CN216946812U - Dehydration and catalytic synthesis device for polymethoxy dimethyl ether - Google Patents

Abstract

The utility model provides a device for dehydration and catalytic synthesis of polymethoxy dimethyl ether, which relates to the technical field of energy and chemical engineering and comprises a dehydration tower, a gasification tower, a mixer and a catalytic rectification tower which are sequentially connected according to a feeding sequence; wherein, the dehydration tower and the catalytic rectification tower are respectively and independently provided with a rectification section, a stripping section and a heater from top to bottom; a catalytic reaction section is arranged between the rectifying section and the stripping section of the catalytic rectifying tower. The device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether provided by the utility model has the characteristics of simple structure and convenience and flexibility in operation, solves the problems that insoluble and infusible solid state is formed when polyformaldehyde is dehydrated to an anhydrous state, and the solid state is low in activity and difficult to convey, and achieves the technical effects of realizing the operation under normal pressure and negative pressure conditions that the whole flow is liquid and gaseous, improving the atom utilization rate and the product purity, being safe and environment-friendly, and being suitable for industrial production.

Description

Dehydration and catalytic synthesis device for polymethoxy dimethyl ether

The present invention claims the priority of the Chinese patent application with patent number 202110364445.8, entitled "dehydration and catalytic synthesis method of polymethoxy dimethyl ether and apparatus thereof", filed on 04/05/2021, the entire contents of which are incorporated herein by reference.

Technical Field

The utility model relates to the technical field of energy and chemical engineering, in particular to a device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether.

Background

Polyoxymethylene dimethyl ethers, also known as paraformaldehyde dimethyl ether, english name: polyoxymethylene dimethylthers, PODE or DMMn for short, are low molecular acetal polymers with dimethoxymethane as matrix and methyleneoxy as main chain, and have the general formula: CH (CH)₃O(CH₂O)_nCH₃. The polyoxymethylene dimethyl ethers with the polymerization degree of 3-8, DMM3-8 for short, are used for cleaning diesel blending components, have physical properties similar to diesel, and do not need to modify an oil supply system of a vehicle engine when blended into the diesel for use; the cetane number of the diesel oil reaches up to 76, the oxygen content is 47-50%, the diesel oil is free of sulfur and aromatic hydrocarbon, the diesel oil is blended in the diesel oil by 10-20%, the cold filter plugging point of the diesel oil can be obviously reduced, the combustion quality of the diesel oil in an engine can be improved, and the diesel oil can be further improvedHigh thermal efficiency. Meanwhile, DMM2, DMM3, DMM4 and DMM5 are solvents with extremely high dissolving capacity, and are applied to paint, coating, printing ink, adhesive, cleaning agent, electrolyte solvent and the like.

Polyoxymethylene dimethyl ethers are generally prepared by reacting methanol or methylal with trioxymethylene or paraformaldehyde in the presence of an acidic catalyst, and the basic equation of the reaction is as follows:

the process of synthesizing polymethoxy dimethyl ether under the catalysis of an acidic catalyst is an equilibrium reaction, the content of a finished product component (DMM3-8) is low, the content of DMM3-8 in a general synthetic liquid is below 40%, however, the existence of a small amount of water promotes the equilibrium to move reversely, the influence is large, a large amount of methanol, formaldehyde, paraformaldehyde, hemiacetal and the like are remained in the reaction liquid, the content of effective components is low, and the difficulty is caused for purifying and preparing the polymethoxy dimethyl ether at low cost. Thus, one would like to use formaldehyde with no or low moisture content, which would like to use trioxymethylene, paraformaldehyde, synthesize anhydrous or low moisture gaseous formaldehyde, or to use a more concentrated aqueous formaldehyde solution to synthesize and think about removing the water of the system during the synthesis.

However, trioxymethylene is synthesized by catalyzing concentrated formaldehyde with sulfuric acid, a large amount of backflow is performed in the production process under the condition of water, the vaporization heat of water is large, the energy consumption is high, solvent extraction and dehydration are required, the synthesis cost is high, and because the melting point of trioxymethylene is high (61 ℃), the trioxymethylene is easy to sublimate, the pipeline blockage is easy to occur, and dangerous accidents are caused; meanwhile, in the process of storing and transporting trioxymethylene, once strong acid substances are mixed, high molecular polymers are formed by polymerization, so that equipment is scrapped.

Meanwhile, paraformaldehyde is a solid form prepared by dehydrating a formaldehyde aqueous solution under a vacuum condition until the water content is below 15%, polymerizing and curing, and then performing processes such as granulation, crushing, drying and the like, although the manufacturing cost is reduced, when the paraformaldehyde is further used as a reactant, the reactivity is low due to the non-fusible and insoluble property, so that the feeding from synthesis to application in the continuous production process is inconvenient; in addition, formaldehyde has large smell and toxicity, which are harmful to the health of workers, and the moisture content of formaldehyde is difficult to reach below 6 percent even after drying, thus greatly affecting the equilibrium reaction of polymethoxy dimethyl ether.

The report of preparing polyoxymethylene dimethyl ether (DMM3-8) by reacting high-concentration formaldehyde aqueous solution (containing more than 20 percent of water) with methanol or methylal is also provided in China, although the process is smooth and convenient to operate theoretically, the problems of difficult re-dehydration of synthetic liquid, low conversion rate, much residual formaldehyde, difficult separation and the like exist, and the high-concentration formaldehyde aqueous solution is easy to polymerize and block pipelines, is immature in process and is difficult to realize industrialization.

Chinese patents 201510128377.X and 201610147992.X disclose that gaseous formaldehyde and methylal undergo a catalytic reaction in the presence of a catalyst to prepare a DMMn synthetic solution, which is then treated and separated to obtain DMM 3-8; however, in the preparation method of gaseous formaldehyde in the patent, monohydric alcohols such as isobutanol and the like are used as auxiliary agents, so that the atom utilization rate is low, the auxiliary agents have low boiling points and easily enter synthetic fluids and finished products along with formaldehyde, and the auxiliary agents are high in price and not beneficial to industrialization; more importantly, the adjuvant has increased water solubility after the hemiacetal is formed, so that the water is difficult to form a layer, or special separation equipment is required, and in the subsequent distillation dehydration process, the reformed auxiliary additive is distilled out and mixed into a dilute formaldehyde solution due to the influence of balance.

Chinese patent 201610076437.2 discloses the preparation of formaldehyde gas by air oxidation of methanol or methylal in an oxidation reactor; and introducing the prepared formaldehyde gas into a cooler to be cooled to 20-99 ℃, and then introducing the formaldehyde gas into a gas-water separator to remove condensed water to obtain the formaldehyde gas. It has been proved that the formaldehyde gas formed by oxidizing methanol contains about 30% of generated moisture, and when the temperature is reduced to 20 to 99 ℃, formaldehyde hydrate (methyl glycol) is quickly formed to be liquefied or polymerization reaction is generated to be liquefied or solidified, which is not favorable for industrialization.

Other conventional methods for preparing anhydrous gaseous formaldehyde are: 1. the paraformaldehyde is heated and depolymerized to prepare gaseous formaldehyde, but the bound water of the paraformaldehyde is about 6%, so that the synthesis yield of DMMn and further recycling of intermediate products are greatly influenced, the preparation of the solid polyformaldehyde is relatively complex, further feeding and conveying are not beneficial to large-scale and continuous large-scale production, and relatively large potential safety hazard exists; 2. trioxymethylene is heated, decomposed and gasified under the action of an acid catalyst, so that trioxymethylene which cannot be decomposed in time is gasified with gaseous formaldehyde, a conveying pipeline is easy to be blocked, and the trioxymethylene is high in cost and not beneficial to realizing industrialization.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether, which is used for relieving the technical problems of poor dehydrating and catalytically synthesizing effects, high cost, complex process and difficulty in industrial production of the polymethoxy dimethyl ether in the prior art.

The utility model provides a device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether, which comprises a dehydrating tower, a gasification tower, a mixer and a catalytic rectifying tower which are sequentially connected according to a feeding sequence;

wherein, the dehydration tower and the catalytic rectification tower are respectively and independently provided with a rectification section, a stripping section and a heater from top to bottom;

a catalytic reaction section is arranged between the rectifying section and the stripping section of the catalytic rectifying tower;

a formaldehyde/ethylene glycol mixture feeding pipe is arranged on a distributor of the dehydration tower and is used for feeding a formaldehyde/ethylene glycol mixture;

the top of the dehydration tower is provided with a first reflux device;

the first reflux device comprises a dilute formaldehyde condenser and a vacuum receiving tank which are communicated in sequence;

the vacuum receiving tank is provided with a vacuum tube for creating vacuum;

the vacuum receiving tank is provided with a water outlet pipe for draining water;

the vacuum receiving tank is communicated with a reflux port of the dehydrating tower through a water reflux pipe;

a flowing polyformaldehyde discharge pipe is arranged at the bottom of the dehydration tower;

the top of the gasification tower is provided with a gas formaldehyde discharge pipe;

the bottom of the gasification tower is provided with an ethylene glycol discharge pipe;

the top of the catalytic rectifying tower is provided with a second reflux device;

the second reflux unit comprises an azeotrope condenser;

the azeotrope condenser is communicated with the reflux port of the catalytic distillation tower through an azeotrope reflux pipe;

the azeotrope condenser is provided with an azeotrope discharge pipe for discharging azeotrope;

a fine methylal feeding pipe is arranged between the catalytic reaction section and the stripping section of the catalytic rectifying tower and is used for feeding methylal;

a crude DMMn discharging pipe is arranged at the bottom of the catalytic rectifying tower;

the mixer is provided with a reclaimed material feeding pipe for feeding reclaimed materials obtained by separating and recycling products extracted from the bottom of the catalytic rectification tower;

the flowing polyformaldehyde discharge pipe is connected with the gasification tower and is used for conveying flowing polyformaldehyde into the gasification tower;

the gas formaldehyde discharge pipe is connected with the mixer and used for conveying gas formaldehyde to the mixer;

the mixer is connected with the distributor of the catalytic rectifying tower through a mixture feeding pipe and is used for conveying the mixture of the gaseous formaldehyde and the reclaimed materials to the catalytic rectifying tower.

Further, the catalytic reaction section of the catalytic distillation tower is used for filling catalyst packing;

the stripping section of the catalytic rectifying tower is used for filling aluminosilicate molecular sieves.

Compared with the existing device for synthesizing the poly methoxy dimethyl ether, the utility model has the following advantages:

the device for dehydrating and catalytically synthesizing polyoxymethylene dimethyl ethers has the characteristics of simple structure and convenience and flexibility in operation, solves the problems that insoluble and infusible solid state is formed when polyoxymethylene is dehydrated, and the solid state is low in activity and difficult to convey, and achieves the purpose of realizing the operation under the normal pressure and negative pressure conditions that the whole flow is liquid and gaseous; meanwhile, a series of problems existing in the existing method for synthesizing the polyoxymethylene dimethyl ether by utilizing paraformaldehyde, trioxymethylene, gaseous formaldehyde or formaldehyde aqueous solution are solved, the continuity and the automation are convenient to realize, the reaction balance can be actively controlled while the dehydration condensation is carried out, and the total yield is improved; in addition, the device provided by the utility model has the advantages of easily available raw materials, low price, low cost, small pollution, safety, environmental protection and suitability for industrial production when used for producing polyoxymethylene dimethyl ethers.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic diagram of an apparatus for dehydration and catalytic synthesis of polymethoxy dimethyl ether according to one embodiment of the present invention;

FIG. 2 is a schematic diagram of an apparatus for dehydration and catalytic synthesis of polymethoxy dimethyl ether according to one embodiment of the present invention;

fig. 3 is a schematic view of an apparatus for dehydration and catalytic synthesis of polymethoxy dimethyl ether according to an embodiment of the present invention.

The figure is as follows: 1-a dehydration column; 2-a catalytic rectification column; 3-dilute formaldehyde condenser; 4-a vacuum receiving tank; 5-a mixer; a 6-azeotrope condenser; 7-a dehydration tower heater; 8-a catalytic distillation column heater; a 9-formaldehyde/ethylene glycol mixture feed pipe; 10-a flowing polyformaldehyde discharge pipe; 11-a water return pipe; 12-vacuum tube; 13-water outlet pipe; 14-reclaimed material feed pipe; 15-mixture feed pipe; 16-fine methylal feeding pipe; 17-azeotrope reflux tube; 18-crude DMMn discharging pipe; a 19-azeotrope discharge pipe; 20-a stripping section of a dehydration tower; 21-a rectifying section of a dehydration tower; 22-a stripping section of a catalytic distillation column; 23-catalytic reaction section of catalytic rectifying tower; 24-a rectifying section of a catalytic rectifying tower; 25-a gasification tower; 26-a vaporization tower heater; 27-a gaseous formaldehyde discharge pipe; 28-ethylene glycol outlet pipe.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The utility model provides a device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether, which comprises a dehydrating tower, a gasification tower, a mixer and a catalytic rectifying tower which are sequentially connected according to a feeding sequence;

wherein, the dehydration tower and the catalytic rectification tower are respectively and independently provided with a rectification section, a stripping section and a heater from top to bottom;

a catalytic reaction section is arranged between the rectifying section and the stripping section of the catalytic rectifying tower;

a formaldehyde/glycol mixture feeding pipe is arranged on a distributor of the dehydration tower and is used for feeding a formaldehyde/glycol mixture, and glycol is used as a carrier of formaldehyde and is polyhydric alcohol including glycol;

the top of the dehydration tower is provided with a first reflux device;

the first reflux device comprises a dilute formaldehyde condenser and a vacuum receiving tank which are communicated in sequence;

the vacuum receiving tank is provided with a vacuum tube for creating vacuum;

the vacuum receiving tank is provided with a water outlet pipe for draining water;

the vacuum receiving tank is communicated with a reflux port of the dehydrating tower through a water reflux pipe;

a flowing polyformaldehyde discharging pipe is arranged at the bottom of the dehydration tower;

the top of the gasification tower is provided with a gas formaldehyde discharge pipe;

the bottom of the gasification tower is provided with an ethylene glycol discharge pipe;

the top of the catalytic rectifying tower is provided with a second reflux device;

the second reflux unit comprises an azeotrope condenser;

the azeotrope condenser is communicated with a reflux port of the catalytic rectifying tower through an azeotrope reflux pipe;

the azeotrope condenser is provided with an azeotrope discharging pipe for discharging azeotrope;

a fine methylal feeding pipe is arranged between the catalytic reaction section and the stripping section of the catalytic rectifying tower and is used for feeding methylal;

a crude DMMn discharging pipe is arranged at the bottom of the catalytic rectifying tower;

the mixer is provided with a reclaimed material feeding pipe for feeding reclaimed materials which are obtained by separating and recycling products extracted from the bottom of the catalytic rectification tower;

the flowing polyformaldehyde discharge pipe is connected with the gasification tower and is used for conveying flowing polyformaldehyde into the gasification tower;

the gas formaldehyde discharge pipe is connected with the mixer and used for conveying gas formaldehyde into the mixer;

the mixer is connected with the distributor of the catalytic rectifying tower through the mixture feeding pipe and is used for conveying the mixture of the gaseous formaldehyde and the reclaimed materials to the catalytic rectifying tower.

In a preferred embodiment, the catalytic reaction section of the catalytic distillation column of the present invention is used for packing catalyst packing; the stripping section of the catalytic rectifying tower is used for filling the aluminosilicate molecular sieve.

A device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether is shown in figure 2 and comprises a dehydration tower 1, a catalytic rectifying tower 2, a dilute formaldehyde condenser 3, a vacuum receiving tank 4, a mixer 5, an azeotrope condenser 6, a dehydration tower heater 7, a catalytic rectifying tower heater 8, a formaldehyde/ethylene glycol mixture feeding pipe 9, a flowing polyformaldehyde discharging pipe 10, a water return pipe 11, a vacuum pipe 12, a water outlet pipe 13, a reclaimed material feeding pipe 14, a mixed material feeding pipe 15, a fine methylal feeding pipe 16, an azeotrope return pipe 17, a crude DMMn discharging pipe 18, an azeotrope discharging pipe 19, a dehydration tower stripping section 20, a dehydration tower rectifying section 21, a catalytic rectifying tower stripping section 22, a catalytic rectifying tower catalytic reaction section 23 and a catalytic rectifying tower rectifying section 24;

specifically, a reflux device is arranged at the top of the dehydration tower 1, the reflux device comprises a dilute formaldehyde condenser 3 and a vacuum receiving tank 4 which are sequentially communicated, the vacuum receiving tank 4 is connected with a reflux port of the dehydration tower 1 through a water reflux pipe 11, the vacuum receiving tank 4 is also provided with a water outlet pipe 13, the dehydration tower 1 is provided with a dehydration tower rectifying section 21, a dehydration tower stripping section 20 and a dehydration tower heater 7 from top to bottom, a formaldehyde/ethylene glycol mixture feeding pipe 9 of the dehydration tower 1 is connected with a distributor at the upper end of the dehydration tower stripping section 20, the bottom of the dehydration tower 1 is provided with a flowing polyformaldehyde discharging pipe 10, the flowing polyformaldehyde discharging pipe 10 is connected with a mixer 5, the mixer 5 is provided with a reclaimed material feeding pipe 14, and the mixer 5 is provided with a mixed material feeding pipe 15;

the top of the catalytic rectifying tower 2 is provided with a reflux device, the reflux device comprises an azeotrope condenser 6, the azeotrope condenser 6 is connected with a reflux port of the catalytic rectifying tower 2 through an azeotrope reflux pipe 17, the azeotrope condenser 6 is also provided with an azeotrope discharge pipe 19, the catalytic rectifying tower 2 is provided with a catalytic rectifying tower rectifying section 24, a catalytic rectifying tower catalytic reaction section 23, a catalytic rectifying tower stripping section 22 and a catalytic rectifying tower heater 8 from top to bottom, a fine methylal feed pipe 16 is also arranged between the catalytic rectifying tower catalytic reaction section 23 and the catalytic rectifying tower stripping section 22, and the bottom of the catalytic rectifying tower 2 is provided with a crude DMMn discharge pipe 18;

the mixture feeding pipe 15 is connected with a distributor at the upper end of the catalytic reaction section 23 of the catalytic rectifying tower.

A typical apparatus for dehydration and catalytic synthesis of polymethoxy dimethyl ether is shown in figures 1 and 3, the device comprises a dehydration tower 1, a catalytic rectification tower 2, a dilute formaldehyde condenser 3, a vacuum receiving tank 4, a mixer 5, an azeotrope condenser 6, a dehydration tower heater 7, a catalytic rectification tower heater 8, a formaldehyde/ethylene glycol mixture feeding pipe 9, a flowing polyformaldehyde discharging pipe 10, a water return pipe 11, a vacuum pipe 12, a water outlet pipe 13, a reclaimed material feeding pipe 14, a mixture feeding pipe 15, a fine methylal feeding pipe 16, an azeotrope return pipe 17, a crude DMMn discharging pipe 18, an azeotrope discharging pipe 19, a dehydration tower stripping section 20, a dehydration tower rectifying section 21, a catalytic rectification tower stripping section 22, a catalytic rectification tower catalytic reaction section 23, a catalytic rectification tower rectifying section 24, a gasification tower 25, a gasification tower heater 26, a gas formaldehyde discharging pipe 27 and an ethylene glycol discharging pipe 28;

specifically, a reflux device is arranged at the top of the dehydration tower 1, the reflux device comprises a dilute formaldehyde condenser 3 and a vacuum receiving tank 4 which are sequentially communicated, the vacuum receiving tank 4 is connected with a reflux port of the dehydration tower 1 through a water reflux pipe 11, the vacuum receiving tank 4 is also provided with a water outlet pipe 13, the dehydration tower 1 is provided with a dehydration tower rectifying section 21, a dehydration tower stripping section 20 and a dehydration tower heater 7 from top to bottom, a formaldehyde/ethylene glycol mixture feeding pipe 9 of the dehydration tower 1 is connected with a distributor at the upper end of the dehydration tower stripping section 20, and the bottom of the dehydration tower 1 is provided with a flowing polyformaldehyde discharging pipe 10;

the flowing polyformaldehyde discharge pipe 10 is connected with a gasification tower 25, a gasification tower heater 26 is arranged at the bottom of the gasification tower 25, an ethylene glycol discharge pipe 28 is further arranged at the bottom of the gasification tower 25, a gas formaldehyde discharge pipe 27 is arranged at the top of the gasification tower, the gas formaldehyde discharge pipe 27 is connected with a mixer 5, a reclaimed material feed pipe 14 is arranged on the mixer 5, and a mixed material feed pipe 15 is arranged on the mixer 5;

the top of the catalytic rectifying tower 2 is provided with a reflux device, the reflux device comprises an azeotrope condenser 6, the azeotrope condenser 6 is connected with a reflux port of the catalytic rectifying tower 2 through an azeotrope reflux pipe 17, the azeotrope condenser 6 is also provided with an azeotrope discharge pipe 19, the catalytic rectifying tower 2 is provided with a catalytic rectifying tower rectifying section 24, a catalytic rectifying tower catalytic reaction section 23, a catalytic rectifying tower stripping section 22 and a catalytic rectifying tower heater 8 from top to bottom, a fine methylal feed pipe 16 is also arranged between the catalytic reaction section 23 and the stripping section 22 of the catalytic rectifying tower, and the bottom of the catalytic rectifying tower 2 is provided with a crude DMMn discharge pipe 18;

the mixture feeding pipe 15 is connected with a distributor at the upper end of the catalytic reaction section 23 of the catalytic rectifying tower.

The device of the utility model is that formaldehyde aqueous solution is mixed with a carrier and then is subjected to vacuum dehydration in a stripping section of a dehydration tower to prepare flowing polyformaldehyde, then the flowing polyformaldehyde is subjected to heating gasification and then is mixed with a reclaimed material, the mixture enters a catalytic rectification tower from the upper part of a section filled with a catalyst filler, the mixture flows downwards in a distributed manner under certain conditions, the mixture passes through a catalyst filler layer and is in countercurrent contact with methylal entering from the lower part of the catalyst filler section (catalytic reaction section) after vaporization, water generated by reaction is azeotropically taken out along with the methylal to generate polymethoxy dimethyl ether to continuously descend, the polymethoxy dimethyl ether crude product is obtained after passing through the stripping section filled with aluminosilicate molecular sieve filler, and low-boiling substances and macromolecules are further separated and recovered to obtain polymethoxy dimethyl ethers with different grades, wherein the basic reaction equation is as follows:

the utility model not only solves the problems of low yield, high energy consumption and high cost when the polyoxymethylene dimethyl ether is produced by taking paraformaldehyde, trioxymethylene and liquid formaldehyde as raw materials and the conventional catalytic synthesis at present, but also solves the problems of higher residual formaldehyde, trioxymethylene and hemiacetal in products, and simultaneously relieves the conditions of more byproducts, difficult product separation and the like; the utility model can realize continuous catalytic synthesis by utilizing the dehydration tower and the catalytic rectification tower, so that the process is simple, the synthesis conversion rate is higher, the product is easy to separate after being reformed by the aluminosilicate molecular sieve filling section, the by-product is less, and the content ratio of the good component DMM3-4 in the product DMM3-8 is higher; the utility model has the advantages of low investment cost, low production and driving risk and rich operating profit.

Example 1

A device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether is shown in figure 2 and comprises a dehydration tower 1, a catalytic rectifying tower 2, a dilute formaldehyde condenser 3, a vacuum receiving tank 4, a mixer 5, an azeotrope condenser 6, a dehydration tower heater 7, a catalytic rectifying tower heater 8, a formaldehyde/ethylene glycol mixture feeding pipe 9, a flowing polyformaldehyde discharging pipe 10, a water return pipe 11, a vacuum pipe 12, a water outlet pipe 13, a reclaimed material feeding pipe 14, a mixed material feeding pipe 15, a fine methylal feeding pipe 16, an azeotrope return pipe 17, a crude DMMn discharging pipe 18, an azeotrope discharging pipe 19, a dehydration tower stripping section 20, a dehydration tower rectifying section 21, a catalytic rectifying tower stripping section 22, a catalytic rectifying tower catalytic reaction section 23 and a catalytic rectifying tower rectifying section 24;

the method for preparing polymethoxy dimethyl ether by using the device of the embodiment comprises the following steps:

continuously feeding aqueous solution of formaldehyde (mass fraction is 37%) into a formaldehyde/ethylene glycol mixture feeding pipe 9 at a speed of 4000mL/h and ethylene glycol at a speed of 170mL/h by using a metering pump, mixing the aqueous solution by using the formaldehyde/ethylene glycol mixture feeding pipe 9, continuously feeding the mixed aqueous solution into a distributor at the upper end of a stripping section 20 of a dehydrating tower 1, maintaining the temperature of the bottom of the dehydrating tower to 90 ℃ after the liquid level of a heater 7 of the dehydrating tower is accumulated to a normal liquid level, pumping the vacuum degree of the system to be above-0.098 MP by using a vacuum receiving tank 4, combining the formaldehyde and a carrier, enabling the formaldehyde to flow downwards, gasifying the water, moving the gasified water to the top of the tower, condensing the gasified water by using a dilute formaldehyde condenser 3, collecting the condensed water in a vacuum receiving tank 4, controlling the temperature of the top of the tower to be 35 ℃ by using the reflux ratio of a water reflux pipe 11, and finally collecting water containing about 5% of formaldehyde from a water outlet pipe 13, a flowing polyformaldehyde discharging pipe 10 at the bottom of the dehydration tower extracts flowing polyformaldehyde (etherified substance between paraformaldehyde and ethylene glycol) with the water content of less than 5%;

the flowing polyformaldehyde is continuously extracted from a flowing polyformaldehyde discharge pipe 10 at the bottom of the dehydration tower and then enters a mixer 5, recovered materials (low-boiling-point substances and macromolecular materials) enter the mixer through a recovered material feed pipe 14 of the mixer 5 and are mixed with the flowing polyformaldehyde to obtain a mixture, the mixture enters a distributor of a catalytic rectification tower from the upper part of a catalytic reaction section 23 of the catalytic rectification tower filled with catalyst fillers through a mixture feed pipe 15 and flows downwards in a distributed manner;

the tower bottom temperature of the catalytic rectifying tower 2 is controlled at 90 ℃, the catalytic reaction section 23 temperature of the catalytic rectifying tower is controlled at 62 ℃ and the tower top temperature of the catalytic rectifying tower 2 is controlled at 41 ℃ according to the tower top reflux ratio of the catalytic rectifying tower heater 8 and the azeotrope reflux pipe 17;

continuously feeding refined methylal from the lower part of a catalytic reaction section 23 of the catalytic rectifying tower at a speed of 17000mL/h, heating and vaporizing the refined methylal, moving the refined methylal upwards to be in countercurrent contact with a dispersed downward flowing mixture, carrying out azeotropic entrainment on water and methanol brought by the flowing polyformaldehyde and water and methanol generated by reaction along with the upward gaseous methylal, condensing the mixture by an azeotrope condenser 6, refluxing a part of the mixture to the tower top through an azeotrope reflux pipe 17, and extracting a part of the mixture through an azeotrope discharge pipe 19;

the catalytic generated polymethoxy dimethyl ether goes down, the hydroxyl in the mixed material is almost completely blocked and etherified, and is concentrated and collected at the bottom of the tower after passing through a stripping section 22 of a catalytic rectifying tower filled with aluminosilicate molecular sieve filler to obtain a polymethoxy dimethyl ether crude product, the polymethoxy dimethyl ether crude product is continuously extracted through a crude product DMMn discharge pipe 18, and low-boiling-point substances and macromolecules (the low-boiling-point substances and the macromolecules are applied to a mixer 5) are further separated and recovered to obtain different grades of polymethoxy dimethyl ether finished products.

After the continuous feeding is carried out for 10 hours in the process, 43.5kg of formaldehyde aqueous solution (mass fraction is 37%) and 1.65kg of ethylene glycol are consumed, 31.5kg of DMM3-8 mixture is obtained after rectification separation, and the total organic matter yield is 98.2%. The weight yield to formaldehyde (dry basis) was 195.7%.

Example 2

Compared with the embodiment 1, the device for dehydration and catalytic synthesis of polymethoxy dimethyl ether of the embodiment is additionally provided with a gasification tower 25 between a dehydration tower 1 and a mixer 5, wherein the tower bottom of the gasification tower 25 is provided with a gasification tower heater 26, the tower bottom of the gasification tower 25 is provided with an ethylene glycol discharge pipe 28, and the top of the gasification tower is provided with a gas formaldehyde discharge pipe 27, and the specific device is shown in fig. 3;

compared with the embodiment 1, in the step of preparing the polyoxymethylene dimethyl ethers, the flowing polyoxymethylene continuously extracted from the bottom of the dehydration tower firstly enters the gasification tower 25, formaldehyde is heated, depolymerized and gasified under the action of the gasification tower heater 26, the carrier is discharged through the ethylene glycol discharge pipe 28 at the bottom of the tower and then returns to the dehydration tower for use, and gaseous formaldehyde enters the mixer through the gas formaldehyde discharge pipe 27 to be mixed with the recovered low-boiling-point substances and macromolecular materials and then enters the catalytic rectification tower for reaction and purification;

the rest steps and parameters are the same as the preparation method of the embodiment 1, and different grades of polymethoxy dimethyl ether finished products are obtained.

45kg of formaldehyde aqueous solution (mass fraction is 37%) and 1.72kg of ethylene glycol are consumed after the continuous feeding is carried out for 10 hours in the process, 28.6kg of DMM3-8 mixture is obtained after rectification and separation, and the total organic matter yield is 97.8% in total. The weight yield to formaldehyde (dry basis) was 171.8%.

In conclusion, the utility model solves the problems that the polyformaldehyde per se forms an insoluble and infusible solid state with low activity and difficult transportation when being dehydrated; the method can promote the reaction balance to move forward by taking out the moisture generated by the reaction through azeotropy, so that all hydroxyl groups are almost completely sealed, the etherification rate is high, the effective product yield is high, and the synthesis efficiency is high; the utility model is a continuous device, has low cost, simple operation and outstanding production efficiency, and is suitable for industrial production.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the utility model has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.

Claims (2)

1. A device for dehydrating and catalytically synthesizing polymethoxy dimethyl ether is characterized by comprising a dehydrating tower, a gasification tower, a mixer and a catalytic rectifying tower which are sequentially connected according to a feeding sequence;

wherein, the dehydration tower and the catalytic rectification tower are respectively and independently provided with a rectification section, a stripping section and a heater from top to bottom;

a catalytic reaction section is arranged between the rectifying section and the stripping section of the catalytic rectifying tower;

a formaldehyde/ethylene glycol mixture feeding pipe is arranged on a distributor of the dehydration tower and is used for feeding a formaldehyde/ethylene glycol mixture;

the top of the dehydration tower is provided with a first reflux device;

the first reflux device comprises a dilute formaldehyde condenser and a vacuum receiving tank which are communicated in sequence;

the vacuum receiving tank is provided with a vacuum tube for creating vacuum;

the vacuum receiving tank is provided with a water outlet pipe for draining water;

the vacuum receiving tank is communicated with a reflux port of the dehydrating tower through a water reflux pipe;

a flowing polyformaldehyde discharge pipe is arranged at the bottom of the dehydration tower;

the top of the gasification tower is provided with a gas formaldehyde discharge pipe;

the bottom of the gasification tower is provided with an ethylene glycol discharge pipe;

the top of the catalytic rectifying tower is provided with a second reflux device;

the second reflux unit comprises an azeotrope condenser;

the azeotrope condenser is communicated with the reflux port of the catalytic distillation tower through an azeotrope reflux pipe;

the azeotrope condenser is provided with an azeotrope discharge pipe for discharging azeotrope;

a fine methylal feeding pipe is arranged between the catalytic reaction section and the stripping section of the catalytic rectifying tower and is used for feeding methylal;

a crude DMMn discharging pipe is arranged at the bottom of the catalytic rectifying tower;

the mixer is provided with a reclaimed material feeding pipe for feeding reclaimed materials obtained by separating and recycling products extracted from the bottom of the catalytic rectification tower;

the flowing polyformaldehyde discharge pipe is connected with the gasification tower and is used for conveying flowing polyformaldehyde into the gasification tower;

the gas formaldehyde discharge pipe is connected with the mixer and used for conveying gas formaldehyde to the mixer;

the mixer is connected with the distributor of the catalytic rectifying tower through a mixture feeding pipe and is used for conveying the mixture of the gaseous formaldehyde and the reclaimed materials to the catalytic rectifying tower.

2. The apparatus of claim 1, wherein the catalytic reaction section of the catalytic distillation column is used for packing catalyst packing;

the stripping section of the catalytic rectifying tower is used for filling aluminosilicate molecular sieves.

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