New Condensers Cool Solvent Without Flowing Water | Chemical & Engineering News
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Web Date: September 26, 2013

New Condensers Cool Solvent Without Flowing Water

Sustainable Chemistry: Chemists modify glassware to save water while running common reactions
Department: Science & Technology | Collection: Green Chemistry
News Channels: Environmental SCENE, Organic SCENE
Keywords: water conservation, condenser, sustainable chemistry, green chemistry
Cooling Fins
A condenser manufactured by Radleys uses a finned aluminum sheath to dissipate heat.
Credit: Radleys
Photo of a condenser made by Radleys
Cooling Fins
A condenser manufactured by Radleys uses a finned aluminum sheath to dissipate heat.
Credit: Radleys
Cooled With Antifreeze
A modified Allihn condenser uses ethylene glycol instead of running water to cool solvent. The glassware is available by special order from ChemGlass.
Credit: ACS Sustainable Chem. Eng.
Photo of a condenser made by ChemGlass
Cooled With Antifreeze
A modified Allihn condenser uses ethylene glycol instead of running water to cool solvent. The glassware is available by special order from ChemGlass.
Credit: ACS Sustainable Chem. Eng.

In a single reaction, synthetic chemists sometimes can run through hundreds of liters of water, possibly without realizing it. The culprit is their solvent condenser, a piece of glassware that uses flowing water to cool solvents refluxing in a reaction vessel. Now two groups of chemists have invented condensers that use little or no water to condense boiling solvents.

A typical condenser consists of a glass tube nested within another. Water flows between these two tubes. A chemist attaches the condenser to the top of a flask so that as refluxing solvent evaporates and travels up through the center tube, the flowing water cools the solvent. It then condenses on the glass surface and drips back into the flask. Depending on the flow rate, a typical condenser uses 1 to 4 L of water per minute, says Dave Perkins, a senior research scientist at AstraZeneca, in the U.K., and an inventor of one of the new condensers.

Some condensers don’t use running water, such as the air-cooled Vigreux condenser and Sigma-Aldrich’s Airflux, which relies on a small amount of static water. But these pieces of equipment work only with solvents that boil at about 60° C or higher.

Perkins and his coworkers wanted to make the Vigreux condenser work with lower boiling point solvents. To do so, they wrap the glassware with an aluminum sheath decorated with 21-mm-thick fins. The inner part of this aluminum jacket is filled with water. The fins increase the surface area of the condenser and allow it to dissipate heat from the solvent.

In trials, their apparatus retained more solvent than both the Airflux and the traditional Vigreux condensers. When the researchers heated 500 mL of dichloromethane at 60° C—about 20° C above its boiling point—for 16 hours, no solvent was left in the setup using a Vigreux column, but their prototype lost only half the dichloromethane (ACS Sustainable Chem. Eng. 2013, DOI: 10.1021/sc400254c). AstraZeneca has since sold the design to Radleys, a British chemical equipment supplier that developed the prototype.

Anne M. Wilson, an organometallic chemist from Butler University, and colleagues at Dow AgroSciences, took a different approach. They improved upon a standard, water-cooled Allihn condenser, whose inner glass tube consists of a series of connected bulbs to improve solvent condensation. Instead of flowing water, they turned to a different, well-known coolant: ethylene glycol. The coolant has a high heat capacity and is cheap and abundant, Wilson says. The team asked the company ChemGlass to plug the water inlet and modify the upper port on the traditional Allihn condenser to allow them to fill it with ethylene glycol. Unlike in a traditional Allihn condenser, the coolant in this one is static and doesn’t flow through the condenser.

When they refluxed 10 mL of dichloromethane for 18 hours, the new condenser lost about half the solvent. A Vigreux condenser lost all the solvent, and a standard Allihn condenser lost about 42% (ACS Sustainable Chem. Eng. 2013, DOI: 10.1021/sc400285y).

Before reading these papers, Kenneth M. Doxsee, an organometallic chemist at the University of Oregon, didn’t appreciate the amount of water wasted by water-cooled condensers. And air-cooled condensers are not really practical alternatives, he says. “I can probably count on one finger how many times I’ve used a condenser and haven’t used cooling water,” he says.

In addition to saving water, these types of condensers may be useful for labs in countries where there isn’t a readily available water supply, Doxsee says. It would also be interesting to see if these condensers can be scaled up for industrial chemical synthesis, he says.

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Ramsey (September 26, 2013 5:27 PM)
Can't one just use a re-circulating chiller filled with water, glycol, or a mixture? That produces no waste and is very efficient. I don't understand the need here.
Ben (October 13, 2013 1:09 PM)
I really don't understand why people don't circulate their water, it is such a waste!
curdled (September 26, 2013 10:26 PM)
These are two underwhelming solutions of a complete non-problem.
desantoos (October 1, 2013 6:01 PM)
Well, if you ever wondered why the university takes such a sizeable chunk of any grant, part if it goes to pay for the utilities you use when you do your research. The water condensers typically used go through a lot of water. It is an expensive and very inefficient. Moreover, lab floods happen all the time from reflux condensers. I know this as a fact from my time having offices right under an organic laboratory. Floods are expensive to clean up and an awful nuisance. So I speak from experience that this is most definitely not a non-problem and that it's about time we moved past the 50's era lab techniques and started using the technology that is at hand.
Cynthia Runkel (October 2, 2013 2:34 PM)
Seven years ago, I was managing Unversity undergraduate organic chemistry Labs, we rigged a plastic bin of water with a fish tank pump for each two set ups on the lab bench. Low cost and little space needed to recycle the coolent water rather than having hundreds of students dump down the sink. Very successful !
DSTgar (October 2, 2013 2:53 PM)
Could be useful for undergraduate teaching labs. The ChemGlass solution is easily created by putting a segment of tubing between the inlet and the outlet (where admittedly it would be pesky to fill the system the one time it is required). Lesson 2: don't use dichloromethane!
Matthew Grist (October 22, 2013 8:48 AM)
Be cautious making a sealed system. If the liquid has a different rate of expansion to the glass you could have quite a mess to clean up. Some sort of buffer volume may be required.
Gustavo (October 10, 2013 10:48 PM)
long time ago we installed a system that cools water by using inexpensive parts bought from a refrigeration store and recirculates it to the condenser. The equipment shown in the article looks nice but unnecessary.
Matthew Grist (October 22, 2013 8:54 AM)
I have been using one of these condensers for some time now. When scaled across our entire lab their usage makes for a significant water saving. When factoring in the cost of the water return of investment is something like 3-6 months.

Whilst recirculating chilled water is an excellent way of saving water the cost is shifted to electricity for circulating and chilling. Both of these examples are completely free.

The first example copes with DCM and ether just fine when heated at 5 deg C above BP. There should be no need for flowing water or chillers in a modern laboratory.
Matt (October 23, 2013 6:30 AM)
I have been using one of these for quite some time now. When heated sensibly (ie about 5 deg C above BP) it holds ether and DCM just fine. Whilst recirculated, chilled water is excellent at reducing water waste (and cost) it is still not free as the cost is simply shifted to the electricity used. These condensers are completely energy free. I believe return on investment comes at 3-6 months.

Chemistry is not the most environmentally friendly activity. We need to be mindful of what we do and its about time people started considering the wider impacts.

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