Editorial

5 pages, 221 KiB

Open AccessEditorial

Pd-Based Membranes: Overview and Perspectives

by Thijs Peters and Alessio Caravella

Membranes 2019, 9(2), 25; https://doi.org/10.3390/membranes9020025 - 01 Feb 2019

Cited by 23 | Viewed by 4197

Palladium (Pd)-based membranes have received a lot of attention from both academia and industry thanks to their ability to selectively separate hydrogen from gas streams. Integration of such membranes with appropriate catalysts in membrane reactors allows for hydrogen production with CO₂ capture [...] Read more.

Palladium (Pd)-based membranes have received a lot of attention from both academia and industry thanks to their ability to selectively separate hydrogen from gas streams. Integration of such membranes with appropriate catalysts in membrane reactors allows for hydrogen production with CO₂ capture that can be applied in smaller bioenergy or combined heat and power (CHP) plants, as well as in large-scale power plants. Pd-based membranes are, therefore, regarded as a Key Enabling Technology (KET) to facilitate the transition towards a knowledge-based, low carbon and resource-efficient economy. This Special Issue of the journal Membranes on “Pd-based Membranes: Overview and Perspectives” contains nine peer-reviewed articles. Topics include manufacturing techniques, understanding of material phenomena, module and reactor design, novel applications, and demonstration efforts and industrial exploitation. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

Research

Jump to: Editorial, Review

13 pages, 3998 KiB

Open AccessArticle

Intensified LOHC-Dehydrogenation Using Multi-Stage Microstructures and Pd-Based Membranes

by Alexander Wunsch, Marijan Mohr and Peter Pfeifer

Membranes 2018, 8(4), 112; https://doi.org/10.3390/membranes8040112 - 19 Nov 2018

Cited by 35 | Viewed by 6462

Abstract

Liquid organic hydrogen carriers (LOHC) are able to store hydrogen stably and safely in liquid form. The carrier can be loaded or unloaded with hydrogen via catalytic reactions. However, the release reaction brings certain challenges. In addition to an enormous heat requirement, the [...] Read more.

Liquid organic hydrogen carriers (LOHC) are able to store hydrogen stably and safely in liquid form. The carrier can be loaded or unloaded with hydrogen via catalytic reactions. However, the release reaction brings certain challenges. In addition to an enormous heat requirement, the released hydrogen is contaminated by traces of evaporated LOHC and by-products. Micro process engineering offers a promising approach to meet these challenges. In this paper, a micro-structured multi-stage reactor concept with an intermediate separation of hydrogen is presented for the application of perhydro-dibenzyltoluene dehydrogenation. Each reactor stage consists of a micro-structured radial flow reactor designed for multi-phase flow of LOHC and released hydrogen. The hydrogen is separated from the reactors’ gas phase effluent via PdAg-membranes, which are integrated into a micro-structured environment. Separate experiments were carried out to describe the kinetics of the reaction and the separation ability of the membrane. A model was developed, which was fed with these data to demonstrate the influence of intermediate separation on the efficiency of LOHC dehydrogenation. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Figure 1

17 pages, 3039 KiB

Open AccessArticle

Recent Developments in Compact Membrane Reactors with Hydrogen Separation

by Alexander Wunsch, Paul Kant, Marijan Mohr, Katja Haas-Santo, Peter Pfeifer and Roland Dittmeyer

Membranes 2018, 8(4), 107; https://doi.org/10.3390/membranes8040107 - 14 Nov 2018

Cited by 18 | Viewed by 6780

Abstract

Hydrogen production and storage in small and medium scale, and chemical heat storage from renewable energy, are of great interest nowadays. Micro-membrane reactors for reforming of methane, as well as for the dehydrogenation of liquid organic hydrogen carriers (LOHCs), have been developed. The [...] Read more.

Hydrogen production and storage in small and medium scale, and chemical heat storage from renewable energy, are of great interest nowadays. Micro-membrane reactors for reforming of methane, as well as for the dehydrogenation of liquid organic hydrogen carriers (LOHCs), have been developed. The systems consist of stacked plates with integrated palladium (Pd) membranes. As an alternative to rolled and electroless plated (Pd) membranes, the development of a cost-effective method for the fabrication of Pd membranes by suspension plasma spraying is presented. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Figure 1

15 pages, 2635 KiB

Open AccessArticle

Application of Pd-Based Membrane Reactors: An Industrial Perspective

by Emma Palo, Annarita Salladini, Barbara Morico, Vincenzo Palma, Antonio Ricca and Gaetano Iaquaniello

Membranes 2018, 8(4), 101; https://doi.org/10.3390/membranes8040101 - 01 Nov 2018

Cited by 31 | Viewed by 4362

Abstract

The development of a chemical industry characterized by resource efficiency, in particular with reference to energy use, is becoming a major issue and driver for the achievement of a sustainable chemical production. From an industrial point of view, several application areas, where energy [...] Read more.

The development of a chemical industry characterized by resource efficiency, in particular with reference to energy use, is becoming a major issue and driver for the achievement of a sustainable chemical production. From an industrial point of view, several application areas, where energy saving and CO₂ emissions still represent a major concern, can take benefit from the application of membrane reactors. On this basis, different markets for membrane reactors are analyzed in this paper, and their technical feasibility is verified by proper experimentation at pilot level relevant to the following processes: (i) pure hydrogen production; (ii) synthetic fuels production; (iii) chemicals production. The main outcomes of operations in the selected research lines are reported and discussed, together with the key obstacles to overcome. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Figure 1

14 pages, 3375 KiB

Open AccessArticle

New Insight to the Effects of Heat Treatment in Air on the Permeation Properties of Thin Pd77%Ag23% Membranes

by Nicla Vicinanza, Ingeborg-Helene Svenum, Thijs Peters, Rune Bredesen and Hilde Venvik

Membranes 2018, 8(4), 92; https://doi.org/10.3390/membranes8040092 - 10 Oct 2018

Cited by 16 | Viewed by 3314

Abstract

Sputtered Pd77%Ag23% membranes of thickness 2.2–8.5 µm were subjected to a three-step heat treatment in air (HTA) to investigate the relation between thickness and the reported beneficial effects of HTA on hydrogen transport. The permeability experiments were complimented by volumetric hydrogen sorption measurements [...] Read more.

Sputtered Pd77%Ag23% membranes of thickness 2.2–8.5 µm were subjected to a three-step heat treatment in air (HTA) to investigate the relation between thickness and the reported beneficial effects of HTA on hydrogen transport. The permeability experiments were complimented by volumetric hydrogen sorption measurements and atomic force microscopy (AFM) imaging in order to relate the observed effects to changes in hydrogen solubility and/or structure. The results show that the HTA—essentially an oxidation-reduction cycle—mainly affects the thinner membranes, with the hydrogen flux increasing stepwise upon HTA of each membrane side. The hydrogen solubility is found to remain constant upon HTA, and the change must therefore be attributed to improved transport kinetics. The HTA procedure appears to shift the transition from the surface to bulk-limited transport to lower thickness, roughly from ~5 to ≤2.2 µm under the conditions applied here. Although the surface topography results indicate that HTA influences the surface roughness and increases the effective membrane surface area, this cannot be the sole explanation for the observed hydrogen flux increase. This is because considerable surface roughening occurs during hydrogen permeation (no HTA) as well, but not accompanied by the same hydrogen flux enhancement. The latter effect is particularly pronounced for thinner membranes, implying that the structural changes may be dependent on the magnitude of the hydrogen flux. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Figure 1

17 pages, 3844 KiB

Open AccessArticle

Grain Boundary Segregation in Pd-Cu-Ag Alloys for High Permeability Hydrogen Separation Membranes

by Ole Martin Løvvik, Dongdong Zhao, Yanjun Li, Rune Bredesen and Thijs Peters

Membranes 2018, 8(3), 81; https://doi.org/10.3390/membranes8030081 - 12 Sep 2018

Cited by 8 | Viewed by 4786

Abstract

Dense metal membranes that are based on palladium (Pd) are promising for hydrogen separation and production due to their high selectivity and permeability. Optimization of alloy composition has normally focused on bulk properties, but there is growing evidence that grain boundaries (GBs) play [...] Read more.

Dense metal membranes that are based on palladium (Pd) are promising for hydrogen separation and production due to their high selectivity and permeability. Optimization of alloy composition has normally focused on bulk properties, but there is growing evidence that grain boundaries (GBs) play a crucial role in the overall performance of membranes. The present study provides parameters and analyses of GBs in the ternary Pd-Ag-Cu system, based on first-principles electronic structure calculations. The segregation tendency of Cu, Ag, and vacancies towards 12 different coherent ∑ GBs in Pd was quantified using three different procedures for relaxation of supercell lattice constants, representing the outer bounds of infinitely elastic and stiff lattice around the GBs. This demonstrated a clear linear correlation between the excess volume and the GB energy when volume relaxation was allowed for. The point defects were attracted by most of the GBs that were investigated. Realistic atomic-scale models of binary Pd-Cu and ternary Pd-Cu-Ag alloys were created for the ∑5(210) boundary, in which the strong GB segregation tendency was affirmed. This is a starting point for more targeted engineering of alloys and grain structure in dense metal membranes and related systems. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Graphical abstract

16 pages, 3951 KiB

Open AccessArticle

“Modified” Liquid–Liquid Displacement Porometry and Its Applications in Pd-Based Composite Membranes

by Lei Zheng, Hui Li, Haijun Yu, Guodong Kang, Tianying Xu, Jiafeng Yu, Xinzhong Li and Hengyong Xu

Membranes 2018, 8(2), 29; https://doi.org/10.3390/membranes8020029 - 08 Jun 2018

Cited by 6 | Viewed by 4750

Abstract

For H₂ separation by Pd-based composite membranes, the pore mouth size distribution of the porous support immediately affects the quality of the deposited layer, including continuity and defect/pinhole formation. However, there is a lack of convenient and effective methods for characterization of [...] Read more.

For H₂ separation by Pd-based composite membranes, the pore mouth size distribution of the porous support immediately affects the quality of the deposited layer, including continuity and defect/pinhole formation. However, there is a lack of convenient and effective methods for characterization of pore mouth size of porous supports as well as of defect distribution of dense Pd-based composite membranes. Here we introduce a novel method by modifying conventional liquid–liquid displacement porometry. When the pore tunnels are filled with Liquid B and the outer surface is occupied by Liquid A, the reopening of the pore mouth depends on the pressure of Liquid B and the interfacial tension at the position of the pore mouth, from which the pore mouth size can be determined according to the Young–Laplace equation. Our experimental tests using this method with model samples show promising results, which are well supported by those obtained using FESEM (fild emission scanning electron microscope), AFM (atomic force microscope), and conventional liquid–liquid displacement porometry. This novel method can provide useful information for not only surface coatings on porous substrates but also for modification of dense membrane defects; thus, broad utilizations of this technique can be expected in future study. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Graphical abstract

Review

Jump to: Editorial, Research

20 pages, 5684 KiB

Open AccessReview

Thermodynamic Aspects in Non-Ideal Metal Membranes for Hydrogen Purification

by Stefano Bellini, Yu Sun, Fausto Gallucci and Alessio Caravella

Membranes 2018, 8(3), 82; https://doi.org/10.3390/membranes8030082 - 16 Sep 2018

Cited by 14 | Viewed by 5821

Abstract

In this paper, an overview on thermodynamic aspects related to hydrogen-metal systems in non-ideal conditions is provided, aiming at systematically merging and analyzing information achieved from several different studies present in the open literature. In particular, the relationships among inner morphology, dissolved hydrogen [...] Read more.

In this paper, an overview on thermodynamic aspects related to hydrogen-metal systems in non-ideal conditions is provided, aiming at systematically merging and analyzing information achieved from several different studies present in the open literature. In particular, the relationships among inner morphology, dissolved hydrogen and internal stresses are discussed in detail, putting in evidence the conformation complexity and the various types of dislocations induced by the presence of H-atoms in the lattice. Specifically, it is highlighted that the octahedral sites are preferentially occupied in the FCC metals (such as palladium), whereas tetrahedral sites are more energetically favored in BCC-structured ones (such as vanadium). These characteristics are shown to lead to a different macroscopic behavior of the two classes of metals, especially in terms of solubility and mechanical failure due to the consequent induced stresses. Furthermore, starting from the expression of the chemical potential generally presented in the literature, a new convenient expression of the activity of the H-atoms dissolved into the metal lattice as a function of the H-concentration is achieved. Such an activity expression is then used in the dissolution equilibrium relationship, which is shown to be the overall result of two different phenomena: (i) dissociative adsorption of molecular hydrogen onto the surface; and (ii) atomic hydrogen dissolution from the surface to the metal bulk. In this way, the obtained expression for equilibrium allows a method to calculate the equilibrium composition in non-ideal conditions (high pressure), which are of interest for real industrial applications. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Figure 1

22 pages, 9348 KiB

Open AccessReview

Progress in Methanol Steam Reforming Modelling via Membrane Reactors Technology

by Adolfo Iulianelli, Kamran Ghasemzadeh and Angelo Basile

Membranes 2018, 8(3), 65; https://doi.org/10.3390/membranes8030065 - 17 Aug 2018

Cited by 23 | Viewed by 6224

Abstract

Hydrogen has attracted growing attention for various uses, and, particularly, for polymer electrolyte membrane fuel cells (PEMFCs) supply. However, PEMFCs need high grade hydrogen, which is difficult in storing and transportation. To solve these issues, hydrogen generation from alcohols and hydrocarbons steam reforming [...] Read more.

Hydrogen has attracted growing attention for various uses, and, particularly, for polymer electrolyte membrane fuel cells (PEMFCs) supply. However, PEMFCs need high grade hydrogen, which is difficult in storing and transportation. To solve these issues, hydrogen generation from alcohols and hydrocarbons steam reforming reaction has gained great consideration. Among the various renewable fuels, methanol is an interesting hydrogen source because at room temperature it is liquid, and then, easy to handle and to store. Furthermore, it shows a relatively high H/C ratio and low reforming temperature, ranging from 200 to 300 °C. In the field of hydrogen generation from methanol steam reforming reaction, a consistent literature is noticeable. Despite various reviews that are more devoted to describe from an experimental point of view the state of the art about methanol steam reforming reaction carried in conventional and membrane reactors, this work describes the progress in the last two decades about the modelling studies on the same reaction in membrane reactors. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Graphical abstract

39 pages, 5321 KiB

Open AccessReview

Review of Supported Pd-Based Membranes Preparation by Electroless Plating for Ultra-Pure Hydrogen Production

by David Alique, David Martinez-Diaz, Raul Sanz and Jose A. Calles

Membranes 2018, 8(1), 5; https://doi.org/10.3390/membranes8010005 - 23 Jan 2018

Cited by 118 | Viewed by 10566

Abstract

In the last years, hydrogen has been considered as a promising energy vector for the oncoming modification of the current energy sector, mainly based on fossil fuels. Hydrogen can be produced from water with no significant pollutant emissions but in the nearest future [...] Read more.

In the last years, hydrogen has been considered as a promising energy vector for the oncoming modification of the current energy sector, mainly based on fossil fuels. Hydrogen can be produced from water with no significant pollutant emissions but in the nearest future its production from different hydrocarbon raw materials by thermochemical processes seems to be more feasible. In any case, a mixture of gaseous compounds containing hydrogen is produced, so a further purification step is needed to purify the hydrogen up to required levels accordingly to the final application, i.e., PEM fuel cells. In this mean, membrane technology is one of the available separation options, providing an efficient solution at reasonable cost. Particularly, dense palladium-based membranes have been proposed as an ideal chance in hydrogen purification due to the nearly complete hydrogen selectivity (ideally 100%), high thermal stability and mechanical resistance. Moreover, these membranes can be used in a membrane reactor, offering the possibility to combine both the chemical reaction for hydrogen production and the purification step in a unique device. There are many papers in the literature regarding the preparation of Pd-based membranes, trying to improve the properties of these materials in terms of permeability, thermal and mechanical resistance, poisoning and cost-efficiency. In this review, the most relevant advances in the preparation of supported Pd-based membranes for hydrogen production in recent years are presented. The work is mainly focused in the incorporation of the hydrogen selective layer (palladium or palladium-based alloy) by the electroless plating, since it is one of the most promising alternatives for a real industrial application of these membranes. The information is organized in different sections including: (i) a general introduction; (ii) raw commercial and modified membrane supports; (iii) metal deposition insights by electroless-plating; (iv) trends in preparation of Pd-based alloys, and, finally; (v) some essential concluding remarks in addition to futures perspectives. Full article

(This article belongs to the Special Issue Pd-based Membranes: Overview and Perspectives)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Pd-based Membranes: Overview and Perspectives

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (10 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI