CA1077966A - Manufacture of ethylbenzene - Google Patents
Manufacture of ethylbenzeneInfo
- Publication number
- CA1077966A CA1077966A CA302,775A CA302775A CA1077966A CA 1077966 A CA1077966 A CA 1077966A CA 302775 A CA302775 A CA 302775A CA 1077966 A CA1077966 A CA 1077966A
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- CA
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- Prior art keywords
- benzene
- ethylene
- reactor
- catalyst
- reaction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- 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
- C07C2/68—Catalytic processes with halides
-
- 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
- C07C2527/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- C07C2527/06—Halogens; Compounds thereof
- C07C2527/08—Halides
- C07C2527/10—Chlorides
- C07C2527/11—Hydrogen chloride
-
- 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
- C07C2527/06—Halogens; Compounds thereof
- C07C2527/125—Compounds comprising a halogen and scandium, yttrium, aluminium, gallium, indium or thallium
- C07C2527/126—Aluminium chloride
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2531/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- C07C2531/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Abstract of the Disclosure Ethylbenzene is prepared by the reaction of ethylene and benzene in the presence of a Friedel-Crafts aluminum chloride catalyst complex, in a process in which the ethylene is initially dissolved in the benzene, prior to contacting with the catalyst. By eliminating the gaseous phase from the reaction it permits the use of a plug flow reactor. As a result, a process is obtained which proceeds in the kinetic region, using much smaller quantities of the Friedel-Crafts catalyst, to produce in short time the desired product, with significantly reduced amounts of byproducts.
Description
10779~6 This invention rel~tes to processes for ~lkylation of benzene, and more particularly to the reaction of benzene with ethylene to produce ethylbenzene.
The prenaratiOn of ethylbenzene from benzene and ethylene is an important commercial process, as one of the steps in the manufacture of styrene mono~er, for polymerization processes. The conventional process of ethylbezene manufactllre is to react ethylene with benzene, in the liquid phzse, in the presence of a Friedel-Crafts li~uid catalyst complex obtained on solubilizing aluminum chloride in benzene alkylate by the addition of a Cl donor such QS hydrogen chloride or ethyl chloride. The ethylene and benzene are contacted together in the presence of the catalyst, in the liquid phase, so as to produce the ethylbenzene, which is then separated fro~ the unreacted benzene and dealkylable polyethylbenzenes, which ~re re-cycled through the process.
The conventional, co~mercial ethylbenzene production process involves a number of significant disadvantages. As noted above, a liquid catalyst co~ple~ is utilized. ~iquid benzene and gaseous ethylene are fed to the reactor to~ether with the liquid catalyst complex. The reaction takes place in the catalyst comple~. The reactants enter the complex by diffusion, and displace the product of reaction into the surrounding liquid medium. In the case o* ethylene, diffusion in the gaseous phase follo~!ed by diffusion in the liquid ~edium and absorption in the complex combined with chemical attraction, "chemisorption", prolongs the process considerably, ~ith the result that the residence time of reactants in contact viith the catalyst is 45-60 minutes. Relatively large a~ounts of aluminum chloride catalyst complex are used, since this is '~
~0779~
necessary not only to catalyse the alkylation reaction but also to "chemisorb~' ethylene. r~oSt of the catalyst remains undis-solved and forms a separate liquid phase ~hich is removed from the alkylate by gravity. ~long with added fresh c2talyst, it is re-cycled to the reactor. The alkylate is water ~ashed to re~ove the ~ineral impurities and distilled to recover the ethylbenzene product. The unreacted benzene and de21kylable polyethylbenzenes sep~rated from the ethylbenzene are re-cycled back to the reactor. Diffusion of gaseous ethylene is a reaction rate limiting factor in the process.
Corrosive conditions due to the presence of the catalyst complex, particularly when hydrogen chloride is used as a promoter, prevent the use of effective means to disperse the gas in the liquid, so as to increase the interfacial area.
The ethylene stream is simply bubbled through the reactio~
mixture. The resulting ~as lift effect has n~ practical influence on the rate of mass transfer. In absence of disper-sion of the gas, the rate of "che~isorption" depends heavily on the ratio of catalyst complex to ethylene. In an attempt to accelerate the dissolution of the g2S~ the reaction temperz-ture is raised in order to increase the concentration of the complex in the reaction mixture. However, raising the temperature has the adverse effect of ~lecreasing the rate of chemisorption.
This conventional alkylation process is accompanied by significant occurrence of side reections, leading to the for~ation of byproducts. One such side reaction is poly-- 21kylation, in ~:hich, in the ~resence of the Friedel-Crc~fts cat21yst, ethylbenzene don~tes an ethyl re,dical to another ~olecule of ethylbenzene, and then to the diethylbenzene product of this reaction, and so on to form a series of poly-ethylbenzenes. The reaction is reversible and relatively slo~q. Providing the residence time in the reactor is very short, the extent of polyalkylation entirely depends upon the phenyl:ethyl ratio, and ~hen the ben~ene:ethylene molar ratio is maint2ined in the range 2:1 to 3:19 as is normal, it should terminate at the formation of smaller quantities of diethyl-benzene, ~ith only tr~ces of triethybenzene. Hor~ever, under the conditions of the conventional ethylbenzene process, the polyalkylation occurs to an uncontrollable extent and as much as 50 pounds of polyethylbenzenes can be produced for e2ch one llundred pounds of ethybenzene. ~l~ilst poylyethybenzenes can be made to react ~ith benzene to re-form ethybenzene, the desired product, it requires continuous re-cycle of large quantities of polyalkylbenzenes to the reactor.
Another side reaction which occurs in the conventional process, particularly when the hydrocarbon reactants and pro-ducts are left in contact ~ h the catalyst ~or lengthy periods of ti~e, is polycondensation and polymerization. PolymerizQ-tion of the ethylbezene may occur to give products such asdiphenylethane and dimethylhydroantrathane in qu~ntities up to 3 pounds per 100 pounds of the desirable product, such compounds being irreversibly formed, ~nd not dealkylable to ethylbenzene.
Also, co~pounds such as butylbenzenes ~ay be formed, by condensation of t~o molecules of etl~ylene to form a single ~olecule of butylene ~hich reacts ~ith benzene to for~ butyl-benzene. This agzin is an irreversible reaction, forming byproducts not easily convertible to the desired product.
I ln the conventional process, long residence ti~es and the use of large a~ounts of Friedel-Crafts catalyst are unavoidable, since one must achieve chemisorption of the gaseous ethylene, as well as alkylation re~ction. Such residence times are of such duration that it is effectively impossible to prevent significant amounts of polyalkylation, polycondensation and polymerization reactions.
A conventional commercial ethylbenzene ~anuf2cturin~
process is estimated to produce up to 55 pounds of-byproducts per 100 pounds of ethylbenzene, this 55 pounds of byproducts comprising approximately 52 pounds of polyethylben~enes, and about 3 pounds of polymerization and polycondensation products, which are useless except as fuel oils.
~ igh activity of the catalyst is essential to proper functioning of the ethylbenzene process. Ho~lever, on the required long residence times in the diffusion controlled, conventional process, the catalyst complex becomes de-activated c~7ing to the retention of heavy products of polycondensation and polymerization of the alkylate, ~hich are difficult to remove. The loss of Cl donor, particularly if hydrogen chloride is used as a promoter, also causes de-activation of the catalyst complex. In oràer to compensate for the catalyst de-activation, it is com~on to use large Quantities of the cat~lyst complex, far in excess of its solubility in the reaction mixture. The sepzrate catalyst phase removed by gravity from the crude alkyl2te is mixed ~ith small quantities of fresh catalyst and re-cycled to the reactor. ~ut such re-cycled catalyst is of lo~:er activity than the fresh catalyst.
fhilst this use of excess c-talyst may be successful in maintai~in~
the rate of uhe process 2t ~le reouired level, it is accomp~nied by an increase in both the consw~ption of eluminum chloride catalyst and in the formation of non-de21kylable ~aste products.
~0779~
To atteinpt to suppress the polyslkylation reactions, it is nor~al to increase the amount of benzene in the feed, so as to increase the benzene:ethylbenzene ratio during the course o~ alkylation and hence shift the equilibrium of the polyzlkylation reaction more favourably to~ards ethylben~ene for~ation. Ho~ever, in the case of the conventional bubbler reactor, this has to be done by increasing the benzene:ethylene ratio in the feed, thus increasing the cost of the process by increasing the amount of unreacted and re-cycled benzene.
For this reason, the benzene:ethylene ratio in the feed usually does not exceed 2.5:1 to 3:1 on a molar basis, with the result that, in the case of the bubbler reactor, the benzene:ethyl-benzene ratio in the reaction mixture remains constant in the ran~e of 1.5:1 to 2:1.
It is an object of the present invention to pro~ide æ ne~ and improved process for alkylation of aron2tic hydro-carbons.
It is a further object to provide a process for producing ethybenzene of substantially improved economics, and in ~:hich the form~tion of byproducts is substantially reduced.
The present invention is based upon the concept that i~proved perform~nce in the process of producing ethylben~ene by reaction of ethylene and benzene in the presence of a Friedel-Crafts catalyst complex can be obtained by dissolving the ~aseous ethylene in the liouid benzene prior to cont2ctin~
the rea~ents ~ith the ~riedel-Cr~fts catalyst. The solution of ethylene in benzene is prepared separately and then fed to the 21kylation reactor. I~ doin~ so, there is eliminated from the alkylation process the diffusion controlled absorption .
of ethylene, and the process perrnits the reaction of ethylene wi-th benzene in the kinetic region, with short residence time in the reactor and at low concen-trations OI the ~riedel-Crafts aluminum chloride catalyst complex in the reaction mixture.
Also~ by eliminating the gaseous ph2se from the reactor, it permits the use of 2 plug flow reactor, or tubul~r reactor for the process, with consequent improve~ent in heat trznsfer capabilities and in benzene:ethylben~ene ratio in the reaction mixture.
Conventional processes have consistently involved eeding OI ~aseous ethylene, liquid benzene and liquid al~ninum chloride catalyst complex separately to the reaction vessel zone. ~ith such processes, the ~aseous ethylene must be dis-solved in the liauid reaction medium before the alkylation reaction can proceed. The diffusion of ethylene in the gaseous ph2se followed by chemisorption of the ethylene is much slorJer than, and i~eally requires different conditions from, the alkylation reactions. The reaction conditions in the reactor are thus adjusted both to che.~isorb the ethylene, and promote the alkylation reaction, and must therefore be a compromise.
They cannot be optimized for either process.
In the kinetic re~ion of the process, i.e. the sta~e of reaction of ethylene with benzene, in the liquid phase, to produce ethylbenzene, only very low concentrations of catalyst are required. In the conventional process, ho~lever, the aluminu~ chloride conplex is used also to chemisorb ethylene, and as noted lpreviously this requires large quantities of 21umim~n chloride catalyst. Use of l~rge ~mounts of catalyst le2ds to increased byproduct formation. In the process of the invention, horever, v~here very lo~ catalyst concentrations ~077~66 are required, the alkylation reaction can be carried out at lower temperature, e.g. 60-70C, just sufficient to keep the required small amount of catalyst in solution. The benefit of reduced reaction temperature is reduced formation of undesirable polyalkylation byproducts.
A number of significant, practical advantages result from the process of the invention. The pxocess conditions can be optimized at each stage to meet desireble criteria, instead of compromise to try and meet required reaction conditions for two different reactions or effects. Thus the efficiency and economics of the overall process can be significantly improved.
The amount of catalyst complex used can be very much reduced, down to the order of 0.1 - 0.2 lbs. thereof per 100 pounds of ethybezene produced. Reduced catalyst usage and consumption entails significant economies in the process as a whole, and also simplifies a waste disposal problem, since recove~ of waste aluminum ion from effluent streams is notoriously difficult. No re-cycle of catalyst complex is required, thus enhancing the economics of the process. Moreover, ;
the reduced consumption and utilization of catalyst is achieved in conjunction with a reduced residence time, further enhancing the economics of the process. Using a plug flow reactor provided with static mixers, effecting lateral mixing, the reactor produc-tivity is increased to 500-1,500 pounds of ethylbenzene per hour per cubic foot, as çompared with 15 pounds of ethylbenze per hour per cubic foot in the conventional diffusion controlled, bubble process.
The temperatures utilized in the reactor in accordance with the invention can be and preferably are lower than those used in conventional processes, since these are optimized on 1(~77966 the basis of the rapid alkylation reaction in the kinetic region, and need have no regard for the chemisorption. The reaction of ethylene and benzene to produce ethybenzene is an exothermic reaction, so that efficient conduction of heat away from the process is required, in order to maintain a desirable reaction temperature according to the invention of 60-70C. For this purpose, it is prferred to use a plug flow reactor, single jacketed or double jacketed, fitted with static mixers, effecting lateral mixing, so as to provide a very high rate of heat removal.
Such high rate of heat removal is necessary so that the process may be operated at the optimum temperature, and therefore produce ethylbenzene at high rate productivity. Suitable reaction pressures are in the range 36.5 - 48.5 atm. abs., i.e. 550-720 psig. With the use of such conditions, the amount of polyethyl-benzenes produced, i.e. the sum of diethylbenzenes and traces of triethylbenzenes, is reduced to as low as 5 parts by weight per 100 parts by weight of ethylbenzene, in a single pass through the alkylation reactor, at a productivity in the range 500-1,500 pounds ethylbenzene per hour per cubic foot of reactor. The formation of polycondensates and polymerizates as byproducts, which are essentially unconvertible back to ethylbenzene, is to a practical extent eliminated.
With these short residence times in the reactor, and low catalyst complex concentrations, the retention of the alkylate in the catalyst complex is reduced to a minimum. With lateral mixing provided by the static mixers of a plug flow reactor, the removal of the product from the complex is instantaneous.
Catalyst de-actovation under the conditions employed according to the invention is reduced to a minimum, with the result that the consumption of aluminum chloride is less than 0.2 pounds 10~ 7~6~
aluminum chloride per 100 pounds ethylbenzene, and may be as low as 0.1 pounds aluminum chloride per 100 pounds ethylbenzene.
In a preferred embodiment of the process, polyalkyla-tion is further suppressed by the addition of benzene to the reactor during the process at a rate which increases steadily with the progress of alkylation. In this way, the decline in benzene:ethylbenzene ratio in the gegion of increased poly-alkylation, due to the formation of ethylbenzene in high concentrations as the reaction proceeds, is decelerated. Under these conditions, the polyalkylbenzenes are prevented from reaching equilibrium, and the reaction leading to their formation is suppressed.
The benzene is added to the reactor in the form of a very dilute solution of aluminum chloride catalyst complex in benzene. The rate of catalyst feed is controlled so as to keep the process rate constant as for as possible, and within the range of the available rate of heat removal, to maintain the ractlon temperature constant within the 60-70C range.
The catalyst complex is prepared by adding ethyl chloride to a suspension of aluminum chloride in polyethyben-zenes, at the correct proportions adjusted to have a single complex phase. The freshly prepared catalyst is very active, and has very low corrosive properties, which is of importance in operating the pIug flow reactor at high fluid velocity.
Preferably, the ethylene is dissolved in benzene, prior to being contacted with the catalyst solution, by absorption of ethylene with benzene from a commercial ethylene stream using an absorption tower or static mixer. The absorp-tion is carried out at a temperature from about 10 C to about 20C, under a pressure of 350-440 psig (25-31 atm.abs.), 1(~77~66 depending upon the required ethylene concentration. For example, if the alkylation is to be carried out at a 3:1 phenyl:ethyl ratio, the solution of ethylene is prepared at a benzene:ethylene ratio
The prenaratiOn of ethylbenzene from benzene and ethylene is an important commercial process, as one of the steps in the manufacture of styrene mono~er, for polymerization processes. The conventional process of ethylbezene manufactllre is to react ethylene with benzene, in the liquid phzse, in the presence of a Friedel-Crafts li~uid catalyst complex obtained on solubilizing aluminum chloride in benzene alkylate by the addition of a Cl donor such QS hydrogen chloride or ethyl chloride. The ethylene and benzene are contacted together in the presence of the catalyst, in the liquid phase, so as to produce the ethylbenzene, which is then separated fro~ the unreacted benzene and dealkylable polyethylbenzenes, which ~re re-cycled through the process.
The conventional, co~mercial ethylbenzene production process involves a number of significant disadvantages. As noted above, a liquid catalyst co~ple~ is utilized. ~iquid benzene and gaseous ethylene are fed to the reactor to~ether with the liquid catalyst complex. The reaction takes place in the catalyst comple~. The reactants enter the complex by diffusion, and displace the product of reaction into the surrounding liquid medium. In the case o* ethylene, diffusion in the gaseous phase follo~!ed by diffusion in the liquid ~edium and absorption in the complex combined with chemical attraction, "chemisorption", prolongs the process considerably, ~ith the result that the residence time of reactants in contact viith the catalyst is 45-60 minutes. Relatively large a~ounts of aluminum chloride catalyst complex are used, since this is '~
~0779~
necessary not only to catalyse the alkylation reaction but also to "chemisorb~' ethylene. r~oSt of the catalyst remains undis-solved and forms a separate liquid phase ~hich is removed from the alkylate by gravity. ~long with added fresh c2talyst, it is re-cycled to the reactor. The alkylate is water ~ashed to re~ove the ~ineral impurities and distilled to recover the ethylbenzene product. The unreacted benzene and de21kylable polyethylbenzenes sep~rated from the ethylbenzene are re-cycled back to the reactor. Diffusion of gaseous ethylene is a reaction rate limiting factor in the process.
Corrosive conditions due to the presence of the catalyst complex, particularly when hydrogen chloride is used as a promoter, prevent the use of effective means to disperse the gas in the liquid, so as to increase the interfacial area.
The ethylene stream is simply bubbled through the reactio~
mixture. The resulting ~as lift effect has n~ practical influence on the rate of mass transfer. In absence of disper-sion of the gas, the rate of "che~isorption" depends heavily on the ratio of catalyst complex to ethylene. In an attempt to accelerate the dissolution of the g2S~ the reaction temperz-ture is raised in order to increase the concentration of the complex in the reaction mixture. However, raising the temperature has the adverse effect of ~lecreasing the rate of chemisorption.
This conventional alkylation process is accompanied by significant occurrence of side reections, leading to the for~ation of byproducts. One such side reaction is poly-- 21kylation, in ~:hich, in the ~resence of the Friedel-Crc~fts cat21yst, ethylbenzene don~tes an ethyl re,dical to another ~olecule of ethylbenzene, and then to the diethylbenzene product of this reaction, and so on to form a series of poly-ethylbenzenes. The reaction is reversible and relatively slo~q. Providing the residence time in the reactor is very short, the extent of polyalkylation entirely depends upon the phenyl:ethyl ratio, and ~hen the ben~ene:ethylene molar ratio is maint2ined in the range 2:1 to 3:19 as is normal, it should terminate at the formation of smaller quantities of diethyl-benzene, ~ith only tr~ces of triethybenzene. Hor~ever, under the conditions of the conventional ethylbenzene process, the polyalkylation occurs to an uncontrollable extent and as much as 50 pounds of polyethylbenzenes can be produced for e2ch one llundred pounds of ethybenzene. ~l~ilst poylyethybenzenes can be made to react ~ith benzene to re-form ethybenzene, the desired product, it requires continuous re-cycle of large quantities of polyalkylbenzenes to the reactor.
Another side reaction which occurs in the conventional process, particularly when the hydrocarbon reactants and pro-ducts are left in contact ~ h the catalyst ~or lengthy periods of ti~e, is polycondensation and polymerization. PolymerizQ-tion of the ethylbezene may occur to give products such asdiphenylethane and dimethylhydroantrathane in qu~ntities up to 3 pounds per 100 pounds of the desirable product, such compounds being irreversibly formed, ~nd not dealkylable to ethylbenzene.
Also, co~pounds such as butylbenzenes ~ay be formed, by condensation of t~o molecules of etl~ylene to form a single ~olecule of butylene ~hich reacts ~ith benzene to for~ butyl-benzene. This agzin is an irreversible reaction, forming byproducts not easily convertible to the desired product.
I ln the conventional process, long residence ti~es and the use of large a~ounts of Friedel-Crafts catalyst are unavoidable, since one must achieve chemisorption of the gaseous ethylene, as well as alkylation re~ction. Such residence times are of such duration that it is effectively impossible to prevent significant amounts of polyalkylation, polycondensation and polymerization reactions.
A conventional commercial ethylbenzene ~anuf2cturin~
process is estimated to produce up to 55 pounds of-byproducts per 100 pounds of ethylbenzene, this 55 pounds of byproducts comprising approximately 52 pounds of polyethylben~enes, and about 3 pounds of polymerization and polycondensation products, which are useless except as fuel oils.
~ igh activity of the catalyst is essential to proper functioning of the ethylbenzene process. Ho~lever, on the required long residence times in the diffusion controlled, conventional process, the catalyst complex becomes de-activated c~7ing to the retention of heavy products of polycondensation and polymerization of the alkylate, ~hich are difficult to remove. The loss of Cl donor, particularly if hydrogen chloride is used as a promoter, also causes de-activation of the catalyst complex. In oràer to compensate for the catalyst de-activation, it is com~on to use large Quantities of the cat~lyst complex, far in excess of its solubility in the reaction mixture. The sepzrate catalyst phase removed by gravity from the crude alkyl2te is mixed ~ith small quantities of fresh catalyst and re-cycled to the reactor. ~ut such re-cycled catalyst is of lo~:er activity than the fresh catalyst.
fhilst this use of excess c-talyst may be successful in maintai~in~
the rate of uhe process 2t ~le reouired level, it is accomp~nied by an increase in both the consw~ption of eluminum chloride catalyst and in the formation of non-de21kylable ~aste products.
~0779~
To atteinpt to suppress the polyslkylation reactions, it is nor~al to increase the amount of benzene in the feed, so as to increase the benzene:ethylbenzene ratio during the course o~ alkylation and hence shift the equilibrium of the polyzlkylation reaction more favourably to~ards ethylben~ene for~ation. Ho~ever, in the case of the conventional bubbler reactor, this has to be done by increasing the benzene:ethylene ratio in the feed, thus increasing the cost of the process by increasing the amount of unreacted and re-cycled benzene.
For this reason, the benzene:ethylene ratio in the feed usually does not exceed 2.5:1 to 3:1 on a molar basis, with the result that, in the case of the bubbler reactor, the benzene:ethyl-benzene ratio in the reaction mixture remains constant in the ran~e of 1.5:1 to 2:1.
It is an object of the present invention to pro~ide æ ne~ and improved process for alkylation of aron2tic hydro-carbons.
It is a further object to provide a process for producing ethybenzene of substantially improved economics, and in ~:hich the form~tion of byproducts is substantially reduced.
The present invention is based upon the concept that i~proved perform~nce in the process of producing ethylben~ene by reaction of ethylene and benzene in the presence of a Friedel-Crafts catalyst complex can be obtained by dissolving the ~aseous ethylene in the liouid benzene prior to cont2ctin~
the rea~ents ~ith the ~riedel-Cr~fts catalyst. The solution of ethylene in benzene is prepared separately and then fed to the 21kylation reactor. I~ doin~ so, there is eliminated from the alkylation process the diffusion controlled absorption .
of ethylene, and the process perrnits the reaction of ethylene wi-th benzene in the kinetic region, with short residence time in the reactor and at low concen-trations OI the ~riedel-Crafts aluminum chloride catalyst complex in the reaction mixture.
Also~ by eliminating the gaseous ph2se from the reactor, it permits the use of 2 plug flow reactor, or tubul~r reactor for the process, with consequent improve~ent in heat trznsfer capabilities and in benzene:ethylben~ene ratio in the reaction mixture.
Conventional processes have consistently involved eeding OI ~aseous ethylene, liquid benzene and liquid al~ninum chloride catalyst complex separately to the reaction vessel zone. ~ith such processes, the ~aseous ethylene must be dis-solved in the liauid reaction medium before the alkylation reaction can proceed. The diffusion of ethylene in the gaseous ph2se followed by chemisorption of the ethylene is much slorJer than, and i~eally requires different conditions from, the alkylation reactions. The reaction conditions in the reactor are thus adjusted both to che.~isorb the ethylene, and promote the alkylation reaction, and must therefore be a compromise.
They cannot be optimized for either process.
In the kinetic re~ion of the process, i.e. the sta~e of reaction of ethylene with benzene, in the liquid phase, to produce ethylbenzene, only very low concentrations of catalyst are required. In the conventional process, ho~lever, the aluminu~ chloride conplex is used also to chemisorb ethylene, and as noted lpreviously this requires large quantities of 21umim~n chloride catalyst. Use of l~rge ~mounts of catalyst le2ds to increased byproduct formation. In the process of the invention, horever, v~here very lo~ catalyst concentrations ~077~66 are required, the alkylation reaction can be carried out at lower temperature, e.g. 60-70C, just sufficient to keep the required small amount of catalyst in solution. The benefit of reduced reaction temperature is reduced formation of undesirable polyalkylation byproducts.
A number of significant, practical advantages result from the process of the invention. The pxocess conditions can be optimized at each stage to meet desireble criteria, instead of compromise to try and meet required reaction conditions for two different reactions or effects. Thus the efficiency and economics of the overall process can be significantly improved.
The amount of catalyst complex used can be very much reduced, down to the order of 0.1 - 0.2 lbs. thereof per 100 pounds of ethybezene produced. Reduced catalyst usage and consumption entails significant economies in the process as a whole, and also simplifies a waste disposal problem, since recove~ of waste aluminum ion from effluent streams is notoriously difficult. No re-cycle of catalyst complex is required, thus enhancing the economics of the process. Moreover, ;
the reduced consumption and utilization of catalyst is achieved in conjunction with a reduced residence time, further enhancing the economics of the process. Using a plug flow reactor provided with static mixers, effecting lateral mixing, the reactor produc-tivity is increased to 500-1,500 pounds of ethylbenzene per hour per cubic foot, as çompared with 15 pounds of ethylbenze per hour per cubic foot in the conventional diffusion controlled, bubble process.
The temperatures utilized in the reactor in accordance with the invention can be and preferably are lower than those used in conventional processes, since these are optimized on 1(~77966 the basis of the rapid alkylation reaction in the kinetic region, and need have no regard for the chemisorption. The reaction of ethylene and benzene to produce ethybenzene is an exothermic reaction, so that efficient conduction of heat away from the process is required, in order to maintain a desirable reaction temperature according to the invention of 60-70C. For this purpose, it is prferred to use a plug flow reactor, single jacketed or double jacketed, fitted with static mixers, effecting lateral mixing, so as to provide a very high rate of heat removal.
Such high rate of heat removal is necessary so that the process may be operated at the optimum temperature, and therefore produce ethylbenzene at high rate productivity. Suitable reaction pressures are in the range 36.5 - 48.5 atm. abs., i.e. 550-720 psig. With the use of such conditions, the amount of polyethyl-benzenes produced, i.e. the sum of diethylbenzenes and traces of triethylbenzenes, is reduced to as low as 5 parts by weight per 100 parts by weight of ethylbenzene, in a single pass through the alkylation reactor, at a productivity in the range 500-1,500 pounds ethylbenzene per hour per cubic foot of reactor. The formation of polycondensates and polymerizates as byproducts, which are essentially unconvertible back to ethylbenzene, is to a practical extent eliminated.
With these short residence times in the reactor, and low catalyst complex concentrations, the retention of the alkylate in the catalyst complex is reduced to a minimum. With lateral mixing provided by the static mixers of a plug flow reactor, the removal of the product from the complex is instantaneous.
Catalyst de-actovation under the conditions employed according to the invention is reduced to a minimum, with the result that the consumption of aluminum chloride is less than 0.2 pounds 10~ 7~6~
aluminum chloride per 100 pounds ethylbenzene, and may be as low as 0.1 pounds aluminum chloride per 100 pounds ethylbenzene.
In a preferred embodiment of the process, polyalkyla-tion is further suppressed by the addition of benzene to the reactor during the process at a rate which increases steadily with the progress of alkylation. In this way, the decline in benzene:ethylbenzene ratio in the gegion of increased poly-alkylation, due to the formation of ethylbenzene in high concentrations as the reaction proceeds, is decelerated. Under these conditions, the polyalkylbenzenes are prevented from reaching equilibrium, and the reaction leading to their formation is suppressed.
The benzene is added to the reactor in the form of a very dilute solution of aluminum chloride catalyst complex in benzene. The rate of catalyst feed is controlled so as to keep the process rate constant as for as possible, and within the range of the available rate of heat removal, to maintain the ractlon temperature constant within the 60-70C range.
The catalyst complex is prepared by adding ethyl chloride to a suspension of aluminum chloride in polyethyben-zenes, at the correct proportions adjusted to have a single complex phase. The freshly prepared catalyst is very active, and has very low corrosive properties, which is of importance in operating the pIug flow reactor at high fluid velocity.
Preferably, the ethylene is dissolved in benzene, prior to being contacted with the catalyst solution, by absorption of ethylene with benzene from a commercial ethylene stream using an absorption tower or static mixer. The absorp-tion is carried out at a temperature from about 10 C to about 20C, under a pressure of 350-440 psig (25-31 atm.abs.), 1(~77~66 depending upon the required ethylene concentration. For example, if the alkylation is to be carried out at a 3:1 phenyl:ethyl ratio, the solution of ethylene is prepared at a benzene:ethylene ratio
2.1, and the balance of benzene may be added to the reactor separately or in the form of catalyst complex solution. Under these conditions, ethylne is soluble in benzene to the extent of from about 1:3 to 1:2 moles per mole, and a solution of the desired amount of ethylene can readily be prepared, and pumped to the reactor. At such a d~ssolved ethylene concentration, desorp-tion of ethylene at the inlet to the reactor is prevented bykeeping the pressure in the reactor in the range 550-720 psig (36.5 - 48.5 atm.abs.). After entering the reactor at such pressures, the mixture is preferably preheated to 55-60C prior to contact with the catalyst. Benzene-catalyst solution and/or alkylate-catalyst solution is fed separately into the reactor, to form the required concentrations therein, and at a suitable rate to maintain the rate of the process as far as possible con-stant, within the limits of the available rate of heat removal to keep the reaction temperature in the 60-70C range, and also to decelerate the decline in benzene:ethylbenzene ratio as the reaction proceeds.
The rate of ethylene reaction with benzene depends on the concentration of the catalyst complex solution in the reac-tion mixture, and the rate of feed of the catalyst complex to the reactor should be controlled so as to adjust the rate of alkylation to suit the available rate of heat removal and keep the reactor tmeperature in the range 60-70C.
As noted, excess benzene is used in the ethybenzene process, to suppress the reversible polyalkylation reactions.
Usually the benzene:ethylene molar ratio in the feed to the reactor 107'79~
is maintained at 2.5:1 - 3:1, (this taking account of all the benzene added, with the ethylene and with the catalyst), with the result that 1.5 to 2 moles of unreacted benzene per mole of etylbenzene produced remain in the product. On fractionation of the crude alkylation product after removal from this reactor, the benzene is separated from the alkylates and can be recycled to the process.
~ he benzene:ethylbenzene ratio which determines the degree of suppression of the polyalkylation follows the progress of the alkylation, and gradually diminishes from the infinity at the start of the reaction, to a fixed value at its completion.
Under these conditions, full advantage of the high benzene:ethyl-benzene ratio can only be taken by carrying out the alkylation reaction in a plug flow reactor, in which the composition of the reaction mixture changes with the progress of the process. The use of the plug flow reactor therefore provides reaction condi-tions not available from the conventional bubbler reactor, in which the composition remains constant and identical with that of the product leaving the reactor. Use of ethylene solution in benzene prepared separately according to the present invention, offers an opportunity to suppress the polyalkylation even further.
By increasing the initial concentration of ethylene in the solu-tion, the balance of the required benzene, alone or in the form of diluted solution in the catalyst complex, can be added gradually along the length of the plug flow reactor to decelerate the decline in benzene:ethylbenzene ratio.
In preparing the catalyst complex, preferably a Cl donor is added to a suspension of aluminum chloride powder in benzene alkylate, at room temperature. This can be done in a mechanically -agitated vessel. 'Hydrogen chloride or ethyl chloride can be used '' , ' .
`7966 as the Cl donor, and polyethylbenzenes alone or mixed with benzene and/or ethyhenzene can be used as the alkylate. It is preferred to use ethyl chloride as the Cl donor, and polyethyl-benzenes alone as the alkylate for the catalyst complex. A single liqùid phase can be obtained, by choice of correct proportions, this complex being sparingly soluble in benzene or ethylbenzene reaction mixture and having very low corrosive properties under the conditions of the alkylation process.
The complex so formed may then be dissolved in hot benzene under pressure, using a steam heated, mechanically agi-tated vessel. ~`he temperature is controlled to get the required concentration of comple~ solution. Then the solution may be pumped to the reactor.
In one embodiment, an absorption tower is used to cont-act counter-currently flowing ethylene stream and benzene stream to form the required solution of ethylene and benzene, the streams being at controlled rates so as to obtain a solution of the required concentration. In another embodiment, a set of tubular static mixers in series can be used to contact the two streams, introducing the ethylene feed at several points along the benzene flow. The undissolved impurities of the gas stream are vented and the ethylene solution is collected in a feed drum, and from there delivered by pump t~ the reactor at a controlled rate.
A specific embodiment of the process of the present invention is illustrated in the accompanying Figure, which is a diagrammatic process flow sheet thereof.
With reference to the accompanying figure, 10 denotes a catalyst preparation vessel, in the form of a vessel provided with a mechanical agitator 12. To the vessel 10 is fed ethyl chloride as Cl donor, through inlet line 14, powdered aluminum chloride ` lV~'796~i through line 16, and polyethylbenzenes through line 18. After mixing these ingredients together in vessel 10, at atmospheric pressure and room temperature, the liquid catalyst complex is fed via outlet 20 to a steam heated tank 22, where it is mixed by means of mechanical agitation 24 with benzene fed from benzene storage Z6 via inlet line 28. The temperature in this vessel 22 is controlled to obtain the required concen-tration of complex in solution. Via outlet line 30 and pump 32, the catalyst complex solution in alkylates and benzene so formed is fed to the reactor.
Ethylene is fed from e-thylene storage 34 via line 36 into an absorption tower 38, in which it is countercurren-tly mixed with downwardly flowing benzene f`rom line 28, entering near the top of the absorption tower 38. Undissolved impurities of the gas stream are vented by suitable vent means 40, to recover and return condensate to the absorption tower 38. The absorption is carried out at a temperature of 10 - 20C in to~er 38, and a total pres-sure depending on the ethylene concentration in solution and the purity of the ethylene stream used. At 95 volume percent ethylene in the stream, and 0.25 - 0.33 mole fraction ethylene in the solution, the absorber pressure is in the range 25-31 atm. abs., i.e. about 350-440 psig.
From the absorber 38, the benzene-ethylene solution exits via outlet line 42 into a feed drum 44, where it is stored and vented to vent means 40 and from there it is delivered by means of outlet line 46 and pump 48 to a feed preheater 50, having a central material feed tube 52 extending longitudinally therethrough, and a water jacket 54 surrounding the tube 52, through which can be fed warm water from inlet pipe 56, to heat the preheater to the desired temperature of 55-60 C, for heating of the ethylene-benzene feed to that temperature.
: .
. . .
~0~9~6 From the exit of the preheater 50, the ethylene-benzene solution is fed to the first of a series of the plug flow reactor sections 58,60,6Z,64,66,68, at the entrance to which it is mixed with a metered, predetermined quantity of catalyst complex solu-tion from vessel 22. Each of the plug flow reactor sections 58, etc. is provided with a cooling jacket fed via an inlet line 70 with cooling water from source 72. The cooling water circulates through the jacket continuously, and exits via line 74 therefrom.
The reaction mixture flows continuously and successively at predetermined rates through the series of the plug flow reactor sections, the rate of feed of the ingredients, and the rate of circulation and temperature of cooling water being adjusted to maintain a reaction temperature within each of the reactor sec-tions in the range 60-70C. At the entrance to the third reactor -section 62, there is provision for addition to the reaction mixture of further quantities of catalyst solution in benzene, via inlet line 76 as indicated. Similarly, further complex solution in benzene can be added at the inlet to reactor section 66, through inlet line 78. Additional quantities of benzene can be added at the entrance to fourth reactor section 64 via benzene inlet line 80, and the entrance of sixth reactor section 68 via benzene inlet line 82. The process is thus conducted continuously, and continuous monitoring of the composition of the feed and the reaction mixuture is undertaken, to maintain the desirable reaction temperature, to ensure adequate suppression of polyalkylation and like side reactions, and to prevent presence of excessive amounts of deactivated catalyst. After exit from the final reactor section 68, the product stream is subjected to water washing to remove mineral impurities, and to distillation to separate ethylbenzene from the residual benzene, and small quantity of polyethylbenzenes.
~077966 The residual benzene is dried and continuously recycled to benzene storage 26, and the accumulated polyethylbenzenes periodically dealkylated by recycling to the reactor and adding to the supple-mentary benzene feed, line 80 or~82.
The form of tubular reactor diagrammatically shown only has a central reactor tube passing through the center of a surround-ing water jacket provided for cooling purposes. It will be appre-ciated that this is diagrammatic only. Suitable forms of plug flow reactors for use in the preferred embodiment of the present invention are available commercially, an example being a Kenics tubular reactor fitted with static mixers to provide lateral mixing. Whilst the illustration shows six reactor sections connected together in series, it will of course be understood that the process can well be conducted in one long tubular reactor, provided with static mixers and having points of addition for benzene and catalyst solution located at appropriate positions along the legth of the single reactor. It is also within the scope of the present invention to use a double jacketed plug flow reactor, having cooling means disposed in the center and outside, with reaction mixture flow through an annular space between the two jackets. Static mixers are suitably provided in any of the reactors used in the present invention. Such forms of tubular plug flow reactors provide the necessary heat transfer capability for maintaining the reaction temperature of the ethylbenzene formation in the desirable 60-70 C temperature range, thereby suppressing formation of byproducts.
Thus, in summary, the process of the present invention prepares a solution of ethybenzene sparately from the reactor, thereby eliminating from the alkylation process the diffusion controlled absorption of ethylene, and thus enables the reaction - J or~966 of the ethylene with benzene to take place in the presence of low concentrations of the Friedel-Crafts aluminum chloride catalyst complex in the kinetic region of the reaction. The process eliminates the gaseous phase from the system, thereby enabling the use of plug flow tubular reactor for alkylation. The use of such reactor leads to the additional benefit of suppression of poly-alkylation reactions by permitting the use of large and controlled benzene:ethylbenzene ratios, these ratios diminishing with the progress of the alkylation from -the reactor inlet to a constant ~alue determined by the composition of the product leaving the reactor. It also enables the use of lower reaction temperatures obtainable by the use of such tubular reactor, further suppressing byproduct formation. By adding benzene in the form of diluted solution of the catalyst complex the decline in the benzene:
ethylbenzene ratio leading to undesirable byproduct formation is decelerated and polyalkylation suppressed further. The rate of benzene addition is gradually increased with the progress of the reaction. The high rates of heat removal in plug flow reac-tors enable production in the range 500 - 1,500 lbs. ethylben-zene per hour per cubic foot of reactor volume, as compared with the fifteen pounds obtained in the commercial bubbler reactor.
Short residence times in the reactor are accomplished, with low concentrations of the catalyst complex and rapid removal of the product from the complex, due to the action of the static mixers provided in the reactor. This prctically eliminates the forma-tion of non-dealkylable waste products in the reactor. The deac-tivation of the catalyst is reduced to a minimum and aluminum chloride usage is drastically reduced, the residues being destroyed on water washing of the crude alkylate, without need for recycle.
Atshort residence times in the reactor, and with the ~79~;6 suppresing action of the high benzen:etylbenzene ratio, the slow polyalkylation reactions at the 60-70C temperature encountered in the process of the present invention do not reach an equi-librium, and depending on phenyl:ethyl ratios used in the process, polyethylbenzenes formation can be reduced to below five pounds per one hundred pounds of ethybenzene.
It is of course to be understood that the foregoing detailed description is by way of illustrative example only, and is not to be construed as limiting. The scope of the present invention is limited only by the scope of the appended claims.
The rate of ethylene reaction with benzene depends on the concentration of the catalyst complex solution in the reac-tion mixture, and the rate of feed of the catalyst complex to the reactor should be controlled so as to adjust the rate of alkylation to suit the available rate of heat removal and keep the reactor tmeperature in the range 60-70C.
As noted, excess benzene is used in the ethybenzene process, to suppress the reversible polyalkylation reactions.
Usually the benzene:ethylene molar ratio in the feed to the reactor 107'79~
is maintained at 2.5:1 - 3:1, (this taking account of all the benzene added, with the ethylene and with the catalyst), with the result that 1.5 to 2 moles of unreacted benzene per mole of etylbenzene produced remain in the product. On fractionation of the crude alkylation product after removal from this reactor, the benzene is separated from the alkylates and can be recycled to the process.
~ he benzene:ethylbenzene ratio which determines the degree of suppression of the polyalkylation follows the progress of the alkylation, and gradually diminishes from the infinity at the start of the reaction, to a fixed value at its completion.
Under these conditions, full advantage of the high benzene:ethyl-benzene ratio can only be taken by carrying out the alkylation reaction in a plug flow reactor, in which the composition of the reaction mixture changes with the progress of the process. The use of the plug flow reactor therefore provides reaction condi-tions not available from the conventional bubbler reactor, in which the composition remains constant and identical with that of the product leaving the reactor. Use of ethylene solution in benzene prepared separately according to the present invention, offers an opportunity to suppress the polyalkylation even further.
By increasing the initial concentration of ethylene in the solu-tion, the balance of the required benzene, alone or in the form of diluted solution in the catalyst complex, can be added gradually along the length of the plug flow reactor to decelerate the decline in benzene:ethylbenzene ratio.
In preparing the catalyst complex, preferably a Cl donor is added to a suspension of aluminum chloride powder in benzene alkylate, at room temperature. This can be done in a mechanically -agitated vessel. 'Hydrogen chloride or ethyl chloride can be used '' , ' .
`7966 as the Cl donor, and polyethylbenzenes alone or mixed with benzene and/or ethyhenzene can be used as the alkylate. It is preferred to use ethyl chloride as the Cl donor, and polyethyl-benzenes alone as the alkylate for the catalyst complex. A single liqùid phase can be obtained, by choice of correct proportions, this complex being sparingly soluble in benzene or ethylbenzene reaction mixture and having very low corrosive properties under the conditions of the alkylation process.
The complex so formed may then be dissolved in hot benzene under pressure, using a steam heated, mechanically agi-tated vessel. ~`he temperature is controlled to get the required concentration of comple~ solution. Then the solution may be pumped to the reactor.
In one embodiment, an absorption tower is used to cont-act counter-currently flowing ethylene stream and benzene stream to form the required solution of ethylene and benzene, the streams being at controlled rates so as to obtain a solution of the required concentration. In another embodiment, a set of tubular static mixers in series can be used to contact the two streams, introducing the ethylene feed at several points along the benzene flow. The undissolved impurities of the gas stream are vented and the ethylene solution is collected in a feed drum, and from there delivered by pump t~ the reactor at a controlled rate.
A specific embodiment of the process of the present invention is illustrated in the accompanying Figure, which is a diagrammatic process flow sheet thereof.
With reference to the accompanying figure, 10 denotes a catalyst preparation vessel, in the form of a vessel provided with a mechanical agitator 12. To the vessel 10 is fed ethyl chloride as Cl donor, through inlet line 14, powdered aluminum chloride ` lV~'796~i through line 16, and polyethylbenzenes through line 18. After mixing these ingredients together in vessel 10, at atmospheric pressure and room temperature, the liquid catalyst complex is fed via outlet 20 to a steam heated tank 22, where it is mixed by means of mechanical agitation 24 with benzene fed from benzene storage Z6 via inlet line 28. The temperature in this vessel 22 is controlled to obtain the required concen-tration of complex in solution. Via outlet line 30 and pump 32, the catalyst complex solution in alkylates and benzene so formed is fed to the reactor.
Ethylene is fed from e-thylene storage 34 via line 36 into an absorption tower 38, in which it is countercurren-tly mixed with downwardly flowing benzene f`rom line 28, entering near the top of the absorption tower 38. Undissolved impurities of the gas stream are vented by suitable vent means 40, to recover and return condensate to the absorption tower 38. The absorption is carried out at a temperature of 10 - 20C in to~er 38, and a total pres-sure depending on the ethylene concentration in solution and the purity of the ethylene stream used. At 95 volume percent ethylene in the stream, and 0.25 - 0.33 mole fraction ethylene in the solution, the absorber pressure is in the range 25-31 atm. abs., i.e. about 350-440 psig.
From the absorber 38, the benzene-ethylene solution exits via outlet line 42 into a feed drum 44, where it is stored and vented to vent means 40 and from there it is delivered by means of outlet line 46 and pump 48 to a feed preheater 50, having a central material feed tube 52 extending longitudinally therethrough, and a water jacket 54 surrounding the tube 52, through which can be fed warm water from inlet pipe 56, to heat the preheater to the desired temperature of 55-60 C, for heating of the ethylene-benzene feed to that temperature.
: .
. . .
~0~9~6 From the exit of the preheater 50, the ethylene-benzene solution is fed to the first of a series of the plug flow reactor sections 58,60,6Z,64,66,68, at the entrance to which it is mixed with a metered, predetermined quantity of catalyst complex solu-tion from vessel 22. Each of the plug flow reactor sections 58, etc. is provided with a cooling jacket fed via an inlet line 70 with cooling water from source 72. The cooling water circulates through the jacket continuously, and exits via line 74 therefrom.
The reaction mixture flows continuously and successively at predetermined rates through the series of the plug flow reactor sections, the rate of feed of the ingredients, and the rate of circulation and temperature of cooling water being adjusted to maintain a reaction temperature within each of the reactor sec-tions in the range 60-70C. At the entrance to the third reactor -section 62, there is provision for addition to the reaction mixture of further quantities of catalyst solution in benzene, via inlet line 76 as indicated. Similarly, further complex solution in benzene can be added at the inlet to reactor section 66, through inlet line 78. Additional quantities of benzene can be added at the entrance to fourth reactor section 64 via benzene inlet line 80, and the entrance of sixth reactor section 68 via benzene inlet line 82. The process is thus conducted continuously, and continuous monitoring of the composition of the feed and the reaction mixuture is undertaken, to maintain the desirable reaction temperature, to ensure adequate suppression of polyalkylation and like side reactions, and to prevent presence of excessive amounts of deactivated catalyst. After exit from the final reactor section 68, the product stream is subjected to water washing to remove mineral impurities, and to distillation to separate ethylbenzene from the residual benzene, and small quantity of polyethylbenzenes.
~077966 The residual benzene is dried and continuously recycled to benzene storage 26, and the accumulated polyethylbenzenes periodically dealkylated by recycling to the reactor and adding to the supple-mentary benzene feed, line 80 or~82.
The form of tubular reactor diagrammatically shown only has a central reactor tube passing through the center of a surround-ing water jacket provided for cooling purposes. It will be appre-ciated that this is diagrammatic only. Suitable forms of plug flow reactors for use in the preferred embodiment of the present invention are available commercially, an example being a Kenics tubular reactor fitted with static mixers to provide lateral mixing. Whilst the illustration shows six reactor sections connected together in series, it will of course be understood that the process can well be conducted in one long tubular reactor, provided with static mixers and having points of addition for benzene and catalyst solution located at appropriate positions along the legth of the single reactor. It is also within the scope of the present invention to use a double jacketed plug flow reactor, having cooling means disposed in the center and outside, with reaction mixture flow through an annular space between the two jackets. Static mixers are suitably provided in any of the reactors used in the present invention. Such forms of tubular plug flow reactors provide the necessary heat transfer capability for maintaining the reaction temperature of the ethylbenzene formation in the desirable 60-70 C temperature range, thereby suppressing formation of byproducts.
Thus, in summary, the process of the present invention prepares a solution of ethybenzene sparately from the reactor, thereby eliminating from the alkylation process the diffusion controlled absorption of ethylene, and thus enables the reaction - J or~966 of the ethylene with benzene to take place in the presence of low concentrations of the Friedel-Crafts aluminum chloride catalyst complex in the kinetic region of the reaction. The process eliminates the gaseous phase from the system, thereby enabling the use of plug flow tubular reactor for alkylation. The use of such reactor leads to the additional benefit of suppression of poly-alkylation reactions by permitting the use of large and controlled benzene:ethylbenzene ratios, these ratios diminishing with the progress of the alkylation from -the reactor inlet to a constant ~alue determined by the composition of the product leaving the reactor. It also enables the use of lower reaction temperatures obtainable by the use of such tubular reactor, further suppressing byproduct formation. By adding benzene in the form of diluted solution of the catalyst complex the decline in the benzene:
ethylbenzene ratio leading to undesirable byproduct formation is decelerated and polyalkylation suppressed further. The rate of benzene addition is gradually increased with the progress of the reaction. The high rates of heat removal in plug flow reac-tors enable production in the range 500 - 1,500 lbs. ethylben-zene per hour per cubic foot of reactor volume, as compared with the fifteen pounds obtained in the commercial bubbler reactor.
Short residence times in the reactor are accomplished, with low concentrations of the catalyst complex and rapid removal of the product from the complex, due to the action of the static mixers provided in the reactor. This prctically eliminates the forma-tion of non-dealkylable waste products in the reactor. The deac-tivation of the catalyst is reduced to a minimum and aluminum chloride usage is drastically reduced, the residues being destroyed on water washing of the crude alkylate, without need for recycle.
Atshort residence times in the reactor, and with the ~79~;6 suppresing action of the high benzen:etylbenzene ratio, the slow polyalkylation reactions at the 60-70C temperature encountered in the process of the present invention do not reach an equi-librium, and depending on phenyl:ethyl ratios used in the process, polyethylbenzenes formation can be reduced to below five pounds per one hundred pounds of ethybenzene.
It is of course to be understood that the foregoing detailed description is by way of illustrative example only, and is not to be construed as limiting. The scope of the present invention is limited only by the scope of the appended claims.
Claims (10)
1. A process for the manufacture of ethylbenzene by reaction of ethylene and benzene in the presence of a Friedel-Crafts catalyst, which comprises the successive steps of:
dissolving the ethylene in gaseous form in at least a portion of the benzene in liquid form, in the absence of cata-lyst, to prepare a preformed ethylene-benzene liquid solution;
contacting said preformed solution in an alkylation reactor with a Friedel-Crafts catalyst under alkylation reaction conditions;
removing the products from said reactor and recovering ethylbenzene therefrom.
dissolving the ethylene in gaseous form in at least a portion of the benzene in liquid form, in the absence of cata-lyst, to prepare a preformed ethylene-benzene liquid solution;
contacting said preformed solution in an alkylation reactor with a Friedel-Crafts catalyst under alkylation reaction conditions;
removing the products from said reactor and recovering ethylbenzene therefrom.
2. The process of claim 1 wherein the preformed ethylene-benzene solution is prepared by contacting gaseous ethylene and liquid benzene at temperatures in the range 10-20°C, and under pressure of from about 350 to about 440 psig.
3. The process of claim 1 wherein the alkylation process is conducted continuously in a tubular reactor equipped with heat transfer means adepted to control the reaction temperature
4. The process of claim 3 wherein the alkylation process is conducted at a temperature in the range 60-70°C.
5. The process of claim 2 wherein the ethylene-benzene solution is preheated to the alkylation reaction temperature prior to entering the alkylation reactor.
6. The process of claim 1 wherein the Friedel-Crafts catalyst comprises a preformed liquid complex of aluminum chloride, polyethylbenzenes and a C1- donor selected from hydrogen chloride and ethyl chloride.
7. The process of claim 6 wherein the Friedel-Crafts catalyst is preformed by mixing under agitation and at ambient temperature aluminum chloride, ethyl chloride and polyethybenzenes so as to form a liquid complex, and subsequently suitably diluting said complex with benzene.
8. The process of claim 1, claim 3 or claim 6 wherein the process is carried out continuously, and wherein a portion of the catalyst is contacted with the ethylene-benzene solution substantially at the entry of the solution into the alkylation reactor, and at least one additional portion of the catalyst is added to the reaction mixture in the alkylation reactor downstream of the entrance thereto.
9. The process of claim 1, claim 2 or claim 6 wherein the process is conducted continuously, and wherein at least one supplementary quantity of benzene is fed to the reaction mixture in the alkylation reactor at a location downstream of the entrance thereto.
10. The process of claim 1, claim 6 or claim 7 wherein the amount of aluminum chloride in the Friedel-Crafts catalyst used is from about 0.1 to about 0.2 pounds per 100 pounds of ethylbenzene produced.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA302,775A CA1077966A (en) | 1978-05-08 | 1978-05-08 | Manufacture of ethylbenzene |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA302,775A CA1077966A (en) | 1978-05-08 | 1978-05-08 | Manufacture of ethylbenzene |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1077966A true CA1077966A (en) | 1980-05-20 |
Family
ID=4111411
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA302,775A Expired CA1077966A (en) | 1978-05-08 | 1978-05-08 | Manufacture of ethylbenzene |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1077966A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115138301A (en) * | 2021-03-31 | 2022-10-04 | 中国石油天然气股份有限公司 | Liquid acid alkylation reaction method and reaction system |
-
1978
- 1978-05-08 CA CA302,775A patent/CA1077966A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115138301A (en) * | 2021-03-31 | 2022-10-04 | 中国石油天然气股份有限公司 | Liquid acid alkylation reaction method and reaction system |
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