Preparation And Immobilization Of Palladium(Ii) And Nickel(Ii) Salen Complexes Onto Mcm-41 From Rice Husk For Suzuki-Miyaura And Oxidation Reactions
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Date
2015-08
Authors
ABBAS, SALIH HAMZA
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Abstract
MCM-41 was successfully prepared from rice husk ash (RHA) using cetyltrimethylammonium bromide as a directing agent via sol-gel method at 100 oC. MCM-41 was functionalized with 3-chloropropyltriethoxysilane (CPTES) as a functioning agent and the solid obtained was labeled as Cl-MCM-41. This was followed by double immobilization of N,Nʹ-bis(4-hydroxysalicylidene)ethylenediimine palladium(II) and N,Nʹ-bis(4-hydroxysalicylidene)ethylenediimine nickel(II) complexes via their two hydroxyl groups onto Cl-MCM-41. Two new heterogeneous catalysts were obtained and designated as MCMSalenPd and MCMSalenNi. The two prepared catalysts were fully characterized and the double immobilization of the two complexes was confirmed using fourier transform infrared (FT-IR), X-ray diffraction (XRD), N2 sorption measurements, transmission electron microscopy (TEM), scanning electron microscopy (SEM), solid state C-13 nuclear magnetic resonance (13C MAS NMR), solid state Si-29 nuclear magnetic resonance (29Si MAS NMR), energy dispersive X-ray elemental analysis (EDX) and atomic absorption spectroscopy (AAS). The MCMSalenPd catalyst was examined for Suzuki-Miyaura C-C coupling reaction of bromobenzene with phenylboronic acid. The catalyst had good stability and excellent activity within 2 hour at 130 oC. The conversion percentage was 98.7% with 100% selectivity. The kinetic studies showed the reaction followed a pseudo first order rate law. The activation energy was determined to be about 0.393 kcal mol-1. The catalyst was reused for more than five catalytic cycles without significant loss of activity. The MCMSalenNi catalyst was examined for the oxidation reaction of benzyl
alcohol using periodic acid as oxidant. The catalyst was found to have good stability and excellent activity. The conversion percentage was 98.4% with 48.8% selectivity when the reaction was carried out for 1.5 hour at 90 oC. The kinetic study showed a pseudo first order rate law and the activation energy was determined to be about 0.0538 kcal mol-1. The catalyst was reused for more than six catalytic cycles with good reusability.
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Preparation And Immobilization Of Palladium(Ii) And Nickel(Ii) Salen Complexes Onto Mcm-41 From Rice Husk , For Suzuki-Miyaura And Oxidation Reactions