Modification Of .como / Tio <sub> 2 </ Sub>-al <sub> 2 </ Sub> O <sub> 3 </ Sub> Hds Catalyst Freon Gas

MoCo/Al2O3-TiO2 catalysts containing fluorine were prepared by pre-fluorination of the support with Freon gas (CFC-12), direct fluorination of MoCo/Al2O3-TiO2 with CFC-12, and pre-fluorination of the support with NH4F, and their HDS activity to thiophene were studied by a flow micro-reactor. The effect of pre-fluorination of the support by using CFC-12 on MoCo/Al2O3-TiO2 in the physical properties was studied by XRD, N2 adsorption, pyridine adsorption IR, TPR, DRS and XPS. The results showed that pre-fluorination of the support by using CFC-12 led to a remarkable enhancement of the catalytic activity of MoCo/Al2O3-TiO2 for hydrodesulfurization of thiophene. And this method was much better than the other two in the catalytic activity of MoCo/Al2O3-TiO2 for hydrodesulfurization of thiophene.The effect of pre-fluorination of the support by using CFC-12 on specific surface area, pore structure, crystalline form, surface acidity, reductive temperature and active phase was examined, and the reason leading to enhancement of the catalytic activity of MoCo/Al2O3-TiO2 for hydrodesulfurization of thiophene was proposed. It's showed that pre-fluorination of the support by using CFC-12 compared to the impregnation of fluoride salt solution, brought no damage to the texture, e.g. surface area of the catalyst, keeping the appropriate specific surface area and pore structure of Al2C>3-TiO2 support. Pre-fluorination of the support by using CFC-12 decreased Lewis and BrOnsted acidic sites. The reductive temperature of MoCo/Al2O3-TiO2 catalyst was greatly reduced if the support was pre-fluorinated with suitable fluorination temperature, time and CFC-12 concentration. Appropriate fluorination condition also led to reduction of content of tetra-Co(II) viz. increase of octa-Co(II), which promoted formation of active phase i.e. Co-Mo-S. Pre-fluorination of the support improved dispersion of active phase. Strong pull of F" ion made Mo" relatively devoid uf electron, promoting the possibility for Movl to accept lone-pair electron of sulfide and keeping Movl high- sulfuration state. Above-mentioned effect led to remarkable enhancement of the catalytic activity of MoCo/Al2O3-TiO2...