Cubane538
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Preparation of silica sulphuric acid
Hi everyone,
I have been trying to prepare SSA Catalyst (Silica Sulfuric Acid) for a few days.
But somehow it fails everytime, I took 20ml of concentrated sulphuric acid and 25g of 20 mesh silica gel. Mixed them together and tried to heat them.
According to the Wikipedia the sulphuric acid is soaked by silica gel and the left liquid is water which should evaporate.But the white smoke started
coming out.
https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://en.m.wikipedia.org/wiki/Silica_sulfuric_acid%23:~:text%3DSil
ica%2520sulfuric%2520acid%2520(SiO,acid%2520catalyst%2520with%2520high%2520acidity.&ved=2ahUKEwiEhvTBua2DAxVZ1zgGHUBNCqcQFnoECBUQBQ&usg=AOvVaw
2HPNkBXidHt0emwvm_lxo4
There's also a different process to make it through chlorosulphonic acid, but I'm not getting chlorosulphonic acid. Making chlorosulphonic acid is
very lengthy process.
If anyone has ever made this please guide me.
[Edited on 26-12-2023 by Cubane538]
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Maurice VD 37
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Explain us what exactly you have done, and observed. And what you should have observed. What is this white smoke coming out ? Out of what ? Was the
mixture hot ?
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RU_KLO
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https://www.sciencedirect.com/science/article/abs/pii/004040...
The catalysts were easily prepared by soaking 20 g of silica-gel with 25 ml of sulfuric acid of an appropriate concentration, followed by 5 h water
pump drying at r.t. and oven drying at 130 ~C for 24 h. Concentrations of sulfuric acid below 70% yielded solid acids that had high acidity without
too much
hygroscopicity. These easy to handle catalysts can be stored indefinitely in a desiccator with blue-indicating silica-gel and re-activated when
needed by heating in the oven for 12 h.
here are examples of H2SO4 molarity, depending of the final use. even oleum is used:
Similarly, satisfactory results for progressively deactivated compounds were found by increasing the "acidity" of the solid catalysts. Bromobenzene
was nitrated to 98 % in 1 h using G-80 as catalyst (from 80 % H2SO4,10.5 mmol H÷/g) and p-dichlorobenzene was nitrated to 97% in 20 h by catalyst
G-90 (from 90% H2SO4, I 1 mmol H+/g). For a extremely deactivate substrate as nitrobenzene, a catalyst (G+20) was /n situ generated from 4 g of dry 18
silica-gel and 1.5 ml 20% oleum (SO3 acted as water scavenger). Using this system and concentrated (90%) nitric acid, 5 mmol of NO2Ph in CH2CCl2 were
converted in 80 min to a mixture of o- (7%), m- (81%) and p- (1%) dinitro-benzenes. A conversion of 90% was observed instead of the poor 3% obtained
when using G-70.
Go SAFE, because stupidity and bad Luck exist.
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Cubane538
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How do I perform waterpump drying?
I only have sulfuric acid silica gel and a hotplate, can't I dry it on the hotplate?
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Dr.Bob
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I think they mean a water aspirator, perhaps? So vacuum drying under a mild vacuum. Heating it will likely decompose the acid on the silica, or
modify its activity.
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RU_KLO
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Quote: Originally posted by Cubane538  | How do I perform waterpump drying?
I only have sulfuric acid silica gel and a hotplate, can't I dry it on the hotplate? |
Like dr Bob said, it seems vacuum is needed for the first removal of water, Maybe it also helps to get the acid inside the silica gel - dont know.
also this is in the report:
Total acidity was proportional to the concentration of the solution of H2SO4 used. Catalysts made from sulfuric acid of concentration >70% were
better handled under an inert atmosphere.
Attachment: 0040-40392902174-4.pdf (269kB)
This file has been downloaded 190 times
Go SAFE, because stupidity and bad Luck exist.
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