Method of producing valuable alkylated aromatic hydrocarbons from tar

Valuable alkylated aromatic hydrocarbons are produced from a tar comprising that fraction of an alkylation reaction product distilling above about 240.degree. C by a method comprising contacting the tar with benzene and/or toluene in the presence of a catalytic amount of a crystalline aluminosilicate molecular sieve catalyst. For example, tar obtained from the alkylation product resulting from alkylating benzene with ethylene in the presence of aluminum chloride, the tar comprising that fraction of the alkylation reaction product distilling above about 240.degree. C, is converted to a reaction product comprising valuable mono- and diethylbenzene by contacting the tar with benzene in the presence of a catalytic amount of a rare earth exchange zeolite Y molecular sieve at a temperature of at least about 240.degree. C and at a pressure of at least about 200 psi.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to valuable alkylated aromatic hydrocarbons. In one 
aspect, this invention relates to a method of producing said hydrocarbons 
from otherwise marginally valuable tar obtained from the reaction product 
of an alkylation process comprising contacting benzene and/or toluene with 
a C.sub.2 -C.sub.3 olefin. In another aspect, this invention relates to 
said method wherein the tar is contacted with benzene and/or toluene in 
the presence of a crystalline aluminosilicate molecular sieve catalyst. 
2. Description of the Prior Art 
The reaction product produced by the alkylation of benzene and/or toluene 
with ethylene and/or propylene (in the presence of an alkylation catalyst 
and at alkylation parameters) comprises both valuable alkylated aromatics, 
such as ethylbenzene, ethyltoluene, cumene, etc., and tar. This tar is a 
problem in as much as it represents lost alkylated aromatic hydrocarbons. 
The size of this problem, of course, is dependent upon the amount of tar 
that can be converted to the alkylated aromatic hydrocarbons. The more tar 
that can be converted, the smaller the size of the problem. Presently, 
only the tar fraction that distills below about 240.degree. C is 
considered convertible while the remaining tar fraction is not so 
considered (and is thus generally burned as fuel, a marginally valuable 
utility). Accordingly, the aforementioned alkylation processes are 
generally conducted in such a manner as to minimize this latter tar 
fraction. This equates with conducting the alkylations at an 
olefin:aromatic mole ratio of substantially less than 1 which results in a 
large amount of unreacted aromatic being present in the resulting reaction 
product. The unreacted aromatic must then be removed from the reaction 
product and eventually recycled. This all translates into a less efficient 
and more expensive alkylation process than a similar process wherein the 
tar fraction above about 240.degree. C is convertible. It is therefore 
desirable to have a method for converting the tar fraction above about 
240.degree. C to valuable alkylated aromatic hydrocarbons. 
SUMMARY OF THE INVENTION 
According to this invention, valuable alkylated aromatic hydrocarbons of 
the formula: 
##STR1## 
wherein R is 
##STR2## 
each R' is individually hydrogen or methyl, and n is 1 or 2, are produced 
from a tar obtained from the reaction product of an alkylation process 
comprising contacting in the presence of an alkylation catalyst and at 
alkylation parameters: 
(a) benzene, toluene or both; with 
(b) ethylene, propylene or both, 
the tar comprising that fraction of the alkylation reaction product having 
a distillation temperature of at least about 240.degree. C, by a method 
comprising contacting at a temperature of at least about 240.degree. C and 
at a pressure of at least about 200 psi: 
(i) the tar; with 
(ii) benzene, toluene or both; in the presence of a catalytic amount of 
(iii) a crystalline aluminosilicate molecular sieve catalyst. This 
invention converts otherwise marginally valuable tar to valuable alkylated 
aromatic hydrocarbons, and thus allows the alkylation processes to be 
conducted in a more efficient and less expensive manner than heretofore 
practical. 
DETAILED DESCRIPTION OF THE INVENTION 
The valuable alkylated aromatic hydrocarbons produced by this invention are 
of the formula: 
##STR3## 
wherein R is 
##STR4## 
each R' is hydrogen or methyl, and n is 1 or 2. Each R can be either 
ortho, meta or para to R' as well as to one another (where n is 2). 
Typically the aromatic hydrocarbons produced are characteristic of the tar 
from which they are made. For example, the tar obtained from the 
alkylation process for ethyltoluene typically produces mono- and 
diethyltoluene when contacted with toluene at conversion conditions. 
Similarly, the tar obtained from the alkylation processes for ethylbenzene 
and cumene typically produces mono- and diethylbenzene and mono- and 
diisopropylbenzene, respectively (when contacted with benzene). R is 
usually ethyl when R' is methyl. 
The tars here used are obtained from the reaction product of an alkylation 
process comprising contacting in the presence of an alkylation catalyst 
and at alkylation parameters: 
(a) benzene, toluene or both; with 
(b) ethylene, propylene or both. 
These alkylation reaction products are generally fractionally distilled to 
recover the various components and the distilland remaining at about 
240.degree. C comprises the tars of this invention. In other words, the 
tars here used comprise that fraction of the alkylation reaction product 
having a distillation temperature of at least about 240.degree. C, the 
desired alkylation product and convertible tars having distillation 
temperatures below about 240.degree. C. Typical alkylation processes 
include the production of ethylbenzene (ethylene and benzene), 
ethyltoluene (ethylene and toluene) and cumene (propylene and benzene). 
The alkylation catalyst and parameters of these processes are not critical 
and thus any suitable catalyst, e.g., aluminum chloride, zinc chloride and 
other Friedel-crafts catalysts, and alkylation parameters, e.g., about 80 
to about 180.degree. C and about 0 to about 200 psi, can be used. 
While the composition of these tars are not known with precision and vary 
from alkylation process to alkylation process, an illustrative composition 
is about: 
(a) 10 weight percent long chain or cyclic hydrocarbon, such as C.sub.6 
-C.sub.20 alkyls, cycloalkyls and derivatives of either; 
(b) 40 weight percent cyclohexylbenzene and derivatives thereof, such as 
various cyclohexylalkylbenzenes; and 
(c) 50 weight percent polyaromatic material, such as 1,4-diphenylbutane, 
1,1-diphenyl-ethane, etc. These tars can be further defined as essentially 
wholly hydrocarbon and substantially free of monoaromatic alkylated 
material, such as di-, tri- and tetraethylbenzene, di- and 
tri-isopropylbenzene, and di- and tri-ethyltoluene. These monoaromatic 
alkylated hydrocarbons are generally considered among the convertible tars 
and are removed by distillation from the reaction product prior to about 
240.degree. C. This invention finds particular utility for tars having a 
distillation temperature of at least about 270.degree. C, with special 
utility for tars having a distillation temperature of at least about 
290.degree. C. 
Crystalline aluminosilicate (zeolite) molecular sieve catalysts are used in 
the practice of this invention. These catalysts include both naturally 
occurring and synthetically prepared zeolites and consist basically of a 
3-dimensional framework of SiO.sub.4 and AlO.sub.4 tetrahedrons 
cross-linked by the sharing of oxygen atoms. The electrovalence of each 
tetrahedra containing aluminum is balanced by the inclusion in the 
framework of a cation, such as an alkali or alkaline earth metal ion. 
These catalysts are known in the art and are further described by Milton, 
U.S. Pat. Nos. 2,882,244; Breck, 3,130,007; Rabo et al., 3,236,761 and 
Bowes et al., 3,578,723, all incorporated herein by reference. 
Preferred molecular sieve catalysts are of the zeolite Y type and have a 
pore size of at least about 6 angstroms, and preferably of at least about 
8 angstroms. These Y catalysts are of the formula: 
EQU 0.9 .+-. 0.2 Na.sub.2 O:Al.sub.2 O.sub.3 :wSiO.sub.2 :xH.sub.2 O 
wherein w is 4-6 and x is 0-9. More preferred Y catalysts comprise about 20 
weight percent of an acid washed inorganic oxide binder and comprise by 
weight about: 
(a) 65 percent SiO.sub.2 ; 
(b) 20 to about 34 percent Al.sub.2 O.sub.3 ; 
(c) 0.15 to about 2 percent Na.sub.2 O; and 
(d) 0 to about 12 percent RE.sub.2 O.sub.3, wherein RE is a rare earth 
metal having an atomic number between 57 and 71, inclusive. 
A rare earth exchange zeolite Y molecular sieve especially preferred is 
SK-500, a Linde molecular sieve manufactured by the Materials Systems 
Division of Union Carbide Corporation. This catalyst comprises about: 
(a) 65 percent SiO.sub.2 ; 
(b) 22.7 percent Al.sub.2 O.sub.3 ; 
(c) 1.6 percent Na.sub.2 O; and 
(d) 10.7 percent RE.sub.2 O.sub.3. 
A catalytic amount of molecular sieve catalyst is required for the practice 
of this invention. Typically, the molecular sieve catalyst is present at a 
minimum sieve:tar weight ratio of about 0.01:1 and preferably of about 
0.1:1. A maximum sieve:tar weight ratio here used is typically about 2:1 
and preferably about 1:1. These maximum sieve:tar weight ratios are only 
typical with the actual maximums determined by practical considerations, 
such as convenience and economy. 
This invention also requires that the tar be contacted with an aromatic, 
typically benzene, toluene or both. The aromatic employed is a matter of 
choice but generally benzene is contacted with tars generated from an 
ethylbenzene or cumene process while toluene is contacted with tars 
generated from a ethyltoluene process. Any suitable amount of benzene 
and/or toluene can be contacted with the tars. Illustrative amounts 
include benzene with ethylbenzene tar at a minimum benzene:tar weight 
ratio of about 0.01:1, and preferably about 0.5:1 and a maximum weight 
ratio of about 5:1 and preferably about 2:1. Like weight ratios for 
benzene and cumene tar and toluene and ethyltoluene tar are used. 
While this invention can be practiced in either the liquid or gaseous 
state, the temperature and pressure parameters here used are generally 
sufficient to maintain the process reagents (excepting the catalyst) in 
the liquid state. The tar and the benzene and/or toluene are contacted at 
a temperature of at least about 240.degree. C and at a pressure of at 
least about 200 psi. A minimum temperature of about 270.degree. C is 
preferred with a maximum temperature of about 400.degree. C, and 
preferably of about 350.degree. C. A pressure of at least about 300 psi is 
preferred, with a maximum pressure of about 900 psi, and preferably about 
600 psi. 
Hydrogen addition to the reaction mixture of tar, benzene and/or toluene, 
and catalyst is generally neither beneficial nor detrimental as regards 
tar conversion to valuable aromatic hydrocarbons. As such, hydrogen is 
generally not added to the reaction mixture. 
This invention can also be practiced either on a batch or a continuous 
basis. Economy and convenience prefers the latter. 
The following examples are illustrative of certain specific embodiments of 
this invention. Unless otherwise noted, all parts and percentages are by 
weight.

SPECIFIC EMBODIMENTS 
EXAMPLE 1 
Ethylbenzene tar (130 gms) obtained from the reaction product of the 
alkylation process comprising contacting benzene and ethylene in the 
presence of aluminum chloride and at a temperature of about 110.degree. C 
and a pressure of about 15 psi (the tar comprising that fraction of the 
alkylation reaction product distilling between a temperature range of 
about 270.degree.-350.degree. C) was added to a batch reactor containing 
benzene (300 gms) and SK-500 (50 gms), a Linde molecular sieve catalyst 
comprising about 65 percent SiO.sub.2, about 22.7 percent Al.sub.2 
O.sub.3, about 1.6 percent Na.sub.2 O, and about 10.7 percent RE.sub.2 
O.sub.3, manufactured by the Materials Systems Division of Union Carbide 
Corporation. The batch reactor was then heated to about 280.degree. C and 
500 psi and maintained thereat for about two hours. The resulting reaction 
product was then distilled and analyzed by vapor phase chromatography. 
Analysis showed a substantial conversion of the ethylbenzene tar and a 
distillate composite (385 g) comprising: 
______________________________________ 
Benzene 70% 
toluene 3.3% 
Ethylbenzene 17.5% 
Diethylbenzene 
and others 9.2% 
______________________________________ 
Residue after distillation comprised about 45 gms. 
EXAMPLE 2 
The residue (45 gms) from Example 1 was added to a batch reactor containing 
benzene (160 gms) and SK-500 catalyst (50 gms). The reactor was then 
heated to about 280.degree. C at 500 psi and maintained thereat for about 
2 hours. Subsequent distillation and vapor phase chromatography showed 
further conversion of the original ethylbenzene tar with a distillate 
composition (183 g) of: 
______________________________________ 
Benzene 90.8% 
Toluene 2.1% 
Ethylbenzene 3% 
Diethylbenzene 
and others 3.8% 
______________________________________ 
A second residue (22 gms) remained after this distillation. 
EXAMPLE 3 
Ethyltoluene tar (130 gms) obtained from the reaction product of the 
alkylation process comprising contacting toluene and ethylene in the 
presence of AlCl.sub.3 at a temperature of about 150.degree. C and at a 
pressure of about 15 psi (the tar comprising that fraction of the 
alkylation reaction product distilling between the temperature range of 
about 240.degree.-350.degree. C) was added to a batch reactor containing 
toluene (270 gms) and SK-500 molecular sieve catalyst (50 gms). The 
reactor was heated to about 320.degree. C and 500 psi and maintained 
thereat for about 2 hours. Subsequent distillation (up to about 
190.degree. C) and vapor phase chromatography revealed a conversion of 
about 64 percent of tar to valuable alkylated aromatic hydrocarbons. The 
reaction product contained about 22 percent ethyltoluene (.apprxeq.88 g). 
EXAMPLE 4 
The procedure of Example 3 was repeated except isopropylbenzene tar 
(250.degree.-350.degree. C) was substituted for ethyltoluene tar and 
benzene was substituted for toluene. Analysis of the reaction product 
revealed about 67 percent conversion of the tar to valuable alkylated 
aromatic hydrocarbons. The reaction product contained about 27 percent 
isopropylbenzene (.apprxeq.108 g). 
Although this invention has been described in considerable detail by the 
preceding examples, it is to be understood that such detail is for 
purposes of illustration only and are not to be construed as limitations 
upon the invention. Many variations may be had upon the preceding examples 
without departing from the spirit and scope of the appended claims.