US3259664A - Solvent extraction of halo-paraffins from paraffins - Google Patents

Description

United States Patent 3,259,664 SOLVENT EXTRACTION OF HALO-PARAFFINS FROM PARAFFINS Gardner C. Ray and Van C. Vives, Bartlesville, Okla.,

assignors to Phillips Petroleum Company, a corporation of Delaware Filed Aug. 21, 1963, Ser. No. 303,584 4 Claims. (Cl. 260652) This invention relates to solvent extraction separations. In another aspect this invention relates to an integrated process for the production of detergent alkylates.

Various chemical processes are being practiced in which halogenated paraffins are used as solvents and employed as intermediates in processes such as .alkylation and hydrolysis. The paraffins are halogenated by various known methods. Several of the processes using halogenated parafiins operate more efficiently if the halogenated paraffins are separated from the paratfinic hydrocarbons prior to their use. Likewise, separation of monoand polyhalogenated hydrocarbons improves the eiticiencies of processes which require the use of one or the other. One such process is the production of detergent alkylate wherein an aromatic such as benzene is alkylated with monochloroalkanes. In this particular process it has been found that polychlorides cause formation of heavy byproducts which rapidly reduce the life of the A101 alkylation catalyst. Cyclic hydrocarbons are also produced from the polychlorides, and these undesired products codistill with the desired alkylate. Because of the adverse eifects of the polychloroalkanes in this process, the n-paraflins are chlorinated at low conversion levels to reduce the formation of polychloroalkanes. Because of the chlorination of paraflins at low conversion levels, if the chlorides are not separated from the paraffins prior to the alkylation step, the problem of recycling large amounts of unchlorinated paraflins is present. It is extremely difficult and expensive to separate mixtures of halogenated parafiins from parafiins when their boiling points do not differ greatly. Mixtures of this type are frequently obtained when a paraffin feed stock containing molecules of consecutive carbon numbers and differing by a spread of more than 2 carbon atoms, for example, a mixture of C C C and C paraffins, is subjected to halogenation.

Accordingly, an object of this invention is to provide a method for the separation of halogenated parafiins from mixtures with paraflinic hydrocarbons.

Another object of this invention is to provide a method for the separation of monohalogenated parafiins from polyhalogenated paraffius. Still another object of this invention is to provide an improved integrated halogenation-separation-alkylation process for the production of detergent grade alkylate.

According to this invention an improved process is provided for the concentration of halogenated paraflins which comprises extracting halogenated paraffins from mixtures with paratfinic hydrocarbons with liquid S0 and removing the liquid S0 from the resulting extract.

In a specific embodiment of this invention an improved integrated process is provided which comprises halogenating parafiinic hydrocarbons, solvent-extracting the resultant halogenated paraffins, and alkylating an aromatic, such as benzene, with the recovered halogenated paraffins.

The solvent extraction process of this invention is applicable for the separation of halogenated paraffins from paraffinic hydrocarbons. It is also applicable to the separation of halogenated paraffins, e.g., the separation of monohalogenated paraffins from polyhalogenated paraffins. This invention is most applicable to the separation of halogenated paraflins containing 8 to carbon atoms per molecule from paraflins of the same range of carbon 3,259,664 Patented July 5, 1966 ice atoms and more preferably of a range of 10 to 16 carbon atoms per molecule. The preferred paraffins to be halogenated are obtained by separating them from a paraflincontaining stream such as kerosene. This separation is made at a temperature of about 600 F. by adsorption of the desired paraffins on SA molecular sieves, which are well known in the art, using vapor phase adsorption and vapor phase desorption. Elution or desorption can be eifected by a variety of methods, as, for example, by decreasing the pressure above the sieve bed containing the adsorbed paraflins. The paraffins are halogenated by contacting them with a halogen, preferably chlorine or bromine, for about 5 to 30 minutes, preferably in the presence of ultraviolet light at a temperature of from about 20 to +40 C., a mol ratio of paraffin/halogen of from 3:1 to 10:1, a pressure up to about 500 p.s.i.a. The extraction process for separating the halogenated parafiins is generally carried out at a temperature of from about -25 to about 50 C., preferably from about -l5 to about 25 C. The volume ratio of liquid S0 to paraffin-halogenated paraffin mixture is generally in the range of about 0.5 :1 to 5: 1. The extraction of the halogenated parafiin with the liquid S0 may be carried out batchwise or continuously and also in a single stage or a multistage operation. The contacting of the feed mixture with the liquid S0 is carried out by various means such as in vessels equipped with stirrers, perforated trays, or other wellknown means for efiecting contacting of the feed with the solvent. Following the contacting of the mixture with liquid $0 the paraffins and some S0 are separated as the raflina-te phase, and the halogenated paraflins are removed with the remainder of the liquid S0 as the extract phase. The raflinate can be recycled to the halogenation zone after removal of the. S0 The extract phase, which contains most of the liquid S0 the halogenated paraffins and some paraffinic hydrocarbons, is processed for removal of S0 after which the extracted material from this first extraction can be further treated with additional liquid S0 to effect separation of the polyhalogenated parafiins and the monohalogenated paraffins. The S0 is separated from the halogenated hydrocarbons by distillation or by treating the extract with water to dissolve the S0 thereafter separating a halogenated hydrocarbon phase from an aqueous phase. The S0 can be recovered from the water and recycled to the extraction step. Preferably, anhydrous liquid S0 is used as the extractant in this invention. However, liquid S0 containing not more than about 2 percent water may be used.

A particular utility for the concentrated, halogenated paraffins produced by this invention is in the alkylation of suitable aromatics, such as benzene, toluene, xylene, naphthalene, biphenyl, phenanthrene, anthracene, pyrene, chrysene, ethylbenzene, and the like. In the alkylation of benzene for use as a detergent alkylate, the chloroand bromo-alk-anes are preferred.

The catalyst employed in the alkylation process can be any suitable alkylation catalyst, that is, sulfuric acid, substantially anhydrous hydrogen fluoride, and the so-called Friedel-Crafts metal halides. Included among said Friedel-Crafts metal halides are those such as aluminum chloride, aluminum bromide, boron trifluoride and a halide of such metals as zinc, tin, arsenic, antimony, zirconium, beryllium, titanium, iron, and the like. These metal halide catalysts are especially effective when used in the form of complexes which are formed by interaction between the metal halide and hydrocarbons. A particularly desirable catalyst is a complex of hydrocarbon with aluminum chloride. An aluminum chloride-hydrocarbon complex catalyst can 'be prepared, for example, by reacting AlCl with isobutane or other branched chain paraflins in the presence of an olefin such as ethylene. Such complexes normally contain about 55-65 percent by weight AlCl the remainder being hydrocarbon. In addition to the catalyst it is desirable that the corresponding hydrogen halide be present in the reaction zone since this material maintains catalyst activity at a high level. The reaction rate in the conversion of the hydrocarbon feed is dependent on the amount of aluminum chloride in the aluminum chloride hydrocarbon complex. While the over-all activity of the catalyst is established by the aluminum chloride content, the presence of hydrogen chloride is required to maintain a high activity. While hydrogen chloride can be added, if desired, the hydrogen chloride produced by the alkylation process itself will generally be sufficient to maintain high catalyst activity.

Conditions employed in an alkylation process will depend somewhat upon the catalyst employed. When employing aluminum chloride hydrocarbon complex catalysts the alkylation will generally be carried out at a temperature within the range of 50 to 135 F. with a pressure sufficient to maintain liquid phase conditions. Flow rates of reactants should be maintained such that the residence time is within the range of about to about 30 minutes, preferably about to about minutes, will be provided.

The mol ratio of aromatic hydrocarbons to halogenated hydrocarbons entering the alkylation process should be such as to furnish at least one mol of aromatic hydrocarbon per gram atom of halogen on the halogenated hydrocarbon. It is preferred to operate wit-h an excess of aromatic hydrocarbons. Thus, the mol ratio of aromatic hydrocarbon to halogenated hydrocarbon is usually maintained within the range of 2:1 to 30:1, preferably 8:1 to 1. The volume ratio of catalyst used to total halogenated parafl'in in the process should be in the range of about 0.5:1 to 10:1, preferably about 2:1.

This invention will now be described more fully with reference to the accompanying drawing which shows a schematic flow diagram and apparatus representative of one embodiment of the invention.

A paraffin stream from a molecular sieve separation (not shown) is introduced into halogenation zone 3 through conduit 1. A halogen is introduced into zone 3 through conduit 5. The reactants are thoroughly contacted in zone 3 and the resulting mixture is withdrawn through conduit 7 and introduced into extractor 9. S01- vent is introduced into extractor 9 through conduit 11. The solvent flows downwardly countercurrent to the paraffin-halogenated parafiin mixture to remove the halogenated parafiins. Rafiinate phase is removed and passed to I stripper 10 through conduit 13. In stripper 10 heat is added by means not shown to vaporize the S0 from the raffinate, and the vaporized solvent is recycled to the extractionzone through conduit 12, cooler 20, and conduit 11. The bottoms from stripper 10 are recycled to zone 3 through conduit 14 and conduit 1. Extract phase is removed through conduit 15 and introduced into stripper 17. Heat is added to stripper 17 by means not shown to vaporize the solvent which is removed through conduit 19, passed through cooler 20 and recycled to extractor 9. Make-up solvent is introduced to conduit 19 ahead of cooler 20. The kettle product from stripper 17 is passed through conduit 21 into extractor 23. Solvent is introduced to extractor 23 through conduit 39. The solvent flows downwardly countercurrent to the kettle product from stripper 17, to remove the polyhalogenated paraffins. Raffinate phase is removed through conduit 25 and introduced into monohalogenated paraflins stripper 27. Heat is added to stripper 27 by means not shown to vaporize solvent which is removed through conduit 29 and introduced into conduit 31. The kettle product from stripper 27 is passed through conduit 43 into alkylation zone 45. The extract phase from exterior 23 is passed through conduit 33 and introduced into polyhalogenated paraffin stripper 35. Polyhalogenated paraifins are removed through conduit 41 as kettle product. Solvent vaporized by heat added to stripper 35 by means not shown is removed through conduit 31. Makeup solvent is added to conduit 31. The combined solvent in conduit 31 is passed through cooler 37, conduit 39 and introduced into extractor 23. Alkylation catalyst is introduced to zone 45 through conduit 47. An aromatic hydrocarbon is introduced to zone 45 through conduit 49. Reaction mixture is removed from zone 45 through conduit 51. This mixture is passed to a recovery system (not shown) for separation of the alkylate, catalyst, unreacted aromatic and halogenated paraifins.

The following specific examples will give a better understanding of the invention but are not intended to limit the invention.

EXAMPLE I A 50 ml. mixture of chlorinated dodecane and dodecane was charged to a vessel along with 100 ml. of liquid S0 The vessel was equipped with a stirrer. After the components were charged to the vessel, the stirrer was turned on, the two phases were mixed together for 45 minutes, at a temperature of 12 C. The dodecanechlorinated dodecane mixture contained 83.1 mol percent dodecane, 15.1 mol percent chlorododecane and 1.8 mol percent dichlorododecane.

The two phases were then allowed to separate and the phases were drawn off. The S0 was flashed from the extract and rafiina te phases, and then both phases were analyzed by gas-liquid chromatography. The chromatography column used was a 10-foot column containing mesh glass beads coated with 0.25 weight percent, based on the beads, n-decylphthalate. The column was operated at 130 C. This column separated the primary and secondary monochlorides, as well as the paraffin and dichloroparafiin.

Results Grams Weight of extract phase 1 2.5 Weight of rafiinate phase 2 34.9 Weight of S0 in extract phase 143 1 (SO free). (S022 free).

Analyses of phases Raifinate phase:

Moles 28.5 grams dodecane 0.1672 5.5 grams sec-chlorododecane 0.0269 0.56 gram primary chlorododec-ane 0.0027 0.35 gram dichlorododecane 0.0014 6.41 grams total chlorides 0.0310 Extract layer:

1.02 grams dodecane 0.0060 1.0 gram sec-chlorododecane 0.0051 0.11 gram primary chlorododecane 0.0005 0.31 gram dichlorododecane 0.0013 1.42 grams total chlorides 0.0068

The above analyses were then used to calculate the relative distribution coetficients and the weight percent solvent load.

The weight percent solvent load is defined as:

Weight percent solvent load:

(Weight of material extracted) (Weight of solvent phase including Aex=moles cholride in extract Araf=moles chloride in ralfinate Bex=moles reference material in extract Braf=moles reference material in raffinate Sample calculation: Relative distribution ooefiicient for chlorides relative to dodecane From these data it is readily apparent that the chlorides have been concentrated in the extract phase of the extraction step.

EXAMPLE II To prepare a detergent alkylate according to the method of this invention, 140 mols of a p-araflin stream containing parafiins of from to 16 carbon atoms per molecule is contacted with 28 mols of chlorine at a temperature of 10 C. and a pressure of 250 p.s.i.:a. in the presence of ultraviolet light for about 10 minutes. Approximately 20 mol percent of the resultant mixture comprises monochlorinated parafiins and polychlorinated paraffins while the remainder of the parafiins are not chlorinated. This mixture of chlorinated parafiins and parafiinic hydrocarbons is then contacted with liquid S0 in a multitray extraction column at a temperature of 10 C. in a volume ratio of liquid S0 to the mixture of 2:1. The phases are separated and the extract phase is heated to vaporize the liquid S0 The stripped extract is then contacted with additional liquid S0; at 10 C. and a volume ratio of liquid S0 to extract of 1:1 in a multitr ay extraction column. The raffinate from this extraction is heated to vaporize residual liquid S0 and recovery of monochlorinated paraflins. These monochlorinated parafiins are then contacted with benzene and aluminum chloride complex catalyst at a temperature of 70 F. and a pressure of 70 p.s.i.'a. for minutes, using mols of benzene per mol of monochlorinated paraffin and two volumes of total feed per volume of aluminum chloride complex catalyst. The alkylation product is separated from the catalyst and the unreacted reactants are removed by distillation to recover a high purity monoalkylated benzene.

In a similar run wherein the chlorination zone effiuent is charged directly to the alkylation step, much shorter catalyst life of the alkylation catalyst is encountered and larger amounts of heavy alkylate :are produced.

Along with the advantages shown from the above data and specific embodiment, the extraction process of this invention provides a ready means for separating halogenated parafiins from paraflinic hydrocarbons, thus allowing one to recycle the paraffins to a 'halogenation zone which, when operating at low conversion for ultimate production of monohalides, a large amount of panaffins travels through the process. Furthermore, if monohalogenated parafiins are to be employed in an alkylation reaction, this process can be utilized for the separation of the monohalides from the polyhalides to obtain longer catalyst life and avoid heavy alkylate by-products. Also, in the alkylation process, the removal of panaflins prior to the alkylation avoids the problem of recycling large amounts of inert material through the alkylation zone.

To one skilled in the art it will be evident that many variations and modifications of this invention can be practiced in view of the foregoing disclosure that will come within the spirit and scope of the invention.

That which is claimed is:

1. A process for separating a mixture of compounds having 8 to 20 carbon atoms per molecule comprising paraflins, mono-halo-paraflins, and poly-halo-parafiins, said halobeing selected from chloroand bromo-, which comprises:

contacting said mixture with liquid S0 at a temperature between 25 and 50 C. with a volume ratio of liquid S0 to mixture of from 0.5 :1 to 5:1

to form an extract phase rich in S0 and said haloparaflins and a raffinate phase rich in said paraflins; separating said phases;

contacting said halo-paraflins in said extract phase with liquid S0 at a temperature between 25 and 50 C. with a volume ratio of S0 to halo-parafiins of from 0.521 to 5:1 to form a raffinate phase rich in mono-halo paraffins and an extract phase rich in poly-halo paraffins;

separating said phase rich in mono-halo-parafiins from said phase rich in poly-halo-paraflins; and recovering said paraflin, said mono-halo parafiin, and said poly-halo-paraflins from their respective phases.

2. The process of claim 1 wherein said compounds have 10 carbon atoms per molecule and said halois chloro-.

3. A process for separating a mixture of compounds having 8 to 20 carbon atoms per molecule comprising paraflins and halo-paraffins, said halobeing selected from the group consisting of chloroand bromo-, which comprises: contacting said mixture with liquid S0 at a temperature between 25 and 50 C. with a volume ratio of liquid S0 to mixture of from 0.5 :1 to 5 :1 to form an extract phase rich in said halo-paraffins and liquid S0 and a raflinate phase rich in said paraffins; and separating the S0 from said extract phase.

4. The process for separating a mixture of compounds having 8 to 20 carbon atoms per molecule comprising monohalo-paraffins and polyhalo-paraffins, said halobeing selected from the group consisting of chloroand brom0-, which comprises: contacting said mixture with liquid S0 at a temperature between 25 and 50 C. with a volume ratio of liquid S0 to mixture of from 0.5 :1 to 5:1 to form an extract phase rich in said polyhaloparalfins and liquid S0 and a rafiinate phase rich in said monohalo-paraffins; and separating the S0 from said extract phase.

References Cited by the Examiner UNITED STATES PATENTS 2,015,748 10/ 1935 Frolich 260660 2,045,806 6/1936 Sloane 260660 2,394,851 2/1946 Flett 260671 2,429,887 10/ 1947 Magoun 260-671 2,463,497 3/ 1949 Smith et a1. 260-671 2,533,517 12/1950 Schwoegler 260671 2,740,807 4/ 1956 Rappen et al 260-671 LEON ZITVER, Primary Examiner.

K. V. ROCKEY, Assistant Examiner.

Claims (1)

1. A PROCESS FOR SEPARATING A MIXTURE OF COMPOUNDS HAVING 8 TO 20 CARBON ATOMS PER MOLECULE COMPRISING PARAFFINS, MONO-HALO-PARAFFINS, AND POLY-HALO-PARAFFINS, SAID HALO- BEING SELECTED FROM CHLORO- AND BROMO-, WHICH COMPRISES: CONTACTING SAID MIXTURE WITH LIQUID SO2 AT A TEMPERATURE BETWEEN -25 AND 50*C. WITH A VOLUME RATIO OF LIQUID SO2 TO MIXTURE OF FROM 0.5:1 TO 5:1 TO FORM AN EXTRACT PHASE RICH IN SO2 AND SAID HALOPARAFFINS AND A RAFFINATE PHASE RICH IN SAID PARAFFINS; SEPARATING SAID PHASE; CONTACTING SAID HALO-PARAFFINS IN SAID EXTRACT PHASE WITH LIQUID SO2 AT A TEMPERATURE BETWEEN -25 AND 50*C. WITH A VOLUME RATIO OF SO2 TO HALO-PARAFFINS OF FROM 0.5:1 TO 5:1 TO FORM A RAFFINATE PHASE RICH IN MONO-HALO PARAFFINS AND AN EXTRACT PHASE RICH IN POLY-HALO PARAFFINS; SEPARATING SAID PHASE RICH IN MONO-HALO-PARAFFINS FROM SAID PHASE RICH IN POLY-HALO-PARAFFINS; AND RECOVERING SAID PARAFFIN, SAID MONO-HALO PARAFFIN, AND SAID POLY-HALO-PARAFFINS FROM THEIR RESPECTIVE PHASES.

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