scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Production of hydrogen and carbon nanotubes from methane decomposition in a two-stage fluidized bed reactor

08 Apr 2004-Applied Catalysis A-general (Elsevier)-Vol. 260, Iss: 2, pp 223-228
TL;DR: In this article, a two-stage fluidized bed reactor with Ni/Cu/Al 2 O 3 catalyst was used to decompose methane with high activity in the high temperature condition and then the carbon produced will diffuse effectively to form carbon nanotubes in both low and high temperature regions.
Abstract: Methane decomposition over a Ni/Cu/Al 2 O 3 catalyst is studied in a two-stage fluidized bed reactor. Low temperature is adopted in the lower stage and high temperature in the upper stage. This allows the fluidized catalysts to decompose methane with high activity in the high temperature condition; then the carbon produced will diffuse effectively to form carbon nanotubes (CNTs) in both low and high temperature regions. Thus the catalytic cycle of carbon production and carbon diffusion in micro scale can be tailored by a macroscopic method, which permits the catalyst to have high activity and high thermal stability even at 1123 K for hydrogen production for long times. Such controlled temperature condition also provides an increased thermal driving force for the nucleation of CNTs and hence favors the graphitization of CNTs, characterized by high resolution transmission electron microscopy (HRTEM), Raman spectroscopy and XRD. Multistage operation with different temperatures in a fluidized bed reactor is an effective way to meet the both requirements of hydrogen production and preparation of CNTs with relatively perfect microstructures.
Citations
More filters
Journal ArticleDOI
TL;DR: In this paper, a review of the recent advances in the reaction mechanism and kinetics on group 8-10 base metal catalysts is presented, with special attention paid to the roles of metal particles and the deactivation mechanism of the catalyst during the reaction.

376 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the catalysts that can be used for methane cracking, and their deactivation and regeneration are discussed, including carbon filament formation, the reaction mechanisms, and the models available in the literature for predicting reaction rates.

325 citations

Journal ArticleDOI
Qiang Zhang1, Jia-Qi Huang1, Meng-Qiang Zhao1, Weizhong Qian1, Fei Wei1 
TL;DR: The state-of-the-art of CNT synthesis is described, with a focus on their mass-production in industry, in processes akin to the continuous tonne-scale mass production of chemical products in the modern chemical industry.
Abstract: Our society requires new materials for a sustainable future, and carbon nanotubes (CNTs) are among the most important advanced materials. This Review describes the state-of-the-art of CNT synthesis, with a focus on their mass-production in industry. At the nanoscale, the production of CNTs involves the self-assembly of carbon atoms into a one-dimensional tubular structure. We describe how this synthesis can be achieved on the macroscopic scale in processes akin to the continuous tonne-scale mass production of chemical products in the modern chemical industry. Our overview includes discussions on processing methods for high-purity CNTs, and the handling of heat and mass transfer problems. Manufacturing strategies for agglomerated and aligned single-/multiwalled CNTs are used as examples of the engineering science of CNT production, which includes an understanding of their growth mechanism, agglomeration mechanism, reactor design, and process intensification. We aim to provide guidelines for the production and commercialization of CNTs. Although CNTs can now be produced on the tonne scale, knowledge of the growth mechanism at the atomic scale, the relationship between CNT structure and application, and scale-up of the production of CNTs with specific chirality are still inadequate. A multidisciplinary approach is a prerequisite for the sustainable development of the CNT industry.

314 citations

Journal ArticleDOI
TL;DR: This review paper summarizes the synthesis of various carbon nanomaterials via the chemical vapor deposition (CVD) method, including fullerenes, carbon nanotubes (CNTs), carbon nanofibers (CNFs), graphene, carbide-derived carbon (CDC), carbon nano-onion (CNO) and MXenes.
Abstract: Carbon nanomaterials have been extensively used in many applications owing to their unique thermal, electrical and mechanical properties. One of the prime challenges is the production of these nanomaterials on a large scale. This review paper summarizes the synthesis of various carbon nanomaterials via the chemical vapor deposition (CVD) method. These carbon nanomaterials include fullerenes, carbon nanotubes (CNTs), carbon nanofibers (CNFs), graphene, carbide-derived carbon (CDC), carbon nano-onion (CNO) and MXenes. Furthermore, current challenges in the synthesis and application of these nanomaterials are highlighted with suggested areas for future research.

262 citations


Additional excerpts

  • ...Horváth et al. [81] produced MWCNTs by the spray-pyrolysis method....

    [...]

  • ... On the other hand, MWCNTs can be defined as concentric  cylinders made from graphene sheets with diameters up to 100 nm [46]....

    [...]

  • ... C nversely, multilaye s of graphene sheets are know   as  m lti‐walled  carbon  nanotubes  (MWCNTs)....

    [...]

  • ... In fact, there are two types of CNTs  i.e.,  single‐walled nanotubes (SWCNTs) and multi‐walled nanotubes (MWCNTs) as shown in Figure 5....

    [...]

  • ...Conversely, multilayers of graphene sheets are known as multi-walled carbon nanotubes (MWCNTs)....

    [...]

Journal ArticleDOI
TL;DR: In this paper, a review of catalytic decomposition of hydrocarbons for the CO2-free generation of hydrogen for fuel cell applications through a single-step cracking (decomposition, decarbonization, dehydrogenation, pyrolysis, splitting, or dissociation) is presented.
Abstract: This review assesses technologies and catalysts pertaining to the catalytic decomposition of hydrocarbons for the CO2-free generation of hydrogen for fuel cell applications through a single-step cracking (decomposition, decarbonization, dehydrogenation, pyrolysis, splitting, or dissociation) of hydrocarbons. It discusses and systematically categorizes the options for hydrocarbon decomposition to hydrogen and carbon. This decomposition helps to reduce green house gases by co-producing valuable carbon products such as carbon black or graphite-like carbon (carbon nanotubes or carbon filaments). The catalytic approach comprises metal and carbon-based catalysts while plasma-based decomposition depends on thermal or non-thermal methods. Almost all the proposed processes are applicable to a variety of gaseous and liquid hydrocarbon fuels, and some of these processes can potentially produce a stream of high-purity hydrogen. There have been successful attempts to use catalysts to reduce the maximum temperature of the thermal decomposition of hydrocarbons. Common catalysts used are noble and transition metals such as Ni, Fe, Pd, Co, Mo, etc., supported on high surface area ceramic substrates such as A12O3 and SiO2, etc. Several other publications disclose the use of carbon-based materials as catalysts for decomposition of hydrocarbons into H2 and carbon. The other non-catalytic decomposition methods include non-thermal low-temperature plasmas such as RF (radio frequency), dc (direct current) generators, microwave plasmatrons, and arc plasma jet.

211 citations

References
More filters
Journal ArticleDOI
TL;DR: The literature treating mechanisms of catalyst deactivation is reviewed in this paper, which can be classified into six distinct types: (i) poisoning, (ii) fouling, (iii) thermal degradation, (iv) vapor compound formation accompanied by transport, (v) vapor solid and/or solid solid reactions, and (vi) attrition/crushing.
Abstract: The literature treating mechanisms of catalyst deactivation is reviewed. Intrinsic mechanisms of catalyst deactivation are many; nevertheless, they can be classified into six distinct types: (i) poisoning, (ii) fouling, (iii) thermal degradation, (iv) vapor compound formation accompanied by transport, (v) vapor-solid and/or solid-solid reactions, and (vi) attrition/crushing. As (i), (iv), and (v) are chemical in nature and (ii) and (v) are mechanical, the causes of deactivation are basically three-fold: chemical, mechanical and thermal. Each of these six mechanisms is defined and its features are illustrated by data and examples from the literature. The status of knowledge and needs for further work are also summarized for each type of deactivation mechanism. The development during the past two decades of more sophisticated surface spectroscopies and powerful computer technologies provides opportunities for obtaining substantially better understanding of deactivation mechanisms and building this understanding into comprehensive mathematical models that will enable more effective design and optimization of processes involving deactivating catalysts. © 2001 Elsevier Science B.V. All rights reserved.

2,526 citations

Journal ArticleDOI
R.T.K. Baker1
01 Jan 1989-Carbon
TL;DR: A review of the information obtained by the author and his many co-workers from studies devoted to the formation of a fascinating material, filamentous carbon, is given in this article.

1,145 citations

Journal ArticleDOI
TL;DR: In this article, a detailed description of the formation and the gasification of filamentous carbon is given, and a thermodynamic basis for the different solubilities is provided, where the segregation of carbon, taking place at the gas side of the nickel particle is added as one of the steps in the global mechanism of carbon filament formation and gasification.

378 citations

Journal ArticleDOI
Ping Chen1, H.-B. Zhang1, G.-D. Lin1, Qingqi Hong1, KR Tsai1 
01 Jan 1997-Carbon
TL;DR: In this paper, the NiO and MgO components in this catalyst precursor formed, due to their highly mutual solubility, a NixMg1 − xO solid solution, and the high dispersion of Ni-species in this solid solution and the effect of valence-stabilization by the mgO crystal field would be in favor of inhibiting deep reduction of Ni2+ to Ni0 and aggregation of the Ni0 to form large metal particles at the surface of catalyst.

337 citations

Journal ArticleDOI
TL;DR: In this paper, a single-step decomposition of methane and other hydrocarbons over carbon-based catalysts in an air/water free environment is discussed, where clean carbon is produced as a valuable byproduct of the process.

326 citations