Browsing by Author "Sahiner, Nurettin"
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Article Citation Count: 0Boric acid versus boron trioxide as catalysts for green energy source H2 production from sodium borohydride methanolysis(2021) İnger, Erk; Ari, Betul; Sengel, Sultan B.; Inger, Erk; Sahiner, Nurettin; Airframe and Powerplant MaintenanceHere, boric acid (H3BO3) and its dewatered form, boron trioxide (B2O3) were tested as catalysts for hydrogen (H2) evolution in the methanolysis of sodium borohydride (NaBH4) in methanol. Parameters such as catalyst types and their amounts, NaBH4 concentration, and the reaction temperature affecting the hydrogen generation rate (HGR) were studied. It has been found that H3BO3 and B2O3 catalyzed methanolysis reaction of NaBH4 follow up first-order kinetics relative to the concentration of NaBH4. Furthermore, the conversion and activity of these catalysts were examined to determine their performance in ten consecutive use. Interestingly, H3BO3 and B2O3 have demonstrated superior catalytic performances in methanolysis of NaBH4 comparing to the studies published in literature with the activation energy of respectively 22.08 kJ.mol-1, and 23.30 kJ.mol-1 in H2 production. The HGR was calculated as 6481 mL.min-1.g-1 and 5163 mL.min-1.g-1 for H3BO3 and B2O3 catalyst, respectively for 50 mg catalyst at 298 K. These results are comparably better than most metal nanoparticle catalysts used for H2 production in addition to the naturally occurring boron-based environmentally friendliness of these materials.Article Citation Count: 16Catalytic activity of metal-free amine-modified dextran microgels in hydrogen release through methanolysis of NaBH4(Wiley, 2020) İnger, Erk; Sunol, Aydin K.; Sahiner, Nurettin; Airframe and Powerplant MaintenancePolymeric microgels were prepared from dextran (Dex) by crosslinking linear natural polymer dextran with divinyl sulfone (DVS) with a surfactant-free emulsion technique resulting in high gravimetric yield of 78.5 +/- 5.3% with wide size distribution. Dex microgels were chemically modified, and then used as catalyst in the methanolysis of NaBH4 to produce H-2. The chemical modification of Dex microgel was done on epichlorohydrin (ECH)-reacted Dex microgels with ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetraamine (TETA) in dimethylformamide (DMF) at 90 degrees C for 12 hours. The modified dextran-TETA microgels were protonated using treatment with hydrochloric acid (HCl) and m-Dex microgels-TETA-HCl was found to be a very efficient catalyst for methanolysis of NaBH4 to produce H-2. The effects of reaction temperature and NaBH4 concentration on H-2 generation rates were investigated and m-Dex microgels-TETA-HCl catalyst possessed excellent catalytic performances with 100% conversion and 80% activity at end of 10 consecutive uses and was highly re-generatable with simple HCl treatment. Interestingly, m-Dex microgels-TETA-HCl catalyst can catalyze NaBH4 methanolysis reaction in a mild temperature range 0 to 35 degrees C with Ea value of 30.72 kJ/mol and in subzero temperature range, -20 to 0 degrees C with Ea value of 32.87 kJ/mol, which is comparable with many catalysts reported in the literature.Article Citation Count: 13PEI modifiednatural sands of Florida as catalysts for hydrogen production from sodium borohydride dehydrogenation in methanol(Wiley-hindawi, 2021) İnger, Erk; Demirci, Sahin; Can, Mehmet; Sunol, Aydin K.; Philippidis, George; Sahiner, Nurettin; Airframe and Powerplant MaintenanceSand samples from Tampa (T) and Panama (P) City beaches in Florida were used as catalysts for dehydrogenation of NaBH4 in methanol. T and P sand samples were sieved to <250, 250 to 500, and >500 mu m sizes, and the smallest fractions resulted in faster hydrogen generation rates (HGR), 565 +/- 18 and 482 +/- 24 mL H-2 (min.g of catalyst)(-1), respectively. After various base/acid treatments, HGR values of 705 +/- 51 and 690 +/- 47 mL H-2 (min g of catalyst)(-1) for HCl-treated T and P sand samples were attained, respectively. Next, T and P sand samples were modified with polyethyleneimine (PEI) that doubled the HGR values, 1344 +/- 103, and 1190 +/- 87 mL H-2 (min.g of catalyst)(-1) and increased similar to 8-fold, 4408 +/- 187, and 3879 +/- 169 mL H-2 (min g of catalyst)(-1), correspondingly after protonation (PEI+). The Ea values of T and P sand samples were calculated as 24.6 and 25.9 kJ/mol, and increased to 36.1, and 36.6 kJ/mol for T-PEI(+)and P-PEI(+)samples, respectively.Article Citation Count: 35Porous carbon particles as metal-free superior catalyst for hydrogen release from methanolysis of sodium borohydride(Pergamon-elsevier Science Ltd, 2020) İnger, Erk; Yildiz, Mustafa; Inger, Erk; Sahiner, Nurettin; Airframe and Powerplant MaintenanceCarbon materials can be readily prepared from wood derivatives, monosaccharaides such as pentose/hexose and/or polysaccharides in addition to many starting materials by treatment of thermal, chemical and hydrothermal methods. Here, the porous carbon (PC) particles were prepared by removal of silica particles from previously prepared carbon-silica composites by hydrothermal and carbonization process from sucrose. Then, PC particles were modified with polyethyleneimine (PEI) to prepared amine functionalized PC-PEI particles and protonated with hydrochloric acid, PC-PEI+. Finally, these prepared carbon-based particles were used as catalyst for H-2 release from NaBH4 methanolysis and PC-PEI+ was found as the most effective catalyst at 25 degrees C with 4040 +/- 126 mL H-2. min(-1).g(-1) HGR value. The E s value of 23.9 kJ/mol in H-2 release reaction from NaBH4 methanolysis catalyzed by PC-PEI+ that is comparable and/or better than most of studies reported in literature. The activity% of PC-PEI+ catalyst was 72% after fifth consequential runs. Additionally, the regeneration ability of PC-PEI+ catalyst was also shown that after fifth regeneration process, there is only 5% decrease in activity%. (C) 2019 Elsevier Ltd. All rights reserved.