Organic compounds -- part of the class 532-570 series – Organic compounds – Carbonate esters
Reexamination Certificate
2001-06-28
2002-07-23
Ramsuer, Robert W. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbonate esters
C558S270000
Reexamination Certificate
active
06423863
ABSTRACT:
BACKGROUND OF INVENTION
The present invention is directed to a method for sustaining the catalytic activity of a catalyst composition, and in particular to a method for sustaining the catalytic activity of a catalyst composition used in the production of aromatic carbonates.
A useful method for the production of aromatic carbonates includes the oxidative carbonylation of aromatic hydroxy compounds, with carbon monoxide and oxygen, which is typically catalyzed by a catalyst composition comprising a Group 8, 9 or 10 metal catalyst, various metal co-catalysts, a salt source, optionally an activating solvent, and optionally a base source. The oxidative carbonylation of aromatic hydroxy compounds is typically performed under elevated reactor pressures between about 5 MPa and about 15 MPa, due to the low solubility of both carbon monoxide and oxygen in typical aromatic hydroxy reagents such as phenol, and elevated reactor temperatures between about 50° C. and about 120° C. to accelerate reaction rates. On a commercial scale, the oxidative carbonylation of aromatic hydroxy compounds could be facilitated if reaction conditions, such as temperature and pressure, could be periodically varied during the course of the reaction, e.g., during temporary reactor shutdown periods, without reducing the activity of the catalyst composition. However, what is typically observed when the elevated pressure in a catalytic oxidative carbonylation reaction of an aromatic hydroxy compound is temporarily reduced to about atmospheric pressure, specifically at reaction mixture temperatures above about 60° C. is an irreversible decrease in the activity of the catalyst composition once the original reaction conditions are re-established. Consequently, a long felt yet unsatisfied need exists for new and improved methods for sustaining the activity of catalyst compositions during and after changes in the reaction conditions of a catalytic oxidative carbonylation reaction.
SUMMARY OF INVENTION
In one embodiment, the present invention is directed to a method for sustaining the catalytic activity of a carbonylation catalyst composition, after changes in reaction conditions, in a catalytic oxidative carbonylation reaction contained in a reactor vessel in which a reaction mixture comprising said carbonylation catalyst composition is disposed, said method comprising the following steps:interrupting said carbonylation reaction with a first reaction condition changing step, which comprises first lowering the temperature of the reaction. mixture from a first temperature T1, to a second temperature T2, followed by lowering the pressure in said reactor vessel from a first pressure P1, to a second pressure P2; optionally, a resting step, which comprises maintaining said reaction mixture at said second temperature T2, and maintaining the pressure in said reactor vessel at said second pressure P2, for a predetermined amount of time; andre-establishing said carbonylation reaction with a second reaction condition changing step, which comprises first raising the pressure in said reactor vessel from said second pressure P2 to a third pressure P3, followed by raising the temperature of said reaction mixture from said second temperature T2 to a third temperature T3; wherein the level of catalytic activity of said carbonylation catalyst composition under said third temperature T3, and said third pressure P3, is comparable to a level of catalytic activity which would be present in an equivalent catalytic oxidative carbonylation reaction in which the temperature and pressure were changed from said first temperature T1 and said first pressure P1 directly to said third temperature T3 and said third pressure P3, in the absence of said first reaction condition changing step, and said optional resting step.
DETAILED DESCRIPTION
The method of the present invention is suitable for a typical carbonylation catalyst compositions comprising a Group 8, 9, or 10 catalyst source, which can catalyze the production of aromatic carbonates via the oxidative carbonylation of aromatic hydroxy compounds with oxygen and carbon monoxide.
In one embodiment, the present invention is directed to a method for sustaining the catalytic activity of a carbonylation catalyst composition, after changes in reaction conditions in a catalytic oxidative carbonylation reaction. In the context of the present invention, the phrase “sustaining the catalytic activity” is defined as prolonging the amount of time during which the catalyst composition is active at producing the desired aromatic carbonate at a predetermined reaction rate. The “predetermined reaction rate” is a rate which is comparable, e.g., having a value that is between about 80% and about 120% of the reference value, to a reaction rate that would be present in a similar oxidative carbonylation reaction in the absence of any changes to the reaction conditions. Herein, the reaction rate is defined in terms of the weight percent of desired aromatic carbonate produced during a predetermined amount of reaction time, e.g., weight % of desired carbonate=[(moles of desired carbonate)(molecular weight of desired carbonate)/mass of reaction mixture].
In the context of the present invention, the term “reaction conditions” is meant to include, but is not limited to, reactor vessel pressure, reactor vessel temperature, reaction mixture temperature, agitation rate, gas flow rates (e.g., carbon monoxide flow rate and oxygen flow rate), gas mixture composition (e.g., ratio of carbon monoxide to oxygen), the weight % of various components of the reaction mixture including, but not limited to, weight % of aromatic hydroxy compound, weight % of desired carbonate and weight % of water, and the pH of the reaction mixture.
In the present invention, the term “reaction mixture” is defined as the total mixture of compounds and gases which results from the carbonylation of an aromatic hydroxy compound using oxygen, carbon monoxide, and a carbonylation catalyst composition typically comprising a Group 8, 9 or 10 metal source as a catalyst, and optionally at least one member selected from the group consisting of a first inorganic co-catalyst (IOCC), a second IOCC, a salt source, an activating solvent, a base source, and any mixtures thereof. During the carbonylation reaction, the reaction mixture typically further comprises the desired aromatic carbonate, unreacted aromatic hydroxy compound, and byproducts of the carbonylation reaction which include, but are not limited to, water, aryl ethers, poly-aromatic hydroxy compounds, phenyl salicylate, and aromatic carbonates other than the desired aromatic carbonate. Suitable types of aromatic hydroxy compounds include, but are not limited to, monocyclic aromatic compounds comprising at least one hydroxy group, and polycyclic aromatic compounds comprising at least one hydroxy group. Illustrative examples of suitable aromatic hydroxy compounds include, but are not limited to, phenol, alkylphenols, alkoxyphenols, bisphenols, biphenols, and salicylic acid derivates (e.g., methyl salicylate).
The carbonylation catalyst composition present in the reaction mixture typically comprises a first metal source selected from a Group 8, 9 or 10 metal source. Typical Group 8, 9 or 10 metal sources include ruthenium sources, rhodium sources, palladium sources, osmium sources, iridium sources, platinum sources, and mixtures thereof. In one embodiment, about 1 ppm to about 10000 ppm of a Group 8, 9, or 10 metal source is present in the catalyst composition. In another embodiment, about 1 ppm to about 1000 ppm of a the Group 8, 9, or 10 metal source is present in the catalyst composition. In yet another embodiment of the present invention, about 1 ppm to about 100 ppm of a Group 8, 9, or 10 metal source is present in the catalyst composition. A typical Group 8, 9, or 10 metal source is a palladium source, including palladium compounds. As used herein, with respect to metal sources in general, the term “compound” includes inorganic , coordination and organometallic complex compounds. The compou
Cabou Christian G.
General Electric Company
Johnson Norren C.
Ramsuer Robert W.
Sackey Ebenezer
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