摘要
采用CO和H2脉冲吸附、程序升温还原、NH3程序升温脱附及X射线衍射等手段对各金属氧化物改性的Pt/Al2O3催化剂进行了表征,研究了助剂形态对Pt/Al2O3催化剂在非临氢条件下催化环己烷脱氢反应性能的影响.结果表明,催化剂稳定性从高到低依次为Zr-Pt/Al2O3>Ca-Pt/Al2O3>Ce-Pt/Al2O3>Zn-Pt/Al2O3>Ba-Pt/Al2O3.加入的助剂通过增加Pt分散度和促进氢溢流来增加催化剂的抗积炭性能,因此助剂需具有较高的热稳定性和化学稳定性,在催化剂的焙烧过程中以氧化物形态均匀分散在载体表面,不能过度聚集、或与载体反应生成铝酸盐、或与活性金属反应形成合金.Ca和La同时改性的催化剂性能不如单一助剂,因为助剂间相互作用导致催化剂酸中心增强,溢流氢能力减弱.
The effects of different promoters on coke deposition over Pt/Al2O3 catalyst for hydrogen-free cyclohexane dehydrogenation were investigated by catalytic tests and a series of analytical techniques such as X-ray diffraction,CO and H2 chemisorption,tempera-ture-programmed desorption of NH3,and temperature-programmed reduction.The stability of different promoters modified catalysts is in the order of Zr-Pt/Al2O3 Ca-Pt/Al2O3 Ce-Pt/Al2O3 Zn-Pt/Al2O3 Ba-Pt/Al2O3.The results clearly show that the addition of promoters to the Pt/Al2O3 catalyst could inhibit coke deposition by increasing Pt dispersion and promoting hydrogen spillover.That is attributed to the high thermodynamic and chemical stability of the metal oxide promoters.They must be highly dispersed and stable without reacting with Al2O3 in calcination or forming alloy with Pt in reduction.The catalytic property of CaLa-Pt/Al2O3 is worse than either Ca-Pt/Al2O3 or La-Pt/Al2O3 because the acidity of catalyst is enhanced and the spillover hydrogen is reduced due to Ca-La strong interaction.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2011年第8期1364-1369,共6页
基金
催化基础国家重点实验室自主研究课题(R201008)~~
关键词
金属氧化物
铂
氧化铝
环己烷脱氢
抗积炭
metal oxide
platinum
alumina
cyclohexane dehydrogenation
coke resistance
