KR102022226B1

KR102022226B1 - Process for Purifying Propene Oxide

Info

Publication number: KR102022226B1
Application number: KR1020187012567A
Authority: KR
Inventors: 베어벨 콜베; 만프레트 베르츠; 마르크 브렌델; 기돈 원; 호진 양; 수현 박; 마이크 베른하르트
Original assignee: 에보닉 데구사 게엠베하; 티센크루프 인더스트리얼 솔루션스 아게
Priority date: 2015-11-26
Filing date: 2016-11-02
Publication date: 2019-09-18
Also published as: AR106813A1; WO2017089080A1; TW201730170A; KR20180069835A

Abstract

The present invention relates to a process for purifying propene oxide, wherein the propene oxide is purified by extractive distillation and 15 to 97% by weight of propene oxide, 2 to 84, to feed point A in the central section of the extractive distillation column. Supplying crude propene oxide comprising wt% methanol, and acetaldehyde; Feeding an aqueous extraction solvent to a feed point B located above a feed point A; And a reactive compound of formula R ¹ -Y-NH ₂ between feed point B, feed point A, or feed point A and feed point B, wherein Y is oxygen or NR ² , and R ¹ and R ² , independent of each other, are hydrogen, Alkyl group or aryl group) or a salt of such a reactive compound; Withdrawing stream S1 from the top of the extractive distillation column to provide a first propene oxide product containing less than 200 ppm water; And withdrawing stream S2 at the withdrawal point located in the theoretical separation stage of 5 to 25 above feed point B to provide a second propene oxide product containing 500-10000 ppm of water.

Description

Process for Purifying Propene Oxide

The present invention relates to a process for purifying propene oxide that provides two propene oxide products of different purity, wherein the first product is suitable for preparing polyether polyols and the second product is 1,2-propane It is suitable for preparing diols or propylene glycol monoethers.

The preparation of propene oxide by reacting hydrogen peroxide with propene in the presence of a titanium zeolite catalyst has the advantage of providing propene oxide without the co-production of other compounds which must be commercially available and also reduces waste compared to conventional chlorohydrin processes. Create The reaction of hydrogen peroxide with propene in the presence of a titanium zeolite catalyst is commonly carried out in methanol solvents to achieve high reaction rates and product selectivity. The crude propene oxide provided by this reaction is a residual methanol solvent and volatile byproducts formed during the reaction and work-up, in particular aldehydes such as formaldehyde, acetaldehyde and propionaldehyde, and methanol and 1,2 -Acetals with propanediol, as well as methyl formate.

Most propene oxides are further reacted with polyether polyols which are used as monomers to make polyurethanes. For this purpose, propene oxide containing less than 200 ppm water, less than 100 ppm methanol and less than 50 ppm acetaldehyde should be of high purity.

A significant portion of propene oxide is further reacted with water with 1,2-propanediol. For this purpose, purity requirements are less stringent and the water content is not critical.

Methanol, acetaldehyde and methyl formate are difficult to remove from propene oxide by simple distillation. In mixtures containing at least 98 mol-% propene oxide, these compounds have essentially the same volatility as propene oxide. Therefore, distillation purification for low levels of methanol, acetaldehyde and methyl formate cannot be realized through conventional distillation.

Although several methods have been developed for removing methanol, acetaldehyde and methyl formate from propene oxide by extractive distillation, many have the disadvantage of requiring several distillation columns to provide high purity propene oxide.

WO 2004/048355 discloses methanol and acetine from crude propene oxide in a single distillation column by extractive distillation wherein a compound containing unsubstituted NH ₂ groups is further fed at or above the feed point of crude propene oxide. A method for removing aldehyde is disclosed. The method provides a high purity propene oxide suitable for preparing polyether polyols.

The inventors of the present invention modify the process of WO # 2004/048355 by using water as the extraction solvent and recovering the second propane oxide from the extraction distillation column above the feed point of the extraction solvent to produce 1,2-propanediol. It has been found to provide a suitable second propene oxide product and to reduce the energy consumption and equipment size of the propene oxide tablets.

The present invention therefore relates to a process for purifying propene oxide, which process comprises:

a) feeding crude propene oxide comprising 15-97 wt% propene oxide, 2-84 wt% methanol and acetaldehyde to feed point A in the central section of the extractive distillation column;

b) feeding an aqueous extraction solvent to feed point B of said extractive distillation column located above feed point A;

c) i) at feed point B,

ii) at feed point A, or

iii) at feed point C between feed point A and feed point B

Reactive compound of formula (I) to the extractive distillation column

(I) R ¹ -Y-NH ₂

Or feeding a salt of a reactive compound of formula (I), wherein Y is oxygen or NR ² , and R ¹ and R ² , independent of each other, are hydrogen, an alkyl group or an aryl group;

d) withdrawing stream S1 from the top of said extractive distillation column to provide a first propene oxide product; And

e) withdrawing stream S2 from said extractive distillation column at a draw point located in the theoretical separation stage of 5 to 25 above feed point B to provide a second propene oxide product.

1 illustrates an embodiment of the invention wherein a reactive compound is fed to an extractive distillation column and mixed with an aqueous extraction solvent.

The process of the present invention for purifying propene oxide is carried out in an extractive distillation column. The extractive distillation column may be a tray column comprising separate trays such as sieve trays or bubble cap trays. The extraction distillation column may also be a packing column, or both random packing as well as structured packing such as metal gauze packing may be used. The extractive distillation column may also combine sections with packing and sections with separate trays. The extractive distillation column will also generally include at least one overhead condenser and at least one column reboiler.

The extractive distillation column has at least two feed points, feed point A for supplying crude propene oxide in the central section of the extractive distillation column and feed point B for supplying an aqueous extraction solvent located above feed point A. . The feed point comprises three sections of the extractive distillation column, a stripping section between the column bottom and feed point A, an extraction section between feed point A and feed point B, and a rectification section between feed point B and the top of the extractive distillation column. Regulate. Preferably, a distillation column is used which has a separation efficiency of 10 to 30 theoretical stages in the stripping section, a separation efficiency of 15 to 40 theoretical stages in the extraction section and a separation efficiency of 20 to 60 theoretical stages in the rectifying section, ie Feed point B is preferably located in the 15 to 40 theoretical separation stage above feed point A and in the 20 to 60 theoretical separation stage below the top of the extractive distillation column.

Crude propene oxide comprising 15-97 wt% propene oxide, 2-84 wt% methanol, and acetaldehyde is fed to feed point A of the extractive distillation column. The crude propene oxide preferably comprises 4 to 4000 ppm by weight of acetaldehyde. Crude propene oxide also contains other aldehydes and ketones such as formaldehyde, propionaldehyde and acetone, as well as acetals of such aldehydes with methanol or 1,2-propanediol such as dimethoxymethane, 1,1-dimethoxy Ethane, 1,1-dimethoxypropane, 4-methyl-1,3-dioxolane, 2,4-dimethyl-1,3-dioxolane and 2-ethyl-4-methyl-1,3-dioxolane You may. Crude propene oxide may also include additional solvents such as ethanol or water.

Crude propene oxide is preferably provided by an epoxidation reaction in which propene is epoxidized in a methanol solvent using a titanium zeolite containing titanium atoms at the silicon lattice position. Preferably, a titanium titanium catalyst having a MFI or MEL crystal structure is preferably used. Most preferably a Titanium Silicalite 1 catalyst having an MFI structure as known from EP 로부터 0 100 119 A1 is used. Titanium silicalite catalysts are preferably used as shaped catalysts in the form of granules, extrudates or shaped bodies. For the molding process, the catalyst may contain 1 to 99% of the binder or tint material, all binders and tint materials which do not react with propene oxide or hydrogen peroxide under the reaction conditions used for epoxidation are suitable, Silica is preferred as a binder. As a fixed bed catalyst, an extrudate of 1 to 5 mm 3 in diameter is preferably used. The methanol solvent may be industrial methanol, a solvent stream recovered in the workup of the epoxidized reactive compound or a mixture of both.

The epoxidation reaction is preferably carried out at a temperature of 20 to 80 ° C., more preferably 25 to 60 ° C. and at a pressure of 1.9 to 5.0 MPa, more preferably 2.1 to 3.6 MPa and most preferably 2.4 to 2.8 MPa. do. The propene is preferably in excess with respect to hydrogen peroxide, preferably in the range of propene of 1.1: 1 to 30: 1, more preferably 2: 1 to 10: 1 and most preferably 3: 1 to 5: 1 Used as the initial molar ratio of hydrogen peroxide. Propene is preferably used in an excess sufficient to maintain an additional liquid phase rich in propene throughout the reaction. The use of excess propene provides high reaction rates and hydrogen peroxide conversion while providing high selectivity for propene oxide. Propene may also comprise propane in a mass ratio of propane to propene and propane combined, preferably 0.07-0.20, more preferably 0.10-0.15.

Hydrogen peroxide may be used as an aqueous solution containing preferably 30 to 75% by weight and most preferably 40 to 70% by weight of hydrogen peroxide.

The epoxidation reaction is preferably carried out with the addition of ammonia to improve propene oxide selectivity as disclosed in EP 0 230 949 A2. Ammonia is preferably added in an amount of 100 to 3000 ppm based on the weight of the water peroxide.

The epoxidation reaction is preferably carried out continuously in a fixed bed reactor by excluding the mixture comprising propene, hydrogen peroxide and methanol from the fixed bed comprising the shaped titanium silicalite catalyst. The fixed bed reactor is preferably provided with cooling means and cooled with a liquid cooling medium. The temperature profile in this reactor is preferably maintained such that the cooling medium temperature of the cooling means is at least 40 ° C and the maximum temperature in the fixed bed is at most 60 ° C, preferably 55 ° C. The epoxidized reactive compound is preferably through the catalyst bed in the downflow mode at an azeotropic velocity of preferably 1 to 100 m / h, more preferably 5 to 50 m / h, most preferably 5 to 30 m / h. Is passed. The tower speed is defined as the ratio of the volume flow rate / section of the catalyst bed. In addition, it is preferred to pass the reactive compound through the catalyst bed at a liquid hourly space velocity (LHSV) of 1 to 20 h ⁻¹ , preferably 1.3 to 15 h ⁻¹ . Particular preference is given to maintaining the catalyst bed in a trickle bed state during the epoxidation reaction. Suitable conditions for maintaining the trickle layer state during the epoxidation reaction are disclosed in page 8, line 23 to page 9, line 9 of WO 02/085873. The methanol solvent is preferably used in the epoxidation in a weight ratio of 0.5 to 20 relative to the amount of aqueous hydrogen peroxide solvent. The amount of catalyst used may vary within wide ranges and is also preferably selected such that consumption of more than 90%, preferably more than 95%, of hydrogen peroxide is achieved within 1 minute to 5 hours under the epoxidation reaction conditions used. Most preferably, the epoxidation reaction comprises a trickle layer at a pressure close to the vapor pressure of propene at the reaction temperature using excess propene providing a reactive compound comprising two liquid phases, a methanol rich phase and a propene rich liquid phase. It is carried out with the catalyst fixed bed kept in the state. Two or more fixed bed reactors may be operated in parallel or in series so that the epoxidation process can be operated continuously when regenerating the epoxidation catalyst. The regeneration of the epoxidation catalyst can be carried out by calcination, by treatment with a heated gas, preferably an oxygen containing gas, or by solvent washing, preferably by periodic regeneration as disclosed in WO 2005/000827.

Unreacted propene may be separated from the reactive compound of the epoxidation reaction, preferably by distillation or by reduced pressure in a flash evaporator. Preferably, unreacted propene is separated by reduced pressure to a pressure of 0.16 to 0.30 MPa.

The remaining liquid mixture after depressurization is preferably separated by distillation in a preliminary separation column to provide an overhead product comprising propene oxide, methanol and residual propene and a bottom product comprising methanol, water and unreacted hydrogen peroxide. do. The preliminary separation column is preferably operated to provide an overhead product comprising 20 to 60% by weight of methanol contained in the liquid phase after depressurization. The preliminary separation column preferably has 5 to 20 theoretical separation stages in the stripping section and less than 3 theoretical separation stages in the rectification section, and most preferably to minimize the residence time of propene oxide in the preliminary separation column. It is operated without the rectifying section and without reflux. The preliminary separation column is preferably operated at a pressure of 0.16 to 0.3 MPa. Propene oxide and methanol are condensed from the overhead product of the preliminary separation column and propene is preferably stripped from the final condensate in a propene stripping column which provides crude propene oxide as a bottoms stream.

In the process of the invention for purifying propene oxide, the aqueous extraction solvent is fed to feed point B of the extractive distillation column. The aqueous extraction solvent preferably comprises more than 80 wt% water, more preferably more than 90 wt% water. Preferably, the aqueous extraction solvent does not contain additional solvent other than water. The extraction solvent is preferably supplied in an amount that provides a mass ratio of the extraction solvent to the amount of methanol contained in the crude propene oxide feed of 0.01 to 1, more preferably 0.03 to 0.2. The use of this amount of aqueous extraction solvent provides effective extraction of methanol with propene oxide product with low content of methanol while simultaneously avoiding hydrolysis of propene oxide in the extractive distillation column.

In addition to the aqueous extraction solvent, the reactive compound of formula (I) is fed to an extractive distillation column,

(I) R ¹ -Y-NH ₂

Wherein Y is oxygen or NR ² , and R ¹ and R ² , independent of each other, are hydrogen, an alkyl group or an aryl group. Alternatively, salts of the compounds of formula (I) may be fed. The reactive compound is preferably a hydrazine, hydrazine hydrate or hydrazinium salt. The reactive compound of formula (I) reacts with the carbonyl compound at extractive distillation conditions to produce a high boiling hydrazone, oxime or oxime ether. The amount of reactive compound fed to the distillation column is preferably selected such that the molar ratio of reactive compound to acetaldehyde is between 0.5 and 2. The use of this amount of the reactive compound of formula (I) provides an efficient conversion of the carbonyl compound to a high boiling compound and also provides a propene oxide product having a low content of acetaldehyde and other carbonyl compounds. At the same time, by-product formation by reaction of reactive compounds with propene oxide can be maintained at low levels.

The reactive compound may be fed to the extractive distillation column at feed point B, at feed point A or at a further feed point C between feed point A and feed point B. Preferably, the reactive compound is fed to the extractive distillation column at feed point B and mixed with the aqueous extraction solvent.

In the process of the present invention for purifying propene oxide, stream S1 is withdrawn from the top of the extractive distillation column to provide a first propene oxide product and stream S2 is fed to the feed point to provide a second propene oxide product. It is withdrawn at the withdrawal point located in the theoretical separation stage of 5 to 25 above B. The first propene oxide product withdrawn as stream S1 from the top of the extractive distillation column has a low content of water and typically comprises less than 100 ppm by weight of water. Propene oxide with such low amounts of water is suitable for the production of polyether polyols that can be used to prepare polyurethanes. The second propene oxide product withdrawn as stream S2 typically comprises a high content of water of 500 to 10000 ppm by weight. Propene oxide having a water content in this range is suitable for the preparation of 1,2-propylene glycol and propylene glycol ethers. All of the propene oxide products have a low content of carbonyl compounds and also typically contain less than 50 ppm by weight acetaldehyde. The mass ratio of stream S1 to stream S2 is preferably 0.5 to 5.0. Stream S2 may be withdrawn as a liquid stream or as a vapor stream and is preferably withdrawn as a vapor stream to provide a higher reflux ratio in the column section above the withdrawal point for stream S2, thereby increasing the purity of stream S1. Improve. Withdrawing a portion of the propene oxide product as side stream S2 with higher water content significantly reduces the energy consumption of the extractive distillation compared to prior art processes where all propene oxide products are withdrawn at or near the top of the column. .

In a further embodiment of the invention, the crude propene oxide is mixed with an aqueous alkaline solution and the final mixture is reacted for 1-60 minutes at a temperature of 20-100 ° C. before the mixture is fed to feed point A. The aqueous alkaline solution is preferably an aqueous solution of sodium hydroxide, potassium hydroxide, or sodium carbonate. Most preferably it is an aqueous sodium hydroxide solution containing 0.1 to 56% by weight sodium hydroxide. The amount of aqueous alkaline solution is preferably selected such that the molar ratio of hydroxide ions introduced into the aqueous alkaline solution is 1.1 to 4 relative to the amount of methyl formate contained in the crude propene oxide. Reacting the crude propene oxide with an aqueous alkaline solution converts it to methanol and formate by hydrolyzing the methyl formate contained in the crude propene oxide. The purified propene oxide obtained with this embodiment of the invention has a reduced content of methyl formate. Preferably the amount of aqueous alkaline solution is chosen to obtain purified propene oxide having a content of methyl formate less than 100 ppm by weight.

1 shows an embodiment of the invention wherein a reactive compound is fed to an extractive distillation column, mixed with an aqueous extraction solvent and stream S2 is withdrawn as a vapor stream. The extractive distillation column 1 has a feed point A 3 to which crude propene oxide 2 is fed and a feed point B 5 to which a reactive compound is fed and mixed with an aqueous extraction solvent 4. The extraction section between feed point A and feed point B comprises a tray, while the stripping section and the rectifying section comprise column packing. Stream S1 (6) is withdrawn from the top of the extractive distillation column and also provides a first propene oxide product with a low content of water, stream S2 (7) gives a second propene oxide product with a high content of water It is extracted from the extractive distillation column at draw point 8 located in the 5 to 25 theoretical separation stage above feed point B to provide. Stream S2 is withdrawn as a vapor stream and also condensed outside the column in a condenser, not shown.

Example

The energy consumption of the column reboiler was 49 wt% propene oxide, 46 wt% methanol, and 400 wt% using a stream of 2000 kg / h of water containing 0.5 wt% hydrazine as the reactive compound and the aqueous extraction solvent. Calculated with simulation software AspenPlus to purify a stream of 25830 kg / h of crude propene oxide containing ppm acetaldehyde. The calculation operates at 0.13 MPa and has 42 theoretical stages in the rectifying section with 14 theoretical stages in the stripping section, 25 theoretical stages in the extraction section, and a draw point for stream S2 (15) at 15 theoretical stages above feed point B. Is performed on an extractive distillation column.

In Example 1 not according to the invention, stream S2 is not withdrawn, and all propene oxide products are withdrawn at the top of the column. A stream S1 of 12500 kg / h of propene oxide with 80 ppm by weight of water is obtained at the top of the column. The energy consumption of the column reboiler is 7.32 MW.

In Example 2 according to the invention, stream S2 of 5000 kg / h propene oxide comprising 2000 ppm by weight of water is withdrawn at the withdrawal point for stream S2 and 7500 kg / h comprising 80 ppm by weight of water. Stream S1 of propene oxide of is withdrawn at the top of the column. In this case, the energy consumption of the column reboiler is 5.23 MW, ie 29% lower than in Example 1.

1 Extraction Distillation Column
2 crude propene oxide
3 Supply Point A
4 Reactive Compounds Mixed with Aqueous Extraction Solvent
5 Feed point B
6 stream S1
7 stream S2

Claims

As a process for purifying propene oxide,
a) crude propene oxide (2) comprising 15 to 97% by weight of propene oxide, 2 to 84% by weight of methanol, and acetaldehyde at feed point A (3) in the central section of the extractive distillation column (1) Supplying;
b) feeding an aqueous extraction solvent (4) to feed point B (5) of said extractive distillation column located above feed point A;
c) i) at feed point B,
ii) at feed point A, or
iii) at feed point C between feed point A and feed point B
Reactive compound of formula (I) to the extractive distillation column
(I) R ¹ -Y-NH ₂
Or feeding a salt of a compound of formula (I), wherein Y is oxygen or NR ² , and R ¹ and R ² , independent of each other, are hydrogen, an alkyl group or an aryl group;
d) withdrawing stream S1 (6) from the top of said extractive distillation column to provide a first propene oxide product; And
e) withdrawing stream S2 (7) from the extractive distillation column at withdrawal point (8) located in the theoretical separation stage of 5 to 25 above feed point B to provide a second propene oxide product
Including a process for purifying propene oxide.

The method of claim 1,
Wherein said reactive compound is a hydrazine, hydrazine hydrate or hydrazinium salt.

The method according to claim 1 or 2,
Wherein said reactive compound is fed to said extractive distillation column at feed point B and mixed with said aqueous extractive solvent.

The method according to claim 1 or 2,
The crude propene oxide comprises 4 to 4000 ppm acetaldehyde by weight.

The method according to claim 1 or 2,
Wherein the molar ratio of reactive compound to acetaldehyde is between 0.5 and 2.

The method according to claim 1 or 2,
Stream S2 is withdrawn as a vapor stream, process for purifying propene oxide.

The method according to claim 1 or 2,
A process for purifying propene oxide, wherein the mass ratio of stream S1 to stream S2 is 0.5 to 5.0.

The method according to claim 1 or 2,
A process for purifying propene oxide, wherein the mass ratio of the extracted solvent supplied to the amount of methanol contained in the crude propene oxide supplied is 0.01 to 1.

The method according to claim 1 or 2,
Feed point B is a process for purifying propene oxide, which is located in the theoretical separation stage of 15 to 40 above feed point A.

The method according to claim 1 or 2,
Feed point B is located in the theoretical separation stage of 20 to 60 below the top of the extractive distillation column.

The method according to claim 1 or 2,
The crude propene oxide is mixed with an aqueous alkaline solution and the final mixture is reacted for 1-60 minutes at a temperature of 20-100 ° C. before the mixture is fed to feed point A. .