Catalytic Upgrading of Vacuum Residue-Derived Cracking Gas-Oil for Maximum Light Olefin Production in a Combination of a Fluidized Bed and Fixed Bed Reactor

Abstract

The article was devoted to investigate some fundamentals about the vacuum residue (VR) hierarchical gas-phase catalytic cracking process which contained the cracking of VR and shape-selective catalytic cracking of cracking gas-oil. First, three heat carriers were tested in the fluidized bed reactor, finding that cracking VR on the calcium aluminate catalyst obtained higher liquid yield and lower coke yield than that on the FCC catalyst and silica sand. Furthermore, gas chromatography/mass spectrometry analysis of three types of cracking oils (F-oil, S-oil, and C-oil) showed that compared with F-oil and S-oil, the C-oil contained more alkenes and alkanes but had less content of aromatics. Then, the major parametric influences (reaction temperature and catalyst filling amount) on the light olefin distribution were studied in the fixed bed reactor. The yield and selectivity of light olefins were 30.95 wt % and 77.05%, respectively, under the optimized operating conditions.