Kinetics modeling for the mixed reforming of methane over Ni-CeO2/MgAl2O4 catalyst

Combined steam and CO2 reforming of CH4 using coke oven gas on nickel-based catalyst: Effects of organic acids to nickel dispersion and activity

“…The previously reported activation energies were also summarized in Table 3 reforming reactions and catalysts [9,17,[38][39][40][41][42][43][44][45][46][47], and the present results on the Ni/Al 2 O 3 (OA) were well matched with those activation energies by showing the them around 72.9-246.0 kJ/mol. To derive the kinetic parameters, the elementary reactions such as CDR, RWGS, SRM1, and SRM2 as listed below, where active sites for these four reactions are assumed as the same sites, were considered based on the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanisms according to our previous work [41]. For deriving two different SRM reactions, the concentrations of intermediates were assumed as lower as possible based on the pseudo-steady-state approximation and Langmuir equilibrium relations.…”

“…The derived kinetic parameters such as the k ref (rate constants for the four assumed reforming reactions) and the activation energies (Ea) are summarized in Table 4. The estimated results of k ref and Ea were also well matched with the previously reported results [9,17,[38][39][40][41][42][43][44][45][46][47] with the values of around 184-6709 and 72.9-246.0 kJ/mol, respectively. For comparisons, the reported activation energies for both SRM1 and SRM2 were found to be around 230 kJ/mol [46,47], which was similar with the present results.…”

The role of CeO2–ZrO2 distribution on the Ni/MgAl2O4 catalyst during the combined steam and CO2 reforming of methane

“…For comparison, the catalytic activity of NMA is also included in Table 2 and its low activity (CH 4 conversion of 77% and CO 2 conversion of 32% at steady-state) is mainly attributed to the formation of larger nickel crystallites and its severe aggregation during the CSCR reaction as reported in our previous work [6]. Even though CH 4 conversion is not much altered from its equilibrium conversion around 78% according to the type of CSCR catalysts due to its high intrinsic activity [10], CO 2 conversion is much lower than that of thermodynamic equilibrium value of 53% at the present reaction conditions; T = 850°C, P = 1.0 MPa and CH 4 /CO 2 /H 2 O/N 2 molar ratio of 3/1.2/3/3. Therefore, we focused on explaining the enhanced catalytic performance on the NCZMA(C) catalyst in terms of CO 2 activation by adopting the positive roles of CeO 2 -ZrO 2 contribution on nickel crystallites.…”

“…The enhanced CO 2 conversion on the NCZMA(C) catalyst compared to that on the NCZMA(SI) and NMA catalysts at steady-state could be mainly attributed to the high surface area of nickel crystallites with the help of CeO 2 -ZrO 2 contribution. Because of the high intrinsic activity on the CSCR reaction [10], CH 4 conversion is not much altered even under the conditions of mild deactivation by aggregation and phase transformation of active nickel crystallites, or coke formation [6, 9,11]. Coke formation on Ni/ZrO 2 -CeO 2 has been reported not to be significant, and the increase of CeO 2 concentration has been also reported with the enhanced stability of ZrO 2 -CeO 2 oxides [9,11].…”

Dynamic Modeling of Integrated Mixed Reforming and Carbonless Heat Systems

“…In addition, the tube model is validated using other experimental data sets reported by Jun et al 34 at equilibrium and nonequilibrium conditions. In this data set, nine cases were studied at equilibrium conditions (cases 1−9 of the study by Jun et al 34 ) and eight cases at nonequilibrium conditions (cases 10−17 of the study by Jun et al 34 ). Similar to the previous case, the fixed bed reactor is embedded inside a heater to keep the tube wall temperature constant, which we replicated in our model for validation purposes by fixing the boundary condition of the inner tube wall temperature accordingly.…”