CN112225645A - Preparation method of m-cresol - Google Patents
Preparation method of m-cresol Download PDFInfo
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- CN112225645A CN112225645A CN202010978269.2A CN202010978269A CN112225645A CN 112225645 A CN112225645 A CN 112225645A CN 202010978269 A CN202010978269 A CN 202010978269A CN 112225645 A CN112225645 A CN 112225645A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
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- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/06—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by conversion of non-aromatic six-membered rings or of such rings formed in situ into aromatic six-membered rings, e.g. by dehydrogenation
- C07C37/07—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by conversion of non-aromatic six-membered rings or of such rings formed in situ into aromatic six-membered rings, e.g. by dehydrogenation with simultaneous reduction of C=O group in that ring
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- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/61—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups
- C07C45/67—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton
- C07C45/68—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms
- C07C45/72—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms by reaction of compounds containing >C = O groups with the same or other compounds containing >C = O groups
- C07C45/74—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms by reaction of compounds containing >C = O groups with the same or other compounds containing >C = O groups combined with dehydration
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- C07C2601/16—Systems containing only non-condensed rings with a six-membered ring the ring being unsaturated
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Abstract
The invention provides a method for synthesizing m-cresol by condensation and dehydrogenation reactions, which comprises the following steps: c4 condensation reaction between aldehyde or ketone and acetone under the catalysis of alkali to obtain 5-methyl-2-cyclohexenone intermediate, and dehydrogenating and aromatizing the intermediate in the presence of dehydrogenation catalyst to obtain m-cresol. The method has a novel synthetic route, uses cheap and easily-obtained C4 aldehyde or ketone and acetone as starting raw materials, obtains m-cresol through 2-step reaction, and has the advantages of short synthetic route, high yield and better cost advantage. Secondly, the invention adopts solid alkali as a catalyst, phosphate ester as a reaction promoter, and a reaction substrate is subjected to condensation reaction in a gas phase to obtain the cyclohexenone intermediate with high selectivity.
Description
Technical Field
The invention belongs to the field of fine chemical engineering, and particularly relates to a method for synthesizing m-cresol by using C4 aldehyde or ketone and acetone as raw materials, firstly performing condensation reaction, and then performing dehydroaromatization.
Background
M-cresol, the scientific name 3-methylphenol, is one of the simplest alkylphenols. The m-cresol is colorless or light yellow liquid, has phenol smell, naturally exists in organisms, and has a boiling point of 202.2 ℃ and a melting point of 12.2 ℃. The m-cresol has wide application range and has corresponding application in the fields of pesticides, medicines, synthetic materials, spices, organic dyes and the like.
In view of the wide application and great demand of m-cresol, there are several industrial processes for m-cresol production, including natural extraction and chemical synthesis. As early as the four and fifty years of the last century, people began extracting m-cresol from coal tar. The coal tar contains various phenolic compounds, such as phenol, m-cresol, p-cresol, xylenol and the like, and generally accounts for 2-5 wt% of the mass fraction of the coal tar. The process for separating cresol from coal tar is complex and high in cost, and the amount of cresol produced by the method is reduced year by year from the nineties of the last century. M-cresol can also be extracted from refinery spent caustic, and only a few U.S. plants currently use this process.
The m-cresol which is sold in the market at present is mainly obtained by artificial synthesis, and the synthesis methods comprise a toluenesulfonic acid alkali fusion method, a chlorotoluene hydrolysis method, an cymene peroxide cracking method and a phenol alkylation method. The toluene sulfonic acid alkali fusion method is to melt the mixture of toluene sulfonic acid and sodium hydroxide at high temperature and promote the reaction of the toluene sulfonic acid and the sodium hydroxide to obtain cresol; however, this process gives predominantly p-cresol, with only a small amount of m-cresol (around 10%) (s.w. eglund, r.s. aries, d.f. othmer, ind.eng.chem.1953,45,189.).
The hydrolysis method of chlorotoluene is one of the main methods for producing m-cresol at present, and the German Bayer company adopts the method to produce m-cresol; the first step of the synthesis, toluene chlorination, gives a mixture of o-chlorotoluene and p-chlorotoluene, which is hydrolyzed at high temperature (above 360 ℃) with aqueous sodium hydroxide to give a mixture of o-, m-and p-cresols in a ratio of more than 1:2:1, predominantly m-cresol (r.n. shreve, c.j. marsel, ind. eng. chem.1946,38,254.). Because the boiling points of m-cresol and p-cresol only differ by 0.4 ℃, the separation of the m-cresol and the p-cresol is very complicated, and the m-cresol and the p-cresol are generally separated by adopting a method of multiple crystallization purification or alkylation-rectification-dealkylation. The peroxide cracking method of cymene is a main method for producing m-cresol, peroxide is involved in the production process, and the obtained mixture of m-cresol and p-cresol is complicated to separate and purify (H.Kaminata, Kagakushi Kenkyu 1998,25, 126).
Patents (US4128728, US3857892) reported that crotonaldehyde or methyl vinyl ketone is condensed with 3-pentanone and then dehydroaromatized to synthesize trimethylphenol by basf and hofmaro, but crotonaldehyde and acetone do not easily react in a liquid state to close a ring, and the condensation of both gives mainly chain-like unsaturated ketones, so that this related method is not used for the synthesis of m-cresol.
In conclusion, m-cresol is a very important basic fine chemical, and is widely used in the fields of medicines, pesticides, perfumes and the like. The existing synthesis method of m-cresol has the problems of harsh reaction conditions (alkali fusion, high-temperature hydrolysis and peroxide cracking), difficult separation and purification of products (separation of m-cresol and p-cresol) and the like. Therefore, the development of a new and efficient synthetic route for m-cresol is urgently needed.
Disclosure of Invention
The invention aims to provide a method for preparing m-cresol, which has mild reaction conditions, does not generate p-cresol which is difficult to separate, is simple and efficient, and reduces the separation cost.
In order to achieve the purpose and achieve the technical effect, the invention adopts the following technical scheme:
a method for preparing m-cresol comprises the following steps: c4 aldehyde or ketone and acetone are used as raw materials, condensation reaction is carried out in a gas phase under the action of a solid base catalyst and a phosphate ester auxiliary agent to obtain a 5-methyl-2-cyclohexenone intermediate, and then the intermediate is subjected to dehydroaromatization under the action of a dehydrogenation catalyst to obtain a metacresol product.
The C4 aldehyde preferably has the formula
the C4 ketone preferably has the structural formula
The reaction scheme is schematically as follows:
in the present invention, the C4 aldehyde or ketone may be, but not limited to, crotonaldehyde, 3-hydroxybutyraldehyde, 3-methoxybutyraldehyde, 3-ethoxybutyraldehyde, 3-acetoxybutyraldehyde, methylvinyl ketone, 4-hydroxy-2-butanone, 4-methoxy-2-butanone, 4-chloro-2-butanone, etc.
In the present invention, the solid base catalyst may be a single metal oxide such as zinc oxide, magnesium oxide, calcium oxide, barium oxide, strontium oxide, etc.; the carrier can be alumina, silica, zirconia, titania, active carbon, etc., and the supported alkali can be metal oxide, metal hydroxide, metal carbonate, metal halide salt, etc., such as lithium oxide, sodium oxide, potassium oxide, magnesium oxide, calcium oxide, zinc oxide, barium oxide, potassium fluoride, sodium hydroxide, sodium carbonate, etc.
In the invention, the condensation reaction is carried out in a gas phase, C4 aldehyde or ketone, acetone and an auxiliary agent are mixed and then vaporized, the mixture passes through a catalyst layer in a gas mode, the condensation reaction is carried out on the surface of a catalyst to obtain cyclohexenone, and the weight hourly space velocity can be 0.01-10.0h-1Preferably 0.1 to 2.0h-1。
In the invention, the feeding molar ratio of the C4 aldehyde or ketone to the acetone can be 5: 1-1: 15, preferably 1: 5-1: 10; the condensation reaction temperature is 200-360 ℃, preferably 260-300 ℃, the reaction pressure is normal pressure or micro positive pressure, and the preferred pressure is not more than 0.5 MPa.
In the invention, the phosphate ester auxiliary agent can be one or more of, but is not limited to, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate and triisobutyl phosphate, and trimethyl phosphate and triethyl phosphate are preferred; the phosphate ester auxiliary agent is used in an amount of 0.01-5.0 mol%, preferably 0.1-1.0 mol% of the molar amount of the C4 aldehyde or ketone; the phosphate ester auxiliary agent and the raw materials are uniformly mixed and then are vaporized and fed together.
In the invention, the condensation reaction is carried out in a continuous mode, the reaction mixture is rapidly cooled after passing through a catalyst layer to obtain a mixture mainly comprising a 5-methyl-2-cyclohexenone intermediate, C4 aldehyde or ketone and acetone, unreacted acetone is separated and recovered by reduced pressure distillation, and then the 5-methyl-2-cyclohexenone intermediate is separated by rectification.
In the present invention, the dehydroaromatization catalyst may be, but is not limited to, palladium carbon, palladium alumina, palladium silica, platinum carbon, ruthenium carbon, rhodium carbon, platinum oxide, etc., and is used in an amount of 0.1 to 5.0 wt%, preferably 0.5 to 2.0 wt%, based on the molar amount of 5-methyl-2-cyclohexenone.
In the present invention, the dehydroaromatization reaction may be carried out without a solvent, or may be carried out in a high boiling point solvent such as trimethylbenzene, tert-butyl, triethylbenzene, decane, undecane, dodecane, etc.; the reaction pressure is normal pressure; and/or the reaction temperature is 150-220 ℃; and/or the reaction time is 2-4 hours.
By adopting the technical scheme, the invention has the following positive effects:
1. the raw materials of the method, such as crotonaldehyde and methyl vinyl ketone, are abundant and easily available, the price is low, the synthetic route is novel, the yield is high, and the cost advantage is achieved;
2. solid alkali is used as a catalyst, phosphate is used as an accelerant to promote main reaction, tar generation is prevented, condensation reaction is carried out in a gas phase mode, and the conversion rate and selectivity of the reaction are obviously improved;
3. the method adopts gas phase condensation to effectively promote intramolecular ring closure of a condensation intermediate; meanwhile, the method is simple and convenient to operate, easy to amplify and good in application prospect.
Detailed Description
The present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.
The main raw material information is as follows:
crotonaldehyde, 3-hydroxybutyraldehyde, 3-methoxybutyraldehyde, Annaiji chemical, 99%; 3-acetoxy butyraldehyde, self-made, with a purity of 99%; methylvinyl ketone, 4-hydroxy-2-butanone, mcelin biochemicals; acetone, trimethyl phosphate, jujude reagent; triethyl phosphate, tripropyl phosphate, saen chemical;
95 percent of zinc oxide, magnesium oxide, barium oxide and Liaoning Haitai; the silicon oxide is loaded with lithium oxide and is prepared by self;
5% palladium carbon, 5% palladium alumina, platinum oxide, and kana catalyst; trimethylbenzene, Shigaku reagent, AR.
The gas chromatography test conditions of the present invention are as follows:
the instrument model is as follows: shimadzu GC-2000; a chromatographic column: agilent Wax (30 m.times.0.25 mm.times.0.25 μm); column temperature: the initial temperature is 40 ℃, the temperature is increased to 100 ℃ at the speed of 5 ℃/min, then the temperature is increased to 250 ℃ at the speed of 15 ℃/min, and the temperature is kept for 6 min; sample inlet temperature: 250 ℃; FID detector temperature: 250 ℃; split-flow sample injection with a split-flow ratio of 40: 1; sample introduction amount: 2.0 mu L; h2Flow rate: 40 mL/min; air flow rate: 320 mL/min.
Example 1:
synthesis of 5-methyl-2-cyclohexenone by vapor phase condensation of crotonaldehyde and acetone
A tubular reactor was used for the vapor phase condensation reaction, the length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle part of the reaction tube was filled with a spherical zinc oxide catalyst (100g, purity 95%), and the top and bottom ends were filled with ceramic ring packings. When the condensation experiment is carried out, firstly, the power supply of the fixed bed reactor is started, the inlet and outlet valves of the carrier gas of the reaction tube are opened, the carrier gas of nitrogen is started, the flow rate is 100mL/min, and the carrier gas of the reaction tube enters from the top and exits from the bottom. Starting a heating sleeve of the reaction tube, and raising the temperature of the reaction tube to 260 ℃; the preheating tank on the feed line was opened for heat tracing and its temperature was raised to 220 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 0.5g/min, and the weight hourly space velocity is 0.3h-1. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. The raw material solution was prepared from crotonaldehyde (154.2g,2.2mol), acetone (638.9g,11.0mol) and triethyl phosphate (3.0g,0.017mol), except forThe solution was observed to be colorless and transparent. After the reaction liquid is discharged from the reaction tube, the reaction liquid is rapidly cooled to change from gas to liquid. The samples were taken periodically and analyzed by GC chromatography after addition of internal standard. The reaction conversion was 59% and the selectivity was 87% (relative to crotonaldehyde).
HRMS-EI M+Calcd for C7H10O:110.0732,found 110.0730。
Example 2:
gas phase condensation synthesis of 5-methyl-2-cyclohexenone from 3-hydroxy butyraldehyde and acetone
A tubular reactor was used for the vapor phase condensation reaction, the length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle part of the reaction tube was filled with a spherical zinc oxide catalyst (100g, purity 95%), and the top and bottom ends were filled with ceramic ring packings. When the condensation experiment is carried out, firstly, the power supply of the fixed bed reactor is started, the inlet and outlet valves of the carrier gas of the reaction tube are opened, the carrier gas of nitrogen is started, the flow rate is 35mL/min, and the carrier gas of the reaction tube enters from the top and exits from the bottom. Starting a heating sleeve of the reaction tube, and raising the temperature of the reaction tube to 270 ℃; the preheating tank on the feed line was opened for heat tracing and its temperature was raised to 220 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 0.17g/min, and the weight hourly space velocity is 0.1h-1. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. The raw material liquid was prepared from 3-hydroxybutyraldehyde (141.0g,1.6mol), acetone (500.0g,8.6mol) and trimethyl phosphate (2.24g,0.016mol), and was a colorless transparent solution in appearance. After the reaction liquid is discharged from the reaction tube, the reaction liquid is rapidly cooled to change from gas to liquid. The samples were taken periodically and analyzed by GC chromatography after addition of internal standard. The reaction conversion rate is 55 percent, and the selectivity is 89 percent.
Example 3:
gas phase condensation synthesis of 5-methyl-2-cyclohexenone from 3-methoxybutyraldehyde and acetone
First, a raw material solution was prepared of 3-methoxybutyraldehyde (143.0g,1.4mol), acetone (813.1g,14.0mol), and trimethyl phosphate (0.2g,0.0014mol), and the appearance was a colorless transparent solution. Starting a power supply of the fixed bed device, introducing 120mL/min of nitrogen carrier gas, and allowing the carrier gas of the reaction tube to enter and exit from the reaction tube; starting a preheating tank and a reaction tube for heating, and respectively heating to 220 ℃ and 280 DEG C. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 1.0g/min, and the weight hourly space velocity is 0.6h-1. The length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle portion of the reaction tube was filled with a spherical barium oxide catalyst (100g, purity 95%), and the top and bottom ends were filled with ceramic ring packings. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. After the reaction liquid is discharged from the reaction tube, the reaction liquid is rapidly cooled to change from gas to liquid. The samples were taken periodically and analyzed by GC chromatography after addition of internal standard. The reaction conversion rate is 53 percent, and the selectivity is 85 percent.
Example 4:
gas phase condensation synthesis of 5-methyl-2-cyclohexenone from 3-acetoxy butyraldehyde and acetone
First, a raw material solution was prepared of 3-acetoxybutyraldehyde (273.3g,2.1mol), acetone (610.0g,10.5mol), and trimethyl phosphate (7.65g,0.042mol), and the appearance was a colorless transparent solution. Starting a power supply of the fixed bed device, introducing nitrogen carrier gas of 200mL/min, and allowing the carrier gas of the reaction tube to enter and exit from the reaction tube; starting a preheating tank and a reaction tube for heating, and respectively heating to 230 ℃ and 300 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 3.3g/min, and the weight hourly space velocity is 2.0h-1. The length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle portion of the reaction tube was filled with a spherical magnesium oxide catalyst (100g, purity 95%), and the top and bottom ends were filled with ceramic ring packings. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. After the reaction liquid is discharged from the reaction tube, the reaction liquid is rapidly cooled to change from gas to liquid. The samples were taken periodically and analyzed by GC chromatography after addition of internal standard. The reaction conversion rate was 53% and the selectivity was 82%.
Example 5:
synthesis of 5-methyl-2-cyclohexenone by vapor phase condensation of methyl vinyl ketone and acetone
A tubular reactor was used for the vapor phase condensation reaction, the length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle part of the reaction tube was filled with a spherical zinc oxide catalyst (105g, purity 95%), and the top and bottom ends were filled with ceramic ring packings. When condensation experiments are carried out, firstly, the power supply of the fixed bed reactor is started, and the carrier gas inlet and outlet valves of the reaction tube are openedAnd starting nitrogen carrier gas, wherein the flow rate is 90mL/min, and the carrier gas enters from the upper part of the reaction tube and exits from the lower part of the reaction tube. Starting a heating sleeve of the reaction tube, and raising the temperature of the reaction tube to 260 ℃; the preheating tank on the feed line was opened for heat tracing and its temperature was raised to 230 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 0.7g/min, and the weight hourly space velocity is 0.4h-1. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. The raw material liquid was prepared from methyl vinyl ketone (161.2g,2.3mol), acetone (801.5g,13.8mol) and tripropyl phosphate (3.9g,0.017mol), and was a colorless transparent solution in appearance. After the reaction liquid is discharged from the reaction tube, the reaction liquid is rapidly cooled to change from gas to liquid. The samples were taken periodically and analyzed by GC chromatography after addition of internal standard. The reaction conversion rate is 61 percent, and the selectivity is 90 percent.
HRMS-EI M+Calcd for C7H10O:110.0732,found 110.0732。
Example 6:
synthesis of 5-methyl-2-cyclohexenone by gas phase condensation of 4-hydroxy-2-butanone and acetone
A tubular reactor was used for the vapor phase condensation reaction, the length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle part of the reaction tube was filled with spherical silica-supported sodium oxide (110g,0.2 wt% sodium oxide), and the top and bottom ends were filled with ceramic ring fillers. When the condensation experiment is carried out, firstly, the power supply of the fixed bed reactor is started, the inlet and outlet valves of the carrier gas of the reaction tube are opened, the carrier gas of nitrogen is started, the flow rate is 90mL/min, and the carrier gas of the reaction tube enters from the top and exits from the bottom. Starting a heating sleeve of the reaction tube, and raising the temperature of the reaction tube to 260 ℃; the preheating tank on the feed line was turned on for heat tracing and its temperature was raised to 210 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 0.83g/min, and the weight hourly space velocity is 0.45h-1. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. The raw material liquid was prepared from 4-hydroxy-2-butanone (176.2g,2.0mol), acetone (581g,10.0mol), and triethyl phosphate (3.64g,0.02mol), and was a colorless transparent solution in appearance. After the reaction liquid is discharged from the reaction tube, the reaction liquid is rapidly cooled to change from gas to liquid. The samples were taken periodically and analyzed by GC chromatography after addition of internal standard. Reaction conversion rate up to55 percent and selectivity is 83 percent.
Example 7:
synthesis of 5-methyl-2-cyclohexenone by vapor phase condensation of methyl vinyl ketone and acetone
First, a feed solution was prepared, and methyl vinyl ketone (287.4g,4.1mol), acetone (1428.7g,24.6mol) and triethyl phosphate (3.7g,0.021mol) were mixed uniformly to obtain a transparent liquid. A tubular reactor was used for the vapor phase condensation reaction, the length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle part of the reaction tube was filled with a spherical zinc oxide catalyst (120g, purity 95%), and the top and bottom ends were filled with ceramic ring packings. When the condensation experiment is carried out, firstly, the power supply of the fixed bed reactor is started, the inlet and outlet valves of the carrier gas of the reaction tube are opened, the carrier gas of nitrogen is started, the flow rate is 150mL/min, and the carrier gas of the reaction tube enters from the top and exits from the bottom. Starting a heating sleeve of the reaction tube, and raising the temperature of the reaction tube to 280 ℃; the preheating tank on the feed line was opened for heat tracing and its temperature was raised to 220 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 1.6g/min, and the weight hourly space velocity is 0.8h-1. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. After the reaction liquid is discharged from the reaction tube, the reaction liquid is rapidly cooled to change from gas to liquid. The reaction mixture was collected for 2 to 8 hours and had a mass of about 570 g. GC detection showed that the reaction had a conversion of 61% and a selectivity of 88%.
Example 8:
synthesis of 5-methyl-2-cyclohexenone by vapor phase condensation of crotonaldehyde and acetone
A tubular reactor was used for the vapor phase condensation reaction, the length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle part of the reaction tube was filled with a spherical zinc oxide catalyst (100g, purity 98%), and the top and bottom ends were filled with ceramic ring packings. When the condensation experiment is carried out, firstly, the power supply of the fixed bed reactor is started, the inlet and outlet valves of the carrier gas of the reaction tube are opened, the carrier gas of nitrogen is started, the flow rate is 35mL/min, and the carrier gas of the reaction tube enters from the top and exits from the bottom. Starting a heating sleeve of the reaction tube, and raising the temperature of the reaction tube to 250 ℃; the preheating tank on the feed line was opened for heat tracing and its temperature was raised to 230 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 1.1g/min, and the weight hourly space velocity is 0.66h-1. Original sourceThe feed liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. The raw material solution was prepared from crotonaldehyde (630.81g,9.0mol), acetone (261.36g,4.5mol), and trimethyl phosphate (1.64g,0.009 mol). After the reaction liquid is discharged from the reaction tube, a cooling tank is carried out, and non-condensable gas such as nitrogen is emptied from the upper part of the cooling tank. Samples were taken periodically and analyzed by GC after addition of internal standard. The reaction conversion rate is 23 percent, and the selectivity is 81 percent.
Example 9:
synthesis of 5-methyl-2-cyclohexenone by vapor phase condensation of crotonaldehyde and acetone
A tubular reactor was used for the vapor phase condensation reaction, the length of the reaction tube was 60cm, the inner diameter was 2.3cm, the middle part of the reaction tube was filled with a spherical zinc oxide catalyst (100g, purity 98%), and the top and bottom ends were filled with ceramic ring packings. When the condensation experiment is carried out, firstly, the power supply of the fixed bed reactor is started, the inlet and outlet valves of the carrier gas of the reaction tube are opened, the carrier gas of nitrogen is started, the flow rate is 100mL/min, and the carrier gas of the reaction tube enters from the top and exits from the bottom. Starting a heating sleeve of the reaction tube, and raising the temperature of the reaction tube to 260 ℃; the preheating tank on the feed line was opened for heat tracing and its temperature was raised to 220 ℃. After the temperature of the preheating tank and the reaction tube is stabilized for 0.5h, starting a feed pump to feed the raw material liquid, wherein the feed speed is 0.5g/min, and the weight hourly space velocity is 0.3h-1. The raw material liquid is vaporized in a preheating tank and passes through the high-temperature catalyst layer in a gas form. The starting solution was prepared from crotonaldehyde (154.2g,2.2mol) and acetone (638.9g,11.0mol), and no phosphate was added. After the reaction liquid is discharged from the reaction tube, a cooling tank is carried out, and non-condensable gas such as nitrogen is emptied from the upper part of the cooling tank. Samples were taken periodically and analyzed by GC after addition of internal standard. The reaction conversion rate is 37 percent, and the selectivity is 72 percent.
The reaction solution prepared in the examples 1 to 8 is distilled to remove light components such as acetone, crotonaldehyde and the like, and finally, the 5-methyl-2-cyclohexenone pure product is obtained by rectification.
Example 10:
5-methyl-2-cyclohexenone dehydroaromatization synthesis of m-cresol under catalysis of 5% palladium carbon
5-methyl-2-cyclohexenone (187.3g,1.7mol) and 5% palladium on carbon (1.9g) were added to a 250mL three-necked flask equipped with a magnetic stirrer in this order at room temperature in the air, and the resulting suspension was put in an oil bath, and after replacing the air in the system with nitrogen gas for 3 times, the oil bath was then started to stir and heat, and the reaction was refluxed with rapid stirring. The condensing tube is connected above the three-mouth bottle to prevent the reaction liquid from volatilizing out of the reaction system. And in the dehydrogenation reaction process, nitrogen is continuously and slowly introduced, and the hydrogen byproduct is removed from the reaction system to promote the dehydrogenation reaction to be completely carried out. After reflux reaction at 200 ℃ for 3.5 hours, a sample was taken and analyzed by GC for the composition of the reaction solution, the conversion of 5-methyl-2-cyclohexenone was 93%, and the selectivity of m-cresol was 99%.
HRMS-EI M+Calcd for C7H8O:108.0575,found 108.0577。
Example 11:
5-methyl-2-cyclohexenone dehydroaromatization synthesis of m-cresol by using 5% palladium-aluminum oxide as catalyst
5-methyl-2-cyclohexenone (157.5g,1.43mol), 5% palladium alumina (3.2g) and a trimethylbenzene solvent (100mL) were added to a 250mL three-necked flask equipped with a magnetic stirrer in this order at room temperature in the air, and the resulting suspension was put in an oil bath, and after the air in the system was replaced with nitrogen gas 3 times, the oil bath was then started to stir and heat, and the reaction was refluxed with rapid stirring. The condensing tube is connected above the three-mouth bottle to prevent the reaction liquid from volatilizing out of the reaction system. And in the dehydrogenation reaction process, nitrogen is continuously and slowly introduced, and the hydrogen byproduct is removed from the reaction system to promote the dehydrogenation reaction to be completely carried out. After reflux reaction at 180 ℃ for 4 hours, sampling and GC analyzing the composition of the reaction solution, the conversion rate of 5-methyl-2-cyclohexenone is 98 percent, and the selectivity of m-cresol is 99 percent.
Example 12:
in the air for synthesizing m-cresol by catalyzing 5-methyl-2-cyclohexenone dehydroaromatization by platinum oxide, 5-methyl-2-cyclohexenone (99.1g,0.9mol) and powdered platinum oxide (0.1g) are sequentially added into a 250mL three-necked bottle provided with a magnetic stirrer at room temperature, the obtained suspension is put into an oil bath, the air in the system is replaced by nitrogen for 3 times, then the oil bath is started for stirring and heating, and the reflux reaction is carried out under the rapid stirring. The condensing tube is connected above the three-mouth bottle to prevent the reaction liquid from volatilizing out of the reaction system. And in the dehydrogenation reaction process, nitrogen is continuously and slowly introduced, and the hydrogen byproduct is removed from the reaction system to promote the dehydrogenation reaction to be completely carried out. After reflux reaction at 170 ℃ for 4 hours, sampling and GC analyzing the composition of the reaction solution, the conversion rate of 5-methyl-2-cyclohexenone is 76 percent, and the selectivity of m-cresol is 99 percent.
Comparative example 1:
liquid phase condensation of crotonaldehyde and acetone
Acetone (493.67g,8.5mol), ethanol (300g) as a solvent and solid potassium hydroxide (4.77g,0.085mol) were added into a 3L three-necked flask, the three-necked flask was put into an oil bath at 80 ℃, after the reflux was started, crotonaldehyde (119.15g,1.7mol) as a raw material was slowly added dropwise, and the reaction solution was changed from a white suspension to a brown suspension during the dropwise addition. After the dropwise addition is finished for 3h, stirring at constant temperature for reaction for 4 h. After filtration, samples were taken for analysis and internal standards were added for GC analysis. The reaction conversion rate is 89%, the obtained products are mainly 3, 5-heptadiene-2-ketone, 2-acetol, isopropylidene acetone and the like, and only a small amount of the target product 5-methyl-2-cyclohexenone (accounting for 17%) is contained in the products.
Claims (10)
1. A method for preparing m-cresol is characterized in that: c4 aldehyde or ketone and acetone are used as raw materials, gas phase condensation reaction is carried out under the action of a solid base catalyst and a phosphate ester auxiliary agent to obtain a 5-methyl-2-cyclohexenone intermediate, and then the intermediate is subjected to dehydrogenation and aromatization under the action of a dehydrogenation catalyst to obtain a m-cresol product.
2. The process for producing m-cresol according to claim 1, characterized in that: the C4 aldehyde preferably has the formula
the C4 ketone preferably has the structural formula
3. The method of claim 1, wherein the C4 aldehyde or ketone comprises but is not limited to crotonaldehyde, 3-hydroxybutyraldehyde, 3-methoxybutyraldehyde, 3-ethoxybutyraldehyde, 3-acetoxybutyraldehyde, methyl vinyl ketone, 4-hydroxy-2-butanone, 4-methoxy-2-butanone, 4-chloro-2-butanone.
4. The preparation method according to claims 1-2, characterized in that the solid base catalyst is a single metal oxide, preferably zinc oxide, magnesium oxide, calcium oxide, barium oxide, strontium oxide; or a supported solid alkali, the carrier is alumina, silica, zirconia, titania or activated carbon, the supported alkali is metal oxide, metal hydroxide, metal carbonate or metal halide salt, preferably lithium oxide, sodium oxide, potassium oxide, magnesium oxide, calcium oxide, zinc oxide, barium oxide, potassium fluoride, sodium hydroxide or sodium carbonate.
5. The method of claims 1-4, wherein the reaction weight hourly space velocity is from 0.01 to 10.0h-1Preferably 0.1 to 2.0h-1。
6. The method according to any one of claims 1 to 5, wherein the C4 aldehyde or ketone and acetone are fed in a molar ratio of 5:1 to 1:15, preferably 1:5 to 1: 10; the condensation reaction temperature is 200-360 ℃, preferably 260-300 ℃, and the reaction pressure is normal pressure or micro-positive pressure.
7. The method of any one of claims 1-6, wherein the phosphate ester adjuvant includes, but is not limited to, one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, triisobutyl phosphate, preferably trimethyl phosphate and triethyl phosphate; the phosphate ester auxiliary agent is used in an amount of 0.01-5.0 mol%, preferably 0.1-1.0 mol% of the molar amount of the C4 aldehyde or ketone; the phosphate ester auxiliary agent and the raw materials are uniformly mixed and then are vaporized and fed together.
8. The method according to any one of claims 1 to 7, wherein the condensation reaction is carried out in a continuous manner, the reaction mixture is rapidly cooled after passing through a catalyst layer to obtain a mixture mainly comprising a 5-methyl-2-cyclohexenone intermediate, C4 aldehyde or ketone and acetone, unreacted raw materials are separated and recovered by reduced pressure distillation, and then the 5-methyl-2-cyclohexenone intermediate is separated by rectification.
9. The method of claim 1 wherein the dehydroaromatization catalyst comprises, but is not limited to, palladium on carbon, palladium on alumina, palladium on silica, platinum on carbon, ruthenium on carbon, rhodium on carbon, platinum oxide in an amount of 0.1 to 5.0 wt%, preferably 0.5 to 2.0 wt% of the molar amount of 5-methyl-2-cyclohexenone.
10. The process of any one of claims 1 and 99, wherein the dehydroaromatization reaction is carried out in the absence of a solvent or in a high boiling solvent of trimethylbenzene, t-butyl, triethylbenzene, decane, undecane, dodecane;
the pressure of the dehydroaromatization reaction is normal pressure; and/or the presence of a gas in the gas,
the temperature of the dehydroaromatization reaction is 150-220 ℃; and/or the presence of a gas in the gas,
the dehydroaromatization reaction time is 2-4 hours.
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