US2319209A - Conversion of hydrocarbons - Google Patents

Description

May 18x, 1943 l D. R. cARMoDY CONVERSION 0F HYDnocARBoNs Filed Feb.' 2e. 1942 Patented May 18, 1943 coNvERsloN oF HYDRocARBoNs Don R. Carmody, Hammond, Ind., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application February 28, 1942,. Serial No. 432,849 I 7 Claims.

This invention relates to a process for the production of gasoline of high octane number from vnormally gaseous hydrocarbons and pertains more particularly to an improved process for the alkylation of isoparainic hydrocarbons with selected normally gaseous olenic hydrocarbons.

It is known that isoparailinic hydrocarbons such as isobutane or isopentane can be alkylated by normally gaseous olelns such as isobutylene, normal butene, or propylene in the presence of sulfuric acid as a catalyst. It'has also been dis covered that'under ordinary alkylating conditions alkylation by ethylene of isobutane or other similar hydrocarbons containing a. tertiary car'- bon atom is not catalyzed by sulfuric acid. It has further been discoveredv that the olenic gases other than ethylene can suitably be converted to the corresponding alkyl sulfates by absorption in sulfuric acid and these alkyl sul-,- fates employed for alkylating isoparainic hydrocarbon's in the presence of sulfuric acid under the usual alkvlating conditions. In carrying out the .step of absorbing oleflns in sulfuric acid and l thereby eliminating undesirable par'ainic hydrocarbons prior to the alkylation step, a loss is incurred in oleflnic material -due to the condensation or polymerization of the olens to products of higher molecular weight which are not suitable for use in alkylation and which cannot be recovered for conversion to gasoline'.

l like products.

' substantially pure oleflnic hydrocarbons under conditions suitable for optimum conversion of each type of olenic hydrocarbon and blending the resulting alkylate. Another object is to provide an improved process for the production o1'v aviation gasoline by carrying out an alkylation processl in such a manner that'the alkylate is formed under the most advantageousconditions for high yield and in sucha manner that' contamination with inert gases is Substantially reduced. Further objects and advantages will become apparent as the description thereof pro ceeds.

The attached drawing which forms a part of the specification is a simple flow diagram illustrating one lpreferred embodiment of my invention. y l

My\process in brief includes the recovery of substantially pure ethylene from a refinery C2 stream, the conversion of C4 and/or C3 olen's to the corresponding alkyl sulfates without substantial formation of polymerization or con- 'densation products, -the alkylation of an isoparaiiinic hydrocarbon with the pure vethylene under alkylation conditions suitable therefor" employing a Friedel-Crafts type catalyst, and

alkylation of an isoparainic hydrocarbon with ered from the cracking, thermal or` catalytic, of,

petroleum, or petroleum fractions, andmay have been separated from gases of higher molecular weight by fractionation, absorption and stripping,

etc. The ethylene gas stream will usually contain ethane as well as varying quantities of methane and hydrogen depending on the previous method of segregating the C3 hydrocarbon cut from higher molecular weight hydrocarbons. Absorber l0 contains concentrated sulfuric acid, preferably of greater concentration 'than 90% H2504 and more desirablyv 94% I-lzSO4v or higher, which. enters through line I2 at the upper portion of the absorber I0. The ethylene-containing gas stream enters the base of absorber Il)` through line I I and the addition of this ethylenecontaining stream is regulated in such a way as to obtainy concentrated sulfuric acid'eester inf-the l'75 F. to about 100 F. The unabsorbed gases,

' which will be mainly ethane together with any methane and hydrogen present, pass overhead -from absorber' II! through line I3 and can be discarded'or used for fuel gas and other similar purposes.

The concentrated ethylsulfuric acid is passed into stripping tower Il from absorber I0 via. line I5; and enters at the upper portion thereof. A gas stream containing unsaturated Cijiydrocar-A bons or unsaturated Crhydrocarbons, or a mixture of the two, with or without the corresponding paraftins, enters stripper I4 through line I6. Although the unsaturated C3 and/or C4 hydrocarbons can be obtained from any suitable source, they are generally easily available, in petroleum renery gas streams particularly from the depropanization or debutanization o1 cracked gasoline. Various methods are well known for fractionating and recovering normally gaseous hydrocarbons from gasoline and any of these may be employed. I especially prefer a fraction rich in C4 olefins. Another source is from the dehydrogenation of natural gas butane or propane. The ethylsulfuric acid is added to stripper I4 and as the gas stream passes countercurrent therethrough the ethylene is liberated and propyl and/or butylsulfuric acid is formed. The ethylene of the ethylsulfuric acid is displaced by propylene and/or butylene and the ethylene.

freed without further absorption. At the same time, the polymerization of the Cs and C4 olens to higher molecularweight hydrocarbons is substantially precluded. The stripper is so regulated as to` temperature, pressure, and velocity of the -gas stream passing therethrough that substantially only alkylsulfuric acid passes out the lower part of the stripper, while substantially` the only olefin passing overhead is ethylene, a1- though the saturated hydrocarbons. which may have been -present in the gas stream are thus withdrawn from the system. Stripper I4 is maintained at about 30 F. and at pressures within the range from about 1 to about 100 atmospheres, preferably at about 5 to about 25 atmospheres pressure.

The butyl sulfuric acid withdrawn from the base of stripper I4 is directed to sulfuric acid alkylator I'I via line I 8. Suilicient `additional strong sulfuric acid is added to alkylator I1 via line I9 and line 20 to maintain the concentration in the alkylaltor between about 90 and 100%, preferably about 95 or 96% H2SO4 based on the water content ofithe acid mixture. Isobutane from any suitable source (not shown) is added through line 2I and line 22 and can be mixed with the 'alkyl sulfaites in line I8 vprior to alkylator I'I or mixed with the sulfuric -acid from line I9 via line 23 be fore injection into alkylator I1. Alkylator I'I is maintained at the usual alkylating conditions found optimum for a process of this type; for example, at a temperature within the range from yabout 20 F. to about 100 F., |but preferably from :about F. to about 80 F., and under suilicient pressure to maintain the reactants in the liquid phase. The reactants are fed to the alkylator at a rate of about 0.01 to about 10 volumes of reactant per volume of strong sulfuric acid per hour. The feed should contain a mol ratio of isoparan toolefin absorbed in the acid within the range of from about 1:1 to about 10:1 and preferably about 4:1. Any suitable apparatus can be used which is capable of insuring intimate contact of the reactants and catalyst, together with means, if necessary; for controlling the temperature of the reaction. A portion of the emulsion of sulfuric acid alkylate, unreacted hydrocarbons, acid and alkylsuliuric acid is recycled through lines 24a, 30 and 20 to alkylator I'I and the remainder withdrawn through line 24 and directed to settler 25 in which stratification of the acid and hydrocarbon layers occurs. The hydrocarbons together with unreacted gases are withdrawn overhead via line 26, neutralized and washed (bv means not shown), if desired. and directed to fractionator 21 via line 28. The acid from the base of settler 25 is withdrawn through line 29 and, if still of alkylating strength, can be recycled via line 30 to line 20 and alkylator II. If the acid is substantially spent for alkylation but is not yet below 90 H2804 titratable acidity, it can be recycled to the ethylene absorption step via line 3l which joins line I 2. If completely spent for either purpose, of course, it can be withdrawn via. line 32. It is to be noted that usually an acid having a titratable acidity of lessythan 90% HzSO4, or in that region, is comparatively ineffective for promoting the alkylation of isoparailns with olefins or alkylsulfates. Apparently the titratable acid strengthis determined in a large'part by the amount of hydrocarbons in the sulfuric acid, and the acidity shown by ordinary titration is based on the weight of the sample which, of course, includes the hydrocarbons present. The acidity based on the water content of the sulfuric acid will still be of the order of 93 to 95% or higher, howevery `and is therefore eminently suitable for vuse in the absorption of ethylene. Accordingly, it is an important step in our process that rthe partially or wholly spent acid from alkylation which still has a hydrocarbon-free acidity of 90% or greater be recycled to the ethylene absorption step.

The ethylene from stripper I4, together with any C4 or Cs paraiinic hydrocarons originally present in the gas stream from line I6 passes overhead through line 33 to alkylator 34 in which the ethylene is contacted with an isoparaiiinic hydrocarbon in the presence of an aluminum halidetype catalyst. Although sulfuric acid does not catalyze the alkylation of an isoparaiiin with ethylene, it has been found that very effective alkylation can be obtained if an aluminum halidetype catalyst such as aluminum chloride or aluminum bromide, or more advantageously an aluminum halide-hydrocarbon complex is employed for promoting the reaction. The aluminum halide can be used as such or supported on various materials such as clays, pumice, kieselguhr, alumina. etc. It can be introduced in the form of a slurry in an inert solvent or be present in the form of lumps over which the reactants pass. A particularly desirable type of catalyst is one formed by the reaction of aluminum chloride with a normallyl liquid hydrocarbon in the presence of a hydrogen halide activator and particularly with a paraihnic hydrocarbon, although aromatic or olefinic hydrocarbons are also useable. The rcaction product is in the form of an aluminum halide-hydrocarbon complex, diilicult to analyze, liquid in form, and usually of modiiled activity, i. e., the extreme activity of pure aluminum chloride is reduced 'rtoa point where undesirable side reactions are minimized or eliminated.

Alkylator 34 is maintained at temperatures from about 0 to about 212 F. or higher and at superatmospheric pressures Within the range from about 30 pounds per square inch to about 500 pounds per square inch, although I prefer that it be maintained within the range from about to about 250 pounds per square-inch. A preferred temperature includes the range from about 80 F. rto about 150 F. and most desirably from about F. to about 135 F. It is desirable to add an activator such as a hydrogen halide, and more particularly hydrogen chloride, to the reaction, usuallyl in amounts of 5% or less based on the' aluminum chloride present, and it can be as low as 0.5%. Intimate contact between the reactants and the catalyst is necessary although it has been ethylene is obtained in concentrated form and found that the reaction can be carried out successfully if the reactants are passed upwardly through a deep pool of catalyst.

Activator is added through line 35 and catalyst through lines 36 and 31. An isoparamn such as 5 isobutane is added from line 2| and line 38 and can be injected directly into the ethylene stream in line 33'or sent directly to alkylator 34 via line 39. The hydrocarbon conversion products, -together with unconverted hydrocarbons, are with- 10 drawn from alkylator 34 through line 40 and sent to settler 4| wherein a separation .is made between the hydrocarbons and any occluded or dissolved catalyst. A cooling coi1 or other similar temperature-reducing means can be inserted in line 40 to precipitate out dissolved aluminum chloride. The separated catalyst is withdrawn from settler 4| via line 42 and can be discarded through line 43 but preferably is recycled through line 44 to line 31 and alkylator'34 until substan- 20 tially spent.

The hydrocarbons together with activator pass overhead from settler 4| through line -45 and through a washing and neutralizing system (not shown) to line 28 leading to fractionator 21. In 25 fractionator 21, which can be any conventional apparatus for the separation of hydrocarbons of Various boiling ranges, unreacted gases," whichr will be chiey parailnic hydrocarbons from gas stream I6, and excess unreacted isobutane from line2| pass overhead through line 46 and can be discarded through line 41 or recycled through line 4B to line 2 I. In the event that the off-gases contain considerable amounts of normal butane or the normal butane tends to build up in the 3:, system, it may be desirable either to fractionate in such a manner as to eliminate the normal butane and recycle only the isobutane, or to direct the total off-gases through an isomerization unit I` wherein the normal .butane is converted to isobutane suitable for use in the alkylation systems. As a further modification it is quite Within the scope of this invention to separate the normal butanes from the isobutanes and to direct only the normal butanes-to isomerl- 4,; zation system I and thence back to the alkylation system where they join the previously searated isobutanes.

Hydrocarbons heavier than aviation gasoline can be withdrawn fromfractionator 21 -through 50 ling 49. In the event that this fraction does not contain too great a quantity of lhydrocarbons of very high molecular weight, it is quite possible to use these heavy hydrocarbons as an aviation safety fuel, or it is equally within the scope of this invention to withdraw the hydrocarbons of safety fuel boiling range as a side stream (not shown) and discard only thev heavy condensation' product through line 49. A blended gasoline of high octane number, balanced volatility, and good lead response is withdrawn as a side stream through line 50. In the system described the chief product of alkylating isobutane, for example, with ethylene in alkylator 34 will be diiso.-

propyl, while the alkylate' from alkylator I1 will 5' be chiefly isooctane, or isoheptanes and isooctanes depending upon the exact oleflns used in the process; The fraction withdrawn through line 50 therefore represents a product eminently suitable for use in aviation engines which demand not only high octane number but a fuel having a definite boiling range and certain volatility characteristics required for ease in starting not possessed by isooctane alone.

My process has the definite advantage that or hydropolymerized without conversion.

substantially free of diluents such as ethane, methane, hydrogen, etc.

isopropyl from refinery light gas streams is concentrating the ethylene therefrom, and my process provides an extremely economical and advantageous process in that respect. Great difficulty has also been encountered in concentrating C3 and particularly C4 olens by conversion to the alkyl sulfate in avoiding excess losses due to the conversion of a part of the olenic feed to polymers and high boiling condensation products. By using ethylsulfuric acid as the absorption medium, the propylene and butylenes are not only converted substantially quantitatively to alkyl sulfuric acid, but there is little or no tendency for a part of the oleflns to be polymerized Furthermore, there is no dilution of the sulfuric acid alkylation catalyst due to the use of diluted, low concentration sulfuric acid for olefin absorption, which is the case under ordinary absorption'conditions used for forming butyl sulfates.

identical. Ordinary absorption of mixed oleflns in sulfuric acid either requires a different strength of acid for each particular olefin or varying pressures if the same strength acid is used throughout. When using ethylsulfuric acid this selectivity appears to be eliminated or reduced to such an extent that the loss of olens is negligible.

Although I have designated the reaction product of ethylene and sulfuric acid as ethylsulfuric acid, and the reaction products of Ca and/or C4A olefins with ethylsulfuric acid as the corresponding alkylsulfuric acids, for the sake of simplicity, I wish to include any and all products formed during either of these kreactions within the scope of my invention.

My process has been illustrated generally, and many details necessary or desirable for the operation of a commercial unit have been omitted for the sake of clarity and simplicity, but these details will readily be-supplied by one skilled in the art. These details include such items as pumps, valves, heat exchangers, washing and" purifying means, etc., all of Which are well-known and their necessity understood. Although I have show n one preferred embodiment of myinvention. it should be realized that this is by way of illustration and not by way of limitation,v and that I intend to be bound only by the scope of the appended claims.

I claim: v

1. A process for the production of a balanced fuel comprising the steps including contacting at least one oleflnic hydrocarbon having more than 2 carbon atoms per molecule with ethylsulfuric acid whereby ethylene is liberated and an alkylsulfuric acid corresponding to said olenic hydrocarbon is formed, contacting said liberated ethylene with an isoparafllnic hydrocarbonin the presence of an aluminum halide type catalyst under alkylation conditions, contacting said alkylsulfuric acid with an isoparaffinie hydrocarbon in the presence of strong sulfuric acid under alkylation conditions, recover-- ing alkylate from each of said last mentioned contacting steps and blending vsaid recovered alkylates.

2. A process for the production of a balanced l* y One ofthe gravest problems in the commercial production of dil The acid strengths in my process are much more nearly gaseous hydrocarbons containing butylene and comprising predominantly oleiins having more than two and less than five carbon atoms per molecule whereby ethylene is liberated and alkyl- Y sulfuric acid corresponding to said oleilns is formed, contacting said liberated ethylene with isobutane under alkylation conditions in the presence of an aluminum halide catalyst to produce an alkylate predominating in diisopropyl, contacting said alkylsulfuric acidI with isobutane in the presence of strong sulfuric acid under alkylation conditions to producean alkylate comprising isooctane and recovering a balanced fuel comprising a blend of the diisopropyl and the isooctane produced in each of said last-mentioned contacting steps.

3. A process for the production of a balanced aviation fuel comprising the steps including forming ethylsulfuric acid from an ethylene-containing gas stream and sulfuric acid, contacting said ethylsulfuric acid with a normally gaseous hydrocarbon stream containing olens having more than two carbon atoms per molecule under conditions whereby said ethylene is liberated from said ethylsulfuric acid and alkylsulfuric acid is formed corresponding to said oleflns in said normally gaseous hydrocarbon stream, separating said liberated ethylene from said alkylsulfuric acid, contacting said liberated ethylene with an isoparailinic hydrocarbon in the presence of an aluminum halide type catalyst under alkylation conditions, contacting said alkylsulfuric acid with an isoparaiiinc hydrocarbon in the presence of strong sulfuric acid under alkylation conditions, recovering alkylate from each of said last mentioned contacting steps and blending said recovered alkylates.

4. A process for the production of a balanced aviation fuel comprising the steps including forming ethylsulfuric acid from an ethylene-containing gas'stream and sulfuric acid, contacting hydrocarbon stream containing olens having more than two carbon atoms per molecule under conditions whereby said ethylene is liberated from said ethylsulfuric acid and alkylsulfuric acid is formed corresponding to said olens in said normally gaseous hydrocarbon stream, separating said liberated ethylene from said alkylsulfuric acid, contacting said liberated ethylene said ethylsulfuric acid with a normally gaseous.

with an isoparaiinic hydrocarbon in the presence of an aluminum halide type catalyst under alkylation conditions, contacting said alkylsulfuric acid with an isoparalnic hydrocarbon in the presence of strong sulfuric acid under alkylation conditions, recovering alkylate from each of said last mentioned contacting steps, returning sulfuric acid from said last mentioned sulfuric acid contacting step substantially spent for alkyation to said ethylsulfuric acid forming step, and blending said recovered alkylates.

5. A process according to claim 3 in which said isoparaflinic hydrocarbon is isobutane.

6. A process according to claim 3 in which said olens in said normally gaseous hydrocarbon stream comprise predominantly olefins having four carbon atoms per molecule.

'1. A process for the production of a'balanced aviation fuel comprising the steps including c'ontacting a light gas stream containing ethylene, ethane and lighter gases with sulfuric acid of greater than H2504 content under conditions adapted to form ethylsulfuric acid,` eliminating gases other than ethylene from said contacting step, contacting said ethylsulfuric acid with a C4 stream containing olefins and paraffns countercurrently underv conditions adapted to liberate ethylene and form butylsulfuric acid, recovering said liberated ethylene and contacting said recovered ethylene with isobutane in the presence of an aluminum chloride-hydrocarbon complex under conditions adapted topromote the alkylation of said isobutane by said ethylene to hydrocarbons having predominantly six carbon atoms per molecule, contacting said butylsulfuric acid with isobutane in the presence of strong sulfuric acid under conditions adapted to promote the alkylation of said isobutane by the butyl radical of said butylsulfuric acid, returning sulfuric acid from said last mentioned contacting step to said ethylene-stream contacting step when substantially spent for promoting said last mentioned alkylation, recovering alkylatev from said aluminum chloride alkylation step and from said sulfuric acid alkylation step, directing said alkylates to a. common fractionation system, and recovering from said fractionation system a balanced aviation fuel.

DON R. CARMODY.

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