US2405874A - Alkylation of aromatic hydrocarbons - Google Patents

Description

E. F. BULLARD ETAL' ALKYLATION OF AROMATIC HYDROCARBONS Filed Nov. 2, 1942 0') invenors'. Edwin F. Bullard g John Anderson I Sumner H. McAlls'fzr bg *heir* AHorneg// i fg,

Patented Aug. 13, 1946 UNITE STATES r vorricle ALKYLATION oF Artor/nrrl'e` HYDRocARBoNs l e Delaware Application November 2, 1942, Serial No. 464,286 l -This invention relates to the reaction of aromatic hydrocarbons with alkylating agents and particularly to the production of motor fuels and motor fuel components by alkyl-ation of such hydrocarbons. It deals with an improved method for carrying out such alkylations whereby products having superior characteristics may be obtained.

An important object of the invention is to provide a more efcient and economical method of alkylating aromatic hydrocarbons in the vapor phase. Another object is to improve vapor phase methods of reacting benzene and the like in the presence of solid acid alkylation catalysts. A further object is to increase the yield of desirable alkylation products by reacting aromatic hydrocarbons with oleiins. Still another object is to produce aromatic alkylation products having superior properties, particularly as regards their motor fuel characteristics. Other objects and advantages of the process of the invention will be apparent from the following description.

Various methods of alkylating benzene and higher aromatic hydrocarbons have been proposed from time to time, but they have not been successful because of their inefficient conversion of the starting materials and/or their poor quality of products. It has now been found that these disadvantages of prior alkylation methods may be overcome by the use of an improved reaction system employing, preferably, more advantageous reaction conditions.

The new process may be applied to the alkylation of a wide variety of aromatic hydrocarbons, although when used for the production of motor fuels or motor fuel components volatility considerations make it more advantageous to use lower boiling aromatic hydrocarbons, particularly benzene and toluene. Where such considerations are of lesser importance, higher boiling compounds may be employed. ThusJ ethyl benzene, the xylenes, propyl or isopropyl benzene, mesitylene,the butyl benzenes, the cymenes, and homologues, naphthalene and its corresponding substitution products, and the like may be used. The source of the aromatic starting material is -not important. The coal tar industry provides la convenient source of benzene, toluene, etc., but petroleum fractions containing these compounds, particularly the highly aromatic fractions obtainable by catalytic reforming or hydroforming, are also useful. Such fractions may advantageously be subjected to extraction with suitable solvents, for example, as described in U. S. Patent 2,114,524, to increase the concentration of the aromatic 11 Claims. (Cl. 26d-671) hydrocarbon to be alkylated before they are used in the process.

Alkylating agents Whichpmay be used in the process include olens, particularly suitable fractions of petroleum crackingvproducts containing ethylene, prop ylena isobutylene, normal butylenes, the amylenesor mixtures of one o1' more such olefms.',1nstead of the olens, polymers thereof'mayg-be used, Not only may ethers, alcohols and esters corresponding to the foregoing olens beemployed, but also ctherethers, alcohols and esters, such as dimethyl, methyl-ethyl,

methyl-isopropyl, di-normal propyl, ethyl-isopropyl and like ethers, methyl and higher primary alcohols, may be used. Either inorganic or organic esters such as halides, ksulfates, phosphates, borates, formates, acetates and the like may be employed as alkylating agents. The alkylating agent-.may be used in a pure or substantiallypure former as', mixtures of one or kmore ,alkylating agents with or without other materials which donot interfere with the desired reaction.v

As catalytsfor the process, acids are used. Most preferably the chosen acid catalyst is employed with a suitable carrier so that it may conveniently be used in solid form as packing for tower or tube type reactors. Acids of phosphorus are particularly suitable for this purpose, particularlymixtures of ortho or meta phosphoric acid or pyrophosphoric` acid with kieselguhr or other suitable clays or earths such as areV described in U..S. Patent 1,993,513. However, other catalysts such as sulfuric acid, hydrogen fluoride or the like adsorbed on porous supports. or as a coating or lm on non-porous packing material or the like may also be used in the process. It is also feasible to 'employ liquid acid alkylation catalysts inthe process.

The alkylation is preferably carried out in the vapor phase with a substantial excess of aromatic hydrocarbonsbased on the alkylating agent used. It has already been Suggested that in alkylating benzene 1an excess be used to suppress formation of higher alkylation products. Such excess benzene is not sucient for most efficient reaction and it has been found desirable to use at least three,l and more preferably ve to ten or more, mols `of the aromatic -hydrocarbons being alkylated per mol Yof olen or equivalent alkylating agentV in the process of the invention. In this way not onlylare undesirable side reactions such as the formation of poly-alkylated products substantially eliminated, but. also high conversions 3 of the alkylating agent to valuable products are obtained.

The reaction is most advantageously carried out under superatmospheric pressure; preferably pressures of 200 toA 400 pounds per square inch are used. The temperature and time of contact which will be most desirable will depend upon the particular catalyst used and the alkylating agent chosen. For the alkylation of benzene with oleiins such as propylene in the presence of phosphoric acid, a temperature of about 200 C. to 400 C., preferably about 250 C, to 300 C., and a hydrocarbon feed rate of about 0.1 to 0.8 gallon per hour per pound of catalyst are most advantageous. This combination of reaction conditions gives results which are markedly superior with respect to yields, conversions and efficiency of operation to those obtained by other methods.

It has previously been considered that alkylation of aromatic hydrocarbons accomplished a suicient purification -of the reactants and products so that no other treatment was" necessary. However, to obtain the -best results according to thepresent invention, it is desirable to treat the feed stocks used, especially the aromatic hydrocarbon, for removal of undesirable components, particularly sulfur-containingoompounds such as thiophen'e, since otherwise these compounds undergosimultaneous reaction and appear in the product, materially reducing its quali-ty especially for motor fuel use. Such treatment not only improves the quality of the product and-simplifies its further processing, but also improves the effective life ofthe catalyst in the process.

For the treatment of benzene, for example, it is-preferredto use sulfuric acid of about 90% to 100% concentration' at a temperature of about 10 Clto. 60 C.,preferably about 98% concentration at about-C. A ratio of acid to benzene above 1 tolO by volume isdesirable 'and ratios of about 0.16:1 to 025:1 are preferred. The acid and benzene may be intimately contacted by agitation in a mixer or other vessel, countercurrent now in a tower which may or may not contain packing to promote-'intimate mix-ing, or. in any other suitable manner. A contact time of acid with. benzenegof at least 3Yminutes, and more preferably/i to -6 minutes or longer, is desirable. 'Contact in a plurality ofreactionstages is advantageous in reducingfthe amount of acid required for treatment of a givenv volume of aromatic hydrocarbon. After thev acid treatment the aromatic hydrocarbon is Washed with a base such asl aqueous caustie soda before being used in the alkylation step of the invention.

Merely treating the feed stocks before alkylation is not suicient to obtain the best results in the present process. It has been found necessary to return to the sulfuric acid treating stage at least a part of the excess unreacted aromatic hydrocarbon recovered from the product. Since this aromatic hydrocarbon has been previously subjected to the sulfuric acid treatment as well as to the alkylating conditions, it would be thought that it would'be ideal material for recycling directly to the alkylation and that further treatment could not possibly be of advantage. It was surprising therefore' to discover that by feeding a part of this stream to the sulfuric acid treating unit instead of to the alkylation reaction, materially improved results, especially with respect to product quality, were obtained. The exact nature of allthe changes in the recycle benzene or other aromatic hydrocarbon which are responsible for the improvedY resultsisV notknown but it has been found desirable to submit at least one-tenth, and preferably at least onefourth, of such aromatic hydrocarbon to treatment with sulfuric acid under the previously describedconditions before returning it to the alkylation unit. The treatment may be effected along with or separately from the treatment of the initial feed.

The attached drawing shows, diagrammatically, an assemblage of apparatus particularly adapted for producing cumene by reaction of benzene with propylene according to the invention. In the drawing only the more important pieces of equipment are indicated for the most part, since the location of auxiliary equipment such as pumps, valves, storage tanks, pressure-, temperatureand flow-regulating and measuring devices, heat exchangers, and the like will be evident to those skilled in the art. In the arrangement of the drawing, benzene from a source not shown,y is fed by line I to a mixer 2 in which it is contacted with sulfuric acid introduced via line 3. The resulting mixture passes by line 4 to settler 5 from which acid is taken olf by line 6 and returned to mixer 2 by lines l and 3. A part of the acid maybe continuously or intermittently withdrawn from the system by line 8. The partially treated benzene is conducted by line 9, together with fresh acid introduced by line I0, to mixer II where a further intimate mixing is effected. The resulting emulsion is taken by line I2 to settler I3 in which the acid and hydrocarbon phases are again separated. The separated acid is taken off byline I4 and a part returned to the second reaction stage by line I5 while the remainder is conducted to line 3 by line I6 to furnish the partially spent acid for the first reaction stage. The thus-treated hydrocarbon is fed by line I'I to mixer I8 which is supplied, continuously or intermittently,` with a caustic from line I9. The caustic-benzene mixture is fed via .line 20 to settler 2l from which caustic is withdrawn by line 22. The withdrawn caustic is returned to mixer I8 for further use by lines 23 and I'I, a part being withdrawn as necessary by line 24. The treated benzene is taken off by line 25 and mixed with propylene or propylene-containing hydrocarbon which may advantageously have been caustic-treated in theY same manner as the acid-treated benzene introduced via lines 26 and 2l. Alternatively, the propylene may be introduced via lines 26 and 29 and thus be caustictreated along with the benzene. In either case the mixture of propylene and treated benzene is conducted by line 29 to reactors30 which are shown as a bank of tubes through which the reaction mixture flows in parallel. The reactors contain Ygranules of phosphoric acid or other suitable acid catalyst not shown and are heated by steam or other means also not shown. They are preferably constructed to withstand pressures of the order of 1000 pounds per square inch. As previously indicated, however, other forms of reactors may be used and the reaction mixture may flow through two or more reactors in series instead of through all reactors in parallel as shown. Line 40 is provided for introducingl steam or other activating or controlling agent as may be required to maintain the activity of the catalyst. l It may also be used to introduce fresh-catalyst or catalyst-regenerating agents.v 1 f The reacted hydrocarbon mixture, comprising cumene and ,unreacted' benzene and propylene and any inert materials introduced-with the feed or otherwise, is withdrawn from the reactors by line 3| and conducted to depropanizer column 32 in which the lower boiling components are separated and taken off overhead by line r3.3.l The remaining cumene and benzene are taken'oi as bottoms by line 34 and fed to debenzeni'zer column 35 from which the unreacted benzene is removed by line 36 and returned to the reaction by line 31 after withdrawal of a part of line 38 for treatment with sulfuric acid in mixersl 2 and Il along with the fresh benzene feed. The cumene produced is recovered by line 39.

The following examples further illustrate the advantages ofthe process, although no limitation on the invention is to be inferred therefrom as the same principles may be applied to the reaction of the same or other aromatic hydrocarbons with other alkylating agents.

Example I Cumene in Propylene Mol ratio benzene to oleiin the product converted p Per cent Per cent VEaxrmple AII The effect of pressure on the reaction was determined in a series of tests using a solid phosphoric acid catalyst and a feed containing 5 mols of benzene per mol of propylene. Y

6 Example IVk The effect of sulfuric acid treatment of the `benzene feed on the quality of the reaction products was shown by the following comparative runs made with coal tar benzene which was reacted with propylene in the presence of solid phosphoric acid catalyst using a reaction temperature of 200 C. to 250 C. and a pressure of 250 pounds per square inch. The benzene in one case was used directly and in the other case was treated with 25 poundsv of 98% sulfuric acid per barrel at about 20 C.. The molar ratio of benzene to olen in each .case was 5:1 and the feed rate was 1800 to 2000 grams,n of ,hydrocarbon per liter of catalyst per hour.

Sulfuric acid- Untreated treated benzene benzene Sulfur in the benzene (wt. per cent) 0. 47 0.06 Oleins in the benzene (wt. per cent) 0. 76 0. 09 Sulfur in the cumene (wt. per cent) 0. 51 0.05

The'propylene conversions and cumene yields for different periods of catalyst use were as follows:

The products were tested as 5% and 10% blends in 100 O. N. aviation gasoline with a nal tetraethyl lead content of 4.0 cc. per gallon.

Rating in 3-C engine test Product from untreated Product from sulfuric Feed rate benzene acid-treated benzene lgrmsof P 1 C y T0931- TOPY @ne mene 5 blend Is -octane 0.7 co. f Is tan 1.1 fle d rssug bumper ggg. Pagar inthe teaming. tristi. a Sq h.1` Der non 111 ture sion Crude 10% blend Isooctane+l.l cc. of Iso-octane-l-L cc. of lead 'I Clisft the feed DTOdllCt n lead tetraethyl. tetractliyl.`

space) Copper dich gum (mg./100 ml.) Per cem) C'. Per cent Per cent 2,030 r2 esta a as 2,0 0 2,000 8.2 20o-250 92 90 Product from 4,000 8.2 200-250 s1 ss 55 untreated treated 4, 000 8.2 20o-250 s2 90 benzene benzene 57 blend 5 1 Example HI 103]o blend 10 2 Effect of temperature was determined in comparative tests using a feed rate of 2000 grams of hydrocarbon per hour per liter of catalyst space, a benzene to propylene mol ratio of 5 to 1, and a pressure of 250 pounds per square inch. The propylene concentration in the feed was 8%-8.2%

Cumene in Propylene Temperature the product converted Per cent yPer cent l200 C 90 60 70 200-250 C 90 90 The catalyst life under these conditions was of the order of gallons of cumene per pound of catalyst. At higher temperatures the life decreases.

Considering the small amount of cumene in these blends, the effect of the sulfuric acid treatment of the benzene is seen to be remarkable.

Example V aetaevfi We claim as our invention:

1. A process of producing cumene which comprises treating benzene with sulfuric acid of at least 90% concentration at about 10 C, to 60 C. for a time sufficient to reduce the thiophene content thereof, admixing the treated benzene with propylene in the ratio of 3 to 10 mols of benzene per mol of olen and contacting the mixture under a pressure of between 250 and 600 pounds with a solid phosphoric acid catalyst at a temperature of 200 C. to 300 C. using a space Velocity of 0.1 to 0.6 gallon of hydrocarbon per pound of catalyst per hour, fractionating the resulting products to separate unreacted benzene, and returning at least 4a part of `the thus-recovered benzene to said sulfuric acid treatment for further reacton in the process.

2. A process of producing cumene which comprises passing a mixture of benzene and propylene in a molar ratio of at least 4 to 1 over a solid phosphoric acid catalyst at a temperature of 200 C. to 300 C. and a pressure of at least 250 pounds per square inch, separating at least a part of the unreacted benzene from the products, contacting at least a part of said separated benzene with sulfuric acid of at least 90% concentration, and returning the acid-treated benzene for further reaction in the presence of said phosphoric acid catalyst.

3. A process of producing cumene which' comprises treating benzene with sulfuric acid of at least 90% concentration for a time suflicient to reduce the thiophene content thereof, reacting the acid-treated benzene with propylene in the presence of a solid phosphoric acid catalyst under a pressure of at least 250 pounds using aV molar ratio of benzene to propylene of at least 4 to 1 and a temperature between 200 C. and 300 C., and recovering the resulting cumene.

L1. A process of producing cumene which comprises contacting benzene with between one-tenth and one-fourth of its volume of sulfuric acid of 95% to 100% concentration for a period of 5 to 10 minutes at about o C. to 30 C. sufficient to materially reduce the thiophene content thereof, neutralizing the acid-treated benzene, and contacting a mixture of said benzene Vand an isopropyl-ating agent containing at least three times the stoichiometric amount of benzene to isopropylating agent with a solid acid alkylation catalyst under alkylation conditions.

5. A process of producing cumene which comprises contacting benzene with concentrated sulfurie acid for a time sucient to substantially reduce the thiophene content thereof, and reacting a molar excess of the resulting benzene with an isopropylating agent in the presence of a solid acid alkylation catalyst under a pressure of 250 to600 pounds.

6. A processof producing cumene which comprises reacting a substantial molar excess of benzene with an isopropylating agent under a pressure of at least 250 pounds per square inch in the presence of a. solid acid alkylating catalyst, separating unreacted benzene from the reaction products and contacting the separated Vbenzene with concentrated sulfuric acid for a time sufci'ent'to substantially reduce the thiophene content thereof, and returning the sulfuric acidtreated benzene to reaction with further isopropylating agent.

7. A process of producing an alkyl benzene which comprises reacting a substantial molar excess of benzene with an alkylating agent under a pressure of at least 250 pounds per square inch in the presence of Ia solid acid alkylating catalyst, separating unreacted benzene from the reaction products and contacting the separated benzene with concentrated sulfuric acid for a time sufcient to substantially reduce the thiophene content thereof, and returning the sulfuric acidtreated benzene to reaction with further alkylating agent.

8. A process of producing an alkyl benzene which comprises contacting benzene with concentrated sulfuric acid for a time suflicient to substantially reduce the thiophene content thereof, and reacting a molar excess of the resulting benzene 'With an alkylating agent in the presence of a solid acid alkylation catalyst under a pressure 0f '250 to 600 pounds. Y

9. A process of alkylating an aromatic hydrocarbon which comprises treating said hydrocarbon with at least one-tenth of its Volume of concentrated sulfuric acid for a time sufficient to materially reduce the thiophene content thereof, and reacting a molar excess of the resulting aromatic hydrocarbon with an alkylating agent under a pressure of at least 250 pounds per square inch in the presence of a solid acid alkylation catalyst under alkylation conditions. y 10. A process of alkylating an aromatic hydrocarbon which comprises treating said hydrocarboniwith sulfuric acid of at least concentration at 10 C. to 60 C. for a time of at least 5 minutes sufiicient to materially reduce the thiophene content thereof, reacting a molar excess of the resulting aromatic hydrocarbon with an alkylating agent in the presence of a solid acid alkylation catalyst under alkylation conditions, separating unalkylated aromatic hydrocarbon from the reaction products, and returning at least a part thereof to said sulfuric acid treatment.

11. A process of alkylating an aromatic hydrocarbon which comprises reacting a molar excess of said hydrocarbon with an alkylating agent under a pressure of at least 250 pounds per square inch in the presence of a solid acid alkylation catalyst under alkylation conditions, separating unalkylated aromatic hydrocarbon from the reaction products and contacting at least a part thereof with sulfuric acid for a time sufficient to materially reduce the thiophene content thereofgand returning the thus-treated hydrocarbon to the alkylation reaction.

EDWIN F. BULLARD. JOHN ANDERSON. SUMNER H. MCALLISTER.

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