July 2, 2012
These catalysts make α-olefins that the market wants. The product slate from full-range linear α-olefin (LAO) processes can be difficult to match with market demands. These processes can make LAOs with carbon numbers from C4 through C20 or more. The three major companies that operate LAO processes, Shell, Ineos, and Chevron Phillips Chemical, have various methods for optimizing their product slates to match their market interests. A key lever for controlling the product slate is fine-tuning the design of the ethylene oligomerization catalyst.
P. Biagini and L. Gila disclose ethylene oligomerization catalysts that give good selectivity to the comonomer-range LAOs 1-butene, 1-hexene, and 1-octene. These comonomers are the fastest growing LAOs because of the strong market growth of linear low-density polyethylene. The catalysts are based on zirconium–sulfone complexes.
In one example, the catalyst solution consists of ZrCl4·2(Me2SO2) (2.5 × 10–4 M) and Et2AlCl in toluene with an Al/Zr mol ratio of 9.7:1. This solution is transferred to a reactor, and ethylene is added at 80 °C and 3.0 MPa pressure. The selectivities to C4, C6, and C8 LAOs are 22.4%, 38.8%, and 23.0%, respectively. In contrast, C10 and C12+ olefins are produced in selectivities of only 9.7% and 6.0%. By comparison, when the catalyst is ZrCl4 alone, the C10 and C12+ olefins are made in much higher amounts: 15.3% and 24.6%, respectively. (Polimeri Europa [Brindisi, Italy]. US Patent 8,198,497, June 12, 2012; Jeffrey S. Plotkin)