催化裂化汽油改质过程中积炭历程及其对烯烃转化的影响

COKE FORMATION AND ITS INFLUENCE ON OLEFIN CONVERSION IN FCC NAPHTHA UPGRADING

利用微反-色谱联合实验装置和固定流化床实验装置,考察了FCC汽油改质过程中,催化剂活性、FCC汽油窄馏分、反应温度和质量空速对催化剂积炭和烯烃转化的影响。利用连续式小型提升管催化裂化实验装置,考察了原料预热温度和催化剂温度等油剂混合区的工艺条件对FCC汽油的生焦过程和改质的影响,并进行了动力学分析。结果表明,大部分焦炭的沉积发生在很短的时间内,并随着催化剂活性、反应物活性和反应温度增加而增加。催化剂温度的降低和原料预热温度的增加,实际上是降低了最初始反应瞬间的反应温度,从而减少了初始热裂化,减弱了最初始阶段的裂化反应的强度,同时也减少了初始焦炭的沉积。在后续的反应中,催化剂活性相对增强,裂化反应的程度加强,从而保持了气相进料改质后汽油的烯烃含量不变,但烯烃的碳数分布发生了变化。

Factors affecting the coke formation and olefins conversion during the upgrading of FCC naphtha, such as catalyst microactivity（MA）, various narrow fractions of FCC naphtha, reaction temperature and MHSV, were studied by using a MAT-GC on-stream analysis system and a fixed fluidized bed device. Influences of feedstock preheated temperature and catalyst temperature on coke formation and olefins conversion in a continuous pilot riser-type FCC unit were also investigated and analyzed by kinetic method. The results showed that the initial coke formation was extremely fast, and the amount of coke increased with the catalyst microactivity（MA）, reactant＇s activity and reaction temperature. The initial thermal cracking and the catalytic cracking reactions could be suppressed by the decrease of catalyst temperature and the increase of feedstock temperature. At the same time, the initial coke formation was reduced, and the catalyst activity was maintained in reaction process. As a result, the olefin content in the upgraded naphtha kept constant, despite of the change in carbon number distribution of olefins.