Process for the liquid phase acylation of aromatic compounds

Details Process for the liquid phase acylation of aromatic compounds Process for the liquid phase acylation of aromatic compounds

2001-03-26

2002-10-01

Padmanabhan, Sreeni (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S313000, C568S319000, C568S328000, C568S331000, C568S392000, C568S406000

Reexamination Certificate

active

06459000

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the liquid phase acylation of aromatic compounds by an acylating agent using a solid catalyst comprising metal oxide(s). The present invention particularly relates to a process for the acylation of aromatic compounds using a reusable solid catalyst comprising metal oxide(s).
BACKGROUND OF THE INVENTION
Friedel Crafts type acylation of aromatic compounds by various acylating agents, using homogeneous Lewis acid catalysts, such as AlCl
0
, BF
3
, ZnCl
2
and other metal chlorides and protonic acid catalysts such as H
2
SO
4
, H
3
PO
4
, HF, etc., are well known in the art [G. A. Olah, in Friedel Crafts and related reactions: vol III, Acylation and related reactions, Wiley-Interscience Publ., New York, 1964].
U.S. Pat. No. 5,476,970 granted to Rains et al. Discloses a homogeneous liquid phase process for the acylation of R
1
R
2
R
6
H
4
by R
3
R
4
R
6
H
3
COCl, wherein R
1
, R
2
, R
3
and R
4
are chemical groups using FeCl
3
catalyst at high pressures. French Patents FR 2768728 (1999) and FR 2768729 (1999) of Baudry et al, disclose liquid phase homogeneous process for the benzoylation of anisole by benzoyl chloride using rare earth halides or uranyl halide.
Japanese patent JP 08277241, A2 (1996) of Kunikata discloses a liquid phase process for the acylation of phenol by phenyl acetyl chloride using a homogeneous AlCl
0
catalyst. A use of AlCl
0
as a homogeneous catalyst is also disclosed by Oono for the acylation of toluene with acetyl chloride at high pressures in Japanese patent JP 09059205, A2 (1997). Japanese patent JP 20000086570, A2 (2000) of Shoji et al discloses a homogeneous liquid phase process for the acylation of toluene by acetyl fluoride using HF-BF
3
as a catalyst.
The main disadvantages of the Friedel-Crafts type acylation processes based on the use of the above mentioned homogeneous acid catalysts are:
1. The separation and recovery of the dissolved acid catalysts from the liquid reaction mixture is difficult.
2. The disposal of the used acid catalysts creates environmental pollution.
3. The homogeneous acid catalysts also result in problems such as high toxicity, corrosion, spent acid disposal and also require use of more than the stoichiometric amounts.
Liquid phase processes for the acylation of aromatic compounds by acyl halides using solid catalysts is also well known in the art.
Japanese patent JP 01089894, A2 (1995) to Myata et al discloses a liquid phase process for the acylation of toluene with benzoyl chloride using ammonium chloride treated H-beta zeolite catalyst under reflux for 3 hours to get para acylated toluene with 28% yield. French patent FR 2745287, A1 (1997) of Barbier et al discloses a liquid phase acylation of anisole by benzoyl chloride under reflux using neodymium chloride deposited on montmorillonite K—10 clay.
Vincent et al (ref Tetrahedron Lett., 35, 1994, 2601) disclose that H-ZSM-5 zeolite can catalyze the acylation of phenol and anisole by benzoyl chloride at 120° C. for 5 hours but not the acylation with benzoyl chloride of benzene and naphthalene.
Acylation of aromatic compounds involves the electrophilic substitution of H from the aromatic nucleus of the aromatic compound. It is well known in the prior art that the electrophilic substitution is favoured by the presence of electron donating groups such as OH, alkyl, alkoxy, phenoxy, amine, alkyl amine, SH, etc., in the aromatic compound. Whereas the electophilic substitution is inhibited by the presence of electron withdrawing groups such as halo, nitro, cyano. Carboxy, aldehyde, etc., in the aromatic compound [G. A. Olah, in Friedel Crafts and related reactions Wiley-Interscience Publ., New York, 1963].
While some limitations of the homogeneous acid catalysed processes are overcome in the prior art heterogeneous solid catalysed processes described above, the acylating activity of the solid acid catalysts used in the prior art processes is low, particularly for acylating aromatic compounds not containing electron donating groups, such as benzene, naphthalene etc. Both the prior art homogeneous and heterogeneous acid catalysts are highly moisture sensitive, and hence demand moisture free or thoroughly dried reactants, solvents and catalyst for Friedel-Crafts type acylation processes. In the presence of moisture in the reaction mixture, both the above homogeneous and heterogeneous catalysts show poor activity in the Friedel-Crafts type acylation processes. Hence there is a need for finding more efficient, reusable and also moisture insensitive solid catalyst for the acylation of aromatic compounds, which overcomes the disadvantages of the prior art discussed above.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a liquid phase process for the acylation of aromatic compounds including those which do not contain electron donating groups, using a solid catalyst, which has high activity when the aromatic ring activating groups (electron donating groups like alkyl, alkoxy, hydroxy, phenoxy, etc.) are present in the aromatic ring to be acylated and also when the ring activating groups in the aromatic ring to be acylated are absent, such that reaction temperature is low and/or reaction time is short.
Another object of the invention is to provide a liquid phase process for acylation of aromatic compounds using a solid catalyst that is easily separable and reusable in the process.
It is another object of the present invention to provide a liquid phase process for the acylation of aromatic compounds that is insensitive the presence of moisture in the reaction mixture.
SUMMARY OF THE INVENTION
Accordingly the present invention provides a liquid phase process for the acylation of aromatic compound of the formula (R
1
R
2
R
3
R
4
)—M—H by an acylating agent of the formula (R
5
R
6
R
7
)—Y—Z to obtain the corresponding acylated compound of the formula (R
1
R
2
R
3
R
4
)—M—Y—(R
5
R
6
R
7
), wherein M is an aromatic nucleus with R
1
R
2
R
3
, and R
4
being the chemical groups attached thereto, Y is the nucleus of the acylating agent and is selected from the group consisting of C—CO, C
n
H
2n−2
CO, C
6
H
2
CO, C
6
H
2
C
n
H
2n
—CO and C
6
H
2
C
n−1
(X)—CO with R
5
, R
6
and R
7
being chemical groups attached thereto Y, Z is selected from the group consisting of Cl, Br, I and OH, X is a halogen, and n is an integer having a value equal to or greater than 1.0, using a solid catalyst comprising a metal oxide of the formula AO
x
with or without a catalyst support, wherein A is a metallic element selected from Ga, In, Tl, Fe and a mixture of two or more thereof, and x is the number of oxygen atoms required to fulfil the valance requirement of A, the said process comprising,
i. pretreating the solid catalyst by contacting it with a dry gas comprising a hydrogen halide in the presence or absence of the aromatic compound to be acylated;
ii. contacting the hydrogen halide pretreated catalyst with a liquid reaction mixture comprising the aromatic compound and the acylating agent in a stirred batch reactor at following reaction conditions: weight ratio of catalyst to acylating agent in the range of about 0.01 to about 2.0, mole ratio of the aromatic compound to the acylating agent in the range of from about 0.1 to 100, weight ratio of non-aqueous solvent to the aromatic compound being in the range of about 0 to about 100, reaction temperature being in the range of about 10° C. to about 300° C., pressure in the range of about 0.5 atm to about 10 atm., gas hourly space velocity of inert gas bubbled through the reaction mixture being in the range of about Oh
−1
to 5000 h
−1
and reaction period in the range of from about 0.02 hours to about 100 hours;
iii. cooling the reaction mixture to a temperature of about 30° C., removing the catalyst from the reaction mixture by filtration and then separating the reaction products from the reaction mixture.
In another embodiment of the invention, R
1
R
2
R
3
, and R
4
are each selected from hydrogen, alkane, olefinin

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