US2263266A - Process of manufacturing motor fuel - Google Patents

Description

Patented Nov. 18, 1941 William E. Forney, Merchantville, N. J., assignor, by mesne assignments. to Cities Service Oil Company, New York, N. Y., a corporation of Pennsylvania Application February 19, 1936, Serial No. 64,671

4 Claims.

This invention relates to the manufacture `of an improved motor fuel product and more particularly to a blending composition adapted to improve the anti-knock qualities of motor fuel or gasolines poor in this respect.

For a number of years past, the demand for high anti-knock motor fuels has been increasing and the petroleum renner has been constantly improving the octane value of the gasolines produced. However, in almost every instance an improvement in the anti-knock character of .the Y gasoline has resulted in the lowering of its ,end point. The higher boiling paraffin hydrocarbons have been found to have lower octane ratings than the lower boiling paraffin hydrocarbons.I It has therefore been necessary to eliminate higher boiling fractions from the gasolines marketed because of the necessity of obtaining a certain specified octane rating,

The refining of cracked gasoline has also materially changed in recent years because of the necessity of avoiding the lowering of the octane rating of the gasoline through treating. Formerly it was the usual practice to renne cracked gasolines with concentrated sulfuric acid, but it is now a recognized fact that sulfuric acid treatment, particularly in the old type agitators, materially lowers the octane Value of the resulting gasoline. Cracked gasolines are therefore now refined to a large extent by treating them with certain agents such as fullers earth and similar adsorbtive materials to avoid as far as possible the destruction 'of the desirable anti-- knock constituents which in most cracked gasoline depends upon its content of unsaturated olefinic hydrocarbons.

The higher boiling hydrocarbon fraction however, which formerly went into the motor fuel product is now eliminated by a fractionating operation and either returned to the 'cracking unit or used as fuel oil.

The primary object therefore of the present invention is to provide a method of refining cracke'd gasolines in order to avoid the necessity of eliminating the heavier constituents which normally should be in the gasoline in order to tion of relatively high 4octane value suitable for blending with straight run gasoline or other rel atively low octane motor fuel.

Accordingly the present invention relates to certain improvements designed to refine the crude cracked gasoline received from the cracking unit by bringing the same into intimate contact with concentrated phosphoric acid under 1such temperature and pressure conditions as to eliminate undesirable gum-forming constituents and at the same time actually increase the octane rating of the gasoline. 'I'he invention also includes the production of a relatively high octane blending product of high boiling point which is particularly adapted for blending with straight run gasoline or natural gasoline to increase the octane rating of the final blend. A further feature of the invention involves the contacting of unsaturated hydrocarbon gases with concentrated phosphoric acid under controlled temperature and pressure conditions to produce a polymerized product of unusual value as a motor fuel, or for blending with relatively low octane gasolines. V Y

Other features and objects of the present invention will be apparent to those skilled in the art from the following more detailed description taken in connection with the accompanying ,drawing in whichi The single figure is a diagrammatic flow sheet showing a combination of apparatus elements particularly adapted for carrying out the improved process of the present invention to propass upwardly in intimate contact with the phosphoric acid maintained in each tray. The concentrated phosphoricl acid used in the tower 4 is introduced through a valved line B, preferably after being heated to a temperature equal to that of the incoming vapors. The refined gasoline vapors treated in the tower 4 are discharged through a vapor line 8 and conducted through one or more valved connecting lines l0, into the lower mid-portion of a bubble plate fractionating tower I2, in which the vapors are fractionated for the purpose of eliminating any undesired high boiling constituents and to give the gasoline the desired end boiling point according to market specifications.

The hot phosphoric acid which is preferably about 85% acid in passing downwardly through the treating column il polymerizes the extremely unsaturated hydrocarbons such as diolenes, as well as'some of the normal olefines. The resulting polymers have been found to compriselnot only the aliphatic hydrocarbons, but to include substantial proportions of naphthenic and aromatic hydrocarbons. The higher boiling polymers produced in column 4 are condensed and flow downwardly through the tower with the phosphoric acid. The phosphoric acid also reacts with olenes contained in the gasoline vapors to form 'certain amounts of alkyl phosphate compounds. The liquid mixture reaching the bottom of the tower d is withdrawn therefrom through a valved line I8 into a separator I6, in which the oil` constituents are separated from thephosphoric acid .and dissolved alkyl phosphates. )if the acid mixture in the tower 4 should become too viscous because of the concentration of the phosphoric acid, a small proportion of steam may be introduced through the line 2. However, at the temperatures used in the tower 4l, very little water is lost from the acid and in no case has the acid mixture been concentrated enoughto affect its flow downwardly through the tower.

The partially spent phosphoric acid and dissolved alkyl phosphates are withdrawn from the separator i6 through aline I8 and all or any desired portion thereof may be withdrawn to storage through a valved line 20, or passed to a suitable apparatus for recovering the alkyl phosphates, or used for the manufacture of alcohols or other organic compounds. A portion of the partially spent acid withdrawn through the line i8 may be conducted through a line 22, a pump 24, and a valved line 28, which serve to reintroduce the partially spent acid back into the tower through the line 6. The acid may be introduced into the mid-portion of the tower instead of the top of the tower by using the valve connecting line 28. used in the top of the tower since the excess water will be removed with the vapor.

Certain gasolines may contain abnormally high proportions of unsaturated hydrocarbons or for some other reason may require a milder treatment than other gasolines. Therefore the phosphoric acid introduced through the line 6 may be modified by adding thereto some of the spent acid from separator I6. It has been found that alkyl phosphates (both the acid and the neutral phosphates) are very effective refining agents for certain types of cracked gasoline. By reintroducing these constituents into the top of the tower` the refining agent in the tower 4 may be controlled very accurately. In the treatment of some gasolines, it is particularly desirable to give it a mild initial treatment in order to polymerize, react with, oI stabilize very unstable compounds, and therefore provision is made for reintroducing the alkyl phosphates into the midportion of the tower 4 so as to independently control the composition of the treating material in the tower 4 and particularly in the lower half of the tower where it first contacts the fresh raw gasoline vapors.

Diiute recovered acid may be- The separator I6 may comprise any suitable 75 type of apparatus such as a gravity separator or a centrifugal separator. The partially spent acid and alkyl phosphates conducted through the lines I8 and 22 may be brought to any desired temperature for reintroduction into the column 4 by passing all or any portion thereof through a valved line 30 and conducting it through a heat exchanger 32 and back into the line 26. Ordinarily the acid passing through the line 30 may need to be heated in order to bring it to the desired temperature, but on the other hand, it may be cooled if for any reason the temperature of the acid discharged from the bottom of tower 4 has been heated too highly by the hot vapors introduced through the line 2.

The polymer oil separated out in the separator I6 which may comprise from 1% to 5% of the gasoline treated in the tower 4 is passed through a valved line 34 into a washer 36 in which the oil may be washed with water or an alkaline solution introduced through a valved line 38. An alkaline solution is preferred since it effectively removes any occluded acid constituents. The wash water or alkaline solution is withdrawn from the washer 36 through a valved line 40, while the refined oil is withdrawn through a line 42. This polymer oil withdrawn through the line 42 has been found to be a very unusual product because according to known practices it would have a relatively low octane rating and be entirely unsuited for use as a motor fuel. However, it was found on testing this product that it contained substantial proportions of aromatic hydrocarbons and that it had a relatively high octane value. .In one particular instance, this polymer oil had a boiling range of from 310 to 486 F., a gravity of 34.7 A. P. I., and when blended in equal parts with Seminole straight run gasoline having an octane number of 50, it raised the octane number of the blend to 61.

The above described operation may be modifled to the extent that hydrocarbon gases,'pref erably gases comprising principally propylene, the butylenes and pentenes, are introduced into column 4 through a line 44, and subjected to the treatment of phosphoric acid along with the gasoline vapors f However, these and similar gases may be treated alone in column 4 with phosphoric acid, but the yield of polymer withdrawn with the phosphoric acid will be substantially lower. The contact of the unsaturated gaseous hydrocarbon with phosphoric acid and alkyl phosphates in column 4, particularly under pressures of from 250 to 350 pounds per square inch effects a substantial polymerization to normally liquid constituents containing appreciable quantities of aromatic and naphthenic hydrocarbons. Most of these normally liquid constituents however will remain in vapor state in the column 4 and pass through the lines 8 and I0 into the tower I2. The same thing is true in the treatment of cracked gasoline in column 4, since substantial polymerization of the lower molecular weight hydrocarbons in the gasoline increases the proportion of aromatic and naphthenic constituents which pass over with the vapors through the line 8. These results have been verified by the fact that the gasoline taken overhead through the line 8 has a substantially higher octane rating than the gasoline introduced into the tower 4 through the line 2. In a particular instance, it was noted that the aromatic hydrocarbon content of the gasoline treated in tower 4 had increased approximately 7%.

aaoaioc from-the. column 4.through the line 8V have the` proper end pointy desir-ed lfor thegasoline, the use of the columnv I2 may be entirely dispensed with,

' `but ordinarily the Vgasoline lmustloe made for a particular market condition `or for a `particular season,so thatin order to give it theproper de- .sired .end point it is subjected to fractionating `'in column I2. -v This column is provided with the coil 46 for maintaining the desired bottom ternperature and temperature gradientin the column; The desired .gasoline fraction is taken overhead from the column I2 through a vapor line 48 to:- gether with any uncondensible gases. This mix? ture is passed'. through a condenser 50 in which,

the gasoline is condensed and thereafter con- A.gases such as cracking still gases and coke oven gases, a recovery of `from 3 to 7 gallons of condensate per thousand cubic feet of gas is obtained, depending upon the unsaturated hydro- 5 carbon `content of the gas. Some 'of thematerial polymerizes to relatively high boiling constituents in the treating column 4, while the lower boiling polymers pass on to the column. I2 and con-v N Y i'lenser-5I'I.` All of the liquid products obtained usual bubble captrays and with a steam heating from the treatmenty of gases 4with the phosphoric separator 54.` Y 'I'he uncondensible'gases separated column I2 may be automatically regulated in` accordance with well-known practices. Apressure substantially equal to that in tower 4 may be held in tower I2 but 50 pounds is usually sufficient.

The final gasoline product recovered in receiver 54 is withdrawn through a valved line 64 into a washer 66 in which it is washed with water or of untreated cracked gasoline and of the treated gasoline made in accordance with the process of ,the present invention,a cracked gasoline containing 18.2% unsaturates; 22.5% aromatics; 36.8% naphthenes; and 22.5% paraiilns, when f treated with phosphoric acidQin accordance with thepresent invention showedan increase in the aromatic hydrocarbon content to 29.5% and from the base of the column,-

alkaline solution introduced through a valved line 68. The spent solution is withdrawn from the washer through a valved line l0, while the p final product is'withdrawn .through a valved line l2. This product may be sent directly to storage or market, or blended with some ofthe higher boiling products produced in the process by passing it through valved lines 14 or 14 and 16, which respectively discharge into blending tanks lI8 and 80.

The heavy naphtha recovered in the base of the tower I2 is not returned to the cracking unit in accordance with the usual practice. It is a very valuable blending stock because of its relatively high content of naphthenic and aromatic hydrocarbons. It particularly contains substantial proportions of branched chain aliphatic and aromatic hydrocarbons which were produced in the column 4 by the action of the phosphoric acid. This heavy blending naphtha is withdrawn from the tower I2 through a valved line 82 and washed in a washer 84 with water or alkaline solution introduced through a valve line 86. The

wash liquor is discharged through a valved lin'e product discharged from the washer 36 throughthe line 42 may .be used as a heavymotor fuel' or conducted through valved lines 96 or v96 and 98 respectively`;=into blending tanks 'I8 and BIJ.` Straight run gasoline or natural gasoline may bev introduced into the blending tanks 'I8 and 80 decrease in the unsaturates to 12.3%.

As a further example of the anti-knock character of the polymer product recovered from the tower 4 a vapor phase gasoline was treated in Vthis-column and the residuc was recovered This residue or polymer oil was redistilled and a heavy naphtha distillate having a gravity of.29.5 A. P. I., and a boiling range of 252 F. to 54Q$, F. was recovered.

A This distillate was blended lequal proportions with a 350 F. end point straight run Pennsylvania gasoline of 51 octane number (by C. F. R.

respectively through valved lines IUI) and |02 to give the desired blends having the proper' initial boiling point andoctane number.

In the treatment of unsaturated hydrocarbon.

motor method). The resultingblend by the same test engine had an octane number of 63.7.

In the treatment of cracked gasolines in the tower i, it is unnecessary to use high pressures. but pressures of approximately 50 lbs. have given satisfactory results. In the treatment of unsaturated hydrocarbon gases however, a high pressure of from 250 to 350 lbs. per square inch gives a longer time reaction and facilitates the polymerization or reactions taking place in the tower 4. The term polymerization may not accurately define the reactions taking place between the unsaturated hydrocarbons and the phosphoric acid, because it is'undoubtedly true that the acid ,enters into the'reaction in many [in the presence of other unsaturated hydrocarbons produces constituents such as naphthenes, branched chain aliphatic and aromatic hydrocarbons, and other products which have superior anti-knock properties.

-1 The reactions carried out in the tower 4 may be effected in the liquid phase by suitably ad- I Justing the temperature and pressure relationship of the constituents introduced thereinto through the lines 2 and 44. -In this vcase only the very heavy hydrocarbons which 'may dissolve in the acid mixturewill be carried out". through the line I4. Practically all of the liquid hydrocarbons 7d will be carried` overhead through the line 8 into the tower I 2 in which the very heavy constituents `used to make up the heavy blendingstock will be separated and withdrawn throughthe line 82.

From the foregoing description i o1' the present invention, it is apparent that certain modiicatons may be made in the operation without departing from the scope thereof. For example, the blended products formed in the blending tanks 'I8 and 80 maybe varied to suit particular conditions, according to the dmands of the market or the particular motor in which the fuel is to be used. In any case, it is apparent that considerable advantage is obtained from the process and that normally waste products or substantially valueless products are converted into products of superior quality.

Having thus described the invention in its preferred form, what is claimed as new is:

1. The process .of manufacturing a high antiknock motor fuel product which comprises passing a hydrocarbon mixture containing substantial proportionsof unsaturated oleflnic hydrocarbons through a zone in intimate contact with phosphoric acid, maintaining a temperature of approximately 375 F. in said zone and a superatmospheric pressure whereby portions of said hydrocarbons are converted into constituents condensable under the conditions obtaining in said zone, withdrawing a liquid oily product formed in said zone therefrom and Washing the same to remove any acidic constituents, and blending the resulting washed'oil with a low octane motor i'uel to substantially increase the octane rating of the low octane motor fuel.

2. The process defined by claim 1 in which the said hydrocarbon mixture is passed in intimate contact with phosphoric acid and a substantial proportion of alkyl phosphates.

3. The process defined by claim 1 in which said mixture of hydrocarbons includes normally gaseous unsaturated hydrocarbons.

4. The process of manufacturing a blendingV stock of high anti-knock properties for blending with poor gasolines, which comprises passing gasoline hydrocarbons containing a substantial proportion'of unsaturated qienic and aromatic constituents together with a mixture of normally gaseous oleflnic hydrocarbons in intimate contact with concentrated phosphoric acid maintained at a temperature of approximately from 300 to 475 F. in a reaction zone whereby a liquefied polymer oil product is formed, discharging the treated gasoline vapors from said reaction zone as a. refined gasoline product, withdrawing said liqueiied product from said reaction zone and washing the same with an alkaline solution to produce said blending stock, and blending the same with a gasoline motor fuel having an octane number of approximately in a proportion sufiicient to provide a. blended product having an octane number in excess of 60.

WILLIAM E. FORNEY.

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