摘要
研究了Pt(NH_3)_4NaY,Pd(NH_3)_4NaY及Co(NH_3)_6NaY沸石在不同热处理条件下红外谱图变化的规律。发现该沸石晶穴中这些络离子在250℃下抽空1小时,其结构均破坏;若再在400～500℃区间加热1小时,其表面均有Si—H键生成,并讨论了Si—H键生成的机理。用D_2交换法证明了这些络离子破坏后,在PtNaY,PdNaY及CoNaY沸石表面分别有Pt-H,Pd—H及Co—H键存在,它们是由于NH_3在这些沸石表面高温分解所放出的H吸附在这些金属离子上的结果。由IR与ESR法证明室温下于NaY沸石晶穴中可合成出[Co(NH_3)_5O_2]^(2+)与[Co(NH_2CH_2CH_2NH_2)_2O_2]^(2+)离子;在适当的条件下,于Y型沸石表面可合成出一种特殊的Co络合物载氧体,ESR证明它易将2,6-二特丁基对甲酚氧化成自由基。
The behaviour of Pt(NH3)4NaY, Pd(NH3)4NaY and Co(NH8)6NaY zeolite catalysts treated at elevated temperature was studied by IR spectroscopy. The results showed that the intrazeolite amine complexes decomposed when they were treated under vacuo at 250℃ for 1 h.A surface Si-H bond was observed on further treating the samples at 400-500℃, and the mechanism of Si-H bond formation was discussed. The formation of Pt-H, Pd-H, and Co-H was also observed as their corresponding amine complexes decomposed,and was further confirmed by D-H exchange with D2. These Metal-Hydrogen bonds were formed as a result of the chemical adsorption of hydrogen, which was produced from the decomposition of NH3 on metal ions. It was also evidenced by IR and ESR that [Co(NH5)5O2)2+ and [Co(NH2CH2CH2NH2)2O2]2+ could be synthesized at room temperature in NaY zeolite. Besides, a special oxygen carrying Co-complex, which oxidized easily 2,6-di-tert-butyl-4-methylphenol to radical species, was formed under certain appropriate conditions.
