Tunable Ptδ+/Pt0 sites by highly dispersed defected TiO2 for efficient catalytic methylcyclohexane dehydrogenation

Dehydrogenation reaction occurs for the hydrogen release process of liquid organic hydrogen carriers (LOHCs), the regenerative cooling of advanced aircraft, etc. But the synergistic effects of Pt active sites are still ambiguous. Herein, a series of Pt-based catalysts with tunable Pt0-Ptδ+ sites were fabricated by changing the ratio of highly dispersed defected TiO2 on MCM-41 (M41) for efficient dehydrogenation of methylcyclohexane (MCH). The characterizations indicate TiO2 nanoparticles (NPs) are highly dispersed on M41 support, and possess abundant Ti3+/oxygen vacancies. The increase of TiO2 loading amount can enhance the interaction between Pt NPs and TiO2, which increases Ptδ+/Pt0 ratio gradually. The dehydrogenation test and theoretical results confirm that the synergistic effect of Pt0 and Ptδ+ sites contributes the optimal dehydrogenation performance, in which Pt0 promotes the consecutive C–H bond cleavage and Ptδ+ significantly decreases the desorption energy barrier for H2 and toluene (TOL). Specifically, the MCH conversion (when applied for LOHCs) is ca. 88 % and the selectivity of TOL is over 99.5 % under 1.0Pt/0.5TiO2/M41, while the high MCH conversion of 90 % and TOL selectivity of more than 86 % are achieved under 1.0Pt/1.0TiO2/M41 (as regenerative cooling for hypersonic vehicle). This work provides the approach of modulating the synergistic active sites to obtain high-performance dehydrogenation catalyst.