Dry Reforming of Methane on Promoted (LA, MG, and RH) NI Based Catalyst Supported on Commercial Silica PDF Download
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Author: Ali khansa
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 60
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Book Description
Author: Ali khansa
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 60
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Abstract : The development of highly efficient and stable catalysts for dry reforming of methane (DRM) and the revealing of catalyst structural evolution during DRM process are necessary. In this dissertation, the research work was focused on (1) DRM performance enhancement of NiO/MgO solid solution by tuning the crystal particle size of MgO, (2) the effect of NiO/MgO solid solution formation on DRM performance, (3) the structural evolution of NiO/MgO catalyst under long-term DRM operation, and (4) the stabilization of Ni/Al2O3 catalyst by a NiAl2O4 isolation layer for DRM. First, the crystal particle size of MgO was tuned by ball-milling and then exploited to prepare NiO/MgO solid solution catalysts. It was revealed that the catalytic activity of NiO/MgO solid solution catalyst for DRM could be promoted by decreasing MgO crystal size. The structures of NiO/MgO catalysts were correlated with their catalytic performance (Chapter 3). The formation effects of the solid solution catalysts were revealed, including the generation of abundant mesopores, the promotion of CO2 absorption, and the limitation of CO adsorption. Consequently, the solid solution catalysts exhibited the excellent catalytic activity and stability for DRM (Chapter 4). The structural evolution of the NiO/MgO solid solution catalyst was examined with long duration test of DRM. It was demonstrated that Ni nanoparticles (NPs) of the catalyst grow from 5 to 36 nm after the operation for 1500 hours, which was resulted from the Ni exsolution induced by the reactant gas, while no coking was formed on the xxii catalyst. The unique bonds between metallic Ni and Mg were firstly found to play an important role in the superior performance of the catalyst (Chapter 5). It was found that a NiAl2O4 spinel isolation layer could be generated when the Ni/Al2O3 catalyst was treated under a repeated reduction-reaction process. The isolation layer can prevent active Ni sites from the contact to Al2O3 surface, thus enhancing the stability of the catalyst (Chapter 6).
Author: Rothman Yu-Fai Kam
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Both dry reforming of methane (DRM) and low-temperature water-gas shift (LT-WGS) processes can be integrated into a fuel cell plant and are utilised for the production of hydrogen as an important energy source for fuel cells. Improvement of current catalytic systems, and identification and development of alternative catalysts for DRM and LT-WGS reactions have formed the basis of this study. In the first stage of the work, the influence of WO3 on a Pt/CeO2 catalyst was investigated for the dry reforming of methane. It was found that Pt/CeO2 catalysts loaded with WO3 at 10 mol% to 20 mol% were very stable during 20 hours of dry reforming of methane operation in comparison to a commercial Ni catalyst. However further addition of WO3 (>70%) promoted coking on the Pt/CeO2 sample, ultimately leading to catalyst deactivation. It was also desirable to develop catalysts with higher activity to reduce operating cost, thus the physicochemical properties of different materials were assessed to identify parameters important for LT-WGS activity. Copper catalysts on metal oxide support (CeO2, ZnO, TiO2, SiO2, Al2O3, ZrO2, MgO and SnO2) were screened, while characterisation showed the catalyst adsorbing H2O and CO was crucial in generating LT-WGS activity, with Cu/ZnO attaining the highest LT-WGS activity. Lanthanum (La) was known to have high affinity for H2O, hence the effects of La doping on Cu/ZnO catalysts for use in LT-WGS reaction was investigated. The findings indicated the La promoter improved activity at a loading of 2.3 wt%, above which the activity significantly decreased. A systematic investigation has also been conducted on the effects of oxygen introduction on the Cu-based and Pt-based catalysts during LT-WGS operation with particular attention on the pyrophoricity (i.e. vulnerability to oxidative sintering) of the catalysts, and the impacts on key material characteristics. The objective was to examine whether the catalysts were suitable for fuel cell applications. It was observed that the Cu-based catalysts were pyrophoric and therefore not a suitable catalyst. No pyrophoricity was observed for Pt-based catalysts. Pt/CeO2 was the only catalyst that retained its activity, displaying no loss in specific surface area or metal dispersion throughout the entire process, rendering it a suitable candidate for fuel cell systems.
Author: Hassana El Zein
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 63
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Author: Muhamad Hisyam Zakaria
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 53
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Syngas (or H2 and CO mixture) production has received significant attention since it is the main feedstock of Fischer-Tropsch synthesis for synthetic fuel manufacture to replace petroleum-based energy. Dry reforming of methane (DRM) has been considered as an efficient and green approach for producing syngas due to greenhouse gas utilization and desired syngas composition. In this research, the objectives were to prepare 3%Ce-10%Ni/Al2O3, to investigate the physicochemical attributes of 3%Ce-10%Ni/Al2O3 catalyst and examine the effect of reactant partial pressure on DRM performance. XRD diffractograms indicated the formation of CeO2, NiO and NiAl2O4 phases corroborated with temperature-programmed calcination (TPC) results. The complete thermal decomposition and oxidation of metal precursors were observed at 750 K during TPC measurement. DRM performance over 3%Ce-10%Ni/Al2O3 catalyst was stable with time-on-stream for all CO2:CH4 ratios. CH4 and CO2 reaction rates enhanced with growing CO2 partial pressure (PCO2) and exhibited a maximum at PCO2=30 kPa. CH4 conversion enhanced with growing CO2 partial pressure (PCO2) and exhibited a maximum at PCO2=40 kPa and CO2 conversion vice versa to the CH4 conversion. H2 , CO selectivity and yield enhanced with lessen CO2 partial pressure (PCO2) and exhibited a maximum at PCO2=20 kPa. Interestingly, H2/CO ratio also reduced with an increase in CO2 partial pressure and the ratio of H2/CO was always inferior to unity for all runs reasonably due to the reverse water-gas shift reaction.
Author: Joudie Youssef
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 64
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Book Description
The reduction of greenhouse gases utilization and emission is the main interest of the scientists all over the world. Dry reforming of methane (DRM) is gaining more attention, due to its consumption of two greenhouse gases, namely methane and carbon dioxide, and its production of syngas. Moreover, the products ratio (1:1) of H2: CO is suitable for Fishcher-Tropsch synthesis. DRM is highly endothermic and requires severe conditions to proceed thermodynamically. Thus, the main challenge is the design a catalyst that can maintain its activity and stability under the reaction conditions. Noble metals have showed great catalytic activity and stability when used as an active phase in DRM catalysts. However, their use is not favored to economic an accessibility reasons. Nickel-based catalysts are an affordable and available promising alternative for noble metals. Thus, Nickel was used as an active phase in this study. The mesoporous based silica support, Santa-Barbara Amorphous material (SBA-15), used as catalytic supports in DRM, provide good dispersion of the active phase and good prevention to sintering. Thus SBA-15 is chosen as a support for Nickel in this study. The main focus of this thesis is to study the effect of the modifications made during SBA-15 synthesis (acidity, stirring rate, hydrothermal treatment, etc) on the activity/stability performance of Ni-based catalyst. In this study, eight supports SBA-15(x) were prepared and characterized by N2 sorption and showed different textural properties. Then, all the samples were impregnated with 5wt % Nickel using the two solvent impregnation method. Finally, eight catalysts Ni5/SBA-15(x) are obtained. The calcined fresh samples are characterized by N2 sorption, TPR, TEM, SEM and XRD. The results suggest similar SBA-15 structures with a small difference in grains shape .In addition, differences in Nickel particles size and localization are observed. A good dispersion of the Nickel particles is noted for all the catalysts. Catalytic activities are measured with a GHSV of 3600mL.g-1.h-1 at temperatures ranging from 200 to 800°C and atmospheric pressure. Stability measurements are conducted with the same GHSV at a fixed temperature of 650°C for 12 hours. The catalysts showed high activity and selectivity toward DRM. No significant deactivation is observed throughout the stability test.The characterizations by SEM and XRD after the test indicate that no sintering took place. The main cause of the small deactivation is due to coke deposition. Further studies of the spent catalysts by TEM are required to determine the type of coke deposited.
Author: Rafael Luque
Publisher: Royal Society of Chemistry
ISBN: 1788014901
Category : Science
Languages : en
Pages : 370
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This book presents an introduction to the preparation and characterisation of nanomaterials and their design for specific catalytic applications.
Author: Ye Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Dry reforming of methane represents an attractive way to the conversion of two greenhouse gases (CO2 and CH4) into valuable products. Transition metal Ni is universally considered as an alternative to noble metal for DRM, due to its high activity and low cost. However, Ni-based catalysts suffered deactivation resulted from sintering of the active phase and carbon deposition, thus its practical application is not actually possible. So, there is a need to develop a cost-effective catalyst, able to withstand high temperatures and able to resist deactivation.First, the Ni-Zr catalysts were prepared by the one step urea hydrolysis method and were evaluated on the dry reforming of methane. Secondly, different promoters (such as Y, Al, Mn, and Mg) with Ni-Zr were co-synthesized by the same method (urea hydrolysis). The relationship between performance and structure is analyzed by activity test and multiple characterizations, such as BET, XRD, H2-TPR, CO2-TPD, TEM, XPS and Raman. Among them, the Y-modified catalysts improved the resistance to carbon deposition by increasing the weak and medium-strength basic sites. Also, the presence of Al could enhance the catalytic performance due to larger pore volume and diameter after aluminum introduction. The addition of Mn led to the increase of the catalytic activity with time on stream because of a more stable structure of ZrO2 species and a redistribution of nickel species.Thus, the choices of different promoters result in diversification in the specific surface area, Ni0 crystallite size, and basicity, which may further affect the catalytic performance of prepared catalysts.
Author: Charles N. Satterfield
Publisher: Krieger Publishing Company
ISBN: 9781575240022
Category : Technology & Engineering
Languages : en
Pages : 554
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Book Description
Blending theory and practice, this text provides the information needed to work with solid catalysts in the laboratory, pilot plant or commercial installation. This revised and expanded edition incorporates recent theories and industrial applications.
Author: Joy Tannous
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 75
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