Hydrogen Production, Separation and Purification for Energy
2: Department of Chemistry, University of Calabria, Calabria, Italy
3: Department of Materials Science and Engineering, Clemson University, Clemson, SC, USA
4: International Association for Hydrogen Energy, FL, USA
Hydrogen is one of the most promising next-generation fuels. It has the highest energy content per unit weight of any known fuel and in comparison to the other known natural gases it is environmentally safe - in fact, its combustion results only in water vapour and energy. This book provides an overview of worldwide research in the use of hydrogen in energy development, its most innovative methods of production and the various steps necessary for the optimization of this product. Topics covered include structured catalysts for process intensification in hydrogen production by reforming processes; bimetallic supported catalysts for hydrocarbons and alcohols reforming reactions; catalysts for hydrogen production from renewable raw materials, by-products and waste; Ni and Cu-based catalysts for methanol and ethanol reforming; transition metal catalysts for hydrogen production by low temperature steam reforming of methane; supercritical water gasification of biomass to produce hydrogen; biofuel starting materials for hydrogen production; modelling of fixed bed membrane reactors for ultrapure hydrogen production; hydrogen production using micro membrane reactors; perovskite membrane reactors; polymeric membrane materials for hydrogen separation; industrial membranes for hydrogen separation; multifunctional hybrid sorption-enhanced membrane reactors; carbon based membranes; and separation of hydrogen isotopes by cryogenic distillation. Hydrogen Production, Separation and Purification for Energy is essential reading for researchers in academia and industry working in energy engineering.
Inspec keywords: hydrogen production; biofuel; renewable materials; separation; chemical reactors; distillation; fuel gasification; catalysts
Other keywords: fixed bed membrane reactors; catalysts; supercritical water gasification; biofuels; hydrogen separation; hydrogen production; micromembrane reactors; perovskite membrane reactors; carbon-based membranes; reforming process
Subjects: Products and commodities; Production equipment; General support functions; Biotechnology industry; Industrial processes; Fuel processing industry; Chemical industry
- Book DOI: 10.1049/PBPO089E
- Chapter DOI: 10.1049/PBPO089E
- ISBN: 9781785611001
- e-ISBN: 9781785611018
- Page count: 480
- Format: PDF
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Front Matter
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1 Structured catalyst for process intensification in hydrogen production by reforming processes
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In the present chapter, a brief outlook on structured catalyst employment for process intensification in hydrogen production processes was provided. The growing interest toward hydrogen, both as valuable chemical for other processes and, mainly, as energetic vector, increased the need to more sustainable routes for H2 producing. Process intensification is "any chemical engineering development that leads to a substantially smaller, cleaner and more energy-efficient technology." In this direction, in the preset chapter, it was demonstrated that structured catalysts emerge as a viable solution in the process intensification of reforming processes for hydrogen production.
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2 Bimetallic supported catalysts for hydrocarbons and alcohols reforming reactions
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This chapter gives a brief resume of the state of the art on bimetallic catalysts for the reforming of hydrocarbons and alcohols. As part of hydrogen production technologies, reforming is the most widely used process, thanks to its low cost and mature technology. The bimetallic catalysts show an improvement in activity, selectivity, and stability with respect to the monometallic systems; their use allows to design systems with unique characteristics, totally different from those of monometallic catalysts. The most diffused reforming technology concerns methane conversion and is mainly used in industrial processes for the production of ammonia, methanol, and the C5-C12 hydrocarbon fractions. However, the reforming of nonfossil sources is the fastest growing research field, due to the renewability and low environmental impact. This chapter is divided into three main sections, reforming of methane, hydrocarbons, and alcohols, which are focused on the description of the main bimetallic catalyst systems, reaction mechanisms proposed and, where possible, comparisons on the performance.
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3 Catalysts for hydrogen production from renewable raw materials, by-products and waste
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Catalytic materials used in hydrogen production processes starting from different raw materials (e.g. fossil (oil, gas and coal), renewables (primary and secondary bio-based raw materials) and waste materials (municipal solid waste (MSW), refuse-derived fuel (RDF), agro-food residues, manure)) are reviewed highlighting the most relevant advances of the last 5 years. The best results obtained mainly in reforming reactions and supercritical water gasification processes, in terms of improved performances such as higher hydrogen yield, lower by-products, coke, tar formation, as well as milder reactions conditions, are discussed and compared taking into account the balance between costs and performances of the used catalytic materials. Moreover, still open issues for the application of these processes (e.g. catalysts stability, low resistance to N, S poisoning) have been pointed out.
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4 Ni- and Cu-based catalysts for methanol and ethanol reforming
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Steam reforming of light alcohols such as methanol and ethanol can be one solution in the transfer towards hydrogen economy. The increasing need of hydrogen pushes the scientists in academia and industry to develop new and efficient catalysts for production of hydrogen. An extensive number of articles have been published on methanol and ethanol steam reforming catalysts based on the transition and precious metals (e.g. Cu, Ni, Pd and Pt) supported on various metal and mixed oxides (e.g. Al2O3, ZnO, TiO2, ZrO2, CeO2, CeO2-ZrO2) as well as on carbon supports (e.g. active carbon (AC), carbon nanotubes (CNTs)). Catalysts' activity, selectivity and tolerance towards deactivation are the main questions in which the answers are needed to be found. In this chapter, the recently developed nickeland copperbased catalysts are presented for steam reforming of light alcohols.
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5 Transition metal catalysts for hydrogen production by low-temperature steam reforming of methane
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This chapter discusses different catalytic systems based on transition metals (nickel, rhodium, ruthenium, platinum) for the hydrogen production by steam reforming (SR) of methane at low temperature (≤823 K). The design of robust catalysts for low temperature (≤823 K) reforming processes is fundamental for an optimized integration between reforming reactors and concomitant separation/purification steps that usually work at low temperature; therefore, the preparation methods will be also described and compared, especially, considering their contribution to develop catalytic materials with properties as high surface area, high active metal dispersion, low particle size, resistance to carbon formation, opportune metal load and so on. All these features and others, which will be discussed along this chapter, are very important to overcome deactivation phenomena related and in some cases enhanced by reforming processes conducted at low temperature. The aim of this chapter is to analyse, from a different point of view, some synthesis routes, generally reported in literature as methods to prepare catalysts for high temperature reforming processes. Thus, correlations between chemical- physical/morphological properties and catalytic activity towards low-temperature SR of methane will be evidenced in order to explore the potential to use the prepared materials for application in integrated processes that combine lowtemperature SR reactions with separation/purification step.
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6 Supercritical water gasification of biomass to produce hydrogen
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Supercritical water gasification (SCWG) processes have recently received significant attention as a sustainable technology for the production of hydrogen starting from wet biomass. In this chapter, the influence of biomass composition for the production of hydrogen under SCWG is evaluated. The influence of the main reaction conditions as temperature, pressure and feed concentration on hydrogen yield are discussed together with a critical rationalization of data.
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7 Biofuels starting materials for hydrogen production
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Future developments in energy-efficient processes and potential solutions for the energy-related environmental tasks are coupled with hydrogen-based technologies. Introductory parts of this chapter are focused on the specifics of H2 generation from biomass. Within the framework of this topic, three platforms are compared: conversion of simple sugars, cellulose, and thermochemical conversion of biomass to hydrogen-containing gaseous mixtures. Three approaches for generation of biofuels starting materials for hydrogen production are considered: the first one includes sugars and organic acids; the second one includes lignocellulose, woodchips, etc.; finally, the third approach considers the possible routes of biomass gasification. In all cases, the hydrogen needs to be separated (to be recovered) from the hydrogen-containing multicomponent gaseous mixtures of biogenic origin. Membrane-based gas separation processes are considered for H2 recovery from gaseous sources, including (1) estimation of commercial and lab-scale polymeric membranes for recovery of H2 from gaseous mixtures, containing additionally CO2, CO, N2, CH4, H2S, with calculation of standard membrane process itself; (2) membrane contactors for hydrogen recovery from H2/CO2 mixtures; (3) combined membrane/pressure-swing adsorption (PSA) systems for hydrogen recovery from gaseous mixtures of biogenic origin. It is shown that H2 recovery can be successfully realized as a combination of standard membrane method (H2 preconcentrating) and PSA (H2 conditioning). Potential of whole process (biomass treatment and H2 recovery as a fuel) requires the active generation of knowledge for development of the desired bioprocesses and highly selective membranes.
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8 Fixed bed membrane reactors for ultrapure hydrogen production: modeling approach
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This chapter deals with the modeling approach toward membrane reactors, making a short overview on the most significative findings in the specialized literature. In detail, 1-D, 2-D, and 3-D models are analyzed, pointing out the role of such parameters as the membrane permeability mechanism and hydrogen flux, reaction kinetics, and heat and mass transport inside the reactor and within the catalyst pellets, able of influencing the accuracy of the model.
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9 Hydrogen production using micro-membrane reactors
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Hydrogen production using micro-membrane reactors or membrane microreactors (MMRs) is a significant component of membrane reactor research. The recent progress of three types of MMRs such as hollow-fiber, microchannel, and monolithic MMRs are reviewed using specific examples. The representative application of MMRs as fuel processors for proton exchange membrane fuel cells are summarized in detail. In addition, the modeling progress about MMRs is also briefly introduced.
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10 Perovskite membrane reactors
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As one of the most promising strategies in chemical process intensification, membrane reactor (MR) technology has attracted considerable worldwide researches in the last three decades, and this subject is still currently undergoing rapid development and innovation. Nevertheless, inorganic MRs such as perovskite MRs have not achieved any large-scale commercial applications, which implies that there are still a lot challenges to their practical applications. In contrast, several novel perovskite membranes and MRs have been developed in recent years. Therefore, this chapter addresses research and development of perovskite MR applications, in which can permeate oxygen and hydrogen at high temperatures. Indeed, in this chapter, is introduced the structure, transport mechanisms, and performance of various perovskite membranes, followed by evaluation of employing perovskite membranes for both oxidative and non-oxidative reactions. In this viewpoint, the perovskite membrane role of either removing a reactant to shift the equilibrium or adding a reactant to control the reaction mechanism and associated side reactions is significant. Furthermore, the advantages and disadvantages of perovskite MRs are mentioned as a developed technology compared to the traditional reactors and the main challenges that must be overcome for industrial startup of MR technology.
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11 Polymeric membrane materials for hydrogen separation
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Contemporary membrane processes for separation of hydrogen from different industrial streams are based on use of polymeric membrane materials. The subject of this chapter is consideration of properties of various membrane materials in respect of hydrogen and other light gases. The effects of properties of gases, polymers, and conditions of separation on the gas permeation parameters are considered. Possible options for improvement of these parameters include crosslinking and introduction of nanoparticles into polymer matrices. The problem of separation of hydrogen isotopes is briefly discussed. The main message of this review is that many existing and widely applied hydrogen-separating membranes can be replaced by novel ones based on polymers with enhanced permeability and/ or selectivity.
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12 Industrial membranes for hydrogen separation
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Production of hydrogen, as an environmentally benign alternative for fossil fuels that mainly contribute to the growing pollutant emissions, has been considered specifically in the last decades. As a result of being associated with other gases, such as CO2, CO and other impurities, the produced hydrogen must be separated and purified before being utilized by various processes. For this purpose, adsorption-based and cryogenic processes are the most conventional methods which encounter some restrictions, related to the required energy and time that make these processes not economically lucrative in some circumstances. As a result, recently, the membrane technology as well as membrane reactors has emerged to deal with these limitations. Among the common types of membranes including organic and inorganic membranes and their subgroups, which offer high selectivity and permeability to hydrogen, the stable, energy-efficient and cost-effective ceramic membranes, which are unaffected by the existing poisonous gases in the gas mixtures, are the most promising candidates for hydrogen separation in an effective manner in near future.
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13 Multifunctional hybrid sorption-enhanced membrane reactor
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The growth of the global hydrogen market demands more efficient industrial processes for its production. Hydrogen can be produced from renewable or nuclear sources, using electricity as an intermediate energy carrier. However, industrially is produced mainly by steam reforming of methane or other hydrocarbons and also by gasification of coal and oil refining residues. Methane steam reforming (MSR) is being used for decades, despite the severe operating conditions (high temperatures and pressures) and low-energy efficiency, which challenges the development of more efficient and reliable processes. The present chapter provides an overview of hydrogen production via MSR, purification processes and procedures for enhancing the hydrogen production. Sorption-enhanced and membrane-enhanced reactors, considering selective CO2 sorption removal from the reaction bulk and selective hydrogen membrane permeation are, respectively, addressed. Particular attention was paid to the recently proposed hybrid sorption-enhanced membrane reactor (HSEMR), in which sorption and permeation processes occur inside the reforming reactor. This technology allows lower operating temperatures, produces hydrogen with higher purity and exhibits higher reaction conversions than sorption or membrane reactors. The major contributions in this field are reviewed and the advantages and drawback of each approach are discussed in detail.
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14 Carbon-based membranes
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Carbon membranes as a promising candidate for energy-efficient gas separation processes have been studied for more than 20 years. This chapter describes the status and perspectives of both self-supported and supported carbon membranes. The key steps on the development of high performance hollow-fiber carbon membranes are discussed, including precursor selection, tuning carbon membrane structure, and regeneration. The module design and continuous carbonization process are pointed out to be the main challenges related to upscaling. Supported carbon membranes open new opportunities for high-temperature and high-pressure applications. The main challenges of supported carbon membranes are the lower packing density and relatively high production cost compared to the self-supported hollow-fiber carbon membranes - this directs their applications more towards the medium to small gas volume processes. Finally, the potential applications of carbon membranes are also briefly mentioned. The recovery of hydrogen from various gas streams may become a major application, as well as olefin-paraffin separation, but also removal of CO2 from natural gas or biogas (CO2-CH4 separation) has a very nice potential. The carbon membranes show great potentials in gas separation applications with the possibility of tailoring/controlling the membrane pore size on a molecular sieving level.
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15 Separation of hydrogen isotopes by cryogenic distillation
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The hydrogen element exists naturally in the form of three isotopes, sharing the same number of proton and electron, which is equal to 1, but not that of neutrons, which ranges from 0 to 2. In order, these isotopes are protium, commonly said light hydrogen and indicated with 1 1H or simply H; deuterium, commonly heavy hydrogen indicated with 2 1H or D; and tritium, 3 1H or T. Naturally, deuterium abundance is 0.0115%, whereas tritium is rare and radioactively unstable. Protium, deuterium and tritium form diatomic molecules bonding together, which can be homonuclear, H2, D2 and T2, or heteronuclear, HD, HT and DT. Homonuclear molecules can exist in either an ortho modification, oH2, oD2, oT2, or a para modification, pH2, pD2, pT2. Hydrogen has the largest isotope effects principally due to the largest differences in the relative mass of its isotopes. Isotope effects are differences in chemical and physical properties arising from differences in the nuclear mass. In particular, lighter hydrogen molecules are characterized by higher vapour pressures than heavier ones; in other words, lighter molecules are more volatile. Among the isotope separation techniques, distillation is adopted in industrial applications because of the advantages of achieving high separation degrees and of processing large quantities of fluids. Distillation is based on the different vapour pressures of the components to be separate and; hence, it requires the coexistence of liquid and vapour phases. Coexistence occurs in the cryogenic range of 10-40 K for molecular hydrogen. The number of cryogenic distillation plants constructed for deuterium and tritium separation is small due to their limited market. One example is the deuterium plant built in Germany in the late 1960s, and another the tritium plant in Canada in the late 1980s. Both plants proved the possibility to achieve high purities, exceeding 99.8%, as well as high separation factors. Today, deuterium is employed mostly as constituent of heavy water as neutron moderator for a number of nuclear fission reactors; it is also utilized for the preparation of nuclear weapons or as a non-radioactive tracer in chemical and metabolic reactions. Tritium is used instead as a radioactive tracer in chemistry and biology. Both deuterium and tritium are adopted for the research on the physics of matter and, notably, they have been selected for the future International Thermonuclear Experimental Reactor nuclear fusion reactor.
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Back Matter
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