【作者】 何勇；

【导师】 童志权；

【作者基本信息】 湘潭大学 ， 环境工程， 2009， 硕士

【摘要】 目前,氨选择性催化还原（Selective Catalytic Reduction, NH3-SCR）技术是火电厂等固定源烟气脱硝的主流技术。研发具有高活性的低温SCR催化剂有利于将脱硝装置置于电除尘器之后,避免商用催化剂V2O5/TiO₂或V₂O₅-WO₃/TiO₂由于高温（350℃以上）、高尘区操作所必需的烟气预热能耗,缓解催化剂的堵塞、磨损和毒化,延长催化剂寿命,降低脱硝成本;且便于与我国现有锅炉系统匹配。另一方面,烟气NOx中90%⁹5%为NO,NO除生成络合物外,无论在水中或碱液中都不被吸收。为了有效地吸收NOx,需寻找一种有效的催化剂将烟气中的NO部分地氧化为NO₂,使NOx氧化度达到50%～60%,再用湿法脱硫的吸收剂吸收,实现湿法一步同时脱硫脱硝。若能达到此目的,将是最具竞争力的硫、硝同脱技术。本文采用共沉淀法制备TiO₂-SiO₂复合载体（TS）,用浸渍法负载CuSO₄和CeO₂,制备了CuSO₄–CeO₂/TS催化剂应用于NOx的催化处理,从选择性催化还原和选择性催化氧化两个角度进行了系统研究。在NOx的氨选择性催化还原研究中,在制得最优催化剂的基础上,考察了各种操作条件以及H₂O和SO₂对CuSO₄-CeO₂/TS催化剂NH3低温选择性催化还原NOx活性的影响。结果表明,在O₂浓度为4%（?） , NO浓度1,000×10-6（?） ,氨氮比NH3/NOx=1.1 ,GHSV=5,000 h-1条件下,当反应温度低于240℃时,水蒸汽（10%, ?）在一定程度上降低了催化活性;当反应温度超过240℃时,这种影响可以完全消除。在单独抗SO₂（350×10?6, ?）试验中,CuSO₄-CeO₂/TS催化剂的活性不仅没有降低,反而从97.9%增加到了99.2%。在同时存在H₂O和SO₂条件下,35h内的催化活性始终保持在95%左右的高水平,这是目前文献报道中同时抗高浓度SO₂和高浓度H₂O毒化能力最强的催化剂。经过51h同时抗SO₂、H₂O之后由于SCR反应中缓慢生成的硫酸铵盐堵塞催化剂微孔、覆盖催化剂表面活性位,以及活性组分CeO₂被缓慢硫酸盐化,导致催化剂逐渐失活。中毒催化剂在350℃下活化热处理后活性基本没有恢复,400℃下活化热处理后活性反而有所下降。在NO的选择性催化氧化研究中,考察了温度、空速、NO进口浓度和O₂浓度等因素对NO氧化活性的影响,结果显示,在进口NO浓度800×10-6（?）、O₂浓度8%（?）,空速为5,000h-1和300³50℃条件下,NO氧化活性可维持在55%左右,能满足高效液体吸收的氧化度要求。350℃下,单独通入10% （?）的水,由于H₂O与NO分子的竞争吸附,活性急剧下降;同时通入10% （?）的H₂O和200×10-6（?）的SO₂后,因CeO₂被硫酸盐化和铅室反应导致NO氧化率迅速下降。在以往国内外SCR和SCO催化剂研究中,都没有见到与CuSO₄-CeO₂/TS组成相同催化剂的报道。更多还原

【Abstract】 At present, selective catalytic reduction （SCR） technology with ammonia has become the best technique in the flue gas De-NOx of thermal power plants and other stationary sources for its mature and highly efficient. However, presently commercial SCR catalyst V2O5/TiO₂ or V2O5-WO3/TiO₂ must be operated at above 350℃. Researching and developing low-temperature catalysts with high activity can make the SCR unit followed by the electrostatic precipitator, which can greatly depress the operation cost and prolong the catalyst life. This disposal avoids flue gas reheating, which is necessary for the commercial catalyst, and decreases the jam, abrasion and poison on the catalyst. Besides, the low-temperature SCR technology can match the existing boiler system without impact on the other related devices. On the other hand, 90%⁹5% of NOx is NO in flue gas, NO can not be absorbed, either in water or alkali solution except for generation of complex. An effective catalyst for the flue gas in part of the NO oxidation to NO₂ is needed in order to absorb the NOx effectively. When NO was oxidized into NO₂, and enhance the NO₂/NOx between 50%⁶0%, the NOx after oxidation is adsorbed by desulfurizer. By this processing technique, we can realize desulfurization and denitration simultaneously. The technique will be the most competitive simultaneously desulfurization and denitration method.In this work, TiO₂-SiO₂ composite support （TS） was prepared by coprecipitation method. CuSO₄–CeO₂/TS catalyst was prepared and applied for SCR of NOx with ammonia as well as for selective catalytic oxidation （SCO） of NO in the presence of excessive oxygen at different temperatures.For the SCR of NOx with ammonia, the effects of H₂O and SO₂ as well as a variety of operating conditions on the catalyst were studied on the base of optimized catalyst. The results showed that H₂O （10%, ?） had not negative impact on the activity when the SCR reaction temperature was above 240℃, in the presence of 4% O₂, NO （ 1,000×10-6, ?）, molar ratio of NH3/ NOx =1.1 GHSV=5,000 h-1. In the test of anti- SO₂ （350×10?6, ?） separately, the activity of CuSO₄-CeO₂/TS catalyst not only did not reduce, but also increased from 97.9% to 99.2%. In addition, as the SCR reaction proceeded in the presence of H₂O and SO₂, the catalytic activity remained at a high level of around 95% within 35h. which was the strongest catalyst of anti-high concentrations of SO₂ and H₂O poison simultaneously to the best of our knowledge. The catalyst was deactivated gradually, in the presence of H₂O and SO₂ for 51h, because of formation of ammonium sulfate and sulfation of CeO₂. There was no resumption of activity after heat treatment at 350℃, and activity of the catalyst declined further after heat treatment at 400℃.For the SCO of NO in this work, the effects of reaction temperature, space velocity, NO inlet concentration and O₂ concentration were studied over the catalyst. The results showed that about 55% NO oxidation activity could be maintained over CuSO₄?CeO₂/TS catalyst between 300³50℃with space velocity of 5000 h?1, NO inlet concentration of 800×10-6（?） and O₂ concentration of 8%（?）,which could meet the oxidation degree demands of high-performance liquid absorption. Activity declined sharply in the presence of H₂O （10%, ?） at 350℃, because of the competitive adsorption of H₂O and NO molecules. when H₂O （10%, ?） and SO₂ （200×10?6, ?） were added to the reactants, the oxidation rate of NO declined rapidly, which was due to sulfation of CeO₂ and Lead chamber reaction.更多还原