Speaker
Description
The storage and handling of liquid hydrogen (LH₂) are critical components of cryogenic hydrogen engineering, particularly as LH₂ is poised to play a pivotal role in future energy systems. At ambient temperature, hydrogen gas consists of approximately 75 % ortho-hydrogen and 25 % para-hydrogen. However, at the normal boiling point of LH₂ (20.3 K), the equilibrium para-hydrogen concentration increases to 99.8 %. Efficient and stable LH₂ storage requires the catalytic conversion of ortho-hydrogen to para-hydrogen during liquefaction, as the exothermic nature of this conversion generates heat that can cause hydrogen boil-off. Ionex, a commercially available catalyst based on hydrous ferric oxide, is widely utilised for ortho-para conversion (OPC) in industrial liquefaction systems. However, the activation and pre-treatment of such catalysts are critical to achieving optimal performance under cryogenic conditions. Despite its importance, the mechanisms underlying pre-treatment methods and their effects on catalyst activity remain poorly understood.
This study investigates the influence of different catalyst pre-treatment methods - including hydrogen flow, vacuum pre-treatment, and helium flow - on the performance of Ionex catalysts. One gram of Ionex was loaded into a fixed-bed reactor and subjected to pre-treatment at temperatures of 140, 160, and 180 °C for varying durations (4 and 16 hours). The OPC performance was evaluated at 77 K (liquid nitrogen bath) using a thermal conductivity detector (TCD) to determine the para-hydrogen concentration. Results demonstrate that vacuum and helium flow pre-treatment yield higher catalyst activity. Advanced characterisation techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and superconducting quantum interference device (SQUID) magnetometry, were employed to investigate catalyst structure, composition, and magnetic properties with pre-treatment conditions and performance.
By identifying improved pre-treatment strategies, this study contributes to enhancing the efficiency of cryogenic hydrogen liquefaction systems. Furthermore, these findings may provide valuable insights into practical industrial activation procedures for next-generation catalysts, enabling more effective and sustainable LH₂ storage and transport.
