Abstract: A vacuum reside was chosen as a coking feed. Three narrow cuts: ＜400 ℃(A), 400-430 ℃(B) , and 430—460 ℃(C) of the coking gas oil in the same refinery were used as hydrogen donors. The hydrogen-donating indexes and structure parameters of three narrow fractions were measured. Under the same coking conditions, the product yields of the residue blending with 10% narrow cut respectively were examined and compared with the results of pure residue without narrow cut. The order of hydrogen-donating indexes of three narrow fractions is A＞B＞C. The same order is for liquid yields for residue blending with three cuts. While the yield of liquid product of vacuum residue with cut A is higher than the pure residue.

Key words: hydrogen donor, coking gas oil, narrow fractions, hydrogen-donating ability