阅读说明：本技术 一种制备高纯度邻甲酚的结晶分离方法 (Crystallization separation method for preparing high-purity o-cresol ) 是由 郝红勋 王娜 侯宝红 黄欣 徐昭 尹秋响 王霆 鲍颖 谢闯 王召 于 2019-09-19 设计创作，主要内容包括：本发明涉及一种制备高纯度邻甲酚的结晶分离方法；向管式结晶器中加入邻甲酚粗品,控制体系温度为35～50℃,恒温静置0～0.5h；之后在0.5～4h内降至26.5～29.5℃,0.33～1h后向结晶器中加入一定量的晶种；再在2～5h内匀速降温至25～28.5℃,养晶1～3h后,排出母液；之后在2～5h内匀速升温至27℃～29.5℃进行发汗,升至发汗操作温度后继续养晶0.5～2h,排出汗液；之后快速升温至35℃～45℃,熔化结晶器中的固体,由结晶器底部排出邻甲酚产品。所得邻甲酚产品的纯度为99.50％～99.99％,收率大于75％。产品纯度高,收率大,操作简便,更容易实现工业生产。(The invention relates to a crystallization separation method for preparing high-purity o-cresol; adding the o-cresol crude product into a tubular crystallizer, controlling the temperature of the system to be 35-50 ℃, and standing for 0-0.5 h at constant temperature; then reducing the temperature to 26.5-29.5 ℃ within 0.5-4 h, and adding a certain amount of seed crystals into the crystallizer after 0.33-1 h; then cooling to 25-28.5 ℃ at a constant speed within 2-5 h, growing the crystals for 1-3 h, and discharging the mother liquor; then raising the temperature to 27-29.5 ℃ at a constant speed within 2-5 h for sweating, continuing growing the crystals for 0.5-2 h after raising the temperature to the sweating operation temperature, and discharging sweat; then the temperature is quickly raised to 35-45 ℃, the solid in the crystallizer is melted, and the o-cresol product is discharged from the bottom of the crystallizer. The purity of the obtained o-cresol product is 99.50-99.99%, and the yield is more than 75%. High product purity, high yield, simple operation and easy realization of industrial production.)

1. A crystallization separation method for preparing high-purity o-cresol comprises the following technical steps:

(1) adding the o-cresol crude product into a tubular crystallizer, controlling the temperature of the system to be 35-50 ℃, and standing for 0-0.5 h at constant temperature;

(2) after the constant-temperature standing is finished, cooling the o-cresol crude product in the step (1) to 26.5-29.5 ℃ within 0.5-4 h, then continuing to keep the constant temperature for 0.33-1 h, and then adding o-cresol seed crystals; after seed crystal is added, growing the crystal for 0.5 to 1.5 hours;

(3) after the crystal growth is finished, uniformly cooling the solid-liquid mixture obtained in the step (2) to 25-28.5 ℃ within 2-5 h, and then growing the crystal for 1-3 h; after the crystal growth is finished, carrying out solid-liquid separation, and discharging the mother liquor to a corresponding mother liquor storage tank;

(4) uniformly heating the residual solid in the crystallizer after the mother liquor is discharged in the step (3) to 27-29.5 ℃ within 2-5 h for sweating treatment, continuing to grow the crystals for 0.5-2 h after the temperature is raised to the sweating operation temperature, then performing solid-liquid separation, and discharging sweat to a corresponding mother liquor storage tank;

(5) and (4) heating the solid product in the tubular crystallizer obtained in the step (4) to 35-45 ℃, melting all solids in the crystallizer, and discharging the final product from the bottom of the crystallizer to a corresponding product storage tank.

2. The method as set forth in claim 1, characterized in that the crude o-cresol in step (1) contains o-cresol 90-98.5 wt% and impurities 1.5-10 wt%.

3. The method as set forth in claim 1, characterized in that the mass of the seed crystal in the step (2) is 0.25-3.0% of the mass of the crude o-cresol.

4. The method according to claim 1, wherein the mother liquor obtained in the step (3) contains o-cresol in an amount of 85 to 95.5%.

Technical Field

The invention belongs to the technical field of chemical engineering separation, and particularly relates to a purification and separation method for preparing high-purity o-cresol.

Background

o-Cresol, also known as o-methylphenol, o-Cresol, 2-methylphenol, 2-hydroxy-1-toluene, 2-Cresol, o-hydroxytoluene, is the second isomer of Cresol, known as o-Cresol and having the molecular formula C₇H₈O, molecular weight: 108.14. the melting point is 30-32 ℃, and the boiling point is 191 ℃. Is a colorless crystal, has strong phenol smell, is slightly soluble in water, and is soluble in ethanol, diethyl ether, chloroform and hot water. The structural formula is as follows:

o-cresol is a fine chemical intermediate with wide application, is an important raw material for synthesizing pesticides, medicines, dyes, resins, spices, antioxidants, polymerization inhibitors and the like, and can be mainly used for preparing p-chloro-o-cresol, o-hydroxybenzaldehyde, o-cresol novolac resin, epoxy-o-cresol novolac resin, o-methyl salicylic acid and the like. It can also be used as diluent, disinfectant and plasticizer for producing sebacic acid. As a relatively scarce fine chemical in China, the fine chemical has good development potential and market prospect, however, at present, no o-cresol production device is available in China, the production process is relatively laggard, the scale is small, the quality is poor, the quantity is small, the purity is low, the development and the application of downstream products are severely restricted, and the demand completely depends on import, so that the development and the optimization of o-cresol preparation and purification processes are problems which need to be solved urgently at present, and the fine chemical has very wide application prospect.

The traditional o-cresol preparation method is a natural separation method, i.e. o-cresol is fractionated from coal tar by using a rectification mode, and the purity of the o-cresol can only reach 98.34%; the currently mainstream preparation method of o-cresol is a chemical synthesis method. The chemical synthesis of o-cresol is carried out by many methods, mainly including toluene sulfonation alkali fusion method, phenol alkylation method, isopropyl phenol method, cresol propylene oxidation method, o-toluidine diazotization hydrolysis method, chlorotoluene hydrolysis method and the like. However, natural separation methods have the disadvantages of low yield, low purity, and numerous separation apparatuses; the o-toluidine diazotization hydrolysis method and the chlorotoluene hydrolysis method have serious corrosion to equipment, long process, high cost and large pollution and are eliminated; in the other chemical synthesis methods, a proper catalyst is required to react under the conditions of high temperature and high pressure, and the defects of difficult preparation, easy inactivation, difficult regeneration, difficult recovery and poor selectivity of the catalyst still exist, so that more byproducts exist in the obtained final o-cresol product, and further separation and purification are needed, which results in overlong synthesis route, difficult control of reaction conditions and increased production cost. Therefore, the traditional synthesis process route is improved, and a new green and clean o-cresol production process route is developed, so that the method has great significance.

World o-cresol production is mainly concentrated in industrially developed countries, such as Merichem corporation, PMG corporation, Stimson Lumber corporation, philies corporation, usa; ruetger swerke, germany; cindu chemical, Netherlands; schweizercsche Teerindustrie, Switzerland; coalite Fucls and Chemicals, UK, and the like. Many documents on o-cresol describe the chemical synthesis process of o-cresol, such as the methods of phenol alkylation such as the U.S. general electric company, the company Asahi Kasei, China patent CN103539637A, China patent CN103483157A, and China patent CN101514144A, which synthesizes o-cresol by performing a gas phase reaction of phenol and methanol in the presence of a high or medium temperature alkylation catalyst, and the selectivity is poor, only 71%, and a large amount of 2, 6-xylenol and a small amount of m-cresol, p-cresol, anisole and other high-grade alkylated products are by-produced. Chinese patent CN102807475A adopts a tubular reactor to hydrolyze chlorotoluene in NaOH solution with mass concentration of 25% to obtain o-cresol with purity as high as 99.5% and yield as high as 95%, but after the method is subjected to high-temperature and high-pressure hydrolysis reaction, the product needs to be cooled and decompressed, and after separation, neutralization, layering, extraction, distillation and rectification, the final o-cresol product can be obtained. Serious corrosion of equipment, long process, large pollution and high cost. No method for separating and purifying the o-cresol by using a crystallization mode is available. Meanwhile, with the further development of coal chemical and petrochemical enterprises, a large amount of phenol tar containing o-cresol is produced as a byproduct of coal coking and oil refining fractions, and because of complex components and more substances, the o-cresol products with high purity are difficult to obtain by using the traditional separation means. Therefore, in order to obtain a high-purity o-cresol product, the conventional synthesis production process needs to be further separated and purified after the reaction is finished. In order to overcome the defects, it is necessary to develop a new, simple, high-efficiency and low-energy-consumption separation and purification process of high-purity o-cresol. The development of the preparation process of the high-purity o-cresol can promote the scientific and technological development of the related fields and obviously improve the economic benefit of enterprises.

Disclosure of Invention

In order to obtain high-purity o-cresol products, the invention discloses a method for separating and purifying o-cresol crude products containing more impurities (mainly tetramethyl benzene, phenol, aniline, naphthalene, m-cresol, p-cresol and the like), wherein the impurities in the crude products are mainly from an upstream process. The invention utilizes the difference of o-cresol and impurities in melting point and solubility to obtain high-purity o-cresol products by a static melting crystallization method, thereby realizing the separation of o-cresol and impurities. The method has the advantages of no solvent, no pollution, low energy consumption, large operable range, high purity of the obtained product, high yield, and is an effective means for efficiently producing high-purity o-cresol.

The invention relates to a method for purifying a crude o-cresol product, which comprises the following technical steps:

(1) adding the o-cresol crude product into a tubular crystallizer, controlling the temperature of the system to be 35-50 ℃, and standing for 0-0.5 h at constant temperature;

(2) after the constant-temperature standing is finished, cooling the o-cresol crude product in the step (1) to 26.5-29.5 ℃ within 0.5-4 h, then continuing to keep the constant temperature for 0.33-1 h, and then adding o-cresol seed crystals; after seed crystal is added, growing the crystal for 0.5 to 1.5 hours;

(3) after the crystal growth is finished, uniformly cooling the solid-liquid mixture obtained in the step (2) to 25-28.5 ℃ within 2-5 h, and then growing the crystal for 1-3 h; after the crystal growth is finished, carrying out solid-liquid separation, and discharging the mother liquor to a corresponding mother liquor storage tank;

(4) uniformly heating the residual solid in the crystallizer after the mother liquor is discharged in the step (3) to 27-29.5 ℃ within 2-5 h for sweating treatment, continuing to grow the crystals for 0.5-2 h after the temperature is raised to the sweating operation temperature, then performing solid-liquid separation, and discharging sweat to a corresponding mother liquor storage tank;

(5) and (4) heating the solid product in the tubular crystallizer obtained in the step (4) to 35-45 ℃, melting all solids in the crystallizer, and discharging the final product from the bottom of the crystallizer to a corresponding product storage tank.

The above steps are shown in fig. 1.

The o-cresol crude product in the step (1) contains 90-98.5% of o-cresol by mass and 1.5-10% of impurities.

The mass of the seed crystal in the step (2) is 0.25-3.0% of the mass of the o-cresol crude product.

The content of o-cresol in the mother liquor obtained in the step (3) is 85-95.5%.

The method for separating and purifying the o-cresol crude product containing various impurities by the static melt crystallization method can achieve the impurity content of 10 percent. The invention strictly controls the temperature and the heating and cooling rates in the crystallization process by utilizing the advantages of the difference of the melting points of the impurities and the o-cresol and the higher solubility of the impurities in the o-cresol without additionally using a solvent, and separates and purifies the o-cresol to obtain the o-cresol product with high purity and high yield. The purity of the obtained o-cresol product can reach 99.5-99.9%, and the yield is 76-85%. The yield calculation formula is as follows:

the invention discloses a static melt crystallization method for separating and purifying an o-cresol crude product containing impurities, which fully utilizes the difference between the impurities and the o-cresol in the melting point and the advantage of higher solubility of the impurities in the o-cresol, and obtains a high-purity o-cresol product by utilizing a static melt crystallization mode. In the process, organic solvent is not additionally used, and the high-efficiency separation of o-cresol and impurities can be completed only by a tubular crystallizer and temperature control equipment, so that the operation is simpler and more convenient; the product does not need to be crushed and dried; the energy consumption is lower, the yield is higher, and the purity is higher; no environmental pollution and other impurities and wastes, meets the requirement of environmental protection and has higher industrial application value.

Drawings

FIG. 1 is a schematic diagram of the melt crystallization of high-purity o-cresol.

Detailed Description