CS258333B1 - Method of morpholine insulation from reaction mixture's aqueous morpholine fraction's from diethylenglykol's hydrogenation amination - Google Patents

Abstract

A method for isolating morpholine from aqueous morpholine hydrogenation reaction mixture fraction amination of diethylene glycol continuous rectification is that it is raw the aqueous morpholine mixture is rectified to the aggregate three columns, on the first column with efficiency 20 to 50 theoretical plates are atmospheric the pressure separates water and most of the impurities taking the distillation residue leaving 2 to 15 wt. water, zbjrtek ee leads to the second column where the remaining ones are separated water while the distillate returns to water first column, distillation left, second The ee column is sprayed into a third column which has an efficiency of 20 to 30 theoretical plates and washing at a pressure of 5 to 20 kPa and on as the overhead product obtains pure morpholine, distillation residue in a proportion of 50 to 100% returning to the crude reaction mixture the amination of diethylene glycol, 0 to 50.5 of the distillation residue is freed of most impurities and obtained crude morpholine returns to the first column.

Description

The invention relates to the isolation of morpholine by a continuous rectification of the reaction mixture obtained by the hydrogenation amination of diethylene glycol.

Morpholine is used for the preparation of sulfonamide rubber vulcanization accelerators, in the production of optical brighteners, pesticides, etc.

Morpholine is currently produced primarily by the hydrogenation amination of diethylene glycol. The reaction proceeds via a hydrogenation-dehydrogenation mechanism in the presence of metal catalysts in a hydrogen atmosphere. Nickel with various impurities, such as copper, chromium trioxide, etc., is used primarily as a catalyst. The amination of diethylene glycol is carried out either in the liquid phase at a pressure of 2 to 30 MPa, or in the gas phase at a pressure of 0.1 to 1 MPa at a temperature of 180 to 250 ° C.

In addition to morpholine, a number of edible products are produced by hydrogenation amination and the yield of reacted diethylene glycol is 60-93%, usually 70-80%. · Ammonia is separated from the reaction mixture and then usually separated into a low-boiling and high-boiling fraction: the proportion contains water, morpholine / t 128 DEG C., 2-methoxyethanol (124 DEG C.), 2-methoxyethylamine (95 DEG C.), N-methylmorpholine (115 DEG C.), N-ethylmorpholine (138 DEG C.), C-methylmorpholine (134 DEG C.). The high boiling portion contains diethylene glycol (245 ° C), 2- (2-amirioethoxy) ethanol (223 ° C), which is an intermediate in the formation of morpholine, 2- (N-). -morpholino / ethoxyethanol, 2,2-di / N-morpholino / diethyl ether, 3-morpholinone and many other substances.

Isolation of pure morpholine from the lower-boiling fraction of the reaction mixture is not easy for near boiling and azeotropic formation

- 2 mixtures. Water can be separated from morpholine by effective rectification, sometimes salting of morpholine with sodium hydroxide is used. The greatest difficulty is the separation of 2-methoxyethanol and C-methylmorpholine from morpholine. It has been found that 2-methoxyethanol forms a boiling peak azeotropic mixture with morpholine, and the azeotrope of 2-methoxyethanol with water is known. at atmospheric pressure 99.9 ° C, 2-methoxyethanol content 15% w / w. Thus, in rectifying the separation of water from morpholine, water tends to carry 2-methoxyethanol through the top of the column, while morpholine extracts it and retains it at the bottom of the column. The distribution of 2-methoxyethanol between the distillate and the distillation residue depends on many factors, in particular the feed composition, column efficiency, etc.

The reaction mixture from the amination of diethylene glycol contains greater or lesser amounts of C-methylmorpholine. The formation of this product upon amination of diethylene glycol is not yet described in the literature. It is probably 5-methylmorpholine. Especially in the parophasic amination process, this may be the major by-product. This substance forms an azeotropic mixture with minimal boiling water with water containing only about 2 to 5% of the organic substance. The liquid-vapor equilibrium of the binary morpholine-G-methylmorpholine mixture has not been measured yet. In the rectifying separation of water from morpholine, C-methylmorpholine is separated between the distillate and the distillation residue similar to 2-methoxyethanol.

N-Methylmorpholine and N-ethylmorpholine form distinctive azeotropic mixtures with a minimum of boiling point with water and both of these amines pass quantitatively into the aqueous distillate without problems. Distilled water also contains all low-boiling hydrogenolysis products such as methanol, ethanol, ethylamine, 2-methoxyethylamine, etc.

Thus, the major difficulty in isolating pure morpholine from the crude aqueous morpholine mixture is the removal of 2-methoxyethanol and C-methylmorpholine. The technical morpholine offered by different companies is contaminated by these two substances and it depends on the predominant mode of amination of diethylene glycol.

- 5 The literature describes rectifying separation of water from morpholine in a carbon dioxide atmosphere, with carbon dioxide still circulating through the rectification column at a weight ratio of about 2 parts of oxide to 1 part of water vapor (NSR 2,405,911, 1974) · Carbon dioxide reduces the relative volatility of primary and secondary amines, and therefore water is easier to separate and no more efficient column is needed than simple rectification. The main drawback of this process is the simultaneous reduction in the relative volatility of C-methylmorpholine, which remains in the heel product, i.e., crude morpholine, and is further converted to pure morpholine. When water is separated from morpholine by sodium hydroxide, C-methylmorpholine also remains quantitatively in the organic layer. In this case, the organic layer also contains all N-ethylmorpholine which is poorly separated from the morpholine by rectification.

These disadvantages and problems are solved by a process for the isolation of morpholine from the aqueous morpholine fraction of the reaction mixture from the hydrogenation amination of diethylene glycol by continuous rectification, characterized in that the crude aqueous morpholine mixture is rectified on a set of three columns. at atmospheric pressure, water and most of the impurities are separated, leaving 2-15% by weight in the distillation residue. The residue is fed to a second column where the remaining water is separated, the distillate being returned to the first column, the distillation residue of the second column being injected into a third column having an efficiency of 20 to 40 theoretical plates and operating at a pressure of 5 to 20. 50 to 100% of the distillation residue is returned to the crude reaction mixture of the amination of diethylene glycol, 0 to 50% of the distillation residue is removed from most impurities and the crude morpholine obtained is returned to the first column.

The best way to separate both incriminated contaminants from morpholine is by rectification with water. According to the invention there is a separation

% Of 2-methoxyethanol and C-methylmorpholine, together with water, is facilitated by leaving between 2 and 15 wt. water in the bottoms product of the first column by increasing the concentration of both impurities in the feed into the first column by recycling the distillation residue from the third column;

- 4 columns. If all the water was distilled off on the first column, the distillate contained only a few of the two impurities mentioned. Without recycling the distillation residue from the third column to the first column, much less impurities are separated along with the water than is generated by the amination of diethylene glycol; for example, the content of 2-methoxyethanol in the aqueous distillate is approximately proportional to its content in the feed into the first column.

By distilling off the water on a second column, the efficiency of which is not very important and therefore not indicated in the invention, the desired water content of the morpholine is usually below 0.5% by weight.

From an energy point of view, it is preferable to feed the distillate from the second column as vapor into the first column.

The efficacy of the first / water / column is 20 to 50 theoretical plates, preferably 30 to 40 theoretical plates, in order to limit the ingress of morpholine into the distilled water, a reflux ratio of 1.8 to 4, preferably 2 to 3 is used. 2 wt. % of methoxyethanol and 0.5 to 2 wt. The C-methylmorpholine, and if other readily volatile materials have not been removed beforehand, are also transferred to the aqueous distillate.

The third (morpholine) column is operated under vacuum, preferably at 7 to 12 kPa, i.e. a column head temperature of 58 to 67 ° C. The pressure reduction facilitates the separation of 2-methoxyethanol from morpholine and at the same time reduces the morpholine content of the azeotropic mixture. The pressure reduction has a slightly negative effect on the separation of C-methylmorpholine from morpholine. Separating both impurities to obtain morpholine containing less than 0.5 wt. admixture, requires rectification efficiency of 20 to 40 theoretical plates, preferably 25 to 35 theoretical plates, and a reflux ratio of 1 to 4. The two key impurities are concentrated at the bottom of the column to 10 to 30% by weight. /together/.

The proportion of the distillation residue that is returned to the reaction mixture and thus further to the first column depends on the composition of the crude reaction mixture, i.e. the selectivity, the hydrogenation amination of diethylene glycol. The main impurity is 2-methoxyethanol and C-methylmorph 253333

- 5 foils are low (liquid phase amination processes), it is possible to return all or almost all the distillation residue to the reaction mixtures. The exact proportion of the distillation residue returned to the reaction mixture must be determined experimentally for the plant together with the adjustment of the reflux ratios and in accordance with the morpholine purity requirements.

Typically, a portion of the distillation residue from the third column must be treated to separate most of the 2-methoxyethanol and C-methylmorpholine, and only the crude morpholine thus obtained can be returned to the reaction mixture or directly to the first column. The residue can be purified in many ways by physical, simple or azeotropic rectification or by a combination of physical chemical methods 8. The distillation residue thus treated is a relatively small amount, 2 to 15 wt. thus the morpholine produced and this part of the refining cannot influence the overall cost of morpholine isolation much. For example, most of the morpholine on the active batch column can be removed from the residue and the distilled morpholine returned to the reaction mixture or directly to the first column, a distillation residue containing not more than 50% by weight. morpholine is a waste. With higher yields of morpholine but with higher heat consumption, it is possible to separate morpholine from 2-methoxyethanol and C-methylmorpholine by rectification with water. To the distillation residue from the third column, which contains 60 to 85% morpholine, is added 5-10 times water and rectified with a reflux ratio of 2 to 3 on the column with an efficiency of about 30 theoretical plates, both impurities distilling with water and remaining as a distillation residue Crude morpholine. 2-Methoxyethanol can also be removed by distillation of the neutralized distillation residue from the third column as well as from the salts with amines released by sodium hydroxide. However, G-methylmorpholine cannot be removed in this way.

For the isolation of the morpholine according to the invention, the aqueous morpholine fraction of the reaction mixture as such or a freely volatile fraction such as methanol, ethanol, ethylamine, N-methylamorpholine, N-ethylmorpholine (both form azeotropes with minimum boiling water) may be used. If an untreated aqueous morpholine fraction is used, all fines will pass

- 6 to an aqueous distillate of the first column. From this distillate, these substances can be easily removed by rectification. The removal of readily volatile substances, even at any stage of the isolation of morpholine, is not related to the invention and is primarily due to the method of waste water disposal. When water distillate is incinerated, there is no point in removing volatile organic compounds, but this may be useful in the case of biological purification.

Example 1

One ton of the aqueous morpholine distillate of the reaction mixture is continuously processed on an array of three columns shown in the attached figure. The feed, including the distillation residue recycle, has a composition of stream A: 60 wt. % morpholine,% wt. water, 5 wt. 2-methoxyethanol, 1 wt. C-methylmorpholine, 2 wt. % N-alkylmorpholines, 1 wt. % of other volatile substances and 1 wt. low volatile high boilers.

Water column 1 has 60 valve plates (about 55 theoretical plates) and operates at a reflux ratio of 2.5. The feed is fed to the 10th floor from below. A mixture containing 8 wt. water. The distillate from the top of the column contains 0.2 wt. % morpholine, 1 wt. % C-methylmorpholine, 1.5 wt. 2-methoxyethanol and all other readily volatile substances.

The distillation residue from the first column was stripped of water to a level of 0.5% and a water distillate containing 50% by weight on a column 2 containing a 6 m pack of Pall rings. The morpholine is passed as vapor to the 15th floor of column 1. The column 2 is refluxed with a deflgmator.

The crude morpholine from the bottom of column 2 is injected onto column 2, which is operated at a pressure of 8.5 kPa and at a head temperature of 60 ° C. The column has an efficiency of 50 theoretical plates and a reflux ratio of 5.

Morpholine with a content of 0.05 wt. % Of C-methylmorpholine and 0.5. Of 2-methoxyethanol (stream B), a residue containing 25% by weight of morpholine was drawn off from the bottom of the column. % Of 2-methoxyethanol and 5 wt. % Of C-methylmorpholine; high-boilers (stream 0). Of this remainder, a 75% share was found in 253333

The original reaction mixture contains both impurities substantially less than the stated composition of the feed to column 1.

A quarter of the distillation residue from column 2 is rectified at a pressure of 8.3 kPa in a batch column. The distillate, i.e. morpholine containing 3 wt. impurities, returned to the aqueous morpholine mixture, distillation residue in the amount of 24 kg. / based on 1 h of continuous rectification / contains 10 kg of 2-methoxyethanol, 1.2 kg of C-methylmorpholine, 2.5 kg of boiling substances and 10.3 kg morpholine.

A total of 18 kg of 2-methoxyethanol and 5.7 kg of C-methylmorpholine Az are removed from the rectification system in the form of aqueous distillate, pure morpholine and distillation residue from the batch rectification, drawn to 1 continuous rectification, which is the amount of these impurities at steady state. which yields a crude reaction mixture from the amination of diethylene glycol.

Example 2

The aqueous morpholine mixture was treated as in Example 1 except that the distillation residue from column 2 was distilled with the addition of water. 250 kg of water are added to the 45 kg of distillation residue and 80% of the 2-methoxyethanol and virtually all C-methylmorpholine distilled off with water. The residue from this rectification containing morpholine, water and only 2 wt. 2-methoxyethanol is returned to the crude reaction mixture. The composition of the feed into the first column and the composition of the other streams do not differ significantly from Example 1.

Compared to Example 1, morpholine losses to waste are reduced by 9 kg / h, but an additional 0.7 t / h of steam is consumed.

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Example 3

In this case, the reaction mixture containing fewer impurities than in Examples 1 and 2 is treated on column 1 and worked

.8 complete recycling of distillation residue from the third column. The feed to the first column contained 60 wt. % morpholine, 43.2 wt. water, 2.2 wt. % 2-methoxyethanol, 0.6 wt. % C-methylmorpholine, 2 wt. % Of N-alkylmorpholine and 1 wt. % of high boilers and 1 wt. easily volatile impurities. A distillate containing practically all 2-methoxyethanol from the original reaction mixture (4 kg / h) and all C-methylmorpholine (3 kg / h) is passed from the top of column 1. The composition of pure morpholine obtained on column 5 is the same as in Example 1. Recycled 2-methoxyethanol represents almost 80% of that contained in column 1 feed;

Claims (3)

A process for the isolation of morpholine from an aqueous morpholine fraction of a reaction mixture from the hydrogenation amination of diethylene glycol by continuous rectification, characterized in that the crude aqueous morpholine mixture is rectified on a set of three columns, water is separated at atmospheric pressure on a first column with 20 to 50 theoretical plates. most impurities, leaving 2 to 15 wt. The residue is fed to a second column where the remaining water is separated, the distillate being returned to the first column, the distillation residue from the second column being injected into a third column having an efficiency of 20 to 50 theoretical plates and operating at a pressure of 5 to 20 50 to 100% of the distillation residue is returned to the crude reaction mixture of the amination of diethylene glycol, 0 to 50% of the distillation residue is removed from most impurities and the crude morpholine obtained is returned to the first column. 2. A process according to claim 1, wherein the distillate is fed from the second column to the first column in the vapor phase. 5. A method according to claim 1 or 2, characterized in that a portion of the distillation residue from the third column is rectified on a column having a efficiency of 20 to 50 theoretical plates, which is separated into crude morpholine which is returned to the first column and distillation column. residue which is waste '. Method according to Claims 1 and 2, characterized in that a part of the distillation residue is from. the third column is rectified by the addition of 5-10 times the amount of water and the distillation residue devoid of most of 2-methoxyethanol and C-methylmorpholine is returned to the reaction mixture.