Single site anchored novel pentacoordinate Schiff-base Co-(II) complexes over SBA-15 for selective oxidation (O-2) of n-alkanes and kinetic study
authors Machado, K; Tavares, PB; Freire, C; Mishra, GS
nationality International
journal POLYHEDRON
author keywords Co complexes; SBA-15; n-Alkanes; O-2 oxidation; Regioselectivity; Kinetics
keywords MODIFIED SILICA-GEL; MOLECULAR-OXYGEN; CYCLOHEXANE OXIDATION; HEXANE; CATALYSTS; DIOXYGEN; HEPTANE; MCM-41; REACTIVITY; RUTHENIUM
abstract Trimethoxysilane pentacoordinate Schiff-base Co-(II) complexes, i.e. Co[Cl-Sal(PMeO-Si)DPTA], (3.a) and Co[F-Sal(PMeO-Si)DPTA], (3.b) and Co[FCl-Sal(PMeO-Si)DPTA], (3.c) (DPTA = bis(aminopropyl)amine, Sal = salicylaldehyde) were synthesized and anchored into SBA-15 matrix to obtain novel supported hybrid catalysts. The catalysts were characterized by FT-IR, TEM, SEM, XRD, TG and BET analysis. These supported complex catalysts were tested in the catalytic oxidation of n-hexane and n-heptane with O-2 under relatively mild and solvent free conditions. A high TON of 3320 with 19.6% yield for n-hexane oxidation and a high TON of 3180 with 17.3% yield for n-heptane oxidation were obtained with 3.b anchored over SBA-15. The oxidation product regioselectivities were obtained as C-1(1):C-2(9.2):C-3(10.7) for n-hexane and C-1(1):C-2(9.0):C-3(9.7):C-4(2.7) for n-heptane. The reaction of kinetics follows a pseudo first-order reaction for both n-alkanes. Enhanced yields (30.6% for n-hexane oxidation and 23.8% for n-heptane oxidation) were obtained with the addition of PCA (pyrazinecarboxylic acid); the catalytic results of reactions made in the presence of radical traps suggested that the catalytic oxidation of n-hexane and n-heptane proceeded via free radicals. The catalyst recycles tests showed that it could be reused up to 7th catalytic cycles. (C) 2013 Elsevier Ltd. All rights reserved.
publisher PERGAMON-ELSEVIER SCIENCE LTD
issn 0277-5387
year published 2014
volume 69
beginning page 119
ending page 126
digital object identifier (doi) 10.1016/j.poly.2013.11.025
web of science category Chemistry, Inorganic & Nuclear; Crystallography
subject category Chemistry; Crystallography
unique article identifier WOS:000331502500016
link http://dx.doi.org/10.1016/j.poly.2013.11.025
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