Kinetic Study of Catalytic Partial Oxidation of Synthetic Diesel for Hydrogen Production

Abstract

The focus of this research is to study the kinetics of the catalytic partial oxidation (CPOX) of synthetic diesel (SD) for hydrogen production. The kinetic experiments were done in a packed bed tubular reactor (PBTR) over a 5wt.%Ni/Ce[subscript 0.5Z]r[subscript 0.33]Ca0.085Y[subscript 0.085] (5N/CZCaY) catalyst prepared by a surfactant-assisted route. The SD is composed of 75 vol.% saturated hydrocarbons and 25 vol.% aromatic hydrocarbons, with an average chemical formula resembling commercial diesel C[subscript 12.87]H[subscript 24.81]. The kinetic experiments were conducted at atmospheric pressure, in the temperature range of 1123-1223K (850- 950 degrees C), with oxygen/synthetic diesel (O2/SD) ratio in the range of 6.7-10.5 and W/FSD,0 weight-time) in the range of 19008-47556 kg[subscript catalyst]*s/kmol[subscript SD]. The experimental results were used to derive an empirical power law rate model. This model was of the form: r'SD = K0e(-E/RT)NmSDNn02. Activation energy was found to be 16kJ/mol and the order of reaction with respect to SD was 1.89 (≈2) and with respect to oxygen was found to be 0.41 (≈1/2). Estimation of the values of the model parameters was based on the minimization of the sum of the residual squares of the reaction rates by Gauss-Newton and Levenberg-Marquardt algorithm using non-linear regression (NLREG) software. Excellent agreement between the experimental and predicted rate was established with an absolute average deviation (AAD) of 8%. The 5N/CZCaY catalyst was tested for an extended time on stream (TOS) operation in order to establish and demonstrate that the catalyst is stable and also to ensure steady state performance. In addition, the effects of reaction parameters such as reaction temperature, feed ratio (O[subscript 2]/SD), and weight-time W/F[subscript SD,0]) on the resultant catalytic activity of the chosen catalyst were also investigated in order to obtain the optimal operating conditions for H[subscript 2] production from CPOX of SD. To the best of our knowledge, the current study is the first of its kind on the CPOX reforming of SD.