(57) A process for high catalytic hydroconversion of heavy liquid hydrocarbon feedstocks,
such as petroleum resid containing at least about 40 vol% material boiling above 975°F+, using two-staged catalytic reactors operated at elevated temperature and pressure
conditions so as to produce increased yields of lower boiling hydrocarbon liquids
and gas products. In the process, the feedstock is reacted with hydrogen in a first
stage catalytic ebullated bed reactor operated at 820-875°F temperature, 1500-3500
hydrogen partial pressure, and 0.30-1.0 Vf/Hr/Vr space velocity. The first stage reactor effluent liquid portion is fed into a second
stage catalytic reactor maintained at lower temperature of 700-800°F, 0.10-0.80 Vf/hr/Vr space velocity. The particulate catalyst material used in each stage reactor contains
2-25 wt.% active metals, and has 0.30-1.50 cm2/gm total pore volume and 100-400 m2/gm surface area. From the second stage reactor effluent, a vacuum bottoms fraction
normally boiling above about 850°F and preferably above 900°F is removed and recycled
back to the first stage reactor, so as to provide a recycle volume ratio to fresh
feedstock of 0.2-1.5/1 and achieve increased hydroconversion to produce lower boiling
liquid products. If desired, used catalyst withdrawn from the second stage reactor
can be treated and passed back to the first stage catalytic reactor for further use
therein before being discarded, so as to provide for matched reaction conditions and
catalytic activity in each stage reactor.
|
|
