US3392206A

US3392206A - Alkylation of benzene

Info

Publication number: US3392206A
Application number: US346098A
Authority: US
Inventors: Daniel J Hurley; Robert W Rosenthal; Roger C Williamson
Original assignee: Gulf Research and Development Co
Current assignee: Gulf Research and Development Co
Priority date: 1964-02-20
Filing date: 1964-02-20
Publication date: 1968-07-09
Anticipated expiration: 1985-07-09

Description

United States Patent 3,392,206 ALKYLATION 0F BENZENE Daniel J. Hurley, Oakmont, Robert W. Rosenthal, P ttsburgh, aud Roger 'C. Williamson, Gibsonia, Pa., ass gnors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Feb. 20, 1964, Ser. No. 346,098 8 Claims. (Cl. 26067 1) This invention relates to a process for alkylating benzene with a mixture of normal alkyl monochlorides in the presence of a Lewis-type alkylation catalyst.

The mixture of normal alkyl monochlorides employed herein is obtained, for example, by chlorinating a mixture of normal parafiins havln-g from six to 20 carbon atoms, preferably having from 10 to carbon atoms, by passing chlorine therethrough in the presence of a light source, such as actinic light, at a temperature of about to about 150 C. and a pressure of about 0 to about 10 pounds per square inch gauge. The normal parafiins employed can be obtained in any suitable manner, but preferably are obtained by treating a kerosene in known manner with urea to form an adduct therewith. The adduct is thereafter decomposed and the desired mixture of nor- "mal paraffins can thereby be obtained. Alternatively, the

normal paraffin mixture can be obtained by treating a kerosene in known manner using molecular sieves to separate the same'therefrom. In order to obtain essentially only normal alkyl monochlorides, primary as well as secondary, and avoid the formation of appreciable amounts of normal alkyl polychlorides, chlorination of said normal parafiins is terminated when about 20 to about 30 percent, preferably about percent, of the available normal paraflins have a hydrogen thereon replaced with chlorine. The mixture obtained, therefore, comprises essentially from about 70 to about 80 percent by weight of unreacted normal parafiins and from about 20 to about percent by weight of primary and secondary normal alkyl monochlorides.

Following this, desirably benzene is reacted with only the normal alkyl monochlorides so produced in the presence of a Lewis-type alkylation catalyst to obtain the desired monoalkyl benzene. The amount of catalyst employed can be, for example, from about one to about 15 percent by weight or higher, preferably from about 2.5 to about six percent by weight, based on the monochlorides present in the original charge. While it would be possible to separate a single carbon number normal paraffin from the same carbon number normal alkyl monochloride, by distillation, for example, it is almost impossible by distillation to separate a number of normal paraflins from a mixture containing the same and a number of normal alkyl monochlorides, since a normal alkyl monochloride will distill at about the same temperature as a normal paraffin having a higher number of carbon atoms. Since the normal parafiins will be virtually unaffected under the alkylation conditions employed, the total mixture of normal paratfins and normal alkyl monochlorides are brought into contact with benzene in the presence of the alkylation catalyst to obtain the desired alkylate. In order to drive the reaction in the desired direction, a molar ratio of about three to about 20 mols of benzene, preferably about five to about eight mols, of benzene, per mol of normal alkyl monochloride is employed. Thus the reaction mixture at the beginning of the reaction contains a large amount of benzene, a

large amount of normal parafiins, a relatively small- T amount of normal alkyl chlorides and the alkylation catalyst.

The mixture described is then subjected to a temperature of about 20 to about 80 C., preferably about 40 to about C., and a pressure of about 0 to about ice 10 pounds per square inch, preferably about 0 to about 5 pounds per square inch gauge, and as a result thereof benzene reacts with the normal alkyl monochlorides to form the desired alkylate and gaseous hydrogen chloride, which is permitted to escape from the reaction zone. Upon termination of the reaction, the alkylation catalyst is permitted to settle in the reaction zone and the supernatantliquid is passed to a distillation zone wherein unreacted benzene, normal parafiins and alkylate are separately recovered therefrom.

The alkylate obtained can be employed in many subsequent reactions and therefore it is critical that it be substantially free of impurity which may create difiiculties in such reactions. An impurity which can easily find its way into the alkylate are unreacted normal alkyl monochlorides. This is so because it is diflicult or virtually impossible to separate the same by distillation from admixture with alkylate having approximately the same number of carbon atoms. Thus, for example, where the alkylate so produced has from 10 to 15 carbon atoms and the same is to be reacted with sulfuric acid for the purpose of preparing a detergent therefrom, the presence of more than about 200 parts per million, especially more than 300 parts per million of bound chlorine, therein is particularly bad, since the product acts as a skin irritant and is corrosive. Accordingly, since there is no easy method commonly available to remove a number of unreacted normal alkyl monochlorides from the reaction mixture described above, and since it was thought that no detrimental results would flow therefrom, it has been the custom to continue the alkylation reaction for an exceedingly long period of time, far beyond the point wherein it was believed alkylation ceased, so that there would be assurance of the virtual disappearance of the objectionable normal alkyl monochlorides from the reaction mixture.

We have found, however, that it is critical in the defined alkylation reaction that the same be terminated within about five minutes, and in any event within about 15 minutes, of the time that the bound chlorine content of the alkylation reaction mixture is less than about 300 parts per million based on the alkyl benzene, preferably at the time the bound chlorine content thereof is less than about 200 parts per million. We have found that if the alkylation reaction is permitted to continue beyond the point wherein all of the normal alkyl monochlorides have disappeared, by reaction with benzene, the alkyl benzenes so obtained will begin to decompose and benzene and the corresponding alkanes, or normal paraffins, will be produced.

This phenomenon, in the present context, was not easily apparent. As noted the reaction mixture contains a large amount of benzene and a large amount of normal paraffins, and only a small portion thereof is made up of normal alkyl monochlorides and/or the desired and corresponding alkyl benzene product. Therefore, when the reaction was permitted to go beyond the point wherein virtually all of the alkyl monochlorides had disappeared, the benzene and normal paraffins resulting from decomposition 'of alkyl benzene were similar to the materials already present in relatively large amounts therein and were therefore almost impossible to detect.

In our work wherein we set out to determine whether or not detrimental results would be obtained when the alkylation reaction was permitted to continue for appreciably long periods of time beyond the point where all of the alkyl monochloride had disappeared, we employed in the reaction only benzene and a single alkyl monochloride and found, unexpectedly, that upon disappearance of the alkyl monochloride progressively larger amount of alkane, or normal paraflin, corresponding to the alkyl monochloride employed 'wa's'foun'd as the reaction was permitted to continue. The amount of benzene was increased in an amount proportional to the amount of alkane obtained. Since there was no alkane present in the original mixture, we concluded that the alkane present and the additional amount of benzene found in the reaction mixture was due to decomposition of alkyl benzene.

The invention can further be illustrated by the following.

Example I Into a flask there were placed 92 grams of benzene, 2.1 grams of aluminum chloride and 100 grams of normal heptane. The normal heptane was added for the purpose of providing an internal standard for gas chromatographic analysis. The mixture was raised to a temperature of about 34 to 35 C. and thereafter maintained at such temperature and atmospheric pressure for the remainder of the run. Over a period of about one minute there was added to the mixture defined above, while the same was stirred, 30 grams of l-chlorododecane. On the basis of the normal alkyl monochloride present, the amount of aluminum chloride present was seven percent by weight. Periodically during the reaction two grams of reaction product was removed from the reaction mixture and analyzed by gas chromatography for its alkyl chloride content and for the amount of normal dodecane present. Since dodecyl benzene produced will decompose to equal molar amounts of benzene and dodecane, it was thus possible to determine the amount of dodecyl benzene that was decomposed. The results are tabulated below in Table I.

TABLE I Time From Start M01 Percent M01 Percent Of Reaction, Monohalide of Alkyl Benminutes Present zone Deeomposed 2. None None 0. 97 None 3. 63 None 5. 68 None 8. 79

Example II Example I was repeated, except that the temperature was maintained at about 39 to 40 C. The results are tabulated below in Table II.

TABLE II Time From Start Mol Percent M01 Percent Of Reaction, Monohalide of Alkyl Benminutes Present zone Decomposed None 0. 61

None 3.10

None 5. 68

None 7. 99

None 9.15

None 9. 80

Example III Example II was repeated, except that the amount of catalyst used was five percent. The results obtained are tatbulated below in Table III.

TABLE III Time From Start Moi Percent Mol Percent Of Reaction, Monohalide of Alkyl Benminutes Present Zeno Decomposed None 0. 48

None 0.96

None 1. 92

None 3. 39

None 4. 55

None 5. 47

4 Example IV Example I was repeated, except that the temperature was maintained at about 27 to 28 C. The results obtained are tabulated below in Table IV.

I Not taken.

Example I was repeated, but this time the catalyst concentration was three percent and the temperature was maintained at about 76 C. The results obtained are tabulated below in Table V.

TABLE V Time From Start Mol Percent Mol Percent of Reaction, Monohalide of Alkyl Benminutes Present zene Decomposed None 1. 30 None 8. 00

As pointed out above, the system employed in each of Examples 1, II, III, IV and V is not identical to the system employed in the process described and defined herein. In the examples only reactants, benzene and a single specific normal primary alkyl monochloride, and the alkylation catalyst were employed, whereas in the defined process a large amount of normal secondary alkyl monochloride and some alkyl polychlorides are also present. The above examples are presented herein merely to emphasize and point out the inventive features of the present process. Since no alkyl polychlorides are present, the reactions described in the examples will go at a faster rate than the claimed reaction. Accordingly in the claimed reaction, the conditions required for the virtual disappearance, as described, of the normal alkyl monochlorides from the reaction mixture will include a temperature of about 20 to about 80 C., preferably about 40 to about 60 C., a pressure of about 0 to about 10 pounds per square inch gauge, preferably about 0 to about 5 pounds per square inch gauge, and a reaction time of about 15 to about 45 minutes, preferably about 20 to about 40 minutes. In any event, the data presented in the tables amply show that as the reaction is permitted to proceed beyond the point wherein all of the normal alkyl monochlorides have disappeared, progressively larger amounts of alkyl benzene is decomposed to unde sirable products. The data further show that with increased temperature and/or increased catalyst concentration, not only does the desired alkylation reaction proceed more quickly to its conclusion, but the amount of decomposition products also increases when the alkylation reaction is not terminated properly.

The alkylation reaction can be quickly terminated at the designated time by turning off the stirrer, permitting the sludge (spent catalyst) to settle and thereafer separating the reaction mixture therefrom. Another method for terminating the reaction involves dumping the total reaction mixture into cold water, permitting the sludge to react with the water and thereafter separating the organic layer, containing the desired product, from the aqueous layer.

The determination as to when the reaction is to be terminated can be made easily. Chromatographic analysis, for its alkyl chloride content, can be made of the reaction product obtained from a process identical to a proposed process. On the basis of the results obtained, the proposed process can be programed so that it can be terminated at the desired time to assure that no appreciable decomposition of alkyl benzene will result. Alternatively, during the process the same can be monitored 5 and the product analyzed for its alkyl chloride content by periodically pulling a sample and analyzing the same by gas chromatography, using either a thermal conductivity detector or preferably an electron capture detector which only shows organic halides.

The process described and defined herein can further be illustrated by the following. Into a reactor equipped with a stirrer there were introduced 113 grams of benzene and 1.14 grams of aluminum chloride. The temperature of this mixture was raised to 63.5 C. and the same was maintained at this temperature level and at atmospheric pressure throughout the run. Over a period of one minute 200 grams of the following mixture was added to the reaction zone: 78 percent by weight of normal paraflins having from 10 to 15 carbon atoms, 0.6 percent by weight of C normal alkyl monochlorides, 4.6 percent by weight of C normal alkyl monochlorides, 4.8 percent by weight of C normal alkyl monochlorides, 5.1 percent by weight of C normal alkyl monochlorides, 3.4 percent by weight of C normal alkyl monochlorides, and 0.3 percent by weight of C normal alkyl monochlorides. Periodically during the reaction samples were withdrawn from the reaction mixture and analyzed by gravimetric analysis for their bound chlorine content and by gas chromatography for the mol percent of alkyl benzene decomposed. The results obtained are tabulated below in Table VI. On the basis 'of the results obtained, a process is programed employing the reaction conditions described in this example wherein the reaction is terminated promptly upon the virtual disappearance of the normal alkyl monochlorides, from the reaction product.

TABLE VI Time From Start Of Bound Chlorine, Mol Percent of Reaction, minutes Parts per Million Alkyl Benzene Deeomposed Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for alkylating benzene with a number of normal alkyl monochlorides at a temperature between about 20 and 80 C. while preventing appreciable decomposition of the alkyl benzene which is formed to benzene and the corresponding alkanes which comprises subjecting to alkylation conditions in the presence of a Lewis-type alkylation catalyst a mixture consisting essentially of benzene, normal paraifin selected from the group having from six to 20 carbon atoms, normal alkyl monochlorides selected from the group having from six to 20 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to about 20 and the weight ratio of said parafiins to said normal alkyl monochlorides is from about 70 to about 80 percent of the former to about 20 to about 30 percent of the latter, passing the hydrogen chloride formed out at the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 300 parts per million, and terminating the alkylation reaction in response to said chlorine determination to prevent appreciable decomposition of alkyl benzene.

2. A process for alkylating benzene with a number of normal alkyl monochlorides at a temperature between about 20 and 80 C. while preventing appreciable decomposition of the alkyl benzene which is formed to benzene and the corresponding alkanes which comprises subjecting to alkylation conditions in the presence of a Lewis-type alkylation catalyst a mixture consisting essentially of benzene, normal parafiins selected from the group having from six to 20 carbon atoms, normal alkyl monochlorides selected from the group having from six to 20 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to about 20 and the weight'ratio of said paraffins to said normal alkyl monochlorides is from about 70 to about percent of the former to about 20 to about 30percent of the latter, passing the hydrogen chloride formed out of the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 200 parts per million, and terminating the alkylation reaction in response to said chlorine determination to prevent appreciabledecomposition of alkyl benzene;

3. A process for alkylating benzene with a number of normal alkyl monochlorides at a temperature between about 20 and 80 C. while preventing appreciable decomposition of the alkyl benzene which is formed to benzene and the corresponding alkanes which comprises subjecting to alkylation conditions in the presence of an aluminum chloride alkylation catalyst a mixture consisting essentially of benzene, normal parafiins selected from the group having from six to 20 carbon atoms, normal alkyl monochlorides selected from the group having from six to 20 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to about 20 and the weight ratio of saidparaffins to said normal alkyl monochlorides is from about 70 to about 80 percent of the former to about 20to about 30 percent of the latter, passing the hydrogen chloride formed out of'the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 300 parts per million, and terminating the alkylation reaction in response to said chlorine determination to prevent appreciable decomposition of alkyl benzene.

4. A process for alkylating benzene with a number of normal alkyl monochlorides at a temperature between about 20 and 80 C. while preventing appreciable decomposition of thealkyl benzene which is formed to benzene and the corresponding alkanes which comprises subjecting to alkylation conditions in the presence of an aluminum chloride alkylation catalyst a mixture consisting essentially of benzene, normal parafiins selected from the group having from six to 20 carbon atoms, normal alkyl monochlorides selected from the group having from six to 20 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to apout 20 and the weight ratio of said parafiins to said normal alkyl monochlorides is from about 70 to about 80 percent of the former to about 20 to about 30 percent of the latter, passing the hydrogen chloride formed out of the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 200 parts per million and terminating the alkylation reaction in response to said chlorine determination to prevent appreciable decomposition of alkyl benzene.

5. A process for alkylating benzene with a number of normal alkyl monochlorides at a temperature between about 20 and 80 C. while preventingappreciable decomposition of the alkyl benzene which is formed to benzene and the corresponding alkanes which comprises subjecting to alkylation conditions in the presence of an aluminum chloride alkylation catalyst a mixture consisting essentially of benzene, normal paraflins selected from the group having from 10 to 15 carbon atoms, normal alkyl monochlorides selected from the group having from 10 to 15 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to about 20 and the weight ratio of said paraflins to said normal alkyl monochlorides is from about 70 to about 80 percent of the former to about 20 to about 30 percent of the latter, passing the hydrogen chloride formed out of the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 300 parts per million, and terminating the alkylation reaction in response to said chlorine determination to prevent appreciable decomposition of alkyl benzene.

6. A process for alkylating benzene with a number of normal alkyl monochlorides at a temperature between about 20 and 80 C. while preventing appreciable decomposition of the alkyl benzene which is formed to hen zene and the corresponding alkanes which comprises sub jecting to alkylation conditions in the presence of an aluminum chloride alkylation catalyst a mixture consisting essentially of benzene, normal parafiins selected from the group having from 10 to carbon atoms, normal alkyl monochlorides selected from the group having from 10 to 15 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to about and the weight ratio of said parafiins to said normal alkyl monochlorides is from about 70 to about 80 percent of the former to about 20 to about 30 percent of the latter, passing the hydrogen chloride formed out of the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 200 parts per million, and terminating the alkylation reaction in response to said chlorine determination to prevent appreciable decomposition of alkyl benzene.

7. A process for alkylating benzene with a number of normal alkyl monochlorides while preventing appreciable decomposition of the alkyl benzene which is formed to benzene and the corresponding alkanes which comprises subjecting to a temperature of about 20 to about 80 C. in the presence of from about one to about 15 percent by weight of an aluminum chloride alkylation catalyst a mixture consisting essentially of benzene, normal parafiins selected from the group having from 10 to 15 carbon atoms, normal alkyl monochlorides selected from the group having from 10 to 15 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to about 20 and the weight ratio of said parafiins to said normal alkyl monochlorides is from about 70 to about 80 percent of the former to about 20 to about 30 percent of the latter, passing the hydrogen chloride formed out of the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 300 parts per million, and terminating the alkylation reaction in response to said chlorine determination to prevent appreciable decomposition of alkyl benzene.

8. A process for alkylating benzene with a number of normal alkyl monochlorides while preventing appreciable decomposition of the alkyl benzene which is formed to benzene and the corresponding alkanes which comprises subjecting to a temperature of about 20 to about 80 C. in the presence of from about one to about 15 percent by weight of an aluminum chloride alkylation catalyst a mixture consisting essentially of benzene, normal paraffins selected from the group having from 10 to 15 carbon atoms, normal alkyl monochlorides selected from the group having from 10 to 15 carbon atoms, wherein the molar ratio of benzene to said normal alkyl monochlorides is from about three to about 20 and the weight ratio of said paratfins to said normal alkyl monochlorides is from about to about percent of the former to about 20 to about 30 percent of the latter, passing the hydrogen chloride formed out of the reaction zone, determining when the bound chlorine content of the reaction mixture falls to less than about 200 parts per million, and termimating the alkylation reaction in response to said chlorine determination to prevent appreciable decomposition of alkyl benzene.

References Cited UNITED STATES PATENTS 1,337,317 4/ 1920 Houlehan 260-672 2,072,061 2/1937 Thomas 260-671 3,235,616 2/1966 Sharman 260-672 1,995,827 3/1935 Thomas 260-671 OTHER REFERENCES Thomas, Anhydrous Aluminum Chloride in Organic Chemistry, Reinhold Publishing Corp., New York (1941), pp. 78 and 79 relied upon.

DELBERT E. GANTZ, Primary Examiner.

CURTIS R. DAVIS, Assistant Examiner.

Claims

1. A PROCESS FOR ALKYLATING BENZENE WITH A NUMBER OF NORMAL ALKYL MONOCHLORIDES AT A TEMPERATURE BETWEEN ABOUT 20* AND 80*C. WHILE PREVENTING APPRECIABLE DECOMPOSITION OF THE ALKYL BENZENE WHICH IS FORMED TO BENZENE AND THE CORRESPONDING ALKANES WHICH COMPRISES SUBJECTING TO ALKYLATION CONDITIONS IN THE PRESENCE OF A LEWIS-TYPE ALKYLATION CATALYST A MIXTURE CONSISTING ESSENTIALLY OF BENZENE, NORMAL PARAFFIN SELECTED FROM THE GROUP HAVING FROM SIX TO 20 CARBON ATOMS, NORMAL ALKYL MONOCHLORIDES SELECTED FROM THE GROUP HAVING FROM SIX TO 20 CARBON ATOMS, WHEREIN THE MOLAR RATIO OF BENZENE TO SAID NORMAL ALKYL MONOCHLORIDES IS FROM ABOUT THREE TO ABOUT 20 AND THE WEIGHT RATIO OF SAID PARAFFINS TO SAID NORMAL ALKYL MONOCHLORIDES IS FROM ABOUT 70 TO ABOUT 80 PERCENT OF THE FORMER TO ABOUT 20 TO ABOUT 30 PERCENT OF THE LATTER, PASSING THE HYDROGEN CHLORIDE FORMED OUT AT THE REACTION ZONE, DETERMINING WHEN THE BOUND CHLORINE CONTENT OF THE REACTION MIXTURE FALLS TO LESS THAN ABOUT 300 PARTS PER MILLION, AND TERMINATING THE ALKYLATION REACTION IN RESPONSE TO SAID CHLORINE DETERMINATION TO PREVENT APPRECIABLE DECOMPOSITION OF ALKYL BENZENE.