An alternative to metal catalysts: Poly(4-vinyl pyridine]-based polymeric ionic liquid catalyst for H-2 generation from hydrolysis and methanolysis of NaBH4

摘要

Monodispersed p(4-VP) (poly(4-vinyl pyridine)) polymeric particles were synthesized via self-emulsion polymerization and modified with 1,2-dibromobutane 1,4-dibromobutane and 1,6-dibromobutane, to obtain polymeric ionic liquid (PIL) particles of poly(4-vinyl pyridine)-dibromoethane (p(4-VP)C-++(2)), poly(4-vinyl pyridine)-dibromobuthane (p(4-VP)C-++(4)), and poly(4-vinyl pyridine)-dibromohexane (p(4-VP)C-++(6)) particles. Highly mono dispersed p(4-VP), p(4-VP)C-++(2), p(4-VP)C-++(4) and p(4-VP)C-++(6) particles were obtained with the sizes of 335 +/- 10, 451 +/- 17, 432 +/- 13 and 443 +/- 24 nm, and the zeta potential values of 6.3 +/- 0.6, 31.2 +/- 2.1, 33.3 +/- 1.0 and 35.5 +/- 1.1 mV. PIL-metal composites of p(4-VP)C-++(6)-Co p(4-VP)C-++(6)-Ni and p(4-VP)C-++(6)-Fe particles were prepared by reducing CoCl2, NiCl2 and FeC13 metal salts loaded into p(4-VP)C-++(6) microgels and then reducing with NaBH4. The prepared PIL-metal composites and PIL particles were used as catalysts in H-2 generation from the hydrolysis and methanolysis of NaBH4. It was found that the prepared PIL-metal composites (e.g., p(4-VP)C-++(6)-Co) showed better catalytic performances than PIL particles (e.g., p(4-VP)C-++(6)) for the hydrolysis reaction of NaBH4 whereas, PIL catalytic performances were much better than PIL-metal composites for the methanolysis of NaBH4. Various parameters affecting the hydrolysis and methanolysis reactions of NaBH4 such as the types of PIL/PIL-metal particle, the amount of PIL particles, the amount of NaBH4 and temperature were investigated. A very high hydrogen generation rate (HGR) value for the methanolysis reaction of 500 mM NaBH4 catalyzed by 50 mg p(4-VP)C-++(6) at 25 degrees C was calculated as 9125 +/- 177 mL H-2 (g of catalyst min)(-1). Furthermore, very low activation energy (Ea), 13.78 +/- 0.23 kJ morl was calculated for the methanolysis of NaBH4 catalyzed by p(4-VP)C-++(6) at temperatures in the range of 0-40 degrees C. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.