Nitrocyclohexane Hydrogenation To Cyclohexanone Oxime Over Mesoporous Carbon-supported Pd Catalyst

Oximes are highly valuable organic intermediates because of their wide applicationfor polymer, perfumes and paints, particularly more attention has been given to thesynthesis of cyclohexanone oxime in view of its usage as the precursor for the productionof ε-caprolactam and Nylon-6. The traditional production method for cyclohexanoneoxime is cyclohexanone–hydroxylamine or ammoximation of cyclohexanone which is lessdesirable owing to its low atom economy, complex technology, serious environmentalproblems, equipment corrosion and so on. To overcome the above-mentioneddisadvantages, there have been many attempts to find novel and environmentally friendlymethods for the production of cyclohexanone oxime. Nitrocyclohexane hydrogenation tocyclohexanone oxime arouses researchers a great deal of interest for the mild reactionconditions and the environmentally friendly technology. This paper focuses on thecatalytic activity of supported palladium catalysts and main effect factors on selectivityhydrogenation of nitrocyclohexane to cyclohexanone oxime by different preparationmethods and characterization analysis.In this study, the raw material nitrocyclohexane is extracted from the nitration ofcyclohexane, the purity keeps above93%. The products of selectivity hydrogenation ofnitrocyclohexane include cyclohexanone oxime, cyclohexylamine, cyclohexanone andN-cyclohexylhydroxylamine identified by GC-MS. In addition, the content of the productswere analysed d by gas chromatogram with a flame ionization detector (FID) usingdimethyl phthalate (DMP) as the internal standard.This paper focus on the nitrocyclohexane hydrogenation to cyclohexanone oximeover activated carbon and mesoporous carbon supported Pd catalyst. Mesoporous carbonmaterials (MC) were prepared by soft template (SMC), hard template (HMC),hydrothermal synthesis method (HTMC) and catalyst activation method (CMC). Andcarbon supported Palladium catalysts were obtained from incipient impregnation method.The prepared samples were characterized by nitrogen adsorption-desorption, X-raydiffraction, transmission electron microscopy and hydrogen chemisorption. Palladiumsupported on mesoporous carbon especially Pd/HMC-1shows better catalyticperformance than Palladium supported on activated carbon under the same mild reactionconditions，which gives78.8%selectivity to cyclohexanone oxime at the nitrocyclohexaneconversion of99.1%. And the reaction process condition of nitrocyclohexanehydrogenation to cyclohexanone oxime by5%Pd/HMC is discussed. The optimal reaction conditions are that reaction time is6h, reaction temperature is323K, hydrogen pressureis0.5MPa. It gives the82.2%selectivity to cyclohexanone oxime at the nitrocyclohexaneconversion of99.4%under the optimum conditions.Furthermore, the experiment of catalyst recycle is studied, it indicates that Pd/HMC-1can be recycled four times without an obvious activity decline. Finally we briefly discussthe process mechanism.