US3474154A - Process for preparing alkyl aryl compounds - Google Patents

Description

United States Patent 3,474,154 PROCESS FOR PREPARING ALKYL ARYL COMPOUNDS Toshio Yamanaka, Shiro Yuki, and Haruo Shibatani,

Yokkaichi-shi, Japan, assignors to Mitsubishi Petrochemical Co., Ltd.

No Drawing. Filed Feb. 14, 1968, Ser. No. 705,304 Claims priority, application Japan, Feb. 17, 1967, 42/ 10,228; Apr. 28, 1967, 42/26,926 Int. Cl. C07c 3/50 US. Cl. 260-671 6 Claims ABSTRACT OF THE DISCLOSURE In a process for the production of an alkyl aryl compound by alkylating aryl compounds with a mono-olefin having 8-18 carbon atoms in the presence of hydrogen fluoride, the improvement which comprises conducting said alkylation reaction at a temperature of from 0 to 35 C. to complete the reaction substantially, and then subjecting the resulting alkylation reaction product to a heat treatment at an elevated temperature of from 40 to 70 C. to give the desired alkyl aryl compound.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process for alkylating aromatic hydrocarbons. More specifically, this invention relates to a process for producing alkyl aryl compounds having excellent sulfonating characteristics by alkylation of aromatic hydrocarbons with a long chain monoolefin in the presence of hydrogen fluoride as a reaction catalyst.

Description of the prior art Generally, alkyl aryl sulfonates used as synthetic detergents are produced by the steps of alkylating aromatic hydrocarbons such as benzene, toluene and the like with long chain mono-olefin having about from 8 to 18 carbon atoms in the presence of a Friedel Crafts catalyst such as hydrogen fluoride and the like, fractionating the resulting alkylation product to separate desired alkyl aryl compounds, i.e. detergent alkylate, sulfonating the alkyl aryl compound with a sulfonating agent such as sulfuric anhydride, fuming sulfuric acid, concentrated sulfuric acid and the like, and neutralizing the resulting sulfonic acid with an alkaline material such as caustic soda and ammonia.

The alkyl aryl compound prepared by the processes known heretofore has a tendency to produce colored sulfonate. That is, the sulfonate produced therefrom has generally undesirable color, and is less valuable as a commercial product. In order to solve said coloring problem of the sulfonate, several processes including bleaching of the colored sulfonate and refining of the starting alkyl aryl compound have been proposed. For example, a process for treating alkyl aryl compounds with oxidizing agent in the presence of water and sulfuric acid, or treating the alkyl aryl compounds with benzene and hydrogen fluoride, in addition to the conventional decoloring process such as clay treatment and sulfuric acid treatment have been proposed.

However, these prior art processes known heretofore have disadvantages in that there are required separation of alkylates and relative expensive reagents for purifying and that the purifying effect is not necessarily remarkable, thus, they cannot be regarded as completely satisfactory.

In the production of alkylate using a straight chain olefin as a starting material, alkyl benzene compounds "ice obtained therefrom are mixtures of various kinds of isomers having the structural formula:

wherein n is a number of carbon atoms in the starting olefin molecule, which is 8n18, and m is an integer of 0mn13. It is understood that the alkyl benzene compounds referred to above contain every and all isomers having various values of m' satisfying the equation, 0mn3, regardless of the type of reactions by which these alkyl benzene compounds are produced.

The isomer distribution in the alkyl benzene compounds depends upon the starting materials and the type of reactions used. Possible difference in the isomer distribution may be shown by the difference in the content of Z-phenyl alkane, which is an isomer having a value of m of zero.

The fact that the 2-pheny1 alkane content affects the properties of soft detergents obtained therefrom as described hereinafter is characteristic of the use of substantially straight chain alkylating agents since no important influence is caused by the difference in the position of a phenyl group upon using branched alkylating agents such as propylene tetramer, conventionally used heretofore.

Therefore, there is a certain problem to be solved in the production of biologically degradable soft detergents, which is not found in the production of hard type detergents.

Each soft alkyl benzene sulfonate obtained from alkyl benzene having higher Z-phenyl alkane content and from that having lower Z-phenyl alkane content, may differ in its property as a detergent. For example, a sulfonate obtained from alkylate having a high 2-phenyl alkane content has excellent biodegradability, whereas a sulfonate obtained from that having a low Z-phenyl alkane content has a feature of excellent foam stability. Since both biodegradability and foam stability are desirable properties as detergent, it is difiicult to determine which alkylate is preferred to the other.

Therefore, choice of alkylate will depend on the desired property of the detergent to be produced, or the manufacturers option.

There are many cases when alkylate having a lower 2-phenyl alkane content is required to prepare detergent having excellent foam stability.

When such alkylate is required, it is more preferable to employ the alkylation process using hydrogen fluoride catalyst than that using aluminum chloride. But even in the process using hydrogen fluoride catalyst, there is a case Where much lower 2-phenyl alkane content in alkylate is required, especially when using u-olefin as a starting material, which gives higher 2-phenyl alkane content than internal olefin.

And on this occasion, it is necessary to employ special technique to reduce the content of 2-phenyl alkane.

SUMMARY OF THE INVENTION An object of this invention is to provide a process for obtaining alkyl aryl compounds having excellent sulfonating characteristics, which may afford alkyl aryl sulfonate having no undesirable color.

Another object of this invention is to provide a process for producing an alkyl aryl compound, more specifically an alkyl benzene, of lower 2-aryl alkane, more specifically 2-phenyl alkane content, which affords sulfonate free from undesirable coloration, from substantially straight chain mono-olefin and benzene using hydrogen fluoride catalyst.

As a result of our thorough study, we have found that an alkyl aryl compound capable of affording sutfonates having less undesirable coloration may be obtained by conducting the alkylation reaction at 40-70 C.

For example, when propylene tetramer or other branched olefin is reacted with benzene at higher temperatures, decomposition of the olefin tends to be increased, thus, the amount of lower molecular weight alkylate, i.e. light alkylate, in the alkylation product is increased, which, in turn, decreases the yield of the desired alkylate, though the coloration of sulfonates obtained therefrom may fairly be improved. Therefore, such high-temperature reaction conditions may not be applicable directly to the alkylation reaction using a branched olefin as alkylating agent.

We have found that if the alkylation reaction is substantially completed at lower temperatures and subsequently the reaction mixture is heated at higher temperature, there is observed practically no formation of short chain alkyl aryl compound, affording the yield of alkylate as high as that in the reaction employing lower temperatures throughout, and that, in addition, the resulting alkylate has a capability of improving the color of sulfonates derived therefrom.

Thus, in accordance with this invention, there is obtained alkylates having excellent sulfonating characteristics by conducting the alkylation reaction at a lower temperature and then subjecting the resulting alkylation product to a heating at a relatively higher temperature, without sacrificing the yield of the alkylate.

In the production of alkylate for detergent using straight chain olefin as a starting material and hydrogen fluoride as a catalyst, there is a close relationship between the reaction temperature and 2-phenyl alkane content, i.e., 2-phenyl alkane content in the alkylate is decreased, when the reaction is carried out at low temperatures.

For example, when the alkylation is conducted at a temperature higher than 35 C., 2-aryl alkane content in the alkylate would remarkably be increased.

Thus, although there may be produced alkylate having lower 2-phenyl alkane content by carrying out the alkylation at a temperature of from to 35 C., there is a disadvantage in that the resulting alkylate tends to give undesirably colored alkyl benzene sulfonates.

In accordance with this invention, an alkyl aryl compound having excellent sulfonating characteristics may be easily produced without accompanying such disadvantage.

The process of this invention comprises the steps of (1) alkylating an aryl compound with a long chain monoolefin having 8-18 carbon atoms in the presence of hydrogen fluoride catalyst at a temperature of from 0 to 35 C., to complete the reaction substantially, and then (2) subjecting the resultant alkylated reaction product to a heat treatment at an elevated temperature of from 40 to 70 C. to give alkyl aryl compounds having excellent sulfonating characteristics.

Although, in general, a satisfactory result may be obtained with regard to the yield of alkylate as well as to the 2-aryl alkane content at lower temperatures, considering the reaction velocity and the cost of production of alkylate on a commercial scale, the above-mentioned first step, i.e. the alkylation reaction according to the process of this invention is carried out at a temperature of from 0 to 35 C. The reaction time employed in the first step may be from 5 to 50 minutes.

The alkylation reaction of the first step must be substantially completed, e.g., more than 90% of theory, and the alkylation product is then subjected to a heat treatment of the second step.

The second step of this process may be conducted without separating the alkylate from the reaction mixture.

As described above, the temperature and the time conditions of the second step of this process are limited to a specific range as mentioned above. But, the temperature and time conditions employed in the second step are preferably determined by the alkylation temperature employed in the first step.

The heat treatment of the second step is advantageously carried out at a temperature above 40 C., and the higher the temperature employed, the better result may be obtained. But at a high temperature of higher than 70 C., it is necessary to use expensive reaction apparatus, and since sufficient effect may be obtained at a temperature lower than 70 C., it is preferred to use a temperature below that level. In the alkylation reaction of the first step, the yield of detergent alkylate may be increased in response to decrease in the reaction temperature employed due to the decrease in the formation of the light alkylate. But, in reality, the formation of heavy alkylate is rather high in the alkylation reaction at lower temperatures.

On the other hand, in the second step, heavy alkylate in the alkylation product decreases in response to the heat treatment time, but, on the contrary, the formation of light alkylate would be increased.

Therefore, the reaction time employed in the second step may be from 30 seconds to minutes. When the alkylation reaction is carried out at a lower temperature of from 5 to 10 0, heavy alkylate is formed in relatively large amounts in the alkylation product, therefore, it is preferred to conduct the heat treatment step in a longer period. On the other hand, when the alkylation reaction is carried out at a higher temperature of about 30 C., heavy alkylate is formed only in small amounts, thus, the second step may be conducted for a short period of time, since the amount of heavy alkylate is small enough to start with and longer heating only leads to undesirable formation of light alkylate.

The second step may be conducted in the same reactor used as the alkylation reactor, or a different reactor maintained at the heat treatment condition.

If necessary, during the second step, hydrogen fluoride may be added to compensate the loss, or other necessary procedures to prevent disproportionation reaction of the alkylate, may be employed.

It has never been expected heretofore that there can be obtained such a satisfactory result by the heat treatment of the second step of the process of this invention. Because there has been a sufficient reason to believe that the yield of the product could be decreased by such heat treatment, considering the fact that the yield of the product is decreased as the temperature is increased in the alkylation reaction, and, in addition, there has been a fear that the exposition of the alkylation reaction mixture to a high temperature may adversely affect the color of the product due to the thermal decomposition thereof.

Contrary to the expectations, however, in accordance with the heat treatment in the process of this invention, there occurs no contamination of the product by the side-reactions of heavy and light alkylates existing in the reaction system, but, there occurs a reaction converting the heavy alkylates into the product alkylate, however a little, which contributes to maintain the yield of product at a high level.

In the second step of this process, a part of byproduct dialkyl benzene formed in the first step alkylation reaction would be converted into mono-alkylate by the trans-alkylation reaction involved. Further, when the first step reaction is carried out at excessively lower temperatures, the product alkylate sometimes contains a small amount of unreacted olefin, but such unreacted olefin may be converted into desired alkylate in the second step of this process.

The reaction conditions employed in the alkylation reaction of the first step mentioned above are substantially the same as those employed in the conventional alkylation reaction known heretofore.

Aromatic hydrocarbon and olefin may be used in this process in a molar ratio of 3:1-2011 or more. The hydrogen fluoride catalyst may be employed in an amount of from to 30 moles or more per mole of elefin used.

The starting olefins which may be used in the process of this invention include branched chain monoolefins such as propylene tetramer and straight chain monoolefins having 8-18 carbon atoms such as internal olefin produced either by the chlorination of straight chain paraffin followed by the dehydrochlorination, or by the dehydrogenation of straight paraffin, and a-olefin produced either by the cracking of paraffin wax or the polymerization of ethylene.

The starting mono-olefins which may be used in the process of this invention further include mixtures of mono-olefin and paraffin, and mixtures of straight chain mono-olefin and branched mono-olefin.

In the foregoing explanations, mainly benzene is exemplified as the aryl compound, but other aryl compounds such as toluene, xylene, naphthalene e-tc., may be used.

The process of this invention may be carried out batchwise, continuously, or in other adequate manners.

The following examples will illustrate this invention more fully. However, it should not be construed that these examples restrict this invention as they are given merely by way of illustration.

EXAMPLE 1 (COMPARATIVE EXAMPLE) This example shows the relationship between a reaction temperature and a Z-phenyl alkane content in the alkylates, and also the relationship between the temperature and color of sulfonate obtained therefrom.

In the example, straight chain olefin having 10-14 carbon atoms produced by cracking of paraffin wax, was used as starting material.

Into a reactor were charged 1 moles of benzene and moles of liquid anhydrous hydrogen fluoride per mole of olefin. Into the reactor was added olefin dropwise at various temperatures specified in the following table, over a period of 5 minutes, and the reaction was continued for an additional minutes to complete the alkylation reaction. From the reaction mixture was removed the catalyst according to the conventional manner, and the product obtained was distilled to separate into initial distillate, main alkylate fraction and final distillate. The main alkylate fraction was analyzed by gas chromatography to determine content of Z-phenyl alkane. Further, bromine number which correlates to color of the sulfonate to be obtained therefrom Was measured according to ASTM/D 1159.

Then the alkylate was sulfonated batchwise by reacting 1.0 mole of the same with 1.05 mole of liquid anhydrous sulfuric acid, while diluting with nitrogen, at 50 C. for 45 minutes. The sulfonic acid obtained was neutralized with sodium hydroxide to form sodium salt of sulfonic acid. Color of the sulfonate was measured by the absorbance of sulfonate solution in 10% alcohol-water solution, using a 10 mm thick cell at a wave length of 420 III/L.

The reaction temperature used and results obtained are tabulated in the following table:

Reaction temperature C O.) 0 10 50 70 Z-phenyl alkane content (percent) Bromine number Color of sulfonate 6 EXAMPLE 2 (COMPARATIVE EXAMPLE) This example is to explain the relationships between an alkylation temperature and yield of alkylate product, and between the temperature and color of the sulfonate obtained.

The reaction was conducted by charging 10 moles of benzene and 20 moles of hydrogen fluoride into an autoclave, and adding dropwise 1 mole of propylene tetramer to the mixture over a period of 5 minutes, with stirring while maintaining at a predetermined temperature as set forth in the following table. The reaction was continued for an additional 25 minutes at the same temperature to complete the alkylation. During the reaction, the reaction mixture was pressurized to maintain a liquid state. After completion of the reaction, the reaction mixture was allowed to stand to separate the catalyst used. Hydrocarbon-phase separated was neutralized with caustic soda, washed with water, dried over calcium chloride and rectified to separate the product into a light alkylate fraction mainly consisting of lower boiling short chain alkyl benzenes, a middle fraction consisting of desired alkylate product and a high boiling fraction consisting of heavy alkylate.

Then bromine number of the product alkylate which correlates to color of sulfonated product to be obtained therefrom was determined according to ASTM/D 1159. Also the alkylate product was sulfonated and the color of the sulfonated product was examined. The color test of the sulfonated product was conducted as follows:

Into 1 mole of alkylate was bubbled 1.05 mole of sulfuric anhydride diluted with nitrogen at 50 C. for 45 minutes to give sulfonated alkyl benzene. The resulting sulfonated alkyl benzene was neutralized with caustic soda to give sodium salt. The color of the sulfonate salt was evaluated as extinction coefficient of 10% alcoholic solution using a 10 mm. thickness cell at a wave length of 420 Ill/.L.

Reaction Temperature C.)

Yield of detergent alkylate (percent by Weight) 84 82 81 76 Bromine number 0.018 0.009 0.005 0.002 Color oisult'ouate 0.21 0.14 0.10 0.08

EXAMPLE 3 The alkylation reaction was conducted under the same reaction conditions as in Example 2, using propylene tetramer as alkylating agent at 10 C. for a reaction period of 30 minutes. After 30 minutes of the reaction, the reaction mixture was heated up to 40 C. in the course of 1 minute with vigorous stirring. Then the mixture was maintained at the same temperature for an additional 10 minutes with stirring. After completion of the reaction, the product obtained was separated, neutralized, washed, dried, and distilled in the same manner as described in the preceding example. The bromine number of the detergent alkylate was determined and also color of sulfonated product was examined. The results obtained are as follows:

Yield of detergent alkylate (percent by weight) 84 Bromine number 0.004 Color of sulfonate 0.09

From the above table, it can be noted that in accordance with the process of this invention, the yield of deter gent alkylate is maintained as high as that in the conventional alkylation reaction conducted at 10 C., while color of the sulfonated product obtained therefrom is remarkably improved.

7 EXAMPLE 4 The alkylation reaction was conducted in the same manner as described in Example 2, at 30 C. for a reaction period of 30 minutes. After the completion of the reaction, the catalyst was removed from the reaction mixture. The mixture free from catalyst was then washed, neutralized and dried. The resulting alkylate was then subjected to a heat treatment. Into an autoclave was charged fresh hydrogen fluoride of the same amount as used in the previous alkylation reaction and heated at 60 C. with stirring. On the other hand, the product obtained in the alkylating reaction was preheated at 60 C. Into the autoclave, was charged dropwise thus preheated product instantaneously. The mixture was maintained at the same temperature for 2 minutes With stirring. After the completion of the reaction, catalyst was removed from the mixture which was then washed with water, neutralized with caustic soda, dried and distilled. The bromine number of the detergent alkylate and color of sulfonate product were determined. The results obtained are as follows:

Yield of detergent alkylate (percent by weight) 81 Bromine number 0.002 Color of sulfonate 0.07

From the table shown above, it can be noted that according to the process of this invention, the yield of detergent alkylate is maintained as high as that in the conventional alkylation reaction conducted at 30 C., while color of the sulfonate obtained therefrom is remarkably improved.

EXAMPLE 5 In this example, the reaction was conducted in the same manner as described in Example 4 except that the heat treatment time and temperature were varied. The heat treatment of this example was conducted at 50 C. for 30 minutes and 60 minutes. The results obtained are as follows:

Heat treatment time min. 30 min. 60 min.

Yield (gercent by weight):

Lig t alkylate 13 16 20 Detergent alkylate. 81 79 76 Heavy alkylate 6 5 4 EXAMPLE 6 In this example, the reaction was conducted in the same manner as described in Example 4, except that the heat treatment condition was altered. The heat treatment of this example was conducted at 50 C. for 30 seconds and 1 minute. The results obtained are as follows:

Heat treatment time 0 see. 30 see. 60 sec.

Bromine number- O. 005 0. 003 0. 003 Color of sulionate 0. 0. 09 0. 09

EXAMPLE 7 Alkylation at 10 C. Alkylation at and Heat treatment 10 C. 40 C. at 40 C Yield of detergent alkylate (percent by weight) 77 75 77 Bromine number- 0. 117 0. 030 0. 030 Color of sulfonate 0. 21 0. 12 0. 12

From the table shown above, it can be noted that the reaction at 10 C. using straight chain olefin gives undesirably colored product and that the reaction at 40 C. only affords lower yield of the detergent alkylate, while both the coloring and the yield are improved in the process of this invention.

EXAMPLE 8 The alkylation reaction was carried out in the same manner as described in Example 1 by using the same reactants and catalyst as used therein except that the reaction temperature was 10 C. Olefin was added dropwise into the reactor over a period of 5 minutes, and the reaction was continued for additional 5 minutes at the same temperature. The reaction mixture was then heated up to 50 C. within a 5-minute period.

The heating was continued for additional 15 minutes at the same temperature.

The reaction mixture was then treated in the same manner as in Example 1, and the 2-phenyl alkane content in a main fraction, and the bromine number and the color of sulfonate obtained therefrom were measured and examined. The results obtained are as follows:

Content of 2-phenyl alkane percent 19 Bromine number 0.012 Color of sulfonate 0.07

From the results obtained, it is obvious that by the process of this invention, the alkylate having lower 2- phenyl alkane content and capable of affording sulfonate having desirable color property can be obtained.

EXAMPLE 9 The reaction was conducted in the same manner as described in Example 1, by adding olefin dropwise to a mixture of benzene and hydrogen fluoride at 30 C. over a period of 5 minutes, and the reaction was continued for additional 15 minutes with stirring. After completion of the reaction, the catalyst used was separated from the reaction mixture. Into an evacuated reactor, the same amount of fresh hydrogen fluoride used as the catalyst in the previous reaction was introduced and heated at 60 C. with stirring. The catalyst-free reaction mixture was then heated at 60 C. and was introduced into the heated hydrogen fluoride instantaneously. The reaction was continued for 10 minutes at the same temperature. Then the reaction mixture was treated in the same manner as in Example 1 and the Z-phenyl alkane content, the bromine number of the alkylate and color of sulfonate obtained therefrom were measured and examined. The results are as follows:

Content of 2-phenyl alkane percent 20 Bromine number 0.011 Color of sulfonate 0.07

From the result obtained, it is understood that according to the process of the invention, alkylate having lower 2-phenyl alkane content and capable of affording sulfonates having desirable color property can be obtained.

EXAMPLE 10 The example is to illustrate the use of an internal olefin together with paraflin as the starting material.

In this example, straight chain olefins having 10-13 carbon atoms obtained by the chlorination of straight chain paraflins followed by the dehydrochlorination of the chlorinated parafiin was used. The starting paraffin was prepared by extracting a kerosene fraction with a molecular sieve. Olefins thus obtained chiefly consisted of internal olefins and contained 4 moles of parafiin per mole of olefins.

The reactions were repeated in the same conventional manner as in Example 1 at 10 and at 50 C., and also as in Example 8 according to the process of this invention.

The content of 2-phenyl alkane in alkylates and the bromine number, and the color of sulfonates were examined. The results obtained are tabulated in the following table:

What is claimed is:

1. In a process for the production of an alkyl aryl compound by alkylating an aryl compound with a monoolefin having 8-18 carbon atoms in the presence of hydrogen fluoride, the improvement which comprises conducting said alkylation reaction at a temperature of from to 35 C. for a period of time of from about to about 50 minutes to complete the reaction substantially, and then subjecting the resulting alkylation reaction product directly to a heat treatment at an elevated temperature of from 40 to 70 C. for a period of time of from about 30 seconds to about 90 minutes to form a second alkylation reaction product containing the alkyl aryl compound.

2. The process of claim 1 wherein the hydrogen fluoride is separated from said resulting alkylation reaction product, fresh hydrogen fluoride is added and the resulting mixture of fresh hydrogen fluoride and the substantially hydrogen fluoride free alkylation reaction product, is then subjected to said heat treatment.

3. The process of claim 1 wherein the aryl compound is benzene.

4. The process of claim 1 wherein the mono-olefin is propylene tetramer.

5. The process of claim 1 wherein the mono-olefin is an alpha mono-olefin.

6. The process of claim 1 wherein the mono-olefin has internal unsaturation.

References Cited UNITED STATES PATENTS 9/ 1958 Shiffler.

OTHER REFERENCES DELBERT E. GANTZ, Primary Examiner CURTIS R. DAVIS, Assistant Examiner US. Cl. X.R. 260-674 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,474 154 October 21 1969 Toshio Yamanaka et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 41, "1 moles" should read 10 moles Signed and sealed this 8th day of December 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. E.

Attesting Officer Commissioner of Patents