CN111978284A - Preparation process and preparation system of dioxolane - Google Patents
Preparation process and preparation system of dioxolane Download PDFInfo
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- CN111978284A CN111978284A CN202010818419.3A CN202010818419A CN111978284A CN 111978284 A CN111978284 A CN 111978284A CN 202010818419 A CN202010818419 A CN 202010818419A CN 111978284 A CN111978284 A CN 111978284A
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- C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
- C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
- C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
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Abstract
The invention relates to a preparation process and a preparation system of dioxolane. The process takes ethylene glycol and formaldehyde aqueous solution as raw materials, and obtains hemiacetal raw material with low water content through condensation and dehydration; then synthesizing the dioxolane under the action of a solid acid catalyst; distilling to obtain a coarse product of the dioxolane; and (3) dehydrating by pervaporation to obtain pure dioxolane. According to the preparation process of the dioxolane, the water content of a reactant is reduced, the reaction rate is improved, and the subsequent separation difficulty is reduced through dehydration in the production process of the hemiacetal; the solid acid catalyst can improve the conversion rate and selectivity, reduce the corrosion of equipment and be easily separated from reaction liquid; and the energy consumption of dehydration separation is reduced by adopting a pervaporation dehydration mode.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a preparation process and a preparation system of dioxolane.
Background
The traditional production process of the Dioxolane (DOL) adopts formaldehyde and Ethylene Glycol (EG) as raw materials, wherein the formaldehyde is mostly paraformaldehyde or formaldehyde aqueous solution with the concentration of more than 50 percent. Sulfuric acid is used as a catalyst to react in a lining zirconium reactor, crude dioxolane is obtained after concentration, sodium chloride is selected to salt out to be used as an extracting agent to separate and dehydrate, and finally, the purified dioxolane is obtained through heavy-boiling substance removal and light-boiling substance removal.
The above-mentioned conventional production process has the following disadvantages: the cost is high, the condensation reaction of the ethylene glycol and the polyformaldehyde is carried out intermittently in the reaction kettle, and water generated in the condensation process cannot be removed from a reaction system, so that the conversion rate of raw materials is low, and the waste of raw materials is caused. Meanwhile, a large amount of wastewater containing formaldehyde and glycol is discharged in the production process, and serious pollution is brought to the environment; the crude product has larger water content, correspondingly increases the load of subsequent refining, and has more used equipment and large energy consumption.
In addition, in the traditional process, sulfuric acid is used as a catalyst, and anticorrosive material zirconium is required to be used for reaction part equipment, so that the equipment investment is large. Meanwhile, the salting-out method of sodium chloride needs to use a large amount of sodium chloride, and the sodium chloride has strong corrosion to equipment, so that anticorrosive materials are needed for preparing the equipment.
Some patents disclose the improvement of the above conventional process, which involves different process steps, such as:
and (3) reaction rectification:
pasteur in Germany reports a process (CN101282958B) in which the starting materials ethylene glycol and aqueous formaldehyde solution are fed from the middle region of a reactive distillation column into the column which has both the process of carrying out the reaction and the separation by distillation. The catalyst used in the process is an acid catalyst such as sulfuric acid, trifluoroboric acid, zinc chloride or an acidic ion exchanger. And (3) rectifying the distillate at the top of the reactive distillation tower again at higher pressure to obtain the 1, 3-dioxolane with the purity of over 90 percent. The process involves the use of multiple rectification columns, resulting in increased equipment costs and energy consumption.
Patent CN102267972A reports that ethylene glycol and 30% formaldehyde aqueous solution by volume concentration are used as raw materials and are subjected to a solid acid catalyst (gamma-Al)2O3、SiO2、SiO2-Al2O3Or ZSM-5 type molecular sieve) to obtain the 1, 3-dioxolane. The solid acid catalyst is arranged in the middle and at the bottom of the reactive distillation column and is also used as a filler. The reactive distillation column is under pressure. Raw materials are added from the bottom of the reactive distillation tower and react in the middle, and the obtained product 1, 3-dioxolane flows out from the top of the reactive distillation tower in a gaseous form and is discharged after being condensed by a condenser.
Patent CN106883209B discloses a method for synthesizing 1, 3-dioxolane by using ethylene glycol and formaldehyde (volume concentration is 37% -45%) as raw materials and placing a strip-shaped solid acid catalyst in the middle of a catalytic rectification tower to play a role of a filler. The crude product of the 1, 3-dioxolane obtained by the method is discharged from the top of a catalytic rectification tower, is subjected to dehydration separation by a molecular sieve membrane (hydrophilic polymer modified carbon nanofiber composite molecular sieve membrane) device, and is separated by a rectification tower to obtain the high-purity 1, 3-dioxolane.
And (3) dewatering and separating:
patent CN102174033A reports a method for preparing 1, 3-dioxolane by using silica gel supported phosphotungstic acid as a catalyst and performing condensation reaction between ethylene glycol and formaldehyde (trioxymethylene, paraformaldehyde, 37% formaldehyde aqueous solution). And distilling the liquid obtained by the reaction under normal pressure to obtain a crude product of the 1, 3-dioxolane, salting out by sodium chloride, dehydrating by anhydrous calcium chloride, and rectifying under normal pressure to obtain the refined 1, 3-dioxolane.
Patent CN106674187A reports a method for synthesizing 1, 3-dioxolane by using N86 type ionic liquid as a catalyst and ethylene glycol and polyformaldehyde as raw materials. Drying and rectifying the obtained crude product by using solid alkali, and finally adding a proper amount of antioxidant 2, 6-di-tert-butyl-p-phenol to obtain the target product 1, 3-dioxolane.
Mitsubishi chemical (CN1149055A) reported a method of extracting and rectifying a 1, 3-dioxolane reaction distillate to obtain high-purity 1, 3-dioxolane by using an alkyl-substituted benzene as an extracting agent.
However, the existing common process and the improved process have the following defects:
1. the concentrated formaldehyde or the paraformaldehyde is adopted as the raw material, so that a large amount of dilute aldehyde is produced by producing the concentrated formaldehyde or the paraformaldehyde, the production cost and the raw material cost are increased, and the pollution is large.
2. When dilute aldehyde is directly used as a raw material, the reaction speed is slow, and the requirement on the water resistance of the catalyst is high if the dioxolane is directly prepared by using the dilute aldehyde as the raw material.
3. The dioxolane can form an azeotrope with water, the azeotropic point is 70-73 ℃, the water content is 6.7%, the separation difficulty is high, and meanwhile, due to the existence of formaldehyde, the local concentration of a separation unit is too high, a formaldehyde polymer is easily formed, so that the pipeline of a rectifying tower is blocked, and the existence of formic acid easily corrodes equipment and pipelines. Low efficiency, high difficulty, high energy consumption, large pollution and the like.
Therefore, none of the above prior art patents fundamentally solves the disadvantages of the prior art.
Disclosure of Invention
The invention provides a preparation process and a preparation system of dioxolane, wherein the preparation process reduces the water content of a reactant, improves the reaction rate and reduces the difficulty of subsequent separation by dehydration in the production process of hemiacetal; the solid acid catalyst can improve the conversion rate and selectivity, reduce the corrosion of equipment and be easily separated from reaction liquid; and the energy consumption of dehydration separation is reduced by adopting a pervaporation dehydration mode.
The technical scheme of the invention is as follows:
a preparation process of dioxolane takes ethylene glycol and formaldehyde aqueous solution as raw materials, and the hemiacetal raw material with low water content is obtained by dehydration after condensation; then producing the dioxolane under the action of a solid acid catalyst, distilling to obtain coarse dioxolane, and dehydrating by pervaporation to obtain pure dioxolane.
Wherein the concentration of formaldehyde in the formaldehyde aqueous solution is more than 5 percent; the water content of the hemiacetal starting material is less than 5%; the molar ratio of the ethylene glycol to the formaldehyde is 1-1.5: 1.
The condensation reaction is carried out in a batch reaction kettle or a reaction rectifying tower at the temperature of 5-150 ℃ and the pressure of-0.1-1 MPa.
When the hemiacetal raw material is prepared in the batch reaction kettle, the stirring speed is 50-500 r/min, and the mixing time is 0.1-50 h.
When the reaction rectifying tower is used for preparing the hemiacetal raw material, the glycol material flow and the formaldehyde water solution flow in the reverse direction.
Wherein the formaldehyde solution is prepared by an Ag method or an iron-molybdenum method, or a dilute formaldehyde solution generated in the production process of formaldehyde derivatives.
Wherein, the hemiacetal raw material is subjected to evaporation dehydration operation, the pressure of the evaporation dehydration is-0.07-0.1 MPa, the temperature of the evaporation dehydration is 60-150 ℃, and the evaporation dehydration equipment is falling film evaporation or reduced pressure evaporation equipment.
Wherein, the hemiacetal raw material adopts membrane dehydration operation, the membrane dehydration is a permeation gasification process, the used membrane material is a hydrophilic molecular sieve membrane, the residual side obtains the hemiacetal raw material with low water content, and the permeation side separates and removes water; the pressure of the retentate side of membrane dehydration is 0-0.5 Mpa, and the temperature is 60-150 ℃; the pressure of the permeation side is-0.06-0.1 MPa.
Wherein the content of formaldehyde in water separated in the condensation dehydration process of the hemiacetal raw material is 0.1-1%, and the water is circulated to an absorption tower of a formaldehyde production unit.
Wherein the acid content of the B acid in the solid acid catalyst accounts for more than 80% of the total acid content; the dosage of the solid acid catalyst is 1-15% of the total mass of the hemiacetal raw material, the reaction pressure is-0.05-0.1 MPa, and the reaction temperature is 80-150 ℃.
Wherein, the crude dioxolane obtained by distillation is separated by a rectifying tower, the crude dioxolane with the formaldehyde content of less than 0.1 percent and the water content of less than 15 percent is obtained at the top of the tower, and the unreacted raw materials and the water mixture produced by reaction are obtained at the top of the tower.
The crude product of the dioxolane is dehydrated by pervaporation through a molecular sieve membrane, water is separated and removed at the permeation side, and the dioxolane is obtained at the residual side; the molecular sieve membrane pervaporation membrane is a hydrophilic NaA molecular sieve membrane, membrane dehydration is a pervaporation process or a gasification permeation process, and the crude dioxolane on the retentate side is liquid or gas on the membrane surface; the pressure of the retentate side of the molecular sieve membrane permeation gasification membrane is 0.1-1.0 Mpa, and the temperature is 80-150 ℃. The pressure of the permeation side is-0.08-0.1 MPa.
A system for preparing dioxolane comprises
A low-water-content hemiacetal raw material preparation section covering a dehydration unit, a crude dioxygen five ring product section covering a dioxygen five ring reactor and a crude dioxygen five ring product separation tower, and a dioxygen five ring purification section covering a dioxygen five ring membrane dehydration unit and a dioxygen five ring recovery tower;
the dehydration unit receives a formaldehyde aqueous solution material flow, an ethylene glycol material flow introduced from the outside, a reactant material flow flowing out of the dioxolane reactor and a dioxolane crude product separation tower kettle material flow;
the dioxygen pentacyclic reactor receives ethylene glycol formal material flow obtained from a tower kettle of a dehydration unit;
the crude dioxolane product separation tower receives a dioxolane mixture material flow obtained from the top of a reaction kettle of a dioxolane reactor;
the dioxygen pentacyclic membrane dehydration unit receives a dioxygen pentacyclic azeotropic material flow obtained at the top of a dioxygen pentacyclic reactor reaction kettle and a dioxygen pentacyclic recovery material flow of a dioxygen pentacyclic recovery tower.
The quinuclidine dioxide recovery column receives a permeate side stream formed by the quinuclidine dioxide membrane dehydration unit and a portion of the dehydrated stream from the dehydration unit.
The invention has the following beneficial effects:
1. according to the invention, through dehydration in the hemiacetal production process, the water content of the reactant is reduced, the reaction rate is improved, the reduction of the production cost and the improvement of the production efficiency can be considered, the subsequent separation difficulty is reduced, the conversion rate can be improved to more than 92% and the selectivity can be improved to about 98% by combining with the solid acid catalyst, the conversion rate is improved to more than 50% compared with the conventional process, the corrosion of equipment and the separation cost are greatly reduced, and the catalyst is easily separated from the reaction liquid; and the energy consumption of dehydration separation is reduced by adopting a pervaporation dehydration mode.
2. The whole process has high utilization rate of raw materials, and water in the preparation process of the raw materials with low water content is circulated to the formaldehyde aqueous solution preparation unit, so that the use of water is reduced. The water produced by the cyclization reaction is recycled to the preparation process of the raw material with low water content, so that the water content in the cyclization reaction process is reduced, the reaction efficiency is improved, and the space-time yield of the dioxolane can be improved by more than 2 times.
3. The condensation reaction of the ethylene glycol and the formaldehyde is continuously carried out in the reaction kettle, the process water generated in the condensation process can be recycled, the conversion rate of the raw materials is high, and the waste of the raw materials is effectively saved; meanwhile, the amount of waste liquid such as dilute aldehyde and the like in the production process is reduced, so that the waste of raw materials and environmental pollution are effectively reduced; the water content of the crude product is small, the load of subsequent refining is effectively reduced, the used equipment is less, and the energy consumption is low.
4. In the preparation of formaldehyde derivatives, large amounts of dilute aldehyde solutions are present due to the strong interaction of formaldehyde and water, which results in large steam consumption, e.g. by separation methods such as distillation. The invention also provides a method for treating dilute aldehyde, which prepares the dioxolane by using hemiacetal synthesized from glycol and formaldehyde.
Drawings
FIG. 1 is a schematic diagram of a system for producing dioxolane in accordance with the present invention.
The reference numbers in the figures denote:
1-aqueous formaldehyde solution material flow, 2-ethylene glycol material flow, 3-low water content hemiacetal raw material flow, 4-dehydration material flow, 5-ethylene glycol formal material flow, 6-ethylene glycol recovery material flow, 7-dioxygen pentacyclic mixture material flow, 8-tower kettle material flow, 9-dioxygen pentacyclic azeotrope flow, 11-permeation side material flow, 10-dioxygen pentacyclic material flow, 13-dioxygen pentacyclic recovery material flow, 12-water material flow, R0101-dehydration unit, R0201-dioxygen pentacyclic reactor, T0201-dioxygen pentacyclic crude product separation tower, T0301-dioxygen pentacyclic recovery tower and M0301-dioxygen pentacyclic membrane dehydration unit.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
The invention relates to a preparation process of a dioxolane, which comprises the following steps:
the method comprises the following steps: mixing the aqueous solution of formaldehyde and ethylene glycol, and dehydrating to obtain a hemiacetal raw material with low water content, wherein the dehydration method can adopt evaporation dehydration or membrane dehydration;
step two: synthesizing a dioxolane by using a hemiacetal raw material with low water content under the action of a solid acid catalyst, and distilling to obtain a coarse dioxolane product;
step three: and (3) dehydrating the crude dioxolane through a molecular sieve membrane permeation gasification membrane, separating and dehydrating water at the permeation side, and obtaining the dioxolane at the residual side.
Further:
in the first step, the formaldehyde solution has a formaldehyde concentration of more than 5%, and can be a formaldehyde solution prepared by an Ag method or an iron-molybdenum method, or a dilute formaldehyde solution generated in the production process of formaldehyde derivatives.
In the first step, the formaldehyde aqueous solution is mixed with ethylene glycol, and the molar ratio of the ethylene glycol to the formaldehyde is 1-1.5.
In the first step, the hemiacetal raw material with low water content is subjected to evaporation dehydration, the pressure of the evaporation dehydration is-0.07-0.1 MPa, the temperature of the evaporation dehydration is 60-150 ℃, and the evaporation dehydration equipment is falling film evaporation and reduced pressure evaporation equipment.
In the first step, the hemiacetal raw material with low water content is subjected to membrane dehydration, the membrane dehydration is a pervaporation process, the used membrane material is a hydrophilic molecular sieve membrane, the hemiacetal raw material with low water content is obtained on the retentate side, and water is separated and removed on the permeate side. The pressure of the retentate side of the membrane dehydration is 0-0.5 Mpa, and the temperature is 60-150 ℃. The pressure of the permeation side is-0.06-0.1 MPa.
In the first step, the content of formaldehyde in the water separated in the preparation process of the hemiacetal raw material with low water content is 0.1-1%, and the water can be recycled to an absorption tower of a formaldehyde production unit.
In the first step, the water content of the hemiacetal raw material with low water content is less than 5 percent after dehydration.
In the second step, the solid acid catalyst is resin or molecular sieve, and the acid content of the B acid in the solid acid catalyst accounts for more than 80% of the total acid content. The resin catalyst can load acidic substances such as sulfonic acid, ionic liquid and the like.
In the second step, the dosage of the solid acid catalyst is 1-15% of the total mass of the hemiacetal raw material with low water content, the reaction pressure is-0.05-0.1 MPa, and the reaction temperature is 80-150 ℃.
In the second step, the hemiacetal raw material with low water content is synthesized into the dioxolane under the action of a solid acid catalyst, and the synthesis can be carried out in a fixed bed, a kettle type and a reaction rectifying tower.
And in the second step, the crude dioxolane obtained by distillation is separated by a rectifying tower, the crude dioxolane with the formaldehyde content of less than 0.1 percent and the water content of less than 15 percent is obtained at the top of the tower, and unreacted raw materials and a water mixture produced by reaction are obtained at the top of the tower.
In the second step, the hemiacetal raw material with low water content synthesizes dioxolane under the action of a solid acid catalyst, and unreacted raw materials and water produced by the reaction are circulated to a hemiacetal raw material production unit with low water content, so that the utilization rate of the raw materials is improved.
In the third step, the molecular sieve membrane pervaporation membrane is a hydrophilic NaA molecular sieve membrane, membrane dehydration is a pervaporation process or a gasification pervaporation process, and the crude dioxolane on the retentate side is liquid or gas on the membrane surface.
In the third step, the pressure of the retentate side of the molecular sieve membrane permeation gasification membrane is 0.1-1.0 Mpa, and the temperature is 80-150 ℃. The pressure of the permeation side is-0.08-0.1 MPa.
In the third step, the residue side is dehydrated to obtain the dioxolane with the water content of less than 0.5 percent, the dioxolane in the residue side can be recovered by rectification, the mixture of the dioxolane with the water content of less than 15 percent is obtained at the top of a rectifying tower, and the water solution with the dioxolane content of less than 0.1 percent is obtained at the bottom of the rectifying tower.
Referring to FIG. 1, a system for the preparation of dioxolane comprises
A low water content hemiacetal feedstock preparation section encompassing dehydration unit R0101, a dioxolane crude product section encompassing dioxolane reactor R0201 and dioxolane crude product separation column T0201, and a dioxolane purification section encompassing dioxolane membrane dehydration unit M0301 and dioxolane recovery column T0301;
the dehydration unit R0101 receives a formaldehyde aqueous solution material flow 1, an ethylene glycol material flow 2 introduced from the outside, a reaction material flow 6 flowing out of the dioxolane reactor R0201 and a dioxolane crude product separation tower T0201 tower kettle material flow 8;
the dioxygen pentacyclic reactor R0201 receives ethylene glycol formal material flow 5 obtained from a tower kettle of a dehydration unit R0101;
the dioxolane crude product separation tower T0201 receives dioxolane mixture material flow 7 obtained from the top of a reaction kettle of the dioxolane reactor R0201;
and the dioxygen pentacyclic membrane dehydration unit M0301 receives a dioxygen pentacyclic azeotropic material flow 9 obtained at the top of a dioxygen pentacyclic reactor R0201 reaction kettle and a dioxygen pentacyclic recovery material flow 13 of a dioxygen pentacyclic recovery tower T0301.
Said dioxygen pentacyclic recovery column T0301 receives a permeate side stream 11 formed by dioxygen pentacyclic membrane dehydration unit M0301 and a dehydrated stream 4 coming out of partial dehydration unit R0101.
Example 1:
the process of the invention is adopted to prepare the dioxolane: 1000g of an aqueous formaldehyde solution having a formaldehyde concentration of 15% and 327.2g of ethylene glycol having a content of 99.5% in a molar ratio of formaldehyde to ethylene glycol of 1:1.05 were mixed under normal pressure and stirred at 50 ℃ for 1 hour, the ethylene glycol and formaldehyde forming a hemiacetal having a water content of 56.51%.
Adopting reduced pressure evaporation equipment for hemiacetal, wherein the water evaporation speed is as follows under the conditions of-0.07 MPa and 90 ℃: under the condition of evaporation dehydration of 100g water/h, dehydration separation is carried out to obtain the hemiacetal raw material with the water content of 5.23 percent.
100g of ZSM-5 molecular sieve catalyst is added into a low-water content hemiacetal raw material, the reaction pressure is normal pressure, the reaction temperature is 90 ℃, and the synthesized dioxolane is extracted from a gas phase outlet of a reactor and is collected and analyzed by condensation.
The method comprises the following steps of firstly, preparing a low-water-content hemiacetal raw material, wherein a mixture of a 15% dilute formaldehyde water solution material flow 1, an ethylene glycol material flow 2, a dioxy pentacyclic reactor R0201 tower bottom ethylene glycol recovery material flow 6 and a dioxy pentacyclic crude product separation tower T0201 tower bottom material flow 8 is a low-water-content hemiacetal raw material flow 3, performing dehydration separation in a dehydration unit R0101 to form hemiacetal from ethylene glycol and formaldehyde, performing reduced pressure distillation to obtain a water solution with the formaldehyde content of 0.1% at the tower top, and obtaining a glycol formal material flow 5 with the water content of 2.6% at the tower bottom. A dehydrated stream 4 is obtained at the top of the column. The pressure of the reduced pressure distillation is-0.07 MPa, and the temperature of the reduced pressure distillation is 90 ℃.
And secondly, a crude dioxolane product working section, wherein the glycol formal material flow 5 with the water content of 2.6 percent enters a dioxolane reactor R0201, a sulfonic acid resin catalyst with the mass content of 10 percent is filled in the reactor, the reaction temperature is 85 ℃, the reaction pressure is 0.02MPa, and the stirring speed is 50R/min. The bottom of the reactor discharges a glycol recovery stream 6 consisting of: formaldehyde 1.76%, water 29.20%, the remainder being ethylene glycol, the top of the reactor yielding a stream 7 of a dioxolane mixture having the composition of ethylene glycol 0.04%, formaldehyde 0.54%, water 12.06, and the remainder being dioxolane. And (3) feeding the stream 7 of the dioxolane mixture into a dioxolane crude product separation tower T0201 for further separation, wherein the number of tower plates of the dioxolane crude product separation tower T0201 is 22, the temperature of a tower kettle is 101 ℃, the temperature of a tower top is 70 ℃, the operation pressure is normal pressure, and the reflux ratio is 0.9. A dioxolane stream 9 with a water content of 9.0 percent is obtained at the top of the tower, and a tower bottom stream 8 with a water content of 75.61 percent, an ethylene glycol content of 13.80 percent and a formaldehyde content of 5.84 percent is obtained at the bottom of the tower. This material was mixed with the diol recovery stream 6 and returned to the dehydration unit R0101.
And the third step, a five-ring dioxide purification section, namely mixing a five-ring dioxide mixture material flow 9 with a five-ring dioxide recovery material flow 13 at the top of a five-ring dioxide recovery tower T0301, and then feeding the mixture into a five-ring dioxide membrane dehydration unit M0301, wherein the dehydration unit is provided with a NaA molecular sieve membrane, the pressure of the retentate side is 0.35MPa, the temperature is 125 ℃, and after dehydration, a five-ring dioxide material flow 10 with the water content of 0.1% is obtained, the pressure of the permeate side is-0.095 MPa, and the composition of the permeate side material flow 11 is that the five-ring dioxide content is 14.5% and the water content is 85.5%. After mixing the permeate side stream 11 and the dehydrated stream 4, the mixture enters a dioxygen pentacyclic recovery tower T0301, the number of tower plates is 15, the temperature of a tower kettle is 100 ℃, the temperature of a tower top is 72 ℃, and the reflux ratio is 1.2. An overhead stream 13 of the recovered dioxolane is obtained at the top of the column, and a water stream 12 containing only water is obtained at the bottom of the column and is discharged from the system.
Example 2
The process of the invention is adopted to prepare the dioxolane: 1000g of an aqueous formaldehyde solution having a formaldehyde concentration of 33.68% and 734.5g of ethylene glycol having a content of 99.5% in a molar ratio of formaldehyde to ethylene glycol of 1:1.05 were mixed under normal pressure and stirred at 50 ℃ for 1 hour, the ethylene glycol and formaldehyde forming a hemiacetal having a water content of 38.23%.
Adopting reduced pressure evaporation equipment for hemiacetal, wherein the water evaporation speed is as follows under the conditions of-0.07 MPa and 90 ℃: under the condition of evaporation dehydration of 100g of water/h, dehydration separation is carried out to obtain the hemiacetal raw material with low water content, and the water content is reduced to 1.58 percent.
100g of ZSM-5 molecular sieve catalyst is added into a low-water content hemiacetal raw material, the reaction pressure is normal pressure, the reaction temperature is 90 ℃, and the synthesized dioxolane is extracted from a gas phase outlet of a reactor and is collected and analyzed by condensation.
The method specifically comprises the following steps: in the first step, a low-water content hemiacetal raw material, namely 33.68% diluted formaldehyde aqueous solution material flow 1, is prepared, the mixture of the low-water content hemiacetal raw material flow 1, ethylene glycol material flow 2, a dioxy pentacyclic reactor R0201 tower bottom ethylene glycol recovery material flow 6 and a dioxy pentacyclic crude product separation tower T0201 tower bottom material flow 8 is low-water content hemiacetal raw material flow 3, dehydration separation is carried out in a dehydration unit R0101, the ethylene glycol and the formaldehyde form hemiacetal, reduced pressure distillation is carried out, and an ethylene glycol formal material flow 5 with the water content of 1.58% is obtained in a tower bottom. A dehydrated stream 4 is obtained at the top of the column. The pressure of the reduced pressure distillation is-0.07 MPa, and the temperature of the reduced pressure distillation is 90 ℃.
The second step is that: preparing a dioxolane crude product, feeding a glycol formal material flow 5 with the water content of 1.58% into a dioxolane reactor R0201, filling a sulfonic acid resin catalyst with the mass content of 10% into the reactor, and carrying out reaction at the temperature of 90 ℃, under the normal pressure and at the stirring speed of 50R/min.
A third part: mixing the purified dioxygen pentacyclic, dioxygen pentacyclic mixture material flow 9 with dioxygen pentacyclic recycle material flow 13 at the top of a dioxygen pentacyclic recycle tower T0301, then entering a dioxygen pentacyclic membrane dehydration unit M0301, wherein the dehydration unit is provided with a NaA molecular sieve membrane, obtaining the top material flow 13 of the dioxygen pentacyclic recycle at the top of the tower, obtaining a water material flow 12 only containing water at the bottom of the tower, and discharging the water material flow from the system.
Comparative example 1
The dioxolane is prepared in a conventional manner using ethylene glycol and formaldehyde: 1000g of an aqueous formaldehyde solution having a formaldehyde concentration of 33.68% and 734.5g of ethylene glycol having a formaldehyde content of 99.5% were mixed in a molar ratio of formaldehyde to ethylene glycol of 1:1.05 and stirred at 50 ℃ for 1 hour under normal pressure, the ethylene glycol and formaldehyde forming the hemiacetal starting material having a water content of 38.23%.
100g of ZSM-5 molecular sieve catalyst is added into a hemiacetal raw material, the reaction pressure is normal pressure, the reaction temperature is 90 ℃, and the synthesized dioxolane is extracted from a gas phase outlet of a reactor and is collected and analyzed by condensation.
When the low water content hemiacetal is used as raw material to prepare the dioxolane, the space-time yield is increased by 2.5 times to almost 4 times, the conversion rate of formaldehyde is increased to a degree of more than 80%, and the selectivity of the dioxolane is increased to more than 80%. It is demonstrated that the reaction efficiency can be greatly improved by the improvement of the process.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A preparation process of dioxolane is characterized by comprising the following steps: using ethylene glycol and formaldehyde aqueous solution as raw materials, and dehydrating the raw materials after condensation reaction to obtain a hemiacetal raw material with low water content; then synthesizing the dioxolane under the action of a solid acid catalyst, distilling to obtain coarse dioxolane, and dehydrating by pervaporation to obtain pure dioxolane.
2. The process for preparing dioxolane according to claim 1, wherein: the formaldehyde concentration of the formaldehyde aqueous solution is more than 5 percent; the water content of the hemiacetal starting material is less than 5%; the molar ratio of the ethylene glycol to the formaldehyde in the ethylene glycol and formaldehyde aqueous solution is 1-1.5: 1, the condensation reaction temperature is 5-150 ℃, the pressure is-0.1-1 MPa, and the condensation reaction can be carried out in an intermittent reaction kettle or a reaction rectifying tower.
3. The process for preparing dioxolane according to claim 1, wherein: the formaldehyde solution is prepared by an Ag method or an iron-molybdenum method, or is a dilute formaldehyde solution generated in the production process of formaldehyde derivatives.
4. The process for preparing dioxolane according to claim 1, wherein: the hemiacetal raw material is subjected to evaporation dehydration operation, the pressure of the evaporation dehydration is-0.07-0.1 MPa, the temperature of the evaporation dehydration is 60-150 ℃, and the evaporation dehydration equipment is falling film evaporation or reduced pressure evaporation equipment.
5. The process for preparing dioxolane according to claim 1, wherein: the hemiacetal raw material adopts membrane dehydration operation, the membrane dehydration is a permeation gasification process, the used membrane material is a hydrophilic molecular sieve membrane, the residual side obtains the hemiacetal raw material with low water content, and the permeation side separates and removes water; the pressure of the retentate side of membrane dehydration is 0-0.5 Mpa, and the temperature is 60-150 ℃; the pressure of the permeation side is-0.06-0.1 MPa.
6. The process for preparing dioxolane according to claim 4 or 5, wherein: and the content of formaldehyde in water separated in the condensation dehydration process of the hemiacetal raw material is 0.1-1%, and the water is circulated to an absorption tower of a formaldehyde production unit.
7. The process for preparing dioxolane according to claim 1, wherein: the acid amount of the B acid in the solid acid catalyst accounts for more than 80% of the total acid amount; the dosage of the solid acid catalyst is 1-15% of the total mass of the hemiacetal raw material, the reaction pressure is-0.05-0.1 MPa, and the reaction temperature is 80-150 ℃.
8. The process for preparing dioxolane according to claim 1, wherein: and (3) separating the crude dioxolane obtained by distillation by using a rectifying tower, obtaining the crude dioxolane with the formaldehyde content of less than 0.1 percent and the water content of less than 15 percent at the tower top, and obtaining a mixture of unreacted raw materials and water produced by reaction at the tower top.
9. The process for preparing dioxolane according to claim 1, wherein: the crude dioxolane is dehydrated by adopting a pervaporation method, namely, the crude dioxolane is dehydrated by a molecular sieve membrane pervaporation membrane, water is separated and dehydrated on a permeation side, and dioxolane is obtained on a retentate side; the molecular sieve membrane pervaporation membrane is a hydrophilic NaA molecular sieve membrane, membrane dehydration is a pervaporation process or a gasification permeation process, and the crude dioxolane on the retentate side is liquid or gas on the membrane surface; the pressure of the retentate side of the molecular sieve membrane permeation gasification membrane is 0.1-1.0 Mpa, and the temperature is 80-150 ℃. The pressure of the permeation side is-0.08-0.1 MPa.
10. A five ring preparation system of dioxide which characterized in that: comprises that
A low water content hemiacetal feedstock preparation section encompassing a dehydration unit (R0101), a dioxolane crude product section encompassing a dioxolane reactor (R0201) and a dioxolane crude product separation column (T0201), and a dioxolane purification section encompassing a dioxolane membrane dehydration unit (M0301) and a dioxolane recovery column (T0301);
the dehydration unit (R0101) receives a reaction material flow (6) flowing out of a dioxypentacyclic reactor (R0201) and a dioxypentacyclic crude product separation tower (T0201) tower kettle material flow (8) from a formaldehyde aqueous solution material flow (1), an ethylene glycol material flow (2) introduced from the outside;
the dioxygen pentacyclic reactor (R0201) receives an ethylene glycol formal material flow (5) obtained from a tower kettle of a dehydration unit (R0101);
the dioxo pentacyclic crude product separation tower (T0201) receives a dioxo pentacyclic mixture material flow (7) obtained at the top of a dioxo pentacyclic reactor (R0201) reaction kettle;
the dioxygen pentacyclic membrane dehydration unit (M0301) receives a dioxygen pentacyclic azeotrope stream (9) obtained from the top of a dioxygen pentacyclic reactor (R0201) reaction kettle and a dioxygen pentacyclic recovery stream (13) of a dioxygen pentacyclic recovery tower (T0301).
Said dioxygen pentacyclic recovery column (T0301) receives a permeate side stream (11) formed by a dioxygen pentacyclic membrane dehydration unit (M0301) and a dehydrated stream (4) coming out of a partial dehydration unit (R0101).
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