Pd particles size-control of Pd/C and its effect on catalytic reduction of polychloronitrobenzene

To control the excessive dechlorination of polychloronitrobenzene hydrogenation to produce polychloroaniline, the effects of nitric acid concentration, catalyst reduction temperature and time in the preparation of Pd/C catalyst on the Pd particle size and catalytic hydrogenation activity and selectivity are investigated. The results indicate that the Pd/C catalytic activity decreases as the Pd particle sizes increase, and the catalyst selectivity goes up; the dispersion and particle sizes of Pd go up first and then down with the increase of nitric acid concentration; the elevated reduction temperature and time yields larger Pd particles; the optimal Pd catalyst with the particle sizes from 16 to 20 nm can be prepared on 15% nitric acid by reduction under hydrogen atmosphere at 200~250°C for 4~5 h; the catalyst shows relatively high hydrogenation activity and selectivity in the hydrogenation reduction of polychloronitrobenzene; the yield can reach more than 99% and the selectivity for pentachloroaniline can reach above 96%.