Author: École polytechnique (Montréal, Québec). Département de génie chimiquePublisher:
ISBN:
Category :
Languages : en
Pages : 150
Book Description
Kinetic Study of the Steam-methane Reforming Over Nickel Catalyst in a Continuous Stirred Tank Reaction
Author: École polytechnique (Montréal, Québec). Département de génie chimiquePublisher:
ISBN:
Category :
Languages : en
Pages : 150
Book Description
Energy Research Abstracts
Author: Studies of Mechanisms and Kinetics of Methane and Ethane Steam Reforming on Nickel Catalysts
Author: Huo-Yen HsiehPublisher:
ISBN:
Category : Ethanes
Languages : en
Pages : 392
Book Description
American Doctoral Dissertations
Author: Publisher:
ISBN:
Category : Dissertation abstracts
Languages : en
Pages : 552
Book Description
Computational Heterogeneous Catalysis Applied to Steam Methane Reforming Over Nickel and Nickel/silver Catalysts
Author: Donnie Wayne BlaylockPublisher:
ISBN:
Category :
Languages : en
Pages : 188
Book Description
The steam methane reforming (SMR) reaction is the primary industrial means for producing hydrogen gas. As such, it is a critical support process for applications including petrochemical processing and ammonia synthesis. In addition, SMR could be an important component of future energy infrastructures as a means for producing hydrogen as an energy carrier for applications including fuel cells in automobiles and direct combustion for electricity generation. Nickel is the preferred SMR catalyst; however, the efficiency of SMR over nickel can be severely hindered by carbon formation, which leads to the deactivation or even destruction of the catalyst particles. Thus, there is significant interest in catalysts that inhibit carbon formation yet retain activity to SMR. In order to develop improved catalysts for SMR, a thorough understanding of the processes occurring on the nickel surface is needed. In this thesis, computational heterogeneous catalysis is applied to investigate steam methane reforming over nickel (Ni) and silver-alloyed nickel (Ni/Ag) catalysts. Electronic structure calculations using density functional theory (DFT) are employed to develop thermochemical landscapes describing the relative stabilities of SMR intermediates on the catalyst surfaces. In addition, DFT calculations are used to obtain kinetic parameters that describe elementary surface reactions taking place during SMR. A detailed statistical thermodynamics framework is developed to allow for the calculation of enthalpies, entropies, and free energies of the surface species at the temperatures and pressures relevant to industrial SMR. The data from the DFT calculations are used to build detailed ab inito microkinetic models of SMR over the multi-faceted nickel catalyst. The resulting microkinetic models are used to provide insight into the processes occurring on the catalyst surface through identifying the most important intermediate species and reactions occurring on the catalyst. The effects of alloying the nickel catalyst with silver are predicted through modeling the dissociative methane adsorption reaction on multiple facets of the Ni/Ag surface with varying concentrations of silver. In addition, DFT calculations are used to investigate carbon formation on the Ni and Ni/Ag catalyst surfaces, including relative stabilities of various carbon-containing intermediates and the effects of alloying the nickel surface with silver on carbon formation.
Experimental Investigation of Methane Reformer with a Continuous Flow Reactor
Author: Xiao Zhang (Ph.D.)Publisher:
ISBN:
Category : Chemical reactors
Languages : en
Pages : 100
Book Description
Over the decades, seeking for an alternative energy source has been more and more significant because of increasing demand with rapid industry expansion. Liquid hydrocarbon from Fischer-Tropsch process is considered as an alternative fuel source because the product is considered as subtle for petroleum-derived. Syngas as feedstock for F-T process plays a crucial role in liquid hydrocarbon production. Among several commercial and experiment technologies, the most common technology for syngas production is natural gas reforming. The product from reforming process has proper carbon monoxide/hydrogen ratio for direct application in F-T synthesis. Meanwhile, combined carbon dioxide into reforming reaction has attracted more and more attention in recent studies, which has great potential to help reduce emission of greenhouse gas. However, the main challenge for reforming process is to maintain reaction for a long period running. In this study, a lab-scale reactor is designed and evaluated to achieve high efficiency for 2 types of reforming reaction, steam reforming and dry reforming. For this reactor, methane, the main content of natural gas, was used as reactant gas in the reactor for progressive understanding of reforming. The Nickel based catalyst supported by SiO2 is preloaded and fixed in the catalyst zone of reactor. The selection and preparation for catalyst and support has been discussed in this study. For Steam Methane Reforming reaction, experimental work is conducted under Steam/Carbon ratio from 1 to 4, temperature range from 700 ̊C to 800 ̊C. Methane is fed to the reactor at flow rate 55 sccm at 1 atm pressure, where experimental conversion data were obtained. The conversion rate of methane is calculated as a standard for evaluation of reactor efficiency. As part of Fischer-Tropsch process, the quality of gas production is evaluated by H2/CO ratio. The catalyst is examined by XRD and EDAX spectrum for carbon formation test. For Dry Methane Reforming reaction, experiment is conducted under a temperature range from 500 ̊ C to 700 ̊ C with molar ratio of CH4/CO2 1. The total flow rate for mixture gas is 65 sccm. The conversion rates for both methane and carbon dioxide are calculated. The product quality is examined by H2/CO ratio. The catalyst stability test is conducted in a high carbon intensity with a CO2/CH4 ratio 4 at 700 ̊ C and total flow rate 65 sccm. The catalyst is separately characterized in 3 different phases by SEM and XRD technology to identify carbon deposition. The results from experiments state that the reactor is able to convert methane to syngas with high efficiency and high tolerance for carbon deposition at high temperature environment. COMSOL software is applied for reforming reaction process simulation, and the results from simulation support the statement from experiment.
Methane Steam Reforming Over Ni-based Catalysts
Author: Fanglin ChePublisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 510
Book Description
Finally, we provide a 'bottom-up' fundamental insight into two debates regarding methane activation over Ni-based catalysts, including the role of a low concentration of carbon or carbide species and the role of electric fields in a fuel cell system. Our DFT results suggest that inducing a local change of the Ni oxidation states can markedly enhance methane activation. Overall, this thesis will be instructive for the design of heterogeneous reactors with tunable metal oxidation states via the modification of the surface carbon or the interface carbide complex as well as the addition of reaction environment factors (e.g., electric fields).
Studies of Mechanisms and Kinetics of Methane and Ethane Steam Reforming on Nickel Catalysts
Author: Larry Steven WigmanMethane Steam Reforming Over LaCr¦1¦-¦xNi¦xO¦3 Perovskite Catalysts
Author: Ram Chandra PaulPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
The kinetics of the steam reforming of methane over perovskite catalysts with the formula LaCr1-xNixO3 (x = 0.25 & 0.40) have been examined over a wide range of temperatures (500°C to 1000°C) and atmospheric pressure. These catalysts work well from 700 to 900°C for methane conversion (space velocity = 13,500 hr-1 , and gas composition is CH4 : H2 : H2 O : Ar = 2 : 3 : 6 : 30), the higher nickel content (Ni = 0.40) catalyst is more active than the lower nickel content (Ni = 0.25) catalyst. The water-gas shift reaction is close to equilibrium, while the steam reforming reaction is not at equilibrium for the conditions studied. Activity behaviour is in agreement with 'Marko's' methane oxidation result (1 ). However, these catalysts are unstable in the reforming environment, as they partially reduce to elemental nickel at high temperatures (worked up to 1000°C. Structural changes (from orthorhombic to rhombohedral) occur at lower temperatures (investigated up to 750°C). The higher nickel content catalysts are less stable than the lower nickel content catalysts.
Comprehensive Dissertation Index
Author: Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 760
Book Description