Supercritical Catalytic Cracking Of N-dodecane On Hzsm-5 And Y Zeolites

The cooling technology using the physical and chemical heat sink of hydrocarbon fuel provides the best means for the thermal management of engine system and the body of advanced aircraft. As can offer sufficient cooling capacity and facility in storage, the endothermic hydrocarbon fuels have been widely studied.The endothermic reactions of endothermic hydrocarbon fuels include thermal cracking, catalytic dehydrogenation and catalytic cracking, during which the catalytic cracking is the most potential process. This paper focused on the catalytic cracking of dodecane on HZSM-5 and Y zeolite under supercritical conditions.As reaction temperature increases, catalytic activity, deactivation rate and coke deposition rate increase. Small molecule products, olefins and aromatics also increase with the increase of reaction temperature. With reaction time increases, catalyst activity decreases, coke deposition increases, but the rate of deactivation and coking decrease gradually and eventually become stable. It illustrates that supercritical fluid has some effect of extraction of the coke.For the HZSM-5, the greater the Si/Al ratio, the lower the initial reaction activity, but the reaction activity decline more slowly, and the final stable reaction activity increases with the increase of Si/Al ratio; the coke increases with the Si/Al ratio reduce. And as the Si/Al ratio increases, the olefin products in gas and the small molecular products in liquid increase, but the yield of aromatics decrease significantly. For different types of Y zeolites, little changes were found among their reaction activity, deactivation characteristics and products distribution.It was found that: the catalytic activity and anti-deactivation capabilities of Y zoelite are far less than HZSM-5, the coke is also much higher than that on HZSM-5; the long-chain alkanes species increase significantly, and the number of branched chain also increases, the aromatic and olefin species are much fewer than that on HZSM-5.The simulation of reaction data demonstrate that: for the same reaction temperature (e.g., 400℃), the deactivation rate of 140H is about 58% that of 25H, the carbon deposition rate of 140H is about 38% that of 25H. For the same catalyst sample (e.g., 140H), the deactivation rate at 400℃is about 66% that at 450℃.