936 PCBs AND ASSOCIATED AROMATICS
TABLE 54Test ASTM test method New oilTypical properties
of oil requiring
reclamationDielectric Breakdown D–877 30 22
(kV) D–1816 56 —
Power Factor 60 Hz, 25°C D–924 0.05 1.6
Neutralization Number (mg KOH/g oil) D–974 0.03 0.40
Interfacial Tension (dynes/cm) D–971 40 18
Moisture Content (ppm) D–1533 — 60anions. Polarographic measurements are usually made in
75% aqueous dioxane solution of the flow of current through
the solution as a function of the applied potential. When
reduction takes place a wave of current is produced. The
potential measured at the mid-point of the wave is referred
to as the e 1/2 , value. The e 1/2 values for some of the aromatic
hydrocarbons which can be used for PCB decontamination
agents, together with values for their electron affinities, are
listed in Table 55.
As one goes down the list, the electron affinity of the
larger aromatic molecules reflects the relative ease with which
an electron added to the system can spread itself through the
structure without causing high energy points of stress. The
relative ease of reduction therefore follows the same order and
anthracene is much more easily reduced than biphenyl. The
reactivity of the radical ions is therefore expected to decrease
down the list. Thus sodium biphenyl has been known for many
years to quickly and quantitatively react with organochlorine
compounds. The reaction is useful for use in the field as an
inexpensive screening tool for potentially contaminated oils.
Also, sodium naphthalenide is used in the Goodyear/(Smith
and Bubbar) process (Smith and Bubbar^107 ) for the PCB
decontamination of fluids. The reactions of alkali metals and
organometallic reagents with the classes of compounds typi-
cally found in insulating oils is perhaps best discussed in terms
of compound classes. A typical distribution of compound
types in mineral transformer oils is shown in Table 46.ALKANESOils which are totally paraffinic are essentially inert to radi-
cal ions. It has been found for example, that when a sodium
dispersion is made in a high molecular weight paraffinic oil
direct from the manufacturer, and then subsequently filtered,
that the oil properties remain unchanged.ALKENESThis class of compounds is not expected to occur in signif-
icant quantities in transformer oils. If they were present,they would most probably undergo their most common
reaction of polymerization and precipitate out of the oil
into the sludge layer. An alternative possibility is that the
olefin may add to the alkyl side chain of an alkyl aro-
matic compound. In either case it is most unlikely that the
products of such reactions would deleteriously affect oil
properties and indeed such reaction products may occur
naturally in some oils.ALDEHYDES AND KETONESAldehydes are a class of compound which, because of their
reactivity, are not expected to be present in oxidized oil in
significant quantities. Ketones, on the other hand, are known
to be present as primary oxidation products (Webber^106 ;
Holy^108 ).
The oxidation of hydrocarbons produces, successively,
hydro-peroxides, alcohols and ketones, and finally acids. The
fuller’s earth reclamation process is effective in the removal
of acids but does not remove their precursors. The presence
of even small quantities of acid can cause a catalytic effect
on the decomposition of ketones to give further acids. Oil
which has been reclaimed by the conventional fuller’s earth
treatment is therefore likely to oxidize more rapidly than
new oil with the same concentration of oxidation inhibitor
and this is usually found in practice.
The reactions of aromatic ketones with radical anions
lead to reduction of the ketone and yield an alcohol as
the major product (Holy^108 ). The importance of alcoholsTABLE 55Compound Electron affinity (eV) e1/2
Biphenyl — 2.70
Naphthalene 0.152 2.50
Phenanthrene 0.308 2.46
Anthracene 0.552 1.9C016_003_r03.indd 936C016_003_r03.indd 936 11/18/2005 1:12:44 PM11/18/2005 1:12:44 PM