Microfibrous Entrapped Catalysts for Cleaning Aircraft Cabin Air: VOC Removal at Ultra-Short Short Contact Times

Abstract

Purification of breathing air in an aircraft cabin is important to ensure the safety and the comfort for both passengers and airline personnel. Among various molecular contaminants, volatile organic compounds (VOCs) are an important class of contaminants that need purification. Therefore, catalytic removal of VOCs (using a catalytic reactor) from cabin air is of utmost importance. Weight and volume of the catalytic reactors are important factors to be considered. Furthermore, the catalytic reactors should be able to operate at high face velocity of the jet engine bleed air. Catalyst-coated-monolith and packed-bed reactors are intended for this purpose but they were originally developed for different operating conditions. These current techniques result high pressure drop, and low fluid-solid mass transfer rate at such high face velocity and operating temperature. A unique class of composite material, microfibrous entrapped catalyst (MFEC), prepared by traditional low cost paper making technique, can entrap small catalyst particulates into sinter-locked networks of metal microfibers. These materials can be tailored to high and variable voidage, and are in the form of thin flexible sheets which have the ability of pleating. MFEC with the pleated configuration (Number of pleat 4) exhibits significant reduction in pressure drop, and higher catalyst utilization. Also, entrapped small particles in MFEC enhance interphase and intra-particle mass transfer rates. Catalytic oxidation of n-hexane (a model VOC), in a prototype aircraft cabin catalytic converter, was investigated at typical face velocities (from 10 to 30 m/s). This high face velocity resulted intra-bed/intra-layer residence times from 350 μsec to 115 μsec. This paper discusses the performance of MFEC for VOC removal from aircraft cabins in terms of pressure drop and oxidation at short contact time. Results of this study have shown significant improvement in overall system performance. Catalyst characterization and detailed reaction kinetics will be discussed using the experimental findings.