Use of an epoxide in order to reduce the formation of heavy ends in a hydroformylation process

Abstract

The present invention refers to the use of an epoxide in order to reduce the formation of heavy ends in a continuous hydroformylation process, where an olefin or olefin mixture is reacted with carbon monoxide and hydrogen in the presence of a rhodium complex catalyst, comprising at least one organobisphosphite ligand, in order to produce an aldehyde. Said epoxide is added to the reaction mixture in an amount of 0.01-1.5 wt %, reducing the formation of heavy ends by 10-80%.

Claims

1. A method for reducing the formation of heavy ends in a continuous hydroformylation process comprising: adding 0.01 to 1.5 wt. % of an epoxide to a reaction mixture comprising an olefin or mixture of olefins, wherein the weight percent is based on the total weight of the reaction mixture; and reacting the olefin or mixture of olefins with carbon monoxide and hydrogen in the presence of a rhodium complex catalyst comprising at least one organobisphosphite ligand to produce an aldehyde, wherein the at least one organobisphosphite ligand is an organobisphosphite ligand of Formula (I) ##STR00005## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are independently hydrogen or a linear or branched alkyl group and Ar is a substituted or unsubstituted aryl group; and wherein the formation of heavy ends is reduced by 10 to 80% compared to an identical method without addition of the epoxide.

2. The method of claim 1, wherein the epoxide is added in an amount of 0.1 to 1 wt. %, based on the total weight of the reaction mixture.

3. The method of claim 1, wherein the epoxide is added in an amount of 0.2 to 0.5 wt. %, based on the total weight of the reaction mixture.

4. The method of claim 1, wherein the epoxide is a cycloaliphatic epoxide.

5. The method of claim 1, wherein the epoxide is cyclohexene oxide, 2,3-epoxynorbornane, 1,2-octene oxide, 1,2-dodecene oxide, 1,2-cyclododecene oxide, 1,2-decene oxide, 1,2-hexadecene oxide, 1,2-octadecene oxide, 1,2-cyclododecene oxide, 1,2-epoxydodecane, 2,3-epoxybutane and 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, or combinations thereof.

6. The method of claim 1, wherein the epoxide is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.

7. The method of claim 1, wherein the olefin or mixture of olefins is/are C2-C6 olefins.

8. The method of claim 1, wherein the olefin or mixture of olefins is/are 1-butene and/or cis- or trans-2-butene.

9. The method of claim 1, wherein the aryl group is represented by Formula (II) or Formula (III) ##STR00006##

10. The method of claim 9, wherein Ar is a group of Formula (II) and R.sup.1, R.sup.3, R.sup.6 and R.sup.8 are independently n-butyl, iso-butyl, or tert-butyl, and R.sup.4 and R.sup.5 are methyl.

11. The method of claim 10, wherein-R.sup.1, R.sup.3, R.sup.6 and R.sup.a are tert-butyl.

12. The method of claim 1, wherein the ligand has the structure of formula (IV): ##STR00007##

13. The method of claim 1, wherein the ligand is in an amount of 0.5 to 15 wt. %, based on the total weight of the reaction mixture.

14. The method of claim 1, wherein the ligand is in an amount of 1 to 5 wt. %, based on the total weight of the reaction mixture.

15. The method of claim 1, wherein the formation of heavy ends is reduced by 50 to 80% compared to an identical method without addition of the epoxide.

16. The method of claim 1, wherein the rhodium is in an amount of 20-1000 ppm, based on the total weight of the reaction mixture.

17. The method of claim 1, wherein the rhodium is in an amount of 50 to 550 ppm, based on the total weight of the reaction mixture.

18. The method of claim 1, further comprising adding an antioxidant to the reaction mixture in an amount of 0.01 to 5 wt. %, based on the total weight of the reaction mixture.

19. The method of claim 18, wherein the antioxidant is a tertiary phosphine.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a graph showing a reduction of heavy ends upon addition of an epoxide to an industrial hydroformylation process;

(2) FIG. 2 is a graph showing an increase in purity of an aldehyde product upon addition of an epoxide to an industrial hydroformylation process;

(3) FIG. 3 is a graph showing a decline in the rate of heavy ends formation as analyzed by gas chromatography (GC) and high pressure liquid chromatography (HPLC);

(4) FIG. 4 is a graph showing a reduction heavy ends by addition of an epoxide to an industrial hydroformylation process; and

(5) FIG. 5 is a graph showing a reduction in ligan hydrolysis by addition of an epoxide to an industrial hydroformylation process. IDC-A2,AMD

DESCRIPTION OF THE INVENTION

(6) It has surprisingly been found that by adding small amounts of an epoxide to a hydroformylation mixture, the amount of heavy ends produced during the hydroformylation process can be drastically reduced. This efficient way of limiting the formation of heavy ends and thus preventing heavy ends from accumulating in the reaction mixture, has also a stabilizing effect on the organobisphosphite ligand of a rhodium complex catalyst in a hydroformylation reaction.

(7) The present invention refers to the use of an epoxide in order to reduce the formation of heavy ends in a continuous hydroformylation process, where an olefin or an olefin mixture is reacted with carbon monoxide and hydrogen in the presence of a rhodium complex catalyst, comprising at least one organobisphosphite ligand, in order to produce an aldehyde. Said epoxide is added to the reaction mixture in an amount of 0.01-1.5 wt %, reducing the formation of heavy ends by 10-80%.

(8) In preferred embodiments of the present invention the formation of heavy ends is reduced by at least 50%. That is a huge benefit for the economy of the hydroformylation process. The present invention is a great way of using an epoxide, as an heavy end inhibitor. Another benefit of the use according to the present invention is that the addition of epoxide increases the purity of the aldehyde product, without any other adjustments to the process.

(9) The amount of epoxide used in accordance with the present invention is an amount sufficient to interact with the acidic ligand decomposition products which cause formation of heavy ends upon reaction with the aldehyde product. Preferably, the epoxide is added in an amount of 0.1-1 wt %, and most preferably 0.2-0.5 wt % of the reaction mixture. The epoxide is suitably a cycloaliphatic epoxide and preferably selected from cyclohexene oxide, 1,2-cyclo-dodecene oxide, 1,2-cyclododecene oxide and 3,4-epoxycyclohexylmethyl-3,4-epoxycyclo-hexanecarboxylate. Most preferably the epoxide is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclo-hexanecarboxylate.

(10) The olefin in the hydroformylation reaction of the present invention is preferably a C2-C6 olefin, such as ethene, propene and/or butene. Most preferably the olefin is 1-butene and/or cis- or trans-2-butene, or a mixture thereof. The butene feed in the hydroformylation reaction of the present invention comprises a maximum of 2 wt % isobutene.

(11) Hydroformylation of mixed butene feeds containing 1-butene and cis- and trans-2-butene, will generate a mixture of n-valeraldehyde and 2-methyl butyraldehyde. The n/iso ratio is affected by the choice of ligand. The ligand used in combination with rhodium in the present invention is an organobisphosphite ligand of Formula (I)

(12) ##STR00001##

(13) wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 individually is hydrogen or a linear or branched alkyl group and Ar is a substituted or unsubstituted aryl group, such as a group of Formula (II) or (III).

(14) ##STR00002##

(15) In preferred embodiments of the present invention, Ar is a group of Formula(II) and R.sup.1, R.sup.3, R.sup.6 and R.sup.8 are n-butyl, iso-butyl or tert-butyl. In a further preferred embodiment, R.sup.4 and R.sup.5 are methyl. Most preferably the ligand has the structure of formula (IV), having CAS no. 198979-98-5, hereinafter designated A4N3.

(16) ##STR00003##

(17) Said Formula (I) ligand is suitably used in an amount of 0.5-15 wt %, such as 1-10 wt % or 1-5 wt % calculated on total reaction mixture.

(18) Due to the reduced amount of heavy ends formed in the hydroformylation process when using an epoxide according to the present invention, a reduced amount of water is present in the reaction mixture and the organobisphosphite ligand is hydrolyzed to a less extent. This allows the time between partial or complete catalyst changes to be dramatically increased.

(19) The continuous hydroformylation process of the present invention is preferably conducted at a temperature in the range of 80 C. to 130 C., and at a total pressure of not more than about 20 bar. A continuous or periodic addition of epoxide to the reaction mixture will maintain a low level of epoxide in the reactor that will keep the heavy ends concentration at a manageable, steady level without autocatalytic degradation of the organobisphosphite ligand. An accurate amount of epoxide addition can be achieved by statistical process control. A device measuring the amount of unreacted epoxide, the amount of formed heavy ends, and/or the amount of acidic ligand decomposition products in the reaction mixture, can be used to calculate the necessary amount of epoxide addition in order to keep a concentration of about 0.5 wt %, preferably 0.1 wt %, epoxide in the reaction mixture.

(20) In circumstances where the organobisphosphite ligand of Formula (I) risk exposure to oxygen, small amounts of one or more less efficient and/or cheaper tertiary phosphines as anti-oxidants can be added in order to avoid or substantially reduce oxidation of the ligand. The anti-oxidant is preferably added in an amount of 0.01-5, such as 0.05-2 wt % of the reaction mixture. Said anti-oxidant is preferably a tertiary phosphine, such as triarylphosphine, dicycloalkylarylphosphine and/or cycloalkyldiarylphosphine. Especially preferred anti-oxidants include, phenyldi(o-, m- or p-tolyl)phosphine, diphenyl(o-, m- orp-tolyl)phosphine, tri(o-, m- orp-tolyl)phosphine, phenyldibenyzylphosphine, diphenylbenzylphosphine, tribenzylphosphine, phenyldinaphthyl-phosphine, diphenylnaphthylphosphine, trinaphthylphosphine, dicyclohexyl-benzylphosphine and/or cyclohexyldibenzylphosphine.

(21) Rhodium is suitably and advantageously present in the reaction mixture of the present invention in an amount of 20-1000, such as 50-550, ppm by weight of the reaction mixture and preferably charged in form of a precursor selected from the group consisting of a hydride, a halide, a nitrate, a carbonyl compound, an acetate and a dicarbonyl-acetylacetonate. In especially preferred embodiments of the present invention, said precursor is selected from rhodium(III)nitrate, rhodium(III)acetate, rhodium(I)acetate, acetylacetonatedicarbonyl rhodium(I), di(rhodium)tetracarbonyl dichloride, dodecancarbonyltetrarhodium and/or hexadecane carbonylhexarhodium.

(22) Solvents may be present in the reaction mixtures of the present invention and are typically saturated hydrocarbons, aromatic hydrocarbons, ethers, aldehydes, ketones, nitriles and aldehyde condensation products. Suitable solvents are for instance pentanes, cyclohexane, benzene, xylene, toluene, diethyl ether, butyraldehyde, valeraldehyde, acetophenone, cyclohexanone and/or benzonitrile.

(23) The hydroformylation process of the present invention preferably involves a catalyst recycle procedure. Catalyst recycle procedures are well known in the art and usually a portion of the liquid reaction solution is continuously removed to a vaporizer/separator. The separated vaporized or distilled aldehyde product may then be condensed and recovered in any conventional manner. The remaining non-volatilized liquid residue which contains rhodium-phosphite complex catalyst, solvent, free bisphosphite ligand and usually some remaining aldehyde product is then recycled back, with or without further treatment, along with by-products and non-volatilized gaseous reactants that might be dissolved in said recycled liquid residue, to the hydroformylation reactor. The reactant gases removed by distillation from the vaporizer may also be recycled back to the reactor.

(24) The following Examples further illustrate the invention without limiting it in any way.

EXAMPLES

(25) Example 1 illustrates a reduction in heavy ends formation, when the use of the present invention is applied to a hydroformylation reaction mixture in an industrial production plant.

(26) Example 2 illustrates an increase in purity of the aldehyde product, when the use of the present invention is applied to a hydroformylation reaction mixture in an industrial production plant.

(27) Example 3 illustrates the effect of the use of the present invention in a pilot scale, evidencing a reduction in the rate of heavy ends formation.

(28) Example 4 is a comparative lab experiment that illustrates the effect of different amounts of epoxide addition to a hydroformylation reaction mixture, evidencing a reduction in heavy ends formation rate and a reduction in ligand hydrolysis.

(29) The added epoxide in all of the examples is 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate:

(30) ##STR00004##

Example 1

(31) The amount of heavy ends removed, along with the aldehyde product, from an industrial hydroformylation process of the present invention was measured during a period of 8 months. During the first 5 months the amount of daily removed heavy ends gradually increased from about 2 tons to 5 tons. After 5 months an epoxide (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate) was added to the reactor in an amount of 1 wt % of the reaction mixture. The epoxide was thereafter periodically added to the reactor in order to keep a concentration of about 0.5 wt % epoxide in the reaction mixture.

(32) The amount of heavy ends leaving with the product decreased drastically during the following month to a daily production level of 1 ton heavy ends, a 80% decrease in heavy ends formation. The result, evidencing a substantial reduction in heavy ends formation upon epoxide addition, is given in attached FIG. 1.

Example 2

(33) The amount of aldehyde in the product stream from an industrial hydroformylation process of the present invention was measured during a period of 11 weeks. During the first 7 weeks the amount of valeraldehyde was below or about 98.5% of the content of the product stream. After 7 weeks the above-described epoxide was added to the reactor in an amount of 1 wt % of the reaction mixture. The epoxide was thereafter periodically added to the reactor in order to keep a concentration of about 0.5 wt % epoxide in the reaction mixture.

(34) The valeraldehyde content of the product stream steadily increased during the following 4 weeks to almost 99.5%, a 1% increase in purity, due to a dramatic decrease in more low-boiling heavy ends. The result, evidencing an increase in purity of the aldehyde product upon epoxide addition, is given in attached FIG. 2.

Example 3

(35) Hydroformylation reactions were conducted for a period of 35 days in a continuous pilot scale process with two stirred tank reactors in series and a liquid recycle. An aged catalyst solution was taken from an industrial process and divided in two. One with an addition of roughly 1 wt % epoxide and the other one without any added epoxide. Samples of the reaction mixture were taken regularly and analyzed with gas chromatography (GC) and high pressure liquid chromatography (HPLC). The result of the analyses are given in attached FIG. 3, evidencing a clear decline in the rate of heavy ends formation. A reduction in the rate of heavy ends formation of up to 65%.

Example 4

(36) Three parallel experiments in lab scale were carried out to illustrate the present invention. An aged catalyst solution was taken from an industrial process and divided in three parts. The reactors were loaded with equal amounts of the reactor solution. In two of the reactors, epoxide was added to the reactor solution in amounts of 0.5 wt % and 1 wt %, respectively. The reactors were heated to 90 C. and pressurized with nitrogen to 14 bar and left for 5 weeks under stirring. Samples of the reaction mixture were taken at regular intervals and concentration of the compounds in the reaction mixture were determined from analysis of GC and HPLC. Obtained result is given in attached FIGS. 4 and 5, illustrating that the addition of an epoxide reduces the rate of heavy ends formation and reduces the ligand hydrolysis reaction, by scavenging the acidic ligand decomposition products. In closed systems with an aged catalyst solution, the addition of the epoxide decreases the heavy ends formation by 50% and the positive effect on the ligand stability is clearly visible.