Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-11-14
2002-05-21
Owens, Amelia (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06392062
ABSTRACT:
INTRODUCTION AND BACKGROUND
The present invention relates to a method for carrying out homogeneously catalyzed reactions in which an educt is converted into a reaction product with or splitting off of a reaction partner or under isomerization in a liquid phase that contains an effective amount of a dissolved catalyst suitable for the desired reaction. The reaction is further accelerated by the method of the invention.
Numerous chemical reactions are carried out for the purpose of accelerating them in the presence of a homogeneous or heterogeneous catalyst. Homogeneous catalysts are those that are molecularly dispersed in the reaction medium, e.g., dissolved in a liquid reaction medium. Heterogeneous catalysts are insoluble in a liquid reaction medium and comprise solid surfaces and particulate substances that comprise the actual catalytically active centers. In as far as two different reactions are not to be carried out substantially simultaneously or in direct succession in a liquid reaction medium, an expert in the art will decide to use a single, that is, a homogeneous or a heterogeneous catalytic system. In order to carry out, e.g., an acid-catalyzed reaction in liquid phase the reaction medium accordingly contains either a dissolved acid as homogeneous catalyst or, as an alternative thereto, the reaction is carried out using a heterogeneous catalyst containing acidic activity centers.
The concept that is customarily employed today to describe the mode of action of a catalyst is the assumption that a center is present on the catalyst which center forms a complex with the reactant and from which the products desorb after the reaction, with the original center being reestablished (see “Heterogeneous Catalysis in Industrial Practice”, Charles N. Satterfield, 2
nd
ed. (1991), p. 8). According to this concept the conversion rate was related as turnover frequency (TON) to a catalytic center (see “Heterogeneous Catalysis in Industrial Practice”, Charles N. Satterfield, 2
nd
ed. (1991), p. 15). An expert in the art would accordingly expect, given the presence of two catalysts or catalytic centers, that the conversion rates of these two would add together.
The so-called heterohomogeneous catalysis is also known (see, e.g., “Heterogeneous Catalysis in Industrial Practice”, Charles N. Satterfield, 2
nd
ed. (1991), pp. 13/14) according to which a heterogeneous catalyst forms radicals, for example, and these radicals initiate a chain reaction in a liquid reaction medium. In the case of heterohomogeneous catalysts the catalytic reaction on the heterogeneous catalyst can also interact with a homogeneous reaction. However, it is not known and is also not rendered obvious by this document that a reaction that has already been catalyzed homogeneously can be further accelerated by porous solid particles that are present and that for their part are not catalytically active or only moderately catalytically active alone as catalyst for the reaction under the reaction conditions in a manner similar to that of the case of the accelerating of the thermal decomposition of gases by the addition of a further inert gas (see “Heterogeneous Catalysis in Industrial Practice”, Charles N. Satterfield, 2
nd
ed. (1991), p. 9).
An object of the invention accordingly is making available a method for carrying out a homogeneously catalyzed reaction of an educt with formation of a reaction product in which the action of the homogeneous catalyst is reinforced and the reaction is further accelerated therewith.
The fact that the effect in accordance with the invention concerns a reinforcing action of the catalyst and not an additional catalyst in accordance with the above definition can be recognized from the fact that the conversion rate is not increased additively by the conversion rate of an additional catalyst, that is, of the porous solid particles, but rather is elevated or reinforced in a multiplicative manner by a certain factor.
SUMMARY OF THE INVENTION
The above and other objects of the invention can be achieved in that the reaction is carried out in the presence of porous solid particles, especially a fixed bed consisting of such porous particles. It is a feature of the invention that the porous solid particles do not act primarily by inserted or adsorbed active centers such as acid or metal centers but rather solely by the three-dimensional structure of the porous particles. An interaction between the three-dimensional structure and/or activity centers of the porous particles with the homogeneous catalyst is not excluded.
Accordingly, the invention features a method for carrying out a homogeneously catalyzed reaction in which an educt is converted into a reaction product with addition or splitting off of a reaction partner or under isomerization in a liquid phase that contains an effective amount of a catalyst suitable for the reaction in dissolved form, which method is characterized in that the educt and the liquid phase containing the homogeneous catalyst as well as, if required, reaction partners to be added are brought into contact with a stationary or moving bed of porous particles, especially conducted through a stationarily arranged fixed bed.
The homogeneously catalyzed, liquid reaction medium as well as, if necessary, reaction partners to be added to an educt can be brought into contact with the porous solid particles in any manner desired in discontinuous or continuous processes. It is therewith possible to allow the liquid reaction medium to stand above a stationary or flowing bed of porous solid particles and to conduct the liquid reaction medium over this fixed bed or to keep the porous solid particles in suspension analogous to a suspension catalyst in the liquid reaction medium.
According to a preferred embodiment the porous solid particles are arranged in a reactor as a fixed bed and liquid reaction medium conducted in a flooded state (=bubble mode of operation) or by trickling (=trickle bed mode of operation) over the fixed bed. The reaction rate is significantly increased by the method of the invention.
The trickle bed mode of operation is especially preferred. Since the liquid holdup in a trickle bed reactor is generally 5 to 20% of the fixed bed volume (see “Multiphase Chemical Reactors”, ed. A. Gianetto and P. L. Silveston, Hemisphere Publ. Corp. (1986), p. 9), the homogeneously catalyzed reaction can be accelerated by more than a factor of 10, as results from the examples in accordance with the invention. The trickle bed mode of operation is particularly suitable in systems in which a gaseous reaction partner such as hydrogen in the case of a hydrogenation participates in addition to the liquid reaction medium.
In addition to the presence of porous solid particles, it is an essential feature of the invention that the reaction is catalyzed by a homogeneous catalyst dissolved in the liquid reaction medium. The method of the invention is substantially independent of the type of catalyst dissolved in the liquid reaction medium and of the catalyzed reaction.
It was determined that acid-catalyzed reactions in aqueous systems can be significantly accelerated even in the absence of an acid catalyst on porous solids added to the reaction medium. In this instance the water functions as homogeneous, acidic catalyst.
The reaction can be, e.g., an acid-catalyzed reaction such as, e.g., an etherification, ether cleavage, esterification, ester cleavage, reesterification, acetalization,, ketalization, iminization, hydrolysis of imines, nitriles and anhydrides, dehydration of alcohols and isomerization of olefinic compounds. In the case of an acid-catalyzed reaction the reaction medium contains an active amount of an organic or inorganic acid, especially a lower carboxylic acid or mineral acid in dissolved form. Even the protons of the water alone can function as acid. The selection and amount of the acidic catalyst are a function of the system considered and of the desired reaction conditions and constitute subject matter for expert optimization.
Reactions catalyzed homogeneously
Degussa - AG
Owens Amelia
Smith , Gambrell & Russell, LLP
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