US2086287A - Treatment of hydrocarbon oils - Google Patents

Description

July 6, 1937.

C. C. TOWNE 2,086,287 TREATMENT OF HYDROCARBON OILS- 4 Filed, May 31, 19:55

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Q 3 Q Q INVENTOR t CHARLES 0. TOWN! ATTORN EY Patented July 6, 1937.

UNITED STATES TREATMENT OF HYDROCARBON OILS Charles C. Towne, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application May 31, 1935, Serial No. 2 4,349

1 Claim.

This application is a continuation in part of my co-pending application, Serial No. 496,038, filed November 15, 1930.

This invention relates to the conversion of hydrocarbon oils and has to do particularly with the catalytic conversion or. reforming in the vapor phase of low boiling hydrocarbons, such as gasoline or naphtha, to improve the anti-knock property.

Most of the gasolines used in internal combustion engines are derived from two general sources. One of these is the straight distillation of crude oil to recover a product known as a straight run gasoline. The other comprises the conversion of high boiling petroleum oils into low boiling products by cracking, hydrogenation or similar processes.- The straight run product, ex cept in the case of gasoline derived from naphthene base crudes, is usually poor in anti-knock quality and causes considerabledetonation when used in internal combustion engines. The cracked gasolines are usually somewhat superior in anti-knock property and have been used ex-' tensively for blending with straight run products to improve the anti-knock quality of the latter.

The standard of quality for anti-knock gasoline has been constantly rising in recent years. Fo'rmerly, it was possible to utilize a straight run product as such, or blends of straight run gasoline with cracked products to produce a satisfactory motor fuel. More recently, either because of the construction of internal combustion engines or to the desire of the motoring public for a superior fuel, gasoline of higher anti-knock property than is possible to be obtained from the ordinary straight run products has been demanded. Consequently, cracked products are now used unblended in the production of suitable motor-fuels and even then it has been necessary in many cases to improve the cracked fuel by addition of certain anti-knock agents. Cracked products no longer are available to blend with straight run gasolines to improve the anti-knock quality, and as a result the problem of disposing 'of straight run gasoline has become of considera ble consequence to refiners. To cope with this situation, it has become customary to load straight run gasoline with large quantities of expensive anti-knock agents such as tetraethyl lead or similar material.

The present invention aims at a method of treating gasolines or naphtha which are undesirable from a knocking standpoint to improve the anti-knock property wthout resorting to the addition of artificial anti-knock materials or, at

least, to convert the original materials into products having an improved anti-knock. property so that the addition of anti-knock agents can be considerably decreased. The invention contemplates the accomplishment of this aim by reforming the compounds which are the principal cause of detonation into products of less knocking property or even into materials which exhibit a positive anti-knock influence. The principal knocking compounds in straight run gasoline from partreatment of such materials. It contemplates the treatment of many other volatile hydrocarbon oils which are undesirable for motor fuels because of the tendency to knock. These may com prise products of somewhat higher boiling range than gasoline but yet yield products boiling subv stantially within the range ofgasoline after treatment. In some instances, therefore, it may be desirable to treat materials within the boiling range of kerosene or gas oil. Distillates which have undergone partial cracking also come within the scope of the invention, as well as other products'which may have some anti-knock characteristics, but it is desirable to increase this property. It may be of advantage in some instances to make a product of high anti-knock property to be marketed as a premium-fuel or it may be de-" sirable to treat a small volume of oil to prepare a material having a high anti-knock character to blend with an undesirable product to produce a satisfactory anti-knock fuel. The scope of the invention will be further observed as the details of the process are described.

More particularly, according to the invention, I

the oil to be treated, for example, an oil boiling substantially within the range of gasoline, such as 1 Pennsylvania straight run gasoline or naphtha, is vaporized and the vapors subjected to the action 'of a suitable catalyst heated to a high temperature. The vapors are converted into unsaturated and aromatic compounds which tend to improve the anti-knock property of the final'prodnot. The conversion may comprise deethanation, demethanation, dehydrogenation or simply cracking of the higher boiling products into lower boiling oils. The catalyst and the high temperature are presumed to have the effect of diwociating hydrogen, methane and ethane from the moloptimum yield of desired compounds.

Catalysts that have been found to be especially active for converting oils according to the process of the invention comprise certain porous inorganic materials or minerals, particularly adsorptive earths and clays. Natural occurring p0- rous minerals such as beauxite and adsorptive clays, such as Attapulgus clay and various domestic and foreign types of fullers earth have been found to be particularly active for this purpose. All of these catalytic, materials are relatively porous and provide large surfaces for contact with the vapors, which presumably promotes the desired reactions. The porosity of the catalytic materials is thought to be further increased by a suitable heat treatment sufficient to dehydrate the materials and referred to hereinafter as activation. I

The natural occurring minute beauxite, presumably the dihydrate of aluminum oxide is considerably more efiicient than artificially prepared aluminum oxide, from which it is to be distinguished. To obtain the maximum benefit from beauxite as a catalyst, it is important that the sample be as pure as possible. Certain samples of beauxite contain considerable quantities of undesirable foreign materials such as iron oxide. It is preferable that the sample used as a catalyst in the process be substantially free from impurities. A small amount of -iron has been found to cause a rapid decrease in activity of the catalyst. Thus, five per cent iron oxide has been noted to cause a sample of beauxite to become inactive as a, catalyst in a relatively short time.

The catalytic efliciency of many of the minerals mentioned heretofore may be increased by the deposition of certain metallic oxides upon the surfaces thereof. Nickel oxide and zinc oxide, for example, deposited in the pores of the catalytic materials have;been found to substantially increase the activity. The impregnation with metallic oxides may be accomplished by soaking the porous materials in a strong solution of salts of the metals, such as the nitrates, and then decomposing the salt into the oxide at a high temperature. The mineral to be impregnated is preferably roasted at a temperature of 500 C.- 700 C. prior to saturation .with the nitrate solution. The saturated material is then heated to about 600 C.-700 C. to decompose the nitrate and deposit the oxide within the pores. By roasting beauxite, for example, at about 700 C., saturating the roasted material with nickel nitrate solution, and then decomposing the nitrate at 600 C.-700 C. to deposit the oxide within .the pores thereof, the emciency of the catalyst was increased so that the temperatm'e for treating hydrocarbon vapors to improve the anti-knock quality could be substantially reduced. Thus,

hydrocarbon vapors can be treated at about 50 C. lower than is ordinarily necessary when using the unimpregnated mineral and yet obtain practically the same results.

,l'.n practicing the invention a straight run gasoline or naphtha is vaporized and the vapors passed through a catalyst at a high temperature, preferably in the neighborhood of 600 C., ranging between 500 C. and 700- C. able that the catalyst be activated by heating to 550 C. or thereabouts, for approximately three hours immediately prior to the treatment of the vapors. The catalytic material should be of relatively coarse mesh, preferably from 12 to 20 mesh, in order that the vapors may readily pass therethrough. While 500 C. .to 700 C.

has been given as a range for the temperatureof treating the vapors, it has been found that the reaction is relatively slow in the neighborhood of 500 C. and at 700 C. the reaction is very rapid, accompanied by high loss as incondensable gases. However, by treating a straight run gasoline of low anti-knock property at about 600 C., an increase in the total aromatic and unsaturated content of the vapors of about 20 to40 percent has been noted. Thus, a sample of Pennsylvania gasoline having a total aromatic and unsaturated content of approximately 9 percent has been converted to a product of approximately 40 percent aromatic and unsaturated content. By coating the catalyst with a metallic oxide, as heretofore described, substan- 'tially the same results may be obtained at a temperature of about 50 C. lower than that in.- dicated above. Beauxite, for example, impregnated with nickel oxide produced results at 550 C comparable with those obtained at 600 C. prior to impregnation. a

On continued use of the catalyst, it has been noted that a gradual decrease in activity occurs. This may be due to deposition of carbon within the pores thereof or a poisoning effect caused by sulfur compounds or other impurities in the oil. It has been found possible, however, to restore the spent catalytic material, particularly beauxite, by a suitable reviviflcation treatment. This treatment consists of passing an oxidizing gas such as oxygen or air through the catalyst at high temperature. A su table temperature for this purpose has been found to be about 700 0.; however, it may be stated that the reviviflcation should be carried out at a temperature not substantially below that at which the vapors have been treated. The effect of treating the catalyst with an oxidizing gas is presumably to burn off the carbon, remove undesirable products deposited in the pores of the catalyst, and,

in general, to reconvert the material into an acticularly at the higher temperatures. This lossmay be reduced by suitable scrubbing of the tail gases to recover the volatilegasoline content.

It is prefer- The recovery may be practiced by processes well known in the art of recovery of gasoline from natural gas. Thus it may be done by absorption of the vapors in charcoal or a liquid absorption medium, such as mineral seal. The vapors recovered from the absorption material are preferably combined with the original distillate obtained during the process and in this way the yield of anti-knock gasoline can be substantially increased.

The accompanying drawing shows one form of apparatus for carrying out the process of the invention wherein the numeral 2 represents a furnace setting which may receive heat from any suitable source such as a burner or electrical means. Located within the furnace setting is a converter 4. This converter is shown as an elongated tube in which the oil is vaporized in the first part'and is then converted in the presence of a catalyst in the latter part thereof; however, it may take other forms, for example, a

heated vaporizing tube and an enlarged conversion chamber. The catalyst is preferably packed in the tube or in the case of a chamber it may otherwise be disposed therein, such as on shelves or trays. Supply line 6 serves to conduct the hydrocarbons to be cracked to the converter while a discharge line 8 is adapted to transfer the cracked products from the converter to a cooler in. The cooler I is shown asan ordinary cooling box which may be supplied with any suitable cooling medium to cool the coil l2 located therein.

Line It serves to conduct the products from the cooler to the separator l6. This separator may be any well-known or preferred type in which distillation and fractionation may or may not occur. The separator 16 is provided with a draw-ofi line l8 for withdrawing the liquid products separated therein. A. vapor line 20 serves to conduct the 'uncondensed vapors and gases. to an absorber 22 and the absorber may be charged with solid absorbent medium such as charcoal. Howev it is preferable to use in the absorber a liquid absorbent which may be introduced in a lean condition through the line 24 and withdrawn in a rich condition through line 26. Dry gases, from which the desired hydrocarbons have been absorbed, are released through line 28.

Referring again to supply line 6, connections 30 and 32 are provided to introduce air or steam respectively to the charge line whereby an oxidizing gas may be contacted with thecatalyst in the heater to revivify the .catalyst when desired.

The gaseous reaction products may then be exhausted, if desired, through a line 34 communieating with the transfer line 8.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

I claim: 4 The method of increasing the anti-knock quality of motor fuel that comprises subjecting a hydrocarbon oil consisting substantially entirely of gasoline of low anti-knock value to a temperature within the range of 500 C. to 700 C. in the presence of bauxite impregnated with nickel oxide. maintaining said oil in the presence of said bauxite for a time adequate to effect transformation of hydrocarbon constituents, without any material increase in the quantity thereof boiling within the gasoline range, into products of increased anti-knockvalue and separating from the resulting products of reaction a gasoline having a high anti-knock value.

' CHARLES C. TOWNE.

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