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用程序升温脱附(TPD)和红外光谱(IR)表征了经高温水蒸汽处理的HZSM-5沸石催化剂的酸性,并且考察了用于正己烷等烃类裂化反应的活性和选择性。实验结果表明,高温水蒸汽处理对催化剂的活性是不利的,如用700℃水蒸汽处理后,转化率降至10%左右。随着处理温度的升高酸性下降,处理温度在500—600℃、处理时间4—6h 时对程脱量和吸附氨中心数影响较为明显,而且对强酸部位的影响比弱酸部位更显著。文中讨论了发生裂化反应的可能的表面酸性部位。
The acidity of high temperature steam-treated HZSM-5 zeolite was characterized by temperature programmed desorption (TPD) and infrared spectroscopy (IR). The activity and selectivity of the catalyst for the cracking of n-hexane and other hydrocarbons were also investigated. The experimental results show that the high temperature steam treatment is unfavorable for the activity of the catalyst. For example, after the steam treatment at 700 ° C, the conversion rate is reduced to about 10%. With the increase of the treatment temperature, the acidity decreased, the treatment temperature was 500-600 ℃, the treatment time 4-6h, the amount of desorption and adsorption of ammonia center number is more obvious, and the impact of strong acid sites more pronounced than the weak acid sites. The paper discusses the possible surface acid sites where a cracking reaction takes place.