GB591347A - Desulphurization of petroleum distillates - Google Patents

Abstract

<PICT:0591347/III/1> Lower boiling petroleum distillates, e.g., naphtha, kerosene, light gas oils &c. are desulphurized by a "fluid catalyist" process comprising continuously passing a mixture of the distillate vapour and hydrogen through a treating zone, contacting the vapour within the treating zone with a desulphurizing catalyst, maintaining the distillate in contact with the catalyst for a period and at a temperature sufficient materially to reduce the sulphur content of the distillate, thereafter continuously removing catalytic material from the treating zone, passing the catalyst so removed through a reactivating zone, treating the catalyst within the reactivating zone with hydrogen-containing gas to desulphurize the catalyst, and returning the desulphurized catalyst to the treating zone. In the plant shown diagrammatically on the drawing, the oil enters the treating chamber 15 through line 10, preheater 11 and furnace 13, wherein it is vaporized and heated to the required reaction temperature, e.g., 400 DEG to 800 DEG F. and preferably between 600 DEG and 700 DEG F. A suspension of finely divided desulphurizing catalyst, e.g., finely divided metallic nickel supported on activated alumina or other metal powders such as copper or zinc, with or without carriers &c. in hydrogen is also introduced through line 16 and the mixture of hydrogen, oil vapours and catalyst pass upwards through the perforated distribution grid 17 into the main body of the treating chamber, the velocity of the gases being preferably so controlled as to permit the catalyst to segregate into a dense turbulent layer in the lower portion of the chamber. The desulphurization is preferably carried out at pressures ranging from atmospheric to 200lbs. per sq. in. The desulphurized oil vapours and hydrogen leave chamber 15 via line 18 and may pass through a cyclone separator 19 for removing entrained catalyst powder which then returns to the chamber 15 through conduit 21. Thereafter the oil vapours and hydrogen pass via heat exchanger 11 and condenser 24 to the receiver 25 in which the desulphurized liquid distillate is separated from the unreacted hydrogen and other gases. The chamber 15 may be provided with a tube 28 in open communication with a vertical conduit 29 for continuously withdrawing spent catalyst from the chamber. The conduit 29 preferably forms a standpipe for generating a fluid pressure for circulating the finely divided spent catalyst through the treating chamber and a reactivating chamber, the catalyst in conduit 29 being maintained in a "fluid" condition by the introduction of a small amount of aerating gas at 31, 32 and 33. The level of the catalyst in chamber 15 is controlled by means of the valve 34. The spent catalyst continuously discharged from the bottom of pipe 29 enters a stream of hydrogen-containing gas either introduced at line 35 or consisting wholly or in part of the gases from the oil-gas separator 25. In the latter case a portion of the gas from the separator may be recompressed in the compressor 37 to the pressure desired for reactivating the catalyst before passing through the furnace 39. The suspension of spent catalyst in hydrogen-containing gas passes from the bottom of 29 into the body of the reactivating chamber 42 through the perforated grid plate 43. The temperature and pressure conditions maintained in the chamber 42 may be substantially the same as those maintained in the chamber 15. The sulphur content of the catalyst is reduced to a very low value in chamber 42 by employing a relatively high hydrogen/sulphur ratio. The gaseous products of catalyst reactivation pass from chamber 42 to a cyclone separator 45, heat exchanger 48 and cooler 51 to scrubber 53 in which they pass in counter-current contact with a weak basic solution such as mono- or diethanolamine or sodium phenolate solution for the removal of hydrogen sulphide. The reactivated catalyst in 42 passes via the tubular conduit 58 and vertical pipe 59 through control valve 61 below which it discharges into the stream of sulphur-free gases from 53 and is thus returned to the treating chamber 15. Any excess gas formed in the process may be removed through line 62. The activity of the catalyst in the treating zone is maintained at a higher level than in current processes where the catalyst is static and regenerated in situ, less degradation of the feed stock occurs and carbon formation is sufficiently low to avoid the necessity of burning carbon off the catalyst.