CA1245234A - Product recovery method for an aromatic hydrocarbon alkylation process - Google Patents
Product recovery method for an aromatic hydrocarbon alkylation processInfo
- Publication number
- CA1245234A CA1245234A CA000509424A CA509424A CA1245234A CA 1245234 A CA1245234 A CA 1245234A CA 000509424 A CA000509424 A CA 000509424A CA 509424 A CA509424 A CA 509424A CA 1245234 A CA1245234 A CA 1245234A
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- Prior art keywords
- product
- column
- hydrocarbon
- stream
- hydrocarbons
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
- C07C15/02—Monocyclic hydrocarbons
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
- C07C2/54—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition of unsaturated hydrocarbons to saturated hydrocarbons or to hydrocarbons containing a six-membered aromatic ring with no unsaturation outside the aromatic ring
- C07C2/64—Addition to a carbon atom of a six-membered aromatic ring
- C07C2/66—Catalytic processes
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
- C07C2/54—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition of unsaturated hydrocarbons to saturated hydrocarbons or to hydrocarbons containing a six-membered aromatic ring with no unsaturation outside the aromatic ring
- C07C2/64—Addition to a carbon atom of a six-membered aromatic ring
- C07C2/66—Catalytic processes
- C07C2/70—Catalytic processes with acids
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2527/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- C07C2527/14—Phosphorus; Compounds thereof
- C07C2527/16—Phosphorus; Compounds thereof containing oxygen
- C07C2527/167—Phosphates or other compounds comprising the anion (PnO3n+1)(n+2)-
- C07C2527/173—Phosphoric acid or other acids with the formula Hn+2PnO3n+1
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2529/00—Catalysts comprising molecular sieves
- C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
- C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
Abstract
"PRODUCT RECOVERY METHOD FOR AN AROMATIC
HYDROCARBON ALKYLATION PROCESS"
ABSTRACT
A fractionation method is disclosed for the recovery of product alkyl-aromatic hydrocarbons produced by the alkylation of aromatic hydrocarbons. Threefractionation columns are employed in series. Aromatic feed hydrocarbons are recycled from the overhead of the first column, which is reboiled by the overhead vapor of the second column. The product alkylaromatic is recovered from the condensate produced in using the second column overhead as a heat source. The product alkylaromatic is also present in the bottoms of the second column which flows into a low pressure stripping column. The entire overhead vapor of the stripping column is compressed and passed into the lower portion of the second column.
HYDROCARBON ALKYLATION PROCESS"
ABSTRACT
A fractionation method is disclosed for the recovery of product alkyl-aromatic hydrocarbons produced by the alkylation of aromatic hydrocarbons. Threefractionation columns are employed in series. Aromatic feed hydrocarbons are recycled from the overhead of the first column, which is reboiled by the overhead vapor of the second column. The product alkylaromatic is recovered from the condensate produced in using the second column overhead as a heat source. The product alkylaromatic is also present in the bottoms of the second column which flows into a low pressure stripping column. The entire overhead vapor of the stripping column is compressed and passed into the lower portion of the second column.
Description
3~
"PRODUCT RECOVERY METHOD FOR AN AROMATIC
HYDROCARBON ALKYLATION PROCESS"
FIELD OF THE INVENTION
The invention relates to the production and recovery of alkylaromatic hydrocarbons by the reaction of an acyclic olefinic hydrocarbon with an aromatic feed hydrocarbon. The invention is directly related to the separa-tion method used to recover the product alkylaromatic hydrocarbons from S the effluent of the alkylation reaction zone. This separation method em-ploys fractional distillation in three fractionation columns in series, with the subiect invention being d;rectly related to the method in which these are interconnected and to the method by which these columns are reboiled.
BACKGROUND OF THE INVENTION
The alkylation of aromatic hydrocarbons such as benzene usin~ s~lid catalysts is a well-deYeloped art which is practiced comrnercially in large scale industrial units. C)ne commercial application o~ this process is the alkylation of benzene with propylene ~o Eorm cumene (isopropylbenzene), which is subsequently used in the production of phenol and acetone. Those skilled in the art are therefore familiar with the ~eneral design and operation o~ such alkylation processes.
The prior art is well described in the literature. For instance, a typical flow scheme suitable for commercial use is depicted in U.S. Patent No. 4,051,191issued to D.~. Ward. This reference describes in some detail catalyst, reaction conditions, and separatiol~ methods suitable for the recovery of cumene. ll-e reactor effluent is passed into a recti~ication zone in which propane, charged to the process in admixture with the feed pr~pylene, is separated ~or recycling and forrejection from the process. Liquid phase hydrocarbons recovered in the rectifi-cation zone are then passed in~o a ~w~column fractionation train comprising ~
recycle column and a cumene or product column. The unreacted portion of benzene feed aromatic hydrocarbon is recycled from the top of the first fractionation column. The product cumene is recovered from the top of the second fractionationcolumn, with heavy aromatic by-products beirlg withdrawn from the bottom of the second co 1 umn. A
_ 1 _ `~
~4S~
somewhat different product recovery fractionation train for commercial use is described in the article at page 32 of the March 21, 1983 edition of Chemical En~ineering magazine. This system employs four fractionation columns in series.
The first fractionation column is a depropanizer column. The third column is a product column in which cumene is removed as the net overhead product. The net bottoms stream oE the product column is passed into a recycle column with the overhead stream of this column apparently being recycled to the reaction zone. The alkylation process described in this article is based upon the use of an aluminum chloride catalyst system as compared to the solid phosphoric acid-type catalyst which is preferred in the previously cited reference.
It is known in the art of fractional distillation that the latent heat present in the overhead vapors of one fractionation column may be employed in the reboiler means of another fractionation column for the purpose of supplying heat to the other fractionation column. This is shown for instance in U.5. Patent No.
3,254,024 issued to H.A. Huckins, Jr. et al. This reference is directed to the separation of close boiling C8 aromatic hydrocarbons. The overhead vapor from a xylene splitter column is therefore used from this reference to reboil an ethyl-benzene column. U.S. Patent No. 4,360,405 issued to U, Tsao is pertinent for itsshowing of a fractionation arrangement for use in the separation of close boiling ~ mixtures in which the overhead vapor of one column is compressed and passed into a bottom portion of an immediately upstream fractionation column. The bottoms liquid from this upstream column flows into the top of the downstream column. This reference indicates this arrangement could be employed Eor the separation of close boiling hydrocarbons exemplified by the xylenes.
BRIEF SUMMARY OF THE INVENTION
The invention provides an improved method for the separation of the reactants and products of a process for the production of an alkylaromatic hydrocarbon by alkylation. The improvement basically relates to increased energyefficiency and elimination of the production of low pressure steam, which has only a small economic value in a typical petroleum refinery or petrochemical installation.
The subject invention is characterized by the use of a relatively high pressure cumene or product column, with the overhead vapor of this column being employed ~52~
to reboil the immediately preceding recycle column. The inYention is also characteri~ed by the passage of a cumene rich bottoms stream from the cumene column to a relatively low pressure stripping column. The overhead vapor stream of the stripping column is rich in cumene and is compressed back into the cumene column. The subject invention is also an improvement in that the bottoms liquid pump normally employed on the bottoms stream of the cumene column is no longer required.
A broad embodiment of the invention may be characterized as a process for the production of an alkylaromatic hydrocarbon which comprises contacting a feed acyclic olefinic hydrocarbon and a feed aromatic hydrocarbon with an alkylation catalyst in an alkylation reaction zone maintained at alkylation-promoting conditions and producing a reaction zone effluent stream comprising the feed aromatic hydrocarbon, a product alkylaromatic hydrocarbon and high-boiling by-product hydrocarbons and subsequently recovering the product alkylaromatic hydrocarbon by a method which comprises the steps of passing a process stream comprising the feed aromatic hydrocarbon, the product alkylaromatic hydrocarbon and the by-product hydrocarbons into a recycle fractionation column operated at conditions which effect the separation of entering hydrocarbons into at least a net overhead stream, which is rich in the feed aromatic hydrocarbon, and a first bottoms stream, which comprises the product alkylaromatic hydrocarbon and the by-product hydrocarbons; passing the first bottoms stream into a product fractionation column operated at conditions effective to separ te entering hydrocarbons into afirst overhead vapor stream, which is rich in the product alkylaromatic hydrocarbon, and a second bottoms stream, which is also rich in the product alkylaromatic hydrocarbon and contains the by-product hydrocarbons; at least partially condensing the first overhead vapor stream in a reboiler means supplying heat to a lower portion of the recycle column, withdrawing a first portion of the resultant condensate from the process as a net product stream and returning a second portion of the condensate to the product column as reflux liquid; passing the second bottoms stream into a stripping column operated at fractional distillation conditions, including a pressure at least 15 psi (103 kPa) lower than maintained in the product fraction--ation column, and effective to separate entering hydrocarbons into a second overhead vapor stream comprising the product alkylaromatic hydrocarbon and a third bottoms stream, which comprises the by-product hydrocarbons and is substantially free of the product alkylaromatic hydrocarbon; and compressing the ~2~L523~
second overhead vapor stream and then passing the second overhead vapor stream into the product fractionation column.
BRIEF DESCRIPTION OF THE DRAWING
The drawing illustrates a preferred embodiment of the invention wherein product cumene is recovered from the overhead vapor of cumene column 22 by condensation of the overhead vapor in the reboiler 20 of the recycle column, with the cumene rich bottoms stream of the cumene column flowing through line 31 intothe low pressure stripper 32 The high~boiiing by-products leave through line 39 while the cumene is recycled by compression in means 35 to the cumene column.
DETAILED DESCRlPll~)N
The production of alkylaromatic hydrocarbons is an important industrial process Although these hydrocarbons can be recovered from reaction products suchas reformates or from natural occurring petroleum, the most commercially feasible route to the production oE alkylaromatics appears to be the direct alkylation of a feed aromatic hydrocarbon with a feed acyclic olefinic hydrocarbon. A wide variety of alkylaromatic product hydrocarbons can be produced because of the various feed hydrocarbons in both the aromatic and acyclic categories which can be supplied to the alkylation zone. For instance, the feed aromatic hydrocarbon can be either benzene or toluene. The acyclic olefin can range from ethylene as in the production of ethyl benzene to a mixture OI C10 to C15 acyclic olefins used in the alkylation processes designed to produce linear alkyl benzenes (LAB) destined for use as precursors in the production of detergents. The subject description will be basically couched in terms of the alkylation of benzene with propylene as this is the preferred embodiment of the invention. However, it is not thereby intended to preclude from the scope of the invention those other alkylation processes and hydrocarbon mixtures to which the subiect invention is applicable.
In the traditional prior art fractionation method of recovering the product alkylarornatic hydrocarbon, the overhead streams of the fractionation columns has ~een condensed in water cooled heat exchangers resulting in the production of relatively low pressure steam. This is shown ~or instance in the ~sz~
previously cited article which illustrates the production of steam in the overhead system of all four fractionation columns. While this low pressure steam does contain a considerable amount of latent heat, it is typically at such a low temperature that the steam cannot be widely applied in the typical refinery. Thelow pressure steam generated in this manner therefore has little or no economic value. This results in all or mos~ of the heat which is discharged in the overhead system of the column being unrecovered and being a net charge against the utility cost of operating the process. lt is an objective of the subject invention to provide an improYed ~ractional distillation type separa~ion method for use in recovering the product o~ alkylation reaction zones. It is a specific objectiYe of the subject invention to reduce the utility costs of operating the fractionation system used to recover a product alkylaromatic hydrocarbon made in an alkylation ~one. It is another objective of the subject invention to minimize the capital cost of a lowutility cost fractionation system.
i 5 In the subject invention, the product alkylaromatic hydrocarbon is recovered as the net ovèrhead products of a relatively high pressure, as compared to the prior art, product column. The product column is the intermediate column of a three column fractionation train employed in the subject invention. The relatively high pressure maintained in the product column results in the overhead vapor of this column being sufficiently hot to reboil the preceding recycle column. The preceding column is referred to as the recycle column in reference to its traditional function of providing a relatively high-purity stream of unconverted feed aromatic hydro-carbon for recycling back to the reaction zone. The overhead product of the product column may therefore be of relatively high purity as the lighter hydro-carbons are removed upstream. For instance, it would normally contain greater than 99 mole percent cumene when cumene is being produced in the product. In thesubject invention, the net bottoms stream removed from the product column will also be rich in the product alkylaromatic hydrocarbon and may have a concentration of the product hydrocarbon greater than 95 mole percent. The other components ofthe bottoms stream of the product column will comprise the high boiling by-products produced in the alkylation zone. These by-products are normally undesirable in the product alkylaroma~ic hydrocarbon, and ~hey are therefore pre~erably withdrawn ~rom the process as a separate stream. The by-products are produced by undesiredoligomerization and alkylation reactions. For instance, in the production of cumene the high-boiling by-products would comprise propylene oligmers and diisopropyl-benzene and possibly triis3propylbenzene.
It is normally desirable to minimize the temperature of that portion of the fractionation equipment in which these high boiling by-products are separated into the by-product stream which is removed from the process. There~ore, the desire to increase the overhea~ temperature of the product cclumn is in conflictwith the desire to minimize the temperature at the bottom of the product column when the high boiling by-products are withdrawn as a concentrated stream from the bottom of the product column. This conflict could be resolved by operating the product column at a relatively low pressure and employing a compressor to increase the temperature of the overhead vapor stream prior to its bein~ used to reboil arecycle colurnn. This is in the fashion of a traditional heat pump sys~em. The overhead vapor stream of the procluct column is, however, normally a rather highvolume vapor stream which would require a large and very expensive compressor and ~ignificant utilities for its operation.
In the subject process, the produc~ rich bottoms stream of the produc~
column is flashed into a relatively low pressure strippin~ column. This column is operated at a lower pressure than the product column. It is preferably operated at a pressure which is below about 25 ps;g (172 kPag). it is preferred that the pro-duct column is operated at a pressure at least 15 psi (103 kPa), andmore preferably 20 psi (138 kPa), greater than ~he pressure maintained in the stripping column.
The temperatures required at the bottom of the stripping column are therefore lower than the temperature which would be required in the bottom of the product column, which is operating at the increased pressure. The cumene rich overhead stream of the stripping column is now compressed into the product column.
This overhead stream is much smaller than the overhead stream of the product column. It therefore can be compressed with a much smaller compressor than wouldbe necessary to compress the overhead vapor stream o~ the product column. The utilities cost of operating this compressor are also greatly lower. It is also significant to point out that the pressure differential between the columns eliminates ~he need for a pump to transport ~he bo~toms liquid of the product column into the stripping column.
The application of the subject invention ~o ~he typical alkylation zone may be discerned by reference to the drawing. In this representati~n of the preferred embodiment, She feed stream of benzene from line 1 is admixed with a propylene-propane feed stream from line 2. High-puri~y propylene could be charged to the process but the normal source of propylene will often contain significant 23~
amounts of propane. The propane passes through the process as an inert compound and does not interfere with the reaction. With the presently preferred solid phosphoric acid (SPA) catalyst system, the presence of propane in the reaction zone is in fact desired and it is therefore partially recycled into the reaction zone from the downstream depropanizing zone. Recycle benzene and propane carried by line 17 are admixed with the feed hydrocarbons and the resultant hydrocarbon admixture is passed through line 3 into the reaction zone 4. The reactants are therein contacted wi~h a suitable alkylation catalyst maintained at alkyla~ion-promoting conditions. Thise~ects the production of a reaction zone effluent stream carried by line 5 whichcomprises an admixture of unreacted benzene, propane, the product cumene and thehigh boiling by-product hydrocarbons formed in the reaction zone. The reactor effluent also contains hexenes and nonenes. The reaction zone effluent stream ispassed into a depropanizing zone 6. The exact form of the depropanizing zone tends to vary between competing processes and differen~ commercial installations. ThislS zone can comprise a single depropanizing column or two rectified flash zones as shown in the prior art. This zone is preferably arranged to produce a net effluent stream of relatively high-purity propane wi~hdrawn through line 7 to balance the ne$
charge rate of propane to the process and a recycle stream transported through line 8 which will contain propane and possibly benzene. A normally liquid phase process stream is removed from the depropanizing zone in line 9 for passage into the fractionation train employed in the subject invention. This process stream will comprise benzene, cumene, and the by-product high-boiling or heavy hydrocarbons.This process stream is passed via line 9 into an intermediate point of the recycle column l O. The recycle column is operated at conditions which effect the separation of the entering hydrocarbons into an overhead vapor stream removed through line ll and the bottoms stream removed in line 18. The overhead vapor stream should be essentially free of cumene and any heavier boiling hydrocarbonswhich enter the column. The overhead vapor stream passes through the overhead condenser 12 and then flows into the overhead receiver 13. The liquid phase benzene which thereby accumulates in the receiver is withdrawn through line 14 and divided into the recycle stream carried by line 16 and the reflux stream re~urned to the recycle column via line 15. Not shown on ~he drawing are the customary effluent streams associated with the upper portion of the recycle solumn. These two streams comprise a vapor off gas line for the overhead receiver and a drag benzene line which may be removed from the recycle column or from the overhead ~29~523~
receiver liquid.
The net bo~toms liquid from the recycle column carried by line 21 comprises the product cumene and the by-product heavy hydrocarbons. It should beessentially free of propane and benzene. The ne$ bottoms stream is passed into the cumene column 22 and is therein separated into a bottoms stream removed in line 28 and an overhead vapor stream removed through line 23. In accordance with the subject invention, the overhead vapor stream passes through the reboiler means 20 of the recycle column thereby supplying heat to the bottom of the recycle column.
This results in at least a partial condensation and preferably a total condensation of the overhead vapor stream and the production of a condensate which is passed into the overhead receiver 24. This condensate liquid is high-purity cumene which is withdrawn through line 25 and divided into ~he reflux stream, returned to the cumene column throu~h line 27 and the net product s~ream of the process which isremoved through line 26. The heat given up by the overhead vapor stream in the reboiler vaporizes at least a portion of the bottom liquid circulating through line l9 to thereby provide vapors which pass into ~he bottom of the recycle column and effect the reboiling of the column.
The cumene column 22 is reboiled by means of h~at supplied to the bottoms liquid circulating through line 29 and partially vaporized in reboiler means 30. The net bottoms stream removed from the cumene column in line 31 is passed through pressure reducing valve 40 into an upper portion of the stripping column 32.
This column is operated at fractionation conditions which are effective to separate the entering hydrocarbons into the overhead vapor stream withdrawn through line 33 and the bottoms liquid withdrawn through line 36. The bottoms liquid of line 36 should be rich in the heavy hydrocarbon by-products of the alkylation reaction. A
portion of the bottoms liquid is circulated through line 37 and the reboiler means 3 which receives heat from an external source such as high pressure steam or hot oil.
The high boiling by-products for the alkylation reaction are therefore concentrated into a relatively small net bottoms stream discharged from the process through line 39. The overhead vapor stream of line 33 has a high concentration (greater than 90 mole percent) of cumene. The overhead vapor stream is preferably heated in the heating means 34 and is then compressed in means 35. The cumene rich overhead vapor stream then continues through line 33 and is pref erably passed into the cumene column at a lower point near or below the lowest most tray within this column. The overhead vapor stream could, however, be passed into the column at -~Z~5:~34 higher points if 50 desired.
The subject invention is practiced wi~h a reaction zone containing a solid catalyst. Preferably, the catalyst is one commonly referred to as an SPA catalyst.
Suitable SPA catalysts are available commercially. As used herein the term "SPA
catalyst" or its equivalent is intended to refer generically to a solid catalyst which contains as one of its principal raw ingredients an acid of phosphorus such as ortho-, pyro- or tetra-phosphoric acid. These catalysts are normally formed by mixing the acid with a siliceous solid carrier to form a wet paste. This paste may be calcined and then crushed to yield catalyst particles, or the paste may be extruded or pelleted prior to calcining to produce more uniform catalyst particles. The carrier is preferably a naturally occurring porous silica-containing material such as kieselguhr, kaolin, infusorial earth and diatomaceous earth. A minor amount of various additives such as mineral talc, fullers earth and iron compounds including iron oxide have been added to the carrier to increase its strength and hardness. The combination of the carrier and the additives normally comprises about 15-30 wt. %
of the catalyst, with the remainder being the phosphoric acid. However, the amount of phosphoric acid used in the manufacture of the catalyst may vary from about 8-80 wt. % of the catalyst as described in U.S. Patent No. 3,402,130. The amount of the additive may be equal to about 3-20 wt. % of the total carrier material. Further details as to the composition and production of typical SPA catalysts may be obtained from U.S. Patent Nos. 3,050,~72; 3,050,473and3,132,109 and from other references.
The subject inventlon is not restricted to use with a SPA type catalyst.
For instance the previously cited article describes the use of AIC13 catalysts and indicates this is a commonly used catalyst in the production of ethyl benzene. In addition, the patent literature describes a vast array of zeolite alkylation catalysts and processes for their use. It is therefore contemplated to practice the subject invention using a catalyst comprising an amorphous or a crystalline alumino silicate such as a "ZSM-5" zeolite. Due to the nature of the aluminosilicates they are normally not used in the pure form but are composited into a porous support matrix in combination with an alumina or silica or clay. The alkylation reactions with these materials have been described as being both vapor-phase and liquid-phase processes.
The reaction conditions for use with differing catalysts, which are set out in the references, will Yary from the preferred conditions set out herein for use in conjunction with SPA-type catalysts. Further information on zeolitic alkylation _g_ ~S%3~
catalysts may be obtained from a number of sources including U.S. Patents No.
3,755,483; 4,300,011; 4,469,90~ and 4,489,214.
The reaction zone is maintained at alkylation-promoting conditions. As previously stated the conditions must be adjusted to compensate for the specificcatalyst being employed and the reactants being charged to the process. In the case of an SPA type catalyst these condltions include a pressure of about 300 to 1000 psig (2069 tD 6895 kPag) and a temperature of about 300 to 600F (149 tD 316~). Theliquid hourly space velocity o~ reactants may range ~rom about 0.5 to 2.5 m 1. It is preferred that an excess of the aromatic hydrocarbon be present in the reaction zone.
The mole ratio of the ~romatic hydrocarbon to the olefin should be within ~he broad range of 3:1 to 20:1. A ra~io of about 8:1 is preferred for the production of cumene.
It is preferred that the reactant stream be mixed-phase through the reactor. The feed stream therefore preferably contains some unreactive light paraffins having the same number of carbon atoms per molecule as the ole~in. In the production of cumene it is preferred that the amount of propane in the reaction zone feed stream be at least equal to the amou~t of propylene in this stream. This may be accomplished by using a dilute propylene feed stream or by recycling propane. The previously cited article indicates representative conditions for the use of an Al C13 catalyst system include a tempera-ture below 275F (135~C) and a pressure of less than 50 psig (345 kPag).
The preferred embndiment of the invention may accordingly be described as a process for the production of an alkylaromatic hydrocarbon which comprises contacting a feed acyclic olefinic hydrocarbon and a feed aromatic hydrocarbon with a solid alkylation catalyst in an alkylation reaction zone maintained at alkylation-promoting conditions and producing a reaction zone effluent stream comprising the feed aromatic hydrocarbon, a monoalkylaromatic product hydro-carbon and highboiling by-product hydrocarbons and subsequently recovering the product alkylaromatic hydrocarbon by a method which comprises the steps of passing a process stream comprising the feed aromatic hydrocarbon, the mono-alkylaroma~ic product hydrocarbon and the by-product hydrocarbons into a recyclefractionation column operated at conditions which effect the separation of entering hydrocarbons into at least a net overhead stream, which is rich in the feed aromatic hydrocarbon, and a first bottoms stream, which comprises the product hydrocarbonand the by-product hydrocarbons; passing the first bottoms stream into a product~ractionation column operated at conditions effective to separate entering hydro-carbons into a first overhead vapor stream, which is rich in the product hydrocarbon ~Z~523~
and slJbstantially free of the by-product hydrocarbons, and a second bottoms stream, which is rich in the product hydrocarbon and also comprises the by-product hydrocarbons; at least partially condensing the first overhead vapor stream in ar~boiler means supplyin~ heat to the bot~om portion of the recycle column, wi~hdrawing a ~irst portion of the resultant condensate from the process as a net product str~am and returning a second portion of the condensate to the product column as reflux liquid; passing the second bottoms stream into a stripping column operated at ~ractiona~ distillation conditions, including a pressure which is at least 15 psi (103 kPa) and more preferably 20 psi (138 kPa) lower than is maintained in the product fractionation column, effective to separate entering hydrocarbons into a second overhead vapor stream comprising the product alkylaromatic hydrocarbon and a third bottoms stream, which comprises the by-product hydrocarbons and is substantially free ofthe product hydrocarbon; and compressing the second oYerhead vapor stream and then passing the second overhead vapor stream into a bottom portion ofthe product fraction column. As used herein the term substantially free is intended to indicate a molar concentration of the indicated substance less than about 2 and preferably less than 1 percent. The term "rich" is in-tended to indicate a concentration of the specified compound or class of com-pounds exceeding about 75 mole percent.
"PRODUCT RECOVERY METHOD FOR AN AROMATIC
HYDROCARBON ALKYLATION PROCESS"
FIELD OF THE INVENTION
The invention relates to the production and recovery of alkylaromatic hydrocarbons by the reaction of an acyclic olefinic hydrocarbon with an aromatic feed hydrocarbon. The invention is directly related to the separa-tion method used to recover the product alkylaromatic hydrocarbons from S the effluent of the alkylation reaction zone. This separation method em-ploys fractional distillation in three fractionation columns in series, with the subiect invention being d;rectly related to the method in which these are interconnected and to the method by which these columns are reboiled.
BACKGROUND OF THE INVENTION
The alkylation of aromatic hydrocarbons such as benzene usin~ s~lid catalysts is a well-deYeloped art which is practiced comrnercially in large scale industrial units. C)ne commercial application o~ this process is the alkylation of benzene with propylene ~o Eorm cumene (isopropylbenzene), which is subsequently used in the production of phenol and acetone. Those skilled in the art are therefore familiar with the ~eneral design and operation o~ such alkylation processes.
The prior art is well described in the literature. For instance, a typical flow scheme suitable for commercial use is depicted in U.S. Patent No. 4,051,191issued to D.~. Ward. This reference describes in some detail catalyst, reaction conditions, and separatiol~ methods suitable for the recovery of cumene. ll-e reactor effluent is passed into a recti~ication zone in which propane, charged to the process in admixture with the feed pr~pylene, is separated ~or recycling and forrejection from the process. Liquid phase hydrocarbons recovered in the rectifi-cation zone are then passed in~o a ~w~column fractionation train comprising ~
recycle column and a cumene or product column. The unreacted portion of benzene feed aromatic hydrocarbon is recycled from the top of the first fractionation column. The product cumene is recovered from the top of the second fractionationcolumn, with heavy aromatic by-products beirlg withdrawn from the bottom of the second co 1 umn. A
_ 1 _ `~
~4S~
somewhat different product recovery fractionation train for commercial use is described in the article at page 32 of the March 21, 1983 edition of Chemical En~ineering magazine. This system employs four fractionation columns in series.
The first fractionation column is a depropanizer column. The third column is a product column in which cumene is removed as the net overhead product. The net bottoms stream oE the product column is passed into a recycle column with the overhead stream of this column apparently being recycled to the reaction zone. The alkylation process described in this article is based upon the use of an aluminum chloride catalyst system as compared to the solid phosphoric acid-type catalyst which is preferred in the previously cited reference.
It is known in the art of fractional distillation that the latent heat present in the overhead vapors of one fractionation column may be employed in the reboiler means of another fractionation column for the purpose of supplying heat to the other fractionation column. This is shown for instance in U.5. Patent No.
3,254,024 issued to H.A. Huckins, Jr. et al. This reference is directed to the separation of close boiling C8 aromatic hydrocarbons. The overhead vapor from a xylene splitter column is therefore used from this reference to reboil an ethyl-benzene column. U.S. Patent No. 4,360,405 issued to U, Tsao is pertinent for itsshowing of a fractionation arrangement for use in the separation of close boiling ~ mixtures in which the overhead vapor of one column is compressed and passed into a bottom portion of an immediately upstream fractionation column. The bottoms liquid from this upstream column flows into the top of the downstream column. This reference indicates this arrangement could be employed Eor the separation of close boiling hydrocarbons exemplified by the xylenes.
BRIEF SUMMARY OF THE INVENTION
The invention provides an improved method for the separation of the reactants and products of a process for the production of an alkylaromatic hydrocarbon by alkylation. The improvement basically relates to increased energyefficiency and elimination of the production of low pressure steam, which has only a small economic value in a typical petroleum refinery or petrochemical installation.
The subject invention is characterized by the use of a relatively high pressure cumene or product column, with the overhead vapor of this column being employed ~52~
to reboil the immediately preceding recycle column. The inYention is also characteri~ed by the passage of a cumene rich bottoms stream from the cumene column to a relatively low pressure stripping column. The overhead vapor stream of the stripping column is rich in cumene and is compressed back into the cumene column. The subject invention is also an improvement in that the bottoms liquid pump normally employed on the bottoms stream of the cumene column is no longer required.
A broad embodiment of the invention may be characterized as a process for the production of an alkylaromatic hydrocarbon which comprises contacting a feed acyclic olefinic hydrocarbon and a feed aromatic hydrocarbon with an alkylation catalyst in an alkylation reaction zone maintained at alkylation-promoting conditions and producing a reaction zone effluent stream comprising the feed aromatic hydrocarbon, a product alkylaromatic hydrocarbon and high-boiling by-product hydrocarbons and subsequently recovering the product alkylaromatic hydrocarbon by a method which comprises the steps of passing a process stream comprising the feed aromatic hydrocarbon, the product alkylaromatic hydrocarbon and the by-product hydrocarbons into a recycle fractionation column operated at conditions which effect the separation of entering hydrocarbons into at least a net overhead stream, which is rich in the feed aromatic hydrocarbon, and a first bottoms stream, which comprises the product alkylaromatic hydrocarbon and the by-product hydrocarbons; passing the first bottoms stream into a product fractionation column operated at conditions effective to separ te entering hydrocarbons into afirst overhead vapor stream, which is rich in the product alkylaromatic hydrocarbon, and a second bottoms stream, which is also rich in the product alkylaromatic hydrocarbon and contains the by-product hydrocarbons; at least partially condensing the first overhead vapor stream in a reboiler means supplying heat to a lower portion of the recycle column, withdrawing a first portion of the resultant condensate from the process as a net product stream and returning a second portion of the condensate to the product column as reflux liquid; passing the second bottoms stream into a stripping column operated at fractional distillation conditions, including a pressure at least 15 psi (103 kPa) lower than maintained in the product fraction--ation column, and effective to separate entering hydrocarbons into a second overhead vapor stream comprising the product alkylaromatic hydrocarbon and a third bottoms stream, which comprises the by-product hydrocarbons and is substantially free of the product alkylaromatic hydrocarbon; and compressing the ~2~L523~
second overhead vapor stream and then passing the second overhead vapor stream into the product fractionation column.
BRIEF DESCRIPTION OF THE DRAWING
The drawing illustrates a preferred embodiment of the invention wherein product cumene is recovered from the overhead vapor of cumene column 22 by condensation of the overhead vapor in the reboiler 20 of the recycle column, with the cumene rich bottoms stream of the cumene column flowing through line 31 intothe low pressure stripper 32 The high~boiiing by-products leave through line 39 while the cumene is recycled by compression in means 35 to the cumene column.
DETAILED DESCRlPll~)N
The production of alkylaromatic hydrocarbons is an important industrial process Although these hydrocarbons can be recovered from reaction products suchas reformates or from natural occurring petroleum, the most commercially feasible route to the production oE alkylaromatics appears to be the direct alkylation of a feed aromatic hydrocarbon with a feed acyclic olefinic hydrocarbon. A wide variety of alkylaromatic product hydrocarbons can be produced because of the various feed hydrocarbons in both the aromatic and acyclic categories which can be supplied to the alkylation zone. For instance, the feed aromatic hydrocarbon can be either benzene or toluene. The acyclic olefin can range from ethylene as in the production of ethyl benzene to a mixture OI C10 to C15 acyclic olefins used in the alkylation processes designed to produce linear alkyl benzenes (LAB) destined for use as precursors in the production of detergents. The subject description will be basically couched in terms of the alkylation of benzene with propylene as this is the preferred embodiment of the invention. However, it is not thereby intended to preclude from the scope of the invention those other alkylation processes and hydrocarbon mixtures to which the subiect invention is applicable.
In the traditional prior art fractionation method of recovering the product alkylarornatic hydrocarbon, the overhead streams of the fractionation columns has ~een condensed in water cooled heat exchangers resulting in the production of relatively low pressure steam. This is shown ~or instance in the ~sz~
previously cited article which illustrates the production of steam in the overhead system of all four fractionation columns. While this low pressure steam does contain a considerable amount of latent heat, it is typically at such a low temperature that the steam cannot be widely applied in the typical refinery. Thelow pressure steam generated in this manner therefore has little or no economic value. This results in all or mos~ of the heat which is discharged in the overhead system of the column being unrecovered and being a net charge against the utility cost of operating the process. lt is an objective of the subject invention to provide an improYed ~ractional distillation type separa~ion method for use in recovering the product o~ alkylation reaction zones. It is a specific objectiYe of the subject invention to reduce the utility costs of operating the fractionation system used to recover a product alkylaromatic hydrocarbon made in an alkylation ~one. It is another objective of the subject invention to minimize the capital cost of a lowutility cost fractionation system.
i 5 In the subject invention, the product alkylaromatic hydrocarbon is recovered as the net ovèrhead products of a relatively high pressure, as compared to the prior art, product column. The product column is the intermediate column of a three column fractionation train employed in the subject invention. The relatively high pressure maintained in the product column results in the overhead vapor of this column being sufficiently hot to reboil the preceding recycle column. The preceding column is referred to as the recycle column in reference to its traditional function of providing a relatively high-purity stream of unconverted feed aromatic hydro-carbon for recycling back to the reaction zone. The overhead product of the product column may therefore be of relatively high purity as the lighter hydro-carbons are removed upstream. For instance, it would normally contain greater than 99 mole percent cumene when cumene is being produced in the product. In thesubject invention, the net bottoms stream removed from the product column will also be rich in the product alkylaromatic hydrocarbon and may have a concentration of the product hydrocarbon greater than 95 mole percent. The other components ofthe bottoms stream of the product column will comprise the high boiling by-products produced in the alkylation zone. These by-products are normally undesirable in the product alkylaroma~ic hydrocarbon, and ~hey are therefore pre~erably withdrawn ~rom the process as a separate stream. The by-products are produced by undesiredoligomerization and alkylation reactions. For instance, in the production of cumene the high-boiling by-products would comprise propylene oligmers and diisopropyl-benzene and possibly triis3propylbenzene.
It is normally desirable to minimize the temperature of that portion of the fractionation equipment in which these high boiling by-products are separated into the by-product stream which is removed from the process. There~ore, the desire to increase the overhea~ temperature of the product cclumn is in conflictwith the desire to minimize the temperature at the bottom of the product column when the high boiling by-products are withdrawn as a concentrated stream from the bottom of the product column. This conflict could be resolved by operating the product column at a relatively low pressure and employing a compressor to increase the temperature of the overhead vapor stream prior to its bein~ used to reboil arecycle colurnn. This is in the fashion of a traditional heat pump sys~em. The overhead vapor stream of the procluct column is, however, normally a rather highvolume vapor stream which would require a large and very expensive compressor and ~ignificant utilities for its operation.
In the subject process, the produc~ rich bottoms stream of the produc~
column is flashed into a relatively low pressure strippin~ column. This column is operated at a lower pressure than the product column. It is preferably operated at a pressure which is below about 25 ps;g (172 kPag). it is preferred that the pro-duct column is operated at a pressure at least 15 psi (103 kPa), andmore preferably 20 psi (138 kPa), greater than ~he pressure maintained in the stripping column.
The temperatures required at the bottom of the stripping column are therefore lower than the temperature which would be required in the bottom of the product column, which is operating at the increased pressure. The cumene rich overhead stream of the stripping column is now compressed into the product column.
This overhead stream is much smaller than the overhead stream of the product column. It therefore can be compressed with a much smaller compressor than wouldbe necessary to compress the overhead vapor stream o~ the product column. The utilities cost of operating this compressor are also greatly lower. It is also significant to point out that the pressure differential between the columns eliminates ~he need for a pump to transport ~he bo~toms liquid of the product column into the stripping column.
The application of the subject invention ~o ~he typical alkylation zone may be discerned by reference to the drawing. In this representati~n of the preferred embodiment, She feed stream of benzene from line 1 is admixed with a propylene-propane feed stream from line 2. High-puri~y propylene could be charged to the process but the normal source of propylene will often contain significant 23~
amounts of propane. The propane passes through the process as an inert compound and does not interfere with the reaction. With the presently preferred solid phosphoric acid (SPA) catalyst system, the presence of propane in the reaction zone is in fact desired and it is therefore partially recycled into the reaction zone from the downstream depropanizing zone. Recycle benzene and propane carried by line 17 are admixed with the feed hydrocarbons and the resultant hydrocarbon admixture is passed through line 3 into the reaction zone 4. The reactants are therein contacted wi~h a suitable alkylation catalyst maintained at alkyla~ion-promoting conditions. Thise~ects the production of a reaction zone effluent stream carried by line 5 whichcomprises an admixture of unreacted benzene, propane, the product cumene and thehigh boiling by-product hydrocarbons formed in the reaction zone. The reactor effluent also contains hexenes and nonenes. The reaction zone effluent stream ispassed into a depropanizing zone 6. The exact form of the depropanizing zone tends to vary between competing processes and differen~ commercial installations. ThislS zone can comprise a single depropanizing column or two rectified flash zones as shown in the prior art. This zone is preferably arranged to produce a net effluent stream of relatively high-purity propane wi~hdrawn through line 7 to balance the ne$
charge rate of propane to the process and a recycle stream transported through line 8 which will contain propane and possibly benzene. A normally liquid phase process stream is removed from the depropanizing zone in line 9 for passage into the fractionation train employed in the subject invention. This process stream will comprise benzene, cumene, and the by-product high-boiling or heavy hydrocarbons.This process stream is passed via line 9 into an intermediate point of the recycle column l O. The recycle column is operated at conditions which effect the separation of the entering hydrocarbons into an overhead vapor stream removed through line ll and the bottoms stream removed in line 18. The overhead vapor stream should be essentially free of cumene and any heavier boiling hydrocarbonswhich enter the column. The overhead vapor stream passes through the overhead condenser 12 and then flows into the overhead receiver 13. The liquid phase benzene which thereby accumulates in the receiver is withdrawn through line 14 and divided into the recycle stream carried by line 16 and the reflux stream re~urned to the recycle column via line 15. Not shown on ~he drawing are the customary effluent streams associated with the upper portion of the recycle solumn. These two streams comprise a vapor off gas line for the overhead receiver and a drag benzene line which may be removed from the recycle column or from the overhead ~29~523~
receiver liquid.
The net bo~toms liquid from the recycle column carried by line 21 comprises the product cumene and the by-product heavy hydrocarbons. It should beessentially free of propane and benzene. The ne$ bottoms stream is passed into the cumene column 22 and is therein separated into a bottoms stream removed in line 28 and an overhead vapor stream removed through line 23. In accordance with the subject invention, the overhead vapor stream passes through the reboiler means 20 of the recycle column thereby supplying heat to the bottom of the recycle column.
This results in at least a partial condensation and preferably a total condensation of the overhead vapor stream and the production of a condensate which is passed into the overhead receiver 24. This condensate liquid is high-purity cumene which is withdrawn through line 25 and divided into ~he reflux stream, returned to the cumene column throu~h line 27 and the net product s~ream of the process which isremoved through line 26. The heat given up by the overhead vapor stream in the reboiler vaporizes at least a portion of the bottom liquid circulating through line l9 to thereby provide vapors which pass into ~he bottom of the recycle column and effect the reboiling of the column.
The cumene column 22 is reboiled by means of h~at supplied to the bottoms liquid circulating through line 29 and partially vaporized in reboiler means 30. The net bottoms stream removed from the cumene column in line 31 is passed through pressure reducing valve 40 into an upper portion of the stripping column 32.
This column is operated at fractionation conditions which are effective to separate the entering hydrocarbons into the overhead vapor stream withdrawn through line 33 and the bottoms liquid withdrawn through line 36. The bottoms liquid of line 36 should be rich in the heavy hydrocarbon by-products of the alkylation reaction. A
portion of the bottoms liquid is circulated through line 37 and the reboiler means 3 which receives heat from an external source such as high pressure steam or hot oil.
The high boiling by-products for the alkylation reaction are therefore concentrated into a relatively small net bottoms stream discharged from the process through line 39. The overhead vapor stream of line 33 has a high concentration (greater than 90 mole percent) of cumene. The overhead vapor stream is preferably heated in the heating means 34 and is then compressed in means 35. The cumene rich overhead vapor stream then continues through line 33 and is pref erably passed into the cumene column at a lower point near or below the lowest most tray within this column. The overhead vapor stream could, however, be passed into the column at -~Z~5:~34 higher points if 50 desired.
The subject invention is practiced wi~h a reaction zone containing a solid catalyst. Preferably, the catalyst is one commonly referred to as an SPA catalyst.
Suitable SPA catalysts are available commercially. As used herein the term "SPA
catalyst" or its equivalent is intended to refer generically to a solid catalyst which contains as one of its principal raw ingredients an acid of phosphorus such as ortho-, pyro- or tetra-phosphoric acid. These catalysts are normally formed by mixing the acid with a siliceous solid carrier to form a wet paste. This paste may be calcined and then crushed to yield catalyst particles, or the paste may be extruded or pelleted prior to calcining to produce more uniform catalyst particles. The carrier is preferably a naturally occurring porous silica-containing material such as kieselguhr, kaolin, infusorial earth and diatomaceous earth. A minor amount of various additives such as mineral talc, fullers earth and iron compounds including iron oxide have been added to the carrier to increase its strength and hardness. The combination of the carrier and the additives normally comprises about 15-30 wt. %
of the catalyst, with the remainder being the phosphoric acid. However, the amount of phosphoric acid used in the manufacture of the catalyst may vary from about 8-80 wt. % of the catalyst as described in U.S. Patent No. 3,402,130. The amount of the additive may be equal to about 3-20 wt. % of the total carrier material. Further details as to the composition and production of typical SPA catalysts may be obtained from U.S. Patent Nos. 3,050,~72; 3,050,473and3,132,109 and from other references.
The subject inventlon is not restricted to use with a SPA type catalyst.
For instance the previously cited article describes the use of AIC13 catalysts and indicates this is a commonly used catalyst in the production of ethyl benzene. In addition, the patent literature describes a vast array of zeolite alkylation catalysts and processes for their use. It is therefore contemplated to practice the subject invention using a catalyst comprising an amorphous or a crystalline alumino silicate such as a "ZSM-5" zeolite. Due to the nature of the aluminosilicates they are normally not used in the pure form but are composited into a porous support matrix in combination with an alumina or silica or clay. The alkylation reactions with these materials have been described as being both vapor-phase and liquid-phase processes.
The reaction conditions for use with differing catalysts, which are set out in the references, will Yary from the preferred conditions set out herein for use in conjunction with SPA-type catalysts. Further information on zeolitic alkylation _g_ ~S%3~
catalysts may be obtained from a number of sources including U.S. Patents No.
3,755,483; 4,300,011; 4,469,90~ and 4,489,214.
The reaction zone is maintained at alkylation-promoting conditions. As previously stated the conditions must be adjusted to compensate for the specificcatalyst being employed and the reactants being charged to the process. In the case of an SPA type catalyst these condltions include a pressure of about 300 to 1000 psig (2069 tD 6895 kPag) and a temperature of about 300 to 600F (149 tD 316~). Theliquid hourly space velocity o~ reactants may range ~rom about 0.5 to 2.5 m 1. It is preferred that an excess of the aromatic hydrocarbon be present in the reaction zone.
The mole ratio of the ~romatic hydrocarbon to the olefin should be within ~he broad range of 3:1 to 20:1. A ra~io of about 8:1 is preferred for the production of cumene.
It is preferred that the reactant stream be mixed-phase through the reactor. The feed stream therefore preferably contains some unreactive light paraffins having the same number of carbon atoms per molecule as the ole~in. In the production of cumene it is preferred that the amount of propane in the reaction zone feed stream be at least equal to the amou~t of propylene in this stream. This may be accomplished by using a dilute propylene feed stream or by recycling propane. The previously cited article indicates representative conditions for the use of an Al C13 catalyst system include a tempera-ture below 275F (135~C) and a pressure of less than 50 psig (345 kPag).
The preferred embndiment of the invention may accordingly be described as a process for the production of an alkylaromatic hydrocarbon which comprises contacting a feed acyclic olefinic hydrocarbon and a feed aromatic hydrocarbon with a solid alkylation catalyst in an alkylation reaction zone maintained at alkylation-promoting conditions and producing a reaction zone effluent stream comprising the feed aromatic hydrocarbon, a monoalkylaromatic product hydro-carbon and highboiling by-product hydrocarbons and subsequently recovering the product alkylaromatic hydrocarbon by a method which comprises the steps of passing a process stream comprising the feed aromatic hydrocarbon, the mono-alkylaroma~ic product hydrocarbon and the by-product hydrocarbons into a recyclefractionation column operated at conditions which effect the separation of entering hydrocarbons into at least a net overhead stream, which is rich in the feed aromatic hydrocarbon, and a first bottoms stream, which comprises the product hydrocarbonand the by-product hydrocarbons; passing the first bottoms stream into a product~ractionation column operated at conditions effective to separate entering hydro-carbons into a first overhead vapor stream, which is rich in the product hydrocarbon ~Z~523~
and slJbstantially free of the by-product hydrocarbons, and a second bottoms stream, which is rich in the product hydrocarbon and also comprises the by-product hydrocarbons; at least partially condensing the first overhead vapor stream in ar~boiler means supplyin~ heat to the bot~om portion of the recycle column, wi~hdrawing a ~irst portion of the resultant condensate from the process as a net product str~am and returning a second portion of the condensate to the product column as reflux liquid; passing the second bottoms stream into a stripping column operated at ~ractiona~ distillation conditions, including a pressure which is at least 15 psi (103 kPa) and more preferably 20 psi (138 kPa) lower than is maintained in the product fractionation column, effective to separate entering hydrocarbons into a second overhead vapor stream comprising the product alkylaromatic hydrocarbon and a third bottoms stream, which comprises the by-product hydrocarbons and is substantially free ofthe product hydrocarbon; and compressing the second oYerhead vapor stream and then passing the second overhead vapor stream into a bottom portion ofthe product fraction column. As used herein the term substantially free is intended to indicate a molar concentration of the indicated substance less than about 2 and preferably less than 1 percent. The term "rich" is in-tended to indicate a concentration of the specified compound or class of com-pounds exceeding about 75 mole percent.
Claims (6)
1. A process for the production of an alkylaromatic hydrocarbon which comprises contacting a feed acyclic olefinic hydrocarbon and a feed aromatic hydrocarbon with an alkylation catalyst in an alkylation reaction zone maintained at alkylation-promoting conditions and producing a reaction zone effluent stream comprising the feed aromatic hydrocarbon, a product alkylaromatic hydrocarbon and high-boiling by-product hydrocarbons and subsequently recovering the product alkylaromatic hydrocarbon by a method which comprises the steps of:
(a) passing a process stream comprising the feed aromatic hydrocarbon, the product alkylaromatic hydrocarbon and the by-product hydrocarbons into a recycle fractionation column operated at conditions which effect the separation of entering hydrocarbons into at least a net overhead stream, which is rich in the feed aromatic hydrocarbon, and a first bottoms stream, which comprises the product alkylaromatic hydrocarbon and the by-product hydrocarbons;
(b) passing the first bottoms stream into a product fractionation column operated at conditions effective to separate entering hydrocarbons into a first overhead vapor stream, which is rich in the product alkylaromatic hydrocarbon, and a second bottoms stream, which is rich in the product alkylaromatic hydrocarbon and also comprises the by-product hydrocarbons;
(c) at least partially condensing the first overhead vapor stream in a reboiler means supplying heat to a lower portion of the recycle column, withdrawing a first portion of the resultant condensate from the process as a net product stream and returning a second portion of the condensate to the product column as refluxliquid;
(d) passing the second bottoms stream into a stripping column operated at fractional distillation conditions, including a lower pressure than is maintained in the product fractionation column, and effective to separate entering hydrocarbons into a second overhead vapor stream comprising the product alkylaromatic hydro-carbon and a third bottoms stream, which comprises the by-product hydrocarbons and is substantially free of the product alkylaromatic hydrocarbon; and, (e) compressing the second overhead vapor stream and then passing the second overhead vapor stream into the product fractionation column.
(a) passing a process stream comprising the feed aromatic hydrocarbon, the product alkylaromatic hydrocarbon and the by-product hydrocarbons into a recycle fractionation column operated at conditions which effect the separation of entering hydrocarbons into at least a net overhead stream, which is rich in the feed aromatic hydrocarbon, and a first bottoms stream, which comprises the product alkylaromatic hydrocarbon and the by-product hydrocarbons;
(b) passing the first bottoms stream into a product fractionation column operated at conditions effective to separate entering hydrocarbons into a first overhead vapor stream, which is rich in the product alkylaromatic hydrocarbon, and a second bottoms stream, which is rich in the product alkylaromatic hydrocarbon and also comprises the by-product hydrocarbons;
(c) at least partially condensing the first overhead vapor stream in a reboiler means supplying heat to a lower portion of the recycle column, withdrawing a first portion of the resultant condensate from the process as a net product stream and returning a second portion of the condensate to the product column as refluxliquid;
(d) passing the second bottoms stream into a stripping column operated at fractional distillation conditions, including a lower pressure than is maintained in the product fractionation column, and effective to separate entering hydrocarbons into a second overhead vapor stream comprising the product alkylaromatic hydro-carbon and a third bottoms stream, which comprises the by-product hydrocarbons and is substantially free of the product alkylaromatic hydrocarbon; and, (e) compressing the second overhead vapor stream and then passing the second overhead vapor stream into the product fractionation column.
2. The process of Claim 1 further characterized in that the stripping column is operated at a pressure at least 15 psi (103 kPa) lower than the pressure at which the product fractionation column is operated.
3. The process of Claim 1 further characterized in that the feed acyclic olefinic hydrocarbon is a C3 to C5 hydrocarbon.
4. The process of Claim 1 further characterized in that the feed aromatic hydrocarbon is benzene.
5. The process of Claim 4 further characterized in that the feed acyclic olefinic hydrocarbon is propylene.
6. The process of Claim 1 further characterized in that the product alkylaromatic hydrocarbon is a bialkylaromatic hydrocarbon.
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| US06/741,331 US4587370A (en) | 1985-06-05 | 1985-06-05 | Aromatic hydrocarbon alkylation process product recovery method |
| US741,331 | 1985-06-05 |
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| CA1245234A true CA1245234A (en) | 1988-11-22 |
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| CA000509424A Expired CA1245234A (en) | 1985-06-05 | 1986-05-16 | Product recovery method for an aromatic hydrocarbon alkylation process |
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| US (1) | US4587370A (en) |
| EP (1) | EP0205003B1 (en) |
| JP (1) | JPS61282325A (en) |
| AT (1) | ATE41648T1 (en) |
| AU (1) | AU588882B2 (en) |
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| US4051191A (en) * | 1977-01-03 | 1977-09-27 | Uop Inc. | Solid phosphoric acid catalyzed alkylation of aromatic hydrocarbons |
| US4108914A (en) * | 1977-04-27 | 1978-08-22 | Uop Inc. | Aromatic hydrocarbon alkylation process |
| CA1104517A (en) * | 1977-08-02 | 1981-07-07 | Polysar Limited | Energy conservation in a butadiene process |
| US4277268A (en) * | 1979-10-17 | 1981-07-07 | Conoco, Inc. | Heat pump fractionation process |
| US4360405A (en) * | 1980-05-12 | 1982-11-23 | The Lummus Company | Process for fractionating close boiling components of a multi-component system |
| US4395310A (en) * | 1981-07-14 | 1983-07-26 | Exxon Research And Engineering Co. | Fractionation system |
| JPS5864101A (en) * | 1981-10-13 | 1983-04-16 | ザ・ル−マス・コンパニ− | Fractionation method and apparatus |
| EP0131932B1 (en) * | 1983-07-13 | 1986-10-22 | Tosoh Corporation | Method for distillation of 1,2-dichloroethane |
| DE3437615A1 (en) * | 1984-10-13 | 1985-05-15 | Günther 4250 Bottrop Richter | Process for working up an alkylated reaction mixture |
| US4587370A (en) * | 1985-06-05 | 1986-05-06 | Uop Inc. | Aromatic hydrocarbon alkylation process product recovery method |
-
1985
- 1985-06-05 US US06/741,331 patent/US4587370A/en not_active Expired - Lifetime
-
1986
- 1986-04-28 IN IN376/DEL/86A patent/IN167306B/en unknown
- 1986-05-16 CA CA000509424A patent/CA1245234A/en not_active Expired
- 1986-05-21 EP EP86106900A patent/EP0205003B1/en not_active Expired
- 1986-05-21 AT AT86106900T patent/ATE41648T1/en not_active IP Right Cessation
- 1986-05-21 DE DE8686106900T patent/DE3662517D1/en not_active Expired
- 1986-05-21 ZA ZA863800A patent/ZA863800B/en unknown
- 1986-05-21 JP JP61114991A patent/JPS61282325A/en active Granted
- 1986-06-04 AU AU58332/86A patent/AU588882B2/en not_active Ceased
- 1986-06-04 FI FI862388A patent/FI82236C/en not_active IP Right Cessation
- 1986-06-04 ES ES555698A patent/ES8707168A1/en not_active Expired
- 1986-06-04 BR BR8602610A patent/BR8602610A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| ZA863800B (en) | 1987-01-28 |
| JPH0411529B2 (en) | 1992-02-28 |
| BR8602610A (en) | 1987-02-03 |
| ATE41648T1 (en) | 1989-04-15 |
| EP0205003A1 (en) | 1986-12-17 |
| US4587370A (en) | 1986-05-06 |
| AU5833286A (en) | 1986-12-11 |
| FI82236B (en) | 1990-10-31 |
| FI862388A0 (en) | 1986-06-04 |
| FI82236C (en) | 1991-02-11 |
| ES555698A0 (en) | 1987-07-16 |
| AU588882B2 (en) | 1989-09-28 |
| DE3662517D1 (en) | 1989-04-27 |
| IN167306B (en) | 1990-10-06 |
| JPS61282325A (en) | 1986-12-12 |
| FI862388A (en) | 1986-12-06 |
| ES8707168A1 (en) | 1987-07-16 |
| EP0205003B1 (en) | 1989-03-22 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |