FCC process for converting C3/C4 feeds to olefins and aromatics

A fluid catalytic cracking (FCC) process for converting a C3/C4-rich feed to olefins and aromatics, comprising:

• cracking a first hydrocarbon feed in a first riser under first-riser FCC conditions to form a first effluent enriched in cracked hydrocarbons, wherein the first hydrocarbon feed comprises heavy hydrocarbons having greater than 12 carbon atoms, and wherein the first-riser FCC conditions include a residence time from 0.1 to 10 seconds;
• cracking a second hydrocarbon feed comprising light hydrocarbons having 12 or less carbon atoms, in a second riser under second-riser FCC conditions to form a second effluent enriched in light olefins and aromatics, wherein the second-riser FCC conditions have a higher severity than the first-riser FCC conditions and include a residence time from 0.1 to 10 seconds and a temperature from 510° C. to 710° C. (950° F. to 1300° F.), wherein the first riser and the second riser contain gallium-promoted alumina catalyst;
• recovering the catalyst from the first riser and the second riser;
• separating hydrocarbons from the first and second FCC effluents to provide:
• a light stream comprising ethane, propane, or a combination thereof;
• an intermediate stream comprising one or more olefins selected from C4 to C6 olefins and mixtures thereof;
• and a heavy stream comprising C6 and higher hydrocarbons;
• regenerating the recovered catalyst by combustion of coke in a common regenerator to obtain hot, regenerated catalyst;
• recirculating the hot regenerated catalyst to the first and second risers;
• and
• recycling the light stream, intermediate stream, and heavy stream to the second riser.

A fluid catalytic cracking (FCC) process for converting a C3/C4-rich feed to olefins and aromatics, comprising:

• cracking a first hydrocarbon feed comprising a heavy hydrocarbon having greater than 12 carbon atoms in a first riser under first-riser FCC conditions to form a first effluent enriched in cracked hydrocarbons, wherein the first-riser FCC conditions include a residence time from 0.1 to 10 seconds;
• cracking a second hydrocarbon feed having 12 or less carbon atoms in a second riser under second-riser FCC conditions to form a second effluent enriched in light olefins and aromatics, wherein the second-riser FCC conditions have a higher severity than the first-riser FCC conditions and include a residence time from 0.1 to 10 seconds and a temperature from 510° C. to 710° C. (950° F. to 1300° F.), wherein the first riser and the second riser contain gallium-promoted alumina catalyst;
• recovering the catalyst from the first and second risers;
• separating hydrocarbons from the first and second FCC effluents to provide:
• a light stream comprising ethane, propane, or a combination thereof;
• an intermediate stream comprising one or more olefins selected from C4 to C6 olefins and mixtures thereof;
• and a heavy stream comprising C6 and higher hydrocarbons;
• regenerating the recovered catalyst by combustion of coke in a common regenerator to obtain hot, regenerated catalyst;
• spraying a solution of gallium onto the hot regenerated catalyst;
• recirculating the hot regenerated catalyst to the first and second risers;
• and
• recycling the light stream, the intermediate stream, and the heavy stream to the second riser.