Ortho-Parahydrogen Mixer, Catalysts, Measurement Devices and their Application

Abstract

For the majority of low temperature hydrogen applications the ortho- to parahydrogen (o-p-H2) spin configuration plays a vital role. Examples are liquid storage (heat of conversion) or neutron moderation (unequal cross section). Decreasing temperatures below ambient imply higher equilibrium p-H2 ratios. Often, rapid conversion close to the equilibrium is beneficial. The rather slow natural conversion can be sped up for example by catalytic contact to paramagnetic substances. For this, the paper gives an overview on published isothermal conversion catalyst data at LN2 temperature. Furthermore, an enhanced Catalyst Test Cryostat (CTC) facilitating new adiabatic and isothermal o-p-H2 catalyst conversion measurements is presented. Precise concentration determination is decisive. Hence, two commercial analyzers, essential for isothermal conversion measurements, using speed of sound or thermal conductivity will be compared to the performance of the independent adiabatic CTC results. Obtained activity data on an industrial catalyst at ≈77.3 K will be provided. Finally, a novel process, batch and closed cycle, providing mixtures with p-H2 contents ranging from 0.25 to ≈1.00 is introduced. The latter enables e.g. neutron moderation at stable, non-equilibrium o-p-H2 ratios.