Methane in zeolite. Molecular graphic showing molecules of methane (CH4) enclosed in pores inside the framework of a zeolite molecule (ZS 5). The zeolite framework is made of oxygen (red) and silicon (yellow) atoms. Methane is blue. Zeolite minerals contain a silica-alumina crystal structure and are used to catalyse hydrocarbon cracking during petroleum refining. Their ability to trap smaller molecules has earned them the nickname insmolecular sieveins. Cracking involves the fragmenting of large molecules into smaller, more stable hydrocarbons.