CN214193104U - Device for preparing trioxymethylene from methanol - Google Patents
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- CN214193104U CN214193104U CN202022538513.1U CN202022538513U CN214193104U CN 214193104 U CN214193104 U CN 214193104U CN 202022538513 U CN202022538513 U CN 202022538513U CN 214193104 U CN214193104 U CN 214193104U
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Abstract
The present disclosure provides an apparatus for preparing trioxymethylene from methanol, comprising: methanol oxidation preparation formaldehyde workshop section: a methanol oxidation reactor and a formaldehyde absorption tower; a trioxymethylene crude product synthesis section: a trioxymethylene synthesis reactor and a trioxymethylene concentration tower; a trioxymethylene refining separation section: a trioxymethylene refining reactor, a trioxymethylene dehydration membrane component and a trioxymethylene dealcoholization tower; a recovery section: and recovering the reaction rectifying tower.
Description
Technical Field
The disclosure relates to the field of chemical production processes, in particular to a device for preparing trioxymethylene from methanol.
Background
Polyoxymethylene (POM), also known as acetal resin and polyoxymethylene, is a thermoplastic engineering plastic with excellent comprehensive properties, is one of five engineering plastics, is an engineering plastic with mechanical properties closest to metal materials in engineering plastics, and is known as "super steel" or "stainless steel". The key monomers for producing polyoxymethylene are trioxymethylene and dioxolane, the purity of which directly affects the polymer properties, thus requiring less than 100ppm total impurities.
The existing synthetic process of trioxymethylene is that trioxymethylene is obtained by the catalytic reaction of a formaldehyde solution with the concentration of more than 60% in a reaction kettle by sulfuric acid, then the trioxymethylene is rectified and concentrated, and a pure trioxymethylene product is obtained by benzene extraction, neutralization (formic acid removal) and purification treatment of a light boiling tower and a heavy boiling tower.
Due to the low equilibrium conversion in trioxymethylene synthesis, a large amount of free formaldehyde is present in the trioxymethylene solution during the separation. Free formaldehyde will condense and polymerize with water, methanol and formaldehyde itself to form hemiacetals, acetals and formaldehyde polymers. The relative volatility of partial hemiacetal, acetal, polymer of formaldehyde and trioxymethylene are similar and cannot be separated by common separation methods. The prior art generally adopts crystallization or extraction method to carry out primary separation on the synthesized product, and refining by rectification. The Asahi Kasei Kogyo CN1169725A (published as 1998, 1.7) discloses a method for producing high-purity trioxymethylene by using aqueous solution of formaldehyde as raw material, synthesizing trioxymethylene with acid catalyst, and extracting to obtain compound containing CH3O(CH2O)nCH3(low polyformaldehyde) and trioxymethylene mixture of formaldehyde, methanol, formic acid and extractant benzene, rectifying to separate benzene and its light boiling components, and obtaining CH-containing material at the bottom of tower3O(CH2O)nCH3The trioxymethylene mixture of (oligo-formal) is contacted with a solid acid catalyst in the presence of water to decompose the oligo-formal, and then the trioxymethylene is obtained through extraction, rectification and separation. CN103420974B (published as 2013, 7 and 29) also discloses a vapor-liquid benzene extraction tower manufactured by China chemical Sading Ningbo engineering Co., LtdA benzene recovery tower and a trioxymethylene rectifying tower. CN110437045A (published in 2019, 8 and 26) discloses a separation process for preparing high-purity trioxymethylene by an alkali-free washing method, crude trioxymethylene of a synthesis unit enters an extraction tank, an extraction phase consisting of trioxymethylene and benzene enters a water washing tower after extraction to obtain trioxymethylene without free aldehyde, and then the trioxymethylene of a polymerization grade can be obtained after light and heavy removal through conventional rectification.
However, with the above separation scheme, trioxymethylene of ultra-purity or near 100% purity is still not obtained, and at the same time, the extraction process introduces new solvent, resulting in more complicated separation system, causing energy consumption and difficulty in recovering diluted aldehyde, and often requiring a separate diluted aldehyde recovery unit for recovery.
On the other hand, a series of side reactions exist in the synthesis process of the trioxymethylene regardless of the catalytic system. The most important of these is the disproportionation of formaldehyde (Cannizzaro) to methanol and formic acid.
The generated formic acid is corrosive, and the increase of the content of the formic acid can corrode equipment and influence the service life of the equipment. The methanol and the formic acid are further esterified to generate methyl formate under the action of a catalyst.
Formaldehyde may also form methyl formate in one step by the Tischenko reaction.
The mixture of trioxymethylene, formaldehyde and water obtained by the reaction and rectification also contains formic acid generated by side reaction,Methyl formate and methanol and the like form a multi-component azeotrope which is difficult to separate, and meanwhile, due to the existence of formaldehyde, the concentration of the formaldehyde in the local part of a separation unit is too high, so that a formaldehyde polymer is easily formed, and the pipeline of the rectifying tower is blocked. In order to remove these impurities, formic acid in the condensation product can be removed by adsorption with an alkaline adsorbent, and then H can be removed by adsorption with an adsorbent such as molecular sieve2And O, then separating and purifying the product by adopting a rectification method. For example: the Noffdards patent company, CN1249047C (4.5.2006), discloses a purification process in which an aqueous mixture of trioxymethylene and formaldehyde obtained in a reactor is reacted with urea to obtain an azeotrope consisting azeotropically of water and trioxymethylene in the gas phase, which does not contain formaldehyde, and formaldehyde and urea in the liquid phase to obtain a urea-aldehyde precondensate, which is then used in the synthesis of urea-aldehyde glues or resins. In CN102702167B (published 2012, 5/11), the gas phase mixture at the outlet of the reactor, which contains formic acid, trioxymethylene, formaldehyde and water, is treated with alkali washing buffer solution of carbonate or phosphate to remove formic acid. Great efforts have been made by BASF corporation to remove formic acid, and CN101896478B (published 2010, 11/24) added a physical (adsorption) or chemical method (such as adding tertiary amine or imine, converting formic acid into salt under the action of catalyst, and removing the formed salt at the bottom of rectification column) to the conventional pressure swing distillation process to remove formic acid.
The separation process is theoretically simple and feasible, but the practical operation and operation process can cause simultaneous absorption or conversion (disproportionation, saccharification, discoloration and the like) of formaldehyde in the processes of absorption deacidification and dehydration due to the complex and changeability of a system containing formaldehyde, and the conventional absorption dehydration method can not remove water combined with the formaldehyde because the formaldehyde exists in the form of the methyl glycol or hemiacetal, so that the difficult problems in the separation processes such as multicomponent azeotropy, self-plugging pipes and the like can not be fundamentally changed.
In summary, the prior art often has the following disadvantages: more trace impurities are inevitably introduced if extraction, rectification and separation are adopted; the formaldehyde or the formaldehyde in the product is adsorbed and removed by adopting the alkaline adsorbent, or the formaldehyde is converted into the polymer, but the desorbed formaldehyde and the formic acid cannot be directly recycled, so that the material consumption is increased, the local formaldehyde concentration of the adsorbent is easily increased after the adsorbent adsorbs the formaldehyde, and the performance of the adsorbent is reduced by formaldehyde polymerization. Therefore, the prior art can not fundamentally change the problems of multicomponent azeotropy, self-polymerization pipe blockage, low purity of trioxymethylene and high material consumption and energy consumption of unit products.
Disclosure of Invention
The utility model provides a preparation facilities of methyl alcohol preparation trioxymethylene, include:
methanol oxidation preparation formaldehyde workshop section: a methanol oxidation reactor and a formaldehyde absorption tower;
a trioxymethylene crude product synthesis section: a trioxymethylene synthesis reactor and a trioxymethylene concentration tower;
a trioxymethylene refining separation section: a trioxymethylene refining reactor, a trioxymethylene dehydration membrane component and a trioxymethylene dealcoholization tower;
a recovery section: and recovering the reaction rectifying tower.
In the working section of preparing formaldehyde by methanol oxidation, a discharge hole of the methanol oxidation reactor is connected with a feed hole of a formaldehyde absorption tower.
In the crude trioxymethylene synthesis section, a cyclization catalyst is filled in the trioxymethylene synthesis reactor in advance.
In the crude trioxymethylene synthesis section, the cyclization catalyst is preferably an acid catalyst, the acid catalyst is preferably a solid acid catalyst, and the solid acid catalyst is one or more selected from resin, a molecular sieve, a supported ionic liquid and alumina.
In the crude trioxymethylene synthesis section, the trioxymethylene synthesis reactor is arranged in a tower kettle or a tower of a trioxymethylene concentration tower.
The trioxymethylene synthesis reactor is a separate kettle-type reactor or fixed bed reactor, or is integrated with the trioxymethylene concentration tower and is arranged in the kettle or the tower of the trioxymethylene concentration tower, and when the kettle-type reactor is adopted and arranged in the kettle of the trioxymethylene concentration tower, the loop is formedThe consumption of the catalyst is 0.1-20% of the reaction liquid, and when a fixed bed is adopted or the catalyst is placed in a trioxymethylene concentrating tower, the volume airspeed of the feeding is 0.2-10 h-1(ii) a The bottom of the trioxymethylene synthesis reactor is provided with a discharge port which can discharge part of reactants and reduce the content of formic acid in the reactor; or partial deactivated cyclizing catalyst can be discharged, and a cyclizing catalyst replenishing port is arranged at the inlet of the trioxymethylene synthesis reactor.
In the crude trioxymethylene synthesis working section, the trioxymethylene is concentrated in a trioxymethylene concentrating tower, and an inlet is arranged in the middle of the trioxymethylene concentrating tower or in a tower kettle and used for receiving a gas phase of a trioxymethylene synthesis reactor.
In the trioxymethylene crude product synthesis section, the trioxymethylene concentrating tower is provided with two discharge ports, wherein the discharge port at the top of the tower is introduced into the feed port of the trioxymethylene synthesis reactor. The trioxymethylene concentrating tower is a plate tower, a partition wall tower or a packed tower.
In the trioxymethylene refining separation working section, a discharge port of the trioxymethylene refining reactor is connected with a trioxymethylene dehydration membrane component.
In the trioxymethylene refining separation section, a refining catalyst is loaded in the trioxymethylene refining reactor.
The refining is carried out by a refining catalyst which has the double functions of hydrogenation and acid catalysis. The refined catalyst has an acid center which decomposes methylal and formaldehyde polymer into formaldehyde or methanol, etc., and a hydrogenation active center.
The hydrogenation active center can catalytically convert formaldehyde, formic acid, methyl formate and the like into methanol.
The preparation method of the refined catalyst comprises the following steps: loading the hydrogenation active component on the acidic active component, or mechanically mixing the hydrogenation active component and the acidic active component and then tabletting for molding, or mechanically mixing the hydrogenation active component and the acidic active component and then adding a binder for strip extrusion molding.
The active component of the hydrogenation active center of the refined catalyst is a Ni-based catalyst system, and the catalyst system comprises Al2O3、SiO2One or more components of active carbon, molecular sieve, Zn, K, Mg, Cu and Cr. As used herein, a Ni-based catalyst system refers to a catalyst supported on nickel oxide with the addition of other elements or substances.
The active component of the acid catalytic active center of the refined catalyst is Al2O3、SiO2Activated carbon and molecular sieve. Meanwhile, the content of active components of the acid catalytic active center is 0.1-10%; when the content of the active component of the acid catalytic active center is more than 10%, the cyclic derivative of formaldehyde is easily decomposed.
In the trioxymethylene refining separation section, the refining reactor is a fixed bed reactor.
In the trioxymethylene refining separation section, the refining reaction conditions are as follows: the reaction temperature is 30-200 ℃, and preferably 80-150 ℃; the reaction pressure is 0-5 Mpa, preferably 0-2 Mpa; the reaction space velocity is 0.1-10 h-1Preferably 0.5 to 5 hours-1. The refining is carried out in one or more mixed atmosphere of hydrogen, nitrogen and argon.
In the trioxymethylene refining separation working section, the permeation side of the trioxymethylene dehydration membrane component is connected with a trioxymethylene dealcoholization tower, and a penetrating fluid material flow taking water as a main component is obtained at the residual permeation side.
In the trioxymethylene refining and separating section, the membrane used in the membrane component is a water-permeable molecular sieve membrane; the temperature of the residual side dehydration operation is 80-150 ℃, and the dehydration pressure is 0.1-1.0 MPa; the pressure of the permeation side is-0.05 to-0.1 MPa, and trioxymethylene at the permeation side can be recovered by rectification and circulated to the inlet of the membrane module unit, and simultaneously water is separated.
In the trioxymethylene refining separation section, a rectifying tower is used for rectifying and separating the methanol, and the rectifying tower is a plate tower, a partition wall tower or a packed tower.
In the trioxymethylene refining separation section, the trioxymethylene dealcoholization tower is provided with two discharge ports, wherein a discharge port at the top of the tower is introduced into a recovery reaction rectifying tower, and a discharge port at the bottom of the tower obtains a trioxymethylene product.
In the recovery working section, the reactive distillation is carried out in a recovery reactive distillation tower, wherein the reactor is arranged to be integrated with the distillation tower and is arranged in a distillation tower kettle or the distillation tower, and the volume space velocity of the feeding is 0.5-50 h-1。
In the recovery working section, the catalyst in the recovery reaction rectifying tower is preferably an acidic catalyst, the acidic catalyst comprises one or a mixture of more of a molecular sieve, resin and alumina, the reaction temperature is 30-200 ℃, and the reaction pressure is 0-1.5 MPa; under the action of an acid catalyst, trioxymethylene reacts with methanol to generate methylal.
In the recovery section, the recovery reaction rectifying tower is provided with two discharge ports, wherein a discharge port at the top of the tower is introduced into a methanol oxidation reactor, and a discharge port at the bottom of the tower obtains a material flow taking water as a main component.
Advantageous effects
The method solves the problem of a plurality of byproducts which are difficult to separate in the trioxymethylene synthesis process, improves the purity and quality of the trioxymethylene, and reduces the impurity content. The production of dilute aldehyde in the separation process is avoided through refining, and the separation efficiency is improved by coupling with a membrane separation technology. The material utilization rate of the whole process is improved by adopting a circulating process.
The present disclosure provides a refining method for converting impurities of formaldehyde, formic acid, methyl formate, methylal and formaldehyde polymer into methanol in the trioxymethylene synthesis process through catalysis, which realizes the purposes of aldehyde removal, deacidification and degreasing, and enables a subsequent separation system to be more easily separated.
The method avoids the blockage of equipment such as pipelines, rectifying towers and the like in the subsequent separation process, reduces the corrosion problem of the equipment to the subsequent pipelines and equipment, and eliminates the appearance of multi-component azeotrope of the system.
Compared with the traditional absorption, adsorption and extraction processes, the catalytic refining process disclosed by the disclosure does not generate waste liquid and waste solids, and the refining process is environment-friendly; meanwhile, the formaldehyde, the formic acid and the methyl formate are converted into the methanol through catalytic refining and then used in the production process of the formaldehyde, so that the atom utilization rate is improved. Meanwhile, no dilute aldehyde is generated in the whole process, and the defects of high energy consumption, high pollution and the like caused by dilute aldehyde recovery are avoided.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the disclosure and together with the description serve to explain the principles of the disclosure.
FIG. 1 is a schematic diagram showing a process flow for preparing trioxymethylene from methanol according to the present disclosure.
Reference numerals:
the device comprises a R0101 methanol oxidation reactor, a T0101 formaldehyde absorption tower, a R0201 trioxymethylene synthesis reactor, a T0201 trioxymethylene concentration tower, a R0301 trioxymethylene refining reactor, an M0301 trioxymethylene dehydration membrane component, a T0301 trioxymethylene dealcoholization tower and a T0401 recovery reaction rectifying tower.
Detailed Description
The present disclosure will be described in further detail with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limitations of the present disclosure. It should be further noted that, for the convenience of description, only the portions relevant to the present disclosure are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict. The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
The preparation process comprises a methanol oxidation formaldehyde preparation working section, a trioxymethylene crude product synthesis working section, a trioxymethylene refining separation working section and a recovery working section, wherein:
methanol oxidation preparation formaldehyde workshop section: a methanol oxidation reactor R0101 and a formaldehyde absorption tower T0101;
a trioxymethylene crude product synthesis section: a trioxymethylene synthesis reactor R0201 and a trioxymethylene concentration tower T0201;
a trioxymethylene refining separation section: a trioxymethylene refining reactor R0301, a trioxymethylene dehydration membrane component M0301 and a trioxymethylene dealcoholization tower T0301;
a recovery section: recovering the reaction rectifying tower T0401.
In a methanol oxidation reactor R0101, after methanol and methylal mixture (a methanol material flow 2 and a recycle material flow 14) is evaporated, the mixture is mixed with air (a material 1) to generate formaldehyde under the action of an iron-molybdenum oxidation catalyst, and water material flow 3 in a formaldehyde absorption tower T0101 absorbs the formaldehyde to obtain a formaldehyde water solution. The aqueous solution of formaldehyde is mixed with an aqueous solution stream 6 of formaldehyde at the tower bottom of the trioxymethylene concentrating tower to obtain a trioxymethylene synthetic stream 4.
ZSM-5 molecular sieve catalyst is pre-loaded in a trioxymethylene synthesis reactor R0201, a trioxymethylene synthesis material flow 4 rapidly reaches reaction balance under the action of the ZSM-5 molecular sieve catalyst, and as the concentration of the trioxymethylene in a gas phase in the reactor is higher than that of the trioxymethylene in a liquid phase, a gas phase material is extracted from an outlet, the reaction is moved towards the positive reaction direction. The gas phase material flow 5 extracted from the outlet of the trioxymethylene synthesis reactor contains the by-products of the trimerization synthesis reaction such as methanol, methyl formate, methylal and formic acid, and unreacted raw material formaldehyde.
And (3) separating the gas-phase material flow 5 extracted from the outlet of the trioxymethylene synthesis reactor by a trioxymethylene concentrating tower T0201 to obtain a trioxymethylene concentrated liquid material flow 7 at the top of the trioxymethylene concentrating tower. And obtaining a formaldehyde aqueous solution material flow 6 at the tower kettle of the trioxymethylene concentrating tower, and circularly returning the material flow to the trioxymethylene synthesis reactor R0201.
Catalytic refining of trioxymethylene concentrate stream 7 containing by-products and unreacted formaldehyde in a hydrogen atmosphere using a fixed bed reactor2O3The refined catalyst is converted into methanol. After the reaction, a refined trioxymethylene material flow 8 is obtained, and is refined by using the same refining catalyst, so that five impurities are converted into one impurity which is easy to separate.
In the trioxymethylene dehydration membrane module M0301, the refined trioxymethylene material flow 8 passes through a NaA molecular sieve membrane permeation gasification membrane. On the permeate side, an anhydrous trioxymethylene mixture stream 10 is obtained. A permeate stream 9 based on water is obtained on the retentate side.
The anhydrous trioxymethylene mixture material flow 10 enters a trioxymethylene dealcoholization tower T0301 to separate methanol, a pure trioxymethylene material flow is obtained at the tower bottom of the trioxymethylene dealcoholization tower, the impurity content of the pure trioxymethylene material flow is less than 100ppm, and a methanol solution material flow 12 of the trioxymethylene is obtained at the tower top of the trioxymethylene dealcoholization tower.
After the methanol solution material flow 12 of the trioxymethylene and the penetrating fluid material flow 9 are mixed, a mixture circulating material flow 14 of the methanol and the methylal is obtained at the top of the recovery reactive distillation tower through a recovery reactive distillation tower T0401. The material flow is recycled to the inlet of a methanol oxidation reactor R0101 to be used as a raw material for producing formaldehyde, so that the material flow can be recycled. Pure water material flow 13 is obtained at the bottom of the recovery reaction rectifying tower and can be used as absorption liquid of a formaldehyde absorption tower for recycling.
Examples
Example 1
The preparation process is performed by: a methanol oxidation reactor R0101 and a formaldehyde absorption tower T0101; a trioxymethylene synthesis reactor R0201 and a trioxymethylene concentration tower T0201; a trioxymethylene refining reactor R0301, a trioxymethylene dehydration membrane component M0301 and a trioxymethylene dealcoholization tower T0301; recovering the reaction rectifying tower T0401.
In a methanol oxidation reactor R0101, after methanol and methylal mixture (a methanol material flow 2 and a recycle material flow 14) is evaporated, the mixture is mixed with air (a material 1) to generate formaldehyde at 260 ℃ and normal pressure under the action of an iron-molybdenum oxidation catalyst, and water material flow 3 in a formaldehyde absorption tower T0101 absorbs the formaldehyde to obtain a formaldehyde water solution. This aqueous formaldehyde solution was mixed with an aqueous formaldehyde solution stream 6 (methanol: 0.67%, formaldehyde: 59.02%, water: 40.15% and formic acid: 0.15%) from the bottom of a trioxymethylene concentrating column to give a trioxymethylene synthesis stream 4 (methanol: 0.83%, formaldehyde: 59.15%, water: 39.92% and formic acid: 0.10%).
A ZSM-5 molecular sieve catalyst is pre-loaded in a trioxymethylene synthesis reactor R0201, the catalyst consumption is 10% of the mass of a reaction liquid, the reaction temperature is 108 ℃, the pressure is normal pressure, a trioxymethylene synthesis material flow 4 rapidly reaches the reaction balance under the action of the ZSM-5 molecular sieve catalyst, and the reaction moves towards the positive reaction direction because the concentration of trioxymethylene in a gas phase in the reactor is greater than that of trioxymethylene in a liquid phase, and a gas phase material is extracted from an outlet. The gas phase material flow 5 extracted from the outlet of the trioxymethylene synthesis reactor consists of methanol: 0.51%, formaldehyde: 40.07%, water: 39.92%, trioxymethylene: 19.19%, methyl formate: 0.05%, methylal: 0.13% and formic acid: 0.10 percent. Wherein methanol, methyl formate, methylal and formic acid are byproducts of the trimerization synthesis reaction, and formaldehyde is an unreacted raw material.
A gas phase material flow 5 extracted from the outlet of the trioxymethylene synthesis reactor is separated by a trioxymethylene concentrating tower T0201, the number of tower plates of the trioxymethylene concentrating tower is 20, the reflux ratio is 4, the operation pressure is-0.010 MPa, and a trioxymethylene concentrated liquid material flow 7 is obtained at the top of the trioxymethylene concentrating tower, and the composition of the material flow is methanol: 0.24%, formaldehyde: 4.75%, water: 39.56%, trioxymethylene: 54.84%, methyl formate: 0.14%, methylal: 0.37% and formic acid: 0.10 percent, which is close to the ternary azeotrope composition of trioxymethylene, formaldehyde and water. Obtaining a formaldehyde aqueous solution material flow 6 at the bottom of the trioxymethylene concentrating tower, wherein the material flow comprises 0.67 percent of methanol, 59.02 percent of formaldehyde, 40.15 percent of water and formic acid: 0.15 percent. This stream is recycled back to the trioxymethylene synthesis reactor R0201.
The trioxymethylene concentrate stream 7 containing by-products and unreacted formaldehyde is refined catalytically in a hydrogen atmosphere using a fixed bed reactor in the presence of Ni/Al2O3Methyl formate, methylal, formic acid and formaldehyde are converted into methanol under the action of a refined catalyst; the reaction pressure is 2.0MPa, the reaction temperature is 120 ℃, and the liquid space velocity is 1.0h-1Space velocity of hydrogen gas of 50h-1. After the reaction, a refined trioxymethylene material flow 8 is obtained, which comprises the following components: methanol: 5.97% and water: 39.41%, trioxymethylene: 54.63%, refined using the same refining catalyst, converting 5 impurities to 1 impurity which is easily separable.
In the trioxymethylene dehydration membrane component M0301, the refined trioxymethylene material flow 8 passes through a NaA molecular sieve membrane permeation gasification membrane, the dehydration temperature is 110 ℃, the pressure of the permeation side is 0.2MPa, and the pressure of the permeation side is-0.095 MPa. On the permeate side, an anhydrous trioxymethylene mixture stream 10 is obtained with a composition of methanol 10.16% and trioxymethylene 89.84%. On the retentate side, a permeate stream 9 is obtained, based on water, with a composition of trioxymethylene of 4.49% and water of 95.51%.
The anhydrous trioxymethylene mixture material flow 10 enters a trioxymethylene dealcoholization tower T0301 to separate methanol, a pure trioxymethylene material flow is obtained at the bottom of the trioxymethylene dealcoholization tower, the impurity content of the pure trioxymethylene material flow is less than 100ppm, a trioxymethylene solution material flow 12 of trioxymethylene is obtained at the top of the trioxymethylene dealcoholization tower, and the components of the water-free trioxymethylene mixture material flow are as follows: trioxymethylene 12.83%, methanol: 87.18 percent. The number of the tower plates of the trioxymethylene dealcoholization tower is 15, the reflux ratio is 2, the temperature at the bottom of the tower is 112 ℃, and the pressure is normal pressure.
After the methanol solution material flow 12 of the trioxymethylene and the penetrating fluid material flow 9 are mixed, the tower plate number of the recovery reaction rectifying tower is 18 through a recovery reaction rectifying tower T0401, the reflux ratio is 2, the temperature is 120 ℃, the pressure is 0.05MPa, the catalyst is a macroporous resin catalyst, and a mixture circulating material flow 14 of the methanol and the methylal is obtained at the top of the recovery reaction rectifying tower, and the composition is as follows: methanol 1.97%, methylal: 98.03 percent. The material is recycled to the inlet of the methanol oxidation reactor and is used as a raw material for producing formaldehyde, so that the material can be recycled. Pure water material flow 13 is obtained at the bottom of the recovery reaction rectifying tower and can be used as absorption liquid of a formaldehyde absorption tower for recycling.
Comparative example 1
The trioxymethylene is prepared by the common technology in the prior art.
First, a hemiformal concentrate a was obtained in a hemiformal production apparatus.
600ml of the hemiformal concentrate A was charged in an autoclave equipped with a 1L pressure vessel, and then formaldehyde was continuously added from the outside thereof. Further, nitrogen gas was supplied as a carrier gas to the autoclave at a constant flow rate (50 to 100 ml/min).
The pyrolysis reaction of hemiformal is carried out at an autoclave liquid temperature of 160 to 170 ℃ to produce a mixed gas of formaldehyde gas and nitrogen gas. Here, the nitrogen flow rate and the decomposition temperature are appropriately adjusted so that the mixing ratio of the formaldehyde gas to the nitrogen gas is higher than 70:30 in terms of molar ratio.
The formaldehyde gas obtained by the thermal decomposition of the hemiformal concentrate A is brought into contact with a solid acid catalyst to carry out the gas phase trimerization of formaldehyde to synthesize trioxymethylene. The trioxymethylene generator was a fixed-bed reactor having an inner diameter of 30mm phi, filled with 135g of a solid acid catalyst prepared in advance, and flowed through a jacket. Heat to 100 ℃ outside the reaction tube. The formaldehyde gas was continuously supplied by downward flow into the fixed bed reactor packed with the solid acid catalyst a 1. The reaction product gas was continuously discharged to the outside of the trioxymethylene generator through an SUS316 pipe maintained at about 125 ℃, and further led to a separation device.
The separation apparatus used a packed column with jacketed double tubes (about 25 mm. phi.). Then, the reaction product gas was continuously supplied from the lower portion of the double tube, and benzene was supplied from the upper portion at a flow rate of 200ml/h, thereby bringing the reaction product gas and benzene into alternating contact. The gaseous trioxymethylene is absorbed by benzene and discharged from the bottom of the packed column as a liquid phase. On the other hand, the unreacted formaldehyde gas is discharged in a gaseous state from the upper part of the packed column without being absorbed by benzene. The temperature in the packed column was adjusted to 30 ℃ by cooling water flowing through the jacket.
Subsequently, the unreacted formaldehyde gas discharged from the upper part of the packed column is circulated and recycled to the trioxymethylene generator.
TABLE 1 composition of the trioxymethylene product obtained
| Example 1 | Comparative example 1 | |
| MeOH(ppm) | 40 | 40 |
| CH3O(CH2O)2CH3(ppm) | 30 | 80 |
| Benzene (ppm) | - | 100 |
| TOX(ppm) | >99.99 | >99.97 |
| TOX yield (%) | 31.4 | 30.4 |
| TOX selectivity (%) | 98.5 | 97.2 |
As can be seen from table 1, the yield of trioxymethylene product is improved and the purity is also improved correspondingly in the product obtained in example 1 of the present disclosure, compared to comparative example 1. According to the method, impurities of formaldehyde, formic acid, methyl formate, methylal and formaldehyde polymer are catalytically refined and converted into methanol, so that the purposes of aldehyde removal, deacidification and degreasing are achieved, a subsequent separation system is more easily separated, the reaction conversion rate is improved, the preparation process of the trioxymethylene is optimized, the raw material utilization rate of the whole system is improved, and the purity of the trioxymethylene product is improved.
The method solves the problem of a plurality of byproducts which are difficult to separate in the trioxymethylene synthesis process, improves the purity and quality of the trioxymethylene, and reduces the impurity content. The production of dilute aldehyde in the separation process is avoided through refining, and the separation efficiency is improved by coupling with a membrane separation technology. The material utilization rate of the whole process is improved by adopting a circulating process.
The present disclosure provides a trioxymethylene synthesis process, which converts impurities of formaldehyde, formic acid, methyl formate, methylal and formaldehyde polymer into methanol through catalytic refining, so as to achieve the purposes of aldehyde removal, deacidification and degreasing, and enable a subsequent separation system to be more easily separated.
The method avoids the blockage of equipment such as pipelines, rectifying towers and the like in the subsequent separation process, reduces the corrosion problem of the equipment to the subsequent pipelines and equipment, and eliminates the appearance of multi-component azeotrope of the system.
Compared with the traditional absorption, adsorption and extraction processes, the catalytic refining process disclosed by the disclosure does not generate waste liquid and waste solids, and the refining process is environment-friendly; meanwhile, the formaldehyde, the formic acid and the methyl formate are converted into the methanol through catalytic refining and then used in the production process of the formaldehyde, so that the atom utilization rate is improved. Meanwhile, no dilute aldehyde is generated in the whole process, and the defects of high energy consumption, high pollution and the like caused by dilute aldehyde recovery are avoided.
In the description herein, reference to the description of the terms "one embodiment/mode," "some embodiments/modes," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/mode or example is included in at least one embodiment/mode or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to be the same embodiment/mode or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/aspects or examples and features of the various embodiments/aspects or examples described in this specification can be combined and combined by one skilled in the art without conflicting therewith.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
It will be understood by those skilled in the art that the foregoing embodiments are merely for clarity of illustration of the disclosure and are not intended to limit the scope of the disclosure. Other variations or modifications may occur to those skilled in the art, based on the foregoing disclosure, and are still within the scope of the present disclosure.
Claims (10)
1. An apparatus for preparing trioxymethylene from methanol is characterized by comprising:
methanol oxidation preparation formaldehyde workshop section: a methanol oxidation reactor (R0101) and a formaldehyde absorption tower (T0101);
a trioxymethylene crude product synthesis section: a trioxymethylene synthesis reactor (R0201) and a trioxymethylene concentrating tower (T0201);
a trioxymethylene refining separation section: a trioxymethylene refining reactor (R0301), a trioxymethylene dehydration membrane component (M0301) and a trioxymethylene dealcoholization tower (T0301);
a recovery section: the reactive distillation column (T0401) was recovered.
2. The apparatus for preparing trioxymethylene from methanol according to claim 1, wherein in said methanol oxidation formaldehyde preparation section, the outlet of said methanol oxidation reactor (R0101) is connected to the inlet of a formaldehyde absorption tower (T0101).
3. Device for preparing trioxymethylene from methanol according to claim 1, wherein in the crude trioxymethylene synthesis section, the trioxymethylene synthesis reactor (R0201) is placed in the tank or in the column of the trioxymethylene concentration column (T0201).
4. Device for preparing trioxymethylene from methanol according to claim 1, wherein in the crude trioxymethylene synthesis section, the trioxymethylene is concentrated in a trioxymethylene concentrating tower (T0201), and an inlet is provided in the middle of the trioxymethylene concentrating tower or in the bottom of the tower, for receiving the gas phase synthesized by the trioxymethylene synthesis reactor.
5. Device for preparing trioxymethylene from methanol according to claim 1, wherein in the crude trioxymethylene synthesis section, the trioxymethylene concentrating tower (T0201) has two discharge ports, and the discharge port at the top of the tower is introduced into the feed port of the trioxymethylene synthesis reactor (R0201).
6. The apparatus for preparing trioxymethylene according to claim 1, wherein in the trioxymethylene refining separation section, the discharge port of the trioxymethylene refining reactor (R0301) is connected to the trioxymethylene dehydration membrane module (M0301).
7. An apparatus for preparing trioxymethylene from methanol according to claim 1, wherein in the trioxymethylene refining separation section, a refining catalyst is loaded in the trioxymethylene refining reactor (R0301).
8. The apparatus for preparing trioxymethylene according to claim 1, wherein, in the trioxymethylene refining separation section, the permeate side of the trioxymethylene dehydration membrane module (M0301) is connected to a trioxymethylene dealcoholization tower (T0301).
9. The device for preparing trioxymethylene from methanol according to claim 1, wherein in the trioxymethylene refining separation section, the trioxymethylene dealcoholization tower (T0301) has two discharge ports, wherein a discharge port at the top of the tower is introduced into a recovery reaction rectifying tower (T0401), and a discharge port at the bottom of the tower is used for obtaining a trioxymethylene product.
10. Device for the preparation of trioxymethylene from methanol according to claim 1, wherein in the recovery section, the recovery reactive distillation column (T0401) has two outlets, wherein the outlet at the top of the column leads to the methanol oxidation reactor (R0101) and the outlet at the bottom of the column leads to a permeate stream comprising water as the main component.
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