Pb掺杂改性对Pt/HZSM-5催化剂结构及其催化合成对氨基苯酚反应性能的影响

针对硝基苯催化加氢合成对氨基苯酚(PAP)反应,以HZSM-5(n(SiO2)/n(Al2O3)=25)为载体,制备了不同Pt负载量的Pt/HZSM-5及Pb-Pt/HZSM-5双功能催化剂,采用透射电镜(TEM)、氢气程序升温脱附(H2-TPD)、CO吸附漫反射红外光谱(DRFTIR)和X射线光电子能谱(XPS)技术对催化剂结构和电子性能进行了表征,同时评价了催化剂催化合成PAP的活性。结果表明,Pb的掺杂改性能有效提高Pt在载体表面的分散度,改性后催化剂Pt的电子密度增大。Pb-Pt/HZSM-5催化剂催化合成PAP的选择性明显高于相同负载量下的Pt/HZSM-5催化剂。由于Pb、Pt之间相互作用导致的Pt活性位上电子密度的增大对苯基羟胺(PHA)连串加氢生成苯胺反应起到了明显的抑制作用。

Effect of Pb Doping on the Structure of Pt/HZSM-5 and Its Catalytic Performance in p-Aminophenol Synthesis

A series of HZSM-5-supported Pt or Pb-Pt catalysts of various Pt loading(Pt/HZSM-5, Pb-Pt/HZSM-5) were prepared for the hydrogenation of nitrobenzene (NB) to p-aminophenol (PAP).The structural modification and change in electronic properties of the catalysts were analyzed by using high-resolution transmission electron microscopy, temperature-programmed desorption of hydrogen, diffuse reflectance infrared Fourier transformation spectroscopy of the adsorbed carbon monoxide and X-ray photoelectron spectroscopy analysis. The catalytic performances of Pt/HZSM-5, Pb-Pt/HZSM-5 in PAP synthesis were evaluated. The Results revealed that Pb doping in the Pt/HZSM-5 catalysts improved the dispersion of Pt species and increased electron density of Pt. The PAP selectivity over Pb-Pt/HZSM-5 was obviously higher than that over Pt/HZSM-5 with the same Pt loading. The increased electron density of Pt caused by the interaction of Pb and Pt plaed a positive role to inhibit the subsequent hydrogenation of PHA to aniline.