CN110981697B - Method for synthesizing 3-methyl-3-butene-1-ol - Google Patents

Abstract

The invention provides a method for synthesizing 3-methyl-3-butene-1-alcohol. The present invention takes isobutene and dimethyldioxane as raw materials, reacts in a fixed bed equipped with a catalyst and obtains 3-methyl-3-butene-1-alcohol, wherein the conversion rate of dimethyldioxane reaches More than 99%, the selectivity is more than 98%. The present invention uses dimethyldioxane as a raw material to synthesize 3-methyl-3-butene-1-alcohol, which reduces production cost and energy consumption, greatly reduces the discharge of three wastes, simplifies the separation process, and has better continuous operability Strong, ideal for scale-up and industrialization.

Description

A kind of method of synthesizing 3-methyl-3-butene-1-alcohol

technical field

The invention relates to a method for synthesizing 3-methyl-3-buten-1-ol as a raw material of a polycarboxylic acid high-efficiency water reducer, and belongs to the technical field of organic chemical synthesis.

Background technique

3-Methyl-3-buten-1-ol is the initiator for the synthesis of polycarboxylate superplasticizer side chain TPEG polyether, which plays a decisive role in the quality and performance of polycarboxylate superplasticizer. In addition, 3-methyl-3-buten-1-ol can also be used to synthesize methyl pyrethroid, an intermediate of high-efficiency and low-toxicity pesticide pyrethroid insecticides, and it is also the main raw material for the artificial synthesis of citral. This further synthesizes menthol and its derivatives, ionone, carotenoids and vitamin A, flavors and fragrances, medical supplies, etc. Therefore, the research on the synthesis of 3-methyl-3-buten-1-ol has broad prospects and greater economic and social benefits.

According to the different raw materials for the synthesis of 3-methyl-3-buten-1-ol, the synthetic route is mainly divided into three categories, the first is the isoprene method, and the second is the methyl butenol isomerization method , the third category is the Prince method, also known as the isobutylene method.

Patent 105541544A discloses a method of using isoprene and hydrogen chloride to catalyze the synthesis of chlorinated isopentene, hydrolyze to obtain methylbutenol and isopentenol, and then perform isomerization to obtain 3-methyl-3-butene-1 -Alcohol, the method is complicated to operate, and the equipment investment is large and high, and hydrogen chloride has relatively large corrosion to the equipment.

Patent 103787834B discloses the addition of acetone and formaldehyde to obtain 4-hydroxy-2-butanone, which is reacted with isobutene through an acid catalyst to obtain intermediate 1, and intermediate 1 is reacted with a methyleneating agent to obtain intermediate 2, After performing the deprotection reaction to obtain 3-methyl-3-buten-1-ol, the method is complicated to operate, has a long process route and high production cost, and is not suitable for continuous industrial operation.

Patent CN102557876A discloses a kind of using paraformaldehyde and isobutylene as raw materials, using chloroform as solvent, using 1.25mol SnCl4 per gram of molecular sieve as catalyst, and preparing 3-methyl-3-butene-1- alcohol.

Patent CN105439823A discloses a method of using formaldehyde methanol solution as a raw material, heating it to a supercritical state and spraying it into the reactor and condensing isobutene to generate 3-methyl-3-buten-1-ol. The pressure is 15-22MPa, the reaction temperature is 220-300°C, the conversion rate of isobutene is 99%, and the selectivity of 3-methyl-3-buten-1-ol is 96%.

Patent CN104130107A discloses a method for synthesizing 3-methyl-3-butene-1-ol with formaldehyde hemiacetal as raw material, which synthesizes aldol condensate with alcohol with 1 to 5 carbons and formaldehyde, under reaction pressure 12-18MPa, and the reaction temperature is 280-350°C. This method not only requires high temperature and pressure, but also produces alcohol with carbon number 1-5 during the synthesis process, which needs to be separated.

In short, the Prince method in the prior art can efficiently prepare 3-methyl-3-buten-1-ol, but the raw material mostly uses formaldehyde or paraformaldehyde, which has a low formaldehyde conversion rate and is difficult to separate and remove formaldehyde , and then lead to residual formaldehyde in the product, which reduces the product quality and affects the downstream application of 3-methyl-3-buten-1-ol.

Contents of the invention

Aiming at the deficiencies in the prior art, the invention provides a method for preparing 3-methyl-3-buten-1-ol with simple process, environment-friendly and high yield, specifically, using isobutylene and dimethyl dimethicone Oxane reaction to produce 3-methyl-3-buten-1-ol.

The present invention adopts following technical scheme in order to achieve its purpose:

A method for synthesizing 3-methyl-3-butene-1-ol, the method comprising: in the presence of a catalyst, reacting isobutene and dimethyldioxane to generate 3-methyl-3-butene- 1-alcohol.

Dimethyldioxane as a raw material can be prepared from formaldehyde and isobutylene under acidic catalyst conditions; the acidic catalyst can be one or more of sulfuric acid, phosphoric acid, hydrochloric acid, solid acid, and heteropolyacid.

In the preparation of dimethyldioxane, the mass ratio of formaldehyde and isobutylene can be 2:1-8:1.

In the preparation of dimethyldioxane, the reaction temperature is preferably 60-100° C., and the reaction time is preferably 4-8 hours.

Preferably, the reaction temperature of isobutene and dimethyldioxane is 150-220°C, more preferably 160-200°C; the reaction pressure is 4MPa-15MPa, more preferably 6MPa-10MPa.

Preferably, the reaction time of isobutene and dimethyldioxane is 10 min to 60 min, more preferably 15 min to 30 min.

Preferably, the molar ratio of isobutene to dimethyldioxane is 3-10:1-5, more preferably 5-8:2-4.

Further, the reaction is carried out under an inert atmosphere such as a nitrogen atmosphere. Furthermore, the reaction is preferably carried out in a fixed bed reactor filled with a catalyst.

The catalyst in the invention includes a main catalyst and a co-catalyst, the main catalyst is a metal oxide, and the co-catalyst is a nitrogen-containing compound. The mass ratio of the main catalyst and the co-catalyst is preferably 6:1-3.

The catalyst in the present invention can be formed by mixing the main catalyst and the co-catalyst.

Preferably, based on the mass of the carrier, the metal oxide loading of the main catalyst is preferably 3-40 wt%, more preferably 5-20 wt%; the nitrogen-containing compound loading of the co-catalyst is preferably 1-15 wt%, more preferably 2-5 wt%.

According to the main catalyst of the catalyst of the present invention, preferably, the metal oxide includes but not limited to two kinds of magnesium oxide, calcium oxide, manganese oxide, barium oxide, iron oxide, copper oxide, zinc oxide, tin oxide, strontium oxide or more, such as manganese oxide and barium oxide, calcium oxide and iron oxide, copper oxide and zinc oxide, strontium oxide and magnesium oxide, preferably comprising at least one alkaline earth metal oxide and selected from the group consisting of iron, copper, tin, manganese, strontium At least one of the oxides, adding metal oxides as the main catalyst, can effectively promote the cracking of dimethyl dioxane, accelerate the reaction with isobutene, reduce the reaction temperature and pressure, reduce the reaction time, and make the reaction conditions more mild .

Preferably, the cocatalyst is selected from one or more of imides, carbonamides, aliphatic amines, aromatic amines, nitrogen-containing heterocycles, and quaternary ammonium bases, including but not limited to phthalimide, propane Amide, caprolactam, dimethylaniline, p-toluidine, methylethylcyclopropylamine, p-chloroaniline, tetradecyldimethylamine, dodecyldimethylamine, dodecyldimethylamine Tertiary amine, didodecyl tertiary amine, bis-octyl methyl tertiary amine, trioctydecyl tertiary amine, octadecyl primary amine, dioctylamine, didecylamine, dodecylamine, diisooctylamine , isooctylamine, n-pentylamine, n-hexylamine, aminopyridine, pyridine, imidazole, pyrrole, dimethylformamide, triethylamine, N-phenylbenzylamine, tetraisopropylamine iodide, hydroxide (2- One or more of hydroxyethyl) trimethylamine. Adding nitrogen-containing compounds promotes the reaction of dimethyldioxane and isobutene on the one hand, improves the selectivity of dimethyldioxane; strengthens the stability of product 3-methyl-3-buten-1-ol on the other hand, Preferably, based on the mass of the carrier, the loading amount of the nitrogen-containing compound may be 1-15 wt%, preferably 2-5 wt%.

According to the carrier of the catalyst of the present invention, preferably, the carrier includes one or more of alumina, silicon oxide and molecular sieve, and has the characteristics of high temperature and high pressure resistance.

The main catalyst can be loaded on the carrier by conventional methods. For example, in the present invention, the main catalyst can be carried on the carrier by the following method:

First weigh a certain mass of one or more of the carrier alumina, silicon oxide, and molecular sieve into the flask, then take two or more metal oxides based on the carrier mass of 5% to 20%, and dissolve them with dilute nitric acid Add the metal oxide to the flask and place it in an ultrasonic container for mixing. The mixed liquid is ultrasonicated for 1 to 4 hours and then allowed to stand for 10 hours before adding a weakly alkaline substance and adjusting the pH of the solution to 10 so that it can be completely solidified on the carrier. After solidification for 5 hours, filter, wash with pure water three times to obtain a solid catalyst, dry the solid catalyst at 125°C, and further roast at 540°C for 4.5h, and finally obtain a composite metal with uniform particle size and good dispersibility catalyst.

In the present invention, cocatalyst can adopt following method to be loaded on the catalyst support that has loaded metal oxide:

First, weigh the carrier particles (such as the composite metal catalyst particles prepared above) loaded with the metal oxide of the main catalyst, heat (for example, add it to an oil bath) to 50-100° C., weigh the nitrogen-containing compound and add it to the heated carrier particles. , and use an organic solvent to dissolve and mix (for example, stirring or ultrasonic 1 ~ 5h), then remove the solvent, wash (for example, use ethanol to wash), and dry the obtained composite metal catalyst loaded with nitrogen-containing compounds (for example, put drying at 120°C), and further calcined (for example, at 250°C for 3 hours), to obtain a composite metal catalyst loaded with nitrogen-containing compounds.

In the preparation method of the catalyst of the present invention, the carrier and the metal oxide are mixed in an ultrasonic container, and the mixed solution is ultrasonicated for 1 to 4 hours and then left to stand for 10 hours. One or more of them, the pH of the solution is adjusted to 10, and the metal oxide can be solidified and completely attached to the carrier. Preferably, the nitrogen-containing compound is blended with the composite metal catalyst particles, and the blended organic solvent includes but not limited to one or more of toluene, xylene, chlorobenzene, dichlorobenzene, ethylbenzene, one preferred In the scheme, it is carried out in a nitrogen atmosphere during the blending process of the nitrogen compound and the composite metal catalyst particles, and specifically, the subsequent processes include solvent washing and drying.

Preferably, the catalyst is mechanically ground, and after adding an appropriate amount of polyvinyl alcohol and azure powder, it is dried, calcined, ground, sieved and separated to obtain a solid catalyst with a particle size of 30-100 mesh, preferably 50-80 mesh.

Since the stability of dimethyldioxane is higher than that of formaldehyde and formaldehyde hemiacetal, and there will be no multiple structures such as monomers, dimers, and polymers, no formaldehyde is generated during the reaction, making the reaction more stable. Adding catalyst, and adjusting temperature and pressure can obtain higher conversion rate and selectivity. Since there is no formaldehyde residue and high polymer in the reaction solution, it is not necessary to remove formaldehyde in the subsequent separation process. Since there is no solvent and other components, the separation process is more efficient, and finally 3-methyl-3 The isolated yield of -buten-1-ol was improved.

According to a more specific embodiment of the present invention, a kind of method for synthesizing 3-methyl-3-buten-1-ol comprises:

(1) first use nitrogen or inert gas to purge the reactor, and completely replace the air in the reactor;

(2) Pass isobutene through a preheater and heat it to the required temperature of 100-300°C, preferably 150-220°C, while preheating dimethyldioxane through the preheater to reach the required temperature of 60-140°C , more preferably 80-120°C;

(3) above-mentioned two stock materials are mixed by mixer, and mixed material enters fixed-bed reactor continuously, reacts and generates 3-methyl-3-butene-1-alcohol under the effect of catalyst;

(4) The reaction solution is subjected to pressurized rectification and separation after cooling down to separate the unreacted isobutene, and the remaining reaction solution enters the weight-removing rectification tower, and 3-methyl-3-butene-1-ol is extracted from the side line Mining, you can get high-purity 3-methyl-3-buten-1-ol.

In the above preparation step (3), the reaction pressure is preferably 6MPa-10MPa, the reaction temperature is preferably 160-200°C, and the reaction time is preferably 15min-30min.

The molar ratio of the feed isobutene and dimethyldioxane in the above preparation step (3) is preferably 5-8:2-4.

Compared with the prior art, the method for preparing 3-methyl-3-buten-1-ol of the present invention has the following beneficial effects:

(1) Using dimethyldioxane instead of formaldehyde, the reaction raw materials are easy to obtain, the by-products are few, and there is no formaldehyde residue, which solves the problems of low formaldehyde conversion rate and difficult separation and removal, and improves product quality;

(2) The reaction conditions are more mild and reliable, the side reactions are reduced, the preparation is simple, the fixed bed operation is used, and the continuous production improves the production efficiency and reduces the operation risk;

(3) The conversion rate of raw material dimethyl dioxane is over 99% and the selectivity of isobutene is over 98%.

detailed description

In order to better understand the technical solution of the present invention, the content of the present invention will be further described below in conjunction with the examples, but the content of the present invention is not limited only to the following examples. The detection method used in the embodiment is described below:

Adopt gas chromatograph to detect dimethyl dioxane conversion rate and selectivity, concrete analysis condition is as follows:

Chromatographic instrument: Agilent 7890A, chromatographic column model: HP-5, inner diameter: 320.00μm, length: 30.0m, maximum temperature: 325.0°C. The temperature rise program, first keep at 40°C for 1 minute, then raise the temperature at 10°C/min to 140°C and hold for 2 minutes, then raise the temperature at 20°C/min to 280°C and keep for 6 minutes, the total running time is 30 minutes.

The dimethyldioxane used in the examples is all obtained from formaldehyde and isobutylene by the following method: first select 500g of Cu-Al-MCM-41 molecular sieve as a catalyst, fill the catalyst in the reactor, and heat up after nitrogen replacement to 96°C, then use the isobutylene replacement reaction system, control the back pressure valve at the outlet of the reactor to adjust the pressure inside the reactor to 2MPa, preheat isobutene to 100°C, feed rate 30g/h, preheat 37% formaldehyde solution to 95°C, the feed rate is 150g/h, the mixing temperature of the two enters the reactor at 96°C, and the reaction time is 5.8h. After the reaction liquid is cooled, dimethyldioxane with a purity close to 100% can be obtained through simple separation. The conversion rate of isobutene reaches over 96%, and the selectivity of dimethyl dioxane is 100%.

Example 1

Catalyst preparation

Weigh 500g of molecular sieve into the flask, then take 25g of manganese oxide and 25g of barium oxide, add dilute nitric acid to dissolve the metal oxide, add it to the flask, and place it in an ultrasonic container for mixing. Add ammonia water after 10 hours, and adjust the pH of the solution to 10, filter after curing for 5 hours, wash with pure water three times to obtain a solid catalyst, dry the solid catalyst at 125°C, and roast at 540°C for 4.5h to obtain Composite metal catalysts. Weigh 12g of tetradecyldimethyl tertiary amine, add toluene to dissolve, take 300g of the prepared composite metal catalyst, mix and add to an oil bath, heat to 80°C, stir or ultrasonic for 2h, then remove the solvent, use ethanol Washing, drying at 120° C., calcination at 250° C. for 3 hours, and final processing to obtain a 60-mesh nitrogen-loaded composite metal catalyst.

Synthesis of 3-methyl-3-buten-1-ol experiment

1) Take 200g of the above-mentioned catalyst and add it to the fixed bed, and use nitrogen to replace the air in the fixed bed;

2) Preheat the isobutylene to 190°C, feed it into the mixer and the fixed bed at a flow rate of 16g/min, set the temperature of the fixed bed to 180°C, adjust the back pressure valve to control the pressure of the reactor at 8MPa, and put the two Methyldioxane was preheated to 120°C, passed into the mixer at a flow rate of 7.5g/min to mix with isobutylene, entered the reactor for reaction, and continued to react for 12 hours;

3) The temperature of the reaction solution is lowered, and the pressure is reduced to 0.5MPa. After isobutene is separated, the reaction solution is rectified and separated to obtain the product 3-methyl-3-butene-1-ol, which is analyzed by gas chromatography. -3-buten-1-ol content, the calculated yield is 97.5%.

Example 2

Catalyst preparation

Weigh 500g of alumina and add it to the flask, then take 30g of calcium oxide and 20g of iron oxide, add dilute nitric acid to dissolve the metal oxide, add it to the flask, and place it in an ultrasonic container for mixing. Add ammonium bicarbonate after standing for 10 hours, and adjust the pH of the solution to 11, filter after curing for 4.5 hours, wash with pure water three times to obtain a solid catalyst, dry the solid catalyst at 125°C, and roast at 540°C 5h, a composite metal catalyst was obtained. Weigh 15g of phthalimide, add toluene to dissolve, take 300g of the prepared composite metal catalyst, mix and add it to an oil bath, heat to 100°C, stir or sonicate for 2h, then remove the solvent, and wash with ethanol , placed in the condition of 120° C. for drying, and calcination for 3.5 hours at 250° C., and finally processed to obtain a 70-mesh nitrogen-loaded composite metal catalyst.

Synthesis of 3-methyl-3-buten-1-ol experiment

Adopt the synthesis method of Example 1, the difference is: isobutylene is preheated to 170 ℃, feeds in the mixer and the fixed bed with the flow rate of 18g/min, and the fixed bed temperature is set at 200 ℃, adjusts the back pressure valve to make the reactor The pressure is controlled at 10MPa. After the pressure is stable, the dimethyldioxane is preheated to 100°C, passed into the mixer at a flow rate of 5g/min to mix with isobutylene, and then enters the reactor for reaction. The reaction is continued for 12 hours, and the final calculation is 3- The yield of methyl-3-buten-1-ol was 97.8%.

Example 3

Catalyst preparation

Weigh 500g of molecular sieve into the flask, then take 26g of copper oxide and 15g of zinc oxide, add dilute nitric acid to dissolve the metal oxide, add it to the flask, and place it in an ultrasonic container for mixing. After 10 hours, add ammonium bicarbonate, and adjust the pH of the solution to 11, filter after curing for 4.5 hours, wash with pure water three times to obtain a solid catalyst, dry the solid catalyst at 125°C, and roast at 540°C for 5 hours , to obtain a composite metal catalyst. Weigh 8.5g of dioctylamine, add toluene to dissolve, take 300g of the prepared composite metal catalyst, mix and add to an oil bath, heat to 100°C, stir or sonicate for 2h, then remove the solvent, wash with ethanol, put Drying was carried out at 120° C., followed by calcination at 250° C. for 3.5 hours. After final processing, an 80-mesh composite metal catalyst loaded with nitrogen was obtained.

Synthesis of 3-methyl-3-buten-1-ol experiment

Adopt the synthetic method of embodiment 1, difference is: isobutylene is preheated to 200 ℃, feeds in the mixer and the fixed bed with the flow rate of 20g/min, and the fixed bed temperature is set as 190 ℃, adjusts the back pressure valve to make the reactor The pressure is controlled at 9MPa. After the pressure is stable, the dimethyldioxane is preheated to 95°C, passed into the mixer at a flow rate of 3g/min to mix with isobutylene, and then enters the reactor for reaction. The reaction is continued for 12 hours, and the final calculation is 3- The yield of methyl-3-buten-1-ol was 97.4%.

Example 4

Catalyst preparation

Weigh 500g of silicon oxide into the flask, then take 40g of strontium oxide and 30g of magnesium oxide, add dilute nitric acid to dissolve the metal oxides, add them to the flask, and place them in an ultrasonic container for mixing. The mixture is ultrasonicated for 8 hours and then allowed to stand After 12 hours, add ammonium bicarbonate, and adjust the pH of the solution to 11, filter after curing for 7.5 hours, wash with pure water three times to obtain a solid catalyst, dry the solid catalyst at 130°C, and roast at 530°C for 8 hours , to obtain a composite metal catalyst. Weigh 25g of propionolactam, add toluene to dissolve, take 300g of the prepared composite metal catalyst, mix and add to an oil bath, heat to 110°C, stir or sonicate for 7h, then remove the solvent, wash with ethanol, put in 130 Drying at ℃, followed by calcination at 250°C for 5 hours, and final processing to obtain 80-mesh nitrogen-loaded composite metal catalyst.

Synthesis of 3-methyl-3-buten-1-ol experiment

Adopt the synthesis method of Example 1, the difference is: isobutylene is preheated to 160 ℃, feeds in the mixer and the fixed bed with the flow rate of 30g/min, and the fixed bed temperature is set as 170 ℃, adjusts the back pressure valve to make the reactor The pressure is controlled at 9MPa. After the pressure is stabilized, the dimethyldioxane is preheated to 110°C. It is passed into the mixer at a flow rate of 4g/min to mix with isobutylene, and enters the reactor for reaction. The reaction is continued for 12 hours, and the final calculation is 3- The yield of methyl-3-buten-1-ol was 97.2%.

Example 5

Catalyst preparation

Weigh 500g of molecular sieve into the flask, then take 15g of barium oxide and 25g of magnesium oxide, add dilute nitric acid to dissolve the metal oxide, add it to the flask, and place it in an ultrasonic container for mixing. The mixed solution is ultrasonicated for 4 hours and then allowed to stand for 6 hours Then add ammonium bicarbonate, adjust the pH of the solution to 11, filter after curing for 4.5 hours, wash with pure water three times to obtain a solid catalyst, dry the solid catalyst at 130°C, and roast at 530°C for 6h. A composite metal catalyst is obtained. Weigh 8g of caprolactam, add toluene to dissolve, take 300g of the prepared composite metal catalyst, mix and add it to an oil bath, heat to 110°C, stir or sonicate for 5h, then remove the solvent, wash with ethanol, and put it in the condition of 130°C drying at 250°C for 4 hours, and finally processed to obtain a 70-mesh composite metal catalyst loaded with nitrogen.

Synthesis of 3-methyl-3-buten-1-ol experiment

Adopt the synthetic method of embodiment 1, difference is: isobutylene is preheated to 160 ℃, feeds in the mixer and the fixed bed with the flow rate of 80g/min, and the fixed bed temperature is set as 180 ℃, adjusts the back pressure valve to make the reactor The pressure is controlled at 10MPa. After the pressure is stabilized, the dimethyldioxane is preheated to 120°C, passed into the mixer at a flow rate of 12g/min to mix with isobutylene, and then enters the reactor for reaction. The reaction is continued for 12 hours, and the final calculation is 3- The yield of methyl-3-buten-1-ol was 97.7%.

Example 6

Catalyst preparation

Weigh 500g of molecular sieve into the flask, then take 50g of manganese oxide and 12g of barium oxide, add dilute nitric acid to dissolve the metal oxide, add it to the flask, and place it in an ultrasonic container for mixing. The mixed solution is ultrasonicated for 7 hours and then allowed to stand for 8 hours Then add ammonium bicarbonate, adjust the pH of the solution to 11, filter after curing for 7.5 hours, wash with pure water three times to obtain a solid catalyst, dry the solid catalyst at 130°C, and roast at 530°C for 8 hours. A composite metal catalyst is obtained. Weigh 22g of dimethylaniline, add toluene to dissolve, take 300g of the prepared composite metal catalyst, mix and add to an oil bath, heat to 110°C, stir or sonicate for 8h, then remove the solvent, wash with ethanol, put Drying was performed at 130° C., followed by calcination at 250° C. for 5 hours, and finally processed to obtain a 65-mesh nitrogen-loaded composite metal catalyst.

Synthesis of 3-methyl-3-buten-1-ol experiment

Adopt the synthetic method of embodiment 1, difference is: isobutylene is preheated to 190 ℃, feeds in the mixer and the fixed bed with the flow rate of 10g/min, and the fixed bed temperature is set at 200 ℃, adjusts the back pressure valve to make the reactor The pressure is controlled at 7MPa. After the pressure is stabilized, the dimethyldioxane is preheated to 110°C. It is passed into the mixer at a flow rate of 2g/min to mix with isobutylene, and then enters the reactor for reaction. The reaction is continued for 12 hours, and the final calculation is 3- The yield of methyl-3-buten-1-ol was 97.1%.

Example 7

Catalyst preparation

Weigh 500g of molecular sieve into the flask, then take 30g of barium oxide and 6g of tin oxide, add dilute nitric acid to dissolve the metal oxide, add it to the flask, and place it in an ultrasonic container for mixing. The mixture is ultrasonicated for 5.5 hours and then left to stand After 7 hours, ammonium bicarbonate was added, and the pH of the solution was adjusted to 11. After solidification for 6.5 hours, it was filtered and washed three times with pure water to obtain a solid catalyst. The solid catalyst was dried at 125°C and roasted at 480°C for 6.5 h, to obtain a composite metal catalyst. Weigh 24g of N-phenylbenzylamine, add toluene to dissolve, take 300g of the prepared composite metal catalyst, mix and add to an oil bath, heat to 115°C, stir or sonicate for 7.5h, then remove the solvent, and use ethanol for Washing, drying at 130°C, calcination at 280°C for 4.5 hours, and final processing to obtain a 70-mesh nitrogen-loaded composite metal catalyst.

Synthesis of 3-methyl-3-buten-1-ol experiment

Adopt the synthesis method of Example 1, the difference is: isobutylene is preheated to 220 ℃, feeds in the mixer and the fixed bed with the flow rate of 20g/min, and the fixed bed temperature is set at 200 ℃, adjusts the back pressure valve to make the reactor The pressure is controlled at 10MPa. After the pressure is stabilized, the dimethyldioxane is preheated to 85°C. It is passed into the mixer at a flow rate of 4g/min to mix with isobutylene, and enters the reactor for reaction. The reaction is continued for 24 hours, and the final calculation is 3- The yield of methyl-3-buten-1-ol was 97.4%.

Comparative example 1

According to the existing technology, formaldehyde methanol hemiacetal is used as raw material to synthesize 3-methyl-3-buten-1-ol. The formaldehyde methanol hemiacetal is first heated to 290°C, pressurized to 19MPa, and isobutylene is heated to 290°C , pressurized to 19MPa, the two are mixed and then enter the tubular reactor, the reaction time is 4min, after the reaction is completed, methanol is rectified and separated, the conversion rate of formaldehyde to methanol hemiacetal is 98.9%, and the selectivity is 98.6%.

Comparative example 2

According to the prior art, paraformaldehyde is used as raw material to synthesize 3-methyl-3-buten-1-ol. Firstly, paraformaldehyde is depolymerized with methylal in the reactor, and the temperature is controlled at 150°C. The reaction is 3 hours to obtain a transparent solution in the state; add isobutene to the reactor, the mass ratio of olefin to aldehyde is 10, the reaction temperature is 230°C, the reaction pressure is 15-16MPa, the reaction time is 3h, the reaction material is released and rectified to separate isobutene, methanol and methylal, corresponding The highest yield of paraformaldehyde is 93.5%.

It can be seen from comparative example 1 that using formaldehyde methanol hemiacetal as a raw material to synthesize 3-methyl-3-buten-1-ol requires high temperature and pressure. From the perspective of reactor design and process safety, it is proposed that The requirement is very large and the cost is higher. Although the methanol produced by the reaction can be reused after rectification and separation, it also increases energy consumption and cost.

Find out by comparative example 2, take paraformaldehyde as raw material to synthesize methylal and then react with isobutene to synthesize 3-methyl-3-buten-1-alcohol, the required reaction time is 3h, because the prolongation of reaction time, production capacity It will be limited. At the same time, the reactor is a tank reactor. In the process of industrial scale-up, there is a problem of difficult reactor design. The methanol and methylal produced by the reaction need to be separated, which relatively increases the energy consumption.

Combining the comparative example and the method of the present invention, it can be more reflected that the present invention has obvious advantages in raw material selection, process conditions and reactor design, and has more industrial application value.

Claims (18)

1. A method of synthesizing 3-methyl-3-buten-1-ol, the method comprising: in the presence of a catalyst, reacting isobutene with dimethyldioxane to generate 3-methyl-3-buten-1-ol, wherein the reaction temperature of isobutene and dimethyldioxane is 150 to 220 ℃, and the reaction pressure is 4 to 15MPa; the reaction is carried out in an inert atmosphere, the catalyst comprises a main catalyst and an auxiliary catalyst, the main catalyst is a metal oxide, the auxiliary catalyst is a nitrogen-containing compound, and the metal oxide is two or more selected from magnesium oxide, calcium oxide, manganese oxide, barium oxide, iron oxide, copper oxide, zinc oxide, tin oxide and strontium oxide;

the cocatalyst is selected from one or more of imide, carbamide, fatty amine, aromatic amine, nitrogen-containing heterocycle and quaternary ammonium base.

2. The process according to claim 1, wherein dimethyldioxane as a starting material is prepared from formaldehyde and isobutylene under acidic catalyst conditions; the acidic catalyst is one or more of sulfuric acid, phosphoric acid, hydrochloric acid, solid acid and heteropoly acid, and the mass ratio of fed formaldehyde to isobutene is (1) - (8).

3. The process as claimed in claim 2, wherein the dimethyldioxane is prepared at a temperature of from 60 to 100 ℃ and a reaction time of from 4 to 8h.

4. The process as claimed in claim 1, wherein the reaction temperature of isobutene and dimethyldioxane is from 160 to 200 ℃; the reaction pressure is 6MPa to 10MPa.

5. The process of claim 4, wherein the reaction time of the isobutylene and the dimethyldioxane is from 10min to 60min.

6. The process as claimed in claim 5, wherein the reaction time of isobutene with dimethyldioxane is from 15min to 30min.

7. The process as claimed in any one of claims 1 to 6, wherein the molar ratio of isobutene to dimethyldioxane is from 3 to 10:1~5.

8. The process of claim 7 wherein the molar ratio of isobutylene to dimethyldioxane is 5~8:2~4.

9. The process according to any one of claims 1 to 6, wherein the reaction is carried out under a nitrogen atmosphere and in a fixed bed reactor filled with a catalyst.

10. The method according to claim 1, wherein the loading amount of the main catalyst metal oxide is 3 to 40wt% and the loading amount of the cocatalyst nitrogen-containing compound is 1 to 15wt% based on the mass of the carrier.

11. The process of claim 10, wherein the main catalyst metal oxide loading is from 5 to 20wt% and the cocatalyst nitrogen-containing compound loading is from 2 to 5wt%, based on the mass of the carrier.

12. The method of claim 1, wherein the metal oxide is manganese oxide and barium oxide, calcium oxide and iron oxide, copper oxide and zinc oxide, or strontium oxide and magnesium oxide.

13. The method of claim 1, wherein the metal oxide comprises at least one alkaline earth metal oxide and an oxide of at least one selected from iron, copper, tin, manganese, strontium.

14. The process according to any one of claims 1, 12 and 13, wherein the co-catalyst is selected from one or more of phthalimide, propiolactam, caprolactam, dimethylaniline, p-toluidine, methylethylcyclopropylamine, p-chloroaniline, tetradecyldimethylamine, dodecyldimethyl tertiary amine, decaalkyldimethyl tertiary amine, didodecyltrimethyl tertiary amine, dioctadecyltertiary amine, octadecylamine, dioctylamine, didecylamine, dodecylamine, diisooctylamine, isooctylamine, N-pentylamine, N-hexylamine, aminopyridine, pyridine, imidazole, pyrrole, dimethylformamide, triethylamine, N-phenylbenzenemethamine, tetraisopropylamine iodide, and (2-hydroxyethyl) trimethylamine hydroxide.

15. The process of any one of claims 1, 12 and 13, wherein the support comprises one or more of alumina, silica, molecular sieves.

16. The process of any one of claims 1, 12 and 13, wherein the promoter is loaded onto the metal oxide-loaded catalyst support by:

firstly weighing a carrier carrying a main catalyst metal oxide, heating to 50-100 ℃, weighing a nitrogen-containing compound, adding the nitrogen-containing compound into the heated carrier, dissolving and mixing the nitrogen-containing compound and the heated carrier by using an organic solvent, then removing the solvent, washing, drying the obtained nitrogen-containing compound-loaded composite metal catalyst, and further roasting to obtain the nitrogen-containing compound-loaded composite metal catalyst.

17. The method according to any one of claims 1-6, wherein the method comprises the steps of:

(1) Firstly, nitrogen or inert gas is used for purging the reactor, and air in the reactor is completely replaced;

(2) Heating isobutene to the required temperature of 100-300 ℃ through a preheater, and simultaneously preheating dimethyldioxane to the required temperature of 60-140 ℃ through the preheater;

(3) Mixing the two materials through a mixer, continuously feeding the mixed materials into a fixed bed reactor, and reacting under the action of a catalyst to generate 3-methyl-3-butene-1-ol;

(4) And (3) cooling the reaction liquid, then performing pressure rectification separation, separating unreacted isobutene, introducing the residual reaction liquid into a de-heavy rectifying tower, and extracting the 3-methyl-3-butene-1-ol from a lateral line to obtain the high-purity 3-methyl-3-butene-1-ol.

18. The process as claimed in claim 17, wherein in step (2), the isobutylene is passed through a preheater and heated to a desired temperature of 150 to 220 ℃, and the dimethyldioxane is simultaneously passed through the preheater and preheated to a desired temperature of 80 to 120 ℃.