This work focused on enhancing catalyst activity and durability by developing a method to control size, dispersion, and exposure. Existing nanocatalysts are typically fabricated in bulk or powder form. There are monolithic catalysts, but they rely on meso-porous materials as supports. Bulk nanocatalysts suffer from a lack of complete exposure to reagents, counteracting the benefits of the nanoparticles. Catalysts upon meso-porous support have limited exposure due to diffusion distances through the porous support. This requires higher catalyst loading, and may lead to particle coalescence and deactivation.
This innovation consists of a hierarchical nanocatalyst support structure for incorporation within microchannel reactors. The hierarchical support consists of a 3D network of open pores within the microreactor structure, which is coated with a nanofabricated support (e.g., nanotubes or nanorods). The nanocatalyst particles are deposited upon the nanofabricated support.
There are no separate parts. The hierarchical support is fabricated or assembled within a microchannel reactor system. The hierarchical support is an integral part of a reactor, and the operation is the same as any conventional reactor. Reagents are supplied and temperature is controlled to the desired values.
The preferred system will have the hierarchical support as an integral part of a microchannel reactor layered structure. An alternate embodiment is to use the hierarchical support structure as monoliths inserted into a confined space to avoid flow bypass.
Catalytic efficiency increases with decreasing catalyst particle size (reflecting higher surface area per unit mass), and chemical reactivity frequently is enhanced at the nanoscale. By virtue of their nanoscale dimensions, nanotubes and nanorods geometrically restrict the catalyst particle size that can be supported upon the tube walls. By confining catalyst particles to sizes smaller than the CNT diameter, a more uniform catalyst particle size distribution may be maintained. The high dispersion provided by the vast surface area of the nanoscale material serves to retain the integrity of the catalyst by reducing sintering or coalescence.