Selective ethylene dimerization by a nickel-exchanged metal-organic framework catalyst

Abstract

Short linear [alpha]-olefins such as 1-butene are valuable commodity chemicals due to their use as comonomers in linear low-density polyethylene. Presently only homogeneous systems are used to catalyze ethylene dimerization in industry, causing many to suffer from quick deactivation and poor selectivity. The metal-organic framework (MOF) CPF-5 Mn₅(TBA)₃(HCOO)₃(OH)(H₂O₂)2]]₄·6DMF where TBA = 4-(l H-tetrazol-5-yl)benzoic acid provides an ideal structural template for the development of a heterogeneous catalyst for ethylene dimerization. Ni exchanged CPF-5 (Ni-CPF-5) treated with diethylaluminum chloride had a maximum turnover frequency of 23,000 mole ethylene per mole Ni per hour, and a maximum selectivity for 1-butene of 80% under optimized conditions. Ethylene pressure strongly influenced the activity and selectivity of Ni-CPF-5. Though the observed activity behavior is similar, the selectivity trends diverged significantly from previously reported MOF dimerization catalysts.