US3006937A - Ester oils and process for their preparation - Google Patents

Description

United States Patent {Office 3,006,937 Patented Oct. 31, 1961 3,006,937 ESTER OHJS AND PROCESS FUR THEE PREPARATION Karl Biichner, Duisburg-Hamborn, and Heinrich Schwarz,

()herhausen-Sterkrade, Germany, assignors to Ruhrchernie Aktiengesellschaft, Oberhausen-Holten, Germany, a corporation of Germany No Drawing. Filed Dec. 15, 1953, Ser. No. 398,416 Claims priority, application Germany Dec. 18, 1952 14 Claims. (Cl. 260-410) This invention relates to new and useful improvements in ester oils.

One object of the invention is valuable ester oils having a low pour point. This, and still further objects will become apparent from the following description:

In accordance with the invention it has been found that esters having a hydroaromatic component and an aliphatic component constitute valuable oils which have a low, pour point. These oils have proven particularly suitable as clock-work oil or lubrication oil for ice machines, and other machines and apparatus which operate at low temperature. The oils have also proven particularly valuable when used alone or in mixture, as circulating oils for turbines or for breaking-in oils for internal combustion engines. Depending upon the chain length of the aliphatic ester portion, the flash point of these oils may be adjusted to the particular level desired, while the pour point, especially in the case of high-molecular weight aliphatic portions, may be kept low by chain branching.

The ester oils in accordance with the invention may be esters of hydroaromatic alcohols and aliphatic carboxylic acids or of hydroaromatic carboxylic acids and aliphatic alcohols. It has been found that if the carbonyl group in the ester is located on the aliphatic side, i.e., the esters are esters of aliphatic carboxylic acids and hydroaromatic alcohols, particularly good viscosity indexes will be obtained.

The hydroaromatic ester components are preferably obtained by the catalytic addition of water gas to terpene hydrocarbons (C H as, for example, are available in turpentine oil.

The catalytic addition of water gas, i.e., carbon monoxide and hydrogen to the terpene hydrocarbons is the conventional aldehyde synthesis and is effected, for example, with cobalt catalysts. The catalysts, gas pressures and temperatures used therein are those as known to any expert familiar with the Oxo synthesis or hydroformylation (see, for example, US. Patents 2,327,- 066, 2,497,303; U.K. Patent 614,010; FIAT Report No. 1000; Petroleum Processing, February 1953, pp. 241- 248). The starting terpene hydrocarbon may constitute the total terpenes or individual fractions of a narrow boiling range. When individual fractions are used, the same may be processed or pretreated with catalysts in the conventional manner for the purpose of rearrangement or cyclization.

The addition products from the catalytic water gas addition may be converted into carboxylic acids or alcohols.

The addition products may be converted into carboxylic acids by oxidation, as, for example, with air or oxygen, or may be converted into carboxylic salts by the addition of mild alkali. The carboxylic acids may be recovered from these salts in the known manner.

The addition products may be converted into alcohols by catalytically hydrogenating the same, or, if desired, by using a hydrating hydrogenation in the known manner for obtaining a higher yield. The alcohols may be used as such or may be converted into corresponding carboxylic acids by treatment with alkali at the melting temperature in the conventional manner.

The starting materials of the process according to the By the catalytic addition of water gas (Oxo synthesis) followed by hydrogenation, there is fdrmed therefrom the terpanol (camphanol) having the following structural formula:

It is possible by oxidation to recover from terpanol of the above structure the terpane-carboxylic acid (camphane carboxylic acid) having the following structural formula:

The dipentene which is isomeric with the camphene has the following structural formula:

Herefrom, by the catalytic addition of water gas followed by hydrogenation, an isomeric terpanol (menthane-methylol) is recovered having the following structural formula:

Herefrom, by oxidation, the corresponding terpane carboxylic acid may be recovered which has the following stru tural formula:

water gas to the terpene hydrocarbon by treatment with oxygen or air, if necessary or desired, in the presence of mild alkali, such as soda. When using the hydroaromatic 1 component in the form of a carboxylic acid, the aliphatic 5 component must, of course, be in the form of an alcohol. H2O CH1 The same considerations should be given when choosing 3; the alcohol as indicated above for the aliphatic carboxylic acid. Thus, branched aliphatic alcohols should be used HG 1n the case of long-chain compounds in order to keep the pour point low. Branched alcohols of this type are H2O CCOOH Obtained, for example, by the catalytic addition of carbon H monoxide and hydrogen to olefins, followed by a catalytic If the hydroaromatic portion is present as an alcohol, treatment with hydrogen if in the fractional distillation fatty acids must, of course, be used for the esterification. of the hydrocarbon-alcohol mixtures the first third or first Alcohols or carboxylic acids of the molecular size C four-tenths of the distillate are collected separately from to C and preferably 0., to C areu sed for the esterificathe remainder. The intermediate fraction obtained betion. The esterification is effected by methods known to tween the hydrocarbon fraction and the alcohol may also any expert which is familiar with the esterification of orbe used for the production of the ester oils of low pour ganic compounds. The esterification conditions used point in accordance with the invention. Esters thus may be seen in detail from the following examples. The 20 produced, however, have the carbonyl group separated use of short-chain acids results in esters of low viscosity by an oxygen bridge on the hydroaromatic ester side. having flash points of about l17-150 C.; pour points As indicated in Examples 5, 6, and 7 of the following below 60 C., and high viscosity indexes. The characexamples, esters of this type exhibit a poorer viscosity teristics of such esters are as follows: index, and their flash points are lower by 10-20" C. than Density no Ester Pour Flash Viscosity Viscosity at 20 0. number pointG. point0. at 0. index Terpane methylol/ester acetic acid. 0. 965 1. 4640 264 66 117 l. 44 +155 Terpane methylolpropionic acid ester. 0. 958 l. 4634 248 68 124 1. 43 +164 Terpane methylolbutyric acid ester. 0. 947 l. 4631 234 -70 129 1. 51 +152 Terpane methylolvaleric acid ester- 0. 939 l. 4612 220 68 144 1. 64 +148 Terpane methylolcaproic acid ester- 0. 93 l. 4631 202 -71 153 1. 77 +157 If the esterification is effected with long-chain fatty those of the corresponding esters produced from terpane acids, ester oils of increased viscosity and having flash methylol and branched fatty acids. points which range above 200 C., are obtained. The The esters themselves may be distilled under reduced viscosity index of these oils ranges above 125. The pour pressure without decomposition and are easily obtained points of these oils, however, are relatively high, so that in this manner in pure form. the same are not high-grade lubricating oils. For ex- The following examples are given by way of illustraample, the stearic ester of terpane methylol C H O has tion and not limitation: the following characteristics: Example 1 :23:32 ig f;;'2?;"': 336 grams (2 mols) rp e y l hHmO, which Ester number D 124 (129) had been obtained from turpentine oil by the catalytic H h 'Z' addition of water gas and by hydrogenation, were boiled as point 216 130 nh d 1 h Viscosity at 30 C E l 4 7 [Wlt gral'ns ace 1c a Y n concentrated Y drochloric acid and 150 cc. benzene for 2 hours under a Viscosity index 138 Pour point C +12 reflux condenser with water separator. Thereafter, the raw product was Washed three times with the Same If, instead of unbranched fatty acids, branched chain volume of water and the benzene was distilled off. A fatty acids are used, as, for example, a branched C fatty raw ester having the following characteristics was obacid, then ster oils are obtained which meet all the retained:

uirements of the highest grade lubricants. An ester iiibricating oil of this kind has the following characterisg i ties for example: Ster Hum 55 (calculated: 267).

Hydroxyl number 0. Density at 20 C 0.910 Density at 20 C 0.965. Refractive index, n 1.4666 Refractive index, n 1.4632. Viscosity: Molecular weight 204 (calculated: 210). 2: a g Engler fi Distillation resulted in a Water-White ester havin a At bolhng point of l19132 C. at 10 mm. Hg and having the followin characteristics- Flash pomt C.-- 218 Pour point C. 58 65 Acid number 0. Viscosity index s er number 264 (calculated: 267). Saponification number 136 Hydroxyl number 0. Molecular weight 390 Density at 20 C 0.965.

Refractive index, n 1.4640. If the hydroaromah'c c mp f h er 1s 1n the Molecum weight 212 (calculated, 210) form of the acid, then, instead of the terpane methylol, 7 p point s C the corresponding terpane carboxylic acid C H O may Flash point C be used. This terpane carboxylic acid may be obtained Viscosity index as an oxidation product of the terpane methylal. The m terpane carboxylic acid may also be obtained from the Example 2 terpane methylal formed by the catalytic addition of the 75 The same mixture as used in Example 1 was used for the esterification with the exception that 180 grams commercial propionic acid were used instead of 130 grams acetic anhydride. During the esterification, a quantity of propionic acid equivalent'to the acid content of the separated water was added. After the distillation, a water-white ester boiling between 129 and 141 C. at 10 mm. Hg, and having the following characteristics, was obtained:

Acid number Ester number 248 (calculated: 250). Hydroxyl number 0. Density at 20 C 0.958. Refractive index, 11 1.4634. Molecular weight 220 (calculated: 224). Pour point 68 C. Flash point 124 C. Viscosity index 164.

Example 3 The same mixture as used in Example 1 was subjected to the esterification with the use of 210 grams commercial butyric acid instead of 130 grams acetic acid. The addition of butyric acid during the esterification was not necessary. A water-white ester boiling between 142 and 154 C. at mm. Hg and having the following characteristics was obtained:

Acid number; 0. Ester number 234 (calculated: 235). Hydroxyl number 0. Density at 20 C 0.947. Refractive index, 12 1.4631. Molecular weight 241 (calculated: 238). Pour point 70 C. Flash point 129 C. Viscosity index 152.

Example 4 The valeric acid ester and caproic acid ester were produced in the manner described in the preceding examples with the use of commercial valeric acid and caproic acid, respectively. To remove the excess acid, the raw esters were washed, prior to the washing with water, with a 2% caustic soda solution until the acid number had dropped to 0. At 143 C. and 5 mm. Hg a valeric acid ester was obtained which had the following characteristics:

Acid number 0.

Ester number 220 (calculated: 222). Hydroxyl number 0.

Density at 20 C 0.939.

Refractive index, r2 1.4612.

Molecular weight 253 (calculated: 252). Pour point 68 C.

Flash point 144 C.

Viscosity index 148.

The corresponding caproic acid ester which had a boiling point of 138 C.l40 C. at 0.8 mm. Hg had the following characteristics:

Acid number 0. Ester number 202 (calculated: 210). Hydroxyl number -1 0. Density at 20 C 0.934. Refractive index, n 1.4631. Molecular weight 263 (calculated: 266). Pour point -71 C. Flash point 153 C. Viscosity index 157.

Example 5 200 grams terp-ane methylol were boiled with 242 gms. of C fatty acid, which had beenproduced by treating a branched C alcohol having a pour point of -29 C.

with alkali at melting temperature, in the presence of cc. toluene and 1 cc. concentrated hydrochloric acid under a reflux condenser with Water separation in the manner described in Example 1. After two hours, the raw product was washed with water to remove the hydrochloric acid and distilled. After the removal of the toluene and of the excess terpane methylol, there was obtained as the main fraction at 208210 C. and 0.8 mm. Hg a viscous ester which had the following characteristics:

228 grams of a branched C alcohol having the characteristics Hydroxyl number 230 Pour point C 30 Density at 20 C 0.840

202 gms. of terpane carboxylic acid produced by treating terpane methylal with alkali at melting. temperature and having the following characteristics:

Acid number 298 (calculated: 308). Density at 20 C 1.015.

Refractive index, 11 1.4778.

Pour point 22C.

200 cc. toluene and 3 gms. of toluene-sulfonic acid were boiled for 3 hours at a reflux condenser with water separation. Following this, the raw product was washed at first with a 2% caustic soda solution until the acid number had disappeared, and then with 50% ethyl alcohol to wash out dissolved soaps. Then it was distilled. At 208 217 C. and 1 mm. Hg the pure ester was obtained which had the following characteristics:

Acid number 0.

Ester number 129 (calculated: 143). Hydroxyl number 0.

Density at 20 C 0.907.

Refractive index, 11 1.4670.

Molecular weight 398 (calculated: 392). Four point -60 C.

Flash point 195 C.

Viscosity at 50 C 2.24 Engler degrees. Viscosity index 96.

The flash point of this ester was lowered by 23 C. and the viscosity index was lower by 36 units as compared with the corresponding ester prepared in accordance with Example 5.

Example 7 150 gms. of a synthetic branched C alcohol having the characteristics:

Molecular weight 186.

Hydroxyl number 300.

Pour point -53 C.

Boiling range 131134 C. at 10 mm. Hg.

were esterified with 180 grns. of terpane carboxylic acid in accordance with Example 6. The ester obtained had the following characteristics:

Density at 20 C 0.918.

Refractive index, n 1.4653.

Ester number 162 (calculated: Hydroxyl number 0.

Acid number 0.

Molecular weight 351 (calculated: 350). Pour point 59 C.

Flash point 185 C.

Viscosity at 30 C 2.96 Engler degrees. Viscosity at 50 C 1.87 Engler degrees. Viscosity index 125 Engler degrees.

The same C alcohol was subjected to the treatment with alkali at melting temperature and then to a treatment with acid, thereby producing the branched C fatty acid which had the following characteristics:

Density at 20 C 0.891.

Refractive index, n L 1.4387.

Acid number 278 (calculated: 279). Four point 40" C.

222 gms. (1.11 mols) of this acid were esterified with 151 gms. (0.9 mol) terpane methylol with the addition of toluene as described in the preceding examples. After the separation of 16 cc. (0.89 mol) of water, the excess acid was removed by washing with 5% aqueous caustic soda solution and 50% ethanol and the raw ester was fractionated. The ester thus obtained in the pure form had the following characteristics:

Density at 20 C 0.910. Refractive index, r1 1.4641. Ester number 162 (calculated: 160). Hydroxyl number 0.1. Molecular weight 350.5 (calculated: 350). Four point 64 C. Flash point 199 C. Viscosity at 30 C 2.72 Engler degrees. Viscosity at 5 0 C 1.775 Engler degrees. Viscosity index 129.

Example 8 370 grams (2.2 mols) terpane methylol C I-I 0 were boiled with 564 grams (2 mols) commercial oleic acid and 180 cc. commercial toluene, to which 3 grams p-toluene-sulfonic acid had been added, for 2 hours in a 2 liter round-bottomed flask with reflux condenser and water separation. During this time, 36 cc. of water which, by azeotropic distillation of the toluene, had been removed from the esterification mixture, accumulated in the water separating vessel. After the termination of the water separation, the toluene was removed from the esterification mixture by distillation under atmospheric pressure. Following this, the excess terpanol was removed by distillation under reduced pressure of about 10-1 mm. Hg at a temperature of 100130 C.

The residue from distillation was now mixed with 8.6 grams magnesia and distilled at 0.4 mm. Hg and bottom temperatures of 225260 C. in a high-vacuum apparatus with short distilling paths as, for example, in a 2 liter flask with ground top to which a downwardly angled, air-cooled ground piece of large diameter was attached which was connected to a 2 liter receiver with ground top. There were obtained 820 grams of an ester which was only weakly yellowish colored and had the following characteristics:

Density at C 0.905. Refractive index, n 1.4720. Molecular weight 432 (calculated: 432). Pour point 28 C. Flash point 227 C. Viscosity at 50 C 2.17 Engler degrees. Viscosity index 140. Color according to Ludwigshafen iodine number scale Below 4. Acid number 0.1. Ester number 131 (calculated: 130) Iodine number 5'7 (calculated: 59). Hydroxyl number 3. Carbonyl number 0.

To remove the low hydroxyl number still present, the ester described above, if desired, may be distilled once more as first runnings. This second distillation, however, is efiected with the addition of 5-8 grams zinc oxide instead of magnesia. The purpose of adding magnesia in the first distillation is to combine the acid still present in the raw ester as, for example, p-toluene-sulfonic acid and small amounts of unesterified oleic acid. This results, however, in a slight ester cleavage which becomes evident in the ester distilled only once by the present hydroxyl number of 3. The addition of zinc oxide in the second distillation does not effect an additional ester cleavage but reduces the darkening of the color of the ester distillates. The change of the physical data of the ester by the removal of the hydroxyl number is only negligible.

Example 9 294 grams (1.75 mols) terpane methylol were esterified with 316 grams (1.93 mols) trichloroacetic acid with the addition of 2 grams p-toluene-sulfonic acid and cc. benzene in the manner described in Example 8. After the termination of the water separation, the excess chloroacetic acid was removed from the esterification mixture by washing the same five times with water, and then the benzene added as the entraining agent for the water was driven ofif by distillation. The remaining raw ester was fractionated at about 5 mm. Hg. At 156-158 C., an ester fraction was obtained which had the following characteristics:

Density at 20 C 1.203. Refractive index, ri 1.4793. Molecular weight 307 (calculated: 313.5). Chlorine content 33.5% (calculated: 34.1%). Flash point 160 C. Pour point 5'5 C. Turbidity point 40 C. Viscosity at 30 C 15.9 cst. Viscosity at 80 C 3.59 cst. Viscosity at 50 C 7.3 cst. Viscosity index 135. Color Water-white.

Example 10 252 grams terpane methylol (1.5 mols) were esterified, in the manner described in the preceding example, with 151 grams pure lactic acid (1.68 mols) with the addition of cc. benzene and 1.5 grams p-toluene-sulfonic acid. After the termination of the water separation, the excess lactic acid, similar to Example 9, was removed from the ester mixture by washing the same five times with water, and then the benzene was driven off. The remaining raw ester was fractionated at 10 mm. Hg. At a temperature between and 173 C., a fractionated ester was obtained which had the following characteristics:

1. A low pour-point oil suitable as a low-temperature lubricating oil, comprising a monocarboxylic acid-monohydric alcohol ester having a terpane compound, obtained by the catalytic addition of carbon monoxide and hydrogen to the alkylene double bond of a terpene hydrocarbon containing an alkylene radical, as one of the monocarboxylic acid and monohydric alcohol compoments, and an aliphatic compound as the other component.

2. Process for the production of low pour-point oils, which comprises in combination the aldehydic catalytic addition of carbon monoxide and hydrogen to the aliphatic double bond of a terpene hydrocarbon containing an aliphatic radical with olefinic unsaturation to form the corresponding aliphatic aldehyde thereof, the treatment of said aldehyde with a member selected from the group consisting of oxygen and hydrogen to form the corresponding terpane carboxylic acid and terpane alcohol respectively, and the esterification of said terpane With an aliphatic compound, one of said terpane and aliphatic compound being a carboxylic acid and the other being an alcohol, and recovering an oil suitable as a low-temperature lubricating oil.

3. Process for the production of low pour-point oils, which comprises in combination the aldehydic catalytic addition of carbon monoxide and hydrogen to the alkylene double bond of a terpene hydrocarbon containing an alkylene radical to form the corresponding alkyl aldehyde thereof, the treatment of said aldehyde with a member selected from the group consisting of oxygen and hydrogen to form the corresponding terpane monocarboxylic acid and terpane monohydric alcohol respectively, and the esterification of said terpane with an aliphatic compound, one of said terpane and aliphatic compound being a monocarboxylic acid and the other being a monohydric alcohol, and recovering an oil suitable as a low-temperature lubricating oil.

4. A low pour-point oil suitable as a low-temperature lubricating oil, comprising a carboxylic acid-alcohol ester having a terpane compound, obtained by the catalytic addition of carbon monoxide and hydrogen to the aliphatic double bond of a terpene hydrocarbon containing an aliphatic radical with olefinic unsaturation, as one of the carboxylic acid and alcohol components, and an aliphatic compound as the other component.

5. Oil according to claim 4, in which said aliphatic compound contains from 2 to 20 carbon atoms.

6. Oil according to claim 5, in which said aliphatic compound is a branched chain monofunctional aliphatic compound containing more than 8 carbon atoms.

7. Oil according to claim 4, in which said ester is a terpane methylol-fatty acid ester.

8. Oil according to claim 4, in which said ester is a terpane carboxylic acid-aliphatic alcohol ester.

9. Process according to claim 2, in which said aliphatic compound contains from 2 to 20 carbon atoms.

10. Process according to claim 9, in which said aliphatic compound is a branched chain monofunctional aliphatic compound having a chain length of more than 8 carbon atoms.

11. Process according to claim 2, in which terpane methylol is esterified with a fatty acid.

12. Process according to claim 2, in which terpane carboxylic acid is esterified with an aliphatic alcohol.

13. Oil according to claim 5, in which said aliphatic compound contains from 4 to 18 carbon atoms.

14. Process according to claim 9, in which said aliphatic compound contains from 4 to 18 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 900,316 Shukofi Oct. 6, 1908 907,941 Zietschel Dec. 29, 1908 969,420 Sulzberger Sept. 6, 1910 2,501,199 Wearn et a1. Mar. 21, 1950 2,668,177 Corbett et a1. Feb. 2, 1954 2,705,724 Cottle et al. Apr. 5, 1955 OTHER REFERENCES Fieser et al.: Organic Chemistry, 1944, page 984.

Lo Cicero et al.: I.A.C.S., vol. 74, No. 8, 1952, pp. 20942097.

Heilbron: Dictionary of Organic Compounds, 1953, page 826 (Norborneol).

Claims (1)

1. A LOW POUR-POINT OIL SUITABLE AS A LOW-TEMPERATURE LUBRICATING OIL, COMPRISING A MONOCARBOXYLIC ACID-MONOHYDRIC ALCOHOL ESTER HAVING A TERPANE COMPOUND, OBTAINED BY THE CATALYTIC ADDITION OF CARBON MONOXIDE AND HYDROGEN TO THE ALKYLENE DOUBLE BOND OF A TERPENE HYDROCARBON CONTAINING AN ALKYLENE RADICAL, AS ONE OF THE MONOCARBOXYLIC ACID AND MONOHYDRIC ALCOHOL COMPOMENTS, AND AN ALIPHATIC COMPOUND AS THE OTHER COMPONENT.