Continuous Dehydrogenation of Perhydro Benzyltoluene in a Catalytic Finned Tube Reactor

Abstract

Storage and transport of hydrogen by charging liquid organic hydrogen carriers (LOHC) has emerged as a promising technology, as these LOHC can be handled within the existing fuel infrastructure. For the release of hydrogen from LOHC on board heavy-duty vehicles, coated reactor systems are advantageous, as the heat transfer to the catalyst is fast and efficient and the immobilized catalyst is protected from movement and abrasion in the reactor. However, the challenge is to provide a sufficient surface area for the catalytic coating, which is required to achieve high volumetric power densities. We here introduce a novel coated finned tube reactor concept for the dehydrogenation of the LOHC compound perhydro benzyltoluene (H12-BT). The reactor consists of a series of vertically arranged stainless-steel finned tubes, coated with a catalytically active layer (Pt–S/Al₂O₃). This results in a large catalytic surface area per reactor volume. Stable coatings have been obtained through dip-coating an Al₂O₃ slurry onto the finned tubes followed by impregnation with a platinum sulfite acid solution. The finned tubes are individually heated from the inside, allowing for a well-defined and manageable temperature distribution and fast responses under dynamic conditions (e.g., during vehicle start-up). The finned tube reactor exhibits plug flow reactor characteristics with increasing degrees of dehydrogenation (DoDh) in the flow direction. We have achieved a power density of more than 1 kW L^–1 reaction volume at degrees of dehydrogenation above 70%. With this performance, the finned tube reactor concept shows high potential compared to state-of-the-art reactor concepts. By combining the new reactor type with a simple active carbon filter, PEM-fuel cell grade hydrogen (CO content <0.1 ppm, methane <70 ppm) was produced. This work demonstrates the finned tube reactor as an attractive concept for efficient hydrogen release from LOHC systems.