Patent GB-896295-A (GB)
Title: Desulfurization of hydrocarbons
Inventor: SLYNGSTAD CHARLES EDWARD
IPC: C10G47/00
Filed: 1960-09-14
Abstract: A process wherein dissimilar hydrocarbon feed materials are catalytically desulphurized by being treated separately in a plurality of desulphurization zones, one such zone being provided for each feed, is characterized in that a substantially constant volume of hydrogen-rich gas is maintained and passed sequentially through the series of zones, the gas led to each zone being heated in indirect heat exchange <PICT:0896295/III/1> by a portion of the product effluent from that zone.  In the preferred embodiment shown, feed material A is passed by line 2 to heat exchanger 6, where it is preheated, and thence by line 8 to a second heat exchanger 10 before passing by line 12 to furnace 14 where it is heated to about 750 DEG F.  The heated feed then passes by line 16 to reactor 18, together with hydrogen-rich gas at 600 DEG F. supplied by line 172.  In reactor 18 the feed material A is desulphurized by passage through a single bed or a plurality of beds of cobalt molybdate catalyst.  The effluent stream 20 is divided, the major stream in line 22 serving to heat feed material in heat exchanger 10, and the minor stream in line 24 being used firstly to heat hydrogen-rich gas entering the reactor in heat exchanger 30, and secondly to heat condensate product in line 40 from separation drum 28 in heat exchanger 34.  Both streams are passed to drum 28, and, as already stated, the condensate product in line 40 which is heated in exchanger 34 is passed by line 42 to stripper 44, steam at 450 DEG C. entering at 46.  The bottom product leaves by line 48, is used to heat incoming feed material A in exchanger 6, is further cooled in 52, and then recovered.  The overhead product of stripper 44 passes by line 56 to cooler 58, and thence by line 60 to drum 62.  Gaseous product is withdrawn by line 64 to be stripped of H2S, while condensate passes by line 68, some being recovered, but most passing as reflux to tower 44. Simultaneously with the processing of material A, feed material B is introduced by line 70 to heat exchanger 74, whence it passes by line 76, heat exchanger 78 and line 80 to furnace 82 where it is heated to 760 DEG F.  Meanwhile, hydrogen-rich gas from separator drum 28 leaves by line 174 and passes to heat exchanger 100, make-up gas being introduced by line 106.  The gas stream at 570 DEG F. then passes by line 178 to be mixed with heated feed material B prior to entry to reactor 88, where the feed material is desulphurized by passage over a plurality of cobalt molybdate catalyst beds.  The product effluent leaves by line 90 and is split, one portion passing by line 94 through heat exchangers 100 and 104, and the other passing by line 92 and through heat exchanger 78, before both streams combine and pass to drum 108 maintained under high pressure at 450 DEG F.  A gaseous stream from drum 108 passes by line 112 through heat exchanger 114 and cooler 118 to drum 122 maintained at much the same pressure as drum 108 but at about 125 DEG F.  Liquid product leaves drum 108 by line 127, and drum 122 by line 124; this latter stream passes to heat exchanger 104 before mixing with the stream from line 127 in line 126, prior to entry into steam stripper 128.  The bottom product from the stripper leaves by line 130 and is used, if desired, to heat incoming feed material B.  The overhead product is treated in a similar way to that from stripper 44 as already described. Hydrogen-rich gas from drum 122 passes by line 160 to amine absorber tower 162 where H2S is removed, and then passes by line 164 to compressor 166, make-up gas being added in line 168. The gas is then passed through exchanger 114, line 170, exchanger 30 and line 172 to be mixed with feed material A in line 16.  A further feed material C of higher A.P.I. gravity than feed material B may be treated subsequently to material B, in which case valve 86 in line 84 is closed and material C is passed by line 180 through some only of the catalyst beds contained in reactor 88, the hydrogen-rich stream continuing to pass through all the catalyst beds.  In general, suitable desulphurization conditions are temperatures of 600 DEG -900 DEG F., pressures of 400-1,200 p.s.i.g., space velocities of 0,5-10 w/hr/w., and ratios of total hydrogen circulated to hydrocarbon feed of 0,5-10 moles/mole.  Suitable desulphurization catalysts are chromia, molybdenum trioxide, nickel or cobalt molybdate on alumina, nickel tungstate on alumina, nickel-cobalt molybdate, platinum and/or palladium on alumina, and such heteropoly acids as phosphomolybdic and phosphotungstic acids, either alone or supported, for example, on silica-alumina.  Oils which may be treated include gasoline, naphtha, kerosene, gas oil, cycle oils from catalytic or thermal cracking, residual oils, thermal and coker distillates, store oils, and diesel fuels, and the hydrocarbons may be treated in a liquid, vapour, or mixed liquid-vapour state, and the process may be carried out either co-currently (as shown) or in countercurrent.