Abstract: A series of Pd/C catalysts for hydropurification of crude terephthalic acid (CTA) were prepared by impregnating with solutions having various pH values, and the prepared catalysts were characterized by XRD and TEM techniques. Effects of impregnation pH values on the performance of catalyst during removing p-carboxy benzaldehyde (4-CBA), the main impurity in CTA, were investigated. Results showed that catalyst prepared with an impregnation solution pH value of 3.0 exhibited the best catalytic activity, under a reaction temperature of 280 ℃, H2 partial pressure of 0.6 MPa and a reaction time of 1.0 h, the conversion of 4-CBA over said Pd/C catalyst was almost 100%. In this catalyst the palladium particles were highly dispersed on the surface of active carbon and presented as microcrystalline structure. A comparison study was carried out between said Pd/C catalyst (prepared at pH value of 3.0) and an import catalyst. Under severe testing conditions and after repeating testing, the deactivation tendency and palladium sintering behavior of these two catalysts were similar, which indicated that the hydropurification performance of these two catalysts was in the same level.

Key words: pH value, terephthalic acid, p-carboxy benzaldehyde, hydropurification, Pd/C catalyst