Synthesis of supported Ni catalysts by atomic layer deposition

• Supported Ni nanoparticles were grown on Al2O3 by atomic layer deposition (ALD).
• Average particle sizes were 2.4–3.3 nm at Ni weight loadings of 4.7–16.7 wt%.
• Carbon monoxide TPD indicated more step and kink sites on ALD catalysts.
• Preparing catalysts by ALD increased propylene hydrogenolysis selectivity.

Nickel nanoparticles grown on an Al2O3 support by atomic layer deposition (ALD) had higher selectivity for propylene hydrogenolysis. The Ni was deposited in a fluidized bed reactor with bis(cyclopentyldienyl)Ni and H2 reactants. Varying the number of ALD cycles varied the Ni loading between 4.7–16.8 wt.% and the average Ni particle diameters between 2.4 and 3.3 nm. The number of surface sites per gram of Ni, determined from CO TPD, was at least five times higher on ALD-prepared catalysts than typical Ni/Al2O3 catalysts prepared by incipient wetness impregnation. The fraction of CO desorbed from steps and kinks on the ALD-prepared catalysts was at least three times higher. Correspondingly, the selectivity for propylene hydrogenolysis, instead of hydrogenation, was above 10% on an ALD-prepared catalyst but below 0.4% on the incipient wetness catalyst. Preparing catalysts by ALD appeared to increase the step and kink site density and thus increase hydrogenolysis selectivity.

Supported Ni nanoparticles were synthesized via atomic layer deposition (ALD) with average particle sizes ranging from 2.4 to 3.3 nm and Ni weight loadings from 4.7 to 16.7%. This scalable gas-phase technique produced supported catalysts with enhanced propylene hydrogenolysis TOFs and selectivities. Enhanced catalytic activity was attributed to the step and kink defects induced from the small particle size. These defects, along with particle size were shown to vary with the number of ALD cycles.Figure optionsDownload high-quality image (63 K)Download as PowerPoint slide