CAS OpenIR
p型金属氧化物臭氧催化分解性能及抗湿性研究
巩书燕
Subtype博士
Thesis Advisor陈运法
2019-07-01
Degree Grantor中国科学院大学
Degree Discipline化学工程
Keywordp 型金属氧化物,臭氧,抗湿性,催化分解
Abstract

臭氧是重要的空气污染物之一,会对公众健康和生活环境产生不利影响。催化分解法是在低温下去除臭氧有效、经济的方法。催化材料的活性组分一般包括一些昂贵的贵金属和更常用的过渡金属氧化物。然而,通常使用的过渡金属氧化物在水蒸气存在情况下倾向于失活,这限制了其更广泛的应用。因此,现在仍然需要开发合成方法简单、成本低、具有高活性、高抗湿性的臭氧分解催化剂。p型金属氧化物已经被证实利于臭氧分解过程中中间产物的脱附,与n型金属氧化物相比具有更优异的臭氧催化去除效果。本论文制备了几种p型金属氧化物(镧铁基钙钛矿,镍氧化物,氧化亚铜及其衍生催化剂),并进行了臭氧催化分解性能测试。研究了催化剂物理化学性质与其催化活性之间的联系并对臭氧催化剂的抗湿性机理进行了探索。主要研究内容和结果如下:(1)钙钛矿LaFeO3基催化剂用于高效臭氧催化分解和抗湿性研究通过溶胶-凝胶法制备了化学计量比、非化学计量比和过渡金属(Mn,Ni)掺杂的LaFeO3催化剂,并进行臭氧催化分解性能测试。结果表明,常规过渡金属氧化物Fe2O3在高相对湿度(RH)90%情况下对200 ppm臭氧转化率仅为25%,而LaFeO3的转化率高达85%。此外,5% mol Ni掺杂的LaFeO3的抗湿性进一步增强,对于1000 ppm臭氧RH 90%时转化率为93%。表征结果表明,在高相对湿度下,水蒸气可以较容易地从这些钙钛矿材料中解吸。此外,原位拉曼光谱显示Fe2O3在高相对湿度下发生结构破坏,臭氧分解的中间产物O22-在Fe2O3表面聚集,导致其催化活性降低。而LaFeO3和LaFe0.95Ni0.05O3的钙钛矿结构在高相对湿度下既不发生变形也没有O22-在其表面积累,因而在高相对湿度的条件下仍然具有高效臭氧分解活性。(2)Ni/NiO异质催化剂用于高湿度下臭氧催化去除采用柠檬酸溶胶-凝胶法制备了纯NiO和Ni/NiO异质催化剂,在合成过程中可通过调节pH值控制Ni/NiO异质结构的组成。臭氧催化分解测试结果表明,在相对湿度较高的条件下,Ni/NiO异质结构对臭氧催化分解具有较高转化率。具体结果如下,经过8 h的测试,Ni/NiO异质催化剂在RH 90%的条件下对1000 ppm臭氧的转化率可高达98%, 这几乎是纯NiO催化效果的两倍。Ni/NiO异质催化剂对臭氧优异的催化性能及高抗湿性可以归因于金属Ni与NiO之间的相互作用,这可以调节催化剂的表面价态、还原性、氧迁移率和水的解吸行为。化学发光(CL)检测也提供了臭氧在干燥及潮湿条件下在催化剂上分解的一些动力学信息。探索性地制备了低压降、操作灵活的Ni/NiO泡沫整体式催化剂用来去除低浓度臭氧。(3)不同形貌和不同复合结构的Cu2O催化剂用于臭氧催化分解通过简单的液相还原路线合成了具有不同形貌及不同复合结构的氧化亚铜。臭氧催化分解测试表明,暴露(100)晶面的立方体Cu2O比暴露(111)晶面的八面体Cu2O具有更高的臭氧催化活性。为获得更高的臭氧催化活性,进一步制备了Cu2O-CuO-Cu(OH)2和Cu2O/rGO复合催化剂。Cu2O-CuO-Cu(OH)2结构的形成机制可以归结为形成过程中氧化刻蚀和酸性蚀刻的协同作用。得到的Cu2O-CuO-Cu(OH)2多级纳米结构对臭氧的分解效率高于纯八面体Cu2O,原因可能是由于其具有较强的电子接受能力和Cu+-Cu2+氧化还原对。原位合成的Cu2O/rGO复合催化剂与纯立方体Cu2O相比具有更高的臭氧分解性能。其优异的性能可以归因于在rGO上形成的具有高活性的超细氧化亚铜纳米颗粒(~ 3 nm),可以促进臭氧分解过程中电子密度转移和中间吸附氧的解吸。(4)不同尺寸立方体Cu2O用于臭氧催化分解及高效超细Cu2O的应用探索在常温下,采用简易的液相还原法制备了粒径范围为40 nm-1000 nm的立方体Cu2O。40 nm的立方体Cu2O对臭氧催化分解具有高的室温和低温活性、高抗湿性及长期稳定性,原因是由于其尺寸较小,臭氧分解过程中的中间吸附氧物种O22-易于从其表面解吸。对优选的小尺寸氧化亚铜进行放大生产,成功制备了产量可达20 g以上的超细氧化亚铜纳米颗粒,其对去除高浓度高湿度臭氧具有显著性能。测试8 h后,对3000 ppm臭氧在RH 90%条件下转化率仍可达到95%以上。最后,将这种高活性的超细氧化亚铜与铝蜂窝结合制成整体式催化剂,用来去除低浓度臭氧,具有一定的应用前景。;Ozone is recognized as one of the critical air pollutants and can bring out detrimental effects on public health and living environment. Catalytic decomposition is an efficient and economical approach to remove ozone at low temperature. The active components of catalytic materials include some costly noble metals and some more commonly used transition metal oxides. However, the generally used transition metal oxides tend to be inactivated in the presence of water vapor, which limits their extensively application. Therefore, it is still necessary to explore ozone decomposition catalysts with facile synthesis method, low cost, highly active and high humidity resistance. P type metal oxides have been proved to facilitate the desorption of intermediates during ozone decomposition, resulting in superior catalytic removal performance of ozone compared with n type metal oxides.In this dissertation, several p type metal oxides (LaFe-based perovskite, nickel oxide, cuprous oxide and their derived catalysts) are successfully prepared and tested for ozone decomposition. The connection between inherent physical-chemical properties and catalytic capability are investigated. Specifically, some works have been done to explore humidity resistance mechanism. The main contents and results are listed below:(1) Perovskite LaFeO3 based catalysts for efficient ozone catalytic decomposition and humidity resistance studyStoichiometric, nonstoichiometric and transition metal (Mn, Ni) doped LaFeO3 are prepared through sol-gel method and tested for ozone decomposition. Conversion is only 25% for 200 ppm ozone over conventional transition metal oxide Fe2O3 at high relative humidity (RH) 90%, however, ozone conversion is still 85% over LaFeO3. Furthermore, 5% mol Ni doped LaFeO3 further enhances humidity resistance with 93% conversion efficiency for 1000 ppm O3 at RH 90%. Characterization results suggest that water vapor can desorb easier form these perovskite materials at high RH. In addition, in-situ Raman spectra reveal that Fe2O3 becomes disordered in O3 decomposition process at high RH and intermediate O22- gathers at Fe2O3 surface, leading depression of catalytic activity. In contrast, LaFeO3 and LaFe0.95Ni0.05O3 show neither deformation nor O22- accumulation at high RH, which is responsible for its strong activity. (2) Heterostructured Ni/NiO composite for ozone catalytic removal under high humidityPure NiO and Ni/NiO heterogeneous catalysts are simply synthesized using citric sol-gel method, the Ni/NiO heterogeneous structure can be adjusted by pH value in synthesis process. Ozone catalytic decomposition results show that Ni/NiO heterogeneous structure could promote ozone conversion at high relative humidity levels. Specificly, the conversion of 1000 ppm ozone over Ni/NiO composite could be as high as 98% at RH 90% after 8 h test,which is almost twice that of pure NiO. The excellent performance and high humidity resistance of Ni/NiO can be ascribed to the interaction between the metallic Ni and NiO, which could modify the surface valence, reducibility, oxygen mobility and desorption behavior of water on its surface. Chemiluminescence (CL) is used to supply some kinetic information of ozone decomposition over catalyst in dry and humid conditions. Ni/NiO foam monolithic catalyst with low pressure drop and flexible operation for ozone decomposition is fabricated to eliminate low-concentration ozone, which is an exploratory work.(3) Cu2O with different morphologies and different compositions for ozone catalytic decompositionCu2O with different shapes and different compositions are synthesized through simple reductive solution chemistry route. Ozone decomposition test shows that (100) plane exposed cubic Cu2O exhibits higher catalytic activity than (111) plane exposed octahedral Cu2O. Cu2O-CuO-Cu(OH)2 and Cu2O/rGO composite catalysts are further tailored to obtain higher ozone catalytic activity. The structure formation mechanism of Cu2O-CuO-Cu(OH)2 could be attributed to the synergistic reaction of the oxidation etching and acidic etching. The obtained Cu2O-CuO-Cu(OH)2 hierarchical nanostructure exhibits higher ozone decomposition efficiency than pure octahedral Cu2O. The excellent performance can be contributed to the stronger electron acceptance property and Cu+-Cu2+ redox couple. In-situ synthesized Cu2O/rGO exhibits much better performance for ozone decomposition than pure cubic Cu2O. The high performance can be attributed to the highly active ultrafine Cu2O nanoparticles (~3 nm) heterogeneously nucleated on rGO, which can promote electron density transfer and desorption of intermediate oxygen species during ozone decomposition process.(4) Cubic Cu2O with different sizes for ozone decomposition and application exploration of highly efficient ultra-fine Cu2OCubic Cu2O with particle size ranging from 40 nm to 1000 nm are synthesized by facile reduction method in aqueous solution at ambient condition. 40 nm cubic Cu2O exhibits high room and low temperature activity, high moisture resistance and long-time stability for ozone decomposition due to the easy desorption of intermediate O22- from the surface of cubic Cu2O with small size. Scale up production of the preferred Cu2O with small size, a large-scale of fine Cu2O nanoparticles with a production of above 20 grams is achieved and the obtained Cu2O with several nanometers exhibits significant performance for removing high concentration and high humidity ozone. The ozone conversion efficiency is still above 95% for 3000 ppm ozone at RH 90% after 8 h running. Finally, the highly active Cu2O combined with Al honeycomb is used as monolithic catalyst to eliminate low level ozone, which shows great potential for applications. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/40645
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
巩书燕. p型金属氧化物臭氧催化分解性能及抗湿性研究[D]. 中国科学院大学,2019.
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