Self-sulfuration oil-soluble molybdenum-tungsten composite catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of heavy oil hydrocracking, and particularly discloses a self-sulfuration oil-soluble molybdenum-tungsten composite catalyst and a preparation method and application thereof.The preparation method comprises the following steps that S1, a sulfuration agent is added into a mixture containing a molybdenum-containing compound and a tungsten-containing compound, stirring reaction is conducted at the temperature of 50-120 DEG C, and a thiomolybdate and thiotungstate mixture is obtained; and S2, stirring the mixture of thiomolybdate and thiotungstate prepared in the step S1 and a long-carbon-chain amide compound at 30-150 DEG C to react, and distilling the reaction product to remove water, thereby obtaining the self-sulfuration oil-soluble molybdenum-tungsten composite catalyst. According to the preparation method, crystallization and washing are not needed, the self-vulcanized oil-soluble molybdenum-tungsten composite catalyst is obtained by directly reacting with the long-carbon-chain amide compound, the prepared product is high in yield, and the problem of loss of effective metal components caused by washing can be avoided.

Description

Technical Field

[0001] The invention relates to the technical field of heavy oil hydrocracking, and in particular to a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst and a preparation method and application thereof. Background Art

[0002] Waste lubricating oil is the waste from used motor vehicles, mechanical equipment, etc. The environmental harm can be reduced by recycling waste lubricating oil.

[0003] Waste lubricating oil regeneration processes are divided into three categories: re-purification process, re-refining process, and re-refining process. Among them, the re-refining process is the mainstream direction of waste lubricating oil regeneration. The re-refining process is developed on the basis of re-purification by adding hydrogenation and other processes. Slurry bed hydrogenation technology is one of the technologies for processing waste lubricating oil. Since the waste lubricating oil slurry bed hydrogenation technology can achieve the conversion of inferior waste lubricating oil, the coke produced will affect the long-term operation of the reactor. Therefore, it is necessary to develop a highly active catalyst to slow down the coking process during the hydrogenation process and extend the operation cycle of the device.

[0004] At present, the catalysts used in the slurry bed hydrogenation process are mainly: solid powder catalysts, water-soluble catalysts, and oil-soluble catalysts. Oil-soluble catalysts have good dispersion performance in waste lubricating oils, high hydrogenation activity, and solve the problem of severe wear of the reaction system due to solid particles. There are currently two types of oil-soluble catalysts: self-sulfurized oil-soluble catalysts and unsulfurized oil-soluble catalysts. Unsulfurized oil-soluble catalysts require the addition of a sulfiding agent to be converted into catalytically active metal sulfides during use. The sulfidation process is prone to insufficient sulfidation and affects the use of the catalyst, ultimately reducing the catalytic hydrogenation activity, resulting in a large amount of addition and increased operating costs; self-sulfurized oil-soluble catalysts do not require the addition of a sulfiding agent when used, and have the advantage of high catalytic hydrogenation activity.

[0005] In the prior art, due to the different preparation processes of self-sulfurized oil-soluble catalysts, the performance of the prepared self-sulfurized oil-soluble catalysts may vary. For example, patent CN201811388624.X discloses a method for preparing a molybdenum-tungsten composite oil-soluble residual oil suspended bed hydrogenation catalyst. The crude product prepared by the method is washed, dehydrated and dried, and then the solvent is removed to obtain the final Mo-W composite oil-soluble catalyst. The defects of this technology or the shortcomings of the present invention are: the crude product needs to be washed and dried, and the effective metal components will be lost during the washing process, which increases the production cost. Summary of the invention

[0006] The purpose of the present invention is to provide a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst and a preparation method and application thereof. The preparation method does not require crystallization and washing, and directly reacts with a long-chain amide compound to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst. The prepared product not only has a high yield, but also can avoid the problem of loss of effective metal components due to washing.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst comprises the following steps:

[0009] S1. Add a vulcanizing agent to a mixture containing a molybdenum-containing compound and a tungsten-containing compound, and stir the mixture at 50 to 120° C. to obtain a mixture of thiomolybdate and thiotungstate;

[0010] S2, stirring the mixture of thiomolybdate and thiotungstate prepared in step S1 and a long-chain amide compound at 30-150° C., and removing water from the reaction product by distillation to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst.

[0011] CN201811388624.X discloses a method for preparing a molybdenum-tungsten composite oil-soluble residue oil suspended bed hydrogenation catalyst. In the catalyst preparation process, catalyst and sulfuric acid need to be added. A large amount of added substances are required, so washing is required to wash away impurities such as the catalyst and sulfuric acid, which will lead to the loss of effective metal components.

[0012] First, in step S1 of the present invention, a mixture of thiomolybdate and thiotungstate is prepared by adding a sulfiding agent, so that the prepared self-sulfurized oil-soluble molybdenum-tungsten composite catalyst can be self-fluidized, and no further sulfidization is required during subsequent use. It can effectively inhibit coking and extend the operating cycle of the device, and is particularly suitable for the pre-hydrogenation process of waste lubricating oil.

[0013] Secondly, step S1 of the present invention uses a mixture of a molybdenum-containing compound and a tungsten-containing compound as a raw material for sulfurization treatment, so that the preparation of the mixture of thiomolybdate and thiotungstate does not need to be crystallized and the prepared mixture of thiomolybdate and thiotungstate does not need to be washed, and the mixture of thiomolybdate and thiotungstate is directly reacted with a long-chain amide compound to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst without adding a catalyst and sulfuric acid and other substances. Therefore, the prepared catalyst does not need to be washed, and a high-quality self-sulfurized oil-soluble molybdenum-tungsten composite catalyst can be obtained directly by distillation and dehydration, and the yield is high. Since the intermediate product and the final reaction product in the preparation method of the present invention do not need to be washed, the problem of loss of effective metal components due to washing can be avoided.

[0014] The present invention adopts a mixture of thiomolybdate and thiotungstate to directly react with a long-chain amide compound to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst, which can realize a one-step preparation of the catalyst; there is no need to first prepare a thiobimetallic compound, and then react with an organic amine after precipitation filtration and water washing as in the process of patent CN201810677699.3, which is a complicated process and has a relatively low yield.

[0015] In a preferred embodiment, in step S1, the sulfiding agent is an ammonium sulfide solution.

[0016] The ammonium sulfide solution is added to the mixture of the molybdenum-containing compound and the tungsten-containing compound to obtain the mixture of thiomolybdate and thiotungstate at one time, thereby reducing the investment in production equipment and production costs.

[0017] In a preferred embodiment, the preparation process of the ammonium sulfide solution is as follows:

[0018] In a closed environment with protective gas, at 20-50°C, hydrogen sulfide is mixed into an aqueous ammonia solution for 20-50 hours to obtain an ammonium sulfide solution.

[0019] In the prior art, there is a method of directly using existing ammonium sulfide as a vulcanizing agent. The present application uses hydrogen sulfide and ammonia water as raw materials to first prepare ammonium sulfide. The specific advantages are: on the one hand, it can make full use of the resources of the current waste oil recycling company itself and save costs; on the other hand, it can accurately control the concentration of ammonium sulfide as needed to prevent the concentration from being reduced due to long-term storage when purchased from outside, thereby affecting the vulcanization effect.

[0020] In a preferred embodiment, in step S1, the molybdenum-containing compound is at least one of molybdenum trioxide, ammonium heptamolybdate and ammonium molybdate.

[0021] In a preferred embodiment, in step S1, the tungsten-containing compound is at least one of tungsten trioxide, sodium tungstate and ammonium metatungstate.

[0022] In a preferred embodiment, in step S1, the molar ratio of the sum of the metals in the mixture of the molybdenum-containing compound and the tungsten-containing compound to the sulfiding agent is 1:3 to 1:8, so that the molybdenum-containing compound and the tungsten-containing compound are fully sulfided.

[0023] In a preferred embodiment, in step S2, the number of carbon atoms in the long carbon chain of the long carbon chain amide compound is 8 to 24.

[0024] In a preferred embodiment, the reaction time of step S1 is 1 to 5 hours; the reaction time of step S2 is 2 to 20 hours.

[0025] In a preferred embodiment, based on the weight of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst, the molybdenum content of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst is 5%-20%, and the tungsten content is 5%-20%.

[0026] A self-sulfurized oil-soluble molybdenum-tungsten composite catalyst prepared by the above preparation method.

[0027] The invention discloses an application of a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst in the hydrocracking of waste heavy oil, wherein the waste heavy oil includes waste lubricating oil.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The present invention adds an ammonium sulfide solution to a mixture of a molybdenum-containing compound and a tungsten-containing compound to obtain a mixture of thiomolybdate and thiotungstate at one time; in this process, the mixture of thiomolybdate and thiotungstate does not need to be crystallized and washed, and then directly reacts with a long-chain amide compound to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst; the reaction product does not need to be washed, and the product can be obtained directly by distilling and removing water. The process is simple, the catalyst yield is high, the production cost is low, and the conditions are mild; it is easy to industrialize production, and the problem of loss of effective metal components caused by washing can be avoided. The process has the advantages of high hydrogenation activity, no need for resulfurization, effective inhibition of coking, and extended device operation cycle, and is particularly suitable for the pre-hydrogenation process of waste lubricating oil. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. The schematic implementation mode of the present invention and its description are only used to explain the present invention and are not intended to limit the present invention. The embodiments described below are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0031] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to those of ordinary skill in the art that these specific details do not have to be employed to practice the present invention. In other embodiments, in order to avoid confusing the present invention, known structures, materials or methods are not specifically described. The materials, instruments and reagents used in the following examples, unless otherwise specified, can be obtained from commercial sources. The technical means used in the examples, unless otherwise specified, are conventional means well known to those skilled in the art.

[0032] In order to solve the problem of loss of effective metal components due to washing of the existing self-sulfurized oil-soluble catalyst, this embodiment provides a method for preparing a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst, comprising the following steps:

[0033] S1. Add a vulcanizing agent to a mixture containing a molybdenum-containing compound and a tungsten-containing compound, control the molar ratio of molybdenum in the molybdenum-containing compound to tungsten in the tungsten-containing compound to be 10:1 to 1:10, stir and react at 50 to 120° C. for 1 to 5 hours; obtain a mixture of thiomolybdate and thiotungstate; in this embodiment, the vulcanizing agent is preferably an ammonium sulfide solution, and the ammonium sulfide solution is added to the mixture of the molybdenum-containing compound and the tungsten-containing compound to obtain a mixture of thiomolybdate and thiotungstate at one time, thereby reducing the investment in production equipment and production costs. The preparation process of the ammonium sulfide solution is as follows:

[0034] In a closed environment with protective gas, at 20-50°C, hydrogen sulfide is mixed into an aqueous ammonia solution for 20-50 hours to obtain an ammonium sulfide solution.

[0035] In the preparation process of the above-mentioned ammonium sulfide solution, the by-product hydrogen sulfide of the waste lubricating oil regeneration company can be used to react with purchased ammonia water to prepare an ammonium sulfide aqueous solution as a sulfiding agent, thereby achieving effective utilization of the by-product hydrogen sulfide and saving production costs.

[0036] Preferably, the molybdenum-containing compound is at least one of molybdenum trioxide, ammonium heptamolybdate and ammonium molybdate; and the tungsten-containing compound is at least one of tungsten trioxide, sodium tungstate and ammonium metatungstate.

[0037] Preferably, the molar ratio of the sum of metals in the mixture of the molybdenum-containing compound and the tungsten-containing compound to ammonium sulfide is 1:3 to 1:8.

[0038] S2. The mixture of thiomolybdate and thiotungstate prepared in step S1 is reacted with a long-chain amide compound under stirring at 30-150° C. for 2-20 hours. The reaction product is distilled to remove water to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst; the molybdenum content of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst is 5%-20% and the tungsten content is 5%-20% based on the weight of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst; wherein the number of carbon atoms in the long carbon chain of the long-chain amide compound is 8-24.

[0039] The self-sulfurized oil-soluble molybdenum-tungsten composite catalyst prepared by the above preparation method has high hydrogenation activity, does not need to be resulfurized, can effectively inhibit coke formation, and prolongs the operation cycle of the device. It is particularly suitable for the pre-hydrogenation process of waste lubricating oil.

[0040] Embodiment 1:

[0041] The vulcanizing agent of this embodiment is ammonium sulfide solution; the molybdenum-containing compound is ammonium heptamolybdate, and the tungsten-containing compound is ammonium metatungstate.

[0042] A method for preparing a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst comprises the following steps:

[0043] S101. In a closed environment with protective gas, hydrogen sulfide is mixed into a 20% concentration ammonia solution at a mixing temperature of 50° C. for 20 hours to obtain an ammonium sulfide solution;

[0044] S102, adding the ammonium sulfide solution to the mixture of ammonium heptamolybdate and ammonium metatungstate, controlling the molar ratio of the total metal to the ammonium sulfide to be 1:3, and the molar ratio of the metal molybdenum to the metal tungsten to be 10:1, stirring and reacting at 120° C. for 1 h to obtain a mixture of thiomolybdate and thiotungstate;

[0045] S103, adding a long carbon chain amide compound (C8H 17 NO), stirred and reacted at 30°C for 20h, the reaction product was distilled to remove water, and a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst was obtained, named M-1. The total metal yield of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst is shown in Table 1.

[0046] Embodiment 2:

[0047] The sulfiding agent of this embodiment is ammonium sulfide solution; the molybdenum-containing compound is ammonium molybdate, and the tungsten-containing compound is sodium tungstate.

[0048] A method for preparing a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst comprises the following steps:

[0049] S101. In a closed environment with protective gas, hydrogen sulfide is mixed into a 25% concentration ammonia solution at a mixing temperature of 40° C. for 30 hours to obtain an ammonium sulfide solution;

[0050] S102, adding the ammonium sulfide solution to the mixture of ammonium molybdate and sodium tungstate, controlling the molar ratio of the total metal to the ammonium sulfide to be 1:5, and the molar ratio of the metal molybdenum to the metal tungsten to be 1:1, stirring and reacting at 80° C. for 3 hours to obtain a mixture of thiomolybdate and thiotungstate;

[0051] S103, adding a long carbon chain amide compound (C106) having 20 carbon atoms to the obtained mixture of thiomolybdate and thiotungstate. 20 H 39 NO2), stirred and reacted at 90°C for 10h, the reaction product was distilled to remove water, and a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst was obtained, named M-2. The total metal yield of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst is shown in Table 1.

[0052] Embodiment 3:

[0053] The sulfiding agent of this embodiment is ammonium sulfide solution; the molybdenum-containing compound is molybdenum trioxide, and the tungsten-containing compound is tungsten trioxide.

[0054] A method for preparing a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst comprises the following steps:

[0055] S101. In a closed environment with protective gas, hydrogen sulfide is mixed into a 28% concentration ammonia solution at a mixing temperature of 20° C. for 50 hours to obtain an ammonium sulfide solution;

[0056] S102, adding ammonium sulfide solution to the mixture of molybdenum trioxide and tungsten trioxide, controlling the molar ratio of total metal to ammonium sulfide to be 1:8, and the molar ratio of metal molybdenum to metal tungsten to be 1:10, stirring and reacting at 50° C. for 5 hours to obtain a mixture of thiomolybdate and thiotungstate;

[0057] S103, adding a long carbon chain amide compound (C103) having 24 carbon atoms to the obtained mixture of thiomolybdate and thiotungstate. 24 H 47 NO2), stirred and reacted at 150°C for 2h, and the reaction product was distilled to remove water to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst, named M-3. The total metal yield of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst is shown in Table 1.

[0058] Comparative Example 1:

[0059] A method for preparing a self-sulfurized oil-soluble molybdenum catalyst comprises the following steps:

[0060] S101. In a closed environment with protective gas, hydrogen sulfide is mixed into a 25% concentration ammonia solution at a mixing temperature of 40° C. for 30 hours to obtain an ammonium sulfide solution;

[0061] S102, adding ammonium sulfide solution to ammonium molybdate, controlling the molar ratio of molybdenum to ammonium sulfide to be 1:5, stirring and reacting at 80° C. for 3 h to obtain thiomolybdate;

[0062] S103, adding a long carbon chain amide compound (C 20 H 39 NO2), reacted with stirring at 90°C for 10h, and the obtained reaction product was distilled to remove water to obtain a self-sulfurized oil-soluble molybdenum catalyst, named N-1. The metal molybdenum yield of the self-sulfurized oil-soluble molybdenum catalyst is shown in Table 1.

[0063] Comparative Example 2:

[0064] A method for preparing a self-sulfurized oil-soluble tungsten catalyst comprises the following steps:

[0065] S101. In a closed environment with protective gas, hydrogen sulfide is mixed into a 25% concentration ammonia solution at a mixing temperature of 40° C. for 30 hours to obtain an ammonium sulfide solution;

[0066] S102, adding ammonium sulfide solution to sodium tungstate, controlling the molar ratio of tungsten to ammonium sulfide to be 1:5, stirring and reacting at 80° C. for 3 h to obtain thiotungstate;

[0067] S103, adding a long carbon chain amide compound (C 20 H 39 NO2), stirred and reacted at 90°C for 10h, the reaction product was distilled to remove water, and a self-sulfurized oil-soluble tungsten catalyst was obtained, named N-2. The metal tungsten yield of the self-sulfurized oil-soluble tungsten catalyst is shown in Table 1.

[0068] Comparative Example 3:

[0069] This comparative example is based on Example 2, and the difference from Example 2 is that the intermediate product prepared in step S102 is washed, filtered, and dried. Specifically:

[0070] The vulcanizing agent of this comparative example is ammonium sulfide solution; the molybdenum-containing compound is ammonium heptamolybdate, and the tungsten-containing compound is ammonium metatungstate.

[0071] A method for preparing a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst comprises the following steps:

[0072] S101. In a closed environment with protective gas, hydrogen sulfide is mixed into a 25% concentration ammonia solution at a mixing temperature of 40° C. for 30 hours to obtain an ammonium sulfide solution;

[0073] S102, adding ammonium sulfide solution to the mixture of ammonium molybdate and sodium tungstate, controlling the molar ratio of total metal to ammonium sulfide to be 1:5, and the molar ratio of metal molybdenum to metal tungsten to be 1:1, stirring and reacting at 80° C. for 3 hours to obtain a mixture of thiomolybdate and thiotungstate, and washing, filtering and drying the mixture of thiomolybdate and thiotungstate to obtain a solid mixture of thiomolybdate and thiotungstate,

[0074] S103, adding 20% ​​of a long carbon chain amide compound (C 20 H 39NO2), reacted with stirring at 90°C for 10h, and the obtained reaction product was distilled to remove water to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst, named N-3. The metal molybdenum yield of the self-sulfurized oil-soluble molybdenum catalyst is shown in Table 1.

[0075] Comparative Example 4:

[0076] A method for preparing a self-sulfurized oil-soluble nickel-tungsten composite catalyst comprises the following steps:

[0077] S101. In a closed environment with protective gas, hydrogen sulfide is mixed into a 20% concentration ammonia solution at a mixing temperature of 40° C. for 30 hours to obtain an ammonium sulfide solution;

[0078] S102, adding the ammonium sulfide solution to ammonium heptamolybdate, controlling the molar ratio of molybdenum metal to ammonium sulfide to be 1:5, stirring and reacting at 80° C. for 3 h to obtain ammonium thiomolybdate;

[0079] S103, dissolving nickel nitrate in ammonia water, adding the ammonia solution of nickel nitrate to the thiomolybdate in S102, controlling the molar ratio of metal nickel to metal tungsten to be 1:1, stirring at 90°C for 2h, to obtain ammonium nickel thiotungstate.

[0080] S104, adding a long carbon chain amide compound (C 20 H 39 NO2), stirred and reacted at 90°C for 10h, the reaction product was distilled to remove water, and a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst was obtained, named N-4. The total metal yield of the self-sulfurized oil-soluble nickel-tungsten bimetallic catalyst is shown in Table 1.

[0081] The yields of Example 1-Example 3 and Comparative Example 1-Comparative Example 4 are shown in Table 1:

[0082] Table 1

[0083] Example Total catalyst metal yield, % Metal molybdenum content, % Tungsten metal content, % Metal nickel content, % Example 1 92 20.43 3.85 / Example 2 93 5.69 10.73 / Example 3 92 0.84 16.33 / Comparative Example 1 91 11.58 / / Comparative Example 2 93 / 20.37 / Comparative Example 3 75 4.52 8.66 / Comparative Example 4 90 / 10.64 3.45

[0084] From the data in Table 1, we can see that:

[0085] 1) When the ammonium sulfide of the present invention is used as a vulcanizing agent, the yield of the bimetallic catalyst (molybdenum-tungsten composite catalyst) prepared is not significantly reduced compared with the yield of the monometallic catalyst (tungsten / molybdenum catalyst), indicating the feasibility of the preparation method of the present invention for preparing the molybdenum-tungsten composite catalyst.

[0086] 2) When washing and other operations are performed on the intermediate product during the preparation of the self-sulfurized oil-soluble molybdenum catalyst, the total metal yield of the catalyst will be reduced, and the contents of metallic molybdenum and metallic tungsten in the prepared self-sulfurized oil-soluble molybdenum catalyst will be reduced, especially the content of metallic tungsten will decrease significantly.

[0087] The catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated using waste lubricating oil as a raw material. The properties of the waste lubricating oil are shown in Table 2. The amount of catalyst added is calculated based on the total amount of molybdenum and / or tungsten or nickel added to the raw material (when the catalyst is a molybdenum-tungsten bimetallic, it is calculated based on the total amount of molybdenum and tungsten metals; when the catalyst is a molybdenum-nickel bimetallic, it is calculated based on the total amount of molybdenum and nickel metals), and are all controlled to be 500 ppm. The amount of catalyst added is shown in Table 2. The reaction was carried out in a kettle hydrogenation reactor, and the hydrogenation conditions were controlled as follows: hydrogenation pressure 8 MPa, hydrogenation temperature 360°C, reaction time 2 h, and the obtained hydrogenated product was filtered and analyzed. The results are shown in Table 2.

[0088] Table 2

[0089]

[0090]

[0091] From the data in Table 2, we can see that:

[0092] 1) Compared with bimetallic and monometallic catalysts, the hydrogenation effect is better.

[0093] 2) When washing and other operations are performed on the intermediate product during the preparation of the self-sulfurized oil-soluble molybdenum catalyst, the dosage will be greatly increased to achieve the same hydrogenation effect. Therefore, the self-sulfurized oil-soluble molybdenum catalyst prepared by the preparation method of the present invention has the technical advantage of better hydrogenation effect under the same dosage conditions, which is beneficial to reducing the dosage of the catalyst in the waste lubricating oil treatment process.

[0094] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst, characterized in that: The following steps are involved: S1. Add a vulcanizing agent to a mixture containing a molybdenum-containing compound and a tungsten-containing compound, and stir the mixture at 50 to 120° C. to obtain a mixture of thiomolybdate and thiotungstate; S2, stirring the mixture of thiomolybdate and thiotungstate prepared in step S1 and a long-chain amide compound at 30-150° C., and removing water from the reaction product by distillation to obtain a self-sulfurized oil-soluble molybdenum-tungsten composite catalyst.

2. The preparation method according to claim 1, characterized in that: In step S1, the sulfiding agent is ammonium sulfide solution.

3. The preparation method according to claim 2, characterized in that: The preparation process of the ammonium sulfide solution is as follows: In a closed environment with protective gas, at 20-50°C, hydrogen sulfide is mixed into an aqueous ammonia solution for 20-50 hours to obtain an ammonium sulfide solution.

4. The preparation method according to claim 1, characterized in that: In step S1, the molybdenum-containing compound is at least one of molybdenum trioxide, ammonium heptamolybdate and ammonium molybdate.

5. The preparation method according to claim 1, characterized in that: In step S1, the tungsten-containing compound is at least one of tungsten trioxide, sodium tungstate and ammonium metatungstate.

6. The preparation method according to claim 1, characterized in that: In step S1, the molar ratio of the sum of metals in the mixture of the molybdenum-containing compound and the tungsten-containing compound to the sulfiding agent is 1:3 to 1:

8.

7. The preparation method according to claim 1, characterized in that: In step S2, the number of carbon atoms in the long carbon chain of the long carbon chain amide compound is 8 to 24.

8. The preparation method according to any one of claims 1 to 7, characterized in that: Based on the weight of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst, the molybdenum content of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst is 5%-20%, and the tungsten content is 5%-20%.

9. A self-sulfurized oil-soluble molybdenum-tungsten composite catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the self-sulfurized oil-soluble molybdenum-tungsten composite catalyst as claimed in claim 9 in the hydrocracking of waste heavy oil, characterized in that: The waste heavy oil includes waste lubricating oil.

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