US2508038A - Process of refining hydrocarbons - Google Patents

Description

Fatenteci May 16, 1950 PROCESS OF REFINING HYDROCARBCNS Earl Manning, Jr., Houston, Tex., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application June 13,

Serial No. 754,597

Claims. 1

t This invention relates to a process of refining paraflinic hydrocarbon compositions. More particularly, the invention is directed to a refining operation designed to increase the normal paraffinic hydrocarbon content of a hydrocarbon fraction which initially contains normal paraffinic hydrocarbons and other types of hydrocarbons,

either or both aromatic and non-aromatic. 7 Various hydrocarbon mixtures may be obtained by the usual oil refinery operations. Thesemixtures usually contain normal paraffinic hydrocarbons in admixture with other types of hydrocarbons, such as iso-paraflinic hydrocarbons, cycloparafiinic hydrocarbons, e. g. naphthenes, and aromatic hydrocarbons. Such is the case of those hydrocarbon fractions having selected boiling ranges, dividing them into fractions, such as the very volatile and easily liquefied butanes, and pentanes, the gasoline hydrocarbons, the gas oil fractions, kerosene, the heavier fuel oils, the lubricating oil fractions, etc. Various chemical and physical processing operations have been utilized in the preparation of these mixtures depending on the uses to which they were to be put and the relationships between the different hydrocarbon types, and even the individual molecular species, and the required characteristics for the intended use. Thus, sulfuric acid treatment has been used to remove olefins and other acid polymerizable substances from gasoline fractions;

a mixture of sulfuric acid and phosphoric acid has available a hydrocarbon fraction with a high content or proportion of normal paraffinic hydrocarbons. Thus, for example, the quality of Diesel fuels as measured by the Diesel index or cetane number is a direct function of the n-paraffinic content. Normally solid, n-paraflin hydrocarbons are known to'crystallize in a form different from the non-normal, i. e. isoand cycloparaflinic hydrocarbons and for some purposes the form of the solid n-parafiin hydrocarbons is preferred.

aromatics, or mixtures thereof.

Although the prior methods of refining and otherwise treating hydrocarbon mixtures are of value in improving on the value of the products thus produced for the intended use, they all possess certain disadvantages or are not applicable at all when the objective is to produce a composition with an increased content of normal parafilnic hydrocarbons, especially when it is desired to produce substantially pure n-parafiinic hydrocarbon compounds or mixtures consisting of n-parafiinic hydrocarbons with different numbers of carbon atoms per molecule.

It is, therefore, a principal object of this invention to provide an improved process for increasing the nparaffinic hydrocarbon content of a hydrocarbon fraction containing initially both normalparamnic and other hydrocarbons, including nonnormal paraflinic and aromatic hydrocarbons. A further object is to provide a process for improving the Diesel index or cetane number of a Diesel fuel. Another object is to provide a process for the separation of normal paraflinic from other hydrocarbons. Still another object of the present invention is to provide a process whereby normaL parafiinic hydrocarbons can be recovered as such, economically and in high yield, from admixtures thereof with iso-paraffins or cyclo-parafilns or These objects will be more clearly understood and other objects will become evident from the description of the invention.

Now, in accordance with this invention, it has been found that normal chain paraflinic hydrocarbons may be effectively separated from other types of hydrocarbons, in mixtures thereof,, by a chemical process, which process comprises treating the admixture of hydrocarbons with a chemical acid treating agent consisting essentially of a mixture of sulfuric .and phosphoric acids, which mixture is free of uncombined water and which acid mixture contains additionally an amount of inorganic acid anhydride which is in substantial excess of that which is required to convert all water, actual or hypothetical, present in the mixture into the normal water-stable acid of said acid anhydride.

Generally described the process of this invention comprises treating a hydrocarbon admixture of normal paraffinic hydrocarbons and other types of hydrocarbons with a liquid chemical treating agent which is a chemical equilibrium system corresponding to a combination of sulfuric acid anhydride (sulfur trioxide) phosphoric acid anhydride (phosphorus pentoxlde) and water in proportions such that, assuming the water reacts with the acid anhydrides according to the equations:

then there is a substantial excess of inorganic acid anhydride, either or both sulfur trioxide or phosphorus pentoxide, over the equivalent amount of water as indicated by the above reactions, and removing reacted material and treating agent from the unreacted normal paraffinic hydrocarbons. Expressed another way, the total acid content of the treating agent, expressed as acid anhydride equivalent, is in substantial excess of the water equivalent thereof to form the water-stable acids from said acid anhydrides.

By treating a mixture of hydrocarbons, containing n-paraiiinic hydrocarbons and other hydrocarbons with the treating agent in accordance with this invention, for example, with a mixture of concentrated sulfuric acid and phosphorus pentoxide, the other hydrocarbons are chemically modified and may be readily separated from the normal paraifinic hydrocarbons, which are not altered. Thus, by practicing this invention aromatic, cycloparafiinic and isoparafiinic hydrocarbons are separated from admixture with normal paraffinic hydrocarbons.

The liquid acid treating agents of this invention may vary considerably in actual composition and/or method of preparation. In fact, the

molecular species actually present is largely a matter of conjecture. Nevertheless, regardless of the molecular species present in a mixture, for example, as made by dissolving one-third A) of a gram-mol of phosphorus pentoxide in one grammol of hydrogen sulfate (100% sulfuric acid), the resulting treating agent is highly effective in removing non-normal parafifinic and aromatic hydrocarbons from admixtures with n-paraflinic hydrocarbons. Thus, the advantage is secured whether the treatin agent is considered to contain uncombined phosphorus pentoxide dissolved in pure hydrogen sulfate; to contain'uncombined sulfur trioxide in phosphoric and/ or sulfuric acids; to contain pyrosulfuric acid in phosphoric acid; or to contain pyrophosphoric and/or metaphosphoric acids in sulfuric acid. In general, the acid treating agent should contain an amount of the inorganic acid anhydride as is equivalent at least to about 3.5% by weight of extra phosphorus pentoxide, or equivalent to a solution of I substantially 100% sulfuric acid admixed with at least about 3.5% by weight of phosphorus pentoxide. Since H2504 and P205 have molecular or formula weights of 98 and 142, respectively, said above solution would correspond to approximately one mol of H2304 per 0.025 mol of P205, or an amount of P205 which is equivalent to 0.075 mol of water to form H2P04. Proportions of acid anhydride as high as 30-40% by weight, based on the total acid content, may be utilized with advantage. It is preferred, however, to use acid treating agents which contain an amount of free acid anhydride of from about by weight, or better about 5 mol per cent calculated as P205, to about by weight (about mol per cent calculated as P205). Examples of suitable acid treating agents are (1) concentrated sulfuric acid (98.5% by weight pure H2S04) containing 5 per cent by weightof phosphorus pentoxide, (2) concentrated (SS-100%) sulfuric acid containing 10 per cent by weight (based on the combined weights) of phosphorus pentoxide and (3) by volume of fuming sulfuric acid (30% by weight excess S03) with 20% by volume of phosphoric (ortho) acid H3PO4).

In practicing the invention, the ratio of the amount of the acid treating agent, as defined and discussed above and which may be represented for simplicity as H2S04-P205 treating agent, to the amount of hydrocarbon mixture may be varied over a considerable range. A suitable range of ratios is from about 2:1 to about 20:1, by volume, a preferred ratio being from about 5:1 to about 15:1. Of course, higher ratios may be utilized, but, in general, it is not economically feasible or desirable to use a higher ratio than is required to obtain the desired results.

The process may be effected at various temperatures, and, in general, suitable temperatures are normal atmospheric temperature and moderately elevated temperatures. For treating a hydrocarbon mixture of the general fluidity and other characteristics of gasoline and kerosene fractions, satisfactory results are obtained by carrying out the process at normal room temperature, except insofar as the temperature of the mixture is increased by the heat of mixing and reaction. For such mixtures, a temperature of from about 10 C. to about 75 C. is preferred. With less reactive materials such as the lower molecular weight (4-5 C's) hydrocarbons, higher temperatures, may be utilized, e. g. up to about C. In some cases, of course, the hydrocarbon mixture may be treated in the gaseous state by the liquid acid treating agent.

It will be understood that the various variable factors such as the ratio of acid treating agent to hydrocarbon mixture, temperature of treat- 1 ment, manner of efiecting contact between the treating agent and the hydrocarbon mixture such as by vigorous agitation in a tank or similar vessel or counter-current contacting in a contacting tower provided with suitable packing or other dispersing means, etc., amount of increase in n-paraffin content which it is desired to obtain in the product, ratio of n-paraflfin hydrocarbons to other hydrocarbons in the mixture being treated, and the like, are inter-related and that i-',;. consideration of these factors together will be necessary, as will be evident to one skilled in the art, for determining the optimum set of operating conditions for a given desired objective.

Although the process of the invention is suitable for treating any mixture of n-paraffin hydrocarbons together with other hydrocarbons for the purpose of enhancing the n-parafiin hydrocarbon content of the recoverable hydrocarbon product, the invention is of particular value for treating n-parafiin hydrocarbon concentrates which contain a major portion of normal paraffinic hydrocarbons, and particularly for the preparation of substantially pure n-parafilnic hydrocarbons from such concentrates.

Having set forth the general nature and objects of the invention, and having described in considerable detail the manner in which it is to be practiced, the invention will be more readily understood and its utility demonstrated by the following illustrative examples.

EXAIVEPLE I Separate portions of a blend of pure hydrocarbons, the composition of which is given in Table I, were subjected to various acid treatments with a ratio of acid to hydrocarbon blend of 1, and at room temperature, except insofar as the temperature was increased by the heat of the reaction. The acid and hydrocarbon blend were acid agent made by dissolving 33 grams of phosphorus pentoxide in 100 ml, of 98% sulfuric acid. The resulting recovered raflinate, after being washed with caustic solution and water was found stirred vigo ously throughout the reaction p d- 5 to have an index of refraction (N0 of 1,3974 as After the treatment was terminated the unrecompared with 1.3975 for pure n-octane. acted hydrocarbon fraction was separated from the acid phase. She separated hydrocarbon EXAMPLE In fraction was washed with alkali and water and A hydrocarbon mixture of 84% volume ndried. The pertinent data are tabulated in 0 octane, 6% v. dimethylcyclohexanes, 5% v. Table II. toluene, and 5% v. 2,2,4-trimethylpentane was TABLE I treated similarly to the n-octane concentrate of Example II. The properties of the recovered co posztzon of hydr c blend product were those of n-octane and the recovery of n-octane was 89% by volume of the n-octane v01. Per present in the mixture treated. A noteworthy Hydrocarbon Cent feature is that the reaction products were all 4 absorbed in the acid phase and that a-redistillag ggalfigf z 31 tion of the separated and washed raffinate gave Tnlnerrn 5.0 no evidence of heavy residual material. 2,2,4-trimethylpentaue 5. 0

m0 0 EXAMPLE IV The treatment of Example II was applied to a TABLE II Acid treatment of hydrocarbon blend R Description of acid $33? Pe t of en y fiffif tlit Time total vol. D4 charged Filming H1SO4(30%) 4min--. 51 1.39747 .39750 10 161mm 2% Z 139765 91 0. 7045 -3 98.5 o $3 1% 2 3g 5 do 82 0.7027 1.397 0 v. unnng 2 4 o 4113"" 77 0.7028 1.39750 20 :85 H PO Bl frz of stazi dai ds pure normal 0.70260 1.39745 octane.

Thus it is seen from the results in Table 11, that treatments 1, 2, 5, 6 and 7 give substantially pure normal octane. However, it is to be noted that treatment 1, which was for the very short period of four minutes, gave only a 51% volume recovery against a theoretical recovery of 86.4% by volume. Also, it will be noted that treatment 2 required an extended period of time to remove the non-normal parafiinic hydrocarbons, as evidenced by the refractive index, and that with this required extended time of treatment the recovery was less than 75% of the theoretical. Treatments 3 and 4 gave good recovery, but the recovered'product contained substantial proportions of non-normal parafiinic hydrocarbons. Treatments 5, 6 and 7, in which cases the acid treating agents were in accordance with the invention, gave good products, 1. e. substantially pure normal octane and at the same time the recovery was about 90% by volume or better. It is observed that treatment 4, which is in accordance with the teaching of the above referred to U. S. Patent No. 2,088,406 is entirely unsatisfactory for the present purpose. results appear to substantiate the teaching of said patent that a mixture of concentrated sulfuric and phosphoric acids does not remove aromatic from n-paraffinic hydrocarbons.

EXAMPLE II A n-octane concentrate containing about 7% by volume of naphthenic hydrocarbons was stirred at room temperature for 16 hours with 10 volumes (per volume of concentrate) of an In fact, the

Diesel reference fuel, and it was found that the Diesel index was increased from 77 to 91, although by a more severe treatment according to the process of this invention it is possible to obtain a fuel having a still higher cetane value.

I claim as my invention:

1. A process of refining a hydrocarbon mixture containing normal paraflinic hydrocarbons and other hydrocarbons, which process comprises treating said hydrocarbon mixture with an anhydrous mixture of sulfuric and phosphoric acids as. obtained by mixing concentrated surfuric acid, with from about 5% to about 30% by weight of phosphorus pentoxide for a period of time whereby substantially all of said other hydrocarbons are reacted with and dissolved in said acid treat:- ing agent, thereby forming a hydrocarbon phase which is enriched in normal paraffinic hydrocarbons and an acid phase which contains a substantial proportion of said other hydrocarbons, and separating said phases.

2. A process of refining a normally liquid hydrocarbon mixture containing normal paraffinic hydrocarbons and other hydrocarbons, which process comprises treating each volume of said hydrocarbon mixture with from about 2 to about 20 volumes of an anhydrous mixture of sulfuric and phosphoric acids as obtained by mixing concentrated sulfuric acid with from about 5% to about 30% by weight of phosphorus pentoxide, said treatment being carried out at a temperature of from about 10 C. to about C., thereby forming a hydrocarbon phase which is substantially enriched in normal parafflnic hydrocarbons .sulfuric acid with a substantial proportion of phosphorus pentoxide, said. treatment being carried out at a Volume ratio of said treating agent to said concentrate and for a period of time whereby substantially all. of said other hydrocarbons are reacted with and dissolved in said acid treating agent and. substantially all of said normal paraffinic hydrocarbon is unaltered, thereby forming a hydrocarbon phase of said normal parafiinic hydrocarbon and an acid phase containing said other hydrocarbons, and separating said phases 4. A process of refining a normally liquid hydrocarbon concentrate of a normal paraffinic hydrocarbon admixed with other hydrocarbons, which process comprises treating each volume of said hydrocarbon concentrate with from about five to about fifteen volumes of an anhydrous mixture of sulfuric and phosphoric acids as obtained by mixing concentrated sulfuric acid with a substantial proportion of phosphorus pentoxide, said treatment being carried out at a temperature of from about 10 C. to about 75 0., thereby forming a hydrocarbon phase which is substantially pure normal parafiinic hydrocarbon and an acid phase containing said other hydrocarbons, and separating said phases.

5. A process of improving the cetane number of a Diesel fuel type hydrocarbon mixture which comprises treating said hydrocarbon mixture with an anhydrous mixture of sulfuric and phosphoric acids as obtained by mixing concentrated sulfuric acid with a substantial proportion of phosphorus pentoxide, thereby forming a hydrocarbon phase having an enhanced cetane number and an acid phase containing reacted hydrocarbons and unreacted acid, and separating said phases.

A process of improving the cetane number of a Diesel fuel type hydrocarbon mixture which comprises treating each volume of said hydrocarbon mixture with from about 2 to about 20 volumes of an anhydrous. mixture of sulfuric and phosphoric acids as obtained by mixing concentrated sulfuric acid with from about 5% to about 30% by weight of phosphorus pentoxide, said treatment being carried out at a temperature of from about C. to about '75? 0., thereby forming a hydrocarbon phase havingan enhanced cetane number and an acid phase containing reacted hydrocarbons and unreacted acid, and separating said phases.

7. A process of refininga liquid hydrocarbon concentrate of normal octane in admixture with other hydrocarbons which are notstraight-chain hydrocarbons, Whichprocess comprisesv treating said admixture with an anhydrous mixture of sulfuric and phosphoric acids as obtained by mixing concentrated sulfuric acid with a substantial proportion of phosphorus pentoxide for a period of timewhereby substantially all of said other hydrocarbons are reacted with and dissolved in said acid treating agent, thereby forming an acid phase which contains substantially all of said other hydrocarbons and a hydrocarbon phase which contains said normal octane and is substantially' free from said other hydrocarbons,.and separating said phases.

8. A process for removing aromatic hydrocarbons, saturated alicyclic hydrocarbons and saturated non-straight-chain acyclic hydrocarbons from normal paraffinic hydrocarbons in admixtures thereof, which process comprises treating said admixtures with an anhydrous mixture of sulfuric and phosphoric acids as obtained by mixing concentrated sulfuric acid with from about 5% to about 30% by weight of phosphorus pentoxide, to thereby form a hydrocarbon phase which is substantially enriched in normal paraffinic hydrocarbons and an acid phase which contains a substantial proportion of the other hydrocarbons, and separating said phases.

9-. A process for removing aromatic hydrocarbons, saturated alicyclic hydrocarbons and saturated non-straight-chain acyclic hydrocarbons from normal paraflinic hydrocarbons in admixtures. thereof, which process comprises treating. said admixtures with an anhydrous sulfuric acid-phosphoric acid treating agent prepared by mixing concentrated sulfuric acid with from about 5% to about 30% by weight of phosphorus pentoxide, to thereby form a hydrocarbon phase which is substantially only normal para-flinic hydrocarbons and an acid phase which contains a substantial proportion of the other hydrocarbons, and separating said phases.

10. A process of refining a petroleum hydrocarbon mixture containing normal parafiinic hydrocarbons and other hydrocarbons, which process comprises treating said petroleum hydrocarbon mixture with an. anhydrous mixture of sulfuric and phosphoric acids as obtained by mixing concentrated sulfuric acid with a substantial portion of phosphorus pentoxide, for a period. of time sufficient to produce a hydrocarbonv phase which is substantially enriched in normal parafiinic hydrocarbons and an acid phase which. contains at least a portion of said other hydrocarbons and producing said hydrocarbon and acid phases and separating said phases.

EARL MANNING, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,853,921 Morrell (B) Apr. 12, 1932 2,029,785 Morrell (A) Feb. 4, 1936 2,039,799 Ipatieff May 5, 1936 2,088,406 Clark July 27, 1937

Claims (1)

1. A PROCESS OF REFINING A HYDROCARBON MIXTURE CONTAINING NORMAL PARAFFINIC HYDROCARBONS AND OTHER HYDROCARBONS, WHICH PROCESS COMPRISES TREATING SAID HYDROCARBON MIXTURE WITH AN ANHYDROUS MIXTURE OF SULFURIC AND PHOSPHORIC ACIDS AS OBTAINED BY MIXING CONCENTRATED SULFURIC ACID WITH FROM ABOUT 5% TO ABOUT 30% BY WEIGHT OF PHOSPHORUS PENTOXIDE FOR A PERIOD OF TIME WHEREBY SUBSTANTIALLY ALL OF SAID OTHER HYDROCARBONS ARE REACTED WITH AND DISSOLVED IN SAID ACID TREATING AGENT, THEREBY FORMING A HYDROCARBON PHASE WHICH IS ENRICHED IN NORMAL PARAFFINIC HYDROCARBONS AND AN ACID PHASE WHICH CONTAINS A SUBSTANTIAL PROPORTION OF SAID OTHER HYDROCARBONS, AND SEPARATING SAID PHASES.