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 H2O2conversion to VO, resulting in both low H2O2 utilization and conversion. We studied the influence of Cd on TS-1 and found that H2O2was 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.

摘要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.

The various metals modified TS-1 (M-TS-1) catalysts were applied to catalyze butadiene epoxidation. The effect of the modified metals on TS-1 was diverse. All metals changed the electronic environment of the Ti active site in TS-1 to some extent via a five-membered-ring intermediate.Figure optionsDownload as PowerPoint slide