US2416227A - Production of diolefins - Google Patents

Description

Feb. 18, 1947. w, D, SEYFRED 2,416,227

PRODUCTION OF DIOLE FINS Filed lay 18, 1944 Wator Quench T I Quench Tower WNVENTOR.

ATTORNEY.

Patented Feb. 18, 1947 UNITED STATES PATENT OFFICE.

PRODUCTION OF DIOLEFINS Wilson D. Seyfried, Wooster, Ten, assignor to Standard Oil Development Company, a corporation of Delaware Application May 18, 1944, Serial No. 536,210

4 Claims.

ducing diolefins of the character of butadieneincludes the steps of subjecting a predominantly olefinic feed stock to dehydrogenation conditions in a dehydrogenation reactor to form diolefins'as well as unsaturated materials, such as acetylencs. The hydrocarbon stream from the dehydrogenation unit is quenched by being brought into intimate contact with a quench oil, and after this quenching step it is further cooled to condense a diolefin-containing fraction which is removed to a suitable stabilization zone. The step in the process of contacting the hydrocarbon fraction removed from the dehydrogenation reactor with a quench oil is essential for profitable commercial operations in order to terminate the reaction and prevent the conversion of diolefins into less desirable materials. The quenching step is necessarily carried out at relatively high temperatures, and if free oxygen is allowed to enter the quenching zone it will react with the unsaturated materials present therein to form peroxides. Such peroxides are to be avoided because they not only are easily detonated, but in addition they catalyze the formation of high molecular weight polymers from the unsaturated hydrocarbons, such as diolefins and acetylenes, present in the hydrocarbon stream.

The product removed from the dehydrogenation reaction does not have free oxygen present therein, so the quenching zone may be maintained oxygen-free by the use of suitable quenching oil. This may conveniently be accomplished by employing initially as a quenching oil an oil previously treated to remove dissolved oxygen therefrom and preventing the contact between the 011 and air or oxygen-containing gas while it is being utilized in the system.

A preferred embodiment of the present invention will now be described in conjunction with the drawing, in which the sole figure is in the form of a diagrammatic fiow sheet.

Turningnow specifically to the drawing, an

olefin-containing feed stock is passed via inlet ll into dehydrogenation reactor I2, maintained under suitable conditions to cause the conversion of substantial amounts of the olefins in the feed stock to diolefins. In addition to the resulting diolefins, minor amounts of acetylenes are also formed in the dehydrogenation reactor. Hot hydrocarbon product is removed from vessel l2'by .line l3, having cooler l4 present therein. The

vapors removed from cooler I4 are still at a relatively high temperature and will cause the conversion of the desirable diolefins into undesirable materials if the temperature thereof is not reduced rapidly, and for this reason the vapors are discharged from line l3 into vessel I5, which serves as a quenching zone. Into an upper portion of tower I5 an oxygen-free heavy quench oil is introduced through inlet l6 and flows downwardly through the tower countercurrent to the hot hydrocarbon vapors let into the tower through line l3. The contacting of the hot vapors with the quenching oil should be under such conditions that the temperature of .the hot vapors is reduced several hundred degrees F. in a very short interval of time. This quenching must be sufiicient to reduce the temperature of the vapor below that at which substantial conversion of the diolefins into other products will take place. The quenched vapors are withdrawn from tower l5 through line H and subjected to cooling steps to cause cooling and condensation of the desired diolefln-containing product. In the drawing the hot vapors pass through linesll into cooler l8 of the heat exchanger type and pass thence through line l9 into tower 20, where they are quenched by contact with water. Quenching water accumulating in the lower portion of the tower is withdrawn through line 2| containing pump 22 and cooling means 23 and recycled back to the tower, being discharged into the upper portion thereof. The hot vapors fiow upwardly through trained water from the hydrocarbon vapors.

Separated water is removed from the lower portion of the drum through outlet 26 and hydrocarbon vapors from the upper portion of the drum through outlet 21 and passed through compressor 28, cooler 29 and a second drum 30. The compression and cooling steps to which the vapors are subjected causes the condensation of the major portion of the diolefin fraction. This desired fraction settles out in drum 30 and may be solved therein may be removed from the lower portion of the tower via line 35 and hydrocarbon gases and vapors are removed from the top of the tower by line 36 and discarded from the system.

A high boiling oil suitable for use in the quenching zone I is passed through inlet 40 and to still 4| provided with a suitable pressurereducing means 42 and a heating means 43. The heavy oil is refluxed under reduced pressure in the still 'to remove therefrom substantially all of the dissolved oxygen therein. The oxygenfree heavy oil is removed from still 4| through line 44 and passed into storage tank 45. Contact with oxygen in tank 45 is prevented by blanketin'g the surface of the oil with an oxygenfree gas. A suitable inert gas for this purpose has been found to be methane, but other oxygenfree gases, such as flue gas or nitrogen, may also be used for this purpose. The inert gas may be 'stored in vessel 46 and removed therefrom to the upper portion of tank 45 by line 41 controlled by valve 48 in order to maintain an oxyp gen-free gas blanketover the quench oil at all times. As oil is needed for the quenching tower l5, it is withdrawn from tank 45 by line 49 controlled by valve 50 and allowed to enter the tower via inlet l6.

The quenching oil accumulated at the bottom of tower l5 has dissolved therein small amounts of the hydrocarbon vapors. This accumulated quench oil is withdrawn from the tower through line 58 containing pump 52 and the stream split, with a portion being returned to the tower by line 53 and the remainder being passed through line 54 to a stripping tower 55 provided with heating means 55. Vapors separated from the quenching oil in stripping tower 55 are returned to quenching tower l5 through line 51. The stripped quenching oil resulting from the stripping action in tower 55 is withdrawn from the bottom of the tower through line 34, passed through a cooler 58 and is then used as the lean absorbent oil in absorption tower 33. The rich absorption oil removed from tower 33 via line 35 is admixed with the oil flowing in line 53 and the mixture returned to quenching tower l5.

As a specific example of the preparation of the quench oil, a Coastal gas oil having an initial boiling point of 590 F., a final boiling pointof 720 F., a viscosity at 100 F. of 77.9 Saybolt seconds, and a gravity of 25.7" A. P. I. was refluxed in a still maintained under a pressure ranging from 2 to 3 mm. absolute until substantially all of the dissolved oxygen originally present in the oil was removed therefrom. This oil was then stored under a blanket of methane in a storage tank and a quench oil was withdrawn therefrom as desired for quenching the hot va pors removed from a. dehydrogenation reactor. The substitution of this oxygen-free quench oil for the quench oil previously employed resulted in a substantial reduction in the polymers formed in the hydrocarbon stream and reduced substantially the fouling of the equipment. As another specific example, a raflinate having an initial boiling point "of"590'F. and a final boiling point of 720 F., and freed from oxygen by refluxing under vacuum, has been employed as a quench oil.

The temperatures of the dehydrogenation reaction and the suitable quenching range for reducing the temperatures of the gaseous product removed from the dehydrogenation reactorcare well known to the art and are described, for example, in detail in U. S. patent application Serial No. 510,204, filed in the name of Carl E. Kleiber et al. on November 13, 1943. As a typical example, it may be stated that the hydrocar-- stood that. these conditions are given by way of example only, and are not intended as limitations of the process.

Having fully described and illustrated the practice of the present invention, what I desire to claim is: 1

1. In a process for treating hydrocarbons including the steps of passing an olefin-containing hydrocarbon feed stock into a dehydrogenation zone and maintaining it in said zone under conditions to cause the. formation of diolefin and acetylene, passing the product through a quenching zone, removing the product from the quenchmg zone, further cooling it to condense at least a portion of the hydrocarbons, separating the condensed hydrocarbons and passing uncondensed hydrocarbons into an absorption zone,

the steps of stripping a heavy mineral oil under conditions of elevated temperature to remove dissolved oxygen therefrom, contacting the dehydrogenated product in the quenching zone with said oxygen-free mineral oil, and contacting the uncondensed hydrocarbons in the absorption zone with said oxygen-free mineral oil.

2. In the treatment of a, hydrocarbon feed stock containing olefins by passing the feed stock the quenching oil in the quenching zone and as the absorption oil in the absorption zone.

3. A process in accordance with claim 2 in which the heavy oil is a, naphthenic gas oil boiling within the rangeof 590 to 720 F.

5 e 4. A method in accordance with claim 2 in which the heavy oil is a raflinate boiling in the FOREIGN PATENTS range to Number Country Date WILSON B E F a 463,244 British Mar. 24, 1937 REFERENCES CITED 0 OTHER REFERENCES The following references are of reccrd in the Scott, Jour. Ind. Eng. Chem, News ed., vol. file of this patent: 18, 404 (1940). (Patent Office Library.)

Pittsburgh, etc., Research Bulletin No. 7381-3,

UNHED STATES PATENIS The Storage of Butadiene, pp. 26 and a1 (1942).

Number Name Date 2,209,215 Wiezevich et a1 July 23, 1940 2,378,067 Dorset et a1 June 12, 1945

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