kilomentor

Is Glycerin a General Green Solution to Solvent Recovery and Replacement for Process Chemistry?

kilomentor | 13 June, 2011 07:15

 At laboratory scale, when one solvent needs to be replaced with another, the solution contents are placed in a r.b. flask, set spinning on the vacuum rotary evaporator with appropriate heating and condensing facilities and when the first solvent has been completely evaporated then the required new replacement solvent is added and the solutes brought back into solution by swirling, scrapping and heating. There is no equivalent procedure for solvent exchanges at scale. In the plant situation, because stirring and heat transfer become ineffective below the minimum stirrable volume, the solvent and substrates combined volumes can never be taken below the minimum stirrable volume. Thus, solvent is never completely removed so no essentially solvent free state arises.  When the solvent replacement is of a more volatile one with a less volatile one, the latter solvent can be used to chase the former in some form of distillation; but when the replacement solvent is of more volatile one, tricks, such as using azeotropes, come into play. Even where an azeotrope can work there are still fractions of mixed solvents that become environmentally troublesome waste. It is proposed that a general solution to this problem is to use the minimum stirrable volume of glycerin as a chaser for the first solvent. Glycerin is cheap, biodegradable and has a bp of 182C @ 10 mm Hg. It would be expected to remain behind in a standard distillation when combined with any of the common organic reaction solvents. Even DMSO (bp 189), DMF (bp153), NMP (bp 81-82 10mm hg) would be expected to be chased by glycerin. All the first solvent could be distilled because the volume in the reactor would not go below the minimum stirrable volume. The less volatile solutes from the starting solvent would be retained in the glycerol although not necessarily kept in solution.  Advantageously glycerol is immiscible with many common organic solvents such as hexane, methylene chloride, acetone, chloroform, benzene, probably toluene. Thus the solutes can be extracted from the glycerin phase into the new lower boiling solvent. If the transfer is inhibited by partition coefficients, the glycerin can be diluted with some water to perhaps improve the transfer. Whatever glycerin is taken into the new lower boiling solvent can be removed using a drying agent that strongly binds it such as calcium chloride. The distilled first solvent contaminated with traces of glycerin upon simple treatment might be ready for reuse. Thus the first solvent is no longer a waste and there are no mixed fractions of solvents to dispose of. The waste glycerin is a biodegradable material and the quantity used is no more than the minimum stirrable volume of the reactor.

 

General | Next | Previous | Comments (6) | Trackbacks (0)


Chemical terms acetone | benzene | boiling | calcium chloride | calcium | chloroform | glycerin | hexane | solution | solvent | toluene | water | work

Comments

Re: Is Glycerin a General Green Solution to Solvent Recovery and Replacement for Process Chemistry?

milkshake | 24/08/2011, 10:59

dude, why dont you measure heat of mixing equal volumes of glycerol with DMSO - I bet it is quite exothermic and it will form an upper (higher-boiling) azeotrope with stuff like DMSO and NMP because of very strong hydrogen bonding - the same goes with water + DMSO or NMP. And glycerol is viscous. I have seen process paper where they used a silicone-based heat transfer fluid (low MW low viscosity cyclic polysiloxanes) - to me it is disgusting to put silicone oil into reaction on purpose but it is soluble in heptanes and nontoxic

Is Glycerin a General Green Solution to Solvent Recovery and Replacement for Process Chemistry?

plumbing | 01/10/2011, 02:09

Glycerin is also use for soap manufacturing. It contains a component of fat and oil.

Re: Is Glycerin a General Green Solution to Solvent Recovery and Replacement for Process Chemistry?

Cocoon Bobbins | 03/10/2011, 00:44

Kilomentor, my hat is off to you. It is not often these days someone actually takes the time to write such a detailed blog post. It is clear you have a real passion for your topic. As an instructor of High School and Community College students, I find your information very helpful. It may help me about related matter. Thanks for sharing. Great job, indeed.

bc real estate

bc real estate | 21/11/2011, 21:06

I'm a blog enthusiast and with so many blogs on the internet now, very few stand out. This blog caught my attention and I thought that I would post to let you know that.

Wordpress Design

Wordpress Design | 14/03/2012, 20:49

Definitely agree with what you stated. Your explanation was certainly the easiest to understand. I tell you, I usually get irked when folks discuss issues that they plainly do not know about. You managed to hit the nail right on the head and explained out everything without complication. Maybe, people can take a signal. Will likely be back to get more.

the solution contents

Pressure Washer | 26/03/2012, 09:03

I was not clear that glycerol is immiscible with many common organic solvents such as hexane, methylene chloride, acetone, chloroform, benzene, probably toluene. thanks for the explanation and sources.

Add comment (SPAM IS DELETED INSTANTLY)
authimage
 
Powered by LT - Design by BalearWeb