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Author: Shamsuddin Ilias Publisher: ISBN: Category : Languages : en Pages :
Book Description
In this work, asymmetric dense Pd/porous stainless steel composite membranes were fabricated by depositing palladium on the outer surface of the tubular support. The electroless plating method combined with an osmotic pressure field was used to deposit the palladium film. Surface morphology and microstructure of the composite membranes were characterized by SEM and EDX. The SEM and EDX analyses revealed strong adhesion of the plated pure palladium film on the substrate and dense coalescence of the Pd film. Membranes were further characterized by conducting permeability experiments with pure hydrogen, nitrogen, and helium gases at temperatures from 325 to 450 C and transmembrane pressure differences from 5 to 45 psi. The permeation results showed that the fabricated membranes have both high hydrogen permeability and selectivity. For example, the hydrogen permeability for a composite membrane with a 20 {micro}m Pd film was 3.02 x 10{sup -5} moles/m{sup 2}.s. Pa{sup 0.765} at 450 C. Hydrogen/nitrogen selectivity for this composite membrane was 1000 at 450 C with a transmembrane pressure difference of 14.7 psi. Steam reforming of methane is one of the most important chemical processes in hydrogen and syngas production. To investigate the usefulness of palladium-based composite membranes in membrane-reactor configuration for simultaneous production and separation of hydrogen, steam reforming of methane by equilibrium shift was studied. The steam reforming of methane using a packed-bed inert membrane tubular reactor (PBIMTR) was simulated. A two-dimensional pseudo-homogeneous reactor model with parallel flow configuration was developed for steam reforming of methane. The shell volume was taken as the feed and sweep gas was fed to the inside of the membrane tube. Radial diffusion was taken into account for concentration gradient in the radial direction due to hydrogen permeation through the membrane. With appropriate reaction rate expressions, a set of partial differential equations was derived using the continuity equation for the reaction system and then solved by finite difference method with appropriate boundary and initial conditions. An iterative scheme was used to obtain a converged solution. Membrane reactor performance was compared to that in a traditional non-membrane packed-bed reactor (PBR). Their performances were also compared with thermodynamic equilibrium values achievable in a conventional non-membrane reactor. Numerical results of the models show that the methane conversions in the PBIMTR are always higher than that in the PBR, as well as thermodynamic equilibrium conversions. For instance, at a reaction pressure of 6 atm, a temperature of 650 C, a space velocity of 900/16.0 SCCM/gm{sub cat}, a steam to methane molar feed ratio of 3.0, a sweep ratio of 0.15, the conversion in the membrane reactor is about 86.5%, while the conversion in the non-membrane reactor is about 50.8%. The corresponding equilibrium conversion is about 56.4%. The effects on the degree of conversion and hydrogen yield were analyzed for different parameters such as temperature, reactor pressure, feed and sweep flow rate, feed molar ratio, and space time. From the analysis of the model results, it is obvious that the membrane reactor operation can be optimized for conversion or yield through the choice of proper operating and design parameters. Comparisons with available literature data for both membrane and non-membrane reactors showed a good agreement.
Author: Shamsuddin Ilias Publisher: ISBN: Category : Languages : en Pages :
Book Description
In this work, asymmetric dense Pd/porous stainless steel composite membranes were fabricated by depositing palladium on the outer surface of the tubular support. The electroless plating method combined with an osmotic pressure field was used to deposit the palladium film. Surface morphology and microstructure of the composite membranes were characterized by SEM and EDX. The SEM and EDX analyses revealed strong adhesion of the plated pure palladium film on the substrate and dense coalescence of the Pd film. Membranes were further characterized by conducting permeability experiments with pure hydrogen, nitrogen, and helium gases at temperatures from 325 to 450 C and transmembrane pressure differences from 5 to 45 psi. The permeation results showed that the fabricated membranes have both high hydrogen permeability and selectivity. For example, the hydrogen permeability for a composite membrane with a 20 {micro}m Pd film was 3.02 x 10{sup -5} moles/m{sup 2}.s. Pa{sup 0.765} at 450 C. Hydrogen/nitrogen selectivity for this composite membrane was 1000 at 450 C with a transmembrane pressure difference of 14.7 psi. Steam reforming of methane is one of the most important chemical processes in hydrogen and syngas production. To investigate the usefulness of palladium-based composite membranes in membrane-reactor configuration for simultaneous production and separation of hydrogen, steam reforming of methane by equilibrium shift was studied. The steam reforming of methane using a packed-bed inert membrane tubular reactor (PBIMTR) was simulated. A two-dimensional pseudo-homogeneous reactor model with parallel flow configuration was developed for steam reforming of methane. The shell volume was taken as the feed and sweep gas was fed to the inside of the membrane tube. Radial diffusion was taken into account for concentration gradient in the radial direction due to hydrogen permeation through the membrane. With appropriate reaction rate expressions, a set of partial differential equations was derived using the continuity equation for the reaction system and then solved by finite difference method with appropriate boundary and initial conditions. An iterative scheme was used to obtain a converged solution. Membrane reactor performance was compared to that in a traditional non-membrane packed-bed reactor (PBR). Their performances were also compared with thermodynamic equilibrium values achievable in a conventional non-membrane reactor. Numerical results of the models show that the methane conversions in the PBIMTR are always higher than that in the PBR, as well as thermodynamic equilibrium conversions. For instance, at a reaction pressure of 6 atm, a temperature of 650 C, a space velocity of 900/16.0 SCCM/gm{sub cat}, a steam to methane molar feed ratio of 3.0, a sweep ratio of 0.15, the conversion in the membrane reactor is about 86.5%, while the conversion in the non-membrane reactor is about 50.8%. The corresponding equilibrium conversion is about 56.4%. The effects on the degree of conversion and hydrogen yield were analyzed for different parameters such as temperature, reactor pressure, feed and sweep flow rate, feed molar ratio, and space time. From the analysis of the model results, it is obvious that the membrane reactor operation can be optimized for conversion or yield through the choice of proper operating and design parameters. Comparisons with available literature data for both membrane and non-membrane reactors showed a good agreement.
Author: Dushyant Shekhawat Publisher: Elsevier ISBN: 0444535640 Category : Technology & Engineering Languages : en Pages : 569
Book Description
Fuel Cells: Technologies for Fuel Processing provides an overview of the most important aspects of fuel reforming to the generally interested reader, researcher, technologist, teacher, student, or engineer. The topics covered include all aspects of fuel reforming: fundamental chemistry, different modes of reforming, catalysts, catalyst deactivation, fuel desulfurization, reaction engineering, novel reforming concepts, thermodynamics, heat and mass transfer issues, system design, and recent research and development. While no attempt is made to describe the fuel cell itself, there is sufficient description of the fuel cell to show how it affects the fuel reformer. By focusing on the fundamentals, this book aims to be a source of information now and in the future. By avoiding time-sensitive information/analysis (e.g., economics) it serves as a single source of information for scientists and engineers in fuel processing technology. The material is presented in such a way that this book will serve as a reference for graduate level courses, fuel cell developers, and fuel cell researchers. Chapters written by experts in each area Extensive bibliography supporting each chapter Detailed index Up-to-date diagrams and full colour illustrations
Author: Ke Liu Publisher: John Wiley & Sons ISBN: 0471719757 Category : Technology & Engineering Languages : en Pages : 572
Book Description
Covers the timely topic of fuel cells and hydrogen-based energy from its fundamentals to practical applications Serves as a resource for practicing researchers and as a text in graduate-level programs Tackles crucial aspects in light of the new directions in the energy industry, in particular how to integrate fuel processing into contemporary systems like nuclear and gas power plants Includes homework-style problems
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
This report summarizes the objectives, technical barrier, approach, and accomplishments for the development of a novel water-gas-shift (WGS) membrane reactor for hydrogen enhancement and CO reduction. We have synthesized novel CO2-selective membranes with high CO2 permeabilities and high CO2/H2 and CO2/CO selectivities by incorporating amino groups in polymer networks. We have also developed a one-dimensional non-isothermal model for the countercurrent WGS membrane reactor. The modeling results have shown that H2 enhancement (>99.6% H2 for the steam reforming of methane and>54% H2 for the autothermal reforming of gasoline with air on a dry basis) via CO2 removal and CO reduction to 10 ppm or lower are achievable for synthesis gases. With this model, we have elucidated the effects of system parameters, including CO2/H2 selectivity, CO2 permeability, sweep/feed flow rate ratio, feed temperature, sweep temperature, feed pressure, catalyst activity, and feed CO concentration, on the membrane reactor performance. Based on the modeling study using the membrane data obtained, we showed the feasibility of achieving H2 enhancement via CO2 removal, CO reduction to (less-than or equal to) 10 ppm, and high H2 recovery. Using the membrane synthesized, we have obtained
Author: A Doukelis Publisher: Elsevier ISBN: 1782422412 Category : Technology & Engineering Languages : en Pages : 403
Book Description
Thanks to their outstanding hydrogen selectivity, palladium membranes have attracted extensive R&D interest. They are a potential breakthrough technology for hydrogen production and also have promising applications in the areas of thermochemical biorefining. This book summarises key research in palladium membrane technologies, with particular focus on the scale-up challenges. After an introductory chapter, Part one reviews the fabrication of palladium membranes. Part two then focuses on palladium membrane module and reactor design. The final part of the book reviews the operation of palladium membranes for synthesis gas/hydrogen production, carbon capture and other applications. Review of manufacture and design issues for palladium membranes Discussion of the applications of palladium membrane technology, including solar steam reforming, IGCC plants, NGCC plants, CHP plants and hydrogen production Examples of the technology in operation
Author: Publisher: ISBN: Category : Languages : en Pages : 65
Book Description
This project was focused on developing a catalytic means of producing H2 from raw, ground biomass, such as fast growing poplar trees, willow trees, or switch grass. The use of a renewable, biomass feedstock with minimal processing can enable a carbon neutral means of producing H2 in that the carbon dioxide produced from the process can be used in the environment to produce additional biomass. For economically viable production of H2, the biomass is hydrolyzed and then reformed without any additional purification steps. Any unreacted biomass and other byproduct streams are burned to provide process energy. Thus, the development of a catalyst that can operate in the demanding corrosive environment and presence of potential poisons is vital to this approach. The concept for this project is shown in Figure 1. The initial feed is assumed to be a>5 wt% slurry of ground wood in dilute base, such as potassium carbonate (K2CO3). Base hydrolysis and reforming of the wood is carried out at high but sub-critical pressures and temperatures in the presence of a solid catalyst. A Pd alloy membrane allows the continuous removal of pure, while the retentate, including methane is used as fuel in the plant. The project showed that it is possible to economically produce H2 from woody biomass in a carbon neutral manner. Technoeconomic analyses using HYSYS and the DOE's H2A tool [1] were used to design a 2000 ton day-1 (dry basis) biomass to hydrogen plant with an efficiency of 46% to 56%, depending on the mode of operation and economic assumptions, exceeding the DOE 2012 target of 43%. The cost of producing the hydrogen from such a plant would be in the range of $1/kg H2 to $2/kg H2. By using raw biomass as a feedstock, the cost of producing hydrogen at large biomass consumption rates is more cost effective than steam reforming of hydrocarbons or biomass gasification and can achieve the overall cost goals of the DOE Fuel Cell Technologies Program. The complete conversion of wood to hydrogen, methane, and carbon dioxide was repeatedly demonstrated in batch reactors varying in size from 50 mL to 7.6 L. The different wood sources (e.g., swamp maple, poplar, and commercial wood flour) were converted in the presence of a heterogeneous catalyst and base at relatively low temperatures (e.g., 310°C) at sub-critical pressures sufficient to maintain the liquid phase. Both precious metal and base metal catalysts were found to be active for the liquid phase hydrolysis and reforming of wood. Pt-based catalysts, particularly Pt-Re, were shown to be more selective toward breaking C-C bonds, resulting in a higher selectivity to hydrogen versus methane. Ni-based catalysts were found to prefer breaking C-O bonds, favoring the production of methane. The project showed that increasing the concentration of base (base to wood ratio) in the presence of Raney Ni catalysts resulted in greater selectivity toward hydrogen but at the expense of increasing the production of undesirable organic acids from the wood, lowering the amount of wood converted to gas. It was shown that by modifying Ni-based catalysts with dopants, it was possible to reduce the base concentration while maintaining the selectivity toward hydrogen and increasing wood conversion to gas versus organic acids. The final stage of the project was the construction and testing of a demonstration unit for H2 production. This continuous flow demonstration unit consisted of wood slurry and potassium carbonate feed pump systems, two reactors for hydrolysis and reforming, and a gas-liquid separation system. The technical challenges associated with unreacted wood fines and Raney Ni catalyst retention limited the demonstration unit to using a fixed bed Raney Ni catalyst form. The lower activity of the larger particle Raney Ni in turn limited the residence time and thus the wood mass flow feed rate to 50 g min-1 for a 1 wt% wood slurry. The project demonstrated continuous H2 yields with unmodified, fixed bed Raney ...
Author: Francesco Frusteri Publisher: Royal Society of Chemistry ISBN: 1788014782 Category : Science Languages : en Pages : 386
Book Description
Biorefineries are becoming increasingly important in providing sustainable routes for chemical industry processes. The establishment of bio-economic models, based on biorefineries for the creation of innovative products with high added value, such as biochemicals and bioplastics, allows the development of “green chemistry” methods in synergy with traditional chemistry. This reduces the heavy dependence on imports and assists the development of economically and environmentally sustainable production processes, that accommodate the huge investments, research and innovation efforts. This book explores the most effective or promising catalytic processes for the conversion of biobased components into high added value products, as platform chemicals and intermediates. With a focus on heterogeneous catalysis, this book is ideal for researchers working in catalysis and in green chemistry.
Author: Angelo Basile Publisher: John Wiley & Sons ISBN: 0470977574 Category : Science Languages : en Pages : 661
Book Description
A membrane reactor is a device for simultaneously performing a reaction and a membrane-based separation in the same physical device. Therefore, the membrane not only plays the role of a separator, but also takes place in the reaction itself. This text covers, in detail, the preparation and characterisation of all types of membranes used in membranes reactors. Each membrane synthesis process used by membranologists is explained by well known scientists in their specific research field. The book opens with an exhaustive review and introduction to membrane reactors, introducing the recent advances in this field. The following chapters concern the preparation of both organic and inorganic, and in both cases, a deep analysis of all the techniques used to prepare membrane are presented and discussed. A brief historical introduction for each technique is also included, followed by a complete description of the technique as well as the main results presented in the international specialized literature. In order to give to the reader a summary look to the overall work, a conclusive chapter is included for collecting all the information presented in the previous chapters. Key features: Fills a gap in the market for a scientific book describing the preparation and characterization of all the kind of membranes used in membrane reactors Discusses an important topic - there is increasing emphasis on membranes in general, due to their use as energy efficient separation tools and the ‘green’ chemistry opportunities they offer Includes a review about membrane reactors, several chapters concerning the preparation organic, inorganic, dense, porous, and composite membranes and a conclusion with a comparison among the different membrane preparation techniques
Author: Shamsuddin Ilias
Author: Shamsuddin Ilias
Author: Dushyant Shekhawat
Author: Ke Liu
Author: James R. Lattner
Author: 
Author: A Doukelis
Author: Dushyant Shekhawat
Author: 
Author: Francesco Frusteri
Author: Angelo Basile