Platinum supported on activated carbon cloths as catalyst for nitrobenzene hydrogenation

Abstract

The use of activated carbon cloth (ACC) as platinum catalyst support has been investigated using four commercial ACC samples. These ACCs have large apparent surface areas and they are essentially microporous. Platinum catalysts, prepared by impregnation, have been characterized by hydrogen chemisorption. Three different reduction treatments have been conducted, the effect of temperature and time of reduction have been analyzed. The results show good dispersion values and present two singular advantages over published data on granular activated carbon supports: (i) they have a remarkable ease of reduction; the reduction of Pt is almost complete at 393 K and (ii) they have proved to be stable at temperatures as high as 623 K and after long reduction time (12 h). Therefore, the great advantage of these catalysts, in addition to the particular shape of the cloth support, is the possibility of being used in a wide range of process temperatures. The behaviour of these Pt ACC catalysts in a low temperature hydrogenation reaction has been tested studying their catalytic activity for nitrobenzene hydrogenation. The catalysts have been reduced, prior to the hydrogenation of nitrobenzene, at a quite low temperature (323 K) and their Pt dispersion has also been measured. Most of Pt ACC catalysts show noticeable catalytic activity for nitrobenzene hydrogenation, carried out at 273 K. The surface area of the ACC supports controls the Pt dispersion, which in turn is responsible for the catalytic activity. A good linear relationship between activity and Pt dispersion (determined at the reduction temperature used during the hydrogenation reaction) has been found. Under the experimental conditions used the hydrogenation of nitrobenzene seems to be a structure insensitive reaction.