US3872181A

US3872181A - Production of ethyl fluoride for hf alkylation

Info

Publication number: US3872181A
Application number: US288937A
Authority: US
Inventors: Charles C Chapman
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1972-09-14
Filing date: 1972-09-14
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18

Abstract

An improved HF alkylation process is described which comprises alkylating an isoparaffin with an olefin, separating a stream containing HF and ethane from the reaction effluent, contacting this separated stream with ethylene to convert the HF content of the stream to ethyl fluoride, thereafter separating ethane free of HF from the ethyl fluoride. A preferred embodiment comprises passing the separated ethyl fluoride to the alkylation zone to provide at least a portion of the ethyl fluoride requirements for an improved ethyl fluoride promoted HF alkylation process.

Description

United States Patent 1191 Chapman Mar. 18, 1975 [54] PRODUCTION OF ETHYL FLUORIDE FOR 2,487,142 11 1949 Kelley 2b()/(183.42 HF ALKYLATION 2,542,927 2/l95l Kelley EGO/(183.48 3,763,265 10/1973 Hutson, Jr. et 111. .1 260/683.48

[75] Inventor: Charles C. Chapman, Bartlesville,

Okla.

[73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

[22] Filed: Sept. 14, 1972 [211 App]. No.: 288,937

[52] U.S. Cl... 260/683.49, 260/683.42, 260/683.51, 208/70 [51] Int. Cl. C07c 3/54 [58] Field of Search 260/683.48, 683.49, 683.42

[56] References Cited UNITED STATES PATENTS 2,399,368 4/1946 Matuszak 260/683.48 2,476,750 7/1949 Matuszak 260/683.48

Primary Examiner-Delbert E. Gantz Assistant Exanzincr-G J. Crasanakis 6 Claims, 1 Drawing Figure is 17 254 l 20\ L LEGEND ALKYLATION I FRACTIONATION ILSLIX ACCUMLIL -\T|ON IH mNvr RSION ISZ HJENTEU 3.872.181

III

LEGEND ALKYLATION I EXTRACTION yI FRACTIONATION 111,111 CRACKING SZII ACCUMULATION 111 ABSORPTION m CONVERSION 'ISZ PRODUCTION OF ETHYL FLUORIDE FOR HF ALKYLATION This invention relates to an improved HF alkylation process for the alkylation of isoparaffins with olefins.

In the practice of HF alkylation processes heretofore it has been generally necessary to remove from the system at least a portion of the ethane and lighter material to prevent the buildup ofthese materials which are normally present in small amounts in the feed to the HF alkylation process and/or are produced therein. However, the ethane stream recovered from the alkylation effluent contained HF, and it was necessary that this HF be removed before the ethane stream would be as able for most purposes. Although the HF could be separated from the ethane and other materials by fractionation, it would be an expensive procedure involving low temperatures. Various chemicals such as bauxite or various metal hydroxides could be employed to react with the HF, but this involves the cost of the chemicals as well as the problem ofdisposal ofthe undesirable HF reaction product.

It has now been found that the ethane effluent stream, comprising ethane and HF, can be efficiently and economically processed to produce a clean (HF- free) ethane stream and an HF reaction product which is useful in the alkylation process by contacting the ethane stream containing HF with an ethylene stream to convert the HF content of the ethane stream to ethyl fluoride. The ethyl fluoride is readily separable from the ethane and can be employed to provide at least a portion of the ethyl fluoride promoter requirements of an ethyl fluoride promoted HF alkylation process. Any methane contained in the ethane stream can be recovered and used as fuel gas with no HF atmospheric pollution. The HF-free ethane can be used as clean fuel or as a clean HF-free charge to a dehydrogenation process to produce ethylene, or the like.

It is an object of this invention to avoid the use of an ethane stream containing HF in hydrocracking processes or as a fuel. Additionally, it is an object to recover and use the HF content of the ethane effluent of an HF alkylation process in the preparation ofethyl fluoride and at the same time produce a clean ethane product stream. The attainment of the foregoing objects and advantages associated therewith will be readily apparent from the following description, drawing and the appended claims.

According to this invention, an improved HF alkylation process has been found which comprises HF alkylation of an isoparaffin with an olefin, separation of the HF catalyst from the alkylation affluent product stream. separation of a by-product stream containing ethane and lighter materials, including HF conversion of the HF content ofthe by-product stream to ethyl fluoride, and separation of an ethane product stream from the ethyl fluoride. An additional embodiment includes the passage of at least a portion of the separated ethyl fluoride to an alkylation reaction zone in order to provide at least a portion ofthe ethyl fluoride promoter requirements for an improved ethyl fluoride promoted HF alkylation process.

The process of this invention will be further illustrated by reference to the single FIGURE of the drawing which is a diagrammatic representation of an exemplary alkylation process embodying the present invention.

A suitable hydrocarbon feedstock is passed to cracking zone VII via conduit stream 15. An ethane, ethylene and lighter first hydrocarbon stream is withdrawn from cracking zone VII and passed via conduit l9 to absorption zone VIII, and if desired a portion thereof is passed via conduit 19' to fuel gas disposal. Lean absorption oil is withdrawn from fractionation zone IX. cooled and passed to absorption zone VIII via conduit 22. A second hydrocarbon stream comprising essentially methane fuel is withdrawn from absorption zone VIII via conduit 21 as a product stream. A third hydrocarbon stream comprising ethane and ethylene absorbed in the absorption oil is withdrawn from absorption zone VIII and passed to fractionation zone IX via conduit 20. A fourth hydrocarbon stream comprising essentially ethylene and ethane is withdrawn from fractionation zone IX, cooled and passed via conduit 23 to conversion zone IV. A first olefin feedstock comprising essentially propylene and butylenes is withdrawn from cracking zone VII and passed via conduit 17 to alkylation zone I. A first isoparaffin feedstock comprising essentially isobutane is withdrawn from cracking zone VII and is passed via

conduits

16 and 18 to alkylation zone I. Additional isoparaffin feedstock comprising essentially isobutane is passed via

conduits

24 and 18 to alkylation zone I. An alkylation effluent product stream is withdrawn from alkylation zone I and passed via conduit l to fractionation zone II. A first alkylation product stream comprising propane and lighter hydrocar bon fractions and HF is withdrawn from fractionation zone ll, partially cooled and passed via conduit 5 to accumulation zone III. A second alkylation product stream comprising C and heavier alkylate products is withdrawn from fractionation zone II via conduit 2 as a motor fuel alkylate product stream. A third alkylate product stream comprising n'butane is withdrawn from fractionation zone ll via conduit 3 as a n-butane product stream. A fourth alkylation product stream comprising isoparaffins, e.g., isobutane, is withdrawn from fractionation zone II and recycled via conduit 4 to alkylation zone I. A first accumulation product stream comprising propane, ethane and lighter hydrocarbon frac tions and HF is withdrawn from accumulation zone III and passed via conduit 6 to a conversion zone IV. A second accumulation zone product stream comprising liquefied HF is withdrawn from accumulation zone III via conduit 7 and is recycled to zone I or alternatively a portion thereof is passed via conduit 7' to conversion zone IV wherein the HF content passed to said conversion IV zone via conduits 6 and 7 is converted to ethyl fluoride by reaction with ethylene passed via conduit 23 to said conversion zone. A first conversion product stream comprising HF-free ethyl fluoride, propane, ethane and lighter hydrocarbon components is withdrawn from conversion zone IV and passed via conduit 8 to fractionation zone V. A first fractionation zone V product stream, comprising essentially ethane and any methane contained therein, is separated via conduit 9 as a product stream free of ethyl fluoride. A second fractionation zone V product stream, comprising essentially propane and ethyl fluoride, is passed via conduit 10 to alkylation zone I. A third accumulation zone stream comprising liquefied propane is withdrawn from accumulation zone III and passed via conduit 11 to fractionation zone II as reflux. A portion of the third accumulation zone lll stream comprising liquefied pro pane is withdrawn from accumulation zone III and passed via conduits 11 and 11' to extraction zone VI. A first extraction zone VI stream comprising propane essentially free of ethyl fluoride, but containing dissolved HF therein is withdrawn from the extraction zone V1 via conduit 12 and charged to a conventional HF stripper (not shown) to yield HF-free LPG qualilty propane product. A second extraction zone VI stream. comprising HF and ethyl fluoride, is withdrawn from extraction zone Vl via conduit 14 and passed to alkylation zone 1.

In general, the alkylation of isoparaffins with olefins can be carried out under any HF alkylation reaction conditions wherein olefins are alkylated with isoparaffins with recovery of substantial quantities of isopentane and heavier alkylate reaction product; A preferred embodiment of this invention comprises the alkylation of isobutane with propylene and/or butylenes carried out in an alkylation zone under ethyl fluoride promoted HF alkylation reaction conditions wherein olefins heavier than ethylene are alkylated with isoparaffins with the recovery of substantial quantities of isopenlane and heavier alkylate reaction product. In general, the practice of the preferred embodiment comprises carrying out the alkylation reactions under alkylation reaction conditions wherein ethyl fluoride is present within the alkylation zone in an amount of from about to about 35 percent by weight based on the total weight of the catalyst system employed including both the ethyl fluoride and the HF. The ratio of isoparaffin to olefin feedstock heavier than ethylene can vary widely; however, preferably it is within the range of from about 2:1 to about 100:1, more preferably from about :1 to about 15:1, and still more preferably from about 11:1 to about 14:1, on a mo] weight basis. The alkylation reactions can be carried out in the alkylation zone at any temperature at which the alkylation reactions occur. In general, suitable alkylation temperatures comprise temperatures of from about 35F to about 200F, more preferably from about 70F to about 120F, with temperatures in the general range of 100F providing generally stable processing temperatures under generally desirable processing conditions. Any

catalyst hydrocarbon volume ratios in the alkylation zone can be maintained which permit alkylation reactions to occur. Generally. ethyl fluoride promoted HF catalyst:hydrocarbon volume ratios in the range of from about Aul to about :1 are acceptable. generally preferred are catalyst:hydrocarbon volume ratios in the range of from about 2:1 to about 10: l, and even more preferred are volume ratios of about 4: 1. ln general any pressure can be employed which maintains a major portion of all of the reactants essentially in a liquid phase. Generally, pressures in the order of about at least 160 psig can be employed with good results; however alkylation zone pressures in the order of about at least 190 psig can often be employed with improved results when contrasted with 160 psig operating conditions. A second preferred embodiment of this invention comprises the alkylation of isobutane with ethylene and propylene and/or butylenes carried out in an alkylation zone under HF alkylation reaction conditions wherein olefins are alkylated with isoparaffins with the recovery of substantial quantities of isopentane and heavier alkylate reaction product. In general, the practice of said second preferred embodiment comprises carrying out the alkylation reactions under alkylation reaction conditions wherein the olefin content of the feedstock heavier than ethylene is present in an amount of from about 5 to about percent by weight based on the total weight of olefins including ethylene in the feedstock. The ratio of isoparaffin to olefin feedstock can vary widely; however, preferably it is within the range of from about 2:1 to about 1, more preferably from about 10:1 to about 15:1, and still more preferably from about 11:1 to about 14:1, on a mo] weight basis. The alkylation reactions can be carried out in the alkylation zone at any temperature at which the alkylation reactions occur. ln general, suitable alkylation temperatures comprise temperatures of from about 35F to about 200F, more preferably from about 75F to about l5(ll with temperatures in the general range of [00F providing generally stable processing temperatures generally desirable processing conditions. Any catalyst hydrocarbon volume ratios in the alkylation zone can be maintained which permit alkylation reactions to occur. Generally, HF catalyst:hydrocarbon volume ratios in the range of from about Aul to about 20:1 are acceptable; generally preferred are catalyst:hydrocarbon volume ratios in the range of from about 2:1 to about 10:1, and even more preferred are volume ratios of about 4:1. In general any pressure can be employed which maintains a major portion of all of the reactants essentially in a liquid phase. Generally, pressures on the order of about at least psig can be employed with good results; however, alkylation zone pressures on the order of about at least psig can often be employed with improved results when contrasted with 160 psig operating conditions.

Set out hereafter is an example in further illustration of the invention, which is not to be considered as unduly limitative thereof.

EXAMPLE Set out hereafter in Tables 1 and 11 are calculated exemplary operating conditions associated with recovery and conversion of the 11F overhead stream from an accumulation zone based on operating conditions associated with the production of 5,000 barrels/day of motor fuel grade alkylate produced by an ethyl fluoridepromoted HF alkylation process wherein propylene, butylenes and isobutane feedstocks are employed. The material flow rates, ethyl fluoride reaction zone conditions, deethanizer zone operating conditions plus the stream compositions are tabulated in Table l in accord with the conduit numbers and zone number descriptions set out in the FIGURE accompanying this specification.

TABLE I1 Fractionation Zone V Operating ClldlllOnS* Conversion Zone lV Operating Conditions Reflux and rcboil conditions not shown The operating conditions for cracking zone VII, absorption zone Vlll, fractionation zones II and IX, and extraction zone Vl are not given since these conditions are known in the art.

Various modifications of the teachings ofthe process ofthis invention will be apparent to those skilled in the art.

What is claimed is:

l. A combination alkylationcracking process which comprises the steps of:

a. subjecting a hyrocarbon feedstream to cracking to produce separate product streams comprising an olefin feedstock including butylenes, an isobutane stream, and an ethylene-containing light gas stream,

b. passing said streams comprising said olefin feedstock and isobutane as at least a part ofthe feed to an HF alkylation zone to produce an alkylation reaction effluent comprising C and heavy alkylate products, unreacted isobutane, butane, propane, ethane, lighter hydrocarbon components, and HF,

c. separating said HF from said alkylation reaction effluent to form an alkylation effluent product stream,

d. separating said alkylation effluent product stream into an overhead stream comprising said propane, said ethane, said lighter hydrocarbon components and HF content remaining in said stream. a bottoms stream comprising said C and said heavier alkylate products, and intermediate streams comprising said butane and said unreacted isobutane,

e. passing said overhead stream to a conversion zone and therein contacting said stream with said ethylene-containing light gas stream produced in said cracking step (a) to convert said HF content in said overhead stream into ethyl fluoride, and

. withdrawing from said conversion zone a stream comprising HF-free ethyl fluoride, propane, ethane, and lighter hydrocarbons and passing said stream to a separation zone wherein the ethane and lighter hydrocarbons are recovered overhead, and propane and ethyl fluoride are recovered as bottoms therefrom.

2. A process according to claim 1 further comprising the step of passing said bottoms in step (f) comprising propane and ethyl fluoride to said HF alkylation zone in step (b).

3. A process according to claim 1 wherein said overhead stream comprising propane, ethane, and lighter hydrocarbons and HF separated in step (e) is cooled to liquefy a portion of the propane and HF contained therein and passing the thus cooled stream into an ac cumulation zone, withdrawing condensed HF as bottoms from said accumulation zone and withdrawing overhead from said accumulation zone an uncondensed stream of propane, ethane and lighter hydrocarbons and HF. and passing said uncondensed stream to said conversion zone in step (e).

4. A process according to claim 3 further comprising the steps of propane withdrawing as bottoms condensed propane and passing at least a part of said condensed propane as reflux to the separation step (c) and passing at least a part of said condensed HF withdrawn as bottoms from said accumulation zone to said conversion zone in step (e).

5. A process according to claim 3 further comprising the step of passing propane and ethyl fluoride recovered as bottoms in step (f) to said alkylation zone in step (b).

6. A process according to claim 5 wherein the amount ofethyl fluoride present in said alkylation zone ranges from about 5 to about 35 percent by weight based on the total weiglit of catalyst employed including both ethyl fluoride and HF.

Claims

1. A COMBINATION ALKYLATION-CRACKING PROCESS WHICH COMPRISES THE STEPS OF: A SUBJECTING A HYDROCARBON FEEDSTREAM TO CRACKING TO PRODUCE SEPARATE PRODUCT STREAMS COMPRISING AN OLEFIN FEEDSTOCK INCLUDING BUTYLENES, AN ISOBUTANE STREAM, AND AN ETHYLENE-CONTAINING LIGHT GAS STREAM, B. PASSING SAID STREAMS COMPRISING SAID OLEFIN FEEDSTOCK AND ISOBUTANE AS AT LEAST A PART OF THE FEED TO AN HF ALKYLATION ZONE TO PRODUCT AN ALKYLATION REACTION EFFLUENT COMPRISING C5 AND HEAVY ALKYLATE PRODUCTS, UNREACTED ISOBUTANE, BUTANE, PROPANE, ETHANE, LIGHTER HYDROCARBON COMPONENTS, AND HF, C. SEPARATING SAID HF FROM SAID ALKYLATION REACTION EFFLUENT TO FROM AN ALKYLATION EFFLUENT PRODUCT STREAM, D. SEPARATING SAID ALKYLATION EFFLUENT PRODUCT STREAM, OVERHEAD STREAM COMPRISING SAID PROPANE, SAID ETHANE, SAID LIGHTER HYDROCARBON COMPONENTS AND HF CONTENT REMAINING IN SAID STREAM, A BOTTOMS STREAM COMPRISING SAID C5 AND SAID HEAVIER ALKYLATE PRODUCTS, AND INTERMEDIATE STREAMS COMPRISING SAID BUTANE AND SAID UNREACTED ISOBUTANE, E. PASSING SAID OVERHEAD STREAM TO A COVERSION ZONE AND THEREIN CONTACTING SAID STREAM WITH SAID ETHYLENECONTAINING LIGHT GAS STREAM PRODUCED IN SAID CRACKING STEP (A) TO CONVERT SAID HF CONTENT IN SAID OVERHEAD STREAM INTO ETHYL FLUORIDE, AND F. WITHDRAWING FROM SAID CONVERSION ZONE A STRE M ING HF-FREE ETHYL FLUORIDE, PROPANE, ETHANE, AND LIGHTER HYDROCARBONS AND PASSING SAID STREAM TO A SEPARATION ZONE WHEREIN THE ETHANE AND LIGHTER HYDROCARBONS ARE RECOVERED OVERHEAD, AND PROPANE AND ETHYL FLUORIDE ARE RECOVERED AS BOTTOMS THEREFROM.

3. A process according to claim 1 wherein said overhead stream comprising propane, ethane, and lighter hydrocarbons and HF separated in step (c) is cooled to liquefy a portion of the propane and HF contained therein and passing the thus cooled stream into an accumulation zone, withdrawing condensed HF as bottoms from said accumulation zone and withdrawing overhead from said accumulation zone an uncondensed stream of propane, ethane and lighter hydrocarbons and HF, and passing said uncondensed stream to said conversion zone in step (e).

6. A process according to claim 5 wherein the amount of ethyl fluoride present in said alkylation zone ranges from about 5 to about 35 percent by weight based on the total weight of catalyst employed including both ethyl fluoride and HF.