Chemistry: fischer-tropsch processes; or purification or recover – Liquid phase fischer-tropsch reaction – Rhodium containing catalyst utilized
Reexamination Certificate
2002-04-30
2004-01-27
Shah, Mukund J. (Department: 1624)
Chemistry: fischer-tropsch processes; or purification or recover
Liquid phase fischer-tropsch reaction
Rhodium containing catalyst utilized
C568S454000
Reexamination Certificate
active
06683118
ABSTRACT:
The invention relates to an improved process for the hydroformylation of olefinically unsaturated compounds in the presence of an aqueous catalyst solution comprising water-soluble rhodium complexes by use of a reaction column as reactor.
The reaction of compounds containing olefinic double bonds with carbon monoxide and hydrogen is the customary industrial method of preparing aldehydes (oxo process).
The process is not restricted to the use of olefinic hydrocarbons, but can be extended to starting materials which not only have a double bond but also bear functional groups, predominantly groups which remain, unchanged under the reaction conditions.
The classical oxo process employs cobalt as catalyst. Its effectiveness is based on the formation of cobalt carbonyl compounds by action of hydrogen and carbon monoxide at pressures above 20 MPa and temperatures of about 120° C. and more on metallic cobalt or cobalt compounds.
In the last 30 years, cobalt has increasingly been replaced by rhodium as catalyst. The platinum metal is used as a complex which comprises, preferably, phosphenes as ligands in addition to carbon monoxide. The use of rhodium as catalyst allows the process to be carried out at lower pressures and, in addition, higher yields are achieved and the unbranched products which are more valuable for further processing are preferentially formed if straight-chain terminal olefins are used as starting materials.
A further refinement of the oxo process comprises the transition from catalysts which are homogeneously dissolved in the reaction medium, i.e. in the starting material and in the reaction product, to aqueous catalyst solutions which are present as a separate phase in addition to that formed by the starting material and reaction product. This variant of the reaction is described, for example, in DE B-26 27 354. Its particular advantage is that the reaction product and the catalyst can readily be separated under mild conditions without use of thermal process steps, so that losses which occur as a result of further reactions of the aldehydes formed are avoided. Furthermore, very high yields are achieved and, when using unbranched terminal olefins, the aldehydes obtained are very predominantly n-aldehydes.
In practice, the oxo process using an aqueous catalyst phase is usually carried out in stirred reactors which have initially been charged with a solution of the catalyst system in water. Olefinically unsaturated compounds and synthesis gas are introduced into the reaction vessel and reacted with one another with intimate mixing. The reaction product leaves the reactor together with aqueous catalyst solution, unreacted starting materials (synthesis gas, olefin) and hydrogenation products of the olefinically unsaturated compounds via an immersed tube. The gas phase, essentially synthesis gas, olefin and saturated hydrocarbon formed from the olefin, is separated from the liquid products in a separation vessel and recirculated to the reactor. Part of the circulating gas is freed of the condensable reaction products in a condenser and is discharged into the waste gas system.
The liquid separated off in the separation vessel is passed to a phase separator. Here, the crude organic reaction product separates from the aqueous catalyst phase. While the organic reaction product is conveyed via a pump to a stripping column, a further pump conveys the aqueous catalyst phase back to the reactor with the heat of the exothermic reaction being removed in a heat exchanger and used to generate process steam. Water can be fed to the reactor together with the cooled catalyst solution to compensate water losses which occur via the waste gas and via the oxo product. The crude oxo product introduced into the stripping column is conveyed in countercurrent to part of the synthesis gas which in this way becomes laden with the olefin dissolved in the crude product. The preheated synthesis gas/olefin mixture is fed to the reactor. A further substream of synthesis gas is preheated in a heat exchanger using process heat. The fresh olefin is also preheated and vaporized in a heat exchanger by means of waste heat from the aldehyde distillation before it enters the reactor, while the crude oxo product from the stripping column is passed directly without cooling to the distillation. Finally, a buffer vessel for temporary storage of product is provided in case of a malfunction in the plant.
In an industrially particularly advantageous embodiment of a production plant for carrying out the oxo process, synthesis gas and olefin are introduced via double roses which serve as predistributors into the reactor in which the aqueous catalyst solution is present. The fine dispersion of the reactants in the reaction mixture is achieved by means of a sparging stirrer. To remove the heat of reaction, the reactor is provided with a cooling matrix. The liquid and gaseous components ascend through a guide tube in the reactor and separate at its upper end. The gas is either recirculated into the reactor or discharged from the reaction system as offgas. The aqueous catalyst solution separates from the crude, organic product. The crude product is introduced into a stripping column, freed of dissolved olefins by means of the synthesis gas passed through the stripping column in countercurrent and finely fractionated into its components in a column. The heat required for the distillation is obtained directly via the cooling matrix. For this purpose, the liquid aldehyde from the bottom of the column is introduced via a phase separator into the cooling matrix in which it vaporizes and it is then conveyed in vapor form via the phase separator back into the column.
The above-described apparatus for carrying out the oxo process using an aqueous catalyst phase has given excellent service in industrial practice. However, there is interest in further optimizing the process. This is an object of the present invention. Specifically, the invention has the object of improving the economics by changing the way in which the process is carried out and/or by simplifying the apparatus employed in the process. Further objects are to increase the conversion and the yield of desired product and to improve safety.
The invention provides a process for the hydroformylation of olefinically unsaturated compounds in a heterogeneous reaction system using a catalyst consisting of an aqueous solution comprising complexes of rhodium with water-soluble organic phosphorus(III) compounds as ligands and, if desired, excess water-soluble organic phosphorus(III) compounds, at pressures of from 0.4 to 10 MPa and temperatures of from 50 to 180° C. According to the present invention, the reaction of the reactants is carried out in a reaction column.
Apart from carrying out the reaction between olefinic compound and synthesis gas in a heterogeneous reaction system using an aqueous catalyst phase, it is an essential feature of the invention that the reaction is carried out in a reaction column as reactor.
The differences between the novel process and the processes customary hitherto which have a stirred tank as central apparatus of the reaction plant are conspicuous. Apart from further changes, the mixing of the reactants and the catalyst solution without use of a stirrer and the absence of a separate stripping apparatus for recovering the olefin dissolved in the product are of particular significance.
For the purposes of the present invention, the term reaction columns refers to the apparatuses used, in particular, for distillation, rectification and extraction in chemical engineering. As hydroformylation reactors, they are provided with feed openings for the reactants and the catalyst solution and with devices for taking off product, catalyst solution and offgas. As reaction columns, it is possible to use the various types of column which are widely used in industrial practice, in particular tray columns and columns with ordered packing or random packing elements. In these, the catalyst solution is fed in at the top of the column, advantageously onto the uppe
Celanese Chemicals Europe GmbH
Muserlian Lucas and Mercanti
Shah Mukund J.
Tucker Zachary C.
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