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以十二胺为模板剂合成了一系列不同Ti含量的介孔分子筛Ti-HMS,并通过高温氨处理对其进行高温改性,在分子筛表面和骨架中引入碱性N原子.分别以改性前后的Ti-HMS为载体使用沉积沉淀法制得纳米金催化剂,并考察氢气、氧气共存条件下催化丙烯气相直接环氧化的催化性能.通过氮气等温吸附-脱附、X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱、紫外-可见漫反射(DR UV-Vis)光谱、电感耦合等离子体原子发射光谱法(ICP-AES)及高倍透射电镜(HRTEM)对载体及纳米金催化剂进行了表征.结果表明:合成的Ti-HMS分子筛试样具有典型的六方介孔特征,Ti以骨架四配位状态存在.以850℃高温氮化改性Ti-HMS为载体制备的纳米金催化剂,在常压、100℃条件下,催化丙烯环氧化,反应30 min后,丙烯的转化率达6.28%,环氧丙烷的选择性为83.10%;反应270 min后丙烯的转化率降至4.74%,环氧丙烷的选择性为82.49%.经高温改性处理后,催化剂的活性及稳定性都得到了大幅度提高.
A series of Ti-HMS mesoporous molecular sieves with different Ti content were synthesized by using dodecylamine as templating agent and were modified by high temperature ammonia treatment at high temperature to introduce basic N atoms into the surface and the framework of the zeolite. The catalytic performance of direct catalytic epoxidation of propylene in the coexistence of hydrogen and oxygen was investigated by using the deposition precipitation method on the Ti-HMS as carrier before and after the precipitation.The nanosized gold catalysts were deposited by X-ray diffraction (XRD) Fourier transform infrared (FT-IR) spectroscopy, UV-Vis diffuse reflectance (DR UV-Vis) spectroscopy, inductively coupled plasma atomic emission spectrometry (ICP- AES) and high-power transmission electron microscopy (HRTEM) The results showed that the Ti-HMS zeolite sample possessed typical hexagonal mesoporous structure and Ti existed in the framework of tetrahedron coordination state.The nano-gold prepared by nitriding modified Ti-HMS at 850 ℃ Catalyst was used to epoxidize propylene at atmospheric pressure and 100 ℃. After the reaction for 30 min, the conversion of propylene reached 6.28% and the selectivity to propylene oxide was 83.10%. After 270 min of reaction, the conversion of propylene decreased to 4.74%, propylene oxide selectivity of 82.49 %. After the high temperature modification, the catalyst activity and stability have been greatly improved.