US2401636A - Process for reducing the olefin content of an olefinic distillate - Google Patents

Description

June 4, 1946 v. HAENSEL ETAI.

PROCESS FOR REDUCING THE OLEFIN CONTENT OF AN OLEFINIC DISTILLATE Filed ont. 12, 1942 fffecf M JJ w y y W if 5 0 o n\ w P r Z a n 5 0 @H x\ o mf. U 0f dwm 0 e m@ J w ,m a x, .a mw m m o\ 7 a 5 m, w 0 WM j, i .M \v w W o\ x/ 4 W w 0 m m Patented June 4, 1946 PROCESS FCR REDUCING THE OLEFIN CON- TENT F AN OLEFINIC DISTILLATE Vladimir Haensel and Vladimir N. Ipatiefl', Chicago, Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation of Dela- Wavre Application ctober 12, 1942, Serial No. 461,772

4 Claims. 1

This invention relates to a method for the reduction of the olen content of a. hydrocarbon fraction. More specifically it is concerned with a method of reducing the bromlne number of a gasoline boiling range fraction to prepare a hydrocarbon fraction suitable for aviation fuel purposes.

Cracking or reforming operations generally produce gasolines which have a high initial octane number but which have a relatively low lead susceptibility because of their high olen content. For this reason, gasolines produced by these processes are usually unsatisfactory as aviation fuel base stocks.

We have found that a gasoline of -low olefin content may be obtained by contacting an olenic gasoline substantially free of added higher boiling hydrocarbons with a particular type of silica base catalyst at proper operating conditions. We have found that when the proper operating conditions are employed, that fraction of the product which boils within the boiling range of the charging material will have a bromine number less than half that of the charging material with a resultant increase in lead susceptibility. In this manner the aviation characteristics of an olefnic gasoline may be improved.

It is, therefore, an object of our invention to produce a fraction boiling in the gasoline range having a bromine numberof less than half that of the corresponding fraction of the charge.

It is a further object of our invention to produce from an olenic naphtha a hydrocarbon product, that fraction of which boiling below the endpoint of the naphtha charge has a l-C octane number with 4 ml. of tetraethyl lead per gallon at least 5 units higher than the corresponding leaded octane number of the charge. Furthermore for most satisfactory use in preparing aviation fuel blends, the 1C octane number of the product with 4 ml. of tetraethyl lead per gallon should be in excess of 85 and preferably in excess of 90. The 1-C method is described in A. S. T. M. 614- 41T.

It is another object of our invention to treat an oleflnic gasoline'fraction in the substantial -absence of added higher boiling hydrocarbons to 2 lysts may be prepared synthetically from compounds of silicon and compounds which will give rise to the other refractory oxide, or they may be obtained .from naturally occurring minerals. Thus, for example, the silica alumina composites which are employed in the present invention may be prepared by precipitation of hydrous silica and hydrous alumina from suitable solutions of compounds of silicon and aluminum, either by successive precipitation or by co-precipitation methods followed by drying and calcining. On the other hand, certain naturally occurring materials such as bentonite, montmorillonite, floridin, and other active clay like materials may be employed in the process of this invention preferably after activation by an acid treatment and/or calcination.

Although these catalysts have been previously used in some refining or treating processes, the purpose of these processes has been merely to remove relatively minor amounts of highly reactive and undesirable constituents of the charge, such as diolens and sulfur `compounds and has not been to effect any substantial reduction in the b'rornine number of the gasoline boiling range fractions to prepare a suitable aviation base blending stock. As previously noted, on the other hand, it is an object of this invention to produce from an olenic gasoline a gasoline fraction having a bromine number less than half that of the corresponding fraction of the original charge and suitable as an aviation base blending stock.

The process of this'invention is conducted at a temperature above 400 F. but below 650"A F. and is preferably within the range of from 450 to 600 F. The pressures which are employed are such that at least a substantial portion of the material in the reaction is in the liquid phase and will therefore usually be above about 300 pounds per square inch. In general pressures below 1000 pounds are adequate, the higher pressures being employed at the higher temperatures in order to aid in maintaining a substantial liquid phase in the reaction zone. The space velocities which are employed are below about 15 and will ordinarily range from about 0.3 to l5 unit weights of charging oil treated per hour per unit Weight of catalyst in the reaction zone. 'I'he preferred range is from about 0.5 to 5 units. A

In the preferred operating range of this in-V vention, the amount of cracking as measured by the accompanying gas formation is negligible and therefore almost 100% of the charge on a weight basis is recovered as a liquid. Since the amount of gas formation is negligible, the amount of catalyst deposit which is formed is also small when operating in the preferred range of temperature, pressure and space velocity. On the other hand, if temperatures are increased above 650 F., cracking begins to take place, gas and catalyst deposit are formed in increasing amounts and in general, the operation is unsuitable for our purposes.

In one specific embodiment, the present invention relates to a method for reducing the olen content of an olen containing fraction boiling in the gasoline range which comprises contacting said fraction in the substantial absence of added higher boiling hydrocarbons with a catalyst comprising an association of silica and at least one compound of an element whose oxide is refractory, at a temperature of above 400 F. but below 650 F without effecting substantial cracking, and at a pressure such that a substantial portion of the hydrocarbons in the reaction zone is in the liquid phase, to form a liquid product, that portion of which having an end boiling point corresponding to that of the fraction charged has a bromine number of less than half that of said fraction.

The charging stock which may be employed in this process may comprise any olenic naphtha fraction, gasoline or pure olenic hydrocarbon boiling in the gasoline range. Ordinarily, olenic naphtha fractions or gasolines \produced by cracking or reforming operations, preferably c talytic, will be employed since these charging materials are abundant and usually possess high initial octane numbers. As previously noted, the reaction is conducted in the substantial absence of added higher boiling hydrocarbons since these materials, as will be later demonstrated by specific examples, have been found detrimental.

The catalyst may be employed either in the form of granules, pellets or other preformed shapes, or in the form of a finely divided powder. In case granules are employed, the reactants may be continuously passed through a bed of the granular catalyst maintained at reaction conditions. If powdered catalyst is employed. the catalyst may be suspended in the reactant stream and conducted through a tubular reaction zone or through a vertical enlarged reaction zone in which the catalyst is maintained in turbulent motion by means of the upwardly rising reactants and conversion products.

The products from the reaction zone may be fractionated to separate a distillate of the desired end point from the bottoms. Any portion of the reaction products may, if desired, be returned to the reaction zone for further treatment.

Unlike other operations for producing aviation base stocks from olefinic hydrocarbons, the catalyst in this operation may be processed for a considerable length of time without having to regenerate. For example, timesof processing may range up to about 75 hours more or less and a product having the necessary low bromine number will be obtainable. Usually however, times of processing longer than two hours are employed for the reason that the catalyst is still active at that time.

When regeneration is required, it may be accomplished in situ by passing oxygen containing gases through the catalyst bed, or the catalyst may be removed to an external zone, regenerated by contact with oxygen containing gases, and returned to the processing zone for further use.

The following examples illustrate the yields and quality of the aviation fuel stock which may be obtained when operating according tothe process of the present invention.

Eample I.--In Tests l through 5, a 300 F. endpoint gasoline obtained by catalytic cracking of gas oil was the charging material. In these tests, the chargingv material was passed over a. silica alumina zirconia catalyst obtained by precipitation methods and the product from each test was fractionated to recover a 300 F. endpoint gasoline on which octane numbers and bromine numbers were obtained. These results of these tests are indicated below:

Ohm? Test No.

ing stock 1 l 2 I 3 4 i s Temperature F 390 475 520 581 639 Pressure lbs./sq. in.. 800 800 800 800 800 Weight hourly space vel ocity 1.8 1.8 1.9. 1.8 1.8 Time of processing. hours.. 18 18 1S 18 18 Distribution of product:

Per cent by weight of 200 F. E. P. gasoline 100.0 75.8 65.5 65.8 71.3 79.5 Per .cent by weight residue 24.2 34.5 34.2 28.7 20.5 300 F. E. P. gasoline` Br. No 57 26 20 27 45 Octane No., C+4

m1. TEL/gal 85.1 90.8 94.5 95.1 94.4 92.0

In each of the tests indicated above, the amount of gas that was produced was negligible and the amount of catalyst depositwas small, generally less than a few tenths of a percent by weight of the charging material.

It will be noted that the temperature in Test 1 was slightly below the preferred temperature range of this process and that the bromine number of the 300 F. endpoint product was greater than half the bromine number of the 300 F. endpoint charge. Tests 2 through `5, on the other hand, all resulted in the formation of 300 F. endpoint gasolines having bromine numbers less than half that of the charge, and it will be noted that the leaded l-C octane number was improved in direct proportion to the bromine number reduction. It will also be noted that a minimum in the bromine number of the product was obtained at about 520 F. as in Test 3 and thereafter increased with increasing temperature. If temperatures of 650 F. or higher are employed, the rate of cracking is sufliciently great so that carbon formation is excessive and as a result the bromine number is not reduced the required amount for the long process periods. The data from Tests 1-5 are shown on the accompanying drawing.

Example 2.-In Test 6 a 275 F. endpoint gasoline obtained from catalytic cracking was the charging material. In this test, the gasoline charge was contacted with a catalyst comprising a calcined mixture of precipitated hydrous silica and precipitated hydrous alumina at the conditions indicated below and the following data were obtained:

In this test the amount of gas formation was negligible and the catalyst deposit amounted to about .1% by weight of the charge, indicating that substantially no cracking had taken place. The high leaded octane number of the product indicated its extreme suitability as an aviation fuel blending stock.

Example 3.-In Test '7, shown below, the catalyst was a silica-magnesia composite prepared by impregnating alkali free silica hydrogel with magnesium nitrate and calcining to produce an active mass. The charging stock was a 278 F. endpoint gasoline obtained from catalytic cracking of a Mid-Continent gas oil. This catalyst, although not quite as active as the catalysts of the silica alumina and silica alumina zirconia type previously illustrated, nevertheless had an appreciable catalytic activity for this reaction. The results of the test are tabulated below:

Charging stock Test 7 Temperature F 531 Pressure lbs lsq. in 800 Weight hourly space velcc 1. 8

Time of processing hours., 16 Distribution of groduct:

280 F. E. gasoline per cent by weight.. 100 85. 4

Br. No 69 28 Octane number, 1-C+4 m1 ....TEL/gal 88. 9 93. 9

The amount of gas formation in Test 'I was negligible and the carbon yield amounted to about .25% by weight of the charge.

Ercample 4.-The following runs were made to determine the eiect of adding a gas oil to the olenic gasoline charge. In Test 8, an olenic gasoline obtained by catalytic cracking of a Mid- Continent gas oil was treated at optimum conditions with a precipitated calcined silica-alumina-zirconia catalyst and the yields and quality of the products were determined. In Test 9, 60% of the same gasoline on a volume basis (55% on a weight basis) was blended with another portion of the same Mid-Continent gas oil that was the cracking stock for the gasoline, and was treated with another portion of the same catalyst used in Test 8 at comparable conditions. The results of the tests are shown below:

As in the previous runs, substantially no gas was produced and formation of catalyst deposit was slight. It will be noted that the presence of the added gas oil in Test 9 was harmful in that the gasoline product had a higher bromine number and a lower leaded octane number than the Charging stock Test l0 Test 1l Temperature. 534 534 Pressure..... 800 800 Weight hourly spec 2. 1l 2. l. Time 0f promising hnnrs 15 15 Distribution of product:

280 F. E. P. asoline eight per cent.. 100. 0 73. 1 72. 6

Residue ,do-.. 26. 9 27. 5 280 F. E. P. gasoline:

Bromine number 69 11 12 O. N., 1-C-l-4 ml. TEL/gal.- 88.9 98.9 98.9

It is evident that the non-precipitated catalysts of the silica alumina type are very eiective in accomplishing this reaction. It should be noted that in the above tests the amount of cracking was negligible and the catalyst deposit amounted to about 0.2% by weight of the charge.

We claim as our invention:

1. A process for reducing the oleiin content of an olenic distillate boiling in the gasoline range which comprises subjecting said distillate to the action of a catalyst comprising precipitated silica and precipitated alumina at a temperature above 400" F. but below 650 F. under a pressure sufiicient to maintain a substantial portion of said distillate in liquid phase and at a weight hourly space velocity of from 0.3 to 15, whereby to form a gasoline fraction having a bromine number less than one-half that of said oleiinic distillate, and recovering said gasoline fraction from the products of the treatment.

2. A process for reducing the olen content of an olenic distillate boiling in the gasoline range which comprises subjecting said distillate to the action of a catalyst comprising silica and zirconia at a temperature above 400 F. but below 650 F. under a pressure suillcient to maintain a substantial lportion of said distillate in liquid phase and at a weight hourly space velocity of from 0.3 to 15, whereby to form a gasoline fraction having a bromine number less than onehalf that of said olefinic distillate, and recovering said gasoline fraction from the products of the treatment.

3. The process as defined in claim 2 further characterized in that said catalyst contains alumina in addition to the silica and zirconia.

4. The process as deilned in claim 1 further characterized in that said catalyst contains precipitated zirconia in addition to the precipitated silica and alumina.

VLADIMIR HAENiSEL. VIADIMIR N. IPATIEFF.

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