丙酮與氫氣在金屬修飾的固體鹼觸媒之直接合成甲基異丁基酮

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Title:	丙酮與氫氣在金屬修飾的固體鹼觸媒之直接合成甲基異丁基酮
Other Titles:	Direct Synthesis of Methyl Isobutyl Ketone from Acetone and Hydrogen with Metal Modified Solid Base Catalyst
Authors:	林凱勛 Lin, Kai-shun
Contributors:	柯安男 Ko, An-Nan 東海大學應用化學系
Keywords:	甲基異丁基酮
Date:	1996
Issue Date:	2011-05-25T08:44:59Z (UTC)
Abstract:	中文摘要本論文使用固定床流動反應器於常壓與175~250℃ 下，經由鹼與金屬鈀觸媒的催化直接合成甲基異丁基酮。使用的觸媒包括(1)鈀與鈉金屬修飾的金屬氧化物系列 (Pd/Na/MgO、Pd/Na/NaOH/γ-Al2O3); (2)沸石系列 (Pd/KZSM-5、Pd/Kβ)。利用原子吸收光譜儀、溫度程控脫附儀、表面積測試儀及掃瞄式電子顯微鏡，鑑定觸媒之組成、鹼強度與鹼量、表面積、以及顆粒結構。利用金屬鈉修飾的氧化鎂系列其鹼量會增加，其中以Pd/0.47wt.- %Na/MgO有最大的鹼量。就不同擔體而言鹼量依序為 Pd/Na/MgO>Pd/Na/NaOH/γ-Al2 O3>Pd/KZSM-5>Pd/Kβ。上述結果與催化活性一致，顯示鹼量越大催化活性越好。金屬Pd的含量在催化反應中亦佔重要因素，當含浸的 Pd 金屬過多時會覆蓋住鹼性點，降低丙酮轉化率與甲基異丁基酮選擇率同時提高2-丙醇的選擇率。反應前使用較高溫度的氫氣還原觸媒時可獲得較佳的丙酮轉化率以及甲基異丁基酮選擇率。當反應溫度增加時，氧化鎂觸媒 (Pd/Na/MgO)的催化活性亦隨之升高，但衰退速率亦變大。改變丙酮與氫氣的莫耳比，發現比例為1時呈現最大的丙酮轉化率。增加接觸時間導致甲基異丁基酮與丙酮、氫氣繼續反應生成二異丁基酮。綜合上述實驗結果，獲知製備甲基異丁基酮的最佳條件為0.5wt.-%Pd/0.47wt.- %Na/MgO、反應溫度200 ℃、丙酮/氫氣莫耳比1、W/Fa 6g.h/mol以及觸媒氫氣還原溫度400℃。根據FT-IR吸附丙酮的實驗結果推論丙酮吸附於觸媒之鹼性點，經由縮合反應、脫水再氫化生成甲基異丁基酮。 Abstract one-step synthesis of methyl isobutyl ketone (MIBK) from acetone and hydrogen over metal modified solid base catalysts has been studied at atmospheric pressure and 175~250℃by using a fixed-bed , integral-flow reactor . Two types of catalysts have been used : (1) metal oxides modified with sodium and palladium (Pd/Na/MgO , Pd/Na/NaOH/γ- Al2O3) ; (2) zeolites modified with palladium (Pd/KZSM-5 , Pd/Kβ) . The catalyst properties , i.e., the composition , the basicity , the surface area and the structure are characterized by the methods of atomic absorption , temperature- programmed desorption , surface adsorption and scanning electron microscopy . Sodium vapor deposition on magnesia followed by impregnation with tetraamine palladium(Π) chloride apparently enhances the catalyst basicity as compared with that of magnesia supported palladium ; Pd/0.47wt.-%Na/MgO exhibits the largest base amount . For catalysts of different supports , the base amount decreases in the order of Pd/Na/MgO > Pd/Na/NaOH/γ-Al2O3 > Pd/KZSM-5 > Pd/Kβ , in accordance with the catalyst activities . As the amount of palladium in Pd/Na/MgO increases , both acetone conversion and MIBK selectivity also increase but then decrease . Better acetone conversion and MIBK selectivity are obtained at higher pretreating temperature of hydrogen . The catalyst activity of Pd/Na/MgO increases with the reaction temperature but the decay rate also increases . The acetone/hydrogen molar ratio of 1 gives the highest acetone conversion . Increasing contact time causes an increase in the selectivity of diisobutyl ketone due to further reaction of MIBK with acetone and hydrogen . Based on the above results , the optimum reaction conditions are 0.5wt.-%Pd/0.47wt.-%Na/MgO , reaction temperature 200℃ , acetone /hydrogen molar ratio 1, W/FA 6g.h/mol and the pretreatment temperature of hydrogen 400℃ . According to the FT-IR results of acetone adsorption on Pd/Na/MgO , the following reaction mechanism is proposed : self condensation of acetone on catalyst base sites followed by dehydration on acid sites and then hydrogenation to yield MIBK .
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