CA1226552A - Integrated fractionation in the recovery of alkylaromatic hydrocarbons - Google Patents
Integrated fractionation in the recovery of alkylaromatic hydrocarbonsInfo
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- CA1226552A CA1226552A CA000492983A CA492983A CA1226552A CA 1226552 A CA1226552 A CA 1226552A CA 000492983 A CA000492983 A CA 000492983A CA 492983 A CA492983 A CA 492983A CA 1226552 A CA1226552 A CA 1226552A
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Abstract
"INTEGRATED FRACTIONATION IN THE
RECOVERY OF ALKYLAROMATIC HYDROCARBONS"
ABSTRACT
A method is disclosed for fractionating a hydrocarbon con-version zone effluent stream comprising at least three components which are to be isolated into separate streams. A two-column system for fractionating the effluent of a benzene alkylation zone is employed.
The overhead vapor of a downstream second column is condensed in a side reboiler of a preceding recycle column. This side reboiler is located between the feed point to the recycle column and a separate reboiler located at the bottom of the recycle column. The utilities cost of performing the fractionation is reduced.
RECOVERY OF ALKYLAROMATIC HYDROCARBONS"
ABSTRACT
A method is disclosed for fractionating a hydrocarbon con-version zone effluent stream comprising at least three components which are to be isolated into separate streams. A two-column system for fractionating the effluent of a benzene alkylation zone is employed.
The overhead vapor of a downstream second column is condensed in a side reboiler of a preceding recycle column. This side reboiler is located between the feed point to the recycle column and a separate reboiler located at the bottom of the recycle column. The utilities cost of performing the fractionation is reduced.
Description
I
"INTEGRATED FRACTIONATION IN THE RECOVERY
OF ~LKYL~ROM~TIC HYDROCARBONS "
_ YIELD OF THE INVENTION
The invention in general relates to the energy efficient processing of hydrocarbons and to the recovery of specific hydrocarbons from the efflu-en of a hydrocarbon conversion process. The invention is directly concerned with the efficient recovery of a product alkylaromatic hydrocarbon from the effluent of an alkylation zone. The invention directly concerns a unique integrated fractional distillation method employed in the separation of an alkylaromatic hydrocarbon from an alkylation zone effluent stream.
BACKGROUND OF _HE_INVEN~ION
The alkylation of aromatic hydrocarbons is a widely pray-tîced commercial process. It may be performed for the production Oman end product or an intermediate product which is the feed stock for a subsequent process or processing step. For instance, Bunsen may be reacted with a linear olefin for the production of linear alkylben-zones suitable for conversion into soft detergent. The subject invent lion is, however more directly concerned with the alkylatlon processes in which a feed aromatic hydrocarbon is reacted with another hydrocar-bun having from two to about four carbon atoms per molecule. In this instance, the difference in the molecular weight and volatility be tweet the feed aromatic hydrocarbon and the product alkylarcmatic ho-2Q drocarbon is less than in the case of the product10n of detergent alkyd late, since the normal olefin feed stock in a detergent alkylation pro-cuss normally has from about 8 to about 15 carbon atoms per molecule.
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typical alkylation process of the type believed most relevant to the subject invention is illustrated in US. Patent 4,051,191. This patent provides a description of the operation of the alkylation zone and the fractionation system used to produce cumin by the alkylation of Bunsen with propylene. This reference illustrates the passage of a net liquid phase alkylation zone effluent stream into a first fractionation column labeled as the recycle column. Unrequited Bunsen is recovered as a net overhead product ox the recycle column and returned to the alkylation zone. bottoms product is removed from the recycle column and passed into a second fractionation column in which the product cumin is swoop crated into a net overhead product. This two column arrangement is similar to that used in the subject invention.
It is well known to those skilled in the art that signify-cant economies can be obtained in a fractionation process by utilizing the heat recovered from the overhead stream of a fractionation column within the fractionation process itself. The overhead vapor stream movie therefore be cooled by indirect heat exchange against a fluid which no-quirks heating or vaporization. on example of this is shown in US.
Patent 3,414,484 issued to D. B< Carson in which the overhead vapor stream of an aromatic fractionation column is compressed to thereby provide a stream having a sufficient temperature to reboil the column from which it is removed. This is normally referred to as a heat pumped fractionation system.
Us Patent 3,254,024 issued to H. A. Hawkins, or. thus-trades a process inn the separation of C8 aromatic hydrocarbons by free-tonal distillation. This reference is believed pertinent for its Lucy-traction of the removal of the overhead vapor stream from the fractionator 7 and the passage of this overhead vapor through the bottom recoiler-I
means emp10yed in the fractionators 2 and 13. This demonstrates that it is known to those skilled in the art that the overhead vapor stream of one fractionation column may be utilized to reboil a different free-tionation column through the proper selection of operational conditions.
A similar but slightly different fractionation method is illustrated in US. Patent 4,170,548 issued to R. G. Ruth. In this reference, the overhead vapor stream of a column 12 is used as the heat source employed in the recoiler 16 of a second column. The overhead vapor stream is then condensed and collected in an overhead receiver. A first portion of the collected condensate is returned to the column 12 as reflex and a second portion is passed into the second column.
BRIEF SUMMARY OF THE INVENTION
The subject invention provides an improved process which no-dupes the utility cost of recovering a product alkylaromatic hydrocar-bun from an admixture comprising both lower boiling and higher boiling aromatic hydrocarbons. The subject process utilizes energy available in the overhead stream of a second fractionation column in a side no-boiler located between the feed try and the bottom of a preceding fractionation column. This significantly reduces the amount of energy required in the recoiler located at the bottom of the first fractional lion column. The subject process may be characterized as comprising the steps of passing the reaction zone en vent stream which comprises a C5-plus aromatic first hydrocarbon, an aromatic second alkylaromatic hydrocarbon and a heavy by-product alkylaromatic third hydrocarbon into a first fractionation column at a first Point. with the first fractionation colunln being maintained at fractionation condîtlons on part through the use of a first recoiler means located at the I
bottom of the first fractionation column, removing an overhead stream which is rich in the first hydrocarbon, from the first fractionation column; removing a first net bottoms stream, which is rich in the alkali-aromatic second hydrocarbon, From the first fractionation column and passing the first net bottoms stream into a second fractionation column;
removing a second net bottoms stream, which is rich in the by-product alkylaromatic third hydrocarbon, from the second fractionation column;
and condensing at least a portion of an overhead vapor stream which is withdrawn from the second fractionation column by indirect heat exchange as the heat source employed in a second recoiler means which vaporizes a portion of the liquid present within the first fractionation column at an intermediate lower second point, and recovering a product strewn which is rich in the product alkylaromatic second hydrocarbon from the condensate which results from this heat exchange on the second recoiler means.
BRIEF DESCRIPTION OF THE DRAWING
The drawing it a simplified flow diagr~n of an alkylation process for producing cumin and which utilizes a preferred embodiment of the invention. A feed stream of relatively high purity Bunsen carried by line 1 together with a propylene-containing feed stream carried by line 2 and the benzene-r1ch recycle stream of line 3 are passed unto the alkylation zone 4. In this zone these three streams are brought into contact with an alkylation catalyst at alkylation-promoting conditions which result in the reaction of a portion of the Bunyan with the available propylene. The material Swing withdrawn from the reaction zone is separated within the alkylation zonk as no-squired by the specific alkylatlon zone and propylene feed streams which are being employed. This may produce recycle streams and off-gas 65~
streams not shown and also produces an alkylation Noah effluent stream removed in line 5. The alkylation zone effluent stream comprises an admixture of Bunsen, cumin, and various higher boiling by-product hydrocarbons produced by reactions other than the intended monoalkyla-lion of the Bunsen.
The alkylation zone effluent stream is passed into a first fractionation column 6 referred to as a recycle column. Substantially all of the Bunsen and any lighter hydrocarbons is concentrated into a net overhead vapor stream removed through line 7 and passed through the overhead condenser 8. The resultant condensate is collected in the overhead receiver 9. Uncondensed gases which may be present and con-dented water may be removed through means not shown. The hydrocarbon condensate is withdrawn from the overhead receiver through line 10 and divided into a first portion which is returned to the recycle column through line 11 as reflex and a second portion which is recycled to the alkylation zone as the Bunsen recycle stream carried by line 3.
Substantially all of the hydrocarbons entering the fractionation got-urn which are less volatile than Bunsen are concentrated into a both toys liquid stream withdrawn from the recycle column in line 12.
first portion of the bottoms liquid is diverted through an external recoiler means 14 via line 13. The fluids discharged from the bottom recoiler 14 are passed into a bottom portion of the recycle column.
The remaining portion of the bottoms stream of line 12 be-comes the weed stream charged to the product column 76 through line 15.
The relatively small amount of high boiling by-products which enters the product column becomes concentrated into a bosoms stream withdrawn in line 17. This bottoms liquid is divided into a portion which is passed through a rubber means 20 via line 19 and a second portion with-drawn as a by-products stream through line 18. The very great majority of the material which enters the product column 16 is concentrated into the overhead vapor stream removed from the products column in line 21.
The overhead vapor stream passes through a side recoiler means 22 wherein it is condensed to form an overhead condensate which is passe into the overhead receiver 25. The condensate is withdrawn through line 26 and divided into a first portion returned to the products got-urn via line 28 as reflex and a second portion which is withdrawn as the cumin product stream through line 27. The substantial amount of heat of vaporization given up my the overhead vapor stream of the prod-vats column is received by a liquid stream withdrawn from an interim-dilate point in the lower half of the recycle column in line 23. this liquid it preferably partially vaporized in the side recoiler 22 to thereby produce a mixed phase stream which is charged to the recycle column 6 through line 24. Line 24 communicates with the recycle got-urn at a point which is at least several trays above the point at which vapors produced by the bottom recoiler means 14 enter the recycle column. This description of a preferred embodiment of the inverltion is not intended lo preclude from the scope of the invention those other embodiments set out herein or which are the result of the normal and expected modification of those embodiments.
DETAILED DESCRIPTION
The alkylation of aromatic hydrocarbons is practiced courier-Shelley on a large scale. One particular example is the alkylation of Bunsen with propylene to form cumin, which is then used to produce phenol and acetone. These alkylation processes are normally performed with the intent of producing a single alkylaromatic product rather than an ad-mixture of alkylaromatics. However, despite the advances in the art which have occurred, the products of the commercial alkylation reactor will normally contain an admixture which contains small amounts of by-products which musk be separated from the reaction zone product. our-then, in an effort to promote monoalkylation, there is normally pro-voided an excess of the feed aromatic hydrocarbon which is to be alkyd fated. The effluent of the alkylation reaction zone therefore tonally contains an admixture of the feed hydrocarbon, the product hydrocarbon, and one or more higher boiling side products. The separation of these materials is normally performed commercially by Fractional distill-lion.
The separation of these sometimes close-boiling hydrocarbons in large quantities and to high purities requires sizable fractionation facilities and consumes a large amount of energy. The utilities cost of the fractionation includes both the cost of heat supplied to the no-boiler of the fractionation column and the cost in terms of cooling water and wasted low level heat which is associated with the condense-ton of overhead vapors The utilities cost of separating the of-fluent stream of the alkylation zone is therefore a significant part of the total cost of operating such an aromatic hydrocarbon alkylation process. It is therefore an objective of the subject process to pro-vise a method ox reducing the utilities cost of operating the fraction-anion section of a process for the alkylation of aromatic hydrooar-buns. It is another objective of the subject invention to provide a method of recovering in a useful manner heat present in the overhead vapor stream of the product column of a two-column aromatic hydrocar-I
bun fractionation system. It is a specific objective of the subject in-mention to reduce the recoiler heating utilities cost of the recycle got-urn of a process in which cumin is produced by tune alkylation of Bunsen.
The subject process may be used to separate the effluent of reaction zones used for transalkylation, alkylaromatic hydrocarbon isomerization, aromatization, etc. However the preferred reaction is alkylation and the process will be described mainly in terms of this one limited embodiment. The preferred feed hydrocarbon for alkylation is Bunsen. The preferred hydrocarbon feed material may be more gent orally characterized as an aromatic C6-plus hydrocarbon such as Bunsen, lot-gene, a zillion, or ethylbenzene. Higher molecular weight hydrocarbons could also be consumed as the feed hydrocarbon. The alkylating agent which is reacted with the feed hydrocarbon to produce the product alkyd-aromatic hydrocarbon may be an olefin-acting compound such as an alcohol, ether or ester including alkylhalides, alkylsulfates and alkylphos-plates. Preferably, the alkylating agent is a moo- or dolphin having from two to five carbon atoms per molecule. The preferred manliness include ethylene, propylene, button, button and isobutylene. These olefins may be used as relatively pure streams containing a single ho-drocarbon species. alternatively, a mixture of a single olefln and a corresponding paraffin may be used or a mixture of two or more olefinic hydrocarbons may be employed as the olefin-containing material charged to the alkylation zone. Typical product hydrocarbons include cumin, ethylbenzene, and Simon (isopropyltoluene).
The hydrocarbon stream charged to the fractionation zone is the effluent stream of a hydrocarbon conversion zone. This effluent stream is preferably the result of a partial separation performed within the conversion zone which results in a reaction zone effluent ~l2~;5~
stream being converted into a conversion zone effluent stream contain in less than 10 mole percent of any hydrocarbon having fewer carbon atoms per molecule than the hydrocarbon which is recovered as the over-head product of the first fractionation column. Preferably, this is achieved through-a partial condensation of the admixture of compounds actually exiting from the reactor to produce a liquid hydrocarbon phase and a vapor phase containing a very great percentage of any ho-drogen and normally gaseous hydrocarbons which exit the catalyst bed.
The liquid phase produced in this manner may be stripped of dissolved light gases if desired prior to being passed into the fractionation zone of the subject invention. The subject improved separation method could be applied in general to the separation of any reaction zone of-fluent stream comprising an admixture of hydrocarbons having the appear-private boiling point characteristics including those processes described above. However, it is greatly preferred that the reaction zone is in-tended to operate as an alkylation zone in which the feed hydrocarbon is consumed in the production of a product hydrocarbon of higher mole-urea weight. This alkylation may be promoted through the use of a wide variety of suitable catalysts such as boron trifluoride, various zoo-litic compounds, hydrogen fluoride, etc. The preferred catalyst for use in the alkylation zone is referred to as a solid phosphoric acid or SPY catalyst.
Suitable SPY catalysts ore available cs~mercia71y. us used herein the term "SPY 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 orate pyre or twitter-phosphoric acid. These catalysts are normally formed by mixing the acid with a siliceous solid carrier to form a wet paste. Thus paste nay be 55~2 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 itemizes 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 de-scribed in US. Patent 3,402,130. The amount of the additive Jay be equal to about 3-20 wt. % of the total carrier material. Further de-tails as to the composition and production of typical SPY catalysts may be obtained from US. Patents 3,0~0,472, 3,050,473 and 31132,109 and from other references.
It is known in the art that the passage of aromatic hydrocar-buns through an alkylation zone tends to leach chemically combined ` water out of an SPY catalyst. This is acknowledged in US. Patents 3,510,534 and 3,520,945, the latter of which is directed to the control of the state of hydration of the catalyst The waxer content of the catalyst is important since dehydration causes the SPY catalysts to deteriorate by powdering and caking, while excess water causes the gala-lusts to soften and eventually form a sludge which would plus the react ion. Water is therefore injected into the feed stream to maintain the catalyst at the proper state of hydration by replacing the water leached from the catalyst. The rate of this injection is used to control the catalyst hydration level, and the feed streams are therefore maintained I
as dry as practical prior to the water injection point. This results in the total water content of the feed being essentially the same as the amount injected. Typical waxer injection rates are from about 100 to 2000 wt. Pam in aromatic hydrocarbon alkylation operations. A pro-furred water addition rate during the production of cumin is from about 200 to 300 wt. Pam of the combined feed to the reaction zone.
The feed hydrocarbon, any recycle streams and the Feed olefin-acting compound are preferably admixed and then passed into a reaction zone. The reaction zone is maintained at alkylation-promoting conditions which include a pressure of about 300 to 1000 prig (2068 to 6895 kPag) and a temperature of about 300~ to 600F (149 to 316C). The liquid hollrly space velocity of reactants may range from about 0.5 to Z.5 hr. 1 It is preferred that an excess of the aromatic hydrocarbon be present in the reaction zone. The mole ratio of the aromatic hydrocarbon to the olefin should be within the broad range of 3:1 to 20:1. ratio of about 8:1 is preferred for the production of cumin. It is preferred that the reactant stream be mixed phase through the reactor. The feed stream therefore preferably con-twins some unreactive light paraffins having the same number of carbon atoms per molecule as the olefin. In the production of cumin it is preferred that the amount of propane in the reaction zone feed stream be at least equal to the amount of propylene in this stream. This may be accomplished by using a dilute propylene feed stream or by recycling propane.
In the preferred embodiment the effluent of the alkylation reactor is passed into a first rectifier column located within the come pled referred to herein as the alkylation zone. This column is normally used in conjunction with either a second rectifier, an absorber or a depropanizer (for alkylation using propylene). The exact form of this _ 1 1 I
system does not influence the subject process. The function of this portion of the alkylation zone is to recover any ole~in-acting compound which may be available for recycling to the reactor and to remove any light hydrocarbons such as propane which enter the alkylation zone.
The preferred form of this portion of the alkylation zone is described in previously referred to US. Patent 4,051,191 and in US. Patent 3,510,534~
The alkylation zone effluent will normally contain most of the excess Bunsen charged to the alkylation reactor to promote moo-alkylation. It is common and preferred practice to first separate the feed Bunsen and other hydrocarbons boiling below the cumin (or other product) in a first fractionation column referred to as a Bunsen colt urn or recycle column The cumin or other product alkylarornatic is then recovered as the overhead of a second column referred to as the cumin column or product column. Further information on the pro-furred alkylation process and possible variations in process flows and operations may be obtained by reference to US. Patents 3,437,706;
3,437,707; 3,437,70~; 39520,g44 and 3,542,892.
The conditions of temperature and pressure maintained in the first and second fractionation columns are interrelated. They may, how-ever, vary over considerable ranges, with exact operating conditions being set by economic and operational considerations which movie be specie lie to individual process units. broad range of conditions for use in the first fractionation column includes a top pressure of about Sty about 150 prig ~34 to 1034 kPag) and a bottoms temperature ox about 270 to about 400F (132 to 204C). A broad range ox conditions for use in the second fractional lion column includes a top pressure of about 15 to about 24Q pug (103 to 1655 kPag) and a bottoms temperature of about 320 to about 470~F ~16Q to 243~C).
These conditions are ~%~
interrelated in that the overhead vapor ox the second column must be at a pressure such that it will be condensed at the temperature of the liquid in the side recoiler of the first column after adjustment for the temperature difference "across" the recoiler. The calculation of such fractionation conditions are well within the expertise of those skilled in hydrocarbon fractionation and may be aided by widely avail-able computerized design systems. The internal design and construction of the columns may he similar to that presently employed in equivalent commercial installations.
The subject process requires a side recoiler to be installed in the first of the two columns. This recoiler is separate and disk tint from the recoiler employed at the bottom of the column. This recoiler is used to vaporize liquid withdrawn from an intermediate point in the column. us used herein, the term "intermediate point" is intended to indicate a point which is separated from each extremity of the column by vapor-liquid contacting material equal to at least two and preferably three theoretical contacting stages (trays). The side recoiler therefore acts upon liquid which has a lower average boiling point than the bottoms liquid entering the bottom recoiler. The side recoiler preferably is located about midway between the bottom of the first column and the feed point to the column. However, the location of the feed point may be varied depending on the composition of the entering alkylation zone feed stream, and the feed may enter at such a level that the side recoiler is optimally placed much closer to the bottom recoiler than to the feed point.
The subject process recovers at least a major portion ox the heat which must be removed in condensing the overhead stream of the second fractionation column. This heat it transferred into the first column. The amount of heat which must be applied to the customary both Tom rebiller of the first column is thereby reduced and the utility cost of operating the column is lowered. For instance, the applique lion of the subject process to a large scale process for the production of four hundred million pounds per year I x 10~ kg/yr3 of cumin is pro-jetted as being able to reduce the Bunsen (first) column recoiler heat require-mints from about 33 million BTU/hr (34.8 x 106 kj/hr) to about 18 million BTU/hr(19 x 105 kj/hr). This would provide a substantial reduction in the cost of operating the Bunyan column. Because the recovered heat is added to the Bunsen (first) column at a point above the bottom of the column, the required temperature of the cumin (second) column overhead vapor stream is worry than if it was attempted to use this overhead vapor as the heat source in the bottom recoiler. This assumes the pressure in the first column is the same during this comparison. The ability to remover heat from the overhead vapor at this lower temperature can be advantageous.
For instance, the ability to apply modern heat recovery techniques to an existing pair of fractionation columns may be limited due Jo the maximum pressures at which the columns can be operated. on example of this would be the inability to operate an existing column at a suffix ciently high pressure to achieve an overhead vapor having a temperature which can be used in reboiling at the bottom of another column. The subject process Will allow heat in the overhead vapor to be used in the preceding column with a smaller pressure differential between the got-urns than the prior art method of consuming this heat at the bottom of the preceding column. The ability to recover heat from overhead vapors without a significant increase in the bottoms temperature of the second column may else be advantageous if the compounds being free-shunted are thermally sensitive.
The subject process may be characterized as a process for recovering an alkylaromatic hydrocarbon from the effluent stream of an aromatic hydrocarbon alkylation zone which comprises the steps of passing an alkylation zone effluent stream which comprises a feed art-matte hydrocarbon, a product alkylaromatic hydrocarbon, and a by-prod-S vat alkylaromatic having a higher boiling point than the product alkyd-aromatic hydrocarbon into a first fractionation column at a first intermediate point, with a first recoiler being located at the bottom of the first fractionation column; recovering a first net overhead product stream, which is rich in the feed hydrocarbon, from the first fractionation column; removing a first net bottoms stream, which is rich in the product alkylaromatic hydrocarbon, from the first fraction-anion column and passing the first net bottoms stream into a second fractionation column; removing a second net bottoms stream, which is rich in the by-product alkylaro~atic hydrocarbon, from the second fractionation column; and condensing at least a portion of an overhead vapor stream withdrawn from the second fractionation column in a sea-on recoiler by indirect heat exchange against liquid withdrawn from the first fractionation column at an intermediate second point located above the first recoiler and below said first intermediate point, and recovering a product stream which is rich in the product alkylaromatic hydrocarbon from thy resultant condensate. as used herein, the term "rich" is intended to indicate that the stream or fluid being described contains over 60 mole percent of the specified compound or class of compounds. When the subject process is applied to conversion processes other than alkylation, the separations may be different from those de-scribed above. For instance, in aromatization processes in which arc-mattes are produced from C3 and/or C4 hydrocarbons, there will prefer-ably be little or no "feed" hydrocarbon entering the first fractional so lion column. In this instance Bunsen could be the top product of the first column, a mixture of Tulane and zillions may be removed as the top product of the second column and a mixture of Cg-plus aromatics withdrawn as the net bottoms product of the second column.
"INTEGRATED FRACTIONATION IN THE RECOVERY
OF ~LKYL~ROM~TIC HYDROCARBONS "
_ YIELD OF THE INVENTION
The invention in general relates to the energy efficient processing of hydrocarbons and to the recovery of specific hydrocarbons from the efflu-en of a hydrocarbon conversion process. The invention is directly concerned with the efficient recovery of a product alkylaromatic hydrocarbon from the effluent of an alkylation zone. The invention directly concerns a unique integrated fractional distillation method employed in the separation of an alkylaromatic hydrocarbon from an alkylation zone effluent stream.
BACKGROUND OF _HE_INVEN~ION
The alkylation of aromatic hydrocarbons is a widely pray-tîced commercial process. It may be performed for the production Oman end product or an intermediate product which is the feed stock for a subsequent process or processing step. For instance, Bunsen may be reacted with a linear olefin for the production of linear alkylben-zones suitable for conversion into soft detergent. The subject invent lion is, however more directly concerned with the alkylatlon processes in which a feed aromatic hydrocarbon is reacted with another hydrocar-bun having from two to about four carbon atoms per molecule. In this instance, the difference in the molecular weight and volatility be tweet the feed aromatic hydrocarbon and the product alkylarcmatic ho-2Q drocarbon is less than in the case of the product10n of detergent alkyd late, since the normal olefin feed stock in a detergent alkylation pro-cuss normally has from about 8 to about 15 carbon atoms per molecule.
Jo ~,.~
typical alkylation process of the type believed most relevant to the subject invention is illustrated in US. Patent 4,051,191. This patent provides a description of the operation of the alkylation zone and the fractionation system used to produce cumin by the alkylation of Bunsen with propylene. This reference illustrates the passage of a net liquid phase alkylation zone effluent stream into a first fractionation column labeled as the recycle column. Unrequited Bunsen is recovered as a net overhead product ox the recycle column and returned to the alkylation zone. bottoms product is removed from the recycle column and passed into a second fractionation column in which the product cumin is swoop crated into a net overhead product. This two column arrangement is similar to that used in the subject invention.
It is well known to those skilled in the art that signify-cant economies can be obtained in a fractionation process by utilizing the heat recovered from the overhead stream of a fractionation column within the fractionation process itself. The overhead vapor stream movie therefore be cooled by indirect heat exchange against a fluid which no-quirks heating or vaporization. on example of this is shown in US.
Patent 3,414,484 issued to D. B< Carson in which the overhead vapor stream of an aromatic fractionation column is compressed to thereby provide a stream having a sufficient temperature to reboil the column from which it is removed. This is normally referred to as a heat pumped fractionation system.
Us Patent 3,254,024 issued to H. A. Hawkins, or. thus-trades a process inn the separation of C8 aromatic hydrocarbons by free-tonal distillation. This reference is believed pertinent for its Lucy-traction of the removal of the overhead vapor stream from the fractionator 7 and the passage of this overhead vapor through the bottom recoiler-I
means emp10yed in the fractionators 2 and 13. This demonstrates that it is known to those skilled in the art that the overhead vapor stream of one fractionation column may be utilized to reboil a different free-tionation column through the proper selection of operational conditions.
A similar but slightly different fractionation method is illustrated in US. Patent 4,170,548 issued to R. G. Ruth. In this reference, the overhead vapor stream of a column 12 is used as the heat source employed in the recoiler 16 of a second column. The overhead vapor stream is then condensed and collected in an overhead receiver. A first portion of the collected condensate is returned to the column 12 as reflex and a second portion is passed into the second column.
BRIEF SUMMARY OF THE INVENTION
The subject invention provides an improved process which no-dupes the utility cost of recovering a product alkylaromatic hydrocar-bun from an admixture comprising both lower boiling and higher boiling aromatic hydrocarbons. The subject process utilizes energy available in the overhead stream of a second fractionation column in a side no-boiler located between the feed try and the bottom of a preceding fractionation column. This significantly reduces the amount of energy required in the recoiler located at the bottom of the first fractional lion column. The subject process may be characterized as comprising the steps of passing the reaction zone en vent stream which comprises a C5-plus aromatic first hydrocarbon, an aromatic second alkylaromatic hydrocarbon and a heavy by-product alkylaromatic third hydrocarbon into a first fractionation column at a first Point. with the first fractionation colunln being maintained at fractionation condîtlons on part through the use of a first recoiler means located at the I
bottom of the first fractionation column, removing an overhead stream which is rich in the first hydrocarbon, from the first fractionation column; removing a first net bottoms stream, which is rich in the alkali-aromatic second hydrocarbon, From the first fractionation column and passing the first net bottoms stream into a second fractionation column;
removing a second net bottoms stream, which is rich in the by-product alkylaromatic third hydrocarbon, from the second fractionation column;
and condensing at least a portion of an overhead vapor stream which is withdrawn from the second fractionation column by indirect heat exchange as the heat source employed in a second recoiler means which vaporizes a portion of the liquid present within the first fractionation column at an intermediate lower second point, and recovering a product strewn which is rich in the product alkylaromatic second hydrocarbon from the condensate which results from this heat exchange on the second recoiler means.
BRIEF DESCRIPTION OF THE DRAWING
The drawing it a simplified flow diagr~n of an alkylation process for producing cumin and which utilizes a preferred embodiment of the invention. A feed stream of relatively high purity Bunsen carried by line 1 together with a propylene-containing feed stream carried by line 2 and the benzene-r1ch recycle stream of line 3 are passed unto the alkylation zone 4. In this zone these three streams are brought into contact with an alkylation catalyst at alkylation-promoting conditions which result in the reaction of a portion of the Bunyan with the available propylene. The material Swing withdrawn from the reaction zone is separated within the alkylation zonk as no-squired by the specific alkylatlon zone and propylene feed streams which are being employed. This may produce recycle streams and off-gas 65~
streams not shown and also produces an alkylation Noah effluent stream removed in line 5. The alkylation zone effluent stream comprises an admixture of Bunsen, cumin, and various higher boiling by-product hydrocarbons produced by reactions other than the intended monoalkyla-lion of the Bunsen.
The alkylation zone effluent stream is passed into a first fractionation column 6 referred to as a recycle column. Substantially all of the Bunsen and any lighter hydrocarbons is concentrated into a net overhead vapor stream removed through line 7 and passed through the overhead condenser 8. The resultant condensate is collected in the overhead receiver 9. Uncondensed gases which may be present and con-dented water may be removed through means not shown. The hydrocarbon condensate is withdrawn from the overhead receiver through line 10 and divided into a first portion which is returned to the recycle column through line 11 as reflex and a second portion which is recycled to the alkylation zone as the Bunsen recycle stream carried by line 3.
Substantially all of the hydrocarbons entering the fractionation got-urn which are less volatile than Bunsen are concentrated into a both toys liquid stream withdrawn from the recycle column in line 12.
first portion of the bottoms liquid is diverted through an external recoiler means 14 via line 13. The fluids discharged from the bottom recoiler 14 are passed into a bottom portion of the recycle column.
The remaining portion of the bottoms stream of line 12 be-comes the weed stream charged to the product column 76 through line 15.
The relatively small amount of high boiling by-products which enters the product column becomes concentrated into a bosoms stream withdrawn in line 17. This bottoms liquid is divided into a portion which is passed through a rubber means 20 via line 19 and a second portion with-drawn as a by-products stream through line 18. The very great majority of the material which enters the product column 16 is concentrated into the overhead vapor stream removed from the products column in line 21.
The overhead vapor stream passes through a side recoiler means 22 wherein it is condensed to form an overhead condensate which is passe into the overhead receiver 25. The condensate is withdrawn through line 26 and divided into a first portion returned to the products got-urn via line 28 as reflex and a second portion which is withdrawn as the cumin product stream through line 27. The substantial amount of heat of vaporization given up my the overhead vapor stream of the prod-vats column is received by a liquid stream withdrawn from an interim-dilate point in the lower half of the recycle column in line 23. this liquid it preferably partially vaporized in the side recoiler 22 to thereby produce a mixed phase stream which is charged to the recycle column 6 through line 24. Line 24 communicates with the recycle got-urn at a point which is at least several trays above the point at which vapors produced by the bottom recoiler means 14 enter the recycle column. This description of a preferred embodiment of the inverltion is not intended lo preclude from the scope of the invention those other embodiments set out herein or which are the result of the normal and expected modification of those embodiments.
DETAILED DESCRIPTION
The alkylation of aromatic hydrocarbons is practiced courier-Shelley on a large scale. One particular example is the alkylation of Bunsen with propylene to form cumin, which is then used to produce phenol and acetone. These alkylation processes are normally performed with the intent of producing a single alkylaromatic product rather than an ad-mixture of alkylaromatics. However, despite the advances in the art which have occurred, the products of the commercial alkylation reactor will normally contain an admixture which contains small amounts of by-products which musk be separated from the reaction zone product. our-then, in an effort to promote monoalkylation, there is normally pro-voided an excess of the feed aromatic hydrocarbon which is to be alkyd fated. The effluent of the alkylation reaction zone therefore tonally contains an admixture of the feed hydrocarbon, the product hydrocarbon, and one or more higher boiling side products. The separation of these materials is normally performed commercially by Fractional distill-lion.
The separation of these sometimes close-boiling hydrocarbons in large quantities and to high purities requires sizable fractionation facilities and consumes a large amount of energy. The utilities cost of the fractionation includes both the cost of heat supplied to the no-boiler of the fractionation column and the cost in terms of cooling water and wasted low level heat which is associated with the condense-ton of overhead vapors The utilities cost of separating the of-fluent stream of the alkylation zone is therefore a significant part of the total cost of operating such an aromatic hydrocarbon alkylation process. It is therefore an objective of the subject process to pro-vise a method ox reducing the utilities cost of operating the fraction-anion section of a process for the alkylation of aromatic hydrooar-buns. It is another objective of the subject invention to provide a method of recovering in a useful manner heat present in the overhead vapor stream of the product column of a two-column aromatic hydrocar-I
bun fractionation system. It is a specific objective of the subject in-mention to reduce the recoiler heating utilities cost of the recycle got-urn of a process in which cumin is produced by tune alkylation of Bunsen.
The subject process may be used to separate the effluent of reaction zones used for transalkylation, alkylaromatic hydrocarbon isomerization, aromatization, etc. However the preferred reaction is alkylation and the process will be described mainly in terms of this one limited embodiment. The preferred feed hydrocarbon for alkylation is Bunsen. The preferred hydrocarbon feed material may be more gent orally characterized as an aromatic C6-plus hydrocarbon such as Bunsen, lot-gene, a zillion, or ethylbenzene. Higher molecular weight hydrocarbons could also be consumed as the feed hydrocarbon. The alkylating agent which is reacted with the feed hydrocarbon to produce the product alkyd-aromatic hydrocarbon may be an olefin-acting compound such as an alcohol, ether or ester including alkylhalides, alkylsulfates and alkylphos-plates. Preferably, the alkylating agent is a moo- or dolphin having from two to five carbon atoms per molecule. The preferred manliness include ethylene, propylene, button, button and isobutylene. These olefins may be used as relatively pure streams containing a single ho-drocarbon species. alternatively, a mixture of a single olefln and a corresponding paraffin may be used or a mixture of two or more olefinic hydrocarbons may be employed as the olefin-containing material charged to the alkylation zone. Typical product hydrocarbons include cumin, ethylbenzene, and Simon (isopropyltoluene).
The hydrocarbon stream charged to the fractionation zone is the effluent stream of a hydrocarbon conversion zone. This effluent stream is preferably the result of a partial separation performed within the conversion zone which results in a reaction zone effluent ~l2~;5~
stream being converted into a conversion zone effluent stream contain in less than 10 mole percent of any hydrocarbon having fewer carbon atoms per molecule than the hydrocarbon which is recovered as the over-head product of the first fractionation column. Preferably, this is achieved through-a partial condensation of the admixture of compounds actually exiting from the reactor to produce a liquid hydrocarbon phase and a vapor phase containing a very great percentage of any ho-drogen and normally gaseous hydrocarbons which exit the catalyst bed.
The liquid phase produced in this manner may be stripped of dissolved light gases if desired prior to being passed into the fractionation zone of the subject invention. The subject improved separation method could be applied in general to the separation of any reaction zone of-fluent stream comprising an admixture of hydrocarbons having the appear-private boiling point characteristics including those processes described above. However, it is greatly preferred that the reaction zone is in-tended to operate as an alkylation zone in which the feed hydrocarbon is consumed in the production of a product hydrocarbon of higher mole-urea weight. This alkylation may be promoted through the use of a wide variety of suitable catalysts such as boron trifluoride, various zoo-litic compounds, hydrogen fluoride, etc. The preferred catalyst for use in the alkylation zone is referred to as a solid phosphoric acid or SPY catalyst.
Suitable SPY catalysts ore available cs~mercia71y. us used herein the term "SPY 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 orate pyre or twitter-phosphoric acid. These catalysts are normally formed by mixing the acid with a siliceous solid carrier to form a wet paste. Thus paste nay be 55~2 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 itemizes 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 de-scribed in US. Patent 3,402,130. The amount of the additive Jay be equal to about 3-20 wt. % of the total carrier material. Further de-tails as to the composition and production of typical SPY catalysts may be obtained from US. Patents 3,0~0,472, 3,050,473 and 31132,109 and from other references.
It is known in the art that the passage of aromatic hydrocar-buns through an alkylation zone tends to leach chemically combined ` water out of an SPY catalyst. This is acknowledged in US. Patents 3,510,534 and 3,520,945, the latter of which is directed to the control of the state of hydration of the catalyst The waxer content of the catalyst is important since dehydration causes the SPY catalysts to deteriorate by powdering and caking, while excess water causes the gala-lusts to soften and eventually form a sludge which would plus the react ion. Water is therefore injected into the feed stream to maintain the catalyst at the proper state of hydration by replacing the water leached from the catalyst. The rate of this injection is used to control the catalyst hydration level, and the feed streams are therefore maintained I
as dry as practical prior to the water injection point. This results in the total water content of the feed being essentially the same as the amount injected. Typical waxer injection rates are from about 100 to 2000 wt. Pam in aromatic hydrocarbon alkylation operations. A pro-furred water addition rate during the production of cumin is from about 200 to 300 wt. Pam of the combined feed to the reaction zone.
The feed hydrocarbon, any recycle streams and the Feed olefin-acting compound are preferably admixed and then passed into a reaction zone. The reaction zone is maintained at alkylation-promoting conditions which include a pressure of about 300 to 1000 prig (2068 to 6895 kPag) and a temperature of about 300~ to 600F (149 to 316C). The liquid hollrly space velocity of reactants may range from about 0.5 to Z.5 hr. 1 It is preferred that an excess of the aromatic hydrocarbon be present in the reaction zone. The mole ratio of the aromatic hydrocarbon to the olefin should be within the broad range of 3:1 to 20:1. ratio of about 8:1 is preferred for the production of cumin. It is preferred that the reactant stream be mixed phase through the reactor. The feed stream therefore preferably con-twins some unreactive light paraffins having the same number of carbon atoms per molecule as the olefin. In the production of cumin it is preferred that the amount of propane in the reaction zone feed stream be at least equal to the amount of propylene in this stream. This may be accomplished by using a dilute propylene feed stream or by recycling propane.
In the preferred embodiment the effluent of the alkylation reactor is passed into a first rectifier column located within the come pled referred to herein as the alkylation zone. This column is normally used in conjunction with either a second rectifier, an absorber or a depropanizer (for alkylation using propylene). The exact form of this _ 1 1 I
system does not influence the subject process. The function of this portion of the alkylation zone is to recover any ole~in-acting compound which may be available for recycling to the reactor and to remove any light hydrocarbons such as propane which enter the alkylation zone.
The preferred form of this portion of the alkylation zone is described in previously referred to US. Patent 4,051,191 and in US. Patent 3,510,534~
The alkylation zone effluent will normally contain most of the excess Bunsen charged to the alkylation reactor to promote moo-alkylation. It is common and preferred practice to first separate the feed Bunsen and other hydrocarbons boiling below the cumin (or other product) in a first fractionation column referred to as a Bunsen colt urn or recycle column The cumin or other product alkylarornatic is then recovered as the overhead of a second column referred to as the cumin column or product column. Further information on the pro-furred alkylation process and possible variations in process flows and operations may be obtained by reference to US. Patents 3,437,706;
3,437,707; 3,437,70~; 39520,g44 and 3,542,892.
The conditions of temperature and pressure maintained in the first and second fractionation columns are interrelated. They may, how-ever, vary over considerable ranges, with exact operating conditions being set by economic and operational considerations which movie be specie lie to individual process units. broad range of conditions for use in the first fractionation column includes a top pressure of about Sty about 150 prig ~34 to 1034 kPag) and a bottoms temperature ox about 270 to about 400F (132 to 204C). A broad range ox conditions for use in the second fractional lion column includes a top pressure of about 15 to about 24Q pug (103 to 1655 kPag) and a bottoms temperature of about 320 to about 470~F ~16Q to 243~C).
These conditions are ~%~
interrelated in that the overhead vapor ox the second column must be at a pressure such that it will be condensed at the temperature of the liquid in the side recoiler of the first column after adjustment for the temperature difference "across" the recoiler. The calculation of such fractionation conditions are well within the expertise of those skilled in hydrocarbon fractionation and may be aided by widely avail-able computerized design systems. The internal design and construction of the columns may he similar to that presently employed in equivalent commercial installations.
The subject process requires a side recoiler to be installed in the first of the two columns. This recoiler is separate and disk tint from the recoiler employed at the bottom of the column. This recoiler is used to vaporize liquid withdrawn from an intermediate point in the column. us used herein, the term "intermediate point" is intended to indicate a point which is separated from each extremity of the column by vapor-liquid contacting material equal to at least two and preferably three theoretical contacting stages (trays). The side recoiler therefore acts upon liquid which has a lower average boiling point than the bottoms liquid entering the bottom recoiler. The side recoiler preferably is located about midway between the bottom of the first column and the feed point to the column. However, the location of the feed point may be varied depending on the composition of the entering alkylation zone feed stream, and the feed may enter at such a level that the side recoiler is optimally placed much closer to the bottom recoiler than to the feed point.
The subject process recovers at least a major portion ox the heat which must be removed in condensing the overhead stream of the second fractionation column. This heat it transferred into the first column. The amount of heat which must be applied to the customary both Tom rebiller of the first column is thereby reduced and the utility cost of operating the column is lowered. For instance, the applique lion of the subject process to a large scale process for the production of four hundred million pounds per year I x 10~ kg/yr3 of cumin is pro-jetted as being able to reduce the Bunsen (first) column recoiler heat require-mints from about 33 million BTU/hr (34.8 x 106 kj/hr) to about 18 million BTU/hr(19 x 105 kj/hr). This would provide a substantial reduction in the cost of operating the Bunyan column. Because the recovered heat is added to the Bunsen (first) column at a point above the bottom of the column, the required temperature of the cumin (second) column overhead vapor stream is worry than if it was attempted to use this overhead vapor as the heat source in the bottom recoiler. This assumes the pressure in the first column is the same during this comparison. The ability to remover heat from the overhead vapor at this lower temperature can be advantageous.
For instance, the ability to apply modern heat recovery techniques to an existing pair of fractionation columns may be limited due Jo the maximum pressures at which the columns can be operated. on example of this would be the inability to operate an existing column at a suffix ciently high pressure to achieve an overhead vapor having a temperature which can be used in reboiling at the bottom of another column. The subject process Will allow heat in the overhead vapor to be used in the preceding column with a smaller pressure differential between the got-urns than the prior art method of consuming this heat at the bottom of the preceding column. The ability to recover heat from overhead vapors without a significant increase in the bottoms temperature of the second column may else be advantageous if the compounds being free-shunted are thermally sensitive.
The subject process may be characterized as a process for recovering an alkylaromatic hydrocarbon from the effluent stream of an aromatic hydrocarbon alkylation zone which comprises the steps of passing an alkylation zone effluent stream which comprises a feed art-matte hydrocarbon, a product alkylaromatic hydrocarbon, and a by-prod-S vat alkylaromatic having a higher boiling point than the product alkyd-aromatic hydrocarbon into a first fractionation column at a first intermediate point, with a first recoiler being located at the bottom of the first fractionation column; recovering a first net overhead product stream, which is rich in the feed hydrocarbon, from the first fractionation column; removing a first net bottoms stream, which is rich in the product alkylaromatic hydrocarbon, from the first fraction-anion column and passing the first net bottoms stream into a second fractionation column; removing a second net bottoms stream, which is rich in the by-product alkylaro~atic hydrocarbon, from the second fractionation column; and condensing at least a portion of an overhead vapor stream withdrawn from the second fractionation column in a sea-on recoiler by indirect heat exchange against liquid withdrawn from the first fractionation column at an intermediate second point located above the first recoiler and below said first intermediate point, and recovering a product stream which is rich in the product alkylaromatic hydrocarbon from thy resultant condensate. as used herein, the term "rich" is intended to indicate that the stream or fluid being described contains over 60 mole percent of the specified compound or class of compounds. When the subject process is applied to conversion processes other than alkylation, the separations may be different from those de-scribed above. For instance, in aromatization processes in which arc-mattes are produced from C3 and/or C4 hydrocarbons, there will prefer-ably be little or no "feed" hydrocarbon entering the first fractional so lion column. In this instance Bunsen could be the top product of the first column, a mixture of Tulane and zillions may be removed as the top product of the second column and a mixture of Cg-plus aromatics withdrawn as the net bottoms product of the second column.
Claims (4)
1. A process for recovering an alkylaromatic hydrocarbon from the effluent stream of an aromatic hydrocarbon alkylation zone which comprises the steps of:
(a) passing an alkylation zone effluent stream which comprises a feed aromatic hydrocarbon, a product alkylaromatic hydrocarbon, and a by-product alkylaromatic having a higher boiling point that the product alkylaromatic hydrocarbon into a first fractionation column at a first intermediate point, with a first reboiler being located at the bottom of the first fractionation column and supplying heat thereto;
(b) recovering a first net overhead product stream, which is rich in the feed aromatic hydrocarbon, from the first fractionation column;
c) removing a first net bottoms stream, which is rich in the product alkylaromatic hydrocarbon, and the by-product alkylaromatic from the first fractionation column and passing the first net bottoms stream into a second fractionation column which is operated to produce an overhead vapor stream column;
(d) removing a second net bottoms stream, which is rich in the by-product alkylaromatic hydrocarbon, from the second fractionation column; and (e) condensing at least a portion of the overhead vapor stream withdrawn from the second fractionation column in a second reboiler by indirect heat exchange against liquid withdrawn from the first fractiona-tion column at an intermediate second point located above the first reboiler and below said first intermediate point, and recovering a product stream which is rich in the product alkylaromatic hydrocarbon from the resultant condensate.
(a) passing an alkylation zone effluent stream which comprises a feed aromatic hydrocarbon, a product alkylaromatic hydrocarbon, and a by-product alkylaromatic having a higher boiling point that the product alkylaromatic hydrocarbon into a first fractionation column at a first intermediate point, with a first reboiler being located at the bottom of the first fractionation column and supplying heat thereto;
(b) recovering a first net overhead product stream, which is rich in the feed aromatic hydrocarbon, from the first fractionation column;
c) removing a first net bottoms stream, which is rich in the product alkylaromatic hydrocarbon, and the by-product alkylaromatic from the first fractionation column and passing the first net bottoms stream into a second fractionation column which is operated to produce an overhead vapor stream column;
(d) removing a second net bottoms stream, which is rich in the by-product alkylaromatic hydrocarbon, from the second fractionation column; and (e) condensing at least a portion of the overhead vapor stream withdrawn from the second fractionation column in a second reboiler by indirect heat exchange against liquid withdrawn from the first fractiona-tion column at an intermediate second point located above the first reboiler and below said first intermediate point, and recovering a product stream which is rich in the product alkylaromatic hydrocarbon from the resultant condensate.
2. The process of Claim 1 further characterized in that the feed aromatic hydrocarbon is toluene.
3. The process of Claim 1 further characterized in that the feed aromatic hydrocarbon is benzene.
4. The process of Claim 3 further characterized in that the product alkylaromatic hydrocarbon is cumene.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000492983A CA1226552A (en) | 1985-10-15 | 1985-10-15 | Integrated fractionation in the recovery of alkylaromatic hydrocarbons |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000492983A CA1226552A (en) | 1985-10-15 | 1985-10-15 | Integrated fractionation in the recovery of alkylaromatic hydrocarbons |
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| CA1226552A true CA1226552A (en) | 1987-09-08 |
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| CA000492983A Expired CA1226552A (en) | 1985-10-15 | 1985-10-15 | Integrated fractionation in the recovery of alkylaromatic hydrocarbons |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113233415A (en) * | 2021-05-24 | 2021-08-10 | 大连理工大学 | Process and device for preparing hydrogen from hydrogen iodide in iodine-sulfur cycle |
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1985
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113233415A (en) * | 2021-05-24 | 2021-08-10 | 大连理工大学 | Process and device for preparing hydrogen from hydrogen iodide in iodine-sulfur cycle |
| CN113233415B (en) * | 2021-05-24 | 2023-05-12 | 大连理工大学 | Process and device for preparing hydrogen from hydrogen iodide in iodine-sulfur cycle |
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