Sciencemadness Discussion Board

Any way to prepare anhydrous ZnCl2 without using gaseous Cl2 or HCl?

Velzee - 10-6-2019 at 11:53

In an attempt to make anhydrous AlCl3 as a catalyst (following some of ChemPlayer's videos), I would like to prepare some zinc chloride. A few searches on the site and the wiki didn't come up with much, so I figured I'd ask you all if you alternative methods of preparing it without dealing with gaseous HCl or Cl2.

Thank you,
—V

Pumukli - 10-6-2019 at 12:13

Drying hydrated ZnCl2 is possible by melting. (Strong heating required, in a stainless steel pot maybe.)

clearly_not_atara - 10-6-2019 at 12:46

Lol wut? ZnCl*6H2O decomposes thermally to zinc oxychlorides.

Instead, I think you can react Zn with anhydrous CuCl2, which can be dried by heating. To expedite the rxn, CuCl2 can be dissolved in a polar aprotic solvent such as acetonitrile or propylene carbonate.

unionised - 10-6-2019 at 13:08

If you can get FeCl3....

lordcookies24 - 10-6-2019 at 13:24

Do you have any other chloride salts on hand?

Chem Science - 10-6-2019 at 16:31

I have dried ZnCl2 by melting without any problems. Maybe decomposition is slow.

Velzee - 10-6-2019 at 20:48

Quote: Originally posted by lordcookies24  
Do you have any other chloride salts on hand?


Yes, and I can prepare most of them if needed. What did you have in mind?

I do NOT have Zn powder, rather I have Zn battery casings, some Zn pieces I melted from coins, and some ZnCO3 I recently prepared.

[Edited on 6/11/2019 by Velzee]

Pumukli - 11-6-2019 at 02:48

I've seen people who made relatively big ammounts (circa 200g) ZnCl2 melt on a strong gas flame in an iron "pan". Then this stuff was good enough for whatever they required anhydrous ZnCl2.


happyfooddance - 11-6-2019 at 03:29

Quote: Originally posted by Pumukli  
I've seen people who made relatively big ammounts (circa 200g) ZnCl2 melt on a strong gas flame in an iron "pan". Then this stuff was good enough for whatever they required anhydrous ZnCl2.



If it is anhydrous it will fuse without decomp. The hydrate decomposes significantly, and vacuum dessication doesn't work either.

There are other threads on this, Velzee, you should UTSE before starting a new thread. This clutters search results and makes it harder for other people to find the information if they search for this subject in the future.

Anhydrous zinc sulfate dry distilled with calcium chloride (or table salt but prob. requires higher temps) was used commercially for many years, you might be able to pull that off. At any rate, you will have to search.

Hope this helps

walruslover69 - 11-6-2019 at 10:17

Could you possibly produce anhydrous ZnCl2 by the reduction/displacment of CuCl2 with zinc metal in a suitable solvent like either?

fusso - 11-6-2019 at 10:46

Anhydrous MnCl2 and CoCl2 can be dehydrated by heating the hydrate.

[Edited on 190611 by fusso]

unionised - 11-6-2019 at 11:40

Quote: Originally posted by fusso  
Anhydrous MnCl2 and CoCl2 can be dehydrated by heating the hydrate.

[Edited on 190611 by fusso]

Not really, no.
They can be prepared by heating the hydrated salts.
It's also unlikely to be relevant.

[Edited on 11-6-19 by unionised]

walruslover69 - 11-6-2019 at 11:52

I believe the hydrates of MnCl2 and CoCl2 can be dehydrated by heating. I know for sure that CuCl2 can be made by dehydration of hydrated CuCl2 made by dissolving basic Copper carbonate or hydroxide in aqueous HCl.

fusso - 11-6-2019 at 12:13

So I think these anhydrous salt can react with Al in organic solvents to make anhydrous AlCl3.

Tsjerk - 11-6-2019 at 12:26



[Edited on 11-6-2019 by Tsjerk]

lordcookies24 - 11-6-2019 at 13:45

Quote: Originally posted by Velzee  
Quote: Originally posted by lordcookies24  
Do you have any other chloride salts on hand?


Yes, and I can prepare most of them if needed. What did you have in mind?

I do NOT have Zn powder, rather I have Zn battery casings, some Zn pieces I melted from coins, and some ZnCO3 I recently prepared.

[Edited on 6/11/2019 by Velzee]


i was thinking about having Zn powder mixed in a solution of CuCl2 and filter of the copper ,but since you do not have zinc powder, that wouldn't be a good option... Tell me again why you cannot just mix HCl with the zinc cassings?

clearly_not_atara - 11-6-2019 at 16:35

Velzee, if you do not have zinc powder, the next question you should ask is "how do I make zinc powder"? Because I do not see the distillation of gaseous ZnCl2 in your future. And the available methods are this one and that one.

There are so many threads which have a question like "how do i make triflic anhydride but without knowing anything or buying anything or doing anything difficult or time-consuming".

Anyway if you dissolve the zinc in some alkali and add some Al, you should see zinc powder forming.

Quote:
Anhydrous zinc sulfate dry distilled with calcium chloride (or table salt but prob. requires higher temps) was used commercially for many years, you might be able to pull that off. At any rate, you will have to search.

This is popular because CaCl2 is a common industrial waste product (Solvay process, others), not because it's practical :p

According to this paper:

https://scripts.iucr.org/cgi-bin/paper?a17499

potassium tetrachlorozincate is obtained by evaporation of a solution containing the appropriate proportions of KCl and ZnCl2. Possibly heating the salt will liberate ZnCl2 gas. Although this is a fool's errand because OP cannot prepare or capture gases as he has already informed us.

walruslover69 - 12-6-2019 at 08:11

if you cut it up into strips or pieces and clean it just alittle bit with steel wool or sand paper then reflux it with CuCl2 in ether you might be able to get it to work. Since the zinc chloride product is very soluble in ether the surface won't be covered/passivated by product like it work be if you were doing it in the solid state with Cl2 or HCL. This might allow you to get by with not having a huge surface area. Still probably have to reflux it potentially over night, but that isn't to much trouble.

I am really interested in this synthesis now, I might have to try it whenever I can find the time.

Pumukli - 12-6-2019 at 12:21

OK, I'm stand corrected!

I asked around and someone told me that those guys I mentioned in my previous post were not preparing anhydrous ZnCl2 by melting the hydrate. They were purifying (I think drying would be a better verb) the originally anhydrous ZnCl2 which was stored in an opened bottle and some humidity found the way into that bottle.

Velzee - 12-6-2019 at 13:22

Quote: Originally posted by clearly_not_atara  
Velzee, if you do not have zinc powder, the next question you should ask is "how do I make zinc powder"? Because I do not see the distillation of gaseous ZnCl2 in your future. And the available methods are this one and that one.

There are so many threads which have a question like "how do i make triflic anhydride but without knowing anything or buying anything or doing anything difficult or time-consuming".

Anyway if you dissolve the zinc in some alkali and add some Al, you should see zinc powder forming.


Thank you. I will try this shortly.

WGTR - 12-6-2019 at 15:48

I was wondering if heating with ammonium chloride would do the trick. Here is a document referencing a similar approach:



Attachment: cdc_10599_DS1.pdf (343kB)
This file has been downloaded 316 times

S.C. Wack - 12-6-2019 at 15:52

In the old lab manuals the water can indeed be removed with heat and some care, perhaps not perfectly.

Metacelsus - 12-6-2019 at 22:32

Yes, I have done this. Adding a little excess HCl helps to avoid decomposition to the oxychloride. The resulting ZnCl2 isn't absolutely dry but it is good enough for most purposes.

fusso - 13-6-2019 at 04:54

Can azeotropic distillation work?

hacker - 14-6-2019 at 09:51

I don't know if azeotropic distillation would work.

This method looks easy. I believe it would produce a superior product.

Quote:
To develop technology to assure an ample supply of zinc and to reduce environmental pollution, the U.S. Bureau of Mines investigated alternatives to the roast-leach process for treating complex sulfide concentrates. Previous studies proved that low-grade zinc sulfide (ZnS) concentrates could be leached using chlorine-oxygen to produce zinc chloride (ZnCl2). The process involves high energy requirements for evaporating the pregnant solution to produce anhydrous ZnCl2 needed for electrolytic cell feed. An efficient hydrometallurgical process would facilitate treatment of lower grade ores than can be used in conventional processing and would render roasting unnecessary.

An alternative method was devised for recovering ZnCl2 from solution. Zinc diammine chloride [Zn(NH3)2Cl2] was precipitated from solution by adding ammonium chloride (NH4Cl) and sparging with ammonia (NH3) to a pH of 6 to 7.5. The spent solution was treated with calcium hydroxide [Ca(OH)2] at 60° to 80° C for 1 to 4 h to remove remaining zinc and NH3. The Zn(NH3)2Cl2 was heated to 300° to 400° C to remove NH3 and produce anhydrous ZnCl2. A possible flowsheet was devised and is included.

S.C. Wack - 14-6-2019 at 13:45

Distillation of the dehydrated hydrate would work, for a pure and anhydrous product. BTW Inorganic Chemical Preparations says any basic chloride produced by the dehydration can be converted back by adding conc. HCl. While stirring at maybe 240C. Thorp advises caution.

maldi-tof - 16-6-2019 at 13:33

There is a patent (if you search it you will find it easily), where NH3 (g) is bubbled through a solution of ZnCl2. The precipitate is separated from the solution (it being Zn(NH3)2Cl2). The solid is then heated in order to obtain ZnCl2 (and liberating NH3 as a sub-product, which can be re-used in the previous phase).


AJKOER - 17-6-2019 at 14:48

Perhaps one does even need a starting aqueous ZnCl2 just Zinc metal, CaCl2, NH3 (aq) and H2O2,. Albeit, I suspect it is likely hard to produce large quantities this way unless one uses NH3/CO2 to dissolve metals as perform in commercial leaching applications.

I suggest reviewing the following path based on my experience of working with Cu, dilute aqueous ammonia, 3% H2O2 (or possibly pumping in air, which I have not tried) and an electrolyte (usually sea salt or ordinary NaCl). I usually jump start this electrochemical reaction in a microwave (which removes the otherwise obvious inception period before the reaction commences). The product is [Cu(NH3)x(H2O)6-x](OH)2 with x varying depending on the concentration of ammonia. I successfully added MgY2 to this salt (which only exists in aqueous solutions) to form salts of the form [Cu(NH3)x(H2O)6-x]Y2 with a precipitate of Mg(OH)2, where Y is an anion of choice.

With Zinc, the path may again be dissolving Zn in dilute aqueous ammonia, 3% H2O2 and an electrolyte (sufficient aqueous NH4Cl from treating aqueous CaCl2 with NH3(aq), see equation below). Again jump start the electrochemical reaction in a microwave. The expected equilibrium product is assuming a simple substitution of Cu with Zn (? see https://www.physicsforums.com/threads/exact-formula-of-tetra... and also this 2010 research work reported at https://www.researchgate.net/publication/44669385_The_stabil... ):

[Zn(NH3)4(H2O)2](OH)2 + 2 NH4Cl = Zn(NH3)4(H2O)2]Cl2+ 2 NH3 + 2 H2O

Adjusting the pH to between 6 and 8 by adding ammonia gas may result in a precipitate of [Zn(NH3)4(H2O)2]Cl2, or not. Perhaps better is add CaCl2 producing a precipitate of Ca(OH)2, removing the Ca(OH)2 and then try the pH adjustment between 6 and 8.

A search of the internet does assert that my tentative rendition of a tetraammine aqua complex for Zinc is likely NOT accurate, that is, the salt is not a hydrate, reputedly like [Zn(NH3)4]Cl2. So, this is how heating this compound avoids the usual problems of working with hydrates to water free salts, and may NOT be a path workable for associated Copper salts.
---------------------------------------------

[Edit] Did come across this reference citing a low hydrate for a related salt: [Zn(NH3)4](NO3)2 . 1/5 H2O

Link: http://ddbonline.ddbst.com/DDBSearch/onlineddboverview.exe?s...

Even if this is correct for the related chloride, this may not be an issue on obtaining the dry ZnCl2, as with mild heating the water is probably loss first, before the underlying tetrammine complex is decomposed.

[Edited on 18-6-2019 by AJKOER]