Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1999-04-01
2000-11-14
Dentz, Bernard
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D30788
Patent
active
061472271
DESCRIPTION:
BRIEF SUMMARY
This application claims priority under 35 U.S.C. 371 from PCT/EP97/05186 filed Sep. 22, 1997.
DESCRIPTION
The present invention relates to a process for preparing phthalides by catalytic hydrogenation of phthalic anhydrides with the aid of suspended Raney catalysts.
DE-C-28 03 319 discloses preparing phthalide by catalytic hydrogenation of phthalic anhydride in the gas phase using copper and aluminum catalysts. However, this process is prohibitively costly in the product isolation stage, involving as it does multistage condensation and a downstream waste gas scrub.
U.S. Pat. No. 4,485,246 discloses preparing phthalide from phthalic anhydride by hydrogenation using homogeneous ruthenium catalysts. Catalyst recovery is difficult in these processes.
EP-A-542 037 discloses a process for preparing phthalides by catalytic hydrogenation of phthalic anhydride over fixed bed catalysts in tubular reactors or tube bundle reactors or suspended catalysts in a stirred autoclave. If batch operated, said process requires large amounts of catalyst and long hydrogenation times. Continuous operation requires high pressures to obtain complete conversion.
EP-B-89 417 describes the catalytic hydrogenation of phthalic anhydride to phthalide with the aid of a nickel catalyst immobilized on a support material using autoclaves with lift stirrer and methyl benzoate as mandatory solvent. The process has the disadvantage of high catalyst requirements and long reaction times.
Houben/Weyl, Methoden der organischen Chemie, 6/2 (1963), pages 732 to 733, and also U.S. Pat. No. 2,114,696 describe the hydrogenation of phthalic anhydride to phthalide with the aid of Raney nickel catalyst in a shaking autoclave, but a hydrogen pressure of 165 bar and ethanol as solvent affords a phthalide yield of only 73%.
It is an object of the present invention to remedy the aforementioned disadvantages of existing processes for the catalytic hydrogenation of phthalic anhydrides.
We have found that this object is achieved by a novel and improved process for preparing phthalides of the general formula I, ##STR3## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently hydrogen, C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -alkoxy, by hydrogenating phthalic anhydrides of the general formula II, ##STR4## where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each as defined above, with hydrogen in the presence of suspended catalysts of the Raney type in a hydrogenation apparatus by using a mixing apparatus to mix a liquid phase, which includes the catalyst and the phthalic anhydride used and resulting phthalide, and a gas phase, which includes the hydrogenating hydrogen, which comprises using the mixing apparatus to introduce a mixing intensity of at least 50 W/l into the liquid phase.
The process of the present invention makes it possible to perform the hydrogenation of phthalic anhydrides to the phthalides at low levels of catalyst, with a good space-time yield and in high selectivity.
Compared with the conventional processes for hydrogenating phthalic anhydride to phthalide with the aid of suspended Raney nickel, the process of this invention makes it possible to reduce the amount of Raney catalysts used appreciably for the same hydrogenation time, or to shorten the hydrogenation time dramatically for a comparable amount of Raney catalysts used.
The process of this invention surprisingly does not give rise to any deactivation of the Raney catalysts as arises with the conventional processes employing the customary mixing intensities in stirred or shaking autoclaves and which leads to long reaction times and correspondingly low space-time yields in such apparatus. In addition, the caking of the Raney catalysts which occurs in the conventional processes and which makes it difficult to remove the Raney catalysts after the reaction does not take place in the process of this invention.
As we have further found, the deactivation of the Raney catalysts which occurs in the conventional processes is likely to be attributable to the acidic by-products formed during t
REFERENCES:
patent: 2114696 (1938-04-01), Austin et al.
patent: 4485246 (1984-11-01), Lyons
patent: 4528385 (1985-07-01), ausderFuenten et al.
patent: 5296614 (1994-03-01), Henkelmann et al.
Houben-Weyl, Methoden der organischen Chemie, 6/2, 1963, pp. 732-733 (along with English translation).
Becker Rainer
Cramers Peter
Massonne Klemens
Nardin Daniel
Neuhauser Horst
BASF - Aktiengesellschaft
Dentz Bernard
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