Very fast H2 production from the methanolysis of NaBH4 by metal‐free poly(ethylene imine) microgel catalysts

The polyethyleneimine (PEI) microgels prepared via microemulsion polymerization are protonated by hydrochloric acid treatment (p‐PEI) and quaternized (q‐PEI) via modification reaction with methyl iodide and with bromo alkanes of different alkyl chain lengths such as 1‐bromoethane, 1‐bromobutane, 1‐bromohexane, and 1‐bromooctane. The bare p‐PEI and q‐PEI microgels are used as catalysts directly without any metal nanoparticles for the methanolysis reaction of sodium borohydride (NaBH₄). Various parameters such as the protonation/quaternization reaction on PEI microgels, the amount of catalyst, the amount of NaBH₄, and temperature are investigated for their effects on the hydrogen (H₂) production rate. The reaction of self‐methanolysis of NaBH₄ finishes in about 32.5 min, whereas the bare PEI microgel as catalyst finishes the methanolysis of NaBH₄ in 22 min. Surprisingly, it is found that when the protonated PEI microgels are used as catalyst, the same methanolysis of NaBH₄ is finished in 1.5 min. The highest H₂ generation rate value is observed for protonated PEI microgels (10 mg) with 8013 mL of H₂/(g of catalyst.min) for the methanolysis of NaBH₄. Moreover, activation parameters are also calculated with activation energy value of 23.7 kJ/mol, enthalpy 20.9 kJ/mol, and entropy ?158 J/K.mol. Copyright © 2016 John Wiley & Sons, Ltd.     

Catalytic activities of non-noble metal catalysts (CuB,FeB, and NiB) with C.Vulgaris microalgal strain support modified by using phosphoric acid for hydrogen generation from sodium borohydride methanolysis

In this study, a novel microalgae based support material was developed and applied. The Chlorella Vulgaris microalgal strain was modified by treating the algal biomass with phosphoric acid for proton binding process (CVMS-H₃PO₄). Ultimately, the CVMS-H₃PO₄-metal (CuB, NiB, or FeB) catalysts were used as highly efficient solid catalysts to produce hydrogen from the methanolysis of NaBH₄. Once the superior metal was identified, the NaBH₄ concentration, metal percentage in the supported-catalyst, catalyst amount, and temperature effect on the methanolysis reaction was thoroughly investigated. The maximum hydrogen production rate for the CVMS-H₃PO₄ supported-catalyst was obtained with the use of 20% Cu metal at 30 °C and it was found to be 6500 mL/min/g_cat. In addition, the maximum hydrogen production rate for the CVMS-H₃PO₄ supported-catalyst was attained with the use of 20% Cu metal at 60 °C and it was found to be 21176 mL/min/g_cat. Also, the activation energy was determined as 23.79 kJ/mol. The re-usability studies of the microalgal strain supported-CuB catalyst were performed and it was found that there was no decrease in % conversion for this catalyst. XRD, FTIR, SEM, and ICP-MS analysis were carried out to characterize CVMS-H₃PO₄CuB catalyst thoroughly.