React. Kinet. Catal. Lett., Vol. 15, No. 1,103-112 (1980) L I Q U I D P H A S E CO + H2 R E A C T I O N S I N P R E S E N C E O F RUTHENIUM CATALYSTS G. Jenner, A. Kiennemann*, E. Bagherzadah and A. Deluzarche Laboratoire de Chimie Organique Appliqu6e, E. R. A. 826, Universit6 Louis Pasteur, Institut de Chimie, 6700 Strassbourg, France Received June 11, 1980 Accepted June 24, 1980 Several effects on the hydrogenation of carbon monoxide in propanol in presence of ruthenium catalysts are examined. The homologation reaction is not observed, only propyl formate and propyl acetate are produced with any ruthenium catalyst. The pH-value is an important parameter: in acid media, the yield of propyl formate is noticeably increased indicating different catalytic active species. The addition of cesium salts is also benefitial for formate formation. This is not the case when water is associated with propanol as solvent. Finally, no ethylene glycol is detected. The process is found to be homogeneous and methanol seems to be the precursor of methyl formate. H3yqeHslpaznHqH~e ~bQbeKTI,I, BnHsIOmHeHa rl4~pHpOBaHHeOKHCHyrnepo~a s nponaHOJIe B HpHcyTCTBHH pyreHHeBblX KaTanH3aTOpOB. P e a K m ~ rOMOHOrHpOBaHI4H He Ha6HIOH~eTCSI, B HpHCyTCTBHH pyzeHHeBoro KaTaYie3aTopa o6pazy[OTC~ nHIlIb d~OpMHaT H atteTaT iipomlna. Ba)KHMM llapaMeTpoM ~IBH~IeTC~I3HaqeHHe pH: B mtcnoR cpe~Ie Bs~xo~t ~OpMHaTa nponHna 3HaqHTenbHO yBenHtmBaeTcH, trro yKa3smaeT Ha pa3nHqHLIe THIU~I KaTa/IHTHqecKH aKTI,mIIMX qaCTHl.t. ,~o6aBKH coHel~ Ue3H.q 6HaroIIpHErCTByIOT o6pa3osaHHIO OpOpMHaTa. B ~TOM cnyqae Bo~a He a c c o ~ H p o s a H a c nponaHonoM, xa.K paCTBOpHTe/leM. B KoHeqHOM HTOFe :~THJIOHrJIHKO/II,He O6Hapy~KeH. l-[pouecc oKaza.~cH FOMOI'eHHbIM H MeTaHO/I, IIOoBK/IHMOMy,~B/I~IeTCHHCTOqHHKOM Me'rH/1OpOpMHaTa.
INTRODUCTION
Homogeneous catalysis by transition metal complexes has obtained increasing attention in the past years, particularly in the Fischer-Tropsch type of hydrogenation of carbon monoxide. The question has been dealt with in recent articles/1-4/. XTo whom all correspondence should be addressed 103
JENNER et at.: CO + H~ REACTIONS Besides cobalt and rhodium catalysts, ruthenium appears to be the most used in catalysis, they are e. g. : h o m o l o g a t i o n / 5 - 6 / , hydrogenation /2/, reaction of water with C O / 8 - 1 0 / , direct synthesis of alcohols / 1 1 - 1 4 / a n d diols /15/. In this article, we investigate the hydrogenation of carbon monoxide in the presence of various ruthenium catalysts (clusters or monometallic compounds) considering several parameters which have hitherto received less attention: the effect of pH, pressure, presence of additives (cesium, benzoate and hydroxide), addition of water.
EXI~I~IMENT AL I) Description of a run The high pressure design has been described elsewhere/18/. The vessel is blowed off under an argon stream and filled up with catalyst(4x 10 -4 mole), solvent (0.04 mole) and additive ( l x 10 . 4 mole), then connected to the high pressure line and brought to the desired pressure.. After deconnection from the line, the vessel is heated and shaken for a constant reaction time. The pressure drop ( A P) can be followed continually by a pressure transducer. After cooling overnight, the vessel is discharged by evacuating the gas phase at a very low rate. After full decompression the liquid phase is isolated and analyzed by gas chromatography (GC), as well as the gas phase. 2) GC conditions x a) Analysis of CO, CO2, H2: chromatograph (F and M 720), detection (catharometer), carrier gas (CH4 15 ml/min), column (Silicagel: 80-100 mesh, length 5 m, diameter 3, 2 ram), temperature (20 ~
- 5 rain, then 140 ~
- 10 rain), injection
and detection (150 oc). b) Analysis of CO2 and gaseous hydrocarbons: chromatograph (Hewlett-Packard 5700), detection (catharometer), carrier gas (He 30 ml/min), column (Chromosorb XWtth the collaboration of Mrs. S. Libs and Miss E. Schleiffer 104
JENNER et al.: CO + H~ REACTIONS 102:80-100 mesh, length 2 m, diameter 3, 2 mm), programmation (from 60 o to 240 ~
- 80C/min), injection and detection (200 ~
c) Analysis of the liquid phase (alcohols, esters): conditions as in b), but column (FFAP, 5% Chromosorb 101:80-100 mesh, length 4 m).
RESULTS AND DISCUSSION a) Effect of catalysts The results with some ruthenium catalysts ate listed in Table 1. Following points must be noticed : with RnO2 wax is produced (42~ in weight) in accordance with the results of Pichler/19/. With other catalysts homologation of propanol is not observed, in contrast to earlier patents /11-12/. Only propyl formate and propyl acetate ate obtained and this result demonstrates that a chaingtowing from CO and H2 is possible. A blank run (propanol + CO) carried out under the same conditions produced only a negligible amount of propyl formate. b) Effect of pH With ruthenium catalysts, the acidity or basicity of the medium seemed to have an important influence on the selectivity : long chain alcohois in alkaline media, solid polymethylens at acidic p H / 1 1 - 1 2 / . The water-gas shift reaction is also affected by the pH 191. When changing the pH from alk,aline to acidic we observe a significant increase of the yield for formate (x 4. 3). In this run dehydratation of propanol and formation of dipropyl ether occurs. During the reaction the pH decreases (from 11 to 9. 5), the decrease is due either to the formation of CO2 or to the consumption of the base to give formates. In alkaline media CO2 is produced in a great quantity (54%), probably in the reaction of water-gas shift reaction catalyzed by 1~ 19/. In acidic media, CO2 is present only in a small amount ( < 2%). In any case, no homologation of propanol could be observed. 105
JENNER ct al.: CO + H2 REACTIONS Table 1 Influence of various ruthenium catalysts (a)
Products (c) AP (b)
propyl formate
propyl acetate
w ater
20
6
0
0
.50
9
1
0
l~(acac)3
35
1.3
1.3
0
RuCI2 (P Ph3)3
20
O. 25
0
0
(d)
120
O. 25
O. 25
13
Catalyst
Ru3(CO)12 RuCI 3, 3H20
~uo 2
(a) T: 205oc. P: 1100 bat, reaction time: 5 h, solvent: PrOH 0.04 mol catalyst: 4. 10-4 tool :, CO :H2 = 1 : 1. 0a) Pressure drop in bar (vessel unheated). (c) Moles of products for one 9-atom of Ru. (d) Heterogeneous catalysis.
Although mechanistic schemes have been proposed for the water-gas shift reaction in alkaline media, the catalysis at acidic pH-values remains an intriguing point. The results of Table 2 can be explained only by supposing the existence of different catalytic active species at different pH-s. H Ra3(CO)11, H4Ru4(CO)12 have been identified in alkaline media, while H2Ru6(CO)18 seems to be in acidic media
/9//20/. c) Effect o~ additives The effect of additives plays an important role in some reactions such as the synthesis of ethylene g l y c o l / 1 7 - 2 1 / a n d the homologation of methanol with Co or Rh as catalysts /16-22/. Table 3 shows our results. The activity of the catalyst increases seven-fold in the formation of propyl formate.. The role of the Cs + cation is probably to stabilize the ruthenium active species, as shown with rhodium/21/. Again we obsexve a decrease of the pH during the reaction. 106
JENNER et al.: CO + H 2 REACTIONS
Table 2 Effect of the pH of the medium (a)
Products (b)
pH
A P (b)
before
1
Propyl
Propyl
Water
formate
acetate
ether
35
1.3
1.3
0
0
30
3.5
2.5
0
0
90 (c)
15
2.3
20
30
reaction
11
Propyl
(a) T: 2 0 5 o c , p: 1100 bar, reaction t i m e : 5 h, solvent: PrOH, 0.04 mol, catalyst: Rn(acac)3: 4x 10 - 4 tool, CO:H,2 = 1:1. (b) see Table 1. (c) In this run, 1. 6% of the products could not be identified.
Table 3 Effect of additives (a)
Products (b)
pH
Additive
before
after
AP (b)
reaction
propyl
propyl
formate
acetate
3.5
2.5
none
11
9.5
30
CsOH
11.5
7
50
23
1.3
(c) B z ~
10.5
9.5
80
26
0.5
Water
(a) T : 205~ P :1100 bar, reaction t i m e : 5 h, solvent: PrOH :0.04 tool. catalyst : Ru(acac) 3 : 4 x 10 -4 mol, additive : l x 10 -4 mol, CO/H2: = 1:1. (b) see Table I (c) Cesium benzoate.
107
JENNER et al.: CO + H: REACTIONS
Table 4 Effect of water (a) ~oducts ~)
[c~esence
pH
A P (b)
Propyl
Propyl
Propyl
water
formate
acetate
ether
3.6
2.6
of
1.4
25
yes
1.0
95
no
11.4
10
yes
11.0
30
4.3 5.0
15
0.4
2.3
20
0.2
0.2
0
no
3.5
2.5
0
10
yes
0.1
0.2
0
35
no
1.3
1.3
0
(a) T :205~ P :1100 bar, reaction time :5 h, solvent :PrOH+ + H 2 0 : 0 . 0 2 tool + 0.09 mol, catalyst :Ru(aeac) 3 : 4x 10 -4 mol, CO H2 = 1:1. (b) see Table 1.
d) Effect of water The effect of partial substitution of PrOH by water at different pH-values is shown in Table I. At any pH, the addition of water hinders the formation of formate. It should be pointed out that these results are conflicting with those extracted from a patent/12/, which indicates that the addition of water is favorable for the synthesis of high boiling alcohols, e) Influence of pressure and temperature As it was impossible to reproduce some results /11-12/obtained with RuO2 with homogeneous catalysts, we have tested the activity of Ru(aeac)..3 in eonditiom close to those used for the synthesis of ethylene g l y c o l / 1 7 / . The results are listed in Table 5. With increasing pressure and temperature, l~(acac)3 dissolved in tetraglyme 108
JENNER ct ai.: CO + H~ REACTIONS Table 5 Hydrocondensation of CO with ruthenium catalysts (a) Catalyst
P(bar)
T (oc)
A P (b)
Solvent
Ru(acac) 3
1i00
205
35
PrOH
Ru(acac) 3
1700
230
130
PrOH
Ru(acac) 3
1700
230
110
Tetraglyme
P-u3(CO)12
1100
205
20
PrOH
Products (b) MeOH Ru(acac) 3
0
Ru(acac) 3
MeFt
MeAc
EtAc
PrEt
0
0
0
1.3
0
0
0
13. 5
PrAc 1.3
HO 2 0
2
4
Ru(acac) 3
3.5
1.8
0.5
0.5
0
0
3
Ru3(CO)I2
0
0
0
0
6
0
0
(a) catalyst :4x 10 -4 mol, solvent: 0.015 mol, reaction time: 5 h, CO:H2 = 1:1. (b) see Table 1. Abbreviations mean, respectively : methanol, methyl formate, methyl acetate, ethyl acetate, propil formate, propyl acetate.
leads to the synthesis of methanol, methyl formate and acetate. These results are similar to Bradley's results /13-14/obtained in tetrahydrofuran at a higher temperature (270 Oc). The higher pressure associated with a lower temperature allows us to avoid the formation of hydrocarbons, which would occur through a heterogeneous process after the decomposition of the c a t a l y s t / 2 8 - 2 4 / . The IR-characterization of Ru(CO)5 at the end of the reaction, as well as the absence of methane suggest that the formation of our products is a homogeneous process. With propanol as solvent, only propyl formate and acetate and traces of methanol are obtained. No ethylene glycol could be detected in the reaction products, unlike in a recent p a t e n t / 1 5 / . 109
JENNER et al.: CO + H2 REACTIONS The mechanism of the synthesis remains hypothetical. Would it be a mechanism through chain-growing as suggested by Olivd for the formation of alcohols / 2 5 / w h e r e alcohols and esters would be formed through a common reaction species ? Or, alternatively, would methanol be a primary product from which the esters would derive or opposite~ Only a partial answer can be proposed : in the same reaction conditions as those defined in Table 1 (catalyst P.u(Acac) 3, the reaction CH3OH + CO leads to the formation of 10% methyl formate (on methanol basis), while the reaction MeFt + H2 gives only CH4, CO and traces of CO2 and H20. Thus methanol appears as a primary product and can produce methyl formate. The results of the present work draw the attention to an important problem. We described previously / 1 7 / t h e synthesis of ethylene glycol with rhodium catalysts, but also in the presence of Rn3(CO)12 at high pressure. Since than, two other works
/15-26/reported similar
results. However, we never could reproduce the run with
Rns(CO)12 when operating in a vessel, which has not been in contact with any rhodium catalyst. We suspect that in the former run, the formation of ethylene glycol was due to catalysis with metallic sediments of rhodium incrusted on the wall of the vessel (we showed that ethylene glycol is produced with an appreciable yield by rhodium foam).
CONCLUSIONS
In the present investigation we studied the catalytic activity of some ruthenium compounds for the hydrocondensation of carbon monoxide. Some effects could be shown: -
the effect of pH on the synthesis of formates
- the important influence of the presence of cesium compounds on the activity of the catalyst -
the formation of methanol and methyl formate at higher pressure and temperature
without the formation of hydrocarbons -
110
the absence of ethylene glycol, in contrast with other works.
JENNER et al.: CO + H: REACTIONS REFERENCES 1. L Wender, P. Pino: Organic Syntheses via Metal Carbonyls, Vol. II, Wiley Interscienc e. 1977. 2. C. Masters: Adv. in Organometall. Chem., 17__,61 (1979). 3. R. Etsenberg, D.F~ Hendricksen: Adv. in Cata1., 28.__,79 (1979). 4. E. L, Muetterties, J* Stein: Chem. Rev., 79, (6)479 (1979). 5. G.N. Butter: U.S. Patent, 3 285 948 (1966). 6. G. Braca, G. Sbrana, G. Valentini, G. Andrich, G. Gregorio: J. Amer. Chem. Soc., 100, 6238 (1978). 7. M. Bianchi, G. Menchi, F. Francalanci, F. Piancenti, U. Matteoli, P. Frediani, C. Botteghi:J. Organometall. Chem., 188, 109(1980). 8. P.M. Laine, P. G. Pinker, P.C. Ford: J. Amer. Chem. Soc., 99__, 252 (1977). 9. C. Ungermann, V. Landis, S.A. Moya. H. Cohen, H. Walker, P. G. Pearson, P.G. Pinker, P.C. Ford:J. Amer. Chem. Soc., 101, 5922 (1979). 10. P.C. Ford, P. G. Rinker, C. Ungermann, P. M. Laine~ S.A. Moya: ~ Amer. Chem. Soc., 100, 4595 (1978). 11. W.F. Gresham : U.S. Patent, 2 535 060 (1949). 12. B.W. Hawk: U.S. Patent, 2 549 470 (1949). 13. L S. Bradley: J* Amer. Chem. Soc., 101, 7419 (1979). 14. J*S. Bradley:Fnndam. Res. Homogeneous Catal., 3_, 165(1979). 15. P.C. WiUiarmon, T.P. Kobylinski: U.S. Patent, 4 170 605 (1979). 16. A. Deluzarche, G. Jenner, A. Kiennemann: Tetrahedron Lett., 3797 (1978). 17. A. Deluzarche, P. Fonseca, G. Jenner, A. Kiennemann: Erd. und Kohle, 32__, 313 (1979). 18. G. Jenner, A. Deluzarche: Chem. Ing. Techn., 49.., 420 (1977). 19. FL Pichler, PL Buffleb:Brennst. Chem., 21.._, 273(1940). 20. C.P. Early, P.F. Jackson, B.F.G. Johnson, J* Lewis, M. M. Malatesta, M. McPartlin, W.J*I-L Neison:j* Chem. Soc. Dalton, 384(1980). 111
JENNER et al.: CO + H2 REACTIONS 21. P,. L. Pcuett, W. E, Walker: U.S. Patent 4 001 289 (1977). 22. H. Dumas, J, Levisalles, H. l~dle~: L OrganometalL Chem., 187..__,j405 (1980). 23. C. Masters, L A. Van Doom : Germ. Patent, 2 644 185 (1977). 24. M. L Doyle, A.P. Kouwenhoven, C.A. Schaap, B. Van Oort: L OrganometalL Chem., 174.., C55 (1979). 25. G. Hemici-Oliv6, S, Oliv6: Angew. Chem., 15.__, 136 (1976). 26. W. Keim, M. Berger, J. Schlupp:'L Catal., 61.__, 359 (1980).
112
