Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 3, 1978 205
Low-Pressure Hydroformylation of Methyl Oleate with an Activated Rhodium Catalyst J. P. Friedrich Northern Regional Research Center, Federal Research, Science and Education Administration, U.S.Department of Agriculture, Peoria, Illinois, 6 1604
Previous work has indicated that pressures of 1000 to 2000 psi (1:l molar mixture of hydrogen and carbon monoxide) are desirable for hydroformylation of fatty derivatives catalyzed by rhodium complexes. This paper reports the hydroformylation of methyl oleate to methyl formylstearate achieved at pressures as low as 200 psi and at temperatures ranging from 110 to 150 'C. Lower temperatures resulted in longer reaction times, whereas higher temperatures caused irreversible decomposttion of the catalyst complex and formation of two unidentified by-products. Nearly quantitative conversion was achieved in 4 h at 120 ' C using triphenyl phosphite and an activated rhodium on alumina catalyst. These findings indicate that large-scale batch reactions previously precluded by high-pressure requirements are now feasible with lower cost conventional hydrogenation equipment.
Introduction At the Northern Center in Peoria, we have been studying catalytic reactions of carbon monoxide (hydroformylation and carboxylation) with soybean oil and its derivatives (Frankel and Pryde, 1977). Hydroformylation as related to petrochemicals has been studied extensively as attested by the numerous literature references, including reviews on mechanism (Orchin and Rupilus, 1972), catalyst development (Paulik, 1972), and applications of the oxo reaction (Falbe, 1970; Pryde et al., 1972). Low molecular weight mono- unsaturated feedstocks such as ethylene and propylene have been used to produce large volume aldehydic intermediates. Although cobalt carbonyl is still the most widely used hydroformylation catalyst, rhodium carbonyl complexes have recently found application in large industrial processes (Fowler et al., 1976; Brewester, 1976). The advantages of rhodium complexes are fourfold: they permit operation a t lower temperatures as well as a t lower pressures, they produce aldehydes exclusively, and reaction conditions can be tailored to produce a high normal to isoaldehyde ratio with terminal olefin. The largest drawback to the use of rhodium catalysts is their cost and recoverability (Cornils et al., 1975). The recovery of catalyst in an active or easily activated form must be virtually quantitative to be of commercial interest. Since this is a homogeneous reaction, extraction of the catalyst or distillation of the product are the two most obvious alternatives. The integrity of the complex can be maintained during distillation provided the products are reasonably volatile. This is not possible, however, with hydroformylated fatty acids or esters. A procedure for extraction of the rhodium complex from hydroformylated fatty derivatives with a mixture of aqueous triethanolamine and HCN has been reported (Dufek and List, 1977);however, the most practical method reported thus far (Friedrich et al., 1973; Friedrich, 1975) employs vacuum distillation of the crude hydroformylated product after which the still bottoms containing the decomposed solubilized catalyst are burned off in the presence of spent rhodium on alumina catalyst. The rhodium is thereby resupported on the alumina in a more active oxide form and recycled. Supported catalysts of this type are not particularly suited to continuous reactors, and large high-pressure (500-1000 psi) batch reactors require 0019-7890/78/1217-0205$01.00/0
a prohibitive capital investment. The lowest pressure previously reported for satisfactory hydroformylation of unsaturated fatty derivatives with a rhodium complex catalyst is 500 psi; attempts to hydroformylate olive oil methyl esters a t 300 psi with a rhodium-triphenylphosphine system were unsuccessful (Frankel, 1971). This paper reports the hydroformylation of methyl oleate at significantly lower pressures, using triphenyl phosphite and a recyclable activated form of rhodium on alumina.
Experimental Section Materials. Methyl oleate (MO) was prepared from Hercules Pamolyn 100, a commericial grade oleic acid, by direct esterification with methanol and sulfuric acid. The washed reaction product was vacuum distilled to give 98% pure MO. The activated rhodium catalyst (ARC) was prepared by heating commercial 5% rhodium on alumina (Englehard, Murray Hill, N.J.) to 600 "C in the presence of air for 3 h (Friedrich et al., 1973). Other reagents were used as supplied: synthesis gas (Matheson Gas Products, New York, N.Y.), triphenyl phosphite (TPP) (Aldrich Chemical Co., Milwaukee, Wis.), and triphenylphosphine (Strem Chemicals Inc., Danvers, Mass.). Equipment. The hydroformylations were conducted in a 300-mL Magne-Drive autoclave (Autoclave Engineers, Erie, Pa.). This electrically heated 316SS vessel was equipped with a sampling tube, cooling coil, and gas dispersing agitator. It is rated at 5000 psi working pressure at 650 O F . Hydroformylation. In a typical run, MO (75 g; 0.253 mol mol), ARC [0.75 g (0.0375 g Rh; 0.05% Rh; 3.64 X Rh)], and TPP (0.75 g; 1% ; 2.42 X mol) were charged to the autoclave. The autoclave was sealed, flushed, and pressurized with synthesis gas (1:lmixture of CO and H,) to 180 psi, and heated to 100 "C at 2 "C/min with stirring (1200-1400 rpm). Hydroformylation began at about 100 OC as evidenced by pressure drop. The pressure was adjusted to 200 psi and the temperature was allowed to increase to 120 'C. The synthesis gas supply was shut off periodically and the vessel headspace pressure monitored. As the rate of synthesis gas uptake began to decrease, samples were taken for GC analysis. After 4 h, GC indicated >99% conversion of MO; the vessel was cooled and vented, and the reaction products were removed and filtered. 0 1978 American Chemical Society
206
Ind. Eng. Chem. Prod. Res. Dev., Vol. 17, No. 3, 1978
Table I. Hydroformylation of Methyl Oleate' GLC, % catalyst run no. ~f
0.05% Rhb
1%ligandC
pressure, psig
temp, "C
time, h
4% commercial Rh on CaCO, commercial commercial ARCg ARC commercial ARC ARC ARC ARC ARC ARC ARC ARC ARC
3.6 % phosphine phosphine phosphite phosphine phosphite phosphite phosphite phosphine phosphite phosphite phosphite phosphite phosphite phosphine phosphine
300 900 900 900 900 200 200 200 200 200 200 200 200 200 200
110 130 130 130 130 120 120 120 110 130 130h 140h 150h 130 140
6 4 211, 1112
conver- steasion rate
Mod
byMFSe product
