Process for the manufacture of pour depressant
US 3126364 A
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March 24, 1964 s. ILNYCKYJ- 3,126,364
V PROCESS FOR THE MANUFACTURE 0F POUR DEPRESSANT Filed May 16. 1961 BENZENE Stephan llnyckyj Inventor BY WNW Patent Attorney United States Patent 3,126,364 PROCESS FOR THE MANUFACTURE OF POUR DEPRESSANT Stephan Ilnyckyj, Sarnia, Ontario, Canada, assignor to Esso Research and Engineering Company, a corporation of Delaware Filed May 16, 1961, Ser. No. 110,423
10 Claims. (Cl. 260-873) The present invention is concerned with the manufacture of improved pour depressants, particularly for use with middle distillates. The pour depressant of the present invention comprises copolymers of ethylene with up to about 50% by weight of an olefinicially unsaturated aliphatic monomer containing from about 3 to 5 carbon atoms per molecule. The copolymers of the desired molecular weight are obtained by controlling the conditions of reaction. The preferred copolymer of the present invention is a particular copolymer of ethylene and vinyl acetate.
The present application is a continuation-in-part of Serial No. 1,838, filed January 5, 1960, entitled Process for the Manufacture of Improved Pour Depressants for Middle Distillates, inventor: Stephan Ilnyckyj.
With the increase in the use of hydrocarbon fuels of all kinds, a serious problem has arisen in areas frequently subjected to low temperatures in the cold test characteristics of fuels. Particularly, serious problems have been encountered with heating oils and diesel and jet fuels that have too high a pour point, resulting either in distributional or operating difficulties or both. For example, the distribution of heating oils by pumping or syphoning is rendered difficult or impossible at temperatures around or below the pour point of the oil. Furthermore, the flow of the oil at such temperatures through the filters cannot be maintained, leading to the failure of the equipment to operate.
Also, the low temperature properties of petroleum distillate fuels boiling in the range between about 250 and about 750 F. have attracted increasing attention in recent years because of the growth of market for such fuels in subarctic areas and because of the development of turbo-jet aircraft capable of operating at altitudes where temperatures of -50 F. or lower may be encountered.
It is, therefore, an object of the present invention to set forth an improved process for the manufacture of very effective pour depressants for middle distillates and lighter oils. In general, these oils boil in the range from about 250 to 750 F.
it is a still further object of the present invention to provide heating oils, diesel fuel oils, kerosines and jet fuels having low pour points. Aviation turbo-jet fuels in which the polymers may be used normally boil between about 250 and about 550 F. and are used in both military and civilian aircraft. Such fuels are more fully defined by US. Military Specifications MILF- 5624C, MILF25554A, MILF255S8A, and amendments thereto. Kerosines and heating oils will normally have boiling ranges between about 300 and about 750 F. and are more fully described in ASTM Specification D396-48T and supplements thereto, where they are referred to as No. 1 and No. 2 fuel oils. Diesel fuels in which the polymers may be employed are described in detail in ASTM Specification D-975-53T and later versions of the same specification.
The process of the present invention produces copolymers of ethylene and up to about 50% by weight of an olefinically unsaturated aliphatic monomer containing from about 3'to 5 carbon atoms per molecule. In general, these compounds may comprise vinyl acetate, vinyl propionate, methyl methacrylate, allyl ethyl ether, divinyl ether, acrylonitrile, vinylacetonitrile and the like.
3,126,354 Patented Mar. 24, 1964 The preferred copolymers comprise ethylene-vinyl acetate copolymer. It is preferred that the parts by weight of ethylene in the copolymer be in the range from about 60 to 99% as compared to parts by weight of vinyl acetate in the range from about 40 to about 1%. A very desirable ethylene vinyl acetate copolymer contains about 15 to 35% by weight of vinyl acetate, as for example, about 30-32 parts by weight of vinyl acetate.
The molecular weights of the ethylene-vinyl acetate copolymer are critical and should be in the range from about 1,000 to 3,500, preferably in the range from about 2,000 to 3,000. The molecular weights are determined by K. Rasts method (Ber. 55, 1051, 3727 (1922)).
The ethylene-vinyl acetate copolymer as described above is used in a concentration in the range from about .001 to 0.2% by weight, preferably in a concentration in the range from about .005 to .1% by weight.
In accordance with the present invention, the polymerization process is conducted in a solvent comprising benzene saturated with water. The initiator comprises any peroxy compound, preferably di-tertiary-butyl-peroxide. The temperature of the polymerization reaction is in the range from about 280 to 340 F. A very desirable temperature is about 300 F. The pressure is in the range from about 700 to 2,000 pounds, preferably 800 or 900 pounds. The autoclave or similar equipment containing the solvent, initiator and vinyl acetate is purged with nitrogen, then with ethylene before charging With a sufiicient amount of ethylene to yield the desired pressure when heated to the reaction temperature. During the polymerization, additional ethylene is added to maintain the pressure at the desired level. Polymerization is considered complete when the pressure drops less than 50 p.s.i.g. per hour. The product is stripped free of solvent and unreacted vinyl acetate under vacuum.
In general, the manufacture of the copolymer of the present invention is carried out at a temperature in the range from about 280 to 340 F., preferably at about 300 F. The pressure is in the range from about 700 to 2,000 pounds for a time period of from 2 to 16 hours. The preferred pressure is in the range from about 800 to 1,000, preferably about 900 pounds. The preferred time of reaction is from about 2 to 6 hours. The concentration of the vinyl acetate in the benzene solution varies from 0.53 to 10%. i
A typical preferred method for conducting a polymerization of the present invention is illustrated in the figure. Referring specifically to the figure, reactor 20 is first purged with nitrogen, introduced by means of line 12 and pump 13. Reactor 20 is then purged with ethylene which is introduced by means of line 12 and pump 13. Gases are removed from reactor 20 by means of line 11. The reactor is maintained at a positive pressure in the range from about 50 to 100 pounds absolute.
Benzene saturated with water is introduced into reactor 20 from benzene storage 1 by means of line 6 and pump 5. Reactor 20 is then raised to a temperature of 300 F. by means of heating element 14 wherein a heating fluid or equivalent is introduced by means of line 15 and withdrawn by means of line 16. Reactor 20 is held at 300 F. during the course of the reaction by the removal of heat or by the addition of heat thereto. Ethylene is introduced by means of line 12 so as to raise the pressure of the reactor to about 900 pounds.
The addition of vinyl acetate and of di-tertiary-butylperoxide is started concurrently. The vinyl acetate is withdrawn from storage zone 3 and introduced into the reactor by means of line 10 and pump 9. Approximately 55 parts by weight of vinyl acetate is added over a two hour period. The peroxide is introduced by passing benzene into storage zone 2 by means of line 4 and then introducing the solution into the reactor 20 by means of Cr line 8 and pump 7. Approximately 5.5 parts by weight of peroxide are combined with 16.5 parts by weight of benzene. The resulting 22 parts by weight of peroxide solution in benzene is added to reactor 20 over a three hour period.
After the addition of the peroxide has been completed, the reactor is held for an additional one-half hour at a temperature of about 300 F. The ethylene is added continuously so as to maintain the pressure at about 900 pounds. In operation, approximately 934 parts by weight of vinyl acetate are used in conjunction with from about 2,800 to 3,800 parts by weight of ethylene.
At the end of the reaction, the reactor is allowed to cool to about 160 F. and the reaction product is then withdrawn by means of line 17 and passed into separation zone 18. Excess ethylene is removed overhead from separation zone 18 by means of line 19. The polymer product comprising the copolymer in a benzene solution may be withdrawn by means of line 22 and further handled as desired. Under certain instances, it may be desirable to separate at least a portion of the benzene from the copolymer. Under these conditions, the benzene copolymer product is passed to separation zone by means of line 21. Benzene is removed overhead by means of line 24, while a copolymer product is withdrawn by means of line 23.
The quantity mentioned above may be somewhat varied. For example, based upon 55 parts by weight of vinyl acetate, the amount of benzene utilized may vary from about 180 to 300 parts by weight, and the amount of ditertiary-butyl-peroxide may vary from about 3 to 8 parts by weight. Also as mentioned, the amount of ethylene utilized varies from about 2,800 to 3,800 parts by weight, or approximately 938 parts by weight of vinyl acetate. The time of reaction also may be varied from about 2 to 4 hours, depending upon other operating variables.
An operation was carried out wherein copolymers were produced under conditions as described except that, in one operation, a dry benzene solvent was used and in a second operation, benzene saturated with water was used. These copolymers were then tested as pour depressants in a blend of virgin gas oil and a catalytically cracked gas oil having an ASTM pour of +20 F. The virgin gas oil boiled in the range from about 350 to 700 F., and the cracked gas oil boiled in the range from about 350 to 650 F. As pointed out heretofore, the critical factors with respect to producing desirable polymers are the molecular weights and the concentration of the vinyl acetate in the polymer. The results of these tests are shown in the following Table I:
TABLE I Copolymerization of Ethylene and Vinyl Acetate Conditions:
Pressure 900 p.s.i.g. Temperature: 300 F. Time: 3 hours. Ingredients:
Ethylene to maintain 900 p.s.i.g. pressure 300 ml. of vinyl acetate added over 2 hours 30 m1. of dit-buty1 peroxide added over 3 hours. 1290 m1. of benzene 50/50 blend of virgin and cracked gas oils.
What is claimed is:
1. Improved process for the manufacture of a pour depressant comprising a copolymer of ethylene and vinyl acetate which comprises reacting ethylene and vinyl acetate in a benzene solvent saturated with water at a temperature in the range of from about 280 to 340 F., and at a pressure in the range of from about 700 to 2,000 pounds for a time period of from about 2 to 16 hours under conditions wherein the concentration of the vinyl acetate in the benzene solution varies from about 0.2 to 10.0% and wherein the pressure is maintained within the desired range by the further addition of ethylene, whereby a polymer having a molecular weight in the range from about 1,000 to 3,500 is secured wherein the concentration of the vinyl acetate in the product will vary from about 1 to 40% by weight.
2. Process as defined by claim 1 wherein the time period is in the range from about 2 to 6 hours, wherein the temperature is in the range of from about 290 to 310 F., wherein the pressure is in the range from about 650 to 1,000 pounds, and wherein the concentration of the vinyl acetate in a benzene solution varies from about .53 to about 10%.
3. Process as defined by claim 1 wherein the reaction is initiated by a peroxy compound, di-tertiary-butylperoxide.
4. Process as defined by claim 1 wherein the reaction is carried out in an autoclave which is purged with nitrogen, then with ethylene and then charged with a sulficient amount of ethylene to yield the desired pressure when heated to the reaction temperature.
5. Process as defined by claim 1 wherein additional ethylene is added to the reaction mixture whenever the pressure drops by about p.s.i.g.
6. Process as defined by claim 1 wherein unreacted vinyl acetate is stripped under vacuum when the reaction is completed.
7. Improved process for the manufacture of a pour point depressant comprising a copolymer of ethylene and vinyl acetate which comprises introducing a solvent for example benzene saturated with Water into a reaction zone, thereafter pumping ethylene into said reaction zone to create a pressure therein between 800 and 1,000 pounds and heating the reactor to a temperature of about 300 F., thereafter continuously adding vinyl acetate and ditertiary-butyl-peroxide to said reaction zone over a period of 2 to 4 hours and maintaining said zone under the conditions specified by the further addition of ethylene.
8. Process as defined by claim 7 wherein the pressure in said reaction zone is maintained at 900 pounds wherein the vinyl acetate is continuously added over about a two hour period and wherein the peroxide is added in a benzene solution saturated with water over about a three hour period.
9. Process as defined by claim 7 wherein approximately 220 parts of benzene are placed in said reaction zone wherein 55 parts by weight of vinyl acetate is continuously added and wherein about 5.5 parts by weight of (ii-tertiarybutyl-peroxide is continuously added.
10. Process as defined by claim 9 wherein said vinyl acetate is added over a two hour period and wherein said di-tertiary-butyl-peroxide is continuously added in a benzene solution over a three hour period.
References Cited in the file of this patent UNITED STATES PATENTS Hanford Mar. 19, 1946 Bartl Aug. 2, 1960 OTHER REFERENCES