US2173452A - Manufacture of high antiknock motor fuels - Google Patents

Description

Sept. 1 9, 1939. s. R. MERL'r-:Y

MANUFACTURE OF HIGH ANTIKNOCK MOTOR. FUELS Filed March 28, 1936 I Patented Sept. 19, 1939 UNITED STATES MANUFACTURE oF man ANTIKNooK Moron FUELSy Sylvan R. Merley, Riverton, N. ,.I., assignor to Power Patents Company, Hillside, N. J., a corporation of Maine Application March 2s, 193s, serial No. '21,378`

2 claims'. t (c1. 19e-40) This invention relates to the production of a improved high anti-knock motor fuel.' 'i The production of cracked gasoline as heretofore practiced has involved a step of chemical re- 5 lining of the cracked gasoline distillate with sulfuric acid followed by redistillation, to obtain a suitable product substantially free of undesirableV gum-forming constituents. The refining of cracked gasoline by sulfuric acid contact as herem tofore practiced results in a product .of lower anti-knock value by reason of the loss of desirable anti-knock constituents originally present in the untreatedf gasoline. .When other methods of refining cracked gasoline are substituted for the sulfuric acid method with a view of improving its anti-knock characteristics, the resulting product will be found to have a lower end point and a lower caloric value by reason of loss of higher boiling parafn hydrocarbon constituents -eliminated because of their lower octane ratings.

The primary object of the present method is to provide a method of treating cracked gasolines in order to improve their anti-knock Value without adversely affecting their calorifc value.

'25 A particular feature of the invention is a novel processof treating crude cracked gasolines with concentrated sulfuric acid under carefully regulated temperature conditions whereby a `motor fuel product results having a higher caloriiic value and a higher octane rating than the crude gasoline as received from the cracking unit.

A further feature of the invention involves treatment of a mixture of crude cracked gasoline and unsaturated hydrocarbon gases with concen- .35 trated sulfuric acid andrefning of the resulting products under-carefully controlled conditions to produce a good yield of high anti-knock motor fuel.

Cracked gasoline distillates as now produced 4'0 comprise a mixture of parainic lhydrocarbons together with substantial-proportions of mono, di, tertiary and more highly unsaturated olefins of different molecular weights. Treatment of such distillates `with concentrated sulfuric acidgprei. 45. sents diiculties which are not encountered'in treating individual olelns, particularly straight chain olefin's of`low`, molecular weight, both because of the diluting effect of the parain hydro` carbons and because of the highly reactivechar- 50. acter of the heavier mono-olefins and the di, tertiary and more highly unsaturated and unstable Aolens present. Particular attention has to be.v

paid'to such reaction conditions as'acid concentration and temperature control in order to in- 552 sure a commercially practicableyield of useful anti-knock motor fuel. The process of the present invention rests largely on the discovery that an operative process requires the use of sulfuric acid of 90%-96% concentration and contact temperatures of not to exceed 70 F. when treat- 5 ing crude cracked distillates in liquid phase in accordance with the method herein described. whereby continuous stage by stage polymerization of highly reactive and less reactive constituents is eiected in the presencel of unreactive l0 hydrocarbons, without substantial production of undesirable sulfur containing products or waste sludges.

Another important object of the inventionis` toprovide a method of treating cracked gasoline 16 with concentrated sulfuric acid so as to effect polymerization of unsaturated constituents while avoiding formation of undesirable sulfur-bearing rconstituents and large sludge losses.

With the above and other objects and features 20 in View, the invention resides in the improved method which is hereinafter described and more particularly deflned by the accompanying claims.

In the accompanying drawing a diagrammatic flow sheet illustrates a desirable apparatus .lay- 25 out for carrying out the process of the present invention.

Referring -to the drawing, Athe crude cracked distillate to be treated is pumped in liquid phase, at a temperatureof not to exceed 70 F. through 30 a valved line I0 into the bottom of a contact tower I2 and thence upwardly therethrough in intimate contact with concentrated (9D-96%) sulf uric acid in amount lslightly in excess of that required to react with the olefins inthe distillate. At the same time a stream of cracking still tail -gas is pumped into the bottom of Atower I2 carry suflicient reactive (olenic) hydrocarbons A tomake up between 25% and 50% of the total reactive hydrocarbons which are introduced to' the base of theytower I2 for treatment. Experience has also shown the advisability of limiting the hydrocarbon charge to the tower I2 to 55 not substantially exceeding 410 F. end point.

Cracking still tail gases have been heretofore .treated with concentrated sulfuric acid at low temperature for conversion of the oleilnic hy-V drocarbon constituents to alkyl sulfates, followed lby hydrolysis of the acid alkyl sulfates to produce alcohols. According to the present invention the unsaturated gaseous and liquid hydrocarbons are first contacted with the sulfuric acid at a time when such acid is diluted with a large amount of alkyl sulfates and liquid hydrocarbons, at a carefully regulated temperature in the 'close neighborhood of 70 F., at which temperature, with the acid concentration employed, a substantial proportion of the olens are polymerized moderately without .production of heavy. polymers (tar) .and avoiding formation of undesirable stable high sulfur compounds including disulfides.

To accomplish strict temperature and acid concentration control the concentrated (93%) 'sulfuric acid is introduced on the second tray below the top of tower I2 through a valved line I6 after passage through a cooler I6 in which the temperature of the acid is adjusted to approximately F. The tower I2 is designed similarly to the usual bubble cap tower or absorber, and as the concentrated acid passes downwardly from the top of the tower it first reacts with .oleiins of the type of. propylene and butylene to form acid alkyl sulfates. By the time the acid liquid reaches a' tray above the mid-section of the tower I2, it consists of a mixture ofV concentrated sul.- furic acid and allwl sulfates in which the acid alkyl sulfates predominate. As the acid alkyl sulfates pass downwardly through the absorber,

they react with additional oleilns to form normal or dialkyl sulfates; and as the concentrated sulfuric acid passes downwardly into the lower portion of the tower, it reacts with the alkyl sulfates and also with the more reactive unsaturated hydrocarbonsA to form aliphatic, naphthenic and aromatic polymers most of which have boiling points within the gasoline range. y

In order to regulate vthe temperature maintained on each tray of the tower l2 within narrow limits, the tower is equipped throughout its length for artificial cooling by cooling coils 20 which are mounted above each trayand through which brine-or other cooling liquid is circulated at controlled rates from valved supply pipes 22.

The olenic hydrocarbons react strongly with` sulfuric acid and acid alkylsulfates, and the re- `\actions are strongly exothermic, so that it is necessary to circulate cooling liquid through coils 26 in order to control the temperatures within the reaction tower at each part thereof to allow moderate, but not excessive, polymerization to take place.

As previouslyindicated, the tower l2 is substantially full of liquids during operation. The liquid and gaseous hydrocarbons entering the base of the tower iiow lupwardly and countercurrently to the saturated acid and alkyl sulfates 'which ow downwardly. To allow for this countercurrent flow, the bubbleplat 23 have short upstanding pipes 24 fixed therein through which the gaseous and liquid hydrocarbons pass up-V wardly. Pipes 24 are covered by bubble caps26 having slotted bottom edges under which the upwardly moving hydrocarbons are forced to pass into the heavier acid liquids on the upper surfaces tion of chamber 40.

'analisis of plates 23. Ihe heavy liquids pass downwardly Vthrough the tower by means of pipes 28 so arranged on the plates 23 that their upper ends serve as overflow weirs at the level at which it is desired to keep the heavy liquid on the trays. The lower ends of pipes 28 dip into the body of heavy liquid heldon plates below the plates to which the pipes are attached. A manifold 30 at one side of the tower is used to supply -cooling liquid to each of the cooling coils 20 through the valved pipes 22, and the cooling liquid is discharged from coils 20 through valved discharge pipes 32 into a manifold 34.

A partition 36 forms the bottom of the absorption tower l2', and the crude distillate and tail gases are introduced into the tower by a perforated ring 36 located immediately above partition 36. A separating chamber 40 is attached to the base 'of the tower below partition 36 within which takes place quiet settling and separation of acid and alkyl sulfates from liquid hydrocarbons. A

pipe 42 extendsthrough partition plate 36 and its upper end forms an overflow wei'r for the heavy liquid on plate 36, such overflow liquid passing downwardly through pipe 42 into the lower por- Upflow pipes 44 are also provided in plate 36 with their lower ends extending mto chamber 46 and their upper ends located above the level of pipe 42. Pipes 44 afford the means for returning liquid hydrocarbons to the absorption zone after\they have separated from the heavier acid liquids in chamber 40.

Chamber 46'is -provided with cooling coils 46 whereby to maintain a temperature therein corresponding to that obtaining on the lower plates of tower I2.

The mixture of gaseous and liquid hydrocarbons which isintroduced to the tower l2 from ring 36 comes immediately into contact with the heavier mixture of sulfuric acid and alkyl sulfates on plate 36. The acid liquid on plate 36 comprises largely acid alkyl sulfates and dialkyl sulfates, together with a smaller proportion (say 20%-25%) of unreacted concentrated sulfuric acid. At the temperature of approximately '70 F. obtaining at the foot of the tower the more reactive olens such as diolefins and tertiary oleiins .which are present in the entering crude distillate and tail gas, are immediately polymerized to higher boiling and more stable hydrocarbon products on contacting the concentrated acid at this temperature. Some of the unsaturated hydrocarbons (particularly straight chain oleiins) entering the tower combine with the sulfuric acid to produce the corresponding acid alkyl sulfate. Some more of the unsaturated hydrocarbons react with acid alkyl sulfates vto -produce dialkyl sulfates. Also at this temperature some of the mono and dialkyl sulfates are decomposed by heat and by contact with concentrated sulfuric acid, and the olens thus liberated are polymerized tohigher boiling stable hydrocarbons. Careful regulation of the temperatures in all zones of the tower is necessary in order to inhibit oxidation reactions between the reactive hydrocarbons and sulfuric acid, with resultant liberation of SO2 and metallic-sulfur and formation of hydrocarbon compounds containing sulfur in chemical combination.

The dialkyl sulfates are oil soluble as well as acid soluble. The monoalkyl sulfates are not oil soluble but they are soluble in dialkyl sulfates as 'formation of polymers.

and unsaturated hydrocarbons, pass upwardly through the tower, while, owing to'the diiference in gravity, the sulfuric acid passes downwardly. Some of thendlalkyl sulfatos are carried upwardly through a portion of the tower, but do not reach the top before they become separated from the oil because of the fact that the alkyl sulfates are more soluble in the acid than in oil. Acid alkyl sulfates such as propyl and butyl acid sulfates are formed high up in the tower b y reaction between the freshly charged sulfuric acid and the lighter straight chain oleflns. As the acid sulfates vflow downwardly into zones of gradually increasing temperature they absorb olens to form normal sulfates such as propylamyl and butyl-hexyl sulfates. As these normal sulfates flow downwardly through the tower they in `turn contact sulfuricacid and higher temperatures and are decomposed to produce acid sulfates, with liberation of. nascent olen-and Likewise the acid sulfates arein turn decomposed andpolymerization of the liberated olen takes place at the tem- I peratures obtaining in the lower portion of the tower.

The importance of maintaining a careful regulation of temperature gradient between about 30 F.-35 F. at the top of the tower to approximately 70 yat the .foot of the tower when treating a mixture of crude light cracked distillate and tail gaswith concentrated acid, canvnot be over-emphasized. Some variation in temperature 'and acid concentration might be permissible in treating a single hydrocarbon, as for example, isobutylene. but in treating a mixture of hydrocarbon such a's present in cracked distillate any material variation in temperature at any point in the tower may inhibit conversion of visobutylene to tri-butylene, for example. and in place thereof produce a mixed polymer with a highly reactive triple bond unsaturated hydrocarbons together with unabsorbed and uncondensed gases, including ethylene, leave the top of the tower I2 through the vapor line 48 and enter separator 50, where the fixed gas is separated from the liquid hydrocarbon and removed through the gas voitake 52. The liquid hydrocarbons are removed from the separator through a line 54, ported out on the opposite side of partition wall 56. Acid which is entrained in the liquid'hydrocarbon leaving the top of the tower I2 collects in tche bottomof separator 50 from whence it may be withdrawn through a line 58 and conducted back into the tower on a tray adjacent the top thereof.

The partially spent sulfuric acid and alkylv sulfates are removed from the separator 40 at thebase of the tower through a valved connection 60 into'al mixer 62. vAt the same time a cracked distillate lpreferably of approximately 400211'. end point, is pumped into the mixer f through line 84. By means of the mixing paddles .68 the charge of mixer 82 is intimately mixed while holding the temperature therein at a point approximating that maintained in separator 40,

by means of cooling coils 88. The distillate A which is added to the spent acid-alkyl sulfate mixture in mixer 82 serves the purpose of promoting rapid separation and extraction of any `liquid hydrocarbons., including polymers, whichv are entrained with the spent acid removed from separator 40. The temperature in the mixer is controlled to prevent any substantial polymerization. In some cases the distillate which is added to mixer 62 through line 64 may have to be of higher boiling point thanv gasoline in order to promote separation of heavy hydrocarbons entrained in' the spent acid. From mixer 62 the charge is conducted through a line 'l0 toa centriiugal separator 12 where the hydrocarbons are separated from the heavier acid-alkyl sulfate mixture, the hydrocarbons being removed from the separator through a line 14 from whence they are pumped into the-foot of a second acid contact tower 'I6 which duplicatesin its design the contact tower I2. While feeding liquid hydrocarbons from the centrifugal separator 12 to the foot of the secondary contactor 16 through line 14, gaseous hydrocarbons are simultaneously pumped into line 'I4 through line 18, which receives the gases from the line 52 leading oil? from the top of separator 50. Concentrated sulfuric acid is supplied to the second from the top tray of contactor 'I6 through cooler 80 and line 82. The liquid and gaseous hydrocarbons which leave the top of contactor 'I8 are conducted through line 84 into separator 50, while the spent acidalkyl sulfate mixture which is removed from k the separator at the foot of tower 'I6 is 'conducted to mixer 62 through a valved line 86. Secondary contactor 16 is substantially identical in design with'contactor I2, ,and its operation is substantially identical with the previously described operation of contactor I2 when practicing the process of the present invention.

'I'he mixture of spent acid and mono and dalkyl sulfates which is discharged from the centrifugal separator 'I2 is conducted by'a line 88 to a desulfating still 90. In this still the centrifuged acidis heated to a temperature of 250 F.350 F. by means of. superheated steam supplied through heating coil 92, and also by direct steam distillation by means of steam introduced through perforated steam inlet 84. In somepases tail gas from the process may be introduced into still 9ll-y quickly to higher boiling hydrocarbon polymers.

The vapors of the hydrocarbon polymers are removed from the still through a vapor line 96 and 'are conducted -into a scrubber'98 wherein the vapors are washed with caustic solution introduced through caustic supply inlet |00. The hydrocarbon vapors are condensed as well as being neutralized in passing through scrubber 9 8 and condenser |02, from whence they pass through valved line |04 into a separator |06. Any fixed gas which is not condensed is removed from the separator through gas outlet |08, and the washed oil leaves through I0, from which it is pumped through line I2 int'othe mid-zone ofa fractionating` column ||4. Condensed water land caustic isremoved from the separator |06 through valve drawof. IIS.

-which have been highly refined in towers I2 and 'I6 by washing with sulfuric acid land alkyl sul'- fates, in admixture with a large. proportion of crude' liquid polymers produced within'the towers by the polymerizing reactions previously described. This mixture, lwhich will be hereinafter through line referred to as crude polymer oil, is conducted by pipe 54 into and upwardly through a sand filter H8. Any sulfuric acid sludge which is cleaned therefrom' by passing through the filter, collects at the bottom of the lter, and is removed through draw-off |22. The thus cleaned polymer oil is' conducted by line |24 into an autoclave mixer |26 which preferably operates under pressure and is provided with heating coils |29 and a caustic supply inlet |30 for subjecting the oil to a strong caustic treatment for the removal of sulfur containing compounds including` oil soluble sulfuric acids. The caustic treated oilis withdrawn from the autoclave |28 into a separator |29 wherein gravity separation takes place, the caustic sludge being removed from the separator through drawoif |3|, while the treated light oil is conducted through oiftake line |32 onto one .of the middle trays of fractionating column I I4.

Fractionation and stabilization of the polymer oil taken off from the tops of-contact towers I2 and 16 and from the desulfator 90 is effected in tower |'4 by heat supplied through the-steam coil |34. The heavy fraction is removed from the base of tower ||4 to storage through drawoff |36, and the light oil vapors are removed from the top of the tower through vapor line |30 into the central zone of a rectifying column |40. The stabilized and rectified polymer oil is withdrawn from the bottom of column |40 to storage through a valved drawoif line |42, and any light gas and vapors removed from the top of the column through vapor line |44 are passed through condenser |46 and `separator |49, with return of `reflux through connection |50.

Certain crude cracked distillates may contain aA large proportion of highly unsaturated hydrocarbons or forsome reason require a milder or more drastic treatment than others. It is preferred that the operating temperatures for the contact towers |2 and 16 which have been specifled shall not vary substantially from the range .'7040 to 35 F., and that thesulfuric acid concentration at the top of the towers lies within the range 90%-96% acid. Therefore any variation inthe strength of treatment is 'preferably eifected by modifying the acid concentration in the middle. and lower portions of the towers by recirculation of spent acid and alkyl sulfates from the separators 40 at the base of each tower, as through connection |52 on tower 16.

Tests on the rened light polymer oil which is removed through line |42 show it to contain a substantial proportion of aromatic hydrocarbons and that. it has a high octane value. In one particular instance when charging the apparatus I0 with a low end point cracked distillate having an A. P. I. gravity of '19.2, an initial B. P. of y'73" FI, and a distillation curve with 10% over at 95 F.. 90% over at 204 F., and an end point of 285 F., a polymerized oil product was recovered having a boiling range of from 85 n F. to 485". F. with 90% over at 410 F., a grayity of 65.0 A. P. I., and a volume about 60% thatof the liquid disyrlate charged to the apparatus.

This light polymer. product Ihad an octane number of between 80 and'90, and a solubility in c cncentrated sulfuric acid of 28% as compared to 19% acid soluble components in the cracked distillate originally charged, showing a large increase `in the content of aromatic hydrocarbons.

' The treatment normally results in an increase in aromatic hydrocarbon content of.,about 33%. as

the :recovered light polymer oil and thel original crude cracked distillate treated. with a corresponding drop of about in the olefin content.

ously introducing a stream composed of a mixture of liquid hydrocarbons produced by cracking petroleum oil and containing parailinic and" primary, secondary, and tertiary olefinic hydrocarbons having a boiling range ,up to approxi-- mately 275 1?'. into the rst of a series of interconnected contact zones, introducing a stream of relatively cool concentrated sulfuric acid into the last of said series of zones. continuously passing said hydrocarbons and said sulfuric acid through said zones counter-current to each other and in intimate contact with each other in each zone. maintaining the first zone of the series at atemperature of about '10 F. and the last zone of the series at a temperature of about 30 F. whereby reaction products formed between said hydrocarbons and said sulfuric acid in the last zone of the series are carried with the acid toward the rst zone of the series and subiected to gradually increasing temperatures thereby converting portions of said oleilnic hydrocarbons into higher boiling products of relatively high octane number, and removing an improved high antiknock motor fuel product from the last zone of the series.

2. In the process of manufacturing a high antiknock motor fuel in which a continuous 'stream of cracked gasoline material. and gaseous olefinic hydrocarbons are subjected to the 'polymerizing action of concentrated sulfuric acid, the improvement which comprises said stream of cracked gasoline and oleilnic hydrocarbon gases upwardly through a contact zone in countercurrent intimate contact with a stream of concentrated sulfuric acid introduced into the upper` part of said zone and acid reaction products resulting from said contact, maintaining a temperature of about F. at the lower end of said zone and about 30 1". at the upper end of said zone, whereby acid reaction products are formed in the upper part of said zone and carried downwardly therethrough to react with the unsaturated hydrocarbons ,introduced into the lower part of. said zone, removing the sulfuric acid residue material from the lower part of said zone and a' liquid hydrocarbon product containing poly- 'merized hydrocarbons from the upper part of ing said stream of cracked gasoline containing the extracted polymerized hydrocarbons removed `from said sulfuricacid residue with the liquid hydrocarbon product removed from the upper part of said zone to produce said high anti-knock motor fuel. i

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