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    Natural Celluloses as Catalysts in Dehydrogenation of NaBH4 in Methanol for H2 Production
    (Amer Chemical Soc, 2020) Can, Mehmet; Demirci, Şahin; Sunol, Aydın K.; Philippidis, George; Şahiner, Nurettin
    Cellulose, the most abundant renewable biopolymer, exists in many forms, such as microgranular cellulose (MGCell), sigmacell cellulose (SCell), cellulose fibers (FCell), and alpha-cellulose (AlfaCell). Several of these cellulose forms were protonated with an amine-containing agent polyethyleneimine (PEI), and the modified celluloses (XCell-PEI+) were studied as catalysts in methanolysis of NaBH4 for hydrogen (H-2) generation. It was found that the SCell-PEI+-catalyzed reaction is the fastest one among the modified celluloses with a hydrogen generation rate of 5520 +/- 119 mL H-2/(g of catalyst x min). The activation energies of MGCell-PEI+, SCell-PEI+, FCell-PEI+, and AlfaCell-PEI+ were determined as +21.7, +23.4, +24.8, and + 21.8 kJ/mol, respectively. Reusability of catalysts was investigated, and regeneration of cellulose based catalysts after the fifth cycle could be readily achieved by HCl treatment to completely recover its activity. Therefore, PEI-modified-protonated cellulose forms constitute sustainable, re-generable, and renewable catalysts for production of H-2, an environmentally benign green energy carrier.
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    PEI modified natural sands of Florida as catalysts for hydrogen production from sodium borohydride dehydrogenation in methanol
    (John Wiley and Sons Ltd, 2021) Inger, Erk; Demirci, Şahin; Can, Mehmet; Sunol, Aydin K.; Philippidis, George; Şahiner, Nurettin
    Sand 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 [removed]500 μm sizes, and the smallest fractions resulted in faster hydrogen generation rates (HGR), 565 ± 18 and 482 ± 24 mL H2 (min.g of catalyst)−1, respectively. After various base/acid treatments, HGR values of 705 ± 51 and 690 ± 47 mL H2 (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 H2 (min.g of catalyst)−1 and increased ~8-fold, 4408 ± 187, and 3879 ± 169 mL H2 (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.