In situ solid-state NMR investigations of the vapor-phase Beckmann rearrangement of 15N-cyclohexanone oxime on MFI-type zeolites and mesoporous SBA-15 materials in the absence and presence of the additive 13C-methanol

摘要: Abstract The stepwise conversion of 15 N-cyclohexanone oxime into e -caprolactam via the vapor-phase Beckmann rearrangement on silicalite-1 ( n Si / Al = 1700 ), siliceous SBA-15 1800 H-ZSM-5 14 and [Al]SBA-15 8.7 ) in absence presence 13 C-methanol was investigated by solid-state N C CP/MAS NMR spectroscopy. MFI-type zeolites materials are characterized different acid strengths pore diameters. surface OH concentrations silicalite-1, SBA-15, H-ZSM-5, were determined to 0.31, 2.81, 1.12, 1.29 mmol g −1 , respectively. 1 H, 29 Si, MAS measurements revealed that Bronsted acidic groups large concentration Q 3 silanol (Si(OSi) OH) led formation O-protonated -caprolactam. On loading heating methanol, water formed dehydration methanol dimethyl ether. These molecules promoted species -aminocapric acid. In addition, both catalysts, partial hydrocarbons, such as isobutane, observed. Furthermore, isopropylamine reaction isobutane byproducts rearrangement, hydroxylamine. contrast, no influence found during mesoporous materials.