Aluminosilicates, which constitute one of the largest classes of minerals,
have, from the earliest times, been used as catalysts or catalyst supports
for a number of commercially important reactions. Acid-treated clays, for
example, were used from the 1920s to the mid-1940s for the cracking of
oils (1) and for the reforming (i.e., the isomerization) of short-chain hy￾drocarbons such as pentanes to octanes (2). Since the early 1960s synthetic
aluminosilicates in the form of zeolites (3-5) have been the dominant
catalysts in the petrochemical industry. Zeolites Y and the so-called pen￾tasils, of which ZSMJ and ZSM-11 are the most renowned (4, 6, 7) mem￾bers, are nowadays extensively used worldwide. Ultrastabilized (8) zeolite
Y, the structure of which is essentially that of the rare zeolite mineral
faujasite (9), is the cornerstone of present-day petroleum cracking and
hydrocracking processes; annual consumption is close to 2000,000 tons.
ZSM-5 is the catalyst of choice in the conversion of methanol to gasoline
and benzene and ethene to ethylbenzene. It is also used in so-called de￾waxing and selectofonning processes (4). Acid-washed mordenite is used
as a catalyst support (for the platnium group metals) for reforming; and
the aluminosilicate mineral erionite, like the pentasils ZSM-5 and ZSM-
11, also finds use as a commercial shape-selective catalyst.