RU2841067C1 - Method of producing process graphite - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for low-temperature graphitisation of carbon material. Method of producing technological graphite involves graphitation of needle coke in the presence of a catalyst. Mixture of needle coke and petroleum tar is used in amount of 10-20% of the weight of the coke. Catalyst used is red mud, which includes iron, silicon, calcium, titanium oxides and their carbonates, in amount of 5 to 8% of weight of needle coke. Graphitization is carried out at temperatures from 850 to 1200 °C.

EFFECT: invention enables to obtain a grade of graphite with improved resistance and electroconductivity.

1 cl, 3 dwg, 3 tbl, 5 ex

Description

The invention relates to a method for low-temperature graphitization of carbon material.

A method for producing thermally expanded graphite is known (RU patent No. 2690449, published on 03.06.2019), which includes heating in the temperature range of 450-650 °C, adding graphite powder to the calculated mass of perchloric acid in a ratio of 1:0.6 - 1:0.85, the intercalation process is carried out in two stages: in the first of which mixing is carried out until a homogeneous consistency of the mixture is obtained, and in the second stage, before heating, the resulting mixture is kept for 5-8 hours.

The disadvantage of the method is the incomplete process of intercalation with chloric acid, the high residual content of sulfur and water compounds adsorbed on the structure of the product, which worsens the adsorption capacity of the modified graphite.

A method for producing pure graphite is known (RU patent No. 2394758, published on 20.07.2010), where difluorochloromethane is used as a refining reagent, the processing of which begins at a temperature of 2100-2200°C, and is carried out during heating to a furnace shutdown temperature of 2700-2800°C, and for 3-4 hours after the furnace shutdown with a uniform hourly consumption equal to 0.7-0.8% of the mass of the blanks, and then to a cooling temperature of the blanks of 1800-1900°C with an hourly consumption of the cleaning reagent of 0.1-0.5% of the mass of the blanks.

The disadvantage of the method is that due to the high temperatures of use of active substances, a reduction in energy costs and the efficiency of obtaining the required grades of graphite are not ensured.

A method for producing oxidized graphite is known (RU patent No. 2118941, published 20.09.1998), which includes treating natural graphite with nitric acid until compounds are formed for introduction into graphite layers, hydrolysis, washing and drying of the oxidized graphite at a temperature of no more than 80°C, characterized in that the treatment is carried out at a mass ratio of fuming nitric acid to graphite of 0.37-0.75: 1.

The disadvantage of this method is its low environmental friendliness when absorbing exhaust gases, and the need to carry out hydrolysis and washing operations.

A method for producing carbon anode material is known (RU patent No. 2370437, published on 20.10.2009), according to which the carbon anode material is obtained by mixing needle and/or petroleum coke and pitch in an amount of 20 to 40% of the coke mass, followed by carbonization at a temperature of 600-1000°C. Medium-temperature pitch is used as pitch, the process is carried out in the presence of a catalyst selected from a series including iron, cobalt, nickel compounds and their alloys, and carbonization is carried out in a reducing or inert environment. According to X-ray phase analysis, the resulting carbon material has a turbostratic structure and has a conductivity comparable to graphite.

The disadvantage of the known method is that the obtained carbon material has a turbostratic structure according to X-ray phase analysis, i.e. it is not graphite.

A method for producing graphite is known (RU patent No. 2476374, published on 27.02.2013), adopted as a prototype, according to which, in the presence of a catalyst and coal tar pitch selected from a series including compounds of iron, cobalt, nickel and any mixtures thereof, and graphitization is carried out at a temperature of 400-590°C in an environment of exhaust reducing gases.

The disadvantage of the known method is that the obtained carbon material does not fully possess the properties of graphite due to its heterogeneity. There are areas of heterogeneity and sintered agglomerates are present. The electrical conductivity properties necessary for graphite are not ensured.

The technical result is the production of a graphite grade with improved resistance and electrical conductivity.

The technical result is achieved by using a mixture of needle coke and petroleum pitch in an amount of 10 to 20% of the coke mass, using red mud as a catalyst, which includes oxides of iron, silicon, calcium, titanium and their carbonates, in an amount of 5 to 8% of the needle coke mass, graphitization is carried out at temperatures from 850 to 1200°C, with the production of calcium orthosilicate and the formation of primary graphite structures.

The method is illustrated by the following figures.

Fig. 1 - diffraction patterns of the obtained graphite samples ;

Fig. 2 - graph of temperature dependence of specific conductivity of graphite;

Fig. 3 - Scanning electron micrograph of the surface of a sample corresponding to the SGL graphite grade, example 3.

The method is carried out as follows. A mixture of needle coke and petroleum pitch in an amount of 10 to 20% of the coke mass is placed in a ball mill. After this, red mud is added in an amount of 5 to 8% of the needle coke mass. Red mud, which includes iron, silicon, calcium, titanium oxides and their carbonates, is used as a catalyst. The prepared mixture is mixed and ground in a ball mill for 1 to 3 minutes. After this, the mixture is placed in a crucible with a lid and weighed, then the crucible is placed in a muffle furnace and heating is started. The heating process is carried out in an inert argon atmosphere. At temperatures from 850 to 1200°C, the processes of transition of silicon and calcium oxides into various polymorphic modifications with the formation of calcium orthosilicate occur _, which ensures the formation of primary graphite structures and their further transformation into a stable state throughout the entire volume of the sample. Upon completion of heating, the crucible is left in a muffle furnace in an inert atmosphere, where it cools to room temperature. After cooling, the crucible is removed from the furnace and weighed, and the carbonization constants k = P _carbon / P _isch are calculated. Then, X-ray phase analysis is carried out, which confirms the presence of the final product - technological graphite - in the carbon material.

The method is illustrated by the following examples.

The compositions of the charge materials for implementing the method of obtaining graphite and their characteristics are presented in Tables 1-3.

Table 1. Chemical composition of the sludge of the Ural Aluminum Plant

Element Fe Ni Cr You Al Mn V Si S P Ca K % 58.71 0.17 0.2 4.84 4.23 0.83 0.13 2.57 0.04 0,00 0.30 0.19

Table 2. Quality indicators of petroleum pitch PNK-2 "Bashneft-Novoil"

Softening temperature,
°C Exit
residual volatile hydrocarbons,
no less,
% Contents S,
no more
% (mass.) Content of α-fractions,
no more,
% Ash,
no more,
% (mass.) 50-90 68 2.5 3 0.5

Table 3. Chemical composition of petroleum coke "SHANDONG GANGDA INTERNATIONAL TRADING CO., LTD" grade GD-CPC-1

C,
no less,
% (mass.) S,
no more,
% (mass.) Ash,
no more,
% (mass.) Residual volatile hydrocarbons,
no more,
% (mass.) Humidity,
no more,
% (mass.) 98.5 0.5 0.5 0.7 0.5

The amount of pitch in the batch determines the uniformity of the distribution of coke particles in the volume of the batch material, ensuring the maximum contact number between them. When less than 10% of pitch by weight of coke is added to the initial batch, the final product will sinter poorly. When more than 20% of pitch by weight of coke is added to the initial batch, the final product will sinter well, but a sufficient contact number between the coke particles will not be ensured and the electrical conductivity of the final product will be low.

Example 1. A 1.1 g sample of red mud with the chemical composition (Table 1) is mixed with 3.5 g of medium-temperature petroleum pitch "Bashneft-Novoil" (Table 2) with a softening point of 50°C and higher, and with 20.0 g of needle coke from "SHANDONG GANGDA INTERNATIONAL TRADING CO., LTD" (China) (Table 3) and mixed for 90 seconds in a ball mill. The presence of iron, silicon and calcium orthosilicate compounds was confirmed by IR spectroscopy.

The resulting mixture is transferred to a crucible with a tight lid and placed for carbonization at a temperature of 700 to 1100 °C for 6 hours. The crucible is cooled to room temperature, and the carbonization constant is k = 0.806. The presence of graphite is confirmed by X-ray phase analysis based on the peaks obtained (Fig. 1, 1).

Example 2. A 1.6 g sample of red mud with the chemical composition (Table 1) is mixed with 3.4 g of medium-temperature petroleum pitch "Bashneft-Novoil" (Table 2) with a softening point of 50°C and higher, and with 20.0 g of needle coke from "SHANDONG GANGDA INTERNATIONAL TRADING CO., LTD" (China) (Table 3) and mixed for 90 seconds in a ball mill. The presence of iron, silicon and calcium orthosilicate compounds was confirmed by IR spectroscopy.

The resulting mixture is transferred to a crucible with a tight lid and placed for carbonization at a temperature of 750 to 1150 °C for 6 hours. The crucible is cooled to room temperature, and the carbonization constant is k = 0.806. The presence of graphite is confirmed by X-ray phase analysis based on the peaks obtained (Fig. 1, 2).

Example 3. A 1.5 g sample of red mud with the chemical composition (Table 1) is mixed with 3.8 g of medium-temperature petroleum pitch "Bashneft-Novoil" (Table 2) with a softening point of 50°C and higher, and with 20.0 g of needle coke from "SHANDONG GANGDA INTERNATIONAL TRADING CO., LTD" (China) (Table 3) and mixed for 90 seconds in a ball mill. The presence of iron, silicon and calcium orthosilicate compounds was confirmed by IR spectroscopy.

The resulting mixture is transferred to a crucible with a tight lid and placed for carbonization at a temperature of 800 to 1200 °C for 6 hours. The crucible is cooled to room temperature, and the carbonization constant is k = 0.806. The presence of graphite is confirmed by X-ray phase analysis based on the peaks obtained (Fig. 1, 3).

Example 4. A 1.0 g sample of red mud with the chemical composition (Table 1) is mixed with 3.3 g of medium-temperature petroleum pitch "Bashneft-Novoil" (Table 2) with a softening point of 50°C and higher, and with 20.0 g of calcined needle petroleum coke from "SHANDONG GANGDA INTERNATIONAL TRADING CO., LTD" (China) (Table 3) and mixed for 90 seconds in a ball mill. The presence of compounds of iron, silicon and calcium orthosilicate was confirmed by IR spectroscopy.

The resulting mixture is transferred to a crucible with a tight lid and placed for carbonization at a temperature of 850 to 1250 °C for 6 hours. The crucible is cooled to room temperature, and the carbonization constant is k = 0.806. The presence of graphite is confirmed by X-ray phase analysis based on the peaks obtained (Fig. 1, 4).

Example 5. A 1.4 g sample of red mud with the chemical composition (Table 1) is mixed with 4.0 g of medium-temperature petroleum pitch "Bashneft-Novoil" (Table 2) with a softening point of 50°C and higher, and with 20.0 g of calcined needle petroleum coke from "SHANDONG GANGDA INTERNATIONAL TRADING CO., LTD" (China) (Table 3) and mixed for 90 seconds in a ball mill. The presence of iron, silicon and calcium orthosilicate compounds was confirmed by IR spectroscopy.

The resulting mixture is transferred to a crucible with a tight lid and placed for carbonization at a temperature of 900 to 1300 °C for 6 hours. The crucible is cooled to room temperature, and the carbonization constant is k = 0.806. The presence of graphite is confirmed by X-ray phase analysis based on the peaks obtained (Fig. 1, 5).

In example 3 the best results were obtained. The presence of graphite is confirmed by X-ray phase analysis based on the obtained peaks. The spectra are consistent with the data of the ASTM card index - diffraction data for graphite. X-ray phase analysis of the processed mixture of carbon materials showed that the obtained product has a layered crystalline structure. According to the assessment of the parameters of the crystal lattice of the carbon material, for which the data on the interplanar distances were used based on the analysis of the values of the diffraction maxima 002 and 100, as well as the average diameter of the hexagonal layers L _a and the average height of the crystallites L _c . Fig. 2 shows the temperature dependence of the specific electrical conductivity of graphite obtained at a temperature of 800 to 1200 °C, which increases with increasing temperature.

A method for producing graphite by crystallizing needle coke with petroleum pitch in the presence of a catalyst in the form of red mud selected from a series including compounds of iron, silicon, titanium and calcium carbonate at a temperature of 800 to 1200°C in a reducing environment of a hydrogen flow or an inert environment of argon. The resulting carbon material, according to X-ray phase analysis, has a graphite structure and has high values of graphite electrical conductivity.

Claims (1)

A method for producing process graphite, including graphitization of needle coke in the presence of a catalyst, characterized in that a mixture of needle coke and petroleum pitch is used in an amount of 10 to 20% of the coke mass, red mud is used as a catalyst, which includes oxides of iron, silicon, calcium, titanium and their carbonates, in an amount of 5 to 8% of the mass of needle coke, graphitization is carried out at temperatures from 850 to 1200°C.