天然沸石负载Pt催化剂的HCHO室温催化氧化研究

发布时间：2018-01-02 21:05

  本文关键词：天然沸石负载Pt催化剂的HCHO室温催化氧化研究　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

  更多相关文章： 贵金属催化剂 Pt 酸脱铝 天然丝光沸石 甲醛催化氧化 碱金属

【摘要】：作为重要的室内空气污染源之一,甲醛的脱除研究一直备受关注。在植物净化、化学吸附、催化氧化等甲醛脱除方法中,催化氧化法由于其具有能耗低、寿命长、无二次污染等特点而更受研究者的关注。根据近十年来甲醛催化氧化的相关研究,贵金属催化剂在甲醛的低温催化氧化方面具有特别的优势。通过对比,贵金属Pt又在众多贵金属中脱颖而出,成为甲醛室温催化氧化的研究重点。本文以天然丝光沸石为载体,成功合成了可以在室温下实现HCHO完全催化氧化的Pt/MORn系列催化剂。首先从载体入手,研究天然丝光沸石的预处理对催化活性的影响。使用到的预处理方式为酸处理、碱处理和离子交换处理。综合对比研究发现,酸处理后的催化剂催化活性最好,碱处理次之,离子交换处理效果最不明显。不同浓度和步骤的酸处理对沸石的除杂和脱铝程度呈规律性变化,但是当酸处理达到一定程度后,其对催化活性的促进作用会明显降低,综合对比后认为6M硝酸处理为最佳酸处理方式;碱处理由于引入了碱金属离子和羟基,对活性也有较大提高,但是由于其除杂效果较差、不能实现脱铝和提高比表面积,因此其催化活性比酸处理后的催化剂低;天然丝光沸石经离子交换处理后负载Pt合成的催化剂对甲醛的室温催化氧化几乎没有效果,将酸处理后的沸石进行离子交换也不能进一步提高其催化活性。除了载体效应的研究,本论文中还探讨了贵金属Pt的负载量、合成过程中的煅烧温度以及不同Na+添加量、不同Na源对催化剂活性的影响。研究表明,以经过6M硝酸处理后的天然丝光沸石作为载体的条件下,Pt负载量在0.1-2.0wt.%区间内的最佳负载量为0.5 wt.%;煅烧温度在200-500 ℃范围内对催化活性的影响较小;分别采用NaOH和Na2C03作为钠添加剂对Pt/MORn催化剂的作用呈现出相似的趋势,NaOH额外引入羟基对催化剂活性并无明显提升;Na添加量对催化剂活性的影响与文献中不完全一致,本研究中Na添加量为0.5 wt.%时,对催化剂活性表现出抑制作用;当Na添加量进一步增加,催化剂活性会不断提高,在添加量为2.0wt.%时的室温甲醛转化率超过95%。
[Abstract]:As one of the most important indoor air pollution sources, formaldehyde removal has attracted much attention. In plant purification, chemical adsorption, catalytic oxidation and other formaldehyde removal methods, catalytic oxidation has low energy consumption. Long life, no secondary pollution and other characteristics have attracted more attention of researchers. According to the research of catalytic oxidation of formaldehyde in recent ten years. Precious metal catalysts have a special advantage in the low-temperature catalytic oxidation of formaldehyde. Through comparison, the noble metal Pt stands out among many precious metals. In this paper, natural mordenite was used as the carrier. A series of Pt/MORn catalysts which can realize the complete catalytic oxidation of HCHO at room temperature have been successfully synthesized. The effects of pretreatment of natural mordenite on catalytic activity were studied. The pretreatment methods were acid treatment, alkali treatment and ion exchange treatment. The comprehensive comparative study showed that the catalyst with acid treatment had the best catalytic activity. After alkali treatment, the effect of ion exchange treatment was the least obvious. The degree of impurity removal and de-aluminization of zeolite changed regularly with different concentration and step of acid treatment, but when the acid treatment reached a certain degree. The promoting effect of 6M nitric acid treatment on the catalytic activity will be obviously reduced, and it is considered that 6M nitric acid treatment is the best way of acid treatment. The alkali treatment can improve the activity greatly because of the introduction of alkali metal ions and hydroxyl groups, but because of its poor impurity removal effect, it can not achieve dealumination and improve the specific surface area. Therefore, its catalytic activity is lower than that after acid treatment. The catalyst supported on Pt synthesis after ion exchange treatment has little effect on the catalytic oxidation of formaldehyde at room temperature. In addition to the study of carrier effect, the loading amount of noble metal Pt was also discussed in this paper. The effects of calcination temperature, Na addition amount and Na source on the activity of the catalyst were studied. The results showed that the natural mordenite treated with 6M nitric acid was used as the carrier. The optimum loading amount of Pt in the range of 0.1-2.0wt.% is 0.5 wt.; The calcination temperature has little effect on the catalytic activity in the range of 200-500 鈩，

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