Abstract
Mesoporous silica (MCM41) is modified with TiO2 nanoparticles by solvolysis of titanium precursor to prepare a series of Ti(x)/MCM41 supports with different titanium contents for chromium based catalytic system. Incipient wetness impregnation method is used to introduce the chromium species to produce a series of Cr(y)/Ti(x)/MCM41 catalysts with different chromium contents. The effect of both titanium and chromium loading on the catalytic performance of Cr(y)/Ti(x)/MCM41 catalysts for the oxidative dehydrogenation of ethane with CO2 was investigated. The prepared catalysts were characterized by XRD, TEM, SEM, EDX-elemental mapping, N-2 sorption analysis, ICP, UV-vis-DSR, XPS and TPR-H-2 techniques. The results show that modification of MCM41 with TiO2 nanoparticles altered the structural properties of the synthesized catalyst, such as, chromium species dispersion and size as well as the chromium-support interaction which in turn affect the catalytic performance of synthesized catalysts. Among the modified support catalysts, the Ti(1.9)/MCM41 has enhanced the concentration and stability of Cr6+ species and resulted in comparable amounts of surface reducible chromium species. The results have revealed that the highest catalytic activity is obtained for Cr-loaded TiO2-modified MCM41 containing 1.9 wt% titanium and 8 wt% chromium. It showed superior performance for ethane dehydrogenation with CO2 at 700 degrees C at 51.87% ethane conversion, and 48.14 and 92.80% ethylene yield and selectivity, respectively.