探討銅錳改質類水滑石完全氧化氣態異丙醇之機制

異丙醇在半導體產業常作為晶圓的清洗溶劑，然而其屬於一種揮發性有機物，經由製程所排放的廢氣將造成人體健康受損和環境污染。觸媒氧化法為最廣泛使用的揮發性有機物控制技術之一，本研究以共沉澱法製備類水滑石作為觸媒，合成鎂鋁、銅鎂鋁與錳鎂鋁三種類型的材料，並同時調控金屬含量與鍛燒溫度形成金屬氧化物，以T95 (95%異丙醇轉換的溫度) 與二氧化碳的產率評估材料與異丙醇之反應性，以及探討可能的反應機制。 X射線繞射光譜結果顯示，銅鎂鋁材料的銅能替換鎂形成含銅的類水滑石，並在鍛燒後形成CuO且晶相強度隨鍛燒溫度上升而增加。錳鎂鋁材料則出現MnCO3晶型，其晶相強度隨錳含量增加而變強，MnCO3經過400°C鍛燒形成低結晶性之ε-MnO2，在更高鍛燒溫度下轉變成Mn2O3。藉由X射線光電子能譜分析儀得知材料過渡金屬與表面氧的型態，銅鎂鋁中CuO/Cu(OH)2與錳鎂鋁材料中Mn+3/Mn+4的比例皆隨鍛燒溫度增加而上升；兩者表面吸附態氧與表面晶格氧的比例皆隨材料的鍛燒溫度升高而降低，與X射線繞射光譜的結果一致。觸媒與異丙醇反應的結果顯示，銅含量越高，降低鍛燒溫度能增加反應效率，以銅含量40 at.%經過500°C鍛燒的材料的T95最低為290°C。錳鎂鋁材料經過400°C鍛燒後，異丙醇之T95隨錳含量增加而降低，以50 at.%錳含量的反應效果最佳，T95為265°C。銅鎂鋁和錳鎂鋁材料在含碳的產物僅有偵測到丙酮與二氧化碳，值得注意的是錳含量為50 at.%的材料經過400、500與600°C鍛燒後，在T95溫度並沒有明顯差距，然而二氧化碳的產率卻從59快速下降至36與25%。造成此一現象的原因與表面吸附態氧與表面晶格氧的比例相關。觸媒與異丙醇在無氧環境下進行反應，都能產生一部分的二氧化碳，且在反應後，材料的晶型由CuO還原為零價金屬Cu；ε-MnO2還原為MnO，顯示表面晶格氧參與異丙醇的完全氧化反應，在反應機制上屬於Mars-van Krevelen。

關鍵字

揮發性有機物；觸媒氧化；類水滑石材料；金屬氧化物； Mars-van Krevelen

並列摘要

Isopropanol (IPA) is widely used as a washing agent in semiconductor industries. However, IPA emissions pose growing threat to human health and environment. Catalytic oxidation is one of the most promising technologies for volatile organic compounds (VOCs) abatement. In this study, metal oxide catalysts obtained from hydrotalcite-like compounds using Mg-Al (MA), Cu-Mg-Al (CMA) and Mn-Mg-Al (MMA), metal content and calcination temperature as variables. The aim of this study was investigated the catalytic performances based on T95 (temperature corresponding to 95% conversion) and CO2 yield (%). Another goal was the recognition of the reaction pathways. X-ray powder diffraction showed Mg replaced by Cu in the structure of CMA. After calcination, phases of hydrotalcite-like compounds transformed to CuO phases. While MnCO3 phases formed in MMA and became ε-MnO2 after thermal treatment at 400°C, transformed to Mn2O3 after calcined above 500°C. X-ray photoelectron spectroscopy (XPS) suggested CuO/Cu(OH)2 in the CMA as well as Mn+3/Mn+4 in the MMA increased with higher thermal treatment. Moreover, the ratio of adsorbed oxygen to lattice oxygen decreased dramatically with increasing calcination temperature. From the point of IPA oxidation, higher content of Cu or Mn with lower calcination temperature of the catalysts exhibited better performance. T95 in the lowest temperature of CMA and MMA were 290 and 265°C, respectively. Acetone and CO2 were the only carbon-containing products detected. CO2 production was observed in IPA decomposition. After the experiment, CuO in the CMA transformed to Cu and ε-MnO2 in the MMA became MnO, which implied the mechanism of IPA oxidation possibly underwent through Mars-van Krevelen (MVK).

並列關鍵字

volatile organic compounds ； catalytic oxidation ； hydrotalcite-like materials ； metal oxides ； Mars-van Krevelen

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