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A comprehensive computational fluid dynamic model has been developed using COMSOL Multiphysics 5.4 software to predict the behavior of a membrane reactor in dehydrogenation of methylcyclohexane for hydrogen production. A reliable reaction kinetic of dehydrogenation reaction and a permeation mechanism of hydrogen through silica membrane have been used in computational fluid dynamic modeling. For performance comparison, an equivalent traditional fixed bed reactor without hydrogen removal has been also modeled. After model validation, it has been used to evaluate the operating parameters effect on the performance of both the silica membrane reactor and the equivalent traditional reactor as well. The operating temperature ranged between 473 and 553 K, pressure between 1 and 2.5 bar, sweep factor from ˜6.22 to 25 and feed flow rate from 1 to 5 × 10−6 mol/s. The membrane reactor performed better than the equivalent traditional reactor, achieving as best result complete methylcyclohexane conversion and 96% hydrogen recovery.

The fourteenth edition of HYdrogen - POwer THeoretical and Engineering Solutions International Symposium (HYPOTHESIS XIV) was held from 24th to 26th April 2019 in Foz-do-Iguaçu (Brazil) and chaired by Dr. Massimiliano Lo Faro, Daniel A. Cantane and Edson A. Ticianelli. The purpose of the HYPOTHESIS series is to provide a forum where representatives from industry, public laboratories, universities and government agencies can meet, discuss and present the most recent advances in Hydrogen and Renewable Energy Sources technologies. The Hypothesis' conferences are traditionally centred on the role of hydrogen and related technologies in the value chain from renewable energy sources to users and represents a stimulating place for a professional development and for establishing fruitful collaborations. In addition to the traditional topics of Hypothesis series, the XIV edition of Hypothesis held at Foz-do-Iguaçu has emphasized also the role of new technologies for power-to-gas and for energy recovery from any renewable source. "Smart technologies for green life" was the motto of this edition of Hypothesis and the well-known hydroelectric power plant of ITAIPU has interpreted at the highest level the role of renewables in this transition. The conference has been supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (# 401555/2018-6 CNPq-Brazil), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (# 88881.290304/2018-01 CAPES-Brazil), the Italian Hydrogen Forum (www.h2forum.it), the International Association of Hydrogen Energy (http://www.iahe.org) and also by the Fundação Parque Tecnológico Itaipu - FTPI (Brazil) and the Institute for Advanced Energy Technologies "Nicola Giordano" of the National Research Council (CNR-ITAE, Italy). Prof. Sanjeev Mukerjee (Northeastern University), prof. Andreas Friedrich (German Aerospace Center), and dr. Cord-Henrich Dustmann (Battery Consult AG) have exposed their recent scientific achievements as plenary speakers. Furthermore, more than 150 people from all over the world have attended with their scientific works, attracted from the themes of Hypothesis XIV and from this unique city hosting one of the seven modern wonders of the world. As a closing remark of this conference, a round-table discussion towards the role of Hydrogen in Latino America has been hosted. We are in debt with prof. Paulo Emilio V. de Miranda which has chaired magnificently this round table which involved as speakers the major players from Latino-American hydrogen societies (i.e. Argentina, Colombia, Brazil, Paraguay, and Mexico). In addition, we are deeply in debt to all the people that contributed to the success of the meeting, and to this special issue. We like to thank to all of the reviewers and authors, who participated in this process, the scientific committee and all the attendants to HYPOTHESIS XIV. Not the least the editorial staff of IJHE for its kindly collaboration. Without them, this special issue would not have been possible. We also like to thank the members of the international board, the scientific board and a special thanks go to Giuseppe Spazzafumo as the coordinator of Conference series and all member of the organizing committees (e.g. Vincenzo Baglio (CNR-ITAE), Liliane Cristina Battirola (UNILA), José Ricardo Cezar Salgado (UNILA), Fabio Coral Fonseca (IPEN), Orazio Di Blasi (CNR-ITAE), Janaina Fernandes Gomes (UFSCAR), Ricardo José Ferracin (PTI), Renata Figueredo Martins (UFMG), Massimo Laganà (CNR-ITAE), Francesco Lufrano (CNR-ITAE), Tulio Matencio (UFMG), Paulo Emilio de Miranda (UFRJ), Flavio Ryoichi Nikkuni, Gaetano Squadrito (CNR-ITAE), Pietro Staiti (CNR-ITAE) and Sabrina Campagna Zignani (CNR-ITAE)) those have spent lot of their energies in the 12 months needed for the conference organisation and realisation. This special issue collects a selection of invited papers covering the topics more related to renewable energy sources and technologies, discussed during the conference. We are confident that the readers of this journal may appreciate the survey of results and progress recently achieved in this field presented in this SI. These papers have undergone a rigorous peer-review process according to the high quality standards of the Journal.

The potentialities of PEEK-WC (thermally treated at 120 °C) and PLA polymers have been studied in the field of membrane technology applied to H 2 separation/purification. In particular, for low/medium temperature operation (80 °C), PEEK-WC membranes (66 μm thick) showed good results in terms of H 2 /CH 4 separation, showing an ideal selectivity value higher than 40. Meanwhile, we observed interesting selectivity also for H 2 /N 2 and H 2 /CO 2 separation, reaching values of 24 and 20, respectively. As expected, for PEEK-WC thermally treated membranes, the H 2 permeating flux increased from 25 to 80 °C and by increasing the transmembrane pressure. Furthermore, H 2 permeability at 80 °C was around 20 barrer. Concerning PLA membranes (26 μm thick), it is worth of noting that this polymer was pioneeristically used in this work as membrane application, showing great results in terms of H 2 /CO 2 separation. Indeed, we overcame the Robeson's upper-bound (2008), achieving an ideal selectivity H 2 /CO 2 around 25 with an H 2 permeability of 25 barrer. Further advantage due to the utilization of PLA membranes was related to the temperature operations set at ambient conditions, constituting a valuable and cost-effective solution for H 2 /CO 2 separation processes via polymeric membrane technology.

The main aim of this work is a comprehensive study on a new Hybrid Sorption-Enhanced Membrane Reactor (HSE-MR) concept, in which a Pd-Ag membrane during water gas shift (WGS) reaction was applied. This purpose was performed by integrating both the WGS and CO2 absorption reactions. To avoid the high experimental test costs, for evaluating the HSE-MR performance during WGS reaction, a 2D model based on Computational Fluid Dynamic (CFD) method was developed. The proposed CFD model provides the local information of pressure and component molar fractions for the driving force analysis at unsteady state conditions. The validation of the HSE-MR during WGS reaction was carried out by experimental data and a good agreement between modeling results and experimental data was found. After model validation, the performance of the HSE-MR has been compared with that obtained by both a Pd-Ag MR and a Sorption-Enhanced Reactor (SER). Moreover, the effects of some significant operating parameters, such as reaction temperature, reaction pressure and gas hour space velocity (GHSV), on the performance of the HSE-MR were studied in terms of CO conversion and hydrogen recovery in compared with both MR and SER. The CFD results show that HSE-MR, during WGS reaction, presents better performance with respect to MR and SER. As a special consequence, CFD simulation results also show that the increasing of operating parameters has a positive effects on the HSE-MR performance during WGS reaction.

In this experimental study, a membrane reactor housing a composite membrane constituted by a thin Pd-layer supported onto Al2O3 is utilized to perform methanol steam reforming reaction to produce high-grade hydrogen for PEM fuel cell applications. The influence of various parameters such as temperature, from 280 to 330 degrees C, and pressure, from 1.5 to 2.5 bar, is analyzed. A commercial Cu/Zn-based catalyst is packed in the annulus of the membrane reactor and the experimental tests are performed at space velocity equal to 18,500 h(-1) and H2O:CH3OH feed molar ratio equal to 2.5:1. Results in terms of methanol conversion, hydrogen recovery, hydrogen yield and products selectivities are given. As a best result of this work, 85% of methanol conversion and a highly pure hydrogen stream permeated through the membrane with a CO content lower than 10 ppm were reached at 330 degrees C and 2.5 bar. Furthermore, a comparison between the experimental results obtained in this work and literature data is proposed and discussed. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

In this work, an experimental study was carried out on the synthesis of silica membrane for hydrogen purification, in which synthesis of γ-alumina intermediate layer using cheaper and safer source was investigated. For this purpose, aluminum hydroxide was selected and the bohmite sols were prepared by acid or base catalyzed hydrolysis of the different salts for comparing with alkoxide source. The SEM micrographs showed no distinct γ-alumina layer on the substrate coated by base catalyzed sol of salt (sample 1), while a homogeneous γ-alumina layer was formed by acid catalyzed sol of salt (sample 2). After γ-alumina layer formation, the gas permeance mechanism was approximately changed. These results were similar to SEM results and N 2 permeance experiments of sample 3 in which substrate was coated with alkoxide sol. However, the γ-alumina layer of sample 2 had no good adhesion to the substrate. Nevertheless, use of aluminum hydroxide can be promised to synthesis of γ-alumina layer; the membrane was synthesized on the modified support with aluminum tri-sec-butylate sol. In particular, in the synthesized silica membrane as the temperature increases, permselectivity of H 2 /CO 2 and H 2 /N 2 increases from 4.7 and 7.3 at room temperature to 9.4 and 11.6 at 100 °C and to 23.4 and 31.3 at 200 °C, respectively.

Proton conducting membranes have been prepared from chloro-sulfonated polyetheretherketone with cardo group polymers at various sulfonation degree via casting solutions using dimethylformamide as a solvent. The proton conductivity of sulfonated polyetheretherketone with cardo group membranes has been evaluated in the temperature range between 80 and 120 degrees C and the best result of this work has been achieved at 120 degrees C and sulfonation degree equal to 60% with a value equal to 6.7.10(-2) S/cm. Furthermore, this sample shows an open circuit voltage varying from 0.881 V at 80 degrees C to 0.867 V at 120 degrees C, pointing out that the membrane performance is not greatly affected by a temperature variation. Nevertheless, an increase of temperature from 80 to 120 degrees C makes possible an increase of the cell resistance varying from 0.17 to 0.24 Omega cm(2). Thus, the present study investigates the performance of sulfonated polyetheretherketone with cardo group membranes in terms of polarization curves, open circuit voltage, cell resistance and proton conductivity in order to propose them for proton exchange membrane fuel cell applications, particularly at T > 100 degrees C. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

A catalytic Pd–Ag membrane reactor has been packed with a Co–Al 2 O 3 catalyst to perform the ethanol steam reforming reaction using a simulated bio-ethanol mixture (H 2 O/C 2 H 5 OH feed molar ratio = 18.7/1). In Part I of this work, low hydrogen recovery (≤30%) and CO-free hydrogen yield (≤20%) were obtained. In this second study the influence of higher pressure and sweep-gas flow rate was studied in order to improve the membrane reactor performances in terms of higher ethanol conversion, CO-free hydrogen yield and hydrogen recovery. The counter-current sweep-gas flow configuration was used for studying the effect of the reaction pressure and the sweep factor on the reaction system, while the co-current flow configuration was also considered for analysing the weight hourly space velocity effect. Moreover, a comparison with a traditional reactor working at the same MR operating conditions was also realized. As best results, the membrane reactor showed 100% ethanol conversion, 95.0% CO-free hydrogen recovery and ∼60.0% CO-free hydrogen yield, operating at 400 °C and 3.0 (abs) bar.

This study focuses on the influence of oxygen addition on ethanol steam reforming (ESR) reaction performed in a dense Pd–Ag membrane reactor (MR) for producing hydrogen directly available for feeding a polymer electrolyte membrane fuel cell (PEMFC). In particular, oxygen addition can prevent ethylene and ethane formation caused by dehydration of ethanol as well as carbon deposition. The MR is operated at 400 °C, H2O:C2H5OH = 11:1 as feed molar ratio and space velocity (GHSV) ∼2000 h−1. A commercial Ru-based catalyst was packed into the MR and a nitrogen stream of 8.4 × 10−2 mol/h as sweep gas was flowed into the permeate side of the reactor. Both oxidative ethanol steam reforming (OESR) and ESR performances of the Pd–Ag MR were analyzed in terms of ethanol conversion to gas, hydrogen yield, gas selectivity and CO-free hydrogen recovery by varying O2:C2H5OH feed molar ratio and reaction pressure. Moreover, the experimental results of the OESR and ESR reactions carried out in the same Pd–Ag MR are compared in order to point out the benefits due to the oxygen addition. Experimentally, this work points out that, overcoming O2:C2H5OH = 1.3:1, ethanol conversion is lowered with a consequent drops of both hydrogen yield and hydrogen recovery. Vice versa, a complete ethanol conversion is achieved at 2.5 bar and O2:C2H5OH = 1.3:1, whereas the maximum CO-free hydrogen recovery (∼30%) is obtained at O2:C2H5OH = 0.6:1.

A dense tubular Pd–Ag membrane reactor was used to carry out the methanol steam reforming reaction for producing a CO-free hydrogen stream. A Cu/Zn/Mg-based catalyst was packed in the lumen side of the membrane reactor and the experimental tests were performed at a reaction temperature of 300 °C and at a H 2 O/methanol feed molar ratio of 3/1. The effects of the different flow configurations, as well as the sweep factor and the reaction pressure were analysed. Experimental results in terms of CO-free hydrogen recovery, hydrogen yield, CO-free hydrogen yield and hydrogen selectivity are presented. Moreover, a comparison between the performances of the membrane reactor and a traditional reactor working at the same operative conditions is proposed and discussed.