首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The sodium borohydride(NaBH4) semi-methanolysis and semi-ethanolysis reactions to produce hydrogen are investigated using phosphoric acid(H3PO4) for the first time. The NaBH4 concentration, H3PO4 concentration, and temperature parameters on these semi-alcoholysis reactions are evaluated. The normalized hydrogen generation rates (HGRs) obtained from the NaBH4 semi-methanolysis and semi-ethanolysis acidified using 0.5 M H3PO4 are 11684 and 9981 ml min−1 g−1, respectively. Moreover, the completion times of these semi-methanolysis and semi-ethanolysis reactions with 0.5 M H3PO4 acid concentration are 0.10 and 0.116 min, respectively. Kinetic studies with the power-law model are evaluated. The activation energies(Ea) obtained for the NaBH4 semi-methanolysis and semi-ethanolysis using 0.5 M H3PO4 are 9.08 and 32.47 kJ mol−1, respectively.  相似文献   

2.
Polymeric catalysts have displayed great performance for catalytic hydrogen generation. However, the reported metal free polymeric catalysts for NaBH4 methanolysis are mainly limited to coating strategy where the catalytic activity fade after few cycles. Herein, we report an interpenetrating polymer network (IPN) strategy for rapid and highly recyclable NaBH4 catalytic methanolysis to produce hydrogen (H2) gas. In this study, we prepared poly(acrylic acid)/polysaccharide IPN via Pickering tempted polymerization. The hydrogen generation performance was studied employing different parameters where maximum HGR of 8182 mL H2 min?1 g?1 of CAP. The activation energy Ea, enthalpy and entropy were calculated to be 62.99 kJ mol?1, 32.25 kJ mol and ?130.92 J mol K?1, respectively. Above all, CAP kept cyclic performance to 100% even at the 7th cycle. We confirmed the reproducibility of approach with other natural polysaccharides. This was due to strong chain entanglement of IPN synthesis which forces the active sites to stay in place during cyclic catalysis reaction. Thus, the IPN strategy ensures longer catalyst life for catalytic methanolysis of NaBH4 for H2 generation.  相似文献   

3.
Metal-free catalysts (SP–KOH–P) doped phosphorus and oxygen as a result of modification with H3PO4 to the surface of the activated carbon sample (SP–KOH) obtained by activation of KOH with Spirulina microalgae were used to obtain hydrogen (H2) from methanolysis of NaBH4. The characteristic structure of SP-KOH-P and SP-KOH metal-free catalysts were examined by XRD, TEM, elemental analysis, FTIR, and ICP-MS. The effects of the amount of catalyst, NaBH4 concentration, reusability, and temperature on H2 production rate from NaBH4 methanolysis reaction were investigated. The hydrogen production rate (HGR) obtained with 25 mg SP-KOH-P was found to be 19,500 mL min?1 g?1. The activation energy (Ea) value of SP-KOH-P metal-free catalyst sample was calculated as 38.79 kJ mol?1.  相似文献   

4.
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   

5.
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   

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.
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   

8.
In this study, organic waste sources (spent coffee ground (SCG)) is used as metal-free catalyst in comparison with conventional noble-metal catalyst materials for hydrogen generation based on the methanolysis of sodium borohydride solution. Spent coffee ground (SCG) is used as a metal-free catalyst for the first time as treated with different chemicals. The aim is to synthesize the metal-free catalyst that can be used for the production of hydrogen, a renewable energy source. SCG, which was collected from coffee shops, was used for preparing the catalyst. To produce hydrogen by sodium borohydride (NaBH4) methanolysis, SCG is pretreated with different chemical agents (H3PO4, KOH, ZnCl2). According to the acid performances, the choice of phosphoric acid was evaluated at different mixing ratios (10%, 20%, 30%, 40%, 50%, 100%) (w/w), different temperatures (200, 300 and 400 °C) and burning times (30, 45, 60 and 90 min) for the optimization of SCG-catalyst. A detailed characterization of the samples were carried out with the aid of FTIR, SEM, XRD and BET analysis. In this study, the experiments were generally carried out effectively under ambient temperature conditions in10 ml methanol solution containing 0.025 g NaBH4 and 0.1 g of the catalyst. The hydrogen obtained in the experimental studies was determined volumetrically by the gas measurement system. When evaluating the hydrogen volume, different NaBH4 concentrations, catalyst amount and different temperature effects were investigated. The effect of the amount of NaBH4 was investigated with 1%, 2.5%, 5%, and 7.5% ratio of NaBH4 while the influence of the concentration of catalyst was carried-out at 0.05, 0.1, 0.15, and 0.25 g catalysts. Four different temperatures were tested (20, 30, 40, 50 and 60 °C) to explore the performance of the catalyst under different temperatures. The experiments by using SCG-catalyst treated with H3PO4 reveal that the best acid ratio was 100% H3PO4. The maximum hydrogen production rate with the use of SCG-catalyst for the methanolysis of NaBH4 was found to be 8335.5 mL min−1gcat−1. Also, the activation energy was determined to be 9.81 kJ mol−1. Moreover, it was discovered that there was no decline in the percentage of converted catalyst material.  相似文献   

9.
Novel proton-conducting polymer electrolyte membranes have been prepared from bacterial cellulose by incorporation of phosphoric acid (H3PO4/BC) and phytic acid (PA/BC). H3PO4 and PA were doped by immersing the BC membranes directly in the aqueous solution of H3PO4 and PA, respectively. Characterizations by FTIR, TG, TS and AC conductivity measurements were carried out on the membrane electrolytes consisting of different H3PO4 or PA doping level. The ionic conductivity showed a sensitive variation with the concentration of the acid in the doping solution through the changes in the contents of acid and water in the membranes. Maximum conductivities up to 0.08 S cm−1 at 20 °C and 0.11 S cm−1 at 80 °C were obtained for BC membranes doped from H3PO4 concentration of 6.0 mol L−1 and, 0.05 S cm−1 at 20 °C and 0.09 S cm −1 at 60 °C were obtained for BC membranes doped from PA concentration of 1.6 mol L−1. These types of proton-conducting membranes share not only the good mechanical properties but also the thermal stability. The temperature dependences of the conductivity follows the Arrhenius relationship at a temperature range from 20 to 80 °C and, the apparent activation energies (Ea) for proton conduction were found to be 4.02 kJ mol−1 for H3PO4/BC membrane and 11.29 kJ mol−1 for PA/BC membrane, respectively. In particular, the membrane electrode assembly fabricated with H3PO4/BC and PA/BC membranes reached the initial power densities of 17.9 mW cm−2 and 23.0 mW cm−2, which are much higher than those reported in literature in a real H2/O2 fuel cell at 25 °C.  相似文献   

10.
Cu based catalysts were synthesized in water and methanol solvents by chemical reduction with sodium borohydride (NaBH4). The obtained catalyst was used to catalyze the NaBH4 hydrolysis reaction with phosphoric acid (H3PO4) including different concentrations. Surface morphology and structural properties of the Cu based catalysts prepared in water and methanol solvents were studied using by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurements and Fourier-transform infrared spectroscopy (FTIR) analyses, respectively. The catalytic activity of the catalysts has been tested by measuring the hydrogen production rate by the acidified hydrolysis of NaBH4. The maximum hydrogen production rates in the hydrolysis reaction including 0.25 M H3PO4 using the Cu based catalyst prepared in water and methanol solvents were 825 and 660 ml g?1min?1, respectively. At the same time, the hydrogen production experiments were carried out from this hydrolysis reaction with only H3PO4 and NaBH4 interactions without using Cu metal catalyst. The activation energy obtained based on the nth order reaction model was found to be 61.16 kJ mol?1.  相似文献   

11.
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   

12.
Inorganic acids such as hydrochloric acid (HCl), nitric acid (HNO3) and sulphuric acid (H2SO4) are generally used in the acid modification of clays. Here, CoB catalyst was synthesized on the acetic acid-activated kaolin support material (CH3COOH -kaolin- CoB) with an alternative approach. This prepared catalyst, firstly, was used to catalyze the hydrolysis of NaBH4 (NaBH4-HR). The structure of the raw kaolin, kaolin-CH3COOH, and CH3COOH-kaolin-CoB samples were characterized by X-ray diffraction spectroscopy (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM), and nitrogen adsorption. At the same time, this catalyst performance was examined by Co loading, NaBH4 concentration, NaOH concentration, temperature and reusability parameters. The end times of this hydrolysis reaction using raw kaolin-CoB and CH3COOH-kaolin-CoB were found to be approximately 140 and 245 min, respectively. The maximum hydrogen generation rates (HGRs) obtained at temperatures 30 °C and 50 °C were 1533 and 3400 mL/min/gcatalyst, respectively. At the same time, the activation energy was found to be 49.41 kJ/mol.  相似文献   

13.
Poly[2-(dimethylamino)ethyl methacrylate] cryogel beads were prepared under cryogenic conditions via free radical polymerization and used as a catalyst in the production hydrogen (H2) from NaBH4 by alcoholysis. The efficiency of the catalyst was investigated in the range of 0–40 °C by both methanolysis and ethylene glycolysis reactions, and its reuse was tested. Accordingly, it was observed that the methanolysis reaction was faster than the ethylene glycolysis reaction. When the hydrogen generation rate (HGR) values between 0 and 40 °C were compared, it was concluded that the methanolysis reaction rate increased from 1550 to 4800 mL.min−1g−1 and the ethylene glycolysis reaction rate increased from 923 to 3551 mL.min−1g−1. In the alcoholysis reaction catalyzed by PDMA cryogel beads, the activation energy was calculated as 19.34 and 22.77 kJ.mol−1 for the methanolysis and ethylene glycolysis reactions, respectively. After six repetitions, the catalyst activity was calculated over 50% for NaBH4 methanolysis and ethylene glycolysis.  相似文献   

14.
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   

15.
In this work, the complex hydrogen sorption behaviors in a 3NaBH4/HoF3 composite prepared through mechanical milling were carefully investigated, including the reactions occurred during ball milling and de-/rehydrogenation processes. Different from other rear earth fluorides, the HoF3 can react with NaBH4 during ball milling, leading to the formations of Na–Ho–F and Na–Ho–BH4 complex compounds. The first dehydriding of the 3NaBH4/HoF3 composite can be divided into 4 steps, including the ion exchange between H and F, the formation of NaHo(BH4)4, the decomposition of NaHo(BH4)4 and reaction of NaBH4 with Na–Ho–F compounds. The final products, HoB4, HoH3 and NaF, can be rehydrogenated to generate NaBH4 and NaHoF4 with an absorption capacity of 2.3 wt% obtained at 400 °C. Based on the Pressure–Composition–Temperature measurements, the de-/rehydrogenation enthalpies of the 3NaBH4/HoF3 composite are determined to be 88.3 kJ mol−1 H2 and −27.1 kJ mol−1 H2, respectively.  相似文献   

16.
Here, for the first time, a metal-free catalyst was synthesized by ethylenediamine tetra-acetic acid (EDTA) modification of the carbon nitride (g-C3N4) sample and protonation of the obtained sample. The catalyst was used for the production of H2 from the methanolysis of sodium borohydride (NaBH4). The EDTA modification and protonation of the g-C3N4 sample was confirmed by XRD, FTIR, SEM-EDX, and TEM analyses. During the hydrogen generation, NaBH4 concentration effect, catalyst amount effect, temperature effect and catalyst reusability were investigated. The HGR value obtained with 2.5% NaBH4 using 10 mg catalyst was 7571 mL min?1g?1. The activation energy (Ea) for the g–C3N4–EDTA-H catalyst was found to be 32.2 kJ mol?1 The reusability of the g–C3N4–EDTA-H catalyst shows a catalytic performance of 72% even after its fifth use.  相似文献   

17.
Micro algae based on Spirulina platensis is successfully used for the synthesis of S and N-doped metal-free carbon materials. The procedure consists of three stages; (i) Activated carbon production by KOH activation in CO2 atmosphere (S-AC), (ii) S atom doping to the obtained S-AC using sulphuric acid by hydrothermal activation (S-AC-S), (iii) N atom doping by hydrothermal activation to S-AC obtained using nitric acid (S-AC-S-N). The S and N doped metal-free catalysts are used for H2 release in NaBH4 methanolysis reaction (NaBH4-MR) for the first time. The metal-free carbon catalysts are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM-EDS), X-ray diffractometer spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption and elemental analysis (CHNS) methods. When the HGR values obtained for S-AC-S-N (26,000 mL min?1 g?1) and S-AC (2641 mL min?1 g?1) are compared, there is a 9.84-fold increase. Activation energy (Ea) value for S-AC-S-N was 10.59 kJ mol?1.  相似文献   

18.
Hydrogen production via chemical processes has gained great attention in recent years. In this study, Co-based complex catalyst obtained by adsorption of Co metal to Amberlite IRC-748 resin and Diaion CR11 were tested for hydrogen production from alkaline NaBH4 via hydrolysis process. Their catalytic activity and microstructure were investigated. Process parameters affecting the catalytic activity, such as NaOH concentration, Co percentage and catalyst amount, as well as NaBH4 concentration and temperature were investigated. Furthermore, characteristics of these catalysts were carried out via SEM, XRD and FT-IR analysis. Hydrogen production rates equal to 211 and 221 ml min−1 gcat−1 could be obtained with Amberlite IRC-748 resin and Diaion CR11 Co based complex catalysts, respectively. The activation energies of the catalytic hydrolysis reaction of NaBH4 were calculated as 46.9 and 59.42 kJ mol−1 for Amberlite IRC-748 resin and Diaion CR11 based catalysts respectively kJ mol−1 from the system consisting of 3% Co, 10 wt% NaBH4 and 7 wt% NaOH as well as 50 mg catalyst dosage. It can be concluded that Co-based resins as catalysts for hydrogen production is an effective alternative to other catalysts having higher rate.  相似文献   

19.
A novel proton conducting polymeric gel membrane that consists of poly(ethylene oxide)-grafted-poly(methacrylate) (PEO-PMA) with poly(ethylene glycol) dimethyl ether (PEGDE) as a plasticizer doped with aqueous phosphoric acid (H3PO4) has been prepared and its physicochemical properties were studied in detail. The ionic conductivity was dependent much on the concentration of H3PO4, the immersion time, and content of the plasticizer. This type of proton conducting polymeric gels shares not only good mechanical properties but also thermal stability. Maximum conductivities up to 2.6×10−2 S cm−1 at room temperature (25 °C) and 2.8×10−2 S cm−1 at 70 °C were obtained for the composition of the polymer matrix to the plasticizer as 35/65 (in mass) after the H3PO4 doping from the aqueous solution with 2.93 mol l−1. FT-IR spectra showed that these high proton conductivities are attributed to the presence of excesses free H3PO4 in the polymeric gel in addition to the hydrogen-bonded H3PO4 to the polymer matrix.  相似文献   

20.
In this study, orange peel (OP), one of the organic wastes, was first used as a metal-free catalyst for the production of hydrogen from sodium boron hydride (NaBH4). In order to prepare an orange peel catalyst (OP–H3PO4-Cat) with the best catalytic activity, experiments were carried out on pure orange peel with different acid types, different burning temperatures and different burning times. As a result of these experiments, it was determined that OP-H3PO4-Cat treated with 30% H3PO4 and burned at 400 °C for 45 min had the best catalytic activity. The OP-H3PO4-Cat material was characterised by several techniques such as FTIR, XRD and SEM. As a result, the hydrogen generation rates (HGR) at 30 °C and 60 °C in the methanolysis reaction of 2.5% NaBH4 catalysed by OP-H3PO4-Cat were found as 45,244 and 61,892 mLmin?1g.cat?1, respectively. The activation energy of OP-H3PO4-Cat catalyst was calculated as 12.47 kJmol-1.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号