柴油烟气净化的四效催化剂研究

发布时间：2018-03-16 03:19

  本文选题：柴油烟气　切入点：烟气净化　出处：《江苏科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：柴油烟气中CO、CxHy、PM和NOx是环境污染的元凶巨恶,催化氧化—还原后处理技术是净化柴油烟气最行之有效的方法。研究价格低廉、催化效率好的催化剂刻不容缓。钙钛矿型四效催化剂对净化柴油烟气的催化效率高,尤其是La-K-Co-Mn-O型催化剂。本文利用化学裁剪法以K离子部分取代钙钛矿LaCoO3 A位上的La离子,以Mn(Mn2+、Mn3+、Mn4+、Mn5+、Mn6+、Mn7+)部分取代LaCoO3 B位上的Co(Co2+、Co3+、Co4+),采用溶胶-凝胶法、柠檬酸络合法及溶液燃烧法合成具有钙钛矿结构的四效催化剂活性组分La1-xKxCo1-yMnyO3。采用溶液浸渍法或悬浊液淤浆法将La1-xKx Co1-yMnyO3浸渍到蜂窝陶瓷载体上,得到钙钛矿型催化剂。通过自制的性能评价装置及柴油机车尾气的模拟烟气进行脱除CO、CxHy、PM和NOx的性能试验,并通过BET、XRD、SEM、EDS等表征方法进行分析。研究结果表明:选取La0.8K0.2Co0.8Mn0.2O3和La0.8K0.2Co0.7Mn0.3O3为研究对象,根据催化氧化还原CO、CxHy、PM和NOx转化率的大小,活性组分的煅烧合成温度排序为:750℃800℃700℃900℃600℃;750℃煅烧6 h合成的催化剂催化氧化CO、CxHy、PM的转化率分别为99.9%、95.4%、90.3%,PM的起燃温度为225℃,最大转化率温度为318℃,NOx的最大转化率为73.6%。以750℃煅烧6 h合成的La0.8K0.2Co0.7Mn0.3O3为对象,溶液浸渍法制备的催化剂比悬浊液淤浆法负载的催化效果好。中间层γ-Al2O3的粘度强度和涂覆量影响催化剂活性组分浸渍量和使用寿命。活性组分含量决定着催化剂的催化性能。试验结果得出:溶液浸渍法、γ-Al2O3含量为载体质量的10%、活性组分含量为载体质量的10%是整体式催化剂最优的选择。空燃比决定CO、CxHy、PM与NOx相互反应的彻底性,实验室模拟试验表明:气体总体积4%的氧对同时去除CO、CxHy、PM和NOx最为合适。x=0.1、0.2、0.3、0.4与y=0.1、0.2、0.3、0.4的La1-x KxCo1-yMnyO3均具有钙钛矿结构晶体的特征峰,K+部分取代LaCoO3的La3+后,部分Co3+向Co4+转变,同时存在Co3+与Co4+,Co4+离子半径小于Co3+,晶格出现细微畸变。Mn取代LaCoO3的Co后,Mn3+的离子半径小于Co3+,也出现晶型畸变。当K和Mn同时取代部分La和Co时,畸变程度增加。少量的晶格畸变使用空隙增大,结构空位及空位氧数量增多,比表面积增大,有利于四效脱除CO、CxHy、PM和NOx。当X=0.2时,催化氧化PM的效果最好,达到93.8%;当y=0.3时,催化氧化还原CO、CxHy、NOx的效果最佳,分别达到100%、99.9%、75.8%。从热力学角度看,CO、CxHy、PM和NOx相互之间反应的吉布斯自由能变量均小于零,说明CO、CxHy、PM均可以还原NOx,但受反应温度的影响大;La0.8K0.2Co0.8Mn0.2O3使得催化氧化—还原CO、CxHy、PM和NOx的反应更易进行,吉布斯自由能变量更低。从动力学角度看,La0.8K0.2Co0.7Mn0.3O3可加快CO、CxHy、PM和NOx被催化氧化还原的速率,四效催化效率提高。
[Abstract]:COC x Hyp PM and NOx in diesel smoke are the most serious environmental pollution. Catalytic oxidation-reduction post-treatment technology is the most effective method for purifying diesel smoke. The catalyst with good catalytic efficiency is urgent. The catalytic efficiency of perovskite-type four-way catalyst for purifying diesel smoke is high, especially for La-K-Co-Mn-O type catalyst. In this paper, K ion is used to partially replace La ion on LaCoO3 A site of perovskite by chemical tailoring method. The Co(Co2 Co _ 3 / Co _ 4 on the LaCoO3 B site was partially replaced by Mn(Mn2 Mn-3 / mn _ 4 / mn _ 5 and mn _ 6 / mn _ 7, and the sol-gel method was used to replace the Co _ (3) and Co _ (4) on the LaCoO3 B site. The active component La1-xKxCo1-yMnyO3 with perovskite structure was synthesized by citric acid complexation method and solution combustion method. La1-xKxCo1-yMnyO3 was impregnated on honeycomb ceramic carrier by solution impregnation or suspension slurry method. Perovskite type catalyst was obtained. The performance test of removing COC x Hyp PM and NOx from diesel engine exhaust gas was carried out by self-made performance evaluation device and simulated flue gas of diesel locomotive tail gas. The results showed that La0.8K0.2Co0.8Mn0.2O3 and La0.8K0.2Co0.7Mn0.3O3 were selected as research objects, and the conversion rates of CX Hydro PM and NOx were determined according to the catalytic redox activity. The order of calcination synthesis temperature of active components is: 1: 750 鈩，

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