Study on the Role of Thermal Cracking in FCC Cycle

Thermal cracking reaction is unavoidable in the FCC reactionsystem. The conversion rate during thermal cracking reac-tion will be enhanced with an increasing process severity,resulting in an increase in dry gas and coke yield in productslate and a reduction of yield and quality of liquidproducts[1]. However, during heavy oil FCC process largeroil and gas molecules can hardly enter the zeolite to com-mence catalytic cracking, and they can be broken down intodebris (or free radicals) prior t…

Study on the Role of Thermal Cracking in FCC Cycle

A bench-scale fixed fluidized bed reactor was used to study the distribution and quality of products derived from thermal cracking of VGO. Test results had shown that the space velocity has minor effect on thermal cracking reaction. The depth of thermal cracking reaction was mainly affected by the reaction temperature.At different reaction temperatures the form of free radicals thus initiated varied, resulting in different product distribution. At low temperature C10= and C11= olefins dominated in thermally cracked gasoline products,whereas at higher temperature C6=-C9= olefins dominated in thermally cracked gasoline products, among which C6 and C7 olefins were mainly composed of 2M 1 Cs= and 2E1C5=. Difference in olefin structure can lead to different reaction pathways of catalytic cycle.