FeMnZrOx catalyst for denitration of tail gas of diesel engine and preparation method of FeMnZrOx catalyst

Abstract

The invention belongs to the technical field of environmental protection, and relates to a FeMnZrOx catalyst for denitration of tail gas of a diesel engine and a preparation method of the FeMnZrOx catalyst. The preparation method comprises the following steps: uniformly mixing zirconium salt, manganese salt, ferric salt and a solvent, adding citric acid, and uniformly mixing to obtain a mixed solution; and heating the mixed solution, and drying and calcining after heating to obtain the FeMnZrOx catalyst. The process for synthesizing the FeMnZrOx catalyst is simple, easy and convenient to operate, low in cost, high in thermal stability and good in poisoning resistance, the prepared catalyst can improve the acidity of the catalyst and promote NH3-SCR reaction, meanwhile, the content of oxygen adsorbed on the surface of the catalyst can be improved, the oxygen storage capacity can be improved, the activity of the catalyst is improved, and the purposes of saving energy and reducing emission are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection and relates to a FeMnZrO x Catalyst and method for preparing the same. Background Art

[0002] With the rapid development of urbanization, fossil fuels such as coal and oil are likely to continue to be an important source of meeting the growing energy demand. However, the uncontrolled consumption of fossil fuels is believed to increase the nitrogen oxides (NO x ) emissions, which can lead to a series of environmental problems such as acid rain, photochemical smog, ozone layer depletion and water eutrophication. x The control and elimination of NO has attracted great attention, and increasingly stringent regulations have been issued to update the NO from flue gases and mobile exhaust. x emission standards.

[0003] To date, various technologies have been developed to reduce NO x The most popular technologies include selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), three-way catalysis (TWC) and NO x Among them, the SCR process using NH3 as a reductant (NH3-SCR) has been demonstrated to remove NO from stationary sources such as power plants, industrial boilers, steel mills and process heaters. x The most effective method. x The control principle is to use urea or NH3 as a reducing agent, and under the action of a catalyst, reduce NO in the exhaust gas to x Catalytic reduction to harmless N2, and the catalyst is the core of this technology. It is widely reported that commercial V2O5-WO3 / TiO2 catalysts show excellent denitration (i.e., denitration performance and sulfur resistance in the NH3-SCR reaction in the range of 300-400°C), but this V2O5-based catalyst is not suitable for the denitration process of low-temperature (below 300°C) flue gas such as garbage incinerators, glass kilns, and steel sintering furnaces.

[0004] Chinese patent CN104801336A discloses a method for reducing NO with NH3 at low temperature. x The ZrMnFe-ZSM5 composite oxide catalyst is based on the molecular sieve ZSM-5 as a carrier, and ZrO2, MnO2, and Fe2O3 as active components, wherein MnO2 and Fe2O3 are the main catalysts, and ZrO2 is the secondary catalyst. The catalyst catalytically reduces NO x The T90 window temperature of (NH3-SCR) is 167~357℃, the low temperature is high and the catalytic efficiency is low.

[0005] Chinese patent CN105618032B discloses a supported manganese-based low-temperature denitration catalyst, which uses titanium oxide as a carrier and iron oxide and manganese oxide as active ingredients. The catalyst catalytically reduces NO x (NH3-SCR), NO at 150℃ x The conversion rate of NO is only 95% at 200℃ x The conversion rate is only 93%. The catalyst has a small activity window, poor low-temperature performance and low catalytic efficiency.

[0006] Chinese patent CN105903464A discloses a NO with a wide active temperature window. x Oxidation catalyst, the catalyst has manganese oxide as the main active component, zirconium and iron as auxiliary active components, the catalyst catalytically reduces NO x (NH3-SCR) NO at 200℃ x The conversion rate of NO is only 90% at about 260℃ x The conversion rate is less than 90%, the catalyst has a small activity window, poor low-temperature performance and low catalytic efficiency.

[0007] Chinese patent CN 108579756B discloses a kelp-like Mn-Fe bimetallic oxide supported CeO2 catalyst, which has a complex preparation process, high raw material cost, and is not easy to industrialize.

[0008] The inventor's early research topic (Modulating the acidity and reducibility of FeMn / TiO2 to boost the low-temperature selective catalytic reduction of NO x .J.Zhu,Y.Shao,Z.Li,et al.Fuel,366(2024),131316.) discloses a method for promoting NO x The low-temperature selective catalyst is based on TiO2 as a carrier and loaded with manganese oxide and iron oxide as active components. The experimental results show that the catalytic effect of the catalyst decreases sharply after being poisoned by SO2. x The conversion rate and selectivity of N2 dropped sharply, and the catalyst had poor anti-poisoning ability. Therefore, the design and development of efficient low-temperature denitrification catalysts is particularly important at present. Summary of the invention

[0009] The technical problem to be solved by the present invention is that the existing oxides in the prior art have poor low-temperature NH3-SCR activity, narrow active temperature window, poor thermal stability, and poor anti-poisoning ability. The present invention aims to provide a catalyst with excellent low-temperature catalytic activity and wide NO x FeMnZrO with operating temperature window, good anti-poisoning ability, low preparation cost and simple preparation method x Catalyst and its preparation method and application.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0011] The invention discloses a FeMnZrO x The preparation method of the catalyst comprises mixing zirconium salt, manganese salt, iron salt and solvent, and then adding citric acid to mix to obtain a mixed solution; then heating the mixed solution, drying after heating, and calcining to obtain FeMnZrO x catalyst;

[0012] Wherein, the zirconium salt is zirconium oxychloride; the manganese salt is manganese nitrate; the iron salt is iron nitrate;

[0013] The molar ratio of the zirconium salt to the manganese salt, the iron salt and the citric acid is 2:0.5-1.5:0.5-1.5:2.

[0014] Wherein, the FeMnZrO x The catalyst is Fe 1-y Mn y ZrOx, 0<y<1.

[0015] In some embodiments, preferably, the molar ratio of the zirconium salt to the manganese salt, iron salt and citric acid is 2:1.0-1.5:0.5-1.0:2, further preferably, the molar ratio of the zirconium salt to the manganese salt, iron salt and citric acid is 2:1.5:0.5:2 or 2:1.0:1.0:2, and further preferably, it is 2:1.0:1.0:2.

[0016] In some embodiments, the zirconium salt is zirconium oxychloride octahydrate; and the iron salt is iron nitrate nonahydrate.

[0017] In some embodiments, the solvent is deionized water.

[0018] There is no special requirement for the amount of the solvent, as long as the raw materials are dispersed evenly.

[0019] In some embodiments, the heating temperature is 80°C to 120°C and the heating time is 4 to 6 hours.

[0020] In some embodiments, preferably, the heating temperature is 80° C. and the heating time is 5 hours.

[0021] In some embodiments, the drying temperature is 80° C. to 100° C. and the drying time is 8 to 15 hours.

[0022] In some embodiments, preferably, the drying temperature is 80° C. and the drying time is 12 h.

[0023] In some embodiments, the calcination temperature is 500° C. to 550° C. and the calcination time is 4 to 8 hours.

[0024] In some embodiments, preferably, the calcination temperature is 550° C. and the calcination time is 5 h.

[0025] The FeMnZrO prepared by the above preparation method x Catalysts are also within the scope of protection of the present invention.

[0026] The above FeMnZrO x The use of the catalyst in the reduction of nitrogen oxides is also within the scope of protection of the present invention.

[0027] Specifically, FeMnZrO x The catalyst performs a selective catalytic reduction reaction at a temperature of 100°C to 450°C.

[0028] Beneficial effects:

[0029] (1) The present application uses Zr oxide as the main catalyst, Mn oxide and Fe oxide as the secondary catalysts, and adjusts the Fe / Mn ratio and the ratio with Zr to regulate the acidity and redox properties of the active sites on the catalyst surface, promotes the formation of active intermediates, thereby improving the redox properties of the catalyst in the low temperature zone and widening the temperature window.

[0030] (2) The present invention synthesizes FeMnZrO x The catalyst has low cost, is easy to operate, can improve the acidity of the catalyst, and is easy to oxidize NO x , which can improve the oxygen content adsorbed on the catalyst surface, increase the oxygen storage capacity, and thus improve the catalyst activity, while achieving the purpose of energy conservation and emission reduction; and the product is not easy to volatilize, non-toxic and harmless, safe and efficient, and suitable for industrial production.

[0031] (3) This application FeMnZrO x After the Fe element is added to the catalyst, the acidity of the catalyst is significantly improved, and at the same time, one Mn in the Mn-Mn dimer is replaced. 4+sites and form a relatively stable Mn-Fe dimer structure with high NO oxidation activity.

[0032] (4) This application FeMnZrO x The catalyst has excellent anti-poisoning ability after introducing Zr and controlling the ratio of Fe, Mn and Zr. The activity of the catalyst is basically not affected after poisoning, and it is suitable for use in industrial production.

[0033] (5) This application is for FeMnZrO x The NO oxidation performance of the catalyst was evaluated. The low-temperature activity was good and the activity window was wide. When the optimal activity temperature reached 158°C, NO x Conversion rate reaches 100%, operation window T 90 It is 135~295℃.

[0034] (6) Synthesis of FeMnZrO by the present invention x The catalyst has a simple process, easy operation, low cost, high thermal stability, and good anti-poisoning ability. The prepared catalyst can improve the catalyst acidity, promote the NH3-SCR reaction, and at the same time improve the oxygen content adsorbed on the catalyst surface, increase the oxygen storage capacity, and then improve the catalyst activity, thereby achieving the purpose of energy saving and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0036] Figure 1 The catalysts prepared in Examples 1 to 5 were used to catalyze NO x Reduced NO x Conversion rate data chart.

[0037] Figure 2 The catalysts prepared in Examples 1 to 5 were used to catalyze NO x Plot of reduced N2 selectivity data.

[0038] Figure 3 This is the catalytic activity data diagram of the catalyst after poisoning. DETAILED DESCRIPTION

[0039] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0040] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0041] Example 1: Synthesis of MnZrO by sol-gel method x catalyst

[0042] 0.02 mol ZrOCl2·8H2O and 0.04 mol 50% Mn(NO3)2 were added to 10 mL deionized water in sequence and magnetically stirred for 30 min to mix; then 0.02 mol anhydrous citric acid was added to the system and stirred for 30 min; then the temperature was raised to 80°C and heated in a water bath for 5 h; after the water bath heating was completed, the reaction solution was dried at 80°C for 12 h; after drying, it was calcined at 550°C for 5 h to obtain MnZrO x catalyst.

[0043] Example 2: Synthesis of FeMnZrO by sol-gel method x catalyst

[0044] 0.02 mol ZrOCl2·8H2O, 0.03 mol 50% Mn(NO3)2, and 0.005 mol Fe(NO3)3·9H2O were added to 10 mL deionized water in sequence and magnetically stirred for 30 min to mix; then 0.02 mol anhydrous citric acid was added to the system and stirred for 30 min; then the temperature was raised to 80°C and heated in a water bath for 5 h; after the water bath heating was completed, the reaction solution was dried at 80°C for 12 h; after drying, it was calcined at 550°C for 5 h to obtain Mn 0.75 Fe 0.25 ZrO x catalyst.

[0045] Example 3: Synthesis of FeMnZrO by sol-gel method x catalyst

[0046] 0.02 mol ZrOCl2·8H2O, 0.02 mol 50% Mn(NO3)2, and 0.01 mol Fe(NO3)3·9H2O were added to 10 mL deionized water in sequence and magnetically stirred for 30 min to mix; then 0.02 mol anhydrous citric acid was added to the system and stirred for 30 min; then the temperature was raised to 80°C and heated in a water bath for 5 h; after the water bath heating was completed, the reaction solution was dried at 80°C for 12 h; after drying, it was calcined at 550°C for 5 h to obtain Mn 0.5 Fe 0.5 ZrO x catalyst.

[0047] Example 4: Synthesis of FeMnZrO by sol-gel methodx catalyst

[0048] 0.02 mol ZrOCl2·8H2O, 0.01 mol 50% Mn(NO3)2, and 0.015 mol Fe(NO3)3·9H2O were added to 10 mL deionized water in sequence and magnetically stirred for 30 min to mix; then 0.02 mol anhydrous citric acid was added to the system and stirred for 30 min; then the temperature was raised to 80°C and heated in a water bath for 5 h; after the water bath heating was completed, the reaction solution was dried at 80°C for 12 h; after drying, it was calcined at 550°C for 5 h to obtain Mn 0.25 Fe 0.75 ZrO x catalyst.

[0049] Example 5: Synthesis of FeZrO by sol-gel method x catalyst

[0050] 0.02 mol ZrOCl2·8H2O and 0.02 mol Fe(NO3)3·9H2O were added to 10 mL deionized water in turn and stirred magnetically for 30 min to mix; then 0.02 mol anhydrous citric acid was added to the system and stirred for 30 min; then the temperature was raised to 80°C and heated in a water bath for 5 h; after the water bath heating was completed, the reaction solution was dried at 80°C for 12 h; after drying, it was calcined at 550°C for 5 h to obtain FeZrO x catalyst.

[0051] Embodiment 6:

[0052] (1) Catalytic reduction of NO x (NH3-SCR)

[0053] The NH3-SCR performance of FeMnZrO2 catalyst at atmospheric pressure was investigated in a micro fixed bed quartz flow reactor. The reaction system consists of a heating furnace and a reactor, which is a quartz tube with an inner diameter of 8 mm. The total flow rate of the raw gas (standard conditions) is 500 mL min -1 , gas hourly space velocity (GHSV) is about 30000h -1 The feed gas mixture consisted of 500 ppm NO x , 500ppm NH3, 5% O2 and N2 as the balance gas. The contents of NO, NO2, NH3, N2O and other gases after the reaction were detected by Fourier transform infrared gas analyzer (Thermo Fisher IGS). The amount of catalyst used was 1mL, 40-60 mesh size, and the catalyst was prepared in Examples 1 to 5. The following equation was used to calculate NO x Conversion and N2 selectivity:

[0054]

[0055] Figure 1 The catalysts prepared in Examples 1 to 5 were used to catalyze NO x Reduced NO x Conversion rate data diagram, where a is the MnZrO prepared in Example 1 x Catalyst; b is Mn prepared in Example 2 0.75 Fe 0.25 ZrO x Catalyst; c is Mn prepared in Example 3 0.5 Fe 0.5 ZrO x Catalyst; d is Mn prepared in Example 4 0.25 Fe 0.75 ZrO x Catalyst; e is FeZrO prepared in Example 5 x Catalyst. As can be seen from the figure, the Mn prepared in Example 3 0.5 Fe 0.5 ZrO x Catalytic reduction of NO x (NH3-SCR), when the optimal activity temperature reaches 158℃, NO x Conversion rate reaches 100%, operation window T 90 It is 135~295℃.

[0056] Figure 2 The catalysts prepared in Examples 1 to 5 were used to catalyze NO x N2 selectivity data of reduction, where a is MnZrO prepared in Example 1 x Catalyst; b is Mn prepared in Example 2 0.75 Fe 0.25 ZrO x Catalyst; c is Mn prepared in Example 3 0.5 Fe 0.5 ZrO x Catalyst; d is Mn prepared in Example 4 0.25 Fe 0.75 ZrO x Catalyst; e is FeZrO prepared in Example 5 x Catalyst. As can be seen from the figure, the selectivity of the catalysts is over 60%, which means that the selectivity is good, indicating that less by-products are produced.

[0057] (2) Water and sulfur resistance test

[0058] The catalyst of Example 3 was poisoned under the conditions of 750°C, 5% H2O, 30ppm SO2 for 12h. The unpoisoned catalyst and the poisoned catalyst were respectively treated with "(1) Catalytic Reduction of NO x (NH3-SCR)" to reduce NO x The experimental results are as follows Figure 3 As shown in the figure, it can be seen that the catalyst activity of the fresh catalyst sample is compared with that of the poisoned catalyst sample. The catalyst of the present invention has a good anti-poisoning ability and the catalytic activity is basically not affected after poisoning.

[0059] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above embodiments, a person skilled in the art should understand that the present invention can still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

[0060] The present invention provides a FeMnZrO x There are many ideas and methods for the catalyst and its preparation method, and there are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. FeMnZrO for diesel engine exhaust denitration x The method for preparing a catalyst is characterized in that: After mixing zirconium salt, manganese salt, iron salt and solvent, citric acid is added and mixed to obtain a mixed solution; the mixed solution is then heated, dried after heating, and calcined to obtain FeMnZrO x catalyst; Wherein, the zirconium salt is zirconium oxychloride; the manganese salt is manganese nitrate; the iron salt is iron nitrate; The molar ratio of the zirconium salt to the manganese salt, the iron salt and the citric acid is 2:0.5-1.5:0.5-1.5:

2.

2. The preparation method according to claim 1, characterized in that: The zirconium salt is zirconium oxychloride octahydrate; and the iron salt is iron nitrate nonahydrate.

3. The preparation method according to claim 1, characterized in that: The solvent is deionized water.

4. The preparation method according to claim 1, characterized in that: The heating temperature is 80°C to 120°C and the heating time is 4 to 6 hours.

5. The preparation method according to claim 1, characterized in that: The drying process has a drying temperature of 80°C to 100°C and a drying time of 8 to 15 hours.

6. The preparation method according to claim 1, characterized in that: The calcination temperature is 500°C to 550°C and the calcination time is 4 to 8 hours.

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

8. FeMnZrO according to claim 7 x Application of catalysts in nitrogen oxide reduction.

9. The use according to claim 8, characterized in that: FeMnZrO x The catalyst performs a selective catalytic reduction reaction at a temperature of 100°C to 450°C.

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