Patent GB-670091-A (GB)
Title: Cyclic adsorption process for the separation of liquid mixtures
IPC: B01D15/08
Filed: 1948-12-23
Abstract: In a process for separating liquid mixtures into fractions by p selective adsorption, the mixture is passed in turn through a series of fixed solid adsorbent masses at the same time as a stripping liquid is passed in turn through a further series of fixed solid adsorbent masses, previously used in a similar separating process, in order to regenerate the adsorbent, the arrangement being such that with each successsive operation of the process the inlets for liquid mixture and stripping liquid are moved one mass along in the direction of liquid flow, the first mass of the adsorption series becoming <PICT:0670091/IV (b)/1> <PICT:0670091/IV (b)/2> <PICT:0670091/IV (b)/3> <PICT:0670091/IV (b)/4> <PICT:0670091/IV (b)/5> <PICT:0670091/IV (b)/6> <PICT:0670091/IV (b)/7> <PICT:0670091/IV (b)/8> the last mass of the regenerating series in the next operation of the process and the first mass of the regenerating series becoming the last mass of the absorption series in the next operation of the process.  Thus in one operation of the process, adsorption towers C, D and E are employed for selective adsorption and adsorption towers F, G, H, A and B are subjected to regeneration as shown in Fig. 2, while in the next operation of the process adsorption towers D, E and F are employed for selective adsorption and adsorption towers G, H, A, B and C are subjected to regeneration as shown in Fig. 4.  The process is applicable to the de-aromatization of Diesel fuels, the dearomatization and desulphurization of kerosene distillates, the de-aromatization of lubricating stocks, the fractionation of aromaticparaffinic (e.g. toluene-octane) or olefinicparaffinic mixtures and the fractionation of liquid organic mixtures containing oxygenated compounds and hydrocarbons such as the reaction products of the Fischer-Tropsch and OXO processes.  The adsorbent may be silica gel, alumina, silica-alumina gel mixtures or charcoal, while the stripping liquid may be iso-octane.  In the case of the treatment of lubricating oil according to the process the oil is preferably diluted with a saturated hydrocarbon containing 3-6 carbon atoms in the molecule and the hydrocarbon employed as diluent is also employed as the stripping liquid.  The process is capable of a number of modifications.  Thus according to Fig. 1, the liquid mixture is fed initially, not into the first tower B of the adsorption series, but into the second tower C.  Simultaneously stripping liquid is fed into tower B until all liquid mixture feed present in the interstices of the adsorbent of tower B has been displaced.  Thereupon the process is continued with the arrangement shown in Fig. 2.  In the next operation of the process, first the arrangement of Fig. 3 and then that of Fig. 4 is employed.  In another modification shown in Fig. 5, either adsorbed material which has previously been stripped from the adsorbent in a regeneration step, or the first effluent of the last tower B of the regeneration zone, is recycled to the first tower C of the adsorption zone while the liquid mixture is fed to the second tower D of the adsorption zone.  In the next operation of the process, the arrangement of Fig. 6 is employed.  In a further modification shown in Fig. 7, regeneration is effected in two stages, a desorbent liquid being employed to remove the adsorbed material from the adsorbent in tower C and a stripping liquid being employed to remove the desorbent liquid in towers G, H, A and B.  Adsorbed material which has previously been stripped from the adsorbent in a regeneration zone is recycled to the first tower D of the adsorption zone, while the liquid mixture is fed to the second tower E of the adsorption zone. A variant of the arrangement of Fig. 7 is shown in Fig. 8, where the recycle of adsorbed material is omitted and the liquid mixture is fed to the first tower D of the adsorption zone.  In the arrangements of Figs. 7 and 8, the fraction of the liquid mixture which is not preferentially adsorbed may be employed as the stripping liquid. In an example, the arrangement shown in Fig. 5 is employed, using silica gel as the adsorbent and iso-octane as the stripping liquid. Straight-run kerosene distillate is employed as the liquid mixture and aromatics are preferentially adsorbed so that the kerosene is separated into two fractions, one containing less than 1 per cent aromatics and the other over 90 per cent aromatics.  The Specification as open to inspection under Sect. 91, refers to an additional example of the de-aromatization of kerosene employing silica gel as adsorbent and iso-octane as stripping liquid.  Examples are also given of the dearomatization of catalytically reformed gasoline employing silica gel as adsorbent and a heart cut of de-aromatized kerosene having a boiling range 387-466 DEG  F. as stripping liquid.  This subject-matter does not appear in the Specification as accepted.ALSO:In a process for separating liquid mixtures into fractions by selective adsorption, the mixture is passed in turn through a series of fixed solid adsorbent masses at the same time as a stripping liquid is passed in turn through a further series of fixed solid adsorbent masses, previously used in a similar separating process, in order to regenerate the adsorbent, the arrangement being such that with each successive operation of the process the inlets for liquid mixture and stripping liquid are moved one mass along in the direction of liquid flow, the first mass of the adsorption series becoming the last mass of the regenerating series in the next operation of the process and the first mass <PICT:0670091/III/1> <PICT:0670091/III/2> <PICT:0670091/III/3> <PICT:0670091/III/4> <PICT:0670091/III/5> <PICT:0670091/III/6> <PICT:0670091/III/7> <PICT:0670091/III/8> of the regenerating serie becoming the last mass of the adsorption series in the next operation of the process.  Thus in one operation of the process, adsorption towers C, D and E are employed for selective adsorption and adsorption towers F, G, H, A and B are subjected to regeneration as shown in Fig. 2, while in the next operation of the process adsorption towers D, E and F are employed for selective adsorption and adsorption towers G, H, A, B and C are subjected to regeneration as shown in Fig. 4.  The process is applicable to the de-aromatization of Diesel fuels, the de-aromatization and desulphurization of kerosene distillates, the de-aromatization of lubricating stocks, the fractionation of aromatic-paraffinic or olefinic-paraffinic mixtures and the fractionation of liquid organic mixtures containing oxygenated compounds and hydrocarbons such as the reaction products of the Fischer-Tropsch and OXO processes.  The adsorbent may be silica gel, alumina, silica-alumina gel mixtures or charcoal while the stripping liquid may be iso-octane.  In the case of the treatment of lubricating oil according to the process, the oil is preferably diluted with a saturated hydrocarbon containing 3-6 carbon atoms in the molecule and the hydrocarbon employed as diluent is also employed as the stripping liquid.  The process is capable of a number of modifications.  Thus according to Fig. 1, the liquid mixture is fed initially, not into the first tower B of the adsorption series, but into the second tower C.  Simultaneously, stripping liquid is fed into tower B until all liquid mixture feed present in the interstices of the adsorbent of tower B has been displaced.  Thereupon the process is continued with the arrangement shown in Fig. 2.  In the next operation of the process, first the arrangement of Fig. 3 and then that of Fig. 4 is employed.  In another modification shown in Fig. 5, either adsorbed material which has previously been stripped from the adsorbent in a regeneration step, or the first effluent of the last tower B of the regeneration zone, is recycled to the first tower C of the adsorption zone while the liquid mixture is fed to the second tower D of the adsorption zone.  In the next operation of the process, the arrangement of Fig. 6 is employed.  In a further modification shown in Fig. 7, regeneration is effected in two stages, a desorbent liquid being employed to remove the adsorbed material from the adsorbent in tower C and a stripping liquid being employed to remove the desorbent liquid in towers G, H, A and B.  Adsorbed material which has previously been stripped from the adsorbent in a regeneration zone is recycled to the first tower D of the adsorption zone, while the liquid mixture is fed to the second tower E of the adsorption zone. A variant on the arrangement of Fig. 7 is shown in Fig. 8, where the recycle of adsorbed material is omitted and the liquid mixture is fed to the first tower D of the adsorption zone.  In the arrangements of Figs. 7 and 8, the fraction of the liquid mixture which is not preferentially adsorbed may be employed as the stripping liquid. In an example, the arrangement shown in Fig. 5 is employed, using silica gel as the adsorbent and iso-octane as the stripping liquid. Straight-run kerosene distillate is employed as the liquid mixture and aromatics are preferentially adsorbed so that the kerosene is separated into two fractions, one containing less than 1 per cent aromatics and the other over 90 per cent aromatics.  The Specification as open to inspection under Sect. 91, refers to an additional example of the de-aromatization of kerosene employing silica gel as adsorbent and iso-octane as stripping liquid.  Examples are also given of the de-aromatization of catalytically reformed gasoline employing silica gel as adsorbent and a heart cut of de-aromatized kerosene having a boiling range 387-466 DEG F. as stripping liquid.  This subject-matter does not appear in the Specification as accepted.