Sciencemadness Discussion Board - Making silicon tetrachloride

Making silicon tetrachloride

Triflic Acid - 8-5-2021 at 10:13

I want to make silicon tetrachloride, but don't want to do the traditional method of heating silicon with chlorine. Instead, I was thinking that reacting silicon with iodine at ~180C under sulfuric acid would create silicon tetraiodide, and reacting that with chlorine gas to give the silicon tetrachloride. Would this work?

vano - 8-5-2021 at 11:41

Look at this:
http://www.sciencemadness.org/talk/viewthread.php?tid=156987...

It works on gallium, but also on antimony. I was surprised when I really made antimony triiodide with this reaction. I think it is worth a try. If you can, once use hydrochloric acid instead of sulfuric acid, I wonder if it will work on silicon.

Triflic Acid - 8-5-2021 at 12:12

The sulfuric acid is just to keep the iodine from sublimating into oblivion, no actual reaction.

vano - 8-5-2021 at 21:31

Of course Yes, but i don't think that it will stop sublimation(At least at the required level) . What percentage of sulfuric acid are you going to use?

[Edited on 9-5-2021 by vano]

Triflic Acid - 8-5-2021 at 21:44

Around 98%, don't have anything stronger. Why won't it stop the sublimation, I've seen people melting and cast iodine under sulfuric acid.

vano - 8-5-2021 at 22:00

Good percentage, maybe it's possible. I thought that you have low percentage acid, because 98% is hard to find in many countries.

Okey, i like you idea. Do you have silicon powder?

Different is that you can dissolve iodine in HCl, i will try this reaction.

vano - 8-5-2021 at 22:17

I think halosilicates are also interesting. I wonder if this is possible on chlorine. Second is easiest i think.

Bedlasky - 9-5-2021 at 01:23

Triflic acid: You can try it. Maybe it work? I really don't know, I just know classical ways like Si + Cl2 or SiO2 + C + Cl2.

Vano: SiCl4 cannot be made so easily like SbI3 or GaI3. Any presence of water will lead to hydrolysis of SiI4 (but I doubt that you can make SiO2 by this way).

Silicon form just hexafluorosilicates, similar chloro complexes doesn't exist.

wg48temp9 - 9-5-2021 at 04:34

Perhaps the silicon tetrachloride could be made from alkoxysilanes which can be made by dissolving silica in ethylene glycol,

see:

Quote: Originally posted by wg48

Don't forget the green route to methylsiloxanes see:

PS: How do I link to a previously posted paper so I don't have to upload it again and how do I reference a previous post without quoting it?

vano - 9-5-2021 at 06:29

Bedlasky:I remembered that calcium hexachlorosilicate exist.

Bedlasky - 9-5-2021 at 13:52

Quote: Originally posted by vano

Bedlasky:I remembered that calcium hexachlorosilicate exist.

Source?

clearly_not_atara - 9-5-2021 at 16:19

You will not successfully convert Si(OR)4 to SiCl4, even if you can obtain the former; the affinity of silicon for oxygen is too high. You may be able to do it with SiF4 but the equipment for handling SiF4 is not any simpler than the equipment for making SiCl4 by the usual direct process.

I don't know about the iodine/sulfuric acid method. It seems possible that all of the following reactions occur in that system:
Si + I2 >> SiI4
SiI4 + 2H2SO4 >> SiO2 + 2SO3 + 4 HI
SO3 + 2 HI >> SO2 + H2O + I2

leading to a net reaction like this:
Si + 2 H2SO4 [cat I2] >> SiO2 + 2 SO2 + 2 H2O

which is, as you have guessed, completely useless. Silicon halides are extremely reactive. They will not form easily and they react with practically any hydroxyl available.

The direct chlorination of metal silicides is preferred for a reason... they react at low temperatures and give no byproducts. Mg2Si can be made by "careful" thermite-like reaction. It can probably be brominated at r.t. as well.

Triflic Acid - 10-5-2021 at 07:21

Would SiI4 really dehydrate sulfuric acid

I have 100g of silicon lumps coming in the mail today. Should I try to get some magnesium silicide as well and try that? Also, if not H2SO4, can you think of a different high boiling solvent with no hydroxyls?

[Edit: If it does dehydrate I'm screwed: https://www.jstor.org/stable/20022852?seq=1#metadata_info_tab_contents]

[Edited on 10-5-2021 by Triflic Acid]

Triflic Acid - 12-5-2021 at 20:19

bump

Boffis - 13-5-2021 at 06:07

Could you use ferrosilicon instead of trying to make magnesium or aluminium silicide. It is easily available off Ebay. You would still need hot chlorine gas but the fine powder may react faster than silicon itself. Let us know how you get on making magnesium silicide; its usually made by reaction dry silica with excess magnesium in a thermite like reaction. Silicon is not very reactive and the mixed element powder will have a lot of void space between the particle full of air so oxide and nitride films are likely to make the reaction difficult unless you can flush or mix the powders in argon first.

rockyit98 - 18-5-2021 at 21:46

one way of making TiCl4 is heating sodium pyrosulfate with NaCl and TiO2. ( 2Na2S2O7 + 4NaCl +TiO2 -----(500C or more)----> TiCl4(g) +4Na2SO4 ) maybe replacing TiO2 with SiO2 will make SiO2 gas.

Triflic Acid - 19-5-2021 at 15:03

Update, the prep I’m following calls for teos so I’m going to make that directly instead of making silicon tetra chloride. There is a new thread on that, since it is unrelated to this one.
[Edit: that thread is in organic, http://www.sciencemadness.org/talk/viewthread.php?tid=157461]

[Edited on 19-5-2021 by Triflic Acid]

Shenno - 23-5-2021 at 05:47

i just wanted to point out that silicon tetrachloride is an evil compound and extremely volatile .. upon my own experience ( i used the chloride + silicon route) it creates pressure inside the storage vessel even if you kept it dissolved in a hydrocarbon. so be very careful while handling this compound

i never had any good yields from my impure silicon powder .. i also tried an indirect route through silicon sulfide which was another pain in the ass

Triflic Acid - 24-5-2021 at 16:15

Welcome to the forum, and thanks for the warning. Also, how did you make the silicon sulfide? I’m trying to make some myself.

Shenno - 4-7-2021 at 11:53

Thanks Triflic Acid

i prepared silicon disulfide through the elemental route + 0.5 mole precipitated silica for every mole of silicon, it seemed to work well but for some reason only 25 % of the mass was reactive when i added anhydrous ethanol

this is the link of the reaction .. i ignited it with magnesium thermite which i ignited with KMnO4 and Glycerin

https://1drv.ms/v/s!Ao-xsE8BnvftmQPgO7y3DdMwfUQq?e=l4tvse

Triflic Acid - 5-7-2021 at 06:08

You mean precipitated sulfur, right?

Shenno - 5-7-2021 at 08:01

silicon 100 micron particles + precipitated sulfur + precipitated silica

Ref: US2766103