The objective of this work is to develop catalysts for the controlled oligomerization of dienes as a route to hydrocarbon fuels. Chromium-based catalysts with bisphosphino-amine ligands demonstrate excellent reactivity with very high selectivity.  Ligand structure plays a key role in controlling selectivity towards trimerized products. These ligands offer the ability to widely vary the electronic and steric environment at the metal center to control product selectivity. However, these homogeneous catalysts may not be directly amenable to industrial use where product separation and catalyst recovery are of prime importance. We are working to develop active heterogeneous Cr-based catalysts, related to those developed by Wass for selective trimerization of dienes.  Our strategy is to first prepare the homogeneous ligands, validate diene oligomerization, then synthesize and test the heterogeneous analogs.  Initial focus is on PNP ligand architectures. The symmetric ligand Ar2PNRPAr2 and unsymmetric ligand Ar2PNRPAr2' are of interest in our work because of the range of active site structures available and the potential routes for surface attachment.  The symmetrical PNP ligand, where Ar is phenyl, and the asymmetrical ligand, where Ar' is O-methoxyphenyl, were synthesized using propyl amine and chloro diarylphosphine (Scheme 1). The PNP ligands were used for the controlled oliomerization of isoprene in the presence of CrCl3(THF)3, and methylaluminoxane (MAO) at 70 �C (Scheme 2).  Synthesis of homogeneous symmetrical PNP ligand.   Trimerization of isoprene using Cr-catalyst and PNP ligand.

Development of catalyst systems for the production of jet fuel blend stocks from dienes

244th National Meeting (2012)

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