CN101829573A - Composite oxidant SCR (Selective Catalytic Reduction) denitrating catalyst, preparation method and applications thereof - Google Patents

Abstract

The invention discloses a composite oxidant SCR (Selective Catalytic Reduction) denitrating catalyst for warm fume in boilers, a preparation method and application thereof. The catalyst comprises the components of transition metal element M and Ti element. As counted by the oxidant, the amount of the transition metal element M accounts for 6.8-20wt% of the total weight of the catalyst. As counted by TiO2, the amount of Ti accounts for 80-93.2wt% of the total weight of the catalyst. Compared with the widely used commercial catalyst, the catalyst decreases the cost by more than 20%, does not contain W, Mo, V and Ce, and has the advantages of low cost, no toxicity, high activity, good sulphate resisting property and the like.

Description

A kind of composite oxidant SCR (Selective Catalytic Reduction) denitrating catalyst and preparation method and application

Technical field

The present invention relates to a kind of composite oxide catalysts and preparation method and application that is used for denitration of boiler smoke, this composite oxide catalysts is applied to NH ₃Nitrogen oxide (NO in temperature (325～425 ℃) flue gas in the SCR _x) the environmental catalysis field.

Background technology

The sulfur dioxide SO of boiler smoke discharging ₂With nitrogen oxide NO _x(NO, NO ₂And N ₂O etc.), be the one of the main reasons that produces acid rain and photochemical pollutant, cause the atmospheric environment problem serious day by day.Current, the flue gas desulfurization technique comparative maturity of China, at the end of Year 2008, the whole nation has formed about 1,000 ten thousand tons of year desulphurizing ability.But the emission control of nitrogen oxide still is in the starting stage, 2008, national discharged nitrous oxides total amount was about 2,000 ten thousand tons, became the first in the world discharging state, as not taking effective measures control, the discharge capacity of China's nitrogen oxide may reach more than 3,000 ten thousand tons to the year two thousand twenty.Thermal power plant, Industrial Boiler flue gas are the main sources of nitrogen oxide in the atmosphere, account for the over half of total emission volumn, from July 1st, 2004, China NO _xDischarging begins charge (0.6 yuan/pollutional equivalent), and control nitrogen oxide total amount also will be included in " 12 " planning thinking.Therefore, the dominate the situation sternness, task of boiler smoke nitrogen oxide is urgent.

The main dependence on import of gas denitrifying technology of present China, technology with independent intellectual property right is few, particularly most SCR (SCR) or SNCR (SNCR) technology introduced of coal steam-electric plant smoke denitration account for 96% and 4% of the market share respectively.With NH ₃NO for reducing agent SCR stationary source (as the thermal power plant) discharging _xBe present commercial Application denitration technology the most widely, commercial catalyst commonly used is V ₂O ₅WO ₃(MoO ₃)/TiO ₂Current domestic flue gas SCR denitration technology still is in introduction, digests and assimilates and the Preliminary Applications stage.SCR technological core---the main dependence on import of catalyst, thereby investment, operating cost height, although domestic some Catalyst Production bases of having built up at present all are to adopt external technology, and even raw material all relies on import, is seriously restricting the development of denitrating flue gas industry.

Therefore, break external SCR catalyst monopolization, development has independent intellectual property right, be applicable to that high activity, high sulfidation resistance, the preparation SCR catalyst simple, with low cost under warm flue gas in the boiler (325～425 ℃) condition seems particularly important, this The Application of Technology will have environment, economic benefit preferably.

There is some defective in the SCR method, and is narrower such as the catalyst activity temperature range, easily generate N ₂O, catalyst life are short, cost is high.The domestic patent of relevant denitration of boiler smoke SCR catalyst is more, oxide with W, Mo, V loads on all kinds of supported catalysts (accounting for more than 70% of this type of patent) in the majority as main active component, as Chinese patent CN1593752A, CN1792431A, CN101433837A, CN101352679A, CN101396655A, CN101422728A, CN101391214A, CN101347722A, CN101185886A etc., W, Mo, V content height in this type of SCR catalyst, thereby cause that manufacturing cost is higher, and V ₂O ₅Has certain toxicity.The SCR catalyst patent that does not contain W or Mo, V component is less, as adopting the composite oxide supported SCR catalyst (CN101380578A) on ceramic honey comb of FeTi of coprecipitation preparation, at NO 500ppm, NH ₃500ppm, air speed 50000h ^-1, under 400 ℃ of conditions, the NO conversion ratio is about more than 80%; The same Fe that adopts also has CN101433855A, CN101417237A as the patent of main active component, and the former is oxide carried at nano-TiO with Fe with infusion process ₂On the material complex carrier of silicate nano hole, at NO 1100ppm, air speed 8000h ^-1, under 350 ℃ of conditions, the NO conversion ratio is about about 80%, and the latter loads on precious metals pt and has obtained NO removal effect preferably on the Fe-ZSM-5 molecular sieve.In addition, adopt the CeTi composite oxide catalysts (CN101204650A) of infusion process or coprecipitation preparation in addition, under 325～425 ℃ of conditions, NO 500ppm, NH ₃480ppm, O ₂5%, the NO conversion ratio remains on about 93%, feeds a small amount of SO ₂Drop to 90% through the 24h activity (100ppm).On the whole, the SCR catalyst exists manufacturing cost higher, and is higher as prices such as active component W, Mo, Pt, Ce, generally the V of Cai Yonging ₂O ₅Be not only a kind of noxious material, also have oxidation SO ₂Become SO ₃Problem, SO ₃With water and NH ₃Generate sulfate and be deposited on catalyst surface, reduce catalyst activity and life-span, simultaneously SO ₃The heavy corrosion pipe-line equipment increases operating cost.Therefore also there is certain limitation in above SCR catalyst.

Summary of the invention

In order to solve the problems of the technologies described above, grasp SCR catalyst core technology, primary and foremost purpose of the present invention is to provide a kind of NH under boiler temperature (325～425 ℃) flue gas condition that is used for ₃The high activity of selective catalyst reduction of nitrogen oxides, low-cost composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst.

Another object of the present invention is to provide a kind of above-mentioned Preparation of catalysts method; This method adopts simple sol-gal process, utilizes citric acid or oxalic acid to make transition metal salt and titanium salt complexing become collosol and gel specifically, is prepared into the composite oxide catalysts based on Ti-O.Above-mentioned catalyst does not contain W, Mo, V, Ce element.

A further object of the present invention is to provide above-mentioned Application of Catalyst.

Purpose of the present invention is achieved through the following technical solutions: a kind of composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst that is used for warm flue gas, this catalyst comprises following component: transition metal M and Ti element.

The addition of described transition metal M is 6.8～20wt% of catalyst gross mass in oxide quality percentage composition; The addition of described Ti element is with TiO ₂Meter quality percentage composition is 80～93.2wt% of catalyst gross mass.

Described transition metal M is two or more among Ni, Fe, Mn, Co and the Cu, and there is the main body that accounts for catalyst in Ti with the Ti-O form.

Described transition metal M in oxide and Ti element with TiO ₂Meter, its mass ratio is 0.07～0.25: 1.

The existing way of described transition metal M is to form composite oxides with Ti; There is the main body that accounts for catalyst in described Ti element with the Ti-O form.

Above-mentioned a kind of preparation method who is used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas comprises following operating procedure:

(1) 0.5～3molL of 30～80 ℃ of preparation ^-1Citric acid solution or oxalic acid solution; In citric acid solution or oxalic acid solution, add nitrate or the acetate of transition metal M, stir 1～3h, obtain mixed salt solution;

(2) add titanium salt in step (1) gained mixed salt solution, stir 2～6h, wherein titanium salt is more than one in butyl titanate, titanium sulfate and the titanium tetrachloride;

(3) dry 12～60h under 100～180 ℃ of constant temperatures obtains raw material solid;

(4) raw material solid is calcined 2～14h in air, calcining heat is 180～800 ℃, obtains composite oxides;

(5) composite oxides are ground, compressing tablet is crossed 40～80 mesh sieves, obtains being used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas.

Transition metal M is in oxide in the described mixed salt solution of step (2), and the mass ratio of total metal oxide and citric acid or oxalic acid is 1: 1～3.

The described calcining of step (4) is to adopt the control of ladder section: calcine 1～2h earlier under 200～300 ℃ of conditions, calcine 2～4h again under 400～500 ℃ of conditions, calcine 4～6h then under 550～800 ℃ of conditions.

Above-mentioned catalyst NH in the warm flue gas in boiler ₃Selective catalyst reduction of nitrogen oxides (NO _x) application, thereby reach the purpose of denitration, described in temperature be 325～425 ℃; Described reducing agent NH ₃Derive from liquefied ammonia or urea pyrolysis.

The present invention adopts the optimal catalyst of Prepared by Sol Gel Method, with NH ₃Be reducing gases, NO _xConcentration is 0.1%, and air speed is 50,000h ^-1, under 325～425 ℃ of conditions, NO _xConversion ratio is more than 95%; In the time of 350 ℃ at the SO of high concentration ₂(0.06%) under the condition of Cun Zaiing, catalyst activity is stable, NO _xRemoval efficiency reaches more than 90%.

The relative prior art of the present invention, have following advantage and beneficial effect: the present invention adopts sol-gal process, is prepared into based on Ti-O, with the composite oxide catalysts of transition metal M formation; Because constituent is different with existing method with the preparation method, this catalyst is applicable in the catalytic reduction boiler nitrogen oxide in temperature (325～425 ℃) flue gas, the ability that under the high-sulfur condition, has the highly active catalytic nitrogen oxides reduction, preparation is simple, and the ability of stronger sulfur poisoning-resistant is arranged simultaneously; This catalyst does not contain W, Mo, V and Ce element, has characteristics such as avirulence, with low cost, active height, with V ₂O ₅WO ₃(MoO ₃)/TiO ₂Compare etc. commercial catalyst, cost reduces more than 20%.

Description of drawings

Fig. 1 is each embodiment catalyst n O under the different temperatures _xConversion ratio figure.

The specific embodiment

Below in conjunction with embodiment, the present invention is described in further detail, but embodiment of the present invention is not limited thereto.

Embodiment 1

(1) Preparation of Catalyst

At first with 6.0g citric acid (C ₆H ₈O ₇) be dissolved in 30 ℃ of deionized waters of 30mL; In citric acid solution, add 6.08g nine nitric hydrate iron (Fe (NO ₃) ₃9H ₂O) and 4.67g Nickelous nitrate hexahydrate (Ni (NO ₃) ₂6H ₂O) (with Fe ₂O ₃Add up to the 12.0wt% that accounts for the catalyst total content with NiO), fully stir 1h, obtain mixed salt solution; With 44.65g titanium tetrachloride (TiCl ₄) slowly join in the mixed salt solution (with TiO ₂Meter accounts for the 88.0wt% of catalyst total content), behind the stirring 2h, in 100 ℃ of dry 36h, the solid that obtains under air conditions in 750 ℃ of roasting 5h, 40～80 order particles are made in compressing tablet, grinding then, obtain being used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas, and are standby.

(2) evaluating catalyst

Above-mentioned gained catalyst is put into the stainless steel reaction pipe, adopt the program temperature controller that fixed bed reactors are heated to certain temperature (275～400 ℃); With simulated flue gas and reducing agent NH ₃Feed reaction tube, wherein simulated flue gas is N ₂, O ₂, NO mixes, and investigates SO ₂During to the influencing of catalyst activity, add SO ₂By the NO of online detection import of flue gas analyzer and outlet, NO ₂, O ₂, SO ₂Concentration, fetching data at fixed temperature point is that continuous 10min collects the mean value of data after the SCR stable reaction under this temperature is carried out 60min, calculates NO by following formula _xConversion ratio:

${\mathrm{NO}}_x\mathrm{conversion}(\%)=\frac{({\left[\mathrm{NO}\right]}_{\mathrm{in}}+{\left[{\mathrm{NO}}_2\right]}_{\mathrm{in}})-({\left[\mathrm{NO}\right]}_{\mathrm{out}}+{\left[{\mathrm{NO}}_2\right]}_{\mathrm{out}})}{({\left[\mathrm{NO}\right]}_{\mathrm{in}}+{\left[{\mathrm{NO}}_2\right]}_{\mathrm{in}})}\×100---\left(1\right)$

The evaluating catalyst result as shown in Figure 1, at volumetric concentration [NO]=[NH ₃]=0.1%, [O ₂]=3%, air speed=50,000h ^-1Under the operating condition, in 325～425 ℃ of scopes, NO _xConversion ratio is all more than 84%, NO in the time of 350 ℃ _xRemoval efficiency reaches more than 96%.Under 350 ℃, the feeding volumetric concentration is 0.06% SO ₂, 4h rear catalyst denitration efficiency is more than 85%, and in 48h backward kept stable.

Embodiment 2

(1) Preparation of Catalyst

At first with 8.1g oxalic acid (C ₂H ₂O ₄2H ₂O) be dissolved in 70 ℃ of deionized waters of 40mL; In oxalic acid solution, add 3.64g Gerhardite (Cu (NO ₃) ₂3H ₂O) and 4.23g four hydration manganese acetate (Mn (CH ₃COO) ₂4H ₂O) (with CuO and MnO ₂Add up to the 13.5wt% that accounts for the catalyst total content), fully stir 1h, obtain mixed salt solution; With 73.72g butyl titanate (Ti (OC ₄H ₉) ₄) slowly join in the mixed salt solution (with TiO ₂Meter accounts for the 86.5wt% of catalyst total content), behind the stirring 3h, in 120 ℃ of dry 24h, the solid that obtains under air conditions in 700 ℃ of roasting 6h, 40～80 order particles are made in compressing tablet, grinding then, obtain being used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas, and are standby.

(2) evaluating catalyst

Evaluating catalyst process such as embodiment 1.

The evaluating catalyst result as shown in Figure 1, at volumetric concentration [NO]=[NH ₃]=0.1%, [O ₂]=3%, air speed=50,000h ^-1Under the operating condition, in 325～425 ℃ of scopes, NO _xConversion ratio is all more than 91%, NO in the time of 350 ℃ _xRemoval efficiency reaches more than 93%.Under 350 ℃, the feeding volumetric concentration is 0.06% SO ₂, 4h rear catalyst denitration efficiency is more than 80%, and in 48h backward kept stable.

Embodiment 3

(1) Preparation of Catalyst

At first with 9.0g citric acid (C ₆H ₈O ₇) be dissolved in 50 ℃ of deionized waters of 40mL; In citric acid solution, add 5.06g nine nitric hydrate iron (Fe (NO ₃) ₃9H ₂O), 2.43g Gerhardite (Cu (NO ₃) ₂3H ₂O) and 2.82g four hydration manganese acetate (Mn (CH ₃COO) ₂4H ₂O) (with Fe ₂O ₃, CuO and MnO ₂Add up to the 14.0wt% that accounts for the catalyst total content), fully stir 1.5h, obtain mixed salt solution; With 40.85g titanium tetrachloride (TiCl ₄) slowly join in the mixed salt solution and (account for the 86.0wt% of catalyst total content), after stirring 4h, in 160 ℃ of dry 12h, the solid that obtains under air conditions in 550 ℃ of roasting 8h, 40～80 order particles are made in compressing tablet, grinding then, obtain being used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas, standby.

(2) evaluating catalyst

Evaluating catalyst process such as embodiment 1.

The evaluating catalyst result as shown in Figure 1, at volumetric concentration [NO]=[NH ₃]=0.1%, [O ₂]=3%, air speed=50,000h ^-1Under the operating condition, in 325～425 ℃ of scopes, NO _xConversion ratio is all more than 95%, NO in the time of 350 ℃ _xRemoval efficiency reaches more than 97%.Under 350 ℃, the feeding volumetric concentration is 0.06% SO ₂, 4h rear catalyst denitration efficiency is more than 91%, and in 48h backward kept stable.

Embodiment 4

(1) Preparation of Catalyst

At first with 9.0g oxalic acid (C ₂H ₂O ₄2H ₂O) be dissolved in 80 ℃ of deionized waters of 36mL; In citric acid solution, add 4.67g Nickelous nitrate hexahydrate (Ni (NO ₃) ₂6H ₂O), 2.43g Gerhardite (Cu (NO ₃) ₂3H ₂O) and 3.38g four hydration manganese acetate (Mn (CH ₃COO) ₂4H ₂O) (with NiO, CuO and MnO ₂Add up to the 16.0wt% that accounts for the catalyst total content), fully stir 2h, obtain mixed salt solution; With 71.59g butyl titanate (Ti (OC ₄H ₉) ₄) slowly join in the mixed salt solution and (account for the 84.0wt% of catalyst total content), after stirring 6h, in 180 ℃ of dry 12h, the solid that obtains under air conditions in 650 ℃ of roasting 8h, 40～80 order particles are made in compressing tablet, grinding then, obtain being used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas, standby.

(2) evaluating catalyst

Evaluating catalyst process such as embodiment 1.

The evaluating catalyst result as shown in Figure 1, at volumetric concentration [NO]=[NH ₃]=0.1%, [O ₂]=3%, air speed=50,000h ^-1Under the operating condition, in 325～425 ℃ of scopes, NO _xConversion ratio is all more than 83%, NO in the time of 350 ℃ _xRemoval efficiency reaches more than 96%.Under 350 ℃, the feeding volumetric concentration is 0.06% SO ₂, 4h rear catalyst denitration efficiency is more than 78%, and in 48h backward kept stable.

Embodiment 5

(1) Preparation of Catalyst

At first with 12g citric acid (C ₆H ₈O ₇) be dissolved in 50 ℃ of deionized waters of 40mL; In oxalic acid solution, add 2.18g cabaltous nitrate hexahydrate (Co (NO ₃) ₂6H ₂O), 3.64g Gerhardite (Cu (NO ₃) ₂3H ₂O) and 3.38g four hydration manganese acetate (Mn (CH ₃COO) ₂4H ₂O) (with Co ₃O ₄, CuO and MnO ₂Add up to the 15.0wt% that accounts for the catalyst total content), fully stir 2h, obtain mixed salt solution; With 51.08g titanium sulfate (Ti (SO ₄) ₂) join in the mixed salt solution (with TiO ₂Meter accounts for the 85.0wt% of catalyst total content), behind the stirring 6h, in 140 ℃ of dry 18h, the solid that obtains under air conditions in 800 ℃ of roasting 3h, 40～80 order particles are made in compressing tablet, grinding then, obtain being used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas, and are standby.

(2) evaluating catalyst

Evaluating catalyst process such as embodiment 1.

The evaluating catalyst result as shown in Figure 1, at volumetric concentration [NO]=[NH ₃]=0.1%, [O ₂]=3%, air speed=50,000h ^-1Under the operating condition, in 325～425 ℃ of scopes, NO _xConversion ratio is all more than 83%, NO in the time of 350 ℃ _xRemoval efficiency reaches more than 93%.Under 350 ℃, the feeding volumetric concentration is 0.06% SO ₂, 4h rear catalyst denitration efficiency is more than 73%, and in 48h backward kept stable.

The foregoing description is a preferred implementation of the present invention; but embodiments of the present invention are not restricted to the described embodiments; other any do not deviate from change, the modification done under spiritual essence of the present invention and the principle, substitutes, combination, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.

Claims (9)

1. composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst that is used for boiler temperature flue gas, it is characterized in that: this catalyst comprises following component: transition metal M and Ti element.

2. a kind of composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst that is used for warm flue gas according to claim 1, it is characterized in that: the addition of described transition metal M is 6.8～20wt% of catalyst gross mass in oxide quality percentage composition; The addition of described Ti element is with TiO ₂Meter quality percentage composition is 80～93.2wt% of catalyst gross mass.

3. a kind of composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst that is used for warm flue gas according to claim 1 is characterized in that: described transition metal M is two or more among Ni, Fe, Mn, Co and the Cu.

4. a kind of composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst that is used for warm flue gas according to claim 1 is characterized in that: described transition metal M in oxide and Ti element with TiO ₂Meter, its mass ratio is 0.07～0.25: 1.

5. a kind of composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst that is used for warm flue gas according to claim 1 is characterized in that: the existing way of described transition metal M is for forming composite oxides with Ti; There is the main body that accounts for catalyst in described Ti element with the Ti-O form.

6. a kind of preparation method who is used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of warm flue gas according to claim 1 is characterized in that may further comprise the steps:

(1) 0.5～3molL of 30～80 ℃ of preparation ^-1Citric acid solution or oxalic acid solution; In citric acid solution or oxalic acid solution, add nitrate or the acetate of transition metal M, stir 1～3h, obtain mixed salt solution;

(2) add titanium salt in step (1) gained mixed salt solution, stir 2～6h, wherein titanium salt is more than one in butyl titanate, phthalic acid and the titanium tetrachloride;

(3) dry 12～60h under 100～180 ℃ of constant temperatures obtains raw material solid;

(4) raw material solid is calcined 2～14h in air, calcining heat is 180～800 ℃, obtains composite oxides;

(5) composite oxides are ground, compressing tablet is crossed 40～80 mesh sieves, obtains being used for the composite oxidant SCR (Selective Catalytic Reduction) denitrating denitrating catalyst of boiler temperature flue gas.

7. preparation method according to claim 6 is characterized in that: transition metal M is in oxide in the described mixed salt solution of step (2), and the mass ratio of total metal oxide and citric acid or oxalic acid is 1: 1～3.

8. preparation method according to claim 6, it is characterized in that: the described calcining of step (4) is to adopt the control of ladder section: calcine 1～2h earlier under 200～300 ℃ of conditions, under 400～500 ℃ of conditions, calcine 2～4h again, under 550～800 ℃ of conditions, calcine 4～6h then.

9. catalyst according to claim 1 NH in the warm flue gas in boiler ₃The application of selective catalyst reduction of nitrogen oxides is characterized in that: temperature is 325～425 ℃ in described; Described reducing agent NH ₃Derive from liquefied ammonia or urea pyrolysis.

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