Palygorskite Supported Platinum Catalysts with High Activity and Selectivity for the Liquid-Phase Hydrogenation of para-Chloronitrobenzene

The palygorskite supported platinum catalysts, Pt/PAL(I), Pt/PAL(II), and Pt/PAL(III) were prepared by different reduction methods (ethanol-isopropanol, H-2, and NaBH4), and exhibited different catalytic properties for the hydrogenation of para-chloronitrobenzene (p-CNB). Over the Pt/PAL(II) catalyst the selectivity of para-chloroaniline (p-CAN) reached 100% and the hydrodechlorination reaction was fully suppressed during the complete conversion of p-CNTB. Superior selectivities of 99.7% and 99.9% for p-CAN were also obtained over Pt/PAL(I) and Pt/PAL(III) catalysts, respectively, although the dehalogenation reaction was not completely avoided. Pt/PAL(I) was the most active catalyst with a turnover frequency (TOF) of up to 27010 h(-1). Pt/PAL(II) and Pt/PAL(III) catalysts showed slightly lower activity with a TOF of 1.7193 and 24871 h(-1), respectively. These excellent catalytic properties are attributed to the effects of Pt particle size and the palygorskite support, which was confirmed by transmission electron microscopy (TEM) images and X-ray diffraction (XRD) patterns of the catalysts as well as Fourier transform infrared (FTIR) spectra of the palygorskite.