ZSM-5

Patented by Mobil Oil Company in 1975,[1] it is widely used in the petroleum industry as a heterogeneous catalyst for hydrocarbon isomerization reactions.

The pentasil chains are interconnected by oxygen bridges to form corrugated sheets with 10-ring holes.

The structure is orthorhombic (space group Pnma) at high temperatures, but a phase transition to the monoclinic space group P21/n.1.13 occurs on cooling below a transition temperature, located between 300 and 350 K.[4][5] ZSM-5 catalyst was first synthesized by Robert Argauer and George Landolt in 1969.

The third solution is the source of silica, one of the basic building blocks for the framework structure of a zeolite.

As early as 1967, Argauer and Landolt worked out parameters for the synthesis of pentasilzeolites, particularly those relating to the following molar ratios: OH−/SiO2 = 0.07–10, SiO2/Al2O3 = 5–100, H2O/SiO2 = 1–240.

Subsequent publications have disclosed methods of conducting the synthesis of pentasil-zeolites without requiring the very expensive, toxic and easily inflammable organic amine templates.

In addition to their expense, toxicity and flammability, such amines are disfavored because they are subject to thermal decomposition which can destroy the zeolite structure.

Further publications have disclosed modifications of the Argauer and Landolt process directed towards improving the reactivity of the SiO2 and Al2O3 starting materials.

The copper is occasionally combined with other metals, such as chromium, to fine tune the diversity and specificity of the products, as there is likely to be more than one.