Exclusive production of chloroaniline from chloronitrobenzene over Au/TiO2 and Au/Al2O3.

The gas-phase continuous hydrogenation of p-chloronitrobenzene (p-CNB) over 1 mol% Au/TiO2 and Au/Al2O3 was compared for the first time. Both catalysts exhibit 100% selectivity in terms of -NO2 group reduction, resulting in the sole formation of p-chloroaniline (p-CAN). Au/TiO2 exhibited a narrower particle size (1-10 nm) distribution than Au/Al2O3 (1-20 nm) and a smaller surface-area-weighted mean Au size (6 nm versus 9 nm). Au/TiO2 delivered a higher specific hydrogenation rate (by a factor of up to four), a response that is discussed in terms of Au particle size and a possible contribution of the support to p-CNB activation. A CNB isomer reactivity sequence was established, that is, o> p> m, which is attributed to resonance stabilisation effects. The results presented establish a basis for the development of a sustainable alternative route for the production of haloamines.