本文關(guān)鍵詞：OMS-2深度催化氧化鄰二甲苯的研究　出處：《河北師范大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 還原劑 Ag/Cu 摻雜 OMS-2 反應(yīng)機理 原位紅外技術(shù) 鄰二甲苯 催化氧化

【摘要】：苯系污染物是最為常見的一類揮發(fā)性有機污染物(Volatile Organic Compounds,VOCs),會對人類和動物的健康造成嚴(yán)重的傷害。催化氧化技術(shù)以低耗能,高效率,無二次污染,可廣泛使用等優(yōu)點,在治理苯系污染物中受到眾多科研工作者的關(guān)注。本文以常見的鄰二甲苯為目標(biāo)污染物,制備得到具有良好催化性能的氧化錳八面體分子篩(OMS-2)催化劑,并對其催化鄰二甲苯的性能進行評價。具體內(nèi)容如下:(1)以KMnO_4為氧化劑,分別以苯甲醇和Mn(NO3)2為還原劑,制備得到OMS-2催化劑(分別表示為B-OMS-2和N-OMS-2)�？疾炝诉�原劑對催化劑的結(jié)構(gòu)和催化氧化鄰二甲苯的性能的影響。SEM(Scanning Electron Microscope)分析表明,催化劑B-OMS-2呈現(xiàn)松散的立方體結(jié)構(gòu);XPS(X-ray Photoelectron Spectroscopy)顯示B-OMS-2中幾乎包含100%的Mn4+;TGA(Thermogravimetric Analysis)表明B-OMS-2中含有一些體相氧空位;FT-IR(Fourier Transform Infrared Spectoscopy)結(jié)果表明,在催化劑B-OMS-2中,苯甲醇可能吸附在MnO2的核上起到配體或結(jié)構(gòu)導(dǎo)向劑的作用,與有機化合物的解吸作用共同導(dǎo)致了體相氧空位的形成。而XPS顯示催化劑N-OMS-2中Mn4+和Mn~(3+)共同存在,且存在小的Mn~(3+)-氧空位基團。活性測試結(jié)果表明,在空速為8000h-1時,B-OMS-2可以在190℃時將鄰二甲苯完全氧化為CO2,比N-OMS-2的溫度低50℃。H_2TPR和O2-TPO結(jié)果表明,催化劑B-OMS-2具有良好的低溫氧化性和較強的與分子氧的交換能力,這可能是其催化性能較好的原因。在抗水蒸氣能力測試中,兩種催化劑鄰二甲苯轉(zhuǎn)化率均為80%時通入5%的水蒸氣,B-OMS-2的轉(zhuǎn)化率降低了39%,N-OMS-2降低了27%,但停止通入后,兩種催化劑的轉(zhuǎn)化率均恢復(fù)到了原來水平。催化劑的原位漫反射紅外光譜分析(In situ DRIFTS)發(fā)現(xiàn),兩種催化劑的催化氧化機理均符合MVK(Mars-van Krevelen)機制。催化劑B-OMS-2在晶格氧作用下120℃時可以氧化鄰二甲苯側(cè)鏈生成鄰苯二甲醇,比N-OMS-2的溫度低30℃。通入分子氧后,在50℃時將鄰二甲苯側(cè)鏈氧化至斷裂,120℃時活化苯環(huán),生成小分子羧酸鹽和碳酸鹽,300℃時將碳酸鹽分解完全。而N-OMS-2在300℃時,中間產(chǎn)物并未被分解。上述結(jié)果表明,B-OMS-2具有更好的催化性能。(2)銀、銅摻雜的催化劑Ag-OMS-2和Cu-OMS-2均可以提高OMS-2的催化性能�；钚詼y試結(jié)果表明,催化劑Ag-OMS-2在190℃就可以將鄰二甲苯完全氧化,比OMS-2和Cu-OMS-2的溫度均低10℃;而催化劑Cu-OMS-2在T20(CO2產(chǎn)率為20%時的溫度)時的溫度為147℃,比OMS-2低了36℃,比Ag-OMS-2低了15℃。催化氧化反應(yīng)前后的XPS表征結(jié)果說明,在催化劑Ag-OMS-2中Ag起著活性中心的作用,加速了活性氧物種的傳遞和循環(huán),加快了整個催化氧化進程;催化劑Cu-OMS-2中仍是MnO2為活性中心,但銅的摻入提高了分子氧在Cu2O上的吸附能力,促進了MnO2/Mn2O3間的交換,有利于鄰二甲苯的催化氧化。在三種催化劑轉(zhuǎn)化率為80%時通入5%的水蒸氣,Ag-OMS-2和OMS-2的轉(zhuǎn)化率均降低了25%,Cu-OMS-2僅僅降低了6%,停止通入水蒸氣后,三種催化劑的轉(zhuǎn)化率都能恢復(fù)到80%。In-situ DRIFTS結(jié)果說明,三種催化劑催化氧化的反應(yīng)機理都遵循MVK機制。催化劑Ag-OMS-2和Cu-OMS-2在晶格氧作用下,100℃時均能氧化鄰二甲苯側(cè)鏈生成鄰苯二甲醇,比OMS-2溫度低了20℃,但Ag-OMS-2在150℃時便能生成馬來酸鹽和碳酸鹽;通入分子氧后,Cu-OMS-2在80℃時便能氧化鄰二甲苯側(cè)鏈,120℃使苯環(huán)活化生成小分子羧酸鹽和碳酸鹽,比Ag-OMS-2的溫度低了20-30℃,但Ag-OMS-2在300℃時便可將鄰二甲苯氧化生成的中間產(chǎn)物完全分解。摻雜銀物種有利于羧酸鹽和碳酸鹽的分解,摻雜銅物種可以加速鄰二甲苯的氧化進程。以上分析結(jié)果說明,銀物種和銅物種的摻入均實現(xiàn)了對催化劑OMS-2的改良。
[Abstract]:Benzene series is the most common type of volatile organic pollutants (Volatile, Organic, Compounds, VOCs) can cause serious harm to human and animal health. Catalytic oxidation technology with low energy consumption, high efficiency, no two pollution, can be widely used in the advantages of treatment by many scientific researchers of benzene the pollutants. This paper takes o-xylene common as target pollutant, prepared has good catalytic performance of manganese oxide eight hedral molecular sieve (OMS-2) catalyst, and its catalytic performance of o-xylene was evaluated. The specific contents are as follows: (1) using KMnO_4 as oxidant, respectively with benzyl alcohol and Mn (NO3 2) as a reducing agent, was prepared by OMS-2 catalyst (denoted as B-OMS-2 and N-OMS-2 respectively). The effects of the performance of reducing agent on the catalyst structure and catalytic oxidation of o-xylene.SEM (Scanning Electron Microscope) analysis Show that the cube structure of catalyst B-OMS-2 presents loose; XPS (X-ray Photoelectron Spectroscopy) that the B-OMS-2 contains almost 100% Mn4+; TGA (Thermogravimetric Analysis) showed that B-OMS-2 contains some bulk oxygen vacancies; FT-IR (Fourier Transform Infrared Spectoscopy). The results showed that in B-OMS- 2 catalyst, benzyl alcohol may play a ligand or adsorption structure guide agent role in the kernel of MnO2, and the desorption of organic compounds leads to the formation of bulk oxygen vacancies. While XPS and Mn showed Mn4+ catalyst in N-OMS-2 ~ (3+) exists, and there is a small Mn~ (3+) - oxygen vacancy group. Activity tests showed that the space velocity is 8000h-1 when B-OMS-2 at 190 DEG C to o xylene complete oxidation of CO2, lower than the temperature of 50 DEG.H_2TPR and O2-TPO N-OMS-2 results showed that B-OMS-2 catalyst has good low-temperature oxidation and a Exchange ability with molecular oxygen, this may be the reason for its good catalytic performance. The steam resistance ability test, two kinds of catalysts of o-xylene conversion rate was 80% by introducing 5% of water vapor, reduce the conversion rate of B-OMS-2 was 39%, N-OMS-2 decreased by 27%, but the stop after conversion of two kinds of catalysts were restored to its original level. In situ analysis of diffuse reflectance infrared spectroscopy of catalyst (In situ DRIFTS) found that the catalytic oxidation mechanism of the two catalysts are in line with MVK (Mars-van Krevelen) mechanism. The catalyst B-OMS-2 can generate side chain oxidation of o-xylene phthalate two methanol in lattice oxygen under the action of 120 DEG C when the temperature of 30 DEG C lower than N-OMS-2. The molecular oxygen, O will be at 50 degrees C - xylene oxidation of side chain to rupture, activation of benzene at 120 DEG, to produce carboxylic acid salt and carbonate of small molecules, 300 degrees will be completely decomposition of carbonate and N-OMS-2 in 300. C, the intermediate product is not decomposed. The results showed that the catalytic performance of B-OMS-2 is better. (2) silver catalyst Ag-OMS-2 and Cu-OMS-2 copper doped can improve the catalytic performance of OMS-2 catalyst activity. The test results show that the Ag-OMS-2 at 190 DEG C can be completely oxidized o two toluene, than OMS-2 and Cu-OMS-2 low temperature of 10 DEG C; and the catalyst Cu-OMS-2 in T20 (CO2 yield is 20% when the temperature) at the temperature of 147 DEG, 36 DEG C lower than the OMS-2, 15 degrees lower than Ag-OMS-2. The characterization of XPS before and after the catalytic oxidation reaction shows that Ag plays a role in the active center of catalyst Ag-OMS-2, accelerated the reactive oxygen species transfer and circulation, accelerate the process of catalytic oxidation; Cu-OMS-2 catalyst is MnO2 as the active center, but the incorporation of copper increased the adsorption capacity of molecular oxygen on Cu2O, to promote the exchange between the MnO2/Mn2O3, is conducive to the neighbor The catalytic oxidation of xylene. The conversion rate of 80% into the 5% water vapor in three kinds of catalysts, Ag-OMS-2 and OMS-2 conversion rate was reduced by 25%, Cu-OMS-2 only decreased by 6%, stop feeding water, the rate of conversion of three catalyst can be recovered to the 80%.In-situ DRIFTS results showed that the reaction mechanism of three the catalyst for catalytic oxidation of the catalyst Ag-OMS-2 and follow MVK mechanism. The effect of Cu-OMS-2 on the lattice oxygen, can generate side chain oxidation of o-xylene phthalate two methanol at 100 DEG, 20 DEG C lower than the temperature of OMS-2, but Ag-OMS-2 at 150 DEG C to generate maleic acid salt and carbonate; pass into molecular oxygen then, Cu-OMS-2 oxidation of o-xylene side chain in 80 DEG, 120 DEG C to generate benzene carboxylic acid salt and carbonate of small molecules, 20-30 C lower than the temperature of Ag-OMS-2, but Ag-OMS-2 at 300 DEG C can be generated in o-xylene oxidation of intermediate product completely The doped silver species are favorable for the decomposition of carboxylate and carbonate. The doped copper species can accelerate the oxidation process of o-xylene. The above analysis results indicate that the incorporation of silver species and copper species has realized the improvement of catalyst OMS-2.

【學(xué)位授予單位】：河北師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：X51;O643.36

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