CA1106407A - Hydroformylation process - Google Patents

Abstract

D-11,270 IMPROVED HYDROFORMYLATION PROCESS

ABSTRACT OF THE DISCLOSURE
In a rhodium-catalyzed hydroformylation process which produces aldehydes from alpha-olefins, the stability of a rhodium catalyst complexed with carbon monoxide and a triarylphosphine ligand is improved by providing an alkyldiarylphosphine ligand in the catalyst-containing reaction medium.

Description

~ FIELD OF THE INVENTION

2 This invention relates to an improved process for the

3 rhodium-catalyzed hydroformylation of olefins, particularly al?ha-

4 olefins, to produce the corrQsponding aldehydes; and more s I particularly to an improved process for the hydroformylation o 6 j alpha-olefins to produce the corresponding aldehydes using rhodium 7 ¦ catalysts whose stability is improved by the use of alkyldiaryl-8 ¦ phosphine ligands.

BACKGROUND OF THE INVENTION
¦ Processes for forming an aldehyde by the reaction of an 2 olefin with carbon monoxide and hydrogen have been known as _ ~3 hydroformylation processes or oxo processes. Por many years, all commercial hydroformylation reactions employed cobalt carbonyl catalysts which required relatively high pressures (often on the ~6 order of 100 atmospheres or higher) to maintain catalyst stability.¦
7 U.S. Patent No. 3,527,809, issued September 8, 1970 to R.L. Pruett and J.A. Smith, discloses a significantly new hydro-formylation process whereby alpha-olefins are hydroformylated j wi~h carbon monoxide and hydrogen to produce aldehydes in high 21 ¦ yields at low temperatures and pressures, where the normal to 22 l iso-tor branched-chaln) aldehyde isomer ratio of the product 23 aldehydes is high. This process employs certain rhodium complex catalysts and operates under defined reaction conditions to ~accomplish the olefin hydroformyla~ion. Since this new process 26 operates at significantly lower pressures than required thereto-27 l fore in the prior art, substantial advantages were realized 28 ¦ including lower initial capital investment and lower operating 29 costs. Further, the more desirable straight-chain aldehyde isomer could he produced in high yields.
3~ The hydr~formylation process set forth in the Pruett ,,, I ' .
~ ~ - 2 - ,, .' l I ` 11~

l and Smith patent noted above includes the following essential 2 reaction conditions:
3 ~1) A rhodium complex catalyst which i5 a complex combination of rhodium with carbon monoxide and a triorganophos-phorus ligand. The term "complex" means a coordination compound 6 formed by the union of one or more electronically rich molecules 7 or atoms capable of independent existence with one or more 8 electronically poor molecules or atoms, each of which is also capable of independent existence. Triorganophosphorus ligands lo whose phosphorus atom has one available or unshared pair of 11 electrons are capable of forming a coordinate bond with rhodium.
2 (2) - An alpha-olefin-feed of alpha-olefinic compounds 13 characterized by a terminal ethylenic carbon-to-carbon bond such 14 as a vinyl group CH2=CH-. They may be straight chain or branched ¦ chain-and may contain groups or substituents which do not essen-16 ¦ tially interfere with the hydroformylation reaction, and they may 17 ¦ also contain more than one ethylenic bond. Propylene is an l~ l example of a preferred alpha-olefin.
¦ (3) A triorganophosphorus ligand such as a triaryl-¦ phosphine. Desirably each organo moiety in the ligand does not 21 ~1 exceed 18 carbon atoms. The triarylphosphines are the preferred z2 ¦ ligands, an example of which is triphenylphosphine.
¦ (4) A concentration of the triorganophosphorus ligand 2~ 1 in the reaction mixture which is sufficient to provide at least 1 two, and preferably at least 5, moles of free ligand per mole of 26 rhodium metal, over and above the ligand complexed with or tied 27 ~ to the rhodium atom.
8 (5) A temperature of from about 50 to about 145C, 29 preferably from about 60 to about 125C.
(6) A total hydrogen and carbon monoxide pressure which is less than 450 pounds per square inch absolute (psia), .
.

preferably less than 350 psia.
(7) A maximum partial pressure exerted by carbon monoxide no greater than about 75 percent based on the total pressure of carbon monoxide and hydrogen, prefer-ably less than 50 percent of this total gas pressure.
It is known that, under hydroformylation conditions, some of the product aldehydes may condense to form by-product, high boiling aldehyde condensation products such as aldehyde dimers or trimers. U.S. patent 4,148,830 discloses the use of these high boiling liquid aldehyde condensation products as a reaction solvent for the catalyst.
In this process, solvent removal from the catalyst, which may cause catalyst losses, is unnecessary and, in fact, a ; liquid recycle containing the solvent high boiling aldehyde condensation products and catalyst is fed to the reaction zone from a product recovery zone. It may be necessary to remove a small purge stream to prevent the buildup of such aldehyde condensation products and poisons to the reaction to excessive levels of concentration.
More specifically, as pointed out in said U.S.
patent 4,148,830 some of the aldehyde product is involved in various reactions as depicted below using n-butyralde-hyde as an illustration:
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OH
2 ~ 2CH3CH2CH2CHO - ~cH3cH~cH2cHc CH2C~3 - ~ cH3cH2cH2cH - CCHO

3 aldol (I) 3 2 4 aldol (I) substituted acrolein (II) 6 l 1 OH ~ loccH2cH2cH3 - 9 , CH3cH2cE~2cHcHcH2cH3 ~ ~ CH3CH2CH2CHICHCH2CH3 ~ 11 CH20H
11 1 CH2OCCH2cH2cH3 ~ . . -13 l (trimer III) (trlmer IV) .

~ heat 12 CH3cH2cH2cHcHcH2cH3 CH3cH2cH2cHcHcH2cH3 18 CH2OH ~ ~~
9 . CH2occH2cH2cH3 21 ¦ (dimer V) (tetramer VI) 22 ¦ In addition, aldol I can undergo the following 23 reaction:

~5 2 aldol I ~ CH3CH2CH2CHCHCH2CH3 27 I . ¦ OH
28 l C~ocH2cHcHcH2cH2cH3 ¦

29 (tetramer VII) ~S~

. ' I " ~1(16~Ci7 1 The names in parentheses in the afoxe-illustrated 2 equations, aldol I, substituted acrolein II, trimer III, 3 trimer IV, dimer V, tetramer VI, and tetramer VII, are for ~ convenience only. Aldol I is formed by an aldol condensation;
s trimer III and tetramer VII are formed via Tischenko reactions;
6 trimer IV by a transesterification reaction; dimer V and 7 tetramer VI by a dismutation reaction. Principal condensation ~ products are trimer III, trimer IV, and tetramer VII, with 9 1 lesser amounts of the other products being present. Such ¦ condensation products, therefore, contain substantial quantities 1 of hydroxylic compounds as witnessed, for example, by trimers III~
12 ¦ and IV and tetramer VII.
13 1 Similar condensation products are produced by self-1~ ¦ condensation of iso-butyraldehyde and a further range of com-¦ pounds is formed by condensation of one molecule of normal 16 butyraldehyde with one molecule of iso-butyraldehyde. Since 17 a molecule of normal butyraldehyde can aldolize by reaction with a molecule of iso-butyraldehyde in two different ways to form v twv different aldols VIII and IX, a total of four possible aldols can be produced by condensation reactions of a normal/iso 21 mixture of butyraldehydes.
2t `OH CH3 CH3CH2CH2CH ~ CH3lcHcH3~ 3 2 2CH 1CH3 2s CHOCHO
26 ~Aldol (VIII) ~H
28 ' --',.1l~CH2CH3 t9 3 CHO
3 : Aldol (IX~

~L~E~ 7 11270-C

Aldol I can undergo further condensation with isobutyraldehyde to form a trimer isomeric with trimer III
and aldols VIII and IX and the corresponding aldol X pro-duced by self-condensation of two molecules of butyralde-hyde can undergo further reactions with either normal or isobutyraldehyde to form corresponding isomeric trimers.
These trimers can react further analogously to trimer III
so that a complex mixture of condensation products is formed.
U.S. patent 4,247,486 discloses a liquid phase hydroformylation reaction using a rhodium complex catalyst, wherein the aldehyde reaction products and s`ome of their higher boiling condensation products are removed in vapor form from the catalyst containing liquid~body (or solution) at the reaction temperature and pressure. The aldehyde reaction products and the condensation products are condensed out of the off gas from the reaction vessel in a product recovery zone and the unreacted starting materials (e.g., carbon monoxide, hydrogen and/or alphaolefin) in the vapor phase from the product recovery æone are recycled to the reaction zone. Furthermore, by recycling gas from the product recovery zone coupled with make-up starting materials to the reaction zone in sufficient amounts, it is possible, using a C2 to C5 olefin as the alpha-olefin starting material, to achieve a mass balance in the liquid body in the reactor and thereby remove f~om the reaction zone at a rate at least as great as their rate of formation essentially all the higher boiling condensation products resulting from self-condensation of the aldehyde product.
More specifically, according to the above latter appllcation, a process for the production of an aldehyde containing from 3 to 6 carbon atoms is disclosed which comprises passing an ~ ~ 7 -.

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alpha-olefin containing from 2 to 5 carbon atoms together with hydrogen and carbon monoxide at a prescribed temperature and 3 pressure through a reaction zone containing the rhodium complex 4 catalyst dissolved in a liquid body, continuously removing a vapor phase from the reaction zone, passing the vapor phase to a 6 ! product separation zone, separating a liquid aldehyde containir.g 7 ¦ product in the product separation zone by condensation from the 8 ¦ gaseous unreacted starting materials, and recycling the gaseous g ¦ unreacted starting materials from the product separa'ion zone to ¦ the reaction zone. Preferably, the gaseous unreacted starting 11 materials plus m-~ke-up starting materials are recycled at a rate 12 at least as great as that required to maintain a mass balance in 13 the reaction zone.
1~ It is known in the prior art that rhodium hydroformyla-tion catalysts, such as hydrido carbonyl tris (triphenylphosphine) 16 rhodium, are deactivated by certain extrinsic poisons which may ' 17 be present in any of the gases fed to the reaction mixture. See, 18 for example, G. Falbe, "Carbon Monoxide in Organic Synthesis", 19 Springer-Verlag, New ~ork, 1970. These poisons (X), termed 0 virulent poisons, are derived from materials such as sulfur-Zl containing compounds (e.g., H2S, COS, etc.), halogen-containin~
22 ¦¦compounds (e.g., HCl, etc.), cyano-containing compounds (e.g., 23 1H~N, etc.~, and the like, and can form R'h-X bonds which are 24 ¦not broken under mild hydroformylation conditions. If one removes 1such poisons from the materials fed to the reaction mixture, to 26 ¦below l part per million (ppm), one would expect therefore that Ino such deactivation of the catalyst would occur. However, it 28 has been found that such is not the case. For example, when very 29 clean gases (<lppm extrinsic poisons) were used in the hydroformy-lation of propylene and the gas recycle technique discussed above was employed, under the following conditions:
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temperature (C.) 100 C0 partial pressure (psia) 36 H2 partial pressure (psia) 75 olefin partial pressure (psia) 40 ligand/rhodium mole ratio 94 the catalyst activity decreased at a rate of 3% per day (based on the original activity of the fresh catalyst). It appears therefore that even the substantially complete removal of extrinsic poisons does not prevent such catalyst deacti-vation.
Copending, commonly assigned Cana~ian patent application Serial No. 295,310, filed concurrently herewith by D.R. Bryant and ~. Billig, indicates that the deactivation of rhodium hydroformylation catalysts under hydroformylation conditions in the substantial absence of extrinsic poisons is due to the combination of the effects of temperature, phos-phine ligand:rhodium mole ratio, and the partial pressures of hydrogen and carbon monoxide and is termed an intrinsic deactivation. It is further disclosed therein that this intrinsic deactivation can be reduced or substantially pre-vented by establishing and controlling and correlating the hydroformylation reaction conditions to a low temperature, low carbon monoxide partial pressure and high free triaryl-phosphine ligand:catalytically-active rhodium mole ratio.
More specifically, this Bryant and Billig appllcation disc~lo~Qes a rhodium-catalyzed hydroformylation process for producing aldehydes from alpha-olefins including the steps of reacting the olefin with hydrogen and carbon monoxide in the~resence of a rhodi~m complex ratalyst consisting essentially of rhodium complexed with carbon monoxide an~
a triarylphosphine, under certain defined reaction conditions, a~ fol}ows:
(1) a temperature of from about 90 to about 130C;
(23 a total gas pressure of hydrogen, carbon monoxide : : ~
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I ¦and alpha-olefin of less than about 400 psia;
2 ¦ (3) a carbon monoxide partial pressure of less than ¦about 55 psia;
~ ¦ (4) a hydrogen partial pressure of less than about 1200 psia;
6 ¦ (5) at least about 100 moles of free triarylphosphine ¦ligand for each mole of catalytically active rhodium metal present ¦in the rhodium complex catalyst;
¦ and controlling and correlating the partial pressure of carbon lo l monoxide, the temperature and the free triarylphosphine:catalyt-~1 l ically active rhodium mole ratio to limit the rhodium complex 12 ¦ catalyst deactivation to a maximum determined percent loss in 13 1 ~activity per day, based on the initial activity of the fresh t4 ¦ catalyst. By "catalytically active rhodium" is meant the rhodium ~ ¦ metal in the rhodium complex catalyst which has not been deacti-U ¦vated. The amount of rhodium in the reaction zone which is catalytically active may be determined at any given time during ¦the reaction by comparing the conversion rate to product based on 19 ~ Isuch catalyst to the conversion rate obtained using fresh catalyst.
20 ~ ~ The manner in which the carbon monoxide partial pres-¦sure~, temperature and free triarylphosphine:catalytically active 22~ ¦;~rhodium mole ratio should be controlled and correlated to thus ; ¦11mit the~d~eactivation of the catalyst is illustrated as follows.
2~ 1~ As an example, for the triarylphosphine ligand triphenyl-25~ Iphosphine, the spec7fic relationship between these three parameters ¦~and catalyst~stability is defined by the formula:

F - y ;
¦where ~ ~
29~ ~ stabillty~factor 30;~ ~ e = Naperian log base (i.e., 2.718281828) Y Xl + R2T + X3P + K4 (L/Rh) ' ~ G64~7 - l 1 T = reaction temperature tC) z P = partial pressure of CO (psia) 3 L/Rh = free triarylphosphine:catalytically active rhodium mole ratio Kl = -8.1126 6 K2 = 0.07919 7 K3 = 0.0278 8 K4 = -0.01155 g As pointed out in the Bryant and Billig application, lo an olefin response factor must-be employed to obtain the stability Sl factor under actual hydroformylation conditions. Olefins l2 generally enhance the stability of the catalyst and their effect~3 on catalyst stability is more fully explained in said Bryant 14 and Billig copending application.
The above relationship is substantially the same for 16 other triarylphosphines, except that the constants-Kl, K2, K3 -and K4 may be different. Those skilled in the art can determine a the~ specific constants for other triarylphosphines with a minimum 2 amount of experimentation, such as by repeating Examples 21-30 below with other triarylphosphines. -1 As can be understood by referring to the above formula, 22~ for given conditions of reaction temperature, carbon monoxide ~partial pressure and free triarylphosphine:catalytically active z~ rhodium mole ratio, the stability factor F can be determined.
z5 Th- stability factor F exhibits a predictive relationship with 6 the rate at which the rhodium complex catalyst is deactivated 7 under hydroformylation conditions. This relationship is illus-trated by Figure 1 of the drawings which shows the variation in the stability factor F for different rates of catalyst activity 0 losses for the triarylphosphine triphenylphosphine. This drawing 1 indicates that the rate of activity loss decreases in a substan-~ - 11- ., ," ~. ' , i . . . .
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~ ¦tially linear relationship with increasing values of the stability 2 ¦factor F. The determination of the maximum permissible rate of 3 lactivity loss of the catalyst must ultimately be based to a large ~ ¦ extent on the economics of the process, including predominantly S ¦ the cost of replacing spent or deactivated catalyst and also the 6 l value of the products, etc. For purposes of discussion only, if 7 ¦it is assumed that the maximum acceptable rate of activity loss 8 ¦ o~ the catalyst is 0.75 percent per day, from Figure 1 it is seen g ¦ that the corresponding minimum stability factor F is about 770.
l The above equation can then be employed to determine the reaction ¦ conditions which will provide this minimum necessary stability 2 ¦ factor F and, as a result this maximum acceptable rate of loss of 13 ¦ catalyst activity.
Inasmuch as the above equation has three variables, 15 1 it can better be understood by reference to Figures 2, 3 and 4 16 ¦ of the drawings which show the effect on the stability factor F
7 ¦ of varying two of these three variables, the other being held 1a 1 constant. More specifically, Figures 2, 3 and 4 ill~strate 19 1 the effect of these three variables on the stability factor F
¦ for the olefin propylene, and for ease of--description, the 21 1 discussion which immediately follows will be limited to 2t ¦ propylene as the olefin. However, it is to be understood that a 23 ¦similar relationship exists for other olefins which could 24 ¦be similarly illustrated as in Figures 2, 3 and 4.
l Referring to Figure 2 the values represented there 26 ¦were obtained by calculating the stability factor F in the hydro-27 ¦formylation o~ propylene at a constant free triarylphosphine:
28 ¦catalytically-active rhodium mole ratio of 170:1 (the specific 2~ ¦triarylphospine being triphenylphospine) and at varying tempera-¦tures and carbon monoxide partial pressures. Lines A, B and C
31 ¦are the areas along which the stability factor F is about 500, 6407 - l ~ ¦800 and 900, respectively. As is apparent from Figure 2, the 2 ¦stability factor F is highest at low carbon monoxide partial 3 ¦pressures and low temperatures, at a fixed free triarylphosphine:
catalytically-active rhodium mole ratio.
¦ Figure 3 illustrates the relationship between the 6 stability factor F and varying temperatures and free triaryl-7 phosphine:catalytically-active rhodium mole ratios (triarylphos-phine = triphenylphosphine), with a constant carbon monoxide 9 partial pressure of 25 psia for the hydroformylation of propylene.
lo Lines A, B and C are the areas along which the stability factor-F-ll is about S00, 800 and 900, respectively. As is apparent fro'm ~2 Figure 3, the stability factor F is highest at-low temperatures 13 and high free triarylphospine:catalytically-active rhodium mole 1~ ratios, at a fixed carbon monoxide partial pressure.
s Figure 4 illustrates the relationship'between the 16 stability factor F and varying carbon monoxide partial pressures 17 and free triarylphosphine:catalytically-active rhodium mole '-~ -18 ratios (triarylphosphine = triphenylphosphine), wi'th a constant reaction temperature of 110C for the hydroformylation of propyl-ene. Lines A, B and C are the areas along which the stability 2I~ ~ factor F is about 500, 800 and 900, respectively. As is apparent 21 ~ from Figure 4, the stability factor F is highest at high free :24 tr~arylpbosphine:catalytically-active rhodium mole ratios and ; low carbon monoxide partial pressures, at a fixed temperature.

26 ~ ~ It should be understood that Figures 2, 3 and 4 of the drawings are intended to be representative only. For example, referring~to Figure 4, if a different fixed constant temperature was~employed, the plotted values of stability factor F would be ' different~.~ The same holds for Figures 2 and 3 if different fixed 30~; ~ value~s of the free triarylphosphine:catalytically-active rhodium mole ratio and carbon monoxide partial pressure were employed.
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In effect, each of Figures 2, 3 and 4 represents a single plane 2 of the three-dimensional relationship which exists between the 3 stability factor F and the conditions temperature, carbon monoxide ~ partial pressure and free triarylphosphine:catalytically-active rhodium mole ratio, the plane of course being the same as the plane of the three-dimensional plot which intersects the selected value of the fixed variable in each case. These two-dimensional representations have been presented for ease of description only.
9 In summary therefore, the conditions of temperature, ; ~o carbon monoxide partial pressure and free triarylphosphine:
catalytically-active rhodium mole ratio which are controlled and , correlated to obtain minimum catalyst deactivation are determined ~3 as follows. The threshold determination is of a maximum accept-t~ able rate of loss o catalyst activity. With this value and ; U using, for example, the relationship illustrated by Figure 1, the minimum stability factor F can be determined. The above equation 7 is then solved to determine the values of the three variables which are adjusted to obtain this minimum stability factor -F, and in this: ~connection, representations such as Figures 2, 3 and 4 20~ are helpful in ascertaining specific conditions which will provide 21~ a~stable catalyst.
22~ ~ Generally, it is desirable that the maximum loss of 23-~ ~ activity of;~the rhodium complex catalyst should be 0.75 percent per;day,~and~highly advantageous results are achieved where the ma~imum;~rate of loss of catalyst activity is 0.3 percent per day, -~ y ~ 26~ ~both~belng based upon the activity of the fresh catalyst. By27 ~ ~the~term~nactivity" is~meant,` for example, the amount of product produced~expressed~as gram-moles/llter-hour. Of course, any 29~ ~o*her~standard-technique can be employed to determine the relative 30 ~ ac~ivity o~f~the;catalyst at any given time. It should be under-tood,~however, that the maximum acceptable rate of loss of ~ : :
:::, . ,,, , ,: . . , l I " 110~

l catalyst activity would depend on many different factors, as 2 pointed out above. The technique disclosed in said Bryant and 3 Billig copending application provides a mechanism for obtaining ~ ~ maximum rate of loss of catalyst activity by the control and s correlation of the hydroformylation reaction conditions. Stated 6 conversely, once a maximum acceptable rate of loss of catalyst 7 activity is determined, the invention disclosed therein provides 9 one skilled in the art with the tools to control and correlate the reaction conditions necessary to obtain catalyst stability.
lo Therefore, the values given above for the maximum rate of loss 11 of catalyst activity are provided merely-to teach those skilled in the art how to practice that invention.
As pointed out above, the presence of the olefin in the hydroformylation reaction enhances the stability of the catalyst;
~5 that is, it inhibits the deactivation caused by the combination ~6 of carbon monoxide, hydrogen, phosphine ligand:rhodium mole ratio ~7 and temperature. One can determine the effect of the olefin upon 18 the stability factor calculation. For example, in the hydroformy-v lation of propylene, reactions conditions that will provide long--term catalyst stability (i.e., a low rate of loss of catalyst 21 activity) give a stability factor F, determined from Figure l 22 with the observed rate of loss of catalyst activity, of about 2J 850. However, by using these conditions and the above formula, a 2~ stability factor F of about 870 is calculated. It is only neces-2s sary to then make the appropriate modification in the above 26 e~uation to include the effect of the propylene on the stability 27 factor. Similar data can easily be obtained for other olefins, ~ and-the necessary modifications can be made in the above formula 29 to determine the actual reaction conditions which should be 3 0 employed to obtain long-term catalyst stability.
31 It has been observed that the presence of an alkyl-,~

1 diarylphosphine (for example, propyldiphenylphosphine or ethyl-2 diphenylphosphine) in the rhodium-catalyzed hydroformylation of 3 the alpha-olefin propylene inhibits catalyst productivity; i.e., ~ the rate at which the desired product aldehydes are formed.
Specifically, the addition of small amounts of propyldiphenyl-6 phosphine or ethyldiphenylphosphine to rhodium hydroformylation 7 solutions (i.e., 250 ppm rhodium and 12% by weight triphenyl-8 phosphine in a mixture of butyraldehydes and butyraldehyde con-9 densation products3 markedly reduced the rate of production of butyraldehydes from propylene, compared to the rate obtained in Il the absence of the alkyldiarylphosphines. T~his is shown by the dat~ in Table below:

; 31 i4~7 ,. ,~
- TABLE I
~pp~l) EDPP~3~ PDPP or Compara-Amount Amount EDPP/ Aldehyde Production R~te tive R~te tw-ight ~ (weight ~ TPP (gram-moles/liter-hour) ~4~ of Produc Entry of solution) of solution) Ratio Observed Predicted tion (5) 1 4 PDPPt0) 01 03 1 02 100 2 1 89 " (2 0) 1 05 0 36 1 06 34 3 3 ~4 " ~0 67) 0 18 0 53 1 02 53 4 4 . 06 n~1 33) 0 33 0 79 1 87 42 3 61 n ~1 33) 0 37 l Sl 3 51 43 6 4 0 " ~0 05)0 013 0 62 1 02 60 ~ 9 " ~1 0) O ll0 60 0 69 87 6 6 n ~1.0) 0 170 54 0 63 86 9 9 ~ ~3 0) 0 330 54 0 72 75 6 " t3 0) 0 50 47 0 68 68 11 9 " ~1 0) O ll0 55 0 69 80 12 6 " ~1 0) 0 170 58 0 63 92 13 9 " ~3 0) 0 330 39 0 ~2 54 14 6 n t3 0) 0 50 52 0 68 77 lS 9 0 80 0 60 greater than 16 o n ~9) ~0 273 0 60 46 1~ 0 n (4 S) ~0 213 0 47 45 18 3 89EDPP~0 67)0 17 0 42 1 02 42 19 3 69~ ~0 67) 0.18--0 42 1 02 42 3 88n (1 33) 0 340 33 1 02 33 21 6.95n (0 67) O.lO0 32 0 82 39 22 6 85~ ~1 33) O l90 24 0 82 29 (1) TPP ~ triphenyiphosphine (2) PDPP - propyldiphenylphosphine , ~3) EDPP - ethyld$phenylphosphine t4) Pr-dicted rate determined from a Xinetic rate expression

(5) Comparative Xate of Production ~ observed rate x 100 preaictes r~te or ~ame con-ditions with ~ame total phos-phine hut ~ PP

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¦ It has therefore been suggested that the presence of 2 ¦alkyldiarylphosphines in rhodium-catalyzed hydroformylation pro-3 ¦cesses should be avoided since their presence does significantly ¦reduce the catalyst productivity. It has been unexpectedly found ¦however, that the stability of such rhodium complex catalysts can ¦be significantly enhanced by providing an alkyldiarylphosphine 7 ¦in the reaction medium. Although this reduces the productivity 8 ¦of the catalyst, the reaction conditions can be adjusted to be 9 more severe in order to regain this apparent loss of catalyst productivity while retaining the enhanced catalyst stability.
11 This is surprising especially in view of the aforementioned 12 Bryant and Billig copending application which discloses that less severe conditions (e.g., lower temperatures) favor catalyst stabi}ity.
lS
i~ SUMMARY OF THE INVENTION -- .
7: ~ The present invention comprises an improved rhodium-18 catalyzed hydroformylation process for the production of aldehydes from alpha-olefins employing a rhodium complex catalyst, where the stability of the rhodium complex catalyst is improved by pro-2t~ ~ viding an amount of an alkyldiarylphosphine ligand in the catalyst-22~ containing reaction medium. The stability of the rhodium complexcatalyst i9 thus significantly improved.
24~
25: : : DESCRIPTION OF THE PREFERRED EMBODIMENTS
26 ~ In its broadest aspects, the present invention is an 27~ ~ 1mprovement in a rhodium-catalyzed process for hydroformylating an~alpha-olefin to produce aldehydes having one more carbon ato~
~: : .
~ 29~ than~the~alpha-olefin, which process includes the steps of :
reacting the alpha-olefin with hydrogen and carbon monoxide, in a liquid reaction medium which contains a soluble rhodium complex : :
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l ¦catalyst consisting essentially of rhodium complexed with carbon 2 Imonoxide and a triarylphosphine ligand, wherein the improvement 3 ¦comprises improving the stability of the catalyst by ~ ¦ providing in the liquid reaction medium containing the ¦catalyst an amount of an alkyldiarylphosphine ligand; and

6 ¦ controlling the hydroformylation reaction conditions

7 ¦ as follows:

8 1 (1) a temperature of from about 100 to about 140C;

9 ¦ (2) a total gas pressure of hydrogen, carbon lo ¦ monoxide and alpha-olefin of less-than about 11 ¦ 450 psia; ~
12 ¦ (3) a carbon monoxide partial pressure of less than 13 1 about 55 psia;
¦ (4) a hydrogen partial pressure of less than about lS ¦ 200 psia; - : - -16 ¦ (5) at least about 75 moles of total free phosphine 17 ¦ ligand for each mole of catalytically-active 18 ¦ rhodium metal present in the rhodium complex s ¦ catalyst.
2 l Generally, the amount of the alkyldiarylphosphine Zl ¦ligand present in the liquid reaction medium is from about 0.1 22 ¦to about 20 percent by weight, based upon the total weight of the liquid reaction medium. When a triarylphosphine ligand is employed ~; ¦in the hydroformylation of an alpha-olefin, some alkyldiarylphos-~ ¦phine is produced in situ, the "alkyl" group thereof being ; 26 ¦derived from the alpha-olefin undergoing hydroformylation and z7 ¦the "aryl" groups thereof being the same as the aryl of the z8 1 triarylphosphine. Thereore, it may not be necessary to add additional alkyldiarylphosphine to the reaction medium to provide la suficient amount of the same therein. The particular amount 31 ¦of alkyldiarylphosphine in the reaction medium will depend on ~` I .
I . - 19 _ ,,- , 1., 1 several factors such as the particular alpha-olefin reacted, the 2 reaction conditions, the desired rate of reaction, etc~ Generally, 3 however, amounts falling within the aforementioned range will ~ provide satisfactory results. Particularly advantageous results are achieved when the amount of alkyldiarylphosphine in the 6 liquid reaction medium is from about 0.5 to about 10 percent by 7 weight, based on the total weight of the liquid reaction medium, 8 and hence this constitutes the presently preferred embodiment.
9 When an alkyldiarylphosphine ligand is present in a o liquid reaction medium containing a rhodium complex catalyst l consisting essentially of rhodium complexed with carbon monoxide ~2 ¦ and a triarylphosphine ligand, the resulting rhodium complex 13 catalyst consists essentially of rhodium complexed with carbon 14 monoxide and either one or both of the triarylphosphine ligand ¦ and the alkyldiarylphosphine ligand. The terminology "consists 16 1 essentially of" is not meant to exclude, but rather to include, 17 hydrogen complexed with the rhodium, in addition to carbon mon-18 oxide and triarylphosphine and/or alkyldiarylphosphine. However, v this language is meant to exclude other materials in amounts which poison or deactivate the catalyst. Furthermore, it is not Zl intended to limit the present invention by the above explanation as to which phosphine is tied to or complexed with the rhodium since it is sufficient for purposes of the present invention to simply provide an a unt of alkyldiarylphosphine in the reaction 2s medium with the triarylphosphine. We do not wish to be bound by 26 any discussion of which phosphine is tied to the rhodium and which 27 is free, although it has been determined that, as between tri-phenylphosphine and propyldiphenylphosphine, the rhodium exhibits a preference for the latter over the former as to which it is tied or bound to. This catalyst is normal~y soluble in the 31 liquids which may be used as a solvent in the reaction, and the 1641~7 1 most desirable catalyst is free of contaminan~s such as rhodium-2 bound halogen such as chlorine and like species. The total 3 amount of triarylphosphine and alkyldiarylphosphine present in 4 the liquid reaction medium is sufficient to provide the above noted minimum number of moles of total free phosphine ligand per 6 mole of catalyticallyactive rhodium metal present in the rhodium 7 complex catalyst. Generally, as long as the total amount of ~ phosphine ligand is sufficient to form the rhodium complex cata-g lyst and to provide this minimum amount of free phosphine, the particular amount of triarylphosphine ligand present in the 11 liquid reaction medium is not particularly criticaI. As a general~
12 rule, the amount of triarylphosphine ligand present in the reaction 13 medium may vary from about 0.5 percent to about 40 percent by ~ weight, based on the total weight of the liquid reaction medium.
Particularly advantageous results are achieved when 16 the amount of total free phosphine ligand in the liquid reaction medium is at least about lO0 moles per mole of catalytically-18 active rhodium metal present in the rhodium complex catalyst. The 19 upper limit of the amount of total free phosphi~e ligand is not Zo particularly ~ritical and would be dictated largely by commercial Z1 and economic considerations. Higher mole ratios of total fxee Z2 phosphine:catalytically-active rhodium metal favor the stability 23 of the catalyst. By "total free phosphine" is meant the triaryl-2~ phosphine and/or alkyldiarylphosphine that is not tied to or Z5 complexed with the rhodium atom in the active complex catalyst.
26 The theory of how such ligands complex with the rhodium is given 27 in said U.S. Patent No. 3,527,809.
Illustrative.triarylphosphine ligands are triphenylphos-29 phine, trinaphthylphosphine, tritolylphosphine, tri(p~biphenyl) phosphine, tri(p-methoxyphenyl) phosphine, p-N,N-dimethylamino-31 phenyl bis-phenylphosphine, and the like. Triphenylphosphine is . - ~ 64~7 --1 the presently preferred triarylphosphine ligand.
2 Illustrative alkyldiarylphosphine ligands are methyl-3 dip~enylphosphine, ethyldiphenylphosphine, propyldiphenylphosphine ~ butyldiphenylphosphine, ethyl-bis(p-methoxyphenyl) phosphine, 5 1 ethyl-phenyl-p-biphenyl phosphine, methyl-phenyl-p(N,N-dimethyl-6 aminophenyl) phosphine, propyl-phenyl-p(N,N-dime~hylaminophenyl) 7 ¦ phosphine, ethyl-bis (tolyl) phosphine, butyl-bis (tolyl) 8 phosphine, methyl-bis (naphthyl) phosphine, propyl-bis (naphthyl) , 9 phosphine, propyl-bis (p-methoxyphenyl) phosphine, butyl-bis (p-methoxyphenyl) phosphine, and the like. Propyldiphenylphosphine 11 is the presently preferred alkyldiarylphosphine 1igand.
1~ The rhodium complex catalyst composed of rhodium com-13 plexed with hydrogen, carbon monoxide and triarylphosphine may be 1~ formed by methods known in the art. For example, a preformed stable crystalline solid of rhodium hydridocarbonyl-tris 16 (triphenylphosphine~, RhH(CO)[P(C6H5)3]3, may be introduced ir.to the reaction medium. This material may be formed for example, by 18 a method disclosed in Brown, et al, Journal of the Chemical ;19 Society, 1970, pages 2753-2764. Alternatively, a rhodium catalyst ; precurser such as Rh203, Rh4(CO)l2~ or Rh6(CO)l6 and the like may Z1 ¦be introduced into the reaction medium. In a preferred embodiment n ~rhodium carbonyl triphenylphosphine acetylacetonate or rhodium di-- . - _ - . . . . . . . . . _ 23 ~carbonyl acetylacetonate are employed. In either event, the activ~
24 rhodium complex catalyst is formed in the reaction medium under z5 the conditions of hydroformylation, wherein the alkyldiarylphos-26 ~phi~e is formed ln situ or is added to the reaction medium, or 27 both. It is also possible to preform a rhodium complex catalyst 8 which contains both triarylphosphine and alkyldiarylphosphine ~1~ 29 complexed with the rhodium.
The amount of catalyst present in the reaction mediu~
31 should be as a minimum that amount which is necessary to cataly7e ¦

~ I , . I
.: I

-~ ll llC~

t ¦the hydroformylation of the-alpha-olefin to`form the product ¦aldehydes. Generally, the rhodium CQncentration in the reaction ¦medium can range from about 25 ppm to about 1200 ppm, preferably ¦ about 50 ppm to about 400 ppm, of catalytically active rhodium Icalculated as the free metal.
6 The process of the present invention is expected to be 7 useful for the hydroformylation of alpha-olefins having up to 20 carbon atoms. The process of the present invention is particu-larly useful for the hydroformylation of alpha-olefins having Io from 2 to 5 carbon atoms, including ethylene, propylene, 1-11 butene, l-pentene and the like, and therefore this constitutes a preferred embodiment. The process of the present invention is 13 especially useful for the hydroformylation of propylene to form l~ butyraldehydes having a high normal to iso ratio; i.e. the butyr-u aldehyde which predominates in the product is the normal butyral-i6 dehyde, and hence this presently constitutes the most preferred l7 ~ ~embodiment. The alpha-olefins used in the process of the inven-tion may be straight-chain or branched-chain and may contain 19 ~ groups or substituents which do not essentially interfere with 20~ thè course of the hydroformylation reaction.
U~ ;~ The~amount of olefin fed to the reaction depends on 22~ ~several factors, such as the size of the reactor, the temperature ~ ~of~reaotion, the total pressure, the amount of catalyst, etc. In 2~ general, the higher the olefin concentration is in the reaction ~medium, the lower usually will be the catalyst concentration that oan~be used to achieve a given conversion rate to aldehyde product~

~in~a~glven size of reactor. Since partial pressures and concentra-s ~ 2~ ~tion~are~related, the use of higher olefin partial pressure leads ~to~`an~lnoreased~proportion of the olefin in the product stream ~1éaving~the reaotlon mixture.~ Further, since some amount of saturated hydrocarbon may be formed by hydrogenation of the ~¦ ~lG64~7 olefin, it may be necessary to purge part of the product gas stream in order to remove this saturated product before any 3 recycle to the reaction zone, and this would be a source of loss ~ for the unreacted olefin contained in the product gas stream.
Hence, it is necessary to balance the economic value of the 6 olefin lost in such a purge stream against the economic savings 7 associated with lower catalyst concentration.
9 The temperature of reaction, as noted above, may vary g from about 100 to about 140C, with the lower temperatures lo favoring catalyst stability and the higher temperatures favoring 11 higher rates of reaction. The paxticular temperature employed in 12 the reaction will of course depend upon the desired stability 13 and rate of reaction, but generally, by controlling the tempera-1~ ture within this range, the advantages of the present invention can be attained. -16 A substantial advantage-of the process disclosed in 17 U.S. Patent No. 3,527,809 is the low total pressure of hydrogen 18 and carbon monoxide required to conduct the hydroformylation 9 reaction. The process of the present invention operates at a low total pressure of hydrogen,~ carbon monoxide and-alpha-olefin 21 of less than about 450 psia, prefera~ly less than about 350 psia.
22 The minimum total pressure of these gases is not particularly 23 critical and is limited predominantly only by the amount of 24 reaction gases necessary to obtain the desired rate of reaction.
The make-up gases fed to the reaction medium would 26 include the olefin, carbon monoxide and hydrogen, usually. As 27 Pointed out previously, extrinsic poisons such as sulfur and U suIfur-containing compounds, as well as halogens and halogen-~ containing compounds, and the like, should be excluded from the make-up gases, since it is known that such materials poison the 31 catalyst and can deactivate the catalyst rather rapidly. Hence, , .

Il 11(1i6~

1 it is desirable to reduce the amount of such poisons in all gases 2 fed to the reaction. Of course, the amount of such poisons that 3 can be tolerated is determined by the maximum acceptable rate of ~ loss of activity of the catalyst. If it is possible to permit some small amount of such poisons and still obtain a catalyst of 6 desired stability, then such small amounts can be tolerated. It ~ is generally desirable to reduce the amounts of such poisons in 8 the make-up gases to below one part per million. This can be 9 ¦ accomplished by methods known in the art.
1 Hydrogen does have some effect on catalyst deactivation.
11 l According to the process of the invention, the partial pressure 12 ¦ of hydrogen should be less than about 200 psia, and preferably it 13 1 should range from about 20 to about 200 psia. Of course, the particular value will be determined depending upon the desired lS stability and rate of reaction and ~he relationship of the -16 hydrogen partial pressure to the carbon monoxide partial pres-17 sure, as discussed below.
18 The partial pressurç of carbon monoxide has a signifi-19 cant effect on the stability of the catalyst, and should generally be less than about 55 psia. Of course, the particular partial 21 ¦pressure employed will depend upon the desired stability and z2 ¦rate of reaction. As a general rule, lower carbon monoxide 23 ¦partial pressures provide more stable catalysts. It is preferred 24 ¦according to the process of the invention tha~ the partial pres-~ ¦sure of carbon monoxide be from about l psia to about S0 psia.
26 ¦The minimum partial pressure of carbon monoxide is not critical ;~ 27 ¦in that it is limited predominantly only by the desired rate of 28 ¦reaction and the possibility of olefin hydrogenation occurring.
29 ¦ It is disclosed in U.S. Patent No. 3,527,809 that the 1 normal to iso aldehyde isomer ratio of the aldehyde products 31 ¦ decreases as the partial pressure of carbon monoxide increases l relative to the hydrogen partial pressure. Similarly, in the 2 process of the present invention, the partial pressure of carbon 3 monoxide relative to the partial pressure of hydrogen has an ~ effect on the isomer ratio of the product aldehydes. Generally, to obtain the more desirable normal aldehyde isomer, the ratio 6 of partial pressures of hydrogen:carbon monoxide should be at 7 least about 2:1, preferably at least about 8:1. As long as the 8 partial pressures of each of carbon monoxide and hydrogen are 9 controlled within the limits described above, there is no critical lo ratio of the hydrogen:carbon monoxide partial pressures.
11 The time of reaction, or residence period of-the olefin 12 in the reaction zone, is generally that time which is sufficient 13 ¦ to hydroformylate the alpha-ethylenic bond of the alpha-olefin.
14 ¦ As a general rule, the residence period in the reaction zone can vary from about several minutes to about several hours in duration 16 and as is apparent, this variable will be influenced, to a certain extent, by the reaction temperature, the choice of alpha-8 olefin and catalyst, the concentration of total free phosphine ligand, the total pressure, the partial pressure exerted by carbon monoxide and hydrogen, the conversion rate and other 21 factors. As a general rule, it is desirable to achieve the ~ highest possible convexsion rate for the smallest amount of u catalyst employed. Of course, the ultimate determination of a 24 conversion rate is influenced by many factors including the economics of the process. A substantial advantage of the present 26 invention is that catalyst stability is greatly improved while 27 obtaining excellent conversion rates over prolonged periods of ~ time.
29 It is preferred to effect the process of the invention in a liquid phase in the reaction zone which contains the rhodium 31 complex catalyst and, as a solvent therefore, the higher boiling 1 1~ 4 ~7 liquid aldehyde condensation products.
By the term "higher boiling liquid aldehyde con-densation products" as used herein is meant the complex mixture of high boiling liquid products which result from the condensation reactions of s~me of the aldehyde product~
of the process of the invention as illustrated hereinabove.
Such condensation products can be preformed or produced in situ in the present process. The rhodium complex catalyst is soluble in these relatively high boiling liquid aldehyde condensation products while exhibiting excellent stability over extended periods of continuous hydroformylation. In a preferred form of the process of the invention the higher boiling liquid aldehyde condensation products to be used as solvents are preformed prior to introduction into the reac-tion zone and the start-up of the process. It is also pre-ferred to maintain the condensation products illustrated by acrolein II above, and its isomers, at low concentrations in the reaction medium, such as below about 5 weight percent based on the total weight of the reaction medium.
These higher boiling liquid aldehyde condensation products are more fully described, and methods for preparing the same are more fully described, in said commonly-assigned copending U.S. patent 4,148,830 and reference can be made to this patent for a more detailed description.
It is also preferred according to th~ process of the invention to employ the gas recycle technique described in said commonly-assigned, copending U.S. patent 4,247,486.
This gas recycle process is broadly described above. If the aforementioned higher boiling liquid aldehyde condensation products are employed as the reaction solvent, the liquid body in the reaction zone will comprise a homogeneous ~ - 27 -.
I
~,. . .

. . , '` ll~

1 mixture containing the soluble catalyst, free phosphine ligand, 2 the solvent, the product aldehydes and the reactants, alpha-3 olefin, carbon monoxide and hydrogen.
~ The relative proportion of each reaction product in S solution is ~ontrolled by the amount of gas passing through the 6 solution. Increasing this amount decreases the equilibrium 7 aldehyde concentration and increases the rate of by-product 8 removal from solution. The by-products include the higher 9 boiling liquid aldehyde condensation products. The decreased aldehyde concentration leads to a reduction in the rate of -11 formation of the by-products. -- -12 The dual effect of increased removal rate and 13 decreased formation rate means that the mass balance in by-1~ products in the reactor is very sensitive to the amount of gas passing through the liquid body. The gas cycle typically 6 includes make-up quantities of hydrogen, carbon monoxide and-17 alpha-olefin. However, the most meaningful factor is-the amount 18 of recycle gas returned to the liquid body since this determines the degree of reaction, the amount of product formed and the amount of by-product (as a consequence) removed.
21 Operation of the hydroformylation reaction with a 2z given flow rate of olefin and synthesis gas (i.e., carbon monoxide and hydrogen) and with a total low amount of gas recycle 2~ less than a critical threshold rate results in a high equilibrium aldehyde concentration in solution and hence, in high by-product 26 formation rates.
27 The rate of removal of by-products in the vapor phase 2~ effluent from the reaction zone (liquid body) under such con-29 ditions will be low because the low vapor phase effluent flow rate from the reaction zone can only result in a relatively low 31 rate of carry-over of b~-products. The net effect is a build-up 1~ - 2~ -1~ llQ64(~7 of by-products in the liquid body solution causing an increase in the solution volume with a consequent loss of catalyst pro-3 ductivity. A purge must therefore be taken from the solution when the hydroformylation process is operated under such low gas flow rate conditions in order to remove by-products and hence 6 maintain a mass balance over the reaction zone.
7 If however, the gas flow rate through the reaction 8 zone is increased by increasing the gas recycle rate the solution 9 aldehyde content falls, the by-product formation rate is de-creased and by-product removal rate in the vapor phase effluent 11 from the reaction zone is increased. ~The net effect-of this 12 change is to increase the proportion of the by-products removed 13 with vapor phase effluent from the reaction zone. Increasing 1~ the gas flow rate through the reaction zone still further by a lS further increase in the gas recycle rate leads to a situation in _ 16 which by-products are removed in the vapor phase effluent from 17 the reaction zone at the same rate as they are formed, thus 18 establishing a mass balance over the reaction zone. This is V the critical threshold gas recycle rate which is the preferred minimum gas recycle rate used in the process of the invention.
21 If the process is opexated with a gas recycle rate higher than ~ this threshold gas recycle rate the volume of the liquid body 23 in the reaction zone will tend to decrease and so, at gas recycle ~2~ rates above the threshold rate, some of the crude aldehyde 2s by-product mixture should be returned to the reaction zone from 26 the product separation zone in order to keep constant the 27 volume of the liquid phase in the reaction zone.
The critical threshold gas recycle flow rate can be found by a process of trial and error for a given olefin and synthesis gas tthe mixture of carbon monoxide and hydrogen) feed 31 rate. Operating at recycle rates below the critical threshold .

64~37 l ¦rates will increase the volume of the liquid phase with time.
z ¦Operating at the threshold rate keeps the volume constant.
3 ¦Operating above the threshold rate decreases the volume. The ¦ critical threshold gas recycle rate can be calculated from the s vapor pressures at the reaction temperature of the aldehyde or 6 aldehydes and of each of the by-products present.
7 With the process operating at a gas recycle rate at or ~ greater than the threshold rate, by-products are removed in the 9 gaseous vapors removed from the reaction zone containing the liquid body at the same rate as or faster than they are formed, Il and thus do not accumulate in the liquid phase-in the reaction-12 zone. Under such circumstances, it is unnecessary to purge the 13 liquid body containing the catalyst from the reaction zone in ~ order to remove by-products.
IS A by-product of the hydroformylation process is the 16 alkane formed by hydrogenation of the alpha-olefin. Thus, for example, in the hydroformylation of propylene a by-product is 18 propane. A purge stream may be taken from the gas recycle stream from~the product recovery zone in order to remove propane and prevent its build-up within the reaction system. This purge 21 ~ stream will contain, in addition to unwanted propane, unreacted tt~ propylene, any inert gases introduced in the feedstock and a mixture of carbon monoxide and hydrogen. The purge stream can, 2~ i~f~desired, be submitted to conventional gas separation techniques, tS~ ~e.g. cryogenic techniques, in order to recover the propylene, t6 ~ or it may be used as a fuel. The composition of the recycle gas t7~ is princlpally hydrogen and propylene. However, if the carbon monoxide is not all consumed in the reaction, the excess carbon ~ monoxide will also be part of the reaycle gas. Usually the ~recycle gas will contain alkane even with purging before recycle.
The preferred gas recyFle is further illustrated with ; ~ - - 30 -~ . , " - , , - . . . ~ ~

ll 11064(~7 1 reference to Figure 5 of the accompanying drawings which 2 schematically shows a diagramatic flowsheet suitable in practising 3 the preferred recycle process of the invention.
Referring to the drawing, a stainless steel reactor 1 is provided with one or more disc impellers 6 containing per-6 pendicularly mounted blades and rotated by means of shaft 7, by a suitable motor tnot shown). Located below the impeller 6 is a circular tubular sparger 5 for feeding the alpha-olefin, and 9 synthesis gas plus the recycle gas. The sparger 5 contains a -lo plurality of holes of sufficient size to provide sufficient 11 gas flow into the liquid body at about the impeller 6 to provide ~z the desired amount of the reactants in the liquid body. The 13 reactor is also provided with a steam jacket (not shown) by means 1~ of which the contents of the vessel can be brought up to IS reaction temperature at start-up and internal cooling coils 6 (not shown). - -17 ~aporous product effluent from the reactor 1 is 18 removed via line 10 to separator 11 where they are passed through 19 a demisting pad lla therein to re~urn some aldehyde and con-densation product and to prevent potential carry-over of catalyst.
Zl The reactor effluent is passed by line 13 to a condenser 14 and then through line 15 to catchpot 16 in which the aldehyde product and any by-product can be condensed out of the off gases 2~ (effluent). Condensed aldehyde and by-products are removed from the catchpot 16 by line 17. Gaseous materials are passed via line 18 to separator 19 containing a demisting pad and recycle 27 line 20. Recycle gases are removed by line 21 to line 8 from ~ which a purge through line 22 is pulled to control saturated hydro-29 carbon ~ontent and maintain desirable system pressure. The remaining and major proportion of the gases can be recycled via 31 line 8 to line 4 into which is fed make-up reactant feeds through - 31 '`

. ... . . . .

' 11 110~ l 1 lines 2 and 3. The combined total of reactants are fed to the 2 reactor l. Compressor 26 aids in transporting the recycle gases.
3 Fresh catalyst solution can be added to the rea~tor l 4 ~y line 9. The single reactor ~ can of course, be replaced by a plurality of reactors.
6 The crude aldehyde product of line 17 can be treated by conventional distillation to separate the various aldehydes ~ and the condensation products. A portion of the crude can be 9 recycled to reactor l through line 23 and fed as indicated by ¦ broken-line 25 to a point above impeller 6 for the purpose of 11 maintaining the liquid level in reactor l if such is required.
12 As pointed out above, the most preferred embodiment 13 of the present invention is the hydroformylation of the alpha-14 olefin propylene to produce butyraldehydes which are predominantly ~S normal. The stability of the rhodium complex catalyst is en-16 hanced by the techniques of the invention, and in the case of 17 propylene, the reaction is controlled within the following -1~ conditions:
19 temperature: about lO0 to about 140C
total gas pressure of hydrogen, carbon monoxide and 21 propylene: less than about 450 psia 22 carbon monoxide partial pressure: about l to about 40 psia 23 hydrogen partial pressure: about 20 to about 200 psia 2~ total free phosphine: catalytically-active rhodium mole ~ ratio: about 75 to about 500 26 triarylphosphine:triphenylphosphine 27 alkyldiarylphosphine:propyldiphenylphosphine 29 The procedure employed in all of these Examples was the same, and was as follows. Into a stainless steel reactor 31 was charged a rhodium hydroformylation solution of an amount of ' .

11 lla64~

1 rhodium as rhodium carbonyl triphenylphosphine acetylacetonate 2 and the amounts of triphenylphosphine and propyldiphenylphosphine 3 shown in ~able II below, in a mixture of butyraldehyde and butyr-aldehyde trimers (predominantly, 3-hydroxy-2,2,4-trimethyl-~ pentylisobutyrate). An equimolar mixture of propylene, carbon 6 monoxide and hydrogen was charged to the reactor, and the rate 7 (rl) of butyraldehyde formation at 100C was determined by 8 measuring the time required for a given pressure drop in the g reactor.
o Following reaction, the gases were removed from the Il reactor and replaced with a mixture of hydrogen and carbon mon-12 oxide at the partial pressures indicated in Table II. The reactor 13 containing the same was heated for about 3 hours at the tempera-t~ ture indicated in Table II. The gases were vented and an equi-~5 molar mixture of propylene, carbon monoxide and hydrogen was 16 again charged ~o the reactor and a second hydroformylation run was conducted at the same temperature as the first run. A second 18 rate (r2) of butyraldehyde production was determined in the same 19 manner as above. The results are shown in Table II below.
Examples 1-20 are within the scope of the present 21 invention and illustrate the improved stability obtained by the 22 provision of an alkyldiarylphosphine in the reaction medium.
~ Examples 21-30 are for purposes of comparison since no alkyl-2~ diarylphosphine was employed.
: 25 .30 .~

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64C~7 1 The predicted activity values given in Table II were 2 derived using the stability formula given above which is disclosed 3 in the aforesaid copending Bryant and Billig application. The ~
~ data in Table II indicate a marked improvement in catalyst sta-bility when propyldiphenylphosphine is present, as can be seen by comparing the higher observed percent activity values in com-7 parison to the predicted percent activities for each Example.

9 The procedure for each of these Examples was sub-o stantially the same and was as follows. A hydroformylation II reaction was conducted in a stainless steel reactor using various 12 alkyldiphenylphosphines in the same manner a~ in Examples 1-30.
13 The initial partial pressures of the reactants propylene, carbon monoxide and hydrogen were the same in each Example. The rate of butyraldehyde formation was determined at several times during the reaotion, d the results are shown in Tlble III below.

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ll ` 11(~64~7 1 As can be seen from Table III, particularly by comparing Examples 32-37 (which illustrate the present invention) with 3 Example 31 (which is for comparison), the provision of an alkyl-~ diphenylphosphine ligand in the reaction medium enhances the S stability of the catalyst.

7 These examples were conducted in the same manner as 8 Examples 31-37 except that the ligand used was an alkyldiphenyl-g phosphine only in Examples 38-42 and 45 and a triarylphosphine lo only in Examples 43 and 44. The present invention is not intended Il ¦ to include the use of each of these ligands alone. The results are shown in T le IV b-low:

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Claims (14)

WHAT IS CLAIMED IS:

1. In a process for hydroformylating an alpha-olefin containing 2 to 20 carbon atoms to produce aldehydes having one more carbon atom than the alpha-olefin by reacting the alpha-olefin with hydrogen and carbon monoxide in a liquid reaction medium which contains a soluble rhodium complex catalyst consisting essentially of rhodium complexed with carbon monoxide and a triaryl-phosphine ligand, and in the presence of free triaryl-phosphine, the improvement comprising improving the stability of the catalyst by:
charging the liquid reaction medium containing the catalyst with from about 0.1 to 20 percent by weight of an alkyldiarylphosphine ligand based on the total weight of the liquid reaction medium, and controlling the reaction conditions to a temperature of from about 100 to about 140°C, a total gas pressure of hydrogen, carbon monoxide and alpha-olefin of less than about 450 pounds per square inch absolute, a carbon monoxide partial pressure of less than about 55 pounds per square inch absolute, a hydrogen partial pressure of less than about 200 pounds per square inch absolute, and at least about 75 moles of total free phosphine ligand for each mole of catalytically-active rhodium metal present in the rhodium complex catalyst which consists essentially of rhodium complexed with carbon monoxide and one or both of said triarylphosphine and said alkyldiarylphosphine.

2. The process of claim 1, wherein said alpha-olefin has from 2 to 5 carbon atoms.

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3. The process of claim 1, wherein said alpha-olefin is propylene.

4. The process of claim 1, wherein said alpha-olefin is ethylene.

5. The process of claim 1, wherein said alpha-olefin is 1-butene.

6. The process of claim 1, wherein said triaryl-phosphine is triphenylphosphine.

7. The process of claim 1, wherein the partial pressure of carbon monoxide is from about 1 to about 50 pounds per square inch absolute.

8. The process of claim 1, wherein said amount of alkyldiarylphosphine is from about 0.5 to about 10 percent by weight, based on the total weight of the liquid reaction medium.

9. The process of claim 35, wherein the total free phosphine:catalytically-active rhodium metal mole ratio is at least about 100.

10. The process of claim 1, wherein the total gas pressure of hydrogen, carbon monoxide and alpha-olefin is less than about 350 pounds per square inch absolute.

11. The process of claim 1, wherein the partial pressure of hydrogen is from about 20 to about 200 pounds per square inch absolute.

12. The process of claim 1, wherein the ratio of partial pressures of hydrogen:carbon monoxide is at least about 2:1.

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13. The process of claim 1, wherein the ratio of the partial pressures of hydrogen:carbon monoxide is at least about 8:1.

14. The process of claim 1, wherein said catalyst is dissolved in a solvent which comprises the high boiling liquid condensation products of said aldehydes.

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