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本文研究浸液pH值对铂催化剂性能的影响。用烷烃连续流动反应技术以及TPR、XPS、DRS和IR等手段表征催化剂表面性质因强酸处理产生的变化。结果表明:浸液pH值显著影响催化剂的反应性能。随浸液酸度增加,正己烷异构化和芳构化选择性呈线性增大,但却不影响铂的脱氢性能;并且酸度增加导致催化剂酸性(异丙苯裂解活性)下降和高温(>300℃)吸氢中心增加。测试数据也表明,酸处理导致载体表面性质发生了较大变化,氧化态铂物种与载体相互作用增强,部分铂变得较难还原。上述现象归因于在酸性条件下,酸解生成的Al~(3+)离子的再吸附,以及催化剂表面铂簇团短程有序结构的形成和非零价铂的存在。
In this paper, the effect of immersion pH on the performance of platinum catalyst was studied. Continuous flow reaction of alkane and TPR, XPS, DRS and IR were used to characterize the changes of catalyst surface properties caused by strong acid treatment. The results showed that the pH value of the immersion solution significantly affected the reactivity of the catalyst. With the increase of acidity, the selectivity of n-hexane to isomerization and aromatization increases linearly, but it does not affect the dehydrogenation performance of platinum. With the increase of acidity, the catalyst acidity (cumene cracking activity) 300 ℃) hydrogen absorption center increased. The test data also showed that the acid treatment led to a large change in the surface properties of the carrier, the oxidation state of platinum species and carrier interaction enhanced, part of the platinum becomes more difficult to restore. The above phenomenon is attributed to the reabsorption of Al ~ (3+) ions generated by acid hydrolysis under acidic conditions, the formation of short-range ordered structure of platinum clusters on the catalyst surface and the existence of non-zero-valent platinum.