The work to be described in this thesis
takes the form of an investigation of the nitrogenous
bases which can be extracted by sulphuric acid from
the Naphthalene Oil and the Benzol Absorbing Oil
fractions of coal tar, after the tar oils have been
freed from phenols by extraction with caustic soda.
The chief objects of the investigation
were :-
(1) To obtain a weight / temperature of
distillation balance for both fractions of bases,
thus showing the relative abundances of the more
common fractions, and possibly indicating where any
previously unidentified bases were liable to occur.
(2) To make a closer study of the fractions
boiling between 180° and 235 °, and over 265 °C /760mm.Hg,
as these two fractions have not been exhaustively
studied in the past, and, where possible, to isolate
and identify pure bases.
The nitrogenous bases which can be extracted
by sulphuric acid from coal tar or coal tar oils
consist mainly of pyridine, quinoline, isoquinoline,
and their homologues, together with small quantities
of pyrrole, aniline, toluidines, xylidines, acridine
and naphthylamines.
According to present industrial practice
the only bases which are extensively utilised are
pyridine and its lower homologues, the commercially
available products being :-
Pure Pyridine - This is obtained by a close
fractionation of the lower tar bases and is used as
an intermediate in the production of "sulpha" drugs
(sulphapyridine), dyestuffs, vulcanisation accelerators
and waterproofing compounds, and as a solvent
and catalyst.
"90 -140° or 90 -160° Bases" - These are
obtained by crude fractionation of the lower tar
bases and are used as denaturants, solvents, level-
lers in leather dyeing, insecticides, and also in the
production of pattern effects on cotton and rayon,
and in lubricating oil refining.
"90 -180° Bases" - These are obtained by
crude fractionation of tar bases and are used as
solvents, in anthracene purification, and as restrainers
in metal pickling baths.
In addition to these main industrial
products the following are produced in smaller
quantities :-
Picolines - These have been produced in
small quantities from time to time, but recently,
owing to the great demand for nicotinic acid as an
accessory dietary factor, an interest has been
aroused in ß- pieoline, and considerable quantities
have been produced for oxidation to nicotinic acid.
I,utidines & Collidines - These have only
been produced in semi -commercial and experimental
quantities.
It is difficult to ascertain the sources
of the above products owing to the differences in
works practice throughout the country, especially
with respect to the temperature ranges of the oil
cuts taken, but it would appear that they are
produced for the most part from the lower boiling
tar oils, and according to present works practice
the bases are seldom removed from the Naphthalene
Oil and Benzol Absorbing Oil fractions.
The total United Kingdom production of
"pyridine bases" amounted to 166,000 gallons in 1948
and to 167,000 gallons in 1949 (Nin. of Fuel & Power),
and there are indications that more could be used if
it were available. If this is the case, it is
possible that the Naphthalene Oil fraction rn1 ht
provide a useful auxiliary source.
Very little work has been carried out on
the utilisation of the tar bases boiling above 180 °C,
such as are obtained from the Benzol Absorbing Oil
fraction, although quinoline and isoquinoline have
been isolated in semi -commercial and experimental
quantities, and during the recent war the xylidines
were separated for use as aviation fuel additives.
It was considered, therefore, that some quantitative
estimate of the constitution of the Benzol Absorbing
oil base fraction would be of considerable value
