US2131191A - Dispersion of olefines in acid polymerization - Google Patents

Description

Patented Sept. 27, 1938 DISPERSION OLEFINES IN ACID POLY MERIZATION I Bruno E. Roetheli 'and- Eldon E. Stahly, Baton.

Rouge, La., assignors to Standard Oil Development Company, a corporation of Delaware Application October 24, 1936, Serial No. 107,322 7 Claims. (01. 196-10) The present invention relates to an improved process for producing polymers suitable for motor fuels and motor fuel constituents from normally gaseous .olefines, and more specifically to an improved method for effecting such polymerization with sulfuric acid. The method will be fully understood from the following description and the drawing.

Referring to the drawing, Fig. 1 shows a sectional elevation of an apparatus for effecting polymerization or condensation of normally gaseous olefines by means of sulfuric acid and the flow of material through the apparatus is indicated. Fig. 2 is a top cross-sectional view of the apparatus shown in Fig. 1 taken along the line X-X. Figs. 3 and 4 are larger scale drawings of the jets which are used to force the olefinic material to be polymerized into the reaction chamber.

2 The polymerizing action of sulfuric acid has been long known, and more recently it has been employed to eifect the polymerization of liquefied normally gaseous olefines, especially isobutylene, to form dimers and trimers which are well suited, especially after hydrogenation, for use as motor fuels or for constituents of motor fuels. The present invention is an improved method for carrying out this reaction and related condensations between various oleflnes.

Turning to the drawing, in Fig. l the numeral I denotes a feed line by which the liquid olefines such as isobutylene or mixtures of isobutylene with propylene, normal butylenes, amylenes or other olefines are forced by means of the feed pump 2. The feed passes through one or the other of the two fine mesh screen filters 3 and 4 which are suitably fitted with valved connections so that the one may be'cleaned while the other is in use. into?" the lower portion of the polymerization chamber 6, into which it is discharged at a high velocity through a plurality of jets I, which will be 1 jacket 8. for heating, but it will'be understoodthat other heating means may be employed if de- 50 tain a relatively deep bath of sulfuric acid, and

therefore it should be constructed of materials capable of withstanding its corrosive action. The diameter of the chamber is determined by the 56 number of jets required. It should be of sum- The material then passes by a pipe 5 sired. The reaction chamber is adapted to maincient height to hold at' least 3 ft. of acid when measured in the quiescent state, and it will be understood that the level will rise considerably thereafter when the olefine ispassed into the material so that the total height of the chamber should be at least 5 ft. and. preferably about 12 ft.

A pipe 9 is provided at the upper end of the chamber for the withdrawal of the mixture of acid and olefine. Pipe 8 may be jacketed with an element 2| in whicha cooling fiuid may be circulated to maintain a uniform temperature of the exit materials or to cool the; same. Pipe 9 discharges into the settling drum 22, which drum is connected by means of line 23 to vent line l8.

A cooler in is provided to reduce the temperature of the mixture as it flows from the settling drum Settling drum 22 22 to the'separation drum II. is also provided with a draw-off line 24.

In the separation drum theacid and the hydrocarbon materials are allowed to stratify; the acid being heavier is found in the lower layer. This is removed by a pipe I2 and recirculated to pump iii to the bottom of the polymerization chamber.'

product from vessel i6 may be recirculated by,

pipe l9 and pump 20.

- Figs. 3 and 4'illustrate the preferred type of the jets I mentioned in connection with Figs. 1 and 2. These jets are preferably replaceable as shown and are in the form of wide tubes narrowed at the end to provide a hole of small diameter, so as to cause the liquid to attain an extremely high velocity in passing into the acid bath. This type of construction minimizes the pressure drop required for the operation. In Fig. 3 thejet is directed upwardly, which is the preferred form,

while in Fig. 4 the jet is directed downwardly against a plate la which may be the bottom of reaction vessel 6, or may be a separate member so placed as to best receive the stream of hydrobreaking it up into tiny droplets.

From the above description of the apparatus,

the operation will be generally understood, but

being maintained at polymerizing strength andtemperature. With more dilute acids, somewhat carbon and reverse its flow, at the same time tion of the isobutylene with another olefine of the such .as propylene orstraight chain type, butylene, higher temperatures of the order of 200 to 300 F. are used. For non-selective polymerization of olefines or oleflne mixtures, temperatures from 300 to 500 F. are employed. Super-atmospheric pressures should be employed with elevated temperatures in order to maintain the normally gaseous hydrocarbons in the liquid condition. Pressures of 300.600 lbs. per square inch are ordinarily required at temperatures of 200-300 F.

The above conditions for the. polymerization are important, and are broadly known in the prior art. It is necessary, however, to combine these conditions with the following specifications in order to obtain the best results. It has been found that a single jet may be employed effectively, and in that case the reaction vessel is best between 6 inches and 12 inches in diameter. For commercial operations it is more desirable to use a plurality of jets in a reaction vessel of larger diameter. The jet diameter may vary from about 0.010 to 0.15 inch and the velocity at the throat of the jet should be of the order of at least 40 feet per second. If the velocity is below this figure, or on the other hand, if the diameter of the jet is larger, the hydrocarbon tends to issue in acontinuous stream and effective polymerization is not obtained. For example, the yield drops off very rapidly because of the loss of interi'acialv ished. If it is attempted to make this up by increasing the height of the acid, it is found that an excessive amount of trimer results which is likewise unde'irable. As indicated before, it has been found that these conditions can' be so balanced that an extremely effective polymeriza-* tion may be obtained with an acid height of 3 to 10 feet for the higher temperatures. indicated above, 200-500 FL, although it is preferred to provide from 5 to 11 feet and to use lower temperatures. This acid height, it will be understood,

reaction is to circulate the acid as shown in Fig. 1.

percentages of 3,4 dimethyl hexene 2.

The rate of flow of acid upwardly .through the reaction chamber proper is relatively slow and the hydrocarbon droplets rise quite rapidly through the acid. The flow of the acid is rapidly increased at. the top of the reaction vessel so that the reaction is substantially stopped when the mixture of acid and hydrocarbon leaves the reaction chamber by the'exit pipe. This effect may be enhanced by cooling the mixture as it is withdrawn and if desired the withdrawal pipe may be packed with acid-resistant shapes so as to assist the coalescence of the hydrocarbon. The actual separation occurs in the drum from which the acid is withdrawn for recirculation and the polymer withdrawn for recovery.

It has been found that by increasing the time of. contact by recirculation of a part of the polymer by means of line I 9 and pump 20, other conditions being the same, the yield of the codimer of iso and normal butylene is increased. Without such recirculation there is a substantial proportion of 2,2,4 trimethyl pentene formed, apparently by polymerization of isobutylene, but by recirculation this can be reduced and 2,2,3 trimethyl pentene substituted, apparently by the copolymerization of iso with normal butylene. At the same time such recirculation allows polymerization of normal butylene to form appreciable Under the optimum conditions 'of acid height, strength, temperature and rate of flow through the orifice, this expedient is not absolutely necessary in order to reach the theoretical codimer, but recirculation is desirable where optimum conditions are not employed.

. Example 1 To illustrate the operation of the present invention, an oleiine mixture consisting mainly of isobutylene and normal butylenes, the latter being in excess, was forced through a jet into the bottom of a bath of 60% sulfuric acid. The temperature of the bath was maintained at 225 F. and a total pressure of 400 lbs. per square inch was employed to maintain the olefine in liquid condition. These conditions are adapted toform copolymers of the isobutylene with normal butylene, and the most effective operation would be one in which a yield from 175 to-200%,

' based on the isobu ylene entering, is obtained olefine was forced in at different feed rates. In

the table below, the feed rate, velocity at the jet orifice, the yield of polymer based on the isobutylene originally present, are given together with the time of contact in minutes, estimated from the jet size, feed rate and the like. These times of contact were also checked against runs in which naphtha or o her like hydrocarbons were dispersed through acid in a glass vessel in which the operation could be put under direct observation The acid in the quiescent Yield based Jet Jet Contact diameter m mm 3 3?: velocity time Liters/tour Percent FL/uc Minute: 1 .018 4 22. 2 l. 11 2 .018 8 44.4 1. 7i 3 018 14 180 77. 7 l. 82

noted that the time of contact was only 1.1 min-' utes and the yield about 129% based on the isobutylene, which means either that the conversion per passwas low and that while some copolymer was produced, it failed by far to reach the theoretically possible quantity. Analysis of the exit gas showed that 90% of the isobutylene in the feed had been polymerized together with 19% of the normal butylenes.

In the second run, twice as much of the olefine was fed through the jet as in the previous run.

The velocity here was therefore twice what it was before, and rose above the critical velocity of about 40 feet per second. In spite of the fact that the rate of flow had been increased twice over the previous run,-the time of contact was also greatly increased due to the fact that very much smaller droplets were produced. There was substantially no continuous stream of they hydrocarbon and consequently very little coalescence. It will be noted that the yield of polymer rose to 160% based on the isobutylene. This increase is quite remarkable in that it is coupled with the fact that a more effective poly butylenes.

.closer to the theoretical copolymer.

'mer is obtained, that is to say, the polymerv is Analysis showed that 92% of the isobutylene was absorbed from the feed together with 33% of the normal The increased throughput is very noticeable, for example, the overall amount of polymer produced in the second run is about 2% times as much as that produced in the first run.

In the third run the rate is even higher and thevelocity is well within the preferred range. .It will be noted that the polymer is even more effective because it approaches even more closely the theoretical copolymer. Analysis shows that 94% of thuisobutylene is converted along with 40% of the normal butylenes. The total polymer produced under these conditionsis about five times as much per hour as is obtained under the slow rate of flow illustrated in Run No. 1.

Example 2 In the following experiments the same mixtures of iso and normal olefines were used as in the prior examples but a larger jet size was employed and the acid height was raised. As .be-

fore the temperature was 225 F., pressure 400 lbs. per square inch.

Table I Run Acid Yield on Jet veloc- No. J Glam height Feed rate isobutylene ity Inches Feet Liters/hr. FL/uc.

1 0. 023 6. 5 12 163 43. 2 2 0.023 3. 0 v 12 134 43.2 3 0. 023 6. 5 18 192 64. 8 4 O. 023 11. 0 18 201 64. 8 5 0. 023 3. O 24 156 86. 4 6 0. 023 6. 5 24 187 86. 4

' 7 O. 023 11. 0 24 191 36. 4 8 O. 018 6. 5 12 188 67. 2 9 O. 018 3. 0 12 180 67. 2

These runs show first that the '11 foot acid head is preferable to the 3 foot or 6.5 foot head. This is illustrated by comparison of Runs 1 to '7, although the improvement in the use of the 11 foot head over that obtained with the 6.5 foot head is not very large, With the smaller jet,.018

of normal bu ylene.

inch in'diameter, 6 feet of acid appears to be perfectly satisfactory.

Runs 4 and '7 should be particularly noted as they appear to employ the best combination of conditions. The polymer yield is very close to that theoretically obtained by copolymerization of isobutylene with normal butylene: moreover, the isobutylene was substantially completely converted to polymer.

Example 3 In order to further illustrate the eflect of the jet velocity, some further runs are included in the following table, beyond the ranges illustrated above.

To illus ratethe polymerization of a normal olefine by the above processes, thefollowing experiment was performed. The acid level was 3 feet in height at a temperature of 225 F. sulfuric acid was used and the feed comprised a liquefied butylene and butane. The feed contained about 18.1% of normal butylene with less 7 than 25% of isobutylene. It was fed in liquid s ate through the jets having a diameter of .018

inch at a rate of 15 liters per hour, which corresponds to a jet velocity of 53.7 feet per second.

The polymer produced amounted to 35.5% of the normal butylene contained in the feed and was based on an analysis of feed and exit products. The polymer consisted of about 86% dimer and 14% trimer, and began to boil at 79 F., 69%

distilled over at about 300 F. and in the distillation a recovery of 74% was obtained. The hydrogenated material had excellent blending value as an antidetonation agent.

Example 5 The following experiment was carried out to illus rate the process of copolymerizing olefines containing three and four carbon atoms.v The reactor was filled with 66% sulfuric acid at a temperature of 200 F., under 600 pounds per square inch of pressure. The jet had a diameter of .018 inch and the velocity of the liquefied hydrocarbon through the jet was 43.2 feet per second. The analyses of the feed and the exit materials were as followsi Fad I Exitgas Percent From these analyses it can be seen that 43% of the propylene present in the feed is extracted and converted to a polymer. 75% of the isobutylene present is likewise converted with 30% The product has a gravity of 55.0 A. P. I. and began boiling at 123 F.; at 335 F.; the aniline point was 34 F.; color 14% (R). 'From the distillation curve it appears a great many individual hydrocarbons are pres ent, showing a large number of combinations of the-propylene with butylene and isobutylene.

In subsequent experiments with various sized jets, it is foundthat a minimum acid height of 3 to 5 feet and a maximum of about 10 to 12 feet is preferable, especially for polymerization of isobutylene or copolymerization of iso with normal trace of isobutylene escapes in the exit liquor and the polymer itself contains less than 10% of trimer.

The present invention is not to be limited to any 7 theory of the operation nor to the reactions involved therein, nor to any particular acid strength, temperature, or the like, but only to the following claims in which it is desired to claim the invention as broadly as the prior art permits.

We claim:

1. In a process for polymerizing liquefied normally gaseous olefines by means of sulfuric acid to form polymers suitable for motor fuels, the steps of maintaining a bath of sulfuric acid at polymerizing strength and temperature, forcing the olefine mixture in a liquefied state into the lower part of the acid bath through a minute diameter orifice at a velocity in excess of 40 feet per second, whereby the liquid olefine is dispersed in small droplets throughout the acid, permitting the droplets to rise through the acid, the height thereof being adapted to provide time for a substantial reaction of the oleflnes, then separating hydrocarbons from the acid and recovering the polymer.

2. In a process for polymerizing liquefied normally gaseous olefines by means of sulfuric acid to form polymers suitable for motor fuels, the steps of maintaining a bath of sulfuric acid at polymerizing strength and temperature, forcing the olefine mixture in a liquefied state into the lower part of the acid bath through a minute diameter orifice having an orifice size within the limts of 0.01 and 0.15 inch at a velocity in excess of 40 feet per second, whereby the liquid olefine is dispersed in small droplets throughout the acid, permitting the droplets to rise through the acid, the height thereof being adapted to provide time for a substantial reaction of the olefines, then separating hydrocarbons from the acid and recovering the polymer.

3. In a process for polymerizing liquefied normally gaseous olefines by means of sulfuric acid to form polymers suitable for motor fuels, the steps,of maintaining a bath of sulfuric acid at polymerizing strength and temperature, forcing the olefine mixture in a liquefied state into the lower part of the acid baththrough a minute diameter orifice having an orifice size within'the limits of 0.01 and 0.15 inchat a velocity in excess of 40 feet per second, whereby the liquid olefine is dispersed in small droplets throughout the' acid, permitting the droplets to rise through the acid, the, height thereof being at from about 3 feet to 10 feet when measured in the quiescent state, then separating hydrocarbons from the acid and recovering the polymer.

' 4. In a process for the polymerization of a mixture of isoand normal olefines to produce polymers suitable for motor fuels, the improved steps which comprise maintaining'a bath of sulfuric acid at polymerizing strength and temperature within the range of 50-80% and 200-300 F., re-

spectively, forcing the olefine through a jet of from 0.01 to 0.15 inch in diameter at a rate in excess of 40 feet per second and providing a height of acid from about 3-10 feet when measured in a quiescent state, then separating the hydrocarbon from the acid and recovering the polymer from the hydrocarbon.

5. A process according to claim 4 in which the sulfuric acid is passed at a slow rate upwardly through the reaction zone, the mixture of acid and hydrocarbon withdrawn rapidly from the reaction zone into a separation zone, and in which the acid is recirculated from the separation zone i to the reaction zone.

6. In a process for polymerizing liquefied normally gaseous olefines by means of sulfuric acid to form polymers suitable for motor fuels, the step of maintaining a ,bath of sulfuric acid at polymerizing strength and temperatures, forcing the olefine mixture in a liquefied state into the lower part of the acid bath through a minute diameter orifice at a velocity in the range from about 40 feet to feet per second, whereby the liquid olefine,

is dispersed in small droplets throughout the acid, permitting the droplets to rise through the acid,

the height thereof being adapted to provide time,

for a substantial reaction of the olefines, then separating hydrocarbons from. the acid and recovering the polymer. i

7. In a process for the polymerization of a mixture of iso and normal olefines to produce polymers suitable for motor fuels, the improved steps which comprise maintaining a bath of sulfuric acid at polymerizing strength and temperature within the range of 50 to 80% and 200 to 300 F., respectively, forcing the olefine through a jet of from 0.01 to 0.15 inch at a ratein the ranged from 40 feet per second to 150 feet per second and providing an acid height of from 3 to 10 feet when measured in a quiescent state, then separating the hydrocarbon from the acid and recovering the polymer from the hydrocarbon.

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