US1967636A - Treatment of hydrocarbon oils - Google Patents

Description

y 24, 1934- c. c. TOWNE ,6

TREATMENT OF HYDROCARBON OILS Filed Oct. 30, 1950 COOLER FU/PNRCE ORNEY Patented July 2 2%,.

PATENT OFFICE TREATMENT OF HYDROCARBON OILS Charlec. Towne, Elizabeth, N. 1., assignor to The Texas Company,-New York, N. Y., a corporation of Delaware Application October 30, 1930, Serial No. 492,371

2 Claim.

This invention relates to the treatment of hydrocarbon oils and has to do particularly with the reforming of oils in the vapor phase to improve the anti-lmock property.

In accordance with the invention, a light oil such as naphtha or gasoline is vaporized and the vapors intimately contacted with a suitable catalyst for a period of time and at a temperature sufllcient to reform the oil into a product having improved anti-lmock quality for use as a fuel in internal combustion engines.

It is well known that gasolines difier widely in anti-knock quality and that it isdesirablethat they be as nearly free from knocking or detonation as possible. Gasolines derived from cracking heavy oils usually exhibit anti-knock properties to a more or less extent, depending on the nature of the oil and the extent of the cracking. Some straight run gasolines also show the same characteristics to some degree, especially those from naphthenic base crudes. Most straight run products, however, have very pronounced knocking tendencies. This is especially true of those derived from the paraflin base crudes as typified by those from the Pennsyl-' The present invention, while particularly adapted to the treatment of low boiling point oils such as straight run gasolines or naphthas, is not wholly limited to these materi As. It contemplates the treatment of many other;volatile hydrocarbon oils which are undesirable for mo.- tor fuels because of the tendency to knock. Dis tillates 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. For example, it may be desirable to make a productof high anti-knock quality to be marketed as a premium fuel or it may be an advantage to treat a small volume of a suitable oil to produce a blending agent having high anti-knock character and then blending this with another product to produce the desired fuel. The scope of the invention will be further observed as the details of the process are described.

More particularly, according to the invention, the oil to be treated, for example Pennsylvania straight run gasoline or naphtha, is vaporized and the vapors consisting of compounds substantially within the boiling range of gasoline are passed over a catalyst at a high temperature. The vapors are cracked or dehydrogenated during this treatment and a product containing relatively large amounts of unsaturated and aromatic hydrocarbons is produced. The catalyst and the high temperature have the efiect of dissociating or releasing the hydrogen from the saturated molecules making up the gasoline, thereby producing unsaturated or cracked products. These products either remain in the cracked or unsaturated form or they may recombine to produce new compounds such as aromatic derivatives. High temperature alone, while capable of producing a certain-degree of conversion, nevertheless is impractical because of the low yield and the excessive losses through incondensable gases, as well as production of bad color and odor. By using an appropriate catalyst, the temperature can be greatly reduced, thereby decreasing the severity of the treatment and at the same time obtaining a selective reaction,. which produces the optimum yield of desired compounds.

Generally, in all catalytic reactions, the type of catalyst is the most important factor contributing to produce the desired results. So, in the process of the invention herein described, the selection of a proper catalyst determines to a large extent the success of the process. This does not mean that other factors also are not important. For example, temperature, time, pressure and purity of the oil must be taken into consideration in determining the optimum conditions. These conditions are not, however, entirely independent of the catalyst. It has been found that the more active the catalyst, the lower the temperature and the shorter the time required. Furthermore, with a given catalyst, a low temperature and a long time or a high temperature and a short time usually will give analogous results.

Catalysts which have been found to be especially eifective for use according to the invention, will now be described. Activated carbons havin the greatest surfaces for adsorption are very effective. Included in these carbons are those which are suitable as decolorizing agents for oils, sugar solutions etc., such as specially prepared vegetable and animal charcoals. It has been noted that carbon deposited on porous contact materials such as silica gel, or other suitable supporting agent, functions to produce substantially carbon, the carbon becomes deposited in the pores 11 of the contact material, and progressively increases the efliciency of the catalyst.

The method of depositing the activated carbon upon the porous material, as outlined above, may be undesirable in some cases. For example, the production of the catalytic carbon from the oil undergoing treatment may be uneconomical and the process unnecessarily time consuming. The invention, therefore, contemplates other means for the production of the activated carbon and subsequent deposition upon the porous supporting material. Thus the carbon may be produced by ordinary methods, such as are well known in the art of production of activated carbon from vegetable or animal sources. The prepared carbon may then be packed into the pores of the contact material and set thereby a suitable heat treatment, if desired. Or again, the carbon may be derived from an extraneous oil, such as a somewhat heavier paraflin oil than the one to be dehydrogenated or an aromatic oil rich in carbon, and deposited in the pores by a preliminary step prior to the treatment of the oil to be dehydrogenated.

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 means such as a burner or by electricity. Located within the furnace setting is a tubular heater 4. This heater is shown as an elongated tube but it may take other forms, for example, an enlarged chamber. The catalyst is preferably packed in the tube or 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 heater while a discharge line 8 is adapted to transfer the cracked products from the heater to a cooler 10. The cooler 10 is shown as an ordinary cooling box which may be supplied with any suitable cooling medium to cool the coil 12 located therein. It is preferable, however, that the cooler assume the form of a heat exchanger in which the charging stock is preheated. It is also contemplated that the cooler may comprise two or more exchangers whereby the rich absorbent oil from the absorber, referred to hereinafter, may receive heat for rerunning or distilling the absorbed hydrocarbons therefrom in a rerun still.

Line 1'4 serves to conduct the products from the cooler to the separator 16. 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 draw-off line 18 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. However, it is preferable to use a liquid absorbent which may be introduced in a lean condition through the line 24 and withdrawn in a rich condition through line 26 and sent to the heat exchanger, as referred to heretofore. 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 wherebyan oxidizing gas may be contacted with the catalyst in the heater to revivify the catalyst when desired. The gaseous reaction products may then be exhausted through a line 34 communicating with the transfer line 8.

memes In practicing the invention a suitable catalyst is selected. If activated carbon alone is used as a catalyst, it is heated to a. temperature in excess of 450 0., preferably 500 C. to 600 C. and vapors of the oil to be cracked passed through the catalyst. If it is desired to use a catalyst consisting of ,carbon deposited on a porous contact material, then a porous material, such as silica gel, preferably about 10 to 20 mesh, is used. This material is heated to a temperature in excess of 450 0., preferably 500 C. to 700 C. and the oil to be treated passed through it at this temperature. The porous material gradually becomes impregnated with active carbon, thereby producing an efficient catalyst. It has been noted that a certain time is required before appreciable dehydrogenation reaction starts; this is presumably an induction'period, during which the porous material is becoming impregnated with the carbon. After the reaction begins, it has been found that there is a progressive increase in efficiency as the oil is treated. The catalyst, however, after prolonged usereaches a maximum of efliciency and begins to degenerate. It is desirable, therefore, after the efliciency has decreased a substantial amount to cease the flow of oil vapors and then pass air through the catalyst to revivify it. A short treatment with an oxidizing gas, such as air or oxygen, at the same temperature removes substantially all the spent carbon from the pores of the material and works almost a complete regeneration of the catalyst. When oil vapors are again passed through the revivified catalyst the dehydrogenation reaction is repeated as described above.

According to another embodiment of the invention, the porous material may be impregnated with carbon wholly or partially, prior to the treatment of the oil to be converted. The methods of impregnation have been described heretofore. If only partial impregnation is made prior to the dehydrogenation treatment then the remainder may be obtained during the operation of the process. The induction period which is noted in the previously described modification wherein the carbon is deposited during the reaction, may be substantially reduced in the present embodiment. The carbon, in this instance also, may be removed. when it becomes spent or inactive by passing air through the catalytic material at a high temperature thereby recovering the porous contact agent which may be impregnated with more carbon to produce a fresh catalyst.

In general, the temperature and the type of catalyst are the most important factors in pracsome instances,. either to increase the severity of the treatment or to decrease the volume of vapors handled, it may be desirable to increase the pressure considerably above atmospheric and the invention accordingly contemplates such conditions. The time of contact of the vapors with the catalyst will of course vary with the type of catalyst, the character of the oil and the desired anti-knock quality of the finished product. It has been observed, however, that the anti-knock value of an average straight run naphtha from parafiin base crudes creased by subjecting peratures to the action of a suitable catalyst at the rate of 25 to 100 arrels of oil per 100 pounds of catalyst.

may be substantially inthe vapors at proper tem- The details in description of the process are made for purposes of illustration and the various modifications that will occur to those skilled in the art and that may be made without departing from the spirit of the invention are intended to be included within the scope of the appended claims.

I claim:

1. In the manufacture of gasoline of high antiknock value, the process that comprises subjecting a straight run petroleum distillate consisting essentially of constituents within the gasoline range, in the vapor phase, to a temperature of 500700 C. while in the presence of silica gel impregnated with activated carbon, whereby transformation 'of hydrocarbon constituents, without any material increase in quantity thereof boiling within said range, into produots'of increased anti-knock value is effected, and separating from the resulting products of reaction a gasoline of said range having a high anti-knock value.

2. In the manufacture of gasoline of high antiknock value, the process that comprises passing a hydrocarbon distillate consisting essentially of straight run gasoline in contact with a silica gel catalyst at a temperature of about 500'700 C. to eii'ect transformation of hydrocarbon constituents into products of increased anti-knock value, regulating the temperature and rate of treatment to cause a gradual increase in efliciency 01' the catalyst by deposition of activated carbon thereon, and separating from the resultant product a gasoline having a high anti-knock value.

CHARLES C. TOWNE.

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