钾调变Mo/SBA-15催化剂用于乙烷选择氧化制乙醛

采用两步浸渍法制备钾改性的Mo/SBA-15 催化剂. 采用N₂吸附，X射线衍射（XRD），透射电镜（TEM），紫外-可见（UV-Vis）吸收光谱，拉曼（Raman）光谱，NH₃程序升温脱附（NH₃-TPD），CO₂程序升温脱附（CO₂-TPD），H₂程序升温还原（H₂-TPR）等手段表征催化剂的物理化学性质. 研究结果表明，在Mo_0.75/SBA-15 中添加K之后，有新物种钾钼酸盐生成，并且当K/Mo的摩尔比不同时，钼物种的存在状态也不同. 添加钾之后，催化剂的活性和总醛（甲醛、乙醛、丙烯醛）的选择性均有所提高，并且受钾的添加量影响. 在575 ℃时，在K_0.25-Mo_0.75/SBA-15催化剂上醛的收率可高达8.5%（摩尔分数）.

Selective Oxidation of Ethane to Aldehydes over Potassium-Promoted SBA-15-Supported Molybdenum Oxide Catalysts

Potassium-modified SBA-15-supported molybdenum oxide catalysts were prepared using a twostep impregnation method. The physical and chemical properties of the catalysts were characterized using N2- adsorption-desorption, X-ray diffraction (XRD), transmission electron microscope (TEM), UV-visible (UV-Vis) spectroscopy, Raman spectroscopy, NH₃ temperature-programmed desorption (NH₃-TPD), CO₂ temperatureprogrammed desorption (CO₂-TPD), and H₂ temperature-programmed reduction (H₂-TPR). The results showed that potassium addition resulted in the formation of new potassium molybdates, and the states of molybdenum species varied with changes in the K/Mo molar ratio. The addition of potassium to Mo_0.75/SBA-15 effectively improved the activity of catalysts and the selectivity to the total aldehydes (formaldehyde, acetaldehyde, and acrolein), especially for acetaldehyde in the selective oxidation of ethane. The turn-over frequency (TOF) and product selectivity depended strongly on the potassium content. The maximum selectivity and yield of aldehydes were obtained by varying the K/Mo molar ratio. At 575 ℃, the maximum yield of aldehydes reached 8.5%(molar fraction) over K_0.25-Mo_0.75/SBA-15 catalyst. The formation of new potassium-molybdates promoted the activities and selectivities of the catalysts.