1. Field of the Invention
The present invention relates to a process for the preparation of n-octadienols by dimerization and hydration of butadiene in the presence of a catalyst and of water.
2. Description of the Related Art
Many processes using such a hydrodimerization and leading to a mixture of octa-2,7-dien-1-ol and octa-1,7-dien-3-ol have been described in the prior art.
Octa-2,7-dien-1-ol is advantageous, in particular, as an intermediate for its hydrogenation to n-octan-1-ol, a product which is used in particular for the manufacture of plasticizers such as di-n-octyl phthalate.
French Patent 2,045,369 (which is a counterpart of GB 1,307,101A) describes a process for the preparation of these octadienols.
When the process of FP 2,045,369 is put into practice, a reaction mixture containing 1,3-butadiene, water and a solvent in which the butadiene and water are at least partially soluble is formed in the presence of a catalyst containing transition metal (palladium or platinum) compounds and a phosphine and of a cocatalyst consisting of carbon dioxide. The phosphine is chosen from known, water-insoluble compounds such as trialkylphosphines, triarylphosphines or tertiary alkylarylphosphines.
The solvent is chosen from dialkyl ethers, cyclic ethers, lower alkyl ethers of polyalcohols or of polyoxyalkylene glycols, alkyloxy- and aryloxypolyalkenoxyalcohols, ketones, amides, pyridine derivatives, sulphoxides, sulphones such as sulpholane, esters, aromatic solvents, aliphatic hydrocarbons or olefins.
Compounds known for reacting with the metal can be added to the reaction mixture. These compounds can be used as additional protection for preventing the deposition of metal during the reaction and during the subsequent treatment for the preparation of the catalyst with a view to recycling.
These compounds are listed in a list of more than 50 nitrogen-containing products comprising, inter alia, trimethylamine, triethylamine, tri-n-octylamine and dimethyldodecylamine.
Tests No. 11, 12 and 17 of Table VII of the abovementioned patent, carried out in the presence of acetone and with or without triethylamine, the other factors remaining constant, show that the addition of triethylamine reduces both the octadienols yield, which falls from 75% to 70% and then to 42%, and also the selectivity of the formation of octa-2,7-dien-1-ol with respect to octa-1,7-dien-3-ol (89/11, 76/24, 73/27). On the other hand, the yield of octatriene, an undesired byproduct, increases and rises from 2% to 9% and then to 15%.
No experimental test using dimethyldodecylamine is described, and nothing suggests that this amine would be less unfavorable than triethylamine.
French Patent 2,366,237 (which is a counterpart of U.S. Pat. Nos. 4,142,060, 4,219,677, and 4,260,750) describes a family of water-soluble tertiary arylphosphines of general formula (A): ##STR2##
This solubility is brought about by the presence of at least one sulphonate group, M being a cationic residue of inorganic or organic origin.
This patent discloses a process for the hydrodimerization of butadiene in the presence of water and of a catalyst consisting of at least one of these soluble phosphines and of a transition metal in the metal form or in the form of a compound of the said metal chosen from Pd, Ni, Pt, Co or Rh, the said catalyst dissolving in the said water.
In order to considerably accelerate the reaction between butadiene and water, certain water-soluble compounds are added. These are alkali metal carbonates and bicarbonates, such as sodium carbonate and bicarbonate, sodium silicate and alkali metal salts of phosphorous, phosphoric and arsenic acid.
This process can also be implemented in the presence of aliphatic or aromatic tertiary amines.
Examples 7 to 16, relating to the synthesis of octadienols, without the presence of either tertiary amine or of solvent, show, Example 10 being the best, a degree of conversion of 76% and a selectivity of 64% towards octa-2-7-dien-1-ol and of 20% for octa-1,7-dien-3-ol from the butadiene consumed, i.e. a 1-ol/(1-ol+3-ol) selectivity equal only to 76% (100.times.64/84).
French Patent 2,479,187 (which is a counterpart of U.S. Pat. No. 4,356,333) proposes a process for the synthesis of n-octadienols in which butadiene and water are reacted in an aqueous sulpholane solution having a water/sulpholane ratio by weight with a value of 20/80 to 70/30 and containing carbonate and/or bicarbonate ions in the presence of:
(1) palladium or of a palladium compound; PA0 (2) a unidentate phosphine of formula (B) ##STR3## with the meanings of the terms as shown in this patent; and (3) a unidentate tertiary amine having a basicity constant (pKa) of 7 or more, in an amount of 1 to 50% by volume based on the sulpholane. PA0 HCO.sub.3.sup.-, CO.sub.3.sup.2-, HSO.sub.3.sup.-, SO.sub.3.sup.2-, SiO.sub.3.sup.2-, PA0 PO.sub.4.sup.3-, HPO.sub.3.sup.2-, AsO.sub.4.sup.3-, SO.sub.4.sup.2-, HSO.sub.4, RSO.sub.3.sup.-, RCO.sub.2.sup.- and OH.sup.-, PA0 wherein R is an alkyl group; said reaction being carried out in the presence of carbon dioxide.
This patent shows that butadiene can be replaced by a "C.sub.4 fraction" but that preferably a butadiene of polymerization quality or a butadiene of chemical reaction quality are reacted, in view of the reaction rate and of the ease of recovery of the unreacted butadiene.
It is specified in French Patent 2,479,187 that useful unidentate amines comprise (lower) trialkylamines such as trimethylamine, triethylamine, tri-n-propylamine or tri-n-butylamine. Triethylamine is preferred on the basis of the yield of the reaction and of its intrinsic properties such as boiling point, solubility and cost.
Examples 3 and 7 of Table 2 of FR 2,479,187 show that the replacement of triethylamine by tri-n-propylamine causes a lowering in octadienols yield.
The presence of sulpholane in this process is a compromise between the advantages and the disadvantages brought about by this presence. In fact, it is shown that a sulpholane concentration of less than 30% by weight gives a significant reduction in the reaction rate. This is illustrated by Example 14 of this same Table 2 which shows that, in the presence of a water concentration of 90% by weight and of triethylamine, the amount of octadienols obtained from 25 g of butadiene (462 mmol) is only 1 mmol.
On the other hand, a sulpholane concentration exceeding 80% by weight leads not only to a reduction in the efficiency of extraction of the octadienols from the reaction mixture after the end of the reaction but also to an increase in the amounts of palladium and phosphine dissolved in the organ extraction phase and to an increase in the amounts of reaction byproducts.
Patent Application EP 0,296,550 (which is a counterpart of U.S. Pat Nos. 4,927,960, 4,992,609 and 5,100,854) discloses a process for the preparation of n-octadienols which is similar to the above, in which the unidentate phosphine of general formula (A) is replaced by a phosphonium salt of general formula (C): ##STR4## the substituents R1 to R6 having the meanings shown in this above application, x representing a hydroxyl, hydroxycarbonyloxy or lower alkylcarbonyloxy group.
This process is implemented with a reaction mixture containing a solvent, in particular sulpholane, and as shown in Examples 7 to 11 and 14 and 15, triethylamine and carbon dioxide.
Patent Application EP 0,411,410 (which is a counterpart of U.S. Pat. No. 5,043,487) dealing with the reaction of 1,3-butadiene with water in the presence of a triorganophosphine oxide, states that an economically very advantageous way of carrying out this reaction comprises using C.sub.4 cuts in place of pure butadiene. The olefins 1-butene, 2-butene and isobutene additionally contained in the C.sub.4 cut neither take part in the reaction nor are detrimental to it.
The C.sub.4 cuts contain, by weight, approximately 45% of 1,3-butadiene, 17% of 1-butene, 10% of 2-butene, 25% of isobutene, the remainder being butane and isobutane.
Patent Application EP 0,436,226 (which is a counterpart of U.S. Pat. No. 5,118,885) teaches that the processes disclosed by U.S. Pat Nos. 4,356,333 and 4,417,079 have disadvantages during their continuous implementation on the industrial scale.
In fact, the components of the catalyst, namely palladium, phosphine, tertiary amine and also the solvent (sulpholane), are eluted in the extract obtained during the separation by extraction of the octadienols from the reaction mixture. When this extract is distilled, the palladium metal precipitates and finishes by fouling the distillation reboiler.
The technical solution proposed in this prior art consists in replacing the phosphine by a phosphonium salt of general formula (C) and in carrying out washings of the organic extraction phase with an aqueous sulpholane solution containing a water-soluble phosphine. This latter treatment complicates the industrial process for the synthesis of 1-octadienol.
An object of the present invention is to find an industrial process for the preparation of octadienols with a degree of conversion and/or an octadienols yield and/or selectivities towards octadienols and octa-2,7-dien-1-ol which are in the region of or higher than those of the prior art by using a particularly stable catalyst which is easy to recycle.