Effect of Pretreatment Conditions on Catalytic Performances of Mesoporous Ni5/SBA-15 Catalyst in Methane Dry Reforming PDF Download
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Author: Charbel Harika Publisher: ISBN: Category : Catalysis Languages : en Pages : 41
Book Description
Researchers have been studying dry reforming of methane (DRM) to produce syngas, a mixture of hydrogen and carbon monoxide, from methane and carbon dioxide. In this study, catalysts containing 5% wt Ni dispersed on SBA-15 support were prepared by "two solvent impregnation" method. Without prior calcination, three samples were pretreated by reduction under different atmospheres (H2/Ar, N2, Ar) at 450°C with a heating rate of 0.5°C/min. Two other samples were reduced under H2/Ar but at different temperatures and heating rates (650°C with 10°C/min, and 450°C with 0.5°C/min). After the catalysts characterization (N2 sorption, XRD and TPR) and the catalytic tests (activity and stability), Ni5/SBA-15(U-H2) (reduced under H2/Ar at 450°C with a heating rate 0.5°C/min) showed the best catalytic performance among the other catalysts studied. The behavior of Ni5/SBA-15(U-H2) is close to the behavior of Ni5/SBA-15 calcined at 450°C with a heating rate 0.5°C/min.
Author: Charbel Harika Publisher: ISBN: Category : Catalysis Languages : en Pages : 41
Book Description
Researchers have been studying dry reforming of methane (DRM) to produce syngas, a mixture of hydrogen and carbon monoxide, from methane and carbon dioxide. In this study, catalysts containing 5% wt Ni dispersed on SBA-15 support were prepared by "two solvent impregnation" method. Without prior calcination, three samples were pretreated by reduction under different atmospheres (H2/Ar, N2, Ar) at 450°C with a heating rate of 0.5°C/min. Two other samples were reduced under H2/Ar but at different temperatures and heating rates (650°C with 10°C/min, and 450°C with 0.5°C/min). After the catalysts characterization (N2 sorption, XRD and TPR) and the catalytic tests (activity and stability), Ni5/SBA-15(U-H2) (reduced under H2/Ar at 450°C with a heating rate 0.5°C/min) showed the best catalytic performance among the other catalysts studied. The behavior of Ni5/SBA-15(U-H2) is close to the behavior of Ni5/SBA-15 calcined at 450°C with a heating rate 0.5°C/min.
Author: Joudie Youssef Publisher: ISBN: Category : Catalysis Languages : en Pages : 64
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: Sreya Mariya Seby Publisher: ISBN: Category : Catalyst supports Languages : en Pages : 56
Book Description
Development of an effective High Temperature Fischer-Tropsch Synthesis (HTFTS) catalyst is of interest in process intensification that combines methane reforming with long chain hydrocarbon production. Literature indicates iron catalysts supported on mesoporous silica performed relatively well in high temperature applications. In this work, we investigated the effect of manganese promoter on iron catalysts for FTS at 430 °C as it was known from previous studies that manganese promotion could enhance the CO conversion with higher hydrocarbon yields. Also, the effect of temperature on FTS activity was evaluated by testing the base and promoted Fe/SBA-15 catalysts for temperature ranging from 370 to 430 °C. Incipient wetness impregnation method was used to prepare the catalysts. The catalysts used in this work were un-promoted iron (15 wt%) and Mn promoted (1.4, 2.8, 4.2, 5.6, 11.2 wt%) iron (15 wt%) catalysts supported on SBA-15. The catalysts were characterized using XRD, TPR, N2 Physisorption, and SEM. These catalysts were first activated in synthesis gas (H2: CO = 2:1) at 430 °C and then tested for their catalytic performance at the same temperature and atmospheric pressure. Prior work with SBA-15 supported iron catalysts showed that manganese promotion could improve the CO conversion when compared to copper and potassium. The main goal of this work was to study the effect of varying the manganese content on SBA-15 supported iron catalysts to determine the optimum loading of Mn along with the effect of temperature. It was found that CO conversion increases from 27% to74% with increasing the amount of manganese. The yield of CO2 increased substantially with higher Mn loadings. When different Mn promoted iron catalysts were compared, the catalysts with 2.8 wt% Mn loading showed the best performance in terms of the CO conversion and yield of C2+ hydrocarbons. Catalyst with 2.8 wt% of manganese loading yielded a CO conversion of 54%, with a methane yield of 17%, 32% (carbon) yield of C2- C4 and 9%(carbon) yields of C5+ hydrocarbon products, respectively. The effect of operating temperature on the catalytic performance of both the base catalyst 15Fe/SBA-15 and the promoted 2.8Mn/15Fe/SBA-15 catalyst was also examined. The unpromoted iron catalyst showed an improved catalytic activity at 400 °C with the total CO conversion of 38% and a higher yields of C5+ hydrocarbons. A significant decrease was also observed in the yields of CH4 and CO2. The methane and carbon dioxide yield increased from 11% and 8% to 25% and 40%, respectively, as the temperature increased from 400 to 450 °C. The catalyst with 2.8 wt% of manganese promotion gave better CO conversion and hydrocarbon product yields at 430 °C. Lower temperature showed negative effect on hydrocarbon product yield for manganese promoted catalysts. promoted catalysts.
Author: Shuo Chen Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The production of fuel additives, having high octane numbers, from biosourced molecules such as 5-hydroxymethylfurfural (HMF), is the subject of many studies. The Pt, Pd and Ru-based catalysts are described as particularly active in the conversion reaction of HMF to 2,5-dimethylfuran (DMF) and to 2,5-dimethyltetrahydrofuran (DMTHF). However, their substitutions in the catalytic formulations are desirable in view of their high cost and low availability. The substitution elements can be transition metals (for example Cu or Ni), which are more abundant, but generally less active. My research has focused on the preparation of catalysts, based on transition metals, active and selective for the hydrogenation of HMF into molecules that can be incorporated into fuels. The active phases studied during my Ph. D. are based on Ni and Cu transition metals. These active phases were supported on mesoporous silica of SBA-15 type. The study is divided into two distinct parts, depending on the metal studied. The first part of the Ph. D. presents the results obtained with Ni supported monometallic catalysts. In a first step, the optimization of the reaction parameters for the selective hydroconversion of HMF to DMF and DMTHF was carried out using a catalyst prepared by the incipient wetness impregnation (IWI) of the nitrate precursor solution (Chapter 3). Optimized reaction parameters include reaction temperature, dihydrogen pressure, HMF/Ni molar ratio, and reaction time. A preliminary kinetic study was also performed. The effect of the dispersion and size of Ni metal particles on the catalytic performance of Ni/SBA-15 catalysts was studied on materials prepared by the melt infiltration (MI) method of nitrate precursors (Chapter 4). The level of dispersion of the nickel was modified using SBA-15 supports containing different interconnection porosities, obtained at different synthesis temperatures. The results show that the Ni/SBA-15 catalyst, prepared by the simple IWI method, achieves high yields of DMF and DMTHF under optimal reaction conditions. The level of Ni dispersion, as observed from the materials obtained by infiltration of molten salts, has a significant effect on the catalytic activity of the catalyst. The second part of my research focuses on the catalytic properties of Cu/SBA-15 monometallic catalysts prepared by different methods, and having different Cu phase division degree (Chapter 5). The methods of preparation applied include the IWI method, the in situ autocombustion method (ISAC) and the deposition-precipitation method (DP). The first part of the study therefore focused on the optimization of the reaction conditions for the selective hydroconversion of HMF to DMF (over the Cu/SBA-15 catalyst prepared by the ISAC method). Optimized reaction parameters, as for Ni/SBA-15, were reaction temperature, hydrogen pressure, HMF/Cu molar ratio, and reaction time. The reuse of the catalyst was also studied, and a kinetic study of the transformation of HMF on Cu/SBA-15 conducted. This part demonstrates that the activity of Cu for the selective conversion of HMF to DMF depends mainly on the state of dispersion of Cu. The use of the DP method led to a highly divided Cu/SBA-15 catalyst, which made it possible to achieve high yields of DMF.
Author: Gregor Koch Publisher: Logos Verlag Berlin ISBN: 9783832541316 Category : Metal catalysts Languages : en Pages : 0
Book Description
In this book, the Cu/SBA-15 model catalyst for methanol steam reforming is described in detail. This study is an exemplarily road map for investigating model catalysts. The mesoporous structure of SBA-15 support, the structure of supported copper nanoparticles and their activity with regard to H2 production are presented. Based on that, structure activity correlations are deduced. Moreover, relationships between the structure of precursors and the structure of active catalysts are deduced. Therefore several analytical are presented: N2 Physisorption, DR-UV/Vis, in situ XANES, TPR, in situ XRD, specific copper surface area (N2O), size and strain analysis of copper nanoparticles, H2 production by methanol steam reforming.The reliable analysis procedure of each experimental method is described and can be principally employed on similarly constructed catalysts.
Author: Leila Karam Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Dry reforming of methane (DRM) is a process that converts CH4 and CO2 gases into syngas, a gaseous mixture of H2 and CO. Ni based catalysts proved to be suitable for the reaction due to their good activity, wider availability and lower cost than noble-based materials. However, these catalysts are not stable due to Ni sintering and coke deposition. In this thesis we developed two different synthesis routes of mesoporous Ni-Al2O3 based catalysts that can occlude Ni inside the pores achieving high activity and stability in DRM. A set of complimentary physicochemical techniques was systematically applied to thoroughly investigate the materials properties at all steps of preparation and activation. The first approach embraces synthesis of mesoporous Ni-Mg-Al2O3 materials by one-pot EISA strategy. Results demonstrate that 15 wt% Mg (optimum loading) based sample contribute to high and homogenous dispersion of both Ni and Mg, preserving ordered mesoporous Al2O3 walls. The good structural and textural characteristics in addition to the enhanced basicity reinforce activity and stability. The second method involves synthesizing new mesoporous Ni-Al2O3 materials using metal-organic framework as sacrificial template. This procedure results in small Ni nanoparticles homogeneously dispersed and stabilized within the high surface area support resisting sintering and inhibiting carbon nanotubes formation during reforming reaction. Based on catalytic tests completed by thermodynamics calculations, the synthesized materials proved to be eficient not only for dry reforming of methane, but also for CO2 methanation reaction and dry reforming of waste pyrolysis products.
Author: Charbel Harika
Author: Charbel Harika
Author: Joudie Youssef
Author: Marie-Nour Kaydouh
Author: Leila Karam
Author: Sreya Mariya Seby
Author: Shuo Chen
Author: Joy Tannous
Author: Gregor Koch
Author: Hassana El Zein
Author: Leila Karam