Preparation method and application of composite catalyst for catalytic oxidation of toluene

Abstract

The invention relates to a preparation method and application of a composite catalyst for catalyzing toluene oxidation. The method comprises the following steps: step 1, dissolving K2FeO4 in water, adding a manganese salt compound, and stirring evenly to obtain a solid-liquid mixture 1; step 2, transferring the solid-liquid mixture 1 obtained in step 1 to a closed container and performing a heating treatment; step 3, filtering the product after the heating treatment in step 2, and washing (repeatedly washing with deionized water or ethanol) to obtain a Mn3O4-Fe2O3 solid; step 4, drying the Mn3O4-Fe2O3 primary solid obtained in step 3 to obtain a Mn3O4-Fe2O3 solid; and step 5, calcining the Mn3O4-Fe2O3 solid obtained in step 4 to obtain the Mn3O4-Fe2O3 catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a preparation method and application of a composite catalyst for catalyzing toluene oxidation, and in particular to a method for preparing a Mn3O4-Fe2O3 composite catalyst by utilizing K2FeO4. Background Art

[0002] Toluene, as a typical VOCs, is considered to be an important air pollutant. Studies have shown that toluene can be oxidized into non-toxic and harmless products such as H2O and CO2 at a lower temperature than direct combustion through catalytic oxidation. Therefore, many researchers have focused their attention on the research of toluene catalytic oxidation treatment, and catalysts are generally considered to be the core of toluene catalytic oxidation. Usually, catalysts are composed of active components, co-catalysts and carriers. However, the activity of active components is affected by many factors such as catalyst particle size, specific surface area, pore volume, catalyst dispersion, pore structure, etc.

[0003] The active components of the catalyst mainly include precious metals and non-precious metal oxides. Supported precious metals often show excellent catalytic performance, but their high prices limit their wide industrial applications. Therefore, transition metal oxide catalysts have attracted more and more attention. Among them, transition metal manganese with many different oxidation states can be converted between several different valence states. Due to its low cost, easy availability, environmental protection and diverse structure, manganese oxides have a wide range of applications in the catalytic decomposition of toluene, especially Mn3O4, which is widely used due to its physical and chemical properties. Compared with other metal oxide catalysts, Mn3O4 shows good catalytic performance in toluene oxidation.

[0004] Chinese patent CN102068994A, by adding polyethylene glycol aqueous solution to divalent manganese salt aqueous solution at a certain temperature, then adding potassium permanganate and trivalent iron salt aqueous solution, stirring to obtain precipitation, filtering the obtained solid as the precursor of the catalyst, drying and then roasting, and crushing the roasted solid into particles to obtain the catalyst. However, this method has complex preparation steps, harsh synthesis conditions, and complex catalyst components. Compared with this method, the preparation method of this patent is simple, the synthesis conditions are wide, and the synthetic product is a mixed crystal form.

[0005] The synthetic reaction formula is: 2Fe 6+ +9Mn 2+ +15H2O→Fe2O3+3Mn3O4+30H + . Summary of the invention

[0006] In order to further improve the catalytic ability of toluene oxidation, the use of new precursors to prepare Mn3O4 materials is studied to increase the specific surface area and the number of active sites exposed on the surface of the prepared catalyst. The present invention provides a method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4. The preparation method of the present invention has a simple process, few steps and is easy to operate. The manganese-based catalyst prepared by the preparation method can efficiently convert toluene in the air into carbon dioxide and water, and the removal temperature is low.

[0007] The object of the present invention is achieved in that:

[0008] A method for preparing a composite catalyst for catalyzing toluene oxidation comprises the following steps:

[0009] Step 1, dissolving K2FeO4 in water, then adding a manganese salt compound, stirring evenly, to obtain a solid-liquid mixture 1;

[0010] Step 2, heating the solid-liquid mixture 1 under closed conditions;

[0011] Step 3, filtering the product after the heating treatment in step 2, and washing (repeatedly rinsing with deionized water or ethanol) to obtain a primary solid of Mn3O4-Fe2O3;

[0012] Step 4, drying the Mn3O4-Fe2O3 primary solid to obtain a Mn3O4-Fe2O3 solid;

[0013] Step 5: calcining the Mn3O4-Fe2O3 solid to obtain the Mn3O4-Fe2O3 catalyst.

[0014] In step 1, the manganese salt compound is selected from manganese sulfate, manganese acetate, or manganese nitrate.

[0015] In step 1, the stirring time is 0.5-2.0 hours. The stirring time is to achieve sufficient stirring of K2FeO4 and manganese oxide, so as to obtain more precipitation products. If the stirring time is too short, the reaction product will be wasted, and if the stirring time is too long, serious energy consumption problems will be caused.

[0016] In step 2, heating under closed conditions refers to heating in a closed container, wherein the closed container is a polytetrafluoroethylene high-pressure reactor.

[0017] The heating temperature is 120-180°C; the heating time is 12-24 hours.

[0018] In step 4, the drying temperature is 80-120° C. and the drying time is 12-24 hours.

[0019] In step 5, the calcination temperature is 350-550° C. and the calcination time is 2-5 hours.

[0020] The catalyst prepared by the preparation method described above also falls within the protection scope of this application.

[0021] The application of the catalyst in the catalytic oxidation treatment of toluene also falls within the protection scope of the present application.

[0022] Furthermore, the manganese salt compound selected is manganese sulfate monohydrate or the like.

[0023] In step 3, the washing is repeated washing with deionized water or ethanol until the filtrate becomes neutral.

[0024] The Mn3O4-Fe2O3 catalyst is used for catalytic oxidation of toluene at low temperature.

[0025] The beneficial effects of the present invention are as follows:

[0026] (I) The key point of the present application is to use potassium ferrate as an oxidant to synthesize Mn3O4-Fe2O3 catalyst in one step through redox reaction, without the need to add iron salt to introduce iron oxide, and the synthesis conditions are wide, and no deliberate hydrothermal time is required. The traditional synthesis method has strict requirements on the addition ratio between the oxidant and the manganese salt and the iron salt, and the synthesis conditions are strict. The present invention realizes the one-step synthesis of Mn3O4-Fe2O3, the method is simple, and the conditions are wide.

[0027] (ii) The preparation method of the present invention has a simple process, few steps and is easy to operate. The Mn3O4-Fe2O3 catalyst prepared by the preparation method can efficiently remove toluene from the air at a low removal temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0029] Figure 1 XRD diagram of Mn3O4-Fe2O3 prepared by Example 1 and Comparative Examples 1-7 of the method of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, some adjustments and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0031] The present invention will be further described below in conjunction with the embodiments.

[0032] Figure 1 XRD diagram of Mn3O4-Fe2O3 prepared by Example 1 and Comparative Examples 1-7 of the method of the present invention.

[0033] In the following examples and comparative examples, the sealed container is a polytetrafluoroethylene high-pressure reactor.

[0034] Example 1

[0035] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps:

[0036] Step 1, weigh 1.9800 g of K2FeO4 and dissolve it in 80 mL of deionized water, then add 1.6900 g of MnSO4·H2O, and then stir at room temperature for 0.5 hour.

[0037] Step 2: transfer the solid-liquid mixture obtained in step 1 into a sealed container, place it in an oven, and treat it at 140° C. for 12 hours.

[0038] Step 3, filtering the solid-liquid mixture obtained in step 2, and repeatedly rinsing it with deionized water until the filtrate becomes neutral, thereby obtaining a Mn3O4-Fe2O3 solid.

[0039] Step 4, transfer the solid obtained in step 3 to an oven and dry it at 80° C. for 12 hours.

[0040] Step 5, transferring the solid obtained in step 4 to a muffle furnace, and calcining it at 400° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0041] Example 2

[0042] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps:

[0043] Step 1: Weigh 1.9800g K2FeO4 and dissolve it in 80mL deionized water, then add 1.6900g

[0044] (CH3COO)2Mn·4H2O, followed by stirring at room temperature for 0.5 hours.

[0045] Step 2: transfer the solid-liquid mixture obtained in step 1 into a sealed container, place it in an oven, and treat it at 140° C. for 12 hours.

[0046] Step 3, filtering the solid-liquid mixture obtained in step 2, and repeatedly rinsing it with deionized water until the filtrate becomes neutral, thereby obtaining a Mn3O4-Fe2O3 solid.

[0047] Step 4, transfer the solid obtained in step 3 to an oven and dry it at 80° C. for 12 hours.

[0048] Step 5, transferring the solid obtained in step 4 to a muffle furnace, and calcining it at 400° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0049] Example 3

[0050] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps: step 1, weighing 1.9800 g of K2FeO4 and dissolving it in 80 mL of deionized water, then adding 1.6900 g of Mn(NO3)2, and then stirring at room temperature for 0.5 hours.

[0051] Step 2: transfer the solid-liquid mixture obtained in step 1 into a sealed container, place it in an oven, and treat it at 140° C. for 12 hours.

[0052] Step 3, filtering the solid-liquid mixture obtained in step 2, and repeatedly rinsing it with deionized water until the filtrate becomes neutral, thereby obtaining a Mn3O4-Fe2O3 solid.

[0053] Step 4, transfer the solid obtained in step 3 to an oven and dry it at 80° C. for 12 hours.

[0054] Step 5, transferring the solid obtained in step 4 to a muffle furnace, and calcining it at 400° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0055] Comparative Example 1

[0056] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps:

[0057] Step 1, weigh 1.9800 g of K2FeO4 and dissolve it in 80 mL of deionized water, then add 1.6900 g of MnSO4·H2O, and then stir at room temperature for 0.5 hour.

[0058] Step 2, filtering the solid-liquid mixture obtained in step 1, and repeatedly rinsing with deionized water until the filtrate becomes neutral, to obtain a Mn3O4-Fe2O3 solid.

[0059] Step 3, transfer the solid obtained in step 2 to an oven and dry it at 80° C. for 12 hours.

[0060] Step 4, transferring the solid obtained in step 3 to a muffle furnace, and calcining it at 400° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0061] Comparative Example 2

[0062] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps:

[0063] Step 1, weigh 1.9800 g of K2FeO4 and dissolve it in 80 mL of deionized water, then add 1.6900 g of MnSO4·H2O, and then stir at room temperature for 0.5 hour.

[0064] Step 2: transfer the solid-liquid mixture obtained in step 1 into a sealed container, place it in an oven, and treat it at 100° C. for 12 hours.

[0065] Step 3, filtering the solid-liquid mixture obtained in step 2, and repeatedly rinsing it with deionized water until the filtrate becomes neutral, thereby obtaining a Mn3O4-Fe2O3 solid.

[0066] Step 4, transfer the solid obtained in step 3 to an oven and dry it at 80° C. for 12 hours.

[0067] Step 5, transferring the solid obtained in step 4 to a muffle furnace, and calcining it at 400° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0068] Comparative Example 3

[0069] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps:

[0070] Step 1, weigh 1.9800 g of K2FeO4 and dissolve it in 80 mL of deionized water, then add 1.6900 g of MnSO4·H2O, and then stir at room temperature for 0.5 hour.

[0071] Step 2: transfer the solid-liquid mixture obtained in step 1 into a sealed container, place it in an oven, and treat it at 200° C. for 12 hours.

[0072] Step 3, filtering the solid-liquid mixture obtained in step 2, and repeatedly rinsing it with deionized water until the filtrate becomes neutral, thereby obtaining a Mn3O4-Fe2O3 solid.

[0073] Step 4, transfer the solid obtained in step 3 to an oven and dry it at 80° C. for 12 hours.

[0074] Step 5, transferring the solid obtained in step 4 to a muffle furnace, and calcining it at 400° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0075] Comparative Example 4

[0076] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps:

[0077] Step 1, weigh 1.9800 g of K2FeO4 and dissolve it in 80 mL of deionized water, then add 1.6900 g of MnSO4·H2O, and then stir at room temperature for 0.5 hour.

[0078] Step 2: transfer the solid-liquid mixture obtained in step 1 into a sealed container, place it in an oven, and treat it at 140° C. for 12 hours.

[0079] Step 3, filtering the solid-liquid mixture obtained in step 2, and repeatedly rinsing it with deionized water until the filtrate becomes neutral, thereby obtaining a Mn3O4-Fe2O3 solid.

[0080] Step 4, transfer the solid obtained in step 3 to an oven and dry it at 80° C. for 12 hours.

[0081] Step 5, transferring the solid obtained in step 4 to a muffle furnace, and calcining it at 600° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0082] Comparative Example 5

[0083] A method for preparing a Mn3O4-Fe2O3 composite catalyst using K2FeO4 comprises the following steps:

[0084] Step 1, weigh 1.9800 g of K2FeO4 and dissolve it in 80 mL of deionized water, then add 1.6900 g of MnSO4·H2O, and then stir at room temperature for 0.5 hour.

[0085] Step 2: transfer the solid-liquid mixture obtained in step 1 into a sealed container, place it in an oven, and treat it at 140° C. for 12 hours.

[0086] Step 3, filtering the solid-liquid mixture obtained in step 2, and repeatedly rinsing it with deionized water until the filtrate becomes neutral, thereby obtaining a Mn3O4-Fe2O3 solid.

[0087] Step 4, transfer the solid obtained in step 3 to an oven and dry it at 80° C. for 12 hours.

[0088] Step 5, transferring the solid obtained in step 4 to a muffle furnace, and calcining it at 300° C. for 3 hours to obtain a Mn3O4-Fe2O3 catalyst.

[0089] Comparative Example 6

[0090] The difference between this comparative example and Example 1 is that K2FeO4 is not added, and specifically comprises the following steps:

[0091] A, weigh 1.6900 g of MnSO4·H2O and dissolve it in 80 mL of deionized water, then stir at room temperature for 0.5 hour to obtain a solid-liquid mixture;

[0092] B. The solid-liquid mixture obtained in step A is transferred into a sealed container, placed in an oven, and treated at 140° C. for 12 hours.

[0093] C. Filter the solid-liquid mixture obtained in step B, and repeatedly rinse with deionized water until the filtrate becomes neutral to obtain a solid.

[0094] D. The solid obtained in step C is transferred to an oven and dried at 80° C. for 12 hours.

[0095] E. The solid obtained in step D is transferred to a muffle furnace and calcined at 400° C. for 3 hours to obtain a Mn2O3 catalyst.

[0096] Comparative Example 7

[0097] The difference between this comparative example and Example 1 is that no manganese salt compound is added, and specifically comprises the following steps:

[0098] A, weigh 1.9800 g of K2FeO4 and dissolve it in 80 mL of deionized water, then stir at room temperature for 0.5 hour to obtain a solid-liquid mixture;

[0099] B. The solid-liquid mixture obtained in step A is transferred into a sealed container, placed in an oven, and treated at 140° C. for 12 hours.

[0100] C. Filter the solid-liquid mixture obtained in step B, and repeatedly rinse with deionized water until the filtrate becomes neutral to obtain a solid.

[0101] D. The solid obtained in step C is transferred to an oven and dried at 80° C. for 12 hours.

[0102] E. The solid obtained in step D is transferred to a muffle furnace and calcined at 400° C. for 3 hours to obtain a Fe2O3 catalyst.

[0103] Application effect detection:

[0104] The catalytic effects of the catalysts prepared in Examples 1, 2, 3 and Comparative Examples 1-7 were tested.

[0105] Test method:

[0106] The test device is mainly composed of four parts: gas distribution system, fixed bed reaction equipment, gas chromatograph and tail gas absorption. The source of toluene is mainly to use air to pass into the toluene analytical pure reagent in the ice water bath, carry it out, and then mix it with another air in the gas mixing bottle before entering the reaction device. The concentration of toluene is mainly controlled by adjusting the air flow rate ratio of the two routes, and the gas flow rate is adjusted by using a mass flow controller. The fixed window reaction equipment is composed of a resistive reaction program heating furnace and a quartz reaction tube. The activity test of toluene catalytic oxidation is carried out in a fixed quartz tube with an inner diameter of 6mm and a tube length of 40cm. The quartz tube is placed in the program heating furnace, and the thermocouple for detecting the reaction temperature is inserted into the position of the catalyst. The catalyst powder is fixed in the middle position of the quartz tube by using quartz wool to ensure the stability of the catalyst. The toluene concentration and CO2 yield at the inlet and outlet are detected on a GC-950HXSP device equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD).

[0107] Test results:

[0108] From Table 1, it can be seen that the catalyst prepared in Example 1 exhibits the best toluene removal ability at different test temperatures, while the catalyst prepared in Comparative Example 7 exhibits the worst toluene removal ability.

[0109] Table 1 Conversion rate of catalytic oxidation of toluene in Examples 1-3 and Comparative Examples 1-6 at different test temperatures

[0110]

[0111]

[0112] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a composite catalyst for catalyzing toluene oxidation, characterized in that: The following steps are involved: Step 1, dissolving K2FeO4 in water, then adding a manganese salt compound, stirring evenly, to obtain a solid-liquid mixture 1; Step 2, heating the solid-liquid mixture 1 under closed conditions; Step 3, filtering the product after the heating treatment in step 2, and washing it to obtain a primary solid of Mn3O4-Fe2O3; Step 4, drying the Mn3O4-Fe2O3 primary solid to obtain a Mn3O4-Fe2O3 solid; Step 5, calcining the Mn3O4-Fe2O3 solid to obtain the Mn3O4-Fe2O3 catalyst; In step 2, the heating temperature is 120-180° C. and the heating time is 12-24 hours; In step 5, the calcination temperature is 350-550° C. and the calcination time is 2-5 hours.

2. The preparation method according to claim 1, characterized in that: In step 1, the molar ratio of the iron element in K2FeO4 to the manganese element in the manganese salt compound is 1:1 to 1:4.

5.

3. The preparation method according to claim 1, characterized in that: In step 1, the manganese salt compound is selected from one of manganese sulfate, manganese acetate and manganese nitrate.

4. The preparation method according to claim 1, characterized in that: In step 1, the stirring time is 0.5-2.0 hours.

5. The preparation method according to claim 1, characterized in that: In step 2, heating under closed conditions refers to heating in a closed container, wherein the closed container is a polytetrafluoroethylene high-pressure reactor.

6. The preparation method according to claim 1, characterized in that: In step 4, the drying temperature is 80-120° C. and the drying time is 12-24 hours.

7. A catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the catalyst as claimed in claim 7 in catalytic oxidation treatment of toluene.

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