Distillation: processes – separatory – With measuring – testing or inspecting – Of temperature or pressure
Reexamination Certificate
2001-06-15
2003-08-12
Manoharan, Virginia (Department: 1764)
Distillation: processes, separatory
With measuring, testing or inspecting
Of temperature or pressure
C203S029000, C203S072000, C203S073000, C203S080000, C558S274000
Reexamination Certificate
active
06605191
ABSTRACT:
The present invention relates to a process for the work up of reaction mixtures containing diaryl carbonate, aromatic hydroxy compound, water, base, quaternary salt and optionally other catalyst constituents, which are obtained in the preparation of diaryl carbonates by direct carbonylation of aromatic hydroxy compounds. In the process according to the invention, the reaction mixture is worked up so gently that the catalyst system is hardly damaged at all and may be subsequently recycled to the reaction step.
EP-A 507 546 discloses a process for the work up of reaction mixtures containing diaryl carbonate which are obtained by direct carbonylation of aromatic hydroxy compounds. Initially the aromatic hydroxy compound is removed from the reaction mixture and in a further step the diaryl carbonate formed is removed completely by distillation. Given the high temperatures and long residence times required for said process, the catalytically active components contained in the reaction mixture are completely deactivated or destroyed. Moreover, losses of yield occur due to side reactions of the diaryl carbonate in the distillation bottoms product.
A process has now been found wherein the reaction mixture is worked up so gently that the catalyst system is hardly damaged at all and may be subsequently recycled to the reaction step. The separation of the diaryl carbonate also takes place so gently that hardly any side reactions occur.
The invention provides a process for the work up of reaction mixtures from the preparation of diaryl carbonates by direct carbonylation of aromatic hydroxy compounds, wherein a reaction mixture containing diaryl carbonate, aromatic hydroxy compound, water, base, quaternary salt and optionally other catalyst constituents is separated in a distillation apparatus having only one theoretical separation step, at pressures from 1 to 100 mbar and at temperatures from 80 to 160° C. into a liquid phase containing diaryl carbonate, aromatic hydroxy compound, base, quaternary salt and optionally other catalyst constituents, and a gas phase (herein “top product”) containing a diaryl carbonate, aromatic hydroxy compound and water, the liquid phase is recycled to the reaction step of direct carbonylation without further work up and the gas phase then undergoes a further work up.
In a further embodiment, the reaction mixture also contains a platinum metal catalyst and a cocatalyst. These remain in the liquid phase after separation and are recycled in said liquid phase, optionally after separation of deactivated catalyst constituents, to the reaction step of direct carbonylation without further work up.
The preparation of diaryl carbonates by direct carbonylation of aromatic hydroxy compounds is well known (see, for example, U.S. Pat. Nos. 4,349,485, 5,231,210, EP-A 667 336, EP-A 858 991, U.S. Pat. No. 5,760,272).
An aromatic hydroxy compound corresponding to the formula
R—O—H (I),
wherein
R means substituted or unsubstituted C
6
-C
12
-aryl, preferably substituted or unsubstituted phenyl, particularly preferably unsubstituted phenyl, is reacted with carbon monoxide and oxygen in the presence of a platinum metal catalyst, a cocatalyst, a quaternary salt and a base at a temperature from 30 to 200° C., preferably 30 to 150° C., particularly preferably 40 to 120° C. and at a pressure from 1 to 200 bar, preferably 2 to 100 bar, particularly preferably 5 to 50 bar.
The composition of the reaction gases carbon monoxide and oxygen may be varied within wide concentration limits, but a CO:O
2
molar ratio (standardised to CO) of 1:(0.001-1.0), preferably 1:(0.01-0.5) and particularly preferably 1:(0.02-0.3) is advantageously obtained. The oxygen partial pressure at these molar ratios is high enough for high space-time yields to be obtained and at the same time to prevent the formation of explosive gas mixtures of carbon monoxide/oxygen. The reaction gases are not subject to any particular purity requirements. So synthesis gas may be used as a source of CO and air as a source of O
2
, but it is important to ensure that no catalyst poisons such as, e.g. sulfur or compounds thereof are introduced. Pure CO and pure oxygen are used in preference.
The aromatic hydroxy compounds capable of reaction are, for example, phenol, p-tert.butylphenol, o-. m- or p-cresol, o-, m- or p-chlorophenol, o-, m- or p-ethylphenol, o-, m- or p-propylphenol, o-, m- or p-methoxyphenol, 2,6-dimethylphenol, 2,4-dimethylphenol, 3,4-dimethylphenol, 1-naphthol, 2-naphthol and bisphenol A, preferably phenol. Generally speaking, in the event of the aromatic hydroxy compound being substituted, 1 or 2 substituents are present, these being C
1
-C
4
-alkyl, C
1
-C
4
-alkoxy, fluorine, chlorine or bromine.
Suitable bases are alkali, quaternary armnonium or quaternary phosphonium salts of aromatic hydroxy compounds corresponding to formula (I) such as, for example, potassium phenolate, sodium phenolate, tetrabutylammonium phenolate. Alternatively, trialkylamines such as tributylamine, diisopropylethylamine, DBU, DBN or other bases e.g. potassium-tert.-butanolate, alkali metal hydroxides and alkaline earth metal hydroxides may be used.
The base is added in an amount independent of the stoichiometry. The ratio of platinum metal, e.g. palladium to base is chosen preferably such that, per gram atom of platinum metal, e.g. palladium, 0.1 to 500, preferably 0.3 to 200 and particularly preferably 0.9 to 130 equivalents of base are used.
The process is carried out preferably without solvent. Of course, inert solvents may also be used. Examples of solvents include dimethylacetamide, N-methylpyrrolidone, t-butanol, cumyl alcohol, isoamyl alcohol, tetramethylurea, diethylene glycol, halogenated hydrocarbons (e.g. chlorobenzene or dichlorobenzene) and ethers, such as dioxane, tetrahydrofuran, t-butylmethylether and etherified glycols.
Suitable platinum metal catalysts are composed of at least one noble metal of group VIII, preferably palladium. It may be added in various forms. Palladium may be used in the metallic form or preferably in the form of palladium compounds in oxidation states 0 and +2, such as, for example palladium (II) acetylacetonate, halides, carboxylates of C
2
-C
6
-carboxylic acids, nitrate, oxides or palladium complexes which may contain, for example, olefins, amnines, phosphines and halides. Palladium bromide and palladium acetylacetonate are particularly preferred,
The amount of platinum metal catalyst is not restricted. The amount of catalyst added is usually such that the concentration of the metal in the reaction batch is 1-3000 ppm, concentrations from 5-500 ppm being preferred.
The cocatalyst used is a metal of groups III A, III B, IV A, IV B, V B, I B, II B, VI B, VII B, the rare earth metals (atomic numbers 58-71) or of the iron group of the periodic system of elements (Mendeleev), whereby the metal may be used in various oxidation states. Mn, Cu, Co, V, Zn, Ce and Mo are used in preference, e.g. manganese (II), manganese (III), copper (I), copper (II), cobalt (II), cobalt (III), vanadium (III) and vanadium (IV). The metals may be used, for example, as halides, oxides, carboxylates of C
2
-C
6
-carboxylic acids, diketonates or nitrates and as complex compounds which may contain, for example, carbon monoxide, olefins, amines, phosphines and halides. Mn, Cu, Mo and Ce are used in particular preference. Manganese compounds are used more particularly preferably in the process according to the invention, particularly preferably manganese (II) complexes, and more particularly preferably manganese (II) acetylacetonate or manganese (III) acetylacetonate.
The cocatalyst is added in an amount such that its concentration is from 0.0001 to 20 wt. % of the reaction mixture; the concentration range is preferably 0.005 to 5 wt. %, particularly preferably 0.01 to 2 wt. %.
The quaternary salts may be, for example, ammonium, guanidinium, phosphonium or sulfonium salts substituted with organic radicals. Ammonium, guanidinium, phosphonium and sulfonium salts bearing C
6
to C
10
-aryl, C
7
to C
12
-aralkyl
Eek Rob
Friedrich Martin
Hallenberger Kaspar
Hesse Carsten
Jansen Ursula
Bayer Aktiengesellschaft
Gil Joseph C.
Manoharan Virginia
Preis Aron
LandOfFree
Method for reprocessing reaction mixtures containing diaryl... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for reprocessing reaction mixtures containing diaryl..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for reprocessing reaction mixtures containing diaryl... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3119068