Preparation method of low-temperature catalytic coal-based graphite and catalyst

Abstract

The invention provides a preparation method of low-temperature catalytic coal-based graphite, which comprises the following steps: step 1, deashing coal to obtain deashed coal; 2, pyrolyzing the ash-removed coal obtained in the step 1 to obtain high-carbon semi-coke; step 3, preparing a multi-metal salt composite catalyst; step 4, uniformly mixing the catalyst prepared in the step 3 with the semicoke obtained in the step 2, putting the mixture into a pyrolyzing furnace, and performing graphitization reaction in a nitrogen atmosphere to obtain coal-based graphite; and 5, carrying out acid pickling, filtering and water washing on the coal-based graphite obtained in the step 4 to obtain the high-purity graphite. The invention further discloses a catalyst used in the low-temperature catalysis coal-based graphite preparation process. The catalyst comprises the eighth-group metal salt and the subgroup metal salt. According to the invention, the temperature required by graphite can be effectively reduced, the energy loss is reduced, the manufacturing cost of graphite is reduced, and a new development path is developed for coal-based graphitization.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite preparation, and particularly relates to a preparation method and a catalyst for low-temperature catalytic coal-based graphite. Background Art

[0002] Due to its excellent chemical stability, electrical conductivity and mechanical properties, graphite has been widely used in many fields, especially as the anode material of lithium-ion batteries. However, natural graphite resources are limited and the mining cost is relatively high. Coal-based graphite is a graphite material prepared from coal through high-temperature graphitization. Coal-based graphite is a potential substitute for natural graphite. However, the preparation of traditional coal-based graphite usually requires a temperature of about 3000°C, and its preparation process has large energy consumption losses and high costs, which limits the commercial application of coal-based graphite. Therefore, it is of great practical significance to develop an efficient and low-cost graphite preparation method. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art, and provide a preparation method and a catalyst for low-temperature catalytic coal-based graphite, which can effectively reduce the temperature required for graphitization, reduce energy loss, and lower the manufacturing cost of coal-based graphite.

[0004] To solve the above problems, the present invention provides a preparation method for low-temperature catalytic coal-based graphite, which is characterized by including the following steps:

[0005] Step 1: Perform deashing treatment on coal to obtain deashed coal;

[0006] Step 2: Pyrolyze the deashed coal obtained in Step 1 to obtain high-carbon semicoke;

[0007] Step 3: Prepare a multi-metal salt composite catalyst;

[0008] Step 4: Mix the catalyst prepared in Step 3 with the semicoke obtained in Step 2 evenly, place it in a pyrolysis furnace, and perform a graphitization reaction under a nitrogen atmosphere to obtain coal-based graphite;

[0009] Step 5: Subject the coal-based graphite obtained in Step 4 to pickling, filtration, and water washing to obtain high-purity graphite.

[0010] The above-mentioned preparation method for low-temperature catalytic coal-based graphite is characterized in that the deashing treatment of coal in Step 1 specifically includes:

[0011] Step 101: Crush the coal through a crushing device and then screen it to obtain coal powder;

[0012] Step 102: Place the coal powder obtained in Step 101 in a mixed acid solution and stir to obtain semi-deashed coal;

[0013] Step 103, filtering the semi-deashed coal obtained in step 102 and washing it to neutrality to obtain deashed coal.

[0014] The above-mentioned method for preparing low-temperature catalytic coal-based graphite is characterized in that the pyrolysis of the deashed coal in the step 2 specifically comprises:

[0015] Step 201, placing the deashed coal obtained in step 1 in a reaction container, and introducing an inert gas into the reaction container;

[0016] Step 202: raising the temperature of the reaction container and then maintaining the temperature constant to obtain high-carbon semi-coke.

[0017] The above-mentioned method for preparing low-temperature catalytic coal-based graphite is characterized in that the preparation of the multi-metal salt composite catalyst includes:

[0018] Step 301, selecting at least one nitrate of a Group VIII metal and at least one nitrate of a sub-group metal;

[0019] Step 302: Grind and sieve the nitrate of the Group VIII metal and the nitrate of the sub-group metal, and mix them thoroughly in a mass ratio of 1:1 to obtain a multi-metal salt composite catalyst.

[0020] The above-mentioned method for preparing low-temperature catalytic coal-based graphite is characterized in that the graphitization reaction in step 4 specifically includes:

[0021] Step 401, mixing the high carbon semi-coke obtained in step 2 with the multi-metal salt composite catalyst obtained in step 3 to obtain mixed semi-coke;

[0022] Step 402: placing the mixed semi-coke obtained in step 401 in the reaction container, introducing an inert gas into the reaction container, and then starting a programmed temperature increase of the reaction container to obtain coal-based graphite.

[0023] The above-mentioned method for preparing low-temperature catalytic coal-based graphite is characterized in that the specific process of obtaining high-purity graphite in step 5 includes:

[0024] Step 501, preparing a pickling solution, preparing a mixture of hydrochloric acid and nitric acid solution with concentrations of 5-15wt% and 10-20wt% respectively;

[0025] Step 502, placing the reacted graphite into 200-500 ml of an acid washing solution, stirring it for 30 minutes to remove residual catalyst;

[0026] Step 503, filter the pickling solution, and then wash the pickled graphite with distilled water for 3-5 times to remove residual acid to obtain high-purity coal-based graphite.

[0027] The above-mentioned preparation method of low-temperature catalytic coal-based graphite is characterized in that

[0028] In step 101, the pulverizing equipment is a sample preparation pulverizer, and the screening is carried out using a 200-mesh sieve;

[0029] In step 102, the ratio of the pulverized coal to the mixed acid solution is (5-20) g:(50-200) ml; the stirring is carried out using a magnetic stirrer, the stirring temperature is 30 °C, and the stirring time is 60 min; the mixed acid solution includes hydrofluoric acid and hydrochloric acid, the mass concentration of the hydrofluoric acid is 10 wt% - 25 wt%, the mass concentration of the hydrochloric acid is 15 wt% - 30 wt%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1:1.

[0030] The above-mentioned preparation method of low-temperature catalytic coal-based graphite is characterized in that the reaction vessels in steps 201, 202 and 402 are all high-temperature electric furnaces;

[0031] The inert gases in steps 201 and 402 are both nitrogen;

[0032] In step 202, the temperature is raised to 800 °C, the heating rate is 10 °C / min, and the constant temperature time is 2 h.

[0033] In step 401, the mixing ratio of the high-carbon semicoke and the catalyst for the low-temperature catalytic coal-based graphite is (10-50) g:(2-10) g;

[0034] In step 402, the programmed temperature rise is specifically: preheating to 200 °C, keeping the temperature constant for 1 h, raising the temperature to 600 °C, keeping the temperature constant for 3 h, raising the temperature to 1200 °C, and keeping the temperature constant for 6 h, and the heating rate is 10 °C / min for all.

[0035] The present invention also discloses a metal salt composite catalyst used in the above-mentioned preparation method of low-temperature catalytic coal-based graphite, which is characterized in that it includes the following chemical components in mass percentage: 50% of group VIII metal salts and 50% of subgroup metal salts; the group VIII metal salts are one or more of iron nitrate, nickel nitrate, and cobalt nitrate, and the subgroup metal salts are one or more of copper nitrate, zinc nitrate, and manganese nitrate.

[0036] The above-mentioned catalyst for low-temperature catalytic coal-based graphite is characterized in that the group VIII metal salts are iron nitrate and cobalt nitrate, and the subgroup metal salts are copper nitrate and zinc nitrate; the mass ratio of iron nitrate to cobalt nitrate is 1:3, and the mass ratio of copper nitrate to zinc nitrate is 1:2.

[0037] The present invention has the following advantages compared with the prior art:

[0038] 1. A catalyst for low-temperature catalytic coal-based graphite prepared by the present invention avoids the use of precious metals by introducing sub-group metal salts and group VIII metal salts, greatly reducing the cost required for coal-based graphitization and significantly improving the preparation efficiency of coal-based graphite.

[0039] 2. In the preparation method of a catalyst for low-temperature catalytic coal-based graphite of the present invention, the preparation method is simple and only requires sufficient mixing of sub-group metal salts and group VIII metal salts. The operation is simple and easy for large-scale preparation and industrial production.

[0040] 3. In the application of a catalyst for low-temperature catalytic coal-based graphite of the present invention, high-purity coal-based graphite can be prepared at a maximum low temperature of 1200 °C. Through X-ray diffraction analysis, the graphitization degree of the high-purity coal-based graphite obtained by the present invention can reach more than 95%.

[0041] 4. The application of a catalyst for low-temperature catalytic coal-based graphite of the present invention has simple steps and low cost, is suitable for large-scale industrial production, and opens up a new development path for coal-based graphitization.

[0042] The following is a further detailed description of the invention through the drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0044] Figure 1 is the X-ray diffraction pattern of the coal-based graphite obtained in five groups of embodiments of the present invention.

[0045] Figure 2 is the scanning electron microscope microscopic morphology structure diagram of the coal-based graphite obtained in Example 1 of the present invention.

[0046] Figure 3 is the scanning electron microscope microscopic morphology structure diagram of the coal sample in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0048] This embodiment provides a method for preparing low-temperature catalytic coal-based graphite, which includes the following steps:

[0049] Step 1: Perform deashing treatment on coal to obtain deashed coal;

[0050] Step 2: Pyrolyze the deashed coal obtained in Step 1 to obtain high-carbon semicoke;

[0051] Step 3: Prepare a multi-metal salt composite catalyst;

[0052] Step 4: Mix the catalyst prepared in Step 3 with the semicoke obtained in Step 2 evenly, place it in a pyrolysis furnace, and carry out graphitization reaction under a nitrogen atmosphere to obtain coal-based graphite;

[0053] Step 5: Subject the coal-based graphite obtained in Step 4 to pickling, filtration, and water washing to obtain high-purity graphite.

[0054] In this embodiment, high-carbon semicoke is prepared from deashed coal powder. Then, after mixing the high-carbon semicoke with a multi-metal salt composite catalyst, a graphitization reaction is carried out. The reaction temperature is low, and high-purity graphite can be obtained through pickling and filtration, reducing energy consumption and cost.

[0055] Further, the deashing treatment of coal in Step 1 specifically includes:

[0056] Step 101: Crush the coal through a crushing device and then screen it to obtain coal powder;

[0057] Step 102: Place the coal powder obtained in Step 101 in a mixed acid solution and stir to obtain semi-deashed coal;

[0058] Step 103: Filter the semi-deashed coal obtained in Step 102 and wash it until neutral to obtain deashed coal.

[0059] That is, deashing treatment is carried out on the coal to remove most of the inorganic salts and minerals.

[0060] First, crush the coal sample to prepare coal powder; second, configure a mixed acid washing solution with the concentrations of hydrofluoric acid and hydrochloric acid being 10-25 wt% and 15-30 wt% respectively; third, mix the coal powder and the acid washing solution in a ratio of (5-20) g:(50-200) ml, and remove most of the inorganic salts and minerals through sufficient stirring; finally, filter and wash multiple times to obtain deashed coal. Through the above steps, most of the inorganic salts and minerals in the coal powder can be removed.

[0061] Further, the pyrolysis of the deashed coal in Step 2 specifically includes:

[0062] Step 201: Place the deashed pulverized coal obtained in Step 1 into a reaction vessel, and introduce an inert gas into the reaction vessel.

[0063] Step 202: Heat up the reaction vessel and then keep it at a constant temperature to obtain high-carbon semicoke.

[0064] That is, put the deashed coal into a pyrolysis electric furnace, carry out pyrolysis under a nitrogen atmosphere, remove volatile components, and generate high-carbon semicoke.

[0065] First, place the deashed coal obtained in Step 1 into a high-temperature electric furnace, set the temperature to 800 °C, the heating rate to 10 °C / min, and the constant-temperature time to 2 h; second, carry out pyrolysis under a nitrogen atmosphere to remove volatile components and generate high-carbon semicoke.

[0066] Further, the preparation of the multi-metal salt composite catalyst includes:

[0067] Step 301: Select at least one nitrate of a Group VIII metal and at least one nitrate of a sub-group metal.

[0068] Step 302: Grind and screen the nitrate of the Group VIII metal and the nitrate of the sub-group metal, and mix them thoroughly according to a mass ratio of 1:1 to obtain a multi-metal salt composite catalyst.

[0069] That is, first, select Group VIII metal salts: nitrates of iron, nickel, and cobalt, and sub-group metal salts: nitrates of copper, zinc, and manganese; second, select at least one Group VIII nitrate and at least one sub-group metal nitrate, and then mix them thoroughly in a ratio of 1:1 to prepare a multi-metal salt composite catalyst.

[0070] Further, the graphitization reaction in Step 4 specifically includes:

[0071] Step 401: Mix the high-carbon semicoke obtained in Step 2 with the multi-metal salt composite catalyst obtained in Step 3 to obtain a mixed semicoke.

[0072] Step 402: Place the mixed semicoke obtained in Step 401 into the reaction vessel, introduce an inert gas into the reaction vessel, and then start a programmed temperature rise for the reaction vessel to obtain coal-based graphite.

[0073] That is, mix the high-carbon semicoke obtained in Step 2 with the multi-metal salt composite catalyst obtained in Step 3 evenly, place the mixture into a pyrolysis furnace with a programmed temperature rise, and carry out a graphitization reaction under a nitrogen atmosphere to obtain coal-based graphite.

[0074] First, weigh the high-carbon semicoke obtained in Step 2 and the multi-metal salt composite catalyst obtained in Step 3, and mix the high-carbon semicoke and the multi-metal salt composite catalyst evenly. Place them in a reaction furnace. The mass ratio of the high-carbon semicoke to the multi-metal salt composite catalyst is (10 - 50 g) : (2 g - 10 g). Secondly, set the programmed heating of the reaction furnace. The mixture is preheated to 200 °C at room temperature and kept at a constant temperature for 1 hour. The heating rate from 200 °C to 600 °C is controlled at 10 °C / min and kept at a constant temperature for 3 hours. The heating rate from 600 °C to 1200 °C is controlled at 10 °C / min and kept at a constant temperature for 6 hours to complete the graphitization reaction. Finally, let the reaction furnace cool naturally to room temperature.

[0075] Further, the specific process of obtaining high-purity graphite in Step 5 includes:

[0076] Step 501: Prepare a pickling solution by mixing hydrochloric acid and nitric acid solutions with concentrations of 5 - 15 wt% and 10 - 20 wt% respectively.

[0077] Step 502: Place the reacted graphite into 200 - 500 ml of the pickling solution, stir well for 30 min to remove the residual catalyst.

[0078] Step 503: Filter the pickling solution, and then wash the pickled graphite with distilled water 3 - 5 times to remove the residual acid, obtaining high-purity coal-based graphite.

[0079] Further, the crushing equipment in Step 101 is a sample preparation crusher, and the screening is carried out using a 200-mesh sieve.

[0080] Further, the ratio of the pulverized coal to the mixed acid solution in Step 102 is (5 - 20) g : (50 - 200) ml. The stirring is carried out using a magnetic stirrer, the stirring temperature is 30 °C, and the stirring time is 60 min. The mixed acid solution includes hydrofluoric acid and hydrochloric acid. The mass concentration of hydrofluoric acid is 10 wt% - 25 wt%, the mass concentration of hydrochloric acid is 15 wt% - 30 wt%, and the volume ratio of hydrofluoric acid to hydrochloric acid is 1 : 1.

[0081] Further, the reaction vessels in step 201, step 202 and step 402 are all high-temperature electric furnaces; the inert gases in step 201 and step 402 are all nitrogen; the temperature in step 202 is increased to 800°C, the heating rate is 10°C / min, and the constant temperature time is 2h. The mixing ratio of the high carbon semi-coke and the low-temperature catalytic coal-based graphite catalyst in step 401 is (10-50)g: (2-10)g; the program temperature in step 402 is specifically: preheating to 200°C, constant temperature for 1h, heating to 600°C, constant temperature for 3h, heating to 1200°C, constant temperature for 6h, and the heating rate is 10°C / min.

[0082] Example 1

[0083] The specific steps of the preparation process of coal-based graphite are as follows:

[0084] 1. Take high carbon coal as raw material, crush it and control the particle size to 50-100μm. Then put 10g of the crushed coal sample into a deashing container, and add 300ml of mixed pickling liquid with hydrofluoric acid and hydrochloric acid concentrations of 15wt% and 20wt% respectively;

[0085] 2. Place the deashed coal in a high-temperature electric furnace, set the temperature to 800°C, the heating rate to 10°C / min, the constant temperature time to 2h, and perform pyrolysis in a nitrogen atmosphere to remove volatiles and generate high-carbon semi-coke.

[0086] 3. Cobalt nitrate and manganese nitrate are fully mixed in a mass ratio of 1:1 to form a multi-metal salt composite catalyst.

[0087] 4. Weigh 20g of high carbon semi-coke and 8g of multi-metal salt composite catalyst respectively, mix them evenly, and place them in the reactor;

[0088] 5. Set the temperature program of the reaction furnace, preheat the mixture to 200°C at room temperature and keep it at a constant temperature for 1 hour, control the rate of temperature increase from 200°C to 600°C at 10°C / min and keep it at a constant temperature for 3 hours, and control the rate of temperature increase from 600°C to 1200°C at 10°C / min and keep it at a constant temperature for 6 hours to complete the graphitization reaction;

[0089] 6. Prepare a mixture of hydrochloric acid and nitric acid solutions with concentrations of 10wt% and 15wt% respectively, place the reacted graphite in 500ml of the pickling solution, stir it thoroughly for 30min to remove the residual catalyst; filter the pickling solution, and then wash the pickled graphite 3 times with distilled water to remove the residual acid, and obtain a high-purity coal-based graphite sample marked as A.

[0090] Example 2

[0091] The specific steps of the preparation process of coal-based graphite are as follows:

[0092] 1. Take high-carbon coal as the raw material, crush it, and control the particle size within 50 - 100 μm. Then put 10 g of the crushed coal sample into the deashing container, and add 25 ml of a mixed acid washing solution with the concentrations of hydrofluoric acid and hydrochloric acid being 25 wt% and 15 wt% respectively;

[0093] 2. Place the deashed coal in a high-temperature electric furnace, set the temperature at 800 °C, the heating rate at 10 °C / min, and the constant temperature time at 2 h. Carry out pyrolysis in a nitrogen atmosphere to remove volatile components and generate high-carbon semi-coke.

[0094] 3. Take ferric nitrate and copper nitrate, and fully mix them in a mass ratio of 1:1 as the multi-metal salt composite catalyst.

[0095] 4. Weigh 50 g of high-carbon semi-coke and 2 g of the multi-metal salt composite catalyst respectively, mix them evenly, and place them in the reaction furnace;

[0096] 5. Set the programmed heating of the reaction furnace. The mixture is preheated to 200 °C at room temperature and kept at a constant temperature for 1 hour. The heating rate from 200 °C to 600 °C is controlled at 10 °C / min and kept at a constant temperature for 3 hours. The heating rate from 600 °C to 1200 °C is controlled at 10 °C / min and kept at a constant temperature for 6 hours to complete the graphitization reaction;

[0097] 6. Prepare a mixed solution with the concentrations of hydrochloric acid and nitric acid being 15 wt% and 10 wt% respectively. Place the reacted graphite into 500 ml of the acid washing solution, stir well for 30 min to remove the residual catalyst; filter the acid washing solution, and then wash the acid-washed graphite with distilled water 3 times to remove the residual acid, obtaining a high-purity coal-based graphite sample labeled as B.

[0098] Example 3

[0099] The specific steps of the preparation process of coal-based graphite are as follows:

[0100] 1. Take high-carbon coal as the raw material, crush it, and control the particle size within 50 - 100 μm. Then put 10 g of the crushed coal sample into the deashing container, and add 100 ml of a mixed acid washing solution with the concentrations of hydrofluoric acid and hydrochloric acid being 10 wt% and 15 wt% respectively;

[0101] 2. Place the deashed coal in a high-temperature electric furnace, set the temperature at 800 °C, the heating rate at 10 °C / min, and the constant temperature time at 2 h. Carry out pyrolysis in a nitrogen atmosphere to remove volatile components and generate high-carbon semi-coke.

[0102] 3. Take nickel nitrate and zinc nitrate, and fully mix them in a mass ratio of 1:1 as the multi-metal salt composite catalyst.

[0103] 4. Weigh 10g of high carbon semi-coke and 2g of multi-metal salt composite catalyst respectively, mix them evenly, and place them in the reactor;

[0104] 5. Set the temperature program of the reaction furnace, preheat the mixture to 200°C at room temperature and keep it at a constant temperature for 1 hour, control the rate of temperature increase from 200°C to 600°C at 10°C / min and keep it at a constant temperature for 3 hours, and control the rate of temperature increase from 600°C to 1200°C at 10°C / min and keep it at a constant temperature for 6 hours to complete the graphitization reaction;

[0105] 6. Prepare a mixture of hydrochloric acid and nitric acid solutions with concentrations of 5wt% and 10wt% respectively, place the reacted graphite in 500ml of the pickling solution, stir it thoroughly for 30min to remove the residual catalyst; filter the pickling solution, and then wash the pickled graphite 4 times with distilled water to remove the residual acid, and obtain a high-purity coal-based graphite sample marked as C.

[0106] Example 4

[0107] The specific steps of the preparation process of coal-based graphite are as follows:

[0108] 1. Take high carbon coal as raw material, crush it and control the particle size to 50-100μm. Then put 10g of the crushed coal sample into a deashing container, and add 400ml of mixed pickling liquid with hydrofluoric acid and hydrochloric acid concentrations of 10wt% and 30wt% respectively;

[0109] 2. Place the deashed coal in a high-temperature electric furnace, set the temperature to 800°C, the heating rate to 10°C / min, the constant temperature time to 2h, and perform pyrolysis in a nitrogen atmosphere to remove volatiles and generate high-carbon semi-coke.

[0110] 3. Thoroughly mix ferric nitrate and manganese nitrate in a mass ratio of 1:1 to prepare a multi-metal salt composite catalyst.

[0111] 4. Weigh 10g of high carbon semi-coke and 10g of multi-metal salt composite catalyst respectively, mix them evenly, and place them in the reactor;

[0112] 5. Set the temperature program of the reaction furnace, preheat the mixture to 200°C at room temperature and keep it at a constant temperature for 1 hour, control the rate of temperature increase from 200°C to 600°C at 10°C / min and keep it at a constant temperature for 3 hours, and control the rate of temperature increase from 600°C to 1200°C at 10°C / min and keep it at a constant temperature for 6 hours to complete the graphitization reaction;

[0113] 6. Prepare a mixture of hydrochloric acid and nitric acid solutions with concentrations of 5wt% and 20wt%, respectively, place the reacted graphite in 500ml of the pickling solution, stir it thoroughly for 30min to remove the residual catalyst; filter the pickling solution, and then wash the pickled graphite 3 times with distilled water to remove the residual acid, and obtain a high-purity coal-based graphite sample marked as D.

[0114] Example 5

[0115] The specific steps of the preparation process of coal-based graphite are as follows:

[0116] 1. Take high carbon coal as raw material, crush it and control the particle size to 50-100μm. Then put 10g of the crushed coal sample into a deashing container, and add 100ml of mixed pickling liquid with hydrofluoric acid and hydrochloric acid concentrations of 25wt% and 30wt% respectively;

[0117] 2. Place the deashed coal in a high-temperature electric furnace, set the temperature to 800°C, the heating rate to 10°C / min, the constant temperature time to 2h, and perform pyrolysis in a nitrogen atmosphere to remove volatiles and generate high-carbon semi-coke.

[0118] 3. Thoroughly mix iron nitrate, cobalt nitrate, copper nitrate and manganese nitrate in a mass ratio of 1:1 to prepare a multi-metal salt composite catalyst.

[0119] 4. Weigh 50g of high carbon semi-coke and 10g of multi-metal salt composite catalyst respectively, mix them evenly, and place them in the reactor;

[0120] 5. Set the temperature program of the reaction furnace, preheat the mixture to 200°C at room temperature and keep it at a constant temperature for 1 hour, control the rate of temperature increase from 200°C to 600°C at 10°C / min and keep it at a constant temperature for 3 hours, and control the rate of temperature increase from 600°C to 1200°C at 10°C / min and keep it at a constant temperature for 6 hours to complete the graphitization reaction;

[0121] 6. Prepare a mixture of hydrochloric acid and nitric acid solutions with concentrations of 15wt% and 20wt% respectively, place the reacted graphite in 500ml of the pickling solution, stir it thoroughly for 30min to remove the residual catalyst; filter the pickling solution, and then wash the pickled graphite 3 times with distilled water to remove the residual acid, and obtain a high-purity coal-based graphite sample marked as E.

[0122] X-ray diffraction was performed on the samples obtained in each embodiment, and the graphitization data obtained were shown in the following table:

[0123] Table 1. Graphitization degree of different samples

[0124] Sample number Graphitization degree A 96％ B 94％ C 96％ D 95％ E 97％

[0125] The graphitization degree of the sample obtained through Example 1 is 96%.

[0126] The graphitization degree of the sample obtained through Example 2 is 94%.

[0127] The graphitization degree of the sample obtained through Example 3 is 96%.

[0128] The graphitization degree of the sample obtained through Example 4 is 95%.

[0129] The graphitization degree of the sample obtained through Example 5 is 97%.

[0130] Combined Figure 1 and Figure 2 Product analysis was carried out on the high-purity coal-based graphite prepared in Examples 1-5. Figure 1 A-E in respectively correspond to the high-purity coal-based graphite in Examples 1-5; in the XRD pattern, the graphite peaks of the high-purity coal-based graphite can be clearly seen, and there are relatively few other miscellaneous peaks, indicating that the graphitization degree of the high-purity coal-based graphite prepared in Examples 1-5 is relatively high.

[0131] Figure 2 is the microscopic morphological structure of the scanning electron microscope of the coal-based graphite sample A. Figure 3 is the microscopic morphological structure of the scanning electron microscope of the coal sample, and the coal sample is marked as F. From Figure 2 and Figure 3 it can be seen that there are no obvious pores or cracks inside the coal particles of the coal sample F, the particle surface is generally smooth and flat, with distinct edges and corners, showing the general characteristics of brittle material fracture. A large number of graphite microcrystalline laminar structures and dense stacking were found in the SEM image of the sample A obtained after high-temperature graphitization treatment.

[0132] In addition, the graphitization degree of the high-purity coal-based graphite prepared in Examples 1-5 was calculated by g = [(0.3440 - c0 / 2) / 0.0086] × 100%. It was obtained that the graphitization degree of the high-purity coal-based graphite A is 96%, the graphitization degree of the high-purity coal-based graphite B is 94%, the graphitization degree of the high-purity coal-based graphite C is 96%, the graphitization degree of the high-purity coal-based graphite is 95%, and the graphitization degree of the high-purity coal-based graphite is 97%, which is in line with Figure 1 the situation where the graphite peaks are obvious and the miscellaneous peaks are few in

[0133] The present invention also discloses a metal salt composite catalyst used in the preparation method of the above-mentioned low-temperature catalytic coal-based graphite, which is characterized in that it includes the following chemical components by mass percentage: 50% of Group VIII metal salts and 50% of sub-group metal salts; the Group VIII metal salts are one or more of iron nitrate, nickel nitrate, and cobalt nitrate, and the sub-group metal salts are one or more of copper nitrate, zinc nitrate, and manganese nitrate.

[0134] Furthermore, the Group VIII metal salts are ferric nitrate and cobalt nitrate, and the sub-group metal salts are copper nitrate and zinc nitrate; the mass ratio of ferric nitrate to cobalt nitrate is 1:3, and the mass ratio of copper nitrate to zinc nitrate is 1:2.

[0135] By introducing the sub-group and Group VIII metal salt catalysts, the present invention reduces the cost required for graphitization and significantly improves the preparation efficiency of coal-based graphite.

[0136] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing low-temperature catalytic coal-based graphite, characterized in that: The following steps are involved: Step 1, deashing the coal to obtain deashed coal; Step 2: pyrolyzing the deashed coal obtained in step 1 to obtain high-carbon semi-coke; Step 3: preparing a multi-metal salt composite catalyst; Step 4: Evenly mix the catalyst prepared in step 3 and the semi-coke obtained in step 2, place them in a pyrolysis furnace, and perform graphitization reaction under a nitrogen atmosphere to obtain coal-based graphite; Step 5: The coal-based graphite obtained in step 4 is acid-washed, filtered and washed with water to obtain high-purity graphite.

2. The method for preparing low-temperature catalytic coal-based graphite according to claim 1, characterized in that: The deashing treatment of coal in step 1 specifically includes: Step 101, crushing the coal by a crushing device and then screening to obtain coal powder; Step 102, placing the coal powder obtained in step 101 in a mixed acid solution and stirring to obtain semi-deashed coal; Step 103, filtering the semi-deashed coal obtained in step 102 and washing it to neutrality to obtain deashed coal.

3. A method for preparing low-temperature catalytic coal-based graphite according to claim 1 or 2, characterized in that: The pyrolysis of the deashed coal in step 2 specifically includes: Step 201, placing the deashed coal obtained in step 1 in a reaction container, and introducing an inert gas into the reaction container; Step 202: raising the temperature of the reaction container and then maintaining the temperature constant to obtain high-carbon semi-coke.

4. A method for preparing low-temperature catalytic coal-based graphite according to claim 1 or 2, characterized in that: The preparation of the multi-metal salt composite catalyst comprises: Step 301, selecting at least one nitrate of a Group VIII metal and at least one nitrate of a sub-group metal; Step 302: Grind and sieve the nitrate of the Group VIII metal and the nitrate of the sub-group metal, and mix them thoroughly in a mass ratio of 1:1 to obtain a multi-metal salt composite catalyst.

5. A method for preparing low-temperature catalytic coal-based graphite according to claim 1 or 2, characterized in that: The graphitization reaction in step 4 specifically includes: Step 401, mixing the high carbon semi-coke obtained in step 2 with the multi-metal salt composite catalyst obtained in step 3 to obtain mixed semi-coke; Step 402: placing the mixed semi-coke obtained in step 401 in the reaction container, introducing an inert gas into the reaction container, and then starting a programmed temperature increase of the reaction container to obtain coal-based graphite.

6. A method for preparing low-temperature catalytic coal-based graphite according to claim 1 or 2, characterized in that: The specific process of obtaining high-purity graphite in step 5 includes: Step 501, preparing a pickling solution, preparing a mixture of hydrochloric acid and nitric acid solution with concentrations of 5-15wt% and 10-20wt% respectively; Step 502, placing the reacted graphite into 200-500 ml of an acid washing solution, stirring it for 30 minutes to remove residual catalyst; Step 503, filter the pickling solution, and then wash the pickled graphite with distilled water for 3-5 times to remove residual acid to obtain high-purity coal-based graphite.

7. The method for preparing low-temperature catalytic coal-based graphite according to claim 2, characterized in that: The pulverizing equipment in step 101 is a sample preparation pulverizer, and the screening is performed using a 200-mesh screen; In step 102, the ratio of the coal powder to the mixed acid solution is (5-20) g: (50-200) ml; the stirring is performed using a magnetic stirrer, the stirring temperature is 30° C., and the stirring time is 60 min; the mixed acid solution includes hydrofluoric acid and hydrochloric acid, the mass concentration of the hydrofluoric acid is 10wt%-25wt%, the mass concentration of the hydrochloric acid is 15wt%-30wt%, and the volume ratio of the hydrofluoric acid to the hydrochloric acid is 1:

1.

8. A method for preparing low-temperature catalytic coal-based graphite according to claim 1 or 2, characterized in that: The reaction vessels in step 201, step 202 and step 402 are all high-temperature electric furnaces; The inert gas in step 201 and step 402 is nitrogen; In step 202, the temperature is raised to 800° C., the heating rate is 10° C. / min, and the constant temperature time is 2 hours. In the step 401, the mixing ratio of the high carbon semi-coke and the low temperature catalytic coal-based graphite catalyst is (10-50) g: (2-10) g; The programmed temperature rise in step 402 is specifically: preheating to 200°C, keeping the temperature constant for 1 hour, heating to 600°C, keeping the temperature constant for 3 hours, heating to 1200°C, keeping the temperature constant for 6 hours, and the heating rate is 10°C / min.

9. A metal salt composite catalyst used in the method for preparing low-temperature catalytic coal-based graphite as claimed in claim 1, characterized in that: The invention comprises the following chemical components in percentage by weight: 50% of Group VIII metal salt and 50% of sub-group metal salt; the Group VIII metal salt is one or more of ferric nitrate, nickel nitrate and cobalt nitrate, and the sub-group metal salt is one or more of copper nitrate, zinc nitrate and manganese nitrate.

10. A catalyst for low-temperature catalytic coal-based graphite according to claim 9, characterized in that: The Group VIII metal salts are ferric nitrate and cobalt nitrate, and the Group VIII metal salts are copper nitrate and zinc nitrate; the mass ratio of ferric nitrate to cobalt nitrate is 1:3, and the mass ratio of copper nitrate to zinc nitrate is 1:2.

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