Distillation: processes – separatory – Plural distillations performed on same material – One a distillation under positive pressure or vacuum
Reexamination Certificate
2000-02-11
2002-07-16
Manoharan, Virginia (Department: 1764)
Distillation: processes, separatory
Plural distillations performed on same material
One a distillation under positive pressure or vacuum
C203S077000, C203S080000, C203S088000, C568S905000, C568S913000
Reexamination Certificate
active
06419797
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing high-purity Guerbet alcohols by condensation of primary and/or secondary alcohols having 2 to 30 carbon atoms in the presence of one or more alkaline catalyst(s) and/or one or more heavy metal catalyst(s).
2. Description of the Prior Art
Guerbet alcohols are known compounds used as base materials for a large number of applications, e. g. in the cosmetic, pharmaceutical, textile and lubricants industries.
Guerbet alcohols can be produced by condensation of primary and secondary alcohols in the presence of strong alkali bases according to the following reaction scheme:
There exist a large number of catalyst systems based on alkali/alkaline earth salts in the presence of heavy metals as co-catalysts.
Among alkaline catalysts, alkali metals, alkali metal hydroxides, alkali metal oxides and alkali metal alcoholates are known. Furthermore, there have been described combinations, such as KOH with ZnO. However, such combinations often have specific disadvantages (see e. g. Soap/Cosmetics/Chemical Specialties, pages 52-55 and 115, April 1987).
Among heavy metals as co-catalysts, there have been described ZnO, PbO, NiO, Pd, Ti and Zr compounds. A large number of useful co-catalysts have been described in German Patent Specification DE 24 00 326. According to German Patent Specification DE 26 34 676, insoluble salts of the group of lead silicates, lead titanates, and lead zirconates(IV) in the presence of alkali bases can also be used as catalysts.
In addition, known co-catalysts are those based on ZnO and insoluble lead salts of the group of lead silicates, lead titanates, and lead zirconates(IV). The lead salts may have discretionary ratios of PbO to SiO
2
, TiO
2
, or ZrO
2
resulting in different basicities of the co-catalysts.
Furthermore, it is known to use heterogeneous catalyst systems, e. g. those consisting of platinum supported on activated carbon having a large surface and potassium or sodium hydroxide.
Although suitable catalyst systems can significantly increase rate and yield of the alcohol reaction providing Guerbet alcohols, the heavy metal salts used require careful separation and disposal because of their detrimental effect to the environment.
There exists yet another problem, that is the crude product obtained by Guerbet reaction normally contains by-products, such as aldehydes, unsaturated compounds and, especially, soaps in different quantities. It is particularly important that the soaps contained in the reaction mixture which are soluble and insoluble at room temperature be separated after the reaction is complete. Said soaps are usually separated by washing with partially acidified aqueous solutions, e. g. 6% sodium chloride solution (DE A1 26 34 676). This treatment produces large quantities of waste water also containing the heavy metals. Subsequent precipitation and separation of said heavy metals used as catalysts or co-catalysts will involve considerable costs. Moreover, using aqueous solutions for this washing treatment has another disadvantage, that is waste water having a high content of organic materials will be obtained and, additionally, the Guerbet alcohols yield will decrease. A theoretical solution to this problem would be using a solid carrier, e. g. activated carbon, for the co-catalysts which can be separated by filtration after the reaction is complete. In practice, however, the supports were found to undergo mechanical and chemical decomposition during the reaction so that complete separation by simple filtration will not produce the desired result. Furthermore, the production of supported co-catalysts instead of employing the transition metal salts and oxides commonly used would result in considerably higher costs.
In order to avoid the problems mentioned hereinabove, it has been suggested in DE 195 31 714 to eliminate the soaps which are difficultly soluble at room temperature by filtration, centrifugation and/or extraction and subsequent distillation. However, the filter cake produced during filtration will increase the amount of waste and the extraction with water will produce waste water having a high content of heavy metals.
SUMMARY OF THE INVENTION
It was the object of the present invention to provide an economic process for producing Guerbet alcohols, wherein waste water usually obtained during conventional purification is completely avoided and which yields metal- and soap-free products.
The subject matter of the present invention is a process for producing high-purity Guerbet alcohols, particularly soap- and heavy metal-free Guerbet alcohols, by condensation of primary and/or secondary alcohols having 2 to 30 carbon atoms in the presence of one or more alkaline catalyst(s) and/or one or more heavy metal catalyst(s), wherein the reaction product is directly split up by distillation, i. e. without any different intermediate purification steps, yielding product alcohol and educt alcohol (starting alcohol), if any, on the one hand and catalyst/catalyst mixture and higher-molecular products, if any, on the other hand, and in which the reaction product can be removed batchwise or continuously from the reaction space.
The reaction product is directly led to the distillation stage without any preceding washing, filtration, centrifugation, steam distillation or other purification steps. The bottoms produced during distillation are highly viscous at room temperature and can readily be disposed of.
It was surprisingly found that according to the process of the invention it is possible to free the reaction mixture obtained by Guerbet reaction from heavy metal ions and alkaline catalyst residues in a simple and economic way by distilling the crude reaction product. Thus, no waste water is produced and loading of waste water with heavy metal ions is prevented. The co-catalysts used are commercially available heavy metal salts. It is not necessary to use any supported compounds. Furthermore, products not containing any heavy metals are obtained which is highly important when said products are to be used in pharmaceuticals and cosmetics.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to this invention, primary and/or secondary, linear or cyclic alkanols having 2 to 30 carbon atoms and alkanols having a methylene group in &agr;-position to the carbon atom bearing the hydroxyl group are reacted to yield the desired Guerbet alcohols which are essentially free from higher-molecular condensation products. Such alkanols used as educts can be represented by the general formula
wherein the residues R
1
and R
2
can be a hydrogen atom, an aryl residue or a straight-chain or branched alkyl group, and R
1
and R
2
can be the same or different. Favorable starting materials are those educts wherein R
1
represents an alkyl group and R
2
is a hydrogen atom, i.e. primary alkan-1-ols. Typical examples of said alkanols each having a terminal OH function are ethanol, propanol, isopropyl alcohol, butanol, pentanol, hexanol, octanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, octadecanol, eicosanol, docosanol, tetracosanol, hexacosanol, octacosanol, and triacontanol, and, furthermore, secondary alkanols, such as 4-methylpentan-2-ol, hexan-2-ol, octan-2-ol, cyclopentanol, cyclohexanol and the corresponding isomers of the primary alkanols mentioned hereinabove.
The educts mentioned hereinabove can be synthetic products, e. g. Ziegler alcohols or oxoalcohols, or natural products. Particularly preferred starting materials are straight-chain primary alkanols having 6 to 22 carbon atoms. Typical examples are caproic-, oenanthic-, capryl- pelargonic-, caprinic-, lauryl-, myristyl-, cetyl-, stearyl-, arachidyl-, and behenyl alcohol.
Said starting materials can also be used as technical-grade mixtures with other alcohols which is common practice in fats chemistry.
Suitable catalysts for the process of the invention are those known in the art. Among alkaline catalysts, the oxides, hydroxides, and alcoholates of the alkal
Herrmann Albert Thomas
Letsch Hans-Jürgen
Scherf Erich
Schröder Clemens
Browning & Bushman P.C.
Manoharan Virginia
Sasöl Germany GmbH
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