Using a fixed-bed aging device,the compounded propylene additives for increasing propylene production in cata-lytic cracking were subjected to 0,4,8,12 h and 24 h of hydrothermal aging under atmospheric pressure at a hydrothermal aging temperature of 800℃and 100% water vapor,respectively,and the aging additives were evaluated for their ACE re-sponses using X-ray diffractometry,N2 adsorption-desorption and pyridine adsorption infrared spectroscopies for the char-acterization of the aging additives.The results showed that as the aging time increased from 0 h to 24 h,the increase in pro-pylene production of the propylene additives was decreased from 7.15% for the fresh additives to 4.02% for the aged 24 h additives,the relative crystallinity was decreased from 20% to 15%,the microporous surface area was decreased from 57 m2/g to 32 m2/g,and the ratio of strong L-acid/total L-acid was decreased from 0.33 to 0.16.The study showed that with the exten-sion of aging time,the relative crystallinity of additive ZSM-5 was decreased,the microporous specific surface area was de-creased,and the ratio of strong L-acid/total L-acid was decreased rapidly,all of which indicated that the decrease in the propylene production enhancement performance of the propylene additives was mainly due to the structural damage of the active component,ZSM-5 molecular sieve,under the condition of high temperature and hydrothermal heat.
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