Method for preparing cyclohexanone catalyst through cyclohexanol gas phase dehydrogenation
By adding silica sol to the CuO/ZnO-based catalyst to form a copper-silicon system and controlling the alkaline ion content, the conversion and selectivity problems caused by the acidity of the catalyst are solved, and efficient cyclohexanol gas-phase dehydrogenation to cyclohexanone is achieved. Reactions, reduce by-products and maintain high selectivity.
Patent Information
- Application Number
- CN202310683479.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-09
- Publication Date
- 2024-12-10
AI Technical Summary
The existing CuO/ZnO-based catalysts have low conversion and selectivity in the early and later stages of operation, and have many by-products, mainly due to the dehydration and aromatization reactions caused by their high acidity.
The copper-zinc mixed solution and the silica sol are used to precipitate in the alkaline solution to form a copper-silicon system catalyst. The pH value is aged and adjusted to ensure that the alkaline ion content in the catalyst is between 900-2000ppm, and side reactions caused by the acidic position are avoided.
At the reaction temperature of 230°C to 240°C, the cyclohexanol conversion rate was maintained at more than 60% and the cyclohexanone selectivity was more than 99%, significantly reducing by-products, shortening the induction period, and maintaining high selectivity after the temperature increased.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of catalyst preparation, and particularly relates to a method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol. Background Art
[0002] Cyclohexanone is an important organic chemical raw material and the main intermediate for the production of caprolactam (raw material for nylon-6) and adipic acid (raw material for nylon-66). In addition, cyclohexanone is also widely used in industrial production processes such as organic solvents, synthetic rubber and industrial coatings. Currently, the production of cyclohexanone is mainly achieved through the catalytic dehydrogenation of cyclohexanol. Among them, how to obtain an efficient catalyst is the key technology in the catalytic dehydrogenation of cyclohexanol to prepare cyclohexanone.
[0003] At present, the conventionally used cyclohexanol gas phase dehydrogenation catalyst for preparing cyclohexanone in industry is a CuO / ZnO catalyst. Compared with the red iron oxide catalyst and zinc catalyst used in the early stage, the CuO / ZnO catalyst can obtain a higher conversion selectivity at a lower catalytic temperature when used. However, the catalyst acidity is relatively high, and the dehydration of cyclohexanol and the dimerization dehydration of cyclohexanone are caused by the acidic sites on the catalyst, and the aromatization of cyclohexanol is caused by the metallic copper active sites in the catalyst, so the catalyst has a lower selectivity in the initial stage of operation, and the by-products are relatively high, so that its induction period is longer. And with the subsequent long-term operation of the catalyst, the conversion rate of the catalyst begins to decline. At this time, in order to maintain the output, the operating temperature of the catalyst must be increased, thus, inevitably resulting in a reduction in the selectivity of the catalyst and an increase in by-products. Summary of the invention
[0004] The present invention aims to solve the technical problems in the prior art that the conversion rate and selectivity of the catalyst are low and more by-products are produced in the early and late stages of operation due to the high acidity of the CuO / ZnO-based catalyst; a preparation method of a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol is proposed to achieve the technical effect of effectively improving the conversion rate and selectivity of the catalyst in the early and late stages of operation and effectively reducing by-products.
[0005] In order to achieve the above object, the present invention adopts the following technical scheme:
[0006] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0007] Step 1, prepare an alkaline solution and heat it to 60-65°C;
[0008] Step 2, adding the copper-zinc mixed solution and the silica sol to the alkaline solution in step 1 in parallel under stirring to perform precipitation, adding an aging agent after the precipitation is completed and adjusting the pH value for a second time to perform aging to obtain a semi-finished product;
[0009] Step 3: Wash, filter, dry, calcine and shape the semi-finished product that has been aged in step 2 to obtain a catalyst, wherein the alkaline ion content of the catalyst is 900-2000ppm.
[0010] Furthermore, the alkaline solution is one of a sodium carbonate solution and a potassium carbonate solution.
[0011] Furthermore, the concentration of copper in the copper-zinc mixed solution is (15-20) g / L.
[0012] Furthermore, the concentration of zinc in the copper-zinc mixed solution is (1-1.4) g / L.
[0013] Furthermore, the precipitation time in step 2 is 20 to 30 minutes.
[0014] Furthermore, the precipitation temperature in the first 10 to 20 minutes of the precipitation process in step 2 is 60-65°C, and the precipitation temperature in the last 10 to 20 minutes of the precipitation process is 57-60°C.
[0015] Furthermore, the pH value at the end of precipitation in step 2 is 7.0-7.5.
[0016] Furthermore, in step 2, the aging agent is an aqueous ammonia solution.
[0017] Furthermore, the pH value of the secondary modulation is 8.0-8.3.
[0018] Furthermore, the molar ratio of the active component Cu2O / ZnO in the catalyst is 2.92-16.65.
[0019] The beneficial effects of the present invention are:
[0020] When the catalyst provided by the present invention is used to produce cyclohexanone through gas phase dehydrogenation, the conversion rate of cyclohexanol can be kept above 60% and the selectivity of cyclohexanone can be kept above 99% in the initial and later stages of operation under the condition of a reaction temperature of 230°C to 240°C, while the technical effect of effectively reducing by-products is as follows:
[0021] Compared with the prior art CuO / ZnO catalysts that blindly pursue low sodium content, the present invention goes the other way. During preparation, silica sol is added to allow the catalyst system to contain silicon elements to form a copper-silicon system catalyst. At the same time, the added silica sol can have a certain coating effect on the alkaline ions during the preparation of the catalyst, avoiding the situation where the alkaline ions are washed away during the washing process of the catalyst, and ensuring that the alkaline ion content in the catalyst is high, reaching 900-2000ppm. At this time, when the alkaline ion content in the catalyst system reaches a certain amount, it can effectively avoid the dehydration of cyclohexanol and the dimerization dehydration of cyclohexanone caused by the acidic site in the catalyst system, thereby effectively avoiding the generation of by-products during the catalytic reaction, effectively shortening the induction period of the catalytic reaction, and when the reaction temperature is increased in the later stage of the operation of the catalyst system, its selectivity is increased while the conversion rate is increased, and its selectivity is still maintained at more than 99%. DETAILED DESCRIPTION
[0022] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be described more clearly and completely below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meaning understood by people with general skills in the field to which the present invention belongs.
[0023] The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "one", "an" or "the" and similar words do not indicate a quantitative limitation, but indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before "include" or "comprise" cover the features, wholes, steps, operations, elements and / or components listed after "include" or "comprise", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.
[0024] Example 1
[0025] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0026] Step 1: Add 2449 ml of 0.5 mol / L sodium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the sodium carbonate aqueous solution to 62°C.
[0027] Step 2: 3733 ml of a copper-zinc nitrate mixed solution containing 15 g / L copper and 1.07 g / L zinc and 1120 g of JN-25 silica sol are added to the open reactor in step 1 under stirring and co-precipitated with a 0.5 mol / L sodium carbonate aqueous solution. The precipitation temperature is controlled at 60-65°C in the early stage and 57-60°C in the later stage. The precipitation time is 20 minutes, and the pH value at the precipitation end point is controlled to be 7.0. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.3 for the second time, and then aged for 30 minutes to obtain a semi-finished product.
[0028] Step 3: Wash, filter, dry, calcine and shape the semi-finished product after aging in step 2 to obtain a catalyst, wherein the alkaline ion content in the catalyst is 900 ppm. The catalyst is named S1.
[0029] Example 2
[0030] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0031] Step 1: Add 2557 ml of 0.5 mol / L potassium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the potassium carbonate aqueous solution to 61°C.
[0032] Step 2: 3441 ml of a copper-zinc nitrate mixed solution containing 17 g / L copper and 1.17 g / L zinc and 1088 g of JN-25 silica sol are added to an open reactor under stirring and co-precipitated with a 0.5 mol / L sodium carbonate aqueous solution. The precipitation temperature is controlled at 60-65°C in the early stage and 57-60°C in the later stage. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.2. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.0 for the second time, and then aged for 30 minutes to obtain a semi-finished product.
[0033] Step 3: Wash, filter, dry, calcine and shape the semi-finished product that has been aged in step 2 to obtain a catalyst, wherein the content of alkaline ions in the catalyst is 1200 ppm. The catalyst is named S2.
[0034] Example 3
[0035] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0036] Step 1: Add 2666 ml of 0.5 mol / L potassium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the potassium carbonate aqueous solution to 61°C.
[0037] Step 2: 3441 ml of a copper-zinc nitrate mixed solution containing 19 g / L copper and 1.26 g / L zinc and 1056 g of JN-25 silica sol are added to an open reactor under stirring and co-precipitated with a 0.5 mol / L sodium carbonate aqueous solution. The precipitation temperature is controlled at 60-65°C in the early stage and 57-60°C in the later stage. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.0. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.0 for the second time, and then aged for 30 minutes to obtain a semi-finished product.
[0038] Step 3: The semi-finished product after aging in step 2 is washed, filtered, dried, calcined and formed to obtain a catalyst, wherein the alkaline ion content in the catalyst is 1000 ppm. The catalyst is named S3.
[0039] Example 4
[0040] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0041] Step 1: Add 2829 ml of 0.5 mol / L sodium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the sodium carbonate aqueous solution to 61°C.
[0042] Step 2: 4000 ml of a copper-zinc nitrate mixed solution containing 16 g / L copper and 1 g / L zinc and 1008 g of JN-25 silica sol are added to an open reactor under stirring to co-precipitate with a 0.5 mol / L sodium carbonate aqueous solution. The precipitation temperature is controlled at 60-65°C in the early stage and 57-60°C in the later stage. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.2. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.1 for the second time, and then aged for 30 minutes to obtain a semi-finished product.
[0043] Step 3: The semi-finished product after aging in step 2 is washed, filtered, dried, calcined and formed to obtain a catalyst, wherein the alkaline ion content in the catalyst is 1600 ppm. The catalyst is named S4.
[0044] Example 5
[0045] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0046] Step 1: Add 2638 ml of 0.5 mol / L sodium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the sodium carbonate aqueous solution to 61°C.
[0047] Step 2: Add 2952 ml of a copper-zinc nitrate mixed solution containing 20 g / L copper and 1.35 g / L zinc and 1064 g of JN-25 silica sol to an open reactor under stirring and co-precipitate with a 0.5 mol / L sodium carbonate aqueous solution. The early precipitation temperature is controlled at 60-65°C, and the late precipitation temperature is controlled at 57-60°C. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.3. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.2 for a second time, and then aged for 30 minutes to obtain a semi-finished product.
[0048] Step 3: The semi-finished product after aging in step 2 is washed, filtered, dried, calcined and formed to obtain a catalyst, wherein the alkaline ion content in the catalyst is 1800 ppm. The catalyst is named S5.
[0049] Example 6
[0050] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0051] Step 1: Add 2276 ml of 0.5 mol / L sodium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the sodium carbonate aqueous solution to 61°C.
[0052] Step 2: Add 2952 ml of a copper-zinc nitrate mixed solution containing 18 g / L copper and 1.40 g / L zinc and 1064 g of JN-25 silica sol to an open reactor under stirring and co-precipitate with a 0.5 mol / L sodium carbonate aqueous solution. The precipitation temperature is controlled at 60-65°C in the early stage and 57-60°C in the later stage. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.5. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.2 for a second time, and then aged for 30 minutes to obtain a semi-finished product.
[0053] Step 3: The semi-finished product after aging in step 2 is washed, filtered, dried, calcined and formed to obtain a catalyst, wherein the alkaline ion content in the catalyst is 2000 ppm. The catalyst is named S6.
[0054] Comparative Example 1
[0055] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0056] Step 1: Add 2829 ml of 0.5 mol / L sodium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the sodium carbonate aqueous solution to 61°C.
[0057] Step 2: 4000 ml of a copper-zinc nitrate mixed solution containing 16 g / L copper and 1 g / L zinc and 1008 g of JN-25 silica sol are added to an open reactor under stirring to co-precipitate with a 0.5 mol / L sodium carbonate aqueous solution. The precipitation temperature is controlled at 60-65°C in the early stage and 57-60°C in the later stage. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.2. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.1 for the second time, and then aged for 30 minutes to obtain a semi-finished product.
[0058] Step 3: The semi-finished product aged in step 2 is repeatedly washed, filtered, dried, calcined and formed to obtain a catalyst, wherein the alkaline ion content in the catalyst is 500 ppm. The catalyst is named S4-1.
[0059] The difference between this comparative example 1 and the above-mentioned example 4 lies in the content of alkaline ions in the catalyst.
[0060] Comparative Example 2
[0061] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0062] Step 1: Add 2829 ml of 0.5 mol / L sodium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the sodium carbonate aqueous solution to 61°C.
[0063] Step 2: 4000 ml of a copper-zinc nitrate mixed solution containing 16 g / L copper and 1 g / L zinc is added to an open reactor under stirring to co-precipitate with a 0.5 mol / L sodium carbonate aqueous solution. The early precipitation temperature is controlled at 60-65° C., and the later precipitation temperature is controlled at 57-60° C. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.2. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.1 for a second time, and then aged for 30 minutes to obtain a semi-finished product.
[0064] Step 3: The semi-finished product aged in step 2 is washed, filtered, dried, calcined and formed to obtain a catalyst, wherein the alkaline ion content in the catalyst is 500 ppm. The catalyst is named S4-2.
[0065] The difference between this comparative example 2 and the comparative example 1 is that no silica sol is added.
[0066] Comparative Example 3
[0067] A method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol comprises the following steps:
[0068] Step 1: Add 2829 ml of 0.5 mol / L sodium carbonate aqueous solution into an open reactor, stir vigorously, and raise the temperature of the sodium carbonate aqueous solution to 61°C.
[0069] Step 2: 4000 ml of a copper-zinc nitrate mixed solution containing 16 g / L copper and 1 g / L zinc is added to an open reactor under stirring to co-precipitate with a 0.5 mol / L sodium carbonate aqueous solution. The early precipitation temperature is controlled at 60-65° C., and the later precipitation temperature is controlled at 57-60° C. The precipitation time is 30 minutes, and the pH value at the precipitation end point is controlled to be 7.2. After the precipitation is completed, an ammonia solution is added and the pH value is adjusted to 8.1 for a second time, and then aged for 30 minutes to obtain a semi-finished product.
[0070] Step 3: The semi-finished product aged in step 2 is washed, filtered, dried, calcined and formed to obtain a catalyst, wherein the alkaline ion content in the catalyst is 300 ppm. The catalyst is named S4-3.
[0071] The difference between this comparative example 3 and the above comparative example 2 is that the content of alkaline ions in the catalyst is different.
[0072] Verification test
[0073] The catalysts obtained in the above Examples 1-6 and Comparative Examples 1-3 were prepared into catalyst samples with a specification of ￠4.5×3.0 mm, and the cyclohexanol gas phase dehydrogenation to cyclohexanone catalytic reaction was carried out in a fixed bed reactor to compare the catalyst activities obtained in the Examples and Comparative Examples. The catalyst loading was 50 ml, the liquid space velocity of the raw material cyclohexanol was 0.60 h -1 , the reducing gas is H2 gas, and the reaction temperatures are 230°C and 240°C respectively. The reaction results at the reaction temperature of 230°C are shown in Table 1, and the reaction results at the reaction temperature of 240°C are shown in Table 2.
[0074] Table 1 Reaction results of catalysts in various embodiments and comparative examples at a reaction temperature of 230°C
[0075]
[0076] Table 2 Reaction results of catalysts in various embodiments and comparative examples at a reaction temperature of 240°C
[0077]
[0078]
[0079] It can be seen from the test data of Examples 1-6 in Table 1 and Table 2 above that the catalyst prepared by the technology of the present invention has excellent catalytic performance in the catalytic reaction of cyclohexanol gas phase dehydrogenation to cyclohexanone. Whether it is 5 hours of reaction or 24 hours of reaction, the cyclohexanol conversion rate can be maintained at more than 60% and the selectivity of cyclohexanone can be maintained at a reaction temperature of 230°C to 240°C. The selectivity is more than 99%, and the by-products are relatively small when the reaction is 5 hours and 24 hours. Comparing the test data of Comparative Examples 1-3 and Example 4 again, it can be seen that adding silica sol to the catalyst system can make the catalyst system form a copper-silicon system catalyst. Although it can improve the effect of the catalytic reaction of cyclohexanol gas phase dehydrogenation to cyclohexanone to a certain extent, it is not the main influencing factor. It is mainly after adding silica sol and controlling the content of alkaline ions in the catalyst to be more than 900ppm that the catalyst can obtain a better catalytic effect in the catalytic reaction.
[0080] In general, compared with the prior art CuO / ZnO catalysts that blindly pursue low sodium content, the present invention takes the opposite approach when preparing the catalyst. By adding silica sol, the catalyst system contains silicon elements to form a copper-silicon system catalyst. At the same time, the added silica sol can have a certain coating effect on the alkaline ions during the preparation of the catalyst, avoiding the situation where the alkaline ions are washed away during the washing process of the catalyst, thereby ensuring that the alkaline ion content in the catalyst is high, reaching 900-2000ppm. At this time, when the alkaline ion content in the catalyst system reaches a certain amount, it can effectively avoid the dehydration of cyclohexanol and the dimerization dehydration of cyclohexanone caused by the acidic sites in the catalyst system, thereby effectively avoiding the generation of by-products during the catalytic reaction. When the reaction temperature is increased in the later stage of the operation of the catalytic system, its selectivity is increased while the conversion rate is increased, and its selectivity is still maintained at more than 99%.
[0081] Finally, it should be noted that these embodiments are only used to illustrate the present invention and do not limit the scope of the present invention. In addition, for those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. The obvious changes or modifications derived from them are still within the scope of protection of the present invention.
Claims
1. A method for preparing a catalyst for preparing cyclohexanone by gas phase dehydrogenation of cyclohexanol, characterized in that: The steps include: Step 1, prepare an alkaline solution and heat it to 60-65°C; Step 2, adding the copper-zinc mixed solution and the silica sol to the alkaline solution in step 1 in parallel under stirring to perform precipitation, adding an aging agent after the precipitation is completed and adjusting the pH value for a second time to perform aging to obtain a semi-finished product; Step 3: Wash, filter, dry, calcine and shape the semi-finished product that has been aged in step 2 to obtain a catalyst, wherein the alkaline ion content of the catalyst is 900-2000ppm.
2. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The alkaline solution is one of a sodium carbonate solution and a potassium carbonate solution.
3. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The concentration of copper in the copper-zinc mixed solution is (15-20) g / L.
4. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The concentration of zinc in the copper-zinc mixed solution is (1-1.4) g / L.
5. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The precipitation time in step 2 is 20 to 30 minutes.
6. The method for preparing a catalyst for preparing cyclohexanone by gas phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The precipitation temperature in the first 10 to 20 minutes of the precipitation process in step 2 is 60-65° C., and the precipitation temperature in the last 10 to 20 minutes of the precipitation process is 57-60° C.
7. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The pH value at the end of precipitation in step 2 is 7.0-7.
5.
8. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: In step 2, the aging agent is an ammonia solution.
9. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The pH value of the secondary modulation is 8.0-8.
3.
10. The method for preparing a catalyst for preparing cyclohexanone by gas-phase dehydrogenation of cyclohexanol according to claim 1, characterized in that: The molar ratio of the active components Cu2O / ZnO in the catalyst is 2.92-16.65.