摘要
以CO吸附红外光谱结合CO化学吸附、透射电镜和能量散射谱等手段,研究了Pt/Al2O3制备过程中还原方法对最终Pt粒子表面活性位分布、粒径大小和表面残余氯等表面性质的影响,重点考察了普通的气相氢气还原和甲酸钠水溶液还原两种方法的对比。结果表明,采用氢气气相还原时,Pt/Al2O3上Pt粒子表面台阶位和平台位比例基本不随焙烧温度而变;而采用甲酸钠水溶液还原时,Pt粒子表面台阶位所占比例随焙烧温度升高而提高。水的存在和还原条件剧烈这两个因素使得水相甲酸钠还原不利于Pt的分散,所得Pt/Al2O3上Pt的分散度比氢气气相还原所得要小。无论何种还原条件,水的存在都有利于Pt前躯体中的氯从Pt/Al2O3表面去除;而氢气气相还原所得催化剂表面则有大量残余氯存在。
Pt/Al2O3 with Pt loading of 5% was prepared and characterized by infrared spectroscopy （IR） combined with CO chemisorption, energy dispersive spectrometry （EDS）, and transmission electron microscopy （TEM）. The effects of reduction methods including commonly used dry reduction by gaseous H2 and wet reduction by sodium formate （HCOONa） aqueous solution on the surface states of Pt/Al2O3 were investigated. The results show that both the calcination and reduction can affect the particle sizes and surface sites of Pt. For the catalyst Pt/Al2O3 reduced by HCOONa solution, the ratio of terrace to step sites on the surface of Pt increases along with the calcination temperature. Subsequent to the identical calcination procedures, the wet reduction by HCOONa solution results in less residual chlorine and lower Pt dispersion than the dry reduction by gaseous H2. The violent reduction condition of HCOONa solution and the presence of water are both responsible for the agglomeration of Pt particles. The presence of water can facilitate the dissolution and removal of chlorine from the catalysts when reduced in an aqueous solution.
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2009年第2期205-211,共7页
Journal of Fuel Chemistry and Technology
基金
国家自然科学基金(20321303,20590363)
