US3209051A

US3209051A - Alkylation of hydrocarbons by reducing organic fluoride content of a stream in the operation

Info

Publication number: US3209051A
Application number: US188019A
Authority: US
Inventors: Robert D Bauer; Joe Van Pool
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1962-04-17
Filing date: 1962-04-17
Publication date: 1965-09-28
Anticipated expiration: 1982-09-28

Description

Sept. 28, 1965 R. D. BAUER ETAL 3,209,051

ALKYLATION OF HYDROCARBONS BY REDUCING ORGANIC FLUORIDE CONTENT OF A STREAM IN THE OPERATION Filed April 17, 1962 2 Sheets-sheet 1 O (i I m Z uaddluis U i Ll. D. I

ACCUM,

R. D. BAUER ETAL 3,209,051 ALKYLATION OF HYDROCARBONS BY REDUCING ORGANIC FLUORIDE CONTENT OF A STREAM IN THE OPERATION 2. Sheets-Sheet 2 Sept. 28, 1965 Filed April 17, 1962 United States Patent O 3,209,051 ALKYLATION F HYDROCARBONS BY REDUC- HNG ORGANIC FLUORIDE CONTENT OF A STREAM IN THE OPERATION Robert D. Bauer and .loe Van Pool, Bartlesville, Okla., as-

signors to Phillips Petroleum Company, a corporation of Delaware Filed Apr. 17, 1962, Ser. No. 188,019 8 Claims. (Cl. 260-683.42)

This invention relates to alkylation of hydrocarbons. In one of its aspects, it relates to the reduction of organic iluorides in a stream in the operation by removing the organic fluorides at a place at which these have been vfound to tend to concentrate. In another aspect of the invention, the organic fluorides which have been recovered, as stated, can be returned to the alkylation operation, for example, to the alkylation reactor or settler for further reaction according to methods now known or described in copending application of W. E. IPlaster, Serial No. 182,- 847, filed March 27, 1962.

The alkylation of hydrocarbons, for example, the alkylation of an isoparain such as isobutane, with an alkylating agent such as propylene and/ or butylenes is known. It is also known to alkylate aromatics with oleiins and with olefin-forming materials.

In the recovery of the products resulting from an alkylation in which propane is produced, as in the alkylation of isobutane with butylenes and/or propylenes in the presence of hydrouoric acid as catalyst, there is practiced a removal of propane which otherwise tends to build up in the operation. Thus, there is fed in such an operation a stream containing propane, isobutane and hydrofluoric acid to a propane fractionator, the overhead from which is propane and HF and the bottoms from which is isobutane. Heretofore, the alkyl fluorides contained in the feed fed to the propane fractionator have been distributed in at least one product removed therefrom. It has now been found that these alkyl fluorides tend to concentrate in the fractionator reaching a maximum concentration at a :point intermediate the removal of bottoms and the taking off of overhead. Based upon this concept, there is the additional concept to remove alkyl fluorides from the propane fractionator at a point of maximum fluoride concentration. Thus, a side cut rich in fluorides is obtained and this can be recycled to the contactors for alkylation or elsewhere to recover the alkylatable uorides, i.e., the fluorides which will act as alkylating agents. The fluorides can otherwise be removed as may be desired.

It is an object of this invention to provide an improved alkylation operation. It is a further object of this invention to reduce the fluoride content of certain streams obtained in the recovery of effluents from an alkylation operation. It is a further object of this invention to substantially reduce or eliminate after treatment of certain streams resulting from a hydrouoric acid alkylation operation, for example, to reduce the size or need lfor so-called bauxite defluorinators. It is a further object of the invention to reduce the fluoride content of the ultimate hydrocarbon or gasoline product which are produced by alkylation.

Other aspects, objects and the several advantages of this invention are apparent from a study of this disclosure, the drawing and the appended claims.

According to the present invention, alkyl uorides, or other fluorides, are removed from. a point in the operation at which these tend to produce a maximum concentration. For example, in the alkylation of an isoparaftin with an olefin wherein propane is formed, it is found, according to the invention, that the alkyl iluorides tend to concentrate at a point intermediate the propane overhead removal and the isobutane bottoms of a propane fractionator.

FIGURE 1 lis a schematic diagram of an alkylation proclCC ess wherein, in the fractionation section, the depropanizing has the side draw removal. The depropanizer has charged thereto the overhead product from the deisobutanizing zone.

FIGURE 2 is a schematic diagram of an alkylation process wherein the depropanizer has the side draw, and a portion of the reactor effluent is the feed to the depropanizer.

Referring now to the drawing, in FIGURE l, there are passed to an alkylation zone 1 by way of 2, 3, and 4, respectively, isobutane, a mixture of butylenes and propylene, and hydrogen fluoride. Upon alkylation, the admixture is allowed to settle, forming a lower acid phase which is returned by way of 5 and a hydrocarbon phase which is passed by 6 into alkylate fractionator 7. In fractionator 7, there is performed a separation of alkylate removed at 8, obtaining overhead a stream containing in addition to some xed gases propane, isobutane and hydrogen fluoride. The overhead passes by 9 into propane fractionator 10 from which an isobutane bottoms 11 is obtained. This isobutane is recycled to alkylator 1 by way of 2. Propane overhead is taken off at 12, together with some HF, and sent to the HF stripper 20 for recovery of propane 21. HF which is recovered is returned for further use in the operation. P-ropane is flared, recovered as L.P.G., or otherwise disposed of. According to the invention, there is taken a fluoride-rich side cut 13 which, in this instance, is controlled as to flow by controller 14 and `control valve 15. The control is so effected as to maintain in tray 16 a high concentration of fluorides. The removed fluorides, as indicated, are returned to the alkylation reactor or to the settler or can be disposed of in fuel gas or any other suitable processing step. In this embodiment, the iluorides are returned to the alkylation operation.

According to the invention, by providing a plurality of trays as indicated at 17 and 1S, it is possible either during the operation or by prior calculation based upon data to determine just where will be the concentration of fluoride such that it should be removed from the tower according to the invention. If, for any reason, a change of position occurs, the plurality of trays'16, 17 and 18 can be operated to yield the fluoride stream which is desired to be removed. One skilled in the art in possession of this disclosure, having studied the same, will understand how these trays can be operated to remove fluorides while removing the least amount of undesired propane. Any isobutane which is removed with the fluoride stream is helpful in conducting this fluoride stream back to the alkylation or otherwise disposing of the same. Obviously, since it is not desired to waste isobutane, at the very least the invention improves the operation by the recovery of the isobutane while at the same time reducing the need for extensive treatment of the propane stream to yrecover lluorides therefrom. By practicing the reduction of uorides, in general, there is obtained a reduction of fluoride content in the various streams in which fluoride normally builds up and, to this extent, the alkylate is found to be low in fluoride content with consequent possibility of reduction or elimination of the after-treaters, `for example. the bauxite defluorinators.

Referring now to FIGURE 2 (to which the example is directed), there are passed to an alkylation zone 101 by way of 102, 103, and 104, respectively, isobutane, a mixture of butylenes and propylene, and hydrogen fluoride. Upon alkylation, the mixture is allowed to settle, forming a lower acid phase which is returned by way of 105 and a hydrocarbon phase of which a portion is passed by way of conduit 106 and conduit 130 into isobutane stripper 107. The bottoms product 108 from stripper comprises normal butane and heavier (including alkylate), and the overhead from 107 is passed by way of conduit 111 as recycled isobutane to the alkylation reaction zone 101. Another portion of the hydrocarbon phase is passed from alkylation zone 101 by way of conduit 106 and conduit 109 as feed for depropanizer 110. Bottoms from tower 110 is passed by way of conduit 114 and also charged to isobutane stripper 107. The overhead yield from depropanizer 110 is charged by way of conduit 119 and conduit 112 to the propane stripper 120. Propane, substantially free of organic uorides is recovered by way of conduit 121. HF which is recovered is recycled to the alkylation zone. According to the invention, there is removed an organic uoride (isopropyl fiuoride) -rich side stream 113 which, in this instance is controlled by controller 122 and valve 115. The control is effected so as to maintain in tray 116 a high concentration of organic uorides whose rate of removal substantially eliminates organic fluorides from the overhead stream 119. The removed fluorides are returned to alkylation, as illustrated, or to any other suitable usage.

According to the invention, a plurality of side draws from

trays

116, 117, and 11S are available for use, and the selection of the proper tray where fluoride concentration is the highest is made.

SPECIFIC EXAMPLE lOperation of propane column (110):

Feed temperature, 150 Top temperature, F 130 Sidedraw tray temperature, F 142 Bottom temperature, 220 Reux temperature, 85

Reflux feed volume ratio, 0.744

Tower 110 is a SO-tray tower of 76 percent eiciency. The side draw is on the forty-third tray from the bottom. The depropanizer overhead is substantially free of isopropyl fluoride.

DEPROIANIZER COLUMN (110) Mol fraction iC3F in Tray number liquid (Concentration (From bottom) gradient) *The maximum isopropyl fluoride content is on the forty-fourth tray.

Conventional operation, saine tower opl-rating conditions STREAM FLOWS, MOLS/HOUR Sido draw (Not used) Overhead (Less reflux) (131) Bottoms Stream component Feed (109) (114) (0. 05376) 4. 2 Trace Truce Trace Trace 425. 8

Hydrogen luoride Propane Isopropyl iuori Isobntane Normal butane Isopentane Light alkylate Heavy alkylate Total It has been estimated that with the use of this invention there is a savings of approximately $70.00 per day on a 2,000 barrel per day throughput in an alkylation unit in which isobutane is alkylated with isobutylene employing hydrouoric acid as a catalyst. Upon improvement of the separation of the organic uorides, according to the invention, it appears that eventual complete elimination of bauxite deuorinators might well be obtained. In any event, a great reduction in their use is permitted by practice of the invention. The invention is of particular interest at this time since it now appears that the Natural Gasoline Association of America will probably set requirements or specifications for alkylate to contain less than 50 parts per million of uorides.

It will be noted that the concept to take advantage of the fact that uorides will concentrate in the depropanizer appears new in the art. Indeed, the discovery that these uorides will concentrate so that they can be removed as a side cut from a depropanizer appears to be novel in the art.

It will be evident to one skilled in the art having studied this disclosure, the drawing and the appended claims that there has been set forth a method for alkylating an alkylatable compound with an alkylating compound in the presence of hydrouoric acid lwherein organic fluorides are formed and tend to concentrate in the system which comprises passing a stream containing said Iluorides to a fractionation operation, therein concentrating the iluorides, and removing the fluorides from said fractionation operation.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, drawing and the appended claims to the invention the essence of which is that a uoride-rich side stream is removed from a product stream fractionator, such as a propane fractionator, in the conventional alkylation operation.

We claim:

1. In a method of alkylating in an alkylation reaction zone an isoparaflin with an olefin to produce an alkylate, wherein propane is formed, and wherein hydrofiuoric acid is used as a catalyst, the steps which comprise in a irst zone fractionating the alkylate produced to obtain a first alkylate stream and a second stream comprising propane, isobutane, hydrouoric acid and alkyl fluorides, in a second zone fractionating said second stream to obtain overhead comprising propane and hydrouoric acid vapors and a bottoms product comprising isobutane, in said second zone at an intermediate locus thereof concentrating alkyl fluorides, removing from said second zone and from said locus a side fraction containing said organic uorides which have concentrated therein, and passing said side fraction to said alkylation reaction zone.

2. In a method of alkylating in an alkylation reaction zone an isoparaiin with an olefin to produce an alkylate, wherein propane is formed, and wherein hydrouoric acid is used as a catalyst, the steps which comprise passing an alkylation reaction mass which is obtained to a settling zone, in said settling zone allowing the reaction mass to settle into at least two phases, an acid phase and a hydrocarbon phase, in a rst zone fractionating the hydrocarbon phase produced to obtain a tirst alkylate stream and a second stream containing propane, isobutane, hydroiiuoric acid and alkyl luorides, in a second zone fractionating said second stream to obtain overhead comprising propane and HF and a bottoms product comprising isobutane, in said second zone at an intermediate locus thereof concentrating alkyl fluorides, removing from said second zone at said locus a side fraction containing said organic iluorides which are concentrated therein and passing said side fraction into said settling zone.

3. An improved method for alkylating an isoparaflin and an olefin employing HF acid catalyst which cornprises contacting said isoparaflin and said olen in presence of said acid in an alkylation reaction zone forming an alkylation reaction zone eluent, separating an acid phase from said elluent, then fractionating said eiuentA to separate an alkylate product containing fraction and a second fraction containing unreacted isoparain, paratin, alkyl fluorides and HF, fractionating said second fraction to recover therefrom, as separate fractions, unreacted isoparafiin, parat-lin and HF, and an alkyl fluorides concentrate, and returning said concentrate to the alkylation reaction.

4. An operation according to claim 3 wherein the isoparaiiin is isobutane and the olefin is at least one olefin selected from the group consisting of butylenes and propylene.

5. An improved method for alkylating isoparaiiin and an olefin employing HF acid catalyst which comprises contacting said isoparain and said olefin in the presence of said acid in an alkylation reaction zone forming an alkylation reaction zone effluent, in a settling zone separating an acid phase from said eiiluent, then fractionating said efuent to separate an alkylate product containing fraction and a second fraction containing unreacted isoparaflin, paraffin, alkyl iiuorides and HF, fractionating said second fraction to recover therefrom as separate fractions unreacted isoparafn, paraiiin and HF and an alkyl fluorides concentrate, and returning said concentrate to said settling zone.

6. An operation according to claim 5 wherein the isoparaiin is isobutane and the olefin is at least one olefin selected from the group consisting of butylenes and propylene.

7. An improved method for alkylating an isoparaiiin and an oleiin employing HF acid catalyst which cornprises contacting said isoparain and said olen in the presence of said acid in an alkylation reaction zone forming an alkylation reaction zone eiiiuent containing low boiling paraiiin, separating an acid phase from said efuent, in a iirst fractionation zone fractionating a portion of said effluent to remove therefrom an alkylate product containing fraction, in a second fractionation zone fraetionating another portion of said eiuent to separate therefromV a iirst fraction containing alkylate product and unreacted isoparaflin, a second fraction containing low boiling parain and HF, and a third fraction containing alkyl iiuorides concentrated therein, which is obtained intermediate said irst and second fractions, and returning said alkyl fluorides to the alkylation operation for further reaction therein.

8. A method according to claim 7 wherein said first fraction containing alkylate product and unreacted isoparaflin is passed to said first fractionation zone.

References Cited by the Examiner UNITED STATES PATENTS 2,347,317 4/44 Gibson 260--683.49 2,914,590 11/59 Van Pool 260-683.48 X 3,073,877 l/63 Sherk 260-683.48 3,073,878 1/63 Johnson 260-683.48

ALPHONSO D. SULLIVAN, Primary Examiner.

Claims

1. IN A METHOD OF ALKYLATING IN AN ALKYLATION REACTION ZONE AN ISOPARAFFIN WITH AN OLEFIN TO PRODUCE AN ALKYLATE, WHEREIN PROPANE IS FORMED, AND WHEREIN HYDROFLUORIC ACID IS USED AS A CATALYST, THE STEPS WHICH COMPRISE IN A FIRST ZONE FRACTIONATING THE ALKYLATE PRODUCED TO OBTAIN A FIRST ALKYLATE STREAM AND A SECOND STREAM COMPRISING PROPANE, ISOBUTANE, HYDROFLUORIC ACID AND ALKYL FLUORIDES, IN A SECOND ZONE FRACTIONATING SAID SECOND STREAM TO OBTAIN OVERHEAD COMPRISING PROPANE AND HYDROFLUORIC ACID VAPORS AND A BOTTOMS PRODUCT COMPRISING ISOBUTANE, IN SAID SECOND ZONE AT AN INTERMEDIATE LOCUS THEREOF CONCENTRATING