I bought some of this...

[Alan]

https://smile.amazon.com/dp/B085W6TXJ8?psc=1&ref=ppx_yo2ov_dt_b_product_details

This is 3A molecular sieve, which is a desiccant. Seven pounds of it come in a gallon plastic container, and the 3A (3 Angstroms or .3 nm) means the pores are really, really small! I bought another plastic filter media holder (https://smile.amazon.com/dp/B093F3HNSG?psc=1&ref=ppx_yo2ov_dt_b_product_details) and the necessary fittings. I put the "dryer" ahead of the silica gel-filled housing, so I could tell when the 3A should be replaced. Supposedly, the 3A material has some sort of color change, but it isn't specified. 

So far, there is virtually no moisture coming from the moisture trap on the Hill EC-3000, when I bleed off the air from my refills.

You can reuse the material, but you need a special kiln to retry it, but since the stuff is relatively cheap, I'm not going to worry too much. after all, having a dry air tank you your airgun is a good thing.

[bnowlin]

I use the same stuff ahead of the compressor and it doesn't or hasn't changed color.  However somewhere I've read where it needs to be under pressure to work properly. I don't know, but it seems as though it works.  I have tried the stuff Hill sells on PA.  It tended to melt and gummed up my compressor and the fill port on my Mrod.
Bobn
 

[T3PRanchAGS]

I get mine here. https://www.deltaadsorbents.com/molecular-sieve/ .  I also have my Federal Alcohol Fuel Production permit and use the same 3A Zeolite to dry the alcohol.

[Alan]

Bob, I know you can buy high-pressure cartridges with molecular sieve material in them, but how do you tell when a new one is needed?

I haven't tried it yet, but I'm going to try and use half sieve and half silica gel, with a separator between them. And I'll probably will order some of the indicating sieve material too, even though it costs 50% more.

[bnowlin]

I really don't know but I think it is a timing deal. I remember a long time ago at work there used to be moisture indicators after the filters on some high-pressure equipment.  when they started turning pink maintenance would change out the molecular sieve.

The 3A that I use is on the low-pressure intake side and seems to work pretty well.  So, when I purge and see liquid then I change it out.  It is so humid here that it doesn't last long.
So, I expect where you are it would last a while.
Bobn