US2246703A

US2246703A - Alkylation

Info

Publication number: US2246703A
Application number: US248188A
Authority: US
Inventors: Ernest W Thiele; Robert C Gunness
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1938-12-29
Filing date: 1938-12-29
Publication date: 1941-06-24
Anticipated expiration: 1958-06-24

Description

atented .inne 24, i941.

Application lilieceinheii'` 29, 193, Seriai No. 248388 (ci. iosa-it) Claims.

This invention relates to alkylation and it pertains more particularly to the alkylation oi isobutane with normally gaseous oleflns.

it has been found that when -a mixture of gaseous oleflns and a larger amount of isobutane are intimately contacted with concentrated sulfuric acid at about room temperature the oleflns chemically combine with the isobutane to form isoheptane, iso-octanes, etc. If this alkylation reaction is carried out under proper conditions the gaseous hydrocarbons may be almost completely converted into a high quality motor' fuel which is characterized by a very high octane number.

The alkylation reaction is-exothermic and it is important that heat vbe abstracted from the system as fast as it is liberated. High temperatures cause excessive oxidation, fouling of the acid and an increase in acid consumption. I ow temperature operation is undesirable because of th`e high viscosity of the acid layer. An object of our method for controlling reaction temperatures so that the acid may be utilized with maximum effectiveness to produce isoparamns of the 'gasoline boiling range.

A further object of our invention is to provide a continuous alkylation system which will give the necessary intimate mixing of acid and hydrocarbone, and which will provide for the most ef 4 fective utilization oi isobutane and oleiins, respectively. Other objects w`ill be apparent as the detailed description of our invention proceeds.

In practicing the invention we subject the hydrocarbon-acid mixture to prolonged and vigorous agitation in a continuous ow system wherein the desired temperature is held within closely den ned limits of about 30 to 100 F., preferably 50 to 60 Close temperature regulation is an important feature of the invention and it is preferably edected by either'direct or indirect evaporatlve cooling producedby the vaporization of liquefied gases introduced into the system or separated from the system. Optimum olen concentration is maintained along the line of flow by the addition of olefins t at spaced points' or by the vaporization of isobutane from the reaction mixture to eect cooling. The acid is continuously Fig. 2 is a ow diagram of another modincation embodying direct evaporative cooling;

Fig. 3 is a diagrammatic vertical section of a fiash drum and condensing system which may be substituted for the corresponding parts of Fig. 2.

The invention is particularly applicable to the alkylation 'of isobutane, although it may also be employed for the alkylation of isohexane and isopentane. ployed in as pure a state as possible, but for practical purposes we employ a natural gas fraction or a refinery butane cut, i. e., a butane fraction obtained from the products of thermal or cata lytic cracking, isomerization or dehydrogenation of hydrocarbon gases or liquids. The olef'lns may be separated from such fractions by solvent extraction or azeotiopic distillation, and the iso- Y butane may be separated from normal butane and invention is to provide an improved means and Y and to introduce further olei'lns from time to time recycled, a part of it being constantly withdrawn for purification and concentration'and makeup acid being constantly added to compensate for that which is withdrawn. r

Other features of the invention will be appar- Fig. 1 is a flow diagram of our improved alkylation system employing indirect cooling;

lines are, of course, unnecessary. We prefer to employ at least 2 volumes of isobutane per volume of butenes or other olens, and for optimum alkylation we prefer to start with about 8 to l0 volumes of isobutane per volume of olefin feed as the reaction proceeds. However, where the available isobutane is small compared to theA available oleflnes, a smaller ratio of isobutane to olens may be employed.

Referring to Fig. 1, sulfuric acid of about to %v concentration is introduced by-pump I6 through line I5 and by pump 25 through line 24,

the combined acidfolen and isobutane being' passed through cooler Il, wherein the heat of the alkylation reaction is absorbed by a refrigeratlng fluid., The reaction requires considerable time and there is a tendency for the emulsion to'break and separate. We therefore pass the partially reacted mixture from cooler I1 into a second mixer I8 wherein the hydrocarbons are again thoroughly and intimately dispersed throughout 'Y The isobutane is preferably em The pressure in the system` the acid. A-small amount of additional liquefied olefin feed may be introduced through line Ita anexos normal butane does not seriously affect the course into or ahead of the mixer. Mixer "discharges into cooler I! which in turn discharges into a third mixer 2l for re-emulsiilcation and intimate mixing of the acid and hydrocarbons with contained and/or further amounts of liquefied oleiin feed added through line 2l. Mixer 2l discharges into a .third cooler 22. uWhile three mixers and coolers are described for the purpose of illustrating the invention, it should be understood that this number may be greatly increased, and the of the reaction, but in a cyclic process of this type suitable provision must, of course, be made to prevent the building up of unlimited accumulation of such inert materials. Any ethane or ethylene which nds its way into the system may be purged therefrom through line 51.

1n Fig. 2 we have shown a modification of our invention wherein the series of alternate mixers exact number of stages will depend upon the intimacy of the mixing obtained in each mixer and vthe time of contact permitted in each cooler. Al-

' withdrawn through line 21 for purification and concentration and an equivalent amount of and coolers is replaced by an elongated reaction vessel 5I which is provided with high speed stirrers driven by a suitable motor 60. In.this

4embodiment the cooling is'eil'ected by the vaporization of isobutane-and olefins directly from the reaction mixture. The elongated agitator and cooler I8 discharge into separator flash drum Si through a relatively large opening so that a substantially uniform gas pressure is maintained throughout the agitator and flash drum. Suitable bailles may be employed in the agitator to prevent short-circuiting and entrainment, and suitable baille plates may be used in the separator drum to` prevent the entrainment of acid with the. gases which pass upwardly therein. The pressure in the agitator and flash drum is maintained at a substantially constant level so that the boiling-point of the isobutane-olefin mixture makeup acid ls introduced through line Il as hereinabove described.

The hydrocarbons from the acid settlerare withdrawn through line 28. the vessel 2l being run full of liquid. A caustic solution is added through line and the mixture passed through mixer 3| to caustic settler 32. Spent caustic wash is withdrawn from the base of settler 32 through line 3l in amounts regulated by ,liquid level control valve 34. Neutralized hydrocarbons' are withdrawn through line to receiver 40. From this receiver they are passed by pump 4I through heater 42 into fractionating system 42 provided; with suitable redux means 44 and reboiler means 4l. Alkylated products, chiey iso-octane and other hydrocarbons of the 'gasoline boiling range are withdrawn through line 46. Condensable gases are taken overhead through line Il and passed through condenser 4I to receiver 49. A part of these liquefied condensables is then forced by pump il through line 5I and branch lines l2 to serve as a cooling fluid for coolers I1, il and 22. 'Ihe heat of alkylation in these coolers vaporizes the condensables and the vapors are withdrawn through branch lines 53 and return line/I4 to compressor 55. I'he compressed gases are then returned through condenser I4I to receiver Il.

The suction pressure at which compressor Ii operates is so regulated that the boiling point of the liqueed condensables is about 20 to 50 F. Thus the heat of alkylation in the coolers causes vaporization of liquefied condensables in the outer shell,A and since the boiling point of the condensables is fixed by the pressure maintained thereon, the temperature of the coolers is maintained at a constant level and within much narrower limits than could be obtained by the use of water or other cooling media.

That portion f the condensables which is not required as a refrigerating medium is withdrawn through line i6. If this fraction contains appreciable amounts of isobutane it maybe recycled with the feed stock. IfI it contains substantial the oondensabl are recycled. The presence of 75 is` maintained at about 50 to 60 F.

The vaporized iso-butane and Yolefin gases are condensed in the upper part of the flash drum by means of cooling coils 62, the amount of cooling fluid in these coils being regulated by pressurecontrolled valve 63 so that if the pressure in the separator drum tends to increase, an additional amount of cooling fluid will be circulated through the coils, and if'the pressure tends to decrease, the amount of cooling fluid will likewise be decreased. Condensed isobutane and olefin hydrocarbons are collected in pan 64 and returned through line 65 with th isobutane feed.

If impure feed gases are employed and there is a tendency toward the accumulation of normal butane, the gases from line 65 may be withdrawn through line I8 for the separation of such normal butane prior to the return of the isobutane to the system. If ethane or ethylene nds its way into the system it may be vented therefrom through line il which is preferably provided with a reflux cooler 68 to prevent the loss of C3 and C4 hydrocarbons.

, It should be noted that the composition of hydrocarbon vapors liberated in the agitator and cooler may not be the same as the composition lof these hydrocarbons which remain in liquid condition. If the oleflns consist chiey of butylene and if the isobutane to butylene ratio is about 8 to 1, the isobutane will be removed from the liquid reaction products more rapidly than the isobutylene, in which case it may be unnecessary to add additional olens through branch lines lia, lsb, 2| and 2Ia. However, if the olefin is chiefly propylene, or if it is used in relatively large amounts, it may, due to its lower boiling point, be present in the vapors in the same or greater proportions than in the liquid Ahydrocarbons. In such cases the olefin concentration should be augmented by introducing additional liquid olefin at spaced points along the agitator vessel through lines Isa, lsb, 2l, Zia, etc.

Instead of placing the cooling coil 62 in the separator drum itself, the condensation of vaporized isobutane and olefin gases may be effected outside of the flash drum as illustrateddn Fig. 3. In this case a large gas line I! leads from the top of the separator drum through cooler 10 to liquid turned through line 65 as hereinabove described. In this modification the uncondensed gases are vented through line l2 instead of through line 6l,

and the pressure in the system may be varied by regulating the iiow of cooling medium in line 13 in accordance with the pressure in the flash drum, or, by regulatingr the valve in line 12 in accordance with such pressure.

In both Figs. 1 and 2 it will be noted that we have provided a continuous process which permits a relatively long time of contact with constant intimate mixing and constant temperature control throughout the alkylation reaction. The reaction temperature is closely controlled in both cases and is held within much narrower limits than is possible in allavlation systems heretofore employed. The ratio of olefin to isobutane is maintained substantially constant throughout the reaction to avoid undesirable polymerization and to obtain maximum utilization of the isobutane.

Condensable gases from the system itself are.

utilized to absorb the heat of reaction.

While we have described certain embodiments of our invention in considerable detail, it should be understood that the invention may be practiced in other types of apparatus than that illustrated and that other equivalents and modifications of the invention will be apparent to those skilled in the art from the above descriptions of preferred embodiments. A

We claim:

1. The method of catalytlcally alkylating an isohydrocarbon of the class consisting of isobutane. isopentane and isohexane'with normally gaseous oleins in the presence of concentrated sulfuric acid which comprises concurrently owing a mixtureof sulfuric acid, liquefied isohydrocarbon and liquefied olefin gases through a longA closed reaction zone, subjecting said mixture to high speed mixing in said reaction zone to obtain a fine 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 of said evolved vapors and returning said condensed vapors to said reaction zone.

2. The method of claim l which includes the further steps of passing the mixture of liquid and vapors from the reaction zone to a separating zone, separating vapors from liquids in said separating zone, cooling the separated vapors and regulating the amount of cooling of said vapors in accordance with the pressure in the separating zone.

3. 'I'he method of alkylating an isohydrocarbon of the class consisting of isobutane, isopentane and isohexane with normally gaseous oleiins in the presence of concentrated sulfuric acid' which comprises concurrently owing a mixture of sulfurlc acid, liquefied isohydrocarbon and liquefied olefin gases through a long closed reaction zone and thence to a separation zone, subjectingthe mixture in the reaction zone to vigorous mechanical agitation, regulating the pressure in said mixing and separating zones to maintain a temperature. therein of about 40 to 100' F., cooling the separated vapors and returning at least a part of the separated vapors to said reaction zone, passing the liquids from said separating zone to a settling zone, removing acid from the 4. A continuous process for the alkylation of and isohydrocarbon of the class consisting of isobutane, isopentane and isohexane in the presence of concentrated sulfuric acid which comprises passing said sulfuric acid through a long closed reaction zone, introducing liqueied isohydrocarboninto said zone and passing it through said zone concurrently with said acid, introducing smaller amounts of liquefied normally gaseous olens into said zone and passing them concurrently with the iiow of acid a'nd isohydrocarbon, intimately mixing said acid, isohydrocarbon and olefin liquids in said zone by high speed mechanical mixing, withdrawing heat from said zone at spaced points along said zone substantially las fast as it is generated, effecting said withdrawal of hearI by the vaporization of a liquefied normally gaseous hydrocarbon in heat exchange relation with said acid, isohydrocarbon and olefin liquids in said zone, maintaining the temperature of the reaction zone at about 40 to 100 F., maintaining an isohydrocarbon concentration in said zone about-two to ten times as great as the concentration of olen hydrocarbons therein, separat-- ing the reaction products from the acid, recycling at least a part of the acid from the separation step to the closed reaction zone, separating isohydrccarbon from the reaction products and returning at least a part of said separated isohydrocarbon tosaid reaction zone.

5. A continuous process for the alkylation of an lsohydrocarbon of the class consisting of isobutane, isopentane and lsohexane by means of normally gaseous oleilns in the presence of concentrated sulfuric acid, which comprises concurrently flowing a mixture of sulfuric acid. liqueiied isohydrocarbon and liquefied olen gases through a long closed reaction zone, mechanically maintaining an intimate mixture and ne 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 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 at spaced points along said reaction zone.

6. A continuous process for the alkylation of isobutane by means of normally gaseous olefins in the presence of concentrated sulfuric acid, which comprises concurrently flowing a mixture of sulfuric acid, liqueed isobutane and liquefied olefin gases through a long closed reaction zone, mechanically maintaining an `intimate mixture and fine 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 is 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 olen 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 ERNEST W. THIELE. ROBERT C. GUNNESS.

mscLMMER 2,246,703.Emest. W. Thiele and Roert 0. Gunness, Chicago, Ill. ALxm'noN. atent dated June 24, 1941. Disclaimer le'd December 26, 1942, by the assignee, Standard Oil Company (Indiana). Hereby enters this disclaimer to claims I1, 5, and 6Min said specification.

[Oficial Gazette February 9, 1948.]