Catalyst as well as preparation method and application thereof

Abstract

The invention relates to a catalyst and a preparation method and application thereof, the catalyst is a NiZnFe-LTH catalyst, in the catalyst, the molar ratio of a nickel element to a zinc element is 1: (0.1-10), and the ratio of the total mole number of the nickel element and the zinc element to the mole number of an iron element is (2.5-3.5): 1. According to the NiZnFe-LTH catalyst with the specific composition, the catalytic activity and stability of the catalyst are jointly improved through mutual cooperation of three transition metal elements, and efficient and stable decomposition of ozone under the condition of relatively high relative humidity is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts and environmental protection, and in particular to a catalyst and a preparation method and application thereof. Background Art

[0002] Ozone is an important atmospheric pollutant and greenhouse gas, which not only causes air quality deterioration and greenhouse effect, but also directly affects human health. Ozone in the atmosphere mainly comes from the photochemical reaction between nitrogen oxides and volatile organic compounds and the injection of stratospheric ozone, while indoor and outdoor air exchange can also lead to indoor ozone pollution. In addition, ozone is often used as an oxidant in the fields of advanced wastewater treatment, sterilization in food processing, and indoor air sterilization. During the application process, ozone residue and leakage often lead to ozone pollution in these places. Studies have shown that long-term exposure to ozone environment can lead to skin aging, respiratory diseases and high mortality, and ozone in the atmosphere can also affect plant growth in nature, leading to crop yield reduction. Therefore, eliminating ozone pollution is extremely important for human health and environmental protection.

[0003] Compared with other methods of eliminating ozone, room temperature catalytic ozone decomposition is currently the best technical choice. Catalysts that can be used for catalytic ozone decomposition can be divided into precious metal catalysts and transition metal oxide catalysts according to their main active components. Precious metal catalysts have good ozone decomposition activity, but the preparation cost is high and they are not suitable for large-scale application. Compared with precious metal catalysts, transition metal oxide catalysts have great advantages in preparation cost, but their active site stability is poor.

[0004] Hydrotalcite has a wide range of applications in the field of catalysis due to its excellent physical and chemical properties. CN118145716A discloses a ternary layered compound for deozonation at 30°C, relative humidity (RH) <5%, and space velocity (WHSV) = 600000 mL·gcat -1 ·h -1 Under the above conditions, the ozone conversion rate is above 98% after 24 hours of reaction. It can be seen that the catalyst has good ozone decomposition activity under dry conditions. However, in the actual application of the catalyst, water vapor often exists, and the relative humidity in the air can even reach 60-70%, and the presence of water molecules often leads to the deactivation of the catalyst.

[0005] In view of the problems existing in existing catalysts, developing a catalyst that can achieve efficient decomposition of ozone at high relative humidity, and providing a catalyst preparation method with simple process, low material cost and large-scale production are technical problems that need to be solved urgently. Summary of the invention

[0006] To solve the above technical problems, the object of the present invention is to provide a catalyst, its preparation method and application. The NiZnFe-LTH catalyst with a specific composition provided by the present invention improves the catalytic activity and stability of the catalyst through the mutual cooperation of three transition metal elements, and is conducive to achieving efficient and stable decomposition of ozone under relatively high humidity conditions.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a catalyst, which is a NiZnFe-LTH catalyst. In the catalyst, the molar ratio of nickel element to zinc element is 1:(0.1-10), and the ratio of the total molar number of nickel element and zinc element to the molar number of iron element is (2.5-3.5):1.

[0009] In some embodiments, the molar ratio of nickel element to zinc element is 1:0.2, 1:0.3, 1:0.5, 1:0.7, 1:0.9, 1:1.0, 1:1.1, 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2.0, 1:2.1, 1:2.3, 1:2.5, 1:2.7, 1:2.9, 1:3.0, 1:3.1, 1:3.3, 1:3.5, 1:3.7, 1:3.9, 1:4.0, 1:4.1, 1:4.3, 1:4.5, 1:4.7, 1:4.9, 1:5.0, 1:5.1, 1:5.3, 1:5.5, 1:5.7, 1:5.9, 1:6.0, 1:6.3, 1:6.5, 1:6.7, 1:7.0, 1:7.5, 1:8.0, 1:8.5, 1:9.0, 1:9.5, 1:10.0 or any value therebetween. In some embodiments, the molar ratio of nickel element to zinc element is 1:(0.2-7). In some embodiments, the molar ratio of nickel element to zinc element is 1:(0.2-5).

[0010] In some embodiments, the ratio of the total molar number of nickel element and zinc element to the molar number of iron element is 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, 3.5:1 or any value therebetween. In some embodiments, the ratio of the total molar number of nickel element and zinc element to the molar number of iron element is (2.8-3.2):1.

[0011] In some embodiments, the chemical formula of the NiZnFe-LTH catalyst is [Ni a Zn b Fe c (OH) y [CO3]x / 2 ·nH₂O

[0012] Among them, a is 0.1 - 5, b is 0.1 - 5, c is 0.1 - 2, y = 2(a + b + c), and x is 0.1 - 2. In the present invention, the selection range of a is "0.1 - 5", such as 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8 or 5, etc.; the selection range of b is "0.1 - 5", such as 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8 or 5, etc.; the selection range of c is "0.1 - 2", such as 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8 or 2, etc.; the selection range of x is "0.1 - 2", such as 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8 or 2, etc.

[0013] In some embodiments, the water content of the NiZnFe - LTH catalyst is 15 wt% or less, such as 15 wt%, 14 wt%, 13 wt%, 12 wt%, 11 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt% or 2 wt%, etc.

[0014] In the present invention, the value range of n in the chemical formula of the catalyst is closely related to the water content of the NiZnFe - LTH catalyst. The present invention limits the value of n by limiting the water content of the NiZnFe - LTH catalyst to 15 wt% or less.

[0015] The NiZnFe - LTH catalyst provided by the present invention contains divalent nickel element, divalent zinc element and trivalent iron element. The three transition metal elements cooperate with each other, which can improve the catalytic activity and stability of the catalyst. Moreover, the introduced divalent zinc element in the catalyst replaces part of the divalent nickel element in the NiFe - LDH catalyst used for ozone decomposition in the prior art. On the one hand, it can fundamentally reduce the cost of the catalyst. On the other hand, it can effectively reduce the content of bound water in the catalyst, thereby improving the catalytic effect of the catalyst. Further, by adopting the NiZnFe - LTH catalyst with a specific chemical formula, the present invention is conducive to the efficient and stable decomposition of ozone under the condition of relatively high humidity.

[0016] Preferably, the specific surface area of the NiZnFe-LTH catalyst is 90-180 m 2 / g, such as 90 m 2 / g, 100 m 2 / g, 110 m 2 / g, 120 m 2 / g, 130 m 2 / g, 140 m 2 / g, 150 m 2 / g, 160 m 2 / g, 170 m 2 / g or 180 m 2 / g, etc.

[0017] The NiZnFe-LTH catalyst provided by the present invention has a relatively high specific surface area, which can improve the catalytic effect of the catalyst and is beneficial to the efficient and stable decomposition of ozone.

[0018] Preferably, the NiZnFe-LTH catalyst has a two-dimensional layered hydrotalcite structure.

[0019] Preferably, the water content of the NiZnFe-LTH catalyst is 2-13 wt%, such as 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt% or 13 wt%, etc.

[0020] In a second aspect, the present invention provides a preparation method of the catalyst according to the first aspect, and the preparation method includes the following steps:

[0021] (1) Mix nickel salt, zinc salt and iron salt with a first solvent in a formula amount for a first mixing to obtain a first mixed solution;

[0022] Mix a first lye and a second lye with a second solvent in a formula amount for a second mixing to obtain a second mixed solution; the anion in the first lye includes hydroxide ion, and the anion in the second lye includes acid radical ion;

[0023] (2) Add the first mixed solution and the second mixed solution into a bottom liquid in a formula amount in a parallel flow manner for a coprecipitation reaction to obtain the catalyst.

[0024] In the present invention, the "in a formula amount" in step (1) and step (2) means that the nickel cations, zinc cations, iron cations, hydroxide ions and acid radical ions involved in the content of the first mixed solution, the second mixed solution and the added first mixed solution and second mixed solution all satisfy the stoichiometric number or molar ratio of each ion in the catalyst.

[0025] In order to ensure that the interlayer anions in the catalyst are all acid radicals, the present invention may choose to add an excessive amount of the second lye.

[0026] The preparation method of the catalyst provided by the present invention uses a mixed salt solution of nickel, zinc and iron and the second lye to carry out a co-precipitation reaction in parallel flow, which can improve the mixing uniformity of raw materials and the sufficiency of the reaction, thereby preparing a catalyst with a uniform distribution of active sites and excellent catalytic effects. The preparation process adopted is simple, the material cost is low, and it is suitable for large-scale production. The prepared catalyst can stably and efficiently decompose ozone under conditions of relatively high humidity.

[0027] Preferably, the nickel salt in step (1) includes any one or a combination of at least two of nickel nitrate, nickel carbonate, nickel chloride, nickel sulfate or nickel phosphate.

[0028] In the present invention, the nickel salt includes a nickel salt or a hydrate of a nickel salt.

[0029] Preferably, the zinc salt in step (1) includes any one or a combination of at least two of zinc nitrate, zinc carbonate, zinc chloride, zinc sulfate or zinc phosphate.

[0030] In the present invention, the zinc salt includes a zinc salt or a hydrate of a zinc salt.

[0031] Preferably, the iron salt in step (1) includes any one or a combination of at least two of iron nitrate, iron carbonate, iron chloride, iron sulfate or iron phosphate.

[0032] In the present invention, the iron salt includes an iron salt or a hydrate of an iron salt.

[0033] Preferably, the total molar concentration of nickel, zinc and iron in the first mixed solution in step (1) is 0.1-5 mol / L, such as 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, etc.

[0034] The preparation method of the present invention regulates the total molar concentration of nickel element, zinc element and iron element in the first mixed solution, aiming to control the reaction process, thereby preparing a catalyst with low water content and large specific surface area, so as to improve the catalytic effect of the catalyst.

[0035] Preferably, the first solvent includes water.

[0036] Preferably, the mixing time of the first mixture in step (1) is 10-30 min, such as 10 min, 15 min, 20 min, 25 min or 30 min, etc.

[0037] Preferably, the first lye in step (1) includes sodium hydroxide.

[0038] In the present invention, the first lye is used to provide hydroxide ions.

[0039] Preferably, the second lye in step (1) includes sodium carbonate.

[0040] In the present invention, the second lye is used to provide carbonate ions.

[0041] Preferably, the second solvent includes water.

[0042] Preferably, the time for the second mixing in step (1) is 10 - 30 min, such as 10 min, 15 min, 20 min, 25 min or 30 min, etc.

[0043] Preferably, in the second mixed solution of step (1), the molar concentration of the first lye is 0.5 - 5 mol / L, such as 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, etc.

[0044] Preferably, in the second mixed solution of step (1), the molar concentration of the second lye is 0.1 - 2 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L or 2 mol / L, etc.

[0045] In the present invention, in order to ensure that the interlayer anions are all carbonate ions, an excessive amount of the second lye can be selected, and those skilled in the art can make a choice according to needs, as long as it can obtain a catalyst with a specific chemical composition.

[0046] Preferably, the bottom liquid in step (2) includes water.

[0047] Preferably, the co - precipitation reaction in step (2) maintains the pH of the solution at 10 - 12, such as 10, 11 or 12, etc.

[0048] Preferably, the temperature of the co - precipitation reaction in step (2) is 60 - 100 °C, such as 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C or 100 °C, etc.

[0049] Preferably, stirring is also accompanied during the co - current process in step (2).

[0050] Preferably, the rotation speed of the stirring is 800 - 1200 rpm, such as 800 rpm, 900 rpm, 1000 rpm, 1100 rpm or 1200 rpm, etc.

[0051] Preferably, after the coprecipitation reaction in step (2), it further includes performing a third mixing on the product obtained by flowing the first mixed solution and the second mixed solution all together into the bottom liquid.

[0052] Preferably, the manner of the third mixing includes stirring.

[0053] Preferably, during the third mixing process, the rotation speed of the stirring is 800 - 1200 rpm, such as 800 rpm, 900 rpm, 1000 rpm, 1100 rpm or 1200 rpm, etc.

[0054] Preferably, the temperature of the third mixing is 60 - 100 °C, such as 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C or 100 °C, etc.

[0055] Preferably, the time of the third mixing is 3 - 10 h, such as 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, etc.

[0056] Preferably, the product obtained after the third mixing is further subjected to post - treatment.

[0057] Preferably, the specific process of the post - treatment includes: cooling, separating, washing and drying the product obtained after the third mixing.

[0058] Preferably, the washing is carried out until the filtrate after washing is neutral.

[0059] In the present invention, "the filtrate after washing is neutral" means that the pH of the filtrate after washing is close to or equal to 7. Exemplarily, the pH of the filtrate after washing is 7.

[0060] Preferably, the temperature of the drying is 60 - 100 °C, such as 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C or 100 °C, etc.

[0061] Preferably, the time of the drying is 12 - 24 h, such as 12 h, 14 h, 16 h, 18 h, 20 h, 22 h or 24 h, etc.

[0062] As a preferred technical solution of the present invention, the preparation method of the catalyst includes the following steps:

[0063] (1) Mix a nickel salt, a zinc salt, and an iron salt with a first solvent in accordance with the formula amounts for 10 - 30 min to obtain a first mixed solution, wherein the total molar concentration of nickel, zinc, and iron in the first mixed solution is 0.1 - 5 mol / L.

[0064] Mix a first lye and a second lye with a second solvent in accordance with the formula amounts for 10 - 30 min to obtain a second mixed solution. In the second mixed solution, the molar concentration of the first lye is 0.5 - 5 mol / L, and the molar concentration of the second lye is 0.1 - 2 mol / L; the first lye includes sodium hydroxide; the second lye includes sodium carbonate.

[0065] (2) Add the first mixed solution and the second mixed solution to a bottom solution in a co-current manner in accordance with the formula amounts, and with stirring at a rotation speed of 800 - 1200 rpm, maintain the pH of the solution at 10 - 12 for a co-precipitation reaction. The temperature of the co-precipitation reaction is 60 - 100 °C. Then, continue to stir at a rotation speed of 800 - 1200 rpm for a third mixing. The temperature of the third mixing is 60 - 100 °C, and the time of the third mixing is 3 - 10 h. Next, cool the product obtained after the third mixing to room temperature, separate it, wash the separated product until the filtrate after washing is neutral, and then dry the washed product at a temperature of 60 - 100 °C for 12 - 24 h to obtain the catalyst.

[0066] In the present invention, the "room temperature" refers to a temperature of 25 ± 5 °C, such as 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, 25 °C, 26 °C, 27 °C, 28 °C, 29 °C, or 30 °C, etc.

[0067] In a third aspect, the present invention provides an application of the catalyst according to the first aspect, and the catalyst is applied to the decomposition process of ozone.

[0068] The catalyst with the specific composition and composition content provided by the present invention is used in the ozone decomposition process, can stably and efficiently decompose ozone under relatively harsh conditions, and is applied to various treatment processes containing ozone gas. The catalyst used can achieve stable and efficient separation of ozone under the condition that the relative humidity reaches 65%.

[0069] Preferably, the catalyst is applied to the decomposition of gaseous ozone.

[0070] Preferably, the catalyst is applied to decompose ozone in a closed space in an indoor environment and in a high-altitude aircraft.

[0071] Preferably, the catalyst is applied to decompose ozone in the atmospheric environment on the outer surface of a building and in a motor vehicle radiator.

[0072] Preferably, the catalyst is applied to the decomposition of ozone in the tail gas of water treatment.

[0073] Compared with the prior art, the present invention has at least the following beneficial effects:

[0074] (1) The NiZnFe-LTH catalyst provided by the present invention contains divalent nickel element, divalent zinc element and trivalent iron element. The three transition metal elements cooperate with each other, which can improve the catalytic activity and stability of the catalyst. Moreover, the introduced divalent zinc element in the catalyst replaces part of the nickel element in the NiFe-LDH catalyst used for ozone decomposition in the prior art. On the one hand, it can fundamentally reduce the cost of the catalyst. On the other hand, it can effectively reduce the water content combined with the catalyst, thereby improving the catalytic effect of the catalyst. Further, by adopting the NiZnFe-LTH catalyst with a specific chemical formula, it is beneficial for the catalyst to achieve efficient and stable decomposition of ozone under conditions of relatively high relative humidity.

[0075] (2) The preparation method of the catalyst provided by the present invention uses a mixed salt solution of nickel, zinc and iron and a second alkali solution to carry out a co-precipitation reaction in a parallel flow manner, which can improve the mixing uniformity of the raw materials and the sufficiency of the reaction, thereby preparing a catalyst with uniform distribution of active sites and excellent catalytic effect. The preparation process adopted is simple and the material cost is low, which is suitable for large-scale production. The prepared catalyst can stably and efficiently decompose ozone under conditions of relatively high relative humidity.

[0076] (3) The catalyst with a specific composition and composition content provided by the present invention can stably and efficiently decompose ozone under relatively harsh conditions during the ozone decomposition process, and is applied to various treatment processes containing ozone gas. The adopted catalyst can achieve stable and efficient separation of ozone under the condition that the relative humidity reaches 65%. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 is the X-ray diffraction pattern of the catalysts provided in Examples 1-5 of the present invention.

[0078] Figure 2 is the field emission scanning electron microscope image (FESEM image) of the catalyst provided in Example 2 of the present invention.

[0079] Figure 3 is the transmission electron microscope image (TEM image) of the catalyst provided in Example 2 of the present invention.

[0080] Figure 4 is the catalysts provided in Examples 1-5 of the present invention during the ozone decomposition process (space velocity is 840000 mL·g -1 ·h -1Relationship diagram between ozone conversion rate and time.

[0081] Figure 5 It is a comparison diagram of X-ray diffraction patterns of the catalyst provided in Example 2 of the present invention before and after 6 h of ozone decomposition (space velocity is 840000 mL·g -1 ·h -1 ).

[0082] Figure 6 It is a relationship diagram between ozone conversion rate and time during the long-term ozone decomposition (space velocity is 600000 mL·g -1 ·h -1 ) of the catalyst provided in Example 2 of the present invention.

[0083] Figure 7 They are X-ray diffraction patterns of the catalysts provided in Comparative Examples 1-3 of the present invention.

[0084] Figure 8 It is a relationship diagram between ozone conversion rate and time during the ozone decomposition (space velocity is 840000 mL·g -1 ·h -1 ) of the catalysts provided in Comparative Examples 1-3 of the present invention. Detailed implementation manners

[0085] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation manners. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0086] Room temperature involved in the following examples refers to a temperature of 25°C.

[0087] Example 1

[0088] This example provides a NiZnFe-LTH catalyst with a two-dimensional layered hydrotalcite structure, and its chemical formula is [Ni 0.5 Zn 2.5 Fe(OH)8][CO3] 0.5 ·nH2O, the water content is 2.8 wt%, and the specific surface area (BET) is 179 m 2 / g.

[0089] This example also provides a preparation method for the above catalyst, which specifically includes the following steps:

[0090] (1) Stir 5 mmol of Ni(NO3)2·6H2O, 25 mmol of Zn(NO3)2·6H2O, and 10 mmol of Fe(NO3)3·9H2O with 50 mL of deionized water for 20 min to obtain a first mixed solution. The total molar concentration of nickel, zinc, and iron in the first mixed solution is 0.8 mol / L.

[0091] Stir sodium hydroxide (NaOH), sodium carbonate (Na2CO3), and 50 mL of deionized water for 20 min to obtain a second mixed solution. In the second mixed solution, the molar concentration of NaOH is 1.6 mol / L, and the molar concentration of Na2CO3 is 0.4 mol / L (the molar concentration of carbonate ions is in excess to ensure that the interlayer anions of the prepared catalyst are all carbonate).

[0092] (2) Add the 50 mL of the first mixed solution obtained in step (1) and the 50 mL of the second mixed solution into deionized water in a co-current manner, with stirring at a rotation speed of 1000 rpm. Maintain the pH of the solution at 12 during the co-current process for a co-precipitation reaction. The temperature of the co-precipitation reaction is 80 °C. Then, continue to stir at a rotation speed of 1000 rpm for 5 h for a third mixing. The temperature of the third mixing is 80 °C. Next, cool the product obtained after the third mixing to room temperature, separate it, wash the separated product until the pH of the washed filtrate is 7, and then dry the washed product at 80 °C for 12 h to obtain the catalyst.

[0093] Example 2

[0094] This example provides a NiZnFe-LTH catalyst with a two-dimensional layered hydrotalcite structure, and its chemical formula is [Ni 1.5 Zn 1.5 Fe(OH)8][CO3] 0.5 ·nH2O, with a water content of 9.9 wt%, and a specific surface area (BET) of 134 m 2 / g.

[0095] This example also provides a preparation method for the above catalyst, which specifically includes the following steps:

[0096] (1) Stir 15 mmol of Ni(NO3)2·6H2O, 15 mmol of Zn(NO3)2·6H2O, and 10 mmol of Fe(NO3)3·9H2O with 50 mL of deionized water for 20 min to obtain a first mixed solution. The total molar concentration of nickel, zinc, and iron in the first mixed solution is 0.8 mol / L.

[0097] Stir sodium hydroxide (NaOH), sodium carbonate (Na2CO3) and 50 mL of deionized water for 20 min to obtain a second mixed solution. In the second mixed solution, the molar concentration of NaOH is 1.6 mol / L, and the molar concentration of Na2CO3 is 0.4 mol / L (the molar concentration of carbonate ions is in excess to ensure that the interlayer anions of the prepared catalyst are all carbonate).

[0098] (2) Add 50 mL of the first mixed solution and 50 mL of the second mixed solution obtained in step (1) into deionized water in a co-current manner, and stir with a rotation speed of 1000 rpm. Maintain the pH of the solution at 12 during the co-current process to carry out a co-precipitation reaction. The temperature of the co-precipitation reaction is 80 °C. Then, continue to stir at a rotation speed of 1000 rpm for 5 h for the third mixing. The temperature of the third mixing is 80 °C. Next, cool the product obtained after the third mixing to room temperature, separate it, wash the separated product until the pH of the washed filtrate is 7, and then dry the washed product at 80 °C for 12 h to obtain the catalyst.

[0099] Example 3

[0100] This example provides a NiZnFe-LTH catalyst with a two-dimensional layered hydrotalcite structure, and its chemical formula is [NiZn2Fe(OH)8][CO3] 0.5 ·nH2O. The water content of the NiZnFe-LTH catalyst is 7.8 wt%, and the specific surface area (BET) is 167 m 2 / g.

[0101] This example also provides a preparation method for the above catalyst, which specifically includes the following steps:

[0102] (1) Stir 10 mmol of Ni(NO3)2·6H2O, 20 mmol of Zn(NO3)2·6H2O and 10 mmol of Fe(NO3)3·9H2O with 50 mL of deionized water for 20 min to obtain a first mixed solution. The total molar concentration of nickel, zinc and iron in the first mixed solution is 0.8 mol / L.

[0103] Stir sodium hydroxide (NaOH), sodium carbonate (Na2CO3) and 50 mL of deionized water for 20 min to obtain a second mixed solution. In the second mixed solution, the molar concentration of NaOH is 1.6 mol / L, and the molar concentration of Na2CO3 is 0.4 mol / L (the molar concentration of carbonate ions is in excess to ensure that the interlayer anions of the prepared catalyst are all carbonate).

[0104] (2) The 50 mL of the first mixed solution and 50 mL of the second mixed solution obtained in step (1) are added in parallel flow to deionized water, accompanied by stirring at a speed of 1000 rpm. During the parallel flow addition, the pH of the solution is maintained at 12 for coprecipitation reaction. The temperature of the coprecipitation reaction is 80 °C. Then, stirring is continued at a speed of 1000 rpm for 5 h for the third mixing. The temperature of the third mixing is 80 °C. Next, the product obtained after the third mixing is cooled to 25 °C, separated, and the separated product is washed until the pH of the washed filtrate is 7. Then, the washed product is dried at 80 °C for 12 h to obtain the catalyst.

[0105] Example 4

[0106] This example provides a NiZnFe-LTH catalyst with a two-dimensional layered hydrotalcite structure, and its chemical formula is [Ni 2.5 Zn 0.5 Fe(OH)8][CO3] 0.5 ·nH2O. The water content of the NiZnFe-LTH catalyst is 12 wt%, and the specific surface area (BET) is 99 m 2 / g.

[0107] This example also provides a preparation method of the above catalyst, which specifically includes the following steps:

[0108] (1) 25 mmol of Ni(NO3)2·6H2O, 5 mmol of Zn(NO3)2·6H2O, and 10 mmol of Fe(NO3)3·9H2O are stirred with 50 mL of deionized water for 20 min to obtain a first mixed solution. The total molar concentration of nickel, zinc, and iron in the first mixed solution is 0.8 mol / L.

[0109] Sodium hydroxide (NaOH), sodium carbonate (Na2CO3), and 50 mL of deionized water are stirred for 20 min to obtain a second mixed solution. In the second mixed solution, the molar concentration of NaOH is 1.6 mol / L, and the molar concentration of Na2CO3 is 0.4 mol / L (the molar concentration of carbonate ions is in excess to ensure that the interlayer anions of the prepared catalyst are all carbonate).

[0110] (2) The 50 mL of the first mixed solution and the 50 mL of the second mixed solution obtained in step (1) are added in parallel to deionized water, accompanied by stirring at a rotation speed of 1000 rpm. During the parallel addition process, the pH of the solution is maintained at 12 for coprecipitation reaction. The temperature of the coprecipitation reaction is 80 °C. Then, stirring is continued at a rotation speed of 1000 rpm for 5 h for the third mixing. The temperature of the third mixing is 80 °C. Next, the product obtained after the third mixing is cooled to 25 °C. After separation, the separated product is washed until the pH of the washed filtrate is 7. Then, the washed product is dried at 80 °C for 12 h to obtain the catalyst.

[0111] Example 5

[0112] This example provides a NiZnFe-LTH catalyst with a two-dimensional layered hydrotalcite structure, and its chemical formula is [Ni2ZnFe(OH)8][CO3] 0.5 ·nH2O. The water content of the NiZnFe-LTH catalyst is 12.1 wt%, and the specific surface area (BET) is 94 m 2 / g.

[0113] This example also provides a preparation method of the above catalyst, which specifically includes the following steps:

[0114] (1) 20 mmol of Ni(NO3)2·6H2O, 10 mmol of Zn(NO3)2·6H2O and 10 mmol of Fe(NO3)3·9H2O are stirred with 50 mL of deionized water for 20 min to obtain a first mixed solution. The total molar concentration of nickel, zinc and iron in the first mixed solution is 0.8 mol / L.

[0115] Sodium hydroxide (NaOH), sodium carbonate (Na2CO3) and 50 mL of deionized water are stirred for 20 min to obtain a second mixed solution. In the second mixed solution, the molar concentration of NaOH is 1.6 mol / L, and the molar concentration of Na2CO3 is 0.4 mol / L (the molar concentration of carbonate ions is in excess to ensure that the interlayer anions of the prepared catalyst are all carbonate).

[0116] (2) The 50 mL of the first mixed solution and the 50 mL of the second mixed solution obtained in step (1) are added in a co-current manner to deionized water, accompanied by stirring at a rotation speed of 1000 rpm. During the co-current addition, the pH of the solution is maintained at 12 for a coprecipitation reaction. The temperature of the coprecipitation reaction is 80 °C. Then, stirring is continued at a rotation speed of 1000 rpm for 5 h for a third mixing, and the temperature of the third mixing is 80 °C. Next, the product obtained after the third mixing is cooled to 25 °C, separated, and the separated product is washed until the pH of the washed filtrate is 7, and then dried at 80 °C for 12 h to obtain the catalyst.

[0117] Comparative Example 1

[0118] The difference between this comparative example and Example 1 is only that: the catalyst provided in this comparative example is a NiFe-LDH catalyst, and its chemical formula is [Ni3Fe(OH)8][CO3] 0.5 ·nH2O, with a water content of 13.8 wt%, and a specific surface area (BET) of 94 m 2 / g; correspondingly, in the preparation method of the catalyst provided in this comparative example, in step (1), 30 mmol of Ni(NO3)2·6H2O and 10 mmol of Fe(NO3)3·9H2O are stirred with 50 mL of deionized water for 20 min to obtain the first mixed solution. The rest of the content is the same as in Example 1.

[0119] Comparative Example 2

[0120] The difference between this comparative example and Example 2 is only that: the catalyst provided in this comparative example is a NiMgFe-LTH catalyst, and its chemical formula is [Ni 1.5 Mg 1.5 Fe(OH)8][CO3] 0.5 ·nH2O, with a water content of 14.2 wt%, and a specific surface area (BET) of 107 m 2 / g; correspondingly, in the preparation method of the catalyst provided in this comparative example, in step (1), 15 mmol of Ni(NO3)2·6H2O, 15 mmol of Mg(NO3)2·6H2O and 10 mmol of Fe(NO3)3·9H2O are stirred with 50 mL of deionized water for 20 min to obtain the first mixed solution. The rest of the content is the same as in Example 2.

[0121] Comparative Example 3

[0122] The difference between this comparative example and Example 2 is only that: the catalyst provided in this comparative example is a NiCoFe-LTH catalyst, and its chemical formula is [Ni 1.5 Co 1.5 Fe(OH)8][CO3]0.5 ·nH2O, with a water content of 13.5 wt%, and a specific surface area (BET) of 80 m 2 / g; correspondingly, in the preparation method of the catalyst provided in this comparative example, in step (1), 15 mmol of Ni(NO3)2·6H2O, 15 mmol of Co(NO3)2·6H2O, and 10 mmol of Fe(NO3)3·9H2O were stirred with 50 mL of deionized water for 20 min to obtain a first mixed solution. The rest of the content was the same as that in Example 2.

[0123] Comparative Example 4

[0124] The difference between this comparative example and Example 4 is only that: the catalyst provided in this comparative example is a NiCoFe-LTH catalyst, and its chemical formula is [Ni 2.5 Co 0.5 Fe(OH)8][CO3] 0.5 ·nH2O; correspondingly, in the preparation method of the catalyst provided in this comparative example, in step (1), 25 mmol of Ni(NO3)2·6H2O, 5 mmol of Co(NO3)2·6H2O, and 10 mmol of Fe(NO3)3·9H2O were stirred with 50 mL of deionized water for 20 min to obtain a first mixed solution. The rest of the content was the same as that in Example 4.

[0125] Comparative Example 5

[0126] The difference between this comparative example and Example 5 is only that: the catalyst provided in this comparative example is a NiCoFe-LTH catalyst, and its chemical formula is [Ni2CoFe(OH)8][CO3] 0.5 ·nH2O; correspondingly, in the preparation method of the catalyst provided in this comparative example, in step (1), 20 mmol of Ni(NO3)2·6H2O, 10 mmol of Co(NO3)2·6H2O, and 10 mmol of Fe(NO3)3·9H2O were stirred with 50 mL of deionized water for 20 min to obtain a first mixed solution. The rest of the content was the same as that in Example 5.

[0127] Take 0.1 g of the catalysts provided in Examples 1-6 and Comparative Examples 1-5, and under the conditions of an ozone concentration of 40 ppm, a temperature of 30 °C, and a relative humidity of 65%, at a test space velocity of 840000 mL·g -1 ·h -1 , test the conversion rate of ozone corresponding to 6 h, and the test results are shown in Table 1.

[0128] Table 1

[0129]

[0130] For the catalyst provided in Example 2, under the conditions of an ozone concentration of 40 ppm, a temperature of 30 °C, and a relative humidity of 65%, at a test space velocity of 600000 mL·g -1 ·h -1 , the conversion rates of ozone corresponding to 6 h and 168 h were tested, and the test results are shown in Table 2.

[0131] Table 2

[0132]

[0133]

[0134] It can be seen from the test results that:

[0135] (1) It can be seen from Examples 1 to 5 that the NiZnFe-LTH catalyst with a specific chemical formula provided by the present invention, through the mutual cooperation of three transition metal elements, jointly improves the catalytic activity and stability of the catalyst, and is conducive to realizing the efficient and stable decomposition of ozone under relatively high relative humidity conditions.

[0136] Figure 1 is the X-ray diffraction pattern (XRD pattern) of the catalyst provided in Examples 1-5 of the present invention. It can be seen from Figure 1 that the catalysts provided in each example all exhibit a typical two-dimensional layered hydrotalcite structure, indicating that each catalyst has been successfully prepared.

[0137] Figure 2 The FESEM image of the catalyst provided in Example 2 is given. Figure 3 The TEM image of the catalyst provided in Example 2 is given. It can be seen from the figure that the catalyst provided in Example 2 has a flaky structure.

[0138] Figure 4 The relationship diagram between the ozone conversion rate and time when the catalysts provided in Examples 1-5 are applied to the ozone decomposition process (space velocity is 840000 mL·g -1 ·h -1 ) is given. It can be seen from the figure that the catalysts provided in Examples 1-5 can maintain a relatively high and stable ozone conversion rate within 0-360 min, thus indicating that the catalyst provided by the present invention has excellent catalytic effect and catalytic stability for ozone decomposition.

[0139] Figure 5 The catalyst provided in Example 2 at a space velocity of 840000 mL·g -1 ·h -1Comparison diagram of X-ray diffraction patterns before ozone decomposition and after 6 h of ozone decomposition under certain conditions. As can be seen from the figure, the XRD of the catalyst provided in Example 2 before the reaction is basically the same as the X-ray diffraction pattern (XRD) after 6 h of ozone decomposition reaction, indicating that the catalyst provided in Example 2 has excellent stability.

[0140] Figure 6 The relationship diagram between ozone conversion rate and time of the catalyst provided in Example 2 during long-term ozone decomposition is given, and the test space velocity is 600000 mL·g -1 ·h -1 Under the conditions, as can be seen from the figure, the catalyst provided in Example 2 can maintain a relatively stable ozone conversion rate within 0 - 168 h, indicating that the catalyst provided by the present invention has high catalytic stability during ozone decomposition.

[0141] (2) By comparing Example 1 with Comparative Example 1, it can be seen that if the zinc element is missing in the catalyst provided by the present invention, the ozone decomposition activity of the catalyst will decrease, resulting in a decrease in the ozone conversion rate during ozone decomposition.

[0142] (3) By comparing Example 2 with Comparative Examples 2 - 3, Example 4 with Comparative Example 4, and Example 5 with Comparative Example 5, it can be seen that if the zinc metal element in the catalyst provided by the present invention is replaced by Mg or Co elements, the catalytic effect of the resulting catalyst on ozone decomposition will become poor, resulting in a significant decrease in the ozone conversion rate under specific relative humidity conditions.

[0143] Figure 7 The X-ray diffraction patterns of the catalysts provided in Comparative Examples 1 - 3 are given. From Figure 7 it can be seen that the catalysts provided in Comparative Examples 1 - 3 also exhibit a typical two-dimensional layered hydrotalcite structure.

[0144] Figure 8 The relationship diagram between ozone conversion rate and time of the catalysts provided in Comparative Examples 1 - 3 applied to the ozone decomposition process (space velocity is 840000 mL·g -1 ·h -1 ) is given. As can be seen from the figure, the catalysts provided in Comparative Examples 1 - 3 have poor catalytic effect and catalytic stability on ozone decomposition within 0 - 360 min.

[0145] In summary, the NiZnFe-LTH catalyst provided by the present invention contains divalent nickel element, divalent zinc element and trivalent iron element. The three transition metal elements cooperate with each other, which can improve the catalytic activity and stability of the catalyst. Moreover, the divalent zinc element introduced in the catalyst replaces part of the nickel element in the NiFe-LDH catalyst used for ozone decomposition in the prior art. On the one hand, it can fundamentally reduce the cost of the catalyst. On the other hand, it can effectively reduce the water content bound to the catalyst, thereby improving the catalytic effect of the catalyst. Further, by adopting the NiZnFe-LTH catalyst with a specific chemical formula, the present invention is conducive to the efficient and stable decomposition of ozone under the condition of relatively high relative humidity.

[0146] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A catalyst, characterized in that The catalyst is a NiZnFe-LTH catalyst, in which the molar ratio of nickel element to zinc element is 1:(0.1-10), and the ratio of the total molar number of nickel element and zinc element to the molar number of iron element is (2.5-3.5):

1.

2. The catalyst according to claim 1, characterized in that In the catalyst, the molar ratio of nickel element to zinc element is 1:(0.2-7), preferably 1:(0.2-5); Preferably, in the catalyst, the ratio of the total molar number of nickel element and zinc element to the molar number of iron element is (2.8-3.2):1; Preferably, the water content of the NiZnFe-LTH catalyst is less than 15wt%; Preferably, the chemical formula of the NiZnFe-LTH catalyst is [Ni a Zn b Fe c (OH) y ][CO3] x / 2 nH2O; Wherein, a is 0.1-5, b is 0.1-5, c is 0.1-2, y=2(a+b+c), and x is 0.1-2; Preferably, the specific surface area of ​​the NiZnFe-LTH catalyst is 90-180m 2 / g; Preferably, the NiZnFe-LTH catalyst has a two-dimensional layered hydrotalcite structure; Preferably, the water content of the NiZnFe-LTH catalyst is 2-13 wt%.

3. A method for preparing a catalyst according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) mixing a nickel salt, a zinc salt, and an iron salt with a first solvent according to a formula amount to obtain a first mixed solution; The first alkali solution and the second alkali solution are mixed with the second solvent according to the formula amount to obtain a second mixed solution; the anions in the first alkali solution include hydroxide ions, and the anions in the second alkali solution include acid ions; (2) Adding the first mixed solution and the second mixed solution into the bottom liquid in parallel according to the formula amount to carry out a co-precipitation reaction to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that: Step (1) The total molar concentration of nickel, zinc and iron in the first mixed solution is 0.1-5 mol / L.

5. The preparation method according to claim 3 or 4, characterized in that: Step (1) the first alkali solution comprises sodium hydroxide; Preferably, the second alkali solution in step (1) comprises sodium carbonate; Preferably, in the second mixed solution of step (1), the molar concentration of the first alkali solution is 0.5-5 mol / L; Preferably, in the second mixed solution of step (1), the molar concentration of the second alkali solution is 0.1-2 mol / L.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The temperature of the coprecipitation reaction in step (2) is 60-100° C. Preferably, the parallel flow process in step (2) is accompanied by stirring.

7. The preparation method according to any one of claims 3 to 6, characterized in that: After the coprecipitation reaction in step (2), the product obtained by combining the first mixed solution and the second mixed solution and flowing into the bottom solution is subjected to a third mixing; Preferably, the third mixing method includes stirring; Preferably, the temperature of the third mixing is 60-100°C; Preferably, the third mixing time is 3-10 hours.

8. The preparation method according to claim 7, characterized in that: The product obtained after the third mixing is further subjected to post-treatment; Preferably, the specific process of the post-treatment includes: cooling, separating, washing and drying the product obtained after the third mixing; Preferably, the washing is performed until the filtrate after washing is neutral; Preferably, the drying temperature is 60-100°C; Preferably, the drying time is 12-24 hours.

9. Use of the catalyst according to claim 1 or 2, characterized in that: The catalyst is applied in the process of decomposing ozone.

10. The use according to claim 9, characterized in that: The catalyst is used to catalyze the decomposition of gaseous ozone; Preferably, the catalyst is used to decompose ozone in enclosed spaces indoors and in high-altitude aircraft; Preferably, the catalyst is applied to the exterior surfaces of buildings and in motor vehicle radiators to decompose ozone in the atmospheric environment; Preferably, the catalyst is used for decomposing ozone in water treatment tail gas.

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