US2361008A - Process for the treatment of hydrocarbons - Google Patents

Description

Oct. 24,1944. 5 u us ETAL I 2,361,008

PROCESS FOR THE TREATMENT OF HYDROCARBONS Filed May 26, 1941 3 Sheets-Sheet 1 O In CONDENSER BOLVNOILDVHJ v Q HOLVNOIL'JVHJ HOLVNOIlDVHJ CATALYTIC CATALYTIC, ENATION FIG. I

BY a .5 MW

A1TORN Get. 24, 1944.

Filed May 26, 1941 5 Sheets-Sheet 2 HOLVNOILDVHJ EUWZMOZOU 4 w 0 u W O H HOLVNOILDVHJ HOLVNOILDV'HA HOLVNOILDVHJ zoF zmwomQ Imo 25 220 1944- E. BuDdRus ETAL 2,361,008

PROCESS FOR THE TREATMENT OF HYDROCARBONS Filed May 26, 1941 3 Sheets-Sheet 3 K] cw 455d 0.. O2 5 2 O Q l 373l ISOHEXANES 3so -ISOPENTANES 32s BUTANES AND LIGHTER i sowAR e oRus |RR|soN LOWE HAYS Patented Oct. 24, 1944 UNITED STATES PATENT PROCESS FOR THE TREATMENT OF HYDROCARBONS Application May 26, 1941, Serial No. 395,266

7 Claims.

combined catalytic desulfurization and dehydro genation treatment wherein hydrocarbons in the natural gasoline range comprise the charge stock to the process.

The advantages to be obtained through the utilization of higher octane number fuels over those of lower octane number in internal combustion engines designed for their use are well known to those who have knowledge of the art. It is also well known that olefin hydrocarbons have a higher octane rating, that is, are lesslikely to cause detonation when used in internal combustion engines than are the corresponding normal paraflin hydrocarbons. It has further been demonstrated that hydrocarbons which belong to the same class and have the same molecular weights exhibit widely diflferent detonation properties. This variation in octane number appears to be a function of the degree of complexity of the structure of the hydrocarbon molecule. For example, hexane, a straight chain parafiin hydrocarbon, has an octane number rating of 59, whereas an isomer, 2,2-dimethy1butane (neohexane) which possesses a highly branched molecular structure, has an octane number rating of 95. Relatively low molecular weight, saturated branch chain hydrocarbons are generally pre-. ferred for use'in aeroplane fuel. Since'the ad-. vantages which accrue from the use of higher octane number fuels are well known, many methods and processes have been evolved for their manufacture.

It has been demonstrated recently that desul furization and dehydrogenation processes have certain advantages when applied to the manufacture of higher octane number hydrocarbons from lower octane number hydrocarbons. For example, Walter A. Schulzi'et a1. .(see 011 and Gas Journal. vol. 34, No. 21, p. 22 (1935)) have proved that it is possible to obtain an increase in antidetonation rating of 2 to 4 octane numbers when tlons.

catalytic desulfurlzation is applied to hydrocar-.

, bon stocks which contain varying concentrations of the sulfur compounds usually found in natural gasoline hydrocarbons. Another beneficial elect noted by these investigators is the increased response of stock so treated to the addition of lead tetraethyL- They observed that an increase in'lead response of the order of 6 to 8 octane numbers was realized through the addition of one cubic centimeter of lead tetraethyl per gallon to a desulfurized hydrocarbon material. It is also now well-known that there is an improvement in detonation characteristics of the order of 6 to 10 octane numbers in natural gasoline stocks which have been subjected to catalytic dehydrogenation. An appreciable increase in the lead susceptibility of the same natural gasoline has been observed following the dehydrogenation treatment.

The demand for extremely high octane number aviation gasoline has promoted extensive research on this subject and various treatments such as desulfurization, isomerization, and the like have been employed to attain octane rating or better to meet government specifica- Unsaturate requirements, however, are correspondingly rigid and such treatments must be carefully controlled to avoid decomposition reactions. As a general rule, complete desulfurization of motor fuel is not essential and government specifications in this case allow a sulfur content up to about one-tenth of one per cent.

An object of the present invention is generally to produce higher octane number normally liquid hydrocarbons from lower octane number normally liquid hydrocarbons in the natural gasoline range.

A further object is the production of hydrocarbons in aviation and motor fuel ranges by com: bined catalytic desulfurization and catalytic-Idehydrogenation means wherein a portionof a hydrocarbon charge stock of any composition whatsoever in the natural gasoline range is subjected to catalytic desulfurization, while the remainder of this hydrocarbon material, combined with a certain portion of the desulfurized product, is subjected to catalytic dehydrogenation.

In a preferred form the invention contemplates thorough desuliurization of hydrocarbons from which aviation fuel is derived, at a temperature regulated to substantially preclude unsaturation, while at the same time subjecting a fraction of the stock to dehydrogenation for the production of an improved octane number motor fuel. The invention also contemplates desulfurization to a desired amount of the motor fuel fraction. More specifically, and in one embodiment of the invention, the processing elements are so arranged that a portion of the charge stock is continuous-- 1y removed from a single coil furnace orheating means at a temperature high enough for desulfurization to proceed but suiiiciently low that splitting or decomposition reactions'will not be appreciable during the desuimrization step. The remainder of the charge stock is preheated to dehydrogenation temperature and the process is so controlled and of such flexibility that the high octane aviation gasoline and high octane motor fuel may be obtained in any desired proportion. The cut withdrawn, following desulfurization, is fractionated to separate aviation and motor fuel fractions either or both of which are combined with fresh charge stock to the preheating coil, thereby regulating sulfur content and character of motor fuel recovered and enabling manufacture of high octane aviation gasoline and high octane motor fuel in any desired proportion whatsoever.

According to this invention, a portion of a feed stock withdrawn at desuli'urization temperature, as heretofore described, is subjected in the presence of a suitable catalyst such as bauxite impregnated with sodium hydroxide to desulfurization under reaction pressure and temperature conditions of the order of to 100 or more pounds per square inch and 500 to 800? F., respectively. Preferably desulfurization is carried out at pressures of from 0 to 50 pounds per square inch and within the temperature range of from 600 to 700 F. to maintain conditions suchthat decomposition or splitting reactions are slight and occur to an extent less than 5% and desirably less than 2% of the charge stock. Under. such conditions desuliurization proceeds with its attendant beneflcial effect, both with respect to octane number and to lead response as heretofore described.

The remainder of the charge stock is subjected in the presence of a suitable catalyst such as chromium oxide gel, chromic oxide carried on a suitable porous support, or bauxite, to dehydrogenation under pressure and temperature conditions of the order of 0 to 100 or more pounds per square inch and 600 to 1200 E, respectively. Dehydrogenatiorr may be accomplished to some extent with certain catalysts, e. g., chromium oxide gel, at the lower temperatures in this range, 1. e., from .600 to 800 F. However, we prefer to operate at temperatures of from 800 to 1200 I". to obtain a substantial degree of dehydrogenation per pass. These conditions are maintained such that not more than 30% of the charge stock is converted per pass through the reaction zone. The suitable exact conditions depend upon the type of feed stock and the catalyst used and are best determined through trial by one who is skilled in the art. Separation steps are employed both hereand in the desuliurization step in order to separate and remove the sufiiciently reacted products from the system. The insumciently reacted hydrocarbons are recycled for further treatment.

The process of this invention may be carried forward in equipment such as is shown in Figure I, which is a diagrammatic side elevation of the various processing elements, and illustrates onemeans by which the process may be practiced.

Referring to Figure I, a natural gasoline feed stock, as heretofore described, is introduced through conduit I, tank 2 and conduit I into pump l, where it is compressed to a pressure suitable for entry into tubular heating coil I! via conduit 5, heat exchanger libeatexchflige with a portion of the dehydrogenation eflluent) and conduit 1. After entering the heating coil,

the charge stock is progressively preheated from i a. relatively low temperature to a higher teniperature suitable for catalytic dehydrogenation.

At some intermediate point in the preheating coil l0, housed in a suitable furnace or heating means II, a portion of the charge is withdrawn for desulfurization. Withdrawal of this preheated portion may be made at any number of points such as through conduits i2 and it and valves is and II, respectively, for regulative purposes. Precautions are taken that the temperature of the stream entering the desulfurization reaction zone will produce materials in the aviation range which will meet the unsaturated specifications for aviation fuels. In order to aid in the control of this part of the process, valves l1 and ||A and conduits l8 and 8 respectively are provided in order to shunt material at a lower temperature around the preheating coil to mix with the hydrocarbons being withdrawn directly by means of. the valves and conduits previously mentioned. The best method of control can be selected by those who are skilled in the art. The preheated desulfurization feed passes through conduit it, together with bypassed material entering through conduit l0, into catalyst case i8 where the desulfurization reaction occurs. Here the hydrocarbon material is subjected to the influence of asuitable catalyst such as bauxite impregnated with sodium hydroxide. The reaction temperature is such that the decomposition of the hydrocarbons so treated will not be more than 2% by weight for contact periods which may vary from 1 to 2 liquid volumes of feed per hour per volume of catalyst, the most suitable exact conditions being determined by tria Following passage through the desulfurization reaction zone, the hot reaction products exchange heat in exchanger 8 with a portion of the recycled feed to the dehydrogenation step and flowing via lines and it into a subsequent portion of the stream being heated in coil Ill. The reaction products then pass via conduit 2|, cooler 22, conduit 23', pump 24 and conduit 25 into fractionator 20, or other suitable separation means where the hydrocarbons lighter than those desired in the aviation fraction are separated therefrom,

pass through conduit 30, condenser and cooler 3i, and conduit 32 into condensate accumulator 38. A portion of the condensate is taken from accumulator 33 through conduit 34 and compressed by means of pump 1! tea pressure sufficiently high to permit introduction as a reflux or coo ing medium near the'top of 26 by means of conduit 8|. A quantity in excess of that required for this purpose is removed from the system through I conduit :1. The bottom product, which comprises hydrocarbons of aviation fuel molecular weight and heavier, passes through conduit ll into separation element a where the hydrocarbons ofaviation fuel molecular weight pass through conduit ,condenser and cooler 4i and'conduit 42,

into condensate accumulator ll. vAs in the preceding step, a portion of hydrocarbon material is introduced near the top of element I9 byv means of conduit 44, pump ll, and conduit II to act asa reflux or cooling medium. Hydrocarbons of aviation fuel grade, in excess of the amount required for this purpose,,are removed from the s'ystemthrough conduit l1, valve l'i-A and conduit fl-B. At times, however, it may be necessary, for purposes of control, to recycle a portion of this stream by way of pump ll, conduit l8-,-A.

valve 48-'B and conduit is directly to the inlet through conduit 49 into element 50. The motor fuel hydrocarbons pass into accumulator 54 via conduit 5|, condenser and cooler 52 and conduit 00. A portion of these motor fuel hydrocarbons are introduced near the top of 60 as reflux or cooling medium by means of conduit 50, pump 50, and conduit 51. The volume of these in excess of the amount required for this purpose is removed from the accumulator and is transferred through conduit 58, pump 59, conduit 80 and conduit BI, into tank 2, where it comprises a portion of the feed to the process. The bottom product is removed from the system through conduit 02.

Motor fuel hydrocarbons passing through conduit 60, together with dehydrogenation liquid recycle stock passing through conduit I04 and raw feed entering through conduit I, comprise the total liquid feed to the dehydrogenation step. This total liquid feed passes from tank 2 through conduit 3 into pump 4 where it is compressed to a suitable reaction pressure. This pressure is between and 100 or more pounds per square inch. Thence, it passes through conduit 5 into heat exchanger 6 where a certain temperature is obtained, as heretofore described, by heat interchange with hot dehydrogenation catalyst chamber efliuent products which are passing through conduit 01. At this pressure and temperature the hydrocarbon material passes through conduit 1 into heating coil I0, as heretofore mentioned, where a portion is removed as desulfurization feed. The remainder passes through the coil together with hydrogen and light hydrocarbons which enter the coil through conduit 8| from elsewhere in the dehydrogenation step. The preheated feed stock then passes through conduit 83 controlled by valve I0-C into a suitable catalyst case 84 where'it is subjected to the influence of a suitable catalyst such as bauxite, chromium oxide gel, or chromic oxide carried on a porous support. Temperature of the dehydrogenation feed may be controlled by passing a portion thereof through conduit Ill-A accurately regulated by valve I0B. Ordinarily, dehydrogenation is carried out at relatively higher temperatures than desulfurization but in accordance with this invention provision is made whereby dehydrogenation may be accomplished to some extent at the same or even lower temperatures under certain circumstances. See for example U. S. Patents 1,905,383; 2,098,959; and 2,205,141 all of which disclose dehydrogenation at temperatures below 800 F. The dehydrogenation reaction temperature is preferably so regulated (between 600 and 1200" F.) that the decomposition of the charge-so treated will not exceed 30% per pass through the reaction zone forgcontact periods which may range from 1 /2 to 3 liquid volumes of gasoline feed per hour per volume of catalyst, the most suitable conditions being determined by trial.

Following passage through the reaction zone,- the hot reaction products pass through conduit ll into cooler 00 where they undergo partial cooling, thence, by way of conduit 01 into exchanger 0 where they .exchange heat with the cold liquid feed, as heretofore described. The reaction products then pass through'conduit 08,, cooler 00, and

conduit I0 into separation element II where a rough separation is obtained between the noncohdensibie gases and heavier materials.

non-condensibles, which may contain a certain percentage of hydrocarbons in the gasoline range, pass through conduit [2 into pump 13 where they are compressed to a pressure which.

ethane and lighter, including hydrogen and some 1 propylene and propane, may be removed from the system through conduit I0. A portion of this material, however, may be recycled to the system through valve I9, conduit 80, heat exchanger 8 and conduit 8I for better control over yield and octane number of desirable products. The butanes and heavier pass from 'Ii through conduit 00 where they mix with the greater bulk of the normally liquid hydrocarbons which have been removed from 1| via conduit 82, pump 03 and conduit 04 for entry into separation element 80. The hydrocarbons lighter than motor fuel pass through conduits! and condenser and cooler 08 into condensate accumulator 09. A portion of the condensate is taken from the accumulator 89 through conduit 00 and compressed by means of pump 0| to a pressure sufllciently high to introduce it as a reflux or cooling medium near the top of 86. A quantity in excess of that required for this purpose is removed from the system through conduit 03. The bottom product, which contains the valuable motor fuel fraction and a small amount of heavier material, passes through conduit 94 into element 05 where the motor fuel fraction passes through conduit 96, and condenser and cooler 01 into condensate accumulator 90. -As in the preceding step, a portion of this material is introduced near the top of 05 by means of conduit 09, pump I00 and conduit IOI, to act as a reflux or cooling medium. A portion of the'amount in excess of this requirement is continuously removed from the system through conduit I02, pump I03, conduit I04; valve I00,

40 and conduit I08 for use as a high octane number motor fuel or as one of its ingredients. The remainder of the excess amount is recycled through conduit I05 totank 2 forycontrol purposes. The bottom product is removed from the system through conduit I01.

- of aviation and motor-fuel respectively recovered may be regulated. Valves I0-B and I0-C provide further means for regulating the relative flow of material tothe respective desulfurizing and dehydrogenating' For instance, by appropriate regulation of these valves the principal portion of the feed stock may be directed through the desulfurization unit and a high proportion of aviation fraction recovered,- while at the same time a substantial quantity of the motor fuel is desulfurized, being returned-through conduit 00 to the tank 2 and combined therein with raw feed stock. On the other hand by diminishing the flow through branch conduits I2 and I4 and where the demand is low for aviation fuel, the bulk of the charge stock may proceed directly through the heating coil to the dehydrogenation unit forproduction of motor fuel. Likewise a low sulfur high-octane motor fuel is obtained by desulfurizing the major portion of the raw feed and either cycling a portion of the aviation hydro-' carbons therewith through dehydrogenation or separating and blending with dehydrogenated motor fuel. It is generally desirable, however, to obtain as complete a recovery as possible oi the desulfurized aviation fuel fraction. Thus the process is of such flexibility that products having also any desired characteristics may be obtained in any desired proportion.

A modified form of the invention is shown in Figure II of the drawings, in which the processing elements are so arranged that the total feed stock is subjected to catalytic desulfurisation in the first step of the process. A desired proportion of the desulfurized products is heated to a suitable dehydrogenating temperature and subjected to catalytic dehydrogenation while the remainder is fractionated for the recovery of high octane aviation fuel. The heavier fraction separated in the last mentioned fractionation step is combined with other desuliurized products in any amount, preheated, and subjected to catalytic dehydrogenation. A particularly advantageous feature resides in the fact that a comparatively small quantity of heat is required to raise the desulfurization eiiluents to the higher dehydrogenating temperature. In the catalytic dehydrogenation step, operating conditions are maintained at such a level that the eiiiuents contain principally a hydrocarbon material suitable for use as an important ingredient in motor fuels, and of higher octane number than materials in the dehydrogenation feed stock of the same boiling range. In a similar manner to that described with respect to Figure I, the process is characterized by flexibility of control so that desired products can be obtained in any proportion. Specifically, means are provided for by-passing a substantial quantity or all or the desulfurized stock in accordance with the demand directly to dehydrogenation.

With reference to Figure II, a raw natural gasoline feed stock as heretofore described is introduced from feed tank 2M through conduit 222 and compressed to a suitable reaction pressure by means of pump 203 together with any insumciently desulfurized material which it may be found to be necessary to recycle (by one who is skilled in the art) which joins 202 through the medium of conduits 24! and 255 which discharge into tanlr 20L. This pressure is between and 100 or more pounds per square inch. The total feed then passes through conduit 204 and thence through heat exchanger 205 where a certain temperature is obtained by heat interchange with hot catalyst chamber eniuent products which are passing through conduit 2| I. At this pressure and temperature, the natural gasoline feedpasses through conduit 203 into preheating coil 2" which is suitably housed in a furnace or heating means 208 and whereinthe temperature of the feed is raised to from 500 to 800 F. and, as previously stated, preferably from 600 to 700 1". The preheated hydrocarbons then pass through conduit 203 into a suitable catalyst case 2|. where they are subjected to the influence of a suitable catalyst such as bauxite impregnated with sodium hydroxide.- The reaction temperature is such that the decomposition of the hydrocarbons so treated will be not more than 2% by weight for contact periods which may vary from 1 to 2 liquid volumes of feed per hour per reaction zone, the hot reaction products exchange heat with the cold feed in exchanger 2" as heretofore mentioned. The reaction products then pass via conduit 2l2, cooler 213, conduit 2|5, pump 216 and conduit 2|! into fractionator M8, or other suitable separation means where the hydrocarbons lighter than those desired in the aviation hydrocarbon fraction are separated therefrom, pass through conduit 2, condenser and cooler 220, and conduit 22| into condensate accumulator 222. A portion of the condensate is taken from accumulator 222 through conduit 222, and compressed by means of pump 224 to a pressure sufliciently high to permit introducing it as a reflux or cooling medium near the top of 213 by means of conduit 225. A quantity in excess of that required for this purpose is removed from the system through conduit 229. The bottom product which comprises hydrocarbons of aviation fuel molecular weight and heavier, passes through conduit 224 to separation element 230 where the hydrocarbons of aviation fuel molecular weight pass through conduit 23l, condenser and cooler 222, and conduit 233, into accumulator 224. As in the preceding step, a portion of this hydrocarbon material is introduced near the top of element 230 by means of conduit 243, pump 22., and conduit 231, to act as a reflux or cooling medium. Hydrocarbons of aviation fuel grade in excess of the amount required for this purpose are removed from the system through conduit 238. At times, however, it may be considered necessary for purposes of control torecycle a portion of this stream by way of conduit 238, valve 240 and conduit 2. The bottom product, which contains hydrocarbons of motor fuel molecular weight and heavier, passes through conduit 242 into element 242. The motor fuel hydrocarbons pass into accumulator. 244 via conduit 244, and condenser and cooler 24!. A portion of these motor fuel hydrocarbons are introduced near the top of 243 as reflux, or cooling medium, by means of conduit 241, pump 24., and conduit 248. The volume of thesein excess of the amount required for this purpose are removed from the accumulator as-the primary raw feed stock to the dehydrogenation step. Provided, however, that if it may be considered to be necessary for control, a portion of this stream may be recycled to the desulfurization step via conduit 253, valve 254, and conduit 2". Means have also been provided, whereby a portion of the bottom product from 213 may be fed directly to the dehydrogenation step by way of valve 221 and conduit 228. Determination of the amount to be diverted directly to the dehydrogenation step will be in accordance with relative demands for aviation and motor fuels.

. The net overhead product from 242, which comprises the motor fuel feed stock to the dehydrogenation step, passes from accumulator 244 volume of catalyst, the most suitable exact conspectively, seem preferable in promoting the desulfurization in order to suppress more than slight decomposition.

Following passage through the desulfurization At this pressure andtemperature the hydrocarthrough conduit 250 and into pump 232 where it is compressed to a suitable reaction pressure. This pressure is between 0 and or more, pounds per square inch. Thence it passes, together with recycle stock from conduit 2". through conduit 256 into heat exchange 241 where a certain temperature is obtained by heat interchange with hot catalyst chamber eiiiuent products which are passing through conduit 2.

bon material passes through conduit 25! into a preheating coil 253 which is suitably housed in a furnace or heating means no and wherein the temperature of the feed is raised to 600 to 1200 F. or as indicated above, preferably from 800 to 1200 F. This may be a portion of furnace coil housing 208 for economy reasons. The preheated feed stock then passes through conduit 26! into a, suitable catalyst case 262 where itis subjected to the influence of a suitable catalyst such as bauxite, chromic oxide gel, or chromic oxide supported on a porous carrier. The reaction temperature is such that the decomposition of the charge so treated will not exceed 30% per pass through the reaction zone for contact periods which may range from 1 to 3 liquid volumes of gasoline feed per hour per volume of catalyst, the most suitable conditions being determined by trial.

Following passage through the dehydrogenation reaction zone, the hot reaction products exchange heat with the cold feed in exchanger 263 as heretofore described. The reaction products then pass through conduit 2, cooler 258, and conduit 266 into separation element 281 where a rough separation is obtained between the noncondensible gases and heavier materials. The non-.condensibles, which may contain a certain percentage of hydrocarbons in the gasoline range, pass through conduit 2 into pump 2 where they are compressed to a pressure which is sufficient to condense nearly all the hydrocarbons heavier than ethane following passage through conduit 210 and cooler 2'. The mixture passes through conduit 2I2into separation element 213, where vapors which comprise essentially ethane and lighter including hydrogen may be removed from the system through conduit 211i. It is considered to be beneficial from the point of view both of increased yields and octane number to recycle a portion of the hydrogen stream through the process together with th liquid feed. This may be done by way of conduit 3il2A, valve Slit-A, and conduit Sill-A. The butane and heavier pass from 213 through conduit 275 where they join the greater bulk of the normally liquid hydrocarbons which have been removed from 281 via conduit 216, pump 2'" and conduit 218 for entry into separation element 219. The hydrocarbons lighter than motor fuel pass through conduit 280, condenser and cooler 28l, and conduit 282 into accumulator 288. A portion of the condensate is taken from accumulator 283 through conduit 28 and compressed by means of pump 285 to a pressure sufflciently high to introduce it as a reflux or cooling medium near the top of 218. A quantity in excess of that required for this purpose is removed from the system through conduit 281. The bottom product, which contains the valuable motor fuel fraction and a small amount of heavier material, passes through conduit 288 into element 289 where the motor fuel fraction passes through conduit 290, condenser and cooler 29!, and conduit 292 into accumulator 293. As in the preceding step, a portion of this material is introduced near the top of 289 by means of conduit 294, pump 295, and conduit 298, to act as a reflux or cooling medium. A portion of the amount in excess of this requirement is continuously removed from the system through valve 299 and conduit 3ililA for use as a high octane number motor fuel or as one of its ingredients. The remainder of the excess amount is recycled throughconduit 298 to the dehydrogenation step for control purposes. The bottom product is removed from the system through conduit flit-A.

In Figure I]! is shown apparatus for carrying out a further modified procedure where individual branch chain isomers are separated which may be used individually or as aviation blending 5 stocks from corresponding normal hydrocarbons which preferably constitute dehydrogenation feed stock. Saturated branch chain hydrocarbons are of optimum octane number and lead susceptibility while unsaturated forms of nor- 1 mal hydrocarbons'are ofincreased octane number over corresponding normal saturated forms.

Therefore by means of the herein described 'in-' tegrated process, maximum efficiency is obtained from charge stock of any constitution whatever in the natural gasoline range.

A raw natural gasoline feed stock is introduced from feed tank 8M through conduit 802 and compressed to a suitable desulfurization reaction feed pressure by means of pump 208 together with any "insufficiently desulfurized material which it may be found to be necessary to recycle (by one who is skilled in the art) which has entered 30! through conduits 395 and till. The pressure is between 0 and 100 or more pounds per square inch. The total feed then passes through conduit 3 and thence through heat exchanger 305 where a certain temperature is obtained by heat interchange with hot catalyst chamber efiiuent products which are passing through conduit 3! I. At this pressure and temperature, the natural gasoline feed passes through conduit 306 into preheating coil 301, which is suitably housed in a furnace or heating means 308. The, preheatedv hydrocarbons then pass through conduit 309 into a suitable catalyst case where they are subjected to the influence of a suitable catalyst such as bauxite impregnated with sodium hydroxide. The reaction temperature is such that the decomposition of the hydro-- 4 carbons so treated will not be more than 2% by weight for contact periods which may vary from 1 to 2 liquid volumes of feed per hour per volume of catalyst, the most suitable exact condit ons'being determined by trial.

Following passage through'the desulmrization reaction zone, the hot reaction products exchange heat with the cold feed in exchanger till: as heretofore mentioned. The reaction products then pass via conduct 3", cooler M3, conduit SIB, pump SI! and conduit 3 into fractionator M9 or other suitable means of separation where hydrocarbons comprising butanes and lighter than those desired as aviation gasoline hydrocarbons are separated therefrom. These pass from the system through conduit 328. Heavier hydrocarbons which may consist of any saturated. straight chain and branched chain hydrocarbons comprise the feed to separation element 328'via. conduit 321. There normal and branched chain isomeric pentanes are removed as an overhead product for feed to separation element 338 through conduit 338. The hexanes and heavier comprise the bottom product which are used as feed to separation element til via conduit 331.

In separation element 838 isopentanes are removed as an overhead product and leave the system through conduit 8230. Normal pentane is removed as abottom product via conduit 348 which joinsdehydrogenation feed conduit 899. The various isomeric hexanes may comprise the overhead product of 8M and serve as feed to separation element 36L Heptanes and heavier prise the bottom product of 35;! and serve as feed to separation element 213. Branched chain hexanes comprise the overhead of 3H and are removed from the system through conduit 313, Normal hexan comprises the bottom product from 36! and serves asone component of the dehydrogenation feed via conduit 369. Isomeric heptanes comprise the overhead product of 314 which feeds separation element 383 via conduit 382. The bottom product of 314 which comprises octanes and heavier hydrocarbons is fed directly to the dehydrogenation step together with other hydrocarbons previously mentioned. Isoheptanes are the overhead product from element 383 and are removed from the system via conduit 393 except for a quantity which it may be found necessary for control to recycle to the desulfurization system through conduit 395. Normal heptane is removed in the bottom product from 383 and comprises another component in the feed to the dehydrogenation step via conduit 395'.

The raw feed to the dehydrogenation step which comprises hydrocarbons passing through conduits 3, as, 396 and 39! passes into feed tank 403 via conduits 399 and 402, except for a portion which may be recycled to the desulfurization system through conduit Ill. Following thorough mixing in 403, together with recycle stock which enters through conduit 450, the feed follows the same path as that shown in the dehydrogenation step of Figure 11. Hydrogen is recycled to the system through conduit 45 for reaction control, butanes and lighter are removed from the system through conduit 438, and hydrocarbons in the motor fuelrarige are removed through conduit 9. A portion of the motor fuel hydrocarbons constitutes liquid recycle stock to the reaction zone via conduit s50. Hydrocarbons heavier than motor fuel are removed from the system via conduit 45 i r In the interest of simplicity, elements of similar function to corresponding elements in Figure 11 have not been speciiicallydelineated or described. The operation of these elements however is readily understood from the foregoing description with respect to Figure II.

The separation steps maybe extended, if desired, to separate normal octane from its branched chain isomers. The latter ispreferably blended with other branched chain and low molecule weight normal hydrocarbons for blending aviation fuel. The normal octane with other straight chain hydrocarbons will constitute dehydrogenation feed stock.

We claim: 1

1. A process for the manufacture of high octane aviation gasoline and high octane motor fuel which comprises passing hydrocarbon charge stock in the gasoline range through an elongated heated passageway, withdrawing at an intermediate point in said passageway a portion of said charge stock at a temperature high enough for catalytio'desulfurization but sufficiently low to prevent decomposition reactions, subjecting said withdrawn portion to catalytic desulfurization, recovering from the eiiluent a relatively low molecular weight hydrocarbonfraction suitable as high octane aviation gasoline, separating from the eilluent another fraction containing relatively high molecular weight hydrocarbons heavier than the aviation gasoline range, and combining the same with new charge stock, passing the remainder of said charge stock through said heated in; said remaining portion to catalytic dehydroq genation for the production of high octane motor fuel.

2. A process for the manufacture of high octane aviation gasoline and high octanemotor fuel which comprises passing hydrocarbon charge stock in the natural gasoline range through an elongated heated passageway, withdrawing at an intermediate point in said passageway a portion of said charge stock at a temperature high enough for catalytic desulfurization but sufficiently low to prevent decomposition reactions, subjecting said withdrawn portion to catalytic desulfurization and recovering from the eflluent a relatively low molecular weight hydrocarbon fraction suitable as high octane aviation gasoline, separating from the eiliuent another fraction containing relatively high molecular weight hydrocarbons heavier than the aviation gasoline range, and combining saidfraction with said original charge stock, passing the remainder of said charge stock through said heated passageway to attain a higher temperature suitable for catalytic dehydrogenation, and subjecting said remaining portion to catalytic dehydrogenation for the' production of high octane motor fuel.

3. A process for the manufacture of high octane aviation gasoline and high octane motor fuel in the desired proportion, which comprises passing hydrocarbon charge stock in the gasoline range through an elongated heated passageway, withdrawing at an intermediate point in said passageway a portion of said charge stock at a, temperature of between 500 to 800 F. and pressure from 0 to pounds per square inch, catalytical- 1y desulfurizing said portion and recovering a relatively low molecular weight fraction therefrom suitable as high octane aviation gasoline, separating from the desulfurization eflluent another relatively higher molecular weight hydrocarbon fraction heavier than the aviation gasoline range and combining the same with fresh charge stock, passing the remainder of the charge stock through said heated passageway to attain a materially higher temperature suitable for catslytic dehydrogenation, subjecting said remaining portion to catalytic dehydrogenation, and recovering-high octane motor fuel from the eflluent.

4. A process for the manufacture of high octane aviation gasoline and high octane motor fuel in the desired proportion, which comprises passing hydrocarbon charge stock in'the gasoline rangethrough an elongated heated passageway, withdrawing at an intermediate point in said passageway a portion of said charge stock at a desulfurlzation temperature of between 600 to 100 F. and pressure from 0 to 100 pounds per square inch, catalytically desulfurizing said portion and recovering a relatively low molecular weight fraction therefrom suitable as high octane aviation gasoline, separating from the desulfurization effluent another relatively higher molecular weight hydrocarbon fraction and combining the same with fresh charge stock, passing the remainder of the charge stock through said heated passageway to attain a dehydrogenation temperature of from 800 to l200 F., subjecting said remaining portion to catalytic dehydrogenation, and recovering high octane motor fuel from the effluent.

5. A method for the treatment of hydrocarbons for the production of separate fractions of desulfurized hydrocarbons and dehydrogenated hydro- ;carbons' which comprises passing hydrocarbon charge stock in the gasoline range through a tubular heating coil and progressively preheating said hydrocarbons from a relatively low temperature to a higher temperature of at least 800 F. suitable for catalytic dehydrogenation, withdrawing a portion of said charge stock at an intermediate temperature substantially below 800 F. and subjecting said portion to catalytic desulfurization at said intermediate temperature, recovering from the eilluent a fraction in the aviation gasoline range and a heavier fraction in the motor fuel range, combining said heavier fraction with said original charge stock, and subjecting the remaining portion of said charge stock at said higher temperature to catalytic dehydrogenation.

6. A process for the manufacture of high octane aviation gasoline and high octane motor fuel which comprises passing hydrocarbon charge stock in the gasoline range through an elongated heated passageway, withdrawing at an intermediate point in said passageway a portion of said charge stock at a temperature high enough for catalytic desulfurization but sufficiently low to prevent decomposition reactions, subjecting said withdrawn portion to catalytic desulfurization, recovering from the eilluent a relatively low molecular weight hydrocarbon fraction suitable as high octane aviation gasoline, separating from the eilluent another fraction containing relatively high molecular weight hydrocarbons heavier than the aviation gasoline range, and combining the same with new charge stock, passing the remainder of said charge stock through said heated passageway to attain a higher temperature suitable for catalytic dehydrogenation, and subjecting said remaining portion to catalytic dehydrogenation, recovering from the catalytic dehydrogenation eflluent a fraction suitable as high octane motor fuel, and recycling a portion of said high octane motor fuel with the aforesaid new charge stock.

'1. A process for the manufacture of high octane aviation gasoline and high octane motor fuel which comprises passing hydrocarbon charge stock in the natural gasoline range through an elongated heated passageway, withdrawing at an intermediate point in said passageway a portion of said charge stock at a temperature high enough for catalytic desulfurization but sufficiently low to prevent decomposition reactions, subjecting said withdrawn portion to catalytic desulfurization and recovering from the eiiluent a relatively low molecular weight hydrocarbon fraction suitable as high octane aviation gasoline, separating from the eflluent another fraction containing relatively high molecular weight hydrocarbons heavier than the aviation gasoline range, and combining said fraction with said original charge stock, passing the remainder of said charge stock through said heated passageway to attain a higher temperature suitable for catalytic dehydrogenation, and subjecting said remaining portion to catalytic dehydrogenation, recovering from the catalytic dehydrogenation efiiuent a fraction suitable as high octane motor fuel, and recycling a portion of said high octane motor fuel with said original charge stock.

EDWARD BUDDRUS. HARRISON L. HAYS.

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