US2381041A - Production of saturated hydrocarbons - Google Patents

Description

Patented Aug. 7, 1945 raonUo'rIoN F sArURa'rEn maooannons Johan Jacob de Jong, Amsterdam, Netherlands, assignor to Shell Development Company, San Francisco, Calii'., a corporation of Delaware No Drawing. Application November 21, 1939, Se- I rial No. 305,498. In the Netherlands November This invention relates to the manufacture of branched chain aliphatic hydrocarbons, particularly the production of branched chain parafiins boiling in the gasoline range and having antiknock properties. It deals with the manufacture of such branched chain paraflins by alkylation of isoparafiins in the presence 01' sulphuric acid catalyst.

One object of the invention is to extend the life of sulphuric acid catalysts used for the alkylation of isoparamns. Another object is to provide a new class of alkylating agents which may be reacted with isoparaihns in the presence of sulphuric acid and which oiler advantages over the oleflnes which hitherto have been the only agents used. Still another object is the more efficient and economical use of oleflnes as starting materials for the alkylation of isoparaffins. It is a further object to reduce the power requirements and distillation expense when using -as starting material oleflnes admixed with normal parafifins.

Heretcfore the only commercially practical method of alkylating isoparafiins has been by reaction with olefines in the presence 'of concentrated sulphuric acid as described for example in copending application Serial No. 150,544 filed .June 26, 1937. This method as preferably carried out with the hydrocarbons in the liquid phase and using an excess of isoparafiln to olefine has been highly successful. It nevertheless has certain undesirable features which it is an object of the present invention to improve upon. Thus, for example, in the alkylation of isobutane with propylene containing propane such as is avail-- able from the cracking of petroleum hydrocarbons, the excess isobutane becomes contaminated by propane and extra distillation expense is necessary 11 the isobutane is to be profitably reused in the process. Also the necessity of compressing and maintaining liquid such low boiling hydrocarbons involves high power costs and.

makes necessary more expensive equipment capable of withstanding the higher pressures involved.

acid can be reacted with branched chain paraffins in the presence of concentrated sulphuric acid to form alkylation products of the isoparaffin. Based upon this discovery a commercially practical method which offers many advantages over the allwlation with an olefinic feed has been 12 Claims. (Cl. 260683.4)

developed. Either neutral esters, e. g. dialkyl sulphates, or acid esters, e. g. mono-alkyl sulphates or mixtures comprising both types of esters may be used for alkylating isoparaffins in accord ance with the invention. It may be that'the reaction with neutral alkyl esters involves acid alkyl esters as intermediates but there are special advantages in using the neutral esters and this important modification of the invention as carried out with dialkyl sulphates, for example, will be described first.

Examples of neutral sulphuric acid alkyl esters used according to the invention, which are conceivable as being derived from primary and secondary aswell as tertiary alcohols and which may also be used as mixtures, are for example: diethyl sulphate, dipropyl sulphate, di-isopropyl sulphate, di-normal butyl sulphate, di-isobutyl sulphate,di-secondary butyl sulphate, di-tertiary butyl sulphate, dipentyl sulphates, diheiwl sulphates, diheptyl sulphates, di-octyl sulphates (e. g. the neutral sulphuric acid, ester of di-isobutene) and didodecyl sulphates (e. g. the neutral sulphuric acid ester of tri-isobutene). Use may also be made of mixed neutral sulphuric acid alkyl esters containing two diilerent alkyl groups in the neutral sulphuric acid ester. Preferably neutral sulphuric acid alkyl esters of branched or non-branched alkenes are used but neutral esters of cyclic oleflnes as dicyclohexyl sulphate and the like may also be employed. Suitable methods for preparing dialkyl sulphates which may be used in the process of the invention are described for example in U. S. Patents 1,854,581 and 1,967,399. The neutral sulphates may be used in the crude form in which they are initially obtained or in admixture with other substances or may advantageously be purified, for example by extraction with cold water or other suitable solvent ior acid alkyl sulphates, prior to use in the alkylation.

Examples of isoparafiins which may be reacted with such neutral sulphuric esters are isobutane, isopentane, 2-methyl pentane, '3-methy1 pentane, 2,3 dimethyl butane, isoheptanes and the like, including for example, higher boiling paraffins obtained in the aliq'lation process. It is further unnecessary to cause pure isoparaflins to react with the neutral sulphuric acid alkyl esters, it being also possible to start from mixtures containing isoparaifins, e. g. mixtures oi isoparamns and normal parafiins.

The neutral sulphate esters are substantially non-reactivewith such isoparafllns in the absence of catalysts but react in the presence of at least an equal molecular amount and more preferably a substantially larger amount of concentrated sulphuric acid. The best results are obtained with sulphuric acid of 90% to 100% concentration at reaction temperatures between about l and +5 C., however somewhat higher or lower acid concentrations and/or temperatures may also be used, the optimum conditions depending upon the particular neutral ester or esters involved and the isoparaflln or isoparafllns being reacted therewith. Whatever the temperature used it is preferred to operate with the reactants in the liquid phase but either or both may also be used in the gaseous state and whether or not the preferred liquid phase method of reaction is employed, the process may, if desired, be carried out in the presence of materials not participating in the reaction which materials may be gases, e. g. hydrogen, methane, nitrogen or carbonic acid, or liquids as nongzeactive hydrocarbons, carbon tetra-chloride, e

It is desirable that at least two, and preferably three to six or more, molecules of isoparaflin should be present to each molecule of neutral sulphuric acid alkyl ester. .One may also use less than two molecules of isoparaflln per molecule of neutral sulphuric acid allwl ester. An excess of lsoparafllns is, however, favorable to a longer activity of the sulphuric acid. It is also desirable in rder that full advantage be derived from the isoparaiflmester ratio used that the alkyl ester be brought rapidly into uniform intimate contact with the isoparaflln and catalyst. To this end it is helpful to premix the alkyl ester with isoparafflnbefore contacting it with the catalyst acid which preferably is also premixed with isoparafiln, when using neutral esters they maybe applied advantageously as a solution in the isoparafdn to be alkylated which solution is fed into a suspension of catalyst acid and isoparafiln-containing hydrocarbon.

A simple method ,of operation comprises feeding the isoparafiln and alkyl ester into an intensively stirred mixture of isoparailins and sulphuric acid in which the temperature may be controlled by circulation of a suitable cooling agent or by evaporation of a part 'of the reaction mixture, e. g. a part of the excess isoparaffin. In batchwise operation the stirring may be discontinued at the end of the reaction period which preferably is extended beyond the time required for addition of the alkyl ester after which the mixture may be stratified in the same or another suitable vessel whereupon the hydrocarbons separate as a top layer which may be separated and the bottom layer of sulphuric acid reused for further alkylation, preferably after separation of a volume at least equivalent to the increase in the acid resulting from the reaction and more preferably a larger amount although most preferably still aminor proportion of the total acid, which excess may be replaced by fresh acid while the withdrawn acid may be used atleast in .part for the preparation of the alkyl sulphate or sulphates being reacted. The separated top layer of hydrocarbon, preferably after water and/or caustic washing or other suitable,

treatment for removal of acid and/or esters if present therein (compensation'for which should be made when adding fresh catalyst-acid) may be fractionated and a water-white sulphur-free stantially consisting of isoparaffins of high antiknock value, obtained. The excess isoparaflln may'be reused in the alkylation process.

Intermittent or continuous methods of operation may also be used and in any case it is de- 5 sirable to mechanically circulate dispersed reaction mixture, for example, by a centrifugal pump taking auction at a suitable point in the reactor and discharging back into the bottom or vice versa. Most preferably the invention is carried out continuously by the method described and claimed in copending application Serial No.

245,714 filed December 14, 1938, by continuously feeding alkyl ester and isoparaffin into a circulating stream of a dispersion of catalyst acid and reacted hydrocarbon mixture comprising the isoparaflln to be alkylated, withdrawing a part of the circulating mixture for separation of reaction product and returning at least a part of the unreacted isoparaflln and a suitable proportion of the catalyst acid to the circulating stream.

Still other methods of carrying out the alkylation reaction of the invention may be used. Multi-stage operation with the alkylation units in series employing either concurrent or countercurrent flow of reactants and catalyst acid with feed of allwl sulphate to one or several or all of the units or other suitable arrangements may be employed.

Whatever the procedure adopted for carrying out the alkylation it'is advantageous to use polyallwl esters of polybasic mineral acid such, for example, as diallwl sulphates, dlor trl-alkyl phosphates, dialkyl borates and the like as feed to the alkylation unit. When employing sulphate esters as the alkylating agent, sulphuric acid from the alkylation stage may be used for the preparation of the ester orv esters. Thus a part of the acid from the stratifler of the alkylation unit may be used to react with oleflnes to form '40 the desired ester. Forthe preparation of polyalkyl esters it is advantageous to contact the oleflne and acid in the proportions of about two mols of oleflne per mol of acid. Where cracked fractions of petroleum hydrocarbons are used as the source of the oleflnes the dialkyl sulphates formed will be present for the most part in the upper layer of hydrocarbon obtainable by stratiflcation of the reacted mixture. Such upper layer will also contain the bulk of the polymers if any are formed during the reaction. This upper layer, preferably after separation of any I normally gaseous hydrocarbons present may be used as the alkylating agent in the process of the invention with or without separation of the 5 polymers. While the polymers may be successfully reacted with isoparaflins along with the alkyl esters and appear to generally give the same type of products it is preferred to operate with minimum polymer formation. To this end it may be desirable when using mixtures of olefines ofdiiferent orders of reactivity to contact the acid with the least reactive oleflne first and use the reaction product to contact the mixture containing the more reactive oleflne. Thus, for

()5 example, a fraction containing isoand normal -butylenes may be contacted with an absorption product of normal butylenes in withdrawn alkylation acid and the residual oleflnes used to form the absorption product employed. Alternatively the more reactive oleflnes maybe flrst'reacted v with more dilute acid. It may be advantageous to carry out the entire oleflne reaction with acid from the alkylation unit which has been suitably diluted to reduce undesirable side reactions. Such dilute acid tends to favor formation of largthe advantageous results which'may be obtained by the method of the invention when using dialkyl sulphates as feed to the alkylation unit.

Example 1 120 parts by weight di-isopropyl sulphate were introduced in about 1% hours during intensive mechanical stirring at 20 C. into a reaction vessel containing 95 parts by weight isopentane and enough for undesirable side reactions such as hydro-polymerization and the like leading to deactivation 01 the catalyst acid through accumulation of organic material therein, to take place. However that may be the following examples show cordance with the nature of the olefine orole- 98 parts by weight sulphuric acid of 98% concenflnes and polybasic mineral acid involved so that tration. The mixture, after having been stirred the desired esteris produced. Thus, for example, for another half hour, was allowed to stratify quite high temperatures are useful when preparwhereby a colourless top layer separated ofl in a ing esters from ethylene while as a general rule quantity of 145 parts by weight, with a. bromine higher secondary. oleflnes are more advantaflgure=0 and containing 80% hydrocarbons with 'geously treated at lower temperatures and teran octane number=93 and boiling between 50 tiary olerlnes at still lower temperatures although and 200 C. with ole'fines of six or more carbon atoms per The bottom layer consisted of 167 parts by molecule the differences between secondary and weight and contained 92.5% sulphuric acid. tertiary olefines are of less importance. The con- In an experiment carried out under approxiditions of al ylation with the alkyl esters are mately the same conditions (98% H2804 at 20 C.) r y analogous to those eq for p it was found that isopentane did not react with tion of the corresponding olefine in the Sense diethyl sulphate but by using higher temper that those which equi higher temperatures tures of the order of about to 40 C. the reacfor their rapid formation are best eacted wit 25 tion may be made to go readily giving equivalent ParafflnS at hi e temperatures t the yields of alkylation products the principal irace more easi y for e e t of o u for tion of whichboil in the isoheptane range. example, while di-isopropyl sulphate reacts only E I H slowly with isobutane or isopentane at temperacamp tures below 0' C. and appears to have an'opti- Di-isopropyl sulphate was reacted with isomum reaction temperature between about 15 butane in a pressure vessel equipped with a high and 25 0., di-secondary butyl sulphate reacts speed stirrer driven by an electric motor enclosed at temperatures as low as l0 C. although betin the same casing and having inlet lines for isoter results are obtained between about 0 and 15 butane and dipropyl sulphate mixture and for C. By using ester mixtures or the correspondsulphuric acid, the former feeding into the botins m xed este s al yl t ons w th t e l ss reactom and the latter at a higher level but below the tive alkyl groups m y bem re e s ly carried out motor. The apparatus was also provided with than by the use of such esters alone. outlet lines at the same levels' as the inlet lines Wit out p yi y limitation 0n the l and was surrounded by a water bath kept agition the following exp ana o s O ed for h 4 tated with air which maintained a reaction temm r vantageous results, particularly with re.- erature of 20 C. The same charge of catalyst Sp t0 C t y life, obtainable by the uSe p yacid was successively used for the reaction of live alkyl esters of polybasic inorganic acids as feed charges of isobutane and di-isopropyl sulphate to the alkylation unit instead of the correspondeach for a period of four hours under the followins oleflnes or mono-alkyl esters. Although dling conditions and with the following results:

. Concentration Mols of di- Wei ht ratio oi stl l l l l g hil l obu filge fii l- 0113180 in isopropyl sulcat yst phase Increase in carbon obtained ation product as the catalyst phato me] to di-isopropyl weight of 7 per kilogram of percent by wt. 0! at start of iso utane sulphate ted catalyst layer catalyst acid the ropylene infeed used Biteke 63 1.01 1.10 0.89 tti 93% 1.05 2.8 31.2 0. as 210 92 1.1 3.84 26.4 0.83 210 H to 1.1 4.74 25.4 0.88 285 says 22.5 0.81 241 Not determined.

The reaction product had a very satisfactory volatility, boiling below C. and having a clear octane number of 88 which was increased to 99 'by addition of 2 ml. of tetraethyl lead per imperial gallon. The remarkably high yield, above the theoretical or 238%, may be accounted for by the possible presence of some di-hexyl sul- Dhate formed from polymers produced during absorption of the propylene in" the preparation of the di-isopropyl sulphate.

Egcample III Gaseous propylene containing hydrocarbon was fed into sulphuric acid which was being vigorously stirred, The reaction vessel was cooled by an acetone-carbon dioxide mixture kept at -15 C.

With 447.5 grams of 100% H2804 and a feed rate of approximately 01-04 gram of propylene per gram of H2804 per hour, 1.90 mols of propylene were absorbed .per mol of H2804 and the product had the following composition:

- Per cent Free acid 1.5 Mono-isopropyl sulphate 15.5 Di-isopropyl sulphate 19.0

slowly to the mixture which was stirred at 1500.

R. P. M. After addition of 120 grams of ester mixture at a rate of 0.18 gram of CaHe per gram of catalyst per hour and a total reaction time of 2 hours, the mixture was stratified and 167 grams of acid layer analyzing 93% free H2804- was separatedfrom 138 grams of hydrocarbon layer. The alkylation products were found to be predominantly branched chain octanes.

A corresponding experiment in which the acid was added to a mixture of isopentane and diisopropyl sulphate gave less satisfactory results.

While reaction with dialkyl sulphates has been emphasized because of the many operating advantages obtainable by the use of this type of polyalkyl ester, particularly the fact that a part, usually of the order of about one-fourth to onetwelfth, preferably about one-tenth, of the alkylationacid may be recycled to the oleflne treatment stage for the formation of the esters and no problem of separation of acids is involved; esters of other polybasic inorganic acids corresponding to any of the sulphates described by way of example may also be used. Thus, for example, methyl ethyl phosphate, dipropyl phosphate, dipropyl secondary butyl phosphate, di-' methyl isopropyl borate and the like may be used in the same manner as sulphate esters provided suitable adjustment of the operating conditions is made. The polyalkyl esters may be produced from the corresponding alcohols or alcohol mix-' tures or by any other suitable manner.

mixture to obtain polymers and alkyl esters of polybasic mineral acids which may be alkylated in accordance with the present invention. The alkyl esters of olefine polymers described in U. S.

Patent 2,139,394 may also be used for effecting used for the subsequent alkylation when using acid of the same concentration in both steps, e. g.

when carrying out the absorption with acid from.

the hvlkylation unit. In general the alkylation with'monoalkyl esters may be carried out in a manner similar to those previously described for the reaction with polyalkyl esters.

The following example shows a typicalapplication of the invention to the alkylation of isoparaffins with alkyl acid sulphates.

Example IV Propyl acid sulphate was prepared by agitating a weighed quantity of a propane propylene fraction containing 80.7%. propylene with 100% H2804 in astirred mixer. After completion of the absorption the charge 'was drained from the mixer which was then recharged with H2804 and isobutane. The isopropyl acid ester was then added dropwise to 'a H2SO4-isobutane mixture at 10 C. and the stirring continued-forv sometime.

The acid phase from the alkylation reaction was analyzed and the hydrocarbon phase was stabilized and distilled.

- Formation of ester:

There is some advantage, particularly in respect to simplicity of operation, to be derived from the use of feeds to the alkylation unit containing alkyl acid esters particularly mono-alkyl sulphates. These may readily be formed by simple absorption of the corresponding olefine in sulphuric acid, preferably sulphuric acid obtained from the alkylation step of the process. Particularly when using recycled alkylation acid from alkylation stage there may be polymers formed during the olefine absorption but these, together with any dialkyl sulphate contained therein may be fed to the alkylationunit, preferably after removal of normal paraillns therefrom, along with the alkyl acid sulphate-containing absorption product and all three reacted with isoparaf- .fln. Suitable methods for carrying out the absorption of oleflnes are described, for example, in U. S. Patents 1,955,873 and 2,106,521. Where mixtures of tertiary and secondary oleflnes are being used the absorption procedure of U. 8. Patent 2,060,143 may be advantageously used {with or without the dilution step between absorption stages described therein since any polymers formed may also be used for aikylation.

. U. $.Patents 1,938,177, 2,007,159 and 2,001,160

Acid charge H2SO4) grams 153 Propylene charge (80.7%) do '72 Recovered acid phase do 202 Initial acidity as per cent E804; 43.6

Per cent free H2804 .176

Total acidity as per cent 112804---- 70.7

Reaction of ester with isobutane: I

Acid charge (100% H2SO4) grams 365 Isobutane (99.5%) do 200 Product from ester formation do 158 Product (acid phase) -do.. 453

Initial acidity as per cent Bison. 96.5"

Per cent free H2804 95.8

' Total acidity as per cent 112804- 96.9 Product (hydrocarbon phase)--gram's-- 220 Debutanized product do 77.4

By a similar procedure using an absorption product of secondary butylenes in sulphuric'acid alkylate yields of the order of 200% to 225% may be obtained from isopentane, with a sulphuric acid catalyst consumption no greater than that obtainable by the direct use of the olefine.

One particularly advantageous method of applying the reaction of alkyl acid sulphates in ac-' cordance with the invention is' in the regeneration of alkylation acid which may advantageously be effected by agitating sulphuric acid whichhas been used for the alkylation of isoparamns, whether with oletlnes or alkyl esters,

with an isoparamn substantially free of oleflnes.

Either the same, or another, isoparaflln may be used for'the reaction which-may be carried out at the same, or preferably a somewhat higher, temperature than was used for the original alkyl.- ation. In this way the alkyl acid sulphate content of the acid may be reacted and'not only may additional valuable isoparaflins be recovered but also the concentration of the acid and its effectiveness in catalyzing further alkylation may be increased.

Still other variations may be made in the process which is not limited to the details described only by way of illustration but only by the ap pended claims.

I claim as my invention:

1. A process for producing gasoline boilinghydrocarbons from normally gaseous hydrocarbons containing an olefine which comprises contacting said hydrocarbon with sulphuric acid of 90% to 100% concentration on a hydrocarbon free basis in the proportion of at least two mols of olefine per mol of sulphuric acid under conditions at which a dialkyl sulphate of said olefine is formed, separating the reaction mixture into a hydrocarbon phase containing said dialkyl ulphate and an acid phase, removing unreacted normally gaseous hydrocarbon from said separated hydrocarbon phase and contacting .the dialkyl sulphate with adispersed mixture of an isoparaflin and sulphuric acid of 90% to 100% concentration. maintainin inthe reaction mixture at least three mols of isoparaflin and at least one andone-half mols of sulphuric acid per mol of dialkyl sluiphate at a temperature between -10 C. and +40 C. at which alkylation of said isoparaflin by said dialkyl sulphate takes place, stratifying the reacted mixture into a hydrocarbon phase containing the alkylation product and an alkylation acid phase, separating a minor part of the latter and supplying it to said olefine contacting stage and returning alarger part to said isopari aflln alkylation.

2. A process for producing gasoline boiling hydrocarbons from isobutane and a normally gaseous olefine which comprises contacting hydrocarbon containing said olefine and sulphuric acid I of at least 90% concentration on a hydrocarbon free basis which has been employed for the alkylation of isobutane in the proportion of at least two mols of olefine per mol of sulphuric acid under conditions at which a dialkyl sulphate corresponding to said olefine is formed. diluting the reaction product with sufficient water to cause separation of a phase containing said dialkyl sulphate substantially free from alkyl acid sulphates. admixing the separated dialkyl sulphate with a molar excess of isobutane in the liquid hase and feeding the resulting mixture into. a dispersion of liquid isobutane and sulphuric acid of 90% to 100% concentration on a hydrocarbon free basis and correlating the amount and concentration of the acid, the reaction temperature and the proportion of dialkyl sulphate to isobutane to effect alkylation of the isobutane as the principal reaction in the process.

3. A process of alkylating isobutane which comprises contacting isobutane and a dialkyl sulphate in the proportions of at least three molecules of isobutane per molecule of said sulphate in the presence of sulphuric acid of 90% to 100% concentration on a hydrocarbon free basis at least equivalent to one mol of acid. per mol of said sulphate at-.a temperature between -10 C. and +40 C. at which alkylation of isobutane takes place.

4. A process of alkylating an isoparaflin which comprises contacting said isoparaffin and a neutral polyalkyl ester of a polybasic mineral acid with concentrated sulphuric acid and correlating the amount and concentration of sulphuric acid. the reaction temperature andtime, and the proondary olefin, which omprises separately converting the more reactive olefin and the less reactive olefin to the corresponding dialkyl sulfates, reacting the dialkyl sulfate from the more reactive tertiary olefin with a low boiling isoparaffin in the presence of concentrated sulfuric -acid of alkylation strength in a reaction zone maintained under less drastic alkylating conditions, and alkylating an isoparaflin with the.

dialkyl sulfate from the less reactive secondary olefin with concentrated sulfuric acid of alkylation strength in another reaction zone maintained under more drastic alkylating conditions.

6. Themethod in the alkylation of a low boiling isoparafiln with a low boiling olefin utilizing an olefinic feed stock containing a more reactive olefin and a less reactive olefin, which comprises separating the more reactive olefin from the less reactive olefin by selective conversion of the former to the corresponding dialkyl sulfate, alkylating an isoparaflin with said dialkyl sulfate, then converting the less reactive olefin to a dialkyl sulfate and alkylating an isoparaifin therewith in the presence of concentrated sulfuric acid at a higher temperature. I

'7. The process which comprises forming a mixture of a polyalkyl ester of a polybasic inorganic acid and the corresponding acid, extracting said polyalkyl ester from said acid with an isoparaflin and contacting the extract with concentrated sulfuric acid under conditions at which alkylation of- 8. A process of alkylating an isoparaffin which comprises adding a substantial amount of a preformed dialkyl sulfate to a molal excess of said isoparaffin in the presence of concentrated sul furic acid and correlating the amount-and concentration of sulfuric acid; the reaction temperature and time, and the proportion of isoparaflin and dialkyl sulfate to effect alkylation of the iso paraflin by said dialkyl sulfate as the principal reaction.

9. The process which comprises forming a mixture of a dialkyl sulfate and sulfuric acid, ex-

tracting saiddialkyl sulfate from said sulfuric acid with an isoparaflin, and contacting said extract with concentrated sulfuric acid under conditions at which alkylation of said isoparafiin is ing said di-isopropyl sulfate from said sulfuric.

acid with isopentane, and contacting the extract with concentrated sulfuric acid under conditions at which alk lation of the isopentane is effected.

12. A process of alkylating an isoparafin which comprises reacting said isoparafiin with a neutral alkyl borate in the presence of concentrated sulfuric acid under alkylating conditions.

JOHAN JACOB m: JONG.