Yazar "Saka, Cafer" seçeneğine göre listele

Listeleniyor 1 - 8 / 8
  • Küçük Resim Yok
    Öğe
    CoB doped acid modified zeolite catalyst for enhanced hydrogen release from sodium borohydride hydrolysis
    (ELSEVIER, 2020) Saka, Cafer; Eygi, Mustafa Salih; Balbay, Asım
    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.
  • Küçük Resim Yok
    Öğe
    Ethylene glycol as an alternative solvent approach for very efficient hydrogen production from sodium borohydride with phosphoric acid and acetic acid catalysts
    (Pergamon-Elsevier Science Ltd, 2022) Saka, Cafer; Balbay, Asim
    For the first time, phosphoric acid (H3PO4) and acetic acid (CH3COOH) catalysts were used for efficient hydrogen (H-2) 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 H-2 production. The hydrogen generation rate (HGR) values obtained for this ethylene glycolysis reaction with 1 M H3PO4 and 1 M CH3-COOH 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(-1) and 33.23 kJ mol(-1), respectively. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Fe doped-CoB catalysts with phosphoric acid-activated montmorillonite as support for efficient hydrogen production via NaBH4 hydrolysis
    (Elsevier Ltd, 2021) Balbay, Asım; Selvitepe, Nuran; Saka, Cafer
    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.
  • Küçük Resim Yok
    Öğe
    Influence of process parameters on enhanced hydrogen evolution from alcoholysis of sodium borohydride with a boric acid catalyst
    (Pergamon-Elsevier Science Ltd, 2020) Saka, Cafer; Balbay, Asim
    The hydrogen evolution via alcoholysis reaction of sodium borohydride with an H3BO3 catalyst was carried out for the first time. In the process of methanol and NaBH4 (NaBH4-MR), the effects of the H3BO3 and NaBH4 concentration, and temperature parameters were examined and evaluated. The hydrogen yields by the NaBH4-MR, NaBH4 ethanolysis (NaBH4-ER) and NaBH4 hydrolysis reactions (NaBH4-HR) with 0.2 M H3BO3 catalyst are 99, 62, and 88% compared to the theoretical hydrogen yield, respectively. The completion times of the NaBH4-MR using the H3BO3 concentrations of 0.2, 0.4, 0.5, 1 M, and saturated acid solution were about 50, 15, 10, 2 and 1 min, respectively. The hydrogen yields obtained with 50, 15, 10, 2, and 1 min for the same acid concentration values were about 100% compared to the theoretical hydrogen value. By increasing the H3BO3 concentration from 0.2 M to the saturated H3BO3 concentration, the completion time of this NaBH4-MR process was reduced by approximately 50 times, resulting in a significant result. The activation energy (Ea) of the NaBH4-MR with the H3BO3 catalyst was 57.3 kJ/mol. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Metal-free catalyst fabrication by incorporating oxygen groups on the surface of the carbonaceous sample and efficient hydrogen production from NaBH4 methanolysis
    (ELSEVIER, 2022) Saka, Cafer; Balbay, Asım
    In the present study, metal-free catalysts for efficient H2 generation from NaBH4 methanolysis was produced for the first time from apricot kernel shells with two-step activation. The first stage of the two-stage activation includes the production of activated carbon with the KOH agent (AKOH), and the second stage includes hydrothermally HNO3 activation with oxygen doping (O doped AKOH + N). The hydrogen production rate (HGR) and the activation energy (Ea) of the reaction with the obtained metal-free catalyst (10 mg) were determined as 14,444 ml min?1 g?1 and 7.86 kJ mol?1, respectively. The structural and physical-chemical properties of these catalysts were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), elemental CHNS analysis, FT-IR (Fourier transform infrared spectroscopy), and nitrogen adsorption analysis. Also, the reusability results of this metal-free catalyst for H2 production are promising.
  • Küçük Resim
    Öğe
    Oxygen and nitrogen-functionalized porous carbon particles derived from hazelnut shells for the efficient catalytic hydrogen production reaction
    (Elsevier, 2021) Saka, Cafer; Balbay, Asım
    Due to their low cost and high availability, interest in biomass materials in catalytic studies is increasing. It is possible to increase the catalytic activities by the development of metal-free catalysts obtained by adding different atoms to carbon materials. Here, oxygen (O) and nitrogen (N) doped metal-free carbon catalysts (N-AC-N) were synthesized using activated carbon (AC) obtained from hazelnut shells by KOH activation. These metal-free catalysts were used successfully for the first time in the NaBH4 methanolysis reaction (NaBH4-MR). The structural and physical-chemical properties of the metal-free catalysts obtained were analysed by XRD (X-ray diffraction), elemental analysis (CHNS), FT-IR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy), and nitrogen adsorption surface analyses. N and O doped metal-free catalyst showed very good catalytic performance against NaBH4-MR. The hydrogen production rate (HGR) with 10 mg metal-free catalyst at 30 °C and the activation energy(Ea) of the reaction were calculated as 16250 mL min?1 g?1 and 11.45 kJ mol?1, respectively. At the same time, with favourable reusability results, this metal-free catalyst is a promising candidate for the hydrogen(H2) generation system.
  • Küçük Resim Yok
    Öğe
    Phosphorus doped carbon nanodots particles based on pomegranate peels for highly active dehydrogenation of sodium borohydride in methanol
    (Pergamon-Elsevier Science Ltd, 2022) Olmez, Saba Samatya; Balbay, Asim; Saka, Cafer
    Here, the carbon nanodots were successfully synthesized from pomegranate peels (PPCD). This obtained PPCD was treated by a hydrothermal process with phosphoric acid for P doping (P doped PPCD) and used as a metal-free catalyst to obtain hydrogen(H2) from so-dium borohydride (NaBH4) methanolysis for the first time. The characteristics of the samples obtained by ultraviolet, fluorescence, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and Inductively coupled plasma mass spectrometry (ICP-MS) analyses were examined. NaBH4 concentra-tion effect, temperature effect and catalyst reusability experiments were carried out. Using 10 mg of the catalyst with 2.5% NaBH4, an HGR value of 13000 mL min-1g-1 was obtained. The activation energy (Ea) for the P-doped PPCD catalyst was 30.96 kJ mol-1.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Zn-doped TiO2 nanocatalyst for enhanced hydrogen generation via NaBH4 methanolysis
    (Elsevier Sci Ltd, 2026) Balbay, Asim; Erdemoglu, Sema; Yilmaz, Hatice Caglar; Saka, Cafer
    In this study, we report for the first time the strategic Zn doping of TiO2 nanoparticles as an innovative approach to dramatically enhance catalytic hydrogen production via sodium borohydride (NaBH4) methanolysis. This novel Zn-TiO2 nanocatalyst was synthesized by a simple sol-gel method with an optimal Zn doping level of 1 wt%, producing uniform nanospheres with an average size of 8.27 nm. Structural characterizations confirmed the successful incorporation of Zn ions into the TiO2 lattice, inducing oxygen vacancies and significantly increasing surface area-two key factors that synergistically boost catalytic activity beyond that of pure TiO2. As a result, the Zn-TiO2 catalyst delivered a remarkable hydrogen generation rate (HGR) of 20160 mLmin(-1)g(-1) at 30 degrees C with 0.125 g NaBH4. Kinetic analyses revealed strong temperature dependence, with HGR rising from 16,965 to 38145 mLmin(-1)g(-1) between 25-40 degrees C and an activation energy (Ea) of 39.1 kJ mol(-1). Increasing NaBH4 concentration produced an exponential HGR increase, reaching saturation at similar to 0.20 g and peaking at 34,950 mLmin(-1)g(-1) with 0.25 g NaBH4. This work uniquely demonstrates that Zn-induced structural modifications can transform TiO2 into a highly efficient, low-cost catalyst for clean hydrogen production, offering a novel pathway toward scalable and sustainable hydrogen energy systems.