Atomic Layer Deposition for Enhanced Reactivity, Stability, and Sulfur Tolerance of Hydrogenation Catalysts

Research output: NRELPresentation


Heterogeneous catalysts are an essential tool in the transition towards a sustainable, bio-based economy for fuels and chemicals. However, many key biomass conversion processes utilize harsh conditions that lead to nanoparticle sintering, support collapse, and metal leaching in conventional PGM catalysts. Active site poisoning resulting from the relatively high sulfur content of most biomass feedstocks further compounds these durability problems. Next-generation catalysts must be developed to address these stability challenges. In this work, we have used atomic layer deposition (ALD), to modify a conventional Pd/Al2O3 hydrogenation catalyst and generate improvements in its stability and sulfur tolerance, as well as overall catalyst activity. Ten cycles of TiO2ALD were applied to Pd/Al2O3 using a proprietary coating process developed by industry partners. The coated catalyst (10cTiO2), alongside uncoated Pd/TiO2 and Pd/Al2O3 controls, was characterized in-depth and naphthalene hydrogenation was used as a probe reaction to assess activity. The 10cTiO2 catalyst was observed to be significantly more active towards hydrogenation than uncoated Pd/Al2O3, despite evidence that the ALD coating suppressed chemisorption uptake through coverage of Pd. In order to reconcile these seemingly contradictory findings, interactions between the Pd nanoparticles and TiO2ALD coating were investigated via XAS and computational modeling. The catalysts were also assessed for their sulfur tolerance, thermal stability, and hydrothermal stability. Each of these catalyst stability parameters was enhanced by application of the TiO2ALD layer; the mechanisms by which the layer may have mitigated these degradation processes will be discussed. ALD technology holds great potential in the development of next-generation catalysts for biofuels and bioproducts and this work constitutes an important examination of the expected and unexpected benefits of applying TiO2ALD coatings to supported Pd hydrogenation catalysts.
Original languageAmerican English
Number of pages18
StatePublished - 2020

Publication series

NamePresented at the PALD Summit, 9-10 December 2020

NREL Publication Number

  • NREL/PR-5100-78301


  • biomass
  • biomass feedstocks
  • conversion
  • heterogeneous catalysts


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