Pr、La和Ce掺杂对钒钛基SCR催化剂性能影响的研究
发布时间：2018-08-02 14:07
【摘要】：氮氧化物(NOx)是大气主要污染物之一,当前,实现NOx控制排放的主流技术是选择性催化还原(SCR)技术,其中催化剂是核心,常用的SCR催化剂为V2O5-WO3(MoO3)/TiO2体系。在工程应用时,SCR催化剂运行一段时间后,催化活性逐渐下降,但是在非电力行业,由于催化剂的运行温度较低,催化剂表面会生成硫酸氢铵,附着于催化剂表面,堵塞催化剂活性位点,致使催化剂活性降低。同时,飞灰或烟气中的碱金属、砷等也是催化剂活性降低的原因。因此,探究不同金属杂质对钒钛催化剂NH3-SCR活性的影响以及催化剂上NH4HSO4的分解规律,对催化剂的工程应用及再生具有重要的意义。本论文主要以V2O5-MoO3/TiO2催化剂为研究对象,考察了Pr、La和Ce掺杂以及碱金属元素Cs和Rb,N族元素Bi和Sb修饰对钒钛催化剂性能的影响。探究了其催化反应机理,并采用TG-MS研究了NH4HSO4在Ce掺杂钒钛催化剂上的分解规律。主要研究结果如下：(1)利用溶胶-凝胶法和浸渍法制备了Pr、La和Ce掺杂的V2O5/TiO2和V2O5-MoO3/TiO2催化剂,并考察其NH3-SCR性能,实验结果表明：掺杂稀土元素Ce(与Pr和La相比)明显提高V2O5/TiO2催化剂的NH3-SCR活性；Pr掺杂的V2O5-MoO3/TiO2催化剂在220～400℃范围内具有良好的脱硝效率、N2选择性和较强的抗SO2和H2O性能；La掺杂和Ce掺杂,均可以提高V2O5-MoO3/TiO2催化剂的NH3-SCR反应活性,并且La和Ce的最佳掺杂量分别为4 wt%和10wt%。掺杂稀土元素(主要分析讨论了Pr和La)可以提高V2O5-MoO3/TiO2催化剂的比表面积、表面化学吸附氧物种浓度、桥式硝酸盐物种和Br(?)nsted酸位数量,从而促进了催化剂上NH3-SCR反应的进行。(2)采用浸渍法添加Pr对工业TiO2进行改性,制备了不同Pr掺杂量和V负载量的V2O5-MoO3/TiO2催化剂,实验结果表明：掺杂少量Pr可以提高3V6MoTi催化剂在低温(100～180℃)及高温(300～400℃)区间的NH3-SCR反应活性,其中Pr最佳掺杂量为1 wt%,在180℃时,IM-3V6MolPrTi催化剂上NO转化率达到了93%。随着V2O5负载量(0.3～3 wt%)的增加,V2O5-MoO3/l wt%Pr6O11-TiO2催化剂的活性随之提高。(3)采用浸渍法将Cs、Rb、Bi和Sb金属元素添加到钒钛催化剂中,并考察其NH3-SCR性能,活性结果表明：当添加少量Cs2O和Rb2O时,对3V6MoTi催化剂上NH3-SCR反应活性影响不大,但是随着Cs20和Rb2O负载量的增加,催化活性也随之降低；当催化剂中添加Sb2O5时,3V6MoTi催化剂在低温区的NH3-SCR反应活性降低,而在高温(350℃)的活性提高；当Bi205的负载量为0.1～0.5 wt%时,可以提高3V6MoTi催化剂的催化活性,但是随着Bi205的负载量的继续增加,催化活性也随之降低。(4)采用TG-MS考察了NH4HSO4在V2O5-MoO3/CeO2-TiO2催化剂上的分解规律,研究发现：在200℃前催化剂上部分NH4HSO4受热分解生成NH3和H20,而S02吸附在催化剂表面,样品表面部分S02在415℃左右脱附,并且当Ce02掺杂量的增加至10 wt%时,在高温区SO2的信号峰温度降低,出现在720℃附近。因此,掺杂Ce可以促进V2O5-MoO3/TiO2催化剂上的NH4HSO4分解,降低其分解温度。反应过程如下：
[Abstract]:Nitrogen oxide (NOx) is one of the main pollutants in the atmosphere. Currently, the mainstream technology to control NOx emission is selective catalytic reduction (SCR) technology, in which the catalyst is the core and the commonly used SCR catalyst is V2O5-WO3 (MoO3) /TiO2 system. In engineering application, the catalytic activity gradually decreases after the SCR catalyst has been running for a period of time, but it is not in power. Industry, due to the low operating temperature of the catalyst, the catalyst surface will produce ammonium hydrogen sulfate, attach to the surface of the catalyst, plug the active site of the catalyst, and reduce the activity of the catalyst. At the same time, the alkali metal in the fly ash or the flue gas and the arsenic are also the source of the reduction of the activity of the catalyst. Therefore, the study of different metal impurities on the vanadium and titanium catalyst NH3-SCR The effect of the activity and the decomposition law of NH4HSO4 on the catalyst have important significance for the engineering application and regeneration of the catalyst. This paper is mainly based on the V2O5-MoO3/TiO2 catalyst as the research object. The effects of Pr, La and Ce doping, the alkali metal elements Cs and Rb, the Bi and Sb modification of the N elements on the performance of the vanadium and titanium catalysts are investigated. The reaction mechanism was studied and the decomposition rules of NH4HSO4 on Ce Doped Vanadium and titanium catalysts were studied by TG-MS. The main results were as follows: (1) the V2O5/TiO2 and V2O5-MoO3/TiO2 catalysts doped with Pr, La and Ce were prepared by sol-gel method and impregnation method, and their NH3-SCR properties were investigated. The experimental results showed that doped rare earth elements Ce (Pr and La) The NH3-SCR activity of V2O5/TiO2 catalyst was obviously improved, and the V2O5-MoO3/TiO2 Catalyst Doped with Pr had good denitrification efficiency in the range of 220~400 C, N2 selectivity and strong resistance to SO2 and H2O; La doping and Ce doping could increase the NH3-SCR reaction activity of V2O5-MoO3/TiO2 catalyst, and the best doping amount of La and impurities could be obtained. 4 wt% and 10wt%. doped rare earth elements (mainly analysis and discussion of Pr and La) can improve the specific surface area of the V2O5-MoO3/TiO2 catalyst, the surface chemical adsorption oxygen species concentration, the bridge type nitrate species and the Br (?) nsted Acid Number, thus promoting the NH3-SCR reaction on the catalyst. (2) adding Pr to the industrial TiO2 with the impregnation method. The V2O5-MoO3/TiO2 catalyst with different Pr doping amount and V load was prepared. The experimental results showed that doping a small amount of Pr could improve the NH3-SCR reactivity of 3V6MoTi catalyst at low temperature (100~180 C) and high temperature (300~400 C), of which the optimum doping amount of Pr was 1 wt%, and the NO conversion rate on IM-3V6MolPrTi catalyst reached to 180. The activity of V2O5-MoO3/l wt%Pr6O11-TiO2 catalyst was increased with the increase of V2O5 load (0.3 ~ 3 wt%). (3) Cs, Rb, Bi and Sb metals were added to the vanadium and titanium catalyst by impregnation, and the properties of NH3-SCR were investigated. The activity results showed that when a small amount of Cs2O and Rb2O were added, the reaction activity on the catalyst was found. However, the catalytic activity decreased with the increase of the load of Cs20 and Rb2O. When Sb2O5 was added to the catalyst, the NH3-SCR reaction activity of 3V6MoTi catalyst decreased at low temperature and the activity at high temperature (350 C) increased. When the load of Bi205 was 0.1 to 0.5 wt%, the catalytic activity of 3V6MoTi catalyst could be improved, but the catalytic activity of 3V6MoTi catalyst could be improved. With the increasing of the load of Bi205, the catalytic activity also decreased. (4) the decomposition rule of NH4HSO4 on V2O5-MoO3/CeO2-TiO2 catalyst was investigated by TG-MS. It was found that the partial NH4HSO4 was decomposed into NH3 and H20 on the catalyst before 200 c, and S02 adsorbed on the surface of the catalyst, and the S02 at the sample surface was around 415. Desorption, and when the amount of Ce02 doping increases to 10 wt%, the signal peak temperature of SO2 in high temperature zone decreases, and occurs near 720 C. Therefore, doping Ce can promote NH4HSO4 decomposition on V2O5-MoO3/TiO2 catalyst and reduce the decomposition temperature. The reaction process is as follows:
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X701;O643.36
本文编号：2159681
[Abstract]:Nitrogen oxide (NOx) is one of the main pollutants in the atmosphere. Currently, the mainstream technology to control NOx emission is selective catalytic reduction (SCR) technology, in which the catalyst is the core and the commonly used SCR catalyst is V2O5-WO3 (MoO3) /TiO2 system. In engineering application, the catalytic activity gradually decreases after the SCR catalyst has been running for a period of time, but it is not in power. Industry, due to the low operating temperature of the catalyst, the catalyst surface will produce ammonium hydrogen sulfate, attach to the surface of the catalyst, plug the active site of the catalyst, and reduce the activity of the catalyst. At the same time, the alkali metal in the fly ash or the flue gas and the arsenic are also the source of the reduction of the activity of the catalyst. Therefore, the study of different metal impurities on the vanadium and titanium catalyst NH3-SCR The effect of the activity and the decomposition law of NH4HSO4 on the catalyst have important significance for the engineering application and regeneration of the catalyst. This paper is mainly based on the V2O5-MoO3/TiO2 catalyst as the research object. The effects of Pr, La and Ce doping, the alkali metal elements Cs and Rb, the Bi and Sb modification of the N elements on the performance of the vanadium and titanium catalysts are investigated. The reaction mechanism was studied and the decomposition rules of NH4HSO4 on Ce Doped Vanadium and titanium catalysts were studied by TG-MS. The main results were as follows: (1) the V2O5/TiO2 and V2O5-MoO3/TiO2 catalysts doped with Pr, La and Ce were prepared by sol-gel method and impregnation method, and their NH3-SCR properties were investigated. The experimental results showed that doped rare earth elements Ce (Pr and La) The NH3-SCR activity of V2O5/TiO2 catalyst was obviously improved, and the V2O5-MoO3/TiO2 Catalyst Doped with Pr had good denitrification efficiency in the range of 220~400 C, N2 selectivity and strong resistance to SO2 and H2O; La doping and Ce doping could increase the NH3-SCR reaction activity of V2O5-MoO3/TiO2 catalyst, and the best doping amount of La and impurities could be obtained. 4 wt% and 10wt%. doped rare earth elements (mainly analysis and discussion of Pr and La) can improve the specific surface area of the V2O5-MoO3/TiO2 catalyst, the surface chemical adsorption oxygen species concentration, the bridge type nitrate species and the Br (?) nsted Acid Number, thus promoting the NH3-SCR reaction on the catalyst. (2) adding Pr to the industrial TiO2 with the impregnation method. The V2O5-MoO3/TiO2 catalyst with different Pr doping amount and V load was prepared. The experimental results showed that doping a small amount of Pr could improve the NH3-SCR reactivity of 3V6MoTi catalyst at low temperature (100~180 C) and high temperature (300~400 C), of which the optimum doping amount of Pr was 1 wt%, and the NO conversion rate on IM-3V6MolPrTi catalyst reached to 180. The activity of V2O5-MoO3/l wt%Pr6O11-TiO2 catalyst was increased with the increase of V2O5 load (0.3 ~ 3 wt%). (3) Cs, Rb, Bi and Sb metals were added to the vanadium and titanium catalyst by impregnation, and the properties of NH3-SCR were investigated. The activity results showed that when a small amount of Cs2O and Rb2O were added, the reaction activity on the catalyst was found. However, the catalytic activity decreased with the increase of the load of Cs20 and Rb2O. When Sb2O5 was added to the catalyst, the NH3-SCR reaction activity of 3V6MoTi catalyst decreased at low temperature and the activity at high temperature (350 C) increased. When the load of Bi205 was 0.1 to 0.5 wt%, the catalytic activity of 3V6MoTi catalyst could be improved, but the catalytic activity of 3V6MoTi catalyst could be improved. With the increasing of the load of Bi205, the catalytic activity also decreased. (4) the decomposition rule of NH4HSO4 on V2O5-MoO3/CeO2-TiO2 catalyst was investigated by TG-MS. It was found that the partial NH4HSO4 was decomposed into NH3 and H20 on the catalyst before 200 c, and S02 adsorbed on the surface of the catalyst, and the S02 at the sample surface was around 415. Desorption, and when the amount of Ce02 doping increases to 10 wt%, the signal peak temperature of SO2 in high temperature zone decreases, and occurs near 720 C. Therefore, doping Ce can promote NH4HSO4 decomposition on V2O5-MoO3/TiO2 catalyst and reduce the decomposition temperature. The reaction process is as follows:
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X701;O643.36
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