Process for producing 1,3-butadiene from a feedstock comprising ethanol

Abstract

Production of 1,3-butadiene ethanol, that is more than 50% of the total weight of feedstock: A) conversion of feedstock and of ethanol effluent from separation B to a conversion effluent being a majority of 1,3-butadiene, water and ethylene, and to a hydrogen effluent, operating at a pressure between 0.1 and 1.0 MPa, a temperature between 300 and 500° C. in the presence of at least one catalyst; B) separation of conversion effluent originating from A and hydration effluent from C to an ethanol effluent, a butadiene effluent, a water effluent and an ethylene effluent; C) hydration of ethylene fed by ethylene effluent and/or water effluent both from separation B, to produce an ethanol hydration effluent then being recycled to separation B.

Claims

1. A process for the production of 1,3-butadiene from a feedstock rich in ethanol, in which the ethanol represents more than 50% of the total weight of said feedstock, comprising at least: stage A) conversion of at least said feedstock rich in ethanol and of ethanol effluent originating from separation stage B to a conversion effluent comprising a majority of 1,3-butadiene, water and ethylene, and to a hydrogen effluent, operating at a pressure of 0.1 to 1.0 MPa, at a temperature of 300 to 500° C. in the presence of at least one catalyst; stage B) separation of at least said conversion effluent originating from A and the hydration effluent originating from C to at least an ethanol effluent, a butadiene effluent, a water effluent and an ethylene effluent; stage C) hydration of the ethylene fed at least by said ethylene effluent and/or said water effluent both originating from stage B, in order to produce a hydration effluent comprising ethanol, said hydration effluent then being recycled to stage B.

2. The process according to claim 1, in which said stage A is operated at a pressure of 0.1 to 0.5 MPa.

3. The process according to claim 1, in which said stage A is operated in one reaction stage and in which said feedstock rich in ethanol is mixed with the ethanol effluent originating from stage B before feeding said stage A.

4. The process according to claim 3, in which said stage A is operated in the presence of a zinc aluminate catalyst or chromium-doped MgO—SiO.sub.2 catalyst, at a temperature of 380 to 430° C.

5. The process according to claim 1, in which said stage A is operated in two reaction stages, a first reaction stage converting the ethanol to acetaldehyde in the presence of a catalyst at a mass ratio of ethanol to acetaldehyde in effluent of said first reaction stage being of 2:1 to 4:1, said feedstock rich in ethanol feeding said first reaction stage and said ethanol effluent originating from stage B feeding said second reaction stage, in a mixture with said effluent from said first reaction stage.

6. The process according to claim 5, in which the second reaction stage of stage A is operated in the presence of a catalyst of silica with an oxide of tantalum, zirconium or niobium, the second reaction stage of stage A being operated at a temperature of 320 to 370° C., the first reaction stage of said stage A being operated at a temperature of 200 to 300° C.

7. The process according to claim, in which stage B is: distillation, cryogenic distillation, washing with solvent, extractive distillation, liquid-liquid extraction, passing through a sieve, membrane separation or combinations thereof.

8. The process according to claim 1, in which said stage C is an indirect hydration, in which, in a first reaction stage, the ethylene reacts in the presence of concentrated sulphuric acid at a reaction temperature of 50 to 150° C., in a two-phase gas/liquid medium and in a second stage, the products formed in the first stage are hydrolyzed in order to form a majority of ethanol at a temperature of 70 and 100° C.

9. The process according to claim 1, in which said stage C is a direct hydration operating in gas phase, at a reaction temperature comprised between 200 and 400° C., in the presence of a heterogeneous catalyst based on inorganic acids.

10. The process according to claim 1, in which said feedstock rich in ethanol comprises acetaldehyde, at a mass ratio of ethanol to acetaldehyde of 2:1 to 4:1.

11. The process according to claim 1, in which the purity of the ethylene flow feeding hydration stage C is 65 to 99.9% by weight.

12. The process according to claim 1, in which the purity of the ethylene flow feeding hydration stage C is 65 to 75% by weight.

13. The process according to claim 5, wherein the catalyst is a mixture of chromium oxide and copper oxide.

14. The process according to claim 9, wherein the heterogeneous catalyst is phosphoric acid deposited on a silica-based support.

15. The process according to claim 1, wherein ethylene effluent is fed to stage C without further purification.

Description

BRIEF DESCRIPTION OF THE FIGURE

(1) The figure shows diagrammatically the process for the production of 1,3-butadiene from a feedstock rich in ethanol according to the invention.

(2) The feedstock rich in ethanol 1 is mixed with the ethanol effluent 6 so as to form a conversion feedstock 2. Said conversion feedstock 2 is sent into conversion stage A so as to produce a conversion effluent 4 and a hydrogen effluent 3.

(3) The conversion effluent 4 originating from stage A and the hydration effluent 13 originating from stage C feed the separation stage B in which an ethanol effluent 6, a butadiene effluent 5, a water effluent 7, an ethylene effluent 8, an effluent of heavy gases 9, and an effluent of oils 10 are separated.

(4) A fraction 7a of the water effluent 7 is bled off. A fraction 8a of the ethylene effluent 8 is bled off. A part of the water effluent 7 and a part of the ethylene effluent 8 feed hydration stage C. An external source of ethylene 11 as well as an external source of water 12 also feed said stage C.

(5) Stage C produces a hydration effluent 13, which feeds separation stage B.

(6) The following examples illustrate the invention without limiting its scope.

EXAMPLES

(7) In the following examples, the performances of the processes are evaluated on the basis of the overall yield of 1,3-butadiene defined as follows: mass flow rate of 1,3-butadiene in the butadiene effluent divided by the mass flow rate of ethanol in the feedstock rich in ethanol.

Example 1

Not According to the Invention

(8) Example 1 illustrates the operation of the Lebedev process according to the prior art. After a conversion stage, the unconverted ethanol, as well as the unconverted acetaldehyde are separated and recycled upstream of said conversion stage.

(9) A feedstock rich in ethanol constituted by 93.3% by weight of ethanol and 6.7% by weight of water feeds conversion stage A. The unconverted ethanol and acetaldehyde present in the conversion effluent are separated in a separation stage B and recycled upstream of stage A.

(10) Separation stage B is operated so that 99% of the ethanol and 100% of the acetaldehyde comprised in the conversion effluent are recycled to stage A.

(11) The overall yield of 1,3-butadiene of the process is 0.383.

Example 2

Not According to the Invention

(12) This example is based on Example 1. After the conversion stage, an ethylene effluent is also separated which is hydrated in a hydration process as known to a person skilled in the art so as to produce a hydration effluent comprising ethanol. Said ethanol effluent is then recycled upstream of the conversion stage (after separation of the ethylene and a part of the water).

(13) Conversion stage A is fed by a feedstock rich in ethanol identical to that of Example 1, as well as by a ethanol effluent originating from separation stage B.

(14) Separation stage B is operated so that 99% of the ethanol and 100% of the acetaldehyde comprised in the conversion effluent are recycled to stage A.

(15) As known by a person skilled in the art, the ethylene sent to the hydration unit must be very pure (Weissermel and Arpe, Industrial Organic Chemistry 4.sup.th edition, Wiley-VCH 2003). The separation and purification of the ethylene contained in said conversion effluent to an ethylene effluent comprising 99.9% by weight of ethylene leads to a 15% loss of ethylene. Thus, separation stage B makes it possible to recover 85% of the ethylene comprised in said conversion effluent.

(16) Said ethylene effluent, as well as a flow of water the origin of which is external to the process, is converted to ethanol in a hydration process as known to a person skilled in the art. At the end of the hydration reaction stage, the ethanol is purified in a dedicated separation unit typical of the hydration processes of the prior art, which produces ethanol at 94.5% by weight, and recycled to the feed of conversion stage A.

(17) The overall yield of the process is 0.395, i.e. 3.1% more than in Example 1.

Example 3

According to the Invention

(18) In this example, according to the invention, the conversion effluent is treated in a separation stage B so as to produce at least one butadiene effluent, one ethanol effluent, one ethylene effluent and one water effluent. The purity specification of the ethylene effluent is lower, and a flow of water which is internal to the process is used for the hydration stage.

(19) Conversion stage A is fed by a feedstock rich in ethanol identical to that of Example 1, as well as by an ethanol effluent originating from separation stage B.

(20) Separation stage B, fed by the conversion effluent originating from said stage A, as well as by the hydration effluent originating from said stage C, makes it possible to produce at least one butadiene effluent, one ethanol effluent, one ethylene effluent and one water effluent. It is operated so that 99% of the ethanol and 100% of the acetaldehyde comprised in the feed of said stage B are recycled to stage A. 99% of the ethylene comprised in said conversion effluent is separated into said ethylene effluent. The purity of ethylene in this effluent is 73% by weight. It is sent, as well as said water effluent, to a hydration stage C

(21) The overall yield of the process is 0.397, i.e. 0.5% better than Example 2 and 3.7% better than Example 1.

(22) With reference to Example 2, the overall performance of the process was able to be maintained, even improved by 0.5% even though the purity of the ethylene sent to the hydration stage is much lower (73% by weight instead of 99.9% by weight). The separation of the ethylene content in the conversion effluent originating from stage A is therefore facilitated, due to a less strict purity requirement, in the example according to the invention, which allows an improved recovery of said ethylene (99% instead of 85%). This lower purity also leads to a separation that has lower energy consumption. Combining the treatment of the conversion effluent originating from stage A and the hydration effluent originating from stage C makes it possible to reduce the quantity of equipment required by 40%.

(23) The process according to the invention therefore allows an improved reuse of the ethylene co-produced in conversion stage A, as 16.4% more ethylene is reused compared with Example 2 (99%/85%).

(24) The hydration of a low-purity ethylene effluent, contrary to the uses known from the prior art, surprisingly has no detrimental effect on the overall yield of 1,3-butadiene of the process. In fact, even if the water effluent and the ethylene effluent which feed said hydration stage comprise impurities, such as for example acetic acid, acetaldehyde, acetylene, propylene and diethyl ether, combining the separation stage B capable of separating these compounds and the recycling to the conversion stage A which converts some of these impurities compensates for the deterioration in the performance of hydration stage C linked to the use of feedstock (effluent ethylene and water) which is not as pure as those usually used in the prior art.