US2396682A

US2396682A - Production of alkyl aromatics

Info

Publication number: US2396682A
Application number: US456769A
Authority: US
Inventors: Don R Carmody
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1942-08-31
Filing date: 1942-08-31
Publication date: 1946-03-19
Anticipated expiration: 1963-03-19

Description

D. R. CARMODY PRODUCTION 0F `ALKYL AROMATICS F'iledl Aug. 31, l942 March 19, 19.46.

. description of my invention proceeds.

Patented Mu. 19, 194e PRODUCTION F ALKYL ARCMATICS l Don R. Carmody, Hammond, Ind., assignor to Standard Oil Company, Chicago, lll., a corporation of Indiana Application August 31, 1942, Serial No. 456,769 G-Claims. (Cl. 26o- 671) This invention relates to the production of alkyl aromatic hydrocarbons and relates more particularly to the production of ethylbenzene by the alkylation of benzene with ethylene'from a dilute ethylene stream.

Monoalkylbenzenes and particularly the lower boiling monoalkylbenzenes such as ethylbenzene or isopropylbenzene have been found to be valuable constituents in aviation fuelsl because of their very high octane number particularly under Supercharged conditions. The amount present in ordinary refinery streams of petroleum hydro carbons is comparatively negligible and even in the products from such processes as catalytic or thermal cracking, catalytic aromatization,. etc., the ultimate yield of low boiling monoalkyl aromatics is comparatively low. It has been known the Contact of the po1ya1ky1 aromatic aikylate thus formed with benzene inthe presence of a. catalyst to form monoalkyl aromatic hydrocarbons.

. Referring now to the drawing, a dilute olefin stream enters absorber I0 via line I I fromv a suitable source (not shown). A particularly suitable olefin feed for my process is a refinery fuel gas stream or dilute ethylene stream containingv not only ethylene but hydrogen, methane, ethane and possibly traces of propane andpropylene. The ethylene content of this stream can vary from about 3% by volume'to about 20% by volume or higher and such gaseous feed streams are for some time that these alkylbenzenes canbe synthesized by the alkylation of aromatic hydrocarbons with olefins in the presence of activating olefin stream be rich 'in oleflns not only because of the great reduction in reaction space thus ob# taine but also because the yield based on olefins fed to the process is much higher when diluting,

inert gases are substantially eliminated.

It is an object of this invention to provide an improved process for the alkylation of aromatic hydrocarbons with olefinic gases from an olefin .stream containing inert gases. Another object of further object of my invention is to provide an improved process wherein hydrocarbons valuable i'orl aviation fuels are prepared from refinery fuel g'ases. and a benzene-rich fraction. Further objects and advantages wil1 become apparent as the The accompanying drawing illustrates apparatus suitable for carrying out one preferred embodiment of my invention and is in the form of a simplified flow diagram.

.Briefly stated my inventioncontemplates the absorption of ethylene from a refinery fuel gas stream in polyalkyl aromatic hydrocarbons and the alkylation of benzene with the absorbed alkyl aromatics of higher molecular weight and to be found in large quantities in any commercial petroleum reiinery being employed therein suitably as fuel gases, etc. Any ethylene-containing stream can be used, however, such as those from gas cracking or catalytic dehydro- 20 genation and the exact source is not critical. In catalysts, etc. It is generallyv desirable that the l absorber I0 the olefin-containing stream is contacted with a polyalkyl aromatic hydrocarbon stock from line I2. This can suitably be a hydrocarbon stock higher boiling thanls generally considered suitable or desirable in gasoline streams and may contain such mixtures as di- -ethylbenzene, ethyltoluene, triethylbenzene, propyltoluene, etc. 'I'he absorber is maintained at a pressure within the approximate range of about atmospheric to about 500 pounds per square inch and at temperatures within the approximate range of 50 to 150 F. Then unabsorbed gases, substantially o1eiinfree,fpass overhead through line I3 while the enriched polyalkylbenzenes are withdrawn from absorber I0 through line It and directed via line I5 and lia and valve I6 to mixer I'I where they are thoroughly mixed with benzene Vfrom line I8 in such proportions that the mol ratio of available olefin to benzene is not greater 0 thany about 1 to 1 and preferably is of the order 01' about 0.4 to 1 t0 0.6 to 1.

The mixture of benzene and absorbate passes Fresh catalyst can be added to alkylator 20 viav lines 2l and 22 and may comprise any of the conventional alkylation catalysts such as the metal halides or their complexes, sulfuric acid, hydrogen iiuoride, etc. vA particularly suitable catalyst is an aluminum chloride hydrocarbon complex having a heat vof hydrolysis within the approximate range of 60 to 75 large calories per gram of active aluminum, as described in co peridingapplication Serial No. 311,950, now U. S. Patent 2,308,560. With this catalyst, alkvlator 20 is operated at temlcieratures` within the approximate range of 100 F. to 300 F., preferably at about 120 to 200 F., and at atmospheric to 1000 pounds per square inch pressure, preferably at pressures within the approximate range of 100 to 300 pounds per square inch. K

An activator can be added through line 23 to mixer Il, or can be absorbed in either of the incoming hydrocarbon streams if desired., It can also be added directly to alkylator 20. The activator suitably can be a hydrogen halide such as )HCL HIBr, or a substance yielding a hydrogen halide under the reaction conditions, as, for example, alkyl halides, chlorine, moisture, etc. It can be present in amounts ranging from about 0.1% to based on the catalyst, preferably about 4%. 'u l From alkylator the reaction mixture passes to settler 2l via line 25 in which separation of the catalyst from the hydrocarbons is accomplished, the catalyst being withdrawn through line 26 and if still active for promoting alkylation is recycled Y via line 21 to line 22 and alkylator 20. If the zenes employed as the absorption medium. In o addition, a certain amount of the polyalkylben zenes will undergo dealkylation, the separated alkyl groups also serving to alkylate the benzene present. These are desirably directed to a flash drum 32 operating at atmospheric pressure or slightly above and at temperatures within -the range of about 80 to 200 F. A'I'he gases are flashed oil together with some benzene and pass overhead through line 33 to scrubber 34.. The

with higher boiling alkylbenzenes from fraction-4 ator 35 which enter scrubber 3l via line 33. If desired -the polyalkylbenzenes from an outside source which may be identical with that for absorber Alli can be substituted, the scrubbing medium entering through line 31 which joins line 33.

. tionator 35 can be any conventional fractionating system which will serve to separate the liquid hydrocarbons into a. benzene fraction, a monoalkylbenzene fraction containing primarily ethyl:- benzene and a polyalkylbenzene fraction. The separated benzene passes overhead and while it may be discarded via line 43, itis preferably recycled via line Il to ,line Il where it is mixed zwith incoming fresh benzene and directed to mixer i1. The polyalkylbenzenes are Withdrawn from the lower portion of fractionator 35 and recycled to absorber i0 via line 45. A portion of the polyalkylbenzenes may be by-passed to scrubber 34 by opening-valve I3 in line 41 which joins line 36, the enriched polyalkylbenzene medium being withdrawn from scrubber 34 through line 48 which rejoins line 45 leading to absorber i0. The desired monoethylbenzene is withdrawn through line I3.

As an alternative method of operation, the absorbate from absorber ill can be directed via line ila to alkylator 50. In alkylator 50 the polyalkylbenzenes containing absorbed olens are contacted wlthlan alkylation catalyst such as aluminum chloride, a hydrocarbon complex containing aluminum chloride, sulfuric acid, hydrogen fluoride, etc. For example, if an aluminum chloride hydrocarbon complex is employed the reaction in alkylator 50 can be carried out at temperatureswithin the approximate range of. 50 to 250 F. and under superatmospheric pressures. The catalyst can be added through line 5I and can be either fresh catalyst from line 52 or recycle catalyst from line 53. An activator, whichv can be a hydrogen halide such as HC1 or HBr or a substance affording a hydrogen halide under the reaction conditions can be added through l line 5l. The product and catalyst pass from al- 70 line 35, it is preferably directed to alkylator 50 gases and benzene are recovered by scrubbing 60 kylator through line 55 to settler 56 wherein a separation is made between the catalyst and the hydrocarbons, the catalyst being withdrawn through line 51 and either discarded through line 58 or recycled through line 59 which joins line 53. As before, a part of the catalyst from settler 56 canbe discarded and theremainder recycled with additional catalyst by the proper adjustment of valves 60 and 6| in

lines

58 and 59 respectively. The product layer is withdrawn through line 62 to line |5a and mixed with benzene from line I8 in mixer l1 and directed to alkylator 20 as previously discussed. In the event that the process is carried out in this manner, the reaction in alkylator 20 is essentially one of dealkylation of the polyalkylbnzene in the presence off excess benzene which in turn is alkylated primarily to monoalkylbenzene. Higher temperatures such as those within the range from about 100 to 300 F. are suitable and the catalyst employed therein should be at least as active as that used in alkylator 50 and preferably of greater activity. The mol ratio of' benzene to polyadkvlbenzenes introduced into alkylator 2l should be at least 1 to 1 and preferably greater than the number of mols of olefin attached to the polyalkylbenzene asthe'alkyl group. The products from alkylator 20 are treated in substantially the same manner as previously described vexcept that it will not be necessary to employ the flash drum scrubber, the products going directly to the caustic washer 39 and fractionator 35 with the appropriate recycle therein described. Alternately, the products can be fractionated to yleldza benzene fraction, a

monoethylbenzene fraction. a light polyalkyl benzene fractionand a heavy polyalkyibenzene fraction. The heavy polyalkylbenzene fraction is returned to absorber i0 via line 45, while the lightpolyalkylbenzene fraction is 'withdrawn through line 64. and although it can be discarded through via lines 33 and lla. In this manner ofvoperation, only the heaviestpolyalkylbenzenes are employed as an absorbing medium, and loss of light products by the sweeping effect ct the entering gases is substantially eliminated. .The lighter practice my invention.

polyalkylbenzenes are added to the alkylator,

however, so that they can also be converted to higher boiling polyalkylbenzenes by ethylene as hereinbefore described. A particularly advantageous method of operation is to introduce fresh catalyst into alkylator 20 via line 2l, and direct the used catalyst from settler 24 into all-:ylator4 50 via

lines

26, 21, 63,v 53 and 5I. lIn this manner, the most active catalyst is employed for the dealkylation-alkylation reaction wihch requires a higher degree of activity than the alkylbenzeneolen alkylation reaction.

The use of polyalkylbenzenes as an absorbing' liquid to concentrate olens has .many advantages. Becauselof the high boiling range of the hydrocarbons, they are not Volatile enough to cause losses by the sweeping effect of the dilute olefin stream. They differ sufilciently from ethylben zene in distillation range so that recovery by fractionation is carried 'out without dimculty. In addition the polyalkylbenzenes not only do not 1lik interfere with the alkylation of the benzeneby the absorbed'oleiins but even appear .to act as an aid by suppressing Ithe formationof diand trialkylbenzenes. An added advantage of the use of an absorbing liquid of this type is in the formation ofadditional amounts of monoalkyl -aromatics. by the dealkylation of the polyalkylbenzene and the alkylation of the benzene by the alkyl radical thus produced.

Although I have described my processwith'.

special reference to one embodiment thereof, it

should be noted that this is by way of illustration I claim: 1. A process for the production of monoalkylaromatic hydrocarbons comprising subjecting an aromatic hydrocarbon to alkylation with at least one polyalkylaroxnatic hydrocarbon in the presence of an alkylation catalyst under `alkylation conditions adapted to yield' both monoand polyalkylaromatic hydrocarbons. separating monoalkylaromatic hydrocarbons from the alkylation product, recovering relatively high boiling and relatively low boiling fractions of the higher a1- kylated aromatic hydrocarbons, absorbing olefins in one of said fractions, subjecting both of said fractions and said absorbed olens-to alkylation in the presence of an 'alkylation catalyst under conditions to yield predominantly polyalkylaromatic hydrocarbons, and supplying said polyalkylaromatic hydrocarbons to the mst-mentioned alkylation.

2. A process for the net production of predominately Amonoalk'ylbenzene which comprises contacting an oleiin-containing gas with a liquid hydrocarbon mixture consisting essentially of polyalkylbenzenes produced in the system, ab-

sorbing oleflns from said-gas in said polyalkyl-- benzenes, contacting said absorbed olen and said polyalkylbenzenes in the presence of an alkylation catalyst under alkylation conditions, recovering a total alkylate predominating' in polyalkylbenzenes, adding benzene to -the total al' kylate, contacting the polyalkylbenzene and benql l zene mixture with a second quantity of a similar alkylation catalyst at a higher temperature than employed in theflrst alkylation, recovering from the second alkylation an alkylate containing sub- 'stanti'al amounts of monoalkylbenzene together with a smaller proportion of polyalkylbenzenc than in the total alkylate, separating the residual polyalkylbenzene and the desired 'monoalkylbenzene in the second alkylate, and recycling the polyalkylbenzene to the first alkylation step.

3. A process according to claim 2 in which the olefin-containing gas comprises dilute olen i stream. I

4. Al process according to claim2 in which said olefin-containing gas is-a dilute ethylene stream.

5. .A process according to claim 2 in which said f olen-containing gas is a refinery fuel gas.

6. A process according to claim 2 in which said I alkylation catalyst is selected from the group consisting of metal halides and metal halide-hydrocarbon complexes.

DON R. CARMODY.