Process for preparing alkyl-substituted aromatic hydrocarbon

An alkyl-substituted hydrocarbon is prepared effectively under mild conditions by alkylating an alkyl aromatic hydrocarbon having at least one hydrogen atom at an alpha-position in a side chain with an olefin in the presence of a solid base which is obtainable by treating a water-containing oxide of an alkaline earth metal with at least one material selected from the group consisting of alkali metals and alkali metal hydrides in an amount of 0.5 to 3.5 equivalents per one mole of water in said oxide in an inert gas atmosphere.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a process for preparing an 
alkyl-substituted aromatic hydrocarbon. More particularly, the present 
invention relates to a process for preparing an alkyl-substituted aromatic 
hydrocarbon by reacting an alkyl aromatic hydrocarbon having at least one 
hydrogen atom at an alpha-position in said alkyl side chain with an olefin 
in the presence of a solid base which is obtainable by heating a 
water-containing oxide of an alkaline earth metal and at least one 
material selected from the group consisting of alkali metals and alkali 
metal hydrides, whereby the hydrogen atom at the alpha-position is 
substituted with an alkyl group. 
2. Description of the Related Art 
The alkyl-substituted aromatic hydrocarbons are useful as intermediates in 
the production of fine chemicals such as agricultural chemicals, 
pharmaceuticals and other chemicals and prepared by reacting the aromatic 
hydrocarbon having the hydrogen atom at the alpha-position in the side 
chain with the olefin in the presence of a base catalyst. 
As the preparation process of the alkyl-substituted aromatic hydrocarbon, 
there are known a process which utilizes a catalyst comprising metal 
sodium and chlorotoluene and a process which utilizes a catalyst 
comprising metal sodium supported on potassium carbonate (cf. J. Am. Chem. 
Soc., 78, 4316 (1956), GB Patent No. 1269280 and Japanese Patent Kokai 
Publication No. 53229/1986). 
However, the conventionally used catalysts have various drawbacks such as 
insufficient catalytic activities, a low yield of the alkyl-substituted 
hydrocarbon per a unit amount of the catalyst and troublesome separation 
of the catalysts from the product. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a base catalyst which 
effectively catalyzes a reaction of an aromatic hydrocarbon having a 
hydrogen atom at the alpha-position in a side chain with an olefin and 
which can be easily separated from the product after the reaction. 
Another object of the present invention is to provide a process for 
preparing an alkyl-substituted hydrocarbon by reacting the alkyl aromatic 
hydrocarbon having the hydrogen atom at the alpha-position in the side 
chain with the olefin. 
Accordingly, the present invention provides a process for preparing an 
alkyl-substituted hydrocarbon comprising alkylating an alkyl aromatic 
hydrocarbon having at least one hydrogen atom at an alpha-position in a 
side chain with an olefin in the presence of a solid base which is 
obtainable by heating and reacting a water-containing oxide of an alkaline 
earth metal and at least one material selected from the group consisting 
of alkali metals and alkali metal hydrides in an amount of 0.5 to 3.5 
equivalents per one mole of water in said oxide in an inert gas atmosphere 
.

DETAILED DESCRIPTION OF THE INVENTION 
The process of the present invention is characterized in the use of the 
specific solid base as the catalyst, which solid base is prepared from the 
water-containing oxide of the alkaline earth metal. The alkaline earth 
metal oxide includes oxides of the elements of Group II of the Periodic 
Table. Preferably, oxides of magnesium and calcium are used. More 
preferably, magnesium oxide is used. Two or more alkaline earth metal 
oxides may be used as a mixture. 
The water-containing oxide of the alkaline earth metal is prepared by 
calcining hydroxide and oxide of the alkaline earth metal. According to 
the calcining temperature and time, the water content varies so that 
various oxide which has desired content of water can be produced. 
The water content may be expressed by weight loss on heating the oxide up 
to 800.degree. C. The water content is usually from 1 to 10% by weight 
based on the weight of the oxide. 
As the alkali metal or its hydride, an alkali metal of Group I of the 
Periodic Table such as lithium, sodium, potassium and rubidium or its 
hydride is used. They may be used as a mixture. Among them, sodium, 
potassium, sodium hydride, potassium hydride, or mixture of them, 
particularly potassium and its hydride are preferred. The amount of the 
alkali metal or its hydride is generally from 0.5 to 3.5 equivalents, 
preferably from 0.9 to 2.5 equivalents per one mole of water contained in 
the alkaline earth metal oxide. 
Examples of the inert gas are nitrogen, helium, argon, and the like. 
In the preparation of the solid base, the watercontaining alkaline earth 
metal oxide and the alkali metal or its hydride are heated in the inert 
gas atmosphere. A heating temperature is usually from 150.degree. to 
600.degree. C., preferably from 180.degree. to 400.degree. C. 
A heating time varies with other reaction conditions such as the reaction 
temperature. It is usually from 10 to 300 minutes. 
By the above heating, the solid base which has high catalytic activity and 
handleability can be obtained. 
In the process of the present invention, the aromatic hydrocarbon having 
the hydrogen atom at the alpha-position in the side chain is reacted with 
the olefin in the presence of the above described solid base as the 
catalyst. 
As such aromatic hydrocarbon, not only monocyclic aromatic hydrocarbon but 
also condensed polycyclic aromatic hydrocarbon may be used. In the 
aromatic hydrocarbons, the side chains may be closed to form a ring. 
Specific examples of the aromatic hydrocarbon are toluene, ethylbenzene, 
isopropylbenzene (cumene), n-propylbenzene, n-butylbenzene, 
sec.-butylbenzene, isobutylbenzene, xylene, cymene, diisopropylbenzene, 
methylnaphthalene, tetrahydronaphthalene, indan and the like. Among them, 
toluene, ethylbenzene and isopropylbenzene are preferred. 
As the olefin, those having 2 to 20 carbon atoms are usually used. The 
olefin may be straight or branched. The carbon-carbon double bond may be a 
terminal or internal double bond. Preferably, the olefin having the 
terminal double bond is used. Specific examples of the olefin are 
ethylene, propylene, 1-butene, 2-butene, isobutylene, 1-pentene, 
2-pentene, 1-hexene, 2-hexene, 3-hexene, 1-heptene, 2-heptene, 3-heptene, 
octene, nonene, 3-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-pentene, 
3-methyl-2-pentene and the like. Among them, ethylene, propylene, 1-butene 
and 2-butene are preferred. 
The alkylation reaction according to the present invention may be carried 
out batchwise or continuously with the use of a fluidized bed or a fixed 
bed. 
The reaction temperature for the alkylation is usually from 0.degree. to 
300.degree. C., preferably from 20.degree. to 200.degree. C. 
The reaction pressure is from atmospheric pressure to 200 kg/cm.sup.2, 
preferably from 2 to 100 kg/cm.sup.2. 
The molar ratio of the olefin to the aromatic hydrocarbon is usually from 
0.1 to 10, preferably from 0.2 to 5. 
In the batchwise reaction, the amount of solid base catalyst to be used is 
from 0.01 to 20% by weight, preferably from 0.05 to 5% by weight based on 
the weight of the aromatic hydrocarbon. The reaction time is generally 
from 0.5 to 50 hours, preferably from 1 to 25 hours. 
In the continuous reaction, the mixture of the aromatic hydrocarbon and the 
olefin in the above molar ratio is supplied at LHSV of 0.1 to 1000 
hr.sup.-1, preferably 0.5 to 500 hr.sup.-1. 
According to the present invention, the alkyl-substituted hydrocarbon is 
effectively prepared in the presence of the solid base catalyst in a small 
amount under the mild conditions. Further, the catalyst to be used 
according to the present invention is easily handled and post-treated 
after the reaction. 
PREFERRED EMBODIMENTS OF THE INVENTION 
Practically and presently preferred embodiments of the present invention 
will be illustrated by following examples. 
The water content in the alkaline earth metal oxide is measured by weighing 
an oxide sample filled in a quartz glass tube in a nitrogen atmosphere, 
heating the sample in a tubular furnace to 800.degree. C. with flowing 
nitrogen in the quartz glass tube, keeping it at the same temperature for 
2 hours, cooling it to room temperature, weighing the sample weight and 
then calculating the water content from the weight loss of the sample. 
Preparation of Solid Bases 
Solid Base A 
Magnesium oxide containing 2.8% by weight of water (a calcined product of 
Starmag U manufactured by Konoshima Chemical Industry Co., Ltd.) (20 g) 
was charged in a 500 ml flask under nitrogen. Then, to the flask 
containing magnesium oxide, metal potassium (1.96 g) was added at 
290.degree. C. under nitrogen while stirring and a resulting mixture was 
stirred at the same temperature for 0.2 hours, followed by cooling to room 
temperature to obtain Solid Base A (21.7 g). 
Solid Base B 
In the same manner as in the preparation of Solid Base A but using 1.62 g 
of metal potassium, Solid Base B was prepared. 
Solid Base C 
In the same manner as in the preparation of Solid Base A but using 2.6 g of 
metal potassium, Solid Base C was prepared. 
Solid Base D 
In the same manner as in the preparation of Solid Base A but using 1.2 g of 
metal potassium, Solid Base D was prepared. 
Solid Base E 
In the same manner as in the preparation of Solid Base A but using 1.2 g of 
metal potassium and adding potassium at 200.degree. C. Solid Base E was 
prepared. 
Solid Base F 
In the same manner as in the preparation of Solid Base A but using 2.1 g of 
metal sodium in place of metal potassium, Solid Base F was prepared. 
Solid Base G 
To calcium oxide containing 1.8% by weight of water (a calcined product of 
First Grade calcium hydroxide) (20 g), metal potassium (0.47 g) was added 
at 290.degree. C. under nitrogen while stirring and a resulting mixture 
was stirred at the same temperature for 0.2 hours, followed by cooling to 
room temperature to obtain Solid Base G. 
Solid Base H 
To the same magnesium oxide as used in the preparation of Solid Base A (20 
g), potassium hydride (1.91 g) was added at 360.degree. C. under nitrogen 
while stirring and a resulting mixture was stirred at the same temperature 
for 0.2 hours, followed by cooling to room temperature to obtain Solid 
Base H. 
Solid Base I 
In the same manner as in the preparation of Solid Base H but using 1.87 g 
of sodium hydride in place of potassium hydride, Solid Base I was 
prepared. 
Solid Base J 
To the same calcium oxide as used in the preparation of Solid Base G (20 
g), potassium hydride (0.88 g) was added at 360.degree. C. while stirring 
and a resulting mixture was stirred at the same temperature for 0.2 hours, 
followed by cooling to room temperature to obtain Solid Base J. 
Solid Base K 
In the same manner as in the preparation of Solid Base A but using 
anhydrous magnesium oxide, Solid Base K was prepared. 
Solid Base L 
To magnesium oxide containing 10.9% by weight of water (20 g), metal 
potassium (1.96 g) was added at 290.degree. C. under nitrogen while 
stirring and a resulting mixture was stirred at the same temperature for 
0.2 hours, followed by cooling to room temperature to obtain Solid Base L. 
Solid Base M 
In the same manner as in the preparation of Solid Base A but using 1.94 g 
of potassium hydride in place of metal potassium, Solid Base M was 
prepared. 
Example 1 
In a 600 ml autoclave equipped with a magnetic stirrer, Solid Base A (0.15 
g) and cumene (240 g) were charged under nitrogen, heated to 160.degree. 
C. while stirring at 1000 rpm and then reacted at the same temperature for 
0.5 hours while supplying ethylene gas under pressure of 10 kg/cm.sup.2 G 
to prepare tert.-amylbenzene (hereinafter referred to as "TAB"). 
After the reaction, the autoclave was cooled, and the catalyst was filtered 
off. The reaction mixture was analyzed by gas chromatography. The results 
are shown in Table 1. 
Examples 2-10 and Comparative Examples 1 and 2 
In the same manner as in Example 1 but using each of Solid Bases A to L and 
carrying the reaction under the conditions shown in Table 1, the 
alkylation was carried out. The results are shown in Table 1. 
In Examples 1 though 10, the catalysts were still active at the end of the 
reaction, and the alkylation could be further carried out by using the 
same catalysts. 
Comparative Example 3 
To a 200 ml autoclave equipped with a magnetic stirrer, anhydrous potassium 
carbonate which had been dried by heating under nitrogen at 400.degree. C. 
for 2 hours (8.19 g), sodium (0.30 g) and cumene (26.7 g) were charged 
under nitrogen and heated to 190.degree. C., followed by stirring at the 
same temperature for 2 hours at 1000 rpm. 
Then, the autoclave was cooled, and cumene (53.3 g) was additionally 
supplied. The mixture was heated to 160.degree. C. while stirring at 1000 
rpm. At the same temperature, the reaction was continued for 3 hours while 
supplying ethylene gas under pressure of 10 kg/cm.sup.2 G. The results are 
also shown in Table 1. 
The selectivity of TAB is calculated according to the following equation: 
TABLE 1 
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##STR1## 
Exam- Solid Reaction Conversion 
Selectivity 
ple Base time of cumene 
of TAB 
No. (g) (hrs) (%) (%) 
______________________________________ 
1 A(0.15) 0.5 98.5 99.3 
2 A(0.16) 0.5 98.7 99.4 
3 B(0.23) 0.5 94.3 96.9 
4 C(0.16) 0.5 58.8 99.9 
5 D(0.18) 0.5 99.7 99.5 
6 E(0.29) 1.0 32.6 99.9 
7 G(1.32) 1.0 99.8 99.9 
8 H(0.16) 2.0 96.5 99.9 
9 I(0.18) 1.0 18.1 99.9 
10 J(0.46) 1.0 38.8 99.9 
Com. 1 K(0.46) 0.5 9.8 61.5 
Com. 2 L(1.29) 0.5 0 0 
Com. 3 Mixture 3 19.4 73.9 
(8.49) 
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Example 11 
In a 300 ml autoclave equipped with a magnetic stirrer, Solid Base D (3.02 
g) and toluene (80 g) were charged under nitrogen and then liquid 
propylene (70 ml) was charged under pressure. The mixture was reacted at 
160.degree. C. for 6 hours while stirring at 1000 rpm to obtain 
isobutylbenzene (hereinafter referred to as "IBB"). 
After the reaction, the product was analyzed in the same manner as in 
Example 1. The results are shown in Table 2. 
Example 12 
In the same manner as in Example 11 but using Solid Base M and carrying out 
the reaction under the conditions shown in Table 2, the alkylation was 
carried out. The results are shown in Table 2. 
In Examples 11 and 12, the catalysts were still active at the end of the 
reaction and the alkylation could be further carried out by using the same 
catalyst. 
Comparative Example 4 
In a 200 ml autoclave equipped with a magnetic stirrer, anhydrous potassium 
carbonate which had been calcined at 400.degree. C. for 2 hours under 
nitrogen (8.45 g), sodium (0.30 g) and toluene (26.6 g) were charged and 
stirred at 1000 rpm at 190.degree. C. for 2 hours under nitrogen. After 
cooling the autoclave, toluene (53.2 g) was further added and then liquid 
propylene (70 ml) was charged under pressure. The mixture was reacted at 
160.degree. C. for 6 hours while stirring. The results are shown in Table 
2. 
The selectivity of IBB is calculated according to the following equation: 
TABLE 2 
______________________________________ 
##STR2## 
Example Conversion Selectivity 
No. Solid base (g) 
of toluene (%) 
of IBB (%) 
______________________________________ 
11 D(3.02) 30.2 87.2 
12 M(3.12) 19.6 89.2 
Com. 4 Mixture (8.75) 
3.5 89.2 
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