n-Heptane isomerization over molybdenum supported on bicontinuous concentric lamellar silica KCC-1: Influence of phosphorus and optimization using response surface methodology (RSM)

Abstract

Molybdenum oxide (MoO3) supported on bicontinuous concentric lamellar silica KCC-1 (MoO3/KCC-1) and phosphorus (P) loaded on MoO3/KCC-1 (P/MoO3/KCC-1) were successfully prepared by physical mixing of MoO3 followed by impregnation of phosphoric acid. The physicochemical properties of the catalysts were characterized by XRD, FESEM, N2 physisorption, 29Si NMR, FTIR and n-heptane isomerization. In the presence of hydrogen, KCC-1, MoO3/KCC-1 and P/MoO3/KCC-1 showed n-heptane rate conversion of 0.02 × 10−8 mol/m2 s, 0.94 × 10−8 mol/m2 s and 4.79 × 10−8 mol/m2 s, respectively at 300 °C. The presence of MoO3 and phosphorus enhanced the rate conversion of n-heptane due to the formation of (MoOx)-(Hy)+ and the participation of acidic centers from the presence of phosphorus in the formation of protons by trapping electrons, respectively. Additionally, the unique morphology of silica KCC-1 also contributed to the high catalytic activity, by allowing high accessibility of bulky mass reactant to the active sites. The analysis of variance (ANOVA) indicated that the reaction temperature was the prominent significant variable in the production of isomers, followed by treatment temperature and treatment time. The optimum yield of isomers predicted from the response surface analysis is 44.9% at reaction temperature of 311 °C, treatment temperature of 464 °C and treatment time of 6 h.