US2366627A

US2366627A - Manufacture of antiknock hydrocarbons

Info

Publication number: US2366627A
Application number: US380930A
Authority: US
Inventors: Lebbeus C Kemp
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1941-02-27
Filing date: 1941-02-27
Publication date: 1945-01-02
Anticipated expiration: 1962-01-02

Description

BY /Pa d ATTORNEYS Original Filed Nov. 4, 1938 L. C. KEMP MANUFACTURE OF ANTIKNQCK HYDROCARBONS` Jan. 2, 1945.

Patented Jan. 2, 1945 MANUFACTURE F A'NTIKNOC HYDROCARBONS Lebbeus C. Kemp, Scarsdale, N. Y., assignor, by

mesne assignments, to The Texas Company.

New York, N. Y., a corporation of Delaware Continuation of application Serial No. 238,715, November 4, 1938. This application February 27, 1941, Serial No. 380,930

1s claims. (cl. 26o-683.4)

This invention relates to the production of high antiknock hydrocarbons, suitable for the manufacture of -gasoline, by the condensation or al\ kylation' of paraftlns with oIens, particularly isoparaiiins with olens, in the presence of a catalyst.

The invention has to do more spcciically with improvements in an alkylation process, wherein isoparaiilns, particularly low boiling isoparaiiins. such as isobutane 'and isopentane, are intimately contacted with an alkylation catalyst, such as aluminum chloride, or, an acid catalyst of the `sulfuric acid type, for example strong'sulfuric acid.

When an isoparaiiin, such as isobutane, and olens, particularly low boiling olens between 3 and 5 carbon atoms, or polymers thereof, are intimately contacted with strong sulfuric acid up to 100% strength, the isoparailln is alkylated by the olefins to produce high antiknock, saturated range. The alkylation or condensation reaction is usually exothermic and an object of the present'invention is to provide means for removing or dissipating the exothermic heat of reaction.

Furthermore, in an alkylation process of the type described, it is often advantageous to carry out the operation over a temperature range or, to utilize a plurality of reaction zones and to maintain a differential temperature in the various zones. Another object of the present invention is to provide means for obtaining this variable, or differential temperature, in the alkylation process.

In accordance with the present invention, evaporative cooling is obtained by vaporizing a. portion of the hydrocarbons undergoing reacalkylating isobutane with a'C'4 unsaturated hydrocarbon fraction, temperatures of about 60 to 100 F. are often used.. At such temperatures the hydrocarbons would normally be substantially in the vapor phase, but'it is customary to main tain suilicient pressure on the hydrocarbons undergoing treatment to maintain the liquid phase and' one method of lobtaining evaporative coolhydrocarbons within the gasoline boiling point tion. When a portion of the hydrocarbons is evaporated, the heat of vaporization may be extracted from the body of liquid to remove heat in situ from the remaining unvaporized hydrocarbons. The removal of such heat may be utilized to prevent undue rise in temperature, to regulate the temperaturel of reaction products, and to produce substantial cooling or refrigeration. The hydrocarbons evaporatedmay be a portion of the nor- I mal charging stock, including those intended for reaction. It is contemplated, moreover, that the hydrocarbons evaporated may be condensed and recycled to the system, whereby depletion in volume of the reaction products is avoided.

The alkylation' process is usually carried out in the liquid phase at temperatures such that normally at least a portion of the. hydrocarbons would be in the vapor phase. For example, when ing, therefore, is to adjust the pressure, whereby the necessary vaporization is produced to obtain thedesired amount of cooling..

In some cases it may be desirable to carry o ut the alkylation operation at suiciently low temperatures, for example around 0 F., whereby the hydrocarbons would normally be inthe liquid phase without the application of the pressure.

In this case the evaporative cooling, according to g l the invention, may be obtained by reducing the pressure by means of a vacuum to obtain partial vaporization and simultaneous evaporative cooling.

The following description of the invention is to be read in connection with the accompanying` drawing, which shows a diagrammatic sketch of one form of apparatus for carrying out the process of the invention.

Referring to the drawing, a paraillnic charging stock, comprising isoparafflns, such as isobutane er isopentane or mixtures thereof, is introduced by the pump I through the une 2 into me first of a plurality of reaction vessels 4, 5, 6, 'i and 8. The reactors are connected in series by the lines I0, Il, I2 and I3, and each is provided with a suitable stirring mechanism. A liquid catalyst,

. such as sulfuric acid, is introduced by the pump I5, through the line I 6, into the reaction chamber 4. The olefin hydrocarbons, which may com prise any normally liquid or normally gaseous olens heavier than ethylene, and preferably va cracked hydrocarbon fraction, such as a Cr fraction, or polymers thereof, are introduced by the pump I 8 through the line I9 into any one or all of the reactors 4, 5, 6 and I through the valveA `controlled branch lines 2I, 22, 23 and 24 respectively. It is preferable to inject the oleiins at multiple paints, preferably into reactors s, 6 and 1.

n Thereactive ingredientsl in the hydrocarbon charge are the isoparafiins and oleiins, although any amount of unreactive hydrocarbons, such as the normal paraiiins, may be present. It is desirable to maintain the ratio of isoparains to olefins at least 1:1 and preferably between :about 3:1 and 5:1. The proportion ofI the catalyst is such as to provide in the case of sulfuric acid be tween about .5 and 1.5 parts o! acid to one part by weight of olein.

The hydrocarbons in the liquid phase are intimately contacted, while passing through the reactors, under time and pressure conditions to produce substantial alkylation of the isoparailins by the oleflns. When using an isoparain, vsuch as isobutane, and a C4y cracked hydrocarbon fraction, temperatures of about 60 to 90 F. and a reaction time of about 30 to 60 minutes have been found satisfactory.

The reactors as shown in the drawing are connected in series so as to provide a concurrent flow of the catalyst and hydrocarbons therethrough. It is to be understood, however, that a countercurrent system may be used, whereby the acid and hydrocarbons are intimately contacted While flowing in a countercurrent direction. It has been found that a five-stage system gives excellent-results, but the number of reactors may vary.

The reaction products are withdrawn from the final reactor 8 through the line 26 to a settler 28,-

oi line 30. The catalyst, if insuflicientiy spent,

may be recycled to the system for further use. 'Ihe hydrocarbons, collecting in the upper portion ofthe settler, are transferred through the line 3l to a mixer 32, provided with a suitable stirring mechanism. 'An alkaline neutralizing agent, such as aqueous caustic soda, is introduced by the pump 34 through the line 35 into the mixer to `contact intimately with the hydrocarbons and to eiect neutralization of any acid constituents. The mixture of neutralizing agent and hydrocarbons passes from the mixer 32 through the line 36'to settler 38, wherein the neutralizing agent is allowed to settle out in the lower portion thereof. The used neutralizer may then be withdrawn through the line 39, or if insufiiciently spent, recycled to thel neutralizing operation, through the branch line 40 and charge line 35.y

The neutralized hydrocarbons are conducted from the settler 38 through line 42 to a. fractionator or stabilizer 43 wherein the libuid hydrocarbons are stripped of substantially all the normally gaseous hydrocarbons. The normal butane and isobutane are vaporized and passed overhead from the fractionator 43 through the vapor line 45 to a fractionator 46. In the fractionator a i separation. is `made between the butane and lighter hydrocarbons, including isobutane. The normal butaneis condensed and collected in the l lower portion of the fractionator and may be withdrawn from the'bottom thereof through the line 48. In case the vapors consist essentially of isobutane, they may be withdrawn from the upper portion of the fractionator 46 through the vapor line 50 and condenser 5I, wherein they are condensed, andthe resultant condensate collected in the accumulator 52. If other hydrocarbons are present with the isobutane in substanoperation by the pump 51 through`the line 58 and charge line 2.

The liquid hydrocarbons, collected in the lower portion of the fractionator 43, are passed through the line 60 to a still or fractionator 6I, and subjected to fractional distillation to remove overhead vapors of gasoline boiling point range. The higher boiling products are withdrawn as bottoms from the lower portion of the fractionator through the line 62. The vapors are passed through the vapor line 64 and condenser 65 to an accumulator 66. The product in the accumulator consists essentially of saturated hydrocarbons of high antiknockvalue suitable for the manufacture 0f gasoline. If desired, all or a portion of the normal butane, withdrawn from the fractionator 46 through the line 48, may be combined'wlth the gasoline product by passing it to the accumulator 66 through the branch line 68.

The reactors 4, 5, 6, 1 and 8 are provided with vapor or gas lines 10, 1|, 12, 13 and 14 respectively, which -communicate with a header or main line 15, in which is located a compressor 16. Each of the vapor release lines is provided with relief valves for maintaining sucient'pressure on the reactors to maintain the hydrocarbons therein substantially in the liquid phase. The pressure usually ranges from slightly above atmospheric to 50 or- 100 pounds, or over, depending on the type of hydrocarbons' treated and the temperatures employed. When charging C4 hydrocarbons, and using temperatures of about 60 to 90 F., pressures of about 15 to 50 pounds are ordinarily used. 'Ihe relief valves may be set at a predetermined point, whereby an increase in pressure, for example as a result of a rise in temperature, causes vapors to be released throughfthe valves. As a result of the evaporation, the temperature in the' reactors will be reduced sufllciently to restore the desired pressure. According to one method of operation, all the relief valves may be set at a given pressure, corresponding to a contemplated maximum temperature. In this way any rise in temperature above that maximum may be avoided by the'evaporative cooling, resulting from the generation and release of vapors when the pressure to which the relief valves are set is exceeded. The temperature may be atmospheric, or whatever it happens to be above atmospheric as a result of the exothermic heat of reaction, and the evaporative cooling may be primarily for the' purpose of removing the excess exothermic heat.v I

According to another method of operation, positive heat may be added to the system, in addition to the exothermic heat of reaction,and the temperature controlled entirely or in part by the evaporative cooling, the extent of which may be controlled by means of the relief valves. In this case the evaporation may be for the purpose of removing either the exothermic heat of reaction, or the excess heat that'may be added unintentionally to the hydrocarbon 'charge/above that necessary to maintain the desired temperature.

According to another method-"of operation, evaporation of the hydrocarbons is utilized to produce positive cooling or refrigeration of the reactors. This method is principally applicable Ito the maintenance of a temperature lower than atmospheric. In case substantially reduced temperatures are desired, for example around 0 F., it may be desirable to maintain a vacuum on the vapor lines, whereby vaporization is inducedas a result of the reduction in pressure.

It :sto be understood that m any or au eases the evaporative cooling may not be depended upon entirely for the regulation of the temperature or for producing the desired amount of cooling or refrigeration, but may be auxiliary to other means which may or may not be the principal source of heat control.

It is also to be understood that the evaporative cases to maintain a progressive increase in temperature from one reactor to another through the series of reactors. Furthermore, any desired temperature may be maintained in a given. reactor which may be different from any one or all of the other reactors.

In case it is desired to maintain a temperature gradient in the various reactors, the pressure on vthe successive reactors may be maintained under increasingly higher pressures. It has been found desirable in some cases .o maintain a temperature gradient, for example from about 'l0 to about 110 F., and in order to assist in maintaining this temperature -'gradient, the relief valves ,may be yset to operate over a pressure range of about to 75 pounds. Thus, the rst reactor may be set at about 25 pounds, whereby a temperature of about '70 F. is maintained, and the second set at A about pounds whereby a temperature of about 80 F. is maintained, the third reactor at about 45 pounds whereby a temperature of about 90 F. is maintained, the fourth reactor at about 55 pounds whereby a temperature of about 100 F. is maintained, andthe fifth reactor at about 75 pounds whereby a temperature of about 110f7 F. is malntained; Suitable pumps (not shown) may be used between the several reactors when they are operated atA varying pressures.

The hydrocarbon vapors collected in the header 15 are compressed by the compressor 16, condensed inv the cooling coil 18 and the resulting condensate collected in the accumulator 80. All or a portion of this condensate may be returned to any one or all of the reactors through the line 8| and

themanifold lines

84, 85, 86, 81 and 88,

the excess being released as vapors from the top of the accumulator through the line 82 or with drawn as liquid from the lower portion thereof through the line 83.

As an example of the operation of the invention, isobutane is mixed with a crackedA hydrocarbon fraction predominating in C4 hydrocar-.

bons, the overall ratio of l isobutane to oleflns in the fresh feed being about 3,:1. The hydrocarbons are intimately contacted inra five-stage concurrent system with sulfuric acid catalyst of about 95% strength, the proportion of catalyst being about 80% by weightbased' on the olefin charge. The isobutane and catalyst are charged to the rst reactor and the oleiins injected equally into the second, third, and fourth reactors. Each reactor is provided with a vapor line in which is located a relief valve set at approximately pounds. Whenever the temperature in thereaction vessels rises above about 90 F., the pressure in the vessels increases above the 45 pounds, resulting in the opening of the relief valves and liberation of some of the hydrocarbons to bring the pressure back to the desired normal. Such reduction in pressure results in the evaporation of hydrocarbons within the vessel with resultant evaporative cooling to lower the temperature back to the normal F., or somewhat below. Inasmuch as isobutane is the lowest boiling hydrocarbon of the C4 charge stock, and as the isobutane is present in a large proportion to provide the substantial molar excess of isobutane to oleflns as specified above, it is obvious that the vapor pressure in each of the reactors is mainlir that of the isobutane. Consequently, hydrocarbons evaporated on a rise in temperature within the reactors consist largely of isobutane. The

vapors released through the vapor lines are col lected in a main gas line, wherein they are picked up by a compressor and compressed to about pounds and then passed through a cooler to effect condensation. The condensate consisting .largely of isobutane is returned to the first reactor to pass again Vthrough the system, thereby serving to maintain the substantial molar excess of isoparan to olelins in the reactors. Areaction time of about 45 minutes is allowed. The acid is then separated from the reaction products andthe hydrocarbons neutralized. The neutralized hydrocarbons are stabilized to remove overhead the normally gaseous hydrocarbons, which are fractionated to separate an isobutane fraction which is returned to the system. The stabilized hydrocarbons are distilled to produce a fraction boiling withinthe gasoline range which is combined with suiiicient excess butane to bring the volatility up to about that of commercial gasoline.

A yield of about based on .the olens charged is obtained. The gasoline is largely saturated and usually has an anti-knock value of about 90.

This is a continuation of my co-pending application, Serial No. 238,715, flied November 4, 1938.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated inA the appended claims.

I claim:

l. The method in the manufacture of high anti-knock saturated hydrocarbons, which comprises reacting a low boiling isoparafin with a somewhat higher boiling olefin in liquid phase in a plurality of reaction zones in the presence of an alkylatlon catalyst maintained under alkylatwhereby heat of reaction produces vaporization of reacting constituents consisting largely of the isoparallin to provide evaporative cooling of each alkylation reaction zone to maintain the predetermined 'temperature therein, releasing vapor-` ized constituents from each of said react-ion zones and combining the released vapors, compressing and cooling said combined vapors Vto produce a condensate consisting largely of said isoparafdn, and continuously recycling said liquefied isoparaiiin to said alkylation reaction zones to maintain in each zone a'substantial molar excess of isoparailln to olefin therein;

2. 'I'he method according to claim 1, in which the recycled liqueiled isoparailln is returned in independently controlled amount to each of a plurality of said alkylation zones.

3. The method according to claim 1, in which the reaction products flow serially through a plurality of the alkylation zones, and the main- I tained pressures on the said plurality of zones are varied in the direction of flow to provide a temperature gradient throughout the said zones.

4.. The method according to claim 1, in which the maintained pressure on at least one of said reaction zones is varied to thereby vary the temperature of said zone during the course of the reaction therein.

5. The method according to claim l, in which the catalyst is strong surfurie acid of alkylation strength, and in which a portion of the vaporized constituents released from the several reaction zones, and which remains uncondensed in the subsequent compression and cooling, is removed from the system.

6. A process for the alkylation of isoparaiilns with oleilns, which comprises serially passing hydrocarbons containing as the lowest boiling essential constituent thereof a low boiling isoparaflin through a plurality of reaction zones wherein the hydrocarbons are intimately contacted in the liquid phase with an alkylationcatalyst under a1- kylating conditions, introducing a somewhat higher boiling olen in portions and in such amounts into a plurality of said reaction zones- 1 that an excess of isoparaln is continuously maintained therein, whereby isoparamn is alkylated by the olen and heat is generated as a result of the reaction, causing a portion of said hydrocarbons consisting largely of the isoparaiiin in each of said zones to evaporate as a result of the generationvof heat and controlling the temperature by such vaporization.

f 7. A process for the alkylation of isobutane with olens, which comprises serially passing isobutane through a plurality of reaction zones wherein the isobutane is intimately contacted in the liquid` phase with concentrated sulfuric acid under alkylating conditions, introducing a normally gaseous C4 olefin by split injection into said reaction zones, regulating the amount of said injections to maintain continuously'an excess of isobutane in the mixture, whereby isobutane is alkylated by the oleilns and heat is liberated as a result of the reaction, causing avportion of the isobutane in each of said zonesv to vaporize as a result of such liberation of heat, thereby controlling the temperature, condensing the vaporized isobutane and returning the condensate tions, whereby isoparaln vis alkylated by olens of said C4 cracked fraction to produce normally liquid saturated hydrocarbons of high anti-knock value, maintaining the pressure on each of said zones at about the boiling point of the isobutane aseaea? for the predetermined temperature employedin each zone,.whereby heat of reaction produces zones, stabilizing the removed alkylate to separate off gases lighter than Ct hydrocarbons, fractionating the separated off gases to separate an isobutane-rich fraction from a normal butane fraction, and recycling the isobutane-rich fraction to the alkylation reaction zones to assist in maintaining the substantial molar excess of isobutane to olein therein.

9. /The method according to claim 8 in which the recycled isobutane condensate is supplied in independently controlled amounts to a plurality of said alkylation reaction zones.

10. A continuous process for the alkylation of isobutane by means of normally gaseous oleilns in the presence of concentrated sulfuric acid. which comprises concurrently flowing a mixture of sulfuric acidl liquefied isobutane and liqueed' olefin gases through a long closed reaction zone, mechanically maintainingan intimate mixture and iine dispersion. of the hydrocarbons in the acid throughout the length of said zone, withdrawing the heat of alkylation from said zone substantially as fast as it isy generated, whereby long and intimate contact is obtained at a substantially constant temperature within the range of about 40 to 100 F., vaporizing isobutane and olefin hydrocarbons directly from the reaction mixture in said zone, condensing said vaporized hydrocarbons, and returning at least' a substantial part of said condensed hydrocarbons to the reaction zone.

ll1. A continuous process for the alkylation of a low-boiling isoparaiiin with an olen in the presence of an alkylation catalyst, which lcomprises concurrently iiowing a mixture of the alkylation catalyst and isoparailn in liquid phase through a reaction zone, introducing the olen at a plurality of spaced Apoints along said reaction zone, whereby the olefin is intimately contacted with the mixture in liquid phasein said zone under alkylating conditions and isoparaftln is alkylated by the olefin, and withdrawing heat from said zone at a plurality of spaced points along said zone throughout the locus of oleiin introduction by internal vaporization of hydrocarbon from the flowing mixture.

12. The method of catalytically alkylating a. low boiling isoparafiin with normallygaseous ole-f fins in the presence of concentrated sulfuric acid. which comprises concurrently ilowing a mixture of sulfuric acid, liqueiied low boiling ioparaiiin and liquefied olen gases through a long closed reaction zone, subjecting said mixture to intimate mixing4 in said reaction zone to'obtain a iine dispersion of the hydrocarbons in the acid throughout the length of said zone, regulating the pressure throughout the length of said zone' whereby the boiling point of the hydrocarbons therein is maintained at about 40 to 100 F..

removing from said'zone the hydrocarbon vapors which are evolved. therein, condensing at least a part ofsaid evolved vapors and returning said .length of vsaid zone, withdrawingthe heat of alkylation from said zone substantially as fast as it is "generated, whereby long and intimate contact is obtained at a substantially constant 'temperature within the range of about 40 to 100 F., and introducing further amounts of liquefied normally gaseous olen hydrocarbons atspaced points along said reaction zone.

14. The method of catalytically alkylating a lowboiling isoparain with an olefin in the presence of an'alkylation catalyst, which comprises concurrently flowing a mixture of the catalyst 'togetherwith the low-boiling isoparaiiin and ole- Viin in liquid phase through a long closed reaction zone, subjecting said mixture to' intimate mixing in said reaction zone to obtain a ne dispersion of the hydrocarbons in the catalyst throughout the length of said zone, regulating the pressure throughout the lengthpf said zone' whereby the boiling point of 'the hydrocarbons therein, is maintained at about to 100 F., re-

moving from said zone the hydrocarbon vapors which are evolved therein, condensing at least a part ot said evolved vapors and returning at least a part of said condensed vapors to said reaction zone. l

.15.' A continuous process for the alkylation of a low-boiling isoparafiin with an olen in the presence of an alkylation catalyst, which comprises concurrently owing a. mixture ofl the catalyst together with the low-boiling isoparaiiin and olefin in liquid phase through a long closed reaction zone, mechanically maintaining an intimate mixture and fine dispersion of the hydrocarbons in the catalyst throughout the length sult of the generation of heat and controlling the temperature by such vaporization, releasing vapors from each of said zones and combining the released vapors, recovering a condensate consisting largely of the said isoparafiin from the relleased vapors, and recycling at least a portion of said condensate to the reaction zones to assist inmaintaining the molar excessr of isopar- 17. The method in the manufacture of high anti-knock saturated hydrocarbons, which comprises reacting a low-boiling isoparafin with an olefin in liquid phase in a plurality of reaction zones in the presence of an alkylation catalyst maintained under alkylating conditions to produce liquid alkylate, introducing the olen by split injection into a plurality of said zones, in-

dependently maintaining the pressure on each of said zones at about the boiling point of said isoparaiin for the predetermined temperature employed in each zone, whereby heat of reaction produces vvaporization of reacting constituents to provide evaporative cooling of each alkylation reaction zone to maintain the predetermined temperature therein, releasing vaporized constituents from each of said reaction zones and combining the released vapors, recovering a condensate consisting largely of said low-boiling isoparafiin from 'said released vapors and continuously recycling at least a portion of said condensate to` said alkylation reaction zonesto maintain in each zone a substantial molar excess of isoparaiiin to olen therein.

18. The method of catalytically alkylating a low-boiling isoparaiiin with somewhat higher boiling olens of a cracked hydrocarbon fraction in the presence `of an alkylation catalyst, which comprises continuouslyintroducing the low-boiling isoparamn and the cracked hydrocarbon fraction, with the low-boiling isoparaiiin in molar excess of the olefins of said fraction, into an alkylation reaction zone and reacting the sanie therein in liquid phase in the presence of an alkylation catalyst under alkylatof said zone, withdrawing the heat of alkylation from said zone substantially as fast as it is generated, whereby long and intimate contact is ob tained at a substantially constant temperature `within the range'of about 0 to 100 F., and introducing further amounts of. olefin ,inV liquid.

passing the isoparaiiin in liquid phase'through I ing conditions, maintaining a pressure-on the alkylation reaction zoneV at'about the ,boiling point of the said low-boiling isoparaiiin at the predetermined' temperature employed, whereby heat ofy reaction produces vaporization of hydrocarbon constituents including `the low-boiling' isoparafiin to provide evaporative` cooling of the alkylation zone to maintain the said rpredef termined temperature, releasing the resulting hya plurality of reaction zon'escontaining an al- -v kylation catalyst and maintained under alkylat-I ing conditions, introducing an olefin in portions and in such amounts into a plurality of said reaction'zones that a molar excess of yisoparaiin'i-,o olen is continuouslygmaintained therein, whereby isoparaffln is alkylated by the olefin and heat is` generated as a result of,.the reaction, causof said plurality of zones to evaporate as a reing-a portion of the hydrocarbons present in eachf drocarbon vapors from the said reaction zone,

subjecting the released vapors to condensation by compression and cooling, passingl` the resulte,

ing compressed and cooled hydrocarbons to an accumulating. zone, removing hydrocarbon vapors from said accumulating zone and discharging the samefrom the system, recycling resulting liquid condensate consisting largely of the said low-boiling isoparaflin from said accumulating zone to the allwlation vreaction zone to assist in maintaining a molar excess of isoparamn to olentherein, and continuouslyremoving alkylatonreaction products from said reaction zone and Vrecovering alkylate therefrom.

LEBBEUS c. Kam;