JP2000229900A - Method for producing aromatic compound having hydroxyl group - Google Patents

Abstract

(57) [Abstract] (with correction) [PROBLEMS] To produce an aromatic compound having a hydroxyl group directly from coal without using coal tar at lower cost. SOLUTION: Coal is subjected to a pressure of 22 to 40 MPa and a pressure of 37 MPa.
Pyrolysis in supercritical water having a temperature of 4-650 ° C. to produce phenol, cresol, polyhydric phenol or mixtures thereof. Further, when pyrolyzing coal in water in a supercritical state, when an alkali catalyst composed of an alkali metal or alkaline earth metal hydroxide is added, or when carbon monoxide is added, the decomposition rate of coal is increased. And the yield of aromatic compounds is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aromatic compound having a hydroxyl group such as phenol, cresol and polyhydric phenol from coal.

[0002]

2. Description of the Related Art Conventionally, in order to obtain an aromatic compound having a hydroxyl group using coal as a raw material, a coal tar has been produced from coal, and the aromatic compound has been produced using the coal tar as a raw material. For example, a coal tar is generated by keeping the pyrolysis temperature in a reactor for rapidly pyrolyzing coal at 750 ° C. or less and keeping the pyrolysis products in the reactor for 10 seconds or less. A method is known in which alkylphenols including cresols and xylenols are separated and recovered at an economical price by a separation method including distillation and extraction with an aqueous alkali solution using tar as a raw material (JP-A-6-172240). ). Further, polyhydric phenols have been produced not through the above-mentioned tar method but through a complicated chemical synthesis process.

[0003]

However, in the above-mentioned conventional tar method, instead of producing an aromatic compound having a hydroxyl group directly from coal, coal tar is once produced from coal, and the coal tar is used as a raw material. Since a group compound is produced, the number of steps and the process time are increased, and further reduction in production cost has been required. In particular, for polyhydric phenols not based on the tar method, a cheaper method has been demanded. An object of the present invention is to provide a method for producing an aromatic compound having a hydroxyl group directly from coal at a lower cost without passing through coal tar.

[0004]

The invention according to claim 1 is
A method for producing an aromatic compound having a hydroxyl group, characterized in that coal is thermally decomposed in water in a supercritical state to produce phenol, cresol, polyhydric phenol or a mixture thereof. Supercritical water (hereinafter referred to as supercritical water)
Inside, the supercritical water acts as a reaction catalyst, so that the coal is thermally decomposed and hydrolyzed in a short time to produce phenol, cresol, polyhydric phenol or a mixture thereof. Since supercritical water has the effect of suppressing the polymerization of these products, the decomposition products can be obtained in a stable state without recombination.

The invention according to claim 2 is the invention according to claim 1, wherein the supercritical water has a pressure of 22 to 40 MPa and a pressure of 3 to 40 MPa.
This is a method for producing an aromatic compound having a hydroxyl group having a temperature of 74 to 650 ° C. The invention according to claim 3 is the invention according to claim 1 or 2, wherein the polyhydric phenol is catechol, resorcin, hydroquinone, 4-methylcatechol, 2-methylresorcin, 4,5-dimethylcatechol, dihydroxy. This is a method for producing an aromatic compound having a hydroxyl group, which is one or more compounds selected from the group consisting of methylbenzene, dihydroxyethylbenzene, dihydroxypropylbenzene, pyrogallol and phloroglucinol. The invention according to claim 4 is the invention according to any one of claims 1 to 3,
Coal is a method for producing an aromatic compound having a hydroxyl group, which is lignite, lignite, subbituminous coal, or a mixture thereof.

[0006] The invention according to claim 5 is the invention according to claims 1 to 4.
An invention according to any of the above, wherein when the coal is thermally decomposed in water in a supercritical state, an alkali catalyst comprising a hydroxide of an alkali metal or an alkaline earth metal is added to the coal in an amount of 0.1 to 0.1%.
This is a method for producing an aromatic compound having a hydroxyl group, in which 3 to 5.0% by weight is added or carbon monoxide gas is added in an amount of 0.1 to 1.0 mol with respect to carbon, considering coal as carbon.
In the above range, when an alkali catalyst or carbon monoxide is added, the decomposition rate of coal is further improved, and the yield of the aromatic compound is accordingly increased.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of coal used in the present invention include lignite, lignite, sub-bituminous coal, peat coal, bituminous coal, anthracite and the like. Of these, relatively young coal types such as lignite, lignite, sub-bituminous coal, or a mixture thereof are preferred because of their high decomposition efficiency. In the present invention, the supercritical state of water is 374 to 6
It means the state of water at a temperature of 50 ° C. and a pressure of 22-40 MPa. The preferred supercritical state of water is 380-380.
It is 25 to 35 MPa at 500 ° C. If the temperature and pressure in the supercritical state are lower than the lower limits, the reaction is slow and the decomposition efficiency of coal is not good. If the temperature and pressure in the supercritical state exceed the upper limits, the load on the decomposition reactor is too high, which is also inefficient.

A product obtained by pyrolyzing coal in water in a supercritical state is a product obtained by pyrolyzing coal in water in a supercritical state. The product is a plurality of aromatic compounds having a hydroxyl group, such as phenol and cresol. And polyhydric phenols (hereinafter, referred to as phenols). Specific examples of polyhydric phenols include catechol, resorcin, hydroquinone,
4-methylcatechol, 2-methylresorcinol, 4,5
-Dimethylcatechol, dihydroxymethylbenzene, dihydroxyethylbenzene, dihydroxypropylbenzene, pyrogallol, phloroglucinol and the like. Conventionally, these polyhydric phenols are high value-added substances produced from a plurality of raw materials through a complicated process by a synthesis method.

When pyrolyzing coal in water in a supercritical state, an alkali catalyst composed of an alkali metal or alkaline earth metal hydroxide is used in an amount of 0.3 to 5.0% by weight based on the coal.
It is preferable to add carbon monoxide gas to carbon in an amount of 0.1 to 1.0 mol based on carbon, considering coal as carbon. Examples of the alkali catalyst include potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide, calcium hydroxide, calcium oxide, calcium carbonate, sodium oxide, potassium oxide and the like. If both the alkali catalyst and the carbon monoxide gas are below the lower limit of the above range, the effect is small, and if it exceeds the upper limit, it is not economical.

In order to obtain an aromatic compound product in the form of a single compound of high purity, it is necessary to separate and purify the product. Examples of the separation / purification method include a solvent extraction method, an alkali extraction method, a hot water extraction method, a membrane separation method, a chromatographic separation method, and a pressure crystallization method. In the present invention, high purity aromatic chemical products can be obtained by using these separation / purification methods alone or in combination.

The solvent extraction method is a method in which phenols obtained by thermal decomposition with supercritical water are formed into an adduct by hydrogen bonding with an alcohol such as methanol, and then methanol is extracted into a water tank by adding water. At this time, the phenols are extracted into the water tank accompanying the methanol. The alkali extraction method has long been practiced in the tar industry. In the present invention, phenols obtained by thermal decomposition with supercritical water are reacted with an aqueous sodium hydroxide solution or another aqueous alkali solution, and separated from the oil layer as a sodium salt (phenolate). The separated phenolate is washed with light oil to remove a small amount of neutral oil, and then the phenolate is decomposed by blowing in carbon dioxide gas and sulfuric acid to obtain high-purity phenols.

The hot water extraction method has many advantages such as excellent process simplicity, inexpensive water as an extractant, and easy separation and recovery of substances whose solubility greatly changes with temperature. is there. In the present invention, high-purity phenols are extracted by contacting phenols obtained by pyrolyzing hot water of about 200 ° C., whose extraction temperature is as low as possible with supercritical water, with a countercurrent hot water apparatus many times, in a countercurrent type hot water apparatus. . The membrane separation method is a separation method having excellent selectivity utilizing solubility in a membrane and diffusion in the membrane. In addition, the chromatographic separation method is a method capable of precise separation utilizing a difference in affinity (adsorption) with a filler.
In the pressure crystallization method, phenols containing impurities obtained by thermal decomposition in supercritical water are subjected to pressure of several thousand atmospheres to crystallize the desired phenol, and then solid-liquid separation is performed while maintaining high pressure To obtain high-purity phenols.

As shown in FIG. 1, in the method of the present invention, coal is pulverized in a pulverizing step 11 to a particle size of several mm or less, preferably 300 μm or less depending on the capacity of the pump. After pulverization, water is added in the stirring step 12 to prepare a coal slurry. This slurry contains 5 to 60% by weight of water. If it is less than 5% by weight, the decomposition efficiency of coal is inferior, and if it exceeds 60% by weight, the slurry lacks fluidity and is difficult to handle. The content of water in this slurry is preferably from 10 to 55% by weight. The coal slurry is pumped by a pump (not shown) to a pyrolysis step 13 using supercritical water. Although not shown, the slurry is heated to 150 to 3 by a heater before the thermal decomposition step 13.
You may heat to about 50 degreeC. In the pyrolysis step 13, the coal slurry is subjected to a pressure of 22 to 40 MPa and 374 to 650.
Maintained at a temperature of ° C., the water in the slurry becomes supercritical water and decomposes coal. Coal is composed of this supercritical water and 0.5 to 1
Contact for a relatively short time of about 0 minutes. As a result, coal is thermally decomposed and hydrolyzed by supercritical water, and phenol,
Produces cresol, polyhydric phenol or mixtures thereof. The pyrolysis step 13 produces product oil, wastewater and residual charcoal. The produced oil is separated into a medium and light oil and a crude phenol in a separation step 14. The wastewater is separated in a separation step 15 by a membrane separation method or the like, and crude phenols contained in the wastewater are recovered. The water after the separation is sent to the thermal decomposition step 13 as industrial water and reused. Residual coal is effectively used as fuel for boilers and the like. In this thermal decomposition step 13, it is also possible to fractionate decomposition products having different boiling points by sequentially lowering the pressure and the temperature from the supercritical state. Separation step 14
The crude phenols obtained in Steps 15 and 15 contain crude polyphenols represented by catechol, as well as crude phenol and crude cresol. The crude phenols are subjected to solvent extraction step 16a, alkali extraction step 16b, hot water extraction step 16c, membrane separation step 16
(d) In a separation / purification step 16 including a chromatographic separation step 16e and a pressure crystallization step 16f, impurities and compounds other than the target are separated, and purified phenols are obtained.

[0014]

As described above, according to the present invention, phenol, cresol, polyvalent, and the like can be obtained in a shorter time by pyrolyzing coal with supercritical water as compared with the conventional method using coal tar as a raw material. Aromatic compounds having a hydroxyl group such as phenol can be produced directly and cheaper from coal.

[Brief description of the drawings]

FIG. 1 is a view showing a process for producing an aromatic compound having a hydroxyl group of the present invention.

[Description of Signs] 11 Crushing step 12 Stirring step 13 Thermal decomposition step 14, 15 Separation step 16 Separation / purification step 16a Solvent extraction step 16b Alkali extraction step 16c Hot water extraction step 16d Membrane separation step 16e Chromatography separation step 16f Pressure crystallization Process

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10G 1/00 C10G 1/00 H 1/02 1/02 // C07B 61/00 300 C07B 61/00 300 (72) Inventor: Kenji Nishimura, 1002, 6-headed, Mukaiyama, Nakamachi, Naka-gun, Naka-gun, Ibaraki Prefecture Inside the Environmental Energy Laboratory, Mitsubishi Materials Corporation (72) Inventor: Shinichi Hasegawa 1-325 Koishikawa, Bunishi-ku, Tokyo No. Mitsubishi Materials Corporation System Business Center F term (reference) 4H006 AA02 AC42 BA02 BA06 BA29 BB31 BC10 BC11 BC34 BE40 BE60 FC52 FE13 4H039 CA60 CK90

Claims (5)

[Claims] 1. A method for producing an aromatic compound having a hydroxyl group, comprising pyrolyzing coal in water in a supercritical state to produce phenol, cresol, polyhydric phenol or a mixture thereof. 2. The method for producing an aromatic compound having a hydroxyl group according to claim 1, wherein the water in the supercritical state has a pressure of 22 to 40 MPa and a temperature of 374 to 650 ° C. 3. The polyhydric phenol is catechol, resorcin, hydroquinone, 4-methylcatechol, 2-methylresorcin, 4,5-dimethylcatechol, dihydroxymethylbenzene, dihydroxyethylbenzene, dihydroxypropylbenzene, pyrogallol. The method for producing an aromatic compound having a hydroxyl group according to claim 1 or 2, wherein the method is one or more compounds selected from the group consisting of and phloroglucinol. 4. The method for producing an aromatic compound having a hydroxyl group according to claim 1, wherein the coal is lignite, lignite, subbituminous coal, or a mixture thereof. 5. When pyrolyzing coal in water in a supercritical state, an alkali catalyst comprising an alkali metal or alkaline earth metal hydroxide is used in an amount of 0.3 to 5.0 with respect to said coal.
5. The aromatic compound having a hydroxyl group according to claim 1, wherein the coal is regarded as carbon, and carbon monoxide gas is added in an amount of 0.1 to 1.0 mol based on the carbon. Production method.