Multi-stage hydrofining-hydrocracking process employing an intermediate treating operation

摘要

In the hydrocracking of liquid hydrocarbon fractions containing nitrogen compounds the feed is first hydrofined in the presence of a sulphur-resistant hydrogenation catalyst at 600 DEG -900 DEG F., not less than 300 p.s.i.g., at an L.H.S.V. of 0,3-5 and ammonia is removed from the effluent, at least part of the normally liquid effluent is then contacted with a siliceous cracking catalyst at a temperature below those at which cracking occurs and at least part of the normally liquid effluent is contacted in a final stage together with at least 1,500 S.C.F. of hydrogen per barrel of feed to the final stage with a catalyst comprising a hydrogenatingdehydrogenating component on an active acidic cracking support at 300 DEG -800 DEG F., an L.H.S.V. of 0,2-5 and at least 400 p.s.i.g., e.g. up to 5,000 p.s.i.g., there being consumed at least 750 S.C.F. of hydrogen per barrel of feed to the final zone converted to products boiling below its initial boiling point. The feed may be a petroleum fraction boiling in the range 200 DEG -850 DEG F., e.g. a heavy cracked or straight-run naphtha, kerosine, or cycle oil. The hydrofining is effected conventionally over oxides or sulphides of Co, Mo, Ni or W with or without oxides or carbonates of K, Ag, Be, Mg, Ca, Sr, Ba, Ce, Bi, Cr, Th, Si, Al or Zr and supported on charcoal, fuller's earth, kieselguhr, silica gel, alumina, bauxite or magnesia. Ammonia is removed by injecting water into the reactor effluent and separating under pressure followed by stripping. In the next stage the catalyst may be silica composited with magnesia, boria, alumina or alumina-zirconia or may be a natural alumino-silicate and is preferably silica-alumina containing 60-99% silica with a surface area of above 200m2/g. The temperature of contacting may be up to 650 DEG F. including ambient temperature. The final zone catalyst employs a cracking support similar to that used in the previous zone on which is deposited a Group VI or VIII metal or oxide or sulphide thereof, e.g. nickel or cobalt, their oxides and sulphides, oxides and sulphides of molybdenum, tungsten and chromium and if desired Group Ib or IIb metals, oxides or sulphides, e.g. copper, zinc or cadmium and their oxides or sulphides, in a total amount of 0,1-35% of the total catalyst.