Faujasite (FAU)

Tl:dr: Here is the printable STL: https://www.thingiverse.com/thing:3676897

Part two of our zeolitic exploration and it is on to one of the most important ones. If you drive, fly or do anything relying on petrol or other short-chain hydrocarbons, then you have faujasite to thank.

Faujasite is a naturally occurring zeolite with sodium (Na, the most dominant), calcium (Ca) and magnesium (Mg) forms. It was first discovered in the early 1840s in Germany and forms exquisite tiny crystals (see: https://www.mindat.org/min-35126.html ). It is one of the key components of a hugely important process called ‘Fluid Catalytic Cracking’ (FCC) which is used to convert crude oil into petrol and other short-chain hydrocarbons we currently use for energy storage and fuelling our cars.

It also has a gorgeous structure, formed of sodalite β cages (like zeolite A: https://crystalprint.home.blog/2019/05/11/zeolite-a-lta/ ) connected by double six rings (d6r):

Gif of FAU framework, sodalite β cages in purple, double 6 rings in blue. The sodium or other extra-framework cation would sit in the pores/holes.

Rare in nature, this structure is commonly used as it’s synthetic versions zeolite X or Y both commonly used as absorbents or as previously mentioned, catalysts.

Right you are now probably thinking – what is the difference between X and Y?

Well these are both synthetic versions of faujasite, discovered by our old friends Robert M. Milton and Donald W. Breck of the Linde Division, Union Carbide Corporation back in the 1950s (along with zeolite A). Zeolite X has a very low silicon to aluminium ratio, the less aluminium, the higher the charge on the framework, the higher the charge on the framework, the more extra-framework cations like sodium or calcium are needed to balance the charge (remember, basic rule of chemistry – everything wants to be stable). So zeolite X is great for cation exchange and can effectively be tailored for different reactions by swapping in and out cations.

Zeolite Y has a much higher silicon to aluminium ratio so it is more stable at higher temperatures and used in FCC.

The print:

I won’t go through the structure modification process here – if you are interested about how I make the models check out my zeolite A post: https://crystalprint.home.blog/2019/05/11/zeolite-a-lta/

After getting rid of some rogue double 6 rings we get something like this:

FAU framework viewed down 111 axis, purple polyhedra are the sodalite β cages, light blue polyhedra are the double 6 rings

Looks gorgeous doesn’t it? Like a strange fractal flower. Imagine trying to make this without a 3D printer, I’m always in awe of the craftsmanship in jewellery or other intricate designs. When I was younger I wanted to be a jeweller – maybe I should look into it again!

Put through our slicing software, rotated and scaled up 130 % we get the following:

Which I’ve uploaded to thingaverse as: https://www.thingiverse.com/thing:3676897

It prints beautifully, after 10 hours a very little post production work we get this:

Success! The printed FAU framework.

I’ve been talking a lot about sodalite in this and the LTA post, so I think with the next post I might take a break from zeolites and try my luck with some unusual filaments and the sodalite structure.. Stay tuned!


Zeolite A (LTA)

Tl:dr: Here is the printable STL:

Now I know I said this was about the naturally occurring zeolites (hydrated aluminosilicates) but I couldn’t carry out this project without a nod to zeolite A (Linde Type A). Possibly one of the most famous zeolites as it is one of the earliest synthetic (no natural version) zeolites discovered.

The first synthesis of a zeolite was reported by St. Claire Deville in 1862 with the formation of levynite.[1] It wasn’t until the incredible work of Richard M. Barrer that things really took off however. He classified the zeolites known at the time by molecular sizes [2] and in 1948 presented the first definitive synthesis of zeolites, an analogue of mordenite [3] and an at the time unknown new synthetic zeolite, which was later identified as the KFI framework. [4]

Barrer’s work inspired Robert M. Milton and Donald W. Breck (both of the Linde Division of Union Carbide Corporation) to investigate zeolite synthesis in search of new ways to separate and purify air. They discovered the new types of synthetic zeolites A, X and Y – which were then commercialised by Union Carbide.

The great thing about zeolite A is that you probably have some in your house right now, it has been extensively used as a water softener in detergent (those pore sizes are just the right size to exchange limescale causing calcium for sodium).

So to the print!

Armed with a crystallographic information file (cif) from the brilliant International Zeolite Association website:
http://europe.iza-structure.org/IZA-SC/material_tm.php?STC=LTA (accessed May 2019)

It was pretty easy to load it up into crystalmaker, however from experience I know that the ball and stick model doesn’t print too well so with a little help from the guys at
http://crystalmaker.com/crystalmaker/video-tutorials/index.html (their video tutorials are great – to do this I used the ‘building massive polyhedra’ video). I managed to create the following model:

Massive polyhedra view of zeolite A, sodalite beta cages in pink, and d4r (double 4 ring) in grey

If you are not used to working in 3D with zeolites, this doesn’t quite get across how they are formed of pores and channels connected by secondary or composite building blocks (the sodalite beta cage and d4r) so I’ve produced a little gif below to help.

Rotation movie of zeolite A massive polyhedra

Much better, these pores and channels are what make zeolites so useful and special, they can trap things (like gases or radioactive isotopes), sieve things (different sized and shaped molecules) and carry out ion exchange.

As this structure is fairly simple I could convert it into a stl and load it into snapmaker with no problems.

Scaled up to 300 %

A good 7 and a half hour print, so time to go to some friends for lunch and go for a walk in a forest..

Ta da!

Looking good – sorry for the mess around it.
After a quick clean up

Success! One out of around 50 done (depends which other synthetic zeolites I print..) Printed really well and easily, a little trouble with the overhangs on the sodalite cages but otherwise I’m very happy.

STL file:

[1] H. de St. Claire Deville, Comptes Rendus Acad. Sci, 1862, 54, 324

[2] R. M. Barrer, J. Soc. Chem. Ind., 1945, 64, 130

[3] R. M. Barrer, J. Chem. Soc., 1948, 2158

[4] R. M. Barrer, J. Chem. Soc., 1948, 127