The Preparation Of Doped Palladium Catalysts Supported On Active Carbon And Study Of Their Properties In Hydrogenation

DSD acid (4,4'-diaminostilbene-2,2'-disulfonic acid) is an important immediate, which is widely used in producing direct dyes, fluorescent brighteners and mothproof agents.It is prepared from DNS(4,4'-dianitrostilbene-2,2'-disulfonic acid), in the process of DNS hydrogenation, side reactions, i.e. saturation of-C=C-double bond to-C-C-and cleavage of-C=C-to-CHO groups, go easily with the main reaction for hydrogenation of-NO2 group to-NH2 group. There are several ways for DSD production. Traditional method to prepare DSD is Bechamp method using Fe powder, which is a well known and thoroughly studied process but results in high pollution of a large amount of ferron slurry. The catalytic hydrogenation process is a environmental friendly method for DSD preparation, this method has received enough attention from researchers.In this paper, different specific surface areas and pore structure of active carbons, soursing from industry petrol coke, were prepared through crushing, screening, baking, impregnation, activation, washing and drying process. The effects of the ratio of alkali to coke and temperature on the performance of carbon were investigated in the preparation process, and this work provided many carries for catalyst preparation.This article also prepared Pd/C catalysts with self-made and other industrial active carbon as the carrier, the hydrogenation of acrylic acid which was as the model system was provied to investigate the catalyst performance of-C=C-double bond to-C-C-. Forthemore, Pd-M/C (M=Fe,Co,Ni,Cu) catalysts were also prepared for the catalytic hydrogenation of DNS. In this research, the effects of modifiers (Fe, Co, Ni, Cu) on the selective hydrogenation of DNS were studied. The results showed that the modifiers could significantly improve the selectivity of DNS to DSD. When theλof M was 0.050, the selectivity of DSD reached 97.83%. Additionally, the reaction conditions such as reaction temperature, hydrogen pressure, agitation speed and other factors on DNS hydrogenation were optimized; the life of catalyst was studied in the optimum reaction conditions, the catalyst maintained a stable activity and selectivity.