Composite waste mineral oil for refining and decolorizing crude titanium tetrachloride and preparation method thereof

Abstract

The invention belongs to the field of organic matter refined titanium tetrachloride decolorization, and particularly relates to compound waste mineral oil for refining and decolorizing crude titanium tetrachloride and a preparation method of the compound waste mineral oil. Transferring the mixed oil product A into a mechanical stirrer for heating, and adding the waste transformer oil to obtain a mixed oil product B; transferring the mixed oil product B into a stirrer for heating, and adding waste engine oil to obtain a mixed oil product C; transferring the mixed oil product C into a stirrer for heating, adding the waste vacuum pump oil to obtain a mixed oil product D, and cooling the mixed oil product D to room temperature to obtain the target composite waste mineral oil. The contents of the waste gasoline, the waste diesel oil, the waste transformer oil, the waste engine oil and the waste vacuum pump oil in the composite waste mineral oil are 5-10%, 5-20%, 10-20%, 20-40% and 20-50% in sequence. According to the method, the content of silicon chloride and ferric chloride can be remarkably reduced while the content of vanadium chloride in the crude titanium tetrachloride is removed.

Description

Technical Field

[0001] The invention belongs to the field of organic matter refining titanium tetrachloride decolorization, and particularly relates to a composite waste mineral oil used for refining and decolorizing crude titanium tetrachloride and a preparation method thereof. Background Art

[0002] Titanium tetrachloride is a key raw material for the production of titanium-based products such as titanium dioxide and titanium sponge. In the production process of crude titanium tetrachloride, some impurities that affect purity, such as ferric chloride, silicon chloride, vanadium chloride, etc., cannot be removed. These impurities increase the chromaticity of crude titanium tetrachloride and affect the processing and use of subsequent products. Refining and decolorizing crude titanium tetrachloride is a necessary production process for the preparation of high-purity titanium at this stage. At present, in the refining process of crude titanium tetrachloride that has been used in actual production, the organic reagent method is significantly superior to the copper wire method, aluminum powder method, and hydrogen sulfide method. It has many advantages such as simple operation, environmental friendliness, and wide sources. According to research reports, the reaction mechanism of organic reagent refining and decolorization is roughly as follows: First, the organic reagent and crude titanium tetrachloride are mixed and heated evenly. When the boiling point of titanium tetrachloride is reached, the organic reagent will be catalytically cracked to generate carbon particles. Subsequently, the carbon particles reduce most of the metal solution salt impurities (such as vanadium trichloride) into metal precipitated salts (such as vanadium dichloride) and are adsorbed on the carbon particles. Finally, the distilled titanium tetrachloride achieves the purpose of refining and impurity removal. It can be seen that the cracking and carbonization efficiency of organic reagents becomes the key to refining and impurity removal. Another study showed that the types of organic matter in organic reagents have different refining and decolorization effects, and the refining effect of unsaturated hydrocarbons is significantly better than that of saturated hydrocarbons. In most research reports on organic reagents, most use commercial finished oils as refining reagents, such as base oils, silicone oils, mineral oils, etc. These oils are expensive to use, and the refining and decolorization effects are unstable, resulting in high chromaticity and poor purity of the refined titanium tetrachloride, making it difficult to meet the production requirements of high-purity titanium tetrachloride (99.99%) products. At the same time, waste mineral oils, such as petroleum, coal, etc., are mineral oils that cannot be used because of source pollution, operational introduction or other improper use during the mining, processing and use of petroleum, coal, etc., which leads to changes in the properties of their components. They have the characteristics of low practical utilization value and high environmental protection treatment requirements. However, the main component of waste mineral oil is a type of C 15 -C 36 Unsaturated hydrocarbons can be used as an effective component for decolorizing crude titanium tetrachloride in organic refining. Therefore, using waste mineral oil to develop a cheap and efficient composite organic matter for refining titanium tetrachloride has very important practical significance and application value for improving the resource utilization rate of waste oil products and protecting the ecological environment.

[0003] Literature 1 (“Application of Continuous Vanadium Removal from Crude Titanium Tetrachloride Mineral Oil in Industrial Production”, Management and Technology of Small and Medium Enterprises (First Half of the Month), 2015(10):199.) introduces a method of using mineral oil as a crude titanium tetrachloride refining reagent, and achieving the production purpose of a continuous refining process of crude titanium tetrachloride by mixing and heating in an evaporator. The vanadium content of the refined titanium tetrachloride under this process is less than 0.0003%, which meets the production requirements of high-purity titanium tetrachloride.

[0004] Reference 2 (“Study on the process of removing vanadium from crude titanium tetrachloride with high vanadium content by organic pretreatment”, “Steel Vanadium Titanium”, 2017, 38(04): 24-28) discloses a pretreatment process for crude titanium tetrachloride with high vanadium content (4.9‰). By pretreating with 3% organic mineral oil for 30 min at 45°C, the vanadium content in the crude titanium tetrachloride can be reduced to 1.667‰, so that it can meet the processing requirements of higher purity under further refining process.

[0005] Document 3 (CN110054218A) discloses a composite organic substance for purifying crude titanium tetrachloride, which mainly includes: mineral base oil, ethers, organic sulfur compounds, metal chlorides, etc. The removal rate of silicon in crude titanium tetrachloride reaches 97.9%, the removal rate of vanadium reaches 99.9%, and the removal rate of iron reaches 99.9%, and titanium tetrachloride can be prepared with high purity.

[0006] Although the mineral oil and compounded organic matter disclosed in the above literature have the effect of refining crude titanium tetrachloride and decolorizing, the raw materials are mostly from finished oil or industrial chemicals, which have high use costs and are not easy to be applied in large-scale industry. In addition, the refining and decolorization effect is limited, and the comprehensive utilization rate of resources is not high. Therefore, the above problems can be solved by studying and utilizing compound waste mineral oil. Summary of the invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide a composite waste mineral oil for refining and decolorizing crude titanium tetrachloride, which can remove the vanadium chloride content in crude titanium tetrachloride and significantly reduce the silicon chloride and ferric chloride contents, and a preparation method thereof.

[0008] To solve the above technical problems, the present invention is achieved as follows: A composite waste mineral oil for refining and decolorizing crude titanium tetrachloride, comprising waste gasoline, waste diesel, waste transformer oil, waste engine oil and waste vacuum pump oil; the mass percentage of the waste gasoline, waste diesel, waste transformer oil, waste engine oil and waste vacuum pump oil in the composite waste mineral oil is 5-10%, 5-20%, 10-20%, 20-40% and 20-50% respectively.

[0009] Furthermore, the waste gasoline comes from the waste gasoline used for washing in the surface treatment workshop. After impurity removal, its organic matter content is less than 0.1%, and the purity of the recovered gasoline is above 99%. Such waste gasoline dissolves a large amount of organic matter during the washing process, such as solid paraffin (boiling point 300°C), vaseline (boiling point 322°C), epoxy resin (boiling point 335°C), etc. Such waste gasoline is distilled (200°C) to remove the above impurities.

[0010] Furthermore, the waste diesel oil is derived from residual diesel oil in waste oil-based drilling fluid. After impurity removal, its solid cuttings content is less than 0.1%, the pH value of the recovered diesel oil is between 6.8 and 7.2, and the purity of the recovered diesel oil rate is above 99%. This type of waste diesel oil is mixed with a large amount of solid cuttings during the drilling process, and the liquid is alkaline. This type of waste diesel oil is first subjected to sedimentation filtration and then acid washing.

[0011] Furthermore, the waste transformer oil is derived from transformer treatment waste after long-term operation of electrical equipment such as transformers. After impurity removal, its water content is less than 0.01%, the oxide content is less than 0.1%, and the purity of the recovered transformer oil is above 99%. Such waste transformer oil absorbs moisture and oxygen in the environment during the operation of the electrical equipment, resulting in the mixing of moisture and some oxidation products into the oil. Such waste transformer oil is subjected to adsorption treatment, and a strong polar adsorbent such as 5A molecular sieve, silica gel, aluminum oxide, etc. is selected. The treated waste transformer oil is used to prepare a composite waste mineral oil product for decolorization of refined titanium tetrachloride.

[0012] Furthermore, the waste oil is derived from the aged lubricating oil replaced after long-term use of gasoline engines. After impurity removal, its solid particulate content is less than 0.01%, and the purity of the recovered oil is above 99%. During use, such waste oil is mixed with dust and metal powders generated by wear of machine parts, causing the color of the oil to turn black and the viscosity to increase. Such waste oil can be first centrifuged and then subjected to solvent refining treatment.

[0013] Furthermore, the waste vacuum pump oil is derived from waste oil after the vacuum pump has been running for a long time. After impurity removal, its water content is less than 0.01%, the organic matter content is less than 0.1%, and the purity of the recovered vacuum pump oil is above 99%. Such waste vacuum pump oil is mixed with a large amount of low-boiling point solvents such as ethanol (boiling point 78°C), water (boiling point 100°C), toluene (boiling point 110°C), etc. during the use of vacuum pumping. Such waste vacuum pump oil is heated and distilled (120°C) to remove low-boiling point impurities.

[0014] The above-mentioned method for preparing the composite waste mineral oil for refining and decolorizing crude titanium tetrachloride can be implemented according to the following steps: (1) placing the waste gasoline to be treated in a distillation reflux device for distillation reflux; collecting the reflux liquid to obtain the waste gasoline; (2) The residual diesel to be treated is placed in an inclined tube sedimentation device to remove solid drilling cuttings, and then sulfuric acid washing liquid is added to the sedimentation tank to neutralize the alkaline waste diesel to obtain waste diesel; (3) placing the transformer waste to be treated in an adsorption tower device to adsorb and remove impurities to obtain waste transformer oil; (4) The aged lubricating oil to be treated is placed in a centrifugal separation device to remove solid dust or metal powder, and then transferred to a solvent refining device to remove other impurities to obtain waste engine oil; (5) placing the waste vacuum pump oil to be treated in a heating distillation device for heating and distillation, removing the low boiling point solvent, collecting the undistilled liquid, and obtaining the waste vacuum pump oil; (6) mixing the waste gasoline obtained in step (1) and the waste diesel obtained in step (2) in a certain proportion, placing the mixture in a magnetic stirrer, and stirring the mixture to obtain a mixed oil product A; (7) The mixed oil product A obtained in step (6) is transferred to a mechanical stirrer for heating, and the waste transformer oil obtained in step (3) is added in proportion, and the mixed oil product B is obtained by stirring; (8) The mixed oil product B obtained in step (7) is transferred to a semi-enclosed mechanical stirrer for heating, and waste engine oil is added in proportion, and mixed oil product C is obtained by stirring; (9) The mixed oil product C obtained in step (8) is transferred to a sealed mechanical agitator for heating, and waste vacuum pump oil is added in proportion. After stirring, a mixed oil product D is obtained, and then the mixed oil product D is cooled to room temperature to obtain the target composite waste mineral oil.

[0015] Furthermore, in the step (1), the heating temperature in the distillation reflux is 200° C., the reflux temperature is 20° C., and the heating time is 30 to 60 minutes; in the step (2), the inclination angle in the inclined tube sedimentation device is 45 to 60 degrees; and 5 to 20% sulfuric acid washing solution is added to the sedimentation tank to neutralize the alkaline waste diesel.

[0016] Furthermore, in the step (3), the adsorption time is 30 to 60 minutes, and the adsorbent is 5A molecular sieve, silica gel or alumina; in the step (4), the centrifugal speed is 5000 to 10000 r / min, and the refining solvent in the solvent refining is propane, furfural or phenol.

[0017] Furthermore, in the step (5), the heating temperature is 120°C and the heating time is 20 to 40 minutes; in the step (6), the temperature is room temperature, waste gasoline and waste diesel are mixed in proportion, the stirring speed is 100 to 1000 r / min, and the stirring time is 10 to 30 minutes; in the step (7), the heating temperature is controlled at 30 to 50°C, waste transformer oil is added in proportion, the speed is 200 to 1000 r / min, and stirring is carried out for 20 to 40 minutes; in the step (8), the heating temperature is controlled at 50 to 70°C, waste engine oil is added in proportion, the speed is 300 to 1000 r / min, and stirring is carried out for 30 to 50 minutes; in the step (9), the heating temperature is controlled at 70 to 90°C, waste vacuum pump oil is added in proportion, the speed is 400 to 1000 r / min, and stirring is carried out for 50 to 70 minutes.

[0018] The present invention uses waste mineral oil as raw material, and after the impurity removal process, the composite waste mineral oil product prepared by the composite blending method has a significant effect on removing impurities such as silicon chloride, iron chloride, and vanadium chloride in crude titanium tetrachloride. The chromaticity of the refined titanium tetrachloride is not higher than 5mg / L (K2Cr2O7), which meets the national high-purity titanium tetrachloride production requirements. In the refined titanium tetrachloride, the titanium tetrachloride content is greater than 99.96%, the silicon chloride content is less than 0.01%, the iron chloride content is less than 0.001%, and the vanadium chloride content is less than 0.0012%. At the same time, the chromaticity of the refined titanium tetrachloride should not be higher than 5mg / L (K2Cr2O7). The composite waste mineral oil product provided by the present invention has a good purification effect on impurities such as silicon chloride, iron chloride, and vanadium chloride during the refining process, and the purification rate can reach 99.9%, and various titanium tetrachloride production indicators all meet the national high-purity first-level standards.

[0019] The present invention can obtain a refined reagent with obvious decolorization effect in the crude titanium tetrachloride refining process. This is because titanium tetrachloride, as a common Lewis acid, can cause organic matter to undergo dehydrogenation reaction. The waste oil after impurity removal contains a large amount of C 15 -C 36 Unsaturated hydrocarbon organic matter is catalytically cracked by titanium tetrachloride, and then undergoes many chemical reactions such as polymerization, isomerization and aromatization to form polycyclic aromatic hydrocarbons. Finally, polycyclic aromatic hydrocarbons are further dehydrogenated and converted into porous carbon by means of structural stacking. This type of porous carbon not only has the ability to adsorb metal impurities, but the free electrons on the surface of the carbon material are conducive to the reduction of metal impurities to form precipitates, which are easy to separate and remove, and are beneficial to the separation and purification of crude titanium tetrachloride refining process, so as to achieve the purpose of preparing high-purity titanium tetrachloride. DETAILED DESCRIPTION

[0020] The specific implementation modes of the present invention will be further explained below through examples, but it does not mean that the protection scope of the present invention is limited to the scope described in the examples. Example

[0021] Table 1, Physical properties of various waste mineral oil products Table 2, Impurity content of various waste mineral oil products Table 1 shows the relevant physical properties of waste mineral oils from different sources. Table 2 shows the impurity content in waste mineral oils from different sources. The impurity removal process of different waste mineral oils is as follows: Waste gasoline from the surface treatment workshop after washing was treated with impurities. First, the waste gasoline was placed in a distillation reflux device, and the heating temperature was set to 200℃, the reflux temperature was 20℃, and the heating time was 30 min. The waste gasoline after impurities removal was collected in the reflux device, and the organic matter content and gasoline purity in the recovered gasoline were determined by gas chromatography.

[0022] The residual diesel from the waste oil-based drilling fluid is treated to remove impurities. First, the waste diesel is placed in an inclined tube sedimentation device with an inclination angle of 45, and a 20% sulfuric acid wash solution is added to the sedimentation tank. The waste diesel after impurities removal is collected at the outlet of the sedimentation tank, and the alkaline content and diesel purity in the recovered diesel are determined by a pH detector.

[0023] Waste transformer oil from long-term operation of electrical equipment such as transformers is treated with impurities. First, the waste transformer oil is placed in an adsorption tower device, and adsorbent 5A molecular sieve is added to the adsorption tower, and the adsorption time is set to 60 minutes. The waste transformer oil after impurities removal is collected at the outlet of the absorption tower, and the content of moisture and oxygen-containing compounds in the recovered waste transformer oil and the purity of the transformer oil are determined by infrared spectrometer.

[0024] The aged lubricating oil replaced after long-term use of the engine is treated with impurities. First, the waste oil is placed in a centrifugal separation device and the centrifugal speed is set to 10,000 r / min. The supernatant obtained after centrifugation is subjected to solvent refining, and the refining solvent is propane. The waste oil after impurities are collected, and the content of solid particles in the recovered waste oil and the purity of the oil are determined by a laser scatterer.

[0025] Waste vacuum pump oil from the long-term operation of vacuum pumps is treated with impurities. First, the waste vacuum pump oil is placed in a heating distillation device, the heating temperature is set to 120°C, and the heating time is 40 minutes. The waste vacuum pump oil after impurities removal is collected from the heating device, and the content of organic matter in the recovered waste vacuum pump oil and the purity of the vacuum pump oil are determined by gas chromatography.

[0026] Table 3, physical properties of various waste mineral oil products after impurity removal Table 4, impurity content of each waste mineral oil after impurity removal Furthermore, the waste mineral oil after impurities removal is compounded to obtain a composite waste mineral oil that can be used for refining and decolorizing crude titanium tetrachloride. The preparation method is as follows: (1) Mix waste gasoline and waste diesel in a certain planned ratio. First, add waste gasoline to a magnetic stirrer, set the temperature to room temperature, let it stand for 5 minutes, turn on the magnetic stirrer, set the speed to 200r / min, then slowly add waste diesel, and continue stirring for 20 minutes until the mixed oil is uniform. Stop stirring, let it stand, and obtain mixed oil A; (2) Transfer the mixed oil product A obtained in step (1) to a mechanical stirrer, turn on the heating to keep the temperature at 40°C, let it stand for 10 min, turn on the mechanical stirrer, set the speed to 400 r / min, and then slowly add the waste transformer oil according to the pre-planned proportion, and continue stirring for 30 min until the mixed oil product is uniform. Stop stirring, let it stand, and obtain mixed oil product B; (3) Transfer the mixed oil product B obtained in step (2) to a semi-enclosed mechanical stirrer, turn on the heating to keep the temperature at 60°C, let it stand for 15 minutes, turn on the mechanical stirrer, set the speed to 600 r / min, and then slowly add the waste oil according to the pre-planned proportion, and continue stirring for 40 minutes until the mixed oil product is uniform. Stop stirring, let it stand, and obtain mixed oil product C; (4) The mixed oil product C obtained in step (3) is transferred to a sealed mechanical stirrer, and the heating is turned on to maintain the temperature at 80°C. The mixture is allowed to stand for 20 min, and the mechanical stirrer is turned on, and the speed is set to 800 r / min. Then, the waste vacuum pump oil is slowly added according to the pre-planned proportion, and the mixture is stirred for 50 min until the mixed oil product is uniform. The mixture is stopped and allowed to stand at room temperature to obtain the mixed oil product D, i.e., the target composite waste mineral oil, which is used for the refining and decolorization of crude titanium tetrachloride.

[0027] Table 5 lists the names and numbers of the composite waste mineral oils and oil products prepared by mixing in certain proportions in Example 1, Example 2, Example 3 and Comparative Example 1 and Comparative Example 2.

[0028] Table 5, blending ratio and naming number of composite waste mineral oil Except for the amount and proportion of waste oil added in Example 1, Example 2 and Example 3, other operating processes and setting parameters are completely the same.

[0029] The physical property indexes of the composite waste mineral oil products are tested to compare with the original waste mineral oil products after impurity removal.

[0030] Table 6 shows the physical properties of the blended composite waste mineral oil products. The test method and condition parameters are consistent with those of the original waste mineral oil products after impurities removal.

[0031] Table 6, Physical properties of composite waste mineral oil products The evaluation method of the composite waste mineral oil product on the refining and decolorization of crude titanium tetrachloride is as follows: The compounded waste mineral oil was added to the crude titanium tetrachloride refining and decolorization experiment at a mass ratio of 1:100. First, the crude titanium tetrachloride solution was placed in a magnetic stirrer, the magnetic stirrer was turned on, the speed was set to 200 r / min, and then the composite waste mineral oil was slowly added and stirred at room temperature for 30 min. Subsequently, the heating was turned on to keep the crude titanium tetrachloride and the composite waste mineral oil at 140°C for distillation of the crude titanium tetrachloride. The collected titanium tetrachloride liquid precipitated by distillation is the refined titanium tetrachloride. The chromaticity and composition identification were performed on it. The test results of the qualified products are specified as titanium tetrachloride content greater than 99.96%, silicon chloride content less than 0.01%, iron chloride content less than 0.001%, vanadium chloride content less than 0.0012%, and chromaticity not higher than 5mg / L (K2Cr2O7). Table 7 is an evaluation of the refining and decolorization effect of composite waste mineral oil on crude titanium tetrachloride.

[0032] Table 7, Experimental results and evaluation of the refining and decolorization of crude titanium tetrachloride by composite waste mineral oil According to the comparison of the evaluation results of the embodiment and the comparative example, it can be seen that the embodiment has a better refining effect on crude titanium tetrachloride, which meets the production requirements of high-purity titanium tetrachloride. It can be seen from Comparative Example 1 that the refining effect of waste gasoline alone on crude titanium tetrachloride is poor, and the chromaticity is high. Combined with Comparative Example 2, it can be seen that the refining effect of crude titanium tetrachloride can be enhanced after a certain proportion of waste gasoline and waste vacuum pump oil are mixed, but it still does not meet the requirements for producing high-purity titanium tetrachloride. Therefore, the composite waste mineral oil prepared in the present invention can not only make full use of a variety of waste oil resources, but also significantly improve the refining effect of crude titanium tetrachloride, so as to meet the production requirements of low-cost preparation of high-purity titanium tetrachloride.

[0033] By comparing the results of oil refining described in the examples with those in the comparative literature, it can be seen that the composite waste mineral oil of the present invention can not only effectively remove the content of vanadium chloride in crude titanium tetrachloride, but also significantly reduce the content of silicon chloride and ferric chloride, further improving the purity of the refined titanium tetrachloride. Compared with the pretreatment method of the comparative literature 2, the composite waste mineral oil of the present invention can be directly used as a refining reagent for crude titanium tetrachloride after impurity removal treatment, saving production costs.

[0034] It is understandable that, for ordinary technicians in this field, various other corresponding changes and extensions can be made based on the technical methods of the present invention, and all these changes and extensions should fall within the protection scope of the claims of the present invention.

Claims

1. A method for refining and decolorizing composite waste mineral oil with crude titanium tetrachloride, characterized in that: It includes waste gasoline, waste diesel, waste transformer oil, waste engine oil and waste vacuum pump oil; the mass percentage of the waste gasoline, waste diesel, waste transformer oil, waste engine oil and waste vacuum pump oil in the composite waste mineral oil is 5-10%, 5-20%, 10-20%, 20-40% and 20-50% respectively.

2. The method for refining and decolorizing composite waste mineral oil using crude titanium tetrachloride according to claim 1, characterized in that: The waste gasoline comes from the waste gasoline used for washing in the surface treatment workshop. After impurity removal, its organic matter content is less than 0.1%, and the purity of the recovered gasoline is above 99%.

3. The method for refining and decolorizing composite waste mineral oil using crude titanium tetrachloride according to claim 2, characterized in that: The waste diesel oil comes from residual diesel oil in waste oil-based drilling fluid. After impurity removal, its solid drilling cuttings content is less than 0.1%, the pH value of the recovered diesel oil is between 6.8 and 7.2, and the purity of the recovered diesel oil rate is above 99%.

4. The method for refining and decolorizing composite waste mineral oil using crude titanium tetrachloride according to claim 3, characterized in that: The waste transformer oil comes from transformer treatment waste after long-term operation of electrical equipment such as transformers. After impurity removal, its water content is less than 0.01%, the oxide content is less than 0.1%, and the purity of the recovered transformer oil is above 99%.

5. The method for refining and decolorizing composite waste mineral oil using crude titanium tetrachloride according to claim 4, characterized in that: The waste engine oil comes from the aged lubricating oil replaced after a gasoline engine has been used for a long time. After being treated to remove impurities, the solid particle content is less than 0.01%, and the purity of the recovered engine oil is above 99%.

6. The method for refining and decolorizing composite waste mineral oil using crude titanium tetrachloride according to claim 5, characterized in that: The waste vacuum pump oil comes from the waste oil after the vacuum pump has been running for a long time. After impurity removal, its water content is less than 0.01%, the organic matter content is less than 0.1%, and the purity of the recovered vacuum pump oil is above 99%.

7. The method for preparing composite waste mineral oil for refining and decolorizing crude titanium tetrachloride according to claim 6, characterized in that: Follow these steps to implement: (1) placing the waste gasoline to be treated in a distillation reflux device for distillation reflux; collecting the reflux liquid to obtain the waste gasoline; (2) The residual diesel to be treated is placed in an inclined tube sedimentation device to remove solid drilling cuttings, and then sulfuric acid washing liquid is added to the sedimentation tank to neutralize the alkaline waste diesel to obtain waste diesel; (3) placing the transformer waste to be treated in an adsorption tower device to adsorb and remove impurities to obtain waste transformer oil; (4) The aged lubricating oil to be treated is placed in a centrifugal separation device to remove solid dust or metal powder, and then transferred to a solvent refining device to remove other impurities to obtain waste engine oil; (5) placing the waste vacuum pump oil to be treated in a heating distillation device for heating and distillation, removing the low boiling point solvent, collecting the undistilled liquid, and obtaining the waste vacuum pump oil; (6) mixing the waste gasoline obtained in step (1) and the waste diesel obtained in step (2) in a certain proportion, placing the mixture in a magnetic stirrer, and stirring the mixture to obtain a mixed oil product A; (7) The mixed oil product A obtained in step (6) is transferred to a mechanical stirrer for heating, and the waste transformer oil obtained in step (3) is added in proportion, and the mixed oil product B is obtained by stirring; (8) The mixed oil product B obtained in step (7) is transferred to a semi-enclosed mechanical stirrer for heating, and waste engine oil is added in proportion, and mixed oil product C is obtained by stirring; (9) The mixed oil product C obtained in step (8) is transferred to a sealed mechanical agitator for heating, and waste vacuum pump oil is added in proportion. After stirring, a mixed oil product D is obtained, and then the mixed oil product D is cooled to room temperature to obtain the target composite waste mineral oil.

8. The method for preparing composite waste mineral oil for refining and decolorizing crude titanium tetrachloride according to claim 7, characterized in that: In step (1), the heating temperature in the distillation reflux is 200° C., the reflux temperature is 20° C., and the heating time is 30 to 60 minutes; in step (2), the inclination angle in the inclined tube sedimentation device is 45 to 60 degrees; and 5 to 20% sulfuric acid washing solution is added to the sedimentation tank to neutralize the alkaline waste diesel.

9. The method for preparing composite waste mineral oil for refining and decolorizing crude titanium tetrachloride according to claim 8, characterized in that: In step (3), the adsorption time is 30 to 60 minutes, and the adsorbent is 5A molecular sieve, silica gel or alumina; in step (4), the centrifugal speed is 5000 to 10000 r / min, and the refining solvent in the solvent refining is propane, furfural or phenol.

10. The method for preparing composite waste mineral oil for refining and decolorizing crude titanium tetrachloride according to claim 9, characterized in that: In step (6), the temperature is room temperature, waste gasoline and waste diesel are mixed in proportion, the stirring speed is 100-1000 r / min, and the stirring time is 10-30 min; in step (5), the heating temperature is 120°C, and the heating time is 20-40 min; in step (7), the heating temperature is controlled at 30-50°C, waste transformer oil is added in proportion, the speed is 200-1000 r / min, and stirring is carried out for 20-40 min; in step (8), the heating temperature is controlled at 50-70°C, waste engine oil is added in proportion, the speed is 300-1000 r / min, and stirring is carried out for 30-50 min; in step (9), the heating temperature is controlled at 70-90°C, waste vacuum pump oil is added in proportion, the speed is 400-1000 r / min, and stirring is carried out for 50-70 min.

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