Demystifying Single-site Catalysts Used in Polyethylene Production

December 3, 2013
Demystifying Single-site Catalysts Used in Polyethylene Production

In detailing the innovative separation technologies used to break apart hydrocarbons, entire libraries could be filled several times over by publications that clarify the near mystical process of turning crude oil into energy. For hundreds of years civilization was happy enough to employ simple oil products, to use kerosene for lighting and tar to shore homes, but these pre-industrial engineers had no idea of what was trapped within the crude black stuff oozing out of the ground. It wasn’t until distillation science came along that we began to tap into the fuels, chemicals, and plastics locked within petroleum deposits.

While distillation, the separation and extraction of pentanes and other fractions by thermal treatment, is the simplest form of refinement to understand, catalytic cracking maintains dominance in several key areas. First of all, catalytic isolation of a particular fraction is a far more targeted process, and, secondly, the chemical process can opt for a reaction dynamic that eliminates thermal treatment. Finally, the introduction of a catalysing agent means low pressures can be maintained. What does all of this chemical mysticism mean to the refining process? Quite simply, vessels and associated piping can be made from thinner metal, fabrication techniques that don’t need reinforcement to deal with high temperatures and even higher temperatures.

It’s not all plain sailing when employing a catalytic approach to cracking. The targeted production of polyethylene, as one engaging example, involves what is known as a transition metal catalyst. Single-site catalysts employ this atom as a central component in the polymer synthesis process. Atoms such as titanium and palladium fit this description. They ally with a ligand set, a functional group of molecules, to form a bond between metal and organic complexes, acting as an initiating group in the catalysing stage for the genesis of polypropylene. Seventy-seven million metric tons of this long-chained polymer are produced annually, and each production environment depends on catalytic cracking through single site catalytic (SSC) processing to maintain this impressive rate of chemical action. That’s a performance ratio distillation technology would be hard-pressed to match.

Highly active and dependable in creating linear polymers, these metallocene compounds promote the principle of singular performance, thus affirming an operation efficacy that embraces reliability and repeated productivity at a commercial level. The ligand or bridged organic component of the molecule can be adapted to finitely control the catalytic properties of the operation, managing graphed characteristics of the polymerization process. This means changes are always possible, and there’s certainly room for change and growth in what is a still developing field of organic chemistry. Single site catalytic cracking does indeed produce polyethylene of an incredibly high grade, power-producing millions of tons of the highly marketable plastic every year.