Aftertreatment - Precious Metals

[ivymike]

How many grams of platinum and rhodium are used in a three-way catalyst for a 200hp natural gas (turbocharged, spark ignited) engine?

 

[dcasto]

ask the vendors

 

[ivymike]

So far they seem reticent to share that info.

 

[ivymike]

Alternatively, if I knew that the catalyst element was 11.5" diameter and 3.5" thick, and that the precious metal loading was 20g/cuft, and that the platinum and rhodium were used in a 4:1 ratio, then I could calculate that the volume is 0.210ft3, the total mass of precious elements is 4.21g, and that 0.84g of that is rhodium, while 3.37g is platinum.

What I don't know is whether the final result makes sense - one thing that I worry about is whether the external dimensions of the catalyst element give an appropriate volume for the precious metals loading calculation (20g/cuft based on external dimensions? based on some sort of pore volume? based on ?)

 

[patprimmer]

If you can afford destructive testing, any metallurgical lab should be able to do a quantitative analyse for you. The Elmer Perkins type atomic absorption spectrophotometer is a name that seems to be rising from memories of my study of the subject in 1960 something or other.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[thruthefence]

Someone developing a "business plan"?

 

[GregLocock]

"the total mass of precious elements is 4.21g"

That is a good, possibly high, estimate. You are short one element, palladium typically. The precise proportions of which metal are used is very variable.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[J42]

Pd is replacing Pt quite a bit in newer catalyst designs. It is cheaper and generally can withstand higher temperatures. Manifold-mounted light-off catalysts are generally Pd-only. Destructive testing is probably the only way to know for sure, but under-floor 3-way catalysts with ~0:16:1 Ptd:Rh and ~30-50 g/ft^3 loading were fairly common for California LEV II and Federal Tier 2 vehicles a few years ago. Vehicles sold in Europe generally have less PGM loading due to their reduced km-useful-life requirements relative to the U.S. standards