A method for the de-aldehyde refining of polymethoxy dialkyl ethers

Abstract

The application discloses a polyoxymethylene dialkyl ether de-aldehyde refining method, which comprises the following steps: (1) sending liquid-phase aldehyde-containing polyoxymethylene dialkyl ether to the top of a de-aldehyde tower, and then flowing downwards after entering the interior of the de-aldehyde tower through a liquid-phase aldehyde-containing polyoxymethylene dialkyl ether feeding port; sending gaseous de-aldehyde agent to the bottom of the de-aldehyde tower, and then flowing upwards after entering the interior of the de-aldehyde tower through a gaseous de-aldehyde agent feeding port, and the liquid-phase aldehyde-containing polyoxymethylene dialkyl ether and the gaseous de-aldehyde agent are countercurrently contacted to remove aldehyde in the de-aldehyde tower; (2) removing liquid-phase polyoxymethylene dialkyl ether products from which aldehyde is removed from the bottom of the de-aldehyde tower, and removing gaseous de-aldehyde agent containing aldehyde and polyoxymethylene dialkyl ether components from the top of the de-aldehyde tower. The de-aldehyde refining method can realize continuous production, does not exist intermittent regeneration process or solid-liquid separation process, avoids aldehyde raw material loss and system pollution, and improves product quality. The method has been successfully applied to an industrial device and ideal de-aldehyde effect is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical production process, and particularly relates to a polyoxymethylene dialkyl ether de-aldehyde refining method. BACKGROUND

[0002] Polyoxymethylene dialkyl ether compounds take methanol and other low-carbon alcohols as main production raw materials, can play a bridging role between coal chemical industry and petroleum chemical industry, and development of a highly efficient polyoxymethylene dialkyl ether production method is beneficial to saving crude oil energy, and has important strategic significance for energy technology reserves and energy security of China.

[0003] Polyoxymethylene dialkyl ether is a kind of acetal compound with a methyleneoxy group as a main chain and a low-carbon alkyl group as a terminal group, and its structural general formula is wherein n is the number of methyleneoxy units, R1 or R2 is an alkyl group in a low-carbon alkyl alcohol, when n = 1, it is also called dialkoxy methane, R1 and R2 in the structural general formula can be the same or different. When R1 and R2 are both methyl groups, the compound is called polyoxymethylene dimethyl ether, and similarly, when R1 and R2 are both butyl groups, the compound is called polyoxymethylene dibutyl ether.

[0004] Polyoxymethylene dialkyl ether compounds are usually used as clean diesel blending components or environmentally friendly solvents. When used as clean diesel blending components, polyoxymethylene dialkyl ether compounds exhibit good environmental protection and application performance, have a high cetane number, a low condensation point, no sulfur and no aromatic hydrocarbons, and good miscibility with diesel distillate, can not only improve the combustion condition of diesel engines, but also can significantly reduce exhaust pollutant emissions, and have a broad application prospect. When used as environmentally friendly solvents, polyoxymethylene dialkyl ether compounds have excellent solubility and low toxicity, and can be widely used in many fields such as metal cleaning, adhesive preparation, printing and dyeing auxiliary preparation, and paint thinner preparation.

[0005] Among the disclosed patent technologies, there are many methods for preparing polymethoxy dimethyl ether, among which the main raw materials for providing formaldehyde monomer include trioxane, polyoxymethylene, aqueous formaldehyde solution, gaseous formaldehyde and low molecular weight dialkoxy methane compounds, etc., and the main raw materials for providing blocking groups include low carbon alkyl alcohol, low molecular weight dialkoxy methane compounds, dimethyl ether, etc. The reactions for synthesizing polymethoxy dialkyl ether compounds from the above raw materials are all reversible equilibrium processes, and the reaction liquid mixture flowing out of the reactor generally contains a large amount of unconverted formaldehyde. Formaldehyde is easy to react with water and alkyl alcohol in the reaction mixture to form methanediol hydrate and hemiacetal. Although such compounds are chemically unstable, they have a high boiling point and are difficult to separate from the target product. When separating the target product in the subsequent separation section, they are easy to remain in the product, which not only affects the continuity of the separation process, but also causes the product quality to decline or even be unqualified. In addition, due to the active chemical properties of formaldehyde, it is easy to undergo disproportionation reaction to produce formic acid during the reaction and separation process, resulting in the presence of trace amounts of formic acid in the reaction liquid mixture flowing out of the reactor and the final product. The stability of polymethoxy dialkyl ether compounds is similar to that of other acetal compounds, and they are easy to decompose and release formaldehyde in an acidic and high-temperature environment. The presence of formic acid and other acidic substances causes continuous product decomposition and release of formaldehyde during the separation process, which is then left in the product.

[0006] The above two reasons cause various polymethoxy dialkyl ether products to generally contain trace amounts of formaldehyde residues. This part of formaldehyde is dissolved in the product in the form of formaldehyde monomer or methanediol hydrate and hemiacetal, which increases the toxic substances in the product and worsens the odor, seriously affecting the product quality and application effect. In order to solve the adverse effects of formaldehyde residues, many physical or chemical de-aldehyde methods are provided in the disclosed patents and other documents.

[0007] Patents with publication numbers CN103333060A, CN103319319A, CN103333061A, and CN104672067A respectively disclose a method for refining and purifying polymethoxy dialkyl ether, characterized by adding sodium hydroxide, sodium percarbonate, sulfite, and ammonia gas into the polymethoxy dialkyl ether equilibrium product to remove residual formaldehyde, and then separating the treated material through filtration, distillation, and other processes to collect polymethoxy dialkyl ether products with different boiling ranges. Patents with publication numbers CN103333059A and CN103333055A respectively disclose a method for catalytic hydrorefining of polymethylal dialkyl ether in a fixed bed and slurry bed, which uses a fixed bed or slurry bed hydrorefining reactor to catalytically hydrorefine the equilibrium system containing formaldehyde and polymethylal dialkyl ether product, and converts formaldehyde into methanol through hydrogenation reaction to remove formaldehyde, so that high-purity polymethylal dialkyl ether can be obtained through subsequent distillation. Patent with publication number CN111672516A discloses a catalyst for refining polymethoxy dimethyl ether condensation product and its preparation method, and patent with publication number CN111689840A discloses a refining process for polymethoxy dimethyl ether condensation product, which utilizes the hydrolysis reaction of water, formaldehyde, and formic acid in the condensation equilibrium product under the action of the catalyst, and the active hydrogen produced under the action of the catalyst reduces unhydrolyzed formaldehyde and formic acid methyl ester into methanol, achieving the multi-effect refining purposes of de-aldehyde, de-acid, de-fat, and de-watering of the condensation equilibrium product, and the refined product is then sent to the subsequent separation unit.

[0008] The above-mentioned patents disclose de-aldehyde refining methods that utilize the chemical reaction characteristics of formaldehyde and de-aldehyde agents for de-aldehyde, and the methods introduced are for de-aldehyde pretreatment of the polymethoxy dialkyl ether equilibrium product flowing out of the reactor, aiming to solve the separation problem of the formaldehyde-containing equilibrium product.

[0009] Patent with publication number CN107793300A discloses a reaction liquid separation process for polymethoxy dimethyl ether, which first separates formic acid and water from the reaction liquid, and then uses a plate de-aldehyde tower, which circulates the material on some of the tower plates through a circulating pump, over-heats it in a heater, and then returns it to the upper tower plates. The heating of the over-heater and the increase in the number of high-temperature section tower plates in the de-aldehyde tower cause the vaporization of heat-sensitive formaldehyde and the thermal decomposition of unstable hemiacetal, thereby obtaining a product with low formaldehyde content at the tower bottom.

[0010] Patent with publication number CN104722275A discloses an adsorption material for adsorbing formaldehyde in polyoxymethylene dialkyl ether and a refining method of polyoxymethylene dialkyl ether. The adsorption material is modified by using silica gel, fiber, resin or activated carbon as a carrier and an organic substance with an amino active group, and can remove formaldehyde in the equilibrium product of polyoxymethylene dialkyl ether. A part of unreacted formaldehyde can be recovered and separated from the subsequent product. The saturated adsorption material can be regenerated at high temperature and recycled. Patent with publication number CN106365960A discloses a device for removing formaldehyde in polyoxymethylene dimethyl ether. The de-formaldehyde tower in the device uses a pervaporation membrane containing an adsorption layer to separate formaldehyde and polyoxymethylene dimethyl ether in the reaction equilibrium product. The adsorption layer is a porous phenolic resin foam or a strong polar polymer with a polyvinyl alcohol polymerization degree of 180000-200000, or an activated carbon modified by the strong polar polymer. Patents with publication numbers CN107935825A and CN207738672U disclose a polyoxymethylene dimethyl ether refining and separating system and a method for preparing polyoxymethylene dimethyl ether by using the system. Patent with publication number CN111153776A discloses a DMMn production process and device. The systems or methods in the above three patents send the separated product into an adsorption tank for impurity adsorption to obtain the final product. The adsorbent molecular sieve filled in the adsorption tank can adsorb water, formic acid and formaldehyde to purify the product.

[0011] In summary, in order to solve the adverse effects of trace formaldehyde residues on the quality of polyoxymethylene dialkyl ether products, the prior art uses various process methods to remove formaldehyde from the equilibrium reaction product or the separated product. However, there are still many disadvantages such as high cost and complex operation, and therefore it is necessary to develop a more simple and efficient formaldehyde removal and refining method. SUMMARY

[0012] Based on the above technical problems, the present application provides a polyoxymethylene dialkyl ether formaldehyde removal and refining method.

[0013] The technical solution adopted by the present application is as follows:

[0014] A polyoxymethylene dialkyl ether formaldehyde removal and refining method, comprising the following steps:

[0015] (1) sending liquid-phase aldehyde-containing polyoxymethylene dialkyl ether to the top of a de-formaldehyde tower, and then flowing downward through a liquid-phase aldehyde-containing polyoxymethylene dialkyl ether feeding port in the de-formaldehyde tower; sending gaseous de-formaldehyde agent to the bottom of the de-formaldehyde tower, and then flowing upward through a gaseous de-formaldehyde agent feeding port in the de-formaldehyde tower, and the liquid-phase aldehyde-containing polyoxymethylene dialkyl ether and the gaseous de-formaldehyde agent are countercurrently contacted in the de-formaldehyde tower to remove formaldehyde;

[0016] (2) The liquid phase polyoxymethylene dialkyl ether product from which formaldehyde is removed is taken from the bottom of the dealkylation tower, and the gaseous phase dealkylation agent containing formaldehyde and polyoxymethylene dialkyl ether components is taken from the top of the dealkylation tower.

[0017] Preferably, the dealkylation tower is one of a bubble tower, a plate tower, and a packed tower; more preferably, the dealkylation tower is a packed tower.

[0018] The liquid phase aldehyde-containing polyoxymethylene dialkyl ether feed inlet is located above the upper portion of the bubble tower, above the first layer of plates of the plate tower, or above the first section of packing of the packed tower, and the gaseous phase dealkylation agent feed inlet is located below the lower portion of the bubble tower, below the last layer of plates of the plate tower, or below the last layer of packing of the packed tower. More preferably, a liquid distributor and a gas distributor are respectively connected to the above-mentioned feed inlets to uniformly distribute the liquid or gas entering the dealkylation tower. The gas-liquid two-phase contact is sufficient after being distributed by the distributors, which can improve the dealkylation efficiency.

[0019] Preferably, a demister is provided at the top of the dealkylation tower, and when the dealkylation tower is a packed tower and the packing is installed in sections, a liquid redistributor is provided between the adjacent two sections of packing.

[0020] Preferably, the gaseous phase dealkylation agent is selected from inert non-condensable gases. The inert non-condensable gases include one or more than two mixtures of nitrogen, argon, and carbon dioxide, and more preferably, nitrogen is used.

[0021] Preferably, the gaseous phase dealkylation agent containing formaldehyde and polyoxymethylene dialkyl ether components taken from the top of the dealkylation tower is purified and treated in a downstream supporting tail gas treatment facility to meet the discharge standard.

[0022] The purification method used in the tail gas treatment facility includes one or more than two combinations of incineration, catalytic combustion, absorption and condensation, activated carbon or molecular sieve adsorption, and the like. More preferably, after most of the formaldehyde and polyoxymethylene dialkyl ether components are recovered by absorption and condensation in a water washing tower, the remaining tail gas is sent to incineration. The formaldehyde and polyoxymethylene dialkyl ether components recovered in the water washing tower are returned to the polyoxymethylene dialkyl ether product synthesis unit for recycling.

[0023] The liquid phase product taken from the bottom of the dealkylation tower is cooled and discharged.

[0024] Preferably, the plate tower or the packed tower contains at least two theoretical plates; more preferably, the plate tower or the packed tower contains 10 to 30 theoretical plates. The height-diameter ratio of the bubble tower is not less than 5:1, and more preferably, the height-diameter ratio of the bubble tower is 10 to 20:1.

[0025] Preferably, the temperature of the liquid phase aldehyde-containing polyoxymethylene dialkyl ether feed is controlled to be 20 to 200°C, and more preferably, the temperature is controlled to be 60 to 120°C. The temperature of the gaseous phase dealkylation agent feed is controlled to be ambient temperature to 200°C, and more preferably, the temperature is controlled to be room temperature.

[0026] The purity of the gas-phase de-aldehyde agent meets the industrial gas standard, and in particular, the gas-phase de-aldehyde agent is a gas after drying treatment, and the dew point under the operating pressure is not greater than -40℃. These gases not only provide an inert environment, but also do not affect the product quality and application when a small amount of the gas is dissolved in the polyoxymethylene dialkyl ether product.

[0027] Preferably, the ratio of the volume flow rate of the gas-phase de-aldehyde agent converted into the standard state (0℃, 101.325KPaA) to the volume flow rate of the liquid-phase aldehyde-containing polyoxymethylene dialkyl ether is not less than 5:1, and more preferably 10~20:1. In actual application, the volume flow rate ratio of the gas-phase de-aldehyde agent to the liquid-phase aldehyde-containing polyoxymethylene dialkyl ether product can be adjusted within a wide range according to the formaldehyde content of the product.

[0028] Preferably, the mass content of alcohol or water in the liquid-phase aldehyde-containing polyoxymethylene dialkyl ether is less than 1%, and the mass content of formaldehyde is less than 5%; preferably, the mass content of alcohol or water is less than 0.5%, and more preferably, the mass content of alcohol or water is less than 0.1%; and more preferably, the mass content of formaldehyde is less than 0.5%.

[0029] In the above steps, the liquid level of the de-aldehyde tower liquid phase material is controlled by adjusting the polyoxymethylene dialkyl ether liquid phase product extraction amount at the bottom of the tower, and the pressure at the top of the de-aldehyde tower is controlled by adjusting the gas-phase de-aldehyde agent discharge amount. The pressure at the top of the de-aldehyde tower is greater than the saturation pressure at the temperature of the liquid-phase aldehyde-containing polyoxymethylene dialkyl ether feed, which can keep the polyoxymethylene dialkyl ether product in a liquid phase state in the de-aldehyde tower, and can reduce the product loss caused by entrainment of the gas-phase de-aldehyde agent.

[0030] The above polyoxymethylene dialkyl ether is a compound having a structural general formula wherein the end-capping groups R1 and R2 are alkyl groups having a structural general formula wherein the number of alkyl carbon atoms m and the number of methyleneoxy units n are both integers from 1 to 10.

[0031] The beneficial technical effects of the present application are as follows:

[0032] The inventors found during long-term research and development of polyoxymethylene dialkyl ether compound production processes that the solubility of formaldehyde in polyoxymethylene dialkyl ether compounds with low water or alcohol impurity content is small, and the thermal stability of the methylene glycol hydrate or hemiacetal compound formed by formaldehyde and trace amounts of water or alcohol impurities is poor, which is easily decomposed and releases monomer formaldehyde molecules when heated. Based on the above research findings, the inventors creatively proposed a simple and efficient polyoxymethylene dialkyl ether product refining and de-aldehyde method.

[0033] The present application adopts the method of refining and de-aldehyding liquid phase polymethoxy dialkyl ether by gas phase de-aldehyding agent, which utilizes the unstable characteristics of methyl glycol hydrate and hemiacetal compounds at high temperature, promotes methyl glycol hydrate and hemiacetal to decompose into monomolecular formaldehyde by heating liquid phase polymethoxy dialkyl ether to a certain temperature, and then reduces the vapor partial pressure of formaldehyde by introducing gas phase de-aldehyding agent, so as to promote the transfer of formaldehyde from liquid phase to gas phase, and finally realizes the physical removal of formaldehyde; the gas phase de-aldehyding agent is countercurrently contacted with the liquid phase polymethoxy dialkyl ether, the reaction and separation are simultaneously carried out and promote each other, the driving force of the transfer of formaldehyde from liquid phase to gas phase is maximized, the de-aldehyding efficiency is significantly improved, and the formaldehyde in the liquid phase polymethoxy dialkyl ether can be almost completely removed. In addition, the gas phase de-aldehyding agent itself is a chemically inert substance, which will not cause product pollution and change of product performance.

[0034] Compared with the existing technologies such as chemical de-aldehyding or adsorption de-aldehyding, the de-aldehyding refining method of the present application can realize continuous production, and there is no intermittent regeneration process or solid-liquid separation process, which avoids the loss of formaldehyde raw material and system pollution, and improves the product quality. The method described in the present application has been successfully applied in an industrial device and ideal de-aldehyding effect has been achieved. BRIEF DESCRIPTION OF DRAWINGS

[0035] The present application will be further described below in combination with the drawings and specific embodiments:

[0036] Figure 1 The flow chart of the de-aldehyding refining method of polymethoxy dialkyl ether of the present application;

[0037] Figure 2 The structural principle schematic diagram of the device involved in the method of the present application.

[0038] In the figure: T-1 is a de-aldehyding tower, E-1 is a polymethoxy dialkyl ether feed preheater, E-2 is a de-aldehyding agent feed preheater, E-3 is a polymethoxy dialkyl ether outlet cooler, P-1 is a de-aldehyding tower bottom pump, V-1 is a polymethoxy dialkyl ether flow regulating valve, V-2 is a de-aldehyding agent flow regulating valve, V-3 is a de-aldehyding tower pressure regulating valve, V-4 is a de-aldehyding tower bottom liquid level regulating valve, N1 is a polymethoxy dialkyl ether feed inlet, N2 is a de-aldehyding agent feed inlet, N3 is a polymethoxy dialkyl ether outlet, and N4 is a de-aldehyding agent outlet. DETAILED DESCRIPTION

[0039] The following examples are only used to illustrate the present application, and are not intended to limit the protection scope of the present application. After reading the present application, various equivalent modifications made by the skilled in the art according to the essential principles of the present application all belong to the scope defined by the claims of the present application.

[0040] As Figure 1 , Figure 2As shown, a polyoxymethylene dialkyl ether dealkylation refining method comprises the following steps:

[0041] (1) Liquid phase aldehyde-containing polyoxymethylene dialkyl ether controlled by polyoxymethylene dialkyl ether flow regulating valve V-1 is preheated by polyoxymethylene dialkyl ether feed preheater E-1, and then sent to polyoxymethylene dialkyl ether feeding port N1 at the top of dealkylation tower T-1, and then distributed by liquid distributor and flowed downward along the packing or tray. Gaseous dealkylation agent controlled by dealkylation agent flow regulating valve V-2 is preheated by dealkylation agent feed preheater E-2, and then sent to dealkylation agent feeding port N2 at the bottom of dealkylation tower T-1, and then distributed by gas distributor and flowed upward through the tray or packing, and the liquid phase aldehyde-containing polyoxymethylene dialkyl ether and the gaseous dealkylation agent are countercurrently contacted in the dealkylation tower T-1 to remove aldehyde.

[0042] (2) Liquid phase polyoxymethylene dialkyl ether product with removed formaldehyde is collected from dealkylation agent outlet N4 at the bottom of dealkylation tower T-1, and then sent to polyoxymethylene dialkyl ether outlet cooler E-3 by dealkylation tower bottom pump P-1. Gaseous dealkylation agent containing formaldehyde is collected from polyoxymethylene dialkyl ether outlet N3 at the top of dealkylation tower T-1. The amount of the product collected from the bottom of the dealkylation tower is adjusted by dealkylation tower bottom level regulating valve V-4 to control the liquid level of the liquid phase material in the dealkylation tower T-1, and the amount of the gaseous dealkylation agent collected from the top of the dealkylation tower is adjusted by dealkylation tower pressure regulating valve V-3 to control the pressure at the top of the dealkylation tower T-1.

[0043] In the above steps, the gaseous dealkylation agent containing formaldehyde and polyoxymethylene dialkyl ether components at the top of the dealkylation tower T-1 is sent to a downstream supporting tail gas treatment facility for purification treatment and then discharged in compliance with the standard.

[0044] In the above steps, the dealkylation tower T-1 is selected from one of a gas-liquid bubble tower, a plate tower and a packing tower. The liquid phase aldehyde-containing polyoxymethylene dialkyl ether feeding port N1 is located above the first layer of tray or packing of the plate tower or the packing tower, or is located at the upper part of the gas-liquid bubble tower; the gaseous dealkylation agent feeding port N2 is located below the last layer of tray or packing of the plate tower or the packing tower, or is located at the lower part of the gas-liquid bubble tower, and the liquid phase aldehyde-containing polyoxymethylene dialkyl ether feeding port N1 and the dealkylation agent feeding port N2 are respectively connected to the liquid distributor and the gas distributor, and the gas-liquid two phases are countercurrently contacted after being distributed by the distributors.

[0045] Preferably, a defoamer is further arranged at the top of the dealkylation tower T-1, and when the dealkylation tower is a packing tower and the packing is installed in sections, a liquid redistributor is arranged between the adjacent two sections of the packing.

[0046] The gaseous dealkylation agent as the feed is an inert non-condensable gas which has no adverse effect on the product quality, and includes one or a mixture of nitrogen, argon and carbon dioxide, and is preferably nitrogen. The purity of the gaseous dealkylation agent meets the industrial gas standard, and in particular, the gaseous dealkylation agent is a gas after drying treatment, and the dew point under the operating pressure is not more than -40℃.

[0047] The plate dealkylation tower or the packed dealkylation tower contains at least two theoretical plates, preferably 10 to 30 theoretical plates, and the height-diameter ratio of the gas-liquid bubbling dealkylation tower is not less than 5:1, and the height-diameter ratio of the preferred gas-liquid bubbling dealkylation tower is 10 to 20:1. The dealkylation tower T-1 pressure is controlled to be greater than the saturated pressure of the liquid phase aldehyde-containing polymethoxy dialkyl ether feed at the temperature by adjusting the amount of the gas phase dealkylation agent overhead discharge by the dealkylation tower pressure regulating valve V-3.

[0048] The mass content of alcohol or water in the liquid phase aldehyde-containing polymethoxy dialkyl ether as the feed is less than 1%, and the mass content of formaldehyde is less than 5%, preferably the mass content of alcohol or water is less than 0.1%, and the mass content of formaldehyde is less than 0.5%. After being heated by the polymethoxy dialkyl ether feed preheater E-1, the feed temperature of the liquid phase aldehyde-containing polymethoxy dialkyl ether reaches 20 to 200°C, and is preferably 60 to 120°C.

[0049] The feed temperature of the gas phase dealkylation agent as the feed is ambient temperature to 200°C, and is preferably room temperature, i.e. the dealkylation agent feed preheater E-2 can be set as needed, and the ratio of the volume flow of the gas phase dealkylation agent converted to the standard state (0°C, 101.325 KPa A) to the volume flow of the liquid phase aldehyde-containing polymethoxy dialkyl ether is not less than 5:1, and is preferably 10 to 20:1.

[0050] The gas phase overhead of the dealkylation tower T-1 containing formaldehyde and gas phase polymethoxy dialkyl ether components enters the downstream supporting tail gas treatment facility for purification treatment. The purification method used by the tail gas treatment facility includes one or a combination of several of incineration, catalytic combustion, absorption condensation, activated carbon or molecular sieve adsorption, etc. The preferred method is to recover most of the formaldehyde and polymethoxy dialkyl ether components by absorption condensation in a water washing tower, and then send the remaining tail gas to incineration, and the formaldehyde and polymethoxy dialkyl ether component-containing material recovered by the water washing tower is returned to the polymethoxy dialkyl ether product synthesis unit for recycling.

[0051] If necessary, the method of the present application can also be used for the batch polyoxymethylene dialkyl ether de-aldehyde refining process. For the batch process, the liquid phase aldehyde-containing polyoxymethylene dialkyl ether is sent to the de-aldehyde column T-1 bottom to establish the liquid level, the liquid phase aldehyde-containing polyoxymethylene dialkyl ether is sent to the polyoxymethylene dialkyl ether feed preheater E1 by the de-aldehyde column bottom pump P-1 for preheating or preheating in other ways, and then sent to the polyoxymethylene dialkyl ether feed port N1 at the top of the de-aldehyde column T-1, distributed by the liquid distributor, and then flows downward along the packing or tray to establish the circulation of the liquid phase material between the top and the bottom of the de-aldehyde column T-1. When the temperature of the material is stable, the preheated or unpreheated gas phase de-aldehyde agent is continuously introduced into the de-aldehyde column T-1 bottom gas phase de-aldehyde agent feed port N2, the liquid phase aldehyde-containing polyoxymethylene dialkyl ether is de-aldehyde with the gas phase de-aldehyde agent in the de-aldehyde column T-1 by countercurrent contact, the residual formaldehyde content of the de-aldehyde column T-1 bottom material is detected periodically, and when the formaldehyde content meets the requirements, the gas phase de-aldehyde agent feed and the liquid phase polyoxymethylene dialkyl ether circulation are stopped, and the qualified product is obtained after cooling.

[0052] The present application is further described below through specific application examples:

[0053] Example 1

[0054] The present embodiment provides a polyoxymethylene dimethyl ether (DMM2 for short) de-aldehyde refining method with the structural formula of The aldehyde-containing material is the DMM2 product obtained by conventional rectification separation, wherein the mass content of formaldehyde, methanol and water is 0.010%, 0.004% and 0.003% respectively, and the rest is the DMM2 product. Pure nitrogen gas with a purity of more than 99.9% is used as the de-aldehyde agent. The de-aldehyde equipment shown in Figure 2 is used, wherein the de-aldehyde column T-1 is a stainless steel rectification column with an inner diameter of 25 mm and a height of 3 m, and the inside is filled with two sections of Φ3 mm θ net ring random packing, and the height of a single section of packing is 1 m. The DMM2 is pressurized by a metering pump and sent to the top feed port of the de-aldehyde column after oil bath preheating, the feed pipe connected to the top feed port goes deep into the center position of the de-aldehyde column and the opening is vertically downward, the gas phase de-aldehyde agent is introduced from the high-pressure nitrogen gas cylinder pressure reducing valve, dried and dehydrated by molecular sieve, metered by a rotor flowmeter, and sent to the bottom feed port of the de-aldehyde column after oil bath preheating, the feed pipe connected to the bottom feed port goes deep into the center position of the de-aldehyde column and the opening is vertically upward. The de-aldehyde column bottom is provided with a quartz liquid level meter, a column bottom discharge cooler and a discharge flow control valve, the de-aldehyde column top gas phase discharge pipeline is provided with a pneumatic regulating valve to control the de-aldehyde column top pressure, and the de-aldehyde column section and the feed pipe are provided with electric heating and good insulation.

[0055] Specifically, the de-aldehyde refining method using the above-mentioned equipment and raw materials comprises the following steps:

[0056] (1) The liquid phase aldehyde-containing DMM2 is continuously sent to the top of the de-aldehyde column and flows downward after being preheated from room temperature to 100-105°C, and nitrogen is continuously sent to the bottom of the de-aldehyde column and flows upward after being preheated from room temperature to 90-100°C, so that the liquid phase aldehyde-containing DMM2 and nitrogen are countercurrently contacted in the de-aldehyde column to remove aldehyde.

[0057] (2) The liquid phase DMM2 product from which aldehyde is removed is collected from the bottom of the de-aldehyde column, and nitrogen containing aldehyde is collected from the top of the de-aldehyde column, the discharge flow of the product at the bottom is adjusted to control the liquid level at the bottom of the de-aldehyde column to about 50%, and the discharge amount of the gas phase at the top is adjusted to control the pressure at the top of the de-aldehyde column to 60-70 KPaG.

[0058] (3) The liquid phase product at the bottom of the de-aldehyde column is collected as a product after being cooled to room temperature by a jacketed cooler, and the gas phase discharge at the top of the de-aldehyde column is vented to safety after being absorbed by water bubbling.

[0059] The metering pump is adjusted to make the flow of the liquid phase aldehyde-containing DMM2 material reach 20 ml / min, and the nitrogen flow is adjusted to 130 ml / min, and when the feed flow, temperature and de-aldehyde column pressure are stable, the average content of residual formaldehyde in the liquid phase product at the bottom is detected to be 2.8 ppm, the average discharge flow at the bottom is about 19 ml / min, the formaldehyde removal rate under the operating conditions is about 97%, and the product yield is about 95%.

[0060] Example 2

[0061] The present embodiment provides a method for refining and de-aldehyde of polyoxymethylene dimethyl ethers (DMM3 for short) with a structural formula of The aldehyde-containing material is a DMM3 product obtained by conventional rectification separation, wherein the mass contents of formaldehyde, methanol and water are 0.18%, 0.1% and 0.005% respectively, the mass contents of DMM2 and DMM4 are 0.22% and 0.39% respectively, and the rest is DMM3 product. Pure nitrogen with a purity of greater than 99.9% is used as a de-aldehyde agent, and the same related equipment such as a packed de-aldehyde column as in Example 1 is used, and the method for de-aldehyde refining of the above-mentioned material comprises the following steps:

[0062] (1) The liquid phase aldehyde-containing DMM3 is continuously sent to the top of the de-aldehyde column and flows downward after being preheated from room temperature to 110-115°C, and room temperature nitrogen is continuously sent to the bottom of the de-aldehyde column and flows upward, so that the liquid phase aldehyde-containing DMM3 and nitrogen are countercurrently contacted in the de-aldehyde column to remove aldehyde.

[0063] (2) The liquid phase DMM3 product from which aldehyde is removed is collected from the bottom of the de-aldehyde column, and nitrogen containing aldehyde is collected from the top of the de-aldehyde column, the discharge flow of the product at the bottom is adjusted to control the liquid level at the bottom of the de-aldehyde column to about 50%. The discharge amount of the gas phase at the top is adjusted to control the pressure at the top of the de-aldehyde column to 50-60 KPaG.

[0064] (3) The liquid phase product from the bottom of the de-aldehyde column is collected as product after being cooled to room temperature by a jacketed cooler. The gaseous phase product from the top of the de-aldehyde column is vented to a safe place after being absorbed by water bubbling.

[0065] The flow rate of the liquid phase aldehyde-containing DMM3 material is adjusted to 25 ml / min by adjusting the metering pump, and the flow rate of nitrogen is adjusted to 600 ml / min. When the flow rate, temperature and pressure of the de-aldehyde column are stable, the average content of residual formaldehyde in the liquid phase product from the bottom of the column is 1 ppm, the average flow rate of the product from the bottom of the column is about 24.4 ml / min, the removal rate of formaldehyde under the operating conditions is about 99.9%, and the product yield is about 97.4%.

[0066] Example 3

[0067] The present embodiment provides a method for refining and de-aldehyde of polyoxymethylene dimethyl ethers (DMM4) with the structural formula of The aldehyde-containing material is a DMM4 product obtained by conventional rectification separation, wherein the mass contents of formaldehyde, methanol and water are 0.08%, 0.02% and 0.004% respectively, the mass contents of DMM3 and DMM5 are 0.62% and 0.14% respectively, and the rest is DMM4 product. Pure nitrogen with a purity of more than 99.9% is used as a de-aldehyde agent, and the same de-aldehyde column and other related equipment as in Example 1 are used. The method for de-aldehyde refining of the above-mentioned material comprises the following steps:

[0068] (1) The liquid phase aldehyde-containing DMM4 is preheated from room temperature to 120-125°C and then continuously sent to the top of the de-aldehyde column and flows downward, and nitrogen at room temperature is continuously sent to the bottom of the de-aldehyde column and flows upward, so that the liquid phase aldehyde-containing DMM4 and nitrogen are countercurrently contacted in the de-aldehyde column for de-aldehyde.

[0069] (2) The liquid phase DMM4 product after removal of formaldehyde is collected from the bottom of the de-aldehyde column, and nitrogen containing formaldehyde is collected from the top of the de-aldehyde column. The flow rate of the product from the bottom of the column is adjusted to control the liquid level of the de-aldehyde column to about 50%. The amount of gaseous phase product from the top of the de-aldehyde column is adjusted to control the pressure at the top of the de-aldehyde column to be 20-30 KPaG.

[0070] (3) The liquid phase product from the bottom of the de-aldehyde column is collected as product after being cooled to room temperature by a jacketed cooler. The gaseous phase product from the top of the de-aldehyde column is vented to a safe place after being absorbed by water bubbling.

[0071] The flow rate of the liquid phase aldehyde-containing DMM4 material is adjusted to 20 ml / min by adjusting the metering pump, and the flow rate of nitrogen is adjusted to 280 ml / min. When the flow rate, temperature and pressure of the de-aldehyde column are stable, the average content of residual formaldehyde in the liquid phase product from the bottom of the column is 2.5 ppm, the average flow rate of the product from the bottom of the column is about 19.9 ml / min, the removal rate of formaldehyde under the operating conditions is about 99.7%, and the product yield is about 99.5%.

[0072] Example 4

[0073] The present embodiment provides a method for refining and de-aldehyde of a polyoxymethylene dimethyl ethers mixture (DMM3-4 for short) with a structural formula of , n = 3-4, wherein the aldehyde-containing material is a DMM3-4 product obtained by conventional rectification separation, the mass content of formaldehyde, methanol and water is 0.14%, 0.07% and 0.011% respectively, the mass content of DMM3 and DMM4 is 38.2% and 61.4% respectively, and the rest is a small amount of methylal and DMM2 component. The method for de-aldehyde refining of the above material comprises the following steps by using the same packing de-aldehyde column and other related equipment as in Example 1 and using nitrogen with a purity greater than 99.9% as the de-aldehyde agent:

[0074] (1) The liquid-phase aldehyde-containing DMM3-4 is continuously sent to the top of the de-aldehyde column after being preheated from room temperature to 115-120°C and flows downward, and the nitrogen gas at room temperature is continuously sent to the bottom of the de-aldehyde column and flows upward, so that the liquid-phase aldehyde-containing DMM3-4 and the nitrogen gas are countercurrently contacted in the de-aldehyde column for de-aldehyde.

[0075] (2) The liquid-phase DMM3-4 product from which formaldehyde is removed is collected from the bottom of the de-aldehyde column, and the nitrogen gas containing formaldehyde is collected from the top of the de-aldehyde column, the product discharge flow rate at the bottom is adjusted to control the liquid level at the bottom of the de-aldehyde column to be about 50%, and the gas-phase discharge amount at the top is adjusted to control the pressure at the top of the de-aldehyde column to be 40-50 KPaG.

[0076] (3) The liquid-phase product at the bottom of the de-aldehyde column is cooled to room temperature by a jacketed cooler and then collected as the product, and the gas-phase discharge at the top of the de-aldehyde column is vented to a safe place after being absorbed by water bubbling.

[0077] The flow rate of the liquid-phase aldehyde-containing DMM3-4 material is adjusted to 28 ml / min by adjusting the metering pump, the flow rate of the nitrogen gas is adjusted to 500 ml / min, and when the flow rate, temperature and pressure of the de-aldehyde column are stable, the average content of residual formaldehyde in the liquid-phase product at the bottom is detected to be 4.1 ppm, the average discharge flow rate at the bottom is about 27.6 ml / min, the formaldehyde removal rate under the operating conditions is about 99.7%, and the product yield is about 98.6%.

[0078] Example 5

[0079] The present embodiment provides a method for refining and de-aldehyde of a polyoxymethylene dimethyl ethers mixture (DMM3-5 for short) with a structural formula of , n = 3-5, wherein the aldehyde-containing material is a DMM3-5 product obtained by conventional rectification separation, the mass content of formaldehyde, methanol and water is 0.041%, 0.017% and 0.005% respectively, and the rest is the DMM3-5 product. The method for de-aldehyde refining of the above material comprises the following steps by using the same packing de-aldehyde column and other related equipment as in Example 1 and using nitrogen with a purity greater than 99.9% as the de-aldehyde agent:

[0080] (1) The liquid phase aldehyde-containing DMM3~5 is continuously sent to the top of the dealkalization tower and flows downward after being preheated from room temperature to 120~125°C, and the nitrogen gas at room temperature is continuously sent to the bottom of the dealkalization tower and flows upward, so that the liquid phase aldehyde-containing DMM3~5 and the nitrogen gas are countercurrently contacted in the dealkalization tower for dealkalization.

[0081] (2) The liquid phase DMM3~5 product from which the formaldehyde is removed is collected from the bottom of the dealkalization tower, and the nitrogen gas containing formaldehyde is collected from the top of the dealkalization tower, the discharge flow of the product at the bottom is adjusted to control the liquid level at the bottom of the dealkalization tower to be about 50%, and the discharge amount of the gas phase at the top is adjusted to control the pressure at the top of the dealkalization tower to be 100~110 KPaG.

[0082] (3) The liquid phase product at the bottom of the dealkalization tower is collected as a product after being cooled to room temperature by a jacketed cooler, and the gas phase discharge at the top of the dealkalization tower is vented to a safe place after being absorbed by water bubbling.

[0083] The flow of the liquid phase aldehyde-containing DMM3~5 material is adjusted to 25 ml / min by adjusting the metering pump, and the nitrogen flow is adjusted to 450 ml / min, when the feed flow, temperature and dealkalization tower pressure are stable, the average content of residual formaldehyde in the product at the bottom is detected to be 5.9 ppm, the average discharge flow at the bottom is about 24.7 ml / min, the formaldehyde removal rate under the operating conditions is about 98.6%, and the product yield is about 98.5%.

[0084] Example 6

[0085] The present embodiment provides a method for refining and dealkalizing polyoxymethylene diethyl ether (DEM2) with a structural formula of The aldehyde-containing material is a DEM2 product obtained by conventional rectification separation, wherein the mass contents of formaldehyde, ethanol and water are 0.013%, 0.004% and 0.002% respectively, and the rest is DEM2 product. Pure nitrogen gas with a purity of greater than 99.9% is used as a dealkalization agent, and the same related equipment such as a dealkalization tower filled with the same packing as in Example 1 is used, and the method for dealkalizing and refining the above-mentioned material comprises the following steps:

[0086] (1) The liquid phase aldehyde-containing DEM2 is continuously sent to the top of the dealkalization tower and flows downward after being preheated from room temperature to 90~95°C, and the nitrogen gas at room temperature is continuously sent to the bottom of the dealkalization tower and flows upward, so that the liquid phase aldehyde-containing DEM2 and the nitrogen gas are countercurrently contacted in the dealkalization tower for dealkalization.

[0087] (2) The liquid phase DEM2 product from which the formaldehyde is removed is collected from the bottom of the dealkalization tower, and the nitrogen gas containing formaldehyde is collected from the top of the dealkalization tower, the discharge flow of the product at the bottom is adjusted to control the liquid level at the bottom of the dealkalization tower to be about 50%, and the discharge amount of the gas phase at the top is adjusted to control the pressure at the top of the dealkalization tower to be 50~60 KPaG.

[0088] (3) The liquid phase product from the bottom of the de-aldehyde column is collected as product after being cooled to room temperature by a jacketed cooler, and the gaseous phase product from the top of the de-aldehyde column is vented to safety after being absorbed by water bubbling.

[0089] The flow rate of the liquid phase aldehyde-containing DEM2 material is adjusted to 15 ml / min by adjusting the metering pump, and the flow rate of nitrogen is adjusted to 250 ml / min. When the flow rate, temperature and pressure of the de-aldehyde column are stable, the average content of residual formaldehyde in the product from the bottom of the column is 2.2 ppm, the average flow rate of the product from the bottom of the column is about 14.8 ml / min, the removal rate of formaldehyde under the operating conditions is about 98.3%, and the product yield is about 98.7%.

[0090] Example 7

[0091] The present embodiment provides a method for refining and de-aldehyde of a polyoxyalkylene mixture of polyoxymethylene dibutyl ethers (DBM1-2) with a structural formula of The aldehyde-containing material is a DBM1-2 product obtained by conventional rectification separation, wherein the mass content of formaldehyde, butanol and water is 0.022%, 0.08% and 0.006% respectively, and the rest is DBM1-2 product. Pure nitrogen with a purity of more than 99.9% is used as a de-aldehyde agent, and the same de-aldehyde column and other related equipment as in Example 1 are used. The method for de-aldehyde refining of the above-mentioned material comprises the following steps:

[0092] (1) The liquid phase aldehyde-containing DBM1-2 is preheated from room temperature to 130-135°C and then continuously sent to the top of the de-aldehyde column and flows downward, and nitrogen at room temperature is continuously sent to the bottom of the de-aldehyde column and flows upward, so that the liquid phase aldehyde-containing DBM1-2 and nitrogen are countercurrently contacted in the de-aldehyde column for de-aldehyde.

[0093] (2) The liquid phase DBM1-2 product after removal of formaldehyde is taken from the bottom of the de-aldehyde column, and nitrogen containing formaldehyde is taken from the top of the de-aldehyde column. The flow rate of the product from the bottom of the column is adjusted to control the liquid level of the de-aldehyde column to about 50%, and the amount of gaseous phase product from the top of the de-aldehyde column is adjusted to control the pressure of the de-aldehyde column to 10-20 KPaG.

[0094] (3) The liquid phase product from the bottom of the de-aldehyde column is collected as product after being cooled to room temperature by a jacketed cooler, and the gaseous phase product from the top of the de-aldehyde column is vented to safety after being absorbed by water bubbling.

[0095] The flow rate of the liquid phase aldehyde-containing DBM1-2 material is adjusted to 20 ml / min by adjusting the metering pump, and the flow rate of nitrogen is adjusted to 210 ml / min. When the flow rate, temperature and pressure of the de-aldehyde column are stable, the average content of residual formaldehyde in the product from the bottom of the column is 1.4 ppm, the average flow rate of the product from the bottom of the column is about 19.9 ml / min, the removal rate of formaldehyde under the operating conditions is about 99.4%, and the product yield is about 99.5%.

[0096] Example 8

[0097] The present embodiment provides a structure formula The present embodiment provides a structure formula

[0098] Specifically, the method for removing formaldehyde by using the above-mentioned equipment and raw materials comprises the following steps:

[0099] (1) The liquid-phase formaldehyde-containing DMM2-4 is continuously fed to the top of the bubble column after being preheated from room temperature to 90-95°C, and the nitrogen is continuously fed to the bottom of the bubble column after being preheated from room temperature to 90-95°C and flows upward, so that the liquid-phase formaldehyde-containing DMM2-4 and the nitrogen are countercurrently contacted in the bubble column to remove formaldehyde.

[0100] (2) The liquid-phase DMM2-4 product from which formaldehyde is removed is collected from the bottom of the bubble column, and the nitrogen containing formaldehyde is collected from the top of the bubble column, the product discharge flow rate at the bottom is adjusted to control the liquid level at the top of the bubble column near the upper inlet, and the gas phase discharge amount at the top is adjusted to control the pressure at the top of the bubble column to be 40-50 KPaG.

[0101] (3) The liquid-phase product at the bottom of the bubble column is cooled to room temperature by a coil cooler and then collected as a product, and the gas phase discharge at the top of the bubble column is bubbled by water and then vented to a safe place.

[0102] The flow rate of the liquid-phase formaldehyde-containing DMM2-4 is adjusted to 50 ml / min, the flow rate of the nitrogen is adjusted to 1000 ml / min, and when the flow rate, temperature and pressure of the bubble column are stable, the average content of residual formaldehyde in the liquid-phase product at the bottom is detected to be 2.2 ppm, the average discharge flow rate at the bottom is about 47.7 ml / min, the removal rate of formaldehyde under the operating conditions is about 98.7%, and the product yield is about 95.4%.

Claims

1. A polyoxymethylene dialkyl ether de-aldehyde refining process characterized by The method comprises the following steps: (1) sending liquid-phase aldehyde-containing polymethoxy dialkyl ether to the top of a de-aldehyde column, and feeding the liquid-phase aldehyde-containing polymethoxy dialkyl ether into the de-aldehyde column through a liquid-phase aldehyde-containing polymethoxy dialkyl ether feeding port, and then flowing downward; sending gaseous de-aldehyde agent to the bottom of the de-aldehyde column, and feeding the gaseous de-aldehyde agent into the de-aldehyde column through a gaseous de-aldehyde agent feeding port, and then flowing upward, so that the liquid-phase aldehyde-containing polymethoxy dialkyl ether and the gaseous de-aldehyde agent are countercurrently contacted in the de-aldehyde column to remove aldehyde; (2) removing liquid-phase polymethoxy dialkyl ether products from which aldehyde has been removed from the bottom of the de-aldehyde column, and removing gaseous de-aldehyde agent containing aldehyde and polymethoxy dialkyl ether components from the top of the de-aldehyde column; The gaseous de-aldehyde agent is selected from inert non-condensable gases; The feeding temperature of the liquid-phase aldehyde-containing polymethoxy dialkyl ether is controlled to be 20-200 ℃, and the feeding temperature of the gaseous de-aldehyde agent is controlled to be ambient temperature to 200 ℃; The gaseous de-aldehyde agent is dry and has a purity meeting the industrial gas standard and a dew point under the operating pressure of not more than -40 ℃; The polymethoxydialkyl ether is a compound having a structural formula wherein the end capping groups R1and R2are alkyl groups having a structural formula wherein the number of alkyl carbon atoms m and the number of methyleneoxy units n are each an integer from 1 to 10.

2. A polymethoxydialkyl ether de-aldehyde refining process according to claim 1, characterized in that: The de-aldehyde column is one of a bubble column, a plate column and a packed column; The liquid-phase aldehyde-containing polymethoxy dialkyl ether feeding port is located at the upper part of the bubble column, above the first layer of plates of the plate column or above the first section of packing of the packed column, and the gaseous de-aldehyde agent feeding port is located at the lower part of the bubble column, below the last layer of plates of the plate column or below the last layer of packing of the packed column.

3. The polyoxymethylene dialkyl ether de-aldehyde refining process of claim 1, wherein: The gaseous de-aldehyde agent containing aldehyde and polymethoxy dialkyl ether components removed from the top of the de-aldehyde column is purified by downstream supporting tail gas treatment facilities and then discharged in compliance with the standard; The purification mode of the tail gas treatment facilities includes one or a combination of more than one of incineration, catalytic combustion, absorption and condensation, activated carbon or molecular sieve adsorption; The liquid-phase product removed from the bottom of the de-aldehyde column is cooled and then discharged.

4. The polyoxymethylene dialkyl ether de-aldehyde refining process of claim 2, wherein: The plate column or the packed column contains at least two theoretical plates, and the height-diameter ratio of the bubble column is not less than 5:

1.

5. The polyoxymethylene dialkyl ether de-aldehyde refining process of claim 1, wherein: The ratio of the volume flow of the gaseous de-aldehyde agent under standard conditions to the volume flow of the liquid-phase aldehyde-containing polymethoxy dialkyl ether is not less than 5:

1.

6. The polyoxymethylene dialkyl ether de-aldehyde refining process of claim 1, wherein: The mass content of alcohol or water in the liquid-phase aldehyde-containing polymethoxy dialkyl ether is less than 1%, and the mass content of aldehyde is less than 5%.

7. The polyoxymethylene dialkyl ether de-aldehyde refining process of claim 1, wherein: The liquid level of the liquid-phase material in the de-aldehyde column is controlled by adjusting the amount of the liquid-phase polymethoxy dialkyl ether product removed from the bottom of the de-aldehyde column, and the pressure at the top of the de-aldehyde column is controlled by adjusting the amount of the gaseous de-aldehyde agent removed from the top of the de-aldehyde column, and the pressure at the top of the de-aldehyde column is controlled to be greater than the saturated pressure at the feeding temperature of the liquid-phase aldehyde-containing polymethoxy dialkyl ether.

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