Kinetics modelling of 2-butene metathesis over tungsten oxide containing mesoporous silica catalyst

This article reports the activity, reaction mechanism and reaction kinetics of 2-butene metathesis over tungsten oxide containing mesoporous silica (SBA-15) catalyst. Physicochemical characterisation of the catalyst indicates that the dispersion and nature of tungsten oxide species on the catalyst are mainly responsible for the metathesis activity. The ample availability of Bronsted acid sites created by tetrahedrally co-ordinated tungsten species also enhances the metathesis reaction. The product analysis indicates that lower temperature favours the butene isomerisation, while higher temperature is required for metathesis. The high temperature is also responsible for cracking reactions. A kinetics model is developed based on the experimental observations and the possible reactions including isomerisation, metathesis and cracking. The model parameters are estimated by fitting the experimental data implemented in MATLAB. The estimated apparent activation energy of 2-butene isomerisation reaction was 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 isomerisation of 2-butene gives 1-butene and it further reacts (cross metathesis) with 2-butene to produce propylene.