Spray Jet Flames for Supported Gold Catalysts: New Catalysts by Intelligent Design

University Of Cincinnati Main Campus, Cincinnati OH

Investigators

Abstract

ABSTRACT Proposal Number: 0626063 Principal Investigator: Beaucage, Gregory Affiliation: University of Cincinnati Main Campus Proposal Title: Spray Jet Flames for Supported Gold Catalysts: New Catalysts by Intelligent Design Intellectual Merit: Flames offer a unique environment for nano-particle growth since they contain high degrees of super-saturation, extremely high temperatures and rapid quench conditions, locking in kinetic structures. Spray jets flames offer the most versatile and controllable of pyrolytic conditions for nano-particle formation. A jet of organometallic liquid spray can be ignited to produce copious quantities of nano-materials with surprisingly controlled morphologies. This spray flame process (SFP) is of great potential for mass production of nano-materials, especially oxides and supported metals. Observation of the growth of such nano-materials is difficult due to light emission, high temperature (> 2000 C), flow rates approaching the speed of sound with the total growth spanning a few milliseconds. The study of the dynamics of particle growth under such rapid growth conditions requires in situ techniques capable of rapid detection and being insensitive to extremely high temperatures, brilliant optical emission, and high noise. This proposal seeks to design SFP synthesis of supported gold nano-catalysts by understanding the basis of structural nucleation and growth in this complex "co-precipitation"- like reaction. Such design can now be made due to recent advances in characterization of nanoparticle nucleation, growth and aggregation in flames using in situ x-ray scattering. In the proposed work, anomalous scattering (ASAXS) is used to isolate the contribution due to gold from that of the support through contrast matching. This is similar to dark field imaging in TEM except that ASAXS has elemental resolution rather than crystallographic resolution. The proposed work will be the first in situ use of ASAXS for multiphase aerosol nano-powders. In situ ASAXS can measure independently the evolution of Au and support (TiO2) Sauter mean diameters, size distribution, volume fraction, number concentration, and aggregate mass fractal dimension, size and number of primary particles per aggregate as well as branch content in the flame with 50 micron spatial resolution and 20 ms exposure time. In collaboration with ETHZ, droplet velocities will be measured by 2D-Phase Doppler Anemometry (PDA) and gas temperature by Fourier transform infrared (FTIR) emission/transmission spectroscopy. In previous measurements on single component spray flames, droplet evaporation, nano-material nucleation and aggregation including details on the rate of particle growth, aggregation and branching have been directly observed. Broader Impacts: The project will support a PhD candidate and 2 undergraduates in this effort. Continued interaction with researchers at ETHZ (Zurich) are planned. The proposal includes continued development of a web course on Nano-powders at UC. The project will also involve development of a new shared course on Nano-Scale Catalytic Technology focusing on supported metal catalysts and nano-size/shape effects that will involve contributions from the Swiss collaborators. This course will be jointly offered at UC and ETHZ. The web course has been an effective means to disseminate information to the community with over 130,000 independent IP hits to the course suite since 2000 (~60/day).