Catalytic HDC/HDN of 4-chloronitrobenzene in water under ambient-like conditions with Pd supported on pillared clay

• The Pd/pillared clay catalyst led to complete dechlorination of 4-chloronitrobenzene and 4-chloroaniline.
• The catalyst showed high activity in denitrogenation at ambient-like operating conditions.
• Acid pH is optimal for aniline denitrogenation and prevents catalyst poisoning from ammonia.
• The catalyst showed high stability in long-term experiments.

Hydrotreatment of 4-chloronitrobenzene in aqueous phase has been carried out under ambient-like operating conditions (25 °C and 1 atm) with H2 using an own-prepared catalyst based on Pd (1 wt%) supported on Al-pillared clay. Nitrobenzene, 4-chloroaniline, aniline and cyclohexanone were identified as reaction byproducts and trace amounts of different azobenzenes were also detected. Complete dechlorination was achieved in around 1.5 h reaction time. Experiments with the aforementioned nitrogenated byproducts were performed to elucidate the reaction pathway. Nitrobenzene was completely converted in short reaction time leading to aniline as main product. Disappearance of 4-chloroaniline was complete after 1 h giving rise to aniline as primary product. An unstable imine/enamine was obtained from aniline, yielding cyclohexanone upon reaction with water. Hydrodenitrogenation of aniline was favored at acidic pH, being released more than 85% N after 10 h. A kinetic analysis is included and values of activation energy are given.

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