Solid acid vanadium phosphorus oxide low-temperature denitration catalyst and preparation method thereof

Abstract

The invention discloses a solid acid vanadium phosphorus oxide low-temperature denitration catalyst and a preparation method thereof, and belongs to the field of low-temperature flue gas denitration. The catalyst takes amine modified amorphous solid acid vanadium phosphorus oxide as an active component and anatase type titanium dioxide as a carrier, and the mass of the active component accounts for 5-20wt% of the weight of the catalyst. The preparation method of the catalyst comprises the following steps: dissolving V2O5 in an oxalic acid solution, heating the mixture to 100 DEG C, and fully stirring to form a dark green solution; then, sequentially adding n-propylamine and hypophosphorous acid in proportion, uniformly stirring and fully reacting; then, evaporating and drying the mixed solution to form a fluffy solid; and fully grinding the obtained solid, calcining in a tubular furnace in a reducing atmosphere, and finally loading on anatase type TiO2. The preparation method is simple, wide in raw material source and low in cost; the prepared amine modified amorphous vanadium phosphorus oxide catalyst has high low-temperature denitration activity and high sulfur resistance, and can promote implementation of pollution reduction and carbon reduction of non-electric industrial flue gas.

Description

Technical Field

[0001] The present invention belongs to the field of low-temperature flue gas denitrification, and specifically relates to a solid acid vanadium phosphorus oxygen low-temperature denitrification catalyst and a preparation method thereof, and particularly relates to an amine-modified amorphous solid acid vanadium phosphorus oxygen low-temperature denitrification catalyst and a preparation method thereof. Background Art

[0002] Nitrogen oxides (NO x ) are one of the main air pollutants. It can damage the ozone layer, induce acid rain and photochemical smog, etc., causing harm to human and animal health. In order to achieve the reduction of NO x emissions from stationary sources such as industrial flue gas, the selective catalytic reduction (NH3-SCR) denitrification technology using NH3 as a reducing agent is being widely used. However, the commonly commercially applied vanadium-based catalysts (V2O5-WO3 / TiO2, V2O5-MoO3 / TiO2) have low catalytic activity at low temperatures (<280 °C) and are not effective in the denitrification of non-electric industrial flue gas. The well-known L-H mechanism in the NH3-SCR process suggests that when both NO and NH3 are adsorbed on the catalyst surface, nitrates and nitrites are important products of NO interfacial transformation. Excellent low-temperature NH3-SCR performance comes from the contribution of the activation of surface active nitrate species by adsorbed NH3. However, some inert nitrate species (such as bridging nitrates and bidentate nitrates) have good thermal stability and are difficult to be activated by adsorbed NH3 species, continuously depositing and occupying the reaction sites, thereby inhibiting the SCR activity.

[0003] Due to abundant defects and coordinatively unsaturated sites, as well as excellent specific surface area and pore structure, amorphous materials often exhibit more excellent catalytic activity than the corresponding crystalline materials and can inhibit the formation of stable nitrates on the catalyst surface (Li S, Molecular Catalysis, 2024, 554: 113767; Wang B, ACS Catalysis, 2020, 10: 9034-9045). Bai et al. studied and pointed out that amorphous FeO x -MnO y mixed oxides have high adsorption and activation abilities for O2 and NO, significantly improving the low-temperature denitrification activity of the catalyst (Bai Y, Fuel, 2023, 349: 128644).

[0004] Traditional metal oxide catalysts are prone to deactivation in low-temperature sulfur-containing flue gas due to factors such as ammonium sulfate deposition and easy sulfation of active components. Non-metal doping (P, S, etc.) can increase the surface and Lewis acid sites to enhance its redox cycle and oxygen transfer ability. In previous work of the research group, a vanadium phosphorus oxide (VPO) low-temperature NH3-SCR denitration catalyst containing (VO)2P2O7 and VOPO4 phases was developed. (VO)2P2O7 and VOPO4 themselves are not easily sulfated and have strong surface acidity, which inhibits the adsorption and catalytic oxidation of SO2. The VPO catalyst has strong sulfur resistance (Jia Yong, Catalysis Letters, 2022, 152: 2215-2226. Jiang Jin, Fuel, 2023, 350: 128780.). Nevertheless, the denitration activities of pure (VO)2P2O7 and VOPO4 are not very high. In order to obtain high low-temperature denitration activity, in the VPO catalysts reported in previous studies by Jia Yong et al., the molar ratio of P to V was controlled to be less than 1. In addition to containing (VO)2P2O7 and VOPO4 components, the active components also contain V2O5 components. V2O5 itself can promote the catalytic oxidation of SO2 to form SO3, and SO3 reacts with the denitration reducing agent NH3 to form (NH4)2SO4 deposited on the catalyst surface. In addition, V2O5 is an amphoteric oxide and can react with SO2 and be sulfated. Therefore, the VPO catalysts reported in the literature have greatly improved sulfur resistance compared with traditional low-temperature denitration catalysts, but further improvement is still needed for long-term stable operation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to develop a low-temperature denitration catalyst with high catalytic activity and strong sulfur resistance, and to provide an amine-modified amorphous solid acid vanadium phosphorus oxygen low-temperature denitration catalyst and a preparation method thereof, in order to enhance the low-temperature denitration activity of the catalyst without changing the phase composition of the solid acid by preparing an amorphous solid acid vanadium phosphorus oxygen active component, thereby enabling the catalyst to have strong sulfur resistance under low-temperature conditions.

[0006] The present invention is achieved through the following technical solutions.

[0007] A solid acid vanadium phosphorus oxygen low-temperature denitration catalyst of the present invention uses amine-modified amorphous solid acid vanadium phosphorus oxygen as the active component, anatase titanium dioxide as the carrier, and the mass percentage of the active component in the catalyst is 5-20 wt.%.

[0008] Further, the amine is n-propylamine, propylamine, butylamine, hexylamine or their isomers.

[0009] Even further, the amine is n-propylamine.

[0010] The present invention also provides a preparation method for the above-mentioned solid acid vanadium phosphorus oxygen low-temperature denitration catalyst, which specifically includes the following steps:

[0011] (1) Preparation of Amine-Modified Amorphous Solid Acid Vanadium Phosphorus Oxide Active Component VPO-N

[0012] (a) Dissolve V2O5 in H2C2O4·2H2O solution, heat to 100 °C and stir thoroughly until dissolved; the molar ratio of V2O5 to H2C2O4·2H2O is 0.5.

[0013] (b) Add n-propylamine and hypophosphorous acid H3PO2 to the solution in step (a) in sequence, and stir evenly; the molar ratio of P to V is 1, and the molar ratio of n-propylamine to V is 1:1 to 5:1.

[0014] (c) Evaporate the mixed solution in step (b) to dryness and then dry to form a fluffy solid.

[0015] (d) Activate the solid in step (c) in a reducing atmosphere to obtain the amine-modified amorphous solid acid vanadium phosphorus oxide active component VPO-N.

[0016] (2) Preparation of Catalyst VPO-N / TiO2

[0017] (a) Add VPO-N and anatase TiO2 to deionized water and stir evenly.

[0018] (b) Dry and grind the mixture in step (2)(1).

[0019] (c) Calcinate the solid in step (2)(3) in an air atmosphere to obtain the amine-modified amorphous solid acid vanadium phosphorus oxide catalyst VPO-N / TiO2.

[0020] Furthermore, in step (1)c, the evaporation to dryness means heating the mixed solution to dryness at 100 °C; the drying means drying at 150 °C for 3 h.

[0021] Furthermore, in step (1)d, the reducing atmosphere is CO / Ar, NH3 / Ar, CH4 / Ar or H2 / Ar; the activation time is 3 h, and the activation temperature is 300 - 500 °C.

[0022] Even further, in step (1)d, the reducing atmosphere is CO / Ar; the activation temperature is 450 °C.

[0023] Furthermore, in step (2)b, the drying means: first drying in a water bath at 80 °C for 4 h, and then drying in air at 105 °C for 3 h.

[0024] Furthermore, in step (2)c, the calcination temperature is 400 °C, and the calcination time is 3 h.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention prepares an amine-modified amorphous vanadium phosphorous oxygen low-temperature denitration catalyst by adding n-propylamine and hypophosphorous acid with strong reducibility, which improves the V 4+ / V 5+ ratio and the content of chemisorbed oxygen in the catalyst, increases the number and strength of weak acid and medium-strong acid sites, promotes the formation of unstable nitrate species, and improves the low-temperature denitration activity of the catalyst. The amine-modified amorphous vanadium phosphorous oxygen catalyst disclosed in the present invention has high low-temperature denitration activity and strong sulfur resistance, which can promote the implementation of pollution reduction and carbon emission reduction in non-electric industrial flue gas.

[0027] 2. The amine-modified amorphous VPO low-temperature denitration catalyst described in the present invention has high low-temperature denitration activity. When the reaction temperature is 180°C, the denitration efficiency can reach 95%, and it can reach 100% in the range of 210-270°C.

[0028] 3. At present, commercial low-temperature denitration catalysts are mainly V2O5-WO3 / TiO2 and V2O5-MoO3 / TiO2, which are suitable for low-sulfur or sulfur-free working conditions. In engineering, a process mode of pre-desulfurization plus temperature-raising flue gas denitration is usually adopted, with high operating energy consumption. The amine-modified amorphous VPO of the present invention also has high catalytic activity under the condition of not containing metal oxide components, so it will not react with SO2 and be sulfated. At the same time, it has the strong acidity of heteropolyacid, which can inhibit the adsorption of SO2 and the formation of ammonium sulfate. The amine-modified amorphous solid acid vanadium phosphorous oxygen catalyst of the present invention has strong sulfur resistance and can stably operate in low-temperature sulfur-containing flue gas at a temperature higher than 180°C, greatly reducing the denitration operation energy consumption and operation cost.

[0029] 4. The preparation method of the present invention is simple, the raw materials are widely available, and the cost is low. Description of the Drawings

[0030] Figure 1 It is a test chart of sulfur and water resistance of the catalyst VPO-N / TiO2 in Example 4 of the present invention.

[0031] Figure 2 It is an XRD diffraction pattern of the catalyst VPO-N / TiO2 in Example 4 of the present invention.

[0032] Figure 3 It is a NO-TPD spectrum of the catalyst VPO-N / TiO2 in Example 4 of the present invention. Detailed Embodiments

[0033] The technical solution content of the present invention will be elaborated in detail below. The described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present invention.

[0034] I. Preparation of catalyst

[0035] Example 1

[0036] (1) Preparation of active component

[0037] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred thoroughly until a dark green solution was formed; propylamine solution was added in a molar ratio of propylamine to V of 1:1, and stirring was continued for 2 hours; then, H3PO2 solution was added in a P / V molar ratio of 1, and stirring was continued for 2 hours; then, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tubular furnace for activation for 4 hours to obtain an amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 450 °C, and the activation atmosphere was H2 / Ar.

[0038] (2) Preparation of catalyst

[0039] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by the impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water in a mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred thoroughly and mixed evenly; then, the mixture was dried in a water bath at 80 °C for 4 h; then, the solid was dried at 105 °C for 3 h and the solid was ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0040] Example 2

[0041] (1) Preparation of active component

[0042] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred thoroughly until a dark green solution was formed. A n-propylamine solution was added in a molar ratio of n-propylamine to V of 3:1, and stirring was continued for 2 hours. Then, an H3PO2 solution was added in a P / V molar ratio of 1, and stirring was continued for 2 hours. Subsequently, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tubular furnace for activation for 4 hours to obtain an amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 450 °C, and the activation atmosphere was H2 / Ar.

[0043] (2) Preparation of the catalyst

[0044] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by an impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water in a mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred thoroughly to mix evenly. Then, the mixture was dried in a water bath at 80 °C for 4 h. Subsequently, the solid was dried at 105 °C for 3 h and the solid was ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0045] Example 3

[0046] (1) Preparation of the active component

[0047] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred thoroughly until a dark green solution was formed. A n-propylamine solution was added in a molar ratio of n-propylamine to V of 5:1, and stirring was continued for 2 hours. Then, an H3PO2 solution was added in a P / V molar ratio of 1, and stirring was continued for 2 hours. Subsequently, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tubular furnace for activation for 4 hours to obtain an amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 450 °C, and the activation atmosphere was H2 / Ar.

[0048] (2) Preparation of the catalyst

[0049] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by the impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water according to the mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred well to mix evenly; then, the mixture was dried in a water bath at 80 °C for 4 h; then, the solid was dried at 105 °C for 3 h and the solid was ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0050] Example 4

[0051] (1) Preparation of the active component

[0052] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred well until a dark green solution was formed; propylamine solution was added according to the molar ratio of propylamine to V of 3:1, and stirring was continued for 2 hours; then, H3PO2 solution was added according to the P / V molar ratio of 1, and stirring was continued for 2 hours; then, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and placed in a tube furnace for activation for 4 hours to obtain the amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 450 °C and the activation atmosphere was CO / Ar.

[0053] (2) Preparation of the catalyst

[0054] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by the impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water according to the mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred well to mix evenly; then, the mixture was dried in a water bath at 80 °C for 4 h; then, the solid was dried at 105 °C for 3 h and the solid was ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0055] Example 5

[0056] (1) Preparation of the active component

[0057] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred thoroughly until a dark green solution was formed. A propylamine solution was added in a molar ratio of propylamine to V of 3:1, and stirring was continued for 2 hours. Then, an H3PO2 solution was added in a P / V molar ratio of 1, and stirring was continued for 2 hours. Subsequently, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tube furnace for activation for 4 hours to obtain an amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 450 °C, and the activation atmosphere was CH4 / Ar.

[0058] (2) Preparation of catalyst

[0059] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by an impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water in a mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred thoroughly to mix evenly. Then, the mixture was dried in a water bath at 80 °C for 4 h. Subsequently, the solid was dried at 105 °C for 3 h and ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0060] Example 6

[0061] (1) Preparation of active component

[0062] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred thoroughly until a dark green solution was formed. A propylamine solution was added in a molar ratio of propylamine to V of 3:1, and stirring was continued for 2 hours. Then, an H3PO2 solution was added in a P / V molar ratio of 1, and stirring was continued for 2 hours. Subsequently, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tube furnace for activation for 4 hours to obtain an amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 450 °C, and the activation atmosphere was CO / Ar.

[0063] (2) Preparation of catalyst

[0064] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by the impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water according to the mass ratio of VPO-N to VPO-N / TiO2 of 15 wt.%, and stirred well to mix evenly; then, the mixture was dried in a water bath at 80 °C for 4 h; then, the solid was dried at 105 °C for 3 h and the solid was ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0065] Example 7

[0066] (1) Preparation of the active component

[0067] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred well until a dark green solution was formed; propylamine solution was added according to the molar ratio of propylamine to V of 3:1, and stirring was continued for 2 hours; then, H3PO2 solution was added according to the P / V molar ratio of 1, and stirring was continued for 2 hours; then, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tubular furnace for activation for 4 hours to obtain the amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 450 °C and the activation atmosphere was CO / Ar.

[0068] (2) Preparation of the catalyst

[0069] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by the impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water according to the mass ratio of VPO-N to VPO-N / TiO2 of 25 wt.%, and stirred well to mix evenly; then, the mixture was dried in a water bath at 80 °C for 4 h; then, the solid was dried at 105 °C for 3 h and the solid was ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0070] Example 8

[0071] (1) Preparation of the active component

[0072] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred thoroughly until a dark green solution was formed. A n-propylamine solution was added in a molar ratio of n-propylamine to V of 3:1, and stirring was continued for 2 hours. Then, an H3PO2 solution was added in a P / V molar ratio of 1, and stirring was continued for 2 hours. Then, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tube furnace for activation for 4 hours to obtain an amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 300 °C, and the activation atmosphere was CO / Ar.

[0073] (2) Preparation of catalyst

[0074] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by an impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water in a mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred thoroughly to mix evenly. Then, the mixture was dried in a water bath at 80 °C for 4 h. Then, the solid was dried at 105 °C for 3 h and the solid was ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0075] Example 9

[0076] (1) Preparation of active component

[0077] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred thoroughly until a dark green solution was formed. A n-propylamine solution was added in a molar ratio of n-propylamine to V of 3:1, and stirring was continued for 2 hours. Then, an H3PO2 solution was added in a P / V molar ratio of 1, and stirring was continued for 2 hours. Then, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tube furnace for activation for 4 hours to obtain an amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 400 °C, and the activation atmosphere was CO / Ar.

[0078] (2) Preparation of catalyst

[0079] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by the impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water according to the mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred well to mix evenly. Then, the mixture was dried in a water bath at 80 °C for 4 h. Next, the solid was dried at 105 °C for 3 h and ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0080] Example 10

[0081] (1) Preparation of the active component

[0082] V2O5 and H2C2O4·2H2O were added to 100 ml of distilled water in a molar ratio of 0.5 and mixed evenly. The mixture was heated to 90 °C and stirred well until a dark green solution was formed. A n-propylamine solution was added according to the molar ratio of n-propylamine to V of 3:1, and stirring was continued for 2 hours. Then, an H3PO2 solution was added according to the P / V molar ratio of 1, and stirring was continued for 2 hours. Next, it was dried at 150 °C for 3 h to form a fluffy solid. Finally, the solid was ground and then placed in a tube furnace for activation for 4 hours to obtain the amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. The activation temperature was 500 °C, and the activation atmosphere was CO / Ar.

[0083] (2) Preparation of the catalyst

[0084] Using VPO-N in (1) as the active component and anatase TiO2 as the carrier, the catalyst VPO-N / TiO2 was prepared by the impregnation method. VPO-N and TiO2 were added to 100 ml of distilled water according to the mass ratio of VPO-N to VPO-N / TiO2 of 5 wt.%, and stirred well to mix evenly. Then, the mixture was dried in a water bath at 80 °C for 4 h. Next, the solid was dried at 105 °C for 3 h and ground. Finally, the powder was calcined in a muffle furnace at 400 °C for 3 hours to obtain the catalyst VPO-N / TiO2.

[0085] II. Performance testing of the catalyst

[0086] 1. Performance test one

[0087] The catalysts in Examples 1 to 10 were respectively tableted and screened to obtain catalyst particles with a particle size of 40 to 60 mesh. Weigh 0.15 mL of the catalyst particles and place them in a fixed-bed denitration reactor (the inner diameter of the reaction tube is 8 mm) to test their denitration performance. The simulated flue gas consists of 500 ppm NO, 500 ppm NH3, 8 vol% O2, and N2 as the balance gas. The total gas flow rate is maintained at 100 mL / min, and the gas hourly space velocity (GHSV) is about 40000 h -1 . The test temperature range is set between 120 and 300 °C, and each reaction temperature is stabilized for 40 minutes. A flue gas analyzer is used to measure the gas concentrations at the inlet and outlet. The NO conversion rate is calculated using the following formula:

[0088]

[0089] The test results are listed in Table 1.

[0090] Table 1 Denitration activity of the catalysts in Preparation Examples 1 to 10 of the catalyst

[0091]

[0092]

[0093] It can be seen from the denitration activity test of the catalyst in Table 1 that in the absence of SO2 and H2O in the flue gas, Example 4 exhibited good denitration activity at 180 °C. The catalyst under the best preparation conditions in Example 4 remained above 96% in the temperature range of 180 °C to 300 °C.

[0094] 2. Performance Test Two

[0095] The catalyst in Example 4 with the best denitration activity was tested for sulfur and water resistance. The catalyst was respectively tableted and screened to obtain catalyst particles with a particle size of 40 - 60 mesh. Weigh 0.15 mL of the catalyst particles and place them in a fixed-bed denitration reactor (the inner diameter of the reaction tube is 8 mm) to test their denitration performance. The simulated flue gas consists of 500 ppm NO, 500 ppm NH3, 8 vol% O2, 200 ppm SO2, and 10 vol% H2O, with N2 as the balance gas. The total gas flow rate is maintained at 100 mL / min, and the gas hourly space velocity (GHSV) is about 40000 h -1 . The test temperature range is set at 200 °C. A flue gas analyzer is used to measure the gas concentrations at the inlet and outlet. The results are as Figure 1 shown.

[0096] From Figure 1It can be seen that when 200 ppm SO2 and 10 vol% H2O are simultaneously introduced into the flue gas, the denitrification efficiency of the catalyst decreases from 99.5% to about 90%. SO2 and H2O inhibit the denitrification activity of the catalyst through physical adsorption. After cutting off SO2 and H2O, the denitrification efficiency can gradually recover to the initial state. The test results show that the amine-modified amorphous solid acid vanadium phosphorous oxygen catalyst VPO-N / TiO2 exhibits strong sulfur and water resistance performance.

[0097] 3. Phase characterization

[0098] The catalyst in Example 4 was subjected to X-ray diffraction testing, and the results are as Figure 2 shown. It can be seen from the figure that no sharp crystalline phase diffraction peaks were found in the amine-modified catalyst, and the catalyst as a whole presented an amorphous phase.

[0099] The present invention provides an amine-modified amorphous solid acid vanadium phosphorous oxygen low-temperature denitrification catalyst and a preparation method thereof. A certain amount of V2O5 is dissolved in an oxalic acid solution, and then the mixture is heated to 90 °C and stirred thoroughly to form a light green solution. Then, n-propylamine and hypophosphorous acid are added in proportion in sequence, stirred evenly and reacted fully. Next, the mixed solution is evaporated to dryness in a water bath, and a fluffy solid is formed after drying. The obtained solid is ground thoroughly, and then placed in a tubular furnace and activated using a reducing atmosphere, and finally an amine-modified amorphous solid acid vanadium phosphorous oxygen low-temperature denitrification catalyst is obtained.

[0100] The main active phases of the solid acid VPO are VOPO4 and (VO)2P2O7, and its denitrification activity is not high by itself. However, VOPO4 and (VO)2P2O7 are not easily sulfated, and their strong surface acidity can inhibit the adsorption and oxidation of SO2, and they have strong sulfur resistance performance. The present invention uses V2O5 as the active precursor, adds n-propylamine and hypophosphorous acid with strong reducibility, and controls the reducing activation atmosphere at the same time to prepare the amine-modified amorphous vanadium phosphorous oxygen catalyst VPO / TiO2. Amine modification effectively increases the electron cloud density of V, promotes the formation of lattice defects in the catalyst, and improves the ratio of V 4+ / (V 5+ + V 4+ ) (85%) and the content of chemisorbed oxygen (52%), and optimizes the redox performance of the catalyst.

[0101] The specific surface area (BET) test results show that the specific surface area of the amine-modified amorphous VPO can reach 140 m 2 / g, which is much higher than the specific surface area of the crystalline VPO (about 4.9 m 2 / g). The pyridine infrared and TPD test results show that the number and strength of weak acid and medium strong acid sites on the surface of the amine-modified amorphous VPO have been improved, enhancing the adsorption ability of NH3 and NO. In addition, the NO-TPD test results (Figure 3 ) The results show that the temperature of the NO desorption peak of amine-modified amorphous VPO (<200 °C) significantly shifts towards lower temperatures, promoting the formation of unstable nitrate species and enhancing the low-temperature denitrification activity of the catalyst.

Claims

1. A solid acid vanadium phosphorus oxygen low-temperature denitration catalyst, characterized in that: Using amine-modified amorphous solid acid vanadium phosphorous oxygen as the active component, anatase titanium dioxide as the carrier, and the mass percentage of the active component accounting for the weight of the catalyst being 5-20 wt.%.

2. The solid acid vanadium phosphorus oxygen low-temperature denitration catalyst according to claim 1, characterized in that, The amine is n-propylamine, propylamine, butylamine, hexylamine or their isomers.

3. The solid acid vanadium phosphorus oxygen low-temperature denitration catalyst according to claim 2, characterized in that The amine is n-propylamine.

4. A preparation method of the solid acid vanadium phosphorus oxygen low-temperature denitration catalyst as described in claim 3, characterized in that It includes the following steps: (I) Preparation of amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N: (a) Dissolve V2O5 in the H2C2O4·2H2O solution, heat to 100 °C and stir well until dissolved; the molar ratio of V2O5 to H2C2O4·2H2O is 0.

5. (b) Sequentially add n-propylamine and hypophosphorous acid H3PO2 to the solution in step (a), and stir well; the molar ratio of P to V is 1, and the molar ratio of n-propylamine to V is 1:1 - 5:

1. (c) Evaporate the mixed solution in step (b) to dryness and then dry to form a fluffy solid. (d) Activate the solid in step (c) in a reducing atmosphere to obtain the amine-modified amorphous solid acid vanadium phosphorous oxygen active component VPO-N. (II) Preparation of catalyst VPO-N / TiO2: (a) Add VPO-N and anatase TiO2 to deionized water and stir well. (b) Dry and grind the mixture in step (II)(1). (c) Calcinate the solid in step (II)(3) in an air atmosphere to obtain the amine-modified amorphous solid acid vanadium phosphorous oxygen catalyst VPO-N / TiO2.

5. The preparation method of the solid acid vanadium phosphorus oxygen low-temperature denitration catalyst according to claim 4, characterized in that, In step (I)c, the evaporation to dryness means heating the mixed solution to dryness at 100 °C; the drying means drying at 150 °C for 3 h.

6. The preparation method of the solid acid vanadium phosphorus oxygen low-temperature denitration catalyst according to claim 4, characterized in that, In step (I)d, the reducing atmosphere is CO / Ar, NH3 / Ar, CH4 / Ar or H2 / Ar; the activation time is 3 h, and the activation temperature is 300 - 500 °C.

7. The preparation method of the solid acid vanadium phosphorus oxygen low-temperature denitration catalyst according to claim 6, characterized in that, In step (I)d, the reducing atmosphere is CO / Ar; the activation temperature is 450 °C.

8. The preparation method of the solid acid vanadium phosphorus oxygen low-temperature denitration catalyst according to claim 4, characterized in that, In step (II)b, the drying means first drying in a water bath at 80 °C for 4 h, and then drying in air at 105 °C for 3 h.

9. The preparation method of the solid acid vanadium phosphorus oxygen low-temperature denitration catalyst according to claim 4, characterized in that, In step (II)c, the calcination temperature is 400 °C, and the calcination time is 3 h.

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