The industrial uses of clay minerals as catalysts date
from the early 'thirties. The application of catalysis to the thermal
cracking of oil started in about 1931; pre-heated oil was passed
downwards through fixed beds of granular catalyst, often attapulgite,
under pressure (80 lb. per sq. in.) and at about 900~ as in the
Houdry and Hydroforming systems. The catalyst had to be periodi-
cally burned off to regenrrate it, and was reintroduced at the top of
the reaction column. An improvement on this static process came
when the granulated catalyst was kept moving counter current to the
pre-heated oil. This led about 1939 to the fluid-flow method of
catalysis in which powdered catalysts are used in a fluid, free-flowing
condition, circulated by the air-rift method well-known in the move-
ment of liquids. The motive power for the circulation of the fluid is
obtained from the static head of gas-solid columns and by the intro-
Although the clay mineralogist is bringing
some order out of chaos in the classification of clays we are faced with
rather a large number of trade names when we come to study the
literature of clay catalysts. I shall name some of the better known
ones, beginning with the kaolinitic group, The clays of this group
have not been much used in catalysis and are not cursed with strange
nomenclature. Dickite, nacrite, and halloysite are not worked
commercially, so we are left with the familiar china clays and ball
clays of commerce. These are clays with a 7 Angstrom unit basal
spacing of the lattice. The 10 Angstrom unit clays or illite group
includes attapulgite, which is the clay mineral of Florida fuller's
earth, Floridin, Florex, and Florigel, the products of Florida and
Georgia in the United States. (I should add that Florite is a bauxite
catalyst made by the same company). These clays in granulated and
powder form are the most important clay catalysts in the world.
They are not known to exist in Britain in commercial quantities;
some Russian clays seem to be similar.
The 14Angstrom clays, or montmorillo