Process for the production of xylenes and light olefins
In a hydrocarbon upgrading process, a hydrocarbon feed is treated in at least one of a steam cracker, catalytic cracker, coker, hydrocracker, and reformer under suitable conditions to produce a first stream comprising olefinic and aromatic hydrocarbons. A second stream composed mainly of C 4 to C 12 + olefinic and aromatic hydrocarbons is recovered from the first stream and blended said second stream with a residual fraction from a steam cracker or an atmospheric or vacuum distillation unit to produce a third stream. The third stream is then catalytically pyrolyzed in a reactor under conditions effective to produce a fourth stream having an increased benzene and/or toluene content compared with said second stream and a C 3 -olefin by-product. The C 3 -olefin by-product is recovered and benzene and/or toluene are recovered from the fourth stream.
1. A hydrocarbon upgrading process comprising:
(a) treating a hydrocarbon feed in at least one of a steam cracker, catalytic cracker, coker, hydrocracker, and reformer under suitable conditions to produce a first stream comprising olefinic and aromatic hydrocarbons;
(b) recovering from said first stream a second stream composed mainly of C 4 to C 12 olefinic and aromatic hydrocarbons;
(c) blending said second stream with a residual fraction from a steam cracker or an atmospheric or vacuum distillation unit to produce a third stream;
(d) catalytically pyrolyzing said third stream in a reactor under conditions effective to produce a fourth stream having an increased benzene and/or toluene content compared with said second stream and a C 3 -olefin by-product;
(e) recovering C 3 -olefins from said fourth stream; and
(f) recovering benzene and/or toluene from said fourth stream.
2. The process of claim 1 , further comprising preheating the second stream before or after the blending (c).
3. The process of claim 1 , further comprising hydrotreating the residual fraction before or after the blending (c).
4. The process of claim 1 , wherein the catalytic pyrolysis is conducted in the presence of a catalyst comprising ZSM-5 and under reaction conditions including a temperature of about 480° C. to about 750° C.
5. The process of claim 4 , wherein the catalyst further comprises a large pore and/or an amorphous cracking component.
6. The process of claim 1 , wherein the catalytic pyrolysis is conducted in a riser reactor.
7. The process of claim 1 , wherein part of the catalyst is removed from the reactor and contacted with an oxygen-containing stream to remove coke from the catalyst and heat the catalyst thereby providing a portion of the heat required for (d).
8. The process of claim 1 , further comprising removing C 4 and C 5 hydrocarbons from the fourth stream and recycling said C 4 and C 5 hydrocarbons to (d).
9. The process of claim 1 , further comprising removing C 8 + hydrocarbons from the fourth stream and recycling said C 8 + hydrocarbons to (d).
10. The process of claim 1 , wherein benzene and/or toluene are recovered from said fourth stream by separating a C 6 and/or C 7 fraction from the fourth stream and removing aliphatic hydrocarbons from the C 6 and/or C 7 fraction to leave an aliphatic depleted fraction.
11. The process of claim 10 , wherein said aliphatic hydrocarbons are removed from the C 6 and/or C 7 fraction by solvent extraction or selective adsorption.
12. The process of claim 11 , wherein said aliphatic hydrocarbons are recycled to (d).
13. The process of claim 10 , wherein said aliphatic depleted fraction is hydrotreated before recovery of said benzene and/or toluene.
14. The process of claim 1 , further comprising:
(g) methylating benzene and/or toluene recovered in (f) with a methylating agent to produce a xylene-enriched stream.
15. The process of claim 14 , wherein said methylating is para-selective.
16. The process of claim 14 , wherein said methylating agent is methanol.
17. The process of claim 14 , further including:
(h) recovering para-xylene from said xylene-enriched stream.
18. The process of claim 1 , wherein the residual fraction comprises heavy tar produced as the product of steam cracking and/or the bottoms product of a vapor liquid separator drum integrated into the steam cracker.