Tuning of catalytic sites in Pt/TiO2 catalysts for the chemoselective hydrogenation of 3-nitrostyrene

Abstract

Tuning the catalytic activities of supported metal nanoparticles can be achieved by manipulating their structural properties using an appropriate design and synthesis strategy. Each step in a catalyst synthesis method can potentially play an important role in preparing the most efficient catalyst for a particular chemical reaction. Here we report the careful manipulation of the post-synthetic heat treatment procedure, together with control over the the amount of metal loading, to prepare a highly efficient 0.2 wt.% Pt/TiO2 catalyst for the chemoselective hydrogenation of 3nitrostyrene. We found that for Pt/TiO2 catalysts with 0.2 and 0.5wt.% loading levels, reduction alone at 450 °C induces the coverage of Pt nanoparticles by TiOx through a strong metal support interaction which is detrimental for their catalytic activities. However, this surface coverage can be avoided by combining a calcination treatment at 450 °C with a subsequent reduction treatment at 450 °C allowing us to prepare a exceptionally active Pt/TiO2 catalyst with the optimum Pt distribution. Detailed characterisation of these catalysts has revealed that the peripheral sites at the Pt metal/TiO2 support interface are the most likely active sites for this hydrogenation reaction.

The dynamics of overlayer formation on catalyst nanoparticles and strong metal-support interaction

“…Subsequent exposure to oxygen segregates the titanium from the alloy, and a thicker titania overlayer forms. This thicker fully oxidized overlayer is stable in oxygen and potentially opens new possibilities for catalysis 10 . The stabilization of the oxide overlayer in oxygen environment shows that the SMSI state can as well be utilized in catalytic oxidation reactions.…”

“…Typically, noble metal catalysts exhibit very high activity but suffer from poor chemoselectivity. Tuning such catalysts by a high-temperature reduction treatment, revealed impressive improvement of the chemoselectivity without loss in catalytic activity [9][10][11] . These reported advances nevertheless lack of an actual understanding how the reductive pretreatment alters the catalyst, but often mainly refer to the original work 5,12 .…”

Chemoselective Hydrogenation of Nitroaromatics at the Nanoscale Iron(III)–OH–Platinum Interface

“…This is because nitroaromatic is prone to adsorb in a flat manner with both the benzene ring and conjugated groups directly interacting with the Pt surface, resulting in an indiscriminate attack by H atoms. To circumvent this problem, numerous efforts have been made, for example, downsizing Pt nanoparticles to clusters, even to single atoms, confining Pt nanoparticles in microporous solids, or adding organic ligands, another metals or metal oxides . These modifications shared the same strategy to modulate the adsorption behavior of nitrobenzene to prevent the flat adsorption through electronic and/or steric effects.…”

Effect of Fe, Co and Ni promoters on MoS2 based catalysts for chemoselective hydrogenation of nitroarenes

“…1,2 However, the selective reduction of functionalized nitro compounds is challenging due to the presence of other highly reducible groups, such as C]C, C]O and C^C groups. 3,4 Traditionally, the noble metal (such as Pt, Pd, Ru, Rh, Au, Ag) catalysts have frequently been reported for this transformation, but the viability and cost of noble metals is a major barrier for their industrial applications. [5][6][7][8][9] Thus, the non-noble metal based catalysts including the base metals, their oxides, carbides and suldes have been extensively studied as the alternatives.…”