(141a) Ozone Removal At Micro-Second Contact Time for Aircraft Cabin Air Using Microfibrous Entrapped Catalysts

Microfibrous Entrapped Catalyst (MFEC) manufactured from 8 μm diameter nickel fibers were engineered into pleated heterogeneous catalytic reactors to improve removal performance from conventional packed bed and monolith reactors, since microfibrous materials can entrap small particles (150-200 μm) which significantly improves inter phase mass transfer. Conventional reactors usually operate with contact time less than 1s. MFEC reactors were able to reduce the contact time to micro seconds while maintaining similar catalytic performance. This gives MFEC a huge advantage in terms of weight and volume saving, since the conventional meter-long reactors were shortened to millimeter thick material sheets. These unique reactors were targeted at ozone, which was widely recognized as No.1 aircraft cabin air pollutant.

In this research, MFEC reactors were investigated under aircraft bleed air conditions of high temperature (100-200°C) and high face velocity (10-30 m/s) resulting an interlayer contact time of 67-200μsec. Precious metal (Pd, Ag) and transition metal (Mn) catalysts were impregnated on entrapped particles (e.g. γ-Al₂O₃) using incipient wetness method. Ozone test concentration was set at a high-demanding 1.5 ppmv. Results showed that a high level of ozone decomposition was achieved with a significant reduction of catalyst consumption. Compared with conventional aircraft filters, this can be a huge advantage in terms of material cost and labor. Reaction kinetics analyses were compared for different catalysts. Results showed that precious metal catalyst performs better at a higher temperature while transition metal catalyst maintains similar conversion when changing temperature. XPS, TPR and TGA tests have been used to evaluate performance of catalysts and modify catalysts to improve conversion rate. Also catalyst aging tests were carried according to the frequency of commercial aircraft ozone reactor replacement, which evaluated long-term performance for actual MFEC reactor usage. In addition, pressure drop improvement by pleating MFEC was also evaluated with comparison of traditional low pressure drop monolith reactors. CFD model has also been established for pressure prediction and comparison. It showed that pleated structure enable MFEC to avoid higher pressure drop and eliminate the problem of direct channeling caused by monolith.