Kinetics of propylene epoxidation using H2 and O2 over a gold/mesoporous titanosilicate catalyst

The kinetics of propylene oxidation to propylene oxide (PO) with H2/O2 mixtures on gold supported on the mesoporous titanium silicate, Ti-TUD, was investigated using Langmuir−Hinshelwood (L−H) models and power−rate law (PRL) models. The catalyst gave stable activity and was appropriate for the kinetic studies, giving high selectivity to PO (>95%) at low conversions of propylene (<6%). The best L−H fit, based on the F test and obtained using nonlinear regression, gave a rate expression of the form, rPO = k[(α(H2)1/2 (O2))/(1 + α(H2)1/2(O2))](H2)1/2[γ(C3H6)/(1 + γ(C3H6))], with an F value of 4.50. The PRL model, also analyzed using nonlinear regression, gave a rate expression, rPO = k(H2)0.60(O2)0.25(C3H6)0.36, which provided a better fit to the data, with an F value of 2.11. The best model was a hybrid of the form rPO = k(H2)l(O2)m(C3H6)/[kD/κ + (C3H6)], with an F value of 1.76. This hybrid model was also proven as the best model based on a model probability criterion. The mechanistic origin of these expre...