Novelties of triphasic phase transfer catalysed Zinin reduction of nitrochlorobenzene by H2S-laden monoethanolamine

Abstract

The kinetics of Zinin reduction between m-chloronitrobenzene (m-CNB) and H₂S-laden monoethanolamine (MEA) in a liquid–liquid–solid (L–L–S) system catalysed by the anion exchange resin Amberlite IR-400 (chloride form) was investigated. The selectivity of the product m-chloroaniline (m-CA) was 100%. The reaction was found to be kinetically controlled with an apparent activation energy of 56.16 kJ mol⁻¹. Parametric studies were performed to find out the kinetics of the Zinin reduction and to optimize the influence of process parameters like stirring speed, concentration of m-CNB, concentration of aqueous sulphide, catalyst concentration etc. on the reaction rate and conversion of m-CNB. The reusability of the catalyst was investigated and the catalytic activity of the used catalyst was found to change little even after three recycle runs in comparison to the fresh catalyst. The kinetic model and mechanism of the complex L–L–S phase transfer catalytic process has been developed and the kinetic model has been validated against experimental data. The present reaction is an example of intensification of a multiphase reaction with 100% selectivity to the desired product and can replace the Claus Process of a petroleum refinery as a key process for utilizing hazardous H₂S gas. Waste minimization was therefore achieved by the use of a reusable catalyst which can also act as a green alternative.