Alkali metals dispersion

Base catalysis is most effective with alkali metals dispersed on solid supports or, in the homogeneous form, as aldoxides, amides, and so on. Small amounts of promoters form organoalkali comnpounds that really contribute the catalytic power. Basic ion exchange resins also are usebil. Base-catalyzed processes include isomerization and oligomerization of olefins, reactions of olefins with aromatics, and hydrogenation of polynuclear aromatics. 

After storage for 16 years in a tin, a sealed bottle originally holding sodium dispersed in xylene was found to contain a yellow/white solid layer in place of the expected supernatant xylene. Scraping the solid out caused a violent explosion. The force of the explosion leads to a suspicion of peroxide formation, but there is no obvious explanation. Reactive materials like alkali-metal dispersions in volatile solvents should not be stored indefinitely, but clearly labeled after receipt or preparation to show the disposal date. Disposal of such dispersions by binning is recommended. Sodium dispersed in toluene might behave in the same way. 

Alkali Metal Dispersions, Fatt, I. et al., London, Van Nostrand, 1961... 

Alkali metal dispersions, or Alkaline earth metal dispersions 1391... 

Dover BT, Kamienski CW, Morrison RC, Currin RT. Process for producing alkali metal dispersions. US Patent, 5567474, 1996. 

I. Fatt, M. Tashima, Alkali Metal Dispersions, D. Van Nostrand, New York, 1961. 

Alkali metal dispersions, 4.3 Alkaline earth metal dispersion, 4.3 Aluminium, powder Aluminium powder, coated, 4.1 Aluminium powder, pyrophoric Aluminium powder, uncoated, 4.3 Aluminium powder, uncoated, non-pyrophoric, 4.3 Antimony powder, 6.1 Barium dispersions Barium, powder Barium powder, pyrophoric, 4.2... 

Alkali Metal Dispersion Alkaline Earth Metal Dispersion Finely divided alkali or alkaline earth metal, e.g. metallic sodium suspended in a flammable liquid such as toluene, xylene, naphtha, kerosene, etc. Reacts violently with moisture, water or acids, evolving hydrogen, which may be ignited by the heat of reaction. IMO 4324... 

The polymers are prepared from disubstituted dichlorosilanes by reacting them with alkali metal dispersions in a reductive coupling process. The polpierizations appear to have the characteristics of chain-growth rather than step-growth reactions. ... 

Alkali metal doped or supported on metal oxides show high activities for alkene double bond migration. Although the states of alkali elements are not known, the reaction intermediates are believed to be anionic, and consequently, it is assumed that the basic sites are operating in the reaction. The most active catalyst among alkali metals dispersed on different metal oxides is sodium dispersed on alumina. The sodium dispersed on alumina shows such a high activity as to proceed double bond migration even at 213 K. ... 

The products of propene dimerization using alkali metals dispersed on a variety of supports are given in Table 4.18. The reactions were performed over a support containing 0.1 mole of dispersed alkali metal at 423 K and about 10 MPa pressure. The main product is 4-methyl — 1-pentene, as expected from the allylic carbanion addition to double bond. 

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