CN109289902B - Method for improving performance of formed MFI molecular sieve in catalyzing Beckmann rearrangement reaction - Google Patents
Method for improving performance of formed MFI molecular sieve in catalyzing Beckmann rearrangement reaction Download PDFInfo
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- CN109289902B CN109289902B CN201811231121.1A CN201811231121A CN109289902B CN 109289902 B CN109289902 B CN 109289902B CN 201811231121 A CN201811231121 A CN 201811231121A CN 109289902 B CN109289902 B CN 109289902B
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
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- C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
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- C07D201/04—Preparation of lactams from or via oximes by Beckmann rearrangement
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- C07D223/00—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom
- C07D223/02—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings
- C07D223/06—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
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Abstract
The invention discloses a method for improving the activity, selectivity and stability of a formed MFI catalyst applied to cyclohexanone-oxime gas-phase Beckmann rearrangement reaction, and particularly relates to a method for preparing an improved catalyst by contacting an extruded catalyst containing an MFI structure molecular sieve, silica sol, sesbania powder and the like with an alkaline aqueous solution containing tetrapropyl cations, performing solid-liquid separation, drying and roasting. The improved catalysts prepared by the process of the present invention have significantly improved activity, selectivity and stability over the unmodified catalysts.
Description
Technical Field
The invention relates to a method for improving the activity, selectivity and stability of a formed MFI catalyst applied to cyclohexanone oxime gas-phase Beckmann rearrangement reaction.
Background
Caprolactam (. epsilon. -Caprolactam, abbreviated as CPL) is an important organic chemical monomer for the synthesis of polyamide 6. At present, concentrated sulfuric acid or fuming sulfuric acid is mainly used as a catalyst for the liquid phase rearrangement reaction of cyclohexanone oxime in industry for preparation. The process technology is mature, the cyclohexanone oxime conversion rate and caprolactam selectivity are high, and the product quality is stable, but the process has the greatest defect that serious environmental protection problems are caused by adopting strong corrosive concentrated sulfuric acid or fuming sulfuric acid; in addition, 0.64t of ammonium sulfate low-efficiency fertilizer is produced as a byproduct when 1t of cyclohexanone-oxime is produced by the process.
In order to develop a green heterogeneous catalyst with higher activity and selectivity, scientific research institutions and industries in various countries around the world invest a great deal of research on more cyclohexanone oxime Beckmann rearrangement reaction catalysts, mainly comprising oxide solid acids, oxide solid acids impregnated with boric acid or phosphoric acid, various molecular sieve catalysts and the like. Among them, reports related to USP5914398, USP5942613, USP1709024, USP3586668 and the like show that the service life of the oxide catalyst is short, the conversion rate of cyclohexanone oxime and the selectivity of caprolactam are not high, and the regeneration effect is not ideal. Chinese patent documents CN 1724366B, CN 102432032B, CN 102050464B, CN 102233277A and CN 101786010B report that the cyclohexanone-oxime conversion rate and caprolactam selectivity are higher and the regeneration effect is also good by adopting a high silicon-aluminum ratio or pure silicon MFI molecular sieve as a catalyst, so that the catalyst has important industrial prospect.
For the MFI molecular sieve catalyst, after the MFI molecular sieve raw powder is synthesized by a hydrothermal method, the catalyst with high cyclohexanone oxime conversion rate and caprolactam selectivity can be obtained by further treatment. USP5403801 Effect of treatment of MFI molecular sieves with different ammonium salt solutions and at least one alkaline substance (trimethylamine, tetrapropylammonium hydroxide) or aqueous ammonia on their activity in order to improve the reactivity of S-1 and TS-1 to Beckmann rearrangement reactions. At 350 ℃, the space velocity is 8h-1Under the condition of methanol as a solvent, the conversion rate of the cyclohexanone-oxime is 99.5 percent and the selectivity of caprolactam is 96.5 percent after 6.25h of TOS. CN1119282C makes MFI molecular sieve contact with organic alkali, and improves the conversion rate of oxime and selectivity of caprolactam. CN1883803A discloses that treating MFI molecular sieve with hydrofluoric acid can also improve oxime conversion and caprolactam selectivity. These patents all use powdered catalysts which are treated to increase the oxime conversion and caprolactam selectivity. They cannot be directly applied to an industrial device, and for industrial application, the molecular sieve must be used after being formed, but various auxiliary agents such as silica sol and the like are required to be added in the forming process, and the auxiliary agents often cause the reduction of the activity, the selectivity and the stability of the catalyst. Therefore, it is necessary to research a treatment method after molding to obtain a gas phase rearrangement catalyst having high activity, high selectivity and stability after molding.
Chinese patent documents CN 1322927C and CN 1014683198B use the MFI structure molecular sieve with high silicon/aluminum ratio after molding in contact with an alkaline buffer solution containing a nitrogen compound for rearrangement reaction. At cyclohexanone oxime weight space velocity (WHSV ═ 16 h)-1) After the reaction is carried out for 8 hours, the conversion rate of the cyclohexanone-oxime is 99.8 percent, and the selectivity of the caprolactam is 95.9 percent. CN 101786010B firstly adopts water solution of nitrogen-containing compound to treat the formed S-1 catalyst, and then adopts water solution of fluorine-containing compound to treat, so as to obtain the gas phase Beckmann rearrangement catalyst. Detected at the cyclohexanone oxime mass space velocity (WHSV of 2 h)-1) After the reaction is carried out for 100 hours, the conversion rate of the cyclohexanone-oxime is more than 99.8 percent, and the selectivity of the caprolactam is more than 95.5 percent.
In summary, although the catalyst prepared by the prior art and used for preparing caprolactam through gas phase rearrangement reaction has good catalytic performance, further research on the post-treatment of the formed catalyst is still needed to obtain a gas phase rearrangement reaction catalyst which has higher activity, selectivity and stability and can be used industrially.
Disclosure of Invention
The invention aims to overcome the defect that the activity and stability of a formed catalyst containing an MFI structure are reduced due to the addition of a silicon binder in the prior art, and provides an improved method for improving the catalytic performance and stability of the formed MFI catalyst when the catalyst is used for preparing caprolactam by cyclohexanone oxime gas phase Beckmann rearrangement. The modified MFI molecular sieve prepared by the method provided by the invention has the advantages that the activity, selectivity and stability of the modified catalyst are obviously improved compared with those of the unmodified catalyst when the molecular sieve forming catalyst containing the MFI structure prepared by the method is used for performing cyclohexanone-oxime gas-phase Beckmann rearrangement reaction.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for improving the catalytic Beckmann rearrangement reaction performance of a formed MFI molecular sieve comprises the steps of mixing the molecular sieve containing an MFI structure with an adhesive and an extrusion aid, extruding the mixture into strips, treating the catalyst after the extrusion into strips with an alkaline aqueous solution containing tetrapropyl cations, carrying out solid-liquid separation after the treatment is finished, and drying and roasting the separated solid to obtain the modified MFI molecular sieve, wherein the adhesive is silica sol, and the extrusion aid is polyethylene glycol 400 and sesbania powder.
As a preferable example of the silica sol of the present invention, 30.56 wt% alkaline silica sol having a pH of 9.3 was used.
In the present invention, the mass ratio of the materials contained in the extrusion molding process is that the MFI structure molecular sieve, silica sol, sesbania powder, polyethylene glycol 400, and water is 1:0.21:0.025:0.018: 0.48.
Preferably, the basic aqueous solution containing tetrapropyl cations is an aqueous solution of TPAOH, or a mixed aqueous solution of TPABr and a fatty amine compound, an alcohol amine compound, or a mixture of both aqueous solutions.
In the present invention, the molar ratio of the TPABr to the fatty amine compound and the alcohol amine compound in the mixed aqueous solution of the TPABr and the fatty amine compound and the alcohol amine compound is preferably 1:1: 1.
Preferably, the fatty amine compound is ethylenediamine, and the alcohol amine compound is ethanolamine.
In the present invention, the concentration of the alkaline aqueous solution containing tetrapropyl cations is preferably 20 to 30 wt%.
Preferably, the amount of the alkaline aqueous solution containing tetrapropyl cations is 5-20 times of the weight of the dry extrusion molding catalyst.
Preferably, when the extruded catalyst is treated by the alkaline aqueous solution containing tetrapropyl cations, the treatment temperature is 120-170 ℃, and the contact time is 6-48 h.
Preferably, the separated solid is dried at the temperature of 60-120 ℃ and roasted at the temperature of 450-550 ℃ for 6-12 h.
Compared with the prior art, the invention has the beneficial effects that:
1. the method has the advantages that the alkaline aqueous solution containing tetrapropyl cations is used for treating the extruded and formed molecular sieve containing the MFI structure, the treatment method is simple and easy to operate, and the catalytic performance of the prepared modified MFI molecular sieve is obviously improved compared with that of the modified MFI molecular sieve before modification.
2. When the molecular sieve forming catalyst containing the MFI structure prepared by the method is used for performing cyclohexanone-oxime gas-phase Beckmann rearrangement reaction, the activity, selectivity and stability of the improved catalyst are obviously improved compared with those of the catalyst which is not improved.
Detailed Description
The present invention will be described in further detail with reference to examples.
The MFI molecular sieve formed in the embodiment and the comparative example of the invention adopts an S-1 molecular sieve, and the preparation process comprises the following steps: according to the molar ratio of each component in the precursor liquid of the pre-synthesized molecular sieve { tetrapropylammonium hydroxide (TPAOH): Tetraethoxysilane (TEOS): H: }2O ═ 0.2:1:20} are weighed into a beaker and added sequentially, stirred for 3h, then raised to 70 ℃ to expel the alcohol for 2h,aging at 45 deg.C for 24 hr, and crystallizing at 170 deg.C for 48 hr. After crystallization is finished, the S-1 molecular sieve is prepared by roasting at 400-600 ℃ after separation and drying.
Comparative example 1
12.005g S-1 molecular sieve, 8.313g of 30.56 wt% of alkaline silica sol (pH 9.3), 0.211g of polyethylene glycol 400 and 0.303g of sesbania powder are weighed according to the mass, evenly mixed and extruded into strips by a mould with the aperture of 2.5 mm; drying at 60 ℃ and roasting at 400 ℃ for 6h to obtain a dried extruded catalyst sample.
Comparative example 2
The extruded catalyst sample obtained according to the comparative example 1 is mixed with a mixed solution of ammonium nitrate and ammonia water according to a mass ratio of 1: 10 mixing, modifying for 1h at 90 ℃, modifying for three times, separating solid from liquid, drying at 60 ℃, and roasting at 450 ℃ for 6h to prepare the catalyst for preparing caprolactam by the gas phase Beckmann rearrangement method.
Example 1
The extruded catalyst sample obtained according to comparative example 1 was mixed with a 25wt% TPAOH solution in a mass ratio of 1: 10 mixing, and crystallizing at 170 ℃ for 24 hours. After separation and washing, the solid is dried at 60 ℃ and roasted at 450 ℃ for 6h to prepare the caprolactam catalyst by the gas phase Beckmann rearrangement method.
Example 2
The extruded catalyst sample obtained according to comparative example 1 was mixed with a 25wt% TPAOH solution in a mass ratio of 1: 10 mixing, and crystallizing at 170 ℃ for 48 hours. After separation and washing, the solid is dried at 60 ℃ and roasted at 450 ℃ for 6h to prepare the caprolactam catalyst by the gas phase Beckmann rearrangement method.
Example 3
Rearrangement reaction performance of catalysts of examples 1 and 2 and comparative examples 1 and 2.
The cyclohexanone oxime gas phase Beckmann rearrangement reaction is carried out in a stainless steel fixed bed reactor having an inner diameter of 6 mm. The catalyst in the form of strips is crushed into particles with a size of 40-60 mm. 0.2000g of catalyst is loaded into a reactor, and 1.000g of 40-60-mesh quartz sand is filled above and below a catalyst bed layer and supported by quartz wool. In a carrier gas N2Heating to 400 deg.C at flow rate of 20mL/min at 13.3 deg.C/min, maintaining for 1h, cooling to 370 deg.C, and HPLC pressureThe ethanol solution (30 wt%) with cyclohexanone oxime as raw material is reacted by a force pump through a fixed bed, and the mass space velocity of the cyclohexanone oxime is 8h-1. Sampling was collected every 2h using a gas-liquid separator cooled with an ice-water mixture for 10min each time.
And analyzing the cyclohexanone oxime gas phase Beckmann rearrangement reaction product by using a gas chromatograph. Capillary chromatography column length 50m (OV1701) using hydrogen flame ion detector. Column temperature programmed conditions: keeping at 150 deg.C for 10min, heating to 225 deg.C at 25 deg.C/min, and keeping at this temperature for 10 min. The vaporization chamber temperature was 270 ℃ and the detector temperature was 280 ℃.
The detection of cyclohexanone oxime (CHO) adopts an internal standard method, an internal standard liquid is dimethyl phthalate, and the calculation formula is as follows:
XCHO＝(nc 0-nc)/nc 0×100％
in the formula, XCHOIs the cyclohexanone oxime conversion; n isc 0And ncThe amounts of substances of cyclohexanone oxime at the start of the reaction and at the end of the reaction, respectively. The content of caprolactam after the reaction is calculated by adopting an area normalization method, and the solvent does not participate in the integral. The reaction results are shown in Table 1.
TABLE 1 results of rearrangement reactions of various examples
After S-1 is formed, the catalytic performance and stability of the catalyst are reduced to a certain extent due to the addition of the silicon binder. The formed S-1 is treated by alkaline aqueous solution containing tetrapropyl cation, so that the catalytic performance and stability of the S-1 can be obviously improved.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above examples, and any other modifications without departing from the scope of the present invention should be replaced by equivalents, and all such modifications are included in the scope of the present invention.
Claims (1)
1. A method for improving the catalytic performance and stability of an S-1 molecular sieve with an MFI structure for catalyzing cyclohexanone oxime gas phase Beckmann rearrangement reaction is characterized by comprising the following steps: mixing an S-1 molecular sieve containing an MFI structure with an adhesive and an extrusion aid, extruding the mixture into strips, crystallizing the extruded catalyst by using an alkaline aqueous solution containing tetrapropyl cations, performing solid-liquid separation after the treatment is finished, and drying and roasting the separated solid at 60 ℃ to obtain the modified S-1 molecular sieve with the MFI structure, wherein the adhesive is silica sol, and the extrusion aid is polyethylene glycol 400 and sesbania powder; the mass ratio of substances contained in the extrusion molding process is that the MFI structure-containing S-1 molecular sieve is composed of silica sol, sesbania powder, polyethylene glycol 400, water =1: 0.21:0.025:0.018: 0.48;
the alkaline aqueous solution containing tetrapropyl cations is a TPAOH aqueous solution;
the concentration of the alkaline aqueous solution containing tetrapropyl cations is 25 wt%;
the dosage of the alkaline aqueous solution containing tetrapropyl cations is 10 times of the weight of the dry extrusion molding catalyst;
when the catalyst formed by extruding is treated by alkaline aqueous solution containing tetrapropyl cations, the treatment temperature is 170 ℃, and the contact time is 48 hours;
the roasting condition is that roasting is carried out for 6 hours at 450 ℃.
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| CN115337958B (en) * | 2022-07-07 | 2023-06-16 | 郑州大学 | Method for improving activity site of gas-phase Beckmann rearrangement reaction of cyclohexanone oxime catalyzed by formed S-1 molecular sieve |
| CN115739168A (en) * | 2022-12-21 | 2023-03-07 | 江苏扬农化工集团有限公司 | Composite molecular sieve and preparation method and application thereof |
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| CN1600428A (en) * | 2003-09-28 | 2005-03-30 | 中国石油化工股份有限公司 | Method for preparing catalyst of containing MFI structured molecular sieve |
| CN101468319A (en) * | 2007-12-28 | 2009-07-01 | 中国石油化工股份有限公司 | Method for preparing catalyst containing molecular sieve of MFI structure |
| CN103464197A (en) * | 2013-09-25 | 2013-12-25 | 大连理工大学 | Propylene epoxidation catalyst, as well as preparation method and application thereof |
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| CN1600428A (en) * | 2003-09-28 | 2005-03-30 | 中国石油化工股份有限公司 | Method for preparing catalyst of containing MFI structured molecular sieve |
| CN101468319A (en) * | 2007-12-28 | 2009-07-01 | 中国石油化工股份有限公司 | Method for preparing catalyst containing molecular sieve of MFI structure |
| CN103464197A (en) * | 2013-09-25 | 2013-12-25 | 大连理工大学 | Propylene epoxidation catalyst, as well as preparation method and application thereof |
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