Pd0.01Ru0.01Ce0.98O2-delta: A highly active and selective catalyst for the liquid phase hydrogenation of p-chloronitrobenzene under ambient conditions

Abstract

Nanostructured bimetal ion substituted ceria, Pd0.01Ru0.01Ce0.98O2−ı (PdRuC2), prepared for the first time by a novel solution combustion synthesis and characterized employing XRD, BET, HRTEM and XPS has been shown to be very active and selective than the monometal ion substituted analogue Pd0.02Ce0.98O2−ı (PdC2), whereas Ru0.02Ce0.98O2−ı (RuC2) is inactive towards liquid phase hydrogenation of p-chloronitrobenzene to p-chloroaniline under ambient conditions. Structural studies show metal ion substituted ceria as the predominant phase. The hydrogenation over PdRuC2 is completed beyond 75 min with 100% selectivity. Conversely, PdC2 hydrogenates ∼40% of p-chloronitrobenzene with 82% selectivity. Increase of temperature from 35 ◦C to 80 ◦C showed a little higher activity of PdRuC2 but with a lower selectivity. The as-prepared and aged forms of PdRuC2 showed similar activity, whereas PdRuC2 heat-treated at 500 ◦C increased the conversion and the 800 ◦C heated catalyst reduced it (both ∼2%) indicating high thermal stability. Maximum hydrogenation activity has been observed in ethanol as compared to methanol and butanol. The PdRuC2 catalyst also shows excellent hydrogenation activity towards o-, m-chloronitrobenzene and nitrobenzene. The enhancement of activity and selectivity of Pd in presence of Ru in the PdRu bimetal ionic catalyst for the hydrogenation reaction has been attributed to involvement of remarkable Ru4+-promotion in Pd0.01Ru0.01Ce0.98O2−ı.