US2400376A - Process for recovering olefins from a hydrocarbon stream - Google Patents

Description

May 14, 1946. J. c. sHowAL-rER PROCESS FOR RECOVERING OLEFINS FROM A HYDROCARBON STREAM Filed Nov. 23, 1944 Q/U/W ATTORNEY.

Patented May 14, 1946 PROCESS FOR RECGVERIG GLEFINS FROM A HYDROCARBON STREAM Jere C. Showalter, Goose Creek, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application November 23, 1944, Serial No. 564,801

6 Claims.

The present invention is directed to a method for concentrating relatively Weak sulfuric acid which has been previously employed for treating hydrocarbons.

More particularly, the present invention is directed to a process comprising the treatment of low molecular weight hydrocarbons including olens with sulfuric acid to form an extract, the recovery of absorbed and reacted hydrocarbons from the extract and the concentration of the recovered acid wherein oil soluble sulfonic acids are employed to prevent foaming of the extract and of the sulfuric acid undergoing concentration.

It is conventional to the art to recover low molecular weight olens from a hydrocarbon mixture by contacting the mixture with 65% sulfuric acid. As an example of a typical operation, a hydrocarbon feed stock including normal butane, isobutlyene and normal butylene may be brought into contact with sulfuric acid in a reaction zone under a pressure substantially in excess of atmospheric in order to form an extract. The pressure on this extract is reduced to substantially atmospheric in a vent drum with the resultant release of the butanes and butylenes previously absorbed therein. The extract is then sent to a regenerator where polymers and alcohols resulting from the reaction of the sulfuric acid with the hydrocarbon mixture are separated as overhead fractions and the acid is concentrated to a 45% strength. The acid is removed from the regenerator to an acid concentrator where its strength is increased to 65% and then returned to the reaction zone of the system. In conventional operations, a substantial foaming is encountered in the vent drum, the regenerator and in the acid concentrator and this foaming requires these portions of the system to be operated at a rate below that which may be employed when foaming is eliminated.

In accordance with the present invention foaming in the vent drum, regenerator and acid concentrator is eliminated by adding small amounts of oil soluble sulfonic acids to the sulfuric acid being circulated in the system. The oil soluble sulfonic acids are preferably added to the extract as it is being passed from the reaction zone to the vent drum, but alternatively the oil soluble sulfonic acids may be added to the stream of sulfuric acid owing through other portions of the system.

Perhaps the best known method of forming oil soluble sulfonic acids is in the refining of lubricating petroleum oils or white oils. When relining petroleum oils, in order to obtain white oils or highly refined lubricating oils, it is common to treat the starting petroleum stock with fuming sulfuric acid in order to eliminate undesirable components. The petroleum sulfonic acids resulting from such treatment may be divided into two general types; green acids which are characterized as being water soluble and mahogany acids which are characterized as being oil soluble. The oil soluble mahogany sulfonates conventionally obtained as a by-product in the refining of white oils and lubricating oils may conveniently be employed as the oil soluble sulfonic acids employed in the present invention to prevent the foaming of the sulfuric acid extract and the sulfuric acid.

in the recovery of the sulfuric acid from the extract.

The invention will now be described in greater detail in conjunctionwith the drawing in which the single figure is in the form of a flowl sheet illustrating a preferred modification of the present invention.

In the drawing a first stage reactor is designated by II, a, iirst stage settling drum by I2, a second stage reactor by I3, a second stage settling drum by It, a vent drum by I5, a regenerator vessel by I6 and an acid concentrator vessel by I'I. The mixture of feed hydrocarbons is passed to the system from a vessel I8.

The system shown in the drawing may be described generally as involving a reaction zone, an acid regenerating zone and an acid concentrating zone. 'I'he reaction or absorption zone is divided into two stages, with hydrocarbons flowing through the first and second stages in sequence,

and sulfuric acid passed into the second stage and 'forming an extract therein, the extract taken from the second stage and enriched `in the first stage, and the resulting extract from the first stage sent, in turn, through acid regeneration and acid concentration zones. The hydrocarbon feed passes first through first stage reactor II, and then through second stage reactor I3. Regenerated acid is fed into second stage reactor I3 and forms an extract therein and this extract is fed to first stage reactor I I to serve as the absorption liquid therein. The enriched extract passes from reactor I I to settling vessel I2 and is taken from settling vessel I2 through vent drum I5, regenerator I6, and acid concentrator I'I, where the acid is restored to its original condition and returned to second stage reactor vessel I3. The vent drum I5 is arranged between settling vessel I 2 and regenerator tower I6 in order to allow the release of pressure from the extract before it is sent to the regenerator tower.

In order to prevent foaming of the acid in vent drum I5, regenerator I3 andacid concentrator I1 an oil soluble sulfonic acid is added to the circulating stream of acid. In the drawing the means for adding the acid is indicated 'as inlet line I9 which adds the sulfonic acids to the extract being sent from first stage settling drum |2 to vent drum I5.

As a typical example, the mixture of hydrocarbon in vessel I3 may consist of 50% of iso and normal butane, 32% normal butylene and 18% isobutylene. This hydrocarbon mixture is passed from vessel I3 via line 20 in which is arranged pump 2| and heat exchanger 22 and discharges through distributing lines 23 and 24 into iirst stage reactor vessel I I. The liquid from the bottom of reactor vessel II is withdrawn through line 25 and the stream split, with a portion -passing through line 26 to first stage settling drum I2 and the remainder being recycled to line 20 via line 21. To the extract flowing through line 21 is added extract withdrawn from the second stage settling drum I4 by line 23. The extract withdrawn from drum I4 and the extract withdrawn from iirst stage reactor vessel I I are mixed in line 21 and the mixture of extract is then discharged into the hydrocarbon stream in line 23.

It is convenient to operate first stage reactor vessel I| at a temperature of 100 F. and at a pressure of 140 pounds per square inch. The. admixture of the extract comprising sulfuric acid with the hydrocarbon mixture in line 20 usually results in such a rise in temperature that it is necessary to cool the mixture with 'heat exchanger 22 in order to maintain the temperature in reactor vessel II at approximately 100 F. 'I'he hydrocarbon vapors in iirst stage reactor vessel I I which are not absorbed or do not react with sulfuric acid therein are removd as overhead via line 23 and are discharged into the upper portion of rst stage settling drum I2. 'I'he unabsorbed hydrocarbons from first stage settling drum I2 are passed through'line 33 containing heat exchanger 3| and are discharged through lines 32 and 33 into second stage reactor vessel I3. Extract from the lower portion of second stage reactor vessel I3 is withdrawn via line 34 and the stream split with a portion passing through line 35 to second stage settling drum I4 and the remainder passing through pump 36 and discharging into the hydrocarbon stream passing through line 30. Regenerated sulfuric acid is discharged into stream 34 through line 31.

Unabsorbed and unreacted hydrocarbon vapors from second stage reactor vessel I3 pass through line 33 to second stage settling vessel I4 and the unreacted and unabsorbed hydrocarbons from vessel I4 comprising principally Iiso and normal butane and normal butylenes are withdrawn from outlet line 39. ond stage reactor vessel I3 at a temperature of 70 F. and under a pressure of 135 pounds per square inch and in order to maintain these temperature and pressure conditions in vessel I3 it will usually be necessary to employ a cooling medium in heat exchanger 3| in order to remove heat resulting from the mixing of hydrocarbons with sulfuric acid in line 30.

With a pressure in first stage reactor vessel I of approximately 140 pounds per square inch and in second stage reactor vessel I3 at approximately 135 pounds per square inch the pressure in iirsi; stage settling drum I2 is also approximately 135 pounds per square inch. In order to It is convenient to operate secpheric by vent line 4 I Extract is withdrawn from vent drum I5 via line 42 and pump 43 and disvcharged into regenerator tower I5. Hydrocarbons in vaporous condition are removed from tower I3 asoverhead via outlet 45 and passed -into scrubber 43 where they are brought into contact with caustic introduced into the scrubber through inlet 41. The vapors from scrubber 43 are` removed through outlet 43 and passed through cooler 43 to'condense the high boiling constituents and the cooled mixture is discharged into accumulator 50. Uncondensed materials, principally isobutylene, are removed in gaseous form from the upper portion of accumulator 50 through outlet 5I. Condensate is removed from vessel 50 through line 52 containing pump 53 and the stream split with a portion being passed through line 54 to serve as a scrubbing material in tower 43, another portion passing through lines 55 and again divided with one portion discharged through line 53 into an upper part of regenerator tower I3 and the remaining portion passing through line 51 containing heater 53 and discharged into regenerator I3 some distance below the point of discharge of line 53. Liquid is withdrawn from the bottom of scrubber 43 through line 53 and has added thereto condensate withdrawn from vessel 53 Ivia line 52, pump 53 and branch line 30. The liquid mixture in line 53 includes alcohol and polymer and is withdrawn from the system to a suitable arrangement for recovering these valuable products.

It is desirable to operate regenerator tower I5 with a bottom temperature of approximately 240 F. and a top temperature of 160 F. In addition to the heat added to the tower by heat exchanger 53 heating the stream tlowingthrough line 51, steam may be inJected into the bottom of the tower through inlet 3|.

Acid is withdrawn from the bottom of the regenerator tower IB at a concentration of approximately 45% and is passed via line 44 to acid concentrator I1. In this vessel the acid is heated by steam passing through coil 32 and the water vapor driven from the acid is discharged through outlet 63. In concentrator vessel I1 the acid is concentrated to a strength of approximately 65% and is discharged through line 34 to vessel 35 containing cooling coil 53-and vent 31. 'I'he acid accumulated in vessel 35 is regenerated acid and is passed through lines 31 and 34 to the hydrocarbon stream passing through line 33 to second stage reactor vessel I3. In order to replace the acid lost in the operation, makeup acid may be introduced in the required amounts through inlet line 38 to the stream of regenerated acid.

When operating the reactor vessels II and I3 at temperatures and pressures of F. and 140 pounds'per square inch and 70 F. and 135 pounds per square inch, respectively, and with a feed stock having the composition given above, it will be found that good results may be obtained when withdrawing 235 gallons of feed per minute from vessel I3 and passing 1360 gallons of regenerated acid per minute through line 31 and into the hydrocarbon stream being passed to the second stage reactor vessel I3.

While I have disclosed the use of oil soluble sulfonic acids as such for eliminating foaming in vessels l5, I6 and I1, it is to be understood that as an alternative, I may form a solution of these acids in a suitable medium such as alcohol and admix the solution of the oil soluble sulfonic acids with the acid stream being circulated through the system. The amount of oil soluble sulfonic acids required to eliminate foaming in the acid recovery portion of the system is so small that it will usualiy be found more convenient to add the oil soluble sulfonic acid vas a solution in order to regulate more precisely the quantity of oil soluble sulfonic acid being added to the circulating acid stream. When using oil soluble mahogany sulfonic acids, it will be found that amounts approximating .005 part per million of sulfomc acids in the sulfuric acid extract being passed to the vent drum will be sufficient t0 eliminate foaming in the drum as well as in the regenerator tower and acid concentrator. Such small amounts of acid may conveniently be added to the sulfuric acid extract by making a solution of the sulfonic acids in tertiary butyl alcohol with a concentration of one part in a thousand, and adding this solution to the sulfuric acid extract. It is to be understood that the sulfonic acids employed in the practice of the present invention have boiling points substantially above the boiling points of the low molecular weight hydrocarbon absorbed or reacted With the sulfuric acid. If desired the regenerated sulfuric acid being returned to the reaction zone may have mixed therewith the oil soluble sulfonic acids and the oil soluble sulfonic acids in view of their high boiling points will remain in the acid while it circulates through the first and second reactor stages and will be present in the sulfuric acid extract being passed to the vent drum and be eective to prevent foaming therein.

- Having fully described the present invention, what I desire to claim is:

l. In a system for recovering olefin from a predominately C4 hydrocarbon feed stock comprlsing olens involving contacting the feed stock with sulfuric acid in a reaction zone under conditions to form an extract, the removal of the extract from the reaction zone to a regeneration zone where the extract is heated under a pressure substantially less than that in the reaction zone to cause vaporization of a major portion of the hydrocarbons from said extract and recovery of the sulfuric acid and the recycling of the recovered sulfuric acid to the reaction zone, the step of adding oil soluble sulfonic acids to the circulating sulfuric acid stream in suillcient amount substantially to eliminate foam in the regeneration zone.

2. A method in accordance with claim 1 in which the oil soluble sulfonic acids are added to the circulating sulfuric acid stream in suiilcient quantity to maintain approximately .005 part of sulfonic acid per million parts of sulfuric acid extract passed to the regeneration zone.

3. In a process for removing olens from a hydrocarbon stream comprising a substantial p0rtion of C4 hydrocarbons and appreciable amounts of oleiins including the Ysteps of contacting the stream with sulfuric acid in a reaction zone under conditions to form an extract and the treatment of the resulting extract in an acid regeneration zone to separate hydrocarbons from the acid and recover acid of approximately the same concentration as employed in the reaction zone, the step of adding to the extract being sent from the reaction zone to the regeneration zone oil soluble sulfonic acids.

4. A process in accordance with claim 3 in which the concentration of the added oil soluble sulfonic acids in the extract are present in amount of .005 part per million of the extract passed to the regeneration zone.

5. A method in accordance with claim 3 in which the oil soluble sulfonic acids are mahogany acids obtained from petroleum.

6. A method in accordance with claim 3 in which the oil soluble sulfonic acids are mahogany acids from petroleum and are added in the form of a solution of sulfonic acids in butyl alcohol to produce a concentration of .005 part per million of sulfonic acids in the sulfuric acid extract passed to the regeneration zone.

JERE C. BHOWAL'I'ER.

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