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‣ Borohydride electrooxidation on Au and Pt electrodes

Lima, Fabio H. B.; Pasqualeti, Anielli M.; Concha, M. Belen Molina; Chatenet, Marian; Ticianelli, Edson A.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
Português
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Direct borohydride fuel cells (DBFCs) are attractive energy generators for powering portable electronic devices, mainly due to their high energy density and number of electrons per borohydride ion. However, the lack of a highly efficient electrocatalyst for the borohydride oxidation reaction limits the performance of these devices. The most commonly studied electrocatalysts for this reaction are composed of gold and platinum. Nevertheless, for these metals, the borohydride electrooxidation reaction mechanism (BOR) is not completely understood, and the total oxidation reaction, involving eight electrons per BH4- species, competes with parallel reactions, with a lower number of exchanged electrons and/or with heterogeneous chemical hydrolysis. Considering the above-mentioned issues, this work presents recent advances in the knowledge of the BOR pathways on polycrystalline (bulk) Au and Pt electrocatalysts. It presents the studies of the BOR reaction on Au and Pt electrodes using in situ Fourier Transform Infrared Spectroscopy (FUR), and on-line Differential Electrochemical Mass Spectrometry (DEMS). The spectroscopic and spectrometric data provided physical evidence of intermediate species and the formation of H-2 in the course of the BOR as a function of the electrode potential. These results enabled to advance in the knowledge about the BOR pathways on Au and Pt electrocatalysts. (C) 2012 Elsevier Ltd. All rights reserved.; CAPESCOFECUB; CAPES-COFECUB [598/0]; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [Proc. Fapesp 2009/07629-6...

‣ Remoção de mercúrio e arsênio em cação-azul, Prionace glauca; Mercury and arsenic removal in blue-shark, Prionace glauca

Macedo, Luciene Fagundes Lauer
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/04/2010 Português
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Os cações são importantes recursos pesqueiros que podem apresentar concentrações de mercúrio (Hg) e arsênio (As) muitas vezes acima do limite de tolerância, o que os tornam impróprios como alimento. No meio aquático estes contaminantes são convertidos em espécies orgânicas, em especial metilmercúrio (MeHg) e arsenobetaína (AB), respectivamente. O MeHg é neurotóxico, sendo o sistema nervoso em desenvolvimento o mais susceptível. A AB é pouco tóxica, no entanto, o As inorgânico está envolvido em processos de estresse oxidativo, mutagênese e principalmente carcinogênese. Neste trabalho, foi avaliada a eficiência da cisteína na remoção de Hg, a ocorência de As total e inorgânico, e a redução de sua concentração com o emprego de borohidreto de sódio e de preparos para o consumo. A redução máxima de Hg, de 59,4%, com cisteína a 0,5% em pH 5,0, não foi reproduzida quando pretendida a reutilização da solução do aminoácido, importante do ponto de vista prático. O cação-azul continha elevados níveis de As total, 1,98 a 22,56 µg/g (base úmida), que foram removidos com borohidreto de sódio em 99%, demonstrando a alta potencialidade do método usado. O As inorgânico, presente na quantidade média de 0...

‣ Preparação e caracterização de eletrocatalisadores PtRu/C, PtBi/C,  PtRuBi/C para eletro-oxidação direta de etanol em células a combustível tipo PEM utilizando  metodologia da redução via borohidreto de sódio; Preparation and characterization of PtRu/C, PtBi/C, PtRuBi/C electrocatalysts for direct eletro-oxidation of ethanol in PEM fuel cells using the method of reduction by sodium borohydride

Brandalise, Michele
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/03/2010 Português
Relevância na Pesquisa
48.48314%
Os eletrocatalisadores Pt/C, PtBi/C, PtRu/C e PtRuBi/C foram preparados a partir do método de redução via borohidreto de sódio e testados na oxidação eletroquímica de etanol. No método de redução via borohidreto, adiciona-se uma solução contendo hidróxido de sódio e borohidreto de sódio a uma mistura contendo água/2-propanol, precursores metálicos e o suporte de carbono Vulcan XC72. Neste trabalho também foi estudada a forma de adição da solução de borohidreto (adição gota a gota ou adição rápida). Os eletrocatalisadores obtidos foram caracterizados por espectroscopia de energia dispersiva de raios X (EDX), análise termogravimétrica (TGA), difração de raios X (DRX), microscopia eletrônica de transmissão (MET) e voltametria cíclica. A eletro-oxidação do etanol foi estudada por voltametria cíclica e cronoamperometria utilizando a técnica do eletrodo de camada fina porosa. Os eletrocatalisadores obtidos foram avaliados em condições reais de operação em célula por meio de testes em células unitárias alimentadas diretamente por etanol. A dissolução de bismuto no eletrocatalisador PtRuBi/C foi avaliada pelas técnicas de voltametria cíclica, cronoamperometria e do eletrodo disco-anel. O eletrocatalisador PtRuBi/C aparentemente mostrou um bom desempenho para a eletro-oxidação do etanol...

‣ Production of hydrogen by borohydride: in search of low cost non-noble efficient catalyst

Rangel, C. M.; Fernandes, Vitor R.; Silva, R. A.; Bonnetot, B.; Laversenne, L.; Buni, A.; Minkina, V.; Perrin, J.
Fonte: WHEC World Hydrogen Technology Conference Publicador: WHEC World Hydrogen Technology Conference
Tipo: Conferência ou Objeto de Conferência
Publicado em //2007 Português
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58.48314%
Hydrogen production by sodium borohydride through hydrolysis in alkaline solutions has been extensively studied as a production/storage option due to the high volumetric and gravimetric efficiency exhibited. The potential application of this option is based on an easily controllable catalysed hydrolysis reaction, non-toxic and recyclable by-products, and the high purity hydrogen produced can be used in fuel cells. This work reports on a comparative study of own-developed, supported and non-supported, nonnoble catalyst. Ru based catalysts are taken as reference. Characterization of the catalyst was accomplished using a FEG-SEM scanning electron microscope and FTIR analysis. Obtained values amount to 10 NLmin-1g-1 for Ni-based catalyst while Ru-based catalyst amount to twice as much in the same experimental conditions. Typical solutions contain sodium borohydride of concentrations between 2 and 10 wt%, stabilized with 3 to 10 wt % NaOH. Produced hydrogen is measured at ambient pressure as a function of catalyst exposure time at controlled temperatures till completion of the reaction. A thorough study of the open literature rendered normalized values for the reaction rate with different catalyst, making comparisons valuable.

‣ Hydrogen production by hydrolysis of sodium borohydride for PEM fuel cells feeding

Silva, R. A.; Paiva, T. I.; Branquinho, M.; Carvalho, S.; Pinto, A. M. F. R.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 15/02/2008 Português
Relevância na Pesquisa
68.316895%
In this work, hydrogen is produced by a hydrolysis process that uses sodium borohydride as a hydrogen carrier and storage media. High purity hydrogen is obtained at low temperatures with high volumetric and gravimetric storage efficiencies; reaction products are non-toxic. The produced hydrogen can be supply on-demand at specified flow by tailor made developed catalyst. Hydrogen feeding to a low power fuel cell was accomplished. According to experimental conditions conversion rates of 100% are possible. Catalyst is demonstrated to be reusable.

‣ Hydrogen production by catalytic hydrolysis of sodium borohydride in batch reactors: new challenges

Ferreira, M. J. F.; Rangel, C. M.; Pinto, A. M. F. R.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 27/09/2010 Português
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The present manuscript faces the study of H2 generation and storage from catalytic hydrolysis of sodium borohydride (NaBH4) under pressure. We revisit several works on this topic developed (or under development) by our team in the last four years on some of the most critical issues in this research area, namely catalyst durability/reutilization, gravimetric hydrogen storage density and recyclability. New results are also presented. Hydrogen generation rates and yields and hydrogen storage capacities can be augmented to reach 6 wt%, by adding small amounts of an organic polymer (CMC) to the classic NaBH4 hydrolysis, performed with stoichiometric amount of water in a batch reactor with a conical bottom shape and in the presence of Ni-Ru based catalyst, reused from 300 times. Sodium tetrahydroxoborate, NaB(OH)4), was produced in the presence of CMC additive, and did not show crystalline water in its crystal structure. This latter finding has potential to reduce recycling costs of NaBO2 back to NaBH4 and also increase the overall storage density of systems based on NaBH4 as hydrogen carrier.

‣ Modeling of self-gydrolysis of concentrated sodium borohydride solution

Retnamma, Rajasree; Rangel, C. M.; Novais, Augusto Q.; Yu, Lin; Matthews, Michael A.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 07/11/2010 Português
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48.4513%
In spite of the US DOE recommendation of no-go for sodium borohydride for on-board vehicular hydrogen storage, a great deal of interest remains particularly with view to portable applications. In this work we report on experimental and modeling studies of the kinetics of self-hydrolysis of concentrated NaBH4 solutions (10 – 20 wt %) for temperatures varying between 25 – 80 0C, based on 11B NMR study. The models studied were a power law model and a model which describes the change in order of borohydride during the course of reaction. The modeling results show an increase in rate constant and decrease in the order of reaction with respect to borohydride with temperature, while reverse trends are observed with increasing initial borohydride concentration. A theoretical analysis based on solubility product constant for precipitate formation is also carried out under the studied experimental conditions and is in good agreement with the experimental observation.

‣ Analysis of a stand-alone residential PEMFC Power system with sodium borohydride as hydrogen source

Pinto, P. J. R.; Fernandes, Vitor R.; Pinto, A. M. F. R.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 10/11/2011 Português
Relevância na Pesquisa
68.316895%
Catalytic hydrolysis of sodium borohydride (NaBH4) has been investigated as a method to generate hydrogen for fuel cell applications. The high purity of the generated hydrogen makes this process an ideal source of hydrogen for polymer electrolyte membrane fuel cells (PEMFCs). In this paper, the possibility of using a NaBH4-based hydrogen generator with a PEMFC for stand-alone residential use is examined. A complete model of the system is developed, based on models taken from literature with appropriate modifications and improvements. Supervisory control strategies are also developed to manage the hydrogen generation and storage and the power flow. The operation and performance of the integrated system over a one-week period under real loading conditions is analyzed through simulation. Finally, results of the analysis are summarized and the limitations/further scope are indicated.

‣ Impact of the reactor bottom shape on the solid sodium borohydride hydrolysis for hydrogen generation

Ferreira, M. F. R.; Fernandes, Vitor R.; Rangel, C. M.; Pinto, A. M. F. R.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 10/11/2011 Português
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68.57204%
Sodium borohydride (NaBH4) is a chemical hydride that produces hydrogen (H2) ‘on-demand’ through the reaction with water, and exhibits high gravimetric hydrogen storage capacity (10.8 wt.%). NaBH4 has been appointed as an efficient energy/hydrogen carrier for use with fuel cells [1-6]. Unfortunately, problems also exist with NaBH4 hydrolysis: H2 production rates are not sufficiently fast, reaction completion is not always reachable and effective gravimetric (and volumetric) H2 storage capacity is far from the theoretical value. The present study reports original experimental work on generation of hydrogen, by hydrolysis of solid sodium borohydride with stoichiometric amount of distilled water (H2O/NaBH4: 2, 3 and 4 mol/mol), in the presence of a powder unsupported Ni-Ru based catalyst, reused about 320 times. The experiments, performed in two batch reactors with equal internal volume but with different bottom shapes (flat and conical), reveal - for the conical bottom shape with any excess of water - 8.1 H2 wt% and 92 kg H2/m3 (materials-only basis), and a H2 rate of 87.4 L(H2) min-1g-1 catalyst. The role of reactor bottom geometry on the solid NaBH4 hydrolysis - with any excess of water - is, as the authors are aware, for the first time here referred.

‣ Innovative reactor prototype for Hydrogen production in a stationary application using sodium borohydride

Barbosa, Rui; Ferreira, V.; Silva, D.; Condes, J.; Ramos, S.; Amaral, V.; Pinto, A. M. F. R.; Figueiredo, A.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 10/11/2011 Português
Relevância na Pesquisa
68.316895%
Hydrogen storage has proved to be the greatest obstacle preventing hydrogen from replacing fossil fuels. Hence, a safe, efficient and economical method of storing hydrogen must be available to turn viable a hydrogen economy based on renewable resources [1]. Hydrogen can be stored in chemical hydrides such as sodium borohydride (NaBH4), with large theoretical H2 content of 10,9 wt%. With the aid of catalysts, and at room temperatures, the alkaline hydrolysis of NaBH4 can be enhanced [2]. In this work, a 100 L innovative reactor for hydrogen production was designed, based on the optimized layout of a laboratorial scale reactor [3], as part of a project financed by the Portuguese financial support program NSRF. The developed system has the capability to feed a 5 kW PEM fuel cell with a maximum hydrogen consumption of 75 slpm. The NaBH4 solution is stored in a 50 L reservoir from where seven consecutive 7,0 L injections to the reactor are possible. The Ni-Ru based catalyst applied can be re-used several times without losing its performance [1] and because of this capacity its replacement will be done, manually, every seven NaBH4 solution injections (simultaneously with the residual solution removal and the reactor cleaning). The catalyst should then be recovered for further utilization. Additionally to the reactor...

‣ The effect of NaOH on the kinetics of Hydrogen production from sodium borohydride using Ni-based catalysts doped with Ruthenium

Fernandes, Vitor R.; Ferreira, M. J.; Pinto, A. M. F. R.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 01/11/2011 Português
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Previous work by the authors has demonstrated a high rate and high yield hydrolysis of sodium borohydride in the presence of a Ni-Ru catalyst synthesized by wet chemistry. The catalyst has been fully characterized and utilized more than 300 times, exhibiting high stability and durability. In this work, the effect of temperature on the reaction rate was studied and the activation energy of the process estimated for temperatures up to 65 ºC. Typical data in the form of an Arrhenius type relationship showed two slope regions suggesting a change of mechanism that lead to a more accentuated role of ruthenium for temperatures higher than 45 ºC. This effect is maintained with increasing Ru doping of the catalyst. The effect of NaOH as a stabilizer was also studied and the role of Ni and Ru in the hydrolysis of sodium borohydride is under study on the basis of data obtained for various Ru concentrations and data for 100% Ni and 100% Ru as catalysts. An increase in the concentration of Ruthenium in the catalyst allowed effective utilization of the catalyst without the need for the stabilizer, minimizing the induction reaction time. Excellent catalytic activity and catalyst minimal deactivation for sodium borohydride hydrolysis are characteristic of the series of Ni-Ru catalyst synthesized by wet chemistry used in this work.

‣ A sodium borohydride hydrogen generation reactor for stationary applications: Experimental and reactor simulation studies

Sousa, T.; Fernandes, Vitor R.; Pinto, P. J. R.; Slavkov, Y.; Bosukov, L.; Rangel, C. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
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68.316895%
Ruthenium on nickel-foam catalyst was prepared for hydrogen production from the hydrolysis reaction of an alkaline NaBH4 solution. Experiments were carried out at five temperatures (30, 40, 45, 50 and 60 °C) in a 0.1 dm3 small batch reactor. To understand the kinetic behaviour of the hydrolysis reaction in the presence of this catalyst, the experimental data were fitted to three kinetic models (zero-order, first-order and Langmuir–Hinshelwood) using the integral method. Results showed that Langmuir–Hinshelwood model described fairly well the reaction for all tested temperatures and for the entire time range. Zero-order could be applied only at low temperatures or until the concentration of NaBH4 remained high in the solution; first-order could be only applied efficiently at 60 °C. In addition to the kinetic study, a dynamic, three dimensional and non-isothermal model was developed to describe a pilot scale reactor for stationary use. The experimental data was used to validate the numerical model which was developed using a commercial solver software. All relevant transport phenomena were treated in detail and the kinetic model developed previously was introduced into the algorithm. Results showed that the reaction rate was extremely affected by the mass transport resistance of sodium borohydride from the bulk to the catalyst surface.

‣ Simulation of a stand-alone residential PEMFC power system with sodium borohydride as hydrogen source

Pinto, P. J. R.; Sousa, T.; Fernandes, Vitor R.; Pinto, A. M. F. R.; Rangel, C. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
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68.316895%
Catalytic hydrolysis of sodium borohydride (NaBH4) has been investigated as a method to generate hydrogen for fuel cell applications. The high purity of the generated hydrogen makes this process a potential source of hydrogen for polymer electrolyte membrane fuel cells (PEMFCs). In this paper, a PEMFC power system employing a NaBH4 hydrogen generator is designed to supply continuous power to residential power applications as stand-alone loads and simulated using Matlab/Simulink software package. The overall system is sized to meet a real end-use load, representative of standard European domestic medium electric energy consumption, over a 1-week period. Supervisory control strategies are proposed to manage the hydrogen generation and storage, and the power flow. Simulation results show that the proposed supervisory control strategies are effective and the NaBH4–PEMFC power system is a technologically feasible solution for stand-alone residential applications.

‣ A dynamic two phase flow model for a pilot scale sodium borohydride hydrogen generation reactor

Sousa, T.; Rangel, C. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 Português
Relevância na Pesquisa
68.316895%
A two-dimensional, non-isothermal and dynamic model was developed to describe a sodium borohydride/hydrogen reactor for stationary use. All relevant transport phenomena were treated in detail and the kinetic model developed previously by the authors was introduced into the algorithm. In this paper the reactive solution was modelled as a two phase flow; with this approach the impact of the hydrogen production on the solution stirring could be observed and quantified. Results showed that not all ruthenium deposited on the nickel foam was used efficiently as catalyst. In fact, most of the reaction occurred in the surface of the catalyst foam and around 70% of the deposited catalyst was not used. The influence of the catalyst foam position in the solution and the design of the perforated plastic support were analysed in order to find the optimum experimental conditions. It was also demonstrated the importance of the two phase flow approach for a correct simulation of the solution stirring and heat transfer.

‣ A conservation law for self-hydrolysis process of aqueous sodium borohydride

Hong-Yan,LIU; Hong-Yan,TU
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 Português
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A conservation law is obtained for self-hydrolysis process of aqueous sodium borohydride, which gives an explicit relationship between the concentrations of NaBH4 and hydrogen ions during the global reaction.

‣ Borohydride fuel cell with multiwalled carbon nanotubes for improved performance

Deshmukh, Kedar; Santhanam, K.S.V.
Fonte: Elsevier: Journal of Power Sources Publicador: Elsevier: Journal of Power Sources
Tipo: Pré-impressão Formato: 6345719 bytes; application/pdf
Português
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Borohydride fuel cell has been constructed using multiwalled carbon nanotubes (MWCNT) as anode and air cell as cathode having an anionic exchange membrane.separating the anode and cathode The fuel cell produced a voltage of 0.95 V and a current density of greater than 40 mW/cm2 at room temperature in a 10% sodium borohydride in 4 M sodium hydroxide medium. Another borohydride fuel cell under identical conditions using carbon as anode produced a cell voltage of 0.90 V and power density of about 20 mW/cm2.The improved performance of the MWCNT is attributed to the higher effective surface area of the nanotubes and catalysis of carbon nanotubes. (Refer to PDF file for exact formulas).; RIT community members may access full-text via RIT Libraries licensed databases: http://library.rit.edu/databases/; The authors with to thank Dr. K.S. Narasimhan (Hoegannes Corporation) for help with SEM and Dr. V. Gupta for XRD recordings.

‣ Use of borohydride to determine the difference in the developable density for a chemically sensitized and non-sensitized emulsion.

Laufer, S.; Golembe, R.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
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An emulsion prepared so as to minimize the effect of any chemical action on the grains was in its "primitive" state, i.e., that no chemical sensitizing had occurred during the formation of the emulsion grains in "inert" gelatin. Another emulsion was made so as to maximize the effect of any chemical action on the grains by chemical sensitizing methods. This emulsion was also prepared in "inert" gelatin. Sodium Borohydride was added at various levels of concentration to chemically fog both emulsions. The developable density was measured. Also, an attempt was made to measure the amount of reduction sensitization occurring if any. The loss of sodium borohydride in a 1.0 N sodium hydroxide solution was minimum for the time used. An appreciable difference in the photographic effect produced by the use of sodium borohydride was measured and observed. Density is proportional to concentration of sodium borohydride added for the primitive emulsion. Some reduction sensitization was measurable on the primitive emulsion.

‣ Kinetics of sodium borohydride hydrolysis in aqueous-basic solutions

Retnamma, Rajasree; Rangel, C. M.; Novais, Augusto Q.; Matthews, Michael A.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
Relevância na Pesquisa
68.40579%
Liquid-phase catalytic hydrolysis of sodium borohydride (NaBH4) for hydrogen production necessitates long-term stability of base-stabilized NaBH4 solutions at higher temperatures. The present paper reports the kinetics of aqueous-basic solutions containing 20 wt% NaBH4 with 1-15 wt% sodium hydroxide (NaOH) at 80 0C. The established kinetic model employs a modified isoconversional method assuming single-step kinetics. The estimation of kinetic parameters is performed by gPROMS (general PRocess Modeling System) parameter estimation tool. The reaction kinetics differs from low to highly-concentrated NaOH solutions. In highly-basic (.10 wt% NaOH), aqueous solutions of NaBH4, the rate is independent of NaOH concentration, while for lower-basic (< 10 wt% NaOH) solutions, the dependence is -0.57, confirming the inhibition of hydrolysis kinetics by NaOH.

‣ A dynamic two phase flow model for a pilot scale sodium borohydride hydrogen generation reactor

Sousa, T.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
Relevância na Pesquisa
68.316895%
A two-dimensional, non-isothermal, and dynamic model was developed to describe a sodium borohydride/hydrogen re-actor for stationary use. All relevant transport phenomena were treated in detail and the kinetic model developed previ-ously by the authors was introduced into the algorithm. In this paper the reactive solution was modeled as a two phase flow; with this approach the impact of the hydrogen production on the solution stirring could be observed and quantified. Results showed that not all ruthenium deposited on the nickel foam was used efficiently as catalyst. In fact, most of the reaction occurred in the surface of the catalyst foam and around 70% of the deposited catalyst was not used. It was also demonstrated the importance of the two phase flow approach for a correct simulation of the solution stirring and heat transfer.

‣ Potentiometric monitoring of sodium borohydride in aqueous solutions

Santos,Diogo M. F.; Sequeira,César A. C.
Fonte: Sociedade Portuguesa de Materiais Publicador: Sociedade Portuguesa de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 Português
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Platinum, palladium, gold, cadmium, nickel and niobium immersed in sodium borohydride alkaline solutions are characterised by electrode responses that allow monitoring the borohydride present in aqueous media. A simple and relatively precise potentiometric titration technique is described and applied for the analysis of borohydride solutions.