Studies on the Catalytic Cracking Performance of Coker Gas Oil

摘要

Catalytic cracking experiments in which various blend levels of coker gas oil (CGO) in fluidized catalytic cracking (FCC) feedstock were reacted over two kinds of commercial equilibrium catalysts (RGD-1 and LBO-16) demonstrate that the blending ratio affects the potential ability of a FCC unit treating CGO obviously. The limits of the blending ratio for Daqing CGO and Dagang CGO are 30 and 20 wt %, respectively, to obtain a desirable product distribution at a relatively high feed conversion. The operating condition of a high catalyst/ oil ratio in combination with a short residence time (or high weight hourly space velocity) and moderate reaction temperature is the optimal operating condition for catalytic cracking of CGO and its mixture. A FCC catalyst, such as RGD-1, which has proper acidities and high accessibility, is suitable for dealing with CGO effectively, which leads to an obvious improvement over conversion and product distribution. The analysis and contrast catalytic cracking experiments of narrow cuts of Daqing CGO show that the fraction of Daqing CGO is accumulated largely in the range of 300-450℃ and there exists high content of basic nitrogen and polycyclic aromatics. The lowest crackability of the cut from 400 to 450℃ constrains total CGO cracking performance, which is caused by a preferential chemisorption of the polycyclic aromatic molecules, and basic nitrogen compounds take place prior to the desirable adsorption of the other hydrocarbons, which is necessary for the cracking reaction to occur.