Pd supported on boron-doped mesoporous carbon as highly active catalyst for liquid phase catalytic hydrodechlorination of 2,4-dichlorophenol

Abstract

Palladium catalysts supported on both ordered mesoporous carbon (CMK-3) and boron-doped mesoporous carbon (B-CMK-3) were synthesized via the complexing–reduction method. These catalysts were characterized using X-ray diffraction, N2 adsorption–desorption, transmission electron microscopy, and X-ray photoelectron spectroscopy, and their catalytic performance was examined for the liquid phase catalytic hydrodechlorination (HDC) of 2,4-dichlorophenol. Characterization results showed that for B-CMK-3 boron was introduced into the framework of the mesoporous carbon. Pd supported on B-CMK-3 had a smaller average Pd particle size and higher Pd2+/Pd0 ratio than that on CMK-3, although B-CMK-3 had slightly lower surface area and pore volume than CMK-3. For Pd/B-CMK-3, increasing Pd loading led to an increase in Pd particle size and a decrease in Pd2+/Pd0 ratio. The liquid phase catalytic HDC of 2,4-dichlorophenol over Pd/B-CMK-3 followed the Langmuir–Hinshelwood model, and the catalytic reaction proceeded in both stepwise and concerted pathways. The initial reaction rates of Pd(2.7)/B-CMK-3 and Pd(2.6)/CMK-3 were 0.608 and 0.207MgCat−1h−1, respectively, reflecting a much higher catalytic activity of Pd/B-CMK-3 than that of Pd/CMK-3. For Pd/B-CMK-3, increasing Pd loading from 1.6 to 2.7wt.% led to an increase in the initial rate from 0.260 to 0.608MgCat−1h−1, but further increase of the loading to 3.9wt.% resulted in a slight decrease in the catalytic activity.