Process For The Production Of Oxygenated Products From Olefiπically Unsaturated Com¬ pounds By Hydroformyl t on With Supression Of Olefin Hydrogenat on.

The present invention relates to an improved preparation of oxygenated organic compounds from olefinically unsaturated compounds, carbon monoxide and hydrogen. More particularly, it relates to a process for hydroformylating olefinic com - pounds, while at the same time suppressing olefin hydrogenation by using, an acid to suppress the side reaction. Background of the Invention

Processes for producing oxygenated products, e.g., aldehydes and/or alcohols, by reaction of olefinically unsatur- atεd'compounds with carbon monoxide and hydrogen at elevated temperatures and pressures in the presence of certain catalysts are well known in the art. The aldehydes and alcohols so pro¬ duced are useful per se and also as intermedi tes in the production of other valuable compounds. The oxygenated compounds generally correspond to addition of a carbonyl or carbinol grouping to the starting material with simultaneous saturation of the olefin bond. Such processes are generally known under varying names, such as the Oxo-procεss or the hydroformylation process. Incorporated herein for background purposes are Bruett et al, U.S. 3,917,6-€1 which deals generally with trie ^' hydroformyl¬ ation of unsaturated organic compounds and Slaugh et al , U.S. 3,239,566, which deals specifically with the hydroformylation of olefins.

A substantial disadvantage in prior art hydroformylation processes is the formation, by a side reaction, of byproducts based on hydrogenation rather than hydroformylation of the olefin bond. In commercial experience, substantial amounts of the olefinically unsaturated substrates are simply converted to nearly useless hydrogenation products, instead of the desired oxygenated compounds. A means to suppress or reduce substrate hydrogenation in such processes and the economic value of such a discovery is self-evident. Such a means is the subject of the present invention.

In essence, the present invention comprises the addition of an acidic compound to the hydroformylat on reaction mixture, in an amount at least sufficient to suppress substrate hydro¬ genation. A preferred acid for this purpose is phthalic acid and related compounds.

The use of phthalic acid and related compounds as co- catalysts in the rhodium carbonyl catalyzed hydroformylation of ally! alcohol or its homologs is described in another con¬ text applicant's co-pending U.S. patent application, Serial No. 849,435, filed November 7, 1977. By way of illustration, phthalic acid and related compounds are shown therein to be particularly effective as co-catalysts (used in conjunction with the rhodium carbonyl/triarylphosphine combination) for the oxo tetrahydrofuranylation process. The designed purpose of the phthalic acid in that process was promotion of the conver¬ sion of the 2-hydroxytεtrahydrofuran intermediate to a stable 2-alkoxytetrahydrofuran (Equation 1)

The phthalic acid has a somewhat rate-retarding effect on the hydroformylation reaction (allyl alcohol) itself, but no particular benefits or deleterious effects in that step of this relatively complicated system were perceived. With a simpler system, however, a dramatic positive consequence of using the phthalic acid catalyst component in the hydroformylation reaction has been discovered. Application of the phthalic acid/triphenylphosphine/rhodium carbonyl catalyst to the hydroformylation of conventional olefins demonstrates an unprecedented effect — the substrate hydro¬ genation side reaction characteristic of the Oxo process can be virtually completely suppressed with this combination. This effect is clearly demonstrated in a comparison of the hydro¬ formylation of 1-hexene in the absence and presence of the phthalic acid catalyst modifier. The results are outlined in Equation 2 and 3. A similar result was obtained with 1-decene as the substrate.

Oftt i

CH ₃ (CH ₂ ) ₃ CH=CH ₂ +C0+H ₂ ^Rh 6 ^(CO hs ^/Ph 3 ^P _; , CH CH H (60%)

(P:Rh = 32) toluene

95°C 0.

(900-1450 psi) ÷CH ₃ (CH ₂ ) ₃ CHCH (21%) (2)

63 - 102 kg/cm ₂ CH ₃

+CH ₃ (CH ₂ ) ₄ CH ₃ (19%)

(3 ÷CH ₃ (CH ₂ ) ₄ CH ₃ (1%

The hydrogenation suppression effect is also operable in the ally! alcohol-oxo tetrahydrofuranylation case. In a controlled comparison as above, the extent of di ect propanol formation wi t and wi thout the phthalic acid co-catalyst is 4% and 21% respectively. If there are no offsetting negati e effects of the phthalic acid, the yield of 1,4-butanediol obtainable on hydrolysis-hydrogenation of the iπtermediate(s) should be correspondingly increased. This has been found qualitatively to be the case. Description of the Invention.

According to the present invention in its broadest aspects there is provided in a process for preparing oxygenated pro¬ ducts by contacting an olefinically unsaturated compound, carbon monoxide and hydrogen with a hydroformylation catalyst, an improvement which comprises adding an acid to the reaction mixture in an amount at least sufficient to suppress hydro¬ genation of said olefinically unsaturated compound.

In preferred features the acid will have an acid strength at least strong enough to suppress hydrogenation but not so strong as to significantly decompose said oxygenated products. Preferably, the acid will have a pk _a of from about 1.5 to about 5.0 in aqueous solution. More preferably, the acid will be selected from organic mono- or poly- carboxylic acids, e.g«» o_-phthalic acid, 4,5-dichlorophthalic acid, or inorganic acids, e.g., phosphoric acid, and the like. Special mention is made of o_-phthalic acid or phosphoric acid.

Other preferred features of the invention include carrying out the process at a pressure in the range of from about atmospheric to (1500 psi) 105 kg/ cm , and especially preferably from( 300-1200 psi) 21-84 kg/cm . Another preferred feature is to carry out the process at a temperature between about 25 C. and 200°C, and especially preferably in the range of 70-150°C.

O PI_

Suitable substrates in the present process are any aliphatic or cycloaliphatic compound having at least one ethyl enic carbon-to-carbon bond. Thus the reaction is useful for the hydroformylation of olefins having, for example, from 2 to 20 carbon atoms to reaction mixtures comprising aliphatic aldehydes and/or alkanols having one more carbon atom than the starting olefin. The invention is used to advantage in the hydroformylation of carbon- to-carbon ethyl enically unsaturated linkages in hydrocarbons. Monoolefins such as ethylene, propylene, butyl ene, penteπes, hexenes, hepteπes, octenes, dodecenes, their ho ologs, etc., are few examples of suitable hydrocarbons. Suitable hydrocarbons include both branched- and straight-chain compounds having one or more ethyl enic or olefinic sites. These sites may be conjugated, as in 1,3-buta- diene, or non-conjugated, as in 1 ,5-hexadieπe. In the case of polyolefins, it is possible to hydroformyl te only one or the olefinic sites or all of the sites. The unsaturated carbon- to-carbon olefinic linkages may be between terminal and their adjacent carbon atoms, as in 1-hexene or 1-decεne, or between internal chain carbon atoms, as in 4-octene.

Hydroformyl tion of macromolecular materials involving acyclic units of the above types such as polydi olefinic like polybutadiene as well as copolymers of olefins and diolefins like the styrene-butadiene copoly er, is also contemplated by this invention. Hydrocarbon cyclic compounds, e.g., cyclo- pentene, cyclohexεne, and the like and equally suitable.

Special mention is made of the use of the process to hydroformylate ethyl enic carbon- to carbon linkages of non- hydrocarbons. It is possible to hydroformylate olefinically unsaturated alcohols, aldehydes, acids, esters, and the like, to obtain corresponding alcohols, aldehydes, acids, esters, and the like, containing an aldehyde or hydroxy group on one of the

carbon atoms previously involved in the olefinic bond of the starting material.

Illustrative olefinic compounds which can be employed as rεactaπts include ethylene, propylene 1-butene, 1-penteπε, 1-hexεne, l-hepteπe,l-octene, 1-decene, 1-dodecεne, 1-octa- decεnε, 2-ethyl -1 -hexene , styrene, 3-phenyl- -propene, ally! chloride, 1 ,4-hexadiene, 1 ,7-octadiene, 3-cyclohexyl-l-butene, ally! alcohol, hex-l-en-4-ol , oct-l-en-4-ol , vinyl acetate, ally! acetate, 3-butenyl acetate, vinyl propionate, ally! propionate, ally butyratε, methyl methacrylate, 3-butεnyl acetate, vinyl εthyl εthεr, vinyl methyl ethεr, all l ethyl ether, n- propyl 7-octenoate, 3-butεhic acid, 7-octenoic acid, 3-buteneni- trile, 5-hexenamide, acrolein and the like. Preferred olefinic compounds include alkenes, alkyl alkεnoatεs, alkenyl alkanoates, alkεnyl alkyl ethers, and alkenols, especially those which con¬ tain up to 20 carbon atoms. Preferred olefinic unsaturated compounds are alkenes and/or alkenols of from 2 to 20 carbon atoms. Special mention is made of 1 -hexene, 1-decεnε and allyl alcohol . Any conventional hydroformylation catalyst known in this art is suitable for the present process. However, it is preferred to use a catalyst comprising a metal selected from rhodium, ruthenium, cobalt, platinum or mixtures of any of the foregoing, alone or in complex combination with carbon monoxide. It is also preferred to carry out the process with a catlayst which also includes triorgano-containing ligands such as the tri alkyl phosphites, the tri cycloalkyl phosphites, the tri aryl phosphites, the triarylphosphines, the triarylstibines, and the tri aryl arsines. Desirably each organo radical in the 1igand does not exceεd 18 carbon atoms. The tri aryl phosphites and the triarylphosphines represent the preferred classes of ligands. Specific examples of ligands which are suitable in

_QMPI_

Ay f _ _^ WIiPpoO ^~ ~ ^ ,- ^'

forming the complex catalysts incl ude tri methyl phosphite, tri- ethy 1 hos phi te , but l di ethyl phosphi te , tri -n-propy 1 phosph i te , tri -n-butyl phosphite , tri-2-ethylhexyl phosphite, tri-n-octyl- phosphite, tri -n-dodecyl phosp ite , tri phenyl phosphite, tri- πaph thy I phosphite , tri phenyl phosp ine , tri (p-chlorophenyl ) phosphite, tri -naphthyl phosphine, phenyl di phenyl phos phi nitε, di phenyl phenyl phosphoπite, di phenyl ethyl phos phonitε, tri- phenyl arsiπe, tri pheiiylsti bine, tris (p-chlorophenyl )-phosphine, tri (p _^ cya no phenyl )phosphitε, tri (p-methoxypheny )-phosρhite, εthyl di phenyl phos phinite, and the l ike.

Especially preferred triorgano l igands comprise a trial kyl phosphite , a tri cycl oal ky phos hi te, a tri aryl phosphite, a tri ryl phosphine, a tri aryl sti bine , a triaryl arsinε or a mixture of any of the foregoing. Special mention is made of a catalyst comprising a rhodi um carbonyl /tri aryl phosphine comples , particularly where tri aryl phosphine is tri phenyl phosphi ne.

The acid employed to suppress hydrocarbon formation can be present during formation of the hydroformylation catal¬ yst, or it can be added after the catalyst i s formed, either be- fore or during the addition of the unsaturated ol efinic substrate.

The process of this invention may be carried out from

2 about atmospheric pressure up to ( 10 ,000 psi g) 703 kg/ cm or

₂ even higher. However, preferably from about (300 psig)21kg/cm

2 to (1200 psig)84 kg/cm will be used. The process may be effected at temperatures ranging from about 10°C. to about 250 C but, it will be preferably in the range of from about 25°C. to

200°C, and most prefεrably to the range of from about 70°C. to about 150°C.

Thε temperature and pressure can be varied within a given reaction so as to improve the efficiency of the hydro¬ formylation of the olefinic starting materials to valuable oxygenated product or products. The ratio of hydrogen to carbon monoxide employed in the present invention may be varied widely. While mole ratios of hydrogen to carbon monoxide as high as 10 or even higher and as 0.1 and even lower may be employed, the preferred ratios are in the range of from about 0.3 to about 2. A more preferable molar ratio of hydrogen to carbon monoxide is in the range of from about 0.8 to about 1.5.

The unsaturated olefinic substrate may also serve as a solvent as well as co-reactant. However, an inert solvent may also be employed to advantage in the disclosed process. For example, a wide variety of solvents, e.g., aromatic and ali¬ phatic hydrocarbons, esters, ethers, nitriles, halogena ed ^• hydrocarbons and the like, including bεnzene, hexane, toluene, esitylene, xylenε, cyclohexane, ethyl acetate, tεtrahydrofuran, chlorobenzene, methylene chloride, acεtonitrile and the like and mixtures thereof may be employed.

The process may be carried out batchwise or on a continuous jor semicontinuous basis. Typically in a continuous or semi- continuous Proce s, the unsaturated organic compound _. is supplied to a reactor in which the temperature and pressure conditions for reaction are already established. The reactor will also contain the solvent and the catalyst. The products can be isolated by distillation, and the catalyst can be recycled to the reactor in the distillation residue.

Such techniques are well known to those of ordinary skill n the art.

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Description of the Preferred Embodiments.

The following examples are set forth to illustrate the present invention. They are not to be construed to limit the claims in any manner whatsoever.

Example 1 Hydroformylation of l-Hexεne in the Presence of 2-Phthalic Acid.

A 300 cc Autoclave Engineers Magnedrivε autoclavε is charged with 50.0 grams of 1-hεxane (594 m ol), 9.6 grams of tri phenyl phosphine (36.6 mmol), 2.9 grams of _-phthalic acid (17.5 mmol), 0.201 grams of hexarhodium hexadecacarbonyl (0.189 mmol, 1.13 eq Rh), and 75 ml of toluene. The mixture is sub¬ jected to 1450 psi of 2:1 H ₂ /C0 and heated to 100°C, the tε pera- turε at which thε exothεrmic rεaction is sεlf-sustaining. Gas is takεn up and rεplenished (1:1 H ₂ /C0) at 900-1450 psi. In 30 minutes at 100°C total gas uptake corresponds to 2700 psi. Quantitative VPC analysis of thε rεaction products shows thε presence of 48,3 grams of n_-heptanal (77% yield), 13.2 grams of 2-methy hexanal (22% yield), and about 0.5 grams of hexanε (1% yiεld). In a duplicate experiment, the yields of these three products are 74%, 25% and 1%, respectively.

Comparative Procedure A Hydroformylation of 1-Hexene in Absence of o-Phthalic Acid.

The procedure outlinεd abovε is followed, but with ormrission of the o_-phthalic acid catalyst component. The exothermic reaction is self-sustaining at 95°C in this case. Quantitative VPC analysis of the reaction products shows the prεsεnce of 40.7 grams of n_-heptanal (60% yield), 14.2 grams of 2-mεthyl- hexanal (21% yield), and 9.7 grams of hexane (19% yield). In a duplicate experiment the yields of these three products are 64%, 18% and 18% rεspεctively.

It can be seen that the presence of -phthalic acid markedly supprεssε≤ double-bond hydrogenation.

-11-

Examole 2 Hydroformylation of 1-Dβcene in the res nce of o-Phth;. lir Arid

Example 1 is repeatεd with 50.0 grams of 1-dεcεnε (356 -mmol) substitutεd for the 1-hexεne, and using _-phthalic acid according to this invention. Analysis of the products of the 5 reaction shows the presence of 38.1 grams of n_-undecanal (53% yield), 7.9 grams of 2-methyl -decanal (13% yield), 10.5 grams of what is tentatively identified as 2-decenε (on the basis of its ir and mass spectra) (21% yield), and only 1.6 grams of decane (3% yield) . 10 Comparative Procedure B

Hydroformylation of l-Oecene in Absence of o-Phthalic Acid.

The procedure of Example 2 is repeated, omitting the o- phthalic acid. The products in this case are 41.4 grams of rπundecanal (68% yield), 12.9 grams of 2-methyl decanal (21% 15 yield), and 5.5 grams of decane (11% yield).

Again, it can be seen that the presence of _-phthalic acid markedly suppresses double-bond hydrogenation.

Example 3 Hydroformylation/Tetrahvdrofuranylization of Allyl Alcohol 20 in Presence of o-Phthalic Acid.

The autoclave is charged with 50.0 grams of allyl alcohol (861 mmol), 9.6 grams of tri phenyl phosphine (36.5 mmol), 2.9 grams of o-phthalic acid (17.5 mmol), 0.201 grams of hexarhodium hexadecacarbonyl (0.189 rr-nol , 1.13 eq Rh), and 75.0 grams of 25 methanol (2.34 mole). The mixture is subjected to 1350 psi of 2:1 H ₂ /C0 and heated at 105°C for 30 minutes, with gas taken up and replenished (1:1 H ₂ /C0) at 700-1350 psi. Direct VPC analy¬ sis of the reaction products shows that 2-methoxytetrahydrofuran is the major product and that only 2.2 grams of jv-propanol 30 (4% yield) is formed.

Comparative Procedure C Hydroformylatioπ/Tetrahydrofuranylization of Ally! Alcohol in Absεπcε of o-Phthalic Acid.

For purposεs of comparison, thε procedure of Example 3 is repεatεd, but with omission of the o_-phthalic acid. ^' Gas uptake is sustained in this case at 90°C. Direct VPC analysis of the products shows that presεncε of a small r amount of 2- ■ ethoxytetrahydrofuran, the branched oxo product 2-(hydroxy- mεthyl) propionaldehyde, and several other higher-and lower- boiling components. Phthalic acid has. a pk a, of 2.89(K, i), and a dissociation constant of 1.3 x 10 ^" in aqueous solution. This level of acid strength is pπ_f<_rr-d for the co-catalysis function as described.

Obviously, minor variations will suggest themselves to those skilled in the art in view of the above- identified description. For examplε, if othεr olεfiπic substrates such ^' as alkenes, methacrylate esters and styrene are employεd, by-product formation duε to olεfinic hydrogenation will be suppressed. Moreover, substituted phthalic acids or other di- carboxylic acid and their derivatives, esters and half esters of phthalic acid, metal phthalates, di-phthalate salts, phthalic 'anhydrides and related πahydrides will be useful. All such obvious modifications are within the full intended scope of the appended claims.