Synergistic structural and electronic influences of Pt bead catalysts on dehydrogenation activity for liquid organic hydrogen carriers

Abstract

Alumina-supported Pt bead catalysts with uniform (Pt-U/theta-Al2O3) or egg-shell (Pt-E/theta-Al2O3) structure and their corresponding potassium-doped counterparts (K-Pt-U/theta-Al2O3, K-Pt-E/theta-Al2O3) were synthesized to elucidate the influence of structure-induced active metal distribution and promotor on the dehydrogenation of liquid organic hydrogen carriers (LOHCs). Characterizations of the catalysts confirmed that different synthetic methods led to distinct Pt distributions on the Al2O3 surface. Pt-E/theta-Al2O3 and K-Pt-E/theta-Al2O3 had an average size of 1 nm with narrow Pt distributions while Pt-U/theta-Al2O3 and K-Pt-U/theta-Al2O3 exhibited bimodal distributions in Pt particle size (<0.2 nm and <0.8 nm), which also influenced the oxidation states. Introducing the promotor (K) facilitated electron transfer into Pt, which resulted in a more metallic state. When applied to the dehydrogenation of two different LOHCs, including methylcyclohexane and perhydro-monobenzyltoluene, K-Pt-E/theta-Al2O3 exhibited superior catalytic activity and durability compared to other catalysts. The improved activity of K-Pt-E/theta-Al2O3 was primarily attributed to the combined electronic influences of the catalyst bulk structure and promotor.