Method for producing 1,3-butadiene from 1,4-butanediol

Abstract

A method for producing 1,3-butadiene from a 1,4-butanediol feedstock: One step for esterification of 1,4-butanediol, One step for pyrolysis of 1,4-butanediol diester, producing butadiene.

Claims

1. A method for conversion of a 1,4-butanediol feedstock, said method comprising at least: a) esterification of the 1,4-butanediol feedstock and a flow comprising more than 50% by weight part carboxylic acid to produce an effluent, and separating the effluent from the reaction section into at least one 1,4-butanediol diester effluent, a water effluent, and a carboxylic acid effluent in at least one separation section, wherein the esterification in said reaction section is implemented in the presence of an acid catalyst at a pressure of between 0.01 and 1.0 MPa and at a flow rate of moles of diol to moles of catalyst in said reaction section of between 0.05 and 25 h.sup.1; and b) pyrolysis of said at least one 1,4-butanediol diester effluent to produce a pyrolysis effluent, wherein said pyrolysis also comprises at least one separation section wherein said pyrolysis effluent is cooled to a temperature that is less than 100 C. to produce at least one liquid pyrolysis effluent and one vapor pyrolysis effluent, wherein said vapor pyrolysis effluent is compressed and/or cooled to condense 1,3-butadiene into a 1,3-butadiene effluent, and separating the liquid pyrolysis effluent by simple distillation to produce a carboxylic acid flow and a 3-buten-1-ol ester flow as a carboxylic acid/3 buten-1-ol ester azeotrope.

2. The method according to claim 1, wherein the flow of carboxylic acid comprises the carboxylic acid effluent that is obtained from the separation section of a).

3. The method according to claim 1, wherein the flow of carboxylic acid comprises external carboxylic acid.

4. The method according to claim 1, wherein said reaction section of a) is implemented in a reactive distillation column, in which the 1,4-butanediol feedstock is introduced into an upper part of the column, and the carboxylic acid is introduced into a lower part of the column, with the ratio of the molar flow rates of 1,4-butanediol and carboxylic acid being between 2 and 6.

5. The method according to claim 1, wherein the carboxylic acid is formic acid, acetic acid, propanoic acid, butanoic acid, or benzoic acid.

6. The method according to claim 5, wherein the carboxylic acid is acetic acid.

7. The method according to claim 6, wherein said separation in a) comprises heterogeneous azeotropic distillation using a driver.

8. The method according to claim 1, wherein said 3-buten-1-ol ester flow is recycled to pyrolysis b) with the 1,4-butanediol diester.

9. The method according to claim 1, wherein a THF effluent is separated from the effluent of said reaction section of a).

10. The method according to claim 9, further comprising c) converting the THF effluent into 1,4-butanediol diester with an acid anhydride effluent in the presence of an acid catalyst to produce an effluent.

11. The method according to claim 10, wherein the effluent that is obtained from c) conversion of THF into 1,4-butanediol diester is sent directly to b) pyrolysis of 1,4-butanediol diester or to a dedicated step for pyrolysis producing more butadiene.

12. The method according to claim 10, wherein the effluent that is obtained from c) conversion of THF into 1,4-butanediol diester is sent back to a) esterification of the 1,4-butanediol feedstock.

13. A method for conversion of a 1,4-butanediol feedstock, said method comprising at least: a) esterification of the 1,4-butanediol feedstock and a flow comprising more than 50% by weight part carboxylic acid to produce an effluent, and separating the effluent from the reaction section into at least one 1,4-butanediol diester effluent, a water effluent, and a carboxylic acid effluent in at least one separation section, wherein the esterification in said reaction section is implemented in the presence of an acid catalyst at a pressure of between 0.01 and 1.0 MPa and at a flow rate of moles of diol to moles of catalyst in said reaction section of between 0.05 and 25 h.sup.1; and b) pyrolysis of said at least one 1,4-butanediol diester effluent to produce a pyrolysis effluent, wherein said pyrolysis also comprises at least one separation section wherein said pyrolysis effluent is cooled to a temperature that is less than 100 C. to produce at least one liquid pyrolysis effluent and one vapor pyrolysis effluent, wherein said vapor pyrolysis effluent is compressed and/or cooled to condense 1,3-butadiene into a 1,3-butadiene effluent, wherein the liquid pyrolysis effluent is separated by distillation with a change in pressure to produce a carboxylic acid flow and a 3-buten-1-ol ester flow.

14. The method according to claim 1, wherein the flow of carboxylic acid comprises said carboxylic acid flow that is obtained from the liquid pyrolysis effluent.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 presents a diagrammatic view of a specific arrangement of the method according to the invention.

(2) FIG. 2 has a particular arrangement of the esterification step with implementation of step c) for conversion of THF of the method according to the invention.

(3) FIG. 3 shows conversion of 2,3-butanediol into monoester and diester over time is followed by gas chromatography.

(4) FIG. 4 shows conversion of 1,4-butanediol into monoester and diester over time is followed by gas chromatography.

(5) The 1,4-butanediol feedstock (1) undergoes a first esterification step a) with a flow of carboxylic acid (9) and a flow that comprises for the most part carboxylic acid (2) to produce a water effluent (3), a 1,4-butanediol diester effluent (5), and a carboxylic acid effluent (2a). During step a), a small fraction of the 1,4-butanediol feedstock is converted into THF, which is eliminated from step a) in the THF effluent 4a). The carboxylic acid effluent (2a) is recycled in a mixture with the flow that comprises for the most part carboxylic acid (2).

(6) The 1,4-butanediol diester effluent (5) feeds a pyrolysis step b) that produces a 1,3-butadiene effluent (7) and a liquid pyrolysis effluent (9) that is recycled to the esterification step a). During the pyrolysis step b), a very small fraction of 1,4-butanediol diester is converted into THF, which can optionally be eliminated from step b) in the 3-buten-1-ol ester effluent 4b) or sent via the flow (9) to step a) ultimately to be eliminated from step a) by the flow 4a).

(7) Furthermore, during the pyrolysis step b), a small fraction of carboxylic acid is cracked. The cracking products are eliminated from step b) in the effluent composed of light compounds (8). The addition of carboxylic acid (2) introduced in step a) compensates for the losses of carboxylic acid in step b). A small proportion of coke is also produced, which is evacuated via the coke effluent (6).

(8) FIG. 2 has a particular arrangement of the esterification step with implementation of step c) for conversion of THF of the method according to the invention.

(9) The esterification step a) is fed with the 1,4-butanediol feedstock (1), on the one hand, and by a flow of carboxylic acid (9) that is obtained from the pyrolysis step (b), the effluent (11) for conversion of the THF that is obtained from step c), and an addition of carboxylic acid (2), on the other hand. Step a) produces a 1,4-butanediol diester effluent (5) that is sent to the pyrolysis step b), a THF effluent (4) that is sent to step c) for conversion of THF, and a water effluent (3) that is eliminated from the method. The pyrolysis step b) is fed with the 1,4-butanediol diester effluent (5) that is obtained from step a) and produces a 1,3-butadiene effluent (7), with an effluent composed of light compounds (8) containing the cracking products of carboxylic acid, and a carboxylic acid flow (9) that is sent back to step a). During pyrolysis, a small proportion of coke is also produced, which is evacuated via the coke effluent (6). Step c) is fed with the THF effluent (4) obtained from step a) and with the acid anhydride effluent (10) and produces an effluent for conversion of THF (11) that is sent back to step a).

EXAMPLES

Example 1Esterification of 2,3-Butanediol (for Comparison)

(10) This example shows the performance of an esterification method that is implemented according to the teaching of the prior art.

(11) The esterification of 2,3-butanediol is carried out in a closed stirred reactor, under the following conditions: A temperature of 110 C. (corresponds to the mean temperature of the reactive zone of the reactive distillation column al)). 6 mol of acetic acid per mol of 2,3-butanediol (corresponding to a large excess of acetic acid). Acid catalyst TA801 at 2.2 mol % in relation to 2,3-butanediol.

(12) The conversion of 2,3-butanediol into monoester and diester over time is followed by gas chromatography (FIG. 3). It should be noted that the kinetics of conversion of the RR, SS and RS forms of 2,3-butanediol are identical, and the proportions of the various diastereoisomers were added. It is possible to note that despite the presence of a large excess of acetic acid, the conversion of 2,3-butanediol is limited, which justifies carrying out reactive distillation in such a way as to shift the balance toward the formation of 2,3-butanediol diester.

(13) Nevertheless, it is possible to note that the esterification kinetics is rather slow despite the presence of the acid catalyst, since it takes more than 20 hours to reach thermodynamic equilibrium.

Example 2Esterification of 1,4-Butanediol (Invention)

(14) This example shows the performance of an esterification method that is implemented according to the invention.

(15) The esterification of 1,4-butanediol is carried out in a closed stirred reactor, under the following conditions: A temperature of 110 C. (corresponds to the mean temperature of the reactive zone of the reactive distillation column al)). 6 mol of acetic acid per mol of 1,4-butanediol (corresponding to a large excess of acetic acid). Acid catalyst TA801 at 2.2 mol % in relation to 1,4-butanediol.

(16) The conversion of 1,4-butanediol into monoester and diester over time is followed by gas chromatography (FIG. 4). It is possible to note that, all other things being equal, the conversion of 1,4-butanediol is much greater than that of 2,3-butanediol. Industrially, this will be reflected by a reduction in the acetic acid/butanediol ratio and therefore by a reduction in operating and investment costs associated with the esterification step.

(17) Furthermore, it is possible to note that the esterification kinetics of 1,4-butanediol is faster than that of 2,3-butanediol, since the thermodynamic equilibrium is reached in 3 hours in the case of the esterification of 1,4-butanediol, versus 20 hours in the case of the esterification of 2,3-butanediol. Industrially, this will be reflected by a reduction in dwell time within the reactive distillation column and therefore by a reduction in investment costs associated with this operation.

Example 3Pyrolysis of 2,3-Butanediol Diacetate (for Comparison)

(18) This example shows the performance of a pyrolysis method that is implemented according to the teaching of the prior art.

(19) A feedstock that consists of 2,3-butanediol diacetate feeds a pyrolysis oven. The temperature of the pyrolysis oven is regulated in such a way as to obtain a reactor outlet temperature of 630 C. The flow rate of 2,3-butanediol diacetate is regulated to obtain a dwell time of between 0.9 and 1.5 seconds. The pyrolysis effluent is quickly cooled to 45 C. with a condenser placed right at the exit from the pyrolysis oven. The conversion of 2,3-butanediol diacetate varies between 96.5% and 99.1% based on the dwell time. The selectivity of transformation of 2,3-butanediol diacetate into 1,3-butadiene is between 78% and 82%. The selectivity of transformation of 2,3-butanediol diacetate into intermediate pyrolysis compounds varies between 17.2% and 20.0%. The selectivity of transformation of 2,3-butanediol diacetate into MEK varies between 0.9% and 1.8%. There is no other conversion product detected.

(20) Among the intermediate pyrolysis compounds, some make it possible to increase the overall diolefin yield of the method if they are recycled in the step for pyrolysis and others do not. Methyl vinyl carbinol acetate (MVCA) and crotyl acetate (CA) make it possible to increase the butadiene yield if they are recycled in the step for pyrolysis, whereas this is not the case of methyl ethyl ketone enol acetate (MEKEA).

(21) However, these intermediate pyrolysis compounds are isomers and therefore have very similar physico-chemical properties. Furthermore, these intermediate pyrolysis compounds are heavily diluted in carboxylic acid. It turns out that when the diol feedstock is a butanediol, regardless of the carboxylic acid being considered, the relative volatility between carboxylic acid and the intermediate pyrolysis compounds is very close to one. All of these elements together make the extraction of the intermediate pyrolysis compounds within the liquid pyrolysis effluentfor the purpose of maximizing the yieldvery difficult.

Example 4Pyrolysis of 1,4-Butanediol Diacetate (Invention)

(22) This example shows the performance of a pyrolysis method that is implemented according to the invention.

(23) A feedstock that consists of 1,4-butanediol diacetate feeds a pyrolysis oven. The temperature of the pyrolysis oven is regulated in such a way as to obtain a reactor outlet temperature of 630 C. The flow rate of 1,4-butanediol diacetate is regulated to obtain a dwell time of between 1 and 2 seconds. The pyrolysis effluent is quickly cooled to 45 C. with a condenser placed right at the exit from the pyrolysis oven. The conversion of 1,4-butanediol diacetate varies between 96.2% and 100% based on the dwell time. The selectivity of transformation of 1,4-butanediol diacetate into 1,3-butadiene is between 96.3% and 100%. The selectivity of transformation of 1,4-butanediol diacetate into 3-buten-1-ol (only intermediate pyrolysis compound) varies between 0% and 3.7%. A formation of THF is not observed. No other product is detected.

(24) With this example, we will demonstrate that the use of 1,4-butanediol as a feedstock of a method for esterification and pyrolysis according to the invention for the production of 1,3-butadiene offers the advantage of having a higher molar yield of butadiene and of forming fewer by-products.

Example 5Production of Butadiene from a 1,4-Butanediol Feedstock (Invention)

(25) This example illustrates the production of 1,3-butadiene from a 1,4-butanediol feedstock by the method according to the invention, in its variant with (variant 5-a) and without (variant 5-b) implemented in step c).

(26) Variant 5-a (Invention), without Implementation of Step c) for Conversion of THF

(27) The table below provides the flow rates and the composition of the various flows within the method according to the invention, with the numbering of the flows being identical to that of FIG. 1.

(28) The 1,4-butanediol feedstock (1) that primarily contains 1,4-butanediol, but also 3.7% by weight of water, feeds an esterification step a). This esterification step a) is furthermore fed with the flow (9) that is obtained from the pyrolysis step b) and that consists primarily of acetic acid and with the flow (2) of pure acetic acid that makes it possible to compensate for the losses of acetic acid within the method. This esterification step a) furthermore produces the water flow (3) that is eliminated from the method, the THF flow (4a) that is eliminated from the method, and the 1,4-butanediol diester flow (5) that is sent to the pyrolysis step b).

(29) The pyrolysis step b) produces a 1,3-butadiene flow (7), a flow (8) of incondensable products obtained from the pyrolysis of acetic acid, and a flow (9) that consists primarily of acetic acid and that is sent back to the esterification step a).

(30) Coke is also produced during pyrolysis, which is eliminated by the flow (6) during the regeneration of the pyrolysis oven.

(31) TABLE-US-00001 Flow (1) (2) (3) (4a) (5) (6) (7) (8) (9) Flow Rate 9358 572 3907 158 17250 344 5186 335 11384 (kg/h) Composition (% by Weight) 1,4- 96.3 Butanediol Water 3.7 100 Acetic Acid 100 0.14 98.94 THF 100 0.06 Diester 99.78 Monoester 0.08 1,3-Butadiene 100 Intermediate 1.00 Compound Incondensable 100 Products Coke 100

(32) Thus, 0.57 ton of butadiene per ton of 1,4-butanediol is produced by the method according to the invention, or a yield of 95.9% of the stoichiometric yield. The yield loss stems from various undesirable reactions: The production of THF by dehydration of 1,4-butanediol in the esterification step a), The production of THF by hydrolysis of the intermediate pyrolysis compound, when the latter is not isolated but directly recycled to the esterification step a), The production of THF by pyrolysis of 1,4-butanediol monoester in the pyrolysis step b), And finally the production of coke.
Variant 5-b (Invention), with Implementation of Step c) for Conversion of THF

(33) The table below provides the flow rates and the composition of the various flows within the method according to the invention, with the implementation of step c) for conversion of THF, with the number of flows being identical to that of FIG. 2.

(34) The 1,4-butanediol feedstock (1) that primarily contains 1,4-butanediol, but also 3.7% by weight of water, feeds an esterification step a). This esterification step a) is furthermore fed with the flow (9) that is obtained from the pyrolysis step b) and that primarily consists of acetic acid, and with the flow (2) of pure acetic acid that makes it possible to compensate for the losses of acetic acid within the method. This esterification step a) furthermore produces the water flow (3) that is eliminated from the method, the THF flow (4) that is sent to step c) for conversion of THF, and the 1,4-butanediol diester flow (5) that is sent to the pyrolysis step b).

(35) Step c) is fed with the flow (4) that is obtained from step a) and with the flow (10) of acetic anhydride and produces a flow (11) that is sent back to the esterification step a).

(36) The pyrolysis step b) produces the 1,3-butadiene flow (7), a flow (8) of incondensable products obtained from the pyrolysis of acetic acid, and a flow (9) that consists primarily of acetic acid and that is sent back to the esterification step a).

(37) Coke is also produced during the pyrolysis, which is eliminated by the flow (6) during the regeneration of the pyrolysis oven.

(38) TABLE-US-00002 Flow (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) Flow Rate 9358 285 3901 155 17623 352 5302 342 11626 255 410 (kg/h) Composition (% by Weight) 1,4- 96.3 Butanediol Water 3.7 100 Acetic Acid 100 0.14 99 Acid Traces 100 9.7 Anhydride THF 100 0.7 Diester 99.86 89.6 Monoester Traces 1,3-Butadiene 100 Intermediate 1 Compound Incondensable 100 Products Coke 100

(39) Thus, 0.59 ton of butadiene per ton of 1,4-butanediol is produced by the method according to the invention, with a step for conversion of THF, or a yield of 98% of the stoichiometric yield. Furthermore, it will be possible to note that in comparison to Example A, the performance of the esterification step a) has been improved, owing to the recycling in step a) of the flow (11) also containing the acetic anhydride that is unconverted at step c. Furthermore, since there is no longer any 1,4-butanediol monoester in the flow (5) that is sent to step b), there is therefore no longer any THF formation in the pyrolysis step c).