HYDROFORM,YLATION CATALYSIS BY ARYLPHOSPHIINE COMPLEXES OF RHODIUM J .
H . CRADDOCK,
ARNOLD
HERSHMAN,
Central Research Department, Monsanto Go., S t . Louis, Mo.
F .
E .
PAULIK,
AND
J .
F .
ROTH
63166
Olefins can catalytically react with hydrogen and carbon monoxide, using the cclmplex Rh(Pas) 2( C0)CI as a homogeneous liquid-phase catalyst, to produce aldehydes selectively ( > 9 9 mole Yo). Normal reaction conditions of 100' to 1 :25' C. and about 500-p.s.i.g. total reactor pressure are employed. The significant differences between the present catalyst system and others reported in the literature are catalyst stability and very high selectivity for aldehyde. N o hydrogenation reactions occur in conjunction with the hydroformylation reaction which might result in formation of alcohols and/or paraffin even at high Hz/CO ratios and high hydrogen partial pressure. When a-olefin feedstocks are employed, isomerization reactions can be effectively controlled to yield aldehydes having a linear content of 75 to 80°/0-e.g., normal aldehyde.
UNTIL recently the best known hydroformylation
(oxo) catalysts consisted of the simple carbonyls of Group VI11 transition metals such as C O ~ ( C O ) ~ . Industrial hydroforimylation processes generally employed simple cobalt carbonyl catalysts a t rather severe reaction conditions. Typical reaction temperatures of 100" to 180" C. required carbon monoxide-hydrogen pressures of 240 to 300 atm. to prevent catalyst decomposition (Bird, 1967; Wender et al., 1957). However, a new generation of hydroformylation catalysts capable of functioning a t mild pressure ( < 500 p.s.i.), reported in the past few years, consists of substituted metal carbonyls having: other ligands in addition to carbon monoxide. Some of these ligands impart unusual properties to the catalyst, such as increased reactivity, selectivity, and/ or stability. Typical ligands include the trialkyl- and triarylphosphines, ph'osphites, arsines, arsenites, and stibines. Hydroformylation catalysts based upon coordination complexes of cobalt, rhodium, and iridium that have received recent attention include: [Co(C0)3PR3]*, [Co(C0)3AsR3]2, Rh(:PBu)*(CO)Cl (Slaugh and Mullineaux, 1963, 1966a,b,c, 1968); Ir(PRa)2(CO)C1(Benzoni et al., 1966); Rh(P+3)3C:13(Osborn et al., 1965); Rh(P@3)3Cl (Jardine et al., 1965); and Rh[P(OR)3]2(CO)C1(Pruett and Smith, 1967). [R = organo-ligands, especially phenyl (a) or butyl (Bu) and substituted phenyl in some cases.] One particularly interesting catalyst is the triarylphosphine rhodium(1) complex, Rh(P@3)2(CO)C1.T o date, only fragmentary reports of the use and properties of this complex as a hydroformylation catalyst have appeared (Osborn et al., 1966). Pruett and Smith (1969) and Evans et al. (1968) have also provided pertinent information.This papeir reports the results of a detailed investigation of olefin hydroformylation employing the catalyst system, Rh(P&)*(CO)Cl, with "excess" triphenylphosphine ligand.
The nominal operating range for the Rh(P@3)2(CO)Clcatalyzed reaction of olefin with carbon monoxide and hydrogen is 100" to 150°C. and about 500-p.s.i.g. total reactor pressure. At these conditions the product is essentially all aldehyde (>99 mole %). The very high selectivity for producing aldehyde accompanied by a favorable ratio of linear to branched product is one of the significant differences between the present catalyst system, Rh(P+3)2(CO)C1,and others reported in the literature. No hydrogenation reactions occur that result in formation of alcohols and/or paraffin even a t high hydrogen-carbon monoxide ratios and high hydrogen partial pressure. Also, when alpha-olefin feedstocks are employed, isomerization reactions can be effectively controlled to yield aldehydes having a linear content of 75 to 80%-e.g., normal aldehyde. Another important feature of the catalyst system is its exceptional stability. Under reaction and product separation conditions the catalyst remains in solution and no evidence of decomposition is observed. Experimental
Apparatus. Experiments were conducted in 300-ml. stainless steel Magnedrive autoclaves (Autoclave Engineers, Erie, Pa.). The hydrogen-carbon monoxide mix was supplied from a 100-ml. high pressure reservoir via a pressure regulator to maintain the autoclaves a t constant pressure. Progress of the reaction was followed by automatic recording of the pressure drop of the 100-ml. high pressure reservoir as a function of time. Temperature was measured by an internal thermocouple in the reaction mixture, and was controlled and maintained automatically by an electronic temperature controller. The solution containing the catalyst was placed in the autoclave and heated to the desired temperature under a pressure of about 100 to 200 p.s.i.g. of the hydrogencarbon monoxide gas mixture. Liquid olefin was then VOL. 8 NO. 3 S E P T E M B E R 1 9 6 9
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injected into the reactor under pressure from a separate reservoir and the reactor was brought up to the desired pressure. The reaction time normally was about 17 hours (overnight). After cooling, the solution was drained from the autoclave and analyzed by gas chromatography (GC). Materials. The rhodium aryl phosphine complex, Rh(P@s)*(CO)Cl,used in this investigation was prepared according to the method of Chatt and Shaw (1966). RhCL. 3H20 and triphenylphosphine were purchased from Matthey-Bishop Co., Malvern, Pa., and M&T Chemicals, Inc., Rahway, N . J., respectively. Other reagents were obtained from commercial sources and were the best chemical grade available (reagent grade or equivalent if possible). Olefins employed were “pure grade” obtained from Phillips Petroleum Co. Carbon monoxide and hydrogen of C.P. grade were obtained from the Matheson Co. Analysis. The reaction products were analyzed quantitatively on a Wilkens Aerograph Model 200 gas chromatograph using a flame detector and a %-foot, %-inch stainless steel column filled with 1% AgN03-18% Carbowax 20 M on 60- to 80-mesh Chromosorb W. After injection of the sample, the column was programmed from 45” to 160°C. at 8’C. per minute. Calibration curves based upon weight per cent were made from solutions of known concentration, using the internal standard method. The hydrogen-carbon monoxide gas mixtures were analyzed isothermally a t 55°C. on a Wilkens Aerograph Model A-90P chromatograph, using a thermal conductivity detector and a 6-foot, %-inch stainless steel column with Linde 5A molecular sieve. Peak areas were obtained using an electronic integrator with digital printout (Infotronics Digital read-out system, Model CRS10HB). Gas chromatograph (GC) mass balances were obtained in several experiments, to demonstrate that gas chromatographic data were truly representative of the actual yields and selectivities and that formation of “high boilers,” etc., not readily detected by the GC method, was actually negligible. The results for a typical run demonstrated that the GC mass balance “closes” to better than 97 weight 70, well within experimental and analytical accuracy. These results indicated that extraneous by-products such as high boilers are produced in this system at relatively low levels. The GC mass balances were based upon two internal standards for quantification. All components present or expected could be determined by the GC method employed, except the metal complex catalyst, excess phosphine ligand and water, or any high boilers that might be formed. Preparation of Catalysts and Reagents. The following procedure was generally used for all the work with rhodium catalyst systems in the stirred autoclaves. All materials were carefully de-aerated and handled to reduce contact with air ( 0 2 to ) a minimum. Solvents and 1-hexene were magnetically stirred under a vacuum of -10 to 15 mm. of Hg until about half of the original volume remained. Nitrogen was added to “break” the vacuum and all subsequent steps were performed under a nitrogen atmosphere until the reagents were charged to the reactor. The rhodium catalyst was weighed out and transferred to a bottle prepurged with nitrogen. De-aerated solvent was added along with a magnetic stirring bar to the bottle described above, which contained a glass pipet connected to a nitro292
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
gen supply and was continuously purged to minimize air. The catalyst was stirred magnetically and the nitrogen purge was continuously bubbled through the stirred solution until all of the solid materials dissolved. Subsequently, “excess” P % ligand was added and dissolved in the stirred, nitrogen-purged solution. The glass pipet was removed, and the bottle was capped and stored until used. Deaerated hexene was prepared as described above or by purging a stirred solution with nitrogen as in the catalyst preparation. Distillation for Catalyst Recycle. Two distillations were conducted. The first (D-1 in Table VII) was on the product of the first batch of blended olefin feed. The second (D-2) was on the product of the recycle catalyst run with a new charge of blended olefin feed. The reaction product solution, including catalyst and any unreacted feedstock, was placed in a round-bottomed flask equipped with a magnetic stirrer, vacuum distillation head coupled to an 18-inch Vigreux distillation column, and a graduated receiver. Partial vacuum was obtained using a water aspirator with a controlled nitrogen leak. Pressure was measured with a mercury manometer, and the distillation pot and head temperatures were measured with laboratory thermometers. A forecut of low boiling material was taken, and then when the head temperature reached the value expected for aldehydes to distill, a product (2nd) cut was made. The vacuum was adjusted so that the pot temperature would not exceed 180”C. Pot and head temperatures as well as the still pressure are reported in Table VII, which also reports the GC analysis of the product cut taken from each distillation. Results and Discussion
Catalyst Systems and Reaction Conditions. The homogeneous catalyst system of this investigation is comprised of the rhodium( I) complex, chlorocarbonylbistriphenylphosphine rhodium(I), Rh(P@3)2(CO)Cl, with “excess” triphenylphosphine ligand (in addition to the stoichiometric ratio in the complex) dissolved in an inert solvent such as benzene, dioctyl phthalate, diphenyl ether, etc. Linear hexenes were employed as the model olefin feed. The hydroformylation reaction was studied over broad ranges of temperature, pressure, H2/CO molar ratio, catalyst concentration, and catalyst composition to determine the effects of these parameters upon catalyst reactivity and stability, and product selectivity including isomer distribution. Typical reaction conditions were in the temperature range of 100” to 150°C. a t 500- to 1000-p.s.i.g. total pressure. A hydrogen-carbon monoxide ratio of 1 to 1 was generally used. Catalyst concentration levels were about lo-’ or lO-‘M in rhodium complex and were used in conjunction with excess triphenylphosphine ligand levels of 0 to >50 triphenylphosphine molecules per rhodium atom. Effect of Catalyst Composition. The catalyst composition-e.g., the form of the rhodium(1) complex and the nature of the ligands of the complex-and the presence of excess ligand, have a significant effect upon product distribution, reaction rate, and catalyst stability. Addition of excess triphenylphosphine ligand to the catalyst solution containing the rhodium complex, Rh(P@a)Z(CO)Cl,improves the selectivity of the reactions for production of normal aldehyde (Table I ) . The selec-
Table 1. Effect of Excess Ligand upon Product Distribution of Alpha-Olefin Feed
Reaction conditions.
a
[P+,] "Excess," M
Ratio, P@3/Rh
0 3.3 x l o - ' 1.3 x lo-' 3.2 x lo-'
0 5 20 50
Hexane 0.3
... ...
Trace
[Rh(P%),(CO)Cl],6.7 x 10 4 M Pressure. 500 p.s.i.g., 1 : l H,/CO Temperature. 100" C. Run time. -17 hours Solvent. 50 mi. benzene, olefin 25 ml. 1-hexene
Product Distribution ISoluent-Free Basis)', Mole 51 2-MethyiHexene 1- H e p t a d hexanal 3.0 3.9 4.8 4.6
40.6 64.0 72.5 72.5
40.9 32.1 22.7 22.6
2-Ethylpentanal
Sc SelectioityD to 1- Heptanal
15.2
42.0 66.7 76.2 76.2
... ... 0.3
No alcohols detected by GC analysis. ' 5; normal aldehyde of total aldehydes.
tivity increases to about 75% normal aldehyde a t a ratio of excess triphenylphosphine ligands-rhodium atom of about 20 and does not significantly change a t higher ratios. The distribution of branched products also demonstrates the effect of excess ligand. Practically no ethyl-branched material was formed from 1-hexene with excess triphenylphosphine ligand, while about 15% ethyl branching occurred when no excess ligand was used. Liquid samples taken during the course of the reaction established that the aldehyde isomer distribution (normal-internal) remained essentially constant as the conversion of l-hexene proceeded. This increase in selectivity may be due to stabilization of the catalyst by excess ligand, thus avoiding decompositiion of the active rhodium hydroformylation complex to other rhodium species that may catalyze the isomerization of olefins. The effect of catalyst composition on product isomer distribution was examined in greater detail, employing the isomeric hexenes This study was carried out using the high boiling solvent, dioctyl phthalate (DOP), which offers certain processing advantages. The liquid product analysis a t the end of the runs is presented in Table I1 in terms of mole per cent conversion of the feed olefin and isomer distribution of the product aldehydes. Neither the paraffin nor alcolhol content of the product is given in Table 11, because the hydrogenated compounds never exceeded 2% even at 200" C. I n runs a t 150" C. the hydrogenated by-product compositions were of the order of tenths of 1%.
The normal content of the aldehydes made from 2-hexene was in the range 35 to 43% when a temperature of 200°C. or no excess ligand was employed; a t 150°C. with excess triphenylphosphine ligand only 16% normal aldehyde was obtained. At the lower temperature of 150"C., the excess ligand apparently retarded internal olefin isomerization to the alpha position, resulting in a higher percentage of branched aldehydes. At the higher temperature of 200" C. or without added triphenylphosphine ligand, more isomerization occurred, resulting in a higher production of normal aldehyde from the internal olefin feedstock. The ratio of the per cent methyl-branched aldehyde product to ethyl-branched aldehyde product was reasonably constant a t 2.5 to 2.8 for all 2-hexene runs, except when isomerization of the 2-hexene was retarded by using the lower temperature-e.g., 150" C.-and excess ligand. Another demonstration that isomerization of internal olefins is very rapid a t 150'C. with no excess ligand is seen in the results with either 1-hexene or a mixture of 2-hexene and 3-hexene as feedstock. (This latter material supplied by Phillips Petroleum Co. was listed as having 1 . 7 5 1-hexene, 79.50; 2-hexene, and 18.9% 3-hexene a t ambient temperature and appears to be approximately the equilibrium composition of hexene isomers.) As can be seen in Table 11, the product distribution for either feed was essentially the same as for the 2-hexene feed and yielded a broad spectrum of isomeric aldehyde products.
Table II. Effect of Excess ligand upon Product Distribution of Internal Olefin Feedstock
Reaction conditions.
[ P a ? ]"Excess,"
Olefin 2-Hexene 2,3-Hexene mix 1-Hexene 2-Hexene 2-Hexene 2-Hexene a
M
Temp., C.
0 0 0 0 7x10' 7x
150 150 150 200 150 200
I n all cases total hydrogenated product-eg
[Rh(Ph),(CO)Cl],1.3 x 10-jM Pressure. 500 p.s.i.g., 1 : l H 2 / C 0 Run time. -17 hours Solvent. 75 mi. dioctyl phthalate, olefin 25 mi.
Isomer Distribution of Aldehyde Producta %Methyl2-Ethyl1 -Heptanal hexanal pentanal 36.8 35.3 40.1 38.5 16.1 43.0
, parafin and alcohols-was
45.5 45.7 41.9 45.1 55.8 41.4
97 wt. % aldehyde Unreacted feed >99 wt. % aldehyde
The catalyst recycle studies were conducted using the Rh(P@3)2(CO)C1-excesstriphenylphosphine catalyst system dissolved in a high boiling solvent, dioctyl phthalate (b.p. ca. 380” a t 1 atm.). The olefin feedstock consisted of a commercial blend of alpha-olefins in the C- to Clo range. Two batch reactions were performed using fresh catalyst solution and a recycle catalyst solution remaining after distillation of product from the first batch run. A GC analysis of the catalyst solution after distillation showed very little aldehyde left, that remaining being mainly the n-C,, aldehyde, which is the highest boiling product. The recycle catalyst solution was diluted with fresh solvent and then used for hydroformylation of a second portion of the olefin blend. Both reaction rate and the visual appearance of the catalyst solution (a bright yellow color) indicated that no deterioration of the catalyst had occurred in handling or distillation. Finally, GC analysis of the reaction product demonstrated that no adverse effects upon product selectivity and isomer distribution had occurred. The results of GC analysis and reaction conditions for the distillation are summarized in Table VII.
Bird, C. W., ‘(Transition Metal Intermediates in Organic Synthesis,” Chap. 6, Logos Press, London, 1967. Chatt, J., Shaw, B. L., J . Chem. Soc. 1966A, 1437. Evans, D., Osborn, J. A., Wilkinson, G., J . Chem. Soc. 1968A, 3133. Hagemeyer, H . J. (to Eastman Kodak Co.), U.S. Patent 2,576,113 (Nov: 27, 1951). Hagemeyer, H. J., Hull, D. C. (to Eastman Kodak Co.), U.S. Patent 2,694,734 (Nov. 16, 1954). Jardine, F. H., Osborn, J. A., Wilkinson, G., Young, J. R., Chem. I n d . 1965, 560. Osborn, J. A., Jardine, F. H., Young, J. F., Wilkinson, G., J . Chem. Soc. 1966A, 1711. Osborn, J. A., Wilkinson, G., Young, J. R., Chem. Comm. 1965, 17. Pruett, R. L., Smith, J. A., Abstracts, 154th ACS Meeting, Sept. 10-15, 1967, Chicago, N-39. Pruett, R. L., Smith, J. A., J . Org. Chem. 34, 327 (1969). Slaugh, L. H., Mullineaux, R. D., J . Organometal. Chem. 13, 469 (1968); U. S. Patent 3,239,566 (1966a), 3,239,569 (1966b), 3,239,570 ( 1 9 6 6 ~ )C; A 59, 1 1 2 6 8 ~(1963). Wender, K., Sternberg, H. W., Orchin, M., in “Catalysis,” P. H. Emmett, Ed., Vol. 5 , Chap. 2, Reinhold, New York. 1957.
Acknowledgment
The authors express appreciation to K. K. Robinson for assistance with experimental work. RECEIVED for review December 30, 1968 ACCEPTED June 1, 1969
literature Cited
Benzoni, L., Andreeta, A., Zanzottera, C., Camia, M., Chem. Id. ( M i l a n ) 48, 1076 (1966).
Presented a t First North American Meeting of Catalysis Society, Atlantic City, KJ.,February 20, 1969.
NAVAL STORES PRODUCTS FROM PONDEROSA PINE STUMPS N.
M A S O N
J O Y E ,
J R . ,
A .
T. P R O V E A U X , A N D R A Y V . L A W R E N C E
Naval Stores Laboratory, Southern Utilization Research and Development Diuision, Agricultural Research Service, U . S . Department of Agriculture, Olustee, Fla. 32072
R O L A N D
1.
BARGER
Rocky M o u n t a i n Forest and Experimental Station, Flagstaff, A r k .
86001
Extractives from ponderosa pine ( Pinus ponderosa Laws) stumps were processed and the rosin, pine oil, and turpentine recovered. Comparison with equivalent connmercial products indicates that further processing would be required before these products could be substituted in most commercial uses.
WOOD rosin, turpentine, and pine oil are produced com-
Method of Sampling
mercially from extractives from southern pine stumps. Other areas of this country have pines and pine stumps that could be utilized by the naval stores industry. Anderson (1947,1954,1955,1962) and Riffer and Anderson (1966) have studied the composition of extracts of ponderosa stumps from recently felled trees as well as new and old stumps. I n this study, rosin was prepared from the extracts, and its physical and chemical constants were determined. I n so far as could be determined, this was the first study on the composition of ponderosa pine oil and rosin.
Stumps from several areas were selected to represent sound ponderosa pine stumps from trees logged between 1909 and 1925. They were sound, with no internal or root rot but without sapwood left. Although stumps were selected to represent average conditions, a much larger selection would be required to give a completely accurate analysis of stump quality. Also, the small samples used in this work probably contained less trash, decayed wood, and other undesirable material than would be present in the wood used in a large scale operation. While the VOL. 8 NO. 3 S E P T E M B E R 1969
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