载Ni沸石上Ni(Ⅱ)的还原作用——Ⅹ.载Ni丝光沸石的XPS、FABMS研究

REDUCTION OF Ni(Ⅱ)IONS ON Ni-CONTAINING ZEOLITES X.STUDY OF Ni-CONTAINING MORDENITE(NiM) BY XPS AND FABMS

本文采用光电子能谱(XPS)、快原子轰击质谱(FABMS)技术研究了载Ni丝光沸石的表面化学组成.结果表明,试样还原前、后表面(Si/Al)_s值与本体(Si/Al)_b值之比小于1,(Si/Al)值随溅蚀时间的增加而增加,表面呈Al富集;表面(Ni/Si)_s值增加,(Al)_s富集程度增加,表面(Ni^(2+))_s(Ni^(2+)或NiO…)被还原,(Si/Al)_s增加,(Al)_s含量降低,Ni^(2+)与沸石间存在较强的相互作用;载Ni试样在氧化-还原循环中,Ni由本体向表面迁移,还是由表面向本体扩散,这与氧化-还原循环中各个阶段有关.

The reduction of Ni (Ⅱ) ions at different reduction temperature and the dispersion of metallic Ni have been studied with a series of nickel zeolites of type Y, M, and ZSM-5. The results indicate that the degree of reduction of Ni (Ⅱ) ions increases with the increase of reduction temperature. On Y or mordenite zeolites, the rate is determined by different steps over the range of the temperature studied and the reduction of Ni (Ⅱ) ions depends on the locations of these cations. On ZSM-5 zeolites,there is only one rate-determining step. The reduction of Ni_((1))^(2+) and Ni_((2))^(2+) ions occurs simultaneously. The dispersion of metallic Ni decreases with the increase of reduction temperature. But no regularity of change in the dispersion of Ni^0 was observed with respect to the change of pretreatment temperature, protonic acidity, or nickel content of zeolites.