METATHESIS OF BUTENE TO PRODUCE PROPYLENE OVER MESOPOROUS TUNGSTEN OXIDE CATALYST: SYNTHESIS, CHARACTERIZATION AND KINETIC MODELING

Metathesis of 2-Butene to produce propylene over tungsten oxide contained on mesoporous catalyst was studied. Mesoporous silica (MCM-41 and SBA-15) having tungsten oxide in the framework was synthesized by hydrothermal crystallization process using CTAB and P123 as structure directing agents, respectively. Tungsten oxide was supported on the MCM-41 and SBA-15 by wet impregnation method for a comparative study. The synthesized materials were characterized by XRD, N2 adsorption isotherm, NH3-TPD, Pyridine-FT-IR, UV-vis DRS, Raman spectroscopy, H2-TPR and SEM techniques. The catalysts were used to perform metathesis reaction of 2-butene in a fixed-bed reactor at different temperatures, different residence time and under atmospheric pressure. This research work also reports the reaction mechanism and reaction kinetics of 2-butene metathesis over tungsten oxide containing mesoporous silica (SBA-15) catalyst. Physicochemical characterization of the catalyst indicates that the dispersion and nature of tungsten oxide species on the catalyst are mainly responsible for the metathesis activity. The estimated apparent activation energy of 2-butene isomerization reaction found to be the lowest (39.4 kJ/mol) among the competing reactions. The activation energy of cross metathesis of 2-butene and 1- butene, self-metathesis of 1-butene and 2-butene cracking are 71.3, 176.9 and 73.1 kJ/mol, respectively. These results are consistent to the product selectivity and the proposed reaction scheme, which suggests that the isomerization of 2-butene gives 1-butene and it further reacts (cross metathesis) with 2-butene to produce propylene