Where Neon, Krypton and Xenon Come From

Commercial neon, krypton and xenon originate primarily from atmospheric air. Industrial plants separate constituents already present in that air, then concentrate and refine the rare gases. Understanding those stages helps a buyer distinguish an upstream source, an intermediate mixture and a finished cylinder supported by analytical evidence.

The starting concentrations are small. Air Liquide reports about 18 parts per million of neon in dry air; its krypton and xenon process description gives approximately 1.1 ppm krypton and 0.086 ppm xenon in ambient air. These figures describe the feed, not a plant's recoverable output. Actual production also depends on how much air is processed and how much of each gas is captured.

The air separation plant is the starting point

A cryogenic air separation unit, or ASU, processes air mainly to produce oxygen and nitrogen, with other products depending on its configuration. Air is filtered and compressed, and water and carbon dioxide are removed before deep cooling. Their removal protects cold passages against solid deposits. Heat exchange and refrigeration bring the cleaned air to the conditions needed for distillation.

In the columns, repeated contact between vapour and liquid separates components according to their different tendencies to evaporate and condense. This creates the main product streams and regions where trace constituents become enriched. Air Liquide's ASU explanation describes this sequence. Rare gas recovery then takes selected streams into additional equipment.

Neon follows the light gas stream

Neon and helium have much lower boiling points than nitrogen and oxygen. At the conditions used to condense nitrogen, they remain comparatively difficult to condense and collect in a gas stream on the nitrogen side of the system. Here, “light” describes their separation behaviour; it does not mean that an ordinary air filter can remove them. ASHRAE's cryogenics chapter explains this enrichment and the need for further purification.

The withdrawn stream is a feed for neon recovery, not finished neon. Nitrogen, hydrogen and other constituents must be addressed, and neon must be separated from helium. Messer describes a dedicated rectification route in which neon is condensed while helium remains gaseous after prior impurity removal. The treatment train and final polishing depend on the incoming mixture and required product specification.

Krypton and xenon follow the oxygen-rich stream

Krypton and xenon are less volatile than oxygen, so they become enriched on the liquid-oxygen side of the separation process. Recovery uses a selected oxygen-rich stream as feed. Additional separation removes much of the oxygen while raising the combined krypton and xenon concentration.

Air Liquide's recovery technology uses an extraction cold box, contaminant removal and a further upgrading stage. Its description includes removal of nitrous oxide and hydrocarbons. The resulting krypton/xenon concentrate still requires downstream separation into the individual gases. A mixture rich in krypton plus xenon is therefore a different commercial material from separately specified krypton or xenon.

Concentration, purity and recovery answer different questions

Concentration describes how much of a named component, or a stated group of components, is present in a mixture. Purity describes the composition of the individual product being supplied. Recovery describes how much of the target gas entering a defined process boundary reaches its intended output. Each requires a clear basis.

For example, a statement about combined krypton-and-xenon content does not establish either gas's individual purity. Nor does a high product purity establish how efficiently the original rare gas was recovered. Our guide to gas purity versus recovery explains how to read those measures separately.

The specification also needs individual impurity limits. Helium can be a relevant impurity in neon, while krypton and xenon can remain as impurities in one another. A grade label should therefore lead to an agreed analytical scope, including the applicable methods and reporting limits. See high-purity gas analysis for the role of complementary measurement methods.

Why not every ASU supplies rare gases

Processing air does not automatically provide a rare gas product. The plant needs suitable stream withdrawals, concentration equipment and a downstream route for refining and filling. Air Liquide explicitly distinguishes the large ASUs capable of producing rare gases. A plant's oxygen or nitrogen rating alone does not establish its neon, krypton or xenon output.

The supply chain can also involve more than one company or site. Linde describes ASU production supported by purification, blending and analytical capabilities. For procurement, identify which stages the offered supply covers and which organization issues the product's analytical documentation. An upstream origin statement and a final batch release record answer different questions.

Helium has a different main commercial origin

The presence of helium in the neon recovery stream does not make air separation the principal commercial source of helium. Linde identifies helium-bearing natural gas as the primary source. Recovery and purification from suitable natural gas streams form a separate industrial route.

Helium recovered alongside atmospheric neon is a possible coproduct of that particular process. It should be distinguished from the much larger commercial supply route based on helium-bearing natural gas. An explanation of rare gases from air cannot be applied unchanged to a helium supply proposal.

What to ask for in a supply discussion

Translate the process explanation into a small set of product questions:

• What material is offered? Identify the individual gas, a specified mixture or an intermediate concentrate. State whether further processing is required.
• What defines acceptance? Agree the minimum product content, individual impurity limits, units, analytical scope and batch identification.
• Which stages are documented? Request the relevant origin, purification, filling and release records for the proposed supply.
• What reaches the receiving connection? Confirm the cylinder, valve, filling basis and handling requirements alongside the gas specification.

Use the neon, krypton and xenon product pages as starting points for the enquiry. The agreed quality documentation and packaging configuration should describe the delivered material and support its intended use.