Hydroxyapatite supported molybdenum oxide catalyst for selective dehydrogenation of cyclohexane to cyclohexene: studies of dispersibility and chemical environment

The selective oxidative dehydrogenation of cyclohexane to cyclohexene was conducted using molybdenum oxide (MoOx) as a catalyst and hydroxyapatite (HAP) and Ca5(OH)(PO4)3 as carriers. Two series of MOx/HAP catalysts with varying MoOx loading capacity and calcination temperature were prepared via the co-impregnation method. The impact of dispersibility and chemical environment on the catalytic performance of MoOx was investigated. The catalysts were characterized using XRD, XPS, H2-TPR, and UV-Vis spectra. These MoOx/HAP catalysts were employed for the oxidative dehydrogenation (ODH) of cyclohexane to cyclohexene. MoOx/HAP catalysts with lower loading capacity exhibited higher dispersion of MoOx and selectivity towards cyclohexane. The calcination temperature directly influenced the chemical environment of MoOx, thereby affecting its catalytic performance. Samples calcinated at lower temperatures (500 degrees C and 600 degrees C) demonstrated higher conversion rates for cyclohexane, while samples calcinated at higher temperatures (above 700 degrees C) displayed greater selectivity towards cyclohexane. At 430 degrees C, when the conversion rate of cyclohexane reached 13.1%, the selectivity of cyclohexene over MHAP-0.05-800 catalyst reached 58.2%.