CN109851483B - Extraction catalytic rectification method for preparing methylal - Google Patents
Extraction catalytic rectification method for preparing methylal Download PDFInfo
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Abstract
An extractive catalytic distillation method for preparing methylal from methanol and formaldehyde aqueous solution comprises the following steps: preparing methylal from methanol and a formaldehyde aqueous solution in a catalyst rectifying tower, wherein the catalyst rectifying tower comprises a reaction section and a rectifying section, and a solid catalyst A is filled in the reaction section; introducing methanol and a formaldehyde aqueous solution into a catalytic rectification tower, and contacting with a solid catalyst A in the reaction section to obtain methylal; the solid catalyst A is a solid acid catalyst; the reaction section contains an extractant. Compared with the traditional catalytic rectification process, the method has the advantages of low content of methanol and formaldehyde in the methylal product, high purity of the methylal product and low energy consumption.
Description
Technical Field
The invention relates to an extraction catalytic rectification method for preparing methylal from methanol and a formaldehyde aqueous solution.
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.
The reaction is limited by chemical equilibrium due to the large amount of water present during the reaction, including water entrained by the aqueous formaldehyde solution and water produced by the reaction. At present, the restriction of chemical equilibrium is broken by generally adopting a catalytic distillation technology, but a larger reflux ratio is needed and the energy consumption is higher.
Disclosure of Invention
According to one aspect of the application, an extractive catalytic distillation method for preparing methylal is provided, wherein methylal is prepared from methanol and formaldehyde aqueous solution, and the extractive catalytic distillation method has the advantage of low energy consumption compared with the traditional catalytic distillation method.
The extraction catalytic distillation method for preparing methylal comprises the following steps: preparing methylal from methanol and a formaldehyde aqueous solution in a catalyst rectifying tower, wherein the catalyst rectifying tower comprises a reaction section and a rectifying section, and a solid catalyst A is filled in the reaction section;
introducing methanol and a formaldehyde aqueous solution into a catalytic rectification tower, and contacting with a solid catalyst A in the reaction section to obtain methylal;
the solid catalyst A is a solid acid catalyst;
the reaction section contains an extractant.
Optionally, the rectification section is located in an upper portion of the reaction section;
and part or all of the rectifying section is filled with a solid catalyst B.
Optionally, the extractant is added to the aqueous methanol and/or formaldehyde solution.
Optionally, the percentage of the extractant in the liquid-phase material in the reaction section is 20 wt% to 80 wt%.
Optionally, the extractant is selected from at least one of halogenated hydrocarbon, aromatic hydrocarbon, alkane and cycloalkane.
Preferably, the halogenated hydrocarbon is at least one selected from dichloroethane, dichloropropane, chlorobenzene and bromobenzene.
Preferably, the aromatic hydrocarbon is at least one selected from benzene, toluene, ethylbenzene, xylene, n-propylbenzene, isopropylbenzene, methyl ethylbenzene and butylbenzene.
Preferably, the alkane is at least one of n-hexane, n-heptane, n-octane and isoparaffin with carbon number of 6-10.
Preferably, the cycloalkane is at least one selected from cyclohexane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane.
Optionally, the solid catalyst A is selected from at least one of strong acid cation exchange resin, molecular sieve, metal oxide and supported metal oxide.
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 solid catalyst A is selected from at least one of sulfonated styrene-divinylbenzene copolymer resin, perfluorinated sulfonic 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 solid catalyst B is at least one selected from silica, alumina, activated carbon, magnesium silicate and potassium aluminosilicate.
Optionally, the operating pressure of the catalytic distillation column is 0-1 MPa gauge pressure. In this application, the pressure is gauge pressure.
Optionally, the temperature of the reaction section of the catalytic distillation tower is 45-180 ℃.
Optionally, the reflux ratio of the catalytic distillation tower is 0.3-3.
Preferably, the reflux ratio of the catalytic distillation tower is 0.5-1.5.
Alternatively, the methanol is fed from a lower portion of the reaction section.
Optionally, the aqueous formaldehyde solution is fed from an upper part of the reaction section, a middle part of the rectification section and/or a lower part of the rectification section.
The molar ratio of methanol to formaldehyde in all the materials introduced into the catalytic distillation tower is 2-2.2.
In the reaction section of the catalytic rectification tower, methanol and formaldehyde aqueous solution are subjected to aldol condensation reaction under the action of a catalyst A to generate methylal, and the general reaction formula is shown as the reaction formula (1). 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, from monomeric formaldehyde hydrate 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 methanol added first reacts with the methylene glycol to form the 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 catalyst A to generate methylal (CH)3OCH2OCH3Abbreviated DMM) according to the following reaction formula:
the generated methylal leaves the reaction 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 rectification tower, so that the chemical balance of the reaction is broken, the forward progress of the reaction is promoted, and the complete conversion of the formaldehyde is achieved.
In each stage of the reaction section, the reaction is still limited by chemical equilibrium, the conversion rate of formaldehyde is generally not more than 50%, and therefore, a larger reflux ratio is needed, and the energy consumption is higher.
The invention provides that the extracting agent with a certain concentration is kept in the reaction section of the catalytic distillation tower, so that the liquid-phase material in the reaction section is divided into two immiscible phases (water phase and extraction phase), the limitation of chemical equilibrium can be further broken, and the formaldehyde conversion rate in each stage of the reaction section greatly exceeds the equilibrium conversion rate, thereby reducing the reflux ratio and reducing the energy consumption.
In the presence of a suitable extractant, methanol and formaldehyde mainly exist in a water phase and can contact with the catalyst A and diffuse into the particles of the catalyst A to react to generate methylal, and the generated methylal enters an extraction phase due to the extraction effect. Under the condition that the extraction phase cannot infiltrate the catalyst A, the extraction phase cannot enter the interior of the particles of the extraction phase to contact with active centers on the surfaces of the particles, namely, methylal in the extraction phase cannot be decomposed under the action of the catalyst A; under the condition that the extraction phase can soak the catalyst A, the catalyst A can be placed in a water phase channel in a reaction section of the catalytic rectification tower only, so that a water phase material is contacted with the catalyst A in sequence and reacts, then contacted with the extraction and extracted, and the reaction and extraction processes are repeated for many times in the reaction section, thereby avoiding the contact of the extraction phase and the catalyst A, namely, methylal in the extraction phase cannot be decomposed under the action of the catalyst A. Thus, while the condensation reaction in the aqueous phase is still limited by chemical equilibrium, the extracted phase is enriched in large amounts of methylal, so that the formaldehyde conversion in each stage of the reaction section can greatly exceed the equilibrium conversion.
The distribution ratio of methylal (the ratio of the concentration of methylal in the extraction phase to the concentration of methylal in the water phase) is greater than that of methanol and formaldehyde (the ratio of the concentration of methanol and formaldehyde in the extraction phase to that of methanol and formaldehyde in the water phase), so that the effect of breaking the chemical equilibrium limitation can be achieved.
The concentration of the extracting agent in the reaction section of the catalytic rectifying tower is kept between 20 and 80 weight percent. In some cases, the extractant is extracted together with the water in the tower bottom, and in order to stabilize the concentration of the extractant in the reaction section within the required range, the extractant with proper flow rate can be introduced into the catalytic rectification tower to supplement the extracted extractant. Ideally, the boiling point of the extractant or the boiling point of the azeotrope formed between the extractant and water is between that of methylal and water, so that the extractant can be maintained at the desired concentration in the reaction zone without being taken out with the overhead and bottom fractions, substantially without replenishment, and the cost of recovering the extractant is saved. When a small amount of extractant and water in the tower kettle are extracted together, the phase-separated extractant phase can be directly returned to the catalytic rectification tower.
One of the functions of the rectifying section of the catalytic rectifying tower is to make formaldehyde in ascending steam enter a liquid-phase material and return to the reaction 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 catalyst B is filled in the rectifying section of the catalytic rectifying tower, so that the free formaldehyde dissolved in the liquid phase can be promoted to react with water to generate the methyl glycol and the polyoxymethylene glycol, or react with the methanol to 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, 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 reaction section for continuous reaction, and the concentration of the formaldehyde in a methylal product is reduced.
The reaction raw material methanol is generally introduced from the lower part of the reaction section of the catalytic distillation tower. The formaldehyde water solution as the reaction raw material can be introduced from the upper end of the reaction section of the catalytic rectifying tower or from the middle part of the rectifying section of the catalytic rectifying tower. Since methylal forms a low boiling azeotrope with methanol (the azeotropic composition is 93 wt% methylal and 7 wt% methanol), the methylal product taken overhead usually contains a certain amount of methanol; the formaldehyde aqueous solution as the reaction raw material is introduced from the middle part of the rectifying section of the catalytic rectifying tower, and the methanol azeotropic with the methylal can react with the methylene glycol in the formaldehyde aqueous solution to generate hemiacetal (104 ℃) with higher boiling point, and the hemiacetal returns to the reaction section, so that the purity of the methylal extracted from the top of the tower can be improved. The catalyst B is filled in the rectifying section to promote the reaction and achieve better effect.
The aqueous formaldehyde solution used as the reaction raw material can be an aqueous solution with a formaldehyde concentration of 10-55 wt%, and can contain a small amount of methanol.
The invention can produce the beneficial effects that: reduce the energy consumption of the methylal production process and improve the purity of the methylal product.
Drawings
FIG. 1 is a schematic diagram of an extractive 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 an extractive 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 an extractive catalytic distillation apparatus for preparing methylal from methanol and formaldehyde according to an embodiment of the present application.
FIG. 4 is a schematic diagram of an extractive catalytic distillation apparatus for preparing methylal from methanol and formaldehyde according to an embodiment of the present application.
Detailed Description
The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Unless otherwise specified, the reaction raw materials, catalysts, packing for catalytic distillation apparatus (phi 3 × 3 mm stainless steel theta mesh ring, phi 5 × 5 mm stainless steel theta mesh ring) and stainless steel wire mesh package in the examples of the present application were all commercially available as analytical pure reagents, wherein the formaldehyde content of the aqueous formaldehyde solution was 38 wt% and methanol was 3 wt%
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.
Example 1
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 uniformly mixed stainless steel wire net bags and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of Nafion-H resin is filled in each stainless steel wire net bag 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 rectifying section to a position 40 cm below the rectifying section; the feeding amount of methanol is 15.2ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extraction agent adopts ethylbenzene, a certain amount of ethylbenzene is added into the tower at a larger flow rate, and then the feeding amount is changed to 0.4 ml/min. 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 reaction section is 50-72 ℃, and the content of ethylbenzene in the gas-phase material of the reaction section is 30-35 wt%; the discharge amount at the top of the tower is 14.8g/min, and the material composition comprises 98.8 wt% of methylal, 1.0 wt% of methanol, 0.2 wt% of water and 0.04 wt% of formaldehyde; the discharge amount of the tower bottom is 12.7g/min, and the material composition comprises 97 wt% of water, 2.8 wt% of ethylbenzene and less than 0.02 wt% of methanol and formaldehyde.
Example 2
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags which are uniformly mixed and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst are filled in the stainless steel wire net bags.
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 rectifying section to a position 40 cm below the rectifying section; the feeding amount of methanol is 15.4ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extractant adopts mixed xylene, a certain amount of mixed xylene is added into the tower at a larger flow rate, and then the feeding amount is changed to 0.5 ml/min. 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 reaction section is 50-72 ℃, and the content of the mixed dimethylbenzene in the gas-phase material of the reaction section is 40-45 wt%; the discharge amount at the top of the tower is 14.9g/min, and the material composition comprises 97.8 wt% of methylal, 2.0 wt% of methanol, 0.2 wt% of water and 0.03 wt% of formaldehyde; the discharge amount of the tower bottom is 12.8g/min, and the material composition comprises 97 wt% of water, 2.9 wt% of mixed dimethylbenzene and less than 0.02 wt% of methanol and formaldehyde.
Example 3
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags which are uniformly mixed and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst are filled in the stainless steel wire net bags.
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%. The feeding amount of the 10 wt% formaldehyde water solution is 46.5ml/min, the feeding temperature is 50 ℃, and the feeding is carried out from the upper end of the rectifying section to the position 40 cm below the upper end of the rectifying section; the feeding amount of methanol is 13.2ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extraction agent is a mixture of isopropyl benzene and dichloroethane (weight ratio is 1: 5), a certain amount of extraction agent is added into the tower at a larger flow rate, and then the feeding amount is changed to 0.6 ml/min. The operating pressure of the catalytic rectifying tower is 0.1MPa (gauge pressure), and the reflux ratio at the top of the tower is 0.7; after the operation is stable, the temperature of the reaction section is 55-78 ℃, and the content of cumene and dichloroethane in the gas-phase material of the reaction section is 28-36 wt%; the discharge amount at the top of the tower is 12.8g/min, and the material composition comprises 97.8 wt% of methylal, 2.0 wt% of methanol, 0.2 wt% of water and 0.03 wt% of formaldehyde; the discharge amount of the tower bottom is 47g/min, and the material composition comprises 99.9 wt% of water and less than 0.1 wt% of others.
Example 4
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags which are uniformly mixed and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst are filled in the stainless steel wire net bags.
Feeding the formaldehyde aqueous solution at the feeding rate of 12ml/min and the feeding temperature of 50 ℃, and feeding the formaldehyde aqueous solution from the upper end of the rectifying section to the lower part of 40 cm; the feeding amount of methanol is 13.2ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extracting agent is a mixture of chlorobenzene and bromobenzene (weight ratio is 9: 1), a certain amount of extracting agent is firstly added into the tower at a larger flow rate, and then the feeding amount is changed to 1 ml/min. The operating pressure of the catalytic rectifying tower is 0.1MPa (gauge pressure), and the reflux ratio at the top of the tower is 0.7; after the operation is stable, the temperature of the reaction section is 55-78 ℃, and the content of chlorobenzene and bromobenzene in the gas-phase material of the reaction section is 20-26 wt%; the discharge amount at the top of the tower is 12.8g/min, and the material composition comprises 97.6 wt% of methylal, 2.2 wt% of methanol, 0.2 wt% of water and 0.04 wt% of formaldehyde; the material discharged from the tower bottom is 11.7g/min, and the material composition comprises 91 wt% of water, 9 wt% of chlorobenzene and bromobenzene, and less than 0.02 wt% of methanol and formaldehyde.
Example 5
As shown in figure 4, the catalytic rectification tower comprises an overhead condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, a phi 2 × 5-7 mm strip molecular sieve catalyst and a phi 5 × 5 mm stainless steel theta net ring are mixed and filled, the volume ratio is 1:2, and the molecular sieve catalyst comprises 70 wt% of HBeta 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. Feeding the 55 wt% formaldehyde water solution at 10.8ml/min and 100 deg.C, and feeding from the upper end of the rectifying section to the lower part of 40 cm; the feeding amount of the methanol is 18ml/min, the feeding temperature is 100 ℃, and the methanol is fed from the lower end of the reaction section; the extractant is a mixture of methyl ethyl benzene and n-propyl benzene (weight ratio is 1: 1), a certain amount of extractant is firstly added into the tower at a larger flow rate, and then the feeding amount is changed to 0.6 ml/min. The operating pressure of the catalytic rectifying tower is 0.5MPa (gauge pressure), and the reflux ratio at the top of the tower is 1; after the operation is stable, the temperature of the reaction section is 110-136 ℃, and the contents of the methyl ethyl benzene and the n-propyl benzene in the gas phase material of the reaction section are 30-35 wt%; the discharge amount at the top of the tower is 16.9g/min, and the material composition comprises 97.9 wt% of methylal, 2 wt% of methanol, 0.1 wt% of water and 0.03 wt% of formaldehyde; the material discharged from the bottom of the tower is 9.3g/min, and the material composition comprises 96.5 wt% of water, 3.5 wt% of methyl ethyl benzene and n-propyl benzene, and less than 0.02 wt% of methanol and formaldehyde.
Example 6
As shown in figure 2, the catalytic rectification tower comprises an overhead condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, a phi 2 × 5-7 mm strip molecular sieve catalyst and a phi 5 × 5 mm stainless steel theta net ring are mixed and filled, the volume ratio is 1:2, and the molecular sieve catalyst comprises 70 wt% of HMCM-22 zeolite and 30 wt% of an alumina binder.
Feeding formaldehyde aqueous solution at a feeding rate of 15.9ml/min and a feeding temperature of 100 ℃, and feeding the formaldehyde aqueous solution from the upper end of the rectifying section to a position 40 cm below the rectifying section; the feeding amount of methanol is 17.4ml/min, the feeding temperature is 110 ℃, and the methanol is fed from the lower end of the reaction section; the extracting agent adopts butylbenzene, a certain amount of butylbenzene is added into the tower at a large flow rate, and then the feeding amount is changed to 0.8 ml/min. The operating pressure of the catalytic rectifying tower is 0.6MPa (gauge pressure), and the reflux ratio at the top of the tower is 1; after the operation is stable, the temperature of the reaction section is 120-142 ℃, and the content of butylbenzene in the gas phase material of the reaction section is 50-56 wt%; the discharge amount at the top of the tower is 16.9g/min, and the material composition comprises 97.9 wt% of methylal, 2 wt% of methanol, 0.1 wt% of water and 0.03 wt% of formaldehyde; the discharge amount of the tower bottom is 14.8g/min, and the material composition comprises 95 wt% of water, 5 wt% of butylbenzene and less than 0.02 wt% of methanol and formaldehyde.
Example 7
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags which are uniformly mixed and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst are filled in the stainless steel wire net bags.
Feeding formaldehyde aqueous solution at 15.9ml/min and 50 ℃ from the upper end of the rectifying section to the lower part of 40 cm; the feeding amount of methanol is 17.4ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extractant is a mixture of n-hexane, n-heptane, iso-heptane, n-octane and iso-octane (each 20 wt%), a certain amount of extractant is added into the tower at a large flow rate, and then the feeding amount is changed to 0.6 ml/min. The operation pressure of the catalytic rectifying 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 reaction section is 50-70 ℃, and the content of the extractant in the gas-phase material of the reaction section is 20-26 wt%; the discharge amount at the top of the tower is 16.9g/min, and the material composition comprises 97.9 wt% of methylal, 2 wt% of methanol, 0.1 wt% of water and 0.03 wt% of formaldehyde; the material discharged from the bottom of the tower is 14.6g/min, and the material composition comprises 96.5 wt% of water, 3.5 wt% of extracting agent and less than 0.02 wt% of methanol and formaldehyde.
Example 8
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags which are uniformly mixed and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst are filled in the stainless steel wire net bags.
Feeding formaldehyde aqueous solution at 15.9ml/min and 50 ℃ from the upper end of the rectifying section to the lower part of 40 cm; the feeding amount of methanol is 17.4ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extractant is a mixture of cyclohexane, methylcyclopentane, methylcyclohexane and ethylcyclohexane (25 wt% of each), a certain amount of extractant is added into the tower at a large flow rate, and then the feeding amount is changed to 0.6 ml/min. The operation pressure of the catalytic rectifying 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 reaction section is 50-70 ℃, and the content of the extractant in the gas-phase material of the reaction section is 35-42 wt%; the discharge amount at the top of the tower is 16.9g/min, and the material composition comprises 97.9 wt% of methylal, 2 wt% of methanol, 0.1 wt% of water and 0.04 wt% of formaldehyde; the material discharged from the bottom of the tower is 14.6g/min, and the material composition comprises 96.4 wt% of water, 3.6 wt% of extracting agent and less than 0.02 wt% of methanol and formaldehyde.
Example 9
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags which are uniformly mixed and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst are filled in the stainless steel wire net bags.
Feeding the formaldehyde aqueous solution at a feeding rate of 12.1ml/min and a feeding temperature of 40 ℃, and feeding the formaldehyde aqueous solution from the upper end of the rectifying section to a position 40 cm below the rectifying section; the feeding amount of the methanol is 14.5ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extraction agent adopts cumene, a certain amount of cumene is added into the tower at a larger flow rate, and then the feeding amount is changed to 0.6 ml/min. The operation pressure of the catalytic rectifying tower is normal pressure, and the reflux ratio at the top of the tower is 0.3; after the operation is stable, the temperature of the reaction section is 45-75 ℃, and the content of the cumene in the gas phase material of the reaction section is 20-28 wt%; the discharge amount at the top of the tower is 13.8g/min, and the material composition comprises 91 wt% of methylal, 8 wt% of methanol, 0.8 wt% of water and 0.03 wt% of formaldehyde; the material discharged from the bottom of the tower is 11.2g/min, and the material composition comprises 95 wt% of water, 5 wt% of isopropyl benzene and less than 0.02 wt% of methanol and formaldehyde.
Example 10
As shown in figure 2, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, silica gel balls with the diameter of 3-5 mm and stainless steel theta net rings with the diameter of 3 × 3 mm are mixed and filled in the rectification section, the volume ratio of the silica gel balls to the stainless steel theta net rings is 1:3, the stainless steel theta net rings with the diameter of 3 × 3 mm are filled in the stripping section, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags and 1300 ml stainless steel theta net rings with the diameter of 5 × 5 mm are filled in the rectification section, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst is filled in each stainless steel.
Feeding the formaldehyde aqueous solution at a feeding rate of 20.2ml/min and a feeding temperature of 60 ℃, and feeding the formaldehyde aqueous solution from the upper end of the rectifying section to a position 40 cm below the rectifying section; the feeding amount of the methanol is 22ml/min, the feeding temperature is 60 ℃, and the methanol is fed from the lower end of the reaction section; the extraction agent adopts 1, 2-dichloropropane, a certain amount of 1, 2-dichloropropane is firstly added into the tower at a large flow rate, and then the feeding is stopped. The operating pressure of the catalytic rectifying tower is 0.2MPa (gauge pressure), and the reflux ratio at the top of the tower is 3; after the operation is stable, the temperature of the reaction section is 70-80 ℃, and the content of 1, 2-dichloropropane in the gas-phase material of the reaction section is 60-80 wt%; the discharge amount at the top of the tower is 21.3g/min, and the material composition comprises 98 wt% of methylal, 1.8 wt% of methanol, 0.1 wt% of water and 0.01 wt% of formaldehyde; the discharge amount of the tower bottom is 17.8g/min, the material composition is 99.9 wt% of water, and the other is less than 0.1 wt%.
Example 11
As shown in figure 3, the catalytic rectification tower comprises an overhead condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, alumina strip-shaped particles with phi 2 × 4-6 mm and stainless steel theta mesh rings with phi 3 × 3 mm are mixed and filled in the rectification section, the volume ratio of the alumina strip-shaped particles to the stainless steel theta mesh rings with phi 3 × mm is 1:3, the stainless steel theta mesh rings with phi 3 × 3 mm are filled in the stripping section, the effective height of the reaction section is 0.97 m, a strip-shaped molecular sieve catalyst with phi 2 × 5-7 mm and a stainless steel theta mesh ring with phi 5 × 5 mm are mixed and filled in the volume ratio of 1:2, and the molecular sieve catalyst comprises 80 wt% of HZSM-5 and 20 wt% of alumina binder.
Feeding formaldehyde aqueous solution at a feeding rate of 13.8ml/min and a feeding temperature of 100 ℃, and feeding from the upper end of the reaction section; the feeding amount of methanol is 16.8ml/min, the feeding temperature is 80 ℃, and the methanol is fed from the lower end of the reaction section; the extractant adopts benzene, a certain amount of benzene is added into the tower at a larger flow rate, and then the feeding amount is changed to 0.5 ml/min. The operating pressure of the catalytic rectifying tower is 0.5MPa (gauge pressure), and the reflux ratio at the top of the tower is 0.5; after the operation is stable, the temperature of the reaction section is 110-140 ℃, and the benzene content in the gas-phase material of the reaction section is 32-50 wt%; the discharge amount at the top of the tower is 16g/min, and the material composition comprises 90 wt% of methylal, 9 wt% of methanol, 0.8 wt% of water and 0.02 wt% of formaldehyde; the discharge amount of the tower bottom is 12.6g/min, and the material composition comprises 96.5 wt% of water, 3.5 wt% of benzene and less than 0.02 wt% of methanol and formaldehyde.
Example 12
As shown in FIG. 4, the catalytic distillation column comprises a top condensing reflux device, a distillation section, a reaction section and a stripping sectionThe inner diameter of a tower body of the rectifying section and the tower kettle is 50 mm, the effective heights of the rectifying section and the stripping section are both 0.57 m, active carbon particles with the diameter of phi 3 × 4-6 mm and stainless steel theta net rings with the diameter of phi 3 × 3 mm are filled in the rectifying section in a mixed mode, the volume ratio of the active carbon particles to the stainless steel theta net rings with the diameter of phi 3 × -6 mm is 1:3, the stainless steel theta net rings with the diameter of phi 3 × 3 mm are filled in the stripping section, the effective height of the reaction section is 0.97 m, a strip-shaped metal oxide catalyst with the diameter of phi 2 × 5-7 mm and stainless steel theta net rings with the diameter of phi 5 × 5 mm are filled in a mixed mode, the volume ratio of the2O3、70wt％TiO2。
Feeding the formaldehyde aqueous solution at 27.5ml/min and the feeding temperature of 150 ℃, and feeding from the upper end of the reaction section; the feeding amount of the methanol is 32.5ml/min, the feeding temperature is 120 ℃, and the methanol is fed from the lower end of the reaction section; the extractant adopts toluene, a certain amount of toluene is added into the tower at a larger flow rate, and then the feeding is stopped. The operating pressure of the catalytic rectifying tower is 1MPa (gauge pressure), and the reflux ratio at the top of the tower is 1; after the operation is stable, the temperature of the reaction section is 160-175 ℃, and the toluene content in the gas-phase material of the reaction section is 50-60 wt%; the discharge amount at the top of the tower is 31.1g/min, and the material composition comprises 92 wt% of methylal, 7.5 wt% of methanol, 0.5 wt% of water and 0.02 wt% of formaldehyde; the discharge amount of the tower bottom is 24.3g/min, and the material composition comprises 99.9 wt% of water and less than 0.1 wt% of others.
Example 13
As shown in figure 2, the catalytic rectification tower comprises an overhead condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, the rectification section is filled with a mixture of magnesium silicate and potassium aluminosilicate particles with the diameters of phi 2 × 4-6 mm and stainless steel theta mesh rings with the diameters of phi 3 × 3 mm in a mixed manner, the volume ratio of the mixture to the stainless steel theta mesh rings is 1:3, the stripping section is filled with stainless steel theta mesh rings with the diameters of phi 3 × 3 mm, the effective height of the reaction section is 0.97 m, a strip-shaped load metal oxide catalyst with the diameters of phi 2 × 5-7 mm and a stainless steel theta mesh ring with the diameters of phi 5 × 5 mm, the volume ratio of the strip-shaped load metal oxide catalyst is 1:2, and the load metal oxide catalyst comprises MoO3/Al2O3。
Feeding formaldehyde aqueous solution at the feeding rate of 9.7ml/min and the feeding temperature of 120 ℃, and feeding from the upper end of the rectifying section to the lower part of 40 cm; the feeding amount of the methanol is 10.8ml/min, the feeding temperature is 90 ℃, and the methanol is fed from the lower end of the reaction section; the extraction agent adopts cyclohexane, a certain amount of cyclohexane is added into the tower at a large flow rate, and then the feeding is stopped. The operating pressure of the catalytic rectifying tower is 0.6MPa (gauge pressure), and the reflux ratio at the top of the tower is 1.5; after the operation is stable, the temperature of the reaction section is 120-135 ℃, and the cyclohexane content in the gas-phase material of the reaction section is 60-70 wt%; the discharge amount at the top of the tower is 10.4g/min, and the material composition comprises 96 wt% of methylal, 3.5 wt% of methanol, 0.4 wt% of water and 0.01 wt% of formaldehyde; the discharge amount of the tower bottom is 8.5g/min, and the material composition comprises 99.9 wt% of water and less than 0.1 wt% of others.
Comparative example 1
Catalytic distillation synthesis of methylal
As shown in figure 1, the catalytic rectification tower comprises a tower top condensing reflux device, a rectification section, a reaction section, a stripping section and a tower kettle, wherein the inner diameter of a tower body is 50 mm, the effective heights of the rectification section and the stripping section are both 0.57 m, a phi 3 × 3 mm stainless steel theta net ring is filled, the effective height of the reaction section is 0.97 m, 15 stainless steel wire net bags which are uniformly mixed and 1300 ml of a phi 5 × 5 mm stainless steel theta net ring are filled, and 500 ml of D005 strong-acid cation exchange resin serving as a catalyst are filled in the stainless steel wire net bags.
Feeding the formaldehyde aqueous solution at a feeding rate of 12.1ml/min and a feeding temperature of 40 ℃, and feeding the formaldehyde aqueous solution from the upper end of the rectifying section to a position 40 cm below the rectifying section; the methanol feed rate was 14.5ml/min, the feed temperature was 60 ℃ and the feed was from the lower end of the reaction zone. The operation pressure of the catalytic rectifying tower is normal pressure, and the reflux ratio at the top of the tower is 0.3; after the operation is stable, the temperature of the reaction section is 45-72 ℃; the discharge amount at the top of the tower is 13.8g/min, and the material composition comprises 85 wt% of methylal, 9.6 wt% of methanol, 1.2 wt% of water and 4.2 wt% of formaldehyde; the discharge amount of the tower bottom is 10.7g/min, and the material composition comprises 97 wt% of water, 1.4 wt% of methanol and 1.6 wt% of formaldehyde.
This comparative example, in comparison with example 9, shows that maintaining a certain concentration of extractant in the reaction zone allows a higher formaldehyde conversion to be achieved and a higher purity methylal product to be obtained at the same lower reflux ratio.
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 (14)
1. An extraction catalytic distillation method for preparing methylal is characterized in that methylal is prepared from methanol and a formaldehyde aqueous solution in a catalyst distillation tower, the catalytic distillation tower comprises a reaction section and a distillation section, and a solid catalyst A is filled in the reaction section;
introducing methanol and a formaldehyde aqueous solution into a catalytic rectification tower, and contacting with a solid catalyst A in the reaction section to obtain methylal;
the solid catalyst A is a solid acid catalyst;
the reaction section contains an extracting agent;
the extractant separates the liquid phase material in the reaction section into two immiscible phases.
2. The process of claim 1 wherein said rectifying section is located in an upper portion of said reaction section;
part or all of the rectifying section is filled with a solid catalyst B;
the solid catalyst B is at least one selected from silicon dioxide, alumina, activated carbon, magnesium silicate and potassium aluminosilicate.
3. The process according to claim 1, characterized in that the extractant is added to the aqueous methanol and/or formaldehyde solution.
4. The method according to claim 1, wherein the extraction agent accounts for 20-80 wt% of the total mass of the liquid phase material in the reaction section.
5. The method of claim 1, wherein the extractant is selected from at least one of halogenated hydrocarbons, aromatic hydrocarbons, alkanes, and cycloalkanes.
6. The method according to claim 5, wherein the halogenated hydrocarbon is at least one selected from dichloroethane, dichloropropane, chlorobenzene and bromobenzene.
7. The method of claim 5, wherein the aromatic hydrocarbon is at least one aromatic hydrocarbon selected from the group consisting of benzene, toluene, ethylbenzene, xylene, n-propylbenzene, isopropylbenzene, methylethylbenzene, and butylbenzene.
8. The method according to claim 5, wherein the alkane is at least one selected from the group consisting of n-hexane, n-heptane, n-octane, and isoparaffin having a carbon number of 6-10.
9. The method according to claim 5, wherein the cycloalkane is at least one selected from the group consisting of cyclohexane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane.
10. The method of claim 1, wherein the solid catalyst A is at least one selected from the group consisting of strongly acidic cation exchange resins, molecular sieves, metal oxides, and supported metal oxides.
11. The method according to claim 1 or 2, wherein the operating pressure of the catalytic distillation column is 0-1 MPa gauge.
12. The method according to claim 1 or 2, wherein the reflux ratio of the catalytic distillation tower is 0.3-3.
13. The method according to claim 1 or 2, wherein the reflux ratio of the catalytic distillation column is 0.5-1.5.
14. The process according to claim 1 or 2, wherein the methanol is fed from a lower portion of the reaction section;
the aqueous formaldehyde solution is fed from the upper part of the reaction section, the middle part of the rectification section and/or the lower part of the rectification section.
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| CN101094825A (en) * | 2004-12-09 | 2007-12-26 | 泰科纳有限公司 | Method for the production of acetals |
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| CN101094825A (en) * | 2004-12-09 | 2007-12-26 | 泰科纳有限公司 | Method for the production of acetals |
| CN101092337A (en) * | 2007-07-03 | 2007-12-26 | 南京师范大学 | Method for preparing methylal by combining reaction rectification and extraction |
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