FI95024B - Method and apparatus for preparing tertiary alkyl ethers - Google Patents

Abstract

The invention relates to a process and an apparatus for preparing tertiary alkyl ethers in a catalytic distillation reactor system comprising a distillation column and at least one first reaction zone connected thereto and containing a catalyst which is comprised of cation exchange resin. According to the process, the C5 to C8 isoolefines contained in the hydrocarbon feedstock are reacted with lower alkanols in order to produce the corresponding ethers within said reaction zone, and the ether product is removed from the bottom of the column. According to the invention a side draw is taken from the lower part of the column and conducted to a separator where the side draw is divided into a low-boiling fraction and a high-boiling fraction. At least a part of the high-boiling fraction is returned to the column and at least a part of the low-boiling fraction is conducted to at least one second reaction zone where it is subjected to an etherification reaction in the presence of a catalyst, after which it is returned to the distillation column. The invention can be used to increase the conversion of the hydrocarbon feed components, in the preparation of TAME that of 2-methyl-2-butene (2M2B) in particular.

Description

95024

Method and apparatus for preparing tertiary alkyl ethers

The present invention relates to a process according to the preamble of claim 1 for the preparation of tertiary alkyl ethers in a catalytic distillation reactor system.

According to such a process, the C5-C8 iso-olefins of the hydrocarbon feedstock are reacted with lower alkanols to produce the corresponding ethers in a reaction zone containing a catalyst consisting of a cation exchange resin.

10

The invention also relates to an apparatus according to the preamble of claim 10 for the preparation of tertiary alkyl ethers. The apparatus typically comprises a distillation column and an associated at least one first reaction zone containing a cation exchange resin catalyst.

15

Our previous applications 921173 and 921174 describe various process solutions for the preparation of tertiary alkyl ethers, especially tertiary methylamylene ether (TAME) and heavier ethers, in a catalytic distillation reactor system. Usually the system consists of a distillation column inside which one or more reaction beds are arranged, or a distillation column and at least one separate reactor (= side reactor) to which a side effluent from the column is fed. The reaction bed can also be traced inside the distillation column so that it can be operated like a side reactor. The above reaction bed (regardless of its location) is hereinafter referred to as the "first reaction zone".

25

In prior art processes, the controllability of the reaction conditions is good. In the side reactor solution, the side reactor can be operated under different conditions than the distillation,. the temperature and pressure of the first reaction zone can be adjusted to the optimum for the reaction. Furthermore, by means of the prior art, the reactive distillation column system can be operated in such a way that, in the preparation of methyl ethers, all the reacted methanol is removed as an azeotrope, so that a separate methanol wash is not required.

2 95024

Although the conversion of 2-methyl-1-butene (2M2B) in the prior art processes is quite good, the conversion of 2-methyl-2-butene (2M2B) remains moderately poor for industrial applications. This is due in part to the difference in boiling point (about 7 ° C) between the 2M2B and 2MlB starting materials of TAME. It is difficult to keep components with different boiling points at the same point in the distillation column. This difficulty is further exacerbated by the different equilibrium conversions and reaction rates of the starting materials. The equilibrium conversion of 2MlB is about 90% and that of 2M2B is only 50-60% under the best reaction conditions. Reaction rate differences are of the same order as conversion differences.

It is an object of the present invention to obviate the drawbacks of the prior art and to provide a novel method and apparatus for the preparation of tertiary alkyl ethers.

The invention is based on the idea that the conversion of 2-methyl-2-butene (2M2B) is increased by connecting a side concentration unit to the etherification process and apparatus described above. Such a unit preferably comprises a separation device to which a side stream can be passed from the bottom of the distillation column, by means of which the side stream can be divided into a light fraction and a heavy fraction, and a reactor to which the light fraction of the separation device can be fed and reacted again in the presence of a catalyst.

More specifically, the method according to the invention is mainly characterized by what is set forth in the characterizing part of claim 1.

The apparatus according to the invention, in turn, is characterized by what is set forth in the characterizing part of claim 10.

! In the process according to the invention, the side stream fed to the side concentrator system is taken from the "bottom" of the column. This term refers to the point located between the bottom of the column and the lowest first reaction zone.

30

According to the invention, the side outlet is passed to a separation device, in which the side outlet is divided into a low-boiling fraction (light fraction) and a high-boiling fraction (heavy fraction).

3,95024

At least a portion of the high boiling fraction is returned to the column, and at least a portion of the low boiling fraction is passed to at least one second reaction zone where it is subjected to an etherification reaction in the presence of a catalyst, after which it is returned to the distillation column. Preferably, the side effluent is divided into said two fractions by distillation, wherein the fraction to be passed to the second reaction zone comprises the distillation excess. Preferably, the excess is condensed and mixed with the alkanol used in the etherification reaction to form a reaction mixture, after which said mixture is passed to a second reaction zone. Part of the product of the reaction zone is returned to distillation and part of the condensed excess is returned to distillation before the addition of the alkanol.

10

According to the invention, the catalysts of the first and second reaction zones preferably consist, in principle, of cation exchange resins generally used in etherification reactions. The catalysts used in the reaction zones may be the same or different, in which case the type of catalyst can be precisely selected. hydrocarbon of the reaction-15 zone suitable for feed.

According to a preferred embodiment of the invention, the present side concentration unit solution is combined with a reactive distillation column system having at least one side reactor connected to a main column for product separation. In such a side reactor-distillation column system, both the starting materials (2MlB very little and • 2M2B a little more, as well as some alkanol (e.g. methanol)) and the product (tertiary ether) flow in the column between the side reactor return point and the bottom of the main column. , such as TAME).

In order to react the remaining starting materials more completely, at least one reactor is required through which the unreacted components can be passed. However, the main column: the bottom product cannot be passed directly through the reactor because 1) the reaction requires more alkanol (e.g. methanol) which remains in the product due to the equilibrium reaction, and 2) a large amount of tertiary alkyl ether (e.g. TAME) reacts back to the starting material. , which degrades overall conversion. In other words, methanol must not remain in the base product, in which case it must be distilled off, and TAME must not enter the reactor because it reacts backwards. For the above reasons, a side concentrating unit system according to the present invention has been developed. A separation device, such as a distillation column, separates the product, i.e., e.g., TAME and other heavier hydrocarbons, from the side stream taken from the distillation column before it is passed to a new reactor, hereinafter referred to as a side concentration reactor. The heavy hydrocarbons are returned to the distillation column as a by-product of the separation device 5. Since the etherification reaction is an equilibrium reaction, unreacted methanol remains in the product of the side concentration reactor. The reactor product is therefore returned to the main column, which distills the methanol away from the bottom product.

The stream passed through the side concentrator reactor can be returned to the column as a whole, but can also be divided into side streams, some of which are returned to the separator, some connected to the separator bottom product, part connected to the distillation column bottom product and / or

If necessary, an alkanol is added to the side stream passing through the side concentration reactor, e.g.

methanol. More alkanol is often needed because its conversion in a reactive distillation column system is up to 99%. In the production of TAME, the required additional methanol can be fed to other addition sites in the distillation reactor system (e.g., a side reactor) because methanol is the lightest component in the side concentration column due to the C5 methanol azeotrope. In the manufacture of TAME, C4 is missing from this part of the process.

• The separation device of the side concentrator unit preferably consists of a conventional distillation column (e.g. a valve, bell or screen bottom column or packing column) and a side concentrator reactor through-flow reactor. The circulation between the column and the reactor can be effected either by forced circulation by means of a pump or by the thermosiphon principle, whereby the heat of reaction boils the liquid, causing this phenomenon. If circulation is forced, the reactor may be of the solid bed, tube or fluidized bed reactor type or any combination thereof, or more than one reactor in series. In a thermosiphon system, only a fixed bed or tubular reactor can be considered.

With regard to the equipment used in the side concentration unit and its operation, reference is made to the description of the distillation column and side reactors given in our FI patent application 921173.

The solution of the invention can be used to prepare TAME and heavier ether products such as tert-amylethyl ether (TAEE) and rerr-hexyl methyl ether (THME). Preferably, the invention is used for the preparation of TAME, the latter methyl ether being formed as a by-product of the preparation.

The present invention provides the advantage that the conversion of TAME and heavier ethers is significantly increased. Based on the results presented in the examples, conversion 10 is improved by TAME to at least 91.0% (increase of 4.1%) and by THME to 49.2% (increase of 3.1%). By optimizing the process, even better conversions are achieved.

The invention will now be described in more detail by means of a detailed description and a few application examples. Of the accompanying drawings 15, Figure 1 shows a process diagram of a first preferred embodiment of the invention, Figure 2 shows a process diagram of a second preferred embodiment of the invention, and Figure 3 shows a process diagram of a third preferred embodiment of the invention.

In the experimental arrangement according to Figure 1 for the production of TAME, a hydrocarbon starting material containing e.g. 2MBB, 2M2B and other C5 hydrocarbons as well as C6 and C6 + hydrocarbons, and the methanol is mixed together, the mixture is heated and passed through the pre-reactor 1. The pre-reactors consist of a reactor filled with an ion exchange resin layer. The type of reactor can be a fixed bed, fluidized bed or tubular reactor. Instead of 25 reactors, two or more reactors can be used, which can be sequenced in series or in parallel. If there are more than two pre-reactors, they can also be arranged in series / in parallel. Due to the reaction, the temperature in the pre-reactor rises by about 5-15 ° C depending on the efficiency of the thermal insulation of the reactor. From the pre-reactor, the mixture is passed to distillation column 1. At the bottom of the distillation column is a steam-heated boiler 10. The distillation column 30 may be of the packing column type or a valve, screen or clock bottom column. From the top of the column, the distillate is taken and passed through the condenser 3 to the condensate tank 4, part of which is passed on for further processing, e.g. the MTBE process, and part is returned to the 6 95024 column. The recovery ratio in the column is preferably about xh to 600. Factory scale columns typically use a recovery ratio of about 50 to 150. In pilot equipment, even larger relationships come into play. Adjacent to the distillation column 3 is a side reactor system, which in this case, for simplicity, is marked with one reactor 5. Depending on the type of recycling, the reactor may be a fixed or fluidized bed reactor or a tubular reactor, as stated in the general description. A liquid stream is drawn from the column into the side reactor, the pressure of which is raised before the reactor. Methanol is added to the side reactor feed if necessary and, if necessary, cooled to the reaction temperature. The temperature in the side reactor rises by only a few degrees. The flow from the side reactor system 10 is directed back to the column 2. In the case of Example 1, the feed is fed to the column below the feed from the pre-reactor 1 so that the ether products are distilled off from the feed of the side reactor system 5.

Connected to the lower part of the column 2 is a side concentration column 6, to which the feed is taken from the main warp 2 2 below the return point of the side reactor 5. The supply can be gas or liquids. If it is gas, the side concentration column 6 does not necessarily need its own boiler, because the gas stream required for distillation already enters the side concentration column 6 with the feed.

If it is a liquid, then the side concentration column 6 needs its own boiler. If the side-lightening column 6 has its own boiler, the feed can be brought elsewhere than to the bottom.

The side concentration column 6 has the necessary number of bottoms (or equivalent separation steps) to divide the side stream fed to it into two fractions, in the lighter fraction of which the number of ethers is substantially reduced relative to the feed of the side concentration column 6. The transition gases from the side concentration column 6 are condensed in the condenser 7 and collected in the transition tank 8. The liquid obtained is partly pumped back to the column 6 and partly to the reactor 9. If necessary, methanol can be added to the stream to the reactor 9.

The reactor 9 may also be located at the location shown in Figure 2 immediately after the transition tank 8 before separating the distillate and the recovery of the column 6 from each other.

In the embodiment of the invention according to Figure 3, the side concentration column 6 is operated as described in our application FI 921174. In this case, a distillate is taken from column 6, which contains mainly only a mixture of C4 hydrocarbons and methanol as an azeotrope. In this case, the feed to the reactor 7 is not taken from the top of the column 6, i.e. the distillate, but at a suitable point between the feed and the top of the column 6, because significant amounts of C5 hydrocarbons are not desired at the top of the column 6. If necessary, methanol is added to the feed of the reactor 9 and it is then passed through the reactor 9. The reactor product obtained from the reactor 9 is returned to the main column 5 2 in the same manner as in the ice arrangement according to Figures 1 and 2.

Figures 1, 2 and 3 show dashed lines for alternative process solutions. If necessary, the reaction product of the reactor 9 can be returned - from the side concentration column 6 back to the main column 2 stream or 10 - from the side reactor 5 back to the main column 2 stream or - directly to the bottom sump of the main column 2.

Thus, a separate unit with its feed arrangements is not required for the main column 2 for the return of the reactor product 9.

The distillate of the main column 2 contains unreacted methanol and if part of the distillate of the main column 2 is run to the top of the column 6, it is not necessary to add methanol to the reactor 9.

Comparative Example 20

Equipment: Main column (2) ......... 30 theoretical bases

Pre-reactor (1) .......... 3 pcs 25 Side reactors (5) ........ 2 pcs

The feed was FCC light gasoline with:

Hydrocarbons / w / w 30 C4 2.1 2M1B 1.8 2M2B 11.7 C5 remaining 32.8 8 95024 C6 reacting 11.3 C6 + remaining 40.4

Methanol 0.0 TAME 0.0 5 THME 0.0

Total 100.0 Amount / kg / h 58.137 10

The process resulted in products:

Table 1 15 Main column Side concentration column

Distillate Bottom Feed Bottom From the reactor p-% p-% p-% p-% p-% C4 86.22 0.21 0.00 0.00 0.00 20 2M1B 0.03 0.08 0.00 0.00 0.00_ 2M2B 0.06 1.55 0.00 0.00__0 ^ 0_ C5 the rest 7.97 31.01 0.00 0.00 0.00 C6 react 0.00 5.78 0.00 0.00 0 .00 C6 + rest 0.00 38.33 0.00 __ (T00__0; 00_ 25 Methanol 5.72 0.00 0.00 __ (T00 __ (TOO_ TAME 0.00 16.20 0.00 0.00 0.00 * THME 0.00 6.84 0.00 __ (TOO__03X) _

Total 100.00 100.00 0.00 __ (T00 __ (T00_ Amount, kg / h 1,275 61,204 0 0 0 30

The methanol feeds to the different locations were as follows: 9,95024

Reactor 1 4,100 kg / h MeOH

Reactor 5 0.24 kg / h MeOH

Reactor 90 kg / h MeOH

5 Example 1

Equipment: Main column (2) ......... 30 theoretical bases 10 Return ratio 97

Pressure 550 kPa

Temperature at peak 58.4 ° C

Bottom temperature 119.5 ° C

Pre-reactors (1) .......... 3 pcs

Reactor 1 64.5-77.2 ° C

Reactor 2 47.3-50.5 ° C

Reactor 3 42.6-43.8 ° C

Side reactors (5) ........ 2 pcs

Reactor 1 67.5-71.6 ° C

Reactor 2 43.8-44.5 ° C

Side concentration column (6) .............. 10 theoretical bases

Return ratio 0.47 25 Pressure 520 kPa

Temperature at peak 78.3 ° C

Bottom temperature 87.2 ° C

Reactor (9) ............. 1 x 60.0 ... 61.6 ° C 30

The feed was FCC light gasoline with: 10,95024

Hydrocarbons / w / w C4 2.1 2M1B 1.8 5 2M2B 11.7 C5 remaining 32.8 C6 reacting 11.3 C6 + remaining 40.4

Methanol 0.0 10 TAME 0.0 THME 0.0

Total 100.0 15 Amount / kg / h 58.137

The process yielded products:

Table 2 Main column Side concentration column 25 Distillate Bottom Feed Bottom From the reactor p-% p-% p-% p-% p-% C4 85.29__022__4J6__M6__019_ 2M1B 0.03 1.04 0.12 0.08 0.07: 2M2B 0.07 1.04 1.49_ 1.23 0.72 30 C5 remaining 8.78 30.85 54.99_ 38.20 61.65 C6 react 0.00__043__031__039__M2_ C6 + remaining 0.00 38.15 13.47 22.13_ 9 , 69

Methanol 5.83__013__18.91__19.92__18.59_ TAME 0.00 16.89 3.88 11.15__009_ 35 THME 0.00__024__068__025__058_

Total 100.00 100.00 100.00__100.00__100.00_ Amount, kg / h 1,276 61,503 50,000 15,000 35,300 j 40 The methanol feeds to the different locations were as follows: “95024

Reactor 1 4,100 kg / h MeOH

Reactor 5 0.24 kg / h MeOH

Reactor 9 0.30 kg / h MeOH

5

Example 2

Equipment: 10 Main column (2) ......... 30 theoretical bases

Return ratio 97

Pressure 550 kPa

Temperature at peak 58.4 ° C

15 Bottom temperature 118.3 ° C

Pre-reactors (1) .......... 3 pcs

Reactor 1 64.5-77.2 ° C

Reactor 2 47.3-50.5 ° C

Reactor 3 42.6-43.8 ° C

20 Side reactors (5) ........ 2 pcs

Reactor 1 67.5-71.6 ° C

Reactor 2 43.8-44.5 ° C

Side concentration - 25 columns (6) ............. 10 theoretical bases: Return ratio 1.0

Pressure 520 kPa

Temperature at peak 78.3 ° C

Bottom temperature 84.8 ° C

30 Reactors (9) ............. 1 pc

60.0-60.8 ° C

The feed was FCC light gasoline with: TT-95024 12

Hydrocarbons / w / w C4 2.1 2M1B 1.8 5 2M2B 11.7 C5 remaining 32.8 C6 reacting 11.3 C6 + remaining 40.4

Methanol 0.0 10 TAME 0.0 THME 0.0

Total 100.0 15 Amount / kg / h 58.137

The process yielded the following products: 20 Table 3 Main column Side concentration column

Distillate Bottom Feed Bottom From the reactor p-% p-% p-% p-% p-% 25 C4__85J1__0 £ 3__3A9__T67__5 £ 8_ 2M1B 0.03 0.05 0.12 0.10 0.03 2M2B 0.07 1.11 1 .57 1.61 0.45 C5 remaining 8.93 30.84 67.12 59.25 74.61 C6 react 0.00 5.67 1.86 3.26 0.22 30 C6 + remaining 0.00 38, 15 10.79__18 / 71_ 2.28

Methanol 5.86 0.25 11.27 __ ^ 48_ 15.83 TAME 0.00 16.79 3.24 6.79_ 1.11 THME 0.00 6.92 0.55 1.13 0.10

Total 100.00 100.00 100.00 100.00 100.00 35 Amount, kg / h 1,276 61,503 50,000 48,827 24,414 40 13,95024

The methanol feeds to the different points were as follows:

Reactor 1 4,100 kg / h MeOH Reactor 5 0.24 kg / h MeOH 5 Reactor 9 0.30 kg / h MeOH

Claims (10)

A process for preparing tertiary alkyl ethers in a catalytic distillation reaction system comprising a distillation column (2) and at least a first reaction zone 5 (5) connected to the column containing a catalyst resin catalyst, according to process C5. -Cg isoefins are reacted with lower alkanols to produce corresponding ethers in said reaction zone (5), and the ether product is removed from the bottom of the column (2), characterized by a side stream being diverted from the column (2) at a point between the bottom of the column and the lowest first reaction zone (5) and divided into a low boiling point fraction and a high boiling point fraction by distillation, at least part of the high boiling point fraction is returned to column (2), and at least part of the low boiling fraction fraction is added to at least one second reaction zone (9) when subjected to an etherification reaction in the presence of a catalyst and then fed back to the distillation column (2). 20 Process according to claim 1, characterized in that the low boiling point fraction comprises the distillation superfluous. 3. A process according to claim 2, characterized in that the excess is condensed and added to the same alkanol used in the etherification reaction to prepare a reaction mixture, after which the mixture is added to the second reaction zone (9). Method according to claim 3, characterized in that part of the product from the reaction zone (9) is fed back to the distillation (6). 30 Process according to claim 3, characterized in that part of the condensed supernatant is fed back to the distillation (6) before the addition of the alkanol. «17 95024 Process according to any of the preceding claims, characterized in that a distillation column (2) is used as a distillation reactor system, to which at least one external reactor (5) is connected. 5 Process according to any of claims 1-6, characterized in that a distillation column is used as a distillation reactor system in which at least one reaction bed is provided. Process according to any of the preceding claims, characterized in that a methyl ether such as TAME and / or THME is prepared. 9. A plant for the preparation of tertiary alkyl ethers of C of a side rectification unit (6, 9) connected to the lower part of the distillation column (2), which consists of a distillation column (6) and a side reactor (9) connected thereto. 10. A plant according to claim 9, characterized in that the condensate container (8) is connected to the distillation column (6) and the side reactor (9) is in flow communication with the condensate container.