WO1991004242A1

WO1991004242A1 - Improved guerbet process

Info

Publication number: WO1991004242A1
Application number: PCT/US1990/005110
Authority: WO
Inventors: Joseph A. Miller; Michael Virnig
Original assignee: Henkel Research Corporation
Priority date: 1989-09-13
Filing date: 1990-09-11
Publication date: 1991-04-04

Abstract

An improved Guerbet alcohol process in which a starting alcohol is condensed in the presence of a base to provide a Guerbet alcohol having more carbon atoms than the starting alcohol. The improvements in the process include (a) the use of certain carbonyl compounds at temperatures of greater than 180 °C to initiate and promote the condensation reaction; (b) the use of certain carbonyl compounds after substantial completion of the reaction to again resume the reaction resulting in increased conversion to the Guerbet alcohol and (c) the use of alcohols, alkoxides and hydrides after completion of the reaction to reduce levels of contaminating compounds.

Description

IMPROVED GUERBET PROCESS BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improvements in the process of preparing Guerbet alcohols and particular to the use of certain compounds as initiators or promoters in the Guerbet reaction, such as certain carbonyl compounds (aldehydes or ketones) .

2. Description of Related Art

The Guerbet reaction as shown in equation 1 below is a well known process for the dimerization of fatty alcohols, yielding a l°-alcohol product with twice the carbon number of the original starting alcohol.

Base

2 RCH₂CH₂OH > R.CH₂CH₂CHCH₂OH + H₂0 (Eq . 1 ) Co-catalyst |

These branched primary alcohols (Guerbet alcohols) offer good oxidative stability, excellent lubricity and e olliency, and in addition, low order, color, and irritation properties. As a result, Guerbet alcohols find applications in cosmetics, pharmaceuticals, plastics additives, functional fluids and lubricants. While the Guerbet reaction can be carried out in some instances using a base (such as KOH) alone, typically a co- catalyst (ZnO, Ni, Rh, and many others) is added in order to accelerate the overall reaction rate. These metal- containing co-catalysts present potential problems of disposal, and discharge of heavy metals into the environment. However, without the co-catalysts, the reaction rate tends to be slow, adding to the overall cost of the reaction. The desired Guerbet alcohols obtained typically are contaminated with varying amounts of aldehydes and unsaturated compounds. Even relatively small quantities of these materials tend to impart undesirable odors to the

^* product, and render it prone toward discolorization and oxidation. In previous mechanistic studies concerning the Guerbet reaction, researchers have established the intermediacy of specific aldehydes, corresponding to either the starting alcohol substrate or the dimerized alcohol product, and have examined their fate in addition experiments. Bolle (Comptes rendue, Acad. Sci., Paris 233, 1628 (1951) demonstrated in 1951 that 2-ethylhexanal is an intermediate in the Guerbet reaction of 1-butanol, and is converted into the corresponding Guerbet alcohol, 2- ethylhexanol. In one experiment, the addition of 6 mole % of 2-ethylhexanal results in the formation of 10 mole % of 2-ethylhexanol, implying a catalytic role. The control experiment without added aldehyde is not reported, so it is unclear how much of the 2-ethylhexanal would have been formed anyway. But even if all the 2-ethylhexanal is attributed to the 2-ethylhexanal, the efficiency of the aldehyde is very low with a catalyst "turnover number" of less than 1.8.

In 1954, Pratt and Kubler (J. Am. Chem. Soc. !____, 52 (1954) also showed that aldehydes play a central role in Guerbet chemistry. They maintain that the conversion of starting alcohol to the corresponding aldehyde "serves primarily to initiate the process", and that thereafter the bulk of this aldehyde is produced by aldehyde/alcohol interchange reactions. However, in their experiment to prove this point by adding n-hexaldehyde to a Guerbet reaction of n-hexanol, the addition of 2 mole % of n- hexaldehyde gave no apparent reaction for 22 hours. When an additional 8 mole % of n-hexaldehyde was added, water was evolved over 12 hours and 11.8 mole % of 2-n- butyloctanol was recovered, equal to a catalyst "turnover number" of about 2.4. This low efficiency would lead one to believe that aldehydes could not be used in a catalytic fashion to achieve economically useful reaction rates and yields comparable to those realized with current commercial systems using the typical co-catalysts.

Viebel and Nielsen (Tetrahedron 2J3, 1723 (1967)), working at 130° and 160°C. , presented evidence pertaining to the importance of carbonyl compounds as intermediates in the "crossed" Guerbet reaction of benzyl alcohol and potassium lactate. They also added intermediate aldehydes to the Guerbet reaction, and state, "An increase of the yield of the final alcohol more than equivalent to the amount of aldehyde added was obtained, indicating that the chain reaction may be initiated by addition of aldehyde."

However, in spite of this observation, and although the authors cite both Bolle and Pratt references, they state that a catalyst able to tansfer hydrogen from one molecule to another, such as Raney-Ni, is essential for a good yield in the Guerbet reaction.

In 1961, Miller and Bennett (Ind. Eng. Chem. 5J3, 33

(1962)) studied the tripotassium phosphate catalyzed Guerbet reaction of n-butanol at temperatures of about

280°C. under pressures of 600-650 psi. They also cited the

Bolle and Pratt references, but reported that addition of several aldehyde intermediates (including butyraldehyde and

2-ethylhexanal) to the Guerbet reaction of 1-butanol in the absence of a co-catalyst did not significantly increase the yield of the 2-ethylhexanal product.

In 1985, Burk, et.al., (J. Mol. Cat. .33_., l (1985)) reported mechanistic studies on intermediates in the Guerbet reaction using a rhodium co-catalyst. They stated that the co-catalyst is required in only two steps of the reaction: formation of aldehyde from the starting alcohol, and reduction of the dimeric allylic alcohol intermediate; each of the other steps proceeds in the absence of co- catalyst. Since these other steps can lead all the way to Guerbet alcohol, they conclude, "in the absence of side reactions, once butyraldehyde is generated, dimer alcohol formation should continue unabated." However, their data does not suppport this hypothesis. When aldehyde intermediates where added to a sodium butoxide-catalyzed Guerbet reaction of butanol in the absence of a co- catalyst, they did not even give an equivalent amount of 2- ethylhexanal, much less catalyze a high conversion of other butanol molecules to the Guerbet product. Secondly, the dimeric allylic alcohol is shown to be a major intermediate, implying that the co-catalyst would be essential to obtaining good conversions to the Guerbet alcohol.

DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of the effect of initial reaction temperature on a 2 mole % decyl aldehyde promoted Guerbet reaction. Figure 2 is a graph of the effect of initial reaction temperature on a 5 mole % decyl aldehyde promoted Guerbet reaction.

Figure 3 is a graph comparing ZnO with decyl aldehyde as a catalyst for the Guerbet reaction at 230°C. Figure 4 is a graph comparing Guerbet reaction rates of 1-decanol using combinations of KOH, decanol and ZnO.

Figure 5 is a graph showing the influence of different carbonyl containing promoters on Guerbet reaction rate.

Figure 6 is a graph showing the influence of different carbonyl containing promoters on Guerbet reaction rate.

Figure 7 is a graph showing rates of water evolution in experiments illustrating the present invention. DESCRIPTION OF THE INVENTION Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about". It has now been discovered that (1) addition of aldehyde intermediates at sufficiently high temperatures will give reaction rates, yields, and product quality comparable or superior to those obtained using metallic co- catalysts, (2) addition of further aldehyde after normal Guerbet reactivity has ceased will cause continued conversion to product alcohol, and (3) these effects can be obtained even when the aldehyde catalyst is replaced with a wide variety of aldehydes and ketones unrelated to the normal intermediates of the Guerbet reaction. It has also been discovered that the amount or level of contaminating aldehyde present in the final Guerbet alcohol product can be reduced by treatment of the Guerbet reaction mixture (at the end of the reaction, prior to cooling) with the addition of an alcohol or a metal alkoxide. This makes possible the preparation of Guerbet alcohols containing lower carbonyl values than those previously reported in the art, without the need for modifying the reaction conditions or the catalyst employed. An improved Guerbet process has accordingly been discovered in which at temperatures above a certain level a wide variety of carbonyl-containing compounds, even those unrelated in structure to the starting alcohol substrate or structure, can initiate the Guerbet reaction and are highly effective as promoters for rate and conversion enhancement in the process. The carbonyl compounds can initiate the Guerbet reaction in the absence of the typical co-catalyst employed in the art, such as the ZnO, Ni, Rh and other metallic catalyst recognized by those skilled in the art, which the art teaches the function of such co-catalysts is to produce aldehyde from the starting alcohol. The carbonyl compounds in addition to being capable of initiating the reactions at the temperature employed, further promote the reaction providing increased rates of reaction and enhanced or increased conversion. While the typical metallic co- catalysts are not necessary and can be replaced by the carbonyl compounds, the carbonyl compounds may be employed in the reaction mixture employing such metal co-catalysts in view of their activity to provide or promote increased rates of reaction and increased yields.

The initiation of the reaction by the carbonyl compounds represents one aspect of the improved process, which may be employed alone in the process or in further combination with the other improvements in the process. As earlier noted generally another aspect of the invention is the discovery that once the Guerbet reaction has proceeded to substantial completion as evidenced by the apparent cessation of water production, the addition of a carbonyl compound to the Guerbet reaction mixture causes the reaction to resume once again, thus increasing the conversion of the starting alcohol to the corresponding Guerbet alcohol. The degree of conversion of starting alcohol into Guerbet alcohol can be even further enhanced by utilizing additional charges of carbonyl promoters each time the reaction slows or stops. The carbonyl compound acting as a promoter for enhanced conversion conveniently is an aldehyde corresponding to the intermediate aldehyde produced in the reaction leading to the Guerbet alcohol desired; however, it need not be the corresponding aldehyde and a wide varitey of aldehydes and ketones may be employed as the carbonyl promoter The last aspect of the present invention lies in the addition of certain alcohols or metal alkoxides to the reaction mixture once the reaction has ceased and prior to cooling and recovering the desired Guerbet alcohols. The addition of these alcohols or metal alkoxides provides for reduced aldehyde contaminating residues in the final Guerbet alcohol product. Unsaturated impurities in the Guerbet alcohol product can impart color, odor and stability problems.

Accordingly, the present invention is concerned with improvements in Guerbet process wherein an alcohol is condensed or dimerized to a branched primary alcohol, the improvement comprising adding to the reaction mixture a carbonyl compound in an amount effective to initiate the reaction and conducting the reaction of a temperature above 180°C. Preferably temperatures above 190°C are employed with the most preferred being above 200°C, at temperatures such as 220 to 260°C, with a temperature of about 230°C being particularly desirable for optimum performance.

The starting alcohols useful in the Guerbet reaction are the aliphatic, cycloaliphatic and araliphatic alcohols containing from 4 to 22, preferably 6-18 carbon atoms. These may be defined by the formula R^H where R₁ is an aliphatic, cycloaliphatic or araliphatic group having from

4 to 22 carbon atoms. Illustrative aliphatic alcohols are butanol, hexanol, the saturated, straight or branched chain alkanols, such as heptanol, octanol, decanol, dodecanol, tridecyl alcohol, octadecanol and the like. Illustrative cycloaliphatic alcohols are cyclohexanol and cyclohexyl ethanol. Illustrative araliphatic alcohols are those containing 7 or more carbon atoms, such as, benzyl alcohol, phenylethyl or phenylpropyl alcohols. The typical Guerbet reaction involve dimerization or self-condensation of a single alcohol. Condensation of two different alcohols is possible. However, as a practical matter the reaction of the self-condensation to provide an alcohol having twice the number of carbon atoms as the starting alcohol is preferred.

The preferred carbonyl compounds employed to initiate and promote the reaction are the aldehydes; however, other carbonyl compounds such as the ketones may be employed. Use of the aldehyde corresponding to the intermediate aldehyde produced during the reaction is particularly desirable as this may also be converted to the desired Guerbet alcohol. However, even those unrelated to the structure of the starting alcohol substrate may be employed. Thus, the aldehydes employed may be defined by the formula R-.CHO where R₂ is H, or an aliphatic, cycloaliphatic or araliphatic hydrocarbon group having from 1-22 carbon atoms, preferably 4 to 22 carbon atoms corresponding to the hydrocarbon group of the starting alcohol. Illustrative aldehydes, other than formaldehyde (paraformaldehyde) , but not limited thereto, are 2- ethylhexanal, decanal, dodecanal, tridecanal, isobutyraldehyde, acetaldehyde, propionaldehyde, butyraldehyde and benzaldehyde. The ketones which may be employed may be defined by the formula R₃-C(0)-R₄ where R₃ and R₄ which may be the same or different, are aliphatic or aromatic hydocarbon groups. The total carbon atoms in the ketone generally will not exceed 12 carbon atoms, and those ketones containing a lesser number of carbon atom will generally be employed, i.e. those containing from 3 to 8 carbon atoms. Those in which R₃ and R₄ are lower alkyl (1- 4C) groups such as methyl and ethyl, or a phenyl group, such as dimethyl ketone (acetone) , diethyl ketone and methylethyl ketone (butanone) may be employed with acetone being preferred.

The aldehyde or ketone may be merely added to the reaction mixture, at room temperature when the reaction is charged with the starting alcohol or it can be added at any temperature up to the reflux temperature of the reactants. If the aldehyde to be employed is the one corresponding to that produced in the reaction and having the structure of the starting alcohol substrate, a small portion of the starting alcohol feed may be oxidized outside of the Guerbet reaction medium in order to supply a sufficient level of aldehyde. Thus, the starting alcohol feed is introduced into the reactor after first passing through a heated bed of dehydrogenation catalyst under conditions which produce the required level of aldehyde. Where the aldehyde is also employed as a promoter of the reaction, a method of continuously producing aldehyde promoter throughout the entire Guerbet reaction may be employed wherein the alcohol condensate collected in a Dean-Stark trap, or its equivalent, is passed through a heated bed of dehydrogeneration catalyst before being reintroduced into the reactor.

As noted in the Guerbet reaction discussed earlier above, the reaction medium includes a base, such as potassium hydroxide, which is generally employed along with a metal co-catalyst. The potassium hydroxide forms an alkanolate with the starting alcohol and at the temperatures of reaction, alcohol condensation takes place leading to an alcohol with double the number of carbon atoms of the starting alcohol. While the Guerbet reaction has been illustrated with KOH, other alkali metal or alkaline earth metal hydroxides or alkoxides may be employed in conjunction with the carbonyl compounds, and where employed any metal complex co-catalysts. Typical metal complex co-catalyst which are employed are those complexes or salts containing a metal such as Al, Ni, B, Mg, Cu, Zn, Sn, Ti or Zr or the group VIII noble metals particularly Pt, Pd, Rh, Ir and Ru.

The amount of carbonyl compound added at the outset to initiate and promote the reaction is added in a small amount, typically several mole percent relative to the starting alcohol, up to 20 mole %. Generally it is not necessary to add more than 5 mole % at the outset. While only a small amount of carbonyl compound will promote the reaction, it is generally desirable from a practical standpoint to employ at least 0.5 and preferably at least 1 mole %. Depending on the amount employed, the rate of the Guerbet reaction can meet or exceed that observed by the typical metal co-catalysts employed in the past. Where metal containing co-catalyst are employed in the reaction along with the carbonyl compound, such co-catalyst may be employed at levels on the order of about 10^*5 to 10 weight %, and preferably on the order of about 10^"3 to 10^"1 weight %. Similarly, the amount of base, such as KOH, will be employed in amounts up to 10 mole %, typically at about 5 mole %. As the presence of base is required for the Guerbet reaction to proceed, the base will generally be present in an amount of at least 1%, preferably at least 2 or 3 mole %.

In the practice of the process, the materials (the alcohol, base, carbonyl compound, and co-catalyst, if any,) are charged to the reactor and the temperature raised to reflux. The amount of water formed is monitored and is an indication of the degree to which the reaction has proceeded. When the water evolution stops the reaction is complete and the reaction product, Guerbet alcohols and any contaminating impurities, are then cooled and removed for further processing and recovery. As noted earlier, another aspect of the present invention lies in the discovery that when the reaction is substantially complete, i.e. when water evolution slows or stops, a carbonyl compound (aldehyde or ketone) may be added to the reaction mixture, and the reaction resumes once again, thus increasing the conversion of starting alcohol to the corresponding Guerbet alcohol. The carbonyl compounds useful here are the same compounds discussed earlier. Each time the reaction slows or stops, additional quantities of carbonyl compound promoters may be added to further enhance the degree of conversion. The carbonyl compounds will generally be added at levels of 1 to 5 mole % based upon starting alcohol.

Accordingly, the present invention also resides in an improvement in the Guerbet process wherein after substantial completion of the reaction a carbonyl compound is added to the reaction mixture in an amount effective to resume the reaction, generally about 1 to 5 mole % based on starting alcohol, thereby providing enhanced conversion of starting alcohol to Guerbet alcohol. This improvement can be employed in a process wherein a carbonyl compound is added at the outset of the reaction to initiate and promote the reaction or may be employed in a process using other co-catalysts, such as the typical metal containing co- catalysts, with no addition of carbonyl compound at the outset.

A further aspect of the present invention is the reduction of contaminating impurities in the final Guerbet alcohol product. Accordingly, the present invention also resides in an improvement wherein after substantial completion of the reaction and prior to cooling of the reaction mixture and recovery of the Guerbet alcohol product, there is added to the reaction mixture, in an amount effective to reduce the level of contamination in the Guerbet alcohol product, an alcohol or alkoxide. In particular, the aldehyde contaminant level is reduced, thereby providing a product with lower carbonyl values than those previously obtained. This improvement can be practiced along with the other improvements discussed earlier namely (a) the addition of a carbonyl compound at the outset of the reaction to initiate and promote the reaction and (b) the addition of a carbonyl compound after substantial completion of the reaction to resume the reaction again thereby providing increased yield or conversion to the desired Guerbet alcohols, or may be used alone to improve the carbonyl values of the final product and improve the color, odor and stability thereof. The compounds which are added after completion of the reaction are selected from certain alcohols or alkoxides. Addition of inexpensive alcohols, such as isopropanol, have been found to reduce typical levels of aldehyde by-products from 0.4 mmole to less than, or about 0.1 mmole. The alcohols which may be employed include the aliphatic and cycloaliphatic alcohols which as methanol, ethanol, n- propanol, isopropanol, n-butanol, sec-butanol, isobutanol and cyclohexanol. Other aliphatic alcohols having up to 20 carbon atoms, and aromatic alcohols may be employed but are generally more expensive and lead to increased cost.

The alcohol may accordingly be defined by the formula R_gOH where R₅ is a hydrocarbon group containing from 1 to 20 carbon atoms, such as an aliphatic, aromatic, cycloaliphatic, or araliphatic group. The preferred alcohols are the aliphatic and cycloaliphatic alcohols having from 1 to 6 carbon atoms, which may be straight or branched chain. The level of addition of the alcohol is relatively small in relation to the Guerbet alcohol product, and will generally be 0.5 to 15 mole %, and preferably 2 to 10 mole % with about 5% most preferred. Isopropanol is particularly effective and is the preferred alcohol for use in the process.

The alkoxides which may be employed are metal alkoxides, which are reducing agents, and may be defined by the fomula M(OR₆)_n where M is selected from B, Al, Mg, Cu, Li, Na,^" K and Zn; R₆ is lower alkyl, branched or straight chain, containing from 1-6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl and the like, and n is a whole integer from 1 to 3. A preferred compound is B(i- PrO)₃, boron isopropoxide, which is especially advantageous. At the end of a typical Guerbet reaction, the addition of from 1-5 mole % of the B(i-PrO)₃ to the reaction mixture, prior to cooling, will quickly reduce the aldehydes present in the medium. The reaction mixture is then cooled and distilled.

The following examples serve to illustrate, but not limit, the invention. All parts and percentages are by weight, unless otherwise noted.

Example I This example is a study of the influence of temperature on the aldehyde promoted Guerbet reaction. A mixture of 30.0 g (190 mmole) of 1-decanol, 3.00 ml (9.69 mmole) of n-heptadecane (internal GC standard), and 0.61 g (5 mole %) of 87.5% KOH was heated in an oil bath preset at 220°C. The pressure in the system was then reduced slightly, producing a vigorous reflux at a pot temperature of 200°C. With both the oil bath and pot temperatures stabilized at 220°C and 200°C, respectively, decyl aldehyde (1.81 ml, 5 mole %) was added to the reaction (representing time =0) . As the Guerbet alcohol formed, the temperature increased up to the temperature of the oil bath. Samples were periodically withdrawn from the reaction mixture, silylated, and analyzed by GC for conversion of starting 1- decanol.

Subsequent experiments were run in which the decyl aldehyde concentration was varied at 5 mole % or 2 mole %, and in which the initial temperature was varied between 160°C and 230°C (atmospheric pressure) , always starting with a oil bath temperature 20°C higher than the pot temperature. Reactions which gave lower conversions did not produce as much temperature rise during the reaction. The percent conversion as a function of time for these reaction is shown in the two graphs, Figures 1 and 2. The results show that temperature is an important factor in obtaining good conversion rates, and that higher levels of added aldehyde co-catalyst will permit the same conversion rate at lower temperatures.

Example II This is a set of experiments comparing (a) the use of decyl aldehyde with a ZnO catalyst in the Guerbet reaction of decanol and (b) the rates of reaction using combinations of KOH, decanol and ZnO.

A mixture of 30.0 g (190 mmole) of 1-decanol and 0.761 g (5 mole %) of 87.5% KOH was heated (using an oil bath) to reflux in a flask equipped with a Dean-Stark trap and treated with decyl aldehyde (1-10 mol %, depending on the experiment) . The initial temperature was 230°C, rising during the reaction to 250°C, the temperature of the oil bath. For the ZnO comparative runs, the ZnO (either

0.015 g (0.05 wt %) or 0.45 g (1.5 wt %) ) was added at 25°C. together with KOH and decanol, and then the mixture was brought to reflux. The amount of water produced in the reaction (a measure of conversion) was monitored as a function of time in order to differentiate the relative reaction rates for the various trials. The graph, Figure

3, shows the rate of water evolution as a function of the amount of decyl aldehyde added; Table 1 below gives the analyses of the corresponding products. The graph, Figure 4, shows the rate of water evolution as a function of different catalyst combinations; Table 2 below gives the water evolution data in tabular form.

As shown in Figure 3, the Guerbet reaction of 1- decanol using 5 mole % of KOH is essentially over after ca. two hours of reaction time. However, if 2 mole % of decyl aldehyde is added at the outset to the otherwise identical reaction mixture, the time required for completion of reaction is much less (ca. 75 min) , demonstrating the rate enhancement achieved from the added aldehyde. Use of even

1 mole % of decyl aldehyde resulted in an accelerated reaction rate, while higher levels (such as 5 or 10 mole %) of decyl aldehyde further shortened the reaction period. The yield of the Guerbet alcohol product, 2-octyldodecanol, was approximately the same in all instances by GC analysis using an internal standard (Table 1) .

Table 1 Products Derived (GC Analysis Using 1-Pentadecanol as an Inter Guerbet Reaction of 1- Decanol (190 mmole) Using KOH (5 mole %) Decyl Aldehyde as a Promoter.

Table 2

COMPARISON OF GUERBET REACTION RATES OF 1-DECA COMBINATIONS OF KOH (5 mole%) , DECANAL (2 mole%) , AND ZnO (0.05 and 1.5 wt%) . (ml water formed)

Example III This is a set of experiments showing the influence of different carbonyl compounds on the Guerbet reaction rate of 1-decanol. A mixture of 30.0 g (190 mmole) of 1-decanol, 0.61 g (5 mole %) of 87.5% KOH, and 2 mole % of an aldehyde or ketone promoter were refluxed (using an oil bath) until water evolution ceased. The initial temperature was 230°C, rising during the reaction to 250°C, the temperature of the oil bath. The relative reaction rates were monitored as water produced versus time, and are shown in the graphs in Figures 5 and 6.

The results show that a wide variety of aldehydes or ketones besides decyl aldehyde are effective as promoters for the Guerbet reaction of 1-decanol. For example, the graphs in Figures 5 and 6 show that 2-ethylhexanal, acetone, 2-butanone, acetophenone, isobutyraldehyde, and benzaldehyde (2 mole % of each carbonyl compound 5 mole % of KOH) are all clearly faster in rate than the otherwise identical reaction using base (5 mole % KOH) alone. The commercially available and relatively inexpensive 2- ethylhexanal afforded a slightly faster Guerbet reaction rate than the other carbonyl compounds, making it a preferred promoter from both standpoints. Again, product distributions and the yields of 2- octyldodecanol determined by GC analysis were similar for all carbonyl promoters (Table 3 below) .

Table 3

Products Derived (GC Analysis using 1-Pentadecanol as an Internal Stndard) From the Guerbet Reaction of 1-Decanol (190 mmole) Using KOH (5 mole %) and a Carbonyl-Containing

Promoter (2 mole %)

Example IV This is a set of experiments showing that the addition of a carbonyl-containing compound to a Guerbet raction which has run until all apparent water production has ceased, causes the reaction to resume once again and, thus, increases the conversion of starting alcohol to the corresponding Guerbet alcohol. For example, a Guerbet reaction of 1-decanol using KOH (5 mole %) and 2- ethylhexanal (2 mole %) typically leaves c_a. 12 % starting alcohol unreacted by GC analysis. However, if an additional charge of 2-ethylhexanal (2 mole %) is added to this apparently "completed" reaction, the Guerbet reaction is again initiated and the amount of residual 1-decanol is cut in half (6 %) , along with a comparable increase in yield of Guerbet alcohol (77% final yield of 2- octyldodecanol by GC analysis) . A third 2 mole % portion of 2-ethylhexanal decreased the amount of residual 1- decanol even further (4 % remaining by GC) . Other carbonyl-containing compounds, such as decyl aldehyde and acetone, were similarly effective at enhancing the conversion of 1-decanol into the corresponding Guerbet alcohol. A representative experiment is given below in Example 6.

Guerbet reactions of 1-decanol were run at a 90 g scale, comparing the following catyalyst systems: no co- catalyst or promoter (Ex. 2-6), and zinc oxide (Ex. 7). Rates of water evolution are given in Table 4 below, and shown in the Graph, Figure 7. Analysis of products are given in Table 5 below. Example l: (Comparative experiment using base alone without carbonyl promoter)

A mixture of 90.2 g (570 mmole) of 1-decanol and 1.88 g (5 mole %) of 87.5% KOH was heated at reflux (using an oil bath) in a flask fitted with a Dean-Stark trap for removal of water. The reaction was carried out for 180 minutes, after which time 4.20 ml of water had formed. The initial temperature was 230°C, rising during the reaction to 250^oC, the temperature of the oil bath. The mixture was then cooled to room temperature and the Dean-Stark trap was replaced with a distillation column. The residual starting 1-decanol was removed in the fore-cut of the distillation, followed by the Guerbet alcohol (58.2g), 2-octyldodecanol, distilling in the temperature range 178-182°C (1.1 torr) . Example 2: (Use of 2 mole % decyl aldehyde as a promoter)

A mixture of 90.2 g (570 mmole) of 1-decanol and 1.88 g (5 mole %) of 87.5% KOH was brought to reflux in a set-up as described above, and then treated dropwise with 1.78 g (2 mole %) of decyl aldehyde. The reaction was carried out for 135 minutes, after which time 4.45 ml of water had been collected. The initial temperature was 230°C, the temperature of the oil bath. The mixture as distilled directly from the reaction flask as above to afford 15.7 g of 1-decanol in the fore-cut, and 58.8 g of 2- octyldodecanol (180-190°C, 1.5 torr) in the main fraction. Example 3: (Use of 2 mole % 2-ethylhexanal as a promoter)

A mixture of 90.2 g (570 mmole) of 1-decanol, 1.88 g (5 mole %) of 87.5 % KOH, and 1.47 g (2 mole %) of 2- ethylhexanal was refluxed (using an oil bath) for 135 minutes, producing 4.30 ml of water.. The initial temperature was 230°C, rising during the reaction of 250°C, the temperature of the oil bath. The mixture was distilled directly from the reaction flask as above to afford 27.4 g of starting 1-decanol in the fore-cut, and 46.8 g of 2- octyldodecanol (170-185°C, 1.0 torr) in the main fraction. Example 4: (Use of 10 mole % 2-ethylhexanal as a promoter)

A mixture of 90.2 g (570 mmole) of 1-decanol, 1.88 g (5 mole %) of 86.5 % KOH, and 7.31 g (10 mole %) of 2- ethylhexanal was refluxed (using an oil bath) for 90 minutes, the reaction of 250°C. the temperature of the oil bath. The mixture was distilled directly from the reaction flask as above to afford 17.3 g of starting 1-decanol in the fore-cut, and 60.0 g of 2-octyldodecanol (178-185°C, 1.2 torr) in the main fraction.

Example 5: (Use of 5 mole % acetone as a promoter) A mixture of 90.2 g (570 mmole) of 1-decanol, 1.88 g (5 mole %) of 87.5 % KOH, and 1.65 g (5 mole %) of acetone was refluxed (using an oil bath) for 135 minutes, producing 4.40 ml of water. The initial temperature was 230°C, rising during the reaction to 250°C, the temperature of the oil bath. The mixture was distilled directly from the reaction flask as above to provide 19.7 g of starting 1-decanol in the fore-cut, and 49.6 g of 2-octyldodecanol (175-185°C, 1.5 torr) in the main fraction.

Example 6: (Use of 2 mole % 2-ethylhexanal as a promoter, followed by a second addition of 2-ethylhexanal for conversion enhancement) .

A mixture of 90.2 g reflux and treated with 1.47 g. (2 mole %) of 2-ethylhexanal. The initial temperature was 230°C, rising during the reaction of 250°C, the temperature of the oil bath. After 120 minutes, water formation (4.5 ml) had ceased and the reaction was then treated at 250°C with another portion of 1.47 g (2 mole %) of 2-ethylhexanal. The reaction was carried out for an additional 30 minutes, producing another 0.45 ml of water. Distillation directly from the reaction flask provided 9.6 g of residual l- decanol and 63.2 g of 2-octyldodecanol (174-186°C, 1.8 torr) in the main fraction.

Example 7: (Comparative experiment using only zinc oxide as co-catalyst)

A mixture of 90.2 g. (570 mmole) of 1-decanol, 1.88 g (5 mole %) of 87.5 % KOH and 0.045 g (0.05 wt %) of ZnO was refluxed (using an oil bath) for 135 minutes in an apparatus similar to the described in Example 1, producing 4.40 ml water. The initial temperature was 230°C, the temperature of the oil bath. The mixture was distilled directly from the reaction flask as above to afford 11.2 g of starting 1-decanol in the forecut, and 60.7 g of 2- octyldodecanol (178-185°C, 0.6 torr) in the main fraction. Comparison of Example 7 with Example l shows the much slower rates when the co-catalyst ZnO is deleted. However, as Examples 2 to 6 show, the rates in the absence of co- catalyst are substantially increased when any of the aldehydes or ketones are added as promoters. The rate of Example 7 can even be exceeded, as shown in Example 4. Example 8: Guerbet reaction of 1-decanol using KOH, 2- ethyhexanal, and ZnO as catalysts; Aqueous workup A mixture of 250 g (1.58 mole) of 1-decanol, 5.21 g (5 mole %) of 85% KOH, 4.05 g (2 mole %) 2-ethylhexanal, and 1.12 g (0.05 wt %) of ZnO was heated to reflux (max. pot temp = 250 °C) in a flask fitted with a Dean-Stark trap and condenser. After about 100 minutes, the head temperature (measured in the Dean-Stark trap) fell to 120 °C, and the reaction was heated at 250 °C for an additional hour. The reaction temperature was cooled to 90-95 °C, and to it was added 150 ml of water preheated to 90 °C. The mixture was stirred gently at 90-95 °C for 30 minutes, and the aqueous phase was removed. The organic layer was dried over anhydrous sodium sulfate, filtered, and distilled to give 176 g of 2-octyldecanol: b.p. 140-152 °C (0.2 torr); iodine value 2.4 eg l²/q; acid value 0.2 mg KOH/g; carbonyl value 0.75 mg CO/g.

Table 4

RATES OF WATER EVOLUTION IN EXPERIMENTS 1-7

Volume of Water (ml)

Exp 3 Exp 4 Exp 5 Exp 6 Exp 7

1.10 1.50 1.00 0.90 0.95

1.25 2.00 1.30 1.30 1.35

1.50 2.55 1.45 1.50 2.20

1.90 3.35 1.60 1.80 2.90

2.50 4.30 1.90 2.50 3.60

3.30 4.40 2.25 3.40 3.90

3.95 4.75 2.70 4.00 4.10

. 4.05 3.30 4.30 4.20

4.20 4.20 4.50 4.30

4.30 4.30 * 4.40

4.40 4.85 4.95

* Add second 2 mole % portion of 2-ethylhexanal

Table 5 Analytical Data From Distilled Samples of 2-0ctyldodecanol Obtained in Examples 1-6

Example V

The example illustrates the use of various alcohols as carbonyl reducing agents at the end of the Guerbet reaction. All the reactions were run in identical fashion using 90.0 g of 1-decanol, 1.83 g of KOH, 1.46 g of 2- ethylhexanal and 14 mole % of the carbonyl reducing alcohol added. A comparison without the alcohol treatment is also included. The following run using isopropanol is representative of the runs made with the vavious alcohols.

A mixture of 90.0 g (570 mmole) of 1-decanol, 1.83 g

(5 mole%) of 87.5% KOH, and 1.46 g (2 mole%) of 2- ethylhexanal was heated to reflux and the Guerbet reaction carried out in a typical fashion. The reaction was heated at 250°C for an additional 30 min. after water production had ended, and to the mixture was then slowly added 4.80 g

(14 mole%) of jl-propanol (which was introduced via syringe with the needle positioned beneath the surface of the reaction solution) . After stirring for an additional 15 min. , the mixture was cooled at 25°C and poured into a separatory funnel containing ether (300 ml) and IN HCl (100 ml) . The layers were separated and the aqueous portion extracted with ether (100 ml) . The combined organic phase was washed with sat. NaHC0₃ and sat NaCl, and then dried

(MgS0₄) . Filtration, concentration, and distillation (bp

165-169°C/0.5 torr) provided 59.5 g of 2-octyldodecanol.

Analytical data for the runs can be seen in Table 6 below.

Table 6

Table 6 above shows that the secondary alcohols are superior to the use of the primary alcohols (ethanol and isobutanol) .

Claims

1. In a Guerbet alcohol process wherein a starting alcohol is condensed in the presence of a base to produce an alcohol having a greater number of carbon atoms than the starting alcohol, the improvement comprising adding a carbonyl compound in an amount effective to initiate and promote the conversion of said starting alcohol to said Guerbet alcohol and conducting said condensation at a temperature greater than 180°C.

2. A process as defined in claim 1 wherein said carbonyl compound is added in an amount of about 0.5 to about 10 mole percent based on said starting alcohol.

3. A process as defined in claim 2 in which said carbonyl compound is selected from the group consisting of an aldehyde and a ketone and said reaction is conducted at a temerature above 200°C.

4. A process as defined in claim 3 wherein said aldehyde has the formula R₂CHO where R₂ is H or. an aliphatic, cycloaliphatic or araliphatic hydrocarbon group having from 1 to about 22 carbon atoms.

5. A process as defined in claim 4 wherein said aldehyde is selected from the group consisting of formaldehyde, 2-ethylhexanal, decanal, dodecanal, tridecanal, butyraldehyde, isobutyraldehyde, propionaldehyde, acetaldehyde and benzaldehyde.

6. A process- as defined in claim 3 wherein said aldehyde is the same as the aldehyde formed in the reaction.

7. A process as defined in claim 6 wherein said aldehyde is formed by oxidation of a portion of the starting alcohol feed prior to introduction into the reactor vessel.

8. A process as defined in claim 7 wherein said starting alcohol feed is passed through a heated bed of dehydrogenation catalyst prior to introduction into the reactor under conditions to produce the amount of aldehyde to iniate and promote conversion of said starting alcohol to said Guerbet alcohol.

9. A process as defined in claim 6 wherein said starting alcohol is decanol and said aldehyde is decanal.

10. A process as defined in claim 3 wherein said aldehyde is different from the aldehyde produced as an intermediate in the reaction.

11. A process as defined in claim 10 wherein said aldehyde is 2-ethylhexanal.

12. A process as defined in claim 3 wherein said carbonyl compound is a ketone having the formula R₃-C(0)-R₄ where R₃ and R₄, which may be the same or different, is an aliphatic or aromatic hydrocarbon group and the ketone contains a total of up to about 12 carbon atoms.

13. A process as defined in claim 12 wherein R₃ and R₄ are selected from the groups consisting of methyl, ethyl and phenyl.

14. A process as defined in claim 12 wherein said ketone is acetone.

15. A process as defined in claim 1 wherein said condensation is conducted at a temperature in the range of about 230 to about 260°C and said carbonyl compound is selected from the group consisting of formaldehyde, 2-ethylhexanal, decanal and acetone, and is added in an amount of about 1 to about 5 mole percent based on the starting alcohol.

16. A process as defined in claim 1 wherein a metal co- catalyst is also present during the condensation reaction.

17. A process as defined in claim 15 wherein said metal cocatalyst is present in an amount of up to about 10 weight percent based on the starting alcohol.

18. A process as defined in claim 17 wherein said metal co-catalyst contains a metal selected from the group consisting of Al, B, Mg, Cu, Sn, Ti, Zr Zn, Ni, and the group VIII noble metals.

19. A process as defined in claim 17 wherein said metal co-catalyst is ZnO present in an amount of about 1 to about 5 mole percent and said temperature is greater than 200°C.

20. A process as defined in claim 19 in which said temperature is in the range of about 230°C to about 250°C.

21. A process as defined in claim 1 wherein said improvement further comprises conducting said condensation to substantial completion and adding a carbonyl compound to the reaction mixture in an amount effective to resume the reaction whereby increased conversion of said Guerbet alcohol results.

22. A process as defined in claim 21 wherein said carbonyl compound is added in an amount of about 1 to about 5 mole percent based on the starting alcohol.

23. A process as defined in claim 22 wherein said carbonyl compound is selected from the group consisting of an aldehyde and a ketone.

24. A process as defined in claim 23 wherein said aldehyde has the formula R₂CHO where R₂ is H or an aliphatic, cycloaliphatic or araliphatic hydrocarbon group having from 1 to about 22 carbon atoms.

25. A process as defined in claim 24 wherein said aldehyde is selected from the group consisting of formaldehyde, 2-ethylhexanal, decanal, dodecanal, tridecanal, butyraldehyde, isobutyraldehyde, propionaldehyde, acetaldehyde and benzaldehyde.

26. A process as defined in claim 24 wherein said aldehyde is the same as the aldehyde formed in the reaction.

27. A process as defined in claim 26 wherein said starting alcohol is decanol and said aldehyde is decanal.

28. A process as defined in claim 24 wherein said aldehyde is different from the aldehyde producd as an intermediate in the reaction.

29. A process as defined in claim 28 wherein said aldehyde is 2-ethylhexanal.

30. A process as defined in claim 23 wherein said carbonyl compound is a ketone having the formula R₃-C(0)-R₄ where R₃ and R₄, which may be the same or different, is an aliphatic or aromatic hydrocarbon group and the ketone contains a total of up to about 12 carbon atoms.

31. A process as defined in claim 30 wherein R₃ and R₄ are selected from the groups consisting of methyl, ethyl and phenyl.

32. A process as defined in claim 30 wherein said ketone is acetone.

33. A process as defined in claim 1 wherein said improvement further comprises adding to the Guerbet alcohol reaction product after completion of the condensation reaction, and prior to cooling said reaction product for subsequent recovery of the Guerbet alcohol, a compound selected from the group consisting of an alcohol and a metal alkoxide.

34. A process as defined in claim 33 wherein said alcohol has the formula R_gOH where E_j is a hydrocarbon group containing from 1 to about 20 carbon atoms.

35. A process as defined in claim 34 wherein R₅ is an aliphatic, aromatic, cycloaliphatic or araliphatic hydrocarbon group.

36. A process as defined in claim 34 wherein R_g is a straight or branched chain, aliphatic or cycloaliphatic hydrocarbon group having from 1 to about 6 carbon atoms.

37. A process as defined in claim 34 wherein said alcohol is isopropanol.

38. A process as defined in claim 34 wherein said alcohol is employed in an amount effective to reduce the residual contaminating aldehyde content whereby the carbonyl value of the Guerbet alcohol product is reduced.

39. A process as defined in claim 33 wherein said alkoxide has the formula M(0R₆)_n where M is a metal selected from the group consisting of B, Al, Mg, Cu, Li, Na, K and Zn; R₆ is a straight or branched chain alkyl group having from 1 to about 6 carbon atoms and n is an integer from 1 to 3.

40. A process as defined in claim 39 wherein said metal alkoxide is B(i-PrO)₃.

41. A process as defined in claim 39 wherein said metal alkoxide is employed in an amount of 1 to about 5 mole percent based on the starting alcohol.

42. In a Guerbet alcohol process wherein a starting alcohol is condensed in the presence of a base to produce an alcohol having a greater number of carbon atoms than the starting alcohol, the improvement comprising conducting the condensation reaction to substantial completion and adding a carbonyl compound to the reaction mixture in an amount effective ^*to resume the reaction whereby increased conversion of Guerbet alcohol results.

43. A process as defined in claim 42 wherein said carbonyl compound is added in an amount of about l to about 5 mole percent based on the starting alcohol.

44. A process as defined in claim 43 wherein said carbonyl compound is selected from the group consisting of an aldehyde and a ketone.

45. A process as defined in claim 44 wherein said aldehyde has the formula R₂CHO where R₂ is H or an aliphatic, cycloaliphatic or araliphatic hydrocarbon group having from 1 to about 22 carbon atoms.

46. A process as defined in claim 45 wherein said aldehyde is selected from the group consisting of formaldehyd, 2-ethylhexanal, decanal, dodecanal, tridecanal, butyraldehyde, isobutyraldehyde, propionaldehyde, acetaldehyde and benzaldehyde.

47. A process as defined in claim 45 wherein said aldehyde is the same as the aldehyde formed in the reaction.

48. A process as defined in claim 47 wherein said starting alcohol is decanol and said aldehyde is decanal.

49. A process as defined in claim 45 wherein said aldehyde is different from the aldehyde produced as an intermediate in the reaction.

50. A process as defined in claim 49 wherein said aldehyde is 2-ethylhexanal.

51. A process as defined in claim 44 wherein said carbonyl compound is a ketone having the formula R₃-C(θ)-R₄, where R₃ and R₄,which may be the same or different, is an aliphatic or aromatic hydrocarbon group and the ketone contains a total of up to about 12 carbon atoms.

52. A process as defined in claim 51 wherein R₃ and R₄ are selected from the groups consisting of methyl, ethyl and phenyl.

53. A process as defined in claim 51 wherein said ketone is acetone.

54. In a Guerbet alcohol process wherein a starting alcohol is condensed in the presence of a base to produce an alcohol having a greater number of carbon atoms than the starting alcohol, the improvement comprising adding to the Guerbet alcohol reaction

. product after completion of the condensation reaction a compound selected from the group consisting of an alcohol and a metal alkoxide.

55. A process as defined in claim 54 wherein said alcohol added after said condensation reaction has the formula R_gOH where R_j is a hydrocarbon group containing from 1 to about 20 carbon atoms.

56. A process as defined in claim 55 wherein R₅ is an aliphatic, aromatic, cycloaliphatic or araliphatic hydrocarbon group.

57. A process as defined in claim 55 wherein R₅ is a straight or branched chain, aliphatic or cycloaliphatic hydrocarbon group having from 1 to about 6 carbon atoms.

58. A process as defined in claim 55 wherein said alcohol is isopropanol.

59. A process as defined in claim 55 wherein said alcohol is employed in an amount effective to reduce the residual contaminating aldehyde content whereby the carbonyl value of the Guerbet alcohol product is reduced.

60. A process as defined in claim 54 wherein said alkoxide has the formula M(OR₆)_n where M is a metal selected from the group consisting of B, Al, Mg, Cu, Li, Na, K and Zn; R₆ is a straight or branched chain alkyl group having from 1 to about 6 carbon atoms and n is an integer from 1 to 3.

61. A process as defined in claim 60 wherein said metal alkoxide is B(i-PrO)₃.

62. A process as defined in claim 60 wherein said metal alkoxide is employed in an amount of 1 to about 5 mole percent based on the starting alcohol.