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1.
Cobalt-boron (CoB) catalyst supported on zeolite modified with hydrochloric acid (CoB-zeolite-HCl) and zeolite modified with acetic acid (CoB-zeolite-CH3COOH) is prepared for the hydrogen (H2) release from sodium borohydride (NaBH4). The supported catalyst samples were characterized by X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR), nitrogen adsorption and, inductively coupled plasma optical emission spectroscopy (ICP-OES). The effects of Co metal loading, NaBH4 concentration, NaOH concentration, temperature, and reusability on the catalytic performance of the CoB-zeolite-HCl catalyst were investigated. The completion time of the reaction using the raw zeolite supported CoB catalyst was about 265 min. However, the completion time of the reaction using the CoB-zeolite-HCl catalyst was decreased to about 80 min. BET surface area values showed that there is a 7-fold increase in the specific surface area for the zeolite activated with HCl compared to the BET surface area for the raw zeolite. The activation energy (Ea) of the catalyzed reaction was 42.45 kJ mol−1.  相似文献   

2.
The aim of this work is to prepare CoB catalysts supported on raw bentonite (CoB/bentonite) and Na-exchanged bentonite (CoB/Na-bentonite) by the impregnation and chemical reduction method. The prepared catalysts were characterized using X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) techniques. The activities of the catalysts were tested in the hydrolysis reaction of sodium borohydride (NaBH4) in a semi-batch system. The volume of the evolved hydrogen gas was determined by a water displacement method. The effects of catalyst amount, NaOH (a base stabilizer) concentration, NaBH4 concentration and solution temperature on the hydrogen generation rate were investigated. The maximum hydrogen generation rates were determined as 921.94 mL/min.gcat for CoB/bentonite and 1601.45 mL/min.gcat for CoB/Na-bentonite when the 5 wt % NaBH4 and 10 wt % NaOH solutions were used at 50 °C. The activation energies (Ea) of the hydrolysis reaction over CoB/bentonite and CoB/Na-bentonite were determined as 55.76 and 56.61 kJ/mol, respectively.  相似文献   

3.
Herein, the CoB catalyst supported on the sepiolite clay treated with phosphoric acid was utilized to produce hydrogen from the NaBH4 hydrolysis. In order to analyse the performance of the phosphoric acid treated sepiolite clay supported-CoB catalyst, the NaBH4 concentration effect, phosphoric acid concentration effect, phosphoric acid impregnation time effect, CoB catalyst percentage effect, and temperature effect were studied. In addition, XRD, XPS, SEM, TEM, BET, and FTIR analysis were performed for characterization of Co–B catalyst supported on the acid-treated sepiolite. The completion time of this hydrolysis reaction with Co–B (20%) catalyst supported on the sepiolite treated by 5 M phosphoric acid was approximately 80 min, whereas the completion time of this hydrolysis reaction with acid-free sepiolite-supported Co–B (20%) catalyst was approximately 260 min. There is a five-fold increase in the maximum production rate. The maximum hydrogen production rates of this hydrolysis reaction at 30 and 60 °C were found as 1486 and 5025 ml min−1g−1catalyst, respectively. Activation energy was found as 21.4 kJ/mol. This result indicates that the acid treatment on sepiolite is quite successful. The re-usability of NaBH4 hydrolysis reaction by CoB catalyst supported on sepiolite treated phosphoric acid for successive five cycles of NaBH4 at 30 °C was investigated.  相似文献   

4.
Acid-catalyzed hydrolysis of sodium borohydride (NaBH4) has been studied (reactivity and kinetics) at high acid concentration (0.32 M). A mineral (hydrochloric acid, HCl) and an organic benign (acetic acid, CH3COOH) acid have been chosen. Our study has three distinct objectives, namely: (i) combining the simplicity of the storage of solid NaBH4 with the simplicity of the aqueous solution of acid; (ii) showing CH3COOH can be as reactive as HCl in specific well-chosen operating conditions; and (iii) emphasizing the relative greenness of the CH3COOH-based process. All of these objectives have been fulfilled and show that CH3COOH is a benign relatively green acid catalyst of choice for catalyzing hydrogen generation from NaBH4, the acid–water–NaBH4 system being quite simple.  相似文献   

5.
Generation of hydrogen by hydrolysis of alkali metal hydrides has attracted attention. Unsupported CoB catalyst demonstrated high activity for the catalytic hydrolysis of NaBH4 solution. However, unsupported CoB nanoparticles were easy to aggregate and difficult to reuse. To overcome these drawbacks, CoB/SiO2 was prepared and tested for this reaction. Cobalt (II) acetate precursor was loaded onto the SiO2 support by incipient-wetness impregnation method. After drying at 100 °C, Co cations were deposited on the support. The dried sample was then dispersed in methanol/water solution and then fully reduced by NaBH4 at room temperature. The catalyst was characterized by N2 sorption, XRD and XPS. The results indicated that the CoB on SiO2 possessed amorphous structure. B and Co existed both in elemental and oxidized states. SiO2 not only affected the surface compositions of CoB, but also affected the electronic states of Co and B. B0 could donate partial electron to Co0. The structure effect caused by the SiO2 support helped to prevent CoB nanocluster from aggregation and therefore the activity increased significantly on hydrolysis of alkaline NaBH4 solution. The CoB/SiO2 catalyst showed much higher activity than the unsupported CoB catalyst. At 298 K, the hydrogen generation rate on CoB/SiO2 catalyst was 4 times more than that on the unsupported CoB catalyst. The hydrogen generation rate was as high as 10,586 mL min−1 g−1 catalyst at 298 K. CoB/SiO2 is a very promising catalyst for this reaction.  相似文献   

6.
In the present study, defatted spent coffee ground (DSCG) treated with different acids was used as a metal-free catalyst for the first time. The aim of undertaken work is to demonstrate that DSCG can be used as a green catalyst to produce hydrogen through methanolysis of sodium borohydride. To produce hydrogen by the sodium borohydride methanolysis (NaBH4), DSCG was pretreated with different acids (HNO3, CH3COOH, HCl). According to the superior acid performance, acetic acid was selected and then different concentrations of the chosen acid were evaluated (1M, 3M, 5M, and 7M). Subsewuently, different temperatures (200, 300, 400 and 500 °C) and burning times (30, 45, 60 and 90 min) for the optimization of DSCG-catalyst were tested. The experiments with the use of CH3COOH treated DSCG-catalyst reveal that the optimal acid concentration was 1M CH3COOH and the burning temperatures and time were 300 °C and 60 min, respectively. FTIR, SEM, ICP-MS and CHNS elemental analysis were carried out for a through characterization of the catalyst samples. In this study, the experiments were carried out with 10 ml methanol solution contained 0.025 g NaBH4 with 0.1 g catalyst at 30 °C unless otherwise stated. The effect of NaBH4 concentration was investigated with use of 1%, 2.5%, 5%, and 7.5% NaBH4, while the influence of catalyst concentration was discovered with the use of 0.05, 0.1, 0.15, and 0.25 g catalyst. Different temperatures were chosen (30, 40, 50 and 60 °C) to explore the hydrogen production performance of the catalyst. In addition, the maximum hydrogen production rate through methanolysis reaction of NaBH4 by this catalyst was found to be 3171.4 mL min−1gcat−1. Also, the activation energy was determined to be 25.23 kJ mol−1.  相似文献   

7.
Hydrogen generation from sodium borohydride (NaBH4) hydrolysis in the presence of metal catalysts is a frequently used and encouraging method for hydrogen storage. Metal nanoparticle-supported catalysts are better recyclability and dispersion than unsupported metal catalysts. In this study, the synthesis and characterization of a polymer-supported catalyst for hydrogen generation using NaBH4 have been investigated. For the synthesis of polymeric material, first of all, kaolin (KLN) clay has been magnetically rendered by using the co-precipitation method (Fe3O4@KLN) and then coated with poly tannic acid (PTA@Fe3O4@KLN). Then, the catalyst loaded with cobalt (Co) nanoparticles have been obtained with the NaBH4 reduction method (Co@PTA@Fe3O4@KLN). The surface morphology and structural properties of the prepared catalysts have been determined using methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS) and vibrating sample magnetometer (VSM). The optimization of the most important variables (NaBH4 amount, NaOH amount, catalyst amount, and metal loading rate) affecting the hydrolysis of NaBH4 using the synthesized polymeric catalysts was carried out using response surface methodology (RSM). Depending on the evaluated parameters, the desired response was determined to be hydrogen production rate (HGR, mL/g min). HGR was 1540.4 mL/gcat. min. in the presence of the Co@PTA@Fe3O4@KLN at optimum points obtained via RSM (NaBH4 amount 0.34 M, NaOH amount 7.9 wt%, catalyst amount 3.84 mg/mL, and Co loading rate 6.1%). The reusability performance of the catalyst used in hydrolysis of NaBH4 was investigated under optimum conditions. It was concluded that the catalyst is quite stable.  相似文献   

8.
Spirulina platensis is defined as the dried biomass of cyanobacteria in commercial use and is biomass with high carbon content. Spirulina platensis microalgae strain supported-CoB catalysts to produce hydrogen from sodium borohydride (NaBH4) were prepared for the first time. The Spirulina platensis microalgae strain was modified with phosphoric acid (H3PO4) to proton. Then, the supported catalyst was performed to produce hydrogen from NaBH4 hydrolysis. The optimum H3PO4 concentration, optimum Co amount, and optimum impregnation time of the H3PO4 with the microalgae strain were investigated. The maximum hydrogen production rate for the 30% CoB catalyst supported on microalgae strain treated with H3PO4 was found to be 3940 mL min−1g−1catalyst. X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and scanning electron microscope (SEM) analysis were performed for characterization of CoB catalyst supported on Spirulina microalgae strain. After four consecutive uses, the performance and conversion values of this catalyst were investigated. At the same time, the effect of temperature on the hydrogen production from this hydrolysis reaction was examined. The activation energy with the CoB catalyst supported on Spirulina microalgae strain was calculated as 35.25 kJ mol−1. According to the kinetic model of a power law, n value was found as 0.25 for kinetic studies.  相似文献   

9.
In this study, grinded apricot kernel shell (GAKS) biobased waste was used for the first time as a cost-effective, efficient, green and metal-free catalyst for hydrogen generation from the hydrolysis reaction of sodium borohydride (NaBH4). For the hydrogen production by NaBH4 hydrolysis reaction, GAKS was treated with various acids (HCl, HNO3, CH3COOH, H3PO4), salt (ZnCl2) and base (KOH). As a result, the phosphoric acid (H3PO4) demonstrated better catalytic activity than other chemical agents. The hydrolysis of NaBH4 with the GAKS-catalyst (GAKScat) was studied depending on different parameters such as acid concentration, furnace burning temperature and time, catalyst amount, NaBH4 concentration and hydrolysis reaction temperature. The obtained GAKScat was characterized by ICP-MS, elemental analysis, TGA, XRD, FT-IR, Boehm, TEM and SEM analyses and was evaluated for its catalytic activity in the hydrogen production from the hydrolysis reaction of NaBH4. According to the results, the optimal H3PO4 percentage was found as 15%. The maximum hydrogen generation rate from the hydrolysis of NaBH4 with the GAKScat was calculated as 20,199 mL min−1 gcat−1. As a result, it can be said that GAKS treated with 15% H3PO4 as a catalyst for hydrogen production is an effective alternative due to its high hydrogen production rate.  相似文献   

10.
A Co/HTNT catalyst is developed by immobilizing Co on the surface of titanate nanotubes. The microstructure and composition of the catalyst are investigated with atomic absorption spectroscopy (AAS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The developed Co/HTNT catalyst shows great performance in catalyzing NaBH4 hydrolysis. The hydrolysis of 25 mg NaBH4 catalyzed by 50 mg Co/HTNT in 10 g NaOH solution (12.5 wt%) provides a hydrogen production rate of 1.04 L min?1 gCo?1 at 30 °C, and the activation energy of the reaction is 29.68 kJ mol?1. The high catalytic activity and economical property make this catalyst a promising choice for on-site hydrogen production from NaBH4 hydrolysis.  相似文献   

11.
In this study, montmorillonite (MMT) clay was modified with different acids to be used as support material. The modified MMT clay was used to obtain hydrogen in the hydrolysis reactions of NaBH4 (NaBH4-HR) as a support material for the Co–B and Co–Fe–B catalyst. During the activation of MMT clay, the effects of different acids, phosphoric acid (H3PO4) concentration, and impregnation time with H3PO4 were investigated. During the hydrogen generation from the NaBH4-HR, effects of Co loading, Fe loading, NaBH4 concentration, temperature and, catalyst durability were investigated. The maximum HGRs for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B treated with 5 M H3PO4 for 7 days were 1869 and 4536 mL/min/gcatalyst, respectively. The activation energies for MMT-H3PO4–CoB and MMT-H3PO4–Co–Fe–B catalyst samples were 49.5 and 38.90 kJ/mol.  相似文献   

12.
Numerous catalysts have been widely investigated for accelerating hydrogen production from NaBH4 hydrolysis. However, these catalysts are usually complicated in structures, costly in fabrication, and hazardous for environment. In this work, cheap and environment-friendly acetic acid, CH3COOH, is employed to promote NaBH4 hydrolysis to produce hydrogen in a considerable rate. The experimental results demonstrate that the addition of suitable amount of CH3COOH into NaBH4 solutions stabilized with NaOH could dramatically accelerate the hydrolysis reaction. Additionally, the start/stop of NaBH4 hydrolysis could be controlled by adding acid or base into the solution to realize “go-as-you-please” on-site hydrogen production.  相似文献   

13.
Hydrogen production through the reaction between sodium borohydride (NaBH4) and water in presence of three different catalysts including; NiB, CoB and NiCoB is studied. The catalysts are synthesized by chemical reduction method at room and 0 °C temperature. The products are characterized by X-Ray Diffraction (XRD), High-Resolution Scanning Electron Microscopy (HRSEM) and Inductively Coupled Plasma-optical emission spectroscopy (ICP). The results showed that carrying out synthesizing process at low temperature, causes decreasing the nuclei size and reducing driving force for the growth stage, and results in a meaningful reduction in size of the produced catalysts particles. Furthermore, it leads to a recognizable change in particles shape to fine spherical with definite boundaries and slightly increase in boron content of each catalyst. These changes, especially in size and shape of the produced catalysts, results in an improvement in catalytic activity of the synthesized catalysts and the rate of hydrogen generation through using them. This achievement were successfully proved for all three NiB, CoB and NiCoB catalysts, although it was more pronounced for CoB so that it was possible to produce 1.4 lit hydrogen in less than 13 s (12,923 ml·min?1.g?1catalyst) by using 0.5 g of CoB catalyst synthesized at 0 °C.  相似文献   

14.
CoB/ZIF-8 supported catalysts were successfully prepared using Co/Zn-ZIF-8 as the precursor by single-step reduction, which was applied in hydrogen release from the hydrolysis of NaBH4. Reducible Co ions of Co/Zn-ZIF-8 can be partially in-situ transformed into CoB by direct reduction, whereas ZIF-8 framework structure can be well preserved due to the resistance of Zn to reducing ambiences. Accordingly, CoB active components can be highly loaded onto ZIF-8 support to produce CoB/ZIF-8 catalysts. The texture evolution of Co/Zn-ZIF-8 during reduction was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscope and nitrogen adsorption–desorption isotherms. Compared with the reduction of Co-ZIF-67, the framework structure of Co/Zn-ZIF-8 can be effectively preserved although Co ions of Co/Zn-ZIF-8 were partially reduced into cobalt-based alloy. In the hydrogen release from hydrolysis of NaBH4, CoB/ZIF-8 supported catalyst exhibits excellent catalytic activity. The effect of NaOH concentration, NaBH4 concentration and reaction temperature on hydrolysis reaction of NaBH4 was deeply studied based on this catalyst. Compared with other published catalysts, this catalyst exhibits relatively low activation energy of about 57.72 kJ mol?1.  相似文献   

15.
The effect of cobalt-based catalysts, i.e. CoCl2(20 wt% Co)/Al2O3 treated by different acids, on NaBH4 hydrolysis was investigated. Five acids were used: oxalic acid, citric acid, acetic acid, sulfuric acid and hydrochloric acid. Two ways of acid treatment were considered: (i) ex-situ addition of acid to CoCl2(20 wt% Co)/Al2O3 at room temperature and (ii) in-situ addition by mixing CoCl2, Al2O3 and acid (one-step process). Both ways showed that adding an acid to the catalyst contributed to an important increase of the catalytic activity towards the NaBH4 hydrolysis. The best performances were obtained with the catalysts treated with either HCl or CH3COOH as the global activity of CoCl2(20 wt% Co)/Al2O3 was increased up to 50%.  相似文献   

16.
For the first time, phosphoric acid (H3PO4) and acetic acid (CH3COOH) catalysts were used for efficient hydrogen (H2) production from sodium borohydride (NaBH4) ethylene glycolysis reaction. In this experimental study, the effects of ethylene glycol/water ratio, ethylene glycol/acid ratio, NaBH4 concentration, acid concentration, and temperature were investigated. These ethylene glycol/water ratio experiments showed that the use of water alongside ethylene glycol negatively affects H2 production. The hydrogen generation rate (HGR) values obtained for this ethylene glycolysis reaction with 1 M H3PO4 and 1 M CH3COOH catalysts are 5800 and 4542 mLmin-1, respectively. Also, the completion times of ethylene glycolysis reactions with these acids are 8 and 10 s, respectively. The n value obtained for ethylene glycolysis reactions according to the power-law kinetic model was 0.50. The activation energies obtained with H3PO4 and CH3COOH catalysts were 24.45 kJ mol?1and 33.23 kJ mol?1, respectively.  相似文献   

17.
Proposing a novel catalyst that achieves catalytic hydrolysis of metal hydrides is an important stage in developing a hydrogen storage system. In this study, a cross-linked gel brush-cobalt (0) composite (Co@P4VPGB@PMC) has been synthesized to obtain hydrogen from NaBH4 solution. The morphology, structure, and composition of the obtained catalyst have been characterized by, FTIR, SEM, EDX, BET, XRD, ICP-MS and XPS. The parameters that significantly affect the hydrolysis of NaBH4 (such as NaBH4 concentration, NaOH amount, catalyst amount, and temperature) have been investigated using response surface methodology (RSM), an optimization method that has gained increasing importance in recent years. The hydrogen generation rate (HGR) was 4499 mL/min gcat for Co@P4VPGB@PMC when the NaBH4 amount was 241.52 mM, NaOH amount 5 wt%, catalyst amount 10.55 mg and temperature 58.9 °C. Moreover, the apparent activation energy (Ea) for the catalytic hydrolysis reaction has been 41.27 kJmol-1 obtained under optimum conditions. Additionally, the Co@P4VPGB@PMC catalyst displayed significant reusability performance for up to five cycles without major loss of its activity. Compared with metal catalysts, this new cross-linked polymer gel brush-cobalt catalyst has excellent potential applications for hydrogen production by hydrolysis of metal hydrides due to its simple synthesis, low cost, and the easy availability of raw materials.  相似文献   

18.
Hydrogen is a sustainable, renewable and clean energy carrier that meets the increasing energy demand. Pure hydrogen is produced by the hydrolysis of sodium borohydride (NaBH4) using a catalyst. In this study, Ni/TiO2 catalysts were synthesized by the sol-gel technique and characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) methods. The effects of Ni loading ratio (20–40%), catalyst amount (75–200 mg), the concentration of sodium hydroxide (NaOH, 0.25–1 M), initial amount of NaBH4 (75–125 mg) and the reaction temperature (20–60 °C) on hydrogen production performance were examined. The hydrogen yield (100%) and hydrogen production rate (110.87 mL/gcat.min) were determined at the reaction conditions of 5 mL of 0.25 M NaOH, 100 mg NaBH4, 100 mg Ni/TiO2, 60 °C. Reaction order and activation energy were calculated as 0.08 and 25.11 kJ/mol, respectively.  相似文献   

19.
The introduction of magnetism into a catalyst can greatly optimize its separation performance. In the present work, a kind of magnetically separable catalysts for promoting NaBH4 hydrolysis have been fabricated by anchoring cobalt nanoparticles on magnetic dendritic KCC-1 nanospheres composed of magnetic Fe3O4 core and fibrous shell. The fabricated catalysts were characterized with various characterization methods, including absorption spectroscopy (AAS), scanning electron microscopy (SEM), high-resolution transmission electronic microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), and Fourier transform infrared (FT-IR), etc. This kind of catalysts exhibit high catalytic activity for promoting the hydrolysis of NaBH4 under alkaline conditions, giving a hydrogen generation rate and activation energy of 3.83 L min−1 gCo−1 (30 °C) and 53.63 kJ mol−1, respectively. After used for 5 cycles, the catalyst showed 36.5% catalytic activity reserved. Most importantly, the magnetism of the catalyst made it easily separated and recycled from the solution after the reaction completed. The development of this kind of catalysts could provide a promising option for catalyzing NaBH4 hydrolysis for portable hydrogen production from.  相似文献   

20.
In the present paper, the blast furnace slag (BFS) supported Co-B catalyst were investigated in detail. The impregnation-chemical reduction method was used while hydrochloric (HCl) acid treated BFS samples (BFS+) were prepared. Catalyst samples were analyzed in three main groups as base BFS (BFS0), BFS0-Co-B and BFS+-Co-B. The effects of these catalyst samples on hydrogen production from the solid-state sodium boron hydride (NaBH4) are analyzed in this study. The effects of some parameters such as the ingredients of blast furnace slag, the molarity of hydrochloric acid treatment, the Co percentages and the solution temperatures were investigated on the hydrolysis performance of NaBH4. The NaBH4 hydrolysis reaction with the BFS0 is treated by the BFS+-Co-B-20% catalyst was completed approximately 25 min and the hydrolysis reaction with the BFS0-Co-B-20% catalyst was completed approximately 20 min whereas the hydrolysis reaction of NaBH4 was completed in 1 h 35 min. The hydrogen production rates at pre-heated to max 40, 50 and 60 °C were measured as 55.12, 64.47 and 70.41 L/min.gcatalyst, respectively. According to another result of the study, the high-efficiency solid-state BFS-Co-B & NaBH4 mixtures were covered with the PVA (Polyvinyl alcohol) film to make them more resistant to environmental effects such as humidity.  相似文献   

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