Bimodal MWD in Solution Reactors

Nova also reports a single-site catalyst based on an organometallic complex with a metal center (Ti, Hf or Zr), and containing a cyclopentadienyl-type ligand and a phosphinimine ligand with methylalumoxane as activator, that produces bimodal MWD resins in the advanced Sclairtech reactor system [44]. The resins provide premium properties in pipe applications. 

The Sclairtech technology also offers lower cost ethylene as an ethylene feed stream of 85% ethylene and 15% ethane maybe used in the process. The cost savings comes from lower ethylene purification requirements in the ethylene plant. 

The Dow Chemical Company developed the solution polymerization process with the Dowlex tradename in the 1970s to manufacture ethylene/1-octene linear low-density polyethylene (LLDPE) copolymers. The process is proprietary and not available for license. The ethylene/1-octene copolymers exhibit many superior physical properties relative to other ethylene copolymers based on 1-butene or 1-hexene. 

However, since the 1990s, Dow scientists discovered a single-site designated as a constrained geometry catalyst system which has been used to significantly expand the product mix available from the Dow solution process. Dow presently produces copolymers based on 1 -butene, 1 -hexene and 1-octene over a wide density and Melt Index range. Note the reader is referred to Chapter 4 of this book, which discusses the Dow catalyst in more detail. 

Chemical Market Resources [45] has reported that the Dowlex process consists of two stirred tank reactors in series with an isoparaffin (mixture of Cg and C ) solvent operating at 160°C and approximately 320 

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