Film Catalyst

[Enthalpy]

Dear all,

here's a suggestion to deposit metal catalysts on a thin supporting film. The resulting specific area is favourable, one machine can deposit about any metal and works quickly.

The machine resembles the ones that deposit aluminium on polyester film for candy wraps and space blankets. It can be adapted from such a machine, new or second-hand. The machine passes the supporting film between two mandrels and deposits meanwhile the catalyst metal under vacuum. Covering both sides of the film is better, at the same pass even better.

 

Ptfe, Pe and Pp resist many chemicals and may be the supporting film, but they can't be very thin. Nickel, cobalt and alloys can be electrodeposited as standalone films with 8µm thickness and up. Tantalum and niobium can be laminated but not as thin. Thin tantalum deposited on supporting nickel-cobalt would improve the chemical resistance, and the catalyst metal could come atop.

Ptfe, Pe and Pp need some surface treatment before the catalyst adheres. A supporting metal film probably needs cleaning. Doing it in the same machine (by plasma?) without breaking the vacuum or low pressure thereafter seems better.

Traditionally for semiconductors, an electron gun evaporates the varied metals, even refractory ones. Sputtering is a more recent source, also flexible. A nanosecond pulsed laser should be considered. A machine for candy wraps takes coils over 1m tall, so stacking several souces of catalyst metal seems better.

Measuring off-the-fly the deposited thickness at various heights to control the sources is advantageous with expensive metals. Observing the light reflectance at few short wavelengths may suffice.

To let the reactants, products and solvents through, the plies must be separated, for instance with a thin wire, as they are stacked or rolled. Alternately, a rolling mill can make corrugations or bumps in the films, possibly at every second ply. If the catalyst coil or stack stays loose, being held together by a loop of metal for instance, it's easier to clean and regenerate - advantage over a sintered ceramic.

When seeking compactness, the channels would be thin too, hampering the flow of liquids. An answer is to provide a set of additional wider ways, possibly cut by laser across the stack or coil, to and from the thin channels - possibly as a tree, like animals have arteries, arterioles, capillaries, venules and veins. This applies to sintered materials too.

 

Marc Schaefer, aka Enthalpy

[StringJunky]

This should be in Speculations.

[Enthalpy]

Thanks for your interest!

 

I've already seen more speculative ideas than thin-film deposition.

[John Cuthber]

The mylar with a layer of Al is shiny.

Catalysts aren't.

That's because the very small particles of catalysts are too small to reflect light properly.

If you make a nice shiny layer of, for example, Pt or Ni it will be a poor catalyst because it won't have much surface area compared to Pt black or Raney Ni.

[Enthalpy]

Hi JC and the others, thanks for the input!

 

There is no hard limit to the thinness of a deposited film. When I worked in this field during the paleomonolithic era, aluminium films were commonly 1µm thick. On a Mylar space blanket it's rather 100nm. Presently with 14nm long transistors, metal layers are thinner than 10nm and still well reproducible.

 

So I'm confident that thickness under 10nm can be achieved, which is adequate for most catalyst metals. Ruthenium and the most expensive metals are made thinner, so film evaporation may not be interesting for them. Fine, no solution is universal.

 

An other criterium is "what catalyst area fits in a given volume". This differs from the thickness of the active metal because ultra-thin catalysts are supported, for instance on grains of an incompletely sintered ceramic, which are less small. The films I propose are few 10µm thick and can be packed to, say, 100µm stacking. This is roughly equivalent to a supporting powder with 100µm grain size, which is already interesting. While a porous sintered ceramic could be finer than 100µm grain size, the production method I propose adapts to about any catalyst metal, and the catalyst can be opened and cleaned.