US3070636A - Process for the preparation of position isomers of c to c monochloro straight-chain paraffins - Google Patents

Description

Dec. 25, 196 J. A. KIERAS 3fi fifi3 PROCESS FOR THE PREPARATION OF POSITION ISOMERS QF' C TO C MONOCHLQRO STRAIGHT-CHAIN PARAF F INS Filed Nov. 25, 1959 WEIGHT PER CENT GHLORINE O 2 4 6 8 IO l2 l4 l6 I820 0 IO 20 3O 4O 50 6O 7O 8O 90 I00 CUMULATIVE MIDv PER GENT POINT JOSEPH A. K! ERAS ATTORNEY United States Patent Ofilice 3,070,636 Patented Dec. 25, 1962 3,070,636 PROCESS FOR THE PREPARATION OF POSITION ISOMERS F C T0 C MONOCHLORO STRAIGHT-CHAlN PARAFFINS Joseph A. Kieras, Lincoln University, Pa., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Nov. 25, 1959, Ser. No. 855,303

4 Claims. (Cl. 260-660) This invention relates to a process for the preparation of position isomers of monochloro straight-chain paraffins in the C to C range and, in particular, it relates to a process for the preparation and separation of the individual position isomers of a single C to C monochloro straight-chain parafiin.

Heretofore, it was believed that the individual isomers of a single paraffin in the C to C range could not be prepared except by exceedingly complex methods of synthesis and, consequently, only a very few of these isomers were synthesized. The production of the individual position isomers of a single monochloro straight-chain paratfin in the range of 18 to 35 carbon atoms has long been desired since these alkyl chlorides can be used to produce the corresponding primary and secondary alcohols. Furthermore, these alkyl chlorides can be used to alkylate aromatics and the resulting alkyl aromatics when sulfonated give oil-soluble detergent compounds having unique and controllable characteristics and properties when employed as additives in motor oils.

A process now has been found whereby it is possible to prepare the position isomers of a high molecular weight straight-chain paraffin bytfirst providing a paraflin wax fraction containing a critical major amount of a single straight-chain paraflin, monochlorinating this wax fraction, dissolving the chlorinated wax fraction in asolvent and fractionally crystallizing from the solvent a plurality of fractions containing respectively the nonchlorinated paratiins and th position isomers of the desired stright-chain parafiin, leaving the higher chlorinated parafiins in solution.

it is therefore an object of this invention to provide a process for the preparation of position isomers of monochloro straight-chain paraflins in the C to C range.

It is another object of this invention to provide a process for the preparation of position isomers of monochloro straightchain p-"tratllns in the C to C range from petroleum parallin wax fractions.

Other objects will be apparent from the description of the invention and the claims that follow.

In accordance with this invention a parafiin wax fraction containing a critical major amount of a single straight-chain paraffin is utilized as the starting material which single straight-chain parafiin constituting the major component of the wax fraction must have a carbon atom content in the range of from 18 to 35 carbon atoms. This paratlin wax fraction is monochlorinated to give a product containing unrcacted paratlin, essentially monochlorinated parafiin and diand polychlorinated parafiin in accordance with the principles of statistical distribution of the chlorine.

The chlorinated product is dissolved in a solvent proportion of a wax solvent which does not contain halogen and thereafter the solution is chilled in successive steps to produce by crystallization a plurality of fractions containing respectively the unreacted paraffin and the individual position isomers of the monochlorinated parafiin leaving the diand polychlorinated parafiins in solution although they may be separated if desired.

The paraffin wax fraction is preferably produced from commercial grade petroleum paratfin waxes although, of course, any source of paraffin wax may be employed such as the synthetic Fischer-Tropsch waxes and the like.

In general, petroleum parafiin wax fractions melting between F. and F. are suitable as well as the,

higher melting synthetic Waxes. The paraflin wax fraction erably at a pressure of from 1 to 10 mm. of mercury to produce a plurality of narrow boiling range fractions. A fraction containing a major amount of the desired paraffin hydrocarbon is selected (C i.e., containing n carbon atoms, wherein n is an integer from 18 to 35. This fraction, in addition to containing the desired straightchain paraflin as the major component, will also contain minor amounts of higher and lower molecular weight straight-chain paraffins together with isoparafiins and cycloparafiins in the same molecular weight range. This fraction is redistilled at sub-atmospheric pressures again preferably in the 1 to 10 mm. of mercury range to pro duce an additional number of narrow boiling range fractions. The intermediate fractions, the so-called heartcut fractions, .from this distillation are selected since they I contain a major amount of the desired sgraight-chain paratfin hydrocarbon with very minor amounts of lower molecular weight straight-chain parafiins, isoparaffins, and cyeloparafiins, but no compounds of higher molecular weight. These intermediate fractions are dissolved in a wax solvent and fractionally crystallized from the solvent to produce a plurality of narrow melting range fractions. The first fraction constituting the highest melting point material is selected since it contains the major quantity of the desired straight-chain paraffin with only very minor quantities of slightly lower molecular weight straight-chain paraflins but no isoparafiins or cycloparaflins. If desired, this fraction may be redissolved in fresh solvent'and recrystallized to produce a paraffinic fraction of high purity. In general, such a fraction will contain at least 97 weight percent of the desired straightchain parafiin (C,,) with the remainder of the fraction being straight-chain parafiins differing by one or two carbon atoms from the number of carbon atoms in the desired major component (C to C wherein n is an integer from 18 to 35.

The solvents which may be used include any of the conventional wax solvents such as methyl ethyl ketone, acetone-benzene. methyl ethyl ketone-benzene-toluene, ethylene dichloride, ethyl acetate, low molecular weight parafiins including liquified normally gaseous paraffins and the like. Since these solvents do not have equal solvent power for dissolving waxes the ratio of solvent to wax may be varied depending upon the solvent used and the molecular weight of the wax fraction which it is desired to obtain. is not critical and, in general, good results are obtained when the solvent to wax ratio ranges between 5:1 and 15:1.

It has been found that the purity of the wax fraction starting material is extremely critical. If the major component is present in an amount less than about 97 Weight percent, or if the straight-chain parafiin hydrocarbons present in minor amounts differ by more than about 2' carbon atoms from the number of carbon atoms in the major component, it is not possible to produce a chlorinated product from which the individual position isomers of the monochloro straight-chain paratlin can be separated. Instead there is obtained a mixture which cannot This ratio, like the solvent employed,

drocarbon is selected and preferably this fraction is redissolved in fresh solvent and recrystallized to produce a more highly purified fraction essentially free of isoparaffins and cycloparafiins but containing straight-chain paraffins both of higher and lower molecular weight as compared with the molecular weight of the desired straight-chain paraffin. This purified fraction is fractionally distilled at sub-atmospheric pressure to produce a fraction containing the desired straight-chain parafiin hydrocarbon in a major quantity in excess of 97 weight percent with only minor amounts of straight-chain par afiins differing by at most 2 carbon atoms in the molecule from the number of carbon atoms in the desired straightchain paraffin major component.

The paraffinic wax fraction containing the critical amount of straight-chain paraffin is monochlorinated in accordance with conventional practices. Thus, gaseous chlorine may be used at temperatures ranging from about 160 F. to 250 F. although somewhat higher or lower temperatures may be employed. Likewise, if desired, liquid chlorine may be utilized either alone or with a suitable solvent at somewhat lower temperatures than those employed with gaseous chlorine to produce the desired chlorinated product. The amount of chlorine employed and the length of time of the chlorination reaction is adjusted so that there is produced a monochlorinated prodnet. It will be understood that monochlorination refers to an average of one chlorine atom per molecule of parafiin although portions of the product will contain two or more atoms of chlorine. A large portion of the product, however, will contain one atom of chlorine per molecule of parafiin. It has been found preferable that the chlorination be regulated so that on the average one atom of chlorine is substituted for one atom of hydrogen in each molecule of the paraflin since excess chlorine lowers the yield of the desired monochloro isomers.

Another convenient method of controlling the chlorination reaction is to measure the increase in weight of the paraffin being chlorinated as the chlorinating proceeds and, when the increase in weight corresponds to a monochlorinated product based on the calculated weight for such product, the reaction is discontinued.

The chlorinated product is dissolved in a solvent of the type that is used for dissolving wax with the exception that wax solvents which contain halogens should be avoided since these have too great a solvent power for the chlorinated paratfins and home do not give clean crystallization separations. Solvents which may be employed include methyl ethyl ketone, ethyl acetate, acetone, isooctane, normal heptane, liquified propane, and the like. The particular solvent employed is not a critical feature of the invention provided that such solvent does not have such a strong solvent power for the chlorinated parafiins that they cannot be crystallized therefrom by fractional crystallization methods. Moreover, since these solvents do not have equal solvent power for the chlorinated compounds, the ratio of solvent to chlorinated product which should be used will depend on the particular solvent and the molecular weight of the chlorinated product. In general, however, a solvent to chlorinated product ratio of from :1 to :1 has been found to be completely satisfactory.

The solution of chlorinated product is chilled in a series of steps to produce a plurality of fractions. The first fractions separated, i.e., those at the higher crystallization temperatures, are the unreacted paraffins containing small amounts of chlorinated paraffins since these fractions have higher melting points than the monochlorinated parafiins. As the crystallization temperatures are lowered, the next fractions to separate are the monochlorinated paraflins. These monochlorinated fractions should be of approximately equal weight and separated in melting point by from at least 3 F. to 5 F. The melting points of the fractions should be separated by at least 3 F. to 5 F. since the isomers differ in melting point by about this amount and the fractions should be of approximately equal weight since the chlorination will produce approximately equal quantities of the isomers most easily formed. It is believed that the isomers most easily formed are those wherein the chlorine is substituted for hydrogen on the carbons near the end of the carbon chain of the paraffin molecule. Finally, only the diand polychlorinated products remain in the solution. If desired, these may be removed as the last crystalline fractions, which fractions need not be separated by at least 3 F. to 5 F. in melting point or be of equal weight since they are not the desired fractions.

The first fractional crystallization can be used to produce isomer fractions in each of which a particular monochloro paraffin position isomer predominates admixed with minor amounts of the other position isomers of the desired monochloro C paraffin and trace amounts of the C to C monochloro paraffins. Each of these fractions may be recrystallized several times if desired to produce extremely pure fractions, each containing a single position isomer of the C monochloro paraffin.

In order to demonstrate a specific embodiment of the invention a ISO-gallon sample of a commercial petroleum paraffin wax having a melting point of 132 F. and a composition shown in Table I was fractionally distilled at 2 mm. of mercury pressure to produce 44 cuts of approxi' mately 3 gallons each and a bottoms fraction. The 16th fraction was selected, melting point 126.6 F., since it contained predominantly C straight-chain parafiin. The approximate composition of this fraction is shown in Table II.

Table I Isoparaffin Straight: chain paraffin Cyclo- Cycloparaffin Carbon content parallln PZ'H NNPE" macawom This 16th fraction was redistilled at 2 mm. of mercury pressure into 10 fractions of approximately equal weight. Fractions 4 to 8 inclusive, the intermediate fractions, weighing 2376 grams were selected and dissolved by heating to about F. in 7 gallons of ethyl acetate, an approximately 9:l volume ratio of solvent to wax.

The solution was cooled to 94 F. and crystallized at this temperature. The first wax fraction recovered having a melting point of 128.2 F. and weighing 1499 grams was redissolved in fresh ethyl acetate with a solvent to wax ratio of about 15:1 and recrystallized at 70 F. to obtain a fraction containing 97.6 weight percent C straight-chain paraffin, 1.7 weight percent C straightnated the weight of the 100-gram sample would have in- I creased to 110 grams, so a slight excess of chlorine was employed. The exact quantity of chlorine used is not extremely critical, since there will always be some wax not chlorinated and some wax diand polychlorinated. The amount of chlorine used should be adjusted, however, to give approximately a theoretical monochlorinated product since, if a large excess is used, little or no monochlorinated paratfins are produced and polychlorinated non-separable mixtures are produced instead. Thus, the objects of the invention are defeated.

A lOO-gram sample of the chlorinated product (melting point 103.8 F.) was dissolved by heating to about 135 F. in 1000 ml. of ethyl acetate. The solution was cooled to 78.5" F. to produce the first crystalline fraction which was separated from the solution by filtration. The crys tals were washed separately with cold ethyl acetate. The dried crystals weighed 14.5 grams and, when the wash solution was evaporated, an additional 3.0 grams of product was obtained. The melting point, refractive index (n and chlorine content of the 14.5-gram fraction were determined. These results are set forth in Table III. The filtrate was cooled to a temperature of 76 F. and a second fraction of crystals separated by filtration. This fraction amounted to 3.5 grams and its melting point, re-

fractive index and percent chlorine determined, all of which art set forth in Table III. These crystals were also washed and the wash solution evaporated to recover an additional 2.5 grams of crystals.

The cumulative mid weight percent point was calculated for each fraction. This was calculated by adding the weight of the preceding fractions together with the weight of the preceding wash recoveries and /2 of the weight of the fraction being calculated. Thus, the cumulative mid weight percent point for fraction No. 2 was determined by adding 14.5, 3.0, and A of the weight of fraction No. 2, i.e., of 3.5 or 1.75 grams, giving a total of 19.25 grams. The cumulative mid weight percent point for fraction No. 3 was found by adding the weight of fraction Nos. 1 and 2 (18.0 grams), wash recoveries of fraction Nos. 1 and 2 (5.5 grams) and /2 of fraction No. 3 (2.75 grams) which equals 26.25 grams. The cumulative mid weight percent point was calculated in the same manner for each fraction. The crystallization temperature, weight of the fractions, weight of the wash recovery, cumulative mid weight percent point, melting point of the fractions, refractive index of the fractions, and weight percent chlorine of the fractions are set forth in complete detail in Table III.

fraction containing at least 97 weight percent of a singleand curve C is the plot of e weight percent chlorine vs. the refractive index.

It will be seen from the data in Table III as illustnatcd in the drawing that the refractive index varies 'directly with the weight percent of the chlorine in accordance with well-known theoretical considerations, namely, that the refraction of light is an additive property dependent upon the composition of the compound and dependent only to a small extent on the structural arrangement of the atoms within the molecule.

very similar, the refractive index is a function solely of the number of chlorine atoms substituted in the molecule. This is demonstrated by the fact that fractions 5, 6, 7, and 8 which contain an amount of chlorine corresponding approximately to the theoretical amount for monochlorin'ation have approximately the same refractive indices as shown by the plateau in curve B. These monochlorinated fractions, however, are shown to be different isomers by their large spread in melting point illustrated by the steep slope of curve A for the portion of the curve encompassing these fractions.

Fractions 1, 2, 3, and 4 which have nearly the same melting point are composed primarily of unreacted parmeric monochloroparaffins in the C to C range, which comprises monochlorinating a straight-chain paratfinic wax fraction containing at least 97 weight percent of a single straight-chain parafiin (C,,) as the major component and as minor components straight-chain paraffins differing by not more than two carbon atoms per. molecule from the major component (C to C wherein n is an integer from 18 to 35, to produce a chlorinated product, dissolving the chlorinated product in a solvent proportion of a halogen-free wax solvent and separating from the solution of the chlorinated product by crystallization essentially unreacted paraffins and a plurality of approximately equal weight fractious differing in melting point by at least 3 F. to 5 F., said fractions comprising the straight-chain isomers of the monochloro straight-chain C paraffin.

2. A process for the preparation of straight-chain isomeric monochloro paraflins in the C to C range, which comprises reacting a straight-chain parafiinic wax Table III Crystalli- Weight of Weight of Cumulative Melting Refractive Weight Fraction zation traction, wash mid weight, oint of in ex, percent number temperagrams recovery, percent raction, m chlorine in ture, F. grams point F. of traction fraction 78. 5 14. 5 3.0 7.25 127. 6 1. 42636 0.02 76.0 3. 5 2. 5 19. 25 127. 4 1. 4%68 0.86 62. 0 5. 5 2. 5 26. 25 126. 9 1. 42694 1. 10 42.0 4.0 1.0 33. 50 124. 2 1. 42858 2.80 26.0 Y 5.0 0. 25 30. 00 107. 0 1. 43442 8. 12.0 5. 5 1.0 44. 50 95.0 1. 43612 10.20 12. 0 9. 0 2.0 52. 72. 5 1. 43708 11.50 24. 0 7. 5 2. 5 63. 00 51.0 1. 43607 11. 5 52. 0 6. 5 0.5 72.50 45. 5 1. 43988 14.00 Residue 23. 0 87. 75 0. 0 1. 45064 21.

In the drawing, the data set forth in Table III are plotted and smooth curves drawn therethrough. Curve A is the plot of melting point of the fractions vs. the cumulative mid percent point, curve B is the plot of straight-chain parafiin (C as the major component and a as minor components straight-chain paraflins differing by not more than 2 carbon atoms per molecule from the major component (C,, to C wherein n is an the refractive index vs. the cumulative mid percent point, 75 integer from 18 to 35 with an amount of chlorine such Since in the, instant situation the chlorine isomers are structurally that an average of one atom of chlorine is substituted for one atom of hydrogen in each molecule of the paraflin thus producing a chlorinated product, dissolving the chlorinated product in a solvent proportion of a halogenfree wax solvent and separating from the solution of the chlorinated product by crystallization essentially unreacted paralfins and a plurality of approximately equal weight fractions differing in melting point by at least 3 F. to 5 F., said fractions comprising the straight-chain isomers of the monochloro straight-chain C paraffin.

3. A process for the preparation of straight-chain isomeric monochloro parafiins in the C to C range, which comprises monochlon'nating a straight-chain paraffinic wax fraction containing at least 97 weight per cent of a single straight-chain parafiin (C as the major component and as minor components straight-ch-ain paraffins difiering by not more than two carbon atoms per molecule from the major component (C to C wherein n is an integer from 18 to 35, to produce a chlorinated product, dissolving the chlorinated product in from 5 to 15 volumes of ethyl acetate per volume of chlorinated product and separating from the ethyl acetate solution of the chlorinated product by crystallization essentially unreacted paraffins and a plurality of approximately equal weight fractions differing in melting point by at least 3 F. to 5 F., said fractions containing the straight-chain isomers of the monochloro straight-chain C paratlin.

4. A process for the preparation of straight-chain isomeric monochloro parafiins in the C to C range, which comprises reacting a straight-chain paraflinic wax fraction containing at least 97 weight percent of a single straight-chain paratfin (C as the major component and as minor components straight-chain paraffins differing by not more than 2 carbon atoms per molecule from the major component (C to C wherein n is an integer from 18 to 35 with an amount of chlorine such that an average of one atom of chlorine is substituted for one atom of hydrogen in each molecule of the parafiin thus producing a chlorinated product, dissolving the chlorinated product in from 5 to 15 volumes of ethyl acetate per volume of chlorinated product and separating from the ethyl acetate solution of the chlorinated product by crystallization essentially unreacted paraffins and a plurality of approximately equal weight fractions differing in melting point by at least 3 F. to 5 F., said fractions containing the straight-chain isomers of the monochloro straight-chain C paraffin.

References Cited in the file of this patent UNITED STATES PATENTS 2,189,924 Pier et a]. Feb. 13, 1940 FOREIGN PATENTS 650,273 Great Britain Feb. 21, 1951 785,969 Great Britain Nov. 6, 1957

Claims (1)

1. A PROCESS FOR THE PREPARATION OF STRAIGHT-CHAIN ISOMERIC MONOCHLOROPARAFFINS IN THE C18 TO C35 RANGE, WHICH COMPRISES MONOCHLORINATING A STRAIGHT-CHAIN PARAFFINIC WAX FRACTION CONTAINING AT LEAST 97 WEIGHT PERCENT OF A SINGLE STRAIGHT-CHAIN PARAFFIN (CN) AS THE MAJOR COMPONENT AND AS MINOR COMPONENTS STRAIGHT-CHAIN PARAFFINS DIFFERING BY NOT MORE THAN TWO CARBON ATOMS PER MOLECULE FROM THE MAJOR COMPONENT (CN-2 TO CN+2) WHEREIN N IS AN INTEGER FROM 18 TO 35, TO PRODUCE A CHLORINATED PRODUCT, DISSOLVING THE CHLORINATED PRODUCT IN A SOLVENT PROPORTION OF A HALOGEN-FREE WAX SOLVENT AND SEPARATING FROM THE SOLUTION OF THE CHLORINATED PRODUCT BY CYSTALLIZATION ESSENTIALLY UNREACTED PARAFFINS AND A PLURALITY OF APPROXIMATELY EQUAL WEIGHT FRACTIONS DIFFERING IN MELTING POINT BY AT LEAST 3*F. TO 5*F. SAID FRACTIONS COMPRISING THE STRAIGHT-CHAIN ISOMERS OF THE MONOCHLORO STRAIGHT-CHAIN CN PARAFFIN.

Images