US2437828A - Alkylation of aromatic hydrocarbons with sulfuric acid catalyst avoiding sulfonationof product - Google Patents

Description

Mardi i6, 1948- D. J. LYoNs ET AL ALKYLATION OF AROMATIC HYDROCARBONS WITH SULFURIC ACID CATALYST AVOIDING SULFONATION OF PRODUCT Filed Feb. 14. 1944 Accordingly, methods have been Patented Mar. 16, 1948 ALKYLATION BONS WITH F AROMATIC HYDROCAR- SULFURIC ACID CATALYST AVOIDING SULFONATION 0F PRODUCT Daniel J. Lyons, Martine ley. and Lloyd L. Ingra ham,

z, Arthur Lazar, Berke- Los Angeles, Calif.,

assgnors to Tide Water Associated Oil Company, San Francisco, Calif., a corporation oi' Delaware Application February 14, 1944, Serial No. 522,304

3 Claims. A l

This invention relates to the alkylation of benz-ene and its homologues to produce alkyl derivatives of benzene, and in a, more speciiic form to the manufacture of aromatic hydrocarbons having superior antiknock characteristics when incorporated into motor fuel.

It is an object of the invention to provide a method whereby benzene and homologues of benzene maybe alkylated to form alkyl derivatives of the same.

Another object is to provide a process for alkylating benzene and its homologues, involving the use of sulphuric acid, in which sulphonation and polymerization is avoided.

An object of a specific embodiment of the invention is to recover, as a high ant-iknock component for motor fuels, the benzene content of petroleum.

Other objects will be apparent from the following description.

In the manufacture of modern aviation gasoline, especially that intended for use in military aviation, it has become common to include a small percentage of isopropyl benzene (cumene) or' of certain other alkyl derivatives of benzene. These aromatic compounds have proven to be very effective in improving the antiknock quality of aviation gasoline, especially during periods of operation on rich fuel-air mixtures. Although 30 cumene and similar aromatic hydrocarbons have been found in petroleum in certain localities, the proportions so present are too small for successful separation or for supplying the required amounts. developed for synthesizing cumene from benzene.

It is known that benzene and propylenewill react. in the presence of concentrated sulphuric acid as a catalyst, to form cumcne in a manner which may be considered superlcially similar to the alkylation of isoparaiins with propylene Vor with other olens. However, the chemical reactions involved are quite dissimilar and the alkylation of benzene with sulphuric acid as a catalyst creates diillcult problems of control due to the formation of sulphonic acids from the benzene, and due to alkyl-sulfates which do'not participate in the alkylation reaction and thus remain inthe iinished product either as such or as sulphates of polyoleilns. In the alkylation of isoparamns the formation of alkyl sulphates is readily controlled by maintaining large amounts o1 the isoparaflln in the reacting mixture. However, when benzene, or an alkyl derivative of benzene, is brought into contact with sulphuric acidof the customary alkylation strength, sulphonation of a substantial proportion of the original aromatic hydrocarbon material occurs. Likewise, in the presence of sulphuric acid ofalkylation strength, sulphonation oi the alkylated aromatic portion occurs even more readily. Theresulting aromatic sulphonic acids are diiilcult to separate economically from the desired alkylated aromatic and, in any event, represent substantial losses of material.

In order to avoid the above difllculties. various processes have been proposed using phosphoric acid, or mixtures of phosphoric acid and sulphurlc acid, as catalyst. Some of these involve high temperatures with and all of them present difficulties in the recovery of the high-priced phosphoric acid.

Some success on a commercial scale has been obtained in the alkylation of benzene with propylene using certain solid catalysts. 'Ihese involve the use of high temperatures in the range of 500 F., require extended time for regenerating the catalyst, in some instances are limited to a single use of the catalyst, and generally produce low conversion of the benzene for each pass through the reactors and subsequent fractionation equipment.

According to the present invention benzene and its homologues are alkylated using alkyl sulphate as the alkylating agent. When an acid-alkyl sulphate, or a. dialkyl sulphate containing even a small amount of acid-alkyl sulphate, is brought into contact with benzene or a homologue of concomitant high pressures,

benzene, alkylation proceeds rapidly at atmos' pheric temperature without further catalyst and without substantial formation of aromatic sulphonic acids. In the presence of stoichiometric amounts, or excess, of the aromatic hydrocarbon the alkyl sulphate is almost completely consumed with the liberation of sulphuric acid, as is illustrated by the following equation showing the reaction of benzene with acid-isopropyl sulphate:

This reaction under atmospheric, or slightly higher than atmospheric, temperature forms substantially theoretical yields of alkylated aromatic hydrocarbon, but does not proceed to the point where the alkylated aromatic is subject to any substantial degree of sulphonation by the sulphuric acid liberated in the reaction.

The acid-alkyl sulphate for the alkylation may readily be prepared by reacting the desired olefin with sulfuric acid in accordance with generally known conditions to reduce the amount of polymerization of the olefin to a minimum. The strength of the sulphuric acid may be between 65% and 100% H2SO4 and the absorption of the olefin by the sulphuric acid should be conducted at a temperature range known to reduce polymex-ization of the olefin to a minimum. For the absorption of propylene a safe temperature range has been found to be not in excess of 60 F. when 4the absorbing acid has a strength between 92l00% H-SO4. With weaker acid, such as 8090% H2504. absorption temperatures up to 80 F. are permissible. However. to obtain optimum yields in the subsequent alkylation and, in particular, to avoid any sulphonation of aromatics during the alkylation. the preferred strength of sulphuric acid to be used in preparinc the acid-alkyl sulphate should not exceed 90% H2804. By using sulphuric acid ci' this low a concentration the sulphuric acid released durina the alkvlation is always below the sulphonation stre ath.

Although. broadly. the invention comprehends the alkylation of ben'rene and benzene homologues with an alkvl sulphate prepared separately and bv any method of preparation. a preferred embodiment includes the formation of the alkyl sulphate in one stage of the process under selected conditions to avoid the formation of polymers of the olefin and` in a separate subsequent stage. the alkyiation of theV aromatic hydrocarbon with the akvl sulphate under different conditions selected to avoid the formation of sulphonated aromatics. In this manner the disadvantages of the usual method of alkylatinz aromatics with oleflns by a sulphuric acid catalyst are avoided.

To this end. as stated above. the oleiln is reacted with'sulphuric acid. preferably of 80-90% strength, at a temperature not exceeding 80 F. until substantially all the sulphuric acid is converted to acid-alkyl sulphate. The acid-alkyl sulphate thus formed is introduced into a body of the aromatic hydrocarbon to be alkylated at a temperature between about 60 F. and 150 F. while maintaining an excess of the aromatic present. For best results the molal ratio of the aromatic present to'the acid-alkyl sulphate introduced should be greater than about 2:1 in order that the acid-alkyl sulphate may be consumed without formation of poly alkyl-aromatica In cases where di-alkyl, tri-alkyl, or tetra-alkylaromatics are desired, the ratio of aromatic hydrocarbon to alkyl sulphate may be changed accordingly. With ratios above about 2:1 the yield of alkylated aromatic is chiey the monoalkyl derivative- With lower ratios, substantial amounts of poly-alkyl derivatives are formed.

For the preparation of the alkyl sulphate the olefin need not be in highly concentrated form, but may be in mixture with substantial amounts of parainic hydrocarbons. For example, if it is desired to alkylate benzene with propylene to form cumene, the propylene may from a C3 fraction derived from petroleum Arefin ery cracking plant gases. In such a case the entire C3 fraction may advantageously be passed through an absorber containing sulphuric acid of the desired strength and at the desired temperature. The propylene is absorbed by the sulphuric acid with the formation of acid-isopropyl sulphate and the non-reactive hydrocarbons are discharged from the absorber for any desired use.

vvenient to operate the The absorption is controlled to bring about a conversion of substantially all the sulphuric acid to alkyl sulphate. The acid-isopropyl sulphate thus formed is passed to the reactor wherein benzene (or homologue of benzene) is to be alkylated.

In commercial operations it is generally inconabsorber," wherein the olefin is converted to alkyl sulphate, and the reactor, wherein the benzene is aikylated with the alkyl sulphate, at all times at such respective rates that the absorber will produce alkyl sulphate only at the rate required by the reactor. Accordingly, an accumulator tank for th'e alkyl sulphate may advantageously be placed between the absorber and the reactor. As it is disadvantageous to store acid-alkyl sulphate for any substantial period of time due to its tendency to deteriorate, when such accumulator tank is used the reaction in the absorber should 4be carried out with the addition of sufficient olefin to produce the more stable dialkyl sulphate, It has been found that di-alkyl sulphate may be stored at atmospheric temperature for appreciably long periods of time without substantial decomposition or deterioration. The Idi-alkyl sulphate may readily be rendered suitable for alkylation according to the invention by the addition of sulphuric acid prior to its introduction into the reactor. The quantity of sulphuric acid so added may be upwards from about 10%, more or less. but the total sulphuric acid, including that combined with the olefin, should not substantially exceed a ratio of 2 mols of sulphurlc acid per mol of olefin absorbed.

The procedure of forming the neutral alkyl sulphate in the absorber and converting at least some of it to acid-alkyl sulphate prior to the alkylation has been found useful also in other cases where there is a substantial lapse of time between the production of the alkyl sulphate and its use; for example, in installations where the absorber is located at some distance from the reactor. Even where no time lapse is involved such procedure may be useful for reducing the amount of control necessary in operating the absorber and the process as a whole. The reaction in the absorber may be allowed to go to completion and the desired amount of sulphuric acid may be added as required.

be obtained esmas- Expetiment Number 1- 2 8 4 5 6 7 8 9 10 1l 12 Formation of alkyl Sulphate:

Strength oi' acid used, r cent HzSO 98. 6 98. 6 98. 6 84.3 98. 6 89. l 85. 5 83.6 86. 3 86. 3 86. 3 86. 3 Volume oi acid used, cc.-. 1,000 540 180 671 800 800 1,000 1,000 1, 500 `1, 500 l, 500 1, 500 Prorylene charged, gms.- 1, 57e 42e 170 483 743 49:3 367 303 693 693 581 69a Mo ratio H1804 to 03H5 1:2 1:1 1:1.2 1:1 1:1.2 1:0. 9 1:0. 6 1:0. 6 1:0.6 1:0. 6 1:0. 6 1:0. 6 Vol. alkyl sulfate reactant-catn'st, 60..-.. 3, 100 1, 130 380 1, 303 1, 870 1, 520 1, 450 1, 550 2, 515 2, 515 2, 515 2, 515 Specliio gravit; l reactant-ca yet l. 104 1'. 32 l. 28 1.26 l. wd l. 292 1. 414 l. 369 1. 349 1. 349 l. 349 1. 349 Per cent mono opropyl sulfate in reactantcatalyst 0 100 87 100 Per cent Diisopropyl sulfate in reactant- Alkylation:

All?) sulfate charge, cc 465 1.100 414 535 395 486 680 687 580 580 580 580 Hy rocarbon charge, oo 1, 000 2, 000 2, 000 1, 000 1, 000 l, 000 750 1, 000 1, 000 1, 000 1, 000 l, 00() Boiling range oi h drocarbon, F 176 148-180 148-180 176 176 176 176 176 176 176 176 176 Per cent Benzene hydrocarbon.- 100 20. 2 2). 2 100 100 100 100 100 100 100 100 100 Contact time, minutes 3() 30 52 16. 5 46 57 70 35 44 74 78 Temperature of agitator, F 76 114 110 '110 110 130 145 130 110 100 Yi lolmtiotoalkylsulfate 2:1 1:2 1.1:1 2.5:1 2.9:1 2.9:1 2.1:1 2.4:1 3:1 3:1 3:1 3:1

Volume offiroduct co 1, 255 2, 350 2, 160 1, 210 1,165 l, 225 965 1, 260 1,195 1, 205 l, 215 1, 215 Per cent A kylate in product 53. 3 34. 6 22.0 45. 6 33. 5 42. 5 56. 0 48. 0 41. 9 45.0 44. 2 42. 0 Per cent Iso ropyl benzene 1.. 54. 3 10. 7 9. 5 46. 3 32. 6 45. 9 63. 7 54. 2 43. 6 47.0 49. 8 43. 7 Per cent Di oprogyl benzene l 8. 6 10.7 10. 2v 4. 6 1. 8 1. 2 3. 2 2. 5 2. 4 2. 9 none 2. 1 Per cent Boiling a ove 410 F none 15.0 none none none none none none none none none none Per' cent Bottoms l 4. 0 4. 3 4. 1 4. 2 4. 7 4. 9 5. 2 3. 8 4. 1 4. 1 3. 9 5. 2 End point of roduct 402 420 388 390 402 394 390 383 386 375 360 398 Recovered acidolume, ce 265 660 240 300 215 235 465 420 465 360 355 360 Recovered acid-B Cc gravity 1. 56 1. 56 1. 55 1. 760 1. 544 l. 730 1. 768 1. 764 1. 618 1. 768 l. 767 1. 771

Recovered acideid strength in per cent l Based on the volume of hydrocarbon charge to lation i In Experiment No. l, carried out with the alkyl s fate, free H1804 (75 ce.) had to be added to initiate the alkylation reaction.

In the accompanying table a series of twelve diilerent experiments is given which shows the results obtained with a. charging stock containing aromatics and with a reactant catalyst of varying composition. More specifically the propylation of benzene is involved and it is shown in what manner the propylation of benzene is aiiected by such variables as: (1) strength of H8204 used in preparing the catalyst reactant, (2) mol ratio of HzSO4 to propylene in the catalyst reactant, (3) ratio of monoto cli-isopropyl sulphate in the catalyst reactant, (4) mol ratio of benzene to propylene contained in the catalyst reactant, (5) contact time, (6) temperature.

The following conclusions can be drawn from the experiments described.

In all cases where 'sulphuric acid of high strength (98%) was used, the strength oi.' the resulting spent acid is considerably below that of the original acid used in preparing the cata- 'lyst-reactant, which seems to indicate that the alkyl sulphate is not fully utilized for alkylation purposes and that possibly other undesirable reactions have taken piace. Refer to experiments 1, 2, 3, and 5.

On the other hand, when the original acid strength was chosen between 83 and 89% HnSO4, the resultant spent acid shows almost the strength of the original acid charged to the absorber for the preparation of the catalystreactant. The restoration of the acid concentration to such a high degree indicates that the alkyl sulphate catalyst-reactant is substantially usedup in the alkylation reaction and that undesirable side reactions have been reduced to a minimum.

As far as the mol ratio of the alkyl sulphate to benzene is concerned, wide variations seem to be permissible. Satisfactory results were vobtained with mol ratios oi 3:1 of benzene to alkyl sulphate, as well as with mol ratios as low as 1:2.

It is evident, however, that a low mol ratio of benzene to alkyl sulphate favors the formation of poly alkylated benzene; therefore, the preferable mol ratio would be closer to 3:1 in such cases where the manufacture of mono-iso-propyl benzene as a blending agent for aviation gasoline is aimed at in order to avoid formation of poly alkylated high boiling aromatics which would be outside of the speciiied boiling range. On the other hand, if recovery of large percentages of di-iso-propyl benzene, tri-iso-propyl benzene, or tetra-iso-propyl benzene is desired, a low mol ratio of benzene to propylene is indicated.

The time-temperature relationship of the alkylation reaction is well indicated in Examples 9, 10, 11, and 12. These four experiments were carried out with catalyst-reactant from the same batch prepared from HzSOi of 86.3% strength and using a constant mol ratio of 3:1 benzene to alkyl sulphate, It will be noted that the shortest contact time was required at the highest contact'temperature, but under these particular-conditions the alkylation reaction was less complete, as indicated by the low specific gravity of the spent acid resulting from the process. The most complete conversion appears to take place at F. where the specific gravity comes back to 1.771, which is only' slightly below the original gravity of 1.80.

Although the involved reactions may be carried out by batch treatment in closed vessels equipped with stirring devices and means for required temperature control, the invention is well suited for the use of continuous operation and various continuous apparatus will suggest themselves ior conducting the reactions. The absorber may advantageously be a tower equipped with bailles or packing in which the sulphuric acid is caused to flow downward countercurrently to a rising stream-of the oleiin or olen-contaim' ing hydrocarbon mixture. The necessary temperature control may be provided by coolers in the gas and/or sulphuric acid stream entering the tower or the tower may contain a cooling jacket or cooling coils. Likewise, for continuous operathough countercurrent flow may be used when desired. If desired, the reactor may comprise a centrifugal pump, which acts as a mixer as weil as providing the propulsion, followed by a reaction chamber of the turbulence mixer type. As

l the alkylation reaction proceeds readily at or near atmospheric temperatures and is only slightly exothermic, temperature control in the reactor is very simple. Both the aromatic charge and the alkyl sulphate may be passed through heat exchangers to accomplish this temperature control.

For satisfactory alkylation, depending, of course, on the degree of agitation and other factors attained in the reactor, a time interval of ten minutes to one hour, or more, is required, following which the sulphuric acid formed by the reaction is separated from the -alkylation product. Under optimum operating conditions the sulphuric acid withdrawn from the alkylation reaction contains a minimum amount of side reaction products and, therefore, may be returned to the absorber for the formation of further alkyl sulphate. It has been found that, when 65% to 90% H2504 was originally used for the formation of the alkyl sulphate, the acid obtained-from the alkylation reactor is sufficiently free fromv sludge as to be useful for several cycles in the process.

The alkylated hydrocarbon layer obtained from the reaction is rst neutralized by washing with an alkaline solution, and then distilled to fractionate out any unreacted aromatic which may be returned to the reactor for a subsequent alkylation cycle.

A particular embodiment of the invention resides in the eilicient utilization of the aromatic content of certain petroleum fractions containing relatively small percentages of aromatic hydrocarbons. In the manufacture of aviation gasoline it is now common practice to separate a petroleum fraction containing predominantly Cs and C1 hydrocarbons. This material is further subjected to so-called "superfractionation" to obtain two fractions: one, predominating in isoparailins, is used as an antiknock component of aviation fuels, while the other, predominately in normal paraffins, is generally disposed of by blending into low grade motor fuels. It has been found that the entire Ce-Cr fraction first mentioned above when derived from California petroleum contains approximately '7% of benzene. Upon superfractionation due to azeotropic eiects caused by the presence of certain naphthenes this benzene is about equally divided between the isoparafnic and normal paraillnic fractions. Thus, the normal paraiiinic fraction contains, roughly, about 7% of benzene of high antiknock value which, in this manner, because of the limitations of commercial fractionating equipment, finds its way only into low grade motor fuel'. In accordance with the invention it has been found that mostof the benzene contained in the normal parafllnic fraction can be salvaged readily by alkylating it to cumene and di-isopropyl benzene which, due to their higher boiling points, may then be readily separated from the bulk of low antiknock hydrocarbons by distillation. The separated alkylated benzene may then be used as a valuable antiknock component of aviation gasoline.

If desired, the entire Ce-Cr fractions may be treated to obtain cumene and di-isopropyl benzene from its total benzene content. Likewise, the invention may be applicable to other hydrocarbon materials containing small amounts of benzene where it is desired to alkylate the benzene.

To this end the hydrocarbon fraction containing the benzene is treated with acid-isopropyl sulphate or normal isopropyl sulphate containing some acid-isopropyl sulphate), prepared by absorption of propylene in sulphuric acid. In

from alkylation cycle in line 24. and passes through line 3 into top of propylene absorber 4. Propane-propylene feed enters through line 6 into the bottom of propylene absorber 4 wherein the propylene reacts with acid to form alkyl sulphate which is discharged through line 5 into surge tank I0. The unreacted gases in propylene absorber 4 are discharged through line 1. The proplylene absorber is provid'ed with a jacket through which is circulated coolingwater as shown by lines 8 and 9. Free sulphurio acid may be drawn from tank I through line 30 into the alkyl sulphate surge tank when operations require such adjustment. The alkyl sulphate from surge tank I0 passes through line II, meeting benzene fraction from line I2, then passing concurrently through heat exchanger I4, through line I5, and into alkylation reactor I6., From alkylation reactor I6, the mixture passes through line I1, through cooling coil I8 and line I9 into separator 20. 'I'he acid layer in separator 2li leaves through line 22 and thence to storage by line 23, or line 24, as recycle acid to charging line 3, as mentioned before. The hydrocarbon layer in separator 20 passes through line 2| to caustic contactor 25 where caustic enters line 21' and spent caustic leaves by line 28. 'I'he neutralized hydrocbarbon layer leaves contacter 25 through line 26 to debenzenizer fractionator 21 where cumene or alkyl aromatic fraction leaves by line 29 to storage and the unreacted benzene passes through 28 as recycle entering the system again through line I2.

In the appended claims the term "benzene hydrocarbon is used to denote one or more hydrocarbons of the group consisting of benzene and those homologues of benzene which are susceptible of further alkylation.

We claim:

l. The method of aikylating benzene hydrocarbons with olefines in which the presence of Water is utilized to dilute sulphuric acid present during the reaction below sulphonating strength, which comprises reacting an oleiin with sulphuric acid of a. concentra-tion between 65% and 90% and in quantity not greater than two mois of acid per-mol of olen, contacting the .reacted mixture with an excess of benzene hydrocarbon, while maintaining the temperature between about 60 F. and about 150 F., water at all times being present in sucient quantity to dilute all sulphuric acid present during and formed by the reaction below 90% strength to avoid sulphonation, separating the contacted mixture into an oil layer and an acid layer, removing the acid layer, neutralizing the acidity of the oil layer, and fractionally distilling the neutral oil layer to separate alkylated hydrocarbons from unreacted hydrocarbons.

2. The method of claim l in which the concentration of the acid is between and 90%.

3. A cyclic process for alkylating benzene hydrocarbons with oleiines in which the presence of water is utilized to dilute sulphuric acid .present during the reaction below sulphonating strength, which comprises flowing a stream of olefinic hydrocarbons through an absorption zone; iiowing a stream of 65% to 90% sulfuric acid through said zone countercurrently to, and in contact' with, said oleiinic hydrocarbons, whereby at least half of said acid becomes combined with olein forming alkyl sulphate, said alkyl sulphate containing water in suiicient quantity to dilute all sulphuric acid present during and formed -by the reaction in the hereinafter specified alkylation zone below 90% strength, withdrawing any unreacted hydrocarbons from said zone; separately withdrawing alkyl sulphate, together with any free sulphuric acid, from said zone; iiowing said alkyl sulphate into an alkylation zone maintained at a temperature between about 60 F. and about 150 F.; owing a stream comprising an excess of a benzene hydrocarbon into said alkylation zone, whereby said alkyl sulphate reacts with said benzene hydrocarbon to form allcyiated benzene hydrocarbons and free sulphuric acid; flowing the reacted mixture from said alkylation zone into a separation zone and therein continuously separating free acid from alkylated and unreacted hydrocarbons; ilowing said alkylated and unxeacted hydrocarbons from said separation zone to a neutralizing zone wherein acidity is neutral- 10 ized by contact with an alkali and thence to a fractionating zone; separating alkylated hydrocarbons from unreacted hydrocarbons in said fractionating zone; and continuously removing free sulphuric acid from said separating zone and recycling said free acid to said absorption ZODB.

DANIEL J. LYoNs. ARTHUR LAzAR. LLOYD n mGRAHAM. REFERENCES CITED The following references are of record in the 111e of this patent:

UNITED STATES PATENTS Number Name Date 1,670,505 Gunther May 28. 1928 1,938,162 Woolcock Dec. 5, 1933 1,994,249 Ipatiefl.' et al. 1.--- Mar. 12, 1935 2,001,907 Ipatiei! May 21, 1935 2,143,493 Stanley et al. Jan. 10. 1939 2,276,171 Ewell Mar. 10, 1942 2,349,415 Draeger et al May 23, 1944 OTHER REFERENCES Guyot: New Method Chem. Abst. vol. 14 (1920) pages 404-405 2 pages).

Ipatiei! et al.: Inuence ot sulfuric Acid Benzene. J. A. C. S.. 582. 919-922 (4 pages), (June, 1936). 26o-671.

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