Palladium phosphine complexes for the telomerization of butadiene

Production of 1-octene via telomerization of butadiene typically occurs when methanol is present with a palladium-phosphine based catalyst in a three step process. In step 1, telomerization of butadiene yields 1-methoxy-2,7-octadiene (MOD-1). In step two, hydrogenation of MOD-1 yields methyloctylether. In step three, methyloctylether undergoes ether cleavage to yield 1-octene and methanol.

A catalytic telomerization combination of a palladium (Pd) salt and triphenylphosphine (TPP) provides less than desirable results in terms of 1-octene yield. This appears to be due, at least in part, to side reactions that lead to formation of 3-methoxy-1,7-octadiene (MOD-3) and 1,3,7-octatriene.

Those who produce 1-octene via butadiene telomerization desire a telomerization catalyst with higher productivity in terms of kilogram (kg) of MOD-1 produced per gram (g) of Pd catalyst largely because of Pd cost.

Skilled artisans recognize from the teachings set forth in European Patent publication (EP) 461222 and EP 561779 that aryl-phosphine ligands with ortho-methoxide substituents tend to enhance selectivity to MOD-1 over side reaction products such as MOD-3 and 1,3,7-octatriene. The increased selectivity is offset by lower Pd complex stability as evidenced by at least one of lower catalyst productivity and increased Pd losses (e.g. via precipitation), especially as methanol (MeOH) concentration increases.

U.S. Pat. No. 7,425,658 (Edwards) discloses a method for producing 1-octene from butadiene by dimerizing and alkoxylating butadiene in the presence of one or more alkoxy substituted phosphine ligands under alkoxydimerization conditions with an alkoxydimerization catalyst. Illustrative phosphine ligands include tris-(2,4,6-trimethoxy phenyl) phosphine and tris-(4-methoxyphenyl) phosphine.

U.S. Provisional Patent Application (USPPA) 61/088,186, filed 12 Aug. 2008 (Briggs et al.) teaches telomerization of 1,3-butadiene in the presence of an organic hydroxy compound, a palladium catalyst and a phosphine ligand. Illustrative phosphine ligands include tris-(2-methoxyphenyl)phosphine, tris-(2,4-dimethoxyphenyl)phosphine, bis-(2-methoxyphenyl)phenylphosphine, tris-(2-methoxy-4-fluorophenyl)phosphine, and tris-(2-methoxy-4-chlorophenyl)phosphine.

U.S. Pat. No. 7,026,523 (Röttger et al.) provides a method for telomerizing non-cyclic olefins that includes use of a palladium carbene complex as a catalyst.

In some aspects, this invention is a phosphine ligand suitable for use in Pd-catalyzed telomerization of butadiene to MOD-1. The phosphine ligand comprises two phenyl groups, a xanthene, the xanthene having an oxygen atom incorporated into a rigid ring structure consisting of two aromatic rings, and a linking phosphorous moiety, the ligand being represented by a formula as follows:

wherein, R 1 are the same and are each H, linear, branched or cyclic C 1 C 20 alkyl, C 6 -C 18 aryl, C 1 -C 20 alkoxy or polyether. All R 3 are the same of dissimilar, and are each H, linear, branched or cyclic C 1 -C 20 alkyl, C 6 -C 18 aryl, halogen, trifluoromethyl, C 1 -C 20 alkoxy, or C 1 -C 20 dialkylamino. X is a bridging moiety consisting of either a dimethyl-substituted carbon (—CMe 2 -) or silicon (—SiMe 2 ) atom.

In some aspects, this invention is a process for synthesizing the xanthene-containing phosphine ligand, the process comprising sequential steps a) monobrominating a xanthene, b) lithiating the monobrominated xanthene, and c) effecting nucleophilic substitution of the lithiated, monobrominated xanthene using a phosphine. Recovery of the ligand occurs via conventional technology, e.g. filtration and solvent removal. Preferred reactants include 2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene as the xanthene and chlorodiphenyl phosphine as the phosphine.

In some aspects, this invention is a process for producing 1-octene which comprises steps: (i) reacting 1,3-butadiene with a primary aliphatic alcohol or aromatic hydroxy compound having formula R—H, in the presence of a telomerization catalyst comprising palladium and a phosphine ligand represented by the above formula to form a 1-substituted-2,7-octadiene of formula CH 2 ═CH—CH 2 —CH 2 —CH 2 —CH═CH—CH 2 —R, in which R represents a residue of the primary aliphatic alcohol or aromatic hydroxy compound; (ii) subjecting the 1-substituted-2,7-octadiene formed in step (i) to hydrogenation in the presence of a hydrogenation catalyst to form a 1-substituted octane of formula CH 3 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —CH 2 —R; and (iii) decomposing the 1-substituted octane formed in step (ii) in the presence of a suitable catalyst to form 1-octene. The primary aliphatic alcohol is suitably methanol or ethanol. The catalyst for step (iii) is desirably an alumina catalyst.

Processes for producing 1-octene from a telomerization product mixture comprising the 1-substituted-2,7-octadiene are known; see e.g., U.S. Patent Application Publication 2005/0038305 and U.S. Pat. No. 7,030,286.

Step (i) preferably occurs in a reaction fluid that comprises the 1,3-butadiene, the hydroxy compound, and the telomerization catalyst. The reaction fluid may further comprise one or more optional component(s), such as an organic solvent, a catalyst promoter, a catalyst stabilizer, or a butadiene polymerization inhibitor. The phosphine ligand is preferably present in an amount sufficient to stabilize palladium. The amount advantageously provides an initial ligand to palladium ratio of at least 1.0, preferably at least 1.5. The initial phosphine ligand to palladium ratio is advantageously less than 50, and preferably less than 40.

The process for producing 1-octene can employ any palladium catalyst or catalyst precursor known in the art, e.g. palladium metal, a palladium(II) compound, a palladium(0) complex, or a mixture thereof.

The process for producing 1-octene advantageously occurs under an inert atmosphere, such as nitrogen, argon, or helium, and at a reaction temperature sufficient to produce the 1-substituted-2,7-octadiene. The reaction temperature is preferably greater than (>) 40° centigrade (° C.), more preferably >50° C., and still more preferably >60° C., and is preferably below (<) 120° C., more preferably <110° C., and still more preferably <100° C.

When ranges are stated herein, as in a range of from 2 to 10, both end points of the range (e.g. 2 and 10) and each numerical value, whether such value is a rational number or an irrational number, are included within the range unless otherwise specifically excluded.

The term “comprising” and derivatives thereof does not exclude the presence of any additional component, step or procedure, whether or not the same is disclosed herein. In order to avoid any doubt, all compositions claimed herein through use of the term “comprising” may include any additional additive, adjuvant, or compound whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, “consisting essentially of” excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term “consisting of” excludes any component, step or procedure not specifically delineated or listed. The term “or”, unless stated otherwise, refers to the listed members individually as well as in any combination.

Expressions of temperature may be in terms either of degrees Fahrenheit (° F.) together with its equivalent in ° C. or, more typically, simply in ° C.

Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percents are based on weight.

For purposes of United States patent practice, the contents of any patent, patent application, or publication referenced herein are hereby incorporated by reference in their entirety (or the equivalent US version thereof is so incorporated by reference) especially with respect to the disclosure of synthetic techniques, definitions (to the extent not inconsistent with any definitions provided herein) and general knowledge in the art.

Descriptions and examples serve to illustrate, rather than define or limit, this invention in any way and do not constitute an exhaustive or all-inclusive listing of all possible embodiments of this invention. To those skilled in the art, other embodiments within the scope of appended claims will be apparent, from consideration of the specification and/or practice of the invention as disclosed herein.

Ligand synthesis occurs via a multi-step process. In step one, monobrominate a xanthene, preferably 2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene. In step two, lithiate the monobrominated xanthene. In step three, effect nucleophilic substitution of the monolithiated xanthene using a phosphine, preferably chlorodiphenylphosphine. In step four, effect ligand recovery, e.g. by filtration and solvent removal.