CN104893750A - Method for extraction of pyridine compounds from coal tar - Google Patents

Abstract

The present invention provides a method for extraction of pyridine compounds from coal tar, the method includes the units of fractional distillation of coal tar into narrow fractions, extraction of phenolic compounds from the narrow fractions, extraction of pyridine compounds from the phenolic compounds by use of solvent I, extraction of pyridine compounds from dephenolized oil by use of pyridine compound salt-base 1, neutralization of pyridine compound salt-base 2 s by use of solvent II, and refining of crude pyridine compounds. By the method, the pyridine compounds in the phenolic compounds and the pyridine compounds in the dephenolized oil are extracted, the goal of full recovery of the pyridine compounds can be achieved, and the entire process is free of pollutants.

Description

A method for extracting pyridine compounds from coal tar

technical field

The invention relates to a method for extracting pyridine compounds from coal tar, belonging to the technical field of coal chemical industry.

Background technique

my country is rich in coal tar resources. Coal tar contains a certain amount of phenolic compounds and pyridine compounds. Although the content of these compounds is not very high, they are rare, rare and valuable resources. But so far, the research basically only considers the separation of phenolic compounds, but does not consider the separation of pyridine compounds, and there is no relevant teaching on how to extract pyridine compounds in coal tar.

However, the existence of pyridine compounds in coal tar has many hazards: hydrogenation of pyridine compounds will generate ammonia, which increases hydrogen consumption on the one hand, and on the other hand, the generated ammonia is likely to poison the hydrogenation catalyst; Pyridine compounds will affect the quality of oil. Even if the separation of phenolic compounds is considered in the whole process, because phenolic compounds and pyridine compounds are in a complex state in coal tar, the extracted phenolic compounds often contain a certain amount of pyridine compounds, and the remaining pyridine compounds are Stay in dephenolized oil.

Therefore, when coal tar is separated, it is hoped that while phenolic compounds can be removed, the separation of pyridine compounds can also be realized, so as to solve the above-mentioned technical problems.

Contents of the invention

The purpose of the present invention mainly provides a kind of method that coal tar extracts pyridine compounds, and it comprises:

(1) Fractionating coal tar into a narrow fraction rich in phenolic compounds and pyridine compounds;

(2) extracting the phenolic compounds in the narrow cut first, and obtaining dephenolized oil simultaneously;

(3) Dehydration and deslagging of the phenolic compound extracted in step (2) and extracting the pyridine compound therein with a solvent one to obtain the pyridine compound base 1, and simultaneously obtain a purified phenolic compound, wherein the solvent one is Polyacid;

(4) extracting the pyridine compound base 1 obtained from the dephenolized oil with the pyridine compound base 1 obtained in step (3) to obtain the pyridine compound base 2, and simultaneously obtain the depyridine oil;

(5) Neutralize and decompose the base 2 of the pyridine compound with solvent 2, and separate to obtain a mixture of crude pyridine compounds and a salt solution or salt precipitate, wherein the solvent 2 has a higher basicity than the pyridine compound;

(6) Dehydrating, deslagging, and rectifying the mixture of crude pyridine compounds to obtain pyridine products.

In one embodiment, the first solvent can be a phosphoric acid solution or a sulfuric acid solution, preferably a phosphoric acid solution with a mass fraction of 30%-85% or a sulfuric acid solution with a mass fraction of 30%-98%.

In another embodiment, solvent two can be sodium hydroxide solution, sodium carbonate solution, ammonia water or milk of lime solution, preferably milk of lime solution. When using phosphoric acid solution or sulfuric acid solution as solvent one, when using milk of lime solution as solvent two, what step (5) of the inventive method obtained was the salt precipitate of tricalcium phosphate or calcium sulfate; Washing with water, drying and calcining to obtain tricalcium phosphate or calcium sulfate products.

In yet another embodiment, the mass ratio of solvent one in step (3) to the phenolic compound extracted in step (2) may be 1:5-1:15, preferably 1:8-1:13.

In yet another embodiment, the mass ratio of the pyridine compound base 1 to the dephenolized oil in step (4) may be 1:1-1:10, preferably 1:5-1:10.

Through the method of the present invention, both the pyridine compounds contained in the phenolic compounds and the pyridine compounds in the dephenolized oil can be extracted, thereby achieving the purpose of completely recovering the pyridine compounds.

Therefore, the method of the present invention is an effective way for high-efficiency utilization of coal tar, which not only helps to make up the shortage of rare resources of some pyridine compounds, but also improves the utilization level of coal tar in my country.

Description of drawings

Fig. 1 is a process flow diagram of extracting pyridine compounds from coal tar according to an embodiment of the inventive method, wherein the specific references of each label are as follows:

1-coal tar, 2-coal tar fractionation, 3-narrow fraction, 4-dephenol, 5-pyridine-containing phenolic compound, 6-solvent one, 7-purified phenolic compound, 8-pyridine compound salt 1, 9-dephenol oil, 10-depyridine oil, 11-lime milk, 12-pyridine compound base 2, 13-crude pyridine compound mixture, 14-rectification, 15-various pyridine products , 16-calcium compound precipitation, 17-water washing, 18-drying, 19-calcination, 20-calcium compound product.

Detailed ways

The method for extracting pyridine compounds from coal tar of the present invention mainly includes the following process units: fractionation of coal tar into narrow fraction units, narrow fraction extraction of phenolic compound units, solvent-extraction of pyridine compound units in phenolic compounds, pyridine compound bases 1. Extracting the pyridine compound unit in the dephenolized oil, the solvent two neutralizing the pyridine compound base unit 2, and the crude pyridine compound refining unit. Through the method of the invention, not only the maximum amount of pyridine compounds is recovered, but also no pollutants are generated in the whole process.

(1) Fractionation of coal tar into narrow fraction units

Coal tar itself is a mixture of wide fractions and complex components, generally including: light oil fraction (before 170°C), phenol oil fraction (170°C-210°C), naphthalene oil fraction (210°C-230°C), Wash oil fraction (230°C-300°C), anthracene oil fraction (300°C-330°C), dianthracene oil fraction (330°C-360°C) and asphalt (>360°C). Most of the phenols and pyridine bases in coal tar are concentrated in the phenol oil fraction and naphthalene oil fraction.

Since the boiling points of phenolic compounds and pyridine compounds are relatively low, in the method of the present invention, the coal tar is heated and fractionated into narrow fractions rich in phenolic compounds and pyridine compounds, so as to concentrate treatment and reduce energy consumption. Considering that phenolic compounds and pyridine compounds are present in each fraction section, in order to recover these substances as much as possible, the range of narrow fractions in the method of the present invention is generally controlled at 60-300°C.

(2) Narrow fraction extraction phenolic compound unit

Extraction of phenolic compounds from a narrow fraction rich in phenolic and pyridine compounds yields simultaneously a dephenolized oil. The methods known in the art for separating and extracting phenolic compounds from coal tar can be used in the method of the present invention, such as alkali washing, sodium hydrosulfide or sodium carbonate solution extraction, hot water extraction, alcohol aqueous solution Extraction method, and ionic liquid extraction method.

Since the phenolic compound and the pyridine compound are in a complex state, the extracted phenolic compound contains a certain amount of the pyridine compound.

(3) Solvent one extracts the pyridine compound unit in the phenolic compound

In order to recover the rare resources of pyridine compounds as much as possible, the pyridine compounds in the phenolic compounds extracted in unit (2) are extracted with a solvent, so that not only the phenolic compounds are purified, but also the pyridine compound salts are obtained Base 1.

In the method of the present invention, theoretically, the solvent one can be various polybasic acids with strong acidity, including inorganic acids or organic acids. Those skilled in the art can select a suitable solvent according to actual needs after understanding the concept of the present invention; but from the perspectives of treatment effect, cost, etc., preferred phosphoric acid solution or sulfuric acid solution, more preferably phosphoric acid with a mass fraction of 30%-85% solution or sulfuric acid solution with a mass fraction of 30%-98%.

The mass ratio of solvent one in this unit to the phenolic compound extracted in unit (2) can be 1:5-1:15, preferably 1:8-1:13. Adopt the mass ratio of this range, guaranteed the quality of the phenolic compound through purification in this unit step (3) on the one hand, on the other hand the excess acid that adds in this step (3) can be utilized in unit step (4) , without waste.

(4) Pyridine compound base 1 extracts the pyridine compound unit in the dephenolized oil

A large number of pyridine compounds in the narrow fraction are enriched in the dephenolized oil obtained in the unit step (2). The pyridine compound base 1 produced by the above unit step (3) is used to re-extract the pyridine compound from the dephenolized oil; by controlling the mass ratio of the pyridine compound base 1 and the dephenolized oil to 1: 1-1: 10, preferably 1:5-1:10, to obtain pyridine base 2 and depyridine oil.

(5) Solvent two neutralizes the base 2 units of pyridine compounds

The base 2 of the pyridine compound obtained in the previous step (4) is neutralized with solvent two, and the mixture of the crude pyridine compound and other salt solutions or salt precipitates can be separated. Solvent 2 is a basic substance that can be specifically selected by those skilled in the art according to the actual process, as long as it has a higher basicity than pyridine compounds. Preferably, the second solvent can be sodium hydroxide solution, sodium carbonate solution, ammonia water or milk of lime solution, more preferably milk of lime solution.

When phosphoric acid solution or sulfuric acid solution is used as solvent one, and lime milk solution is used as solvent two, what is obtained after neutralization and separation is the precipitation of calcium compounds that are insoluble in water. In this case, the calcium compound precipitate can be washed with water, dried, and calcined to remove a small amount of organic matter contained in the precipitate, and finally obtain calcium compound products such as tricalcium phosphate or calcium sulfate.

(6) Dehydration, slag removal, rectification and purification unit for the mixture of crude pyridine compounds

Step (5) separates and obtains a mixture of crude pyridine compounds, which can further obtain various pyridine products such as pyridine, picoline, lutidine, ethyl pyridine, etc. pyridine etc.

The "slag removal" mentioned in this article refers to the process of distilling the mixture, distilling the target components from the top of the tower, and separating the substances outside the target components (called slag) from the bottom of the tower.

The advantages of the method for extracting pyridine compounds from coal tar provided by the present invention are mainly reflected in the following aspects:

(1) The most valuable rare resources of pyridine products are recovered;

(2) Phenolic compounds have also been purified while reclaiming pyridine compounds;

(3) In addition to pyridine compound products, calcium compound products can also be obtained at the same time;

(4) No waste is generated during the process.

Example

Below in conjunction with accompanying drawing, the technical method of the present invention is specifically described by example, so that understand the present invention better. All percentages mentioned herein are by mass unless otherwise stated.

Example 1:

A medium-temperature coal tar in northern Shaanxi has a density of 1.042g/cm ³ at 20°C, an initial boiling point of 165°C, an end boiling point of 612°C, a sulfur content of 0.16%, and a nitrogen content of 1.2%.

The coal tar 1 is fractionated 2 by a coal tar fractionation tower to obtain a narrow distillate 3 at 165-300°C. Firstly, the narrow distillate oil is washed with 20% sodium hydroxide solution for dephenolization 4, the phenolic compounds in the distillate oil are changed into phenolic sodium salt, and then the phenolic sodium salt and dephenolic oil 9 are separated by using the density difference , sodium phenolate is decomposed by carbon dioxide to obtain pyridine-containing phenolic compounds, then use 80% phosphoric acid solution as solvent-6 to dehydrate and deslag-containing pyridine-containing phenolic compounds 5 at 1:12 (phosphoric acid solution and pyridine-containing The mass ratio of the phenolic compound) is used to extract the pyridine compound, and the density difference is used to separate 8, that is, the pyridine compound base 1, and the purified phenolic compound 7 is also obtained.

The pyridine compound base 1 and the dephenolized oil 9 were extracted again at a mass ratio of 1:8, and the pyridine compound base 2 and the depyridine oil 10 were obtained by standing and separating by density difference to obtain 12. The pyridine compound base 2 is neutralized with lime milk 11, and the pH of the reaction solution is controlled to 8.4 to obtain a mixture 13 of crude pyridine compounds and a tricalcium phosphate precipitate as a calcium compound precipitate 16. The mixture of crude pyridine compounds is dehydrated, slag removed, and rectified 14 to obtain various pyridine products including pyridine, picoline, lutidine, ethylpyridine, etc. 15 . The tricalcium phosphate precipitate is washed with water 17 , dried 18 , and calcined 19 to obtain tricalcium phosphate as a calcium compound product 20 .

Example 2:

A certain low-temperature coal tar in Xinjiang has a density of 0.97g/cm ³ at 20°C, an initial boiling point of 145°C, an end boiling point of 585°C, a sulfur content of 0.12%, and a nitrogen content of 0.94%.

The coal tar 1 is fractionated 2 by a coal tar fractionation tower to obtain a narrow distillate 3 at 145-280°C. Firstly, the narrow distillate oil is washed with 20% sodium hydroxide solution for dephenolization 4, the phenolic compounds in the distillate oil are changed into phenolic sodium salt, and then the phenolic sodium salt and dephenolic oil 9 are separated by using the density difference , sodium phenate is decomposed by carbon dioxide to obtain pyridine-containing phenolic compounds, then use 98% sulfuric acid solution as solvent-6 to dehydrate and deslag-containing pyridine-containing phenolic compounds 5 at 1:10 (sulfuric acid solution and pyridine-containing The mass ratio of the phenolic compound) is used to extract the pyridine compound, and the density difference is used to separate 8, that is, the pyridine compound base 1, and the purified phenolic compound 7 is also obtained.

The pyridine compound base 1 and the dephenolized oil 9 were extracted again at a mass ratio of 1:9, and the pyridine compound base 2 and the depyridine oil 10 were obtained by static separation using the density difference to obtain 12, that is, the pyridine compound base 2 and the depyridine oil 10. The pyridine compound base 2 is neutralized with milk of lime 11, and the pH of the reaction solution is controlled to 8.2 to obtain a mixture 13 of crude pyridine compounds and a calcium sulfate precipitate as a calcium compound precipitate 16. The mixture of crude pyridine compounds is dehydrated, slag removed, and rectified and refined 14 to obtain various pyridine products including pyridine, picoline, lutidine, ethyl pyridine, etc. 15. The calcium sulfate precipitate is washed with water 17, Calcium sulfate is obtained as calcium compound product 20 after drying 18 and calcining 19 .

Claims (7)

1. coal tar extracts a method for pyridine compounds and their, it is characterized in that described method comprises:

(1) coal tar fractional distillation is become to be rich in the narrow fraction of phenolic compound and pyridine compounds and their;

(2) phenolic compound in described narrow fraction is first extracted, obtain dephenolize oil simultaneously;

(3) extract pyridine compounds and their wherein with solvent one after step (2) being extracted the phenolic compound dehydration obtained, de-slag, obtain pyridine compounds and their alkali 1, obtain purified phenolic compound simultaneously, wherein solvent one is polyprotonic acid;

(4) the pyridine compounds and their alkali 1 that dephenolize oil step (3) obtains is extracted pyridine compounds and their wherein, obtain pyridine compounds and their alkali 2, obtain de-pyridine oil simultaneously;

(5) pyridine compounds and their alkali 2 solvent two is carried out middle Sum decomposition, then be separated the mixture and salts solution or salt throw out that obtain crude pyridine compounds, wherein solvent two has the alkalescence higher than pyridine compounds and their;

(6) mixture of crude pyridine compounds is carried out dewater, de-slag, rectified purified, obtain pyridines product.

2. method according to claim 1, is characterized in that solvent one is for phosphoric acid solution or sulphuric acid soln.

3. method according to claim 2, is characterized in that solvent one is the phosphoric acid solution of massfraction 30%-85%, or the sulphuric acid soln of massfraction 30%-98%.

4. according to the method in any one of claims 1 to 3, it is characterized in that solvent two is for sodium hydroxide solution, sodium carbonate solution, ammoniacal liquor or lime milk solution.

5. method according to any one of claim 1 to 4, is characterized in that the mass ratio that the middle solvent one of step (3) and step (2) extract the phenolic compound obtained is 1: 5-1: 15.

6. method according to any one of claim 1 to 5, is characterized in that in step (4), pyridine compounds and their alkali 1 is 1: 1-1: 10 with the mass ratio of dephenolize oil.

7. method according to any one of claim 1 to 6, it is characterized in that solvent one is for phosphoric acid solution or sulphuric acid soln, solvent two is lime milk solution, the salt throw out of what step (5) obtained is tricalcium phosphate or calcium sulfate, and described salt throw out carried out wash, after dry, calcining, obtain tricalcium phosphate or calcium sulfate product.