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Topic: High Polarity, Low Volatility Organic Solvent  (Read 4459 times)

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Offline ejnov

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High Polarity, Low Volatility Organic Solvent
« on: November 11, 2014, 08:16:43 PM »
Hi Organic Chemistry Forums,

I'm searching for a very polar, reasonably safe (max. Health Code of 2) organic solvent. I've read through polarity indexes, such as this one: http://macro.lsu.edu/howto/solvents/Polarity%20index.htm, although the organic solvents listedseem to be pretty limited. I'm currently using Glycerol and PEG 200 in my system. Please let me know of any organic solvents you recommend.

Thank You,

Ethan

Offline Babcock_Hall

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Re: High Polarity, Low Volatility Organic Solvent
« Reply #1 on: November 11, 2014, 08:27:20 PM »
What is your application?

Offline ejnov

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Re: High Polarity, Low Volatility Organic Solvent
« Reply #2 on: November 11, 2014, 09:05:19 PM »
I'm trying to separate Sulfur Dioxide gas and Carbon Dioxide gas. I'm looking for a high polarity organic solvent that will dissolve the Sulfur Dioxide at high concentrations and the Carbon Dioxide at very low concentrations.

Offline Enthalpy

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Re: High Polarity, Low Volatility Organic Solvent
« Reply #3 on: November 12, 2014, 03:20:42 PM »
Apologies for the vague answer, but...

One solvent would be SO2. That is, if you accept to compress or cool the mixture.

Both molecules have a strong quadripolar field that overshadows the small (for SO2) or approximately zero (CO2) dipolar field. If the solvent has a brutal +- transition between two neighbour atoms, these will interact with C-O as well as S-O. It could be more efficient if the solvent's +- transition takes three atoms distance, so its electric field interacts weakly with OCO.

Please take with caution.

Offline ejnov

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Re: High Polarity, Low Volatility Organic Solvent
« Reply #4 on: November 16, 2014, 02:20:38 PM »
Hi Enthalpy,

I will not be able to compress and cool the system so that SO2 would work. I'm searching for a solvent that has a higher boiling point (at least 80C) and dissolves NH3 at high concentrations and CO2 at very low concentrations.

Offline Enthalpy

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Re: High Polarity, Low Volatility Organic Solvent
« Reply #5 on: November 17, 2014, 03:49:41 PM »
What compound do you want to dissolve? Previously it was SO2, now it's NH3. I have some doubts that NH3 dissolved in high concentration anywhere would let CO2 pass by without reacting.

Can "dissolving" involve some reaction? Water would dissolve SO2 but little CO2, and I expect water to dissolve very little CO2 once it is saturated with SO2; you could have several dissolution steps, where water and the gas take the steps in opposite directions, so the gas is very clean at the end while the solvent is saturated. This saves solvent and minimizes the amount of dissolved CO2.

Offline Enthalpy

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Re: High Polarity, Low Volatility Organic Solvent
« Reply #6 on: November 19, 2014, 05:20:48 PM »
DMSO, dimethyl sulfoxide, is more selective than water in favouring SO2 over CO2. A free Pdf called "Dimethyl Sulfoxide (DMSO) Solubility Data" tells 574g/kg and 0.5g/kg at RT. It's also less volatile than water, with bp=+189°C.

Though, it dissolves SO2 by a reaction, as water does. Health code is 1, flammability 2, and it lets perceive a bad odour.
http://en.wikipedia.org/wiki/Dimethyl_sulfoxide

Did you check sulfuric acid to dissolve SO2? Provided it's acceptable for your use.

With some solvents, you won't desire a fog to exit your machine. You might consider rotating disks to put the gas and the solvent in contact, a usual construction resembling the sketch there
http://www.chemicalforums.com/index.php?topic=56452.0
despite it is to serve different purposes in that other discussion.

The multistep dissolution suggested on Nov 17 applies to any solvent.

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