摘要
用溶胶 凝胶法以磷钼酸 (MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2 催化剂 .使用ICP、XRD、TG DTA、IR、TPD MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能 .杂多钼酸盐与TiO2 通过O2 -在TiO2 表面发生了键合 .在 6 2 3K下 ,杂多阴离子仍保持原有的Keggin结构 .CO2 在Lewis酸位Ni(Ⅱ )和Lewis碱位Ni-O -Mo的桥氧协同作用下生成CO2 卧式吸附态Ni(Ⅱ )←O - (CO)← (O--Ni) .丙烯有多种吸附态在催化剂上吸附 .在 5 6 3K、1MPa和空速 15 0 0h-1的反应条件下 ,丙烯的摩尔转化率为 3.2 % ,产物MAA选择性为 95 % .
The NiPMo/TiO2 catalysts were prepared from hydrolysis tetrabutyl titanate by aqueous solutions of Ni salts of the 12-molybdophosphoric acid via the sol-gel method. Chemical composition, thermal stability, chemisorption character and reaction behaviours have been studied by various techniques, such as, X-ray diffraction, thermogravimetric analysis, infrared spectrum analysis, inductively coupled plasma atomic emission spectroscopy, temperature-programmed desorption, and microreactor. The experimental results showed that inorganic precursor polyoxomolybdate was introduced to the surface of titanium dioxide and formed the NiPMo/TiO2 hybrid materials. Therefore, a coordination structure of the NiPMo/Ti catalysts was proposed. At the temperature of 623 K, the catalyst still remained the original Keggin structure of polyoxomolybdate. The chemisorbed IR showed that CO2 chemisorbs at bridging oxygen of Ni-O-Mo (Lewis base site) and Ni2+ (Lewis acid site) forming bridged absorption states Ni (II)<--O-(CO)<--(O--Ni), and propylene chemisorbs on the surface of catalyst with three absorption states. Under the reaction conditions of 563 K and 1 MPa, the main reaction products of CO2 and propylene on the surface of catalysts were MAA, the conversion of propylene was 3.2%,and the selectivity of MAA was 95%.
基金
TheNationalKeyBasicResearchProjectofChina (2 0 0 1CCA0 36 0 0 )
