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Author: Sahiner, NurettinPublisher: Wiley

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    Article
    Citation - WoS: 27
    Citation - Scopus: 29
    Catalytic activity of metal-free amine-modified dextran microgels in hydrogen release through methanolysis of NaBH4
    (Wiley, 2020) Inger, Erk; Sunol, Aydin K.; Sahiner, Nurettin
    Polymeric 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.
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    Article
    Citation - WoS: 4
    Citation - Scopus: 3
    Crosslinked Polyethyleneimine-Based Structures in Different Morphologies as Promising Co2 Adsorption Systems: a Comprehensive Study
    (Wiley, 2024) Demirci, Sahin; Inger, Erk; Bhethanabotla, Venkat; Sahiner, Nurettin
    Although there are many studies on CO2 adsorption via PEI-modified carbon particles, metal-organic frameworks, zeolitic imidazolate frameworks, and silica-based porous structures, only a limited number of studies on solely cross-linked PEI-based structures. Here, the CO2 adsorption capacities of PEI-based microgels and cryogels were investigated. The effects of various parameters influencing the CO2 adsorption capacity of PEI-based structures, for example, crosslinker types, PEI types (branched [bPEI] or linear [lPEI]), adsorbent types (microgel or cryogel), chemical-modification including their complexes were examined. NaOH-treated glycerol diglycidyl ether (GDE) crosslinked lPEI microgels exhibited higher CO2 adsorption capacity among other microgels with 0.094 +/- 0.006 mmol CO2/g at 900 mm Hg, 25 degrees C with 2- and 7.5-fold increase upon pentaethylenehexamine (PEHA) modification and Ba(II) metal ion complexing, respectively. The CO2 adsorption capacity of bPEI and lPEI-based cryogels were compared and found that lPEI-GDE cryogels had higher adsorption capacity than bPEI-GDE cryogels with 0.188 +/- 0.01 mmol CO2/g at 900 mm Hg and 25 degrees C. The reuse studies revealed that NaOH-treated GDE crosslinked bPEI and lPEI microgels and cryogels showed promising potential, for example, after 10-times repeated use >50% CO2 adsorption capacity was retained. The results affirmed that PEI-based microgels and cryogels are encouraging materials for CO2 capture and reuse applications.