低碳烃芳构化催化剂结炭规律的研究

Investigation on the Deposition of Coke and Deactivation on Lower-Paraffine Aromatization Catalyst

测定了低碳烃芳构化过程中Ga-ZSM-5的活性、结炭量、结炭C/H比、酸密度等,考察了结炭量与它们间的关系,提出了Ga-ZSM-5的多层多中心结炭失活模型:(1)结炭先发生在沸石晶体外表面(结炭2％前);然后主要在孔道交叉点结炭(2—8％间);结炭8％后,一些小分子烃被阻封在孔内,构成孔内积炭。(2)对Ga-ZSM-5,酸中心先结炭,只酸中心中毒。引起的失活效应小;当它与Ga中心同时结炭时,产生协同失活效应,引起的失活较显著。

The activity, amount and C/H ratio of coke, and the acidity of the Ga-ZSM-5 catalyst for lower-paraffine aromatization were determined under different reaction conditions, and the relationship between the amount of coke and the rest was further investigated. A 'multilayer-multicenter coking and deactivation model' for Ga-ZSM-5 was postulated. (1) coke deposits initially on the external surface of Ga-ZSM-5 at a lower coke amount of<2%; then it deposits mainly in the channel intersection at a coke content of 2% to 8%. Some small molecular hydrocarbons will be trapped inside the channel when the coke content become>8%, forming 'intrapore coke'. (2) For Ga-ZSM-5, coke is formed first over the acidic sites, causing a relatively low deactivation. Coke deposited on both the acidic sites and the gallium sites creates a co-deactivating effect leading to a pronounced deactivation.