CN109851484B - Catalytic rectification device and method for preparing methylal from methanol and formaldehyde - Google Patents
Catalytic rectification device and method for preparing methylal from methanol and formaldehyde Download PDFInfo
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Abstract
The application discloses catalytic rectification equipment for preparing methylal from methanol and a formaldehyde aqueous solution and a using method thereof, and belongs to the field of chemical equipment. The catalytic rectification equipment comprises a stripping section, a first catalytic rectification section and a second catalytic rectification section. The first catalytic rectification section is filled with a first catalyst, and the first catalyst is selected from at least one of solid acids such as strong-acid cation exchange resin, acidic molecular sieve catalyst and the like; the second catalytic rectifying section is positioned above the first catalytic rectifying section and is filled with a second catalyst, and the second catalyst is selected from one or more of silicon dioxide, alumina, activated carbon, magnesium silicate and potassium aluminosilicate. Compared with the traditional catalytic rectification equipment, the equipment can be operated under a lower reflux ratio, so that the energy consumption is reduced, the content of methanol and formaldehyde in the prepared methylal product is low, and the purity of the methylal product is high.
Description
Technical Field
The application relates to a catalytic rectification device and a catalytic rectification method, in particular to a catalytic rectification device and a catalytic rectification method for preparing methylal from methanol and a formaldehyde aqueous solution, and belongs to the field of chemical industry.
Background
Methylal is also called dimethoxymethane and has a molecular formula of CH3OCH2OCH3It is a colorless, nontoxic and environment-friendly chemical raw material. Usually, methanol and formaldehyde aqueous solution are used for preparing the catalyst through aldol condensation reaction, and the reaction formula is as follows,
the japanese asahi chemical company, chinese patent CN 1020450C, discloses a catalytic rectification method for producing methylal from aqueous formaldehyde solution and methanol, which adopts a form of a secondary reactor arranged outside a catalytic rectification column and takes macroporous or gel type cation exchange resin as a catalyst.
Chinese patent CN 102351666 a discloses a catalytic rectification method for continuously producing high-concentration methylal from formaldehyde solution and methanol, which also adopts a form of secondary reactor.
Chinese patent No. CN 100344596C discloses a method for preparing methylal by combining continuous reactive distillation and liquid-liquid extraction, wherein the mixture of methylal, methanol and water obtained after reactive distillation is extracted in a liquid-liquid extraction tower to obtain methylal, and the extractant is glycerol or dimethanolamine.
Chinese patent CN 102070417 a discloses a catalytic rectification process for producing methylal from formaldehyde solution and methanol and a production device thereof, wherein cation exchange resin is used as a catalyst, and a catalytic rectification tower filled with a catalyst bundling bag is adopted.
Chinese patent CN 106268247 discloses a catalytic absorption method of formaldehyde, which absorbs formaldehyde from a gas phase material containing formaldehyde into a liquid absorbent, wherein the liquid absorbent is contacted with a solid catalyst; the method is used for producing formaldehyde, can reduce the absorption temperature, is more beneficial to obtaining high-concentration formaldehyde solution, and can also reduce the required theoretical plate number of the absorption tower.
Formaldehyde exists in various forms in water and methanol solutions, including formaldehyde monomer molecules, methylene glycol, polyoxymethylene glycol with different polymerization degrees, and hemiacetal with different polymerization degrees, which can be mutually converted without a catalyst. The characteristic causes that the methylal prepared by the catalytic distillation process contains a certain amount of formaldehyde, which affects the product quality.
Disclosure of Invention
According to one aspect of the application, a catalytic rectification device for preparing methylal from methanol and formaldehyde is provided, and the device has the advantages of low content of methanol and formaldehyde in the prepared methylal product, high purity of the methylal product and low energy consumption.
The catalytic rectification device for preparing methylal from methanol and formaldehyde comprises a first catalytic rectification section and a second catalytic rectification section;
the second catalytic distillation section is connected in series with the upper part of the first catalytic distillation section;
a first catalyst is filled in the first catalytic rectification section;
at least a portion of the second catalytic distillation section is packed with a second catalyst.
Optionally, the first catalyst is selected from at least one of solid acid catalysts.
Further, the solid acid catalyst is selected from at least one of a strong acid cation exchange resin and an acidic molecular sieve catalyst.
Further, the strong-acid cation exchange resin is selected from at least one of sulfonated styrene-divinylbenzene copolymer resin and perfluorinated sulfonic acid resin.
Further, the acidic molecular sieve catalyst is selected from at least one of HZSM-5 molecular sieve, HBeta zeolite molecular sieve and HMCM-22 zeolite molecular sieve.
Still further, the first catalyst is at least one selected from sulfonated styrene-divinylbenzene copolymer resin, perfluorosulfonic acid resin, HZSM-5 molecular sieve, HBeta zeolite molecular sieve and HMCM-22 zeolite molecular sieve.
Optionally, the acidic molecular sieve catalyst is made from at least one of the acidic molecular sieves and a binder. Further, the binder is alumina.
Optionally, the second catalyst is selected from at least one of silica, alumina, activated carbon, silicates, aluminosilicates. Wherein the silica includes various silica gels.
Further, the silicate is selected from one or more of calcium silicate, iron silicate, magnesium silicate and aluminum silicate.
Still further, the silicate is magnesium silicate.
Further, the aluminosilicate is selected from one or more of potassium aluminosilicate, sodium aluminosilicate, magnesium aluminosilicate and calcium aluminosilicate.
Further, the aluminosilicate is potassium aluminosilicate.
Optionally, a methanol feedstock feed inlet is located at least one location in a lower portion of the first catalytic distillation section.
Optionally, a formaldehyde feed inlet is located in an upper portion of the first catalytic distillation section and/or at least one location of the second catalytic distillation section.
Optionally, the formaldehyde feedstock is an aqueous formaldehyde solution.
According to yet another aspect of the present application, there is provided a process for the preparation of methylal from methanol and formaldehyde using at least one of the above-described catalytic distillation apparatus.
Optionally, the operating pressure of the catalytic distillation device is 0-0.6 MPa gauge pressure.
In this application, the pressure is gauge pressure.
The temperature of the first catalytic distillation section is 45-160 ℃.
The reflux ratio of the catalytic rectification device is 0.3-3.
Furthermore, the reflux ratio of the catalytic rectification device is 0.5-1.5.
In a first catalytic rectifying section of a catalytic rectifying tower, methanol and formaldehyde aqueous solution are subjected to aldol condensation reaction under the action of a first catalyst to generate methylal, and the total reaction formula is as follows:
in fact, only a very small portion of the formaldehyde in the aqueous formaldehyde solution exists as formaldehyde monomer molecules, and the vast majority of the formaldehyde exists as methylene glycol (HOCH)2OH, abbreviated as MG, formed by the hydration of monomeric formaldehyde and polyoxymethylene glycols of different degrees of polymerization (HO (CH)2O)nH, abbreviated as MGn，n>1) Exist in the form of (1). MG, MGnAnd water and monomer formaldehyde can be mutually converted without a catalyst.
The raw material methanol firstly reacts with methyl glycol to generate hemiacetal (HOCH)2OCH3Abbreviated as HF), the reaction proceeds without a catalyst and has the following formula:
the hemiacetal can be reacted with methanol under the action of the first catalyst to generate methylal (CH)3OCH2OCH3Abbreviated DMM) according to the following reaction formula:
the generated methylal leaves the first catalytic rectification section under the rectification action and is enriched and extracted to the top of the tower, and the water generated by the reaction and the water brought by the formaldehyde aqueous solution are extracted from the bottom of the catalytic distillation tower, so that the chemical balance of the reaction is broken, the reactions (2) and (3) are promoted to be carried out in the positive direction, and the complete conversion of the formaldehyde is achieved.
One of the functions of the second catalytic distillation section of the catalytic distillation tower is to make formaldehyde in ascending steam enter a liquid phase material and return to the first catalytic distillation section for continuous reaction. The process can be regarded as a reaction absorption process, namely formaldehyde in steam is firstly dissolved into a liquid phase in a monomer molecular form, and the formaldehyde dissolved in the liquid phase reacts with water or methanol in the liquid phase to generate the methylene glycol or the hemiacetal; the reaction process can be carried out without a catalyst, but the reaction speed is slow.
The inventor of the application finds that the second catalyst is filled in the second catalytic rectification section of the catalytic distillation tower, so that the reaction of the free formaldehyde dissolved in the liquid phase and water can be promoted to generate the methyl glycol and the polyoxymethylene glycol, or the reaction of the free formaldehyde dissolved in the liquid phase and the methanol can generate the hemiacetal, and the decomposition of the methyl acetal is avoided; therefore, the reaction speed of formaldehyde to generate the methylene glycol or the hemiacetal can be greatly improved, so that the concentration of formaldehyde monomer molecules in liquid-phase materials is rapidly reduced, the driving force of the formaldehyde absorption process is improved, the formaldehyde in rising steam returns to the first catalytic rectification section to continue to react, and the concentration of the formaldehyde and the methanol in a methylal product is reduced.
The inventors of the present application have found that, in the case where the formaldehyde feed is fed to the second catalytic distillation stage, the catalytic distillation apparatus can achieve higher product purity with lower reflux ratio and lower energy consumption. Since methylal forms a low boiling azeotrope with methanol (azeotropic composition: methylal 93 wt%, methanol 7 wt%), the methylal product taken at the top of the catalytic distillation unit usually contains a certain amount of methanol; the formaldehyde aqueous solution as the reaction raw material is introduced from at least one position of the second catalytic distillation section of the catalytic distillation device, so that methanol azeotropic with methylal can react with formaldehyde to generate hemiacetal with a higher boiling point (104 ℃) and returns to the first catalytic distillation section, thereby further reducing and improving the content of methanol in the methylal extracted from the top, and the second catalyst filled in the second catalytic distillation section can promote the reaction to obtain better effect.
Optionally, in the feed of the catalytic rectification device, the molar ratio of methanol to formaldehyde is (2-2.2): 1. in the present application, in the molar ratio of methanol to formaldehyde, the mole number of methanol to formaldehyde is the mole number of methanol to formaldehyde in the whole feed.
Optionally, the formaldehyde raw material is a formaldehyde aqueous solution with a formaldehyde mass percentage of 10 wt% to 55 wt%.
Furthermore, the formaldehyde aqueous solution also contains 0.01 wt% -10 wt% of methanol.
The beneficial effects that this application can produce include:
1) compared with the traditional catalytic rectification equipment, the catalytic distillation equipment for preparing the methylal from the methanol and the formaldehyde aqueous solution has the advantages that the content of the methanol and the formaldehyde in the prepared methylal product is low, and the purity of the methylal product is high;
2) compared with the traditional catalytic rectification process, the method for preparing the methylal from the methanol and the formaldehyde aqueous solution has the advantages that the content of the methanol and the formaldehyde in the prepared methylal product is low, and the purity of the methylal product is high; the catalytic rectification tower can be operated at a lower reflux ratio, so that the energy consumption is reduced, and the purity of methylal can still be ensured.
Drawings
FIG. 1 is a schematic diagram of a catalytic distillation apparatus for preparing methylal from methanol and formaldehyde according to an embodiment of the present application.
FIG. 2 is a schematic diagram of a catalytic distillation apparatus for preparing methylal from methanol and formaldehyde according to an embodiment of the present application.
FIG. 3 is a schematic diagram of a catalytic distillation apparatus for preparing methylal from methanol and formaldehyde according to an embodiment of the present application.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
Unless otherwise specified, the reaction raw materials, catalysts, packing materials for catalytic distillation apparatus (phi 3 x 3 mm stainless steel theta mesh ring, phi 5 x 5 mm stainless steel theta mesh ring) and stainless steel wire mesh bags in the examples of the present application were all purchased commercially, and all the raw materials were analytical reagents.
Among them, perfluorosulfonic acid resin (Nafion-H resin for short) was purchased from DuPont, U.S.A. The sulfonated styrene-divinylbenzene copolymer strongly acidic cation exchange resin was purchased from Dandong Mingzhu Special resin Co.Ltd (product No. D005).
The analysis method in the examples of the present application is as follows:
the gas chromatography is used for analyzing the components of the material, namely the content of methylal, methanol, water, formaldehyde and other components.
The discharge of the top and bottom of the column was measured using an electronic balance and stopwatch.
In the following examples and comparative examples, not illustrated, the formaldehyde content of the aqueous formaldehyde solution was 38 wt% and the methanol content was 3 wt%.
Example 1
As shown in fig. 2, the catalytic distillation column comprises, from top to bottom, an overhead condensate reflux device, a second catalytic distillation section, a first catalytic distillation section, a stripping section and a column bottom reboiler.
The inner diameter of the tower body is 50 mm, and the effective heights of the second catalytic distillation section and the stripping section are both 0.57 m; spherical silica gel with the diameter of phi 3-5 mm and stainless steel theta net rings with the diameter of phi 3 multiplied by 3 mm are mixed and filled in the second catalytic rectification section, and the volume ratio of the spherical silica gel to the stainless steel theta net rings is 1: 3; the stripping section is filled with stainless steel theta net rings with the diameter of phi 3 multiplied by 3 mm. The effective height of the first catalytic rectification section is 0.97 m, 15 stainless steel wire mesh bags which are uniformly mixed and 1300 ml of stainless steel theta mesh rings with phi 5 multiplied by 5 mm are filled, and 500 ml of Nafion-H resin is filled in the stainless steel wire mesh bags to serve as a catalyst.
Feeding the formaldehyde aqueous solution at a feeding rate of 14mL/min and a feeding temperature of 40 ℃, and feeding the formaldehyde aqueous solution from the upper end of the second catalytic distillation section to a position 40 cm below the upper end of the second catalytic distillation section; the feeding amount of methanol is 16.2mL/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the first catalytic rectification section; the operation pressure of the catalytic distillation tower is normal pressure, and the reflux ratio at the top of the tower is 1. After the operation is stable, the temperature of the first catalytic distillation section is 45-68 ℃, and the discharge amount at the top of the tower is 15.6 g/min; the material composition is 94 wt% of methylal, 5.8 wt% of methanol, 0.1 wt% of water and 0.01 wt% of formaldehyde; the discharge amount of the tower bottom is 12.4g/min, the material composition is 99.9 wt% of water, and the other is less than 0.1 wt%.
Example 2
The same catalytic distillation column as in example 1 was used.
Different from the embodiment 1, the second catalytic rectification section is mixed and filled with alumina strip-shaped particles with the diameter of 2 x 4-6 mm and stainless steel theta net rings with the diameter of 3 x 3 mm, and the volume ratio of the alumina strip-shaped particles to the stainless steel theta net rings is 1: 3; the first catalytic rectification section is filled with 15 stainless steel wire net bags and 1300 ml stainless steel theta net rings with phi 5 multiplied by 5 mm which are uniformly mixed, and the stainless steel wire net bags are filled with 500 ml D005 type strong acid cation exchange resin as a catalyst.
Feeding the formaldehyde aqueous solution at 16mL/min and 40 ℃ from the upper end of the second catalytic distillation section to the lower part of the second catalytic distillation section; the feeding amount of methanol is 18.6mL/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the first catalytic rectification section; the operating pressure of the catalytic distillation tower is normal pressure, and the reflux ratio at the top of the tower is 1.5. After the operation is stable, the temperature of the first catalytic distillation section is 50-70 ℃, and the discharge amount at the top of the tower is 17.8 g/min; the material composition is 93.4 wt% of methylal, 5.8 wt% of methanol, 0.8 wt% of water and 0.01 wt% of formaldehyde; the discharge amount of the tower bottom is 14.2g/min, the material composition is 99.9 wt% of water, and the other is less than 0.1 wt%.
Example 3
The catalytic distillation column used was the same as in example 2 except for the feed position of the formaldehyde raw material, as shown in FIG. 1.
Feeding formaldehyde aqueous solution at the temperature of 40 ℃ at the feeding amount of 15.7mL/min and the feeding temperature of 40 ℃ from the upper end of the first catalytic rectification section; the feeding amount of methanol is 18.5mL/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the first catalytic rectification section; the operating pressure of the catalytic distillation column was 0.1MPa (gauge pressure), and the overhead reflux ratio was 0.8. After the operation is stable, the temperature of the first catalytic distillation section is 55-80 ℃, and the discharge amount at the top of the tower is 17.7 g/min; the material composition is 92.2 wt% of methylal, 6.8 wt% of methanol, 1 wt% of water and 0.02 wt% of formaldehyde; the discharge amount of the tower bottom is 13.9g/min, the material composition is 99.9 wt% of water, and the other is less than 0.1 wt%.
Example 4
The same catalytic distillation column as in example 2 was used.
Feeding formaldehyde aqueous solution at the feeding rate of 15.1mL/min and the feeding temperature of 50 ℃, and feeding the formaldehyde aqueous solution from the upper end of the second catalytic distillation section to a position 40 cm below the upper end of the second catalytic distillation section; feeding methanol at 17.8mL/min and 70 ℃ from the lower end of the first catalytic rectification section; the operating pressure of the catalytic distillation tower was 0.1MPa (gauge pressure) and normal pressure, and the reflux ratio at the top of the tower was 0.3. After the operation is stable, the temperature of the first catalytic distillation section is 55-82 ℃; the discharge amount at the top of the tower is 17g/min, and the material composition comprises 92.3 wt% of methylal, 6.8 wt% of methanol, 0.9 wt% of water and 0.03 wt% of formaldehyde; the discharge amount of the tower bottom is 13.4g/min, the material composition is 99.9 wt% of water, and the other is less than 0.1 wt%.
Example 5
The same catalytic distillation column as in example 1 was used.
The analytically pure formaldehyde aqueous solution reagent is diluted by water to the formaldehyde content of 10 wt% as a reaction raw material, wherein the methanol content is diluted to 0.78 wt%. Feeding the 10 wt% formaldehyde aqueous solution at 81mL/min and 60 ℃ from the upper end of the second catalytic distillation section to a position 40 cm below the upper end of the second catalytic distillation section; the feeding amount of the methanol is 22.4mL/min, the feeding temperature is 70 ℃, and the methanol is fed from the lower end of the first catalytic rectification section; the operating pressure of the catalytic distillation column was 0.2MPa (gauge pressure), and the overhead reflux ratio was 1.5. After the operation is stable, the temperature of the first catalytic distillation section is 70-90 ℃; the discharge amount at the top of the tower is 21.7g/min, and the material composition comprises 96.8 wt% of methylal, 2.8 wt% of methanol, 0.4 wt% of water and 0.01 wt% of formaldehyde; the discharge amount of the tower bottom is 78.8g/min, the material composition is 99.9 wt% of water, and the other is less than 0.1 wt%.
Example 6
The catalytic distillation column used is as shown in FIG. 1, and is the same as in example 3 except that the first catalytic distillation section is filled with a different catalyst.
The first catalytic rectification section is filled with a phi 2X 5-7 mm strip molecular sieve catalyst and a phi 5X 5 mm stainless steel theta mesh ring in a mixed mode, the volume ratio of the catalyst to the theta mesh ring is 1:2, and the molecular sieve catalyst comprises 80 wt% of HZSM-5 and 20 wt% of alumina binder.
Feeding formaldehyde aqueous solution at the temperature of 90 ℃ at the feeding rate of 23mL/min and at the upper end of the first catalytic rectification section; the feeding amount of methanol is 26.8mL/min, the feeding temperature is 80 ℃, and the methanol is fed from the lower end of the first catalytic rectification section; the operating pressure of the catalytic distillation column was 0.5MPa (gauge pressure), and the overhead reflux ratio was 0.5. After the operation is stable, the temperature of the first catalytic distillation section is 110-140 ℃; the discharge amount at the top of the tower is 25.7g/min, and the material composition comprises 92.9 wt% of methylal, 6.3 wt% of methanol, 0.8 wt% of water and 0.02 wt% of formaldehyde; the discharge amount of the tower bottom is 20.3g/min, the material composition is 99.9 wt% of water, and the other is less than 0.1 wt%.
Example 7
The catalytic distillation column used is as shown in FIG. 1, and is the same as that used in example 3 except that the first and second catalytic distillation sections are filled with different catalysts. Different from the embodiment 1, the upper half section of the second catalytic rectification section is filled with activated carbon particles with phi 3 x 4-6 mm and stainless steel theta net rings with phi 3 x 3 mm in a mixed mode, the volume ratio of the activated carbon particles to the stainless steel theta net rings is 1:3, and the lower half section of the second catalytic rectification section is filled with the stainless steel theta net rings with phi 3 x 3 mm; the first catalytic rectification section is filled with a phi 2 x 5-7 mm strip molecular sieve catalyst and a phi 5 x 5 mm stainless steel theta mesh ring in a mixed mode, the volume ratio of the catalyst to the theta mesh ring is 1:2, and the molecular sieve catalyst comprises 70 wt% of HBeta zeolite and 30 wt% of alumina binder.
Feeding the formaldehyde aqueous solution at the temperature of 100 ℃ at 18.4mL/min from the upper end of the first catalytic distillation section; feeding methanol at 21.6mL/min and 120 ℃ from the lower end of the first catalytic rectification section; the operating pressure of the catalytic distillation column was 0.5MPa (gauge pressure), and the overhead reflux ratio was 2. After the operation is stable, the temperature of the first catalytic distillation section is 112-130 ℃; the discharge amount at the top of the tower is 20.7g/min, and the material composition comprises 92.2 wt% of methylal, 6.8 wt% of methanol, 1 wt% of water and 0.02 wt% of formaldehyde; the discharge amount of the tower bottom is 16.2g/min, and the material composition comprises 99.9 wt% of water and less than 0.1 wt% of others.
Example 8
As shown in FIG. 3, the catalytic distillation column used was the same as in example 1 except that the first and second catalytic distillation stages were filled with the catalyst and the feed position of the formaldehyde raw material were different. Different from the example 1, the upper half section of the second catalytic rectification section is mixed and filled with a mixture of magnesium silicate and potassium aluminosilicate particles with the diameter of 2 multiplied by 4-6 mm, wherein the mixture is 50 wt% of each particle, and a stainless steel theta mesh ring with the diameter of 3 multiplied by 3 mm, the volume ratio of the stainless steel theta mesh ring is 1:3, and the lower half section is filled with the stainless steel theta mesh ring with the diameter of 3 multiplied by 3 mm; the first catalytic rectification section is filled with a phi 2 x 5-7 mm strip molecular sieve catalyst and a phi 5 x 5 mm stainless steel theta mesh ring in a mixed mode, the volume ratio of the catalyst to the theta mesh ring is 1:2, and the molecular sieve catalyst comprises 70 wt% of HMCM-22 zeolite and 30 wt% of alumina binder.
Mixing a paraformaldehyde reagent with a proper amount of water, heating and dissolving to prepare a formaldehyde aqueous solution with the formaldehyde content of 55 wt% as a reaction raw material, wherein methanol is not contained. The total feeding amount of 55 wt% formaldehyde aqueous solution is 12.5mL/min, the feeding temperature is 100 ℃, and half of the feeding is respectively carried out at the position 40 cm below the upper end of the second catalytic rectification section and at the upper end of the first catalytic rectification section; the feeding amount of methanol is 22mL/min, the feeding temperature is 120 ℃, and the methanol is fed from the lower end of the first catalytic rectification section; the operating pressure of the catalytic distillation column was 0.6MPa (gauge pressure), and the overhead reflux ratio was 3. After the operation is stable, the temperature of the first catalytic distillation section is 140-; the discharge amount of the tower bottom is 10.6g/min, and the material composition comprises 99.9 wt% of water and less than 0.1 wt% of others.
Comparative example 1
The same catalytic distillation column as in example 1 was used. Unlike example 1, the second catalytic distillation section was completely packed with Φ 3 × 3 mm stainless steel θ mesh rings. The feed position, flow rate, temperature and operating pressure and reflux ratio of the catalytic distillation column were the same as in example 1.
After the operation is stable, the temperature of the first catalytic rectification section is 45-68 ℃, the discharge amount at the top of the tower is 15.6g/min, and the material composition comprises 90.5 wt% of methylal, 8.4 wt% of methanol, 1 wt% of water and 0.1 wt% of formaldehyde; the discharge amount of the tower kettle is 12.4g/min, and the material composition comprises 99 wt% of water and 1 wt% of the rest.
This comparative example, in comparison to example 1, shows that packing the silica gel catalyst in the second catalytic distillation section under substantially the same conditions yields a higher purity methylal product.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.
Claims (11)
1. A method for preparing methylal from methanol and formaldehyde is characterized in that a catalytic rectification device is adopted to prepare methylal;
the catalytic rectification device comprises a first catalytic rectification section and a second catalytic rectification section;
the second catalytic distillation section is connected in series with the upper part of the first catalytic distillation section;
a first catalyst is filled in the first catalytic rectification section;
at least a portion of said second catalytic distillation section is packed with a second catalyst;
the first catalyst is selected from at least one of solid acid catalysts;
the second catalyst is at least one selected from silica, alumina, activated carbon, silicate and aluminosilicate;
the method comprises the following steps:
in the first catalytic rectifying section of the catalytic rectifying tower, methanol and formaldehyde aqueous solution are subjected to aldol condensation reaction under the action of the first catalyst to generate methylal;
in the second catalytic distillation section of the catalytic distillation tower, formaldehyde in ascending steam enters a liquid phase material and returns to the first catalytic distillation section for continuous reaction; meanwhile, the second catalyst catalyzes the reaction of the free formaldehyde dissolved in the liquid phase with water to generate the methylene glycol and the polyoxymethylene glycol, or reacts with the methanol to generate the hemiacetal, and does not decompose the methylal.
2. The method of claim 1, wherein the solid acid catalyst is selected from at least one of a strong acid cation exchange resin, an acidic molecular sieve catalyst.
3. The method according to claim 2, wherein the strong-acid cation exchange resin is at least one selected from sulfonated styrene-divinylbenzene copolymer resin and perfluorosulfonic acid resin.
4. The method of claim 1, wherein the first catalyst is selected from at least one of sulfonated styrene-divinylbenzene copolymer resin, perfluorosulfonic acid resin, HZSM-5 molecular sieve, HBeta zeolite molecular sieve, and HMCM-22 zeolite molecular sieve.
5. The method of claim 1,
a feed inlet for the methanol feedstock is located in at least one location in the lower portion of the first catalytic distillation section;
a feed inlet for the formaldehyde feed is located in the upper part of the first catalytic distillation section and/or at least one position of the second catalytic distillation section; the formaldehyde raw material is a formaldehyde aqueous solution.
6. The method of claim 1, wherein the operating pressure of the catalytic distillation unit is 0 to 0.6Mpa gauge.
7. The process of claim 1 wherein the temperature of the first catalytic distillation section is from 45 ℃ to 160 ℃.
8. The method according to claim 1, wherein the reflux ratio of the catalytic distillation device is 0.3-3.
9. The method according to claim 1, wherein the reflux ratio of the catalytic distillation device is 0.5-1.5.
10. The method according to claim 1, wherein the molar ratio of methanol to formaldehyde in the feed of the catalytic distillation unit is (2-2.2): 1.
11. the method according to claim 1, wherein the mass percentage of formaldehyde in the aqueous formaldehyde solution is 10 wt% to 55 wt%.
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| CN1107136A (en) * | 1994-07-16 | 1995-08-23 | 广西大学 | Method and equipment for continuous catalyzing rectifying production of n-butyester acetate |
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| CN1107136A (en) * | 1994-07-16 | 1995-08-23 | 广西大学 | Method and equipment for continuous catalyzing rectifying production of n-butyester acetate |
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| CN109851484A (en) | 2019-06-07 |
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