Mass-Transfer Characterization of Metallic Foams as Supports for Structured Catalysts

Abstract

Open-celled metal foams have been characterized as supports for structured catalysts, considering their utilization in gas−solid catalytic processes with short contact times and high reaction rates, typically controlled by gas−solid diffusional mass transport. Examples of such processes are found in the field of environmental catalysis, including, e.g., catalytic combustion, selective catalytic reduction (SCR-DeNOx), and automotive exhaust gas after treatment. In this work, foams with different cell sizes were coated with a thin layer of palladium−alumina and tested in a 9-mm inner diameter tubular reactor by performing the catalytic oxidation of CO at empty tube velocities in the range of 0.8−2.6 m/s. The coated foams exhibited sufficient catalytic activity to achieve mass-transfer-limited operation in the temperature range of 300−450 °C. Under such conditions, mass-transfer coefficients were determined according to a simple one-dimensional model of the test reactor. Adopting the average diameter of the ...