本研究採用沉積沉澱法，以Mg2AlO-hydrotalcite為擔體，不預先調整金溶液pH值，將擔體緩慢置入金溶液中，利用擔體本身鹼性特質，提升溶液pH值，製備具高活性的金觸媒，用於巴豆醛選擇性氫化反應研究。 2%Au/Mg2AlO觸媒對C=O鍵有較優勢氫化效果，對C=C鍵之吸附微弱，因此巴豆醛較優勢被選擇氫化成巴豆醇，且無法繼續被氫化成正丁醇，得到選擇率約60%的巴豆醇。而非定域化使得共軛Cδ+ Cδ-鍵會被氫化得到丁醛，具單一C=O鍵的丁醛會繼續被氫化成正丁醇，兩者的選擇率總和保持在約40%。 2%Au/Mg2AlO觸媒，隨著Mg2AlO擔體煅燒溫度升高，觸媒金價態Au3+/Au0比值逐漸降低，巴豆醛反應活性及巴豆醇選擇率隨之降低，在煅燒溫度100°C時，Au3+/Au0比值最高，於巴豆醛氫化反應有最佳活性與選擇率。Au/Mg2AlO觸媒煅燒溫度升高亦有相同趨勢。排除金負載量與金顆粒大小的影響下，Au3+/Au0比值為影響觸媒活性與選擇率之重要因素，Au3+/Au0比值越高，觸媒催化活性與選擇率越好。 不同於第VIII族金屬觸媒，非極性溶劑之反應活性較極性溶劑為佳，且醇類溶劑的碳數增加，有利於反應活性，活性大小依序為環己烷 ≈ 正己烷 ≈ 正庚烷 > 異丙醇 > 戊醇 > 丙醇。提高巴豆醛濃度，選擇率沒有明顯變化，反應活性卻逐漸降低。反應壓力增加可提升反應速率，且巴豆醇選擇率幾乎不變。提升反應溫度可提升轉化率，而巴豆醇選擇率幾乎不受影響。反應溫度超過160°C，反應活性與選擇率驟降，160°C反應後觸媒之Au3+/Au0比值也明顯下降。觸媒中添加鐵、鉬或鎢等促進劑對Au3+/Au0比值影響不大，但皆能促進巴豆醛反應活性且不影響巴豆醇選擇率。 將金擔載於FeOOH、Fe2O3、TiO2、CeO2及γ-Al2O3等擔體，反應活性及Au3+/Au0比值遠不及Au/Mg2AlO觸媒。觸媒經300°C煅燒後，Au3+/Au0比值下降至0，活性普遍下降，唯獨Au/TiO2觸媒活性明顯上升，顯然不同擔體的金觸媒，無法單獨以Au3+/Au0比值來論斷金觸媒之活性，擔體本身的性質也將影響觸媒活性。Au/(MgOx%/Al2O3)觸媒之 Au3+/Au0比值幾近0，但反應活性可以媲美Au/Mg2AlO觸媒，巴豆醇選擇率則遠不及Au/Mg2AlO觸媒，不飽和醇選擇率仍受Au3+/Au0比值之影響。鹼性擔體於液相巴豆醛氫化反應具優勢，可製備具有高活性的金觸媒。 Liquid-phase hydrogenation of crotonaldehyde(UAL) to crotyl alcohol(UOL) was investigated on gold catalysts supported on a solid base of Mg2AlO-hydrotalcite. The Au/Mg2AlO catalysts were prepared using a modified deposition precipitation method without adjusting the pH of the initial HAuCl4 solution. The 2% Au/Mg2AlO catalyst hydrogenation for C=O bonds were more advantage than C=C bonds. The order of hydrogenation activity for different function groups over 2% Au/Mg2AlO catalyst was C=O (SAL)>C=C/C=O (UAL)>C=C (SOL). The selectivity of UOL was about 60%, and the selectivity of SAL+SOL was about 40%. Calcination temperatures of the Mg2AlO support and Au/Mg2AlO catalyst determined the ratio of gold states (Au3+/Au0) on the catalyst. A correlation between the gold states and the activity and selectivity of UOL was found. Increasing the Au3+/Au0 ratio of the Au/Mg2AlO catalysts increased the activity and selectivity of UOL. The effects of various parameters that are involved in the hydrogenation were studied, including the influences of solvent, reaction pressure, concentration of UAL, reaction temperature, and the addition of promoter. Au/Mg2AlO catalyst was different with the conventional hydrogenation catalysts, the activity of non-polar solvents were better than polar solvents. Increasing reaction pressure or decreasing concentration of UOL could improve activity. The activity and selectivity suddenly dropped with the reaction temperature up to 160°C. The doping of Fe significantly enhanced the activity, and slightly increased the selectivity. Gold catalysts supported on FeOOH, TiO2 and CeO2 also exhibited a high selectivity (> 60%), but they were much less active than that of 2%Au/Mg2AlO. However, the gold states could not determine the activity of gold catalysts with different supports, the nature of support would affect the reaction activity. Gold catalysts supported on a solid base of MgOx%/Al2O3 showed well activity comparing favorable with Au/Mg2AlO catalyst. Using solid base supports could prepare high activity gold catalysts for the liquid-phase hydrogenation of crotonaldehyde.
