Studies on Nickel-Containing Ziegler-Type Catalysts. III. Dimerization of Propylene to 2,3-Dimethylbutenes. Part-I

Abstract

Abstract A new selective catalyst was developed for the dimerization of propylene to 2,3-dimethylbutenes (DMBS). It comprises five components: nickel naphthenate (Ni(naph)2)/AlEt3/PR3/diene/chlorinated phenol. Among them, chlorinated phenol is an essential component for activating the catalyst. Both the dimerization of propylene and the isomerization of the produced 2,3-dimethyl-1-butene (DMB-1) to 2,3-dimethyl-2-butene (DMB-2) are accelerated in proportion to the content of the chlorinated phenol as well as to the number of chlorine atoms on the chlorinated phenol. These effects are attributed to the Lewis acidity of the reaction product between AlEt3 and the chlorinated phenol. Thus, either DMB-1 or DMB-2 can be produced selectively by controlling the composition of the catalyst. The content of DMBS mainly depends upon the phosphine ligand; this ligand effect is discussed in terms of the 31P NMR chemical shift. A high content of DMBS of up to 85% in propylene dimers was attained when phosphines with chemical shifts between 0 and −30 ppm were used.