Abstract: Disclosed is a combined process for hydrotreating and catalytic cracking of residue, wherein the residue, catalytic cracking heavy cycle oil with acidic solid impurity being removed, optional distillate oil and adistillate of catalytic cracking slurry oil from which the acidic solid impurity is removed are fed into residue hydrotreating unit, the hydrogenated residue obtained and optional vacuum gas oil are fed into catalytic cracking unit to obtain various products; the catalytic cracking heavy cycle oil from which the acidic solid impurity is removed is circulated to the residue hydrotreating unit; the catalytic cracking slurry oil is separated by distilling, the distillate of the catalytic cracking slurry oil after removing off the acidic solid impurity is circulated to the residue hydrotreating unit.

Abstract: A catalytic conversion process which comprises catalytic cracking reaction of a hydrocarbon feedstock contacting with a medium pore size zeolite enriched catalyst in a reactor, characterized in that reaction temperature, weight hourly space velocity and catalyst/feedstock ratio by weight are sufficient to achieve a yield of fluid catalytic cracking gas oil between 12% and 60% by weight of said feedstock, wherein said weight hourly space velocity is between 25 h?1 and 100 h?1, said reaction temperature is between 450° C. and 600° C., and said catalyst/feedstock ratio by weight is between 1 and 30. This invention relates to a catalytic conversion process, especially for heavy feedstock oil to produce higher octane gasoline and an enhanced yield of propylene. More particularly, the invention relates to a process to utilize petroleum oil resources efficiently for decreasing the yield of dry gas and coke significantly.