Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-03-30
2001-11-13
Reamer, James H. (Department: 1614)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06316674
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved process for the preparation of acyl aromatic ethers from aromatic ethers. More particularly, this invention relates to an improved process for the preparation of acyl aromatic ethers from aromatic ethers using C2-C8 acid anhydrides, acetic anhydride to benzoic anhydride as acylating agents in the presence of nano- or microcrystalline zeolite beta catalysts. Aromatic ethers are useful and important intermediates for drugs and pharmaceuticals.
This invention particularly relates to an ecofriendly process for acyl aromatic ethers from aromatic ethers using acid anhydrides as acylating agents and zeolite beta as catalyst dispensing the use of stoichiometric amounts of corrosive, toxic aluminium chloride and hydrogen fluoride as Friedel-Crafts reagents.
BACKGROUND OF THE INVENTION
Conventional processes for the acylation of aromatic compounds, in particular the ethers of phenols consist of carrying out a Friedel-Crafts acylation reaction. The aromatic compound is reacted with an acylation agent in the presence of aluminium chloride
The inherent disadvantages in the use of conventional Lewis acid metal chlorides for Friedel-Crafts acylation are that they are non-regenerable and require more than stoichiometric amounts because of strong complexation with the carbonyl product formed. Work-up to decompose the resultant intermediate complex by hydrolysis forms a large amount of waste product and separation of the product involves lengthy, cumbersome and expensive procedure.
Reference may be made to a publication by Choudary et al., Applied Catalysis A; 171,159, 1998 wherein aromatic ethers are acylated with acid anhydrides in the presence of metal ion exchanged clays with moderate yields. The drawbacks are that the conversions are moderate with low space time yields.
Reference may be made to a U.S. Pat. No. 4,960,943 wherein a process for the acylation of anisole with acid anhydrides in the presence of zeolite catalysts is disclosed. The drawbacks in this process are moderate yields and the reaction is carried out at high temperatures and pressures.
Reference may be made to a publication by Gaare et al. Journal of Molecular Catalysis, 109, 177, 1996 wherein anisole is acylated by acetyl chloride and acetic anhydride by modified zeolites.
Reference may be made to a U.S. Pat. No. 5,817,878 wherein substituted aromatic ethers, in particular anisole is acylated with an acylating agent in the presence of zeolite beta catalyst.
Reference may be made to a U.S. Pat. No. 6,013,840 wherein substituted aromatic ethers, in particular veratrole and anisole are acylated with an acylating agent in the presence of a Y zeolite, dealuminated and metal exchanged Y zeolite and H
+
-zcolite beta catalyst.
Although the above inventions afforded good selectivity and activity, the object of the present invention is to devise a catalyst of enhanced activity and higher space time yields to reduce the capital and operative costs.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide an improved process for the preparation of acyl aromatic ethers which are important intermediates for drugs and pharmaceuticals by reacting an aromatic ether selected from anisole, veratrole and ethyl phenyl ether with C2-C8 acid anhydrides as acylating agents employing nano- or microcrystalline zeolite beta as catalyst, in a stirred batch reactor or a continuous fixed bed reactor at temperatures in the range of 60-165° C. for a period of 224 h, and separating the acyl aromatic ethers by a conventional method, which obviates the drawbacks as detailed above.
It is another object of the invention to provide a process for the preparation of acyl axiomatic ethers that is safe and environmentally friendly.
It is another object of the invention to provide a process for the preparation of acyl aromatic ethers that eliminates the use of corrosive and stoichiometric amounts of aluminium chloride.
It is a further object of the invention to provide a process for the preparation of acyl aromatic ethers wherein the yields are quantitative.
It is yet another object of the invention to provide a process for the preparation of acyl aromatic ethers wherein the reactions are faster and of shorter duration.
It is a further object of the invention to provide an economical process for the preparation of acyl aromatic ethers.
Another object of the present invention is to, provide a process for the preparation of acyl aromatic ethers wherein nano- or microcrystalline zeolite beta are used as catalysts.
Another object of the present invention the particle size of nano crystalline or microcrystalline zeolite beta are 10 nm to 100 nm and 1 &mgr;m to 50 &mgr;m.
Another object of the present invention is the use of nano- or microcrystalline zeolite beta for enhanced activity as evident through higher space time yields.
Another object of the present invention is the use of nano- or microcrystalline zeolite beta for high space time yields to reduce capital investment by 20-30%.
Another object of the present invention is acylation conducted both on a batch mode in a stirred reactor and on a continuous mode in a fixed bed reactor.
Another object of the present invention is the option of continuous mode in a fixed bed reactor to save time spent on charging the reactant into the reactor, discharging the reaction mixture from the reactor, and filtration of the catalyst.
Another object of the present invention is the option of continuous mode in a fixed bed reactor to reduce both capital and operation costs.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a process for the preparation of acyl aromatic ethers useful as important intermediates for drugs and pharmaceuticals, said process comprising reacting an aromatic ether selected from anisole, veratrole and ethyl phenyl ether with an acylating agent selected from C2-C8 acid anhydrides employing nano- or microcrystalline zeolite beta as catalyst, at a temperature in the range of 60-165° C. for a period of 2-24h, and separating the acyl aromatic ethers by a conventional method.
In an embodiment of the invention, the zeolite beta catalyst used is nano or microcrystalline zeolite beta of size ranging between 10 nm to 100 nm and 1 &mgr;m to 50 &mgr;m.
In an embodiment of the invention, the acylating agents used are selected from the group comprising acetic anhydride to benzoic anhydride.
In a further embodiment of the present invention, the reaction in the batch mode is preferably effected at a temperature in the range of 80 to 130° C. for 2-12hrs.
In another embodiment of the present invention acylation is conducted both on a batch mode in a stirred reactor and on a continuous mode in a fixed bed reactor.
In a further embodiment of the invention, the ratio of aromatic ether to acylating agent is from 5:1 to 1:5.
In another embodiment of the invention, the weight of the catalyst is 1 to 50% by weight with respect to the aromatic ether.
DETAILED DESCRIPTION OF THE INVENTION
The novelty of the present invention lies in the use of nanocrystalline or microcrystalline zeolite beta for the acylation of aromatic ethers. Decrease in particle size of zeolite beta, enhances the density of acidic sites and surface area of zeolites, which are essential factors to increase the activity of acylation reaction. As a result of this, the space time yields are increased almost three-fold. This is established in t the experimental section when compared with the results obtained using microcrystalline or zeolite beta as synthesised. Eventually, the capital investment for this process is expected to reduce considerably by 20-30% in view of the higher space time yields. The reaction is also conducted in liquid phase on a continuous mode by pumping a mixture of acetic anhydride and aromatic ethers into a fixed bed packed with microcrystalline zeolite beta in pellet form, while the reaction mixture is continuously withdrawn from the reactor. Three fold enhanced activity is observed in this case. This continuous operation offers f
Choudary Boyapati Manoranjan
Kantam Mannepalli Lakshmi
Prakash Billakanti Veda
Raghavan Kondapuram Vijaya
Sateesh Mutyala
Council Scientific and Industrial Research
Ladas & Parry
Reamer James H.
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