Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-11-14
2004-08-17
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S436000, C568S454000
Reexamination Certificate
active
06777579
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for hydroformylating a compound having at least one olefinic carbon-to-carbon bond (also called an olefinic compound herein).
BACKGROUND OF THE INVENTION
Various processes for producing aldehyde and/or alcohol compounds by the reaction of a compound having at least one olefinic carbon-to-carbon bond with carbon monoxide and hydrogen in the presence of a catalyst are known. Typically, these reactions are performed at elevated temperatures and pressures. The aldehyde and alcohol compounds that are produced generally correspond to compounds obtained by the addition of a carbonyl or carbinol group, respectively, to an olefinically unsaturated carbon atom in the starting material with simultaneous saturation of the olefin bond. Isomerization of the olefin bond may take place to varying degrees under certain conditions with the consequent variation of the products obtained. These processes are typically known as hydroformylation reactions and involve reactions which may be shown in the general case by the following equation:
In the above equation, each group R
1
to R
4
may independently represent an organic radical, for example a hydrocarbyl group, or a suitable atom such as a hydrogen or halogen atom, or a hydroxyl group. The above reaction may also be applied to a cycloaliphatic ring having an olefinic linkage, for example cyclohexene.
The catalyst employed in a hydroformylation reaction typically comprises a transition metal, such as cobalt, rhodium or ruthenium, in complex combination with carbon monoxide and ligand(s) such as an organophosphine.
Representative of the earlier hydroformylation methods which use transition metal catalysts having organophosphine ligands are U.S. Pat. Nos. 3,420,898, 3,501,515, 3,448,157, 3,440,291, 3,369,050 and 3,448,158.
In attempts to improve the efficiency of a hydroformylation process, attention has typically focussed on developing novel catalysts and novel processes for recovering and re-using the catalyst. In particular, novel catalysts have been developed which may exhibit improved stability at the required high reaction temperatures. Catalysts have also been developed which may permit the single-stage production of alcohols rather than a two-step procedure involving separate hydrogenation of the intermediate aldehyde. Moreover, homogeneous catalysts have been developed which may permit improved reaction rates whilst providing acceptable yields of the desired products.
The present invention seeks to solve problems associated with a hydroformylation process that employs a cobalt catalyst.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention provides a hydroformylation process comprising reacting a compound having at least one olefinic carbon-to-carbon bond with hydrogen and carbon monoxide in the presence of a cobalt catalyst and a sulfur-containing additive which suppresses the formation of cobalt carbide during the reaction.
DETAILED DESCRIPTION OF THE INVENTION
We have detected that cobalt catalysts comprising cobalt in complex combination with carbon monoxide and a ligand may decompose during the reaction to produce cobalt carbide (a compound of cobalt and carbon, empirical formula Co
x
C, where x is 2 or 3). Cobalt carbide is catalytically inactive in hydroformylation reactions, thereby resulting in an increased rate of catalyst usage. The cobalt carbide is not only catalytically inactive in hydroformylation reactions but also has a relatively bulky, porous structure and is insoluble in the reaction medium. This represents a significant disadvantage, particularly for homogeneous cobalt catalysts, because the cobalt carbide typically tends to agglomerate and form detrimental deposits on the internal surfaces of the production facility. The deposition of cobalt carbide impedes the running of a hydroformylation production facility with optimal efficiency.
The process according to the present invention addresses the aforementioned problems associated with hydroformylating a compound having an olefinic carbon-to-carbon bond in the presence of a cobalt catalyst. The inclusion of the sulfur-containing additive in the reaction mixture suppresses the formation of cobalt carbide compared with performing the corresponding hydroformylation reaction in the presence of the cobalt catalyst but without the additive. Thus, the formation of the cobalt carbide is suppressed during the hydroformylation reaction when the formation of cobalt carbide in the presence of the cobalt catalyst with the sulfur-containing additive is less than the formation of cobalt carbide in the presence of the cobalt catalyst without the sulfur-containing additive. Suitably, the additive reduces the formation of catalytically inactive cobalt carbide. The reduction in the formation of cobalt carbide may result in a decrease in the rate of cobalt catalyst consumption, thereby increasing the efficiency and productivity of the hydroformylation reaction. Suitably, the reduction in the formation of cobalt carbide in the process of the present invention may decrease the amount of cobalt carbide deposited on the internal surfaces of the production facility. Consequently, an increase in efficiency may be achieved.
Typically, during a hydroformylation reaction a cobalt catalyst may decompose to a minor extent to form precipitates of metallic cobalt. Although any decomposition of the cobalt catalyst represents loss of catalyst, the metallic cobalt precipitate is relatively innocuous compared with cobalt carbide formation. Typically, the metallic cobalt precipitates have a relatively small surface area compared with cobalt carbide having the same weight of cobalt and unlike cobalt carbide they typically do not agglomerate and cause the same problems of deposition on the internal surfaces of the production facility. However, although only theory, it is believed that the metallic cobalt precipitates may absorb carbon monoxide from the reaction mixture and promote the dissociation of the carbon monoxide to form cobalt carbide. It is believed that the additive used in the process of the present invention is absorbed by the metallic cobalt precipitate in preference to carbon monoxide, thereby suppressing the absorption of carbon monoxide and the formation of cobalt carbide in the reaction mixture.
The additive may be an inorganic compound which includes a sulfur atom, preferably in an anion.
A preferred inorganic sulfur-containing additive is any sulfur-containing compound that is capable of forming a sulfide anion (S
2−
) in the reaction mixture, able to be absorbed, preferably in preference to carbon monoxide, by the metallic cobalt precipitate. Such additives may include a sulfide anion (S
2−
) per se, for example an inorganic sulfide such as sodium sulfide. Alternatively, or additionally, such additives include those compounds which do not include a sulfide anion (S
2−
) per se, but are capable of generating a sulfide anion during the hydroformylation reaction, for example sodium hydrogen sulfide.
Thus, preferred inorganic sulfur-containing additives include: metal sulfides, preferably of empirical formula M
x
S
y
where M is a metal cation and either x is 1 or 2 and y is 1, or x is 2 and y is, 3; metal hydrogen sulfides, preferably of empirical formula M(SH)
z
where M represents a metal cation and z is 1, 2 or 3; and hydrogen sulfide. Preferably x is 1 or 2 and y is 1. Preferably z is 1 or 2. Suitably, the metal cation M is selected from alkali and alkaline earth metals; preferably from sodium, potassium, calcium, magnesium and zinc. Most preferably the metal cation is potassium, or especially, sodium.
Especially preferred inorganic sulfur-containing additives include sodium sulfide (Na
2
S), hydrogen sulfide and, especially, sodium hydrogen sulfide (NaHS).
The additive may be an organic sulfur-containing compound. Preferred organic sulfur-containing additives include thiols, disulfides, thioethers and thiophene compounds. A preferred thiol is represented by the general formula R
Arnoldy Peter
Ellison Robert Hardy
Kuipers Herman Pieter Charles Eduard
Moene Robert
Van Der Steen Frederik Hendrik
Shell Oil Company
Witherspoon Sikarl A.
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