GB966000A - Process for the separation of a mixture in the liquid phase using a solid selective adsorbent - Google Patents

Abstract

A slurry of silica gel activated carbon or ion-exchanger, suspended in a carrying material, such as a non-aromatic hydrocarbon mixture, e.g. a paraffinic mixture, is introduced by means of a line 21 into the top of an adsorption rotating disc contacting apparatus 22. A feed mixture containing an impurity or other more readily adsorbed material is introduced into the lower portion of the apparatus 22 through a line 23 and contacts the descending adsorbent in a countercurrent manner. Since there exists a concentration gradient in the apparatus 22, the separated or purified mixture, essentially free from the impurity or other material and containing some carrying material can be withdrawn from the apparatus 22 as a side stream by means of a line 24, viz. at an optimum point in the apparatus 22 where the concentrations of more readily adsorbed components and of carrying liquid are at a minimum. The slurry of adsorbent with impurity or other material adsorbed therein is withdrawn from the bottom of the apparatus 22 by means of a line 25. This slurry will also contain some of the carrying material and a minor amount of the original mixture. The majority of the slurry-carrying material passes overhead and out of the apparatus 22 by means of a line 26 and is introduced as a desorbent into the bottom of a desorption rotating disc contacting apparatus 27. The slurry withdrawn from the apparatus 22 is introduced into the top of the apparatus 27 by means of a line 25. The rate of flow of desorbent introduced into the lower section of the apparatus 27 is so adjusted that there is essentially complete desorption of more readily adsorbed components from the adsorbent. The adsorbent slurry now free from these components and consisting essentially of the adsorbent and the desorbent (although it may contain some of the original mixture withdrawn from the apparatus 22 by means of the line 25) is then recycled to the adsorption <PICT:0966000/C1/1> apparatus 22 by means of the line 21. The overhead stream withdrawn from the apparatus 27 by means of a line 2 consists essentially of the impurity or other more readily adsorbed components and some desorbent and may also contain a minor amount of the original mixture. The desorbent may be removed from the more readily adsorbed components, e.g. by means of distillation (not shown). Fig. 2 of the drawing (not shown) is a schematic diagram of a further embodiment of the invention wherein the slurry-carrying desorbent material is withdrawn from the adsorption rotating disc contacting apparatus zone not separately from, but along with the purified mixture. Specification 659,241 is referred to.ALSO:<PICT:0966000/C4-C5/1> A slurry of adsorbent, such as silica gel, suspended in a carrying material, such as a non-aromatic hydrocarbon mixture, e.g. a paraffinic mixture, is introduced by means of a line 21 into the top of an adsorption rotating disc contacting apparatus 22. A feed mixture, such as a material to be subjected to an isomerization treatment, containing an impurity or other more readily adsorbed material, e.g. one or more aromatics, such as benzene, is introduced into the lower portion of the apparatus 22 through a line 23 and contacts the descending adsorbent in a countercurrent manner. Since there exists a concentration gradient in the apparatus 22, the separated or purified mixture, essentially free from the impurity or other material and containing some carrying material can be withdrawn from the apparatus 22 as a side stream by means of a line 24, viz. at an optimum point in the apparatus 22 where the concentrations of more readily adsorbed components and of carrying liquid are at a minimum. The slurry of adsorbent with impurity or other material adsorbed therein is withdrawn from the bottom of the apparatus 22 by means of a line 25. This slurry will also contain some of the carrying material and a minor amount of the original mixture. The majority of the slurry-carrying material passes overhead and out of the apparatus 22 by means of a line 26 and is introduced as a desorbent into the bottom of a desorption rotating disc contacting apparatus 27. The slurry withdrawn from the apparatus 22 is introduced into the top of the apparatus 27 by means of a line 25. The rate of flow of desorbent introduced into the lower section of the apparatus 27 is so adjusted that there is essentially complete desorption of more readily adsorbed components from the adsorbent. The adsorbent slurry now free from these components and consisting essentially of the adsorbent and the desorbent (although it may contain some of the original mixture withdrawn from the apparatus 22 by means of the line 25) is then recycled to the adsorption apparatus 22 by means of the line 21. The overhead stream withdrawn from the apparatus 27 by means of a line 2 consists essentially of the impurity or other more readily adsorbed components and some desorbent and may also contain a minor amount of the original mixture. The desorbent may be removed from the more readily adsorbed components, e.g. by means of distillation (not shown). Fig. 2 of the drawing is a schematic diagram of a further embodiment of the invention wherein the slurry-carrying desorbent material is withdrawn from the adsorption rotating disc contacting apparatus zone not separately from, but along with the purified mixture. The technique may be applied to ion-exchange molecular sieve separation and is particularly suitable for the separation of hydrocarbon mixtures, e.g. petroleum oils and fractions thereof. It further is especially advantageous for the separation of aromatic hydrocarbons, particularly benzene, from mixtures containing them, e.g. as an impurity. In this case, use is preferably made of an at least substantially paraffinic desorbent; "paraffin" is here meant to include not only alkanes, but also cycloparaffins or naphthenes. Among the various petroleum materials which can advantageously be treated according to the invention are, e.g., kerosene distillates (which may be dearomatized and desulphurized to produce a material of superior quality), gasolines (which may also be desulphurized and furthermore partially deparaffinized to produce a gasoline of higher octane number) diesel oils (which may be dearomatized to produce a product with high octane number), lubricating oils (which may be dearomatized and deasphaltized to give an oil of high quality); furthermore, narrow boiling aromatic, paraffinic, or elefinic-paraffinic fractions may be separated by the present method in order to produce pure aromatic, paraffinic, and/or olefinic compounds. It is also adaptable to the separation of a, normally gaseous, butene-butadiene liquid mixture by slightly increasing the operation pressures, so that the mixture becomes liquid. Also, a normally solid naphthalene fraction may be separated according to the invention by conducting the adsorption step at a moderately elevated temperature so as to melt the naphthalene material. Benzene may be removed from a mixture of C6 hydrocarbons containing contaminating amounts thereof so that the Friedel-Crafts type catalysts may be used in isomerization processes. Activated carbon is capable of selectively absorbing non-plar compounds, for example hydrocarbons, from polar compounds such as alcohols and ketones. Specification 659,241 is referred to.