Dehydrogenation of 2-[(n-Methylcyclohexyl)Methyl]Piperidine over Mesoporous Pd-Al2O3 Catalysts Prepared by Solvent Deficient Precipitation: Influence of Calcination Conditions

Abstract

A pair of 2-[(n-methylcyclohexyl)methyl]piperidine (H12-MBP) and its full dehydrogenation product (H0-MBP) has recently been considered as a potential liquid organic hydrogen carrier with 6.15 wt% H2 storage capacity. In the discovery of an active and stable catalyst for H2 discharge from H12-MBP at lower temperatures, a mesoporous Pd-Al2O3 catalyst (MPdA) was synthesized by a one-pot solvent deficient precipitation (SDP). In the present work, the sensitivity and effectiveness of the SDP method are examined by varying the calcination temperature and time in the preparation of the MPdA catalyst. The characterization revealed that the final properties of the MPdA catalyst greatly rely on both the calcination temperature and time. The MPdA catalyst showed better dehydrogenation activity for calcination at 600 °C than at other temperatures, because of Pd particles of smaller size with higher dispersion. Although the MPdA catalysts calcined at 600 °C for different periods of time have similar size and dispersion of Pd particles, the dehydrogenation efficiency was superior as the calcination time became shorter (e.g., 1 h), which originated from the better arrangement of Pd particles over a higher surface area. These MPdA catalysts, irrespective of the calcination time, displayed a remarkable stability in the dehydrogenation of H12-MBP owing to the protection of Pd particles by the Al2O3 layer.