Preparation method and application of ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst

Abstract

The invention discloses a preparation method and application of an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst, and the preparation method comprises the following preparation steps: step 1, uniformly mixing an Ag < + > solution and a Zn < 2 + > solution in proportion to form a mixed solution; 2, under ultrasonic assistance and mechanical stirring, adding a molecular sieve into the mixed solution obtained in the step 1 to achieve equivalent-volume impregnation, and continuously carrying out ultrasonic stirring reaction; and step 3, after the reaction is finished, drying and roasting the obtained product to obtain the Zn-Ag bimetallic loaded molecular sieve catalyst. The method has the advantages that the prepared Zn-Ag bimetallic loaded molecular sieve catalyst can completely catalyze, oxidize and decompose ethylene gas generated in fruits under the conditions that the temperature is 10 DEG C or above and the ethylene airspeed is 300,000 mL / (g.h) or below, so that the mature period of the fruits is prolonged, and the purpose of preserving the fruits is achieved.

Description

Technical Field

[0001] This invention relates to the field of catalyst materials technology, specifically to a method for preparing and applying an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst. Background Technology

[0004] From a technical perspective, in addition to traditional refrigeration, there are the following methods for preserving fruit: 1) Extend shelf life by inhibiting fruit respiration and microbial growth; 2) Ethylene is a key factor leading to fruit spoilage, and its effective removal is crucial for preservation. Catalytic oxidation technology is a highly efficient method for removing ethylene.

[0005] This technology uses a catalyst to oxidize and decompose ethylene into carbon dioxide and water using oxygen in the air. It not only eliminates secondary pollution, but also allows the catalyst to be recycled.

[0006] In the prior art, CN109287738A discloses an apparatus and method for enriching and removing ethylene during fruit storage. The apparatus includes a controlled atmosphere storage room for fruit, an ethylene enrichment and removal device, an ethylene sensor, an ozone sensor, an air pump, and an automatic control system. This invention also discloses a method for enriching and removing ethylene during fruit storage based on the aforementioned apparatus. This invention not only reduces the ethylene concentration in the controlled atmosphere storage room for fruit, slows down the respiration and aging rate of fruit, and extends shelf life, but also ensures the sensory and nutritional quality of the product. It is environmentally friendly, efficient, and leaves no waste gas residue, making it suitable for large-scale controlled atmosphere storage of fruit.

[0007] In summary, based on the urgent need for fruit preservation and the need for efficient catalytic oxidants for ethylene removal, this invention provides a method for preparing and applying an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing and applying an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst.

[0009] The Zn-Ag bimetallic molecular sieve catalyst prepared by this invention can be used for the efficient oxidative decomposition of ethylene indoors, and can also be applied to actual production with a simple and efficient synthesis method.

[0010] By utilizing highly dispersed Ag nanoparticles, the content of surface hydroxyl groups and the proportion of surface active oxygen are increased, enhancing the migration ability of active oxygen. This allows ethylene adsorbed on the catalyst surface to react rapidly with the active oxygen in the catalyst, generating non-toxic and harmless carbon dioxide and water.

[0011] Innovatively, silver was supported on solid-phase ZSM-48, which greatly improved the room-temperature degradation activity of ethylene on the catalyst, thus enabling the catalyst to maintain its activity at temperatures of 10°C and above for 100,000 h. -1 It can completely purify and eliminate ethylene produced during fruit preservation under air velocity conditions of 1000 h⁻¹ and below.

[0012] To achieve the above objectives, the following technical solutions are used: A method for preparing an ultrasound-assisted Zn-Ag bimetallic molecular sieve catalyst includes the following preparation steps: Step 1: Add Ag + Solution and Zn 2+ The solutions are mixed in proportion to form a mixed solution; Step 2: Under ultrasonic assistance and mechanical stirring, the molecular sieve is added to the mixed solution obtained in Step 1 to achieve equal volume impregnation, and the reaction is continuously ultrasonically stirred. Step 3: After the reaction is complete, dry and calcine the obtained product to obtain the Zn-Ag bimetallic supported molecular sieve catalyst.

[0013] As a further preferred option, The Zn 2+ Solution and Ag + In solution, Zn 2+ and Ag + The mass ratio is 200:1 to 1:1.

[0014] As a further preferred option, The Zn 2+ and Ag + The total mass concentration is 0.1~20 g / 100mL, and the total mass content of Zn-Ag active components is 0.1%~20%.

[0015] As a further preferred option, The Zn 2+ The solution is at least one of ZnNO3, Zn(CH3COO)2, ZnCl2, ZnSO4, and Zn(ClO3)2.

[0016] As a further preferred option, The Ag 2+ The solution contains at least one of AgNO3, CH3COOAg, Ag2SO4, and AgClO3.

[0017] As a further preferred option, The reaction time for ultrasonic-assisted mechanical stirring is 10 min to 8 h.

[0018] As a further preferred option, In step 3), after the reaction is complete, the obtained product is dried and then calcined in a muffle furnace at a temperature of 300℃~800℃ for 1 h~4 h.

[0019] An application of a Zn-Ag bimetallic supported molecular sieve catalyst: The Zn-Ag bimetallic supported molecular sieve catalyst prepared by the ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst preparation method is applied to the catalytic oxidation-decomposition reaction of ethylene in fruit preservation.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The Zn-Ag bimetallic supported molecular sieve catalyst prepared by this invention can completely catalytically oxidize and decompose ethylene gas produced in fruits under conditions of temperature at or above 10℃ and ethylene space velocity at or below 300,000 mL / (g·h), thereby extending the ripening period of fruits and achieving the purpose of preserving fruits. More specifically: the catalyst of the present invention can operate over a wide temperature range (10°C and above) and a wide space velocity range (100,000 h⁻¹). -1 It maintains an ethylene oxidation decomposition efficiency of over 99% within air velocity conditions (and below), making it particularly suitable for the complete elimination of ethylene generated during fruit preservation. 2) The raw materials and preparation process conditions of this invention are all non-toxic and harmless, and will not cause harm to human health and the ecological environment. The preparation method is simple and easy to implement.

[0021] 3) Compared with existing precious metal catalysts for room temperature catalytic oxidation of ethylene, the Ag-supported solid-phase ZSM-48 catalyst is relatively inexpensive and more suitable for large-scale application. Attached Figure Description

[0022] Figure 1 The ethylene conversion of Zn-Ag / ZSM48 catalyst at different space velocities; Figure 2 Ethylene conversion of Zn-Ag / ZSM48 catalyst at different temperatures; Figure 3 The ethylene conversion rate of the Zn-Ag / ZSM48 catalyst at 20℃; Figure 4 This is a photograph of the Zn-Ag / ZSM48 catalyst. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with embodiments and accompanying drawings: Example 1 First, mix the Zn(NO3)2 solution and the AgNO3 solution according to m(Zn 2+ ): m(Ag + The Zn-Ag bimetallic molecular sieve was mixed in a ratio of 999:1 to form a 100 mL mixed solution with a total metal ion content of 0.1 g. Under ultrasonic assistance and mechanical stirring, 100 g of ZSM-48 molecular sieve was added to the mixed solution to achieve equal volume impregnation, and the reaction was continuously ultrasonically stirred for 10 min. After the reaction was completed, the resulting product was dried and placed in a muffle furnace for calcination at 300℃ for 1 h to obtain a Zn-Ag bimetallic supported molecular sieve catalyst with a total Zn-Ag active component content of 0.1%. The catalyst was pulverized and sieved, and particles smaller than 50 mesh were collected for later use.

[0024] Example 2 The preparation method is the same as in Example 1, except that the total mass content of the Zn-Ag active component is 0.5%, and m(Zn 2+ ): m(Ag + =199:1, ultrasonic stirring reaction for 30 min, calcination at 350℃ for 2 h.

[0025] Example 3 The preparation method is the same as in Example 1, except that the total mass content of the Zn-Ag active component is 1%, and m(Zn 2+ ): m(Ag + The ratio of 99:1 was used for ultrasonic stirring reaction for 1 h, followed by calcination at 400℃ for 3 h.

[0026] Example 4 The preparation method is the same as in Example 1, except that the total mass content of the Zn-Ag active component is 2%, and m(Zn 2+ ): m(Ag + The ratio of 49:1 was used for ultrasonic stirring reaction for 1 h, followed by calcination at 450℃ for 4 h.

[0027] Example 5 The preparation method is the same as in Example 1, except that the total mass content of the Zn-Ag active component is 5%, and m(Zn 2+ ): m(Ag + The ratio of 19:1 was used for ultrasonic stirring reaction for 2 h, followed by calcination at 500℃ for 2 h.

[0028] Example 6 The preparation method is the same as in Example 1, except that the total mass content of the Zn-Ag active component is 10%, and m(Zn 2+ ): m(Ag + The ratio of 9:1 was used to react the mixture with ultrasonic stirring for 2 hours, followed by calcination at 600℃ for 2 hours.

[0029] Example 7 The preparation method is the same as in Example 1, except that the total mass content of the Zn-Ag active component is 15%, and m(Zn 2+ ): m(Ag + The ratio of 4:1 was used for ultrasonic stirring reaction for 4 h, followed by calcination at 700℃ for 2 h.

[0030] Example 8 The preparation method is the same as in Example 1, except that the total mass content of the Zn-Ag active component is 20%, and m(Zn 2+ ): m(Ag + The mixture was stirred at a ratio of 1:1 for 4 hours with ultrasonic stirring, followed by calcination at 800℃ for 2 hours.

[0031] Example 9 The preparation method is the same as in Example 1, except that the active component contains only Zn. 2+ The total mass content is 5%, and the reaction is ultrasonically stirred for 2 hours and then calcined at 500℃ for 2 hours.

[0032] Example 10 The preparation method is the same as in Example 1, except that the active component contains only Ag. + The total mass content is 5%, and the reaction is ultrasonically stirred for 2 hours and then calcined at 500℃ for 2 hours.

[0033] Example 11 The preparation method is the same as in Example 5, except that a mixed impregnation solution is formed by using Zn(CH3COO)2 solution and CH3COOAg solution.

[0034] Example 12 The preparation method is the same as in Example 5, except that a mixed impregnation solution is formed using ZnSO4 solution and Ag2SO4 solution.

[0035] Example 13 The preparation method is the same as in Example 5, except that a commercial 5A molecular sieve is used as the carrier.

[0036] Example 14 The preparation method is the same as in Example 5, except that commercial 13X molecular sieve is used as the carrier.

[0037] Validation of the catalytic decomposition effect of the catalyst on ethylene The material prepared in Example 5 was used as a catalyst to catalyze the oxidative decomposition reaction of ethylene. The test conditions are shown in Table 1. Table 1. Different reaction conditions for the catalytic oxidative decomposition of ethylene (different catalyst amounts and ethylene space velocity). The catalyst dosage and ethylene space velocity are shown in Table 1, and the reaction temperature was 20℃. The obtained catalyst was placed in a fixed-bed reactor, and the ethylene gas concentration was controlled at 100 ppm to test the catalytic ethylene oxidation efficiency. After the reaction reached steady state, the composition of the reaction gases was determined. Both CO2 and ethylene gases were measured online using gas chromatography (GC-2014C; CO2 was measured using a TCD detector, a 5A molecular sieve packed column, and N2 as the carrier gas; ethylene was measured using an FID detector, a capillary column, and N2 as the carrier gas). The catalytic activity of the catalyst for ethylene oxidation under four test conditions (conditions 1, 2, 3, and 4) is shown in Table 1. Figure 1 As shown, the catalyst exhibits excellent catalytic oxidation and decomposition activity of ethylene at room temperature. Under conditions 1 and 2, its ethylene conversion rate is above 99%; while under the relatively extreme conditions 3 and 4, its ethylene conversion rate still remains above 50%, indicating that the catalyst has very excellent ethylene catalytic oxidation performance.

[0038] The material prepared in Example 5 was used as a catalyst to catalyze the oxidative decomposition reaction of ethylene. The test conditions are shown in Table 2. Table 2. Different reaction conditions (different reaction temperatures) for the catalytic oxidative decomposition of ethylene. The catalyst dosage was 250 mg, and the ethylene space velocity was 100,000 mL / (g·h). The obtained catalyst was placed in a fixed-bed reactor, and the ethylene gas concentration was controlled at 100 ppm. The catalytic ethylene oxidation efficiency was tested. After the reaction reached steady state, the composition of the reaction gases was determined. Both CO2 and ethylene gases were analyzed online using gas chromatography (GC-2014C; CO2 was analyzed using a TCD detector, a 5A molecular sieve packed column, and N2 as the carrier gas; ethylene was analyzed using an FID detector, a capillary column, and N2 as the carrier gas). The catalytic activity of the catalyst for ethylene oxidation was as follows under four test conditions: 5, 6, 7, and 8 (ambient temperature regulated by air conditioning). Figure 2 As shown, the catalyst exhibits excellent catalytic oxidation and decomposition activity of ethylene at temperatures ranging from 10 to 40°C. Under conditions 5, 6, and 7, the ethylene conversion rate is above 99%; while under the relatively low temperature condition 8, the ethylene conversion rate remains above 80%, indicating that the catalyst has excellent ethylene catalytic oxidation performance at room temperature and above.

[0039] Using the material prepared in Example 5 as a catalyst, the oxidative decomposition reaction of ethylene was catalyzed: The catalyst dosage was 250 mg, the ethylene space velocity was 100,000 mL / (g·h), and the reaction temperature was 20℃. The obtained catalyst was placed in a fixed-bed reactor, and the ethylene gas concentration was controlled at 100 ppm. The catalytic ethylene oxidation efficiency was tested. After the reaction reached steady state, the composition of the reaction gases was determined. Both CO2 and ethylene gases were determined online using gas chromatography (GC-2014C; CO2 was detected using a TCD detector, a 5A molecular sieve packed column, and N2 as the carrier gas; ethylene was detected using an FID detector, a capillary column, and N2 as the carrier gas). The catalytic activity of the catalyst for ethylene oxidation is as follows: Figure 3 As shown, under the conditions of 250 mg catalyst, ethylene space velocity of 100,000 mL / (g·h) and reaction temperature of 20℃, the ethylene conversion rate is as high as 99% or more and the catalytic lifetime is greater than 240h, indicating that the catalyst has excellent ethylene catalytic oxidation performance.

[0040] The catalysts prepared in Examples 1-14 were used in the catalytic oxidative decomposition reaction of ethylene: 250 mg of the catalysts corresponding to Examples 1-14 were placed in a fixed-bed reactor. The ethylene space velocity was controlled at 100,000 mL / (g·h), the reaction temperature at 20℃, and the ethylene gas concentration at 100 ppm. The catalytic ethylene oxidation efficiency was tested. After the reaction reached steady state, the composition of the reaction gas was determined. CO2 and ethylene gases were measured online using gas chromatography (GC-2014C; CO2 was measured using a TCD detector, a 5A molecular sieve packed column, and N2 as the carrier gas; ethylene was measured using an FID detector, a capillary column, and N2 as the carrier gas). The catalytic oxidation activity of the catalysts is shown in Table 3. It can be seen that the catalysts exhibited excellent catalytic ethylene oxidation decomposition activity under different Zn-Ag loadings, different Zn-Ag addition ratios, different Zn-Ag salt sources, and different supports. However, the Zn-Ag bimetallic supported catalyst was significantly better than the single-metal supported catalyst. Zn derived from nitrates… 2+ and Ag + It is also significantly superior to other types of salt sources; in addition, due to its unique pore structure and excellent thermal stability and acidity, ZSM48 molecular sieve exhibits superior catalytic oxidation and decomposition activity of ethylene compared to other molecular sieve supports.

[0041] Table 3 Ethylene conversion rates of Zn-Ag / ZSM48 catalysts in various examples The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent modifications made using the present invention are within the patent protection scope of the present invention.

Claims

1. A method for preparing an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst, characterized in that, comprising the following preparation steps: Step 2: under ultrasonic assistance and mechanical stirring, the molecular sieve is added to the mixed solution obtained in step 1 to achieve equal-volume impregnation, and ultrasonic stirring reaction is continued; Step 1 : Ag + solution and Zn 2+ solution were mixed in proportion to form a mixed solution; Step 3: after the reaction is completed, the obtained product is dried and calcined to obtain a Zn-Ag bimetallic supported molecular sieve catalyst. 2.The method for preparing an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst according to claim 1, characterized in that, 3.The method for preparing an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst according to claim 1, characterized in that, The Zn 2+ solution and Ag + solution, the mass ratio of Zn 2+ and Ag + is 200:1~1:

1. 4.The method for preparing an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst according to claim 1, characterized in that, The total mass concentration of Zn 2+ and Ag + is 0.1-20 g / 100 mL, and the total mass content of Zn-Ag active component is 0.1%-20%. The reaction time of the ultrasonic assistance and mechanical stirring is 10 min to 8 h. The Zn 2+ The solution is at least one of ZnN03, Zn(CH3COO)2, ZnCl2, ZnS04, Zn(Cl03)2.

5. The method for preparing the ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst according to claim 1, characterized in that, The Ag 2+ The solution is at least one of AgNO3, CH3COOAg, Ag2SO4, AgClO3. 6.The method for preparing an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst according to claim 1, characterized in that, In the step 3), after the reaction is completed, the obtained product is dried, and then calcined in a muffle furnace at a temperature of 300 ℃ to 800 ℃; the calcination time is 1 h to 4 h.

7. The method for preparing the ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst according to claim 1, characterized in that, The Zn-Ag bimetallic supported molecular sieve catalyst prepared by the method for preparing an ultrasonic-assisted Zn-Ag bimetallic molecular sieve catalyst according to any one of claims 1 to 7 is applied to a catalytic oxidation ethylene decomposition reaction in fruit preservation.

8. Use of a Zn-Ag bimetallic supported molecular sieve catalyst, characterized in that, ​

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