distillation

8 Articles

A laboratory benchtop is shown. To the left, there is a distillation column above a collecting flask, with a tube leading from the flask to an adapter. The adapter has a frame holding a glass tube with a teflon stopper at one end, into which a smaller glass tube leads. At the other end of the larger tube is a round flask suspended in an oil bath.

Building A Rotary Evaporator For The Home Lab

September 8, 2025 by 6 Comments

The rotary evaporator (rotovap) rarely appears outside of well-provisioned chemistry labs. That means that despite being a fundamentally simple device, their cost generally puts them out of reach for amateur chemists. Nevertheless, they make it much more convenient to remove a solvent from a solution, so [Markus Bindhammer] designed and built his own.

Rotary evaporators have two flasks, one containing the solution to be evaporated, and one that collects the condensed solvent vapors. A rotary joint holds the evaporating flask partially immersed in a heated oil bath and connects the flask’s neck to a fixed vapor duct. Solvent vapors leave the first flask, travel through the duct, condense in a condenser, and collect in the second flask. A motor rotates the first flask, which spreads a thin layer of the solution across the flask walls, increasing the surface area and causing the liquid to evaporate more quickly.

Possibly the trickiest part of the apparatus is the rotary joint, which in [Markus]’s implementation is made of a ground-glass joint adapter surrounded by a 3D-printed gear adapter and two ball bearings. A Teflon stopper fits into one end of the adapter, the evaporation flask clips onto the other end, and a glass tube runs through the stopper. The ball bearings allow the adapter to rotate within a frame, the gear enables a motor to drive it, the Teflon stopper serves as a lubricated seal, and the non-rotating glass tube directs the solvent vapors into the condenser.

The flasks, condenser, and adapters were relatively inexpensive commercial glassware, and the frame that held them in place was primarily made of aluminium extrusion, with a few other pieces of miscellaneous hardware. In [Markus]’s test, the rotovap had no trouble evaporating isopropyl alcohol from one flask to the other.

This isn’t [Markus]’s first time turning a complex piece of scientific equipment into an amateur-accessible project, or, for that matter, making simpler equipment. He’s also taken on several major industrial chemistry processes.

Replacing Crude Oil Fractional Distillation With Microporous Polyimine Membranes

June 21, 2025 by 12 Comments

Currently the typical way that crude oil is processed involves a fractional distillation column, in which heated crude oil is separated into the various hydrocarbon compounds using distinct boiling points. This requires the addition of significant thermal energy and is thus fairly energy intensive. A possible alternative has been proposed by [Tae Hoon Lee] et al. with a research article in Science. They adapted membranes used with reverse-osmosis filtration to instead filter crude oil into its constituents, which could enable skipping the heating step and thus save a lot of energy.

The main change that had to be made was to replace the typical polyamide films with polyimine ones, as the former have the tendency to swell up – and thus becomes less effective – when exposed to organic solvents, which includes hydrocarbons. During testing, including with a mixture of naphtha, kerosene and diesel, the polyimine membrane was able to separate these by their molecular size.

It should be noted of course that this is still just small scale lab-testing and the real proof will be in whether it can scale up to the flow rates and endurance required from a replacement for a distillation column. Since this research is funded in part by the fossil fuel industry, one can at least expect that some trial installations will be set up before long, with hopefully positive results.

Big Chemistry: Fuel Ethanol

May 21, 2025 by 73 Comments

If legend is to be believed, three disparate social forces in early 20th-century America – the temperance movement, the rise of car culture, and the Scots-Irish culture of the South – collided with unexpected results. The temperance movement managed to get Prohibition written into the Constitution, which rankled the rebellious spirit of the descendants of the Scots-Irish who settled the South. In response, some of them took to the backwoods with stills and sacks of corn, creating moonshine by the barrel for personal use and profit. And to avoid the consequences of this, they used their mechanical ingenuity to modify their Fords, Chevrolets, and Dodges to provide the speed needed to outrun the law.

Though that story may be somewhat apocryphal, at least one of those threads is still woven into the American story. The moonshiner’s hotrod morphed into NASCAR, one of the nation’s most-watched spectator sports, and informed much of the car culture of the 20th century in general. Unfortunately, that led in part to our current fossil fuel predicament and its attendant environmental consequences, which are now being addressed by replacing at least some of the gasoline we burn with the same “white lightning” those old moonshiners made. The cost-benefit analysis of ethanol as a fuel is open to debate, as is the wisdom of using food for motor fuel, but one thing’s for sure: turning corn into ethanol in industrially useful quantities isn’t easy, and it requires some Big Chemistry to get it done.
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Retrotechtacular: The Story Of Turpentine

December 4, 2023 by 33 Comments

If someone in 2023 has ever had much call to use turpentine, chances are good it was something to do with paint or other wood finishes, like varnish. Natural turpentine is the traditional solvent of choice for oil paints, which have decreased in popularity with the rise of easy-to-clean polymer-based paints and coating. Oh sure, there are still those who prefer oil paint, especially for trim work — it lays up so nice — but by and large, turpentine seems like a relic from days gone by, like goose grease and castor oil.

It wasn’t always so, though. Turpentine used to be a very big deal indeed, as shown by this circa 1940 documentary on the turpentine harvesting and processing industry. Even then it was only a shadow of its former glory, when it was a vital part of a globe-spanning naval empire and a material of the utmost strategic importance. “Suwanee Pine” shows the methods used in the southern United States, where fast-growing pines offer up a resinous organic gloop in response to wounds in their bark. The process shown looks a lot like the harvesting process for natural latex, with slanting gashes or “catfaces” carved into the trunks of young trees, forming channels to guide the exudate down into a clay collecting cup.

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Diesel Station Wagon Runs On Plastic

November 15, 2023 by 58 Comments

Old diesel engines from various car manufacturers like Mercedes and Volkswagen are highly prized even in modern times. Not only were these engines incredibly reliable and mechanically simple, but they can easily be modified to run on a wide variety of fuels. It’s common to see old Volkswagen Jettas or Mercedes 300Ds running on used vegetable oil or any other free flammable liquid that might otherwise end up in the garbage. [Gijs Schalkx] has an diesel Volvo 240 wagon, and rather than compete with all the other diesel owners looking for cooking oil, he modified this one to run on plastic waste instead. (Google Translate from Dutch)

While our Dutch language skills aren’t the best, what we gather about this project is that it uses standard solid plastic waste for fuel, but an intermediate step of cooking the plastic into a liquid is first needed. The apparatus on the roof is actually a plastic refinery which uses a small wood fire to break the plastic molecules into usable hydrocarbons, which are then sent to the engine for burning. The car is street legal and seems to operate like any other diesel of this vintage, although the fuel delivery system may not be able to provide it enough to get it going at very high speeds.

While it is possible to use wood to produce wood gas for fuel in an internal combustion engine like this wood gas-powered lawnmower, the hydrocarbon strings in plastic are essentially stabilized hydrocarbons from refining oil and have potentially much more available energy. Releasing this energy is generally difficult enough that used plastic is simply landfilled. [Gijs Schalkx] has made plenty of alternative fuel vehicles, too, like this moped that used locally-harvested swamp gas to ride around town.

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Mining And Refining: Helium

June 15, 2022 by 46 Comments

With a seemingly endless list of shortages of basic items trotted across newsfeeds on a daily basis, you’d be pardoned for not noticing any one shortage in particular. But in among the shortages of everything from eggs to fertilizers to sriracha sauce has been a growing realization that we may actually be running out of something so fundamental that it could have repercussions that will be felt across all aspects of our technological society: helium.

The degree to which helium is central to almost every aspect of daily life is hard to overstate. Helium’s unique properties, like the fact that it remains liquid at just a few degrees above absolute zero, contribute to its use in countless industrial processes. From leak detection and welding to silicon wafer production and cooling the superconducting magnets that make magnetic resonance imaging possible, helium has become entrenched in technology in a way that belies its relative scarcity.

But where does helium come from? As we’ll see, the second lightest element on the periodic table is not easy to come by, and considerable effort goes into extracting and purifying it enough for industrial use. While great strides are being made toward improved methods of extraction and the discovery of new deposits, for all practical purposes helium is a non-renewable resource for which there are no substitutes. So it pays to know a thing or two about how we get our hands on it.

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Electric Vehicles, The Gasoline Problem, And Synthetic Fuels

October 18, 2021 by 115 Comments

When you’re standing at the gas station filling up your car, watching those digits on the pump flip by can be a sobering experience. Fuel prices, especially the price of gasoline, have always been keenly watched, so it’s hard to imagine a time when gasoline was a low-value waste product. But kerosene, sold mainly for lighting, was once king of the petroleum industry, at least before the automobile came along, to the extent that the gasoline produced while refining kerosene was simply dumped into streams to get rid of it.

The modern mind perhaps shudders at the thought of an environmental crime of that magnitude, and we can’t imagine how anyone would think that was a good solution to the problem. And yet we now face much the same problem, as the increasing electrification of the world’s fleet of motor vehicles pushes down gasoline demand. To understand why this is a problem, we’ll start off by taking a look at how crude oil is formed, and how decreasing demand for gasoline may actually cause problems that we should think about before we get too far down the road.

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