Effect of Isomerization on the Reversible Reaction of Hydrogenation‐Dehydrogenation of ortho‐Terphenyl on a Pt/C Catalyst

Abstract

Reversible catalytic hydrogenation-dehydrogenation reactions of ortho-terphenyl (o-terphenyl) as one of the most promising materials for hydrogen storage were investigated. The conversion of o-terphenyl is 100 % and the selectivity to perhydro-o-terphenyl reaches 99 % in the first cycle of hydrogenation on a commercial Pt/C catalyst. The dehydrogenation process in a flow reactor is accompanied by the formation of isomerization products of o-terphenyl, in particular, exhaustively and partially hydrogenated compounds formed from meta-terphenyl (m-terphenyl) and triphenylene. These substrates are subject to hydrogenation independently during the second hydrogenation cycle, which reduces the selectivity of recyclization of o-terphenyl. Dodecahydrotriphenylene demonstrates a higher reactivity during the second cycle of dehydrogenation compared to perhydroo-terphenyl. The amount of generated hydrogen is consistent with the kinetic data.

Recent Advances in Homogeneous/Heterogeneous Catalytic Hydrogenation and Dehydrogenation for Potential Liquid Organic Hydrogen Carrier (LOHC) Systems

“…Kalenchuk et al reported reversible carbon-supported platinum-catalyzed hydrogenationdehydrogenation of o-terphenyl, which is among the most promising materials for LOHC [59]. For the hydrogenation of o-terphenyl, Pt/C is an effective catalyst, delivering perhydro-oterphenyl in full conversion with a high selectivity of 97%-99%.…”

Benzyltoluene/perhydro benzyltoluene – pushing the performance limits of pure hydrocarbon liquid organic hydrogen carrier (LOHC) systems

“…This is in contrast with literature findings reporting ortho -, meta -, and para -isomerisation with xylene during hydrogenation 62 and terphenyl during hydrogenation 63 and dehydrogenation. 64 Based on our results with the Cl#102 catalyst we can state, that neither accumulation of low boiling compounds nor indications of C–C bond cleavage was observed even under these extended and harsh operation conditions.…”

Toward a Hydrogen Economy: Development of Heterogeneous Catalysts for Chemical Hydrogen Storage and Release Reactions

“…217 Interestingly, an isomerization of perhydro-o-terphenyl into perhydrotriphenylene was also observed in dehydrogenation reactions in a flow reactor. 218 Another potential LOHC is the dibenzyltoluene (DBT) and octadecahydro (or "perhydro-")dibenzyltoluene (H 18 -DBT) pair, which provides reasonable hydrogen storage capacity (6.2 wt%) and is reported to be less toxic. 60 In 2014, Wasserscheid and co-workers reported a hydrogen storage−release method based on benzyltoluene or DBT mixtures using two different catalysts: (a) Ru/Al 2 O 3 (5 wt%) for the hydrogenation step and (b) Pt/C (1 wt%) for the dehydrogenation reaction.…”

“…The groups of Kustov, Bogdan, and Kalenchuk described the application of a series of aromatic hydrocarbons as LOHCs, including terphenyls/​perhydro­terphenyls (2013), m- terphenyl/​perhydro- m ‑terphenyl (2018), triphenylene/​perhydro- o ‑terphenyl (2018), and biphenyl/​bicyclo­hexyl (2020) . Compared to many of the previously discussed systems, they performed a remarkable number of hydrogen storage cycles (up to 20) with Pt/Mg 2 NiH x as catalyst and terphenyls as substrates .…”