Controlling the rate of change of Ni dispersion in commercial catalyst by ALD overcoat during dry reforming of methane. (28th April 2020)

• Record Type: Journal Article
• Authors: Afzal, Shaik; Prakash, Anuj V.; Littlewood, Patrick; Marks, Tobin J.; Weitz, Eric; Stair, Peter C.; Elbashir, Nimir O.
• Is Part Of: International journal of hydrogen energy. Volume 45:Number 23(2020)
• Page Start: 12835
• Page End: 12848
• Publication Date: 2020-04-28
• Subjects: Chemisorption -- Atomic layer deposition (ALD) -- Dispersion -- Methane dry reforming (DRM) -- Ni catalyst; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2020.03.008
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: This study investigates changes in dispersion with time-on-stream of a Ni catalyst coated with alumina by Atomic Layer Deposition (ALD) in Dry Reforming of Methane (DRM) conditions. A 20 wt% commercial Ni catalyst is coated with 5, 10, and 20 ALD cycles and tested for DRM at 650 °C, 1 atm for 40 h. Using an in-situ H2 –CO pulse chemisorption technique, it is found that the rate of decline in catalyst dispersion is more rapid in the uncoated catalyst (~0.11%h −1 ) than 5-ALD catalyst (~0.025%h −1 ). TEM images before and after reaction show that the average particle size for the uncoated catalyst increases from 8.5 nm to 24.5 nm, indicating sintering, whereas the 5-ALD catalyst retained the initial particle size. The reduced particle size also explains the 50% reduction in carbon formation-rate in the 5-ALD catalyst. The developed sequential H2 –CO chemisorption technique reliably measures in-situ dispersion in uncoated and ALD coated catalysts with exposed active sites. Graphical abstract: Image 1 Highlights: A dual H2 –CO chemisorption method for in-situ estimation of catalyst metal dispersion. Rate of dispersion loss much lower in ALD-coated Ni catalysts than uncoated catalyst. Chemisorption results contrasted with TEM. Unusual CO adsorption and H2 desorption patterns for ALD catalysts.