Electrocatalytic Hydrogenation of Toluene in a PEM Reactor As a Study of a Model Reaction for Hydrogen Storage

Abstract

Chemical conversion of toluene (TL) to methylcyclohexane (MCH) has been examined to develop a novel organic chemical hydride system. One of the most promising hydrogen storage techniques relies on the organic chemical hydride because of its safety and feasible handling. To produce methylcyclohexane effectively, we investigated electrochemical hydrogenation of toluene using PEM (Proton Exchange Membrane) reactor with various noble metal supported catalysts and found that PtRu/C catalyst afforded excellent current efficiencies for the hydrogenation. However, it has not been made clear whether by-products (e.g. partially hydrogenated products) are produced in the hydrogenation of toluene. In this work, we demonstrated a systematic study on the electrocatalytic hydrogenation of toluene to methylcyclohexane in order to clarify the above question.As a results, Methylcyclohexane was obtained as a main product with high current efficiencies in all cases. However, small amounts of the partially hydrogenated product such as 1-methyl-1-cyclohexene (1-ene) was also produced. In addition, very small amounts of 3-methyl-1-cyclohexene and 4-methyl-1-cyclohexene were also detected by using the Ru catalyst. Among the all tested catalysts, the use of PtRu catalyst gave better selectivity and higher current efficiency (>99%) for the desired product like methylcyclohexane. Hence, it can be stated that PtRu is the most suitable catalyst for the electrochemical hydrogenation of toluene. Probably, PtRu/C catalyst exhibited dual functions such as the high catalytic activity of the rich Had on Pt and the strong toluene adsorption by Ru. This synergy would result in excellent current efficiencies for the hydrogenation of toluene to methylcyclohexane. Figure 1