CA2015574C - Method for the preparation of methyl tertiary butyl ether - Google Patents
Method for the preparation of methyl tertiary butyl etherInfo
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- CA2015574C CA2015574C CA002015574A CA2015574A CA2015574C CA 2015574 C CA2015574 C CA 2015574C CA 002015574 A CA002015574 A CA 002015574A CA 2015574 A CA2015574 A CA 2015574A CA 2015574 C CA2015574 C CA 2015574C
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
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Abstract
A method and apparatus for conducting a catalytic distillation process is provided which allows for maintaining a liquid level in selected portions of the catalyst bed. Three particular processes disclosed are the production of methyl tertiary butyl ether, tertiary butyl alcohol and cumene. A
method for the production of methyl tertiary butyl ether by reaction of isobutene with methanol in a distillation reaction column is disclosed wherein a liquid level in maintained in the distillation reaction zone.
method for the production of methyl tertiary butyl ether by reaction of isobutene with methanol in a distillation reaction column is disclosed wherein a liquid level in maintained in the distillation reaction zone.
Description
- ~01 ~574 -8 Field of the Invention 9 The present invention relates to an improvement in the manner of conducting concurrent reactions and distillations 11 wherein the catalyst is also the distillation structure.
12 Related art 13 Recently a new method of carrying out catalytic reactions 14 has been developed, wherein the components of the reaction system are concurrently separable by distillation, using the catalyst 16 structures as the distillation structures. This method is now 17 generally known as catalytic distillation and any reference to 18 catalytic distillation herein will be taken to mean this method 19 or process. Such systems are described variously in U.S. Patents 4,215,011; 4,232,177; 4,242,530; 4,302,356; 4,307,254;
21 4,336,407; 4,439,350; 4,443,559; and 4,482,775 commonly assigned 22 herewith.
23 Briefly, a preferred and commercial catalyst structure 24 described in the above patents comprises a cloth belt with a plurality of pockets spaced along the belt and containing 26 particulate catalyst material, said cloth belt being wound in a .~ crl.pat~1176A.app ~. . . .........
- ~9~ i7~
~ helix about a spacing material such as stainless steel knitted 2 mesh. These units are then disposed in the distillation column 3 reactor. In addition, commonly assigned U.S. Patent Nos.
12 Related art 13 Recently a new method of carrying out catalytic reactions 14 has been developed, wherein the components of the reaction system are concurrently separable by distillation, using the catalyst 16 structures as the distillation structures. This method is now 17 generally known as catalytic distillation and any reference to 18 catalytic distillation herein will be taken to mean this method 19 or process. Such systems are described variously in U.S. Patents 4,215,011; 4,232,177; 4,242,530; 4,302,356; 4,307,254;
21 4,336,407; 4,439,350; 4,443,559; and 4,482,775 commonly assigned 22 herewith.
23 Briefly, a preferred and commercial catalyst structure 24 described in the above patents comprises a cloth belt with a plurality of pockets spaced along the belt and containing 26 particulate catalyst material, said cloth belt being wound in a .~ crl.pat~1176A.app ~. . . .........
- ~9~ i7~
~ helix about a spacing material such as stainless steel knitted 2 mesh. These units are then disposed in the distillation column 3 reactor. In addition, commonly assigned U.S. Patent Nos.
4 4,443,559 and 4,250,052 disclose a variety of catalyst structures for this use and are incorporated herein.
6 The success of catalytic distillation lies in an 7 understanding of the principles associated with distillation.
8 First, because the reaction is occurring concurrently with 9 distillation, the initial reaction product is removed from the reaction zone as quickly as it is formed. The removal of the 11 reaction product minimizes further reaction, decomposition, 12 polymerization and the like. Second, because in a distillation 13 the compounds are boiling, the temperature of the reaction is 14 controlled by the boiling point of the mixture at the system lS pressure. The heat of the reaction simply creates more boil up, 16 but no increase in temperature. Third, the reaction has an 17 increased driving force because the reaction products have been 18 removed and cannot contribute to a reverse reaction (Le 19 Chatelier's Principle).
The distillation parts of the above disclosures have been 21 conventional, i.e., counter-current vapor liquid flow in the 22 packed catalyst bed with the catalyst acting as the contact 23 structure, at least in the reaction zone. The reaction zone 24 having the catalyst packing is designated the reaction distillation zone to distinguish it from other distillation zones 26 which contain either inert packing or conventional distillation crl.pat\1176A.app 2 5~
~_ trays. The conventional distillation zones may be above or below 2 the distillation reaction zone according to the separation 3 desired.
4 In one particular embodiment for making methyl tertiary butyl ether, the physical embodiment of the distillation column 6 reactor includes a separate distillation zone below the 7 distillation reaction zone to insure that the unreacted feed 8 components are removed from the ether product which is taken off 9 as bottoms product. In at least one case the lower distillation zone is a separate distillation column connected to another 11 distillation column which contains the catalyst. Vapor and 12 liquid flow lines are provided so that essentially the two 13 columns act as one.
14 Because of the nature of the distillation the reactants and products are separated. Depending upon the components, however, 16 the reactants may be separated before the desired reaction is 17 completed requiring recycle. It was thus seen to be desirable to 18 retain the reactants in contact with the catalyst while still 19 separating out the products.
SUMMARY OF THE INVENTION
21 Briefly the present invention is the discovery that the 22 reaction rate can be increased by improving the contact of the 23 liquid with the catalyst, which is accomplished by increasing the 24 liquid level in the reaction distillation zone. This is achieved by a liquid flow restrictor between the distillation 26 reaction zone and the lower distillation zone. That is, the cr l . p~t\11 76A . app 3 57a~
r- vapor from below may rise up to (and through) the reaction 2 distillation zone as in a conventional or prior operation but a 3 portion of the liquid is maintained there. If a single 4 distillation column reactor is used, a conventional distillation tray with the downcomer area blocked is located between the 6 reaction distillation zone and the distillation zone. A by pass 7 line for liquid flow is provided about the tray and a valve is 8 provided in the liquid flow conduit to restrict liquid downflow 9 and thereby to build up a liquid level above that tray just below the catalyst bed. Alternatively a perforated plate may be used 11 to support the catalyst and cause a liquid pressure drop in the 12 column thus building up a level in the catalyst. If the two 13 column system is used, then a valve or other restriction means is 14 placed in the liquid flow line between the two columns.
While the particular position of the liquid level has been 16 described above to be at the lower end of the distillation 17 reaction zone, it could just as easily be placed anywhere in the 18 catalyst bed depending upon the desired reactions.
19 The term "liquid level" is used herein to mean an increased density of the material in the reaction distillation zone over 21 that of a pure distillation as distinguished to a continuous 22 liquid phase. The phase system as present in the reaction 23 distillation zone is physically a froth. This is the result of 24 the vapor traveling up through the liquid retained in the zone.
Another way of viewing this is that in normal distillation 26 there is a vapor with liquid (internal reflux) trickling down crl.p8t~1176~.8pp 4 1 through the vapor and contracting the catalyst whereas in the 2 present "flooded" system the vapor is traveling up through a 3 liquid phase to create the froth or foam.
4 Hence in essence the benefits of the distillation are still obtained, i.e., separating the various components by the 6 distillation whereas the increased liquid volume in contact with 7 the catalyst improves the synthesis reaction.
8 BRIE~ DESCRIPTION OF THE DRAWING
9 Fig. 1 is a flow diagram of one embodiment of the invention showing separate columns for the distillation and reaction 11 zones.
12 Fig. 2 is a plan view of the liquid flow restriction in a single 13 column.
14 Fig. 3 is top view of a perforated plate useful in the column of Fig. 2.
17 Referring now to the Fig.s a detailed description of the 18 preferred embodiments can be appreciated.
19 Fig. 1 shows a simple flow diagram of a process using the present invention. The particular process shown is for the 21 production of methyl tertiary butyl ether (MTBE) from the 22 reaction of methanol and isobutene in a mixed butene/butane feed 23 stream. For a detailed description of the process the reader is 24 referred to U.S. Patent 4,307,254. Generally there is shown a -first distillation column 1 which contains an acid cation ex-26 change resin packing 7 suitable cr l . pa t~11 76A . app 5 for the reaction. The acid cation exchange resin catal 2 suitably disposed in the column 1 as described in U.S. Patent 3 4,307,254 to act as both a catalyst and distillation structure.
4 The methanol and mixed butene/butane stream is fed to the first 5 column 1 into the catalyst 7 in a feed zone via flow lines 5 and 6 6. The methanol reacts with the isobutene in the catalyst bed or 7 reaction distillation zone to form MTBE. The unreacted 8 components of the mixed butene/butane stream are distilled off 9 overhead and recovered via flow line 8. At the same time the 10 MTBE product is distilled off toward the bottom since the 11 temperature of the catalyst (reaction distillation) zone is 12 maintained at the boiling of the reactants at the operating 13 pressure of the column, which is lower than the boiling point of 14 the MTBE.
The bottoms liquid product containing MTBE and some 16 dissolved unreacted methanol and C4 hydrocarbons is carried out 17 the bottom of the first column 1 via flow line 3 to the top of 18 second column 2 where the MTBE is more completely separated from 19 any dissolved methanol or C4's in a conventional distillation 20 column 2 having trays as shown or inert packing and recovered via 21 flow line 9. The unreacted materials are recovered overhead via 22 flow line 4 which carries them back as vapors to the bottom of 2 3 the first column 1. A level controller 10 is secured to the 24 first column l and senses a liquid level in the first column 25 (as by a differential pressure) and operates flow control valve 26 11 which acts as a liquid flow restriction between the two crl.pat\1176A.app 6 2~ S~
~Sr columns and maintains a desired preset liquid level in the 2 catalyst bed 7 of column 1. Note the level control 10 may be 3 positioned to detect the level over any portion of the column 1.
4 Pumps, compressors, and other operating equipment are not shown as they are conventional and readily selected by those of 6 ordinary skill in the art of distillation column design. Example 7 I shows a comparison of one such unit operated with and without 8 the liquid level in the catalyst bed.
9 Fig. 2 illustrates an arrangement which may be used if only one column is used. Only that portion of the column is 11 illustrated that is used to maintain the liquid level in the 12 catalyst bed.
13 In Fig. 2 the column 200 has a bed of catalyst 201 which 14 acts as a distillation structure. Directly below the catalyst bed 201 is shown a perforated plate 202 which supports the 16 catalyst bed 201. The plate 202 as indicated in Fig. 3 is 17 perforated to allow gas passage upward into the catalyst bed 201 18 yet provides a sufficient pressure drop to allow a liquid level 19 to build up above the plate in the bed 201. The plate is approximately 5-20 percent open space. A liquid bypass flow 21 line 203 is provided about the plate 202 to give added control of 22 the level. Valve 204 in bypass 203 may be opened or closed in 23 response to a differential pressure (indicating liquid level) to 24 control the liquid level. If desired the valve can be part of a control loop (not shown) responding to a liquid level controller.
26 Alternatively a standard distillation tray may be crl.pat\1176A.app 7 2~ 57~
~~ substituted for the perforated plate 202. The downcomer area of 2 the standard tray is blocked and the by pass flow line 203 used 3 to control the liquid level in the bed.
A commercial catalytic distillation process for the 6 production of MTBE was operated according to that disclosed in 7 U.S. Patent 4,307,254. Following an incident in which the 8 catalyst was partially deactivated, the operation was changed to 9 maintain the liquid level at the top of the catalyst zone. The arrangement was similar to that shown in Fig. 1. A control 11 valve acted as a restriction in the liquid flow line 3 to control 12 the liquid level which was sensed by a differential pressure in 13 the distillation reaction column 1. Unexpectedly, the 14 performance of the commercial unit with the damaged catalyst was almost equal to the unit with undamaged catalyst.
18 The method and structure have been found to be particularly 19 useful for conducting the catalytic distillation production of tertiary butyl alcohol (TBA) from the hydration of isobutylene.
21 In the TBA process a stream containing isobutylene is fed to the 22 column below the catalyst bed and water is fed above the 23 catalyst bed. The catalyst bed contains an acid cation exchange 24 resin as described in U.S. Patent 4,307,254 and is placed into the one inch laboratory column in the manner described therein.
26 Unreacted butylene, water and inerts (such as other C4's) are crl.pat\1176A.app 8 201 557~
-1 taken overhead and the TBA product is recovered as bottoms.
2 Water must be present in amounts sufficient to maintain the 3 catalyst in a hydrated state plus enough for the reaction and to 4 accommodate the water azeotropes in the system. One method of control is to measure the amount of water present in the TBA
6 fraction within the column and to maintain that amount above 7 zero but below the azeotropic concentration at the temperature 8 and pressure used.
9 ~ithout the liquid level, the catalyst performs satisfactorily at first but quickly loses its selectlvity due to ll loss of water despite the control technique outlined above. This 12 may be attributed to mass transfer and distribution problems 13 within the catalyst bed. It has been found that maintaining a 14 liquid level in the catalyst bed using the technique of Fig.s 2 and 3 maintains the wetted state of the catalyst and allows high 16 selectivity toward tertiary butyl alcohol production. Table I
17 below compares the results of the process with and without the 18 liquid level in the bed. The liquid level in the catalyst bed is 19 indicated by the high differential pressure across the bed. In the test runs, a 1" diameter tower was used ten feet in length.
21 Four feet of Rohm and Haas AMBE~L~ST* 15 catalyst was inserted 22 into the column in a pocketed belt twisted with wire mesh.
* Trademark f' ( '; cr l . pat~11 76A - ~ 9 2f)l 5574 1 _ TABLE I
4 Standard Process L i q u i d i n Catalyst Bed 6 Overhead pressure,psig 160 165 7 Feed Rates, ml/min.liq 8 C 4~S (42%IB) 5.0 5.0 9 H2O 0.68 0.78 Column Temp., ~F
11 Overhead 168 165 12 Cat. Zone 165 185 13 Bottoms 230 315 14 lDiff. Press. Across Cat. Zone 0.0 72 16 Bottoms analysis,wt.%
17 Lt. Ends (C4 + Cs) 46.9 5.3 18 TBA 18.0 93.7 19 DIB 35.1 1.0 21 1Differential pressure is measure as % change in pressure in 22 normal distillation pressure in catalyst zone and when totally 23 flooded with liquid in catalyst zone.
EXAMPLE III
26 In one other example the pilot plant was run as described 27 in commonly assigned U.S. Patent No. 4,849,569 issued July 18, 28 1989 using a 3" pilot plant column with Union Carbide LZY-82 29 molecular sieve in the pockets of the catalyst structure for the production of cumene form the alkylation of benzene with 31 propylene.- Again, the use of the liquid level as measured by the 32 differential pressure across the bed improved performance of the 33 catalyst and process. Table II below shows comparative data 34 between the normal operation and with the liquid level.
crl.pat\1176A.~pp 10 ~al 5574 .
5Standard Process L i q u i d i n 6 Catalyst Bed 7 Overhead Pressure, psig . 109 109 8 Differential across bed, psi 1.7 7.2 9 Feed rate, lb/hr Benzene 15.1 16.6 11 Propylene 12.1 13.1 12 Reaction Temp. ~F 336 340 13 Propylene conversion,% 73.7 91.0 14 While particular configurations have been shown, it should be understood that the liquid level may be maintained at any 16 location within the catalyst bed using the techniques disclosed 17 in either Fig. 2 or 3.
crl.pat\1176A.app 11
6 The success of catalytic distillation lies in an 7 understanding of the principles associated with distillation.
8 First, because the reaction is occurring concurrently with 9 distillation, the initial reaction product is removed from the reaction zone as quickly as it is formed. The removal of the 11 reaction product minimizes further reaction, decomposition, 12 polymerization and the like. Second, because in a distillation 13 the compounds are boiling, the temperature of the reaction is 14 controlled by the boiling point of the mixture at the system lS pressure. The heat of the reaction simply creates more boil up, 16 but no increase in temperature. Third, the reaction has an 17 increased driving force because the reaction products have been 18 removed and cannot contribute to a reverse reaction (Le 19 Chatelier's Principle).
The distillation parts of the above disclosures have been 21 conventional, i.e., counter-current vapor liquid flow in the 22 packed catalyst bed with the catalyst acting as the contact 23 structure, at least in the reaction zone. The reaction zone 24 having the catalyst packing is designated the reaction distillation zone to distinguish it from other distillation zones 26 which contain either inert packing or conventional distillation crl.pat\1176A.app 2 5~
~_ trays. The conventional distillation zones may be above or below 2 the distillation reaction zone according to the separation 3 desired.
4 In one particular embodiment for making methyl tertiary butyl ether, the physical embodiment of the distillation column 6 reactor includes a separate distillation zone below the 7 distillation reaction zone to insure that the unreacted feed 8 components are removed from the ether product which is taken off 9 as bottoms product. In at least one case the lower distillation zone is a separate distillation column connected to another 11 distillation column which contains the catalyst. Vapor and 12 liquid flow lines are provided so that essentially the two 13 columns act as one.
14 Because of the nature of the distillation the reactants and products are separated. Depending upon the components, however, 16 the reactants may be separated before the desired reaction is 17 completed requiring recycle. It was thus seen to be desirable to 18 retain the reactants in contact with the catalyst while still 19 separating out the products.
SUMMARY OF THE INVENTION
21 Briefly the present invention is the discovery that the 22 reaction rate can be increased by improving the contact of the 23 liquid with the catalyst, which is accomplished by increasing the 24 liquid level in the reaction distillation zone. This is achieved by a liquid flow restrictor between the distillation 26 reaction zone and the lower distillation zone. That is, the cr l . p~t\11 76A . app 3 57a~
r- vapor from below may rise up to (and through) the reaction 2 distillation zone as in a conventional or prior operation but a 3 portion of the liquid is maintained there. If a single 4 distillation column reactor is used, a conventional distillation tray with the downcomer area blocked is located between the 6 reaction distillation zone and the distillation zone. A by pass 7 line for liquid flow is provided about the tray and a valve is 8 provided in the liquid flow conduit to restrict liquid downflow 9 and thereby to build up a liquid level above that tray just below the catalyst bed. Alternatively a perforated plate may be used 11 to support the catalyst and cause a liquid pressure drop in the 12 column thus building up a level in the catalyst. If the two 13 column system is used, then a valve or other restriction means is 14 placed in the liquid flow line between the two columns.
While the particular position of the liquid level has been 16 described above to be at the lower end of the distillation 17 reaction zone, it could just as easily be placed anywhere in the 18 catalyst bed depending upon the desired reactions.
19 The term "liquid level" is used herein to mean an increased density of the material in the reaction distillation zone over 21 that of a pure distillation as distinguished to a continuous 22 liquid phase. The phase system as present in the reaction 23 distillation zone is physically a froth. This is the result of 24 the vapor traveling up through the liquid retained in the zone.
Another way of viewing this is that in normal distillation 26 there is a vapor with liquid (internal reflux) trickling down crl.p8t~1176~.8pp 4 1 through the vapor and contracting the catalyst whereas in the 2 present "flooded" system the vapor is traveling up through a 3 liquid phase to create the froth or foam.
4 Hence in essence the benefits of the distillation are still obtained, i.e., separating the various components by the 6 distillation whereas the increased liquid volume in contact with 7 the catalyst improves the synthesis reaction.
8 BRIE~ DESCRIPTION OF THE DRAWING
9 Fig. 1 is a flow diagram of one embodiment of the invention showing separate columns for the distillation and reaction 11 zones.
12 Fig. 2 is a plan view of the liquid flow restriction in a single 13 column.
14 Fig. 3 is top view of a perforated plate useful in the column of Fig. 2.
17 Referring now to the Fig.s a detailed description of the 18 preferred embodiments can be appreciated.
19 Fig. 1 shows a simple flow diagram of a process using the present invention. The particular process shown is for the 21 production of methyl tertiary butyl ether (MTBE) from the 22 reaction of methanol and isobutene in a mixed butene/butane feed 23 stream. For a detailed description of the process the reader is 24 referred to U.S. Patent 4,307,254. Generally there is shown a -first distillation column 1 which contains an acid cation ex-26 change resin packing 7 suitable cr l . pa t~11 76A . app 5 for the reaction. The acid cation exchange resin catal 2 suitably disposed in the column 1 as described in U.S. Patent 3 4,307,254 to act as both a catalyst and distillation structure.
4 The methanol and mixed butene/butane stream is fed to the first 5 column 1 into the catalyst 7 in a feed zone via flow lines 5 and 6 6. The methanol reacts with the isobutene in the catalyst bed or 7 reaction distillation zone to form MTBE. The unreacted 8 components of the mixed butene/butane stream are distilled off 9 overhead and recovered via flow line 8. At the same time the 10 MTBE product is distilled off toward the bottom since the 11 temperature of the catalyst (reaction distillation) zone is 12 maintained at the boiling of the reactants at the operating 13 pressure of the column, which is lower than the boiling point of 14 the MTBE.
The bottoms liquid product containing MTBE and some 16 dissolved unreacted methanol and C4 hydrocarbons is carried out 17 the bottom of the first column 1 via flow line 3 to the top of 18 second column 2 where the MTBE is more completely separated from 19 any dissolved methanol or C4's in a conventional distillation 20 column 2 having trays as shown or inert packing and recovered via 21 flow line 9. The unreacted materials are recovered overhead via 22 flow line 4 which carries them back as vapors to the bottom of 2 3 the first column 1. A level controller 10 is secured to the 24 first column l and senses a liquid level in the first column 25 (as by a differential pressure) and operates flow control valve 26 11 which acts as a liquid flow restriction between the two crl.pat\1176A.app 6 2~ S~
~Sr columns and maintains a desired preset liquid level in the 2 catalyst bed 7 of column 1. Note the level control 10 may be 3 positioned to detect the level over any portion of the column 1.
4 Pumps, compressors, and other operating equipment are not shown as they are conventional and readily selected by those of 6 ordinary skill in the art of distillation column design. Example 7 I shows a comparison of one such unit operated with and without 8 the liquid level in the catalyst bed.
9 Fig. 2 illustrates an arrangement which may be used if only one column is used. Only that portion of the column is 11 illustrated that is used to maintain the liquid level in the 12 catalyst bed.
13 In Fig. 2 the column 200 has a bed of catalyst 201 which 14 acts as a distillation structure. Directly below the catalyst bed 201 is shown a perforated plate 202 which supports the 16 catalyst bed 201. The plate 202 as indicated in Fig. 3 is 17 perforated to allow gas passage upward into the catalyst bed 201 18 yet provides a sufficient pressure drop to allow a liquid level 19 to build up above the plate in the bed 201. The plate is approximately 5-20 percent open space. A liquid bypass flow 21 line 203 is provided about the plate 202 to give added control of 22 the level. Valve 204 in bypass 203 may be opened or closed in 23 response to a differential pressure (indicating liquid level) to 24 control the liquid level. If desired the valve can be part of a control loop (not shown) responding to a liquid level controller.
26 Alternatively a standard distillation tray may be crl.pat\1176A.app 7 2~ 57~
~~ substituted for the perforated plate 202. The downcomer area of 2 the standard tray is blocked and the by pass flow line 203 used 3 to control the liquid level in the bed.
A commercial catalytic distillation process for the 6 production of MTBE was operated according to that disclosed in 7 U.S. Patent 4,307,254. Following an incident in which the 8 catalyst was partially deactivated, the operation was changed to 9 maintain the liquid level at the top of the catalyst zone. The arrangement was similar to that shown in Fig. 1. A control 11 valve acted as a restriction in the liquid flow line 3 to control 12 the liquid level which was sensed by a differential pressure in 13 the distillation reaction column 1. Unexpectedly, the 14 performance of the commercial unit with the damaged catalyst was almost equal to the unit with undamaged catalyst.
18 The method and structure have been found to be particularly 19 useful for conducting the catalytic distillation production of tertiary butyl alcohol (TBA) from the hydration of isobutylene.
21 In the TBA process a stream containing isobutylene is fed to the 22 column below the catalyst bed and water is fed above the 23 catalyst bed. The catalyst bed contains an acid cation exchange 24 resin as described in U.S. Patent 4,307,254 and is placed into the one inch laboratory column in the manner described therein.
26 Unreacted butylene, water and inerts (such as other C4's) are crl.pat\1176A.app 8 201 557~
-1 taken overhead and the TBA product is recovered as bottoms.
2 Water must be present in amounts sufficient to maintain the 3 catalyst in a hydrated state plus enough for the reaction and to 4 accommodate the water azeotropes in the system. One method of control is to measure the amount of water present in the TBA
6 fraction within the column and to maintain that amount above 7 zero but below the azeotropic concentration at the temperature 8 and pressure used.
9 ~ithout the liquid level, the catalyst performs satisfactorily at first but quickly loses its selectlvity due to ll loss of water despite the control technique outlined above. This 12 may be attributed to mass transfer and distribution problems 13 within the catalyst bed. It has been found that maintaining a 14 liquid level in the catalyst bed using the technique of Fig.s 2 and 3 maintains the wetted state of the catalyst and allows high 16 selectivity toward tertiary butyl alcohol production. Table I
17 below compares the results of the process with and without the 18 liquid level in the bed. The liquid level in the catalyst bed is 19 indicated by the high differential pressure across the bed. In the test runs, a 1" diameter tower was used ten feet in length.
21 Four feet of Rohm and Haas AMBE~L~ST* 15 catalyst was inserted 22 into the column in a pocketed belt twisted with wire mesh.
* Trademark f' ( '; cr l . pat~11 76A - ~ 9 2f)l 5574 1 _ TABLE I
4 Standard Process L i q u i d i n Catalyst Bed 6 Overhead pressure,psig 160 165 7 Feed Rates, ml/min.liq 8 C 4~S (42%IB) 5.0 5.0 9 H2O 0.68 0.78 Column Temp., ~F
11 Overhead 168 165 12 Cat. Zone 165 185 13 Bottoms 230 315 14 lDiff. Press. Across Cat. Zone 0.0 72 16 Bottoms analysis,wt.%
17 Lt. Ends (C4 + Cs) 46.9 5.3 18 TBA 18.0 93.7 19 DIB 35.1 1.0 21 1Differential pressure is measure as % change in pressure in 22 normal distillation pressure in catalyst zone and when totally 23 flooded with liquid in catalyst zone.
EXAMPLE III
26 In one other example the pilot plant was run as described 27 in commonly assigned U.S. Patent No. 4,849,569 issued July 18, 28 1989 using a 3" pilot plant column with Union Carbide LZY-82 29 molecular sieve in the pockets of the catalyst structure for the production of cumene form the alkylation of benzene with 31 propylene.- Again, the use of the liquid level as measured by the 32 differential pressure across the bed improved performance of the 33 catalyst and process. Table II below shows comparative data 34 between the normal operation and with the liquid level.
crl.pat\1176A.~pp 10 ~al 5574 .
5Standard Process L i q u i d i n 6 Catalyst Bed 7 Overhead Pressure, psig . 109 109 8 Differential across bed, psi 1.7 7.2 9 Feed rate, lb/hr Benzene 15.1 16.6 11 Propylene 12.1 13.1 12 Reaction Temp. ~F 336 340 13 Propylene conversion,% 73.7 91.0 14 While particular configurations have been shown, it should be understood that the liquid level may be maintained at any 16 location within the catalyst bed using the techniques disclosed 17 in either Fig. 2 or 3.
crl.pat\1176A.app 11
Claims (16)
1. A method of preparing methyl tertiary butyl ether comprising:
(a) feeding (1) a mixture containing isobutene and normal butene and (2) methanol to a distillation column reactor into a feed zone, (b) concurrently in said distillation column reactor:
(1) contacting said mixture and said methanol with a fixed bed acid cation exchange resin packing in a distillation reaction zone thereby catalytically reacting the isobutene with methanol to form methyl tertiary butyl ether and (2) fractionating the resulting mixture of ether and unreacted isobutene and normal butene while maintaining a liquid level in said fixed bed acid cation exchange resin packing, (c) withdrawing the ether from the distillation column reactor at a point below said feed zone and (d) withdrawing the unreacted isobutene and normal butene from the distillation column reactor at a point above said feed zone.
(a) feeding (1) a mixture containing isobutene and normal butene and (2) methanol to a distillation column reactor into a feed zone, (b) concurrently in said distillation column reactor:
(1) contacting said mixture and said methanol with a fixed bed acid cation exchange resin packing in a distillation reaction zone thereby catalytically reacting the isobutene with methanol to form methyl tertiary butyl ether and (2) fractionating the resulting mixture of ether and unreacted isobutene and normal butene while maintaining a liquid level in said fixed bed acid cation exchange resin packing, (c) withdrawing the ether from the distillation column reactor at a point below said feed zone and (d) withdrawing the unreacted isobutene and normal butene from the distillation column reactor at a point above said feed zone.
2. The method according to claim 1 wherein the temperature of said column is the boiling point of the mixture and said methanol under the pressure in said column.
3. The method according to claim 2 wherein said reacting and fractionating are carried out at a pressure in the range of 10 to 300 psig.
4. The method according to claim 1 wherein isobutene is removed from the mixture in said process thereby producing an overhead having a substantially reduced amount of isobutene therein.
5. The process according to claim 1 wherein said methyl tertiary butyl ether is recovered.
6. The method according to claim 1 wherein the feed into the distillation column reactor contains less than 1 mole % water.
7. The method according to claim 1 wherein said feed zone is at the lower end of said fixed bed acid cation exchange resin packing.
8. The method according to claim 1 wherein any unreacted isobutene and unreacted methanol dissolved in the ether product is separated in a distillation zone below said distillation reaction zone thereby distilling said unreacted isobutene and unreacted methanol back up into said distillation reaction zone.
9. The method according to claim 8 wherein essentially all of said isobutene and methanol is reacted to form methyl tertiary butyl ether producing an overhead stream containing essentially pure normal butene and a bottoms stream containing essentially pure methyl tertiary butyl ether.
10. In a process for the simultaneous catalytic reaction of reactants and fractional distillation of the reaction products and/or reactants in a distillation reaction column having a fixed bed of catalyst which acts as a distillation structure, the improvement comprising maintaining a liquid level in selected portions of the catalyst bed.
11. A method for operating a catalytic distillation process, comprising the steps of:
(a) introducing reactants into a feed zone of a distillation reaction column having a reaction distillation zone;
(b) simultaneously in said reaction distillation zone (1) reacting at least a portion of the reactants to form reaction products, and (2) separating the reaction products and/or reactants by fractional distillation;
and (c) restricting the downward flow of internal reflux at selected points in said reaction distillation zone to maintain a liquid level above the restriction for additional contact and reaction of the liquid and distillation vapors.
(a) introducing reactants into a feed zone of a distillation reaction column having a reaction distillation zone;
(b) simultaneously in said reaction distillation zone (1) reacting at least a portion of the reactants to form reaction products, and (2) separating the reaction products and/or reactants by fractional distillation;
and (c) restricting the downward flow of internal reflux at selected points in said reaction distillation zone to maintain a liquid level above the restriction for additional contact and reaction of the liquid and distillation vapors.
12. An apparatus for conducting a catalytic distillation process, comprising:
(a) a first distillation column containing catalyst which acts as a distillation structure and defines a reaction distillation zone:
(b) a second distillation column containing conventional inert distillation packing or trays;
(c) a first flow line connecting the lower end of said first distillation column to the top of said second distillation column to carry liquid bottoms from said first distillation column to the top of said second distillation column;
(d) a second flow line connecting the top of said second distillation column to the bottom of said first distillation column to carry vapor overheads from said second distillation column to the bottom of said first distillation column; and (e) a restriction means in said first flow line to maintain a desired liquid level in said distillation reaction zone when said first and second distillation columns are operating at equilibrium.
(a) a first distillation column containing catalyst which acts as a distillation structure and defines a reaction distillation zone:
(b) a second distillation column containing conventional inert distillation packing or trays;
(c) a first flow line connecting the lower end of said first distillation column to the top of said second distillation column to carry liquid bottoms from said first distillation column to the top of said second distillation column;
(d) a second flow line connecting the top of said second distillation column to the bottom of said first distillation column to carry vapor overheads from said second distillation column to the bottom of said first distillation column; and (e) a restriction means in said first flow line to maintain a desired liquid level in said distillation reaction zone when said first and second distillation columns are operating at equilibrium.
13. The apparatus of claim 12 further comprising a liquid level sensing/control means fitted to said first distillation column and wherein said restriction means comprises a flow control valve which operates in response to said liquid level sensing/control means.
14. An apparatus for conducting a catalytic distillation process, comprising:
(a) a distillation column reactor containing conventional inert distillation packing or trays defining a distillation zone, and a packing of catalyst above said distillation zone which acts as a distillation structure defining a reaction distillation zone; and (b) liquid flow restriction means between said distillation zone and said reaction distillation zone to maintain a desired liquid level within said reaction distillation zone when said distillation column reactor is operating at equilibrium.
(a) a distillation column reactor containing conventional inert distillation packing or trays defining a distillation zone, and a packing of catalyst above said distillation zone which acts as a distillation structure defining a reaction distillation zone; and (b) liquid flow restriction means between said distillation zone and said reaction distillation zone to maintain a desired liquid level within said reaction distillation zone when said distillation column reactor is operating at equilibrium.
15. The apparatus of claim 14 wherein said restriction means comprises a perforated plate within or below said distillation reaction zone.
16. The apparatus of claim 14 further comprising a liquid by pass line about said liquid flow restriction means and a control valve in said by pass line to control the liquid level above said plate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002015574A CA2015574C (en) | 1989-03-23 | 1990-04-11 | Method for the preparation of methyl tertiary butyl ether |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US32848789A | 1989-03-23 | 1989-03-23 | |
| CA002015574A CA2015574C (en) | 1989-03-23 | 1990-04-11 | Method for the preparation of methyl tertiary butyl ether |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2015574A1 CA2015574A1 (en) | 1991-10-11 |
| CA2015574C true CA2015574C (en) | 1998-09-29 |
Family
ID=25674102
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002015574A Expired - Fee Related CA2015574C (en) | 1989-03-23 | 1990-04-11 | Method for the preparation of methyl tertiary butyl ether |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2015574C (en) |
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1990
- 1990-04-11 CA CA002015574A patent/CA2015574C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2015574A1 (en) | 1991-10-11 |
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