Preparation method of environment-friendly coal pitch with high coking value and low quinoline insolubles

Abstract

The invention discloses a preparation method of environment-friendly coal pitch with high coking value and low quinoline insolubles, which comprises the following steps: adding purified medium-temperature pitch into a vacuum evaporator, carrying out vacuum evaporation at the temperature of 320-380 DEG C and the evaporation pressure of 0-1000Pa, and cooling and molding to obtain the environment-friendly coal pitch with high coking value and low quinoline insolubles, the softening point of the purified medium-temperature pitch is 80-95 DEG C, the coking value is 47-52%, and the quinoline insoluble is less than or equal to 0.5%. According to the method, purified medium-temperature pitch is used as a raw material, and the purposes of effectively removing benzopyrene, remarkably increasing the coking value and only slightly increasing quinoline insoluble substances are achieved through vacuum evaporation.

Description

Technical Field

[0001] The invention belongs to the technical field of coal chemical industry, and in particular relates to a method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insoluble matter. Background Art

[0002] Carbon refractory binders, lithium battery negative electrode material coating agents, etc. all require high coking values ​​and low quinoline insolubles to improve their antioxidant properties and high temperature resistance. At the same time, it is also necessary to reduce the benzopyrene content to reduce pollution. In order to improve the coking value of coal tar, high-temperature thermal polymerization, chemical catalysis, air oxidation, vacuum flash evaporation, etc. are usually used. Although these methods can improve the coking value of coal tar, the content of quinoline insolubles (QI) will also increase a lot at the same time; too high quinoline insolubles will seriously affect the performance of coal tar. For example, when high QI coal tar is used in carbon refractory binders, it is easy to generate a mosaic intermediate phase during carbonization, which will affect the antioxidant properties of the refractory material; when high QI coal tar is used as a coating agent for lithium battery negative electrode materials, its coating layer is easy to fall off and damage, affecting the overall performance of the negative electrode material. At the same time, the above methods cannot effectively remove polycyclic aromatic hydrocarbons such as benzopyrene in coal tar, which will cause serious environmental pollution during the use and processing of coal tar.

[0003] Chinese patent CN201210541359.0 discloses a method for producing high coking value coal tar pitch: medium-temperature coal tar pitch (softening point 80-95°C, coking value ≥48%, quinoline insoluble matter ≤0.2%, toluene insoluble matter ≥15%, ash content ≤0.2%) is directly added into a stirred reactor, and air, air-nitrogen mixed gas or nitrogen-oxygen mixed gas is continuously introduced, and the temperature is raised to 200-210°C at 15-25°C / min, and kept warm for 0.5-1.5h, and then the temperature is raised to 330-340°C at 5-10°C / min, and kept warm for 1-20h to obtain high softening point coal tar pitch (softening point 260-280°C, coking value ≥75%, quinoline insoluble matter 30±5%, toluene insoluble matter ≥50%, ash content ≤0.4%).

[0004] Chinese patent CN201610765770.4 discloses a method for producing high-coking value and low-quinoline-insoluble coal tar pitch: using high-purity impregnating agent asphalt (quinoline insoluble content is less than 0.05%, coking value is greater than 47%) as raw material, first passing through a self-cleaning reactor, fully reacting at 280-300°C, and oxidizing with air; then passing through a thin film evaporator, devolatilizing at 260-300°C, to obtain high-coking value and low-quinoline-insoluble coal tar pitch (coking value 55-65%, quinoline insoluble content 0.5-2%).

[0005] Chinese patent CN201510015083.6 discloses a method for preparing environmentally friendly asphalt: using one or more of aromatic heavy oil, coal tar and modified asphalt as raw materials, adding modifiers and promoters, mixing and stirring evenly, heating to 120-350°C under nitrogen or argon protection, and polymerizing at a constant temperature for 1-20 hours; stopping nitrogen or argon, distilling at a pressure of 0-30 kPa, and obtaining environmentally friendly asphalt with a benzopyrene content of less than 500 mg / kg.

[0006] Chinese patent CN201510015149.1 discloses a method for preparing high-performance environmentally friendly asphalt: using one or two of aromatic heavy oil and coal tar as raw materials, using coal-based or petroleum-based aromatic heavy oil with a benzopyrene content of less than 300 mg / kg as a regulator, heating to 350-500°C at a rate of 0.1-10°C / min, and thermally polymerizing for 0.5-30h at a pressure of 0.1-10MPa to obtain polymerized asphalt, and evaporating the polymerized asphalt in a thin film evaporator or a short-path evaporator to obtain high-performance environmentally friendly asphalt. The product has quinoline insoluble matter <15%, coking value >80%, and benzopyrene <400 mg / kg.

[0007] In 2014, Lai Shiquan et al. published a paper on the preparation of impregnating asphalt by oxidative thermal polymerization of coal tar soft pitch in Carbon Science and Technology. Low QI coal tar soft pitch (QI < 0.1%) was used as raw material and air oxidative thermal polymerization was adopted to prepare impregnating asphalt. The reaction temperature was 240-260°C, the reaction time was 3-4h, and the air flow rate was 0.4-0.5L / min. The softening point of the obtained impregnating asphalt was 95-110°C and QI < 0.2%.

[0008] In 2020, Sun Shushuang et al. published the preparation and characterization of high softening point coated asphalt in Applied Chemical Industry. They used polycondensation purified asphalt (softening point 80°C, coking value 50.9%, QI 0.39%) as raw material and air oxidation thermal polymerization method to prepare high softening point coated asphalt. The reaction temperature was 300°C, the reaction time was 6h, and the air flow rate was 160L / h. The prepared coated asphalt had a softening point of 215°C, a coking value of 75.8%, and a QI of 8.4%.

[0009] In 2021, Ma Xiaolong et al. published a study on the preparation of coated asphalt using coal-based soft asphalt in "Fuel and Chemical Engineering". Using coal asphalt as raw material, refined medium-temperature asphalt (softening point 240-260°C, QI < 0.01%) was obtained through solvent extraction, sedimentation separation, and vacuum distillation. The refined medium-temperature asphalt was then placed in a reactor at a reaction temperature of 300°C, a reaction time of 7h, and an air flow rate of 3m3 / h. The prepared coated asphalt has a softening point of 250°C, a coking value of QI 73.2%, and a QI of 7.8%.

[0010] The products obtained by the above technologies either have a low coking value, or a high quinoline insoluble matter, or cannot effectively remove benzopyrene, and cannot simultaneously meet the requirements of high coking value, low quinoline insoluble matter, and environmental protection. In addition, most of the above technologies use high-temperature thermal polymerization (or oxidative thermal polymerization) plus vacuum distillation, which has many steps, cumbersome operations, and greater environmental pollution. Summary of the invention

[0011] In view of the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles, which uses purified medium-temperature asphalt as raw material and achieves the purpose of effectively removing benzopyrene and significantly improving the coking value with only a slight increase in quinoline insolubles through vacuum evaporation.

[0012] To achieve the above object, the present invention adopts the following technical solution:

[0013] The present invention provides a method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insoluble matter, wherein the purified medium-temperature asphalt is added into a vacuum evaporator, vacuum evaporated at a temperature of 320-380° C. and an evaporation pressure of 0-1000 Pa, and the environmentally friendly coal tar pitch with high coking value and low quinoline insoluble matter is obtained after cooling and molding;

[0014] The softening point of the purified medium-temperature asphalt is 80-95° C., the coking value is 47-52%, and the quinoline insoluble matter is ≤0.5%.

[0015] Preferably, during the vacuum evaporation process, the evaporation pressure is 100-1000 Pa.

[0016] Preferably, in the vacuum evaporation process, the evaporation time is 2 to 60 minutes.

[0017] Preferably, the benzopyrene content in the purified medium-temperature asphalt is 1.2-1.5 wt%.

[0018] Preferably, the high coking value and low quinoline insoluble environmentally friendly coal tar has a coking value of ≥80%, benzopyrene ≤200 mg / kg, and quinoline insoluble matter ≤2%.

[0019] Preferably, the softening point of the environmentally friendly coal tar pitch with high coking value and low quinoline insoluble matter is 200-300°C.

[0020] The method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles provided by the present invention has the following beneficial effects:

[0021] 1. The present invention obtains environmentally friendly asphalt with high coking value and low quinoline insolubles by vacuum evaporation of purified medium-temperature asphalt (softening point 80-95°C, quinoline insoluble matter ≤ 0.5%);

[0022] 2. In the vacuum evaporation process of the present invention, due to the low evaporation pressure, light components such as polycyclic aromatic hydrocarbons in medium-temperature asphalt can be efficiently removed and purified, the coking value of the product is significantly increased, and benzopyrene is reduced to an extremely low level; due to the low evaporation temperature and short evaporation time, quinoline insolubles only increase slightly;

[0023] 3. The method of the present invention has a simple process, and does not require the addition of any auxiliary materials or reagents during the production process. The operation is simple, and the obtained asphalt product has a high coking value, low quinoline insoluble matter, and extremely low benzopyrene. When the environmentally friendly coal tar with high coking value and low quinoline insoluble matter is used as a refractory binder, it can improve the product's compressive strength, flexural strength, oxidation resistance, and thermal shock resistance. It can also be used as a coating agent for lithium-ion battery negative electrode materials and as a raw material for high-end carbon materials such as mesophase carbon microspheres and spinning asphalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0025] Figure 1 The present invention is a schematic flow chart of the method for preparing the environmentally friendly coal tar pitch with high coking value and low quinoline insoluble matter. DETAILED DESCRIPTION

[0026] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0027] Combination Figure 1 As shown, the present invention provides a method for preparing an environmentally friendly coal tar pitch with high coking value and low quinoline insolubles, and the specific process is as follows:

[0028] The purified medium-temperature asphalt is added into a vacuum evaporator, and vacuum evaporated at a temperature of 320-380°C and an evaporation pressure of 0-1000Pa. After natural cooling and forming in the evaporator, environmentally friendly coal tar with high coking value and low quinoline insoluble matter is obtained; wherein, the softening point of the purified medium-temperature asphalt is 80-95°C, the coking value is 47-52%, and the quinoline insoluble matter (QI) is ≤0.5%.

[0029] In a preferred embodiment, during the vacuum evaporation process, the evaporation pressure is 100-1000 Pa and the evaporation time is 2-60 min.

[0030] In a preferred embodiment, the content of benzopyrene in the purified medium-temperature asphalt is 1.2-1.5 wt%.

[0031] The prepared high coking value and low quinoline insoluble environmentally friendly coal tar has a coking value ≥80%, benzopyrene ≤200 mg / kg, and quinoline insoluble matter ≤2%; the high coking value and low quinoline insoluble environmentally friendly coal tar has a softening point of 200-300°C.

[0032] During the vacuum evaporation process of the present invention, due to the low evaporation pressure, light components such as polycyclic aromatic hydrocarbons in medium-temperature asphalt can be efficiently removed and purified, the coking value of the product is significantly increased, and benzopyrene is reduced to an extremely low level; due to the low evaporation temperature and short evaporation time, quinoline insolubles only increase slightly.

[0033] The preparation method of the environmentally friendly coal tar pitch with high coking value and low quinoline insolubles of the present invention is further introduced below with reference to specific examples.

[0034] Example 1

[0035] The preparation process of the environmentally friendly coal tar pitch with high coking value and low quinoline insolubles in this embodiment is as follows:

[0036] Purified medium-temperature asphalt (softening point 85°C, coking value 48%, QI 0.4%, benzopyrene 1.4%) was added into a vacuum evaporator and evaporated for 60 minutes at an evaporation temperature of 320°C and an evaporation pressure of 100 Pa. After cooling to room temperature, environmentally friendly coal tar with high coking value and low quinoline insoluble matter was obtained. The coking value was 82%, the softening point was 248°C, the QI was 0.8%, and the benzopyrene was 150 mg / kg.

[0037] Example 2

[0038] The preparation process of the environmentally friendly coal tar pitch with high coking value and low quinoline insolubles in this embodiment is as follows:

[0039] Purified medium-temperature asphalt (softening point 88°C, coking value 50%, QI 0.45%, benzopyrene 1.3%) was added into a vacuum evaporator and evaporated for 30 minutes at an evaporation temperature of 360°C and an evaporation pressure of 1000Pa. After cooling to room temperature, environmentally friendly coal tar with high coking value and low quinoline insoluble matter was obtained. The coking value was 81%, the softening point was 235°C, the QI was 1.8%, and the benzopyrene was 200 mg / kg.

[0040] Example 3

[0041] The preparation process of the environmentally friendly coal tar pitch with high coking value and low quinoline insolubles in this embodiment is as follows:

[0042] The purified medium-temperature asphalt (softening point 92°C, coking value 52%, QI 0.5%, benzopyrene 1.2%) was added into a vacuum evaporator and evaporated for 20 minutes at an evaporation temperature of 380°C and an evaporation pressure of 500 Pa. After cooling to room temperature, environmentally friendly coal tar with high coking value and low quinoline insoluble matter was obtained. The coking value was 86%, the softening point was 280°C, the QI was 2%, and the benzopyrene was 50 mg / kg.

[0043] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles, characterized in that: Add the purified medium-temperature asphalt into a vacuum evaporator, perform vacuum evaporation at a temperature of 320-380°C and an evaporation pressure of 0-1000Pa, and obtain environmentally friendly coal tar with high coking value and low quinoline insoluble matter after cooling and molding; The softening point of the purified medium-temperature asphalt is 80-95° C., the coking value is 47-52%, and the quinoline insoluble matter is ≤0.5%.

2. The method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles according to claim 1, characterized in that: During the vacuum evaporation process, the evaporation pressure is 100-1000 Pa.

3. The method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles according to claim 1, characterized in that: During the vacuum evaporation process, the evaporation time is 2 to 60 minutes.

4. The method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles according to claim 1, characterized in that: The content of benzopyrene in the purified medium-temperature asphalt is 1.2-1.5 wt%.

5. The method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles according to claims 1 to 4, characterized in that: The high coking value and low quinoline insoluble environmentally friendly coal tar pitch has a coking value of ≥80%, benzopyrene ≤200 mg / kg, and quinoline insoluble matter ≤2%.

6. The method for preparing environmentally friendly coal tar pitch with high coking value and low quinoline insolubles according to claim 5, characterized in that: The softening point of the environmentally friendly coal tar pitch with high coking value and low quinoline insoluble matter is 200-300°C.

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