Recommend the length of a catalyst bed required for 99.5% control of hexane in air. The airflow rate is 10,000 cfm (at 30 ft/sec), and the channels in the particular honeycomb catalyst that will be used have an effective diameter of 0.05 in. The diffusivity of hexane in air is 0.075 cm2/sec. Assume flow in the channels is laminar.