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Article Citation - WoS: 15Citation - Scopus: 17Pei Modifiednatural Sands of Florida as Catalysts for Hydrogen Production From Sodium Borohydride Dehydrogenation in Methanol(Wiley-hindawi, 2021) Inger, Erk; Demirci, Sahin; Can, Mehmet; Sunol, Aydin K.; Philippidis, George; Sahiner, NurettinSand 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 Boric Acid Versus Boron Trioxide as Catalysts for Green Energy Source H2 Production From Sodium Borohydride Methanolysis(2021) Demirci, Sahin; Ari, Betul; Sengel, Sultan B.; Inger, Erk; Sahiner, NurettinHere, 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 - WoS: 4Citation - Scopus: 3Crosslinked Polyethyleneimine-Based Structures in Different Morphologies as Promising Co2 Adsorption Systems: a Comprehensive Study(Wiley, 2024) Demirci, Sahin; Inger, Erk; Bhethanabotla, Venkat; Sahiner, NurettinAlthough 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.
