Process for making aromatic aldehydes

Details Process for making aromatic aldehydes Process for making aromatic aldehydes

1999-09-10

2001-10-16

Richter, Johann (Department: 1621)

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

Organic compounds

Oxygen containing

C562S418000, C562S480000, C562S889000

Reexamination Certificate

active

06303827

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for making alkyl aromatic aldehydes and aromatic acids from alkyl aromatic compounds and to catalysts useful therein.
2. Description of the Related Art
Carbonylation of an alkyl aromatic compound to form an aldehyde can be carried out by a reaction generally referred to as the Gatterman-Koch reaction. Published in 1897, Gatterman and Koch described the direct carbonylation of various aromatic compounds by the use of carbon monoxide and hydrogen chloride in the presence of aluminum chloride and cuprous chloride (Gatterman, L. and Koch, J. A., Chem. Ber., 30, 1622 (1897)). The reaction was subsequently expanded to include other Lewis acids. Further, it was discovered that the cuprous chloride could be eliminated if the CO pressure was increased. A review of such reactions is set forth in Olah, G. A., “Friedel-Crafts and Related Reactions”, Wiley-Interscience , N.Y., Vol. III, 1153 (1964).
U.S. Pat. No. 2,485,237, for example, describes replacing the hydrogen chloride and aluminum chloride catalyst combination with hydrogen fluoride and boron trifluoride. Further use of the HF—BF
3
catalyst is described in U.S. Pat. No. 3,284,508 where the recovery of the fluorides is stated to be improved.
The HF—BF
3
catalyst combination is sometimes modified to a two step process where a toluene—HF—BF
3
complex is preformed and reacted with CO to form tolualdehyde. Afterward, make-up CO and optionally additional toluene are added to the reaction medium. An example of such a process is set forth in U.S. Pat. No. 3,948,998.
Other catalysts that have been reported for use in a Gatterman-Koch type carbonylation reaction include combinations of Lewis and strong Bronsted acids such as SbF
5
—HF as is described in U.S. Pat. No. 4,218,403. The use of Bronsted superacids alone, such as fluorosulfonic acid or trifluoromethane sulfonic acid, were also reported to be effective catalysts. See for example Olah, G. A., Laali, K., and Farooq, O.,
J. Org. Chem.,
50, 1483 (1985).
However, the catalysts used in a Gatterman-Koch carbonylation reaction are typically complexed with the aldehyde product. Thus, a stoichiometric amount of catalyst is “consumed” in the reaction. Further, in order to obtain the aldehyde product in a complex-free form, a separation step is needed. For instance, water can be added to a tolualdehyde—AlCl
3
complex to obtain the aldehyde product in a complex-free form. However, this step also chemically alters and destroys the utility of the catalyst. Such a separation, which leads to a one time use of catalyst renders this process commercially unattractive as catalyst regeneration and recycle would be prohibitively expensive.
A method that includes catalyst recycling is proposed by Olah, G. A. et al.,
J. Am. Chem. Soc.,
98:1, 296 (1976). Here, a modified Gatterman-Koch reaction that employs BF
3
—HF as a catalyst complex is used to form the aldehyde. The reaction is carried out at low temperatures, typically from 0-20° C., and with excess HF. The catalyst is separated from the aldehyde-catalyst complex by a distillation technique wherein the BF
3
and HF are boiled off, condensed and returned to the carbonylation reactor.
While this method is useful, it is generally desirable to have a method that avoids the use of HF, a material which requires special containment and handling facilities. Also, it would be desirable to provide an alternate method for separating the aldehyde from the catalyst.
SUMMARY OF THE INVENTION
The present invention relates to a process for forming alkyl aromatic aldehydes using novel reaction or separation conditions in a Gatterman-Koch reaction and to the optional oxidation of the aldehydes to form aromatic acids and anhydrides. More specifically, one aspect of the present invention provides a process that comprises (a) reacting an alkyl aromatic compound with carbon monoxide in the presence of a high boiling point carbonylation catalyst to form an alkyl aromatic aldehyde and (b) separating the alkyl aromatic aldehyde from the carbonylation catalyst by selectively volatilizing the alkyl aromatic aldehyde. Because the carbonylation catalyst has a high boiling point, the alkyl aromatic aldehyde can be boiled off, thereby disengaging the aldehyde from the aldehyde-catalyst complex. The catalyst can be recycled to the carbonylation reaction or reused in a subsequent carbonylation reaction. To avoid undesired degradation and side reactions, the selective volatilization is preferably carried out quickly at high temperatures and/or reduced pressures.
A second aspect of the invention provides a process that comprises reacting an alkyl aromatic compound with carbon monoxide in the presence of a carbonylation catalyst selected from the group consisting of perfluoroalkyl sulfonic acids having 2 to 18 carbon atoms, perfluoroether sulfonic acids having 4 to 18 carbon atoms, GaBr
3
, GaCl
3
, TaF
5
, NbF
5
, NbBr
5
, and BF
3
·(ROH)
x
wherein R represents CH
3
or H and X is a number from 0.2 to 2, to form an alkyl aromatic aldehyde, with the proviso that when the catalyst is TaF
5
, NbF
5
, or NbBr
5
, then said reaction takes place in the absence of added HF. For convenience, it is preferable that all of the catalysts in this embodiment are used in the absence of added HF, and more preferably all of the catalyst in all embodiments of the invention are used in the absence of added HF.
The alkyl aromatic compounds are typically toluene or xylenes, although other aromatics are also suitable, which are converted to p-tolualdehyde and dimethyl benzaldehydes, respectively. A further application of the invention is to subject the isolated aldehydes to oxidation to produce an aromatic acid or, after dehydration, an anhydride. For example, p-tolualdehyde can be oxidized to terephthalic acid, a commonly used monomer in the production of commercial polyesters. Similarly, dimethyl benzaldehyde can be oxidized to obtain trimellitic acid and subsequently dehydrated to trimellitic anhydride. This also relates to a third aspect of the present invention which involves (a) reacting a mixture of ortho-, meta-, and para-xylenes with CO in the presence of a carbonylation catalyst to form a mixture of dimethylbenzaldehydes; (b) oxidizing the mixture of dimethylbenzaldehydes to form trimellitic acid; and (c) dehydrating the trimellitic acid to form trimellitic anhydride. In this way, trimellitic anhydride can be made from a mixed xylene feed. Thus, the present invention can also provide a convenient and economical route to the production of these and other valuable aromatic acid compounds.
Another application of the present invention is to reactively separate xylene isomers by carbonylation. This fourth aspect of the invention relates to separating para-xylene from a mixture of xylenes by reacting a mixture of ortho-, meta-, and para-xylenes with CO in the presence of a carbonylation catalyst to convert substantially all of the ortho- and meta-xylenes to dimethylbenzaldehydes and then isolating the unreacted para-xylene.
DETAILED DESCRIPTION OF THE INVENTION
Many carbonylation catalysts are already known in the art. For purposes of the present invention, a “carbonylation catalyst” is any compound, mixture of compounds or element that can catalyze the reaction of an alkyl aromatic compound with CO to form an alkyl aromatic aldehyde. Generally, carbonylation catalysts are Lewis and/or Bronsted acids. “High boiling point carbonylation catalyst” means a catalyst as just described that has a boiling point that is higher than the targeted aromatic aldehyde to be produced. Typically, the high boiling point carbonylation catalyst has a boiling point of at least 210° C., preferably at least 230° C., and more preferably at least 250° C. The catalyst can be in liquid or solid form, the latter including supported and unsupported catalysts. Suitable support materials are, in general, well known in the catalyst art and include zeolites, ceramics and polymeric supports. Specific examples include aluminas and

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