CN105964295A - Manganese-rich Mn-SAPO-34 molecular sieve catalyst as well as preparation method and application thereof - Google Patents

Abstract

The invention discloses a manganese-rich Mn-SAPO-34 molecular sieve catalyst, a preparation method and application thereof. The steps of the method are as follows: mix orthophosphoric acid and deionized water, then add pseudo-boehmite, add silica sol after mixing evenly, then add manganese acetate solution, add triethylamine and diisopropylamine dropwise after stirring, and stir Put the complete gel into a hydrothermal reactor for crystallization, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, dry, and roast at 500-600°C in the air to obtain manganese-rich Mn‑SAPO‑ 34 molecular sieve catalyst. The present invention adopts a one-step hydrothermal synthesis method, and by controlling the input amount of manganese acetate, triethylamine, diisopropylamine, silica sol and roasting temperature, a manganese-rich Mn-SAPO-34 molecular sieve catalyst is obtained, which improves the dispersion of active components properties, so that the catalyst exhibits excellent low-temperature NH ₃ ‑SCR performance in the low-temperature range (below 250°C).

Description

A kind of manganese-rich Mn-SAPO-34 molecular sieve catalyst and its preparation method and application

technical field

The invention belongs to the field of environmental protection and environmental catalysis, and in particular relates to a manganese-rich Mn-SAPO-34 molecular sieve catalyst and its preparation method and application.

Background technique

Nitrogen oxides (NO _x ) are one of the main air pollutants. In addition to directly endangering human health, it is also one of the important precursors for generating ozone, and is also an important cause of regional haze and fine particle pollution. Nitrogen oxides mainly come from the combustion of fossil fuels. According to statistics, 66.7% of the national industrial nitrogen oxides emissions come from the power and heat production and supply industries, which are the largest emitters of nitrogen oxides in my country. Among them, the thermal power industry’s nitrogen oxides contribute Therefore, the power industry is the key field for controlling nitrogen oxide emissions in my country. Among many nitrogen oxide pollution control technologies, selective catalytic reduction (SCR) flue gas denitrification technology is mature and effective, and is widely used in the flue gas purification process of coal-fired power plants.

Catalysts are the key to SCR flue gas denitrification technology. At present, commercial SCR catalysts are mainly V ₂ O ₅ -WO ₃ (MoO ₃ )/TiO ₂ series catalysts, and their active temperature window is 300-450°C. High, the SCR denitration device is generally placed before the dust removal and desulfurization device, so the catalyst is easily washed and blocked by dust, and the service life is reduced. When the denitrification device is placed after the dust removal and desulfurization device, it is necessary to install a flue gas preheating device to meet the requirements of catalytic activity. In contrast, low-temperature SCR catalysts can work below 300°C, so denitrification devices equipped with low-temperature SCR catalysts can be installed directly after dust removal and desulfurization devices, which has better economic benefits.

Molecular sieve catalysts with regular and uniform pore structure have attracted much attention in SCR technology because of their high catalytic activity and wide active temperature range. Among them, SAPO-34 is one of the silicoaluminophosphate series molecular sieves with CHA type topology, belonging to microporous molecular sieves. In recent years, SAPO-34 molecular sieve has been widely used in the field of catalysis due to its suitable acidity and regular pore structure, which can make active components well dispersed on its surface when used as a carrier. Some scholars have also studied the application of SAPO-34 molecular sieves in SCR. Fe/SAPO-34 and Cu-SAPO-34 have shown excellent activity in SCR respectively.

CN102409141A discloses a method for preparing Cu-SAPO-34 denitration catalyst. In the method, pseudo-boehmite is added into deionized water for stirring, and then one of silica sol and orthophosphoric acid are added, and copper sulfate and orthophosphoric acid are added after mixing. Tetraethylenepentamine, and add diethylamine, triethylamine or n-propylamine after stirring well. Put the fully stirred gel into a hydrothermal reaction kettle for crystallization, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, dry, and roast to obtain Cu-SAPO-34 molecular sieve catalyst. However, the Cu-SAPO-34 denitration catalyst is mainly aimed at the removal of _NOx from mobile source tail gas, and the temperature window and operating conditions of the catalyst are quite different from the flue gas environment of stationary sources (such as coal-fired power plants).

Therefore, the present invention aims at the problems existing in the denitrification of flue gas from fixed sources, and through one-step hydrothermal synthesis of a manganese-rich Mn-SAPO-34 molecular sieve catalyst, the dispersion of the active components is improved, and the specific surface area and acidity of the catalyst are increased simultaneously, so that The catalyst exhibits excellent low-temperature NH ₃ -SCR performance in the low-temperature range (below 250°C).

Contents of the invention

In view of the problems in the prior art, the object of the present invention is to provide a manganese-rich Mn-SAPO-34 molecular sieve catalyst and its preparation method and application. The catalyst obtained by the method has excellent low-temperature NH ₃ -SCR catalytic activity.

The present invention adopts the following technical solutions.

A preparation method of manganese-rich Mn-SAPO-34 molecular sieve catalyst, said method may further comprise the steps:

(1) Mix orthophosphoric acid and deionized water, then add pseudo-boehmite, add silica sol after mixing evenly, add manganese acetate solution after mixing well, add organic amine template agent triethylamine dropwise after fully stirring and diisopropylamine;

(2) Put the fully stirred gel obtained in step (1) into a hydrothermal reaction kettle for crystallization, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, dry, and store in the air at 500-600 °C Roasting, get a kind of manganese-rich Mn-SAPO-34 molecular sieve catalyst; In this method, control the consumption of each reactant so that each material in the reaction system has the following proportioning relationship, with 1.0mol pseudo-boehmite, 1.0 mol orthophosphoric acid, 1.0mol silica sol, 1.0mol manganese acetate, 1.0mol triethylamine and 1.0mol diisopropylamine were used with 0.5molAl ₂ O ₃ , 0.5molP ₂ O ₅ , 1.0molSiO ₂ , 1.0molMnO, 1.0molTEA and 1.0mol molDIPA (here "representing 1.0 pseudo-boehmite with 0.5Al ₂ O ₃ " means that 1.0 mol pseudo-boehmite contains 0.5 mol Al ₂ O ₃ ), that is

The molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is 1:1:80:(0.2～1.0):(0.05～0.6):(1.0～3.5): (0~1.5).

In the preparation process of the manganese-rich Mn-SAPO-34 molecular sieve catalyst, the calcination temperature directly affects the crystallinity and catalytic activity of the molecular sieve, and the transition metal manganese is different in the state and distribution of the manganese due to its loading, resulting in low-temperature SCR catalytic activity. There is a big difference. The silicon content and substitution mode affect the structure and surface acidity of the catalyst to a certain extent, and also have a great impact on the low-temperature SCR catalytic activity. The present invention adopts a one-step hydrothermal synthesis method to prepare manganese-rich Mn-SAPO-34 molecular sieve catalyst, and further controls the manganese loading to be 0-15 wt% by controlling the input of manganese acetate and triethylamine, and controls the input of silica sol to Control the silicon content at 5-15 wt% and control the calcination temperature at 500-600°C to obtain the manganese-rich Mn-SAPO-34 molecular sieve catalyst with excellent low-temperature SCR activity.

In the present invention, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is mainly controlled to be 1:1:80:(0.2～1.0):(0.05～0.6) :(1.0～3.5):(0～1.5), the preferred ratio is 1:1:80:0.6:0.4:1.5:1.5.

Preferably, the hydrothermal crystallization temperature is controlled, and the crystallization temperature is 190-210°C, preferably 190°C, 200°C and 210°C respectively.

Preferably, the hydrothermal crystallization time is controlled, and the hydrothermal crystallization time is 24 to 96 hours, preferably 24 hours, 48 hours and 96 hours respectively.

Preferably, the drying temperature is controlled, and the drying temperature is 100-120°C, preferably 100°C, 110°C and 120°C respectively. The drying time is 6-15 hours.

Preferably, the calcination temperature is controlled, and the calcination temperature is 500-600°C, more preferably 500°C, 550°C and 600°C.

Preferably, the calcination time is controlled, and the calcination time is 3 to 9 hours, preferably 3 hours, 6 hours and 9 hours respectively.

Preferably, the temperature rise rate of the calcination is controlled, and the temperature rise rate during the calcination process is 0.5-1.5°C/min, preferably 0.5°C/min, 1°C/min and 1.5°C/min respectively.

As a preferred technical solution of the present invention, a method for preparing a manganese-rich Mn-SAPO-34 molecular sieve catalyst, the method comprises the following steps: after mixing orthophosphoric acid with a certain amount of deionized water, then slowly adding pseudo-thin water Aluminum stone, add silica sol after mixing evenly, add a certain mass fraction of manganese acetate solution after mixing evenly, add triethylamine and diisopropylamine dropwise after fully stirring;

Put the fully stirred gel into a hydrothermal reaction kettle for crystallization, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, dry, and roast at 550 °C in air;

In this method, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is controlled to be 1:1:80:0.6:0.4:1.5:1.5.

The Mn-SAPO-34 molecular sieve catalyst prepared by the preferred method has excellent low-temperature NH ₃ -SCR catalytic activity, and it has a NO _x conversion rate and N ₂ selectivity higher than 90% within 200-400 ° C. After reacting at ℃ for 12 hours, it still has high SCR activity. Therefore, in the above technical scheme, by controlling the addition of template agent, silica sol, manganese and calcination temperature of 550°C, a manganese-rich Mn-SAPO-34 molecular sieve catalyst was prepared, and the molecular sieve exhibited excellent low-temperature NH ₃ -SCR Catalytic activity and stability.

A manganese-rich Mn-SAPO-34 molecular sieve catalyst prepared by the above preparation method.

The use of the above-mentioned manganese-rich Mn-SAPO-34 molecular sieve catalyst is used for stationary source flue gas denitrification, ie low-temperature NH ₃ -SCR reaction.

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

The manganese-rich Mn-SAPO-34 molecular sieve catalyst of the present invention is prepared by a one-step hydrothermal synthesis method, which is simple and controllable, and the manganese loading of the active component can be adjusted within a wide range. The Mn-SAPO-34 molecular sieve catalyst improves the dispersion of active components, making the catalyst exhibit excellent low-temperature NH ₃ -SCR performance in the low temperature range (below 250°C).

Description of drawings

Fig. 1 is the NO _x conversion activity evaluation figure of the catalyst that embodiment 1 makes;

Fig. 2 _is the NO conversion rate activity evaluation figure of the catalyst that embodiment 2 makes;

Fig. 3 is the NO _x conversion rate activity evaluation figure of the catalyst that embodiment 3 makes;

Fig. 4 is the NO _x conversion activity evaluation figure of the catalyst that embodiment 4 makes;

Fig. 5 is the NO _x conversion rate activity evaluation figure of the catalyst that embodiment 5 makes;

Fig. 6 is the NO _x conversion rate activity evaluation figure of the catalyst that embodiment 6 makes;

Fig. 7 is the N of the catalyst that embodiment ₄ makes Selective evaluation figure;

Fig. 8 is the stability evaluation figure of the catalyst that embodiment 4 makes;

FIG. 9 is an XRD pattern of the catalyst prepared in Example 4.

detailed description

The present invention provides a manganese-rich Mn-SAPO-34 molecular sieve catalyst as well as its preparation method and application. The present invention will be further described below in conjunction with specific embodiments. However, the embodiments of the present invention are not limited thereto, and if there are any process parameters that are not specifically noted, it can be performed with reference to conventional techniques.

In the present invention, the evaluation of catalyst adopts following method: get the Mn-SAPO-34 molecular sieve catalyst of 0.90 mL, 40-60 order, put into catalyst activity evaluation device respectively, adopt laboratory simulation flue gas condition, embodiment and relative The ratio prepared catalyst was placed in a quartz tube fixed bed reactor for activity evaluation, using _NH3 as the reducing gas, the test conditions were: the volume fractions of NO and _O2 were 0.1% and 5%, respectively, and the ammonia nitrogen ratio was 1:1, Ar is the balance gas, and the space velocity is 40,000h ^-1 . The analysis of NO _x adopts American Thermo Fisher42i-HL flue gas analyzer, the test of N ₂ adopts GC9560 gas chromatograph, and the packed column is 5A molecular sieve.

Example 1

Mix 13.835 g of orthophosphoric acid with a mass fraction of 85% and 70.710 g of deionized water, then slowly add 8.880 g of pseudo-boehmite, and add a certain amount of silica sol (SiO ₂ and Al ₂ When the molar ratio of _O3 is 0.6, the amount of silica sol is 7.211 g), after mixing evenly, add 7.350 g of manganese acetate solution with a mass fraction of 20%, and after fully stirring, add 18.821 g of template triethylamine dropwise;

Put the fully stirred gel into a hydrothermal reaction kettle for crystallization reaction at 200°C, the crystallization time is 48 hours, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, and dry at 110°C for 12 hour, in the air with 1 ℃ / min heating up to 550 ℃ roasting for 6 hours, to obtain a manganese-rich Mn-SAPO-34 molecular sieve catalyst;

In this method, the amount of each reactant is controlled so that the reaction system has the following ratio relationship, that is, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is 1 :1:80:0.2～1.0:0.1:3.0:0, wherein the molar ratio of SiO ₂ to Al ₂ O ₃ is controlled at 0.2, 0.4, 0.6, 0.8, 1.0.

Figure 1 shows the catalytic performance evaluation diagram of molecular sieve catalysts with different Si contents, which shows that the Mn-SAPO-34 molecular sieves with different Si contents show different catalytic activities, among them, the best SiO ₂ and Al ₂ O ₃ The molar ratio is 0.6.

Example 2

After mixing 13.835 g of orthophosphoric acid with a mass fraction of 85% and 53.070 g of deionized water, slowly add 8.880 g of pseudo-boehmite, and add 7.211 g of silica sol after mixing evenly. Add a certain amount of manganese acetate solution with a mass fraction of 20% (when the ratio of MnO and Al ₂ O ₃ is 0.4, the mass of the corresponding manganese acetate solution is 29.400 g), stir well and add 18.821 g of template triethylamine dropwise;

Put the fully stirred gel into a hydrothermal reaction kettle for crystallization reaction at 200°C, the crystallization time is 48 hours, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, and dry at 110°C for 12 hour, in the air with 1 ℃ / min heating up to 550 ℃ roasting for 6 hours, to obtain a manganese-rich Mn-SAPO-34 molecular sieve catalyst;

In this method, the amount of each reactant is controlled so that the reaction system has the following ratio relationship, that is, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is 1 :1:80:0.6:0.1～0.6:3.0:0, wherein the ratio of MnO to Al ₂ O ₃ is controlled at 0.1, 0.2, 0.4, 0.6.

Figure 2 shows the catalytic performance evaluation diagram of molecular sieve catalysts with different Mn contents. The activity evaluation results show that Mn-SAPO-34 molecular sieves with different Mn contents show different catalytic activities. Among them, the best manganese acetate and Al ₂ O ₃ The ratio is 0.4.

Example 3

Mix 13.835 g of orthophosphoric acid with a mass fraction of 85% and 53.070 g of deionized water, then slowly add 8.880 g of pseudo-boehmite, and add 7.211 g of silica sol after mixing evenly. Adding 29.400g mass fraction is 20% manganese acetate solution, after fully stirring, drop template agent triethylamine 15.786 g and diisopropylamine 3.035g;

Put the fully stirred gel into a hydrothermal reaction kettle for crystallization reaction at 200°C, the crystallization time is 48 hours, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, and dry at 110°C for 12 hour, in the air with 1 ℃ / min heating up to 550 ℃ roasting for 6 hours, to obtain a manganese-rich Mn-SAPO-34 molecular sieve catalyst;

In this method, the amount of each reactant is controlled so that the reaction system has the following mass ratio relationship, that is, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is 1:1:80:0.6:0.4:2.6:0.5.

Shown in Fig. 3 is the catalytic performance evaluation figure of the molecular sieve catalyst prepared after adding organic amine template agent DIPA in the preparation process, activity evaluation result shows, after adding organic amine template agent DIPA, Mn-SAPO-34 molecular sieve catalyst has better low-temperature denitrification activity.

Example 4

After mixing 13.835 g of orthophosphoric acid with a mass fraction of 85% and 53.070 g of deionized water, slowly add 8.880 g of pseudo-boehmite, and add 7.211 g of silica sol after mixing evenly. Adding 29.400g mass fraction is 20% manganese acetate solution, and after fully stirring, 9.110 g of template triethylamine and 9.110 g of diisopropylamine are added dropwise;

Put the fully stirred gel into a hydrothermal reaction kettle for crystallization reaction at 200°C, the crystallization time is 48 hours, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, and dry at 110°C for 12 hour, in air at 1°C/min to 550°C for 6 hours to obtain a manganese-rich Mn-SAPO-34 molecular sieve catalyst;

In this method, the amount of each reactant is controlled so that the reaction system has the following mass ratio relationship, that is, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is 1:1:80:0.6:0.4:1.5:1.5.

Figure ₄ is the catalytic performance evaluation diagram of the catalyst prepared in this example, which shows that the ratio of manganese acetate to _Al2O3 is 0.4, the calcination temperature is 550 °C, and the molar ratio of TEA and DIPA is 1.5:1.5. Manganese-rich Mn-SAPO-34 molecular sieve, which exhibits excellent low-temperature NH ₃ -SCR catalytic activity. Figure 7 and Figure 8 respectively show the _N2 selectivity and catalyst stability tests of the catalyst prepared in this example. _The evaluation results show that: the ratio of manganese acetate to _Al2O3 is 0.4, the calcination temperature is 550 ° C, the TEA, DIPA The Mn-rich Mn-SAPO-34 zeolite was prepared with a molar ratio of 1.5:1.5, which not only exhibited excellent _NOx conversion, but also excellent _N2 selectivity and catalyst stability. Fig. 9 is the XRD characterization test of the catalyst prepared in this example. The analysis shows that the manganese-rich Mn-SAPO-34 molecular sieve prepared in this example has a good chabazite topological structure and good crystallinity.

Example 5

After mixing 13.835 g of orthophosphoric acid with a mass fraction of 85% and 53.070 g of deionized water, slowly add 8.880 g of pseudo-boehmite, and add 7.211 g of silica sol after mixing evenly. Adding 29.400g mass fraction is 20% manganese acetate solution, and after fully stirring, 9.110 g of template triethylamine and 9.110 g of diisopropylamine are added dropwise;

Put the fully stirred gel into a hydrothermal reaction kettle for crystallization reaction at 190°C, the crystallization time is 24 hours, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, and dry at 100°C for 12 hour, in the air with 0.5 ℃/min heating up to 500 ℃ and roasting for 3 hours to obtain a manganese-rich Mn-SAPO-34 molecular sieve catalyst;

In this method, the amount of each reactant is controlled so that the reaction system has the following mass ratio relationship, that is, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is 1:1:80:0.6:0.4:1.5:1.5.

Figure 5 is a diagram of the catalytic performance evaluation of the catalyst prepared in this example, which shows that changing the crystallization time and crystallization temperature of the molecular sieve catalyst during the preparation process (such as reducing the crystallization temperature) will obviously affect the catalyst. Compared with the low-temperature denitration activity of the catalyst prepared in Example 4, the low-temperature denitration activity of the catalyst prepared in this example is significantly worse.

Example 6

After mixing 13.835 g of orthophosphoric acid with a mass fraction of 85% and 53.070 g of deionized water, slowly add 8.880 g of pseudo-boehmite, and add 7.211 g of silica sol after mixing evenly. Adding 29.400g mass fraction is 20% manganese acetate solution, and after fully stirring, 9.110 g of template triethylamine and 9.110 g of diisopropylamine are added dropwise;

Put the fully stirred gel into a hydrothermal reaction kettle for crystallization reaction at 210°C, the crystallization time is 96 hours, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, and dry at 120°C for 12 hour, in the air with 1.5 ℃/min heating up to 600 ℃ roasting for 9 hours to obtain a manganese-rich Mn-SAPO-34 molecular sieve catalyst;

In this method, the amount of each reactant is controlled so that the reaction system has the following mass ratio relationship, that is, the molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, and DIPA is 1:1:80:0.6:0.4:1.5:1.5.

Figure 6 is the catalytic performance evaluation diagram of the catalyst prepared in this example, which shows that changing the crystallization time and crystallization temperature of the molecular sieve catalyst during the preparation process (such as increasing the crystallization temperature) will obviously affect The denitration activity of the catalyst, compared with the low-temperature denitration activity of the catalyst prepared in Example 4, the low-temperature denitration activity of the catalyst prepared in this example is significantly worse.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (10)

1. a preparation method of manganese-rich Mn-SAPO-34 molecular sieve catalyst, is characterized in that, comprises the following steps: (1) Mix orthophosphoric acid and deionized water, then add pseudoboehmite, add silica sol after mixing evenly, add manganese acetate solution after mixing well, add organic amine template agent triethylamine dropwise after fully stirring and diisopropylamine; (2) Put the fully stirred gel obtained in step (1) into a hydrothermal reaction kettle for crystallization, then cool at room temperature, separate the solid crystalline product from the mother liquor, wash until neutral, dry, and store in the air at 500-600 °C Roasting, get a kind of manganese-rich Mn-SAPO-34 molecular sieve catalyst; In this method, control the consumption of each reactant so that each material in the reaction system has the following ratio relationship, namely The molar ratio of Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, triethylamine, and diisopropylamine is 1:1:80:(0.2～1.0):(0.05～0.6):(1.0 ~3.5): (0~1.5). 2. The preparation method according to claim 1, characterized in that, in the method, the amount of each reactant is controlled so that each substance in the reaction system has the following ratio relationship, that is, Al ₂ O ₃ , P ₂ O ₅ , H ₂ O, SiO ₂ , MnO, TEA, DIPA ratio is 1:1:80:0.6:0.4:1.5:1.5. 3 . The preparation method according to claim 1 , wherein the crystallization temperature in step (2) is 190-210° C., and the crystallization time is 24-96 hours. 4 . 4. The preparation method according to claim 3, wherein the crystallization temperature is 200° C., and the crystallization time is 48 hours. 5. The preparation method according to claim 1, characterized in that the drying temperature in step (2) is 90-110 °C, and the drying time is 6-15 hours. 6. The preparation method according to claim 5, characterized in that, the drying temperature is 110° C., and the drying time is 12 hours. 7. The preparation method according to claim 1, characterized in that the calcination in step (2) is carried out by raising the temperature at 0.5-1.5 ℃/min to 500-600 ℃ for 3-9 hours. 8 . The preparation method according to claim 1 , wherein the calcination is performed by raising the temperature at 1° C./min to 550° C. for 6 hours. 9. A kind of manganese-rich Mn-SAPO-34 molecular sieve catalyst prepared by the preparation method described in any one of claims 1-8. 10. A manganese-rich Mn-SAPO-34 molecular sieve catalyst as claimed in claim 9 is used in low temperature NH ₃ -SCR reaction.