Method for preparing Ti-MOR catalyst through one-pot post-treatment and application of Ti-MOR catalyst

Abstract

The invention provides a method for preparing a Ti-MOR catalyst through one-pot aftertreatment and application of the Ti-MOR catalyst, and relates to the field of molecular sieve catalyst material preparation.The method comprises the following steps that acid liquor, a titanium source and deionized water are mixed, and a co-treating agent is obtained; adding a fresh MOR molecular sieve into the co-treatment agent in a stirring state, uniformly mixing, and pretreating to obtain pretreated mixed gel; putting the pretreated mixed gel into a reaction kettle, heating, and carrying out heat preservation for post-treatment; and after heat preservation is finished, cooling, washing with water, drying and roasting to obtain the Ti-MOR catalyst. According to the method, an acid and titanium source co-treating agent one-step liquid-phase titanium loading process is adopted to replace a traditional two-step method, efficient titanium loading of the MOR molecular sieve is achieved through the acid synergistic effect, and the catalytic conversion rate and selectivity are both improved to 95% or above; and the co-treatment agent can be recycled for three times, so that the utilization rate of the acid liquor is increased, the emission of waste acid is reduced by 30% or above, and an innovative solution is provided for industrial production of the Ti-MOR which is simplified in process, controlled in cost and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the field of molecular sieve catalyst material preparation, and in particular relates to a method for preparing a Ti-MOR catalyst by post-processing in one pot and an application thereof. Background Art

[0002] TS-1 is widely used industrially in the continuous ammoximation of cyclohexanone. However, the preparation cost of the TS-1 support, Silicate-1, is high, and the synthesis process requires extremely low Al content in the raw materials, with a Si / Al ratio of >1000. This results in significant investment in equipment and raw materials, leading to a sharp increase in the production cost of cyclohexanone oxime. In recent years, reports have suggested that Ti-MOR could be used as an alternative catalyst to TS-1 for the continuous ammoximation of cyclohexanone. MOR has a straight, one-dimensional, twelve-membered ring pore. Currently, there are no reports demonstrating the direct synthesis of Ti-MOR molecular sieves in a hydrothermal system; these are typically obtained via a two-step post-processing process.

[0003] Research has reported the preparation of Ti-MOR molecular sieves using a two-step gas-solid phase post-treatment method. This method first involves acid washing and deep dealumination of the hydrothermally synthesized MOR molecular sieve. During high-temperature drying, the dealuminated MOR molecular sieve is treated with helium containing TiCl4 vapor, thereby introducing titanium species into the silanol pockets of the molecular sieve, forming tetracoordinated Ti active species. However, this dealumination and titanium-addition process requires high temperatures and contains large amounts of hydrogen chloride gas in the exhaust, which causes equipment corrosion and waste acid emissions, limiting large-scale industrial production.

[0004] Invention Publication No. CN 118371261A discloses the use of a liquid-phase titanium-supported method to prepare Ti-MOR catalysts. This method uses a titanium tetrachloride aqueous solution as the titanium source, mixed with a dealuminated MOR molecular sieve, and then adds titanium in the liquid phase. This method is easier to adjust than high-temperature vapor-phase titanium support. However, this liquid-phase titanium supplementation method still requires a two-step post-processing step: acid treatment for dealumination followed by liquid-phase titanium supplementation. This process also presents the problem of waste acid disposal and is more complex.

[0005] Invention Publication No. CN110127717A discloses a method for obtaining a Ti-MOR molecular sieve by fully mixing acid-dealuminized MOR with an organic solvent containing a titanium source and then subjecting it to dynamic crystallization. However, the catalyst obtained by this method has a low cyclohexanone conversion rate, indicating that this method of first dealumination and then crystallization cannot achieve the desired effect. Summary of the Invention

[0006] To address the complex multi-step preparation process, waste acid emissions, and low catalyst conversion rates associated with traditional catalysts, the present invention provides a one-pot post-treatment method for preparing Ti-MOR catalysts. This method utilizes a one-step liquid-phase titanium loading process using an acid and titanium source co-treatment agent, replacing the traditional two-step dealumination-titanium loading process. This synergistic acidic effect allows for efficient titanium loading of MOR molecular sieves, boosting catalytic conversion and selectivity to over 95%. The co-treatment agent can be recycled three times, improving acid utilization and reducing waste acid emissions by over 30%. This innovative solution provides a streamlined, cost-effective, and environmentally friendly solution for industrialized Ti-MOR production.

[0007] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0008] The present invention provides a method for preparing a Ti-MOR catalyst by post-treatment in one pot, comprising the following steps:

[0009] (1) mixing an acid solution, a titanium source, and deionized water to obtain a co-treatment agent;

[0010] (2) adding fresh MOR molecular sieve to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 100 to 700 rpm, stirring and mixing for 2 h, and then pretreating at 50 to 120° C. for 4 to 48 h to obtain a pretreated mixed gel;

[0011] (3) The pretreated mixed gel obtained in step (2) is placed in a reaction kettle, heated to 130-200° C., and kept warm for 30 min-4 h;

[0012] (4) After the insulation is completed, the temperature is lowered, the catalyst is washed with water and dried, and then calcined at 400-550 degrees to obtain the Ti-MOR catalyst.

[0013] Preferably, the acid in step (1) is one or more of nitric acid, hydrochloric acid, sulfuric acid, formic acid or citric acid.

[0014] Preferably, the titanium source in step (1) is one or more of TiCl4, titanium powder, tetraethyl titanate or tetrabutyl titanate.

[0015] Preferably, in step (1), the acid concentration of the co-treatment agent is 1-5 mol / L; the titanium source concentration is 0.1-2 mol / L.

[0016] More preferably, in step (1), the acid concentration of the co-treatment agent is 1-3 mol / L, and the titanium source concentration is 0.2-1.5 mol / L.

[0017] Preferably, the silicon-aluminum molar ratio Si / Al of the MOR molecular sieve in step (2) is 20-400.

[0018] More preferably, the silicon-aluminum molar ratio Si / Al of the MOR molecular sieve in step (2) is 80-300.

[0019] Preferably, the silicon-titanium molar ratio Si / Ti of the Ti-MOR catalyst obtained in step (4) is 10-150.

[0020] More preferably, the silicon-titanium molar ratio Si / Ti of the Ti-MOR catalyst obtained in step (4) is 20-130.

[0021] The present invention also provides an application of the Ti-MOR catalyst prepared by the method in ammoximation reaction of cycloalkanone.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) through a one-pot post-treatment process, the washing and drying steps after the traditional acid dealumination are omitted, the operation process is simplified, and the feasibility of industrial production is significantly improved; (2) by configuring an acid-titanium co-treatment agent, the co-treatment agent is recycled, the utilization rate of the acid component is effectively improved, and the waste acid discharge is simultaneously reduced; (3) the titanium loading in the catalyst is increased through a pretreatment process; (4) the prepared Ti-MOR catalyst exhibits broad-spectrum catalytic activity in the cycloalkanone ammoximation reaction, and its raw material conversion rate and product selectivity are both greater than 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The XRD pattern of Ti-MOR prepared by the method of this application is shown in FIG.

[0024] Figure 2 The UV spectrum of Ti-MOR prepared by the method of the present application is shown in FIG. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with embodiments:

[0026] Example 1

[0027] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0028] (1) mixing HCl, TiCl4 and deionized water to obtain a co-treatment agent with an acid concentration of 1 mol / L and a titanium source concentration of 2 mol / L;

[0029] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=400) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 300 rpm, stirring and mixing for 2 h, and pretreating at 50° C. for 24 h to obtain a pretreated mixed gel;

[0030] (3) The pretreated mixed gel obtained in step (2) was placed in a reaction kettle, heated to 160°C, and kept warm for post-treatment for 1 hour;

[0031] (4) After the heat preservation is completed, the temperature is lowered, the catalyst is washed with water and dried, and then calcined at 550°C to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=10). The XRD pattern of the prepared Ti-MOR catalyst is shown in FIG. Figure 1 As shown; the UV spectrum is as Figure 2 shown.

[0032] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0033] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0034] Example 2

[0035] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0036] (1) mixing HCl, tetraethyl titanate, and deionized water to obtain a co-treatment agent having an acid concentration of 5 mol / L and a titanium source concentration of 0.1 mol / L;

[0037] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=300) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 700 rpm, stirring and mixing for 2 h, and pretreating at 90° C. for 4 h to obtain a pretreated mixed gel;

[0038] (3) The pretreated mixed gel obtained in step (2) was placed in a reaction kettle, heated to 130° C., and kept warm for 4 h for post-treatment;

[0039] (4) After the insulation is completed, the temperature is lowered, the mixture is washed with water and dried, and then calcined at 500° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=130).

[0040] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0041] The resulting Ti-MOR was used in the ammoximation reaction of cyclopentanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.3g of cyclopentanone, 5.4g of hydrogen peroxide, and 16.8g of aqueous ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0042] Example 3

[0043] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0044] (1) mixing HCl, titanium powder, and deionized water to obtain a co-treatment agent having an acid concentration of 3 mol / L and a titanium source concentration of 1 mol / L;

[0045] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=200) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 500 rpm, stirring and mixing for 2 h, and pretreating at 80° C. for 4 h to obtain a pretreated mixed gel;

[0046] (3) The pretreated mixed gel obtained in step (2) was placed in a reaction kettle, heated to 180°C, and kept warm for 30 minutes for post-treatment;

[0047] (4) After the heat preservation is completed, the temperature is lowered, the catalyst is washed with water and dried, and then calcined at 450° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=60).

[0048] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0049] The resulting Ti-MOR was used in the ammoximation reaction of cycloheptanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 4.6g of cycloheptanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0050] Example 4

[0051] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0052] (1) HNO3, TiCl4 and deionized water were mixed to obtain a co-treatment agent with an acid concentration of 2 mol / L and a titanium source concentration of 1.5 mol / L;

[0053] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=80) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 600 rpm, stirring and mixing for 2 h, and pretreating at 70° C. for 12 h to obtain a pretreated mixed gel;

[0054] (3) The pretreated mixed gel obtained in step (2) was placed in a reaction kettle, heated to 160°C, and kept warm for post-treatment for 1 hour;

[0055] (4) After the insulation is completed, the temperature is lowered, the catalyst is washed with water and dried, and then calcined at 550° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=20).

[0056] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0057] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0058] Example 5

[0059] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0060] (1) acetic acid, tetrabutyl titanate and deionized water are mixed to obtain a co-treatment agent with an acid concentration of 1 mol / L and a titanium source concentration of 0.2 mol / L;

[0061] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=400) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 400 rpm, stirring and mixing for 2 h, and pretreating at 80° C. for 4 h to obtain a pretreated mixed gel;

[0062] (3) The pretreated mixed gel obtained in step (2) was placed in a reactor, heated to 170°C, and kept warm for post-treatment for 1 hour;

[0063] (4) After the insulation is completed, the temperature is lowered, the mixture is washed with water and dried, and then calcined at 500° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=150).

[0064] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0065] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0066] Example 6

[0067] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0068] (1) Sulfuric acid, titanium powder and deionized water are mixed to obtain a co-treatment agent with an acid concentration of 3 mol / L and a titanium source concentration of 0.5 mol / L;

[0069] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=200) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 400 rpm, stirring and mixing for 2 h, and pretreating at 70° C. for 6 h to obtain a pretreated mixed gel;

[0070] (3) The pretreated mixed gel obtained in step (2) was placed in a reactor, heated to 150° C., and kept warm for 50 min for post-treatment;

[0071] (4) After the insulation is completed, the temperature is lowered, the mixture is washed with water and dried, and then calcined at 500° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=150).

[0072] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0073] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0074] Example 7

[0075] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0076] (1) mixing formic acid, titanium powder and deionized water to obtain a co-treatment agent with an acid concentration of 3 mol / L and a titanium source concentration of 0.5 mol / L;

[0077] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=100) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 400 rpm, stirring and mixing for 2 h, and pretreating at 60° C. for 24 h to obtain a pretreated mixed gel;

[0078] (3) The pretreated mixed gel obtained in step (2) was placed in a reactor, heated to 200°C, and kept warm for 30 minutes for post-treatment;

[0079] (4) After the insulation is completed, the temperature is lowered, the mixture is washed with water and dried, and then calcined at 500° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=150).

[0080] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0081] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0082] Example 8

[0083] This example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0084] (1) Collect the HCl and TiCl4 co-processed solution (HCl concentration is about 2.6 mol / L, Ti concentration is about 0.2 mol / L) circulated three times in Example 1.

[0085] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=400) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 400 rpm, stirring and mixing for 2 h, and pretreating at 50° C. for 24 h to obtain a pretreated mixed gel;

[0086] (3) The pretreated mixed gel obtained in step (2) was placed in a reactor, heated to 150°C, and kept warm for 2 hours for post-treatment;

[0087] (4) After the insulation is completed, the temperature is lowered, the mixture is washed with water and dried, and then calcined at 500° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=130).

[0088] This embodiment also provides an application of the Ti-MOR catalyst prepared by the method in a cycloalkanone ammoximation reaction, which specifically comprises the following steps:

[0089] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0090] Comparative Example 1

[0091] The preparation method of this comparative example is basically the same as that of Example 1, except that the acid concentration of the co-treatment agent obtained in step (1) of this comparative example is 6 mol / L.

[0092] This comparative example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0093] (1) mixing HCl, TiCl4 and deionized water to obtain a co-treatment agent with an acid concentration of 6 mol / L and a titanium source concentration of 2 mol / L;

[0094] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=400) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 300 rpm, stirring and mixing for 2 h, and pretreating at 50° C. for 24 h to obtain a pretreated mixed gel;

[0095] (3) The pretreated mixed gel obtained in step (2) was placed in a reaction kettle, heated to 160°C, and kept warm for post-treatment for 1 hour;

[0096] (4) After the heat preservation is completed, the temperature is lowered, the catalyst is washed with water and dried, and then calcined at 550° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=10).

[0097] This comparative example also provides an application of the Ti-MOR catalyst prepared by the method in the ammoximation reaction of cycloalkanone, which specifically comprises the following steps:

[0098] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0099] Comparative Example 2

[0100] The preparation method of this comparative example is basically the same as that of Example 4, except that in step (3), the reactor is heated to 210°C.

[0101] This comparative example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0102] (1) HNO3, TiCl4 and deionized water were mixed to obtain a co-treatment agent with an acid concentration of 2 mol / L and a titanium source concentration of 1.5 mol / L;

[0103] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=80) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 600 rpm, stirring and mixing for 2 h, and pretreating at 70° C. for 12 h to obtain a pretreated mixed gel;

[0104] (3) The pretreated mixed gel obtained in step (2) was placed in a reaction kettle, heated to 210°C, and kept warm for post-treatment for 1 hour;

[0105] (4) After the insulation is completed, the temperature is lowered, the catalyst is washed with water and dried, and then calcined at 550° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=20).

[0106] This comparative example also provides an application of the Ti-MOR catalyst prepared by the method in the ammoximation reaction of cycloalkanone, which specifically comprises the following steps:

[0107] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0108] Comparative Example 3

[0109] The preparation method of this comparative example is basically the same as that of Example 5, except that the pretreatment time in step (2) is shortened to 2 hours.

[0110] This comparative example provides a one-pot post-treatment method for preparing Ti-MOR catalysts. A mixture of acid and titanium source is used as a co-treatment agent, and fresh MOR molecular sieve is mixed to prepare Ti-MOR. The specific steps are as follows:

[0111] (1) acetic acid, tetrabutyl titanate and deionized water are mixed to obtain a co-treatment agent with an acid concentration of 1 mol / L and a titanium source concentration of 0.2 mol / L;

[0112] (2) adding fresh MOR molecular sieve (silicon-aluminum molar ratio Si / Al=400) to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 400 rpm, stirring and mixing for 2 h, and pre-treating at 80° C. for 2 h to obtain a pre-treated mixed gel;

[0113] (3) The pretreated mixed gel obtained in step (2) was placed in a reactor, heated to 170°C, and kept warm for post-treatment for 1 hour;

[0114] (4) After the insulation is completed, the temperature is lowered, the mixture is washed with water and dried, and then calcined at 500° C. to obtain a Ti-MOR catalyst (silicon-titanium molar ratio Si / Ti=150).

[0115] This comparative example also provides an application of the Ti-MOR catalyst prepared by the method in the ammoximation reaction of cycloalkanone, which specifically comprises the following steps:

[0116] The resulting Ti-MOR was used in the ammoximation reaction of cyclohexanone. 0.12g of the catalyst, 16.8g of tert-butyl alcohol, 3.9g of cyclohexanone, 5.4g of hydrogen peroxide, and 16.8g of ammonia were added sequentially to a three-necked flask. The flask was then heated in a 60°C oil bath. Once the temperature reached 60°C, a 2-hour timer was started. After the reaction was complete, the flask was cooled naturally to room temperature to obtain the reaction product.

[0117] Test example

[0118] The reaction products obtained by using the Ti-MOR catalyst in Examples 1-8 and Comparative Examples 1-3 were analyzed by gas chromatography, and the cycloalkanone conversion rate and cycloalkanone selectivity of the catalyst were calculated. The results are shown in Table 1.

[0119] Table 1

[0120] As can be seen from the data in Table 1, the technical solution of the present invention achieves a simultaneous improvement in the cycloalkanone conversion rate (95.8%-99.9%) and the cycloalkanone oxime selectivity (96.2%-99.9%) through formulation and parameter optimization, showing significant technical advantages over the comparative example.

[0121] In Example 8, the co-treatment agent recycled three times in Example 1 was used, and its cycloalkanone conversion rate and cycloalkanone oxime selectivity were still at a high level, verifying the effectiveness of this scheme in improving the recycling rate of acid resources and simultaneously achieving waste acid emission reduction and production cost optimization.

[0122] The acid concentration of the co-treatment agent in Comparative Example 1 exceeds the preferred range of the present invention, and its cycloalkanone conversion rate is reduced by 9.5% and the selectivity is reduced by 4.3% compared with Example 1. This is because the excessively high acid concentration causes local collapse of the MOR molecular sieve framework, and the resulting amorphous silicon / aluminum species clog the pore surface, which not only reduces the effective loading area of the titanium species, but also destroys the stereoselectivity of the active center. This confirms that the precisely controlled acid concentration of the present invention plays a key role in maintaining the integrity of the framework and the titanium loading efficiency.

[0123] In Comparative Example 2, the heating temperature of the reactor in step (3) was increased, and the cycloalkanone conversion rate dropped from 99.9% to 94.8%, and the selectivity dropped sharply from 99.9% to 89.1%. The mechanism is that excessively high temperatures cause the titanium precursor to undergo uncontrolled polycondensation, generating amorphous TiO2 aggregates with a particle size greater than 50nm. These large-sized particles cannot be effectively embedded in the MOR molecular sieve. This confirms that the temperature range screened by the present invention can effectively inhibit the excessive aggregation of titanium species and ensure the orderly anchoring of active Ti species in the molecular sieve framework.

[0124] The reduction in pretreatment reaction time in Comparative Example 3 resulted in a significant decrease in catalyst performance. The mechanism is that when the pretreatment time is insufficient, the removal process of the aluminum element from the molecular sieve framework is not fully completed, and the number of framework vacancies is limited, which directly affects the effective formation of four-coordinate active titanium species. This result confirms the core design of the present invention: through a pretreatment process of a specific length, the molecular sieve framework reconstruction process is precisely regulated, the aluminum element is continuously stripped under mild conditions and a stable vacancy structure is formed, creating favorable conditions for the embedding of titanium species, thereby enhancing the titanium loading capacity and improving the catalytic efficiency.

[0125] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a Ti-MOR catalyst by post-treatment in one pot, characterized in that: The following steps are involved: (1) mixing an acid solution, a titanium source, and deionized water to obtain a co-treatment agent; (2) adding fresh MOR molecular sieve to the co-treatment agent obtained in step (1) under stirring at a stirring speed of 100 to 700 rpm, stirring and mixing for 2 h, and then pretreating at 50 to 120° C. for 4 to 48 h to obtain a pretreated mixed gel; (3) The pretreated mixed gel obtained in step (2) is placed in a reaction kettle, heated to 80-200° C., and kept warm for 30 min-4 h for post-treatment; (4) After the insulation is completed, the temperature is lowered, the catalyst is washed with water and dried, and then calcined at 400-550 degrees to obtain the Ti-MOR catalyst.

2. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to claim 1, wherein: The acid solution in step (1) is one or more of nitric acid, hydrochloric acid, sulfuric acid, formic acid or citric acid.

3. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to claim 1, characterized in that: In the step (1), the titanium source is one or more of TiCl4, titanium powder, tetraethyl titanate or tetrabutyl titanate.

4. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to claim 1, characterized in that: In the step (1), the acid concentration of the co-treatment agent is 1-5 mol / L, and the titanium source concentration is 0.1-2 mol / L.

5. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to any one of claims 1 or 4, characterized in that: In the step (1), the acid concentration of the co-treatment agent is 1-3 mol / L, and the titanium source concentration is 0.2-1.5 mol / L.

6. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to claim 1, characterized in that: The silicon-aluminum molar ratio Si / Al of the MOR molecular sieve in step (2) is 20-400.

7. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to claim 1 or 6, characterized in that: The silicon-aluminum molar ratio Si / Al of the MOR molecular sieve in step (2) is 80-300.

8. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to claim 1, characterized in that: The silicon-titanium molar ratio Si / Ti of the Ti-MOR catalyst obtained in step (4) is 10-150.

9. The method for preparing a Ti-MOR catalyst by post-treatment in one pot according to claim 1 or 8, characterized in that: The silicon-titanium molar ratio of the Ti-MOR catalyst obtained in step (4) is Si / Ti=20-130.

10. Use of the Ti-MOR catalyst prepared by the method for preparing a Ti-MOR catalyst by one-pot post-treatment according to any one of claims 1 to 9 in ammoximation of cycloalkanone.

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