金属对钛硅分子筛TS-1催化丁二烯环氧化性能的影响

制备了不同金属改性的钛硅分子筛样品M-TS-1 (M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, La, 负载量为1%), 并研究了其催化丁二烯环氧化反应的性能. 结果表明, V, Cr, Mn的加入导致H₂O₂无效分解, 因而在丁二烯环氧化反应中表现出较高的H₂O₂转化率和较低有效利用率; Fe, Co, Ni以及稀土金属La均在一定程度上促进了TS-1对H₂O₂的有效利用; Cu, Zn抑制了H₂O₂的转化, 使得H₂O₂转化率和有效利用率都较低; Cd有效提高了TS-1的催化活性, H₂O₂转化率和有效利用率均接近100%. 采用X射线衍射、N₂吸附-脱附、X射线光电子能谱、傅里叶变换红外光谱等手段表征了上述各金属的改性对TS-1骨架结构以及Ti活性中心周围电子环境的影响. 结果表明, 各M-TS-1样品的骨架结构都仍保持原有的MFI构型, 但是TS-1中Ti活性中心周围的电子环境受到来自各种金属的不同程度影响, 关联催化活性时没有特定的规律性.

Effect of metals on titanium silicalite TS-1 for butadiene epoxidation

The titanium silicalite-1 (TS-1) modified by various metals (M-TS-1; M = V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, La, 1% metals loading) catalysts were employed to catalyze butadiene epoxidation. The metals influenced the TS-1 activity in various ways. V, Cr, and Mn caused H₂O₂ decomposition. Although the H₂O₂ conversion was high, its utilization was relatively low. The introduction of Fe, Co, Ni, and La into TS-1 promoted the vinyloxirane (VO) yield and H₂O₂ utilization to some extent. Cu and Zn modification inhibited the H₂O₂ conversion to VO, resulting in both low H₂O₂ utilization and conversion. We studied the influence of Cd on TS-1 and found that H₂O₂ was almost totally converted to VO over the Cd-TS-1 catalyst, and the turnover number of VO reached 1197. Powder X-ray diffraction, N₂ adsorption and desorption, X-ray photoelectron spectroscopy, and Fourier transformed infrared spectra were employed to characterize the specific metal role at the Ti site in the M-TS-1 catalysts. The TS-1 remained as MFI structure with doped metals. The added metals effectively changed the electron environment of the Ti active site. However, no universal trend in behavior was observed for these metals.