【作者】 章凌；

【导师】 肖丰收； 孟祥举；

【作者基本信息】 浙江大学 ， 化学， 2017， 硕士

【摘要】 作为备受关注的主要室内空气污染物,甲醛(HCHO)会对人类身体健康与环境造成巨大破坏。在消除HCHO的众多方法中,室温完全催化氧化法被认为是最有效的方法,而催化剂的设计和制备是该法的关键。由于沸石分子筛负载Pt催化剂同时具有分子筛和贵金属组分,它具备二者的组合优势,因此正逐渐成为室温完全催化氧化HCHO的最有潜力的催化剂之一。目前已经有相关沸石分子筛负载Pt催化剂低温完全催化氧化HCHO的探索工作,但在室温下完全催化氧化HCHO依然是一个巨大的挑战。本论文主要开展了一系列沸石分子筛负载Pt催化剂用于室温完全催化氧化HCHO的活性研究,着重考察了分子筛载体的酸密度、骨架外阳离子种类和硅铝比等因素对催化剂催化活性的影响。本文有四章,第一章为前言,第二章为实验部分,研究结果主要在第三与第四章。在第三章中,我们将富铝H-Beta分子筛负载Pt催化剂(Pt/H-Beta-SDS)与传统H-Beta负载Pt催化剂(Pt/H-Beta-TEA)的活性作相比,结果前者表现出更为优异的HCHO催化氧化性能。Pt/H-Beta-SDS催化剂在室温条件下(25℃)实现对400 ppm HCHO的完全催化氧化,而在同样条件下,Pt/H-Beta-TEA催化剂则需45 ℃。Pt/H-Beta-SDS如此高的HCHO室温催化活性归因于活性组分Pt具有更高的分散度和分子筛载体更加优异的HCHO吸附能力。同时,我们也对比了Pt/H-Beta-SDS, Pt/Na-Beta-SDS和Pt/K-Beta-SDS催化剂的催化性能,结果发现Pt/H-Beta-SDS的催化活性远远高于后二者,我们通过反应拆分的手段证明了Na型和K型催化剂不利于HCHO氧化为甲酸的反应步骤,从而影响整个反应活性。在第四章中,我们通过制备了一系列不同硅铝比(60,100,300,∞)与不同阳离子(H+,Na+,K+)的ZSM-5沸石分子筛,然后通过等体积浸渍法制备了上述分子筛负载1%Pt催化剂。反应结果表明,Pt/H-ZSM-5催化剂的催化活性远远高于Pt/Na-ZSM-5和Pt/K-ZSM-5催化剂,与第三章中结论一致。同时,分子筛硅铝比同样也影响着催化剂的催化活性,Pt/ZSM-5-Si催化剂具有最为优异的室温催化氧化甲醛的活性,我们把原因归结于分子筛硅铝比升高,导致催化剂疏水性也逐渐提高,这一方面增强了催化剂对HCHO的吸附能力。另一方面使得H20能更快地从催化中心脱附,从而促进反应的进行。最后,反应气氛围中引入水汽或者改变空速反应条件对上述催化剂的活性没有显著影响,而且更为重要的是催化剂的活性稳定,寿命优异。这表明这类催化剂具有较好的工业应用前景。更多还原

【Abstract】 Formaldehyde (HCHO) is one of the major components in indoor air pollutants, which are great threats to the human health and also the environment. Up to now, many techniques for the removing of HCHO have been well developed. Among them, completely catalytic oxidation HCHO at room temperature has been identified as one of the most efficient routes. Zeolite supported Pt has been proved to be one of the superior catalysts for catalytic removal of HCHO, due to the combination of the advantages of both noble metal and zeolite. Recently, it has been reported that zeolite-supported Pt catalysts are active for HCHO oxidation at low temperatures, but they are still unable to completely oxidized HCHO at room temperature. In this dissertation, a series of zeolite supported Pt catalysts have been successfully synthesized and tested in the catalytic oxidation HCHO at room temperature. What’s more, the influences of zeolite’s cation, Si/Al ratio and acidic density on the performance of catalysts have been carefully studied.This thesis mainly include introduction (chapter 1), experimental section (chapter 2), and results and discussion (chapters 3 and 4). In chapter 3, H-form of Al-rich Beta supported Pt catalyst (Pt/H-Beta-SDS) is very active for catalytic oxidation of HCHO, giving full conversion at room temperature (25 ℃), which is much more active than a conventional H-Beta-supported Pt catalyst (Pt/H-Beta-TEA), giving the temperature for complete oxidation of HCHO at 45 ℃. The higher activity of the Pt/H-Beta-SDS catalyst than that of the Pt/H-Beta-TEA catalyst is related to the advantages of higher Pt dispersion and higher adsorption of HCHO. Meanwhile, Pt/H-Beta-SDS also exhibits much higher catalytic activity than the Pt/Na-Beta-SDS and Pt/K-Beta-SDS catalysts. These results could be positively related to that Na-type and K-type catalysts would inhibit the conversion of formaldehyde into formate.In chapter 4, a series of ZSM-5 zeolite with different Si/Al ratios (60,100,300, and oo) and various cations (H*, Na+, and K*) supported Pt catalysts have been prepared by three different way:hydrothermal synthesis, ion-exchange, and impregnation. And we found out that both the zeolite’s cation and Si/Al ratio strongly influence the activity of Pt/ZSM-5. Catalytic tests in HCHO catalytic oxidation show that Pt/ZSM-5-Si exhibits the highest activity, which proves that higher Si/Al ratios in the zeolites are helpful for improvement of zeolite hydrophobicity, which could enhance the adsorption ability of HCHO and accelerate the reaction product of water away from the catalytic system.In addition, these catalysts are very active and stable, which would be potentially useful for the removal of HCHO in the future.更多还原