Coking and Sintering Resistance of ALD Catalyst for Dry Reforming of Methane

Atomic Layer Deposition (ALD) is a technique to coat thin films in the order of nanometers on solid substrates. It has been shown that the selectivity/activity of catalysts can be altered by the proper tuning of these overcoats¹.

In this work, the objective is to investigate the effect of ALD on the performance of a commercial 20% Ni/Al₂O₃ catalyst in dry reforming conditions. Using TMA as precursor, various cycles of alumina are overcoated on the commercial catalyst. This catalyst is tested against the uncoated catalyst at different temperatures. Apart from stability testing, the crystallite size of the nickel nanoparticles is determined after definite time periods. The crystallite size is calculated from the dispersion which is obtained from H₂ chemisorption. The ALD coating on the nickel active material is purported to prevent sintering by anchoring the nickel nanoparticles. The amount of coke deposited after each run is also estimated by a Temperature-Programmed-Oxidation (TPO) done at the end of each run. At lower temperatures (~600 °C), coking is supposed to be the dominant deactivation mechanism and at higher temperatures (~800 °C), it is sintering. By studying both these phenomena at different temperatures for ALD with different number of cycles, this work will help better understand the role of the overcoat in the performance of ALD catalysts, and help identify the operating conditions where ALD catalysts have a positive effect on catalytic performance.

REFERENCES

(1) O, B. J.; K Jackson, D. H.; Lee, J.; Canlas, C.; Stair, P. C.; Marshall, C. L.; Elam, J. W.; Kuech, T. F.; Dumesic, J. A.; Huber, G. W. Catalyst Design with Atomic Layer Deposition. ACS Catal. 2015, 5, 1804−1825.