CN104801335A - Zr-Ce-Mn/ZSM-5 complex oxide catalyst adopting NH3 to reduce NOx at low temperature as well as preparation method of Zr-Ce-Mn/ZSM-5 complex oxide catalyst - Google Patents

Abstract

The invention discloses a Zr-Ce-Mn/ZSM-5 complex oxide catalyst adopting NH3 to reduce NOx at the low temperature as well as a preparation method of the Zr-Ce-Mn/ZSM-5 complex oxide catalyst. The Zr-Ce-Mn/ZSM-5 complex oxide catalyst comprises ZrO2, CeO2, MnO2 and ZSM-5, wherein the mass of the Mn element accounts for 5%-24% of the mass of a raw material HZSM-5 molecular sieve; a mole ratio of Ce to Mn is (1-4):1; a mole ratio of Zr to Mn is (0.3-0.75):2; a mole ratio of SiO2 to Al2O3 in the HZSM-5 molecular sieve is (25-50):1. According to the preparation method, the elements are supported by an excessive solution with an impregnation method, are stirred and evaporated to dryness through water bath at the temperature of 90-100 DEG C, are dried for 2-8 h at the temperature of 110-125 DEG C in the air atmosphere and are subjected to calcination for 3-4 h at the temperature of 500-550 DEG C. The catalyst has better low-temperature ignition and stable conversion rate reaction window performance as well as excellent performance of catalyzing and purifying NOx in diesel vehicle (engine) tail gas or stationary-source tail gas at the low temperature, and the production process is simple.

Description

Low temperature NH 3reductive NO xzr-Ce-Mn/ZSM-5 composite oxide catalysts and preparation method thereof

Technical field

The present invention relates to one at low temperatures with ammonia (comprising the amino that urea etc. decomposes) for NO in reducing agent catalytic purification diesel vehicle (machine) tail gas or stationary source tail-gas _xthe base supported oxide catalyst of ZSM-5 and preparation method thereof.

Background technology

Nitrogen oxide (NO _x) be one of major pollutants of photochemical pollution and haze formation, with ammonia (NH ₃) or the amino (-NH that decomposes such as urea ₂) compound is NO in reducing agent selective catalysis purification of diesel car (machine) tail gas or stationary source tail-gas _x(NH ₃-SCR) be the most suitable effective technology.At the NO of stationary source (as boiler of power plant etc.) cigarette tail gas _xin purification applications, increasing user makes SCR device change in advance to avoid catalyst to be subject to the contamination and plugging of dust and heavy metal and reduces the maintenance cleaning work of device after wishing that SCR reaction unit is installed on electric cleaner and desulfurizer.But cigarette tail gas its temperature after electric cleaner and desulfurizer is very low, often only has about 80-120 DEG C.At diesel vehicle (machine) the emission NO of moving source _xin the application reality removed, owing to can be used as CO and CH of reducing agent in diesel vehicle (machine) emission _xconcentration is lower, Catalytic Reducing Purification NO _xremoval efficiency limited, strict state's IV and state's V discharge standard be met and only have and adopt with ureaclastic amino (-NH ₂) compound is NO in reducing agent selective catalysis purification of diesel car (machine) tail gas _xcatalysis technique.But, because diesel vehicle (machine) delivery temperature under startup and speed operation is lower, to delivery temperature during clarifier installation site usually only less than 100-150 DEG C.In actual applications, the ignition of catalyst when being vented low temperature becomes diesel vehicle (machine) tail gas NO _xreach the crucial application technology of the discharge standard of increasingly stringent.Therefore, above-mentioned NO _xin purification applications, the initiation temperature (T requiring catalyst to provide ₅₀) more low better, and there is wider stable conversion rate temperature window, with the change of adaptation condition.Molecular sieve due to its water resistant heat endurance and sulfur resistive toxicity good, be NO in diesel vehicle (machine) emission or stationary source flue gas _xthe comparatively suitable catalyst active carrier removed.Usually, molecular screen base oxide catalyst is applied to hot conditions usually, more than 400 DEG C NO _xthe NH of purification ₃-SCR performance is better, and the load of active component is prepared with ion-exchange.For this reason, be necessary that developing a kind of is NO in reducing agent catalytic purification diesel vehicle (machine) tail gas or stationary source tail-gas for ammonia (comprising the amino that urea etc. decomposes) _xtake molecular sieve as the low temperature catalyst of carrier, catalyst can ignition at a lower temperature, and has wider stable conversion temperature window, and production technology is easy.

Summary of the invention

The object of this invention is to provide one at low temperatures with ammonia (comprising the amino that urea etc. decomposes) for NO in reducing agent catalytic purification diesel vehicle (machine) tail gas or stationary source tail-gas _xzSM-5 base supported composite oxides Zr-Ce-Mn/ZSM-5 Catalysts and its preparation method, the catalyst of this invention can ignition at a lower temperature, and has wider stable conversion rate temperature window, and production technology is easy.

The Zr-Ce-Mn/ZSM-5 composite oxide catalysts that the present invention relates to is by ZrO ₂, CeO ₂, MnO ₂with ZSM-5 composition, wherein: Mn element quality is 5 ~ 24%, Ce/Mn mol ratios of raw material HZSM-5 molecular sieve quality be 1 ~ 4/1, Zr/Mn mol ratio is 0.3 ~ 0.75/2, SiO in raw material HZSM-5 molecular sieve ₂/ Al ₂o ₃mol ratio is 25 ~ 50/1.

Preparation method's concrete steps of Zr-Ce-Mn/ZSM-5 composite oxide catalysts are:

(1) with HZSM-5 molecular sieve (SiO ₂/ Al ₂o ₃mol ratio is 25 ~ 50/1) quality meter, Zr-Ce-Mn/ZSM-5 composite oxide catalysts active component consists of: Mn element quality be HZSM-5 molecular sieve quality 5 ~ 24%, Ce/Mn mol ratio be 1 ~ 4/1 and Zr/Mn mol ratio be 0.3 ~ 0.75/2.

(2) nitrate or the acetate of step (1) Mn, Ce and Zr respective quality is taken respectively, join deionized water for stirring in the lump to make to dissolve completely to make salting liquid, heat solution to 50 ~ 60 DEG C to promote the dissolving of nitrate in course of dissolution, deionized water consumption at least can excessive submergence molecular sieve powder carrier each component salt being dissolved with solution, and research on maximum utilized quantity is 4 times of molecular sieve quality.

(3) HZSM-5 molecular sieve is submerged in step (2) gained salting liquid, with 90 ~ 100 DEG C of water bath methods under stirring, then 110 ~ 125 DEG C of dryings roasting 3 ~ 4 hours at 2 ~ 8 hours, 500 ~ 550 DEG C under air atmosphere, obtains Zr-Ce-Mn/ZSM-5 composite oxide catalysts.

Obtained Zr-Ce-Mn/ZSM-5 composite oxide catalysts powder adding additives after citric acid or the pre-clayization of acetic acid prepares pulping, is coated on drying roasting on metallic plate, metal beehive and ceramic honeycomb and is prepared into applicable product.

The NH of obtained Zr-Ce-Mn/ZSM-5 composite oxide catalysts ₃selective Catalytic Reduction of NO _x(NH ₃-SCR) activity rating simulation exhaust gas purifying catalyst evaluation system on carry out.40-60 object particle need be got after compressing tablet and fragmentation, the then direct sample evaluation of cellular sample when Zr-Ce-Mn/ZSM-5 composite oxide catalysts powder is evaluated.Reaction mixture gas consists of NO≤0.2 vol.%, NH ₃/ NO mol ratio 1.0 ~ 1.15, O ₂6.0 ~ 12.0 vol%, N ₂for Balance Air, reaction velocity controls in 20000 ~ 60000mL/ (g.h) scope.Adopt the NO before and after Foshan Analyzer Co., Ltd. FGA-4100A type flue gas analyzer on-line analysis reaction _xand O ₂concentration.

Gained molecular screen base Zr-Ce-Mn/ZSM-5 oxide catalyst of the present invention, its NH ₃selective Catalytic Reduction of NO _x(NH ₃-SCR) initiation temperature is low, T ₅₀less than 120 DEG C can be low to moderate; T ₉₀window is wide, can reach 150 ~ 340 DEG C, stablizes optimal conversion window and can reach 160 ~ 310 DEG C, has preferably low temperature ignition and stable conversion rate Process window performance, not only has NO in superior low-temperature catalyzed purification of diesel car (machine) tail gas or stationary source tail-gas _xperformance, and production technology is simple.

Accompanying drawing explanation

Fig. 1 is the NH of Zr-Ce-Mn/ZSM-5 catalyst of the present invention ₃selective Catalytic Reduction of NO _x(NH ₃-SCR) active figure, air speed 30000mL/ (g.h).

Detailed description of the invention

Below by way of specific embodiment, the present invention is described in detail, but should be appreciated that the present invention is not only limited to described embodiment.

Embodiment:

(1) taking 76.9g mass percent concentration is 50% manganese nitrate (Mn (NO ₃) ₂) (being equivalent to the Mn element of HZSM-5 molecular sieve quality 11.8%), 280g six water cerous nitrate (Ce (NO ₃) ₃6H ₂o) (being equivalent to Ce/Mn mol ratio is 3/1) and 25.3g zirconium nitrate (Zr (NO ₃) ₄) (being equivalent to Zr/Mn mol ratio is 0.69/2).

(2) raw material of step (1) is joined in 250g deionized water in the lump, to stir and solution to 55 DEG C of heating makes salt dissolve completely.

(3) by 100g HZSM-5 molecular sieve (SiO ₂/ Al ₂o ₃mol ratio is 38/1, Shandong Qilu Huaxin High-technology Co., Ltd. produces) be submerged in step (2) gained salting liquid, with 100 DEG C of water bath methods under stirring, then in the lower 110 DEG C of dryings of air atmosphere roasting 4 hours at 6 hours, 550 DEG C, obtain Zr-Ce-Mn/ZSM-5 composite oxide catalysts and be designated as nZr:Ce:Mn=0.69:6:2/ZSM-5.

The NH of Zr-Ce-Mn/ZSM-5 composite oxide catalysts ₃selective Catalytic Reduction of NO _x(NH ₃-SCR) activity rating simulation exhaust gas purifying catalyst evaluation system (manufacture of Chemistry and Chemical Engineering College of University Of Tianjin) on carry out.Zr-Ce-Mn/ZSM-5 composite oxide catalysts gets 40-60 object particle after compressing tablet and fragmentation.Reaction mixture gas consists of NO 0.1 vol.%, NH ₃0.11 vol.%, O ₂6.0 vol.%, N ₂for Balance Air, air speed 30000mL/ (g.h).Adopt the NO before and after Foshan Analyzer Co., Ltd. FGA-4100A type flue gas analyzer on-line analysis reaction _xand O ₂concentration.Catalyst light-off temperature T ₅₀it is 120 DEG C; T ₉₀window 151-339 DEG C, stablizes the window 160 ~ 310 DEG C of optimal conversion 98%.

Its NH of Zr-Ce-Mn/ZSM-5 composite oxide catalysts prepared by the embodiment of the present invention ₃selective Catalytic Reduction of NO _x(NH ₃-SCR) activity is shown in accompanying drawing 1.Can see, under air speed 30000mL/ (g.h), its initiation temperature of n Ce:Mn=6:2/ZSM-5 catalyst T ₅₀it is 140 DEG C; T ₉₀window 167 ~ 338 DEG C, stablizes the window 181 ~ 319 DEG C of optimal conversion 98%.By contrast, after mixing Zr component, its initiation temperature of nZr:Ce:Mn=0.69:6:2/ZSM-5 catalyst T ₅₀be offset to 120 DEG C to low temperature, reduce 20 DEG C; T ₉₀window is offset to 151 ~ 339 DEG C to low temperature, and window has broadened 16 DEG C to low temperature; Stablize the window 160 ~ 310 DEG C of optimal conversion 98%, window has broadened 21 DEG C to low temperature.

As can be seen here, prepared by the present invention take ZSM-5 molecular sieve as the Zr-Ce-Mn/ZSM-5 composite oxide catalysts of carrier, its NH ₃selective Catalytic Reduction of NO _x(NH ₃-SCR) initiation temperature is significantly to low temperature skew with stablize optimal conversion window and significantly widen nearly 20 DEG C to low temperature, the low temperature NH of Zr-Ce-Mn/ZSM-5 composite oxide catalysts ₃-SCR performance is significantly improved and improves.This shows, the Zr-Ce-Mn/ZSM-5 composite oxide catalysts prepared by the present invention has preferably low temperature ignition and wider stable conversion rate Process window performance, not only has NO in superior low-temperature catalyzed purification of diesel car (machine) tail gas or stationary source tail-gas _xperformance, and production technology is simple.

Claims (2)

1. a Zr-Ce-Mn/ZSM-5 composite oxide catalysts, is characterized in that Zr-Ce-Mn/ZSM-5 composite oxide catalysts is by ZrO ₂, CeO ₂, MnO ₂with ZSM-5 composition, wherein: Mn element quality is 5 ~ 24%, Ce/Mn mol ratios of raw material HZSM-5 molecular sieve quality be 1 ~ 4/1, Zr/Mn mol ratio is 0.3 ~ 0.75/2, SiO in raw material HZSM-5 molecular sieve ₂/ Al ₂o ₃mol ratio is 25 ~ 50/1.

2. the preparation method of Zr-Ce-Mn/ZSM-5 composite oxide catalysts according to claim 1, is characterized in that concrete steps are:

(1) in HZSM-5 molecular sieve quality, SiO in HZSM-5 molecular sieve ₂/ Al ₂o ₃mol ratio is that 25 ~ 50/1, Zr-Ce-Mn/ZSM-5 composite oxide catalysts active component consists of: Mn element quality be HZSM-5 molecular sieve quality 5 ~ 24%, Ce/Mn mol ratio be 1 ~ 4/1 and Zr/Mn mol ratio be 0.3 ~ 0.75/2;

(2) take respectively step (1) Mn, Ce and Zr respective quality nitrate or acetate, join deionized water for stirring in the lump to make to dissolve completely to make salting liquid, heat solution to 50 ~ 60 DEG C to promote the dissolving of nitrate in course of dissolution, deionized water consumption at least can excessive submergence molecular sieve powder carrier each component salt being dissolved with solution, and research on maximum utilized quantity is 4 times of molecular sieve quality;

(3) HZSM-5 molecular sieve is submerged in step (2) gained salting liquid, with 90 ~ 100 DEG C of water bath methods under stirring, then 110 ~ 125 DEG C of dryings roasting 3 ~ 4 hours at 2 ~ 8 hours, 500 ~ 550 DEG C under air atmosphere, obtains Zr-Ce-Mn/ZSM-5 composite oxide catalysts.