CA1146583A - Process for production of ethyl acrylate - Google Patents
Process for production of ethyl acrylateInfo
- Publication number
- CA1146583A CA1146583A CA000370145A CA370145A CA1146583A CA 1146583 A CA1146583 A CA 1146583A CA 000370145 A CA000370145 A CA 000370145A CA 370145 A CA370145 A CA 370145A CA 1146583 A CA1146583 A CA 1146583A
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- Prior art keywords
- ethyl acrylate
- sulfuric acid
- wiped
- residue
- film evaporator
- 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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Abstract
IMPROVED PROCESS FOR PRODUCTION OF ETHYL ACRYLATE
ABSTRACT
A process is provided for the continuous production of ethyl acrylate from ethylene and acrylic acid in the presence of sulfuric acid. The process includes the removal of impurities from the reaction system by passing minor portions of sulfuric acid residue from the process through a wiped-film evaporator whose initial sections are heated to a specific temperature range and whose last or withdrawal section(s) are cooled to a specific temperature range. This treatment prevents foaming of the used sulfuric acid residue. The treated sulfuric acid residue in the wiped-film evaporator is withdrawn from the reaction system.
If foaming of the sulfuric acid residue occurs, the foamed residue can back up into the reaction system requiring a shutdown of the entire process.
An additional aspect of this process is the passing of at least 50 weight percent of the ethyl acrylate product residue from the finishing distillation tower into the wiped-film evaporator at the same time that the sulfuric acid residue is being treated. The treatment of the ethyl acrylate product residue recovers additional ethyl acrylate product and acrylic acid starting material from the wiped-film evaporator while the remainder of the ethyl acrylate product residue containing polymerization initiators which can cause undesirable polymerized product, is removed from the reaction system.
ABSTRACT
A process is provided for the continuous production of ethyl acrylate from ethylene and acrylic acid in the presence of sulfuric acid. The process includes the removal of impurities from the reaction system by passing minor portions of sulfuric acid residue from the process through a wiped-film evaporator whose initial sections are heated to a specific temperature range and whose last or withdrawal section(s) are cooled to a specific temperature range. This treatment prevents foaming of the used sulfuric acid residue. The treated sulfuric acid residue in the wiped-film evaporator is withdrawn from the reaction system.
If foaming of the sulfuric acid residue occurs, the foamed residue can back up into the reaction system requiring a shutdown of the entire process.
An additional aspect of this process is the passing of at least 50 weight percent of the ethyl acrylate product residue from the finishing distillation tower into the wiped-film evaporator at the same time that the sulfuric acid residue is being treated. The treatment of the ethyl acrylate product residue recovers additional ethyl acrylate product and acrylic acid starting material from the wiped-film evaporator while the remainder of the ethyl acrylate product residue containing polymerization initiators which can cause undesirable polymerized product, is removed from the reaction system.
Description
BACKGROUND OF THE INVENTION
Processes for the production of ethyl acrylate by interacting acrylic acid with ethylene in the presence of sulfuric acid are well known;
see for example, U. S. Patent No. 3,703,539, issued November 21, 1972 to DiLiddo; U. S. Patent No. 3,539,621, issued November 10, 1970 to Cipollone et al; and U. S. Patent No. 3,834,076, issued July 8, 1975 to Van Duyne et al. As described in these and other references, the reaction -1- ~
,. .
~ 7 . .. ._ ..
is believed to involve first the formation of intermediate sulfates from the reaction of ethylene with sulfuric acid. These sulfates then react with acrylic acid to form ethyl acrylate. To provide a product in good overall yields with high carbon efficiencies, the unreacted ethylene, acrylic acid and the sulfuric acid residue must be recycled to the reactor.
The residence times of some of these reactants can be long enough to result in the formation of partially polymerized products which can plug the process equipment. Additionally, these processes operating on a continuous basis for extended periods of time, produce impurities in the reaction system which must be efficiently removed. The present invention provides an efficient method for the removal of such impurities by treating the sulfuric acid residue in a particular way while at the same time removing polymerization initiators from the reaction system.
In the chemical industry, it is common to ~se a wiped-film evaporator for processing highly viscous solutions and for vacuum evaporator.
Typical of the units that can be used and are known are the types described in a three part report in Chemical F.ngineering, September 13, 1965, pages 175-190, entitled "Agitated Thin-Film Evaporators". Modifications of these types of evaporators are described in the art for example, in U. S. Patent 3,292,683 entitled "Wiped Falling Film Evaporator" issued December 20, 1966 to Buchi et al; U. S. Patent 3,464,478 entitled "Horizontal-Type High Vacuum Film Evaporator For Highly Viscous Solutions" issued September 2, 1969 to Tomohane Veda et al; U. S. Patent 3,695,327 entitled "Wiped Thin Film Evaporation and Treatment Process" issued Octob~r 3, 1972 to Widmer; among others. This equipment is normally used to separate highly viscous materials from volatile material with the objective to separate the materials at the highest efficiencies in the least amount of time. Under these conditions, these evaporators are maintained at the highest possible temperatures for the most efficient periods of time. None of the processes and equipment known in the use of wiped-film evaporators area are known to evaporate and cool within the same unit. In the process of producing ethyl acrylate by the reaction of ethylene and acrylic acid in the presence of sulfuric acid, it is the technique of heating the initial stages of the evaporator and cooling the last or withdrawal section(s) which provides the highly efficient and desirable process of separating the highly viscous sulfuric acid residue from the volatile products such as ethyl acrylate and acrylic acid while maintaining foaming of the evaporating material at a workable and controllable minimum.
SUMMARY OF THE INVENTIQN
The process of the present invention involves the treatment of a minor portion of the sulfuric acid residue in a wiped-film evaporator operated under unusual conditions in the production of ethyl acrylate from ethylene and acrylic acid in the presence of sulfuric acid. For purposes of this invention ethyl acrylate is produced using the following steps:
(a) reacting ethylene and acrylic acid in the presence of sulfuric acid to form a reaction product;
(b) separating said reaction product into crude ethyl acrylate and a sulfuric acid residue;
(c) separating the light end materials from said crude ethyl acrylate and other reaction products to obtain a partially purified ethyl acrylate;
(d) separating and recovering a substantially pure ethyl acrylate from said partially purified ethyl acrylate leaving an ethyl acrylate product residue; and (e) recycling a major portion of the sulfuric acid residue of step ~b) to step (a).
In accordance with this invention, a minor portion of the sulfuric acid residue of step (b) is passed to a wiped-film evaporator which is heated in its initial sections so that the sulfuric acid residue reaches a temperature i583 in the range from about 300F. to about 360F., and cooled in its last or withdrawal section(s) to cool the sulfuric acid residue to a temperature in the range from about 230F. to about 280F. After cooling, the sulfuric acid residue is removed from the process.
Cooling the last or withdrawal section(s) of the wiped-film eva-porator substantially eliminates foaming of the spent sulfuric acid residue.
If the sulfuric acid residue is not cooled, foaming of the residue in the wiped-film evaporator can be sufficiently severe that the foam can back through the lines leading to the wiped-film evaporator from the recovery d~stillation tower and/or the finishing distillation tower, requiring shutdown of the process.
An additional feature of this invention involves passing at least about 50 weight percent of the ethyl acrylate product residue from the finishing distillation tower together with the minor portion of the sulfuric acid residue obtained from the recovery distillation tower through the wiped-film evaporator using the same conditions as described above. Ethyl acrylate product and acrylic acid reactant can be recovered from the treat-ment of the sulfuric acid residue and the ethyl acrylate product residue in the wiped-film evaporator. The remaining residues containing poly~eri-zation initiators and other impurities in the wiped-film evaporator are removed from the reaction system to ensure a smooth and extended continuous operation. This in combination with the other described improvements provides improved overall yields and efficiencies of the process of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a simplified schematic flow sheet exemplifying the preparation of ethyl acrylate from ethylene and anhydrous acrylic acid in the presence of substantially anhydrous sulfuric acid showing the use of a wiped-film evapor2tor for removal of a portion of the spent sulfuric acid ~6583 residue and at least about 50 weight percent of the ethyl acrylate product residue from the finishing distillation tower.
Figure 2 is a schematic representation of a wiped-f~lm evaporator which heats the feed of sulfuric acid residue on the init~al sections of the evaporator and cools the spent sulfuric acid residue at the last or withdrawal section(s).
DETAILED DESCRIPTION OF T~E INVENTION
The process of the present invention is schematically represented in Figure 1, in which a combination of substantially anhydrous sulfuric acid medium supplied through line 11 and ethylene supplied through line 12 is sprayed into reactor tower 10 and mixed. The sulfuric acid medium is comprised of sulfuric acid residue or bottoms from the product recovery distillation tower 13 along with make-up sulfuric aGid added through line 14. The sulfuric acid residue (sometimes referred to in the industry as "black acid") recovered from the recovery distillation tower 13 is a mixture of various compounds and contains sulfuric acid, intermediate sulfates from the reaction of ethylene and sulfuric acid, unreacted acrylic acid, some small amounts of ethyl acrylate, and various other compounds.
In the reactor tower 10, the main reaction of concern is the liquid phase reaction of the ethvlene enriched liquid with sulfuric acid to give the various intermediate sulfate salts, such as ethyl hydrogen sulfate and diethyl sulfate, which will then further react with acrylic acid, supplied through line 15, to Eorm ethyl acrylate. Adequate mixing of the reaction mixture in the reaction tower 10 can be obtained by mechanical stirringor recycle of the reaction products. (Neither mixing techniques are shown in the drawings). The reactants' residence time in the reactor tower 10 must be sufficient to obtain substantially (preferabl, at least a 90% completion) complete reaction of ethylene and acrylic acid. Tempera-tures in the reaction tower should be maintained within the range of about 1~4~583 .
100C. to about 150C., preferably 110C. to 130C. and the pressure should be maintained within the range of about 100 to about 300 psig, preferably 130 to 200 psig.
The reaction products from the reactor tower 10 is withdrawn through line 16 and passed through a pressure redurtion valve (not shown) and thence to the recovery distillation tower 7 3. The distillation section of the recovery distillation tower may be a conventional design, and may contain packing, sieve type trays or dual flow trays. ~he distillation section should contain an equivalent of at least four theoreticaly trays.
A vacuum is maintained in the recovery distillation tower 13 by conventional means so that the pressure is less than about 200mm of mercury absolute and preferably within the range of 20 to 150mm of mercury absolute. The still pot temperature should be maintained ~7itkin the range of about 100C.
to about 170C., preferably 110C. to 130C., and the still overhead temperature within the range of about 28C. to about 45C., preferably 30C. to 40C.
The feed line 17 to the recovery distillation tower 13 is directed preferably to the lower third and more preferably to the base of the tower.
In the recovery distillati^n tower 13, the light ends of crude ethyl acrylate comprising mainly of ethyl acrylate, small amounts of unreacted ethylene and other uncondensables, are removed overhead through line 18 and passed to the light ends distillation tower 19 (of conventional distillation design).
Rartially purified ethyl acrylate product is removed as ~ottoms through line 20. A stream comprising mainly unreacted ethylene is removed from the light ends distillation tower 19 through line 21 and may be disposed of or recycled (not shown) to the reactor tower 10 as desired, although if recycled a scrubbing to remove sulfur oxides is recommended. As pointed out above, operation according to the present invention generally results in a very small amount of unreacted ethylene such that the amounts of ethylene removed through line 21 will be relatively small. The partially purified ethyl 1~L46S83 acrylate product recovered through line 20 is further treated by fraction-ation in the finishing distillation tower 22 to obtain, through line 23, a substantially pure ethyl acrylate having a purity greater than 95 percent, preferably about ~9.9 percent or higher.
In operating the recovery distillation tower 13, the residence time of the reaction products in the base of the tower should be as low as possible because at temperatures required in the reboiler for vaporization some polymerization may occur. It is desirable to have a feed stream lean in acrylic acid being fed to the recovery distillation tower since it will result in less polymer formation.
The sulfuric acid residue or black acid stream referred to above containing sulfuric acid, intermediate sulfates, unreacted acrylic acid and the like is removed as bottoms residue from the recovery distillation tower 13 through line 24. A blowdown of a minor portion of the bottoms stream or sulfuric acid residue which is approximately 1 to 5 percent by weight of the total sulfuric acid residue is taken by means of line 25 so as to preven, the build up of impurities in the system. The remaining major portion of the sulfuric acid residue can be recycled through line 11 to the reactor tower 10 in combination with ethylene.
This portion of the sulfuric acid residue is passed through line 25 to a horizontal wiped-film evaporator 26 whlch heats the sulfuric acid residue to temperatures in the range from about 300F. to about 360F., and preferably 325F. to 350F. in the initial portion of the wiped-film evaporator 26. At the last Dr withdrawal sections of the wiped-film evaporator 26, the spent sulfuric acid residue is cooled to temperatures in the range from about 230F. to about 280F. and preferably 240F. to 270F. for removal from the system through line 27. During the treatment of the sulfuric acid residue and the ethyl acrylate product residue for the process of this invention, the wiped-film evaporator 26 is maintained under reduced pressure in the range from about 40 to about 150mm of mercury absolute and preferably in the range from about 50 to about xOmm of mercury absolute. Ethyl acrylate and acrylic acid can be recovered through line 28 from the wiped-film evaporator 26. The preferred procedure for ethyl acrylate and acrylic acid removed from the wiped-film evaporator is to recycle these products to the recovery distillation tower 13 for reprocessing.
(Not shown on the drawing).
In heating of the wiped-film evaporator so as to raise the temperature o the residue to a level, from about 300F. to about 360F., necessary to recover the available monomers or products from the sulfuric acid residue, excessive foaming in the evaporator unit caused by gas evolution associated with decomposition of the completely stripped residue can cause temporary shutdown of the entire system due to the backing up of the foam to line 25 from the recovery distillation tower 13 or into line 11 leading to the reaction tower 10 or to lines 30 and 29 back to the finishing distillation tower 22. Cooling of the last or withdrawal section(s) of the wiped-film evaporator 26 to provide a sulfuric acid residue having temperatures in the range from about 230F. to about 280F. substantially eliminates the foaming problem. This also results in an improvement in overall process efficiency and an increase in ethyl acrylate yields based on acrylic acid compared to the standard procedure of not cooling any part of the wiped-film evaporator.
Although not shown on the drawing, the addition of a polymerization inhibitor is generally desirable when producing or purifying ethyl acrylate.
Such inhibitors are well known and can be materials soluble in the reaction medium or soluble in the product obtained from the recovary distillation tower. Suitable polymerization inhibitors include hydroquinone, phenothiazine, the methyl ether of hydroquinone, quinone and the like. The polymerization inhlbitor can be introduced to the reaction vessel in the sulfuric acid residue or through any other convenient part of the system. It is required that the inhibitor be added to lines 18, 21 and 23. The inhibitor can be 13~46583 added in line 18 from whence it i5 carried through to the light ends dis-tillation towcr 19, then into the finishing distillation tower 22 and into the residue of the finishing distillation tower 22.
The ethyl acrylate product residue of the finishing distillation tower 22 containing the polymerization inhibitor is removed through line 29 and the ethyl acrylate product residue can be divided wherein at least 50 weight percent of the residue can be passed through line 31 into the wiped-film evaporator 26 for recovery of organic products such as ethyl acrylate and acrylic acid. The preferred process is to pass all of the ethyl acrylate product residue into the wiped-film evaporator 26. If only a portion of the ethyl acrylate product residue is passed into the wiped-film evaporator 26 the remaining portion can be passed through line 30 into line 17 which is combined with the reaction products passed into the recovery distillation tower 13 and firlally combined with the sulfuric acid residue to be recycled through line 24 back to the reactor tower 10. If all of the ethyl acrylate product residue from the finishing distillation tower is recycled to the recovery tower 13 d~rectly, the result can be a greater degree of fouling in the recovery distillation tower caused by black ~cid viscosity increase and a subsequent loss of product polymer. Passing the ethyl acrylate product residue from the finishing distillation tower to the wiped-film evaporator, an improvement in the overall process efficiency is achieved since the fouling of the recovery distillation tower is sub-stantially decreased with less polymer being formed.
The types of wiped-film evaporator which can be used in the process of the present invention can be a vertical or horizontal unit. For this invention, a horizontal unit is preferred. Typical of the units can be used and are known are the types described in a three part report in Chemical Engineering, September 13, 1965, pages 175-190, entitled "Agitated Thin-Film Evaporators". The one essential criterion of the wiped-film evaporator used in this process is the capability of cooling the latter 1~6i583 section of the evaporator to provide a residue having specif;c temperature ranges as described herein. N~rmally the use of a wiped-film evaporator is for separating and recovering the low boiling materials f.om the high boiling viscous materials using as much heat as possible over as much heating surface as possible to achieve and maintain high temperatures for fast and efficient separation. Under these conditions one would normally not consider cooling any portion of the treating surface of the ~.~iped-film evaporator. The unique problem of this invention in the treatment of the combination of the viscous sulfuric acid residue and the ethyl acrylate product residue is the foaming of the residue in the latter section(s) of the wiped-film evaporator on heating at temperatures in the range from about 300F. to about 360F. These temperatures are needed to effectively and efficiently separate ethyl acrylate and acrylic acid from the sulfuric acid residue. The foaming of the treated residue can be so severc that the foamed material can back up into the purification system requiring the shutdown of the process. This foaming can be substantially eliminated by cooling the last or withdrawal section(s) of the wiped-film evaporator' to temperatures in the range from about 230F. to about 280F. It is indeed a surprising result wherein a wiped-film evaporator is used efficiently by heating the initial sections of the unit and cooling the last or with-drawal sections of the unit.
Figure 2 is a schematic representation of the wiped-film evaporator 40 which can be used in the present invention. The sulfuric acid residue is fed through lines 41 to the evaporator 40 which contains various sections 42 through 47. Sections 42 through 45 can be heated by hot oil entering the jacket of section 42 through line 48 to heat the sulfuric acid residue to temperatures in the range from about 300F. to about 360F. and preferably in the range from about 325F. to about 350F. The oil can be remov2d from section 45 through line 49 for reuse. Sections 46 and 47 can be cooled by a coolant such as steam, water and the like entering through line 50 to s ~J: ~
~46~583 cool the sulfuric acid residue to temperatures in the range from about 230F.
to about 280F., preferably in the range from about 240F. to about 270F.
Care must be exercised that the coolant is not excessively cool to prevent thermal stressing resulting in metal fatigue and/or mechanical damage to the unit. The coolant can be removed through line 51 for reuse. The spent sulfuric acid residue can be removed from evaporator 40 and the system through line 52. The acrylic acid reactant and ethyl acrylate product can be recovered from line 53.
To illustrate the procesQ of this invention, referring to Figure 1, and using the conditions as described, 3055 pounds per hour of ethylene and 7850 pounds per hour of acrylic acid are added to the reactor tower 10 into which 92,967 pounds per hour of sulfuric acid medium is recycled with 879 pounds of anhydrous sulfuric acid makeup is added. From the recovery distillation tower 13, 14,199 pounds per hour of crude ethyl acrylate product are obtained overhead through line 18. From the bottom of the recovery distillation tower 13, 2789 pounds per hour of sulfuric acid residue are removed from the recycle sulfuric acid medium and passed through the wiped-film evaporator 26. l4,]99 pounds per hour of crude ethyl acrylate product is passed through line 18 to the light ends distillation tower 19.
157 pounds per hour of light ends are recovered in the ^verhead line 21 and 13,962 pounds per hour of partially purified ethyl acrylate product is passed through line 20 to the finishing distillation tower 22. 9380 pounds per hour of purified ethyl acrylate are recovered through line 23 and 4582 pounds per hour of ethyl acrylate product residuQ are recovered through line 29 and passed through line 31 to the wiped-film evaporator 26.
2789 pounds per hour of sulfuric acid residue and 4582 pounds of ethyl acrylate product residue are pas.sed through the wiped-film evaporator 26. 5158 pounds per hour of ethyl acrylate and 215 pounds per hour of acrylic acid are recovered through 28 from the wiped-film evaporator. The material removed from the wiped-film evaporator and the reaction system .
are 879 pounds per hour of sulfuric acid and 1099 pounds per hour of polymeric acrylates among other products.
The wiped-film evaporator was operated under reduced pressure of 70mm absolute. The temperatures of the oil used in the initial sections of the wiped-film evaporator were maintained in the range from 360F. to 370F.
The coolant in the last or withdrawal section(s) of the wiped-film evaporator was hot condensate (steam) maintained at temperatures in the range from 250F. to 270F.
Processes for the production of ethyl acrylate by interacting acrylic acid with ethylene in the presence of sulfuric acid are well known;
see for example, U. S. Patent No. 3,703,539, issued November 21, 1972 to DiLiddo; U. S. Patent No. 3,539,621, issued November 10, 1970 to Cipollone et al; and U. S. Patent No. 3,834,076, issued July 8, 1975 to Van Duyne et al. As described in these and other references, the reaction -1- ~
,. .
~ 7 . .. ._ ..
is believed to involve first the formation of intermediate sulfates from the reaction of ethylene with sulfuric acid. These sulfates then react with acrylic acid to form ethyl acrylate. To provide a product in good overall yields with high carbon efficiencies, the unreacted ethylene, acrylic acid and the sulfuric acid residue must be recycled to the reactor.
The residence times of some of these reactants can be long enough to result in the formation of partially polymerized products which can plug the process equipment. Additionally, these processes operating on a continuous basis for extended periods of time, produce impurities in the reaction system which must be efficiently removed. The present invention provides an efficient method for the removal of such impurities by treating the sulfuric acid residue in a particular way while at the same time removing polymerization initiators from the reaction system.
In the chemical industry, it is common to ~se a wiped-film evaporator for processing highly viscous solutions and for vacuum evaporator.
Typical of the units that can be used and are known are the types described in a three part report in Chemical F.ngineering, September 13, 1965, pages 175-190, entitled "Agitated Thin-Film Evaporators". Modifications of these types of evaporators are described in the art for example, in U. S. Patent 3,292,683 entitled "Wiped Falling Film Evaporator" issued December 20, 1966 to Buchi et al; U. S. Patent 3,464,478 entitled "Horizontal-Type High Vacuum Film Evaporator For Highly Viscous Solutions" issued September 2, 1969 to Tomohane Veda et al; U. S. Patent 3,695,327 entitled "Wiped Thin Film Evaporation and Treatment Process" issued Octob~r 3, 1972 to Widmer; among others. This equipment is normally used to separate highly viscous materials from volatile material with the objective to separate the materials at the highest efficiencies in the least amount of time. Under these conditions, these evaporators are maintained at the highest possible temperatures for the most efficient periods of time. None of the processes and equipment known in the use of wiped-film evaporators area are known to evaporate and cool within the same unit. In the process of producing ethyl acrylate by the reaction of ethylene and acrylic acid in the presence of sulfuric acid, it is the technique of heating the initial stages of the evaporator and cooling the last or withdrawal section(s) which provides the highly efficient and desirable process of separating the highly viscous sulfuric acid residue from the volatile products such as ethyl acrylate and acrylic acid while maintaining foaming of the evaporating material at a workable and controllable minimum.
SUMMARY OF THE INVENTIQN
The process of the present invention involves the treatment of a minor portion of the sulfuric acid residue in a wiped-film evaporator operated under unusual conditions in the production of ethyl acrylate from ethylene and acrylic acid in the presence of sulfuric acid. For purposes of this invention ethyl acrylate is produced using the following steps:
(a) reacting ethylene and acrylic acid in the presence of sulfuric acid to form a reaction product;
(b) separating said reaction product into crude ethyl acrylate and a sulfuric acid residue;
(c) separating the light end materials from said crude ethyl acrylate and other reaction products to obtain a partially purified ethyl acrylate;
(d) separating and recovering a substantially pure ethyl acrylate from said partially purified ethyl acrylate leaving an ethyl acrylate product residue; and (e) recycling a major portion of the sulfuric acid residue of step ~b) to step (a).
In accordance with this invention, a minor portion of the sulfuric acid residue of step (b) is passed to a wiped-film evaporator which is heated in its initial sections so that the sulfuric acid residue reaches a temperature i583 in the range from about 300F. to about 360F., and cooled in its last or withdrawal section(s) to cool the sulfuric acid residue to a temperature in the range from about 230F. to about 280F. After cooling, the sulfuric acid residue is removed from the process.
Cooling the last or withdrawal section(s) of the wiped-film eva-porator substantially eliminates foaming of the spent sulfuric acid residue.
If the sulfuric acid residue is not cooled, foaming of the residue in the wiped-film evaporator can be sufficiently severe that the foam can back through the lines leading to the wiped-film evaporator from the recovery d~stillation tower and/or the finishing distillation tower, requiring shutdown of the process.
An additional feature of this invention involves passing at least about 50 weight percent of the ethyl acrylate product residue from the finishing distillation tower together with the minor portion of the sulfuric acid residue obtained from the recovery distillation tower through the wiped-film evaporator using the same conditions as described above. Ethyl acrylate product and acrylic acid reactant can be recovered from the treat-ment of the sulfuric acid residue and the ethyl acrylate product residue in the wiped-film evaporator. The remaining residues containing poly~eri-zation initiators and other impurities in the wiped-film evaporator are removed from the reaction system to ensure a smooth and extended continuous operation. This in combination with the other described improvements provides improved overall yields and efficiencies of the process of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a simplified schematic flow sheet exemplifying the preparation of ethyl acrylate from ethylene and anhydrous acrylic acid in the presence of substantially anhydrous sulfuric acid showing the use of a wiped-film evapor2tor for removal of a portion of the spent sulfuric acid ~6583 residue and at least about 50 weight percent of the ethyl acrylate product residue from the finishing distillation tower.
Figure 2 is a schematic representation of a wiped-f~lm evaporator which heats the feed of sulfuric acid residue on the init~al sections of the evaporator and cools the spent sulfuric acid residue at the last or withdrawal section(s).
DETAILED DESCRIPTION OF T~E INVENTION
The process of the present invention is schematically represented in Figure 1, in which a combination of substantially anhydrous sulfuric acid medium supplied through line 11 and ethylene supplied through line 12 is sprayed into reactor tower 10 and mixed. The sulfuric acid medium is comprised of sulfuric acid residue or bottoms from the product recovery distillation tower 13 along with make-up sulfuric aGid added through line 14. The sulfuric acid residue (sometimes referred to in the industry as "black acid") recovered from the recovery distillation tower 13 is a mixture of various compounds and contains sulfuric acid, intermediate sulfates from the reaction of ethylene and sulfuric acid, unreacted acrylic acid, some small amounts of ethyl acrylate, and various other compounds.
In the reactor tower 10, the main reaction of concern is the liquid phase reaction of the ethvlene enriched liquid with sulfuric acid to give the various intermediate sulfate salts, such as ethyl hydrogen sulfate and diethyl sulfate, which will then further react with acrylic acid, supplied through line 15, to Eorm ethyl acrylate. Adequate mixing of the reaction mixture in the reaction tower 10 can be obtained by mechanical stirringor recycle of the reaction products. (Neither mixing techniques are shown in the drawings). The reactants' residence time in the reactor tower 10 must be sufficient to obtain substantially (preferabl, at least a 90% completion) complete reaction of ethylene and acrylic acid. Tempera-tures in the reaction tower should be maintained within the range of about 1~4~583 .
100C. to about 150C., preferably 110C. to 130C. and the pressure should be maintained within the range of about 100 to about 300 psig, preferably 130 to 200 psig.
The reaction products from the reactor tower 10 is withdrawn through line 16 and passed through a pressure redurtion valve (not shown) and thence to the recovery distillation tower 7 3. The distillation section of the recovery distillation tower may be a conventional design, and may contain packing, sieve type trays or dual flow trays. ~he distillation section should contain an equivalent of at least four theoreticaly trays.
A vacuum is maintained in the recovery distillation tower 13 by conventional means so that the pressure is less than about 200mm of mercury absolute and preferably within the range of 20 to 150mm of mercury absolute. The still pot temperature should be maintained ~7itkin the range of about 100C.
to about 170C., preferably 110C. to 130C., and the still overhead temperature within the range of about 28C. to about 45C., preferably 30C. to 40C.
The feed line 17 to the recovery distillation tower 13 is directed preferably to the lower third and more preferably to the base of the tower.
In the recovery distillati^n tower 13, the light ends of crude ethyl acrylate comprising mainly of ethyl acrylate, small amounts of unreacted ethylene and other uncondensables, are removed overhead through line 18 and passed to the light ends distillation tower 19 (of conventional distillation design).
Rartially purified ethyl acrylate product is removed as ~ottoms through line 20. A stream comprising mainly unreacted ethylene is removed from the light ends distillation tower 19 through line 21 and may be disposed of or recycled (not shown) to the reactor tower 10 as desired, although if recycled a scrubbing to remove sulfur oxides is recommended. As pointed out above, operation according to the present invention generally results in a very small amount of unreacted ethylene such that the amounts of ethylene removed through line 21 will be relatively small. The partially purified ethyl 1~L46S83 acrylate product recovered through line 20 is further treated by fraction-ation in the finishing distillation tower 22 to obtain, through line 23, a substantially pure ethyl acrylate having a purity greater than 95 percent, preferably about ~9.9 percent or higher.
In operating the recovery distillation tower 13, the residence time of the reaction products in the base of the tower should be as low as possible because at temperatures required in the reboiler for vaporization some polymerization may occur. It is desirable to have a feed stream lean in acrylic acid being fed to the recovery distillation tower since it will result in less polymer formation.
The sulfuric acid residue or black acid stream referred to above containing sulfuric acid, intermediate sulfates, unreacted acrylic acid and the like is removed as bottoms residue from the recovery distillation tower 13 through line 24. A blowdown of a minor portion of the bottoms stream or sulfuric acid residue which is approximately 1 to 5 percent by weight of the total sulfuric acid residue is taken by means of line 25 so as to preven, the build up of impurities in the system. The remaining major portion of the sulfuric acid residue can be recycled through line 11 to the reactor tower 10 in combination with ethylene.
This portion of the sulfuric acid residue is passed through line 25 to a horizontal wiped-film evaporator 26 whlch heats the sulfuric acid residue to temperatures in the range from about 300F. to about 360F., and preferably 325F. to 350F. in the initial portion of the wiped-film evaporator 26. At the last Dr withdrawal sections of the wiped-film evaporator 26, the spent sulfuric acid residue is cooled to temperatures in the range from about 230F. to about 280F. and preferably 240F. to 270F. for removal from the system through line 27. During the treatment of the sulfuric acid residue and the ethyl acrylate product residue for the process of this invention, the wiped-film evaporator 26 is maintained under reduced pressure in the range from about 40 to about 150mm of mercury absolute and preferably in the range from about 50 to about xOmm of mercury absolute. Ethyl acrylate and acrylic acid can be recovered through line 28 from the wiped-film evaporator 26. The preferred procedure for ethyl acrylate and acrylic acid removed from the wiped-film evaporator is to recycle these products to the recovery distillation tower 13 for reprocessing.
(Not shown on the drawing).
In heating of the wiped-film evaporator so as to raise the temperature o the residue to a level, from about 300F. to about 360F., necessary to recover the available monomers or products from the sulfuric acid residue, excessive foaming in the evaporator unit caused by gas evolution associated with decomposition of the completely stripped residue can cause temporary shutdown of the entire system due to the backing up of the foam to line 25 from the recovery distillation tower 13 or into line 11 leading to the reaction tower 10 or to lines 30 and 29 back to the finishing distillation tower 22. Cooling of the last or withdrawal section(s) of the wiped-film evaporator 26 to provide a sulfuric acid residue having temperatures in the range from about 230F. to about 280F. substantially eliminates the foaming problem. This also results in an improvement in overall process efficiency and an increase in ethyl acrylate yields based on acrylic acid compared to the standard procedure of not cooling any part of the wiped-film evaporator.
Although not shown on the drawing, the addition of a polymerization inhibitor is generally desirable when producing or purifying ethyl acrylate.
Such inhibitors are well known and can be materials soluble in the reaction medium or soluble in the product obtained from the recovary distillation tower. Suitable polymerization inhibitors include hydroquinone, phenothiazine, the methyl ether of hydroquinone, quinone and the like. The polymerization inhlbitor can be introduced to the reaction vessel in the sulfuric acid residue or through any other convenient part of the system. It is required that the inhibitor be added to lines 18, 21 and 23. The inhibitor can be 13~46583 added in line 18 from whence it i5 carried through to the light ends dis-tillation towcr 19, then into the finishing distillation tower 22 and into the residue of the finishing distillation tower 22.
The ethyl acrylate product residue of the finishing distillation tower 22 containing the polymerization inhibitor is removed through line 29 and the ethyl acrylate product residue can be divided wherein at least 50 weight percent of the residue can be passed through line 31 into the wiped-film evaporator 26 for recovery of organic products such as ethyl acrylate and acrylic acid. The preferred process is to pass all of the ethyl acrylate product residue into the wiped-film evaporator 26. If only a portion of the ethyl acrylate product residue is passed into the wiped-film evaporator 26 the remaining portion can be passed through line 30 into line 17 which is combined with the reaction products passed into the recovery distillation tower 13 and firlally combined with the sulfuric acid residue to be recycled through line 24 back to the reactor tower 10. If all of the ethyl acrylate product residue from the finishing distillation tower is recycled to the recovery tower 13 d~rectly, the result can be a greater degree of fouling in the recovery distillation tower caused by black ~cid viscosity increase and a subsequent loss of product polymer. Passing the ethyl acrylate product residue from the finishing distillation tower to the wiped-film evaporator, an improvement in the overall process efficiency is achieved since the fouling of the recovery distillation tower is sub-stantially decreased with less polymer being formed.
The types of wiped-film evaporator which can be used in the process of the present invention can be a vertical or horizontal unit. For this invention, a horizontal unit is preferred. Typical of the units can be used and are known are the types described in a three part report in Chemical Engineering, September 13, 1965, pages 175-190, entitled "Agitated Thin-Film Evaporators". The one essential criterion of the wiped-film evaporator used in this process is the capability of cooling the latter 1~6i583 section of the evaporator to provide a residue having specif;c temperature ranges as described herein. N~rmally the use of a wiped-film evaporator is for separating and recovering the low boiling materials f.om the high boiling viscous materials using as much heat as possible over as much heating surface as possible to achieve and maintain high temperatures for fast and efficient separation. Under these conditions one would normally not consider cooling any portion of the treating surface of the ~.~iped-film evaporator. The unique problem of this invention in the treatment of the combination of the viscous sulfuric acid residue and the ethyl acrylate product residue is the foaming of the residue in the latter section(s) of the wiped-film evaporator on heating at temperatures in the range from about 300F. to about 360F. These temperatures are needed to effectively and efficiently separate ethyl acrylate and acrylic acid from the sulfuric acid residue. The foaming of the treated residue can be so severc that the foamed material can back up into the purification system requiring the shutdown of the process. This foaming can be substantially eliminated by cooling the last or withdrawal section(s) of the wiped-film evaporator' to temperatures in the range from about 230F. to about 280F. It is indeed a surprising result wherein a wiped-film evaporator is used efficiently by heating the initial sections of the unit and cooling the last or with-drawal sections of the unit.
Figure 2 is a schematic representation of the wiped-film evaporator 40 which can be used in the present invention. The sulfuric acid residue is fed through lines 41 to the evaporator 40 which contains various sections 42 through 47. Sections 42 through 45 can be heated by hot oil entering the jacket of section 42 through line 48 to heat the sulfuric acid residue to temperatures in the range from about 300F. to about 360F. and preferably in the range from about 325F. to about 350F. The oil can be remov2d from section 45 through line 49 for reuse. Sections 46 and 47 can be cooled by a coolant such as steam, water and the like entering through line 50 to s ~J: ~
~46~583 cool the sulfuric acid residue to temperatures in the range from about 230F.
to about 280F., preferably in the range from about 240F. to about 270F.
Care must be exercised that the coolant is not excessively cool to prevent thermal stressing resulting in metal fatigue and/or mechanical damage to the unit. The coolant can be removed through line 51 for reuse. The spent sulfuric acid residue can be removed from evaporator 40 and the system through line 52. The acrylic acid reactant and ethyl acrylate product can be recovered from line 53.
To illustrate the procesQ of this invention, referring to Figure 1, and using the conditions as described, 3055 pounds per hour of ethylene and 7850 pounds per hour of acrylic acid are added to the reactor tower 10 into which 92,967 pounds per hour of sulfuric acid medium is recycled with 879 pounds of anhydrous sulfuric acid makeup is added. From the recovery distillation tower 13, 14,199 pounds per hour of crude ethyl acrylate product are obtained overhead through line 18. From the bottom of the recovery distillation tower 13, 2789 pounds per hour of sulfuric acid residue are removed from the recycle sulfuric acid medium and passed through the wiped-film evaporator 26. l4,]99 pounds per hour of crude ethyl acrylate product is passed through line 18 to the light ends distillation tower 19.
157 pounds per hour of light ends are recovered in the ^verhead line 21 and 13,962 pounds per hour of partially purified ethyl acrylate product is passed through line 20 to the finishing distillation tower 22. 9380 pounds per hour of purified ethyl acrylate are recovered through line 23 and 4582 pounds per hour of ethyl acrylate product residuQ are recovered through line 29 and passed through line 31 to the wiped-film evaporator 26.
2789 pounds per hour of sulfuric acid residue and 4582 pounds of ethyl acrylate product residue are pas.sed through the wiped-film evaporator 26. 5158 pounds per hour of ethyl acrylate and 215 pounds per hour of acrylic acid are recovered through 28 from the wiped-film evaporator. The material removed from the wiped-film evaporator and the reaction system .
are 879 pounds per hour of sulfuric acid and 1099 pounds per hour of polymeric acrylates among other products.
The wiped-film evaporator was operated under reduced pressure of 70mm absolute. The temperatures of the oil used in the initial sections of the wiped-film evaporator were maintained in the range from 360F. to 370F.
The coolant in the last or withdrawal section(s) of the wiped-film evaporator was hot condensate (steam) maintained at temperatures in the range from 250F. to 270F.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for the production of ethyl acrylate compris-ing the steps of:
(a) reacting ethylene and acrylic acid in the presence to sulfuric acid to form a reaction product;
(b) separating said reaction product into crude ethyl acrylate and a sulfuric acid residue;
(c) separating the light end materials from said crude ethyl acrylate and other reaction products to obtain a plurality purified ethyl acrylate;
(d) separating and recovering a substantially pure ethyl acrylate from said partially purified ethyl acrylate leaving an ethyl acrylate product residue; and (e) recycling a major portion of said sulfuric acid residue from step (b) to step (a);
the improvement comprising passing a minor portion of said sulfuric acid residue from step (b) to a wiped-film evaporator which is heated in its initial section so that said sulfuric acid residue reaches a temperature in the range from about 300°F.
to about 360°F. and cooled in its withdrawal section to cool said sulfuric acid residue to a temperature in the range from about 230°F. to about 280°F. and removing said cooled sulfuric acid residue from the process.
(a) reacting ethylene and acrylic acid in the presence to sulfuric acid to form a reaction product;
(b) separating said reaction product into crude ethyl acrylate and a sulfuric acid residue;
(c) separating the light end materials from said crude ethyl acrylate and other reaction products to obtain a plurality purified ethyl acrylate;
(d) separating and recovering a substantially pure ethyl acrylate from said partially purified ethyl acrylate leaving an ethyl acrylate product residue; and (e) recycling a major portion of said sulfuric acid residue from step (b) to step (a);
the improvement comprising passing a minor portion of said sulfuric acid residue from step (b) to a wiped-film evaporator which is heated in its initial section so that said sulfuric acid residue reaches a temperature in the range from about 300°F.
to about 360°F. and cooled in its withdrawal section to cool said sulfuric acid residue to a temperature in the range from about 230°F. to about 280°F. and removing said cooled sulfuric acid residue from the process.
2. The process of claim 1 wherein the temperature of said sulfuric acid residue in the initial stages of said wiped-film evaporator is in the range from about 325°F. to about 350°F. and the temperature of said sulfuric acid in the last or withdrawal sections of said wiped-film evaporator is in the range from about 240°F. to about 275°F.
3. The process of claim 1 wherein at least about 50 weight percent of said ethyl acrylate product residue is passed to said wiped-film evaporator and the remainder of said ethyl acrylate product residue is recycled to the separation step (b).
4. The process of claim 1 wherein all of said ethyl acrylate product residue is passed to said wiped-film evaporator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000370145A CA1146583A (en) | 1981-02-05 | 1981-02-05 | Process for production of ethyl acrylate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000370145A CA1146583A (en) | 1981-02-05 | 1981-02-05 | Process for production of ethyl acrylate |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1146583A true CA1146583A (en) | 1983-05-17 |
Family
ID=4119088
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000370145A Expired CA1146583A (en) | 1981-02-05 | 1981-02-05 | Process for production of ethyl acrylate |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1146583A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108864420A (en) * | 2018-08-17 | 2018-11-23 | 沧州市骏驰伟业化工有限公司 | A kind of continuous esterification production equipment and process of allyl polyether |
-
1981
- 1981-02-05 CA CA000370145A patent/CA1146583A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108864420A (en) * | 2018-08-17 | 2018-11-23 | 沧州市骏驰伟业化工有限公司 | A kind of continuous esterification production equipment and process of allyl polyether |
| CN108864420B (en) * | 2018-08-17 | 2023-11-21 | 沧州骏驰新材料科技有限公司 | Continuous esterification production process of allyl polyether |
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