Abstract
Benzyl alcohol was oxidized by an “in situ generated” hydrogen peroxy species, formed from a dilute mixture of hydrogen and oxygen, under mild conditions at a high rate over gold, palladium and gold–palladium nanoparticles supported on hierarchical titanium silicate materials. Hierarchical TS-1 supports were obtained from the crystallization of silanized protozeolitic units, being characterized by having a secondary porous system within supermicro/mesopore range and an enhanced surface area over a standard reference TS-1 material. The presence of the secondary porosity not only improves the accessibility to the active sites of the relatively large reactant molecules but also enhances the metal dispersion, leading to an improved catalytic performance for alcohol oxidation. The catalytic activity of metal loaded hierarchical TS-1 materials was found to be higher in reactions conducted in the presence of diluted hydrogen and oxygen, resulting in a 5-fold increase in the yield of benzaldehyde at 30 °C with an AuPd catalyst with secondary porosity. The improvement in rate observed is due to the oxidizing efficacy of in situ generated hydroperoxy species as compared to molecular oxygen alone as the terminal oxidant.
Highlights
Hierarchical TS-1 has been obtained with hard-templates based on porous carbon9,10 and soft templates such as surfactants or organosilane molecules.11,12 Recently, it has been reported the preparation of hierarchical TS-1 materials from the crystallization of silanized protozeolitic units.13,14 In this strategy, an organosilane compound is added to a solution of protozeolitic units, formed previously by a precrystallization step
In this paper we report the application of in situ generated hydroperoxy species at low concentrations with hierarchical TS-1, prepared from silanized protozeolitic units, as a support to gold and palladium nano-particles for benzyl alcohol oxidation as a model reaction
Hierarchical titanium silicates materials (TS-1), prepared by silanization of protozeolitic units,13,14 were used as a support for gold and palladium nanocrystals (Au, Pd)
Summary
Hierarchical TS-1 has been obtained with hard-templates based on porous carbon9,10 and soft templates such as surfactants or organosilane molecules.11,12 Recently, it has been reported the preparation of hierarchical TS-1 materials from the crystallization of silanized protozeolitic units.13,14 In this strategy, an organosilane compound is added to a solution of protozeolitic units, formed previously by a precrystallization step. In this paper we report the application of in situ generated hydroperoxy species at low concentrations with hierarchical TS-1, prepared from silanized protozeolitic units, as a support to gold and palladium nano-particles for benzyl alcohol oxidation as a model reaction. The production rate of benzaldehyde from the oxidation of benzyl alcohol will be used to evaluate these hierarchical materials as catalysts with dual functionality.
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