US2385981A - Separation of organic compounds - Google Patents

Description

Patented Oct. 2, 1945 r 2,885,981 SEPARATION or ORGANIC COMPOUNDS Bernard S. Friedman, Riverside, 111., asslgnor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing.

12 Claims.

This invention relates to the separation of organic compounds having different degrees of saturation and more particularly to a novel solvent therefor and to a process using the same.

The invention-is particularly applicable to the treatment of hydrocarbon fractions which, as usually recovered from various sources, contain saturated and unsaturated hydrocarbons. For example, normally liquid products of a cracking process contain oleflns, aromatics, paraflins and naphthenes. Likewise, the products recovered by distillation of crude oil contain parafflns, naphthenes, aromatics and, in most cases. a small amount of oleflns. Likewise, normally gaseous products of a cracking process contain oleflnic gases such as propylene and butylenes, and paraflinic gases such as propane and butanes.

In many cases, it is desirable to separate the unsaturated from the saturated hydrocarbons, but this cannot be accomplished by purely fractional distillation means in practical operations because of the similarity in boiling points of the various hydrocarbons.

Other organic compounds are recovered from various sources including synthetic processes, wherein the products contain organic compounds of diflerent degrees of saturation. For example, saturated and unsaturated glycerides are frequently recovered in admixture, and their separation cannot be effected by purely fractional distillation means-in practical operations.

In a broad aspect the present invention relates to a process for separating a mixture of organic compounds of difiering degrees of saturation, which comprises treating said mixture with a solvent comprising an aliphatic sulfonamide.

In another aspect the present invention relates Application November 29, 1943, Serial No. 512,238

to the separation of a mixture of hydrocarbons I having difiering degrees of saturation and similar boiling points, which comprises treating said mixture with a solvent comprising an aliphatic sulbons is intended to include the paraflins and/or naphthenes, while the term unsaturated hydrocarbonsis intended to include the oleflns and/or aromatics. The olefins include both the mono and poly-olefinic hydrocarbons.

Thus, the invention may be utilized for the separation of olefins and/or aromatics from parafiins and/or naphthenes. Likewise, the invention may be utilized forthe separation of, monoolefins from di-olefins.

The present invention is characterized by a novel solvent which comprises an aliphatic monoor poly-sulfonamide, and more particularly an aliphatic monoor di-sulionamide.

In accordance with the invention, thealiphatic portion of the solvent preferably contains from 1 to about 6 carbon atoms per atom of sulphur. Particularly preferred solvents comprise propane mono-sulfonamide (CaHvSOzNHz) and butane mono-sulfonamide (C4H9S02NH2) The aliphatic group may be straight chain or branched chain structure or mixtures thereof, such as certain eutectic mixtures which a number of these mixed compounds form.

It is also within the scope of the invention to include derivatives of the aliphatic sulfonamides. Examples of such derivatives may comprise compounds in which one or more of the hydrogen atoms attached to the aliphatic group is replaced by a hydroxy group, a halogen group,an amino group, or the like. 7

It is to be noted that a number of different compounds may be satisfactorily employed in the process of the present invention, but it isunderstood that these various alternative compounds are not necessarily equivalent in their effectiveness. The choice as to preferred solvent to be employed in any given operation will depend upon the characteristics of the charging stock and the type of separation to be efiected.

In cases where the unsaturate'content of the mixture is high, it may be necessary to dilute the solvent with water, alcohol, glycol, etc. For example, it has been found that butane sulfonamide is mutually miscible with a normal heptane-benzene mixture having a benzene content of about 84%. The amount of water, alcohol, glycol or the like to be added should be suflicient so that a separation of an extract phase and a raflinate phase occurs. For example, in the case of the butane sulfonamide and 84% benzene mixture heretofore set forth, a satisfactory solvent was prepared containing 91% by volume of butane sulfonamide and 9% by volume of water.

The solvents of the present invention may in fonamide and 9% by volume of water.

many cases be obtainable in the open market or,

.if a particular solvent is not so obtainable, it may be readily synthesized by well-known means.

Thus, for example, butane sulfonamide may be prepared by reacting butane with a mixture of sulphur dioxide" and chlorine in the presence of light to produce butane sulfonyl chloride, and the butane sulfonyl chloride may then be reacted with ammonia to produce the butane sulfonamide.

' The operation of the solvent extraction process is relatively simple and may. comprise introducing the hydrocarbon mixture to be extracted into a suitable extraction zone. The extraction zone may or may not contain baiiie plates, bubble decks, side to side pans, or other suitable packing. The extraction zone may be equipped with stirring or other contacting means in order to obtain emcient contacting of the hydrocarbons and solvent. The solvent extraction is effected under conditions of temperature and pressure in order to form an extract phase containing a major portion of the solvent and a major portion of the unsaturated hydrocarbons, and a raffinate phase containing a major portion of the saturated hydrocarbons.

The temperature employed is preferably atmospheric or slightly superatmospheric but it should be high enough to maintain the solvent in liquid phase in caseit is solid at ordinary temperatures, but must be below that at which decomposition of the solvent or hydrocarbons occurs. The pressure to be employed is usually atmospheric or moderately superatmospheric but likewise should be sufllcient in order to maintain the hydrocarbons and solvent in liquid phase. When treating normally gaseous hydrocarbons, a higher superatmospheric pressure is employed in order to maintain the hydrocarbons in substantially liquid phase.

Usually more than one extraction is required in order to effect substantially complete separation of the unsaturated from the saturated hydrocarbons. In some cases, however, one extraction may be sufllcient when it is required to lower only slightly the concentration of the unsaturated hydrocarbons in the mixture or in case the charging stock originally contains only a small percentage of unsaturated hydrocarbons.

After formation of the extract and rafflnate phases, the solvent may be separated from the hydrocarbons by various means including: (1) distillation at increased temperature and/ or reduced pressure; (2) adding water or the like in order to decrease the solubility of the hydrocarbons in the solvent and (3) counter-extracting the hydrocarbons from the solvent by contacting the extract phase with a secondary solvent which is immiscible with the first solvent and may comprise, for example, a parafiinic or naphthenic hydrocarbon of higher or lower boiling point than the solute. The second solvent is then separated from the solute by ordinary fractional distillation means.

The following examples are introduced for the purpose of further illustrating the novelty and utility of the present invention but not with the intention of unduly limiting the same.

In the following "examples the solvent com prised a mixture of 91% by volume of butane sul- The experiments were all conducted at room temperature and atmospheric pressure. These experiments were batch tests in which the hydrocarbon mixture and the solvent were stirred in a mixing zone and thereafter allowed to settle in order to separate an extract phase and a raflinate phase.

. The results shown in the following examples are based upon a single extraction. It is understood that further separation is obtainable by the use of additional extraction stages.

E'zample I to 14% in the rafllnate in one extraction. By additional extractions the benzene content of the ramnate may be reduced to alower amount.

Example I! In this example the charging stock contained 28.5% by volume of benzene and 71.5% by volume of normal heptane. It was likewise treated with an equal volume of the butane sulfonamidewater solvent. The hydrocarbons in the extract phase comprised 76.5% by volume of benzene. while the hydrocarbons in the rafllnate phase comprised 22% by volume of benzene. Thus the volume of benzene in the charge was reduced in one extraction from 28.5% to 22% in the ramnate.

Example III The charging stock in this example contained 49% by volume of benzene and 51% by volume of normal heptane. It was likewise treated with an equal volume of the butane sulfonamide-water solvent. The hydrocarbons in the extract phase comprised 83% by volume of benzene and the hydrocarbons in the rafllnate phase comprised 40.5% by volume of benzene. Here, one extraction reduced the volume of benzene from 49% in the charge to 40.5% in the rafiinate.

I claim as my invention:

1. A process for separating a mixture of organic compounds of different degrees of saturation which comprises treating said mixture under conditions to form an extract phase and a railinate phase with a solvent comprising an alkyl sulfonamide containing the NHz group.

2. In a solvent extraction process for separating a, mixture of hydrocarbons into fractions of difiering degrees of saturation with respect to carbon-hydrogen ratio, the step of extracting said hydrocarbons with an alkyl sulfonamide containing the NHz group under conditions to form an extract phase and a rafflnate phase.

3. A process for separating a mixture of hydrocarbons of differing degrees of saturation which comprises treating said mixture under conditions to form an extract phase and a rafflnate phase with a selective solvent comprising an alkyl sulfonamide containing the NH: group .and in which the alkyl group contains from 1 to about 6 carbon atoms per atom of sulphur.

4. A process for separating a mixture of hydrocarbons of differing degrees of saturation which comprises treating said mixture under conditions to form an extract phase and a rafilnate phase with a selective solvent comprising an alkyl mono-sulfonamide in which the alkyl group contains from 1 to about 6 carbon atoms.

5. A process for separating a mixture of hydrocarbons of difiering degrees of saturation which comprises treating said mixture under conditions to form an extract phase and a raflinate phase with a selective solvent comprising an alkyl di-sulfonamide in which the alkyl group contains from 1 to about 6 carbon atoms per atom of sulphur.

6. A process for separating unsaturated hydrocarbons from saturated hydrocarbons which comprises treating a mixture of unsaturated and saturated hydrocarbons under conditions to form an extract phase and a raflinate phase with a selective solvent comprising an alkyl mono-sulfonamide in which the alkyl group contains from 1 to about 6 carbon atoms.

7. The process of claim 6 further characterized in that said unsaturated hydrocarbons comprise olefins and aromatics.

8,. The process of claim 6 further characterized in that said unsaturated hydrocarbons comprise olefins.

9. The process of claim 6 further characterized in that said unsaturated hydrocarbons comprise aromatics.

10. A process for separating an aromatic hydrocarbon from a mixture thereof with a saturated hydrocarbon which comprises treating the mixture with butane sultonamide under conditions to form an extract phase and a rafllnate phase.

11. A process for separating an aromatic hydrocarbon from a mixture thereof with a saturated hydrocarbon which comprises treating the mixture with a butane sulfonamide-water solvent under conditions to form an extract phase and a rafiinate phase.

12. A process for separating an aromatic hydrocarbon from a mixture thereof with a saturated hydrocarbon which comprises treating the mixture with propane sulfonamide under conditions to form an extract phase and a raflinate phase.

BERNARD S.