Anhydrous formaldehyde alcohol solution as well as preparation method and application thereof

Abstract

The invention relates to an anhydrous formaldehyde alcohol solution as well as a preparation method and application thereof, the preparation method comprises the following steps: (1) under the action of an inorganic base catalyst, carrying out first mixing on paraformaldehyde and an alcohol solution for depolymerization reaction to obtain a formaldehyde alcohol solution containing inorganic base; and (2) carrying out separation treatment on the formaldehyde alcohol solution containing the inorganic base to obtain the anhydrous formaldehyde alcohol solution. According to the preparation method, the catalyst-containing polyoxymethylene alcohol solution is firstly obtained, then the catalyst in the polyoxymethylene alcohol solution is separated out, and the anhydrous formaldehyde alcohol solution is obtained, so that the anhydrous formaldehyde alcohol solution can stably exist and can be used in aldol condensation reaction, and the preparation method provided by the invention is simple in process, easily available in raw materials and low in cost. The method is suitable for large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of paraformaldehyde depolymerization technology, and in particular to an anhydrous formaldehyde alcohol solution, its preparation method, and its application. Background Technology

[0002] Formaldehyde is an important organic chemical raw material that can be used as a disinfectant and preservative. It is also used to prepare a variety of products such as phenolic resin, urea-formaldehyde resin, or vinylon, and has wide applications in the petroleum, textile, and pharmaceutical industries.

[0003] Formaldehyde is a major downstream product of methanol. Currently, the most common method is to obtain a 37wt%-55wt% formaldehyde aqueous solution via methanol oxidation. However, the high water content of formaldehyde aqueous solutions is detrimental to water-sensitive synthesis reactions, especially in reactions involving formaldehyde in the preparation of high-performance engineering plastics and the aldol condensation process for the preparation of unsaturated carboxylic acid esters such as acrylates. Therefore, the preparation of anhydrous formaldehyde has become a research hotspot with greater economic value and industrial prospects.

[0004] CN116217359A discloses a method for catalytically preparing anhydrous formaldehyde. In a fixed-bed reactor, methanol is vaporized and, after dilution with or without an inert gas, reacts with a high-entropy alloy catalyst of a selected element combination to produce formaldehyde. No water is produced during the reaction, and hydrogen is co-produced. The high-entropy alloy is one or more of the following: a high-entropy alloy composed of TiVMnFeCoZr, a high-entropy alloy composed of TiVCrMnFeZr, a high-entropy alloy composed of TiCrMnFeNiZr, a high-entropy alloy composed of TiVCrFeNiZr, a high-entropy alloy composed of TiVZrNbHf, a high-entropy alloy composed of TiVZrNbMo, a high-entropy alloy composed of TiZrNbTa, a high-entropy alloy composed of TiCrVNb, a high-entropy alloy composed of MgTiFeCoNiZr, a high-entropy alloy composed of AlCrMnFeNiW, a high-entropy alloy composed of VMnFeNiLa, and a high-entropy alloy composed of TiVCrFeCoZr. The selected element combination is a predetermined combination.

[0005] CN116813457A discloses a method for depolymerizing paraformaldehyde, comprising the following steps: First, paraformaldehyde particles and a depolymerization catalyst comprising 0.03% to 0.05% of the mass of the paraformaldehyde particles are added to the bottom of a microwave reaction vessel equipped with a stirring device. Then, silicone oil is added, with the silicone oil level exceeding the paraformaldehyde particles. An alcohol solvent is then added to the silicone oil surface, and the mixture separates into layers. The stirring paddle of the stirring device is placed below the silicone oil surface. The depolymerization catalyst is copper naphthenate or copper stearate. Second, stirring is turned on, and microwave heating is performed intermittently for 3 to 5 minutes. After microwave heating and reflux for 43 to 51 minutes, the mixture is allowed to stand and separate into layers. The alcohol solvent solution is then separated and recovered to obtain the depolymerized formaldehyde solution.

[0006] CN111217687A discloses a method for preparing anhydrous formaldehyde. The anhydrous formaldehyde is prepared using PtSn / SiO2 as a catalyst, which is shaped and loaded into a reaction tube, and then filled into a fixed-bed reactor. Under normal pressure, methanol is injected by a horizontal flow pump, an inert gas is used as the carrier gas, the methanol feed ratio is 10~60 vol%, the methanol feed rate is 0.10~0.30 mL / (gcat.·min), and the reaction is carried out at 350~500℃.

[0007] CN105601487A discloses a method for preparing anhydrous formaldehyde, comprising the following steps: using methanol as raw material and an inert gas as a carrier, reacting in a fluidized bed reactor; filling a catalyst in the reaction tube of the reactor and then placing it in the reactor; the reaction temperature is 200~400℃; the catalyst is a rare earth compound; the rare earth complex is Ln[CH(CH2)nR]3·xH2O·yL; wherein, Ln is a rare earth element, L is an electron-donating ligand, R is a phenyl group; 1<x≤6, 1≤y≤6, and n is 3~15.

[0008] CN106699536A discloses a method for preparing anhydrous formaldehyde alcohol solution, comprising the following steps: (1) After controlling the formaldehyde content in the dilute formaldehyde aqueous solution to ≥35%, pump it into a formaldehyde concentration device for concentration to obtain a concentrated formaldehyde aqueous solution with a formaldehyde content of ≥50%, then pump it into an integrated drying, polymerization and depolymerization reactor, add a polymerization catalyst, and perform vacuum dehydration and drying under vacuum conditions of 80-101kPa and 50-70℃, while a polymerization reaction occurs simultaneously. Control the reaction time to 3-5 hours to obtain a polyoxymethylene polymer; (2) Add the dehydration and drying agent to the dehydration and drying reactor. Alcohol is added to the polyoxymethylene polymer in the integrated reactor for drying, polymerization and depolymerization. The molar ratio of alcohol to polyoxymethylene polymer is controlled at (0.7~1.4):1. At the same time, a depolymerization catalyst is added. The reaction temperature is controlled at 35-55℃ and the reaction time is controlled at 30-120 minutes to obtain an alcohol solution of formaldehyde. A stabilizer is then added to it. After stirring and mixing evenly, an anhydrous formaldehyde alcohol solution product is obtained and sent to the anhydrous formaldehyde alcohol solution storage tank. (3) The tail gas removed from the top of the integrated reactor is mainly composed of formaldehyde and water. After cooling and washing with water, dilute formaldehyde is obtained and returned to the dilute formaldehyde aqueous solution storage tank for reuse.

[0009] Although the above methods can produce anhydrous formaldehyde, they all use different types of complex catalysts or specific reaction devices, which are not suitable for large-scale development and production.

[0010] In summary, there is a need to develop a method for preparing anhydrous formaldehyde alcohol solution that is suitable for large-scale industrial applications, and that the prepared anhydrous formaldehyde alcohol solution can exist stably and be used in aldol condensation reactions. Summary of the Invention

[0011] To address the aforementioned technical problems, this invention provides an anhydrous formaldehyde alcohol solution, its preparation method, and its application. The invention first obtains a depolymerized formaldehyde alcohol solution containing a catalyst, then separates the catalyst from the depolymerized formaldehyde alcohol solution to obtain an anhydrous formaldehyde alcohol solution. This allows the anhydrous formaldehyde alcohol solution to exist stably and be used in aldol condensation reactions. The preparation method provided by this invention is simple, uses readily available raw materials, and is suitable for large-scale industrial applications.

[0012] To achieve this objective, the present invention adopts the following technical solution:

[0013] In a first aspect, the present invention provides a method for preparing anhydrous formaldehyde alcohol solution, the method comprising the following steps:

[0014] (1) Under the action of an inorganic base catalyst, paraformaldehyde and alcohol solution are first mixed to carry out depolymerization reaction to obtain formaldehyde alcohol solution containing inorganic base;

[0015] (2) The formaldehyde alcohol solution containing inorganic base is separated to obtain anhydrous formaldehyde alcohol solution.

[0016] This invention uses inexpensive and readily available paraformaldehyde as a raw material and an inorganic base as a catalyst. After complete depolymerization in an alcohol solution, a depolymerized formaldehyde alcohol solution containing the inorganic base is obtained. This overcomes the problem of requiring complex catalysts and specific equipment in the preparation of anhydrous formaldehyde. Furthermore, the inorganic base is separated from the depolymerized formaldehyde alcohol solution to obtain an anhydrous formaldehyde alcohol solution without the base. The anhydrous formaldehyde alcohol solution prepared by this invention is stable and can be used in aldol condensation reactions. The preparation method provided by this invention is simple, uses readily available raw materials, and is suitable for large-scale industrial applications.

[0017] As a preferred technical solution of the present invention, the mass ratio of paraformaldehyde in the first mixture to alcohol in the alcohol solution is 1:(1~2.2), for example, it can be 1:1, 1:1.2, 1:1.5, 1:2 or 1:2.2, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0018] Preferably, the alcohol solution includes any one or a combination of at least two of methanol solution, ethanol solution or isopropanol solution, wherein typical but non-limiting combinations include: a combination of methanol solution and ethanol solution, a combination of methanol solution and isopropanol solution, a combination of ethanol solution and isopropanol solution, and a combination of methanol solution, ethanol solution and isopropanol solution.

[0019] As a preferred embodiment of the present invention, the inorganic base catalyst comprises any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or magnesium hydroxide, wherein typical but non-limiting combinations include: a combination of sodium hydroxide and potassium hydroxide, a combination of sodium hydroxide and magnesium hydroxide, a combination of potassium hydroxide and magnesium hydroxide, and a combination of sodium hydroxide, potassium hydroxide, and magnesium hydroxide.

[0020] Preferably, the mass of the inorganic base catalyst is 2 to 8‰ of the total mass of paraformaldehyde and alcohol solution, for example, it can be 2‰, 4‰, 5‰, 6‰ or 8‰, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0021] This invention limits the amount of inorganic base catalyst added in the depolymerization reaction to ensure that paraformaldehyde is fully depolymerized into formaldehyde. If the amount of inorganic base catalyst added is too small, the reaction efficiency will be reduced and paraformaldehyde will be difficult to fully depolymerize. If the amount of inorganic base catalyst added is too large, the excess base will react with formaldehyde in a Cannizzaro disproportionation reaction to generate formate byproducts.

[0022] As a preferred technical solution of the present invention, the temperature of the depolymerization reaction is 50~80℃, for example, it can be 50℃, 60℃, 70℃ or 80℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] Preferably, the depolymerization reaction takes 3 to 8 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] As a preferred embodiment of the present invention, the depolymerization reaction is carried out under stirring.

[0025] Preferably, the stirring speed is 300~600 rpm, for example, it can be 300 rpm, 400 rpm, 500 rpm or 600 rpm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] As a preferred embodiment of the present invention, the separation process includes rotary evaporation.

[0027] Preferably, the water bath temperature for the rotary evaporation is 55~90℃, for example, it can be 55℃, 60℃, 70℃, 80℃ or 90℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0028] This invention limits the water bath temperature of rotary evaporation to 55~90℃ to effectively remove trace amounts of inorganic alkali from formaldehyde alcohol solutions containing inorganic bases, thereby obtaining an anhydrous formaldehyde alcohol solution. This allows the anhydrous formaldehyde alcohol solution to exist stably and be used in aldol condensation reactions. If the water bath temperature is below 55℃, the vaporization rate of the rotary evaporation solution will be too low, affecting the rotary evaporation efficiency and the concentration of anhydrous formaldehyde in the product. If the water bath temperature is above 90℃, the vaporization rate of the rotary evaporation solution will be too high, allowing trace amounts of inorganic alkali to enter the product.

[0029] Preferably, the reflux temperature of the rotary evaporator is -8 to -20°C, for example, it can be -8°C, -10°C, -12°C, -15°C or -20°C, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] Preferably, the rotational speed of the rotary evaporator is 20~45 r / min, for example, it can be 20 r / min, 25 r / min, 30 r / min, 35 r / min or 45 r / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] This invention effectively removes trace amounts of inorganic alkali from a formaldehyde alcohol solution containing inorganic bases by limiting the rotary evaporation speed to 20-45 r / min, resulting in an anhydrous formaldehyde alcohol solution. This ensures the stability of the anhydrous formaldehyde alcohol solution and its suitability for aldol condensation reactions. If the speed is below 20 r / min, the rotary evaporation solution will be heated unevenly, leading to inconsistent vaporization rates of the solution components and affecting the anhydrous formaldehyde concentration in the product. If the speed is above 45 r / min, the vaporization rate of the rotary evaporation solution will be too high, allowing trace amounts of inorganic alkali to enter the product.

[0032] Preferably, the rotary evaporation time is 1 to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] As a preferred embodiment of the present invention, the rotary evaporation is performed under vacuum.

[0034] Preferably, the vacuum degree of the rotary evaporation is -0.08 to -0.1 MPa, for example, it can be -0.08 MPa, -0.085 MPa, -0.09 MPa, -0.095 MPa or -0.1 MPa, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] This invention removes trace amounts of inorganic alkali from a formaldehyde alcohol solution containing inorganic alkali using a rotary evaporator at 55~90℃ and under negative pressure, to obtain an anhydrous formaldehyde alcohol solution, so that the anhydrous formaldehyde alcohol solution can exist stably and can be used in aldol condensation reactions.

[0036] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0037] (1) Under the action of an inorganic base catalyst, at 50~80℃, paraformaldehyde and alcohol solution are first mixed according to the mass ratio of paraformaldehyde to alcohol in alcohol solution of 1:(1~2.2) to carry out depolymerization reaction for 3~8h to obtain formaldehyde alcohol solution containing inorganic base.

[0038] (2) Under a vacuum of -0.08 to -0.1 MPa, the formaldehyde alcohol solution containing inorganic base is subjected to rotary evaporation treatment at a water bath temperature of 55 to 90°C, a reflux temperature of -8 to -20°C, a rotation speed of 20 to 45 r / min, and a time of 1 to 5 h. The distillate from the rotary evaporation treatment is an anhydrous formaldehyde alcohol solution.

[0039] In a second aspect, the present invention provides an anhydrous formaldehyde alcohol solution, which is prepared by the preparation method described in the first aspect.

[0040] The anhydrous formaldehyde alcohol solution provided by this invention does not contain a catalyst, can exist stably, and can be used in aldol condensation reactions.

[0041] Preferably, the concentration of formaldehyde in the anhydrous formaldehyde alcohol solution is ≤36wt%, for example, it can be 17wt%, 20wt%, 25wt%, 30wt% or 36wt%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0042] Thirdly, the present invention provides an application of the anhydrous formaldehyde alcohol solution according to the second aspect, wherein the anhydrous formaldehyde alcohol solution is used in an aldol condensation reaction.

[0043] The anhydrous formaldehyde alcohol solution provided by this invention does not contain a catalyst, can exist stably, and can be used in aldol condensation reactions.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] This invention uses inexpensive and readily available paraformaldehyde as a raw material and an inorganic base as a catalyst. After complete depolymerization in an alcohol solution, a depolymerized formaldehyde alcohol solution containing the inorganic base is obtained. This overcomes the problem of requiring complex catalysts and specific equipment in the preparation of anhydrous formaldehyde. Furthermore, the inorganic base is separated from the depolymerized formaldehyde alcohol solution to obtain an anhydrous formaldehyde alcohol solution without the base. The concentration of the anhydrous formaldehyde alcohol solution prepared by this invention can be controlled within the range of 17-36 wt%, ensuring its stability and suitability for aldol condensation reactions. The preparation method provided by this invention is simple, uses readily available raw materials, and is suitable for large-scale industrial applications. Detailed Implementation

[0046] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0047] Example 1

[0048] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution, the preparation method comprising the following steps:

[0049] (1) 210g of paraformaldehyde (Maclean, P804536) and 224g of anhydrous methanol were mixed to obtain a first mixture. 1.3g of sodium hydroxide was added to the first mixture to carry out a depolymerization reaction at a temperature of 60℃, a stirring speed of 400rpm and a time of 3h to obtain a formaldehyde alcohol solution containing sodium hydroxide.

[0050] (2) The formaldehyde alcohol solution containing sodium hydroxide was subjected to rotary evaporation treatment at a vacuum of -0.095 MPa, with a water bath temperature of 75°C, a reflux temperature of -15°C, a rotation speed of 25 r / min, and a time of 3 h. The distillate from the rotary evaporation treatment was an anhydrous formaldehyde alcohol solution.

[0051] Example 2

[0052] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution, the preparation method comprising the following steps:

[0053] (1) 210g of paraformaldehyde (Maclean, P804536) and 448g of ethanol were mixed to obtain a first mixture. 5.26g of potassium hydroxide was added to the first mixture to carry out a depolymerization reaction at a temperature of 50℃, a stirring speed of 300rpm and a time of 8h to obtain a formaldehyde alcohol solution containing potassium hydroxide.

[0054] (2) Under a vacuum of -0.08 MPa, the formaldehyde alcohol solution containing potassium hydroxide was subjected to rotary evaporation treatment at a water bath temperature of 55°C, a reflux temperature of -20°C, a rotation speed of 20 r / min, and a time of 5 h. The distillate from the rotary evaporation treatment was an anhydrous formaldehyde alcohol solution.

[0055] Example 3

[0056] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution, the preparation method comprising the following steps:

[0057] (1) 210g of paraformaldehyde (Maclean, P804536) and 336g of isopropanol were mixed to obtain a first mixture. 1.092g of magnesium hydroxide was added to the first mixture to carry out a depolymerization reaction at a temperature of 80℃, a stirring speed of 600rpm and a time of 5h to obtain a formaldehyde alcohol solution containing magnesium hydroxide.

[0058] (2) Under a vacuum of -0.1 MPa, the formaldehyde alcohol solution containing magnesium hydroxide is subjected to rotary evaporation treatment at a water bath temperature of 90°C, a reflux temperature of -8°C, a rotation speed of 45 r / min, and a time of 1 h. The distillate from the rotary evaporation treatment is an anhydrous formaldehyde alcohol solution.

[0059] Example 4

[0060] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the depolymerization reaction time is adjusted from 3h to 5h, while the rest is the same as Example 1.

[0061] Example 5

[0062] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the depolymerization reaction time is adjusted from 3h to 5h and the rotary evaporation time is adjusted from 3h to 1h. All other aspects are the same as in Example 1.

[0063] Example 6

[0064] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the mass of anhydrous methanol in step (1) is adjusted to 336g, the mass of sodium hydroxide is adjusted to 1.64g, and the depolymerization reaction time is adjusted to 5h. All other aspects are the same as in Example 1.

[0065] Example 7

[0066] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the mass of anhydrous methanol in step (1) is adjusted to 448g, the mass of sodium hydroxide is adjusted to 1.97g, and the depolymerization reaction time is adjusted to 5h. All other aspects are the same as in Example 1.

[0067] Example 8

[0068] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the mass of anhydrous methanol in step (1) is adjusted to 448g, the mass of sodium hydroxide is adjusted to 1.97g, the depolymerization reaction time is adjusted to 5h, and the vacuum degree in step (2) is adjusted to -0.08MPa. All other aspects are the same as in Example 1.

[0069] Example 9

[0070] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the temperature of the depolymerization reaction in step (1) is adjusted to 55°C and the time is adjusted to 5h, and the reflux temperature of the rotary evaporation treatment in step (2) is adjusted to -8°C. All other aspects are the same as in Example 1.

[0071] Example 10

[0072] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the temperature of the depolymerization reaction in step (1) is adjusted to 55°C and the time is adjusted to 5h, and the water bath temperature of the rotary evaporation treatment in step (2) is adjusted to 65°C. All other aspects are the same as in Example 1.

[0073] Example 11

[0074] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the amount of sodium hydroxide added in step (1) is adjusted from 1.3g to 0.5g. All other steps are the same as in Example 1.

[0075] Example 12

[0076] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the amount of sodium hydroxide added in step (1) is adjusted from 1.3g to 5g, while the rest is the same as in Example 1.

[0077] Example 13

[0078] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the water bath temperature for rotary evaporation is adjusted from 75°C to 40°C. All other aspects are the same as in Example 1.

[0079] Example 14

[0080] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the water bath temperature for rotary evaporation is adjusted from 75°C to 100°C. All other aspects are the same as in Example 1.

[0081] Example 15

[0082] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the rotation speed of the rotary evaporation process is adjusted from 25 r / min to 10 r / min. All other aspects are the same as in Example 1.

[0083] Example 16

[0084] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the rotation speed of the rotary evaporation process is adjusted from 25 r / min to 60 r / min. All other aspects are the same as in Example 1.

[0085] Example 17

[0086] This embodiment provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the rotary evaporation treatment is not carried out under vacuum, i.e., the pressure of the rotary evaporation treatment is 0.1 MPa. All other aspects are the same as in Example 1.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing anhydrous formaldehyde alcohol solution. The only difference from Example 1 is that the preparation method does not include step (2), i.e., the formaldehyde alcohol solution containing sodium hydroxide is referred to as anhydrous formaldehyde alcohol solution. All other aspects are the same as in Example 1.

[0089] The anhydrous formaldehyde alcohol solution provided in this comparative example contains an inorganic base. Since the inorganic base will destroy the structure of the aldol condensation catalyst and reduce its catalytic performance when it enters the aldol condensation reaction system, this anhydrous formaldehyde alcohol solution cannot be used in the aldol condensation reaction.

[0090] The formaldehyde concentration in the anhydrous formaldehyde alcohol solutions obtained in the above examples and comparative examples was detected using ultraviolet spectrophotometry. Specifically, 20 μL of anhydrous formaldehyde alcohol solution sample was taken into a 100 mL volumetric flask, the sample mass was accurately recorded, and then the volume was adjusted. 0.3 mL of the adjusted liquid was then taken into a colorimetric tube, diluted to 10 mL, and 1 mL of 0.32 wt% acetylacetone solution was added. After shaking well, the solution was heated in a 60 °C water bath for 15 min. After cooling to room temperature, ultraviolet detection was performed, and the formaldehyde concentration was calculated. The content of inorganic base catalyst in the anhydrous formaldehyde alcohol solution was determined by potentiometric titration, and the water content in the anhydrous formaldehyde alcohol solution was determined by a Karl Fischer moisture analyzer. The detection results are shown in Table 1.

[0091] Table 1

[0092]

[0093] The test results show that:

[0094] (1) As can be seen from Examples 1 to 10, the present invention uses inexpensive and readily available paraformaldehyde as raw material and inorganic base as catalyst. After fully depolymerization in alcohol solution, a depolymerized formaldehyde alcohol solution containing inorganic base is obtained. The inorganic base in the depolymerized formaldehyde alcohol solution is separated to obtain an anhydrous formaldehyde alcohol solution without base. The concentration of the anhydrous formaldehyde alcohol solution prepared by the present invention can be controlled in the range of 17~36wt%, so that the anhydrous formaldehyde alcohol solution can exist stably and can be used in aldol condensation reaction.

[0095] (2) As can be seen from Examples 1 and 11-12, in Example 1, the amount of inorganic base catalyst sodium hydroxide added in the depolymerization reaction was 1.3g, that is, the mass of sodium hydroxide was 3‰ of the total mass of paraformaldehyde and alcohol solution, and the concentration of formaldehyde in the anhydrous formaldehyde alcohol solution prepared was 26.49wt%; while in Example 11, the amount of inorganic base catalyst sodium hydroxide added in the depolymerization reaction was 0.5g, that is, the mass of sodium hydroxide was 1.1‰ of the total mass of paraformaldehyde and alcohol solution, and the concentration of formaldehyde in the anhydrous formaldehyde alcohol solution prepared was 26.49wt%. The formaldehyde concentration in the solution was 7.11 wt%. In Example 12, the amount of inorganic base catalyst sodium hydroxide added in the depolymerization reaction was 5 g, that is, the mass of sodium hydroxide was 11‰ of the total mass of paraformaldehyde and alcohol solution. The formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 9.05 wt%. It can be seen that the present invention, by limiting the amount of inorganic base catalyst added in the depolymerization reaction, enables the paraformaldehyde to be fully depolymerized into formaldehyde, and the formaldehyde concentration in the obtained anhydrous formaldehyde alcohol solution can be controlled within the range of 17~36 wt%.

[0096] (3) As can be seen from Examples 1 and 13-14, the water bath temperature for rotary evaporation in Example 1 was 75°C, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 26.49 wt%, and the sodium hydroxide content was 0. In Example 13, the water bath temperature for rotary evaporation was 40°C, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 5.78 wt%, and the sodium hydroxide content was 0. In Example 14, the water bath temperature for rotary evaporation was 100°C, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 1... The content of sodium hydroxide is 0.08 wt%, which is 0.45 wt%. Therefore, this invention effectively removes trace amounts of inorganic alkali from the formaldehyde alcohol solution containing inorganic alkali by limiting the water bath temperature of rotary evaporation to 55~90℃, thereby obtaining an anhydrous formaldehyde alcohol solution with a formaldehyde concentration in the range of 17~36 wt%. This allows the anhydrous formaldehyde alcohol solution to exist stably and be used in aldol condensation reactions. If the water bath temperature is too low, the concentration of formaldehyde in the anhydrous formaldehyde alcohol solution will decrease, and if the water bath temperature is too high, trace amounts of inorganic alkali will enter the anhydrous formaldehyde alcohol solution.

[0097] (4) As can be seen from Examples 1 and 15-16, in Example 1, the rotary evaporation speed was 25 r / min, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 26.49 wt%, and the sodium hydroxide content was 0; while in Example 15, the rotary evaporation speed was 10 r / min, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 7.48 wt%, and the sodium hydroxide content was 0; in Example 16, the rotary evaporation speed was 60 r / min, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was... With a concentration of 11.09 wt% and a sodium hydroxide content of 0.05 wt%, this invention effectively removes trace amounts of inorganic alkali from a formaldehyde alcohol solution containing inorganic alkali by limiting the rotary evaporation speed to 20-45 r / min, resulting in an anhydrous formaldehyde alcohol solution with a formaldehyde concentration in the range of 17-36 wt%. This ensures the anhydrous formaldehyde alcohol solution can exist stably and be used in aldol condensation reactions. Too low a rotation speed will reduce the formaldehyde concentration in the anhydrous formaldehyde alcohol solution, while too high a rotation speed will cause trace amounts of inorganic alkali to enter the anhydrous formaldehyde alcohol solution.

[0098] (5) As can be seen from Examples 1 and 17, the rotary evaporation process in Example 1 was carried out under a vacuum of -0.095 MPa, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 26.49 wt%; while the rotary evaporation process in Example 17 was carried out under a pressure of 0.1 MPa, and the formaldehyde concentration in the anhydrous formaldehyde alcohol solution prepared was 2.47 wt%. It can be seen that the rotary evaporation process of the present invention must be carried out under a vacuum negative pressure to increase the formaldehyde content in the distillate and obtain an anhydrous formaldehyde alcohol solution with a formaldehyde concentration in the range of 17~36 wt%.

[0099] (6) As can be seen from Example 1 and Comparative Example 1, the present invention must undergo a rotary evaporation process to remove the inorganic base catalyst and obtain an anhydrous formaldehyde alcohol solution without the inorganic base catalyst in order to make the anhydrous formaldehyde alcohol solution usable for aldol condensation reaction.

[0100] In summary, this invention uses inexpensive and readily available paraformaldehyde as raw material and an inorganic base as catalyst. After complete depolymerization in an alcohol solution, a depolymerized formaldehyde alcohol solution containing an inorganic base is obtained. The inorganic base in the depolymerized formaldehyde alcohol solution is then separated to obtain an anhydrous formaldehyde alcohol solution without an alkali. The concentration of the anhydrous formaldehyde alcohol solution prepared by this invention can be controlled within the range of 17~36wt%, allowing the anhydrous formaldehyde alcohol solution to exist stably and be used in aldol condensation reactions.

[0101] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing anhydrous formaldehyde alcohol solution, characterized in that, The preparation method includes the following steps: (1) Under the action of an inorganic base catalyst, paraformaldehyde and alcohol solution are first mixed to carry out depolymerization reaction to obtain formaldehyde alcohol solution containing inorganic base; (2) The formaldehyde alcohol solution containing inorganic base is separated to obtain anhydrous formaldehyde alcohol solution.

2. The preparation method according to claim 1, characterized in that, In the first mixture, the mass ratio of paraformaldehyde to alcohol in the alcohol solution is 1:(1~2.2); Preferably, the alcohol solution includes any one or a combination of at least two of methanol solution, ethanol solution or isopropanol solution.

3. The preparation method according to claim 1 or 2, characterized in that, The inorganic base catalyst includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or magnesium hydroxide. Preferably, the mass of the inorganic base catalyst is 2-8‰ of the total mass of paraformaldehyde and alcohol solution.

4. The preparation method according to any one of claims 1-3, characterized in that, The temperature of the depolymerization reaction is 50~80℃; Preferably, the depolymerization reaction takes 3 to 8 hours.

5. The preparation method according to any one of claims 1-4, characterized in that, The depolymerization reaction was carried out under stirring; Preferably, the stirring speed is 300~600 rpm.

6. The preparation method according to any one of claims 1-5, characterized in that, The separation process includes rotary evaporation; Preferably, the water bath temperature for the rotary evaporation is 55~90℃; Preferably, the reflux temperature of the rotary evaporator is -8 to -20°C; Preferably, the rotary evaporation speed is 20~45 r / min; Preferably, the rotary evaporation time is 1 to 5 hours.

7. The preparation method according to claim 6, characterized in that, The rotary evaporation is carried out under vacuum; Preferably, the vacuum degree of the rotary evaporation is -0.08 to -0.1 MPa.

8. The preparation method according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) Under the action of an inorganic base catalyst, at 50~80℃, paraformaldehyde and alcohol solution are first mixed according to the mass ratio of paraformaldehyde to alcohol in alcohol solution of 1:(1~2.2) to carry out depolymerization reaction for 3~8h to obtain formaldehyde alcohol solution containing inorganic base. (2) Under a vacuum of -0.08 to -0.1 MPa, the formaldehyde alcohol solution containing inorganic base is subjected to rotary evaporation treatment at a water bath temperature of 55 to 90°C, a reflux temperature of -8 to -20°C, a rotation speed of 20 to 45 r / min, and a time of 1 to 5 h. The distillate from the rotary evaporation treatment is an anhydrous formaldehyde alcohol solution.

9. An anhydrous formaldehyde alcohol solution, characterized in that, The anhydrous formaldehyde alcohol solution is prepared by the preparation method according to any one of claims 1-8.

10. An application of the anhydrous formaldehyde alcohol solution according to claim 9, characterized in that, The anhydrous formaldehyde alcohol solution is used in the aldol condensation reaction.

Images