed CDNG reaction under a quasi-isothermal regime without any pressure drop, irrespective of operating conditions and the extent of carbon formation, are discussed.

Catalytic decomposition of natural gas to hydrogen for fuel cell applications

This paper presents a concept for a fuel processor based on the catalytic decomposition of natural gas to hydrogen for fuel cell applications. In this concept, natural gas is decomposed over a catalyst; carbon is deposited on the catalyst and hydrogen is produced. Once the catalytic bed is filled with carbon, it is regenerated by burning the carbon in air. A fuel processor based on this concept instead of steam reforming of natural gas (the process currently in use) would produce a hydrogen gas stream with purity greater than 95% (compared to 75% with conventional steam reforming) that would not contain any CO or CO 2. Such a system would be potentially simpler, smaller and less expensive compared to the current fuel processor technology based on steam reforming. The proposed fuel processor concept is particularly attractive for fuel cells requiring pure hydrogen feed streams, such as SPFCs.