IIR document

Prepurification unit (PPU) process for the production of ultrahigh purity nitrogen.

Author(s) : JAIN R., ACHARYA D.


Nitrogen of ever higher purity is needed by the electronics industry for the manufacture of chips with ever increasing line densities. In order to meet chip manufacturers' needs, the reactive impurities in nitrogen, CO and hydrogen have to be removed to extremely low levels; typically less than 10 parts per billion each. Conventionally, these impurities have been removed by heating the feed air to 150-200 deg C, and then passing it over a precious metal catalyst bed for the oxidation of impurities. PreAir(TM) PPU process, a recent patented BOC development utilizes catalysts active at PPU operating temperature (5-50 deg C) in the PPU bed itself to oxidize CO and hydrogen. The reaction products (carbon dioxide and water) are subsequently removed by adsorption. Because this process does not require any additional equipment for impurities removal (the existing PPU vessels are used), PreAir(TM) process represents a dramatic decrease in the cost of reactive impurities removal.

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  • Original title: Prepurification unit (PPU) process for the production of ultrahigh purity nitrogen.
  • Record ID : 1998-0049
  • Languages: English
  • Source: MUST 1996. Meeting on Air Separation Technology
  • Publication date: 1996/10/10
  • Document available for consultation in the library of the IIR headquarters only.


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