Continuous synthesis method of 3-methyl-3-butene-1-ol
By using a combination of weakly basic compounds and specific catalysts in the production of 3-methyl-3-butene-1-ol, the problems of low yields and equipment blockage are solved, and efficient and safe continuous production is achieved, which is suitable for industrial applications.
Patent Information
- Application Number
- CN202410106704.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-25
- Publication Date
- 2025-07-25
AI Technical Summary
In the prior art, the yield of 3-methyl-3-butene-1-ol is relatively low during the continuous production process, and there are problems of blockage of reaction equipment and safety risks.
A weakly basic compound is used as the first catalyst, combined with methanol and a specific second catalyst such as hydroquinone or para-hydroxyanisole, and the Pulis reaction is carried out through a high-pressure tube reactor, followed by flash evaporation and continuous purification to avoid self-polymerization and blockage of formaldehyde and achieve continuous production.
It improves the yield and production efficiency of 3-methyl-3-butene-1-ol, reduces production costs, realizes continuous and safe processes, and is suitable for industrial production.
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of chemical intermediate synthesis, and in particular, to a continuous synthesis method of 3-methyl-3-buten-1-ol. Background Art
[0002] 3-Methyl-3-buten-1-ol is an important chemical intermediate and has a wide range of applications in the synthesis of spices, pesticides, and pharmaceuticals. 3-Methyl-3-buten-1-ol can be transposed to form isoprenol, which is used in the production of citral, an important intermediate in spices.
[0003] Currently, the mainstream production process for synthesizing 3-methyl-3-buten-1-ol uses formaldehyde and isobutene as raw materials to obtain 3-methyl-3-buten-1-ol through the Prins reaction. In many patents, paraformaldehyde is depolymerized into formaldehyde and then reacted with isobutene to produce 3-methyl-3-buten-1-ol. The depolymerization process of paraformaldehyde can only be carried out in batches, making it difficult to achieve continuous production, resulting in low production efficiency. Moreover, the depolymerized formaldehyde is extremely prone to self-polymerization and is likely to undergo chain scission and cyclization to form polyoxymethylene such as trioxane during the long-term reaction with isobutene, clogging the reaction equipment, increasing the safety risks in the production process, and also making it difficult to achieve continuous production. Summary of the Invention
[0004] The main object of the present invention is to provide a continuous synthesis method of 3-methyl-3-buten-1-ol to solve the problem of low yield in the continuous production process of 3-methyl-3-buten-1-ol in the prior art.
[0005] To achieve the above object, according to one aspect of the present invention, there is provided a continuous synthesis method of 3-methyl-3-buten-1-ol. The continuous synthesis method includes: a reaction raw material system formed by mixing aqueous formaldehyde solution, a first catalyst, a second catalyst, methanol, and isobutene undergoes a Prins reaction in a high-pressure tubular reactor to generate a 3-methyl-3-buten-1-ol product system; the 3-methyl-3-buten-1-ol product system is flash-vaporized to obtain recycled isobutene and a bottom liquid, and the bottom liquid is continuously purified to obtain a 3-methyl-3-buten-1-ol product; wherein, the first catalyst is a weakly basic compound, and the second catalyst includes any one or more of hydroquinone and p-hydroxyanisole.
[0006] Furthermore, the mass concentration of the aqueous formaldehyde solution is 30% to 37%;
[0007] Preferably, the dosage of the second catalyst is 0.008% to 0.02% of the mass of the aqueous formaldehyde solution.
[0008] Further, the first catalyst is selected from any one or more of sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, ammonium carbonate, and ammonium oxalate;
[0009] Preferably, the addition amount of the first catalyst is 0.01% - 0.1% of the mass of the aqueous formaldehyde solution.
[0010] Further, the mass ratio of isobutene to the aqueous formaldehyde solution is 5 - 9:1.
[0011] Further, the mass ratio of methanol to the aqueous formaldehyde solution is 0.2 - 1:1.
[0012] Further, the temperature of the Prins reaction is 240°C - 280°C, the pressure is 15 MPa - 18 MPa, and the retention time is 120 - 150 min.
[0013] Further, the continuous synthesis method includes: preheating the reaction raw material system and then feeding it into a high-pressure tubular reactor; preferably, the reaction raw material system is preheated to 240 - 260°C.
[0014] Further, the continuous synthesis method includes: first mixing the aqueous formaldehyde solution with the first catalyst, then mixing it with the methanol solution dissolved with the second catalyst to form a first stream, preheating the first stream and isobutene respectively, mixing them through a mixer, and feeding them into a high-pressure tubular reactor;
[0015] Preferably, the total feeding rate of the first stream and isobutene is 27 g / min - 46 g / min.
[0016] Further, the aperture of the high-pressure tubular reactor is 25 mm, and the length of the tube bundle is 8 - 15 m.
[0017] Further, the continuous purification includes: separating methanol in the bottom liquid by distillation, separating the remaining components by liquid-liquid separation to obtain an aqueous layer and an organic layer, and subjecting the organic layer to vacuum distillation to obtain 3-methyl-3-buten-1-ol product;
[0018] Preferably, 3-methyl-3-buten-1-ol in the aqueous layer is recovered by vacuum distillation.
[0019] Applying the technical solution of the present invention, by using a weakly basic compound as the first catalyst, the formic acid in the aqueous formaldehyde solution can be neutralized, avoiding its adverse effect on the Prins condensation reaction of formaldehyde and isobutene; further, adding methanol to the system can reduce the blockage problem caused by the polymerization and coking of formaldehyde during the reaction; finally, and most importantly, selecting a specific second catalyst can not only catalyze the reaction to accelerate the reaction rate and promote the complete reaction of formaldehyde, but also itself is a polymerization inhibitor, which can prevent the polymerization and coking of formaldehyde or the product itself during the reaction, thus completely solving the problems of reactor blockage and pipeline coking in the post-treatment process of the reaction solution, realizing the continuous reaction of the whole process, with high production efficiency, can be produced under closed conditions, high safety, and is more suitable for industrial production. Detailed implementation mode
[0020] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.
[0021] As introduced in the background art of the present application, there is a problem of low yield in the continuous production process of 3-methyl-3-buten-1-ol in the prior art. To solve this problem, the present application provides a continuous synthesis method of 3-methyl-3-buten-1-ol, which includes: a reaction raw material system formed by mixing aqueous formaldehyde solution, a first catalyst, a second catalyst, methanol and isobutene undergoes a Prins reaction in a high-pressure tubular reactor to generate a 3-methyl-3-buten-1-ol product system; the 3-methyl-3-buten-1-ol product system is flash-evaporated to obtain recycled isobutene and a bottom liquid, and the bottom liquid is continuously purified to obtain a 3-methyl-3-buten-1-ol product; wherein, the first catalyst is a weakly basic compound, and the second catalyst includes any one or more of hydroquinone and p-hydroxyanisole.
[0022] In the present application, by using a weakly basic compound as the first catalyst, the formic acid in the aqueous formaldehyde solution can be neutralized, avoiding its adverse effect on the Prins condensation reaction of formaldehyde and isobutene; further, adding methanol to the system can reduce the blockage problem caused by the polymerization and coking of formaldehyde during the reaction; finally, and most importantly, selecting a specific second catalyst can not only catalyze the reaction to accelerate the reaction rate and promote the complete reaction of formaldehyde, but also itself is a polymerization inhibitor, which can prevent the polymerization and coking of formaldehyde or the product itself during the reaction, thus completely solving the problems of reactor blockage and pipeline coking in the post-treatment process of the reaction solution, realizing the continuous reaction of the whole process, with high production efficiency, can be produced under closed conditions, high safety, and is more suitable for industrial production.
[0023] It should be noted that the first catalyst and the second catalyst of the present application not only have good catalytic effects on this reaction, but are also inexpensive and easily available, thus significantly reducing the production cost of 3-methyl-3-buten-1-ol.
[0024] In some embodiments of the present application, in order to further improve the preparation efficiency of the product, the mass concentration of the aqueous formaldehyde solution is 30% to 37%, preferably 35% to 37%, and more preferably 37%. In some preferred embodiments of the present application, the dosage of the second catalyst is 0.008% to 0.02% of the mass of the aqueous formaldehyde solution, which can fully exert the catalytic effect of the second catalyst on hydroquinone and p-methoxyphenol, and further improve the yield of 3-methyl-3-buten-1-ol. Preferably, the dosage of the second catalyst is 0.009% to 0.015% of the mass of the aqueous formaldehyde solution.
[0025] In some typical embodiments of the present application, in order to better exert the catalytic effect of the first catalyst, the above-mentioned first catalyst is selected from any one or more of sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, ammonium carbonate, and ammonium oxalate. It can not only act as a pH regulator to neutralize the acid in the formaldehyde solution, but also better cooperate with the above-mentioned second catalyst to prevent isobutene from reacting with water to form tert-butanol, and the above effects can be achieved with very little dosage. Especially ammonium carbonate and ammonium bicarbonate among them not only have relatively significant catalytic effects, but also have good solubility in the reaction raw material system, which is convenient for subsequent separation and purification, and has outstanding effects on improving the operation convenience and safety of the continuous synthesis method. Preferably, the addition amount of the above-mentioned first catalyst is 0.01% to 0.1% of the mass of the aqueous formaldehyde solution, and more preferably 0.04% to 0.09%, which is more conducive to the exertion of the above effects.
[0026] In some embodiments of the present application, in order to further improve the yield of 3-methyl-3-buten-1-ol, the mass ratio of isobutene to the aqueous formaldehyde solution is 5 to 9:1. For example, the mass ratio of isobutene to the aqueous formaldehyde solution can be 5:1, 6:1, 7:1, 8:1, or 9:1, and preferably 7 to 9:1.
[0027] In some embodiments of the present application, in order to better exert the catalytic effects of the first catalyst and the second catalyst and fully solve the problem of pipeline blockage caused by formaldehyde polymerization, in the above-mentioned reaction raw material system, the mass ratio of methanol to the aqueous formaldehyde solution is 0.2 to 1:1, and preferably 0.5 to 0.8:1.
[0028] Furthermore, the temperature of the above-mentioned Prins reaction is 240°C to 280°C, and the pressure is 15 MPa to 18 MPa, which has a relatively high reaction rate and conversion rate. Preferably, the residence time is 120 to 150 minutes, the methanol is converted more fully, and the yield of 3-methyl-3-buten-1-ol product is relatively high. Preferably, the reaction temperature is 260°C to 270°C, and the preferred reaction pressure is 16 MPa to 17 MPa. At this time, various substances reach the supercritical state, which is beneficial to the progress of the reaction.
[0029] In some typical embodiments of the present application, in order to further improve the reaction efficiency, the above-mentioned continuous synthesis method includes: preheating the reaction raw material system and then introducing it into a high-pressure tubular reactor; preferably, the reaction raw material system is preheated to 240 to 260°C.
[0030] In order to better exert the functions of the first catalyst and the second catalyst and improve the reaction rate and selectivity, in some preferred embodiments of the present application, the above-mentioned continuous synthesis method includes: first mixing the aqueous formaldehyde solution with the first catalyst, and then mixing it with the methanol solution dissolved with the second catalyst to form a first stream. After preheating the first stream and isobutene respectively, they are mixed through a mixer and introduced into a high-pressure tubular reactor; First, mixing the first catalyst with the aqueous formaldehyde solution can neutralize the acid in the raw material aqueous formaldehyde solution before the Prins reaction, prevent isobutene from reacting with water to form tert-butanol, and improve the selectivity of the reaction raw materials. Then, mixing it with the methanol solution containing the second catalyst can inhibit the polymerization of formaldehyde and prevent coking. Preferably, the preheating temperature of the first stream is 110 - 135°C to prevent side reactions of formaldehyde, and the preheating temperature of the second stream is 240 to 260°C. Preferably, the total feeding rate of the first stream and isobutene is 27 g / min to 46 g / min, preferably 35 g / min to 40 g / min.
[0031] The high-pressure tubular reactor for carrying out the Prins reaction can be selected from the prior art, and the present application has no limitation. To improve the efficiency, it is preferred that the aperture of the high-pressure tubular reactor is 25 mm and the tube length is 8 to 15 m.
[0032] The 3-methyl-3-buten-1-ol product system obtained after the reaction is flash distilled to obtain recycled isobutene and bottom liquid. The recycled isobutene can be used again as a raw material in the above-mentioned Prins reaction. The bottom liquid can be continuously purified to obtain the 3-methyl-3-buten-1-ol product. The specific method of continuous purification can refer to the prior art. In some embodiments of the present application, the above continuous purification includes: first, methanol is separated by atmospheric distillation. The remaining components are divided into an aqueous layer and an organic layer. The aqueous layer is separated, and the organic layer is subjected to vacuum distillation to obtain the 3-methyl-3-buten-1-ol product. The separated methanol can be recycled and enter the reaction raw material system as a raw material. The 3-methyl-3-buten-1-ol in the aqueous layer is recovered by vacuum distillation. After the post-treatment, the COD of the aqueous layer after recovering organic substances such as methanol and 3-methyl-3-buten-1-ol is lower than 100 ppm, the process is environmentally friendly, and the continuity of the whole process is realized.
[0033] In some typical embodiments of the present application, the above continuous synthesis method includes: 1) Mixing an aqueous formaldehyde solution with a first catalyst, and then adding a methanol solution dissolved with a second catalyst and mixing evenly; 2) Feeding the raw materials in 1) to a preheater 1 with a metering pump, and at the same time feeding isobutene to a preheater 2 with a feed pump; 3) After the two streams of materials are preheated, they are fully mixed through a mixer and continuously condensed in a reactor at a set temperature and pressure to generate 3-methyl-3-buten-1-ol; 4) After the reaction solution is cooled by a condenser, it enters a flash distillation column to recover the excessive isobutene. The bottom liquid is then recycled with methanol, the aqueous layer is separated, and vacuum distillation is carried out to obtain high-quality 3-methyl-3-buten-1-ol; 5) Part of the 3-methyl-3-buten-1-ol dissolved in the aqueous layer is recovered by vacuum distillation, and the aqueous layer is discharged after the COD reaches the standard.
[0034] In some embodiments of the present application, through the above continuous synthesis method, the conversion rate of the raw material formaldehyde is above 99%, the selectivity of 3-methyl-3-buten-1-ol is 96.5% - 98%, and the yield of the 3-methyl-3-buten-1-ol product with a purity of above 99.5% is as high as above 95%.
[0035] The following will further illustrate the beneficial effects that can be achieved by the present application in combination with examples and comparative examples.
[0036] The content and purity of the products in the following examples and comparative examples are detected by a gas chromatograph.
[0037] Example 1
[0038] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 5 kg of 37% formaldehyde aqueous solution is added with 4 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of hydroquinone is added and mixed evenly. It is transported to preheater 1 by a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is transported to preheater 2 by a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to formaldehyde aqueous solution is controlled at 8, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. The retention time is 140 min. After the discharge, isobutene is recovered by flash evaporation and then cooled with water. The content of the reaction solution is detected in real time and detected by a gas chromatograph. The formaldehyde in the raw materials is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 96.9%. Methanol in the reaction solution is recovered by distillation, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. Part of the 3-methyl-3-buten-1-ol dissolved in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 5045 g, with a content of 99.5% and a yield of 95.0% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h without coking in the reactor.
[0039] Example 2
[0040] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 5 kg of 37% formaldehyde aqueous solution is added with 4 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of hydroquinone is added and mixed evenly. It is transported to preheater 1 by a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is transported to preheater 2 by a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to formaldehyde aqueous solution is controlled at 8, and the total feeding rate of the two materials is controlled at 40 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. After the discharge, isobutene is recovered by flash evaporation and then cooled with water. The content of the reaction solution is detected in real time and detected by a gas chromatograph. The conversion of formaldehyde in the raw materials is 99.7%, and the selectivity of the product 3-methyl-3-buten-1-ol is 97.1%. After the reaction solution is recovered of methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. Part of the 3-methyl-3-buten-1-ol dissolved in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 5056 g, with a content of 99.5% and a yield of 95.2% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h without coking in the reactor.
[0041] Example 3
[0042] The tubular reactor has a size of φ25*10m. The reactor is heated to 270°C and kept at a constant temperature. 5 kg of 37% formaldehyde aqueous solution is added with 4 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of hydroquinone is added and mixed evenly. It is transported to preheater 1 by a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is transported to preheater 2 by a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to formaldehyde aqueous solution is controlled at 8, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. After the outlet material is flashed to recover isobutene, it is cooled by water and the content of the reaction solution is detected in real time. It is detected by a gas chromatograph. The formaldehyde in the raw materials is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 96.4%. After the reaction solution recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. The partially dissolved 3-methyl-3-buten-1-ol in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 5003 g, with a content of 99.4% and a yield of 94.2% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h without coking in the reactor.
[0043] Example 4
[0044] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and kept at a constant temperature. 5 kg of 37% formaldehyde aqueous solution is added with 4 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.75 g of hydroquinone is added and mixed evenly. It is transported to preheater 1 by a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is transported to preheater 2 by a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to formaldehyde aqueous solution is controlled at 8, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. After the outlet material is flashed to recover isobutene, it is cooled by water and the content of the reaction solution is detected in real time. It is detected by a gas chromatograph. The formaldehyde in the raw materials is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 97.2%. After the reaction solution recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. The partially dissolved 3-methyl-3-buten-1-ol in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 5078 g, with a content of 99.5% and a yield of 95.6% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h without coking in the reactor.
[0045] Example 5
[0046] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 5 kg of 37% formaldehyde aqueous solution is added with 4 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of hydroquinone is added and mixed evenly. It is pumped by a metering pump to preheater 1 and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped by a metering pump to preheater 2 and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to formaldehyde aqueous solution is controlled at 8, and the total feeding speed of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 18 MPa. After the discharge, isobutene is recovered by flash evaporation and then cooled with water. The content of the reaction solution is detected in real time and detected by a gas chromatograph. The formaldehyde in the raw material is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 97.1%. After the reaction solution recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol of high quality is obtained by vacuum distillation. Part of the 3-methyl-3-buten-1-ol dissolved in the water layer is recovered by vacuum distillation. 5083 g of high-quality 3-methyl-3-buten-1-ol with a content of 99.5% and a yield of 95.7% (calculated based on formaldehyde) are obtained. The tubular reactor can operate for 1500 h without coking in the reactor.
[0047] Example 6
[0048] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 5 kg of 37% formaldehyde aqueous solution is added with 3.2 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of hydroquinone is added and mixed evenly. It is pumped by a metering pump to preheater 1 and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped by a metering pump to preheater 2 and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to formaldehyde aqueous solution is controlled at 9, and the total feeding speed of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 18 MPa. After the discharge, isobutene is recovered by flash evaporation and then cooled with water. The content of the reaction solution is detected in real time and detected by a gas chromatograph. The formaldehyde in the raw material is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 97.3%. After the reaction solution recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol of high quality is obtained by vacuum distillation. Part of the 3-methyl-3-buten-1-ol dissolved in the water layer is recovered by vacuum distillation. 5099 g of high-quality 3-methyl-3-buten-1-ol with a content of 99.6% and a yield of 96.0% (calculated based on formaldehyde) are obtained. The tubular reactor can operate for 1500 h without coking in the reactor.
[0049] Example 7
[0050] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and kept at a constant temperature. 5 kg of 37% aqueous formaldehyde solution is added with 4 g of ammonium carbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of hydroquinone is added and mixed evenly. It is pumped to preheater 1 by a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped to preheater 2 by a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to aqueous formaldehyde solution is controlled at 8, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. After the discharge is flashed to recover isobutene, it is cooled by water and the content of the reaction solution is detected in real time. It is detected by a gas chromatograph. The formaldehyde in the raw materials is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 96.3%. After the reaction solution recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. The partially dissolved 3-methyl-3-buten-1-ol in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 5019 g, with a content of 99.5% and a yield of 94.5% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h, and no coking occurs in the reactor.
[0051] Example 8
[0052] The tubular reactor has a size of φ25*10m. The reactor is heated to 240°C and kept at a constant temperature. 5 kg of 37% aqueous formaldehyde solution is added with 4 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of hydroquinone is added and mixed evenly. It is pumped to preheater 1 by a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped to preheater 2 by a metering pump and preheated to 240°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to aqueous formaldehyde solution is controlled at 8, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. After the discharge is flashed to recover isobutene, it is cooled by water and the content of the reaction solution is detected in real time. It is detected by a gas chromatograph. The formaldehyde in the raw materials is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 96.8%. After the reaction solution recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. The partially dissolved 3-methyl-3-buten-1-ol in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 4992.5 g, with a content of 99.5% and a yield of 94% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h, and no coking occurs in the reactor.
[0053] Example 9
[0054] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 5 kg of 37% formaldehyde aqueous solution is added with 4 g of ammonium bicarbonate to adjust the pH, and then 2.5 kg of methanol dissolved with 0.5 g of p-methoxyphenol is added and mixed evenly. It is pumped to preheater 1 by a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped to preheater 2 by a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to formaldehyde aqueous solution is controlled at 8, the total feeding rate of the two materials is controlled at 35 g / min, and the reaction pressure is adjusted by a needle valve at the outlet to control the reaction pressure at 16 MPa. After the discharge, isobutene is recovered by flash evaporation, and the reaction liquid content is detected in real time by water cooling and detected by a gas chromatograph. The conversion rate of formaldehyde in the raw materials is 99%, and the selectivity of the product 3-methyl-3-buten-1-ol is 97.0%. After the reaction liquid is recovered from methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. Part of the 3-methyl-3-buten-1-ol dissolved in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 5067 g, with a content of 99.5% and a yield of 95.4% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h without coking in the reactor.
[0055] Example 10
[0056] The difference from Example 1 is only that the addition amount of hydroquinone is 1 g, that is, the addition amount of hydroquinone is 0.02% of the mass of the formaldehyde aqueous solution.
[0057] The conversion rate of formaldehyde in the raw materials is 100%, and the selectivity of the product 3-methyl-3-buten-1-ol is 96.4%.
[0058] 5019 g of 3-methyl-3-buten-1-ol fine product is obtained, with a content of 99.5% and a yield of 94.5% (calculated based on formaldehyde). The tubular reactor can operate for 1500 h without coking in the reactor.
[0059] Example 11
[0060] The difference from Example 1 is only that the addition amount of hydroquinone is 1.5 g, that is, the addition amount of hydroquinone is 0.03% of the mass of the formaldehyde aqueous solution.
[0061] The conversion rate of formaldehyde in the raw materials is 100%, and the selectivity of the product 3-methyl-3-buten-1-ol is 93.2%.
[0062] 4853 g of 3-methyl-3-buten-1-ol fine product is obtained, with a content of 99.5% and a yield of 91.4% (calculated based on formaldehyde). The tubular reactor can operate for 1000 h, and black particles begin to appear when continuing to operate.
[0063] Example 12
[0064] It is only different from Example 1 in that ammonium bicarbonate is replaced with the same mass of sodium bicarbonate.
[0065] The conversion rate of formaldehyde in the raw materials is 100%, and the selectivity of the product 3-methyl-3-buten-1-ol is 96.7%.
[0066] 5035 g of high-quality 3-methyl-3-buten-1-ol with a content of 99.5% and a yield of 94.8% (calculated based on formaldehyde) are obtained. The tubular reactor can operate for 1500 h without coking in the reactor.
[0067] Example 13
[0068] It is only different from Example 1 in that ammonium bicarbonate is replaced with the same mass of zinc hydroxide.
[0069] The conversion rate of formaldehyde in the raw materials is 98%, and the selectivity of the product 3-methyl-3-buten-1-ol is 85%.
[0070] 4407 g of high-quality 3-methyl-3-buten-1-ol with a content of 99% and a yield of 83% (calculated based on formaldehyde) are obtained. The tubular reactor can operate for 200 h, and coking begins in the reactor.
[0071] Example 14
[0072] The size of the tubular reactor is φ25*10 m. The reactor is heated to 260 °C and kept at a constant temperature. 4 g of ammonium bicarbonate, 0.5 g of hydroquinone, 2.5 kg of methanol, and 40 kg of isobutene are added to 5 kg of 37% aqueous formaldehyde solution, mixed evenly, and then pumped to the preheater by a metering pump and preheated to 250 °C; after the material is preheated, it continuously reacts through the tubular reactor. The total feeding rate of the material is controlled at 35 g / min, and the reaction pressure is controlled at 16 MPa by adjusting the needle valve at the outlet; after the material is discharged, isobutene is recovered by flash evaporation, and then the reaction solution content is detected by water cooling in real time and detected by a gas chromatograph. The conversion rate in the raw materials is 100%, and the selectivity of the product 3-methyl-3-buten-1-ol is 90%. After the reaction solution recovers methanol, the water layer is separated, and high-quality 3-methyl-3-buten-1-ol is obtained by vacuum distillation. The partially dissolved 3-methyl-3-buten-1-ol in the water layer is recovered by vacuum distillation. 4690 g of high-quality 3-methyl-3-buten-1-ol with a content of 99.2% and a yield of 88.3% (calculated based on formaldehyde) are obtained. The tubular reactor can operate for 500 h, and coking occurs in the reactor and the preheater.
[0073] Comparative Example 1
[0074] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 5 kg of 37% aqueous formaldehyde solution is pumped to preheater 1 through a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped to preheater 2 through a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to aqueous formaldehyde solution is controlled at 9, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. After the discharge, isobutene is recovered by flash evaporation, and the reaction liquid content is detected in real time by water cooling and detected by a gas chromatograph. The formaldehyde in the raw materials is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 76.5%. After the reaction liquid recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. The partially dissolved 3-methyl-3-buten-1-ol in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 3941 g, with a content of 98.5% and a yield of 74.2% (calculated based on formaldehyde). The tubular reactor runs for 400 h, and the reactor begins to coke and clog, and the reaction discharge is not smooth.
[0075] Comparative Example 2
[0076] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 4 g of ammonium bicarbonate is added to 5 kg of 37% aqueous formaldehyde solution to adjust the pH, and then it is pumped to preheater 1 through a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped to preheater 2 through a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they are continuously reacted through the tubular reactor. The mass ratio of isobutene to aqueous formaldehyde solution is controlled at 9, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is adjusted by a needle valve at the outlet, and the reaction pressure is controlled at 16 MPa. After the discharge, isobutene is recovered by flash evaporation, and the reaction liquid content is detected in real time by water cooling and detected by a gas chromatograph. The formaldehyde in the raw materials is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 79.0%. After the reaction liquid recovers methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. The partially dissolved 3-methyl-3-buten-1-ol in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 4111 g, with a content of 98.6% and a yield of 77.4% (calculated based on formaldehyde). The tubular reactor runs for 480 h, and the reactor begins to coke and clog, and the reaction discharge is not smooth.
[0077] Comparative Example 3
[0078] The tubular reactor has a size of φ25*10m. The reactor is heated to 260°C and maintained at a constant temperature. 5 kg of 37% aqueous formaldehyde solution is added to 2.5 kg of methanol dissolved with hydroquinone g and mixed evenly, and then pumped to preheater 1 through a metering pump and preheated to 130°C. The isobutene storage tank maintains a pressure of 0.4 MPa. At this time, isobutene is in a liquid state and is pumped to preheater 2 through a metering pump and preheated to 250°C. After the two materials are preheated and mixed evenly, they react continuously through the tubular reactor. The mass ratio of isobutene to aqueous formaldehyde solution is controlled at 9, and the total feeding rate of the two materials is controlled at 35 g / min. The reaction pressure is controlled at 16 MPa by adjusting the reaction pressure with a needle valve at the outlet. After the discharge, isobutene is recovered by flash evaporation and the reaction liquid content is detected in real time by water cooling and detected by a gas chromatograph. The formaldehyde in the raw material is completely converted, and the selectivity of the product 3-methyl-3-buten-1-ol is 85.6%. After the reaction liquid is recovered from methanol, the water layer is separated, and 3-methyl-3-buten-1-ol fine product is obtained by vacuum distillation. Part of the 3-methyl-3-buten-1-ol dissolved in the water layer is recovered by vacuum distillation. The fine product of 3-methyl-3-buten-1-ol is 4494 g, with a content of 98.8% and a yield of 84.5% (calculated based on formaldehyde). The tubular reactor operates for 500 h, and then the reactor starts to coke and block, and the reaction discharge is not smooth.
[0079] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: By using a weakly basic compound as the first catalyst, it can neutralize formic acid in the aqueous formaldehyde solution and avoid its adverse effect on the Prins condensation reaction of formaldehyde and isobutene; further, adding methanol to the system can reduce the blockage problem caused by the polymerization and coking of formaldehyde during the reaction process; finally, and most importantly, selecting a specific type of second catalyst can not only catalyze the reaction to accelerate the reaction rate and promote the complete reaction of formaldehyde, but also itself is a polymerization inhibitor, which can prevent the polymerization and coking of formaldehyde or the product itself during the reaction process, thus completely solving the problems of reactor blockage and pipeline coking in the post-treatment process of the reaction liquid, realizing the continuous reaction of the whole process, with high production efficiency, being able to produce under closed conditions, high safety, and being more suitable for industrial production.
[0080] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A continuous synthesis method of 3-methyl-3-buten-1-ol, characterized in that, Including: A reaction raw material system formed by mixing aqueous formaldehyde solution, a first catalyst, a second catalyst, methanol and isobutene undergoes a Prins reaction in a high-pressure tubular reactor to generate a 3-methyl-3-buten-1-ol product system; The 3-methyl-3-buten-1-ol product system is flash distilled to obtain recycled isobutene and bottom liquid, and the bottom liquid is continuously purified to obtain a 3-methyl-3-buten-1-ol product; Among them, the first catalyst is a weakly basic compound, and the second catalyst includes any one or more of hydroquinone and p-hydroxyanisole.
2. The continuous synthesis method according to claim 1, wherein The mass concentration of the aqueous formaldehyde solution is 30% to 37%; Preferably, the dosage of the second catalyst is 0.008% to 0.02% of the mass of the aqueous formaldehyde solution.
3. The continuous synthesis method according to claim 1, wherein The first catalyst is selected from any one or more of sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, ammonium carbonate and ammonium oxalate; Preferably, the addition amount of the first catalyst is 0.01% to 0.1% of the mass of the aqueous formaldehyde solution.
4. The continuous synthesis method according to claim 1, characterized in that, The mass ratio of isobutene to the aqueous formaldehyde solution is 5 to 9:
1.
5. The continuous synthesis method according to claim 1, characterized in that The mass ratio of methanol to the aqueous formaldehyde solution is 0.2 to 1:
1.
6. The continuous synthesis method according to claim 1, wherein The temperature of the Prins reaction is 240°C to 280°C, the pressure is 15 MPa to 18 MPa, and the residence time is 120 to 150 min.
7. The continuous synthesis method according to any one of claims 1 to 6, characterized in that, The continuous synthesis method includes: preheating the reaction raw material system and then introducing it into the high-pressure tubular reactor; Preferably, the reaction raw material system is preheated to 240 to 260°C.
8. The continuous synthesis method according to any one of claims 1 to 6, characterized in that, The continuous synthesis method includes: first mixing the aqueous formaldehyde solution with the first catalyst, then mixing it with a methanol solution dissolved with the second catalyst to form a first stream, preheating the first stream and the isobutene respectively, mixing them through a mixer, and introducing them into the high-pressure tubular reactor; Preferably, the total feeding rate of the first stream and the isobutene is 27 g / min to 46 g / min.
9. The continuous synthesis method according to any one of claims 1 to 6, characterized in that, The aperture of the high-pressure tubular reactor is 25 mm, and the length of the tube bundle is 8 to 15 m.
10. The continuous synthesis method according to any one of claims 1 to 6, characterized in that, The continuous purification includes: distilling off methanol in the bottom liquid by rectification, separating the remaining components by liquid-liquid separation to obtain an aqueous layer and an organic layer, and subjecting the organic layer to vacuum rectification to obtain a 3-methyl-3-buten-1-ol product; Preferably, 3-methyl-3-buten-1-ol in the aqueous layer is recovered by vacuum rectification.