635299-18-2Relevant articles and documents
Novel alkoxysilane pentacoordinate O=V(IV) complexes as supported catalysts for cyclohexane oxidation with dioxygen
Mishra, Gopal S.,Kumar, Anil,Mukhopadhyay, Suman,Tavares, Pedro B.
, p. 136 - 146 (2010)
A variety of newly synthesized and well characterized alkoxysilane pentacoordinate Oxovanadium(IV) complexes, VO[Sal(PMeOSi)DPTA] 3[a], VO[Cl-Sal(PMeOSi)DPTA] 3[b], VO[Sal(PMeOSi)DETA] 6[a] and VO[Cl-Sal(PMeOSi)DETA] 6[b], (Sal = salicylaldehyde, DPTA = bis(aminopropyl)amine, DETA = diaminoethylamine), have been anchored by covalent bond into the surface of SiO2 and/or Al2O3 via silicon-alkoxide route by a condensation process as supported catalysts. These solid supported catalysts (abbreviated as catalysts A to H) showed high catalytic efficiency in the selective oxidation reaction of cyclohexane using molecular oxygen under relatively mild condition in a micro-batch reactor. The Catalyst C (SiO 2/3[a] complex) system exhibits best activity, overall yield 38.5% (TONs, ca. 5.0 × 103) as well as high selectivity 98% (cyclohexanol 74%, cyclohexanone 24%). Notably, cyclohexane shows significantly improved yield 44.0%, by the addition of pyrazinecarboxylic acid as a co-catalyst. The TGA indicates these catalysts are stable up to maximum reaction temperature, ca. 473 K and ICP analysis shows there is negligible vanadium loss from the supported catalyst after the reaction, allowing further use of the V-catalyst. The various factors influences (i.e. temperature, O2 pressure, reaction time, catalyst amount) were also investigated in the systematic way, to optimize the reaction processes. The impact of radical traps and detection of intermediate peroxy radical were also investigated to establish a radical mechanism.
Single site anchored novel Cu(II) catalysts for selective liquid-gas phase O2 oxidation of n-alkanes
Mishra, Gopal S.,Kumar, Anil,Tavares, Pedro B.
scheme or table, p. 125 - 132 (2012/05/20)
The pentacoordinate schiff-base trialkoxysilane Cu(II) complexes, i.e. Cu[Sal(PMeOSi)DPTA], (III-a) and Cu[Cl-Sal(PMeOSi)DPTA], (III-b) were synthesized and covalently anchored on SiO2 and Al2O 3 matrixes as supported hybrid catalysts (i.e. III-a/SiO2 as Catal.-1, III-b/SiO2 as Catal.-2, III-a/Al2O 3 as Catal.-3 and III-b/Al2O3 as Catal.-4). The characterization of supported Cu(II) complexes were performed with SEM-EDX, TGA, ICP, FT-IR and EPR analysis. Catalytic tests were conducted in the oxidation (O2) of n-alkanes under relatively mild conditions, in a batch rocking type reactor. Remarkable high catalytic TONs, from 1468 up to 2422, were observed. Catal.-2 provided the best overall yield, 25.2% with 92% selectivity for n-hexane and 20.1% with 75% selectivity for n-heptane. A 20% improvement in the yields was obtained with PCA as co-catalyst. The impact of both C- and O- centred radical traps were also assessed in order to establish a radical mechanism.
