Unraveling property-performance relationships by surface tailoring of oxidation catalysts via ALD

Atomic layer deposition (ALD) of POx on V2O5 powder was applied as a tool to tailor active and selective sites of a bulk catalyst. ALD leads to homogeneous P deposition on the V2O5 surface with linear increase of P content with each ALD cycle. The catalyst performance was evaluated and correlated to structural motifs identified by detailed characterization methods. The catalytic conversion of butane to maleic anhydride (MAN) was chosen as proof-of-concept reaction. The selectivity towards MAN increases with ALD cycle number from 1–3 ALD cycles and remains constant at higher ALD cycles. Restructuring of the catalyst surface is induced by steam during reaction conditions at elevated temperatures. Excessive P is migrating away from the catalyst surface to form various VOPO4 polymorphs revealing partially but homogeneously covered V2O5 by P. The formed VOPO4 species barely contribute to the yield to MAN. Solid-state 31P-NMR was used to identify fingerprints relevant for selectivity and activity. This work shows that synthesizing model catalysts by atomic layer deposition combined with detailed analytics can reveal property-performance relationships.DFG, 390540038, EXC 2008: Unifying Systems in Catalysis "UniSysCat