The Botany petrochemical complex

In the 1960s, Australia had a healthy industry in basic chemicals, but the new plastics industries overseas were based on petrochemical plants grouped around very large crackers of naphtha. By contrast, in Australia, up to the sixties, ICI Australia's production of PVC and polythene had made do with feedstock available from local resources, ethylene cracked from ethyl alcohol as discussed earlier, and acetylene. These could no longer compete with ethylene from crackers nor could the plants cope with growth. The combined PVC and polythene capacity in Australia was 15,000 tonnes. Overseas hydrocarbons were produced from plants ten times larger, (then) 100,000 to 200,000 tonne ethylene crackers. What the Australian petrochemical industry needed to get to the take-off point was a plant approaching world scale.

Oxychlorination -a new vinyl chloride process:
international success and an Australian plant

Corporate planners dealing with a multiplicity of relatively small markets for the individual plastics and derivatives looked for ways of supplying these from a single cracker, preferably one common raw material, so that the combined demand would reach minimum viable scale for the cracker -100,000 tonnes. Even then the existing products -PVC and polythene -might not provide adequate volume. Planners and research chemists jointly searched for existing processes anywhere in the world, and perhaps, at much longer odds, new routes and/or new products which could be grouped around ethylene or perhaps a cracker producing both ethylene and acetylene -the so-called mixed gas scheme.

Chemical engineers are realists; they wanted to use processes which were well developed, as the acetylene based process was then in Australia. Also, they thought in engineering terms. So they looked for a scheme in which both raw materials, acetylene and ethylene, came from one cracker. The difficulty with this so-called mixed gas scheme was to match the changing market demand for the different gases.

The problem was posed in 1961 in a discussion between plastics technical staff and research staff. A few days later a patent chemist noted in a patent that, given the right catalyst, a similar reaction did proceed with another hydrocarbon in the presence of oxygen. Part of this was really historic schoolboy chemistry, the old Deacon reaction, which everyone knew but no one used any more. The problem was given to a young chemist[120] -would it work with ethylene? It did -but only just well enough to give some hope. Two thermodynamically conflicting reactions proceeding simultaneously required different conditions. The process was viable only if yields were high. Management called for an integrated team study. Physical chemists and chemical engineers examined catalysts, thermodynamics, rate constants, safety aspects, explosive limits, reactor design and materials of construction. A team of more than 20 staff worked on the project. For some time, hopes were high that a basic new route to vinyl chloride, one of the principal building blocks of the world's plastics, had been invented; indeed, the trend towards a single feedstock for the two main mass plastics, PVC and polyethylene, was a world-wide need, the market was growing fast and the opportunity was immense.

Australian Academy of Technological Sciences and Engineering