Propane steam reforming over promoted Ni–Ce/MgAl2O4 catalysts: Effects of Ce promoter on the catalyst performance using developed CCD model

Abstract

In this work, the effects of Ni metal phase and Ce promoter over xNi-yCe/MgAl2O4 (x = 2.75, 5, 10, 15, 17.07 wt% and y = 0.17, 1, 3, 5, 5.83 wt%) catalysts were systematically studied in steam reforming of propane (SRP). Catalysts were synthesized by co-impregnation of Ni(NO3)2.6H2O and Ce(NO3)2.9H2O on the co-precipitated support with MgO/Al2O3 stoichiometric ratio of 1.0. Based on the catalyst structure, the XRD, N2 adsorption-desorption, H2-TPR, SEM, EDX mapping, TG-DTA, and Raman spectroscopy were used to explain the catalyst performance. The C3H8 conversion, H2 yield, and stability were evaluated at T = 600 °C, GHSV = 30000 ml/(h.grcat), H2O/C3H8 = 3, and P = 1 atm during 420 (min) reaction time. Loading Ni on the MgAl2O4 support resulted in beneficial C3H8 conversion and H2 yield, however, it worsens the catalyst performance in long term reaction as a result of more coke formation. The good performance of Ce-promoted catalysts might be attributed to small crystallite size, high specific surface area, and low carbon deposition on the catalyst surface. Moreover, as suggested by TPR and XRD, the interaction between Ce and Ni may prevent Ni from distributing inside the support structure (solid solution), avoiding the catalyst from later coking. The optimum catalyst of 11.85Ni-3.55Ce was achieved using the central composite design (CCD) method, considering the maximum C3H8 conversion and H2 yield as well as minimum deactivation. The C3H8 conversion, H2 yield, and deactivation were experimentally lead to 96%, 63%, and 1%, respectively, and were in good agreement with predicted data by developed CCD method.