CATALYTIC CONVERSION OF ETHYLENE ON SYSTEMS BASED ON THRICHLOROTRIS-(TETRAHYDROFURANATE)CHROMIUM(III) WITH SOS-TYPE LIGANDS IN COMBINATION WITH VARIOUS ORGANOALUMINUM COCATALYSTS

Abstract

This work presents the results of studying the behavior of catalytic systems formed on the basis of trichlorotris-(tetrahydrofuranate)chromium(III) in the presence of sulfur-containing tridentate SOS-type ligands and activated by various organoaluminum compounds. In the formation of catalytic systems, the following compounds were used: SOS-type ligands - bis-(2-methylthioethyl) ether, bis-(2-ethylthioethyl) ether and bis-(2-phenylthioethyl) ether, organoaluminum compounds - triethylaluminum, triisobutylaluminum, tributylaluminum and methylaluminoxane. In the course of test experiments aimed at choosing an activator at a temperature of 40 °C and an ethylene pressure of 2 MPa, the best results were obtained for triethylaluminum. Therefore, further experiments on the catalytic conversion of ethylene were carried out only with this activator. To study the effect of the reaction temperature and ethylene pressure in the reaction zone, catalytic systems of the trichlorotris-(tetrahydrofuranate)chromium(III)/ligand/triethylaluminum composition were studied in the temperature range from 40 to 80 °C and an ethylene pressure of 2 - 3 MPa with a molar ratio of components Cr : L : AlEt3 = 1 : 1 : 20. As a result of studies, it was shown that in all cases when using tridentate ligands of the SOS type, the catalytic systems formed by us showed a tendency not only to polymerization, but also to oligomerization of ethylene. The best results in the field of ethylene oligomerization into hexenes were shown by the system of the composition trichlorotris-(tetrahydrofuranate)chromium(III) / bis-(2-methylthioethyl) ether/triethylaluminum, in which the content of the hexene fraction is 54 - 55 wt.%, while the selectivity to hexene-1 reaches 88 - 89%.