无粘结剂5A分子筛吸附分离正构烃的结焦失活研究

对比了1-己烯、正己烷和环己烯在无粘结剂5A分子筛上的结焦情况。探讨了吸附温度、吸附质分压及粘结剂对结焦性能的影响。对5A分子筛的结焦机理进行了分析。并对1-己烯在无粘结剂分子筛上的结焦动力学进行了研究。结果表明，1-己烯更易引起分子筛的结焦失活。分子筛的结焦量和失活度随温度和吸附质分压的增加而增加。有粘结剂分子筛的结焦量和失活度大于无粘结剂分子筛。温度623 K、时间30 min、吸附质分压40 KPa时，1-己烯在无粘结剂和有粘结剂分子筛上的结焦量分别为0.019 g/g和0.026 g/g，相应失活度分别为16.4%和28.2%。烯烃分子通过氢转移、环化和聚合等反应生成焦炭。结焦过程遵循连串反应机理。温度在623 K时，1-己烯在无粘结剂5A分子筛上的结焦反应速率可表示为：C = 1.37×10-3(1-DD/100)pHt。

STUDY ON COKING DEACTIVATION OF BINDERLESS 5A MOLECULAR SIEVES USED IN ADSORPTION FOR NORMAL HYDROCARBON

The coking properties of 1-hexene, n-hexane and cyclohexene on binderless 5A molecular sieves were compared. The influences of temperature, adsorbate pressure, and binder on coke content and deactivation degree were investigated and discussed. Also the coke formation mechanism was analyzed. Furthermore, the coking kinetics from 1-hexene on binderless 5A molecular sieves was studied. The results indicated that 1-hexene had more obvious coking trend compared to n-hexane and cyclohexene. The coke content and deactivation degree increased with temperature or adsorbate pressure. The coke content and activation degree on 5A molecular sieves with binder were higher than these on binderless samples, respectively. Under adsorption temperature of 623 K, adsorption time of 30 min and 1-hexene pressure of 40 KPa, the coke contents on binderless molecular sieves and the samples with binder were 0.019 g/g and 0.026 g/g, respectively, and the corresponding deactivation degrees were 16.4% and 28.2%. Coke were formed through hydrogen transfer, cyclization and polymerization of olefin molecules. Coke formation processes can be explained using consecutive reaction mechanism. In the temperature of 623K, the rate equation of coke formation from 1-hexene on binderless 5A molecular sieves can be expressed as C = 1.37×10-3(1-DD/100)pHt.