CN108395367B - Method for separating phenolic compounds from coal tar - Google Patents

Abstract

The invention provides a method for separating phenol in coal tar by using piperazine compounds as extractant. The method uses piperazine substances as extractants, and uses water and n-butyl ether as back-extractants to recover piperazine substances. The oxazine interacts with phenolic substances to form eutectic substances or complexes that are insoluble in the oil phase. This method has a high extraction rate, avoids the pollution of phenol-containing wastewater caused by the traditional acid-base separation method, and the extractant and back-extractant can be recycled for multiple times, and the removal rate of phenolic compounds is above 95%. , which belongs to the green separation method of high value-added product phenol.

Description

A kind of method for separating phenolic compounds in coal tar

technical field

The invention relates to the separation field of coal chemical industry and petrochemical products, in particular to a method for separating phenolic compounds from coal tar, low-temperature coal pyrolysis oil, and mixtures of other oils and phenols.

Background technique

my country's coal pyrolysis oil chemical industry is still in the rough processing stage, and currently only more than 40 kinds of products can be extracted. Coal pyrolysis oil processing technologies at home and abroad are all developed for high temperature coal pyrolysis oil, and there are few studies and utilization of medium and low temperature coal pyrolysis oil. Due to the characteristics of composition and properties of low temperature coal pyrolysis oil, its processing route and product structure are quite different from higher temperature coal pyrolysis oil, and it is necessary to develop a high-efficiency cascade separation of mild, high efficiency and low energy consumption. technology.

Phenolic compounds are one of the basic chemical raw materials and are widely used in fiber, plastic, pesticide, medicine, preservative, explosive synthesis and other fields. They are mainly derived from direct coal liquefaction products, coal tar and petroleum products. In recent years, research on the extraction of phenolic compounds from direct coal liquefaction products, coal tar and petroleum products has attracted extensive attention from researchers at home and abroad. The traditional method is to use sodium hydroxide solution for elution. The principle of the elution method is to use phenolic compounds with weak acidity and react with strong bases to form a water-soluble sodium phenolic salt solution to remove phenolic compounds from oil. The phase is transferred to the aqueous phase to achieve the purpose of separation. The process is as follows: contacting the phenol oil mixture with an aqueous solution of sodium hydroxide, the phenol reacts with sodium hydroxide to form sodium phenolate, the sodium phenolate is soluble in water, but the oil is insoluble in water, so as to separate the aqueous sodium phenolate solution from the dephenolized oil. . The regeneration process of sodium phenolate is as follows: pure sodium phenolate and a certain concentration of sulfuric acid solution are sent into the reactor at the same time, and the reaction product enters the primary separator after cooling. The crude phenol obtained by the reaction is discharged from the upper part of the separator, and the sodium sulfate solution is discharged from the bottom.

The advantage of the extraction method with alcohol aqueous solution is that the extraction agent is low in cost and easy to recover, but the extraction rate is low. The extraction method of aqueous salt solution is to extract phenolic substances by using the solubility of some aqueous solutions of salts to phenolic substances, but like other extraction methods, this process inevitably produces a large amount of phenol-containing wastewater that needs to be treated, which will undoubtedly increase The difficulty and production cost of subsequent processing are reduced.

The existing coal pyrolysis oil separation method uses strong acid and alkali or has low extraction rate and selectivity. It is necessary to develop a new type of extractant suitable for the substance to be separated according to the characteristics of the substance to be separated. For phenols, the Bronsted acidity makes it possible to separate by hydrogen bonding with Lewis bases. On this basis, it is necessary to establish the principle of extractant screening and develop a green separation method for phenolic substances.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the present invention provides a mixture of coal tar, low-temperature coal pyrolysis oil and other straight-chain alkane oils and phenol, using piperazine compounds as extractants to separate phenol, and the method uses piperazine compounds as extractants. The substance is used as an extractant, and water and n-butyl ether are used as a back-extractant to recover piperazine substances, and through the interaction of piperazine substances and phenol substances, eutectic substances or complexes insoluble in oil phase are formed. This method has a high extraction rate, avoids the generation and pollution of phenol-containing wastewater caused by the traditional acid-base separation method, can realize the reuse of the extractant, and the separation efficiency is almost not decreased; effectively reduces the production cost; High separation efficiency.

The invention is characterized in that the extraction efficiency is high, strong acid and alkali are not used, a large amount of waste water is not generated, and the process is environmentally friendly. The method can reuse the extractant, reduce the separation cost, simplify the separation process, and has certain practical and environmental protection significance.

The method for separating phenolic compounds from coal tar disclosed in the invention innovatively adopts piperazine compounds as extractants, and forms eutectic substances or complexes insoluble in oil phase through the interaction between piperazine and phenolic substances. and recovering piperazines with water and n-butyl ether as back-extracting agents, so as to realize the separation of oleyl phenol mixture and the recovery of piperazines.

The invention discusses the separation process conditions in detail, and lists the extraction effect of the extractant and phenol under different molar ratios of (0.1-1:1), the extraction effect under different stirring times of 5-60min, and the reaction temperature of 0-90°C. The comparison of the extraction effect below, and the comparison of the extraction effect when piperazine compounds are used as extractants. After a large number of experimental demonstrations, the data are reliable and detailed. Under the process conditions, the molar ratio of extractant to phenol is preferably 0.5:1, the stirring time is preferably 10min, the reaction temperature is preferably 30-60°C, and 2-methylpiperazine and 1-phenyl are preferred when piperazine compounds are used as extractants. One or both of piperazines.

Piperazines also include piperazine, hexahydrate and piperazine, homopiperazine, 1-methylpiperazine, 2-methylpiperazine, N-methylpiperazine, N-ethylpiperazine, 1-benzene piperazine.

Concrete steps in the present invention are as follows:

(1) Prepare an oil phenol mixture with a phenol concentration of 10-400g/L;

(2) Using piperazine compound as extractant, the molar ratio of extractant and phenol is 0.1:1~1.2:1, extract and separate real coal tar, low temperature coal pyrolysis oil or oil phenol mixture prepared in step (1). The phenolic compound obtained is a mixture phase of oil phase, extractant and phenol;

(3) Put the mixture in a water bath, control the reaction temperature at 0-100°C, stir for 5min-1h, and let stand to separate the upper oil phase and the lower complex or DES phase;

(4) After the separation of the upper layer and the lower layer, use water and n-butyl ether for reverse extraction on the lower layer. The volume ratio of water and n-butyl ether is 1:1-1:2, and the volume ratio of water and n-butyl ether is preferably 1:1. After stirring for 30min Let stand for 20min, the lower water phase is subjected to vacuum distillation to recover piperazine compounds, and the upper layer is distilled to extract phenols with n-butyl ether, so as to realize the recycling and reuse of the extractant;

In the composition of oil in the oil-phenol mixture, most of them are straight-chain alkanes. One or more of cresol, p-cresol, o-cresol, alkylphenol, naphthol, resorcinol, etc. The oil phenol mixture contains 1%-40% by mass of phenol.

The molar ratio of the added piperazine compound and the phenolic compound in the oil is 0.5:1, the separation temperature is 30-60 DEG C, and the separation time is 0.1-2h. In step (4), when using the mixture of n-butyl ether and water to back-extract the piperazine compounds, the operating temperature is 0-50°C, the time is 2-30min, and the back-extraction phase is 10:10 compared with the piperazine compounds. 1. Back-extraction times 1-3 times.

Detailed ways

Example 1: Preparation of phenol-n-hexane monophenol simulated oil, concentration: 40.1 g/L, piperazine was used as extractant to separate phenol. The reaction temperature was 30° C., the molar ratio of extractant to phenol was 0.5:1, and the reaction time was 30 min. Take 0.75g of piperazine and add it to 40mL of phenol simulated oil, in a water bath at 30°C, stir for 30min and then stand for 15min, separate the upper oil phase and the lower complex by vacuum filtration, measure the volume of the upper oil phase and use GC Measure the phenol concentration, the extraction rate of piperazine to phenol is 98.9%, add 5 mL of water and 5 mL of n-butyl ether as the back-extracting agent in the lower layer complex, stir for 30 min and let stand for 20 min, and the lower water phase is subjected to vacuum distillation and recovery The extractant is piperazine, and the upper layer of n-butyl ether is distilled to extract phenol. The recovery rate of piperazine is about 85%, and its extraction rate is over 95% after three cycles.

Example 2: Preparation of o-cresol-n-hexane monophenol simulated oil, concentration: 147.58 g/L, and homopiperazine was used as extractant to separate o-cresol. The reaction temperature was 30° C., the molar ratio of extractant to o-cresol was 0.5:1, and the reaction time was 30 min. Take 3.41 g of piperazine and add it to 50 mL of o-cresol simulated oil, stir for 30 min in a water bath at 30°C, and then let stand for 15 min, separate the upper oil phase and the lower DES phase, measure the volume of the upper oil phase, and use GC to measure the adjacent Cresol concentration, the extraction rate of o-cresol by piperazine was 97.9%.

Example 3: Preparation of m-cresol-n-hexane monophenol simulated oil, concentration: 200.56 g/L, and piperazine was used as an extractant to separate m-cresol. The reaction temperature was 30° C., the molar ratio of extractant to m-cresol was 0.5:1, and the reaction time was 30 min. Take 1.60g of piperazine and add it to 20mL of m-cresol simulated oil, in a water bath at 30°C, stir for 30min and then let stand for 30min, separate the upper oil phase and the lower DES phase, measure the volume of the upper oil phase, and use GC to determine the m-cresol concentration, the extraction rate of piperazine to m-cresol was 95.2%, 10 mL of water and 15 mL of n-butyl ether were added to the lower eutectic phase as a back-extracting agent, stirred for 30 min, and then allowed to stand for 20 min, and the lower aqueous phase was decompressed The extractant piperazine is recovered by distillation, and the upper layer of n-butyl ether is distilled to extract m-cresol. The recovery rate of piperazine is about 80%, and its extraction rate is over 90% after three cycles.

Example 4: Preparation of p-cresol-n-hexane monophenol simulated oil, concentration: 147.58 g/L, and piperazine hexahydrate was used as extractant to separate p-cresol. The reaction temperature was 30° C., the molar ratio of extractant to p-cresol was 0.5:1, and the reaction time was 30 min. Add 6.63 g of piperazine hexahydrate into 50 mL of p-cresol simulated oil, stir for 30 min in a water bath at 30°C, and then let stand for 15 min, separate the upper oil phase and the lower complex by vacuum filtration, and measure the volume of the upper oil phase. , the concentration of p-cresol was determined by GC, and the extraction rate of p-cresol was 95.1%.

Embodiment 5: prepare phenol-m-cresol-o-cresol-p-cresol simulated oil, mass ratio is 2:1:1:1, total phenol concentration is 202.98g/L, prepares phenol-m-cresol-o-cresol Phenol-p-cresol simulated oil, using n-hexane as solvent, the mass ratio is 2:1:1:1, the concentration of phenol is 90.38g/L, the concentration of p-cresol is 41.2412g/L, and the concentration of m-cresol is 40.9803g/L , o-cresol concentration 40.3824g/L. Piperazine was used as the extractant, stirred at room temperature for 30min, and stood for 30min, and the influence of adding different molar ratios of the extractant on the extraction effect was investigated, as shown in Table 1. Table 1 shows that in the molar ratio of extractant to phenol (0.1-1:1), the extraction rate of phenol is relatively high, and most of them reach more than 95%. The best molar ratio is 0.5:1.

Table 1 The effect of different molar ratios of extractants on the extraction effect.

The molar ratio of m (piperazine) phenol m-cresol p-cresol o-cresol 0.1:1 0.3377 87.40% 78.51% 84.76% 85.48% 0.3:1 1.012 98.63% 93.09% 96.39% 96.47% 0.5:1 1.6884 99.84% 98.02% 99.07% 99.08% 0.7:1 2.3637 99.77% 97.88% 98.88% 98.91% 0.9:1 3.0397 99.76% 98.02% 98.94% 98.98% 1:1 3.7144 99.76% 97.96% 98.90% 98.93% 1.1:1 4.052 99.71% 97.84% 98.83% 98.87%

Embodiment 6: prepare phenol-m-cresol-o-cresol-p-cresol simulated oil, take n-hexane as solvent, mass ratio is 2:1:1:1, phenol concentration is 90.38g/L, p-cresol concentration 41.2412g/L, m-cresol concentration 40.9803g/L, o-cresol concentration 40.3824g/L. Add 1.69 g of piperazine and 20 mL of simulated oil, stir at room temperature and let stand for 30 min to investigate the influence of stirring time on the extraction rate, as shown in Table 2. Table 2 shows that the stirring time ranges from 5 to 60 minutes, preferably 10 minutes from a technological point of view.

Table 2 The effect of stirring time on extraction rate.

time (min) phenol m-cresol p-cresol o-cresol 5 99.94% 95.09% 97.38% 97.29% 10 99.98% 97.64% 98.68% 98.63% 15 99.98% 97.45% 98.62% 98.56% 30 99.98% 97.58% 98.72% 98.67% 45 99.98% 97.76% 98.70% 98.65% 60 99.98% 97.81% 98.74% 98.70%

Embodiment 7: prepare phenol-m-cresol-o-cresol-p-cresol simulated oil, the mass ratio is 2:1:1:1, and the total phenol concentration is 202.98g/L, and n-hexane is used as a solvent, and the phenol concentration is 90.38g/L, p-cresol concentration 41.2412g/L, m-cresol concentration 40.9803g/L, o-cresol concentration 40.3824g/L. The total phenol molar ratio in piperazine and n-hexane was 0.5:1. After taking 20 mL of simulated oil, about 1.69 g of piperazine was added. After stirring for 30 min in a water bath, let stand for 30 min. The influence of reaction temperature on extraction effect was investigated, as shown in Table 3. . Table 3 shows that the reaction temperature is preferably 30-60°C.

Table 3 Influence of reaction temperature on extraction effect.

Reaction temperature (℃) phenol m-cresol p-cresol o-cresol 0 97.54% 94.67% 96.31% 96.41% 10 99.03% 95.54% 97.30% 97.32% 20 99.93% 98.57% 99.41% 99.40% 30 99.78% 97.85% 98.97% 98.96% 45 99.95% 99.13% 99.67% 99.66% 50 99.95% 99.29% 99.71% 99.70% 60 99.94% 99.26% 99.72% 99.72% 70 99.94% 99.22% 99.71% 99.71% 80 99.91% 98.81% 99.45% 99.43% 90 99.93% 99.04% 99.66% 99.59%

Embodiment 7: prepare phenol-m-cresol-o-cresol-p-cresol simulated oil, the mass ratio is 2:1:1:1, the total phenol concentration is 202.98g/L, and the phenol concentration is 90.38g/L. The cresol concentration was 41.2412g/L, the m-cresol concentration was 40.9803g/L, and the o-cresol concentration was 40.3824g/L, and piperazine was used as the extractant. Take 20 mL of simulated oil, add 1.69 g of piperazine, stir for 30 min at 30°C in a water bath, and then let stand for 30 min. Measure the volume of the upper layer and measure the phenol content in the upper phase by GC. The extraction rate of each phenol is: 98.43% phenol; Phenol 97.50%; p-cresol 98.15%; m-cresol 97.94%. Remove the upper phase, add 10 mL of water and 15 mL of n-butyl ether to the lower solid, stir at 10°C until the solid is completely dissolved, the lower aqueous phase is distilled under reduced pressure to recover the extractant, and the recovery rate is about 85%. Extraction rate: 96.81% phenol, 95.50% m-cresol, 97.01% p-cresol, 95.16% m-cresol.

Embodiment 8: prepare phenol-m-cresol-o-cresol-p-cresol simulated oil, the mass ratio is 2:1:1:1, the total phenol concentration is 202.98g/L, the phenol concentration is 90.38g/L, and the The cresol concentration was 41.2412g/L, the m-cresol concentration was 40.9803g/L, the o-cresol concentration was 40.3824g/L, and homopiperazine was used as the extractant, and the reaction temperature was 30° C. After stirring and standing. Take 20 mL of simulated oil, add 2.1248 g of homopiperazine, stir for 40 min at 30°C in a water bath, and then stand for 20 min. Measure the volume of the upper layer and measure the phenol content in the upper phase by GC. The extraction rate of each phenol is: 98.43% of phenol; Cresol 97.50%; p-cresol 98.15%; m-cresol 97.94%.

Embodiment 9: prepare phenol-m-cresol-o-cresol-p-cresol simulated oil, the mass ratio is 2:1:1:1, the total phenol concentration is 202.98g/L, and the phenol concentration is 90.38g/L. The cresol concentration was 41.2412g/L, the m-cresol concentration was 40.9803g/L, the o-cresol concentration was 40.3824g/L, and homopiperazine was used as the extractant, and the reaction temperature was 30° C. After stirring and standing. In this example, the influence of different substituents of piperazine on the extraction effect is investigated, and there are the following piperazine compounds: 1-methylpiperazine, 2-methylpiperazine, 1-ethylpiperazine, 1-phenylpiperazine The above-mentioned extractant was added to the simulated oil of 20 mL respectively, stirred for 40 min under 30° C. water bath conditions, left standstill for 15 min, and the phenol content in the upper layer was measured by measuring the volume of the upper layer and the GC measurement of the upper layer. The extraction rate of phenol is shown in Table 4. Table 4 shows that 2-methylpiperazine and 1-phenylpiperazine exhibit higher extraction rates, and when piperazine compounds are used as extractants, one of 2-methylpiperazine and 1-phenylpiperazine is preferred. species or both.

Table 4 The effect of different substituents of piperazine on the extraction effect.

1-Methylpiperazine 2-Methylpiperazine 1-Ethylpiperazine 1-Phenylpiperazine phenol 87.24% 98.06% 79.05% 96.68% o-cresol 78.92% 96.14% 73.70% 94.18% p-cresol 84.38% 97.27% 76.10% 95.57% m-cresol 84.34% 97.19% 76.03% 95.43%

Embodiment 10: cut out the fraction before 230 ℃ in the medium and low temperature coal tar, after standing for stratification, the upper layer oil phase is taken as the experimental object, and the phenol content in a small amount is analyzed by GC-MS to be 38%, and piperazine is used as extraction The molar ratio of piperazine to phenol was about 0.5:1, and the mixture was stirred and allowed to stand in a water bath. Under the condition of 30 ℃ water bath, add 2.76g piperazine to 80.1g of medium and low temperature coal tar, stir for 50min and then let stand for 30min, separate the upper and lower liquid layers, measure the volume of the upper layer, and measure the phenol content in the upper oil phase by GC-MS, The extraction rate was about 90%, the upper layer was removed, 10 mL of water and 25 mL of n-butyl ether were added, and the water layer was distilled under reduced pressure to recover piperazine, and the recovery rate was about 65%.

Claims (2)

1. a method for separating phenolic compounds in coal tar, is characterized in that taking piperazines as extractant, piperazines are one or more, and described piperazines comprise homopiperazine, 1- Methylpiperazine, 2-Methylpiperazine, N-Methylpiperazine, N-Ethylpiperazine, 1-Phenylpiperazine; Form insoluble in oil through the interaction of piperazines and phenols Eutectic substance or complex, and reclaim piperazines as back extraction agent with water and n-butyl ether, thereby realize the step of oil phenol mixture separation and piperazines recovery, concrete steps are as follows: (1) Prepare an oil phenol mixture with a phenol concentration of 10-400g/L; (2) Using piperazine compounds as extractant, the molar ratio of extractant to phenol is 0.5:1, extracting and separating phenolic compounds in real coal tar, low-temperature coal pyrolysis oil or oil-phenol mixture prepared in step (1). , obtain the mixture phase of oil phase, extractant and phenol; (3) Put the mixture in a water bath, control the reaction temperature at 30-60°C, stir for 5-60min, and let stand for 0.1-0.5h to separate the upper oil phase and the lower complex or DES phase; (4) After the separation of the upper layer and the lower layer, use water and n-butyl ether for reverse extraction on the lower layer. The volume ratio of water and n-butyl ether is 1:1. After stirring for 30 minutes, let stand for 20 minutes, and use n-butyl ether for the upper layer to distill and extract phenols. The lower water phase is subjected to vacuum distillation to recover the piperazine compounds, so as to realize the recycling and reuse of the extractant; The composition of oil in the oil-phenol mixture is straight-chain alkane, and the straight-chain alkane is specifically one or more of n-hexane, n-heptane, n-octane, n-dodecane, and the phenolic compound is phenol , one or more of m-cresol, p-cresol, o-cresol, alkylphenol, naphthol and resorcinol, and the oil phenol mixture contains 1%-40% of phenol by mass. 2. the method for separating phenolic compounds in a kind of coal tar according to claim 1 is characterized in that in described step (4), when using n-butyl ether and water back extraction piperazine compounds, the operating temperature is 0 -50°C, the time is 2-30min, the back-extraction phase is 10-1 compared with the piperazine compounds, and the back-extraction times are 1-3 times.