US2001906A - Treatment of hydrocarbon oils - Google Patents

Description

' Patented Mn 21, 1935 UNITED STATES No Drawing.

omusams.

Serial No. $.18

3 Claims. (01. 13-10) This invention relates to the treatment of hydrocarbon oil, and refers more particularly to the' treatment of the low boiling naphthas and gasolines produced from crude petroleum by frac- 5 tionation under conditions involving substantially no cracking.

In a more specific sense the invention has reference to a process for treating said straight run" gasolines to improve their quality with respect to gum and color-forming compounds present and in a specific sense in regard to improving their anti-knock value and increasing their yield. The details of the process whereby these desirable refining eiIects are accomplished are given in the following specification.

In a general way the gasoline fractions present in crude petroleums referred to as straight run gasolines, which may be removed therefrom by fractionation at moderate temperatures and pressures, reflect the character of the crude petroleum, that is, the proportions of such hydrocarbon groups as paraiilns, olefins, naphthenes, aromatics and the sulfur and nitrogen compounds are usually present in approximately the same ratio as '25 they are present in the crude petroleum as a whole. Although there are cases of considerable divergence from this rule, it has been repeatedly noted that the gasolines from paraiiinic crudes such as those from the Pennsylvania and some of so the Mid-Continent fields are highly parafilnic and highly blocking in character. The gasolines from the Mid-Continent field crudm and some of the Gulf crudes have an intermediate character in respect to anti-knock value, indicating possibly the presence of relatively higher percentages of cyclic compounds of the nature of naphthenes or of isoparaillns. Certain crude oils from the Pacific Coast producing areas and some Texas fields yield gasolines of comparatively hieh anti-knock 40 value, owing to the cyclic character of the crude oils.

These observations as to the variable character of straight run gasolines are merely adduced in a general way to show that diiferent gasolines or naphthas may require difierentdegrees of treatment according to the process of the invention to be presently disclosed in order to render them up to the prevailing market standards for antiknock value.

The present invention comprises a process of treatment whereby the character of the hydrocarbons present in straight run gasolines is altered in the direction of increased anti-knock value so that the need for excessive cracking of heavy hydrocarbon fractions to produce high anti-knock blending gasolines and the losses attendant upon such a type of operation are in many cases obviamd.

The process furthermore efiects a conservation of some of the waste products'of cracking proc- 5 cases which are caused to combine with certain hydrocarbon groups in straight run gasolines so that the overall yield of product is increased.

In one specific embodiment the invention comprises treatment of straight run gesolines with 10 olefins in the presence of sulfuric acid to produce hydrocarbons which add anti-knock value to the gasoline and at the same time to produce other desirable treating effects.

The term olefin" as used within the concept 15 of the present invention comprises any compound of carbon and hydrogen of open chain structure and containing one or more double bonds between carbon atoms. The following tabulation'gives a few of the lower boiling members of the ethylene 20 series which consists of homologues of the base substance ethylene containing one double bond:

Beginning with compounds of four carbon atoms. the table shows that a number of isomers are possible corr sponding to difierent positions of the double bond and the presence of tertiary 45 or quaternary carbon atoms, the number of possible isomers increasing as the number of carbon atoms increases. From these considerations it is evident that for the ethylene series alone a large number or difi'erent olefins may 50 be employed either singly or in admixture for condensation with gasoline hydrocarbons according to the process of the invention.

The invention may further comprise the utilination of open chain unsaturated hydrocarbons of the acetylene or the diolefln series comprising such compounds as acetylene, butadiene, etcetera, and their homologs. While pure compounds of this character and even ethylene itself do not react readily even with aromatics in the presence of sulfuric acid catalyst, there is apparently some alkylation by these compounds when used in admixture with other olefins as occurs in the case of gases from cracking processes.

The reactions involved in treatments according to the process of the invention are of considerable complexity owing to the large number of hydrocarbon types represented in the gasolines treated on the one hand and the large number of olefins which may be employed on the other hand to alter the character of the gasoline. Merely to exemplify to some extent the character of the reactions which may occur, those which take place when a single olefin such as propylene is caused to join with benzol to produce an alkylated derivative may be considered. When gaseous propylene is passed into a wellstirred mixture of benzol and concentrated sulfuric acid in proper proportions, the propylene is apparently sulfonated at first to produce a mono-propylsulfuric acid, and there are indications that the benzol may be sulfonated to some extent. The sulfuric acid derivatives then react to form a propylated benzol and regenerate to a large extent the sulfuric acid so that the net result of the reactions is expressed by the following equations which show the formation of monoand di-isopropyl benzol:

H 80 a u o o oHsa 1 Propylene Benrcl Mono-isopropyl benzol H2 2C H a o om-( 3 7): Propylene Benzol Di-isopropyl benzol The relative proportions of the monoand diderivatives will depend upon such factors as the relative proportions of the two hydrocarbons employed, the rate of introduction of the propylene into the acid-aromatic mixture, the strength of the acid and particularly the temperature which in the majority of cases of this character is best maintained at least at atmospheric temperature to minimize loss of olefins by polymerization. In the above reactions propylene represents any of the homologs of ethylene, although ethylene itself is not specially reactive. Similarly, benzol represents any of the aromatic series of hydrocarbons and may also typify the polynuclear aromatics such as naphthalene and anthracene. However, the proportion of these polynuclear aromatics is undoubtedly very small in straight run gasoline fractions which commonly boil under 437 F.

The reactions given above in connection with olefins and aromatics are obvious and readily understandable to persons versed in organic chemistry. However, it is advanced as a particular feature of the present invention that unusual and unexpected results have been obtained when treating gasolines with olefins and olefin mixtures in the presence of sulfuric acid when the gasolines are of a parafiinic character as produced from Pennsylvania crude oils and contain substantially no hydrocarbons of a distinctly aromatic character though. possibly a considerable percentage of naphthenes. Owing to the difiiculties of exact analysis in the case of hy-- drocarbon oil mixtures only a limited amount of data is available on the subject of the proximate composition of gasolines, but considerable qualitative and some semi-quantitative experiments have indicated'that the so-calle'd paraflinic gasolines may consist not only of normal or straight chain parafflns, but also to a large extent of so-called iso or branched chain paraflins and cyclic compounds of a saturated or partially saturated character such as the naphthenes and mixed alkyl derivatives thereof. The course of the reactions which lead to the improvements noted in the case of straight run paraflinlc gasolines when treated by the process of the present invention may consist in re-arrang'ements among the substituting groups either in the open chain or closed chain hydrocarbons, or it may comprise the direct addition of olefins to central carbon atoms in the parafilnic chains. Such reactions cannot be closely followed owing to the difficulties in securing reliable analytical data.

The following equations in addition to those previously given suggest further reactions which may take place when olefins are contacted withstraight run gasoline in the presence of sulfuric acid under regulated conditions. In the case of a straight chain paraflln such as pentane, the following equation expresses a possible reaction:

nzso.

Isopropyl pontane Owing to the observed increase in anti-knock value which occurs many times in the alkylation pf straight run gasolines according to the process of the invention it is probable that at least some of the methyl or other alkyl groups attach to the carbon chain in a central position so that lso compounds are formed, since it is known that hydrocarbons of higher anti-knock value are obtained when the carbon atoms are arranged more compactly.

The equation given below suggests a reaction which might be presumed to take place between an olefin and a naphthene 'or a partially hydrogenated aromatic of a mixed or terpene-like character a t i o s e 1' a 1 Propylene Dihydrobonzol Diliydro isopropyl bcnzol Similar reactions may occur with aromatic hydrocarbons which may be present in straight run gasolines. The foregoing suggested reactions merely indicate possible trends and many other and more complicated reactions may occur owing to the possibility of the shifting of labile hydrogen atoms and alkyl groups such as methly, ethyl, propyl, etcetera.

Also, where olefins are contacted with sulfuric acid some polymerization will occur among the olefins themselves as well as the alkylation reactions described. Also, these reactions may be controlled by proper contacting of the olefinic hydrocarbons with the gasoline hydrocarbons so that there is a decreased tendency toward the formation of compounds of high molecular weight. Owing to the low formation of tarry polymers observed in practically all cases it is probably that if polymerization reactions occur that they do not pass beyond the stage of dimers and trimers which of themselves are valuable compounds and add anti-knock value to the gasoline hydrocarbon mixture.

In some cases the sludge from the process may be recirculated and reused. It is to be pointed out that sulphuric acid sludges resulting from the treatment, or from some similar treatment, may

be employed either alone or in combination with fresh acid. A commercial application of the process of the invention is well exemplified in the a spray or other distributing means. It is usually preferable to have cooling coils immersed in the reaction mixture so that excessive temperature rise is avoided.

. mixture containing The use of towers makes possible continuous operation, the acid, oleflnic gases and gasoline being separately injected into a mixing box of some character at the top of the column and the mixture allowed to flow by gravity down over pans or perforated plates so that more or less com. plete reaction is assured by the time the reaction constituents reach the bottom of the tower. In some cases the acid and gasoline may be caused to counterflow treatment.

An example involving the treatment of a Pennsylvania straight run when a blend of 90 parts of a' test gasoline showing 67.5 octane number and 10 parts of this gasoline were tated. an anti-knock value of 52 octane number was obtained.

This gasoline was treated with an olefinic gas approximately 40% propylene by volume, this gas being produced in conjunction with cracking thefuel oil distillate to produce gasoline. Acid of 1.835 specific gravity was used. In the run of the straight run gasoline, 3.5 gallons of acid alkylated hydrocarbons was produced based on as conducted 5.5 gallons ing the volume of the original gasoline. The properties of the alkylated product were as follows:

Gravity A. P. I. 55. 6 Initial boiling point F 86 10% over at 177 F. 20% over at 210 30% over at 238 40% over at 258 over at 298 over at 344 over at 397 over at 490 End boiling point 542 When this product was again used in 10% blend with the reference fuel of 67.5 octane number, the blend tested 83 octane number which indicates the remarkable improvement effected by the treatment since the average boiling point of the product was considerably higher than the original gasoline and yet the anti-knock value was much higher as shown by comparing the octane numbers.

The blending fluid thus produced could be distilled after a caustic wash with no change in color or odor or the development of sulfur compounds due to decomposition of soluble acid esters.

The foregoing specification has described and disclosed the general and broad character of the invention and the example is sufliciently indicative of its value from a commercial standpoint. owever, the invention is not limited in scope to e exact details of the descriptive material or the experimental data given.

I claim as my invention:

1. A process for the production of high antiknock motor fuel, which comprises simultaneously subjecting a straight run distillate containing gasoline hydrocarbons and gases resulting from a cracking. Process to the action of sulphuric acid, and reacting oleflns contained in the gases with a portion of the distillate to form alkylated derivatives of high anti-knock rating.

2. A process for the production of high antiknock motor fuel, which comprises simultaneously subjecting a straight run distillate containing gasoline hydrocarbons and gases containing olefin hydrocarbons to the action of sulphuric acid, and reacting olefins contained in the gases with a portion of the distillate to form alkylated derivatives of high anti-knock rating.

3. A process for the production of high antiknock motor fuel, which comprises simultaneously subjecting a straight run distillate containgasoline hydrocarbons of a predominately paramnic character and gases containing olefin hydrocarbons to the action of sulphuric acid, and reacting oleflns contained in the gases with a portion of the distillate to form alkylated derivatives of high anti-knock rating.

' VLADIMIR IPATIEFF.