Alkylation process with settler effluent recycle
View Patent ↗A system and/or process for increasing the isobutane to olefin ratio in an alkylation process/system is disclosed. The system and/or process includes provisions for charging a portion of the settler effluent as a feed to at least one reaction zone downflow from the first reaction zone of a multi-zone alkylation reactor along with a portion of the olefin feed to the multi-zone alkylation reactor.
1. A process comprising:
a) mixing i) a first isobutane-containing feed stream selected from the group consisting of a portion of a fresh isobutane stream, a portion of a recycle isobutane stream, and combinations thereof; and ii) a first olefin stream with an alkylation catalyst stream in a first reaction zone, to thereby form a first reaction zone effluent;
b) passing said first reaction zone effluent to a second reaction zone for mixture with i) a second isobutane-containing feed stream selected from the group consisting of a portion of said fresh isobutane stream, a portion of said recycle isobutane stream, a portion of a settler effluent stream, and combinations of any two or more thereof; and ii) a second olefin stream to thereby form a second reaction zone effluent;
c) alternatively:
I) passing said second reaction zone effluent to a settler vessel for separation into a hydrocarbon phase comprising alkylate and isobutane and an acid phase; or
II) 1) passing said second reaction zone effluent to a third reaction zone for mixture with i) a third isobutane-containing feed stream selected from the group consisting of a portion of said fresh isobutane stream, a portion of said recycle isobutane stream, a portion of said settler effluent stream, and combinations of any two or more thereof; and ii) a third olefin stream to thereby form a third reaction zone effluent; and 2) passing said third reaction zone effluent to a settler vessel for separation into a hydrocarbon phase comprising alkylate and isobutane and an acid phase; and
d) removing at least a portion of said hydrocarbon phase to thereby form said settler effluent stream comprising alkylate and isobutane; and
e) removing isobutane from the remainder of said hydrocarbon phase to thereby form said recycle isobutane stream; and wherein at least a portion of said settler effluent stream comprising alkylate and isobutane is mixed with at least one of:
1) said first reaction zone effluent in said second reaction zone in step b), and
2) said second reaction zone effluent in said third reaction zone in step c) II).
2. A process in accordance with claim 1 further comprising the step:
f) removing at least a portion of said acid phase for use as said alkylation catalyst stream.
3. A process in accordance with claim 1 wherein said fresh isobutane stream comprises at least about 60 wt. % isobutane, said recycle isobutane stream comprises at least about 60 wt. % isobutane, and said settler effluent stream comprises at least about 40 wt. % isobutane.
4. A process in accordance with claim 1 wherein said first, second and third olefin streams each separately comprise a C 4 olefin selected from the group consisting of isobutene, butene-1, butene-2, and combinations thereof.
5. A process in accordance with claim 4 wherein each of said first, second and third olefin streams separately further comprise propene and an olefin containing five carbon atoms per molecule.
6. A process in accordance with claim 1 wherein said alkylation catalyst stream comprises an acid selected from the group consisting of sulfuric acid and hydrofluoric acid.
7. A process in accordance with claim 1 wherein said alkylation catalyst stream comprises hydrofluoric acid and a volatility reducing additive.
8. A process in accordance with claim 7 wherein said volatility reducing additive is sulfone.