Hydrogen storage in liquid organic hydride: Selectivity of MCH dehydrogenation over monometallic and bimetallic Pt catalysts

• By-products of MCH dehydrogenation fall into two categories based on precursors.
• The increase in W/F enhanced the toluene demethylation.
• The increase in reaction pressure enhances toluene disproportionation.
• Increase in pressure enhances toluene condensation and ring-opening reactions.
• By-product formation can be reduced by using an optimum H2/MCH ratio.

Hydrogen storage for mobile and stationary applications is an expanding research topic. One of the more promising storage techniques relies on the reversibility, high selectivity, and high hydrogen density of liquid organic hydrides, in particular methylcyclohexane (MCH). Catalyst evaluation for MCH dehydrogenation to toluene is based on three catalytic parameters: activity, selectivity, and stability. Current catalysts, optimized for catalytic reforming, do not meet the targeted aromatic selectivity (+99%) for MCH dehydrogenation. Therefore, a range of Pt catalysts was prepared and compared with commercially available catalysts in a fixed-bed reactor under operating conditions suitable for mobile and stationary applications. The best overall performance was realized by a particular monometallic Pt catalyst. This catalyst showed superior activity, selectivity, and stability compared with other prepared and commercial catalysts. As an effort to further enhance the aromatic selectivity, this study identified the main side-reactions associated with MCH dehydrogenation, the effect of operating parameters on by-product yields, and the effect of catalyst deactivation on long-term selectivity.