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题名: 不同载体Pd 基催化剂催化氧化邻-二甲苯研究
作者: 胡 凌 霄1
学位类别: 硕士
答辩日期: 2017-05
授予单位: 中国科学院大学
授予地点: 北京
导师: 贺泓
关键词: 邻-二甲苯,钯基催化剂,催化氧化,氧化铝,ZSM-5 ; o-Xylene, Palladium based catalyst, Catalytic oxidation, γ-Al2O3, ZSM-5
其他题名: Study on catalytic oxidation of o-xylene by Pd catalyst withdifferent supports
学位专业: 环境工程
中文摘要: 挥发性有机物(Volatile Organic Compound, VOCs)是大气污染物的重要成分 之一,对环境及人体的健康具有严重危害。其中,苯系物(苯、甲苯和二甲苯) 是最为典型的VOCs,因此有效消除苯系物污染具有重要的环境和健康意义。催 化氧化法消除VOCs 是最具实用前景的VOCs 控制技术。负载型贵金属催化剂具 有起燃温度低、净化效率高、使用寿命长等特性而受到广泛研究,其中Pd 基催 化剂因其较好的低温活性和选择性是最常用的贵金属催化剂。研究表明,活性中 心Pd 的价态、粒径、载体类型等对Pd 基催化剂的性能有显著影响。本论文考察 了γ-Al2O3 粒径尺寸和Pd/ZSM-5 制备方法对Pd 基催化剂氧化邻-二甲苯性能的 影响,阐明了小粒径的γ-Al2O3(nano)负载Pd 催化剂促进其催化氧化邻-二甲苯 性能的机制,并解释了原位合成法制备Pd/ZSM-5 时无需预处理就具有较高催化 氧化苯系物性能的原因。论文主要取得了以下研究成果: 发现载体的尺寸显著影响Pd/γ-Al2O3 催化氧化邻-二甲苯的性能,高度分散 的还原态Pd 是邻-二甲苯催化氧化的活性位。以粒径约10 nm 的γ-Al2O3(nano) 和粒径约200 nm 的γ-Al2O3(usual)为载体,采用浸渍法制备了1 wt.% Pd/γ-Al2O3 催化剂,Pd/γ-Al2O3(nano)具有更为优异的催化氧化邻-二甲苯的性能,H2 还原 后催化活性显著提高:在空速为60,000 mL·g-1h-1 下,Pd/γ-Al2O3(nano)催化氧 化邻-二甲苯的T90 约为150 °C。利用X 射线衍射(XRD)、比表面积(BET)、 透射电镜(TEM)、X 射线光电子能谱(XPS)等手段对催化剂进行了表征,结 果表明还原态Pd 是催化氧化邻-二甲苯的活性位点;γ-Al2O3(nano)与Pd 之间 的强相互作用促进了Pd 的分散,是Pd/γ-Al2O3(nano)催化氧化邻-二甲苯性能 优异的主要原因。 发现原位合成法制备的Pd/ZSM-5 较传统的负载方法制备的催化剂具有更为 优异的催化氧化邻-二甲苯的性能。原位制备的Pd/ZSM-5 催化剂无需经过焙烧和 还原处理,大大简化了Pd/ZSM-5 催化剂的制备过程,有利于其在实际中的广泛 应用。利用X 射线衍射(XRD)、比表面积(BET)、X 射线光电子能谱(XPS) 等表征手段,发现在原位制备Pd/ZSM-5 催化剂的过程中,具有还原性的模板剂 将Pd 原位还原为金属态是其催化性能优异的关键。
英文摘要: Volatile organic compounds (VOCs) is one of the most important components of air pollutants, which is harmful to the environment and human health. Among them, BTEX (benzene, toluene, o-xylene) are most typical. Therefore, it is of great significance to eliminate VOCs pollution represented by benzene homologues effectively. Catalytic oxidation is one of the most promising technologies to eliminate VOCs, because of its high purification efficiency, wide application, low energy consumption and less secondary pollution. The noble metal catalysts have attracted much attention due to their low ignition temperature, high efficiency and long service life. Pd based catalysts are especially paid more attention due to their better activity and selectivity at low temperature. A large number of studies show, the chemical state and particle size of Pd and supports type and properties play important roles in performance of Pd-based catalysts. In view of this, the effect of the particle size of γ-Al2O3 and the preparation method of Pd/ZSM-5 on the performance of Pd based catalyst for the oxidation of o-xylene was investigated, the mechanism of the performance of small diameter Al2O3 (nano) supported Pd catalyst for the oxidation of o-xylene and the preparation of highly active Pd/ZSM-5 by in situ synthesis were elucidated,and explains the reasons for its high activity. It was found that the size of the carrier significantly affected the performance of Pd/γ-Al2O3 catalytic oxidation of o-xylene, and the highly dispersed Pd was the active site for the catalytic oxidation of o-xylene. γ-Al2O3 (nano) with particle size of about 10 nm and Al2O3 (usual) with particle size of about 200nm The 1 wt.% Pd/γ-Al2O3 catalyst was prepared by impregnation method, and the Pd/γ-Al2O3 (nano) has better catalytic performance for the oxidation of o-xylene. The catalytic activity of H2 was significantly improved after the reduction: Pd/γ-Al2O3 (nano) catalyzes the oxidation of o-xylene to T90 at about 150 °C at a speed of 60000 mL·g-1h-1. By using X ray diffraction (XRD), specific surface area (BET), transmission electron microscopy (TEM), X ray photoelectron spectroscopy (XPS) characterization methods, results show that reduced Pd is catalytic oxidation of o-xylene active sites; γ-Al2O3 (nano) and the strong interaction between Pd and promote Pd the dispersion is Pd/γ-Al2O3 (nano) the main reason of catalytic oxidation of o-xylene with excellent performance. It is found that the Pd/ZSM-5 prepared by in-situ synthesis method has better catalytic performance than the conventional method. The Pd/ZSM-5 catalyst prepared in situ does not need to be calcined and reduced, which greatly simplifies the preparation process of Pd/ZSM-5 catalyst and is widely used in practice. By using X ray diffraction (XRD), specific surface area (BET), X ray photoelectron spectroscopy (XPS) characterization methods, results showed that process of preparing Pd/ZSM-5 catalyst in situ system, with reduction of Pd in situ template will be reduced to the metallic state, is the key to its excellent catalytic properties.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38634
Appears in Collections:大气污染控制中心_学位论文

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作者单位: 1.中国科学院生态环境研究中心

Recommended Citation:
胡 凌 霄. 不同载体Pd 基催化剂催化氧化邻-二甲苯研究[D]. 北京. 中国科学院大学. 2017.
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