The method of obtaining monomeric formaldehyde


C07C47/045 - having unsaturation outside the rings

 

(57) Abstract:

The invention relates to a method of obtaining from semiformal Monomeric formaldehyde high purity, used as a monomer in the production of high molecular polyacetylenic resins, as well as in the synthesis of numerous organic compounds based on it. The method of producing formaldehyde containing impurities of 0,03 0,003% by weight, with the release of 29.3 - 72,7% is thermal decomposition of semiformal methanol with a concentration of formaldehyde of 40 to 90 wt.% with the subsequent absorption of alcohol and impurities from the resulting gas-vapor mixture with an organic solvent at a temperature of from 0oC to the temperature of condensation of formaldehyde. Gas-vapor mixture formed during thermal decomposition, it may be subjected to partial condensation at a temperature of from +10oC to -10oC to achieve the concentration of formaldehyde in the vapor phase above 90% with the separation of the condensation products, and the stage partial condensation and absorption can be carried out in the presence of a gas inert to formaldehyde, or under vacuum. Thus, the formaldehyde with a total impurity content of 0.004 wt.% with the release of 29.3% obtained by thermal decomposition at 11 is mechaniem the resulting gas-vapor mixture with nitrogen (2.3 m3/h), the partial condensation of the mixture at the 5oC with separation of the liquid phase and the absorption of the vapor phase at -25oC white spirit. 2 C. and 8 C.p. f-crystals, 1 table.

The invention relates to a method of obtaining pure Monomeric gaseous formadehyde from semiformally. Obtained by this method formaldehyde can be used as a starting monomer in the production of high molecular polyacetylenic resins, and for the synthesis of numerous organic compounds based on formaldehyde.

Using semiformally (polypharmacy) to obtain pure formaldehyde is preferable for industrial scale. This was first proposed in 1958 [1].

Cleaned, practically anhydrous formaldehyde (water content of 40-100 hours per million) was obtained from the product of the interaction of formaldehyde-water compositions, containing at least 1% water, but mostly 30-45% formaldehyde, and alcohol with a boiling point at atmospheric pressure below 95oC, freed from water and represents semiformal, followed by thermal decomposition of the formed semiformal, separation of the resulting vapor and the release of high-purity formal the product of the partial concentration of vapours, formed by thermal decomposition of semiformal, as well as the introduction of the inert gas system before thermal decomposition.

A method of producing anhydrous Monomeric formaldehyde using semiformally polynuclear alcohols with a boiling point above 200oC and a vapour pressure of less than 2 mm RT. Art. at 100oC, in particular 1,1,1-trimethylolpropane (preferably), pentaerythritol and others [2] . The method consists in the concentration of gas-vapor stream containing formaldehyde with an aqueous solution of polynuclear alcohol with subsequent evaporation of the water content less than 0.5% and thermal decomposition of the resulting semiformal. The described method involves the use of contact gas production of formaldehyde by oxidation of methanol as formaldehydefree gas stream.

In later works, for continuous production of high-purity gaseous formaldehyde by thermal decomposition of semiformal high-boiling alcohols, the focus is on the development of technological parameters of thermolysis of semiformal and separation of the products of thermolysis.

In accordance with the joint Russian-German R the following condensation of a part of the resultant gas mixture, containing alcohol, formaldehyde and impurities in the heat exchanger in the presence of vapors of alcohol at a mass ratio of the vapor of the alcohol and formaldehyde from 5 : 1 to 1 : 3 when the linear velocity of the gas stream at the inlet of the machine from 5 to 30 m/s and the specific gravity irrigation resulting from the condensation surface of the heat exchanger at least 2.5 10-5m3/m2at the exit of the apparatus. According to the invention, it is preferable to use semiformal cyclohexanol containing 23-27% formaldehyde [3].

Semiformal with higher levels of formaldehyde used in the technical solution under the application of Japan [4], in which it is proposed to carry out thermolysis of semiformal high-boiling polynuclear alcohol at a pressure of 1 to 7 kg/cm2temperature 160-230oC and a contact time of less than 60 C., In particular from semiformal of trimethylolpropane containing 42.3% of formaldehyde, 1,23% water and 0.12% methanol, at thermolysis for 14 h at a speed of 30 g/min and a pressure of 2.5 kg/cm2when 160-210 was obtained formaldehyde containing significant amounts of water of 3.46-to 4.52% and 0.35-0.43 percent methanol.

The closest to the technical nature of the claimed method is a method of manufacturing anhydrous Monomeric formalize the Ares of the alcohol solvent, having a boiling point lower than the boiling point of the alcohol. Gas-vapor mixture obtained by thermolysis of semiformal, is sent to the scrubber column, where a counter is solvent with a boiling point of 80-160oC. the solvent can be used acyclic, cyclic, aromatic solvents and substituted hydrocarbons [6]. However, the high temperature absorption is not possible to obtain formaldehyde high purity because of the pollution it pairs high-boiling alcohol.

In this case, all known methods, including the method according to the prototype, involve the use of semiformal higher or polynuclear alcohols, the concentration of formaldehyde which is low. The content of formaldehyde semiformal methanol than other alcohols. This can significantly reduce transportation costs, to make production processes based on it is more economical from the point of view of energy consumption. In addition, semiformal methanol has a genetic relationship to the industrial method of production of formaldehyde by the catalytic dehydrogenation of methanol, which allows you to combine the processes of synthesis of formaldehyde, get gamefor the EIW of semiformal methanol was not used to obtain Monomeric formaldehyde due to the high volatility of methanol and the resulting complexity of the vapor-gas mixture separation, obtained by thermolysis of semiformal methanol.

The technical objectives of the proposed method is to increase the yield of the target product and the receipt of formaldehyde higher degree of purity.

The task is solved by the fact that in the method of obtaining pure formaldehyde from semiformal by thermal decomposition with subsequent absorption of methanol and impurities from the resulting gas mixture with an organic solvent as semiformal apply semiformal of methanol, and the absorbance is carried out at a temperature in the range of 0oC to the temperature of condensation of formaldehyde. In this case, applying semiformal methanol with a concentration of formaldehyde of 40-90 wt.%.

In order to increase the yield of the target product obtained by thermal decomposition of gas-vapor mixture, it is advisable to first subjected to a partial condensation at a temperature in the range from +10oC to - 10oC to achieve the concentration of formaldehyde in the vapor phase above 90% with the separation of the condensation products.

At this stage partial condensation and absorption can be performed in the presence of inert to formaldehyde gas, such as nitrogen, oxide of carbon is Ansatie and absorption under vacuum at a residual pressure of up to 250 mm RT. Art., preferably 700-500 mm RT. Art.

The temperature of the condensation of formaldehyde determined by the partial pressure of vapor in the system and is in the range from - 19oC to - 35oC.

As the organic solvent can be used which is inert to formaldehyde acyclic, cyclic, aromatic, naphthenic hydrocarbons or their mixtures with a melting point above 40oC. Preferred solvents: N. heptane, N. octane, called Noonan, toluene, gasoline, solvents, white spirit.

As the source semiformal, as mentioned above, apply semiformal methanol, which is a mixture of polyoxyethylenesorbitan General formula CH3O-(CH2O)n-H with a number n from 1 to 6, the concentration of formaldehyde which is 40-90%. This semiformal can be obtained by heating polyethylenoxide, such as paraform, in methanol to 120oC followed by cooling or by contacting gaseous formaldehyde in a distillation column with methanol at a temperature of not less than 50oC with output close to quantitative [5].

When using semiformal of methanol with formaldehyde content below 70% after the="ptx2">

The essence of the process lies in the fact that after thermal decomposition of semiformal the resulting gas-vapor mixture, consisting mainly of vapors of formaldehyde and methanol is brought into contact with the cooled organic solvent, resulting in the absorption of methanol vapor liquid and vapour after separation from the liquid phase remains practically free from methanol.

When the partial condensation meteorologico gas mixture is enriched gas mixture formaldehyde up to 90-95%, which is beneficial to the yield of the target product when conducting subsequent absorption of methanol.

Example 1. Semiformal of methanol containing 40 wt.% formaldehyde and 1.7% water, continuously will destroy with the speed of 10.4 kg/h at a temperature of 115oC. Formed during the degradation of a pair of formaldehyde, methanol and water mixed with nitrogen supplied in the amount of 2.3 m3/h, and the resulting gas-vapor mixture is subjected to partial condensation at a temperature of 10oC in the heat exchanger. When this occurs, the condensation of vapors of methanol, water and partially formaldehyde. The liquid phase is separated. The concentration of formaldehyde in the mixture relating serves down the absorption column diameter 60 mm, top of which is irrigated with white spirit, cooled to a temperature of - 25oC. the feed Rate of white spirit of 8.0 kg/h from the Top of the column selected purified gaseous formaldehyde with nitrogen containing impurities of methanol and water in total, the number of 0.004%. The release of formaldehyde from the submitted semiformal is 29.3 per cent.

Example 2. Semiformal methanol containing 72,3 wt.% formaldehyde will destroy continuously at the speed of 1230 g/h at a temperature of 123oC. the Resulting gas-vapor mixture of formaldehyde and methanol countercurrent serves down the absorption column with a diameter of 40 mm, which is on top of irrigate N. octane, cooled to a temperature of - 19oC. the feed Rate of N. octane 12 kg/h from the Top of the column select 507 g/h of purified gaseous formaldehyde, which is 65,6% of the submitted semiformal. The residual methanol content of 0.03%.

Example 3. Semiformal methanol containing 90.0% of formaldehyde, will continuously destroy with a speed of 1.4 kg/h at a temperature of 128oC. the Resulting gas-vapor mixture of formaldehyde and methanol is sent to the mixer of the type Venturi pipe, which serves toluene in the amount of 9.8 kg/h with a temperature of 0oC. After separation of gas and liquid phases in gas-the">

Example 4. Semiformal methanol containing 48.3% formaldehyde, continuously will destroy with the speed of 1.26 kg/h at a temperature of 117oC. the Resulting gas-vapor mixture of formaldehyde and methanol is sent to the heat exchanger, cooled to a temperature of - 10oC, where partial condensation of vapors of methanol and formaldehyde (partially). The liquid phase is separated. The concentration of formaldehyde in the vapor phase with respect to the remaining methanol is increased to 95.8%. Fortified gas-vapor mixture is fed down the absorption column with a diameter of 60 mm, which is above irrigated decaline cooled down to - 26oC, in the amount of 8.5 kg/h At this stage partial condensation and absorption of methanol in the column work under vacuum residual pressure 520 mm RT. Art. on Top of the column selected purified gaseous formaldehyde containing impurities of methanol in the amount of 0.003%. The release of formaldehyde from the submitted semiformal is 34.8%.

Example 5. Semiformal methanol containing 68% formaldehyde, continuously will destroy in the amount of 6.2 kg/h at a temperature of 118oC. Formed during the degradation of a pair of formaldehyde, methanol and water mixed with nitrogen, is fed in to the>C in the heat exchanger. When this occurs, the condensation of vapors of methanol, water and partially formaldehyde. The liquid phase is separated. The concentration of formaldehyde in the vapor phase with respect to the remaining methanol and water is increased to 90.3 per cent. Fortified by formaldehyde vapor-gas mixture is fed down the absorption column with a diameter of 60 mm, which is above water white spirit, cooled to a temperature of - 35oC. the feed Rate of white spirit 8.5 kg/h from the Top of the column selected purified gaseous formaldehyde with nitrogen containing traces of methanol. The release of formaldehyde and 33.4%.

Example 6 (control, prototype). Semiformal of cyclohexanol in the amount of 4.3 kg/h containing 23.2% of formaldehyde, will continuously destroy at a temperature of 158oC. Formed by decomposition of a gas-vapor mixture of formaldehyde and cyclohexanol sent down the absorption column with a diameter of 40 mm, which is on top of irrigate N. Dean at a temperature of 100oC in the amount of 5.6 kg/h from the Top of the column selected purified gaseous formaldehyde containing impurities of cyclohexanol in the amount of 0.17%. The release of formaldehyde from the original semiformal amounts to 19.4%.

Example 7 (control, similar to [3]). is mperature 140oC. Formed by decomposition of a gas-vapor mixture of formaldehyde and cyclohexanol is directed to a tubular heat exchanger in which the temperature of 25oC. in the heat exchanger is provided by the specific gravity irrigation 2,8 10-5m3/m2speed parogazovogo flow is 3.3 10-5m3/m2. After the separation of gas and liquid phases in gas-separator select the purified formaldehyde containing 0.12% admixture of cyclohexanol. The release of formaldehyde from the original semiformal at 17.8%.

Information on examples 1-7 are presented in the table.

As can be seen from the data on yield and quality of the resulting formaldehyde proposed method outperforms the methods on the prototype and similar.

Inventive step of the proposed solution is that for the first time implemented in a cost-effective and technically simpler way of obtaining pure formaldehyde from semiformal methanol, who had to carry out was not possible.

1. The method of obtaining Monomeric formaldehyde from semiformal by thermal decomposition with subsequent absorption of methanol and impurities from the resulting gas mixture org is orblue carried out at a temperature in the range of 0oC to the temperature of condensation of formaldehyde.

2. The method according to p. 1, characterized in that use semiformal methanol with a concentration of formaldehyde of 40 to 90 wt.%.

3. The method according to PP.1 and 2, characterized in that the absorption is carried out in the presence of inert to formaldehyde gas.

4. The method according to p. 3, characterized in that inert to formaldehyde gas using nitrogen.

5. The method according to PP. 1 and 2, characterized in that the absorption is carried out under vacuum.

6. The method of obtaining Monomeric formaldehyde from semiformal, including its thermal decomposition and absorption of methanol and impurities from the resulting gas mixture with an organic solvent, characterized in that as semiformal use semiformal methanol, and formed by thermal decomposition of gas-vapor mixture is subjected to partial condensation at a temperature in the range from +10oC to -10oC to achieve the concentration of formaldehyde in the vapor phase above 90% with the subsequent absorption at a temperature in the range from 0 to the temperature of condensation of formaldehyde.

7. The method according to p. 6, characterized in that the applied semiformal methanol concentration formaldehyde in the presence of inert to formaldehyde gas.

9. The method according to p. 8, characterized in that inert to formaldehyde gas using nitrogen.

10. The method according to PP. 6 and 7, characterized in that the partial condensation and absorption is carried out under vacuum.

 

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