A modified silicon molecular sieve catalyst, preparation method and application thereof

Abstract

The present invention provides a modified silicon molecular sieve catalyst, a preparation method and application thereof. The preparation method thereof is as follows: S1, mixing an organosilicon compound, water and a quaternary ammonium template, and then sequentially performing a hydrolysis reaction and a distillation treatment to obtain a colloid and a fraction; secondly, subjecting the colloid to a crystallization reaction to obtain a solid-liquid mixture; S2, adjusting the pH of the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate; S3, subjecting the filter cake to a first calcination treatment to obtain a catalyst precursor and decomposed organic amines, and condensing and collecting the decomposed organic amines to obtain an organic amine mixture; S4, mixing the fraction, the catalyst precursor and the organic amine mixture, and performing a modification treatment to obtain a modified product; S5, subjecting the modified product to solid-liquid separation to obtain a solid material, and subjecting the solid material to a second calcination treatment to obtain a modified silicon molecular sieve catalyst. The modified silicon molecular sieve catalyst of the present invention has the advantages of good catalytic activity and high selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical industry, and in particular to a modified silicon molecular sieve catalyst, a preparation method and application thereof. Background Art

[0002] Caprolactam is an important intermediate in the industrial production of nylon, and the Beckmann rearrangement of cyclohexanone oxime is one of the key steps in the production process of caprolactam. At present, the traditional liquid phase rearrangement process using concentrated sulfuric acid as a catalyst is mainly used in industry. Although the reaction conditions of this process are relatively mild, the conversion rate and selectivity are also relatively ideal, a large amount of ammonium sulfate is produced as a by-product, and it is easy to cause equipment corrosion and environmental pollution. In order to overcome the above shortcomings, the gas phase Beckmann rearrangement process of cyclohexanone oxime catalyzed by solid acids such as molecular sieves has attracted attention in recent years. However, the reaction temperature required for the gas phase Beckmann rearrangement process is high, the stability of the catalyst is poor, the deactivation is fast, and the selectivity of the catalyst is also relatively low.

[0003] USP4061724, JP59164617 and CN1338427 etc. all report the synthesis method of MFI type silicon molecular sieve, which can be used for the synthesis of caprolactam. However, all the above molecular sieve catalysts have the disadvantages of low catalyst activity, low selectivity and poor stability during the gas phase rearrangement of cyclohexanone oxime, which is difficult to be used for industrial applications. In order to solve the above problems, the composition and quantity of the acid sites are adjusted by alkali modification, and the morphology structure of the MFI type silicon molecular sieve is optimized to improve its performance of catalyzing the gas phase Beckmann rearrangement of cyclohexanone oxime. Although CN1164576 and CN104307556 both use aliphatic amines and quaternary ammonium bases to modify the MFI molecular sieves, so that the cyclohexanone oxime conversion rate is greater than 99% and the caprolactam selectivity is greater than 95%, it is difficult to shape and still cannot meet the needs of industrialization. Moreover, the organic bases such as aliphatic amines and quaternary ammonium bases are expensive, and the discharge of "three wastes" is large, which increases the cost of the catalyst. CN114349018A discloses a method for in-situ modification of silicon molecular sieves using organic amines produced by high-temperature pyrolysis, thereby avoiding the use of other alkaline modification agents. However, the loss of carbon components in the catalyst prepared by this method is difficult to control during the regeneration process, the performance is prone to significant decline, and the total life is short.

[0004] Therefore, it is more advantageous to develop liquid phase modification technology using organic bases in the synthesis process of silicon molecular sieve catalysts. Summary of the invention

[0005] The main purpose of the present invention is to provide a modified silicon molecular sieve catalyst, a preparation method and application thereof, so as to solve the problem in the prior art that modified silicon molecular sieve catalysts are difficult to achieve good catalytic activity, low production cost, environmental friendliness and ease of industrial production.

[0006] In order to achieve the above object, according to one aspect of the present invention, a method for preparing a modified silicon molecular sieve catalyst is provided, the preparation method comprising the following steps:

[0007] S1, mixing an organosilicon compound, water and a quaternary ammonium template, and then sequentially performing a hydrolysis reaction and a distillation treatment to obtain a colloid and a fraction; secondly, performing a crystallization reaction on the colloid to obtain a solid-liquid mixture;

[0008] S2, adjusting the pH of the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate;

[0009] S3, performing a first calcination treatment on the filter cake to obtain a catalyst precursor and decomposed organic amine, and condensing and collecting the decomposed organic amine to obtain an organic amine mixture;

[0010] S4, mixing the fraction, the catalyst precursor and the organic amine mixture, and performing a modification treatment to obtain a modified product;

[0011] S5, performing solid-liquid separation on the modified product to obtain a solid material, and performing a second calcination treatment on the solid material to obtain a modified silicon molecular sieve catalyst.

[0012] Furthermore, the molar ratio of the organosilicon compound, water and quaternary ammonium template is 1:(10-50):(0.1-1); preferably, in step S1, an aluminum source and / or a titanium source are mixed simultaneously in the mixing step; more preferably, the molar ratio of the organosilicon compound and the aluminum source is 1:(0.0005-0.005), and the molar ratio of the organosilicon compound and the titanium source is 1:(0.0005-0.01).

[0013] Furthermore, the aluminum source is sodium aluminate and / or potassium aluminate; the titanium source is one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate.

[0014] Furthermore, the organosilicon compound is one or more of ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate; preferably, the quaternary ammonium template is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium chloride and tetrapropylammonium chloride.

[0015] Furthermore, the temperature of the hydrolysis reaction is 20-40°C, and the time is 2-4h; preferably, the temperature of the distillation treatment is 70-120°C, and the time is 1-12h; more preferably, the temperature of the distillation treatment is 80-100°C, and the time is 6-12h; preferably, the temperature of the crystallization reaction is 150-200°C, and the time is 48-96h.

[0016] Further, in step S2, an organic acid is used to adjust the pH; preferably, the organic acid is one or more of formic acid, acetic acid, propionic acid, oxalic acid, 1,3-propanedioic acid, benzoic acid, terephthalic acid, phthalic acid, isophthalic acid and trimesic acid; more preferably, the organic acid is one or more of formic acid, acetic acid and oxalic acid; preferably, in step S2, the pH value is adjusted to 7.0-10.0; more preferably, the pH value is adjusted to 7.5-8.5.

[0017] Furthermore, the temperature of the first calcination treatment is 400-600° C., and the time is 1-72 hours; preferably, the heating rate of the first calcination treatment is 0.1-20° C. / min.

[0018] Furthermore, the first roasting treatment adopts a multi-gradient temperature increase;

[0019] More preferably, the multi-gradient temperature increase includes a first stage and a second stage; wherein, in the first stage, the temperature is increased to 200-300°C at a heating rate of 0.5-5°C / min, and then kept warm for 1-24h; in the second stage, the temperature is increased to 400-600°C at a heating rate of 0.5-5°C / min to perform the first roasting treatment.

[0020] Furthermore, the condensation temperature is -20 to 0°C.

[0021] Furthermore, the weight ratio of the fraction, the catalyst precursor and the organic amine mixture is (1-4):1:(0.05-2).

[0022] Furthermore, the temperature of the modification treatment is 120 to 200° C., and the time is 6 to 180 hours; more preferably, the time of the modification treatment is 12 to 48 hours.

[0023] Furthermore, the temperature of the second calcination treatment is 350-550° C., and the time is 1-24 h; more preferably, the time of the second calcination treatment is 2-12 h.

[0024] In order to achieve the above object, according to one aspect of the present invention, a modified silicon molecular sieve catalyst prepared by the above preparation method is provided.

[0025] According to another aspect of the present invention, there is provided a use of the above-mentioned modified silicon molecular sieve catalyst in catalyzing the preparation of caprolactam from cyclohexanone oxime.

[0026] By applying the technical scheme of the present invention, a preparation method of a modified silicon molecular sieve catalyst is provided. The preparation method of the present invention utilizes the organic amine generated by the decomposition of the template agent during the roasting process as a modification reagent, and utilizes the fraction generated during the distillation process as a modification solvent to modify the outer surface of the synthesized silicon molecular sieve, and utilizes an amine organic base to react with the terminal silanol groups in the silicon molecular sieve that are prone to side reactions, thereby significantly reducing the number of terminal silanol groups in the silicon molecular sieve after roasting, and relatively increasing the content of nested silanol groups that are beneficial to the Beckmann rearrangement of cyclohexanone oxime. The preparation method of the present application optimizes the modification process, improves the utilization rate of materials, reduces the emission of "three wastes", has low production costs, and is easy to industrialize. The molecular sieve prepared by the preparation method of the present application can be used as an efficient catalyst for the synthesis of caprolactam by gas-phase rearrangement of cyclohexanone oxime, and the catalyst has the advantages of good catalytic activity and high selectivity. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0028] In order to solve the problems in the prior art as described above, according to one aspect of the present invention, a method for preparing a modified silicon molecular sieve catalyst is provided, the preparation method comprising the following steps:

[0029] S1, mixing an organosilicon compound, water and a quaternary ammonium template, and then sequentially performing a hydrolysis reaction and a distillation treatment to obtain a colloid and a fraction; secondly, performing a crystallization reaction on the colloid to obtain a solid-liquid mixture;

[0030] S2, adjusting the pH of the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate;

[0031] S3, performing a first calcination treatment on the filter cake to obtain a catalyst precursor and decomposed organic amine, and condensing and collecting the decomposed organic amine to obtain an organic amine mixture;

[0032] S4, mixing the fraction, the catalyst precursor and the organic amine mixture, and performing a modification treatment to obtain a modified product;

[0033] S5, performing solid-liquid separation on the modified product to obtain a solid material, and performing a second calcination treatment on the solid material to obtain a modified silicon molecular sieve catalyst.

[0034] The preparation method of the present invention utilizes the organic amine generated by the decomposition of the template agent during the roasting process as a modification reagent, and utilizes the fraction generated during the distillation process as a modification solvent to modify the outer surface of the synthesized silicon molecular sieve, and utilizes an amine organic base to react with the terminal silanol groups in the silicon molecular sieve that are prone to side reactions, thereby significantly reducing the number of terminal silanol groups in the silicon molecular sieve after roasting, and relatively increasing the content of nested silanol groups that are beneficial to the Beckmann rearrangement of cyclohexanone oxime. The preparation method of the present application optimizes the modification process, improves the utilization rate of materials, reduces the emission of "three wastes", has low production costs, and is easy to industrialize. The molecular sieve prepared by the preparation method of the present application can be used as an efficient catalyst for the synthesis of caprolactam by gas-phase rearrangement of cyclohexanone oxime, and the catalyst has the advantages of good catalytic activity and high selectivity.

[0035] In the present invention, the main components of the fraction referred to are water and alcohol produced by the hydrolysis of organic silicon compounds; in the process of modification, it acts as a solvent and can effectively play the role of dispersing the macromolecular organic amines produced by thermal decomposition, thereby not only reducing the discharge of three wastes, but also providing a reaction environment that is conducive to the etching of the modified silicon molecular sieve by the macromolecular organic amines, thereby making the prepared modified silicon molecular sieve catalyst have excellent cyclohexanone oxime gas-phase rearrangement catalytic performance.

[0036] In the actual operation of the present invention, preferably, after the solid-liquid separation step, the obtained solid phase component still having a certain humidity is washed, dried, etc.

[0037] In step S3, the filter cake is preferably dried before the first calcination, preferably at a drying temperature of 40 to 120°C, and preferably for a drying time of 4 to 120 hours.

[0038] In step S5, the solid material is preferably washed and dried before the second roasting. The solvent used for washing is preferably one or more of water, methanol, ethanol, isopropanol, n-butanol, acetonitrile, formamide, and acetone. The drying temperature is preferably 50 to 160° C., and the drying time is 1 to 180 hours.

[0039] In order to further improve the effect of silicon molecular sieve modification, in a preferred embodiment, the molar ratio of organosilicon compound, water and quaternary ammonium template is 1: (10-50): (0.1-1); preferably, in step S1, aluminum source and / or titanium source are mixed in the mixing step at the same time; more preferably, the molar ratio of organosilicon compound and aluminum source is 1: (0.0005-0.005), and the molar ratio of organosilicon compound and titanium source is 1: (0.0005-0.01). When no aluminum source or titanium source is added, the present invention prepares all-silicon molecular sieve Silicalite-1; when an aluminum source is added, an aluminum molecular sieve ZSM-5 is prepared; when a titanium source is added, a titanium silicon molecular sieve TS-1 is prepared. The above-mentioned addition amount is preferred, which is more conducive to better modification of the organic amine produced by the decomposition of the template.

[0040] In order to further improve the effect of silicon molecular sieve modification, in a preferred embodiment, the aluminum source is sodium metaaluminate and / or potassium metaaluminate; the titanium source is one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate. The above aluminum source and titanium source are preferred, which is more conducive to the preparation of silicon molecular sieve catalysts with excellent performance.

[0041] In order to further improve the catalytic effect of the catalyst, in a preferred embodiment, the organosilicon compound is one or more of ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate; preferably, the quaternary ammonium template is one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium chloride and tetrapropylammonium chloride. The above types of raw materials are preferred, which is more conducive to forming a suitable organic amine / fraction mixed modification system and improving the modification effect.

[0042] In order to make the surface modification more complete, in a preferred embodiment, the temperature of the hydrolysis reaction is 20-40°C and the time is 2-4h; the temperature of the distillation treatment is preferably 70-120°C and the time is 1-12h; more preferably, the temperature of the distillation treatment is 80-100°C and the time is 6-12h; the temperature of the crystallization reaction is preferably 150-200°C and the time is 48-96h. The above hydrolysis reaction conditions are preferred, which are more conducive to the smooth and slow hydrolysis reaction of the organosilicon compound, avoiding the appearance of solid silicon oxide or gel, and obtaining a crystallized precursor with uniform distribution of polysilicate anions and quaternary ammonium cations. The above distillation treatment conditions are preferred, on the one hand, to better remove the alcohol in the system, and on the other hand, to obtain a suitable fraction, which can be used for subsequent further modification. The above crystallization conditions are preferred, which can better obtain a crystallized molecular sieve and can avoid the coking of organic amines produced by partial decomposition of the template.

[0043] In a preferred embodiment, in step S2, an organic acid is used to adjust the pH; preferably, the organic acid is one or more of formic acid, acetic acid, propionic acid, oxalic acid, 1,3-propanedioic acid, benzoic acid, terephthalic acid, phthalic acid, isophthalic acid and trimesic acid; more preferably, the organic acid is one or more of formic acid, acetic acid and oxalic acid; preferably, in step S2, the pH value is adjusted to 7.0-10.0. More preferably, the pH value is adjusted to 7.5-8.5 using an organic acid, and adjusting the pH value to the above range is more conducive to the separation of the crystallized molecular sieve from the reaction system, and avoids excessive deposition of amorphous silicon species, thereby affecting the modification effect.

[0044] In order to more fully complete the first calcination treatment and better reduce the number of terminal silanol groups in the silicon molecular sieve, in a preferred embodiment, the temperature of the first calcination treatment is 400-600°C and the time is 1-72h; preferably, the heating rate of the first calcination treatment is 0.1-20°C / min.

[0045] In order to further improve the effect of the first roasting treatment, in a preferred embodiment, the first roasting treatment adopts a multi-gradient temperature increase;

[0046] More preferably, the multi-gradient temperature increase includes a first stage and a second stage; wherein, in the first stage, the temperature is increased to 200-300°C at a heating rate of 0.5-5°C / min, and then kept warm for 1-24h; in the second stage, the temperature is increased to 400-600°C at a heating rate of 0.5-5°C / min to perform the first roasting treatment.

[0047] More organic amines can be obtained in the first heating stage, which is more conducive to avoiding direct carbonization of the organic template due to direct heating to the high temperature range, thereby resulting in a low recovery rate of the organic amine and being unfavorable for subsequent modification.

[0048] In order to further improve the effect of the first calcination treatment, in a preferred embodiment, the condensation temperature is -20 to 0° C. The above condensation temperature is preferred, which is more conducive to fully capturing the organic amines generated by decomposition during the temperature increase process of the first calcination treatment.

[0049] In order to better improve the modification effect, in a preferred embodiment, the weight ratio of the fraction, the catalyst precursor and the organic amine mixture is (1-4):1:(0.05-0.8). The above ratio is preferred, which can better disperse and mix the catalyst precursor and the organic amine and give full play to the modification effect of the organic amine.

[0050] In order to improve the modification effect, in a preferred embodiment, the modification treatment temperature is 120-200°C and the time is 6-180 hours; more preferably, the modification treatment time is 12-48 hours. The above ratio is preferred to better modify the silanol sites on the molecular sieve surface and reduce its acidity.

[0051] In order to better improve the modification effect, in a preferred embodiment, the temperature of the second calcination treatment is 350-550°C and the time is 1-24 hours; more preferably, the time of the second calcination treatment is 2-12 hours. The above-mentioned second calcination treatment conditions are preferred to better remove water and organic matter adsorbed deep in the molecular sieve pores.

[0052] According to another aspect of the present invention, a modified silicon molecular sieve catalyst prepared according to the above preparation method is also provided. The molecular sieve prepared by the preparation method of the present application can be used as an efficient catalyst for the gas phase rearrangement of cyclohexanone oxime to synthesize caprolactam, and the catalyst has the advantages of good catalytic activity and high selectivity.

[0053] According to another aspect of the present invention, there is also provided a use of the modified silicon molecular sieve catalyst in catalyzing the preparation of caprolactam from cyclohexanone oxime. The catalyst has the advantages of good catalytic activity and high selectivity.

[0054] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0055] Example 1

[0056] 416 g of tetraethyl orthosilicate, 200 g of 40% tetrapropylammonium hydroxide aqueous solution and 160 g of ultrapure water were mixed and hydrolyzed at room temperature for 3 h, then heated to 80 ° C and kept at a constant temperature for 3 hours to remove alcohol, and the alcohol removal rate reached more than 70%. 445 g of the fraction was collected, and then the colloid was transferred to an autoclave and heated to 170 ° C for crystallization for 72 h;

[0057] 59.2 g of acetic acid was added dropwise to the mixture under mechanical stirring, the pH was adjusted to 8.26, filtered, washed with ultrapure water, and then dried at 120° C. for 24 h; then heated to 200° C. at a heating rate of 2° C. / min, maintained for 24 h, and then heated to 500° C. at a heating rate of 5° C. / min and calcined for 8 h, with the cold trap capture temperature controlled at -20° C., to obtain 23.0 g of an organic amine mixture and 113.9 g of a catalyst precursor;

[0058] 113.9 g of catalyst precursor all-silicon molecular sieve Silicalite-1, 23.0 g of organic amine and 445 g of fraction were put into an autoclave, reacted at 160° C. for 20 h under autogenous pressure to obtain a product system, the product system was separated, the wet solid was washed with 95% ethanol, dried at 80° C. for 16 h, and then calcined in a muffle furnace at 500° C. for 4 h to obtain a modified molecular sieve.

[0059] Prepared with 20% cyclohexanone oxime ethanol solution, nitrogen was used as carrier gas, and the space velocity was 0.8h -1 The cyclohexanone oxime / ethanol solution was mixed with ammonia and passed through a 360°C bed to undergo a rearrangement reaction to generate caprolactam. The cyclohexanone oxime conversion rate was 99.7%, the caprolactam selectivity was 96.8%, and the stable operation lasted for 1650 hours.

[0060] Example 2

[0061] Take 416g of tetraethyl orthosilicate, 0.81g of sodium aluminate, 200g of 40% tetrapropylammonium hydroxide aqueous solution and 160g of ultrapure water, mix and hydrolyze at 40°C for 2h, then heat to 70°C and keep constant temperature to remove alcohol for 6h, the alcohol removal rate reaches more than 70%, collect 410g of fractions, then transfer the colloid into an autoclave and heat to 200°C for crystallization for 48h;

[0062] 61.7 g of acetic acid was added dropwise to the mixture under mechanical stirring, the pH was adjusted to 7.02, filtered, washed with ultrapure water, and then dried at 120°C for 4 h; then the temperature was increased to 300°C at a heating rate of 0.5°C / min, maintained for 1 h, and then the temperature was increased to 600°C at a heating rate of 0.5°C / min and calcined for 1 h, the cold trap capture temperature was controlled to 0°C, and 14.3 g of an organic amine mixture and 106.5 g of a catalyst precursor were obtained;

[0063] 106.5 g of catalyst precursor silica-alumina molecular sieve ZSM-5, 5.3 g of organic phase and 106 g of fraction were put into an autoclave, reacted at 200 ° C for 6 hours under autogenous pressure to obtain a product system, the product system was separated, the wet solid was washed with 95% ethanol, dried at 160 ° C for 1 hour, and then calcined in a muffle furnace at 550 ° C for 1 hour to obtain a modified molecular sieve.

[0064] Prepared with 20% cyclohexanone oxime ethanol solution, nitrogen was used as carrier gas, and the space velocity was 0.8h -1 The cyclohexanone oxime / ethanol solution was mixed with ammonia and passed through a 360°C bed to undergo a rearrangement reaction to generate caprolactam. The cyclohexanone oxime conversion rate was 99.9%, the caprolactam selectivity was 96.7%, and the stable operation lasted for 1430 hours.

[0065] Example 3

[0066] 416 g of tetraethyl orthosilicate, 6.80 g of tetrabutyl titanate, 200 g of 40% tetrapropylammonium hydroxide aqueous solution and 160 g of ultrapure water were mixed and hydrolyzed at 20°C for 4 h, then heated to 100°C and kept at a constant temperature to remove alcohol for 1 hour, and the alcohol removal rate reached more than 70%. 440 g of the fraction was collected, and then the colloid was transferred to an autoclave and heated to 150°C for crystallization for 96 h;

[0067] 53.1 g of acetic acid was added dropwise to the mixture under mechanical stirring, the pH was adjusted to 10.00, filtered, washed with ultrapure water, dried at 40°C for 120 h, heated to 300°C at a heating rate of 5°C / min, maintained for 4 h, and then heated to 400°C at a heating rate of 5°C / min and calcined for 72 h, with the cold trap temperature controlled at -20°C, to obtain 24.3 g of an organic amine mixture and 109.1 g of a catalyst precursor;

[0068] 109.1 g of the calcined catalyst precursor titanium silicon molecular sieve TS-1, 24.3 g of the organic phase and 250 g of the fraction were put into an autoclave, reacted at 120°C for 180 h under autogenous pressure to obtain a product system, the product system was separated, the wet solid was washed with 95% ethanol, dried at 50°C for 180 h, and then calcined in a muffle furnace at 350°C for 96 h to obtain a modified molecular sieve.

[0069] Prepared with 20% cyclohexanone oxime ethanol solution, nitrogen was used as carrier gas, and the space velocity was 0.8h -1 The cyclohexanone oxime / ethanol solution was mixed with ammonia and passed through a 360°C bed to undergo a rearrangement reaction to generate caprolactam. The cyclohexanone oxime conversion rate was 99.9%, the caprolactam selectivity was 97.1%, and the stable operation lasted for 1520 hours.

[0070] Embodiments 4 to 13

[0071] The types of acid and solvent were changed on the basis of Example 1, and the performance evaluation of the catalyst is shown in Table 1.

[0072] Table 1

[0073]

[0074] Embodiment 14

[0075] The difference from Example 1 is that in the first calcination treatment, the temperature was directly raised to 500°C at a heating rate of 2°C / min for 8 hours, and 4.2 g of organic amine was obtained by cold trapping, all of which was used for modification. The performance evaluation of the catalyst is shown in Table 1.

[0076] Comparative Example 1

[0077] The difference from Example 1 is that the fraction obtained by distillation is not added to the modification step. The performance evaluation of the catalyst is shown in Table 1.

[0078] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0079] The molecular sieve prepared by the preparation method of the present application can be used as a highly efficient catalyst for the gas-phase rearrangement of cyclohexanone oxime to synthesize caprolactam, and the catalyst has the advantages of good catalytic activity and high selectivity.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified silicon molecular sieve catalyst, characterized in that: The preparation method comprises the following steps: S1, mixing an organosilicon compound, water and a quaternary ammonium template, and then sequentially performing a hydrolysis reaction and a distillation treatment to obtain a colloid and a fraction; secondly, subjecting the colloid to a crystallization reaction to obtain a solid-liquid mixture; the distillation treatment temperature is 70-120° C., and the time is 1-12 hours; S2, adjusting the pH of the solid-liquid mixture to neutral or alkaline, and then filtering to obtain a filter cake and a filtrate; S3, performing a first calcination treatment on the filter cake to obtain a catalyst precursor and decomposed organic amine, and condensing and collecting the decomposed organic amine to obtain an organic amine mixture; S4, mixing the fraction, the catalyst precursor and the organic amine mixture, and performing a modification treatment to obtain a modified product; S5, performing solid-liquid separation on the modified product to obtain a solid material, and performing a second calcination treatment on the solid material to obtain the modified silicon molecular sieve catalyst.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the organosilicon compound, the water and the quaternary ammonium template is 1:(10-50):(0.1-1).

3. The preparation method according to claim 2, characterized in that: In the step S1, an aluminum source and / or a titanium source are mixed simultaneously in the mixing step.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the organosilicon compound to the aluminum source is 1:(0.0005-0.005), and the molar ratio of the organosilicon compound to the titanium source is 1:(0.0005-0.01).

5. The preparation method according to claim 3, characterized in that: The aluminum source is sodium aluminate and / or potassium aluminate; the titanium source is one or more of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate and tetrabutyl titanate.

6. The preparation method according to any one of claims 1 to 5, characterized in that The organic silicon compound is one or more of ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate.

7. The preparation method according to any one of claims 1 to 5, characterized in that The quaternary ammonium template is selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetraethylammonium chloride and tetrapropylammonium chloride.

8. The preparation method according to any one of claims 1 to 5, characterized in that The temperature of the hydrolysis reaction is 20-40° C. and the time is 2-4 hours.

9. The preparation method according to any one of claims 1 to 5, characterized in that The distillation treatment is carried out at a temperature of 80-100° C. and for a time of 6-12 hours.

10. The preparation method according to any one of claims 1 to 5, characterized in that: The crystallization reaction temperature is 150-200° C. and the time is 48-96 hours.

11. The preparation method according to any one of claims 1 to 5, characterized in that: In the step S2, an organic acid is used to adjust the pH.

12. The preparation method according to claim 11, characterized in that: The organic acid is one or more of formic acid, acetic acid, propionic acid, oxalic acid, 1,3-propanedioic acid, benzoic acid, terephthalic acid, phthalic acid, isophthalic acid and trimesic acid.

13. The preparation method according to claim 11, characterized in that: The organic acid is one or more of formic acid, acetic acid and oxalic acid.

14. The preparation method according to claim 11, characterized in that: In step S2, the pH value is adjusted to 7.0-10.

0.

15. The preparation method according to any one of claims 1 to 5, characterized in that: The temperature of the first calcination treatment is 400-600° C., and the time is 1-72 hours.

16. The preparation method according to claim 15, characterized in that: The heating rate of the first calcination treatment is 0.1-20°C / min.

17. The preparation method according to claim 16, characterized in that: The first roasting treatment adopts a multi-gradient temperature increase, which includes a first stage and a second stage; wherein, the first stage increases the temperature to 200-300°C at a heating rate of 0.5-5°C / min, and then keeps the temperature for 1-24h; the second stage increases the temperature to 400-600°C at a heating rate of 0.5-5°C / min to carry out the first roasting treatment.

18. The preparation method according to any one of claims 1 to 5, characterized in that: The condensation temperature is -20~0℃.

19. The preparation method according to any one of claims 1 to 5, characterized in that: The weight ratio of the fraction, the catalyst precursor and the organic amine mixture is (1-4):1:(0.05-2).

20. The preparation method according to any one of claims 1 to 5, characterized in that: The temperature of the modification treatment is 120-200° C. and the time is 6-180 hours.

21. The preparation method according to claim 20, characterized in that: The modification treatment time is 12 to 48 hours.

22. The preparation method according to any one of claims 1 to 5, characterized in that The temperature of the second calcination treatment is 350-550° C., and the time is 1-24 hours.

23. The preparation method according to claim 22, characterized in that: The second calcination treatment time is 2 to 12 hours.

24. A modified silicon molecular sieve catalyst prepared by the preparation method according to any one of claims 1 to 23.

25. Use of the modified silicon molecular sieve catalyst according to claim 24 in catalyzing the preparation of caprolactam from cyclohexanone oxime.

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