Solvent Purification in Academic Research Laboratories: A Comparison of Old and New Technologies

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Solvent Purification in Academic Research
Laboratories A Comparison of Old and New
Technologies
UCRL-PRES-148503
Kurt W. Dreger, MBA, CIH Lawrence Livermore
National Laboratory Steven F. Pedersen,
P.h.D. College of Chemistry University of
California, Berkeley
This work was performed under the auspices of the
U. S. Department of Energy by the University of
California, Lawrence Livermore National
Laboratory under Contract No. W-7405-Eng-48.
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Overview

• Introduction-The need for ultra-pure solvents
• The old way- Reflux/Distillation
• Hazards of traditional reflux/distillation
• The new way-Push Stills
• The need for design criteria
• Future challenges for safety folks

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The lifeblood of organic/inorganic syntheses

• Solvent purity makes or breaks experiment
• Oxygen/water are intolerable contaminants
• Larger and larger quantities in demand

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The Traditional Ketyl Still

• Solvents are
• Heated to boiling
• Refluxed over sodium
• Distilled and recovered for use

Courtesy of UC Irvine, Environment, Health and
Safety Department
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Benzophenone ketyl indicator
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Ketyl Still Hazards

• Heating of low flash pt. solvents
• Can overheat easily
• Alkali metals and hydrides
• Quenching procedure
• Mercury bubblers are common
• Fragile glassware

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Fires Involving Ketyl Stills
1. UC Irvine, Independent Accident Investigation,
Final Report-Injury and Fire Resulting from
Benzene Vapor Explosion in Reines Hall, July 23,
2001
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Incidents!
1995 - UC Berkeley
2001 - UC Irvine
Photo courtesy of UC Irvine, EHS Department
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Push Stills
R.H. Grubbs, et.al. Organometallics, 1996, Vol.
15, p. 1518-1520

• Input solvents very pure
• Nitrogen pushes solvent through alumina/copper
  catalyst (in column)

• Obvious Safety Benefits
• Elimination of Ignition Source
• No reactive metals/hydrides

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Several Types of Push Stills
Kilo-lab containers
Pure-Pak containers
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Push Stills are not without problems

• Lack of design standards
• We have seen
• Un-rated solvent source containers
• Tygon tubing for solvent delivery
• Un-safe solvent collection methods

• Scale
• Exceeds fire code
• Often located outside fume hood

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The Future of Push Stills

• Use will increase because
• Proven quality of solvents
• Market driven (supply and demand)
• Faculty/PI perception of safety

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Challenges Facing Safety Professionals

• Assuming Push Stills are here to stay we need to
• Develop or adopt design criteria
• Determine if benefits outweigh the risks of
  larger volumes
• Some questions to consider
• Are push stills indeed safer than ketyl stills?
• How do we enforce our design criteria?
• Should push stills be required to reside in
  hoods?
• Should we relax fire code requirements to
  accommodate this technology?

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Ketyl Stills Vs. Push Stills

• Questions? / Discussion