Thin-felt microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalyst for high-throughput CO oxidation

Abstract

Gold nanoparticles supported on Fe2O3 are a promising type of catalyst for CO oxidation. One challenge for their application in the real world is developing novel monolithic catalytic packings to meet the fundamental criteria (for example, high catalyst utilization efficiency and low pressure drop) needed for such high-throughput reaction process. Herein, a highly active and efficient thin-felt microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalyst with unique form factor and high permeability is fabricated for the low-temperature CO oxidation. Initially, thin-felt Al-fiber felt (60 μm diameter; 85 vol% voidage) undergoes a steam-only oxidation and calcination to create a 0.7 μm mesoporous layer of γ-Al2O3 nanosheets (ns-γ-Al2O3) along with the Al-fiber. Subsequently, α-Fe2O3 is hydrothermally grown onto the ns-γ-Al2O3 layer followed by Au nanoparticle deposition via urea-assistant deposition-precipitation method. As-resulted microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalysts effectively and efficiently couple the low-temperature activity and improved water vapor tolerance with enhanced catalyst accessibility and high permeability. The promising microfibrous-structured catalyst with only 0.14 wt% Au and 1.4 wt% α-Fe2O3 is capable of fully or 40% oxidizing CO into CO2 at 25 °C or 0 °C for a feed gas of 2 vol% CO and 0.3 vol% water vapor in air at a high linear velocity of 0.7 cm s−1, using a high gas hourly space velocity of 25,200 mL g−1 cat h−1. Moreover, the microfibrous-structured catalyst performs robustly for at least 232 h under the changeable temperature conditions. Interestingly, 3D hierarchical porous flake structure of α-Fe2O3 nano-sheets is detected other than the irregular micron-sized particles, leading to a 3-fold increase in the intrinsic activity (TOF of 0.46 s-1 for the Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber vs. 0.11 s−1 for the Au-α-Fe2O3 powder at 25 °C).