Low-temperature selective catalytic dehydrogenation of methylcyclohexane by surface protonics

Abstract

The methylcyclohexane (MCH)-toluene cycle is a promising liquid organic hydride system as a hydrogen carrier. Generally, MCH dehydrogenation has been conducted over Pt-supported catalysts, for which it requires temperatures higher than 623 K because of its endothermic nature. For this study, an electric field was applied to Pt/TiO 2 catalyst to promote MCH dehydrogenation at low temperatures. Selective dehydrogenation was achieved with the electric field application exceeding thermodynamic equilibrium, even at 423 K. With the electric field, "inverse" kinetic isotope effect (KIE) was observed by accelerated proton collision with MCH on the Pt/TiO 2 catalyst. Moreover, Pt/TiO 2 catalyst showed no methane byproduction and less coke formation during MCH dehydrogenation. DRIFTS and XPS measurements revealed that electron donation from TiO 2 to Pt weakened the interaction between catalyst surface and p-coordination of toluene. Results show that the electric field facilitated MCH dehydrogenation without methane and coke by-production over Pt/TiO 2 catalyst. † Electronic supplementary information (ESI) available. See

Enhanced activity of catalysts on substrates with surface protonic current in an electrical field – a review

“…There are three important phenomena: (i) In-situ DRIFTS measurements to evaluate the behavior of surface adsorbents showed proton hopping on the catalyst support surface based on the Grotthuss mechanism 34,35 . (ii) Considering the "inverse" KIE theory, protons with kinetic energy collide with stable reactants and accelerate the rate-determining step of the reaction 34,37,38 . (iii) EIS measurements revealed that surface ionic conduction occurs on the catalyst support at lower temperatures 34,36 .…”

“…Equally interestingly, in the presence of an electric field, some reactions appear to proceed beyond thermodynamic equilibrium. This has been suggested to be due to the activation of irreversible reaction pathways 18,19,34,35,37,38,49,52 .…”

“…To exceed this equilibrium limitation and promote the dehydrogenation at low temperatures irreversibly, we have investigated irreversible MCH dehydrogenation with a DC electric field over supported Pt catalysts 37,38,49 . Results presented in Table 5 show that the catalytic activity was enhanced markedly by the DC electric field at low temperatures.…”

Effects of A-site composition of perovskite (Sr1−xBaxZrO3) oxides on H atom adsorption, migration, and reaction

“…[1][2][3][4] In addition, the active migration of H atoms promotes heterogeneous catalytic reactions. [5][6][7] In such cases, the migration of H atoms on metal oxide surfaces (proton, H + ) induced by an electric eld contributes to cleavage of the rigid bonding in the stable molecules such as N^N bonding (for NH 3 synthesis [8][9][10][11][12] ), and C-H bonding (for steam reforming of CH 4 , [13][14][15] dehydrogenation of methylcyclohexane 16,17 ). H atoms mobility and reactivity play important roles in the catalytic reactions described above.…”

First observation of surface protonics on SrZrO3 perovskite under a H2 atmosphere

“…[4][5][6] Recently, an important role of surface protonics during heterogeneous catalytic reactions was found in an electric field under both H 2 O and H 2 atmospheres. [7][8][9][10][11][12][13][14][15][16][17][18][19] It promotes low-temperature catalysis for hydrogen production, ammonia synthesis, and other processes. Electrochemical impedance spectroscopy (EIS) of oxide surfaces under a H 2 O atmosphere has been investigated to elucidate the correlation between catalysis in an electric field and surface protonics (Scheme 1).…”