US2404050A - Production of motor fuels - Google Patents

Description

July 16, 1946. G. R. GILBERT PRODUCTION OF MOTOR FUELS Filed Feb. 22, 1943 Y, 2:52am 0:2200 o .252...

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Patented July 16," 1946 2,404,050 PRODUCTION OF MOTOR FUELS George R. Gilbert, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application February 22, 1943, Serial No. 476,709

cerned with a process for the simultaneous pron duction of a relatively high octane number motor fuel, a high octane number aviation-gasoline and an olelinic gas.

In the alkylation of normally gaseous olens with isoparaiiins such as isobutane and isopentane using sulfuric acid as the catalyst there i's produced a saturated mixture of liquid hydrocarbons boiling in the range between about 120 F. and 500 F. The material boiling between the ranges of 120 F. and about 275 F. is usually removed frorn the product by fractional distillation and is used as such in aviation fuels because of its saturated nature and high octane number. The fraction boiling between 275 F. and about 320 F. or higher is used as an aviation blend stock while the fractions boiling above 320 F. are usually blended into fuels for use in automotive equipment. The present invention is concerned with a conversion of these higherboiling fractions produced by alkylation of isoparaflins with oleiins into motor fuels of suitable boiling range for use in internal combustion engines and of an appreciably higher octane number than that of the heavier fractions removed from the alkylation product. An important feature of the present invention is the production of large quantities of gases rich in olefmic constituents which find wide use in syntheses In its broadest aspects, the present invention contemplates a process for the production of three valuable constituents from olens and isoparaflins, by reacting an isoparaflin with an olelin by the well known sulfuric acid alkylation process, separating the resulting alkylation product so that isobutane is recovered for recycling to the process, normal butano is discarded and aviation gasoline is segregated for use as such, and submitting the heavier fractions to thermal or catalytic reforming. The products from the thermal or catalytic reforming are then submitted to a fractionation whereby constituents comprising propane or lighter hydrocarbons are separated and olenic fractions comprising the C4 hydrocarbons are obtained. A heavier fraction boiling in the gasoline range having an appreciably higher octane number than that of the heaviest fraction in the original alkylate is removed and recovered.

1 Claim. (Cl. 19E-52) invention, the material of high octane number produced by thermal or catalytic reforming of the heaviest alkylate fraction is largely saturated in nature and thus finds ready acceptance as a motor fuel. While this fraction is suitable for use as a motor fuel by virtue of its high concentration of isoparaiinic hydrocarbons, it also may be adapted for use in aviation gasoline provided the small amount of olefins contained therein are removed so that the desirable isoparans may be recovered.

The olefinic fractions resulting from the present operation find ready acceptance for production of still larger amounts of the constituents of aviation fuel by recycling them to the alkylation Zone or they may be used as raw materials for the production of the diolens which nd ready use in the manufacture of synthetic rubber.

In fact, the invention specifically contemplates that the heaviest alkylate fractions may be thermally or catalytically reformed in the presence of steam for high conversions of the alkylate fractions to isobutylene, which is an important ingredient in the manufacture of butyl rubber.

In the foregoing discussion the term thermal or catalytic reforming has been used frequently. By thermal or catalytic reforming is meant conversion of the hydrocarbon molecules of the heaviest alkylate fraction into components of a less saturated nature having a lower molecular weight and lower boiling points than that of the material charged to the thermal or catalytic reforming Zone, It is understood that this term employed hereinbefore and hereinafter may also include rearrangement as well as cleavage reactions of the hydrocarbon molecules. The degree of conversion is so regulated in the practice of the present invention by adjustment of the temperature and pressure in the conversion that it does not substantially exceed 30% by weight of the charge.

The invention will be more fully described by reference to the accompanying drawing in which the single figure is a flow diagram illustrating a general method of ow for the process of the present invention.

Referring now to the drawing, an olel'lnic hydrocarbon feed, which for purposes of illustration will be assumed to comprise the C4 mono-olefins, is introduced into the system by means of line I and is charged into alkylation zone 2 along with a stream of an isoparain, such as isobutane, which admixes with' the olen feed in line I by way of line 3. Alkylation Zone 2 is understood to YBy operating in accordance, with the present comprise a sulfuric acid alkylation system or any other catalytic alkylation system whereby isoparafhn and oleiins are caused to react. Since alkylation is a well established reaction the details of its operation will not be gone into at this time.

The product resulting from the reaction of olefins and isoparaflin in alkylation reaction zone 2 are discharged therefrom by way of line 4 into fractionation Zone 5. Fractionation zone 5 may comprise one or more fractionation towers Whereby provision is made for discarding propane and lighter hydrocarbons therefrom through line 6, segregation of unreacted isoparafiins by way of line l, removal of normal butanefrom .the system through line 8 and recovery of a fraction suitable for aviation gasoline from fractionation Zone 5 by Way of line 9. After removal of these several fractions from the alkylate there remains.

a fraction boiling between about 320 F. and 500D F. which is unsuitable for use other than in motor fuel.

The latter fraction is withdrawn from fractionation Zone 5 by way of line l@ and is introduced thereby into thermal or catalytic reforming Zone H in which by application of suitable temperatures and pressures or by the effect of catalysis the heavy alkylate material is converted into constituents of lower molecular weight and boiling points. This latter fraction is discharged from thermal or catalytic reforming zone l l through reducing valve I2 located in line i3 which connects to fractionation zone i4. The reformed material introduced into fractionation zone I4 by way of line I3 is subjected to suitable conditions of temperature and pressure whereby propane and lighter fractions are distilled therefrom and removed from the system by way of line i5 and a C4 fraction comprising the olefinic constituents is discharged from the fractionation Zone Iii by way of line l5 which connects into line 3 whereby they admix with isobutane recycled from fractionation Zone 5 by Way of line l and 3 for mixing With the o-len feed in line i. Make-up isobutane to provide a high ratio of isoparaiiins to olefins is introduced into line 3 by way of line i9.

The olenns discharged from fractionation zone iii by line l5 may either be recycled to the alkylaticn Zone as described or may be discharged from the system through branch line ll; thereafter they may be subjected to further treatment 50 for production of diolens for use in the manufacture of synthetic rubbers.

.a fraction having an appreciably higher octane number than that of the material discharged from fractionation zone 5 through line lil is recovered from fractionation Zone i4 by way of line i3 and may be used as such asa motor gasoline 0r it may be submitted to further treatment for separation therefrom of isoparaninic constituents which find usage in aviation fuels.

In thermal or catalytic reforming Zone Il, the conditions of temperature and pressure will vary widely depending on whether merely thermal or catalytic treatment is employed. When operating with thermal treatment solely a temperature between about 900 F. and 1100 F. Yand a pressure of iGO to 600 lbs/sq. in. gauge will give good results. When operating with catalytic treatment somewhat milder conditions will obtain. Temperatures in the range from about 750 F. to about 900 F. and pressures up to 150 lbs/sq. in. gauge have been found suitable. Silica-alumina catalysts and the like have been found suitable fox` these types of vreforming operations. Also activated alumina, specially treated clays, chromium oxide-alumina combinations and the like may be used.

Mention has been made hereinbefore of reforming the heaviest alkylate fraction by thermal treament in the presence of steam to produce isobutylene. When operating in this particular manner employing steam, a pressure up to about lb./sq. in. gauge and a temperature of about 1000 F. with' about 60 mol per cent of steam based on the charge included with the feed, gave high conversions 0f heavy alkylate fractions to isobutylene with yields of about 30 lbs. of isobutylene per bbl. of charge at about 30 per cent feed conversion with a short contact time 0f the f order of about 15 to 30 seconds.

It is to be emphasized in the practice of the present invention that the conditions of thermal or catalytic reforming should not be too severe since severe conditions might cause serious coking but should be severe enough to allow obtaining of the desired results. This particular feature is obtained by careful control of temperatures and pressures and time of contact.

In thermal reforming operations, the time of contact of the hydrocarbon at the high temperatures specified should not exceed 60 seconds. Preferably the contact times should range between one and forty seconds.

The invention will be further described by reference to the following examples in which typical operations of reforming in accordance with the present invention are illustrated. In each 0f the examples given below the charge stock to the reforming operation was derived from an alkylation process in which isobutane was alkylated with butylenes in one system and isobutane was allylated with pentylenes in another system. Both systems employed sulfuric acid as a catalyst with the two alkylates being debutanized and depentanized separately and the combined heavier fractions from the debutanization and depenta, nization fractionally distilled in another fractionation stage to discard a fraction Vboiling be- 10W 280 F. and to obtain a heavier boiling material. This latter heavy material was employed as a charge stock in the several reforming runs described below. This material was characterized by having an A. P. I. gravity of 55.5 F., a boiling range of 303 F. to 500 F., an ASTM octane number of 80.4, and a C. F. R. octane number of 74.8.

Example 1 A portion of the above described charge stock was passed through a thermal reforming unit operating at a maximum tube metal temperature of 950 F., a gauge pressure of 150 lbs/sq. in. and under ow conditions such that 15.3 per cent by weight of the charge stock was converted into hydrocarbons of different bo-iling range. The product from this reforming operation was debutanized and a 400 F. end point material fractionated out of the total product. This latter material had an A. P. I. gravity of 57.4, a boiling range of 82 F. to 382 F. and a C, F, R. octane number of 85.8. In addition to this material of improved-octane number, gases containing 1.2 per cent by Weight of ethylene, 6.3 per cent by weight of propylene, 24.2 per cent by weight of butyienes and 25.5 per cent of pentylenes were obtained, Each of the latter three constituents have been found suitable in alkylatio-n reactions.

Example 2 A portion of the same charge material employed in Example 1 was charged to a reforming unit operating at a maximum tube metal temperature of 1000o F., 500 lbs/sq. in. gauge pressure and under fiow conditions such that 29.2 per cent by weight of the charge was converted into hydrocarbons of diierent boiling range. The product from this reforming operation was debutanized and a fraction having a 57.6 A. P. I. gravity, a boiling range of 108-394" F. and a C. F. R. octane number of 88.4 was obtained.

Besides the large increase in octane number resulting from this operation, the gases segregated by distillation of the reformed product contained 1.8 per cent by weight of ethylene, '1.5 per cent by Weight of propylene, 23.1 per cent by weight of butylenes and 14.2 per cent by weight of pentylenes. It was found that the quantity of gasoline in the charge stock of the reforming operation was only 54.5 per cent by volume while the reformed product contained, in this particular instance, 57 per cent of gasoline.

In operations such as those described in Example 1, the amount of gasoline in the reformed product was increased to 72.2 per cent. While the conversion of the heavy alkylate is increased by raising temperatures and pressures, it is at the sacrice of gasoline constituents as evidenced by the data. Operations at lower temperatures of about 950 F. and pressures in the range of about Cil 350 to 500 lbs/sq. in gauge were observed to give the best results in the particular thermal operations described.

While the present invention has been described with relation to the alkylation of butylenes with isobutane, it is to be clearly understood that other olens and other isoparalins besides those mentioned may be used with equal success.

The nature and objects of the present invention having thus been fully described and illustrated, what I desire to claim as new and useful and to secure by Letters Patent is:

A process for converting products resulting from the alkylation of isoparaflins with olefns into materials of higher octane number and materials of a less saturated nature which comprises reforming an alkylate fraction boiling above 300 F. at temperatures between 750 F. and 1100 F. and at pressures between 100 pounds per square inch gauge and 600 pounds per square inch gauge for a time suicient for production of a product of lower molecular weight and boiling point than the charge to an extent of not substantially more than 30% by weight of said charge, and recovering by distillation of said product olens and a high octane number substantially saturated fuel.

GEORGE R. GILBERT.

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