Structuring-agent role in physical and chemical properties of Mo/SiO2 catalysts by sol-gel method

摘要

Molybdenum supported on silica was prepared by the sol-gel method by hydrolysis of tetraethylortosilicate (TEOS) using oxalic acid (OA) or citric acid (CA) as a template through a chelating effect. The effect of the type of template and the molybdenum loading on the structural properties was studied. The relationship between the structure of materials and physical and chemical properties was identified by XRD, FTIR, Raman spectroscopy, H-2-TPR, SEM-EDX, and N-2 adsorption/desorption techniques. The XRD patterns illustrate that materials prepared varying the type of template and molybdenum loading are in different MoOx species. TPR-H-2 analysis shows three different regions attributed to the process of reducing the molybdenum oxide (VI) to molybdenum metal. N-2 adsorption/desorption studies reveal the influence of the metal loading and the type of template in the surface area and pore diameter obtained in all the cases values greater when oxalic acid was used. SEM-EDX studies show the similar morphological structures related to silica materials. Finally, the oxalic acid carbonyl groups are less separated which orientates the structure of the silicon oxide towards smaller pores and therefore, larger surface-specific areas with respect to citric acid.