Method of separating methanol from a by-product of the synthesis of 1,4 - butandiol

 

(57) Abstract:

The invention relates to chemical technology, more specifically to an improved method of separating methanol from a by-product of the synthesis of 1,4-butandiol (1,4-BID), obtained by the interaction of formaldehyde and acetylene, which finds application in the production of polymeric materials. With the aim of improving the quality target of 1.4-BID, reduce energy consumption and utilization of methanol proposed to carry out rectification by-product 1,4-BID, containing in addition to methanol, water, and admixture of formaldehyde and formic acid, in column efficiency 25-30 theoretical plates at a pressure in the cube column 400-1300 mm RT.art., pressure difference in the cube and in the top of the column 100-400 mm RT.article and the temperature difference at the fifth-eighth theoretical plate and the top of the column 25-35oC. the Distillation is carried out in the presence of a separating agent, which is used as the ultimate and unsaturated aliphatic alcohols WITH3-C5when the mass ratio of a separating agent: the amount of formaldehyde and formic acid, is equal to (0,2-4): 1. On the top of the column outline the targeted methanol, bottom - water formaldehyde mixed with formic acid and RT, propargilovyh alcohol and other alcohols WITH3-C5. This method allows you to improve the quality of 1,4-butandiol and reduce energy costs.

The invention relates to chemical technology, more specifically to an improved method of separating methanol from a by-product of the synthesis of 1,4-butandiol (1,4-BID), obtained by the interaction of formaldehyde and acetylene.

1,4-BID is the intermediate production of N-methylpyrrolidone is a highly effective solvent used in the manufacture of heat-resistant polymeric materials, and processes selection aromatic diene hydrocarbons from their mixtures with paraffin hydrocarbons by extraction and extractive distillation.

In the production process of 1,4-BID from acetylene and formaldehyde, the latter is used in the form of an aqueous solution containing methanol. An additional amount of methanol formed as a by-product during the synthesis of 1,4-BID from the source of formaldehyde. (Reference oil, so 2. - L.: Chemistry, 1978 - 592 S.).

In the purification and concentration of 1,4-BID as a by-product is derived distillate distillation purification of 1,4-BID, containing 15-30 % wt. methanol, 1-10 % wt. formaldehyde, tanol second grade, used as a component in the manufacture of solvents, absorbents and azeotropic agent in the allocation of xylenes from catalization reforming, must contain a minimum of 99.7 wt.%. the basic substance, not more than 0.15 wt.%. aldehydes, no more than 0,003% wt. acids, not more than 0.08 wt.%. water (C. E. Emelyanov, S. S. Zhukov, "the separation of xylenes". - M.: Chemistry, 1975, 160 C.).

Currently, technology selection, technical methanol from a by-product of the synthesis of 1,4-BID containing impurities of formaldehyde and formic acid, is absent, resulting in the specified by-product is sent for incineration.

The difficulty of separating methanol from these mixtures is due to the fact that the relative volatility of the system methanol - formaldehyde hydrate (hereinafter for brevity - just formaldehyde) in the presence of formic acid impurities close to unity. When the concentration of formaldehyde in methanol less than 1% wt., what takes place in the upper part of the distillation column for the separation of methanol, the relative volatility of the system methanol - formaldehyde is in the range of 1.06-1,12 that indicates the impossibility of separating methanol concentration of 99.7 wt.%. and above by the method of simple distillation. This is confirmed but - the methanol - formaldehyde solution under pressure at the top of the distillation column of 0.10 MPa at the bottom to 0.14 MPa, a temperature of the top - 65oC, bottom - 110oC, reflux among 12-15, at the top of the column into methanol with a concentration of 95-95,5% wt., with a formaldehyde content of 0.4-0.5% wt., water 4,0-4,6% wt

Known methods of separation of aliphatic aldehydes and alcohols by means of extractive distillation (Japan Patent N 5427311, publ. 8.09.79 class. 13/71327 C 07 C 31/02, the Federal Republic of Germany Patent N 1366548, CA 61 14531 that is). For this purpose, as extractive separating agent in the above methods is used: formamide, pyrrolidone, furfural, diamines, diethylsulfoxide.

According to these methods, a mixture of aliphatic aldehyde and alcohol is served in the middle part of the column extractive distillation efficiency 30-40 T. so , in the upper part of the column serves one of the above separating agents in the ratio of a separating agent:a mixture of (1-5):1 at reflux including 5-10.

As the distillate of the column extractive distillation produce aldehyde, as the cubic product is a mixture of alcohols and separating agent. Target alcohol is separated from the extractant by simple distillation. Data on concentration of impurities, and outputs the high thermolability proposed separating agents in the presence of water and acids, their hygroscopicity, resulting in the contamination of the target alcohols decomposition products. In addition, these agents are corrosive and require expensive equipment steels.

The known method of separation of methanol and aqueous formaldehyde by distillation with a separating agent, which is used as a hydrocarbon with a boiling point 30-120oC (Ed. mon. USSR N 431154 publ. 22.11.74, class C 07 C 45/24, C 07 C 47/04) (prototype method).

According to the prototype method, a separating agent is introduced into the raw material of the column in a mass ratio to the raw material, is equal to (0.2 to 0.5):1. On the top of the column allocate ternary azeotrope of hydrocarbon - methanol - water, from which the methanol washed with additional water. Target the methanol can be separated from aqueous solution by distillation on a column efficiency of 15-25 so so at reflux the number 3-7, depending on the content of methanol in aqueous solution. After washing the methanol hydrocarbon recycle to the column azeotropic distillation.

The disadvantage of the prototype method is technological complexity and high power consumption of the process of separation of methanol: must evaporate included in the ternary azeotrope hydrocarbon and water, and tada and water (Walher J. K. Formaldehyde 3d. ed New York - London Reinhold Corp., 1964) in the azeotrope of methanol - hydrocarbon - water the inevitable admixture of formaldehyde, which after washing azeotrope with water and re-rectification gets into the targeted methanol.

As follows from the data of example 13 of the present application, despite the efficiency of the used columns and high values of reflux ratio of 1 ton target of methanol, while working on the prototype method it is necessary to spend 5,73 tons of heating steam pressure of 5 MPa, and in the target methanol is present 0,37% wt. formaldehyde and 0,022% wt. formic acid.

The purpose of the present invention is the utilization of methanol contained in the by-product of the manufacture of 1,4-BID, improving quality, reducing energy costs.

The objective is achieved by distillation by-product 1,4-BID in column efficiency 25-30 so so, when the pressure in the cube column 400-1300 mm RT. Art., the pressure difference in the cube and in the top of the column 100-400 mm RT. Art. and the temperature difference at the fifth - eighth from the bottom of theoretical plates and the top of the column 25-35oC, with a separating agent, which is used as the ultimate and unsaturated aliphatic alcohols C3-C5when the mass ratio is shared by the mA impurities, formaldehyde and formic acid is designated by the term "impurities").

On the top of the column outline the targeted methanol, bottom - water formaldehyde mixed with formic acid and separating agent. As the separating agent is proposed to use propyl, propargilovyh, butyl, amyl alcohols and other alcohols C3-C5.

Salient features of the invention are:

the process of separation of methanol from mixtures containing formaldehyde, water, formic acid, by distillation with a separating agent, which is used as the ultimate and unsaturated alcohols C3-C5when the mass ratio of a separating agent:"impurities" in the power of the column (0,2-4):1;

the process of separation of methanol in a distillation column at a pressure in the cube column 400-1300 mm RT. Art., the pressure difference in the cube and in the top of the column 100-400 mm RT. Art., the temperature difference of the fifth - eighth of theoretical plates from the bottom of the column and the top of the column 25-35oC.

Failure to follow the above ranges of the proposed options do not allow to separate the methanol that meets the requirements of THE indicators: mass fraction of the basic substance, the concentration of impurities (formaldehyde, formic acid and water).Agueda method of separating methanol of high purity from mixtures containing impurities, considered similar by-product of the production of 1,4-BID. This indicates compliance with the essential distinctive features of the way the criteria of novelty and non-obviousness.

The conditions of the distinctive features related to the differential pressure of the cube and top, as well as the temperature difference of the fifth - eighth from the bottom of theoretical plates and the top of the column is achieved by regulating the flow of heating steam in the reboiler of the column and the cooling water in the reflux condenser.

The advantage of the proposed method compared with the method of the prototype is to simplify the process of extracting methanol, increasing the purity of the target product, reducing energy consumption for separation.

The method is illustrated by the following examples.

Example 1

(Average values of the requested parameters)

A byproduct of the synthesis of 1,4-BID composition, % wt.: methanol - 23,5; formaldehyde - 6,1; formic acid - 0,25; water - 70,15 with a flow rate of 1000 kg/h is sent to the power rectification column efficiency 30 so so together with the separating agent propargilovyh alcohol in the amount of 63.5 kg/hour, operating at a pressure in the cube column 970 mm RT. Art., the pressure difference between the us and the top of the column 29oC. the Mass ratio of a separating agent:"impurities" in the power of the column is equal to 1: 1. The temperature of the top of the column - 65,2oC, irrigation - 35oC cube column - 105,4oC.

On the top of the column outline the targeted methanol in the amount of 235 kg/h composition, % wt. : methanol 99,83; formaldehyde - 0,125; formic acid - 0,0027; water - 0,04. On bottom of the column produce the product in the quantity 828,5 kg/h composition, % wt.: methanol - 0.05; formaldehyde - 7,33; formic acid - 0,30; water - 84,66; propargilovyh alcohol - 7,66 which is sent to the column regeneration separating agent.

Consumption of heating steam pressure of 5 MPa for 1 tonne of methanol is 1,63 m/T. the Output target of methanol is 99,84 % wt. from the potential content in raw materials.

Example 2

The lower limit of the ratio of the separating agent:"impurities")

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that the ratio of a separating agent: "impurities" corresponds to the bottom of the claimed boundary, namely 0,2:1.

As a result, there target the methanol composition, % wt.: efficiency of 99.78; formaldehyde - 0,148; formic acid - 0,003; water - 0,069.

The flow rate of heating water vapor per 1 ton of methanol tx2">

Example 3

(The upper limit of the ratio of the separating agent:"impurities")

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that the ratio of a separating agent: "impurities" corresponds to the upper declare the border, namely 4:1.

As a result, there target the methanol composition, % wt.: 99,90; formaldehyde - 0,048; formic acid - 0,0017; water - 0,05.

The flow rate of heating water vapor per 1 ton of methanol to 1.58 t/T.

The yield of the desired methanol is 99.89 per cent wt. from the potential content in raw materials.

Example 4

The lower limit of the pressure in the cube column)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that the pressure in the cube column corresponds to the bottom of the claimed boundary, namely 400 mm RT. Art.

As a result, there target the methanol composition, % wt.: 99,92; formaldehyde - 0,044; formic acid - 0,0014; water - 0,03.

The flow rate of heating water vapor per 1 ton of methanol is 1.75 t/T.

The yield of the desired methanol is 99,86% wt. from the potential content in raw materials.

Example 5

(Upper limit pressure in the cube Colo is in that the pressure in the cube column corresponds to declare the border, namely 1300 mm RT. Art.

As a result, there target the methanol composition, % wt.: 99,80; formaldehyde - 0,149; formic acid - 0,0029; water - 0,05.

The flow rate of heating water vapor per 1 ton of methanol is of 1.93 t/T.

The yield of the desired methanol is 99,63% wt. from the potential content in raw materials.

Example 6

The lower limit of the pressure difference between the cube and the top of the column)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that the pressure difference between the cube and the top of the column corresponds to the bottom of the claimed boundary, namely 100 mm RT. Art.

As a result, there target the methanol composition, % wt.: 99,82; formaldehyde - 0,121; formic acid - 0,0019; water - 0,06.

The flow rate of heating water vapor per 1 ton of methanol is 1,68 m/so

The yield of the desired methanol is 99,52% wt. from the potential content in raw materials.

Example 7

(Upper limit of the pressure difference between the cube and the top of the column)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that different is S="ptx2">

As a result, there target the methanol composition, % wt.: efficiency of 99.78; formaldehyde - 0,147: formic acid - 0,0027; water - 0,07.

The flow rate of heating water vapor per 1 ton of methanol is 1,72 m/so

The yield of the desired methanol is 99,64% wt. from the potential content in raw materials.

Example 8

The lower limit of the temperature difference between the fifth theoretical plate from the bottom of the column and the top of the column)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that the temperature difference between the fifth theoretical plate from the bottom of the column and the top of the column corresponds to the bottom of the claimed boundary, namely 25oC.

As a result, there target the methanol composition, % wt.: 99,79; formaldehyde - 0,134; formic acid - 0,0026; water - 0,07.

The flow rate of heating water vapor per 1 ton of methanol is 1,96 t/T.

The yield of the desired methanol is 99,25% wt. from the potential content in raw materials.

Example 9

The upper boundary of the temperature difference between the fifth theoretical plate from the bottom of the column and the top of the column)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, for sootwetstwuet claimed the top border namely, 35oC.

As a result, there target the methanol composition, % wt.: 99,81; formaldehyde - 0,115; formic acid - 0,0025; water - 0,07.

The flow rate of heating water vapor per 1 ton of methanol is 1.36 t/T.

The yield of the desired methanol is 99,68% wt. from the potential content in raw materials.

Example 10

(N-propyl alcohol as a separating agent)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that as a separating agent used propyl alcohol in a ratio of 1:1 to the "impurities" in the power of the column.

As a result, there target the methanol composition, % wt.: 99,84; formaldehyde - 0;09; formic acid - 0,0024; water - 0,07.

The flow rate of heating water vapor per 1 ton of methanol is 1,79 m/so

The yield of the desired methanol is 99,32% wt. from the potential content in raw materials.

Example 11 N-amyl alcohol as a separating agent)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that as a separating agent used amyl alcohol in a ratio of 1:1 to the "impurities" in the power of the column.

The flow rate of heating water vapor per 1 ton of methanol is 1,96 t/T.

The yield of the desired methanol is 99,15% wt. from the potential content in raw materials.

Example 12

(Without a separating agent for comparison)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that the process is conducted without separating agent and the temperature difference between the fifth theoretical plate from the bottom of the column and the top of the column 23oC.

As a result, there target the methanol composition, % wt.: to 99.00; formaldehyde - 0,23: formic acid - 0,0093; water - 0,76.

The flow rate of heating water vapor per 1 ton of methanol is 2,94 t/T.

The yield of the desired methanol is 98,56% wt. from the potential content in raw materials.

Example 13

(method prototype)

Raw materials of the composition shown in example 1, is subjected to separation as in example 1, except that as a separating agent using n-hexane. The mass ratio of a separating agent:raw materials equal to 0.45: 1. On the top of the column at a temperature of 58oC allocate mixture in an amount of 702,68 kg/h composition, % wt.: methanol - 32,83: n-hexane - 64,04: formaldehy MESI aqueous solution of methanol, mixed with formaldehyde composition, % wt.: methanol - 76,80; formaldehyde - 0,29; formic acid - 0,01; water - 22,90 sent to distillation column efficiency 30 so so, where at reflux the number 2 on the top of the column produce the target product composition, % wt.: methanol - 99,17; formaldehyde - 0,37; formic acid - 0,022; water - 0,438.

The heating steam consumption per 1 ton of methanol is 5,73 t/T.

The yield of the desired methanol is 98,17% wt. from the potential content in raw materials.

Method of separating methanol from a by-product of 1,4-butynediol containing in addition to methanol, water, and admixture of formaldehyde and formic acid by rectification with a separating agent, characterized in that the process of allocation of methanol are in a distillation column at a pressure in the cube columns 400 - 1300 mm RT.article the pressure difference between the cube and the top of the column 100 - 400 mm RT.art., the temperature difference between the fifth-eighth theoretical plate from the bottom of the column and the top of the column 25 - 35oC, and as a separating agent use limit and unsaturated aliphatic alcohols WITH3-C5when the mass ratio of the power of the column separating agent : amount of impurities, formaldehyde and formic acid, is equal to (0,2 - 4) : 1, vyd

 

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