Conversion rate of para-hydrogen to ortho-hydrogen by oxygen: implications for PHIP gas storage and utilization

摘要

Object To determine the storability of para-hydrogen before reestablishment of the room temperature thermal equilibrium mixture. Materials and methods Para-hydrogen was produced at near 100 % purity and mixed with different oxygen quantities to determine the rate of conversion to the thermal equilibrium mixture of 75: 25 % (ortho: para) by detecting the ortho-hydrogen 1H nuclear magnetic resonance using a 9.4 T imager. Results The para-hydrogen to ortho-hydrogen velocity constant, k, near room temperature (292 K) was determined to be 8.27 ± 1.30 L/mol·min~(-1). This value was calculated utilizing four different oxygen fractions. Conclusions Para-hydrogen conversion to ortho-hydrogen by oxygen can be minimized for long term storage with judicious removal of oxygen contamination. Prior calculated velocity rates were confirmed demonstrating a dependence on only the oxygen concentration.