US2001907A - Treatment of motor fuel - Google Patents

Description

May 21, 1935- v. IPATIEFF TREATMENT OF MOTOR FUEL Filed Oct. 276, 1932 .NWUWWQWN NN Nw *m MM, Sm A Wm, M MM EW RWM, NW A QM. W @1N m@ e 5min QN Nm. RNHRUBRW AN QN Qwwm bw, AN DMW *N Patented May 2l, 1935V UNITED sTATEs PATENT v"OFFICE versal Oil Products Company,

Chim. lll.. s

corporation of Delaware Application October 26, 1932, Serial No. 839,618

2 Claims.

This invention relates to the treatment of motor fuel and refers more particularly to the treatment of gasolines produced in the normal or straight run distillation of crude petroleums though similar hydrocarbon fractions produced as a result of the pyrolysis of heavy hydrocarbons or from other sources may also be treated.V

More speciilcally, the invention is concerned with a process for increasing the quality of gasolines in respect to their anti-knock value, though other desirable refining effects in the direction of improved color and gum content are concurrently produced. To eiect these desirable objects use is made of both decomposition and synthetic reactions so that the chemical nature of the gasoline is altered.

Owing to the adoption of high compression ratios in automobile engines to increase their thermodynamic efficiency, a demand has been made upon the petroleum refining and other industries which furnish hydrocarbon motor fuels, for fuels of a high anti-knocking or slow burning character.

According to the process of the present invention gasolines produced either by straight distilling methods or by cracking operations upon relatively high boiling oils are subjected first to a controlled pyrolysis which is followed by a step in which certain of the products of the pyrolysis are caused to enter into new chemical combinations which produce compounds of higher antiknock value and conserve to a large extent the gaseous products of the crackingl reactions. Other incidental improvements will be mentioned as the invention is described in detail.

In one specific embodiment the invention comprises first cracking gasoline hydrocarbon fractions to increase the content of olefinic and cyclic hydrocarbons and then causing the chemical combination of olefins and the other hydrocarbon products particularly the gaseous products produced by cracking in the presence of sulphuric acid. E

It is recognized that the cracking or so called reforming of gasolines to increase their antiknock value is already'known in the art. However, in such operations there must always be an economic balance between the loss of suitable boiling range material and the increased value of the product from an anti-knock standpoint.

According to the present invention it is still economical to subject gasolines to such intensive conditions of cracking as, for example, temperatures of 975 to 1050 F., since a large portion of the oleiins which are ordinarily lost in the gases or treated out of the liquid fractions to insure their stability, are utilized to form new ccmpounds with the aromatic and other reactive cyclic hydrocarbons.

The reactions involved when olefinsn are reacted with cyclic hydrocarbons according to the second stage or the treatment are essentially similar to those between oleflns and aromatics and as a typical example of this type of reaction those which occur between propylene and benzol in the presence of sulphuric acid at moderately low temperatures may be cited. While such relatively low temperatures such as, for example C., may be desirable and a part of the invention, temperatures on either side of this point may be employed according to the results desired. Temperatures which have been employed in some cases with good results are comprised within the approximate range of 40 C. to +10 C. When gaseous propylene is passed into a well stirred mixture of benzol and concentrated sulphuric acid in proper proportions, the main product is mono-iso-propyl benzol according to the following reaction:

C3H+CHs=CsHsC3Hz Propylene Benzol Mono-iso-propyl benzol There may be also produced concurrently a limited yield of di-iso-propyl benzol according to the following equation:

2C3Hs +CsHc=CsH4- (03H7) z Propylene Benzol Di-iso-propyl benzol l It has been found that such alkylated derivatives of aromatics and other reactive hydrocarbons have consistently higher anti-knock value than the original hydrocarbon, the values obtained in the derivatives being of the order of 50% higher than the original and many times still higher. The mixed character of gasoline hydrocarbons and also the variations in composition and proportion of the oleilns in both gases and liquid produced in their cracking according to the rst stage of the process precludes any statement as to the absolute rules governing the 'interaction ot these hydrocarbons in the pres-l ence of sulphuric acid. However, as will be dement of suitably interconnected parts in which the essential steps of the process may be conducted. 'I'he drawing does not show such obvious and weil known expedients as heat exchangers nor any special detail except as the same may be r essential to the operation of the process.

, in the final product.

Referring to the drawing the plant will be seen to consist essentially of a cracking plant of a type at present used extensively in the art followed by a treating plant in which the olens and the other hydrocarbon products of the rst step of the process are caused to recombine. Gasolines or naphthas may be introduced to the cracking unit through a line i containing a control valve 2 and be pumped by pump 3 through a line 4 containing control valve 5 through a tubular heating element 6 disposed to receive haat from a furnace 1. Intermediate insufficiently converted refiuxes may be returned by wayof line 22 for further decomposing reactions as will be laterdescribed. The temperatures and pressures employed in the heating and conversion zones of the cracking unit will depend upon a number of factors among which are ,the character of the gasoline charged in regard to volatility and chemical composition, the products obtainable by cracking themunder diierent conditions of time, temperature and pressure and the qualtiy desired Thus when parafiinic gasolines are employed which yield only limited amounts of high anti-knock gasoline under ordinary cracking conditions, the temperature and pressure may be modified to produce more intensive cracking and increase at the same time the relative amounts of olefns and cyclic hydrocarf bons produced. When more readily decomposible gasolines are employed conditions of less severity may be preferable, the object of the cracking process being to produce olefins and hydrocarbons reactive therewith in such amounts and in such proportions that maximum yields of gasoline of a given anti-knock value are possible as a result of the primary and secondary steps.

'I'he products from the heating element may be discharged through a transfer line 8 containing control valve 9 and pass through a well-insulated vaporizing and reaction chamber I in which conversion reactions proceed to the establishment of a. substantial equilibrium and the'total products of the conversion may then be passed through a line II containing a control valve I2 into a reduced pressure evaporator i3 which functions principally as a Vseparator for heavy tar fractions unsuited to further heat treatment on account of their coke depositing tendencies, such heavy residuals being removed through line I4 containing control valve i5, and either coked separately or utilized as fuel oil or asphalt stock. As a generalrule the amount of these heavy tar fractions is quite small and in some cases the evaporator 'may be omitted and the reaction chamber products admitted directly to a fractionator.

Lighter products comprising ilxed gases and vapors consisting in turn of liquid o! desired boiling range and heavier reiluxes may be passed through a line i5 containing a control valve I1 and enter a fractionator i3 o'f suitable design and capacity for effecting efficient segregation of recycle refiuxes from gaseous and gasoline hydrocarbons. 'I'he recycle stocks may be taken from the bottom of the iractionator through line i9 containing control valve and pumped by pump 2| through line 22 and valve 23 t0 line 4 as already mentioned. The amount o! reflux thus returned will to some extent determine the character of the conversion step.

Fixed gases and light hydrocarbon vapors may pass through a vapor line 24 containing control -valve 25 and theliquids condensed during their passage through a condenser 28, the cooled liquids and fixed gases passing together through rundown line 29 and a control valve 30 to a receiver 3|. Line 26 containing control valve 21 typiiies any line or combination of lines which may be employed to take oil? one or a number of side cuts concurrently with the overhead stock and produce a distillate of varying character. In receiver 3i gases and liquids separate and such po'rtions of either as are not to be employed in the final recombining or synthesizing step may, be I withdrawn through line 32 containing control valve 33 and line 34 containing control valve 35 respectively.

In the second step of the process the olefins and other groups of hydrocarbons are recombined in suitable proportions through the agency of sulphuric acid to produce increase 'in yield and anti-knock valueA of gasoline fractions. Of the three groups of hydrocarbons other than olens to-wit; aromatics, naphthenes and parafflns,

which are present, their reactivity with olens to form alkylated derivatives with olens diminishes generally in the order given. However,

the exact course of the reactions cannot be followed exactly and there is evidence to indicate that even with parains there is some combination, possibly due to the presence of compounds of isomeric or condensed structure. To utilize the olenic content of the gases produced they are withdrawn in proper amount from receiver 3| through a line 36 containing control valve 31 by a pump or blower 38 discharged through a line 39 containing a control valve 40 into the upper part of a reactor 54. At the same time the proper amount of condensed liquid as determined by tests is taken from the receiver through line 4I containing control valve 42 and discharged by a pump 43 through a line 44 containing a control valve 45 into line 49 where it comes in contact with a stream of sulphuric acid commonly of 93% strength (though acids of from 80 to 98% may be used) the acid being furnished by a pump 48 which takes suction upon the source of supply not shown through line 46 and valve 41A and discharges the acid through line 49 and valve 50. Obviously other alternative modes of transferring acid may be employed such as blow cases and elevated tanks. -The amount of acid necessaryv for producing best results will usually range from 5 to 10% by volume of the liquid hydrocarbons undergoing reaction. As a general rule there is a given quantity and strength representing a total amount of 100% acid below which the acid is consumed in sulfonating reactions and very little of the desired alkylating of the gasoline hydrouse after suitable regenerating steps.

The reactor may contain perforated platesor bafiles indicated by 52 and 53 for further breaking up the acid and oil into iinestreams after the, coalescence following the first atomizing. There is a tendency toward increased temperature in the reactor due to the exothermic character of the reactions and cooling means may be employed either in the reactor or immediately subsequent thereto to retard the progress ofundesirable side reactions and favor the combination'of the oleflns with the cyclic 'and other hydrocarbons rather than their polymerization among themselves, though this cannot be entirely avoidedeven under the best of circumstances. However, gums and resins and similar high boiling polymers are seldom encountered in this stage of the process, which indicates that polmerization insofar as it occurs proceeds mainly to the formation of dimers and trimers which have boiling points lying within the range desired in the nnished gasoline. The liquid products of the reaction' comprising what may be termed alkylated hydrocarbons, polymers, unchanged oil and partly spent acid may be passed to a separator l through a line 55 containing control valve 56, wherein residual gases devoid of olefns separate in space 58, hydrocarbon liquids in space 59 and spent acid in space 60, the latter being drawn off throughva line 'Il containing a valve 15 and either discarded or returned for further The gases may be drawn oil and vented by way of line 63, valve 6I, line 65 and valve 66, a line 6I containing a control valve 62 leading from reactor 54 so that gases may also be withdrawn from this element as may be necessary or desirable.

The final hydrocarbon composite from the process which consists of gasoline having improved ranti-knock characteristics may-be continuously withdrawn from the separator through line 61 containing control valve 68 to a receiver 69 having a gas release line 'I0 containing a control valve 'H and a liquid draw line '12 containing a control valve 13. The product usually requires neutralizing and washing according to established procedure following sulphuric acid treatments and may require redistillation to eliminate hydrocarbon fractions boiling above the end point desired in the gasoline. 'I'he redistilling step is usually neeessary even though previous operations have been directed toward the production of a rela.- tively light gasoline fraction since the synthetic reactions resulting in the fixation of alkyl residues on the reactive gasoline hydrocarbons results in the formation of a certain percentage of what may be termed alkylated compounds of high boiling point. 'I'hese products may be returned to the cracking unit if desired andreconverted in order to conserve the yield.

As an example of the results obtainable in the direction of improved yields and quality of gasoline byI the use of the present process the following results are cited. Pennsylvania straight run gasoline having the following properties may be treated:

Gravity-11;?. I 64.6 100 cc. A. S. T. M. distillation- I. B. P.-F 106 154 20 186 50 242 90 328 E. P 386 Recovery percent 96.5 Reid vapor pressure at 100 F lbs 8.0 Octane number 50 Results of primary or cracking step Unstabilized gasoline, 85 A.

P. I. gravity 85% by volume Heavy tar, about 5 to 10 A. P. y

I 1.5% by volum Fixed gases, 1.23 specific gravity 475 cu. ft./bbl. o

gasoline cracked.

The gas produced from the process may have the following composition:

Analysis of gas from cracking Percent Hydrogen 8 Methane 19 Ethane 14 Ethylene 9 Propane 'I Propylene 23 Butane and lsobutane 2 Butylenes 10 Pentanes 6 Amylenes 2 The unstabilized gasoline upon removal of dissolved propane and propylene and a sufficient quantity of the butanes and butylenes to obtain the required vapor pressure may yield a product having the following properties in an amount equal to 76.5% by weight of the original gasoline charged.

Properties of stabilized gasoline The combined gaseous products from the cracking operation and the stabilization of the gasoline may be recontacted with the stabilized gasoline at a pressure of 100 pounds per square inch in the presence of 10% by volume of 90% sulphuric acid. There may be produced by this oping the folowing properties:

Gravity-"A. P. I i 68.0 Initial boiling point-F 95 over at 120 50% over at 240 90% over at 340V Endpoint 400? Reid vapor pressure at 100 F.-lbs 9 Octane number. 85

eration a yield of 4stabilized gasoline equivalent to 84% of the original gasoline treated and havdevelopment on storage and ordinarily requires no further treatment. I

While the partly spent acid from the alkylation step has been designated as sludge acid", it should not be considered in the same light as the waste refinery products to whichy this term is customarily applied since the acid used may be employed for a large number of treatments be'- fore its efiiciency is diminished to an impractical degree. When the acid becomes saturated with soluble products of an'ester character it may be hydrolyzed by treatment with water or steam and a number of by-products recovered such as isoalcohols and further yields of hydrocarbons. The actual consumption of acid per gallon of finished gasoline produced is approximately in line with that ordinarily employed in treating cracked lllvhthas. l

'I'he foregoing specification and numerical data presented are sumcient to define the character oi the invention and show its merits but neither is to be considered as imposing undue limitations upon its generally' broad scope.

I claim as my invention:

l. A process tor increasing the anti-knock value of light hydrocarbon distillates containing a substantial quantity of hydrocarbons within the gasoline boiling range, which comprises reforming the distillate by, pyrolytic conversion thereby forming condensible aromatica and gaseous oletins, reacting such oleilns and aromatica in the presence oi' sulphuric acid to-form alkylated derivatives, and recovering a liquid product containing said derivatives.

2. A process for increasing the anti-knock value oi light hydrocarbon distillates containing a substantial quantity of hydrocarbons within the gasoline boiling range, which comprises reforming the distillate by pyrolytic conversion thereby forming condensible aromatics and gaseous olens, condensing the vapors and separating the resultant condensate from the gases, contacting at least a portion oi' the gases with the condensate in the presence of sulphuric acid and reacting oleilns contained in the gases with aromatics contained in the condensate to form alkylated derivatives, and recovering as the product of the process the alkylated condensate thus formed.

' VLADIMIR IPATIEFF.

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