I'm trying to make TEOS(tetraethyl-orthosilicate) for some experiments, but I don't like the normal Si --> SiCl4 --> Si(OEt)4 route. The two
attached papers look promising. I'm leaning Cheng2000 paper, since it is slightly easier for me to replicate. Would reacting ethanol with the
diethylene orthosilicate intermediate that they product create TEOS? Also, in the patent, how do they prevent the ethanol from boiling off?
Attachment: cheng2000.pdf (275kB) This file has been downloaded 393 times
Attachment: US4288604.pdf (930kB) This file has been downloaded 358 times
[Edited on 5-20-2021 by Texium]Triflic Acid - 19-5-2021 at 17:20
bump...rockyit98 - 19-5-2021 at 21:27
Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. not Si-O-C bonds.
if you to follow first PDF you need amorphous SiO2 like from rice hull ash or silica fume.Greener Silica From RiceTriflic Acid - 20-5-2021 at 06:48
I was thinking of using kitty litter silica gel, would that work? Also, sorry about the naming mistake, I'll try to change it to tetraalkyl
orthosilicates.
[Edit: can a mod do that, I don't think I can]
[Edit2: Thanks Texium]
[Edited on 20-5-2021 by Triflic Acid]
[Edited on 20-5-2021 by Triflic Acid]rockyit98 - 20-5-2021 at 09:12
maybe catalytic amounts of anhydrous Hydrogen fluoride or much more obtainable anhydrous Ammonium fluoride in anhydrous ethanol can be electrolyzed
with Si anode and Ni cathode to make solution of Tetraethyl orthosilicate in anhydrous ethanol.(total hypothesis based on guesswork)Triflic Acid - 20-5-2021 at 09:14
Maybe, but I'm don't really like the idea of having to use HF, since then I can't use a glass system. And if I could deal with HF I would just make
some SiF4 from SiO2 and go that way.
[Edited on 20-5-2021 by Triflic Acid]rockyit98 - 20-5-2021 at 09:35
Ammonium fluoride is much safer and i think tiny bit should work just to dissolve SiO2 layer on Si and also make the solution conductive. just use
plastic and i think you can't make orthosilicates with SiF4 gas, too stable to react with alcohols, maybe with alkoxides. SiF4 is made at room with
SiO2 with HF and with more HF to H2SiF6.Triflic Acid - 20-5-2021 at 09:43
But, assuming that I decide to stick to the first paper(Cheng2000) I posted, since I don't have ammonium fluoride at hand. Could I make tetraethyl
orthosilicate by reacting the diethylene orthosilicate with ethanol. It seems like it should work, since ethylene glycol is a better leaving group
than ethanol. I kind of liked the Cheng paper since its so simple and I already have all the chemicals.
[Edit: Fixed some grammar mistakes]
[Edited on 20-5-2021 by Triflic Acid]njl - 20-5-2021 at 10:05
Problem is EG is much less volatile than ethanol. So there's nothing driving the equilibrium towards your products other than initial concentrations.Triflic Acid - 20-5-2021 at 10:18
Shoot, maybe an alkoxide salt? That isn't volatile at all.Triflic Acid - 21-5-2021 at 10:16
Wait, I'm an idiot, the ethoxide will react with the ethylene glycol. Ethylene glycol has a pKa1 of ~15, around that of water.unionised - 21-5-2021 at 15:14
There's no clear "driving force".
But it's easy to add 20 times as much ethanol.
Then neutralise the catalyst and distill off a lot of "spare ethanol for re-use, some tetraethoxysilane as product , and finally some glycol.
Then play the game again with fresh catalyst and ethanol. Triflic Acid - 22-5-2021 at 07:51
And another note all together, would reacting sodium silicate with ethyl bromide make tetra ethyl orthosilicate? The constant ethanol cycle seems
tiresome. Problem is that sodium silicate decomposes in most organic solvents . Would something like dioxane or dcm work?clearly_not_atara - 22-5-2021 at 08:11
Supposing that the tetrakis-(2-hydroxyethoxy)-silane can be isolated and solubilized, one might consider the simple Williamson etherification to
tetrakis-(2-methoxyethoxy)-silane with MeI and catalytic base. This should proceed easily at reasonable temperature, and while it won't make TEOS, it
should be an effective replacement in any reaction calling for an orthosilicate.
Another, sort of weird possibility, is to try the rxn of your spiro-bis-ethylene-1,2-dioxysilane with diethoxymethane (bp 88 C) and
some appropriate catalyst, with dioxolane (bp 74 C) forming and hopefully boiling off before any other component. If the reactions can proceed without
reverting to silica, this system makes ethylene glycol (just barely) more volatile than ethanol! An excess of diethoxymethane may assist the
equilibrium.Bedlasky - 24-5-2021 at 03:30
Thanks for that link Bedlasky. Ill run a few experiments to try and make that in good yield from silica gel and sulfur. If that doesn't work, I'll
have to get out my precious silicon lumps and pulverize them.clearly_not_atara - 24-5-2021 at 06:08
^The Wiki seems to say you need to use aluminium sulfide, not sulfur, to obtain this compound. I'd be amazed if sulfur would reduce silica.Triflic Acid - 24-5-2021 at 07:14
Quote:
The material is formed by heating silicon and sulfur or by the exchange reaction between SiO2 and Al2S3
I think that heating sulfur might displace the oxygen, creating silicon disulfide. The oxygen would then react to make the SO2.njl - 24-5-2021 at 07:18
I think you would need very high temperatures for that, maybe higher than the boiling point of sulfur.Triflic Acid - 24-5-2021 at 08:26
Boiling sulfur. What fun. I guess I'll stick to grinding up silicon and reacting that. Anyone have any experience with that reaction? Could I do it in
a test tube or would a clay pot be needed?Bedlasky - 25-5-2021 at 05:49
Boiling sulfur. What fun. I guess I'll stick to grinding up silicon and reacting that. Anyone have any experience with that reaction? Could I do it in
a test tube or would a clay pot be needed?
Check out the autoignition temperature of sulfur. It's not a
simple apparatus. Triflic Acid - 25-5-2021 at 14:05
No, I meant if I'm using the silicon and sulfur method, not the silicon dioxide. That wouldn't need boiling sulfur, right?rockyit98 - 3-6-2021 at 07:27
Direct synthesis of tetraalkoxysilanes from silica and alcohols
Norihisa Fukaya*a, Seong Jib Choia, Toshio Horikoshia, Sho Kataokaa, Akira Endoa, Hiroshi
Kumaib, Minoru Hasegawab, Kazuhiko Satoa and Jun-Chul Choi*a A new simple and efficient process for synthesizing tetraalkoxy-silanes (TROS) directly from silica and alcohols was developed using molecular
sieves as dehydrating agents. Using this method, a variety of TROS (R = ethoxy, n-propoxy, or n-butoxy) were obtained over 60% yields within 6 h. We
also employed various natural silica sources in this process for practical applications. a - National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
b - COLCOAT Co., LTD, Tokyo, Japan
Honestly, it's pretty amazing that this hasn't gotten more attention. Aerogels for everyone! Get your aerogels!
Attachment: fukaya2017.pdf (1.4MB) This file has been downloaded 271 times
EDIT: Oh, and it gets better. Much better.
A Facile Preparation of Ambient Pressure–Dried Hydrophilic Silica Aerogels and Their Application in Aqueous Dye Removal
Xianghua Yang1*, Zhixu Wu1, Haifeng Chen1, Qixuan Du1, Lin Yu1, Ruiyang Zhang2 and
Ying Zhou2* Highly porous hydrophilic silica aerogels (SAs) are potentially excellent adsorbents in aqueous media, which are generally synthesized via a
standard sol–gel method followed by the relatively complex and specialized high pressure–requiring supercritical fluid drying process. Herein, a
facile and novel synthetic method applying ambient pressure–drying technology for the rapid preparation of hydrophilic SAs is reported, and they are
simply soaked with metal cation solutions without the need of traditional surface modification or supercritical fluid drying process. Chemical and
physical properties of the hydrophilic SAs were characterized and compared with a trimethylchlorosilane (TMCS)-modified hydrophobic silica aerogel. In
addition to the integrity and low shrinkage of the as-prepared products, Fourier transform infrared (FTIR) spectra and integrated thermal analyzer
(ITA) results revealed the presence of hydroxyl groups as well as the absence of multitudinous hydrophobic groups on the silica surface after soaking.
Field emission scanning electron microscope (FE-SEM) and Brunauer–Emmett–Teller (BET) measurements confirmed the mesopores inside the aerogel
skeleton. Among the tested metal cations, the Mg2+-soaked SAs demonstrated the best pore properties (pore diameter 9.35 nm and pore volume 1.09 cc/g),
and the Fe3+-soaked ones got the biggest surface area (855.62 m2/g) in contrast to other metal cations. Rhodamine B and Methylene blue solutions are
used to check the absorption ability of the SAs in aqueous media, in which the best adsorption capacity for Rhodamine B and Methylene blue reached 2.8
and 40.4 mg/g, respectively, implying their potential application in aqueous pollutant removal. 1 - Guangdong University of Technology, Guangzhou, China
2 - Southwest Petroleum University, Chengdu, China
In sum: direct reaction of silica with ethanol to TEOS, sol-gel formation and ambient-pressure drying of the aerogel after treatment with MgCl2!
Aerogel never seemed so possible.
[Edited on 23-6-2022 by clearly_not_atara]Triflic Acid - 23-6-2022 at 20:33
I'm going to try this. Funny how some of my old threads are getting bumped up lol. I never really continued on this idea, but I have the silica gel
and the molecular sieves. I'll probably bake both in a microwave before running the experiment. And a good set of steel pipes welded together should
suffice for my autoclave substitute.
[Edited on 24-6-2022 by Triflic Acid]clearly_not_atara - 25-6-2022 at 13:44
The first paper is pretty cool, the second one is downright shocking. Aerogel at ambient pressure from cheap materials? After 80 years of
supercritical drying? I'd be more skeptical, but they have photographsTwospoons - 14-9-2022 at 21:34
Stumbled on this today : direct synth of tetraethyl orthosilicate from ethanol and silicon using a catalyst of either magnesium ethoxide, tin
tetrachloride or tin(II) oxide.
