WO2019233035A1 - 一种解决低温scr脱硝催化剂so 2中毒的方法 - Google Patents

一种解决低温scr脱硝催化剂so 2中毒的方法 Download PDF

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WO2019233035A1
WO2019233035A1 PCT/CN2018/114662 CN2018114662W WO2019233035A1 WO 2019233035 A1 WO2019233035 A1 WO 2019233035A1 CN 2018114662 W CN2018114662 W CN 2018114662W WO 2019233035 A1 WO2019233035 A1 WO 2019233035A1
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catalyst
low
poisoning
scr denitration
temperature scr
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French (fr)
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马朝霞
盛丽萍
陈诗园
杨杭生
王勇
张泽
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浙江大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/90—Regeneration or reactivation
    • B01J23/92—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/90—Regeneration or reactivation
    • B01J23/94—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the iron group metals or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/90—Regeneration or reactivation
    • B01J23/96—Regeneration or reactivation of catalysts comprising metals, oxides or hydroxides of the noble metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • B01J38/04—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst
    • B01J38/08—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst using ammonia or derivatives thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • B01J38/04—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst
    • B01J38/12—Treating with free oxygen-containing gas
    • B01J38/14—Treating with free oxygen-containing gas with control of oxygen content in oxidation gas

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  • the invention belongs to the field of energy and environmental materials, and particularly relates to a method for solving poisoning of SO 2 by a low-temperature SCR denitration catalyst.
  • SCR denitration facilities have been popularized in domestic coal-fired power plants, so that nitrogen oxide emissions from coal-fired power plants have been effectively controlled.
  • the conventional (V 2 O 5 -WO 3 (MoO 3 ) / TiO 2 ) high-temperature denitration catalysts are used, and the working temperature is 320-420 ° C.
  • most common SCR denitration facilities are arranged before the dust removal and desulfurization facilities, that is, installed in the high ash section. Due to the fast flow of flue gas and a large amount of dust, the catalyst is severely washed away.
  • Alkali metal oxides, alkaline earth metal oxides, arsenic oxide and other substances in the dust can easily cause catalyst poisoning, shorten the catalyst service life, and increase the SCR denitration technology Operating costs. Therefore, the researchers proposed to install the SCR catalyst after the dust removal and desulfurization device.
  • the temperature of the flue gas is relatively low ( ⁇ 250 ° C).
  • the traditional high-temperature denitration catalyst (V 2 O 5 -WO 3 (MoO 3 ) / TiO 2 ) has a significantly reduced activity in this temperature range, so , SCR catalyst with low temperature and high activity has become a research focus in recent years.
  • CN107252693A discloses a low-temperature denitration catalyst using attapulgite clay as a carrier, supported active components being ⁇ -Fe 2 O 3 and MnO 2 , and finally coated with a V 2 O 5 protective layer.
  • the catalyst has the highest active temperature Low temperature, wide temperature range, high stability.
  • CN106732799A discloses a catalyst using a metal organic complex as a support and a metal oxide MnO X as an active component. The catalyst has excellent low-temperature SCR catalytic activity, a wide operating window, and high stability.
  • CN106732542A discloses a sheet-shaped manganese dioxide / carbon fiber low-temperature denitration catalyst.
  • the catalyst can convert more than 98% of nitrogen oxides at 180 ° C.
  • CN106391040A discloses a catalyst using V 2 O 5 as a catalyst, Fe 2 O 3 and CeO 2 as auxiliary agents, and microporous carbon fiber as a carrier. The catalyst can achieve 80% nitrogen oxide conversion rate at 86-102 ° C. The denitration efficiency at 120 ° C is greater than 95%.
  • CN106540710A discloses a manganese-cerium-supported cobalt oxide low-temperature denitration catalyst. The catalyst can achieve a NO conversion rate of more than 99% at 125 ° C.
  • CN106215949A discloses a catalyst using multi-walled carbon nanotubes as a carrier, FeO X as a promoter, and MnO X as an active component.
  • the catalyst exhibits good denitration catalytic activity in a temperature range of 180-240 ° C.
  • CN105854932A discloses a catalyst using H-SAPO-34 as a carrier and a composite oxide of transition metals Cu and Mn as an active component.
  • the conversion rate of NO can reach more than 90% at 180-350 ° C.
  • CN104162349A discloses the use of a reaction between NO 2 and an ammonium salt deposited on the surface of a low-temperature denitration catalyst to effectively suppress the deposition of ammonium salts such as ammonium sulfate and ammonium sulfite caused by the reaction of SO 2 and ammonia gas, so as to suppress the SO 2
  • ammonium salts such as ammonium sulfate and ammonium sulfite caused by the reaction of SO 2 and ammonia gas
  • the purpose of the present invention is to provide a method for solving the poisoning of SO 2 in a low-temperature SCR denitration catalyst, which can effectively prolong the service life of the catalyst and reduce the operating cost of the SCR denitration system.
  • the method for solving the SO 2 poisoning of the low-temperature SCR denitration catalyst by the present invention is to use alkaline gas to react with metal sulfate deposited on the catalyst surface to replace the metal oxide and restore the catalyst activity; and use NO 2 or NO and O 2
  • the low-temperature decomposition of the ammonium salt deposited on the catalyst surface is avoided to prevent the catalyst from being covered; the surface of the catalyst metal sulfate and the generation and decomposition of the ammonium salt reach a dynamic equilibrium, so that the metal oxide active component in the SCR catalyst is neither lost nor degraded. It is covered with ammonium salt, thereby solving the problem of SO 2 poisoning of the low-temperature SCR de-selling catalyst.
  • the alkaline gas may be directly obtained by using ammonia gas, ammonia water, urea, or ammonium carbonate or ammonium bicarbonate.
  • the metal sulfate may be formed by reacting SO 2 in the flue gas with the active components of the catalyst; it may also be formed by reacting the SO 2 in the flue gas with a metal oxide adsorbed on the catalyst surface in the flue gas; or It is a metal sulfate directly adsorbed on the catalyst surface in the flue gas.
  • the ammonium salt may be formed by reacting SO 2 in the flue gas with an alkaline reducing agent; it may also be formed by reacting an alkaline reducing agent with a metal sulfate deposited on a catalyst surface.
  • the active component of the catalyst is usually one or more of Pt, Pd, Au, MnO X , CuO X , FeO X , CoO X , CeO 2 , CrO X , NiO X and mixed in any ratio.
  • the catalyst is usually one or more of traditional catalyst supports such as CeO 2 , TiO 2 , Al 2 O 3 , ZrO 2 , SiO 2 , attapulgite, activated carbon and the like, and the mixture is active in any proportion.
  • the mass percentage of the components is 0.1-30%.
  • the metal sulfate deposited on the catalyst surface undergoes a metathesis reaction with an alkaline reducing agent to replace the metal oxide, especially the active component of the catalyst that reacts with SO 2 in the flue gas, thereby restoring the activity of the catalyst;
  • Use NO 2 also can be NO + O 2
  • ammonium salts such as ammonium sulfate and ammonium bisulfate deposited on the catalyst surface, so that these ammonium salts are directly decomposed at low temperature, so that the catalyst surface is not covered by the ammonium salt;
  • the catalyst surface is The formation and decomposition of metal sulfates and ammonium salts such as ammonium sulfate and ammonium bisulfate reached a dynamic equilibrium, which successfully solved the problem of catalyst poisoning caused by SO 2 at low temperatures.
  • the method of the present invention is different from the conventional method of solving catalyst poisoning by preventing the formation of metal sulfates and ammonium salts on the catalyst surface.
  • the method of the present invention takes a different approach, using NO 2 (or NO + O 2 ) and introducing alkaline gas (such as NH 3 ).
  • alkaline gas such as NH 3 .
  • the formation and decomposition of ammonium salts and metal sulfates such as ammonium sulfate and ammonium hydrogen sulfate on the catalyst surface reach a dynamic equilibrium during the denitration process, which can restore the active components of the catalyst and avoid the ammonium salt on the catalyst surface.
  • the method of the present invention can also make full use of the residual metal oxide dust in the flue gas to transform them Effective catalyst active ingredient.
  • the method of the invention can not only regenerate the poisoned catalyst offline, but also solve the problem of SO 2 poisoning of low-temperature SCR denitration catalyst online, and can also be used to regenerate other catalysts poisoned by SO 2 , such as methane catalytic oxidation catalyst SO. 2 Regeneration after poisoning.
  • the invention is suitable for low-temperature SCR denitration treatment of flue gas generated in many fields such as coal-fired power plants, gas boilers, glass kiln, steel smelting, cement kiln, waste incineration and other fields.
  • FIG. 1 is a schematic diagram of a conversion process of a catalyst surface active component
  • FIG. 2 shows the anti-SO 2 poisoning and denitration performance of the catalysts of Examples 1, 2, and 3.
  • CeO 2 was used as a low-temperature denitration catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 5 vol% O 2 , Ar was an equilibrium gas, the gas flow rate was 500 ml / min, and the reaction temperature was 250 ° C.
  • the performance of the denitration test catalyst first increased and then decreased in the first 5 hours, and remained unchanged at 53% in the final 40 hours.
  • CeO 2 was used as a low-temperature denitration catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 5 vol% O 2 , Ar was an equilibrium gas, the gas flow rate was 500 ml / min, and the reaction temperature was 200 ° C. The performance of the denitration test catalyst remained unchanged at 38% over 40 hours.
  • MnO X / CeO 2 (MnO X loading amount is 3% by weight) was used as a catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 10 vol% O 2 , Ar was a balanced gas, a gas flow rate was 500 ml / min, and a reaction temperature was 200 ° C. The performance of the denitration test catalyst remained unchanged at 63% during 3 to 40 hours of SO 2 introduction .
  • CeO 2 was used as a low-temperature denitration catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , Ar was an equilibrium gas, the gas flow rate was 500 ml / min, and the reaction temperature was 250 ° C.
  • the denitration performance of the catalyst was less than 20% within 40 hours.
  • Pd / CeO 2 (Pd loading is 5 wt%) was used as a catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 5 vol% O 2 , Ar was a balanced gas, the gas flow rate was 500 ml / min, and the reaction temperature was 200 ° C. The performance of the denitration test catalyst remained unchanged at 70% over 40 hours.
  • Pt / CeO 2 (Pt loading amount is 3% by weight) was used as a catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 5 vol% O 2 , Ar was a balanced gas, a gas flow rate was 500 ml / min, and a reaction temperature was 200 ° C. The performance of the denitration test catalyst remained unchanged at 68% over 50 hours.
  • Pd-Pt / CeO 2 -Al 2 O 3 -SiO 2 Pd loading is 5 wt%, Pt loading is 5 wt%, CeO 2 is 30 wt%, Al 2 O 3 is 20 wt%, and SiO
  • the proportion of 2 is 40% by weight) as a catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 5 vol% O 2 , Ar is an equilibrium gas, the gas flow rate is 500 ml / min, and the reaction temperature is 200 ° C.
  • the performance of the denitration test catalyst remained unchanged at 74% over 70 hours.
  • CuO X / CeO 2 (CuO X loading amount is 15% by weight) was used as a catalyst, 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 10 vol% O 2 , Ar was a balanced gas, a gas flow rate was 500 ml / min, and a reaction temperature was 250 ° C. The performance of the denitration test catalyst remained unchanged at 60% within 50 hours.
  • FeO X / CeO 2 FeO X loading amount is 10% by weight
  • 800 ppm NO, 800 ppm NH 3 , 200 ppm SO 2 , 10 vol% O 2 , Ar as a balanced gas
  • a gas flow rate of 500 ml / min a reaction temperature of 250 ° C.
  • the performance of the denitration test catalyst remained unchanged at 56% over 40 hours.
  • MnO X -CrO X -NiO X / CeO 2 - activated carbon (MnO X loading of 6wt%, loading of CrO X is 9wt%, NiO X loading of 5wt%, the content of CeO 2 is 30wt%, the activated carbon an amount of 50wt%) as the catalyst, 800ppm NO, 800ppm NH 3, 200ppm SO 2, 10vol% O 2, Ar is a balance gas, a gas flow rate of 500ml / min, a reaction temperature of 220 °C. The performance of the denitration test catalyst remained unchanged at 68% during 3 to 60 hours of SO 2 introduction .
  • CeO 2 was used as a low-temperature denitration catalyst, 800 ppm NO, 800 ppm NH 3 , 400 ppm SO 2 , 1 vol% O 2 , Ar was an equilibrium gas, the gas flow rate was 500 ml / min, and the reaction temperature was 250 ° C. The initial denitration performance of the catalyst was 52%. After 10 hours of reaction, the catalyst was poisoned by SO 2 and the denitration performance decreased to 14%. Then, the NH 3 and SO 2 gases were turned off, the O 2 concentration was increased to 10%, and the gas decomposed by heating ammonium bicarbonate was passed into the catalyst and treated for 5 hours.
  • CeO 2 was used as a low-temperature denitration catalyst, 800 ppm NO, 800 ppm NH 3 , 400 ppm SO 2 , 3 vol% O 2 , Ar was an equilibrium gas, the gas flow rate was 500 ml / min, and the reaction temperature was 200 ° C. The initial denitration performance of the catalyst was 38%. After 10 hours of reaction, the catalyst SO 2 was poisoned and the denitration performance decreased to 10%. Then the NH 3 and SO 2 gases were turned off, the O 2 concentration was increased to 8%, and the gas decomposed by heating ammonium carbonate was passed into the catalyst, and treated for 8 hours.
  • MnO X / CeO 2 (MnO X loading amount is 3% by weight) as a catalyst, 800 ppm NO, 800 ppm NH 3 , 400 ppm SO 2 , 3 vol% O 2 , Ar as a balanced gas, a gas flow rate of 500 ml / min, and a reaction temperature of 200 ° C.
  • the initial denitration was measured at 63%. After 4 hours, the catalyst was poisoned and the efficiency dropped to 17%.
  • the SO 2 gas was then turned off, the O 2 concentration was increased to 10%, and the treatment was performed for 8 hours.
  • Pd / CeO 2 (5% by weight of Pd loading) was used as a catalyst, 800 ppm NO, 800 ppm NH 3 , 400 ppm SO 2 , 1 vol% O 2 , Ar was a balanced gas, the gas flow rate was 500 ml / min, and the reaction temperature was 200 ° C. The initial denitration measurement was 70%. After 4 hours, the catalyst was poisoned and the denitration efficiency decreased to 21%. The SO 2 gas was then turned off, the O 2 concentration was increased to 12%, and the treatment was performed for 8 hours.
  • the denitration performance was tested again at 800 ppm NO, 800 ppm NH 3 , 1 vol% O 2 , Ar as an equilibrium gas, a gas flow rate of 500 ml / min, and a reaction temperature of 200 ° C., and maintained at 68-71% within 60 hours.
  • Embodiment 16 is a diagrammatic representation of Embodiment 16:
  • Pd / CeO 2 (1% by weight of Pd) was used as a catalyst, 0.2% CH 4 , 6% O 2 , 93.8% N 2 , 10 ppm SO 2 , the total flow rate was 100 ml / min, and the reaction temperature was 450 ° C.
  • the initial methane oxidation efficiency was 85%, and after 9 hours, the methane oxidation efficiency decreased to 20%.
  • CH 4 and SO 2 were turned off and treated for 6 hours under the conditions of 800 ppm NO, 800 ppm NH 3 , 10 vol% O 2 and N 2 as an equilibrium gas. Tested again under the conditions of 0.2% CH 4 , 6% O 2 , 93.8% N 2 , the methane oxidation performance was maintained at 55-60% for 20 hours.
  • Pd / CeO 2 (3% by weight of Pd) was used as a catalyst, 0.2% CH 4 , 6% O 2 , 93.8% N 2 , 20 ppm SO 2 , the total flow rate was 100 ml / min, and the reaction temperature was 450 ° C.
  • the initial methane oxidation efficiency was 85%, and after 9 hours, the methane oxidation efficiency decreased to 50%.
  • CH 4 and SO 2 were turned off and treated for 6 hours under the conditions of 800 ppm NO, 800 ppm NH 3 , 10 vol% O 2 and N 2 as an equilibrium gas. Tested again under the conditions of 0.2% CH 4 , 6% O 2 , 93.8% N 2 , the methane oxidation performance was maintained at 94-98% over 40 hours.

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Abstract

一种解决低温SCR脱硝催化剂SO 2中毒的方法，利用碱性气体与沉积在催化剂表面的金属硫酸盐反应，置换出金属氧化物，恢复催化剂活性；并利用NO 2或NO及O 2使沉积在催化剂表面的铵盐分解，避免催化剂被覆盖；该方法既可离线使已中毒的催化剂再生，也可在线使得催化剂表面金属硫酸盐、及铵盐的生成和分解达到动态平衡，催化剂活性组分既不流失，也不被铵盐覆盖，达到低温SCR脱硝催化剂抗SO 2中毒的目的。该方法还可以用于其它被SO 2中毒的催化剂如甲烷催化氧化催化剂SO 2中毒后的再生。在线使用时该方法还可将烟气中的一些金属氧化物粉尘转变成催化剂的有效活性成分。该方法可有效延长催化剂的使用寿命，降低SCR系统的运行成本。

Description

一种解决低温SCR脱硝催化剂SO 2中毒的方法 技术领域
本发明属于能源与环境材料领域，特别涉及一种解决低温SCR脱硝催化剂SO 2中毒的方法。
背景技术
目前，我国大气污染问题非常严峻，主要是由于二氧化硫、氮氧化物、粉尘颗粒等污染性气体的超标排放。其中氮氧化物可直接刺激人体肺部，引起呼吸系统疾病，同时也是形成光化学烟雾和酸雨的一个重要原因。因此，控制并减少氮氧化物排放是保护大气环境的重要措施。为此，我国出台了严格的氮氧化物排放标准，其中北京要求全市新建锅炉执行30mg/m 3的排放限值，该标准限值已接近于目前全世界最严的锅炉排放标准。选择性催化还原技术(SCR)具有高效、经济、实用的特点，已经成为脱除氮氧化物的关键技术，在国际上得到了大量工业化应用，高效、高活性、长寿命催化剂的制备是该技术的核心。
目前，国内燃煤电厂已经普及了SCR脱硝设施，使燃煤电厂的氮氧化物排放得到了有效的控制。所采用的都是传统的(V 2O 5-WO 3(MoO 3)/TiO 2)高温脱硝催化剂，其工作温度在320-420℃。鉴于传统催化剂狭窄的工作温度区间，通用的SCR脱硝设施大都布置在除尘和脱硫设施之前，即安装在高灰段。由于烟气流速快并伴随大量粉尘，催化剂遭受严重冲刷，且粉尘中的碱金属氧化物、碱土金属氧化物、氧化砷等物质极易引起催化剂中毒，使催化剂使用寿命缩短，从而增加SCR脱硝技术的运行成本。因此，研究人员提出将SCR催化剂安装于除尘与脱硫装置之后。然而，在经过除尘与脱硫后，烟气温度偏低(<250℃)，传统的高温脱硝催化剂(V 2O 5-WO 3(MoO 3)/TiO 2)在此温度区间活性显著降低，因此，具有低温高活性的SCR催化剂成为近年的研究热点。例如，CN107252693A公开了一种以凹凸棒黏土为载体，负载的活性组分为γ-Fe 2O 3和MnO 2，最后包覆V 2O 5保护层的低温脱硝催化剂，该催化剂具有最高活性温度低、温度区间广、稳定性高的特点。CN106732799A公开了一种以金属有机配合物为载体，金属氧化物 MnO X为活性组分的催化剂，该催化剂具有优异的低温SCR催化活性、宽的操作窗口及高的稳定性。CN106732542A公开了一种片状二氧化锰/碳纤维低温脱硝催化剂，该催化剂在180℃可转化98％以上的氮氧化物。CN106391040A公开了一种以V 2O 5为催化剂，Fe 2O 3和CeO 2为助剂，微孔碳纤维为载体的催化剂，该催化剂在86-102℃可实现80％氮氧化物转化率，在120℃脱硝效率大于95％。CN106540710A公开了一种锰铈负载氧化钴低温脱硝催化剂，该催化剂在125℃可实现99％以上NO转化率。CN106215949A公开了一种以多壁碳纳米管为载体，FeO X为助催剂，MnO X为活性组分的催化剂，该催化剂在180-240℃的温度范围内都表现出很好的脱硝催化活性。CN105854932A公开了一种以H-SAPO-34为载体，过渡金属Cu和Mn的复合氧化物为活性组分的催化剂，在180-350℃内NO的转化率均可达到90％以上。CN104162349A公开了利用NO 2和低温脱硝催化剂表面沉积的铵盐之间的反应，有效抑制SO 2和氨气反应引起的硫酸铵、亚硫酸铵等铵盐在低温脱硝催化剂表面的沉积，达到抑制SO 2引起的低温SCR脱硝催化剂中毒的目的。
如上所述，大量的催化剂都显示了良好的低温脱硝性能，然而，低温下SO 2引起的催化剂的中毒，是一个世界性的难题，是目前困扰低温脱硝催化剂应用的关键。即使在经过脱硫装置后，烟气中残留的少量SO 2，一方面与还原剂氨气发生反应，生成硫酸铵盐，堵塞催化剂的孔洞并覆盖催化剂的活性位，降低催化剂的活性，另一方面SO 2与催化剂中的金属氧化物活性成分直接反应，生成金属硫酸盐，引起催化剂的SO 2中毒(RSC Adv.,2017,7,26226；Catalysis,2017,7,199)。鉴于此，只有解决低温脱硝催化剂的SO 2中毒问题才能实现低温脱硝催化剂的工业应用。
从大量文献来看，由于已经明确催化剂表面金属硫酸盐和硫酸铵盐的生成是低温SCR脱硝催化剂SO 2中毒的原因，因此，现有的研究主要是从防止催化剂表面这两种硫酸盐的生成入手。例如，利用CeO 2首先与SO 2反应生成硫酸铈，暂时保护活性成分MnO X不与SO 2反应，就可以短时间内抑制SO 2引起的催化剂中毒(RSC Adv.,2017,7,26226；Appl Catal B-Environ.,2014,148-149,582-588)。
而实际情况是，大多数的低温活性催化剂的催化性能足以催化SO 2氧化生成SO 3，因此，抑制催化剂表面硫酸盐的生成难以实现，从而催化剂的低温SO 2中 毒问题实质上没有得到解决。
发明内容
本发明的目的是提供一种解决低温SCR脱硝催化剂SO 2中毒的方法，该方法可以有效延长催化剂的使用寿命，降低SCR脱硝系统运行成本。
本发明的解决低温SCR脱硝催化剂SO 2中毒的方法，是利用碱性气体与沉积于催化剂表面的金属硫酸盐反应，以置换出金属氧化物，恢复催化剂活性；并利用NO 2或者NO及O 2使沉积于催化剂表面的铵盐低温分解，避免催化剂被覆盖；催化剂表面金属硫酸盐、以及铵盐的生成和分解达到动态平衡，使得SCR催化剂中金属氧化物活性组分既不流失，也不会被铵盐覆盖，从而解决低温SCR脱销催化剂SO 2中毒的问题。
上述技术方案中，所述的碱性气体可以直接使用氨气、氨水、尿素，也可以使用碳酸铵、碳酸氢铵分解得到。
所述的金属硫酸盐可以是烟气中的SO 2与催化剂的活性组分反应而生成；也可以是烟气中的SO 2与烟气中吸附在催化剂表面的金属氧化物反应而生成；或者是烟气中直接吸附在催化剂表面的金属硫酸盐。
所述的铵盐可以是烟气中的SO 2与碱性还原剂反应生成；也可以是由碱性还原剂与沉积于催化剂表面的金属硫酸盐反应生成。
所述的催化剂的活性成分通常为Pt、Pd、Au、MnO X、CuO X、FeO X、CoO X、CeO 2、CrO X、NiO X中的一种或几种以任意比例的混合。
所述的催化剂通常是以CeO 2、TiO 2、Al 2O 3、ZrO 2、SiO 2、凹凸棒土、活性炭等传统催化剂载体中的一种或几种以任意比例的混合为载体，且活性组分的质量百分含量为0.1-30％。
本发明中，催化剂表面沉积的金属硫酸盐与碱性还原剂发生复分解反应，置换出金属氧化物，尤其是与烟气中的SO 2反应的催化剂的活性组分，从而恢复催化剂的活性；此外利用NO 2(也可以是NO+O 2)，与催化剂表面沉积的硫酸铵、硫酸氢铵等铵盐反应，使这些铵盐直接低温分解，从而避免催化剂表面被铵盐覆盖；最终使催化剂表面金属硫酸盐及硫酸铵、硫酸氢铵等铵盐的生成与分解达到动态平衡，成功解决低温下SO 2引起的催化剂中毒的问题。
本发明的有益效果在于：
本发明方法与常规通过防止催化剂表面金属硫酸盐和铵盐的生成来解决催化剂中毒的方法不同，本发明方法另辟蹊径，利用NO 2(或者NO+O 2)及引入碱性气体(如NH 3)使催化剂表面硫酸铵、硫酸氢铵等铵盐及金属硫酸盐的生成与分解在脱硝过程中达到动态平衡，既可以恢复催化剂的活性组分，又可以避免催化剂表面铵盐的覆盖，两个过程相辅相成，从而达到低温脱硝催化剂抗SO 2中毒的目的，可以有效延长催化剂的使用寿命，降低SCR系统的运行成本，同时本发明方法还可以充分利用烟气中残留的金属氧化物粉尘，使它们转变成催化剂的有效活性成分。本发明的方法，既可以离线使已经中毒的催化剂再生，也可以在线解决低温SCR脱硝催化剂SO 2中毒的难题，还可以用于别的被SO 2中毒的催化剂的再生，例如甲烷催化氧化催化剂SO 2中毒后的再生。本发明适用于燃煤电厂、燃气锅炉、玻璃窑炉、钢铁冶炼、水泥窑、垃圾焚烧等众多领域产生的烟气的低温SCR脱硝处理。
附图说明
图1为催化剂表面活性组分的转化过程示意图；
图2为实施例1、2、3催化剂的抗SO 2中毒脱硝性能。
具体实施方式
以下结合附图和具体实施例对本发明做进一步说明，但并不因此将本发明限制在所述的实施例范围之内。
实施例1：
以CeO 2为低温脱硝催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，5vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度250℃。脱硝测试催化剂的性能在前5小时先上升后下降，最终40小时内保持在53％不变。
实施例2：
以CeO 2为低温脱硝催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，5vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。脱硝测试催化剂的性能在40小时内保持在38％不变。
实施例3：
以MnO X/CeO 2(MnO X负载量为3wt％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，10vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。脱硝测试催化剂的性能在SO 2通入3小时到40小时内保持在63％不变。
实施例4：
以CeO 2为低温脱硝催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，Ar为平衡气体，气体流速500ml/min，反应温度250℃。催化剂的脱硝性能在40小时内低于20％。
实施例5：
以Pd/CeO 2(Pd负载量为5wt％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，5vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。脱硝测试催化剂的性能在40小时内保持在70％不变。
实施例6：
以Pt/CeO 2(Pt负载量为3wt％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，5vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。脱硝测试催化剂的性能在50小时内保持在68％不变。
实施例7：
以Pd-Pt/CeO 2-Al 2O 3-SiO 2(Pd负载量为5wt％，Pt的负载量为5wt％，CeO 2的比例为30wt％，Al 2O 3的比例为20wt％，SiO 2的比例为40wt％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，5vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。脱硝测试催化剂的性能在70小时内保持在74％不变。
实施例8：
以CuO X/CeO 2(CuO X负载量为15wt％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，10vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度250℃。脱硝测试催化剂的性能在50小时内保持在60％不变。
实施例9：
以FeO X/CeO 2(FeO X负载量为10wt％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，10vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度250℃。 脱硝测试催化剂的性能在40小时内保持在56％不变。
实施例10：
以CuO X-MnO X/CeO 2-TiO 2(CuO X的负载量为10wt％，FeO X的负载量为5wt％，CeO 2的比例为40wt％，TiO 2的比例为45％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，10vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度250℃。脱硝测试催化剂的性能在40小时内保持在65％不变。
实施例11：
以MnO X-CrO X-NiO X/CeO 2-活性炭(MnO X负载量为6wt％，CrO X的负载量为9wt％，NiO X的负载量为5wt％,CeO 2的含量为30wt％，活性炭的含量为50wt％)为催化剂，800ppm NO，800ppm NH 3，200ppm SO 2，10vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度220℃。脱硝测试催化剂的性能在SO 2通入3小时到60小时内保持在68％不变。
实施例12：
以CeO 2为低温脱硝催化剂，800ppm NO，800ppm NH 3，400ppm SO 2，1vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度250℃。催化剂的初始脱硝性能为52％，经过10小时的反应后，催化剂SO 2中毒，脱硝性能下降到14％。然后把NH 3和SO 2气体关闭，把O 2浓度提高到10％，并把碳酸氢铵加热分解的气体通入到催化剂中，处理5小时。重新在800ppm NO，800ppm NH 3，1vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度250℃的条件下，测试脱硝性能，40小时内保持在53％不变。
实施例13：
以CeO 2为低温脱硝催化剂，800ppm NO，800ppm NH 3，400ppm SO 2，3vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。催化剂的初始脱硝性能为38％，经过10小时的反应后，催化剂SO 2中毒，脱硝性能下降到10％。然后把NH 3和SO 2气体关闭，把O 2浓度提高到8％，并把碳酸铵加热分解的气体通入到催化剂中，处理8小时。重新在800ppm NO，800ppm NH 3，3vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃的条件下，测试脱硝性能，40小时内保持在38-40％。
实施例14：
以MnO X/CeO 2(MnO X负载量为3wt％)为催化剂，800ppm NO，800ppm NH 3，400ppm SO 2，3vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。初始脱硝测为63％。经过4小时后，催化剂中毒，效率下降到17％。然后把SO 2气体关闭，把O 2浓度提高到10％，处理8小时。重新在800ppm NO，800ppm NH 3，3vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃的条件下，测试脱硝性能，40小时内保持在60-65％。
实施例15：
以Pd/CeO 2(Pd负载量为5wt％)为催化剂，800ppm NO，800ppm NH 3，400ppm SO 2，1vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃。初始脱硝测为70％，经过4小时后催化剂中毒，脱硝效率下降到21％。然后把SO 2气体关闭，把O 2浓度提高到12％，处理8小时。重新在800ppm NO，800ppm NH 3，1vol％O 2，Ar为平衡气体，气体流速500ml/min，反应温度200℃的条件下，测试脱硝性能，60小时内保持在68-71％。
实施例16：
以Pd/CeO 2(Pd负载量为1wt％)为催化剂，0.2％CH 4,6％O 2,93.8％N 2,10ppm SO 2，总流速100ml/min，反应温度450℃。初始甲烷氧化效率为85％，经过9小时后，甲烷氧化效率下降到20％。然后把CH 4,SO 2关闭，在800ppm NO，800ppm NH 3，10vol％O 2，N 2为平衡气体条件下处理6小时。重新在0.2％CH 4,6％O 2,93.8％N 2条件下测试，甲烷氧化性能在20小时保持在55-60％。
实施例17：
以Pd/CeO 2(Pd负载量为3wt％)为催化剂，0.2％CH 4,6％O 2,93.8％N 2,20ppm SO 2，总流速100ml/min，反应温度450℃。初始甲烷氧化效率为85％，经过9小时后，甲烷氧化效率下降到50％。然后把CH 4,SO 2关闭，在800ppm NO，800ppm NH 3，10vol％O 2，N 2为平衡气体条件下处理6小时。重新在0.2％CH 4,6％O 2,93.8％N 2条件下测试，甲烷氧化性能在40小时保持在94-98％。
上述具体实施方式仅是本发明的一些具体实施例子，本发明不限于以上实施例子，在本发明的精神和权利要求的保护范围内，对本发明作出的任何修改和改变，均应认为是落入本发明的保护范围。

Claims (8)

  1. 一种解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于：利用碱性气体与沉积在催化剂表面的金属硫酸盐反应，以置换出金属氧化物，恢复催化剂活性；并利用NO 2或者NO及O 2使沉积在催化剂表面的铵盐低温分解，避免催化剂被覆盖；催化剂表面金属硫酸盐、以及铵盐的生成和分解达到动态平衡，从而解决低温SCR脱硝催化剂SO 2中毒的问题。
  2. 根据权利要求1所述的解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于，所述的碱性气体为直接使用氨气、氨水、或尿素，或者使用碳酸铵、或碳酸氢铵分解得到。
  3. 根据权利要求1所述的解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于，所述的金属硫酸盐为烟气中的SO 2与催化剂的活性组分反应而生成；或者为烟气中的SO 2与烟气中吸附在催化剂表面的金属氧化物反应而生成；或者是烟气中吸附在催化剂表面的金属硫酸盐。
  4. 根据权利要求1所述的解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于，所述的铵盐为烟气中的SO 2与碱性气体反应生成；或者是由碱性气体与沉积在催化剂表面的金属硫酸盐反应而生成。
  5. 根据权利要求1所述的解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于，所述的催化剂的活性成分为Pt、Pd、Au、MnO X、CuO X、FeO X、CoO X、CeO 2、CrO X、NiO X中的一种或几种以任意比例的混合。
  6. 根据权利要求1所述的解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于，所述的催化剂是以CeO 2、TiO 2、Al 2O 3、ZrO 2、SiO 2、凹凸棒土、活性炭中的一种或几种以任意比例的混合为载体，且活性组分的质量百分含量为0.1-30％。
  7. 根据权利要求1所述的解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于，该方法采用离线方式使已经中毒的催化剂再生，或采用在线方式避免低温SCR脱硝催化剂SO 2中毒。
  8. 根据权利要求1所述的解决低温SCR脱硝催化剂SO 2中毒的方法，其特征在于，该方法还可以用于其他被SO 2中毒的催化剂的再生，如甲烷催化氧化催化剂SO 2中毒后的再生。
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CN112495368A (zh) * 2020-12-21 2021-03-16 中节能万润股份有限公司 一种高效脱硝活性催化剂的制备方法
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