Molecular graphics representation of the structure of the synthetic zeolite catalyst ZSM-5, showing its microchannel architecture. Zeolite minerals containing a silica-alumina crystalline structure are used as catalysts in the cracking process by which petroleum is refined. ZSM-5 forms the basis of the conversion of methanol to gasoline - an alternative to petroleum. A MOBIL commercial plant running this process is in operation in New Zealand in 1991. Environmental pressure will undoubtedly ensure that this & similar processes continue to evolve commercially.