Ethylene-to-liquids systems and methods
Integrated systems are provided for the production of higher hydrocarbon compositions, for example liquid hydrocarbon compositions, from methane using an oxidative coupling of methane system to convert methane to ethylene, followed by conversion of ethylene to selectable higher hydrocarbon products. Integrated systems and processes are provided that process methane through to these higher hydrocarbon products.
1. A method, comprising:
(a) in an oxidative coupling of methane (OCM) reactor, reacting oxygen (O 2 ) with methane (CH 4 ) in an OCM process to yield an OCM product stream comprising (i) compounds with two or more carbon atoms (C 2+ compounds), including ethylene (C 2 H 4 ), and (ii) carbon monoxide (CO) or carbon dioxide (CO 2 ), wherein said OCM process liberates heat;
(b) directing said OCM product stream comprising (i) said C 2+ compounds, including C 2 H 4 , and (ii) carbon monoxide (CO) or carbon dioxide (CO 2 ), from said OCM reactor directly into a cracking vessel, and in said cracking vessel, cracking ethane (C 2 H 6 ) with the aid of said heat liberated in (a), thereby increasing a concentration of C 2 H 4 and hydrogen (H 2 ) in said OCM product stream;
(c) directing said OCM product stream from said cracking vessel into a treatment unit, and in said treatment unit reducing the concentration in said product stream of (i) compounds having triple bonds or (ii) compounds having more than one double bond, wherein said reducing is accomplished by a separations process or a reaction process;
(d) directing said OCM product stream from said treatment unit into an ethylene-to-liquids (ETL) reactor, and in said ETL reactor converting said C 2 H 4 in said OCM product stream to yield an ETL product stream comprising higher hydrocarbon products;
(e) directing said ETL product stream from said ETL reactor to a separations module and recovering from said ETL product stream a liquid stream comprising said higher hydrocarbon products and a gas stream comprising H 2 and CO or CO 2 ; and
(f) directing said gas stream into a methanation reactor, and in said methanation reactor reacting said H 2 with said CO or said CO 2 to form CH 4 .
2. The method of claim 1 , further comprising directing said CH 4 from said methanation reactor into a sales gas pipeline.
3. The method of claim 1 , further comprising directing said CH 4 from said methanation reactor into said OCM reactor.
4. The method of claim 1 , wherein said OCM reactor has a reactor inlet temperature between about 450° C. and about 600° C. and a pressure between about 15 pounds per square inch gauge (psig) and about 125 psig, and wherein said OCM process has a C 2+ selectivity of at least about 50%.
5. The method of claim 1 , wherein said product stream, when directed into said ETL reactor in (d), comprises less than about 100 parts per million (ppm) of acetylene.
6. The method of claim 1 , wherein said product stream, when directed into said ETL reactor in (d), comprises less than or equal to about 5 mol % CO.
7. The method of claim 1 , wherein said treatment unit comprises an acetylene hydrogenation catalyst with a lifetime of at least about 6 months.
8. The method of claim 1 , wherein said treatment unit comprises a guard bed.
9. The method of claim 1 , wherein said higher hydrocarbon products are generated at a single pass conversion of at least about 40%.
10. The method of claim 1 , wherein at least a portion of said C 2 H 6 that is cracked in (b) is produced in said OCM reactor.
11. The method of claim 1 , wherein at least a portion of said C 2 H 6 that is cracked in (b) is input to said cracking vessel along a stream external to said OCM reactor.
12. The method of claim 1 , wherein said cracking vessel is integrated with said OCM reactor.
13. The method of claim 1 , wherein said ETL reactor is operated at a temperature greater than or equal to about 200° C.
14. The method of claim 1 , wherein said ETL reactor is operated at a pressure greater than or equal to about 200 pounds per square inch.
15. The method of claim 1 , wherein said ETL product stream in (d) comprises less than 50 weight percent (wt %) water.
16. The method of claim 1 , wherein said OCM reactor is a fixed bed OCM reactor.
17. The method of claim 1 , wherein said cracking vessel is substantially adiabatic.
18. The method of claim 1 , wherein an inlet temperature of said OCM reactor is at most about 600° C.