US3420907A - Hydrocarbon conversion process - Google Patents

Description

Jan. 7, 1969l J. T. CABBAGE HYDROCARBON vCONVERSION PROCESS Filed May 2, 1966 s Sanoma @U5 wv R n.. o mzoN rm N NB n zozkzwooar ...A m 1 Snoommozzw wzmNzmm ,f n om f J. B530 @v +Qu mo mu vm )Nv Y, a Y .uzou mzwNzmm w s vv .a Y .w Qu+m w, w22-20% \/m ov Cmzv zmwoar m H. v WM f O 1 .2.63 W l wzoN o @z zom u zookxw P zwow ,u t N Nm f Nm.\/ mm wm mznm I @n mu mo No 96mm om )mm ozouma 20E E. z. mzoN Q H lllwl w15 @MON m zounooma f QH )wm w Omni.. ImDaS: mZmJ-.m mu O NU )N @N5 1a z Nm N. E N1 50m E cov om "No man wmm United States Patent O 7 Claims This invention relates to an improved process for the conversion of hydrocarbons to more useful product streams.

In the petroleum industry various available hydrocarbon streams are utilized to produce more desirable hydrocarbon product streams. To illustrate, in one petroleum refinery a 400 F. end point naphtha is hydrodesulfurized in admixture with hydrogen in contact with a hydrodesulfurization catalyst (cobalt molybdate) and the desulfurized naphtha is passed to a catalytic reforming zone containing a suitable reforming catalyst (platinum-alumina). The reformate is separated into a light hydrocarbon stream (C and lighter) and an aromatic-rich stream, the latter being solvent extracted to recover a principally aromatic stream of benzene, toluene and heavier, and the raffinate being recycled to the reforming zone. The aromatic-rich stream is separated into a benzene concentrate and a toluene and heavier stream, the benzene concenrate being hydrogenated in a hydrogenation zone in admixture with hydrogen in contact with a nickel hydrogenating catalyst (nickel on kieselguhr) to produce cyclohexane as a product of the process.

It requires a relatively pure hydrogen stream free of CO in the hydrogenation zone because of the susceptibility of nickel to poisoning by CO. A CO-free stream of H2 is produced as an effluent from the reforming zone but this stream must be divided between the benzene hydrogenation zone and the` naphtha hydrodesulfurization zone to which it is passed in a once-through operation because of the sour condition of the hydrogen off-gas (high concentration of HZS therein). Cyclohexane production in this type of operation is greatly curtailed by the lack of a larger volume hydrogen-rich stream free of CO.

This invention is concerned with the more efficient utilization of refinery streams, particularly hydrogen-rich streams produced in refinery operations.

Accordingly, it is an object of the invention to provide an improved hydrocarbon conversion process which elfects more efiicient utilization of available hydrocarbon streams produced by different refinery operations. Another object is to provide a hydrocarbon conversion operation which is more economical in the use of available hydrocarbon streams from normal conversion operations. A further object is to provide a refinery process which increases the production of cyclohexane from a naphtha stream. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention as applied to simultaneous hydrodesulfurization of the naphtha stream, catalytic reforming Iof the naphtha stream to produce an aromatic-rich stream, solvent extracting the latter stream to separate an aromatics stream and a lighter rafiinate, separating a benzene concentrate from the toluene and heavier aromatics, and hydrogenating the benzene concentrate over a nickel hydrogenation catalyst to produce cyclohexane, comprises passing all of the relatively pure (CO-free) hydrogen stream from the catalytic reforming zone as the hydrogen feed to the benzene hydrogenation zone which avoids poisoning of the nickel catalyst, dehydrogenating ethane and/ or propane to produce ethylene and an impure H2-rich stream, and passing the impure hydrogen-rich stream produced in the ethylene production zone to the hydrodesulfurization zone which can tolerate ice the impurities in this stream (CO). An additional aspect of the invention comprises separating the C2-C5 hydrocarbon produced in the reforming zone into a ligiht stream and a heavier stream, and passing the light stream as feed to the ethylene production zone.

The invention is best understood by reference to the accompanying schematic drawing Which is a process flow or arrangement of apparatus in accordance -with the invention.

Referring to the drawing, a suitable feed for the production of ethylene is passed through line 10 into ethylene production zone 12 for thermal cracking and dehydrogenation to ethylene. The feed in line 10 may consist essentially of ethane, propane, or a mixture of these hydrocarbons. A residual material is recovered through line 14, an ethylene-rich stream through line 16, and an irnpure hydrogen stream containing CO through line 18.

A naphtha stream, such as one having a 400 F. end point, is fed through line 20 into dehydrosulfurization zone 22 and is hydrodesulfurized therein in admixture with the impure hydrogen stream from line 18 in contact with a suitable hydrodesulfurization catalyst such as cobalt molybdate on alumina. A sour H2 gas is recovered through line 24 and the desulfurized naphtha is recovered through line 26 and passed into catalytic reforming zone 28 in admixture With recycle rafiinate from line 30. The reforming in zone 28 is elfected in contact with a couventional reforming catalyst, such as platinum on alumina which may or may not have been fluorinated. The reformate in zone 28 is separated into a light hydrocarbon stream containing principally C2-C5 hydrocarbons which are passed through line 31 to further treatment described below, an aromatic-rich stream which is passed through line 32 into solvent extraction zone 3S, and a hydrogenrich stream substantially free of CO which is recovered through line 34. Solvent extraction zone 35, 'which utilizes any suitable liquid .solvent for aromatics, produces a raffinate in line 36 relatively free of aromatics a portion of which is recycled through line 30 to the reforming zone and an aromatics-rich stream in line 38 which is passed to benzene concentration zone 40. An effluent toluene-andheavier stream is recovered through line 42 from benzene concentration zone 40 and a separate benzene-rich stream is passed through line 44 into benzene hydrogenation zone 46 along with the relatively pure hydrogen stream from line 34. Zone 46 is provided with a nickel catalyst which is preferably deposited on a solid porous support such as a kieselguhr or silica gel. The cyclohexane produced in zone 46 is recovered as a product of the process through line 48 and residual hydrocarbons are recovered through line 50 following their separation from the cyclohexane.

The C2-C5 hydrocarbon stream from line 31 is passed into a separation zone 52 for separation and recovery of a heavier fraction through line 54 and a lighter fraction through line 56, the latter being passed toethylene production zone 12 via line 10 in admixture with the feed to this zone. When the feed in line 10 is principally ethane, sparation zone 52 is operated substantially as a deethanizer. When the feed in line 10 is a mixture of ethane and propane, as it well may be, separation zone 52 is operated so as to take overhead substantially all of the ethane and propane in the stream from line 31, the C4s and C5s and heavier being recovered through line 54.

The various hydrocarbon conversion and separation zones referred to and shown in the drawing are 'operated in conventional manner, each of these steps being commonly practiced in petroleum refineries. The conditions of operation in the various conversion and separation zones are not a part of the invention, and specific details of these operations need not be delineated herein. The invention is in the sequence of and relationship between the various steps in the complete process. Thus, by adding ethylene production to the combination, the impure hydrogen stream in line 18 can be utilized in hydrodesulfurization zone 22 in contact with a cobalt molybdate catalyst, as well as other hydrodesulfurization catalysts, without appreciable detriment to the catalyst. However, this stream cannot be utilized in benzene hydrogenation zone 46 vbecause of the presence therein of CO in a concentration highly detrimental to the nickel catalyst therein. By utilizing all of the CO-free hydrogen stream from line 34 in benzene hydrogenation zone 46 instead of a portion thereof in hydrodesulfurization zone 22, the poisoning of the nickel catalyst in the hydrogenation zone is avoided and all of the hydrogen stream in line 34 is fed to benzene hydrogenation zone 46 along with all of the benzene concentrate from line 44 to greatly increase cyclohexane production. In addition, the process makes specific use of the ethane and/ or propane from line 31 in the ethylene production zone l2, thereby materially increasing ethylene yield and the cooperation between the various operational steps in the unitary process.

To Vfurther illustrate the invention, one set of conditions represetning plant operation of the invention are presented in the example below. The data in the example are merely illustrative and are not to be interpreted as unnecessarily limiting the invention.

EXAMPLE Flow rates:

Ethane feed (line 10) 3, 300 Reformer feed (line 26) 30 Impure hydrogen (line 1 Hydrogen Cyclohexane product (line 48) (99 pure) 1, 800 Pure hydrogen (line 34) 8, 000 Hydrogen 85. 5 do G. 1

Propane (plus) 5. 3 Carbon monoxide None H Trace Ethane to charge (line 56) 200 Toluene product (line 42) 200 Unit operations Temp. F. Pressure, p.s.i.g.

Ethylene production zone 1, 500 10 I-Iydrodesulfurization zone 650 400 Reforming zone 925 500 Solvent extraction zone 250 135 Benzene hydrogenation zone 400 500 Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A process comprising the steps of:

( l) dehydrogenating a feed stream of ethane, propane, or a mixture thereof to produce an ethylene stream as a product of the process and an impure stream rich in H2 containing a minor concentration of CO;

(2) hydrodesulfurizing a naphtha-rich stream in admixture with the impure Hz-rich stream of step (1) in contact with a catalyst immune to CO poisoning to produce' 'a substantially sulfurLfre'e, naphtha-rich stream;

(3) catalytically reforming the resulting naphtha-rich stream of step (2) to produce a substantially CO- free H2 stream, an aromatics-rich stream, and a lighter C2C5 stream; f

(4) solvent-extracting the aromatics-rich stream of step (3) to separately recover a principally aromatics stream and a rainate stream of principally non-aromatics;

(5) separating the aromatics stream of step (4) into a principally benzene stream and a toluene and heavier stream as a product of the process; and

(6) hydrogenating the benzene stream of step (5) in admixture with the CO-free H2 stream of step (3) in contact with a nickel hydrogenation catalyst to produce a cyclohexane stream as a product of the process.

2. The process of claim 1 including the steps of:

(7) separating the C2-C5 stream of step (3) into a lighter stream containing at least ethane and a heavier stream as a product of the process; and

(8) passing the lighter stream of step (7) to step (l) as a portion of the feed thereto.

3. The process of claim 1 wherein the catalyst in step (2) comprises essentially cobalt molybdate, the catalyst of step (3) comprises essentially a supported platinum catalyst, and the catalyst of step (6) comprises essentially nickel supported on silica.

4. The process of claim 1 wherein the feed stream of step (l) is principally ethane, the feed stream of step (2) is a 400 F. end-point naphtha, and the lighter stream of step (7) is principally ethane.

5. The process of claim 4 wherein the catalyst in step (2) comprises essentially cobalt molybdate, the catalyst of step (3) comprises essentially a supported platinum catalyst, and the catalyst of step (6) comprises essentially nickel supported on silica.

6. The process of claim 2 wherein the catalyst in step (2) comprises essentially cobalt molybdate, the catalyst of step (3) comprises essentially a supported platinum catalyst, and the catalyst of step (6) comprises essentially nickel supported on silica.

7. The process of claim 2 wherein the feed stream of step (l) is principally ethane, the feed stream of step (2) is a 400 F. end-point naphtha, and the lighter stream of step (7) is principally ethane.

References Cited UNITED STATES PATENTS 3,012,961 12/1961 Weisz 260-667 3,070,637 12/1962 Honeycutt 20S-96 3,108,946 10/1963 Makin 260-667 43,227,768 1/1966 Cole 260-667 3,234,121 2/1966 Machaneu 260-667 3,253,047 5/1966 Belinger 260-667 3,274,275 9/1966 Hutto et al. 260-667 3,347,779 10/1967 Grocacudaal 260-667 DELBERT E. GANTZ, Primary Examiner.

VERONICA OKEEFE, Assistant Examiner.

U.S. Cl. X.R. 260-677; 208-214

Claims (1)

1. A PROCESS COMPRISING THE STEPS OF: (1) DEHYDROGENATING A FEED STREAM OF ETHANE, PROPANE, OR A MIXTURE THEREOF TO PRODUCE AN THEYLENE STREAM AS A PRODUCT OF THE PROCESS AND AN IMPURE STREAM RICH IN H2 CONTAINING A MINOR CONCENTRATION OF CO; (2) HYDRODESULFURIZING A NAPHTHA-RICH STREAM IN ADMIXTURE WITH THE IMPURE H2-RICH STREAM OF STEP (1) IN CONTACT WITH A CATALYST IMMUNE TO CO POISONING TO PRODUCE A SUBSTANTIALLY SULFUR-FREE, NAPHTHA-RICH STREAM; (3) CATALYTICALLY REFORMING THE RESULTING NAPHTHA-RICH STREAM OF STEP (2) TO PRODUCE A SUBSTANTIALLY COFREE H2 STREAM, AN AROMATICS-RICH STREAM, AND A LIGHTER C2-C5 STREAM; (4) SOLVENT-EXTRACTING THE AROMATICS-RICH STREAM OF STEP (3) TO SEPARATELY RECOVER A PRINCIPALLY AROMATICS STREAM AND A RAFFINATE STREAM OF PRINCIPALLY NON-AROMATICS; (5) SEPARATING THE AROMATICS STAREAM OF STEP (4) INTO A PRINCIPALLY BENZENE STREAM AND A TOLUENE AND HEAVIER STREAM AS A PRODUCT OF THE PROCESS; AND (6) HYDROGENATING THE BENZENE STREAM OF STEP (5) IN ADMIXTURE WITH THE CO-FREE H2 STREAM OF STEP (3) IN CONTACT WITH A NICKEL HYDROGENATION CATALYST TO PRODUCE A CYCLOHEXANE STREAM AS A PRODUCT OF THE PROCESS.

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