Functional Nano Porous Materials for Environmental Catalysis Applications
Creators: name: Jince, Libitha
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 401807
subject: Nanomaterials
classificationCode: 400408
subject: Reaction engineering (excl. nuclear reactions)

description: Catalytic processes that can reduce the emission of environmentally unacceptable compounds are commonly referred as environmental catalysis. Catalytic oxidation of these pollutants under ambient conditions is considered as an emerging candidate to control their presence in the environment and the reduce their impact to the environment. Nanostructured gold catalysts have been demonstrated as green catalysts for the oxidation of hydrocarbons, alcohols, amines, and aldehydes. The major objective of this thesis was the rational design of nanostructured gold catalysts deposited on three different kinds of support materials for the removal of diesel soot particles,and volatile organic carbon oxidation removal. This unique approach of using nanostructured gold catalysts in environmental catalysis exemplifies the adaptation of catalytic clean-up technologies and sustainable practices to reduce the environmental impact.

In the first part of this work, calcined hydrotalcite supported nanostructured gold catalysts were synthesized and catalytic oxidation of diesel soot particles were investigated over these catalysts. Five different amino acid molecules including aspartic acid, histidine, lysine, tryptophan and tyrosine were used to intercalate the layers between hydrotalcites and these amino acids reduce the gold ions into gold nanoparticles within these layers. Subsequent calcination of these materials led to the formation of nanostructured gold catalysts and investigated for catalytic oxidation of diesel soot particles. Interestingly, the Calcined hydrotalcite supported gold catalysts using the histidine and lysine amino acid exhibited a remarkable higher soot oxidation activity with a T50 of 460 °C. The enhancement in the soot oxidation activity has been attributed to a strong interaction between the highly dispersed gold nanoparticles and calcined hydrotalcite support. The effects of the crystalline phase of the support, nature of amino acid and the activation conditions were also assessed in the case of soot particles oxidation.

The second part of this work describes the preparation, characterization and application of mesoporous carbon supported nanogold catalysts towards the oxidation of volatile organic compounds. The mesoporous carbon support was synthesized from the carbonization of F127 templated Resorcinol-Formaldehyde resin. Five different amino acids (aspartic acid, histidine, lysine, tryptophan and tyrosine) and chloroauric acid were added during the F127 templated RF gel formation and subsequent carbonization to obtain the porous carbon material supported gold nanoparticles. These nanoparticles were screened for their selective oxidation of carbon monoxide under ambient conditions. Oxidation of CO was observed at room temperature was observed over these mesoporous carbon-supported gold catalysts. Mesoporous carbon support favor the formation of very small gold nanoparticles, with gold loading of 1 wt%, estimated by elemental analysis. The fresh and spent catalysts were characterized using different characterising technology; BET, XRD, TGA, XPS and TEM, to understand stability and activity of these catalysts.

These findings were elucidated using amino acids to functionalize different supports by gold nanoparticles and studying them for the removal of soot particles, and VOC oxidation . Overall, this work demonstrates the growing applications of functional gold catalysts in environmental catalysts and aids in the understanding of the catalytic activity of gold on different support and their role in catalytic oxidation.