強酸與金屬共同改質沸石吸附劑對NH3吸附效能之研究

Abstract

本研究主要以金屬及酸化改質前處理，達到提高去除效率與吸附量之目的，同時進行進行物化特性分析與吸附容量測試，最後利用自製金屬改質溶液的方式降低吸附劑成本。 研究結果發現，各項沸石擔體的90%工作吸附量以NaY的64.3 mg/g最高，其次為13X的52.7 mg/g，最差的為ZSM-5的24.5 mg/g。在經過金屬、強酸改質後之吸附劑與金屬種類則以NaY及銅金屬表現最好，故選擇NaY沸石及銅金屬為擔體和改質的金屬種類，來進行離子交換製程參數探討，參數包含攪拌時間、金屬濃度、鍛燒溫度，結果以1.5小時、0.15M、無鍛燒最佳，pH值部分則以pH 5有最高金屬置換率。此外無鍛燒及550℃鍛燒之吸附劑經XPS分析結果均顯示，其表面銅包含經由離子交換於沸石結構內的Cu(OH)+，以及以含浸方式披覆於沸石表面之CuO。ICP及BET分析結果顯示，沸石耐酸度約在pH值0.7到1.3之間，沸石在低於此pH值的環境下，會使沸石中鋁結構骨架(Al framework)破壞，造成比表面積及孔洞體積下降。將酸或鹼含浸與銅離子交換法結合，能使沸石同時擁有含氧官能基及金屬活性位置，當中以酸含浸與pH 5離子交換改質之90%工作吸附量為最好，其吸附量為127.6mg/g，高於僅以pH 5離子交換改質的90%工作吸附量112.6 mg/g。自製金屬溶液改質吸附劑之吸附量則以自製硝酸銅為最好，自製 Cu/NaY(0.05M)吸附劑擁有最低的吸附劑成本，吸附1g 氨氣僅需10.7 NTD。將吸附劑物化特性與氨氣吸附量作關聯性分析，由BET結果顯示發現物理特性中，比表面積和孔洞體積與吸附量成正比；化性方面，由TPD結果顯示，吸附劑總酸量越高，氨氣吸附量越高，ICP結果顯示銅含量越高，吸附量越高。

This study intends to modify zeolite by different metals and/or strong acids to increase the adsorption capacity of ammonia. The physical/chemical characteristics of the modified zeolite are also analyzed. The results show that NaY zeolite has the highest 90% working capacity(64.25 mg/g)﹐which is followed by 13X(52.69 mg/g). Among the modification of zeolite with strong acids and metals﹐copper is the best metal species which lead to the best adsorption performance. The test parameters of modification include stirring time﹐copper concentration, calcination temperature and pH value. The results showed that ion exchange time of 1.5hr with 0.15M copper precursor concentrationat pH 5 and under no calcination resulted in the best adsorption performance. Besides﹐both adsorbents of without calcination and calcined at 550℃ showed similar XPS results that copper was presented as Cu(OH)+ which came from ion exchange, and as CuO which came from impregnation. The ICP and BET results revealed that acid resistance of zeolite was between pH value of 0.7 to 1.3, below which the Al framework of zeolite will be leached out. Adsorbent which was modified by both impregnation (acid or base) and copper ion exchange generated oxygen functional groups and metal active sites. Among them, adsorbent which was modified by acid impregnation and copper ion exchange at pH 5 has the best NH3 capacityof 127.6mg/g, this is better than the capacity of adsorbent just modified by copper ion exchange at pH 5(112.6mg/g). The NH3 capacity using adsorbent modified by home made copper nitrite precursor (98.8mg/g) was better than that from purchased chemical of copper nitrite (88.1mg/g), the Cu/NaY-HM(0.05M) also had the lowest manufacture cost (10.7NTD/g NH3). The BET, TPD and ICP results revealed that the specific surface area, pore volume, total acidity and copper loading were highly correlated to the NH3 capacity.