Improving Methylcyclohexane Dehydrogenation with ex-Situ Hydrogen Separation in a Reactor-Interstaged Membrane System

The potential utilizations of energy sources such as hydropower would be increased if effective energy storage systems were available. H{sub 2} storage, in the form of liquid organic hydrides, e.g., methylcyclohexane (MCH), was proposed for the seasonal storage of electricity. In summer, low-cost electricity is used for electrolysis of water to yield H{sub 2} which can be catalytically combined with toluene (TOL) to MCH. In winter, catalytic dehydrogenation of MCH releases the H{sub 2} for application as electricity by means of a turbine generator or fuel cells. A system of two plug-flow reactors with an interstaged tubular palladium-silver (Pd-Ag) membrane to ex-situ remove H{sub 2} was used to improve the efficiency of MCH dehydrogenation. A monometallic noble metal catalyst produced yields of TOL and hydrogen from MCH which were much higher than those corresponding to equilibrium at industrially relevant conditions. Experiments in this system at 593--673 K, 1--2 MPa, and overall liquid hourly space velocities of 1--2.6 h{sup {minus}1} afforded conversions up to 52% greater than those without membrane and 35% greater than the equilibrium values for a conventional reactor. However, the equilibrium conversions for the system itself were never exceeded. The membrane capacity was adequate to remove {approximately} 90%more » of the H{sub 2} present in the first reactor product. Results obtained with the two reactors--membrane system were close to those predicted using first reactor conversion data.« less