Sciencemadness Discussion Board

Synthesis of zeolite

Rainwater - 14-7-2023 at 17:08

Unfortunately, the best reference I have is behind a pay-wall
Synthesis of zeolite T powders by direct dissolution of rice husk ash
DOI 10.1007/s10853-013-7499-y

Im not sure what details I can put here without causing copyright issues, so I will withhold the exact details outlined in the paper.

In short the paper describes a procedure that generates zeolite with pour sizes between 0.5nm ~ 0.7nm using mostly common reagents.

They go on to document the effects of using a nasty template molecule with prolonged reaction times. Basicly the longer the crystallization takes place, the larger the pour sizes.

tetramethylammonium hydroxide is their template molecule
The downside is the use of this highly toxic compound (LD 0.001g/kg)

With aluminum metal, NaOH, KOH, SiO2 and the template molecule, the paper describes reaction at 100c and 1atm that can be easily done with simple appratus.
The crystallization around the template molecule which has a size of about 0.6nm. Results in pour sizes of a similar diameter.

1) Does the tetramethylammonium serve another purpose in this reaction?

2) What would be some good compound to replace this exotic and deadly ingredient?

3) What other properties of a template molecule are desirable?

My ultimate goal would be the production of 0.3nm pours for the purpose of drying solvents. And a writen procedure anyone with a charcoal grill amd lawnmower chippings could follow.

So question 3, im thinking the low thermal decomposition temperature combined with the volatile decomposition products(wiki says methanol, nitrogen gas) provide an easy way to remove the template after formation of the desired crystals.

Tsjerk - 14-7-2023 at 23:48

Rainwater - 15-7-2023 at 17:21

Thanks for the link.

After further searching, i do not believe there is a direct method to synthesis 3a zeolite.
This lead to more googleing, then I found this 1989 paper about how to shrink pores in zeolite
Control of Pore-Opening Size of Zeolites

They use a moderately difficult to make compound refered to as TMOS
They gave no name for this compound, but did mentioned a possible reaction and listed the formula Si(OCH3)4
Synthesis referance

By weighing the sample before and after the procedure they where able to directly measure the amount of silicone oxide added to the sample. Then provide some easy to follow charts to estimate how much the pours where closed/shrunken.

sceptic - 16-7-2023 at 02:06

According to this reference, Zeolite A might work well for you. The sodium form has pore sizes of about 0.4 nm, but when potassium ions take their place, the pores shrink to 0.3 nm. The authors of this paper synthesized Zeolite A without a structure-directing agent from a solution of sodium silicate and sodium aluminate. The most successful solution was aged at 25 Celsius for half an hour and then crystallized at 96 Celsius for three hours.

It should be possible to exchange the sodium ions for potassium ions after the Zeolite crystals are grown.

Edit: some other resources I found: a short book about zeolites with a brief section about synthesis, and a much longer book with a list of structure-directing agents on pages 13-14.

[Edited on 16-7-2023 by sceptic]

Rainwater - 16-7-2023 at 18:12

You just made my day. Thank you.