Patent ID: 7029571
Filing Date: 2006-04-18
Classification: C10G

Abstract:
1. A multi stage selective catalytic cracking process, for producing high yield of middle distillate products having carbon atoms in the range of about C 8 to C 24 from heavy hydrocarbon feed stocks in the absence of added hydrogen, said process comprising the steps of: i) contacting preheated feed stock with a mixed catalyst in a first riser reactor under catalytic cracking conditions including catalyst to oil ratio of about 2 to 8, WHSV of about 150–350 hr ii) separating the first cracked hydrocarbon products from the first riser reactor into a first fraction comprising hydrocarbons with boiling points less than or equal to about 370° C. and a second fraction comprising hydrocarbons with boiling points greater than or equal to about 370° C., comprising unconverted hydrocarbons; iii) cracking the second fraction from the first riser reactor comprising hydrocarbons having boiling points greater than or equal to about 370° C., in the presence of regenerated catalyst, in a second riser reactor operating under catalytic cracking conditions including WHSV of about 75–275 hr iv) separating the catalytically cracked products from the second riser reactor along with the cracked products comprising hydrocarbons having boiling points less than or equal to about 370° C., from the first riser reactor to yield cracked products comprising dry gas, LPG, gasoline, middle distillates, heavy cycle oil and slurry oil; and v) recycling substantially the entire heavy cycle oil comprising hydrocarbons having boiling points in the range of about 370° C. to 450° C. and at least part of the slurry oil having boiling points greater than or equal to 450° C., into the second riser reactor at a vertically displaced position lower than the position of introduction of the main feed, comprising bottom unconverted hydrocarbon fraction having boiling points greater than or equal to about 370° C., from the first riser reactor to obtain middle distillate products comprising hydrocarbons having carbon atoms in the range of C