前驱体结构对多环芳烃选择性开环Pt/Beta催化剂的影响

以海绵铂为原料合成出［Pt（NH₃）₆］Cl₄络合物，采用热重分析（TG）、扫描电镜-能谱（SEM-EDS）、紫外-可见分光光度计（UV-Vis）、质谱（MS）、X射线光电子能谱（XPS）等手段确定了［Pt（NH₃）₆］Cl₄的结构组成；以H₂PtCl₆、Pt（NH₃）₄Cl₂和［Pt（NH₃）₆］Cl₄为前驱体，采用等体积浸渍法制得Pt/Beta催化剂，采用X射线衍射（XRD）、X射线荧光光谱（XRF）、氨程序升温脱附（NH₃-TPD）、氢氧滴定（H₂-O₂）、透射电镜（TEM）、氢气程序升温脱附（H₂-TPD）等表征了Pt/Beta催化剂的物化性质，并考察了Pt/Beta催化剂的多环芳烃选择性开环性能。结果表明，［Pt（NH₃）₆］Cl₄络合物具有更高的“抗自还原”能力，可从前驱体结构上降低铂氨前驱体受热分解时的自还原现象。前驱体结构对铂纳米颗粒的几何尺寸及分布有较大影响，一方面络合物的价态显著影响前驱体与分子筛间的静电作用，进而影响铂纳米颗粒的落位与尺寸；另一方面络合物的空间结构影响前驱体在分子筛微孔中的分布，影响铂纳米颗粒的Ostwald熟化速率。前驱体结构可调变Pt/Beta催化剂的双功能匹配关系，显著影响Pt/Beta催化剂转化甲基萘的活性、稳定性，采用［Pt（NH₃）₆］Cl₄前驱体制备的Pt/Beta催化剂具有更优的活性及长周期稳定性。

Effect of precursor structure on selective ring opening Pt/beta catalyst for polycyclic aromatic hydrocarbons

The hexaammineplatinum chloride（［Pt（NH₃）₆］Cl₄） was synthesized from sponge platinum，and the geometrical structure of ［Pt（NH₃）₆］Cl₄ was determined by thermogravimetric analysis（TG），scanning electron microscopy energy spectrum（SEM-EDS），ultraviolet visible spectrophotometer（UV Vis），mass spectrometry（MS），X-ray photoelectron spectroscopy（XPS），etc.Pt/Beta catalysts were prepared by impregnation method using H₂PtCl₆，Pt（NH₃）₄Cl₂ and ［Pt（NH₃）₆］Cl₄ as precursors.The physicochemical properties of these catalysts were characterized by X-ray diffraction（XRD），X-ray fluorescence spectrum（XRF），ammonia temperature programmed desorption（NH₃-TPD），hydrogen oxygen titration（H₂-O₂），transmission electron microscope（TEM），hydrogen temperature programmed desorption（H₂-TPD），and their performance on selective ring opening of polycyclic aromatics was investigated.The results showed that ［Pt（NH₃）₆］Cl₄ had higher“anti self reduction”ability，which could reduce the self reduction phenomenon of platinum ammonia precursor during thermal decomposition.The precursor structure had great influence on the geometric size and distribution of Pt nanoparticles.On the one hand，the valence state of the complex significantly affected the electrostatic interaction between the precursor and the molecular sieve，and then affected the location and size of Pt nanoparticles.On the other hand，the spatial structure of the complex affected the distribution of precursors in the micropores of molecular sieve and the Ostwald ripening rate of Pt nanoparticles.The structure of precursor could adjust the bifunctional matching relationship of Pt/Beta catalyst，which significantly affected the activity and stability of Pt/Beta catalyst for the conversion of methylnaphthalene.The Pt/Beta catalyst prepared by ［Pt（NH₃）₆］Cl₄ precursor had better activity and long?term stability.