Published August 2014
Most commercial linear alpha-olefin (LAO) plants produce a broad range of even-numbered alpha-olefins based on ethylene oligomerization technologies. Although initially targeted for plasticizer and detergent end-uses, LAO processes have become an important source of production for butene-1, hexene-1, and octene-1, comonomers used in the production of polyethylene to enhance certain physical properties. As the polyethylene industry has evolved, demand for comonomers has increased, and the growth has led to a supply/demand imbalance in the distribution of LAOs, which serve a broad range of end-use applications. This, in turn, has created opportunities for alternative comonomer production routes through on-purpose technologies, such as ethylene tetramerization, ethylene dimerization, and ethylene trimerization.
Another variation of on-purpose alpha-olefin production can be found at the Sasol Chemical Industries plant in South Africa. The Sasol facility is unique in that C5-C8 alpha-olefins are recovered from a light oil stream generated by coal gasification and Fischer-Tropsch conversion. Sasol commissioned their first octene-1 extraction train in 1999, with a second train following in 2002. With these two trains, Sasol was effectively extracting all the available octene from the light oil stream. In order to keep up with growing demand for octene-1, Sasol commissioned a third train in 2008 using a novel process to convert heptene-1 to octene-1.
This Review presents a techno-economic evaluation of the Sasol heptene-1 to octene-1 technology. The analysis that follows is based on a plant with an annual capacity to produce 225 million pounds (~100 thousand metric tons) of octene-1. In the process, a heptene stream is first separated from a Fischer-Tropsch light oil fraction. The heptene feed then undergoes hydroformylation using synthesis gas in the presence of a rhodium-ligand catalyst complex to produce octanal. The octanal product is subsequently hydrogenated to octanol, with the resulting alcohol then dehydrated to octene-1.
While the economic results presented herein are on a US Gulf Coast basis, the accompanying iPEP Navigator Excel-based data module (available with the electronic version of this Review) allows for viewing results for other major regions along with conversion between English and metric units.