US2175437A - Treatment of light petroleum distillates - Google Patents

Description

Patented Oct. 10, 1939 UNITED STATES mama's or near rmomm DISTIILATES h Arthur Lazar and Thomas F. McCormick, Associated, Caiih, assignors, by mesne assignments, to

Tide Water Associated Oil Company. San

Francisco, Calif.. a corporation of Delaware No Drawing. Application January 24, 1938,

Serial NO. 60320 iclaims.

This invention relates to an improved process of preparing sulphonic acids from petroleum.

Another object is to provide an improved process for isolating groups of aromatic hydrocarbons, or sulphonio acids derived therefrom.

Another object is to provide for the separation of a petroleum distillate so that substantially pure saturated hydrocarbons (paraflines and naphthenes) and pure aromatic hydrocarbons can be recovered.

Further objects will become apparent as the invention becomes more fully disclosed hereinafter.

Certain mineral oil distillates, such as those produced from California crudes, contain appreciable quantities of non-hydrocarbon impurities, In refining such distillates, particularly those comprising the normal boiling point range of gasoline, petroleum spirits, and kerosene, it is found that the presence of these non-hydrocarbons interferes to a certain extent with the usual treating methods applied on said distillates.

Chemically speaking these non-hydrocarbons consist of organic acids, such as naphthenic acids, phenols, and the like, sulphur compounds of acidic nature like mercaptans and thimphenols, other sulphur compounds, and nitrogen bases.

Inasmuch as organic acids and nitrogen bases present in the distillates are attacked by sulphuric acid, these compounds should be removed before the distillates are treated with the concentration of sulphuric acid for the recovery ofdesired hydrocarbons herein set forth.

In addition it has often been found that dis- 35 tillates containing such impurities cause difficulties in subsequent processing. For example, if the distillates containing said non-hydrocarbons are treated with liquid sulphur-dioxide or other solvents according to the well-known Edeleanu process, it has been found that salts of nitrogen bases and resinous deposits are formed in the treating equipment. The salt crusts represent reaction products of sulphurous and sulphuric acid with nitrogen bases mixed with resinous 45 material, which has been formed by polymerization of the phenols. Such deposits often are quite troublesome and can be the cause of the emulsions in the S0: or other treating process, or.

when accumulated in large quantities can in- 50 terfere with heat transfer in the exchangers and evaporators of the treating unit, or when accumulated in lines and pumps, can interfere with the throughput of the plant.

It is therefore an object of this invention to submit mineral oil distillates composed of a plurslity of fractions to a number of treating steps in the proper sequence and thereby to split the fractions up in such a manner that substantially go pure aromatic sulfonic acids are obtained which heretofore could not be obtained from mineral oils in any appreciable quantity.

Broadly speaking, the invention involves the treatment of a petroleum distillate (cracked. or uncracked) with specific reagents in such sequence of steps that such reagents, which cannot under usual conditions exercise their function of selectivity, are enabled to be applied with complete selectivity.

This will be better understood if, for instance, the reactions of sulphuric acid with hydrocarbons is considered when a certain concentration of sulphuric acid is ineffective to dissolve, or react with, unsaturated and aromatic hydrocarbons while other concentrations may be used to efiectively separate unsaturated and aromatic hydro- 15 carbons from saturated hydrocarbons and from each other. In consequence, this selective action of sulphuric acid and of solvents such as liquid sulphur dioxide, benzol-sulphur dioxide, phenol, furfural, nitrobenzene, dichlorethylether, a mix- 20 ture of propane and cresylic acid, and .like solvents, or a combination of any ofthese solvents with each other or with liquid $02, for hydrocarbons and impurities in hydrocarbons, is so utilized herein that a refined petroleum distillate of improved qualities is obtained while pure hydrocarbons of definite characteristics and pure by-products are made available for varied uses in the arts.

Referring to theoperation of the process, a light raw distillate obtained from California crude petroleum, such as the gasoline, kerosene, or petroleum spirits fractions thereof is the original stock to be treated.

Such raw distillate may be, merely by way of illustration and not of limitation, a selected cut from a crude all within the boiling range of a specification gasoline desired as a final product, or of any desired cut within such boiling range suitable for treatment to provide a finished cut 40 available for blending to yield a specification gasoline. I

If it be assumed that such raw distillate is from a California crude oil, the same may contain fractions of the pal-affine, naphthene, olefine, dioleflne, and aromatic hydrocarbons together with organic acids, nitrogenous bases, and various forms of sulphur compounds, and may have the following physical characteristics:

Grav. A. P. I "50.7 I. B. P

Sulphur -..per cent- Nitrogen do Aniline Pt F:

as before stated. it must be understood as steps of the process are particularly applicable which ranges in volatility from the light gasoline cuts right through the various boiling ranges of petroleum spirits, kerosene, gas oil, spindle oil, and spray oils down to heavy viscous lubricating oils and the treatment of a gasoline fraction is described as being illustrative of a fuller range of operations which will include the recovery of a very superior motor fuel as well as other included purified products.

The raw distillate, depending on its boiling range, is subjected to a series of steps for the removal of impurities and recovery of finished products.

Preferably the raw distillate is first treated with a solution of alkali, such as caustic soda solution of a concentration of about from 15 B. to 30 B. which serves with proper agitation to combine with the organic acids in the distillate and to break up the combination between the organic acids and nitrogen bases in the distillate while polymerizing certain unstable resinous compounds therein and the thus reacted caustic with absorbed material is removed from the distillate.

The distillate is then agitated with sufficient quantity of dilute sulphuric acid, which is of a concentration less than 90% acid and preferably of about 50% to 60% acid, which serves to react with nitrogenous bases in the distillate and the spent acid is then withdrawn to leave the distillate free from organic acids and nitrogenous bases.

The spent acid may be separated by gravity settling or the settling can be accelerated by centrifugal action. Any of the well known methods can be used for removing the spent acid in order to prepare the distillates for solvent refining. In commercial operation certain stocks may require the neutralization of the last traces of sulphuricacid with caustic soda or other alkalies before solvent refining.

The thus withdrawn caustic solution may be acidified with fresh acid which serves to throw the abmrbed organic acids out of solution for recovery as such. while the spent dilute acid may be causticized with fresh caustic soda solution to throw out the nitrogenous bases for recovery as such.

It must be understood that while the above described removal of organic acids and nitrogenous bases is preferably done as the first step of the process so that the remaining steps of. the process may be more clearly illustrated and facilitated,

such removal is not essential as a first step but may' be'performed as a'later step as will be later more fully described.

The thus purified distillate is then subjected to treatment with a solvent such as liquid sulphur dioxide, or any of the other described and well known selective solvents, in a well known manner to separate the distillate into two portions or layers. The upper layer is known as the rafiinate composed of the parafilne and naphthene series of hydrocarbons and the lower layer (termed the extract) consists mainly of the olefine, dioleflne, and aromatic series of hydrocarbons together with a certain percentage of saturated hydrocarbons of the parafiine and naphthene series and certain sulphur compounds.

Depending on required uses, the extract after removal of S02 therefrom may either be used as is or first subjected to treatments in certain steps to derive certain products or to leave a fraction of high anti-knock value to be added to said ramnate.

The extract of gasoline boiling range is first treated with sulphuric acid of a concentration from 90% H1804 up to a fuming acid containing 20% depending on the action desired on the extract, and all treatments of the distillate or extract with the reagents described and used herein are preferably conducted for the fullest contact efilciency as for example in accordance with the method disclosed in a co-pending application of Edwards and Stark, Serial No. 532,000, filed April 22, 1931, issued as U. 8. Letters Patent 2,052,852, September 1, 1936, the range of temperatures used therewith being regulated from below 0 F. up as high as 80 F., depending on the solvent or sulphonating effect required from the sulphuric acid.

If organic acids and nitrogenous bases have already been removed from the extract of definite boiling range, the extract will be contacted with sulphuric acid of concentration, or greater, in such quantity and at such temperature as to leave an extract composed mainly of hydrocarbons of a cyclic structure, such as aromatics and hydroaromatics.

In addition to the many functions already described the practically complete removal of active sulphur compounds is desired during the, acid treatment of sulphur dioxide or other solvent refined extracts. This is accomplished by the use of relatively low sulphuric acid rates normally below ten (10) pounds per barrel and not over 30 pounds per barrel on extracts of high sulphur content. Solvents manufactured in this manner have excellent stability and are particularly adapted for use by the paint, varnish, and lacquer industry where stability against light and weathering is of primary importance and there is no tendency for corrosion due to the elimination of active sulphur compounds.

In order to obtain other products, if it is not desired to use the treated extract as above set forth, or as raw material for solvents, the whole, or part, of the extract may be further treated with up to or more of its volume with concentrated sulphuric acid (varying from 90% acid up to 20% fuming acid) under such conditions of temperature that all the aromatics in the extract are sulphonated and the remainder of the extract will consist of more saturated hydrocarbons (mainly naphthenes and hydroaromatics) which, when neutralized. are especially valuable as special petroleum spirits, thinners, Stoddard solvent, or similar solvents in which extremely low sulphur content, or complete freedom from both active and less active sulphur compounds is required. I

If the extract has been treated in the first place with but a small amount of concentrated sulphuric acid, for the production of solvents or motor fuel not more than. about 10 pounds of acid to the barrel, merely for partial sulphur reduction, the acid sludge therefrom may be discarded, but if it has. been treated with acid up to as high as 30 pounds of acid per barrel of ex- .tract for further sulphur reduction, the acid sludge may contain a similar concentration of sulphonic acids as is contained in the acid sludge resulting from treatment of the extract with 100% of its volume of concentrated sulphuric acid, and the succeeding steps are applicable thereto.

Depending on the sulphur content of the extract the sulphuric acid treatment may be carriedoutinoneormore'stepsbutpreferablyinat least two stages for the subsequent recovery of sulphonic acids, naphthenes, and pure aromatics. The initial purification with strong acid is particularly necessary if the sulphur content of the extract is high, and may require up to 30 pounds of sulphuric acid per barrel for de'sulphurisation purposes. The degree of sulphuric acid treatment in one or more stages will depend on the sulphur content of the extract and quality and purification of solvents, motorfuel, sulphonic acids, saturated oils, and other by-products desired. In the acid treatment with two or more stages the initial treatment removes the more easily attacked substances such as non-hydrocarbons, di-olennes, etc. and the subsequent treat ments will start to actively sulphonate aromatics.

The acid sludges from the later treats may be contaminated with a small quantity of non-hydrocarbons and sulphonic acid recovery is somewhat more dimcult than when these non-hydrocarbons are completely eliminated and only the acid sludges from the concentrated heavy acid treatment of up to 100% by volume or more of sulphuric acid is used.

To definitely illustrate, we can treat a high sulphur extract with 30 pounds per barrel of strong acid in six treats oi five pounds per barrel each. The first one or two treats will yield sludges contaminated with the reaction products of non-hydrocarbons which may be discarded in order to avoid contamination of sludges later derived. The remaining treats yield sludges containing substantial quantities of sulphonic acids as the sulphuric acid treatment starts to attack the aromatic hydrocarbons to anappreciable extent. These sludges may be a suitable'source of slightly contaminated sulphonic acids although more purified by-products are obtained particularly pure sulphonic acids from acid sludges formed in later treatment.

with acid sludges containing relatively high percentages of sulphonic acids. as described, novel steps are next used on said sludges for the recovery of sulphonic acids and pure aromatics, and such steps are applicable to any acid sludges containing sulphonated compounds whether derived from the before described treatment or derived from any other sulphuric acid treatment of other hydrocarbons and shows great improvement over the usual and conventional methods of treating acid sludges.

In the usual method, the acid sludge consisting of sulphonic acids and sulphuric acid is neutralizedwith calcium hydroxide which converts all the acids present into. calcium salts, such as calcium sulphate and calcium sulphonates, which mixture is washed with water to leachout the water soluble sulphonates and leaves the water insoluble calcium sulphate, and the sulphonates are then concentrated. This procedure is verytedious and costly as the sulphuric acid is converted into calcium sulphate, a product of low value. The neutralization costs are greater and the sulphuric acid cannot be recovered for future use. The calcium sulphates must alsobe acidified to obtain free sulphonic acids.

On" the other hand, the acid sludges derived from the above described treatments may be mixed with a volume of water amounting to about one-third (Vi) of the sulphuric acid used on the extract which, after agitation and settling. Drovides two layers of liquids due to the salting out effect of the free mineral acid on the free sulphonic acids. As a result, the mineral acid content of the upper'iavcrn greatly reduoedand the lower layer retains a minimum of organic compounds.

In consequence the upper layer consists mainly of sulphonic acids and the lower layer consists 5 mainly of sulphuric acid of a relatively low degree of concentration.

The lower layer may then be drawn off and distilled under such conditions of temperature and pressure that any traces of sulphonic acids contained therein will be split by heat to free the aromatic hydrocarbons which can be carried oi! as an overhead vapor and condensed to yield pure aromatics. The liquid in the still I consists of dilute sulphuric acid which may be 15 concentrated and recovered in any well known manner for use and is especially adapted for such recovery because of its purity and freedom from nitrogen bases earlier removed from the distillate. While small amounts of aromatics may be further recovered from the dilute sulphuric acid during concentration, the sulphur compounds and other impurities contained in the acid sludge are apparently destroyed during distillation and concentration because the aromatics recovered during these steps are free of such impurities.

The supper sulphonic layer can be isolated for further purification, or treated by a hydrolizing steam distillation to drive on the aromatics as overhead which are condensed and may be mixed with the aromatics derived from the lower layer while the .remainder oi" the upper layer consists oi dilute sulphuric acid which can be concentrat' ed for use as described for the remainder of the:

lower layer. v

In the event that the upper, or sulphonic, layer is permitted to stand for some time without distillation, it has been noted-that there is a tendency for the formation of crystals of pseudocu-- mene sulphonic acid and such crystals may be; readily separated from said sulphonic layer by a. centrifuge prior to subjecting the remainder of the sulphonic layer to thelmirolising steam distillation before described.

The aromatic hydroccbons thus derived by the aforesaid treatments of the upper and lower layera are exceptionally pure and require only the; usual neutralising and. washing treatments prior to use and such purity i dueto the prior treat;- ment of the distillate for the removal 010mm acids which otherwhe would contaminate the sulphonic layer and cause secondary It may readily be perceived. for instance, tins if phenols were notthus' removed they wouB be sulphonated along with the aromatics and then later reappear as contaminating substances in the resultant products 1 I At the same time it must be noted that while, the described removal. of organic acids and nitrogenous bases in the orisinal .raw distillate is preferably accomplished as an initial step of the process, such removal may be 'eifectesl at any time prior to, orasfar as the nitrogen bases are concemed, during the initial step of subsequent treatment with strong sulphuric acid.

The S02 extract may therefore be treated with caustic solution for the removal oi organic acids at any time prior to treatment with concentrated sulphuric acid.

Likewiseif the 80: extract is first treated with 70 caustic soda solution and then treated with concentrated sulphuric acid in relatively small volume, as described, so as only to elect sulphur removal with low sulphonatlon'of aromatics, the extract will then be free of nitrogenous bases be- 7;

7 cause they will be removed by the concentrated phonation to yield pure aromatics.

It is apparent that by suitable variations of the treatments with concentrated sulphuric acid with regard to time of contact, temperature of contact, method of contact, quantity of acid, concentration of acid, the extract can be modified to yield products suitable for the uses enumerated and that such products may yield various types of aromatics.

For instance, if the extract is treated with acid in a plurality of steps including a first step with a small quantity of acid, the aromatics most readily attacked by acid can be extracted first and successive variations of treatment can be used to provide pure aromaticsof desired characteristics. Such treatments by selective reactivity of sulphuric acid accomplishes partial separation without distillation.

Modifications and alternations of treatment of the raw distillate are provided in addition to those stated.

For instance, while the treatment of a raw gasoline distillate has been described to yield a finished motor fuel of high anti-knock value, if the raw distillate initially is of gasoline boiling range, or of any other overlapping boiling range, the S0: or other extract derived therefrom may be distilled to yield a light fraction within the gasoline boiling range and bottoms heavier than such range. Such bottoms can then be recovered as a dark liquid of high fluidity and penetrating power suitable for use for the destruction of plant life, or a so-called weed killer, as a fuel for certain types of Diesel engines, a cutback oil or solvent for asphalt, pitch, coke, heavy residua, or due to its penetrating power and wetting ability, as a flotation oil.

The light fraction may then be treated according to the described steps for the same uses as described.

It is thus clear by the steps enumerated that the treatment of a raw distillate may be so conducted that not only is the distillate recovered in a pure state, but thatevery step assures the recovery of products of value which heretofore in most cases have been useful in only a minor degree.

It is understood that in referring to the boiling or distillation range of any particular distillate that the limits of such distillation range are those included in the every day, or commercial sense, such for instance as are found in the U. S. Government or A. P. I. specifications.

It will be noted that, while certain of the described steps have been shown as batch operations for the sake of simp icity, many of the same may be carried on in well known continuous operations and therefore such descriptive operations impose no limitations beyond the scope of the appended claims.

Although the above inventions have been directed towards the processing of distillates and the recovery of valuable by-products therefrom, it should be understood that we also include the refinement of those light and heavy crudes containing substantial quantities of non-hydrocarbons heretofore defined. Certain California crudes such as those originating from the Ventura, Southern California, Kettleman Hills and Belridge fields contain appreciable'quantities of non-hydrocarbons and/or unsaturated and aromatic hydrocarbons which are desirable sources of by-products. Depending on the nature of the crude and the particular by-product recovery desired distillation may be first used to greater advantage in the later stages of processing and this mode of operation is also claimed, utilizing the inventions fully described for the preferred treatment of light distillates.

This application is a continuation in part of our co-pending application Serial No. 521,626, filed March 11, 1931.

We claim:

1. A process of treating oils which comprises: treating a petroleum oil containing aromatic hydrocarbons with separate dosages of an aqueous alkaline solution to remove organic acidic compounds and of sulfuric acid having a concentration less than 90% H1504 to remove nitrogenous bases, extracting the thus purified oil with a selective solvent whereby an extract rich in aromatic hydrocarbons is obtained, sulfonating said extract with sulfuric acid of a concentration greater than 90% H2504, and recovering the sulfonated products.

2. A process of treating oils which comprises: treating a petroleum oil containing aromatic and unsaturated hydrocarbons with separate dosages of an aqueous alkaline solution to remove organic acidic compounds and of sulfuric acid having a concentration less than 90% HzS04 to remove nitrogenous bases, extracting the thus puri fied oil with a selective solvent whereby an extract containing aromatic and unsaturated hydrocarbons is obtained, treating said extract with sulfuric acid of a concentration greater than 90% H2804 first at a rate of less than 30 pounds oi vacidper barrel of oil to remove said unsaturated hydrocarbons then at a rate up to 100% acid by volume to sulfonate said aromatic hydrocarbons,

and recovering the sulfonated aromatic hydro- Y carbons.

3. A process of treating oils which comprises: treating a petroleum oil containing aromatic hydrocarbons with 15 to 30 B. caustic soda solution, removing the spent caustic solution, contacting the treated oil with sulfuric acid of a concentration of 50% to 60% H2804, removing the acid solution, extracting the contacted oil with a selective solvent whereby an extract rich in aromatic hydrocarbons is obtained, sulfonating said extract with sulfuric acid of a concentration greater than 90% E2804, and recovering the sulfonated products.

4. A process of treating oils which comprises: treating a petroleum oil containing aromatic and unsaturated hydrocarbons with 15 to 30 B. caustic soda solution, removing the spent caustic solution, contacting the treated oil with sulfuric acid of a concentration of 50% to 60% H2804, removing the acid solution, extracting the contacted oil with a selective solvent whereby an extract containing aromatic and unsaturated hydrocarbons is obtained, treating said extract with sulfuric acid of a concentration greater than 90% H1804 at a rate of less than 30 pounds of acid per barrel of oil suflicient to suiphonate the unsaturated hydrocarbons withv out substantial sulphonation of the aromatic hydrocarbons, removing the spent acid, treating the thus purified oil with sulfuric acid of a concentration greater than 90% H2804 at a rate up to 100% by volume to sulfonate said aromatic hydrocarbons, and recovering the sulfonated aromatic hydrocarbons.

ARTHUR LAZAR.

THOMAS F. MCCORMICK.