Process for preparing an anticorrosion component for an antifreeze

Abstract

A process for preparing an anticorrosion component for an antifreeze by oxidizing an oxydiol of the formula (I) ##STR00001##
with molecular oxygen at a temperature of 20 to 100 C. and a partial oxygen pressure of 0.01 to 2 MPa in the presence of water and of a heterogeneous catalyst. The catalyst contains platinum to form an oxydicarboxylic acid of the formula (II) ##STR00002##
The process has the steps of conducting the oxidation
(a) at a molar ratio of
0.002n(Pt)/[n(oxydiol (I))+n(oxydicarboxylic acid (II))]0.019;
(b) at a concentration of water of 50% to 95% by weight in the liquid phase; and
(c) at a pH of 1 to 7.

Claims

1. A process for preparing an anticorrosion component for an antifreeze by oxidizing an oxydiol or a mixture of oxydiols of the general formula (I) ##STR00015## in which x is a positive integer from 1 to 10 with molecular oxygen at a temperature of 20 to 100 C. and a partial oxygen pressure of 0.01 to 2 MPa in the presence of water and of a heterogeneous catalyst comprising platinum to form an oxydicarboxylic acid of the general formula (II) ##STR00016## in which y is a positive integer from 1 to 10, which comprises conducting the oxidation (a) at a molar ratio of
0.002n(Pt)/[n(oxydiol (I))+n(oxydicarboxylic acid (II))]0.019; where n(Pt) is the molar amount of platinum, n(oxydiol (I)) is the molar amount of oxydiol (I) and n(oxydicarboxylic acid (II)) is the molar amount of oxydicarboxylic acid (II); (b) at a concentration of water of 50% to 95% by weight in the liquid phase; and (c) at a pH of 1 to 7.

2. The process according to claim 1, wherein he oxydiol (I) in which x is a positive integer from 1 to 5 is used.

3. The process according to claim 1, wherein the mixture of oxydiols (I) having an average molar mass of 150 to 300 g/mol is used.

4. The process according to claim 1, wherein a heterogeneous catalyst comprising 0.1% to 10% by weight of platinum on charcoal is used.

5. The process according to claim 1, wherein a heterogeneous catalyst having a total content of cadmium, lead and bismuth of 0% to 0.1% by weight, based on the amount of platinum, is used.

6. The process according to claim 1, wherein the process is conducted at a molar ratio of
0.005n(Pt)/[n(oxydiol (I))+n(oxydicarboxylic acid (II))]0.015;

7. The process according to claim 1, wherein a reaction mixture having a content of glycolic acid of 0% to 1% by weight, based on the oxydicarboxylic acid (II), is obtained.

8. The process according to claim 1, wherein water is removed by distillation from the reaction mixture obtained.

9. The process according to claim 8, wherein a processed reaction mixture having a water content of 0% by weight to 40% by weight is produced.

10. The process according to claim 1, wherein the process is conducted at a molar ratio of
0.007n(Pt)/[n(oxydiol (I))+n(oxydicarboxylic acid (II))]0.015;

11. The process according to claim 1, wherein the process is conducted at a molar ratio of
0.005n(Pt)/[n(oxydiol (I))+n(oxydicarboxylic acid (II))]0.017;

12. The process according to claim 1, wherein the process is conducted at a molar ratio of
0.007n(Pt)/[n(oxydiol (I))+n(oxydicarboxylic acid (II))]0.017;

13. The process according to claim 1, wherein the mixture of oxydiols (I) having an average molar mass of 125 to 500 g/mol is used.

14. The process according to claim 1, wherein the mixture of oxydiols (I) having an average molar mass of 140 to 400 g/mol is used.

Description

EXAMPLES

(1) Gas Chromatography Analysis

(2) The oxydiol (I) used in the examples and the reaction product obtained were each analyzed by gas chromatography for their organic components. The procedure for this purpose was as follows: Gas chromatograph: Agilent 7890B Column: Rxi-1ms (length 30 m, 0.25 mm (ID), 0.25 m (film) Temperature program: 3 minutes at 60 C., heating from 60 C. to 290 C. at 5 C./min, 12 minutes at 290 C. Sample preparation: The catalyst was filtered off and the water was removed. 50 mg of the anhydrous mixture were then mixed with 1 mL of MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide) and heated to 80 C. for 1 hour, and the sample was injected into the gas chromatograph.

Example 1 (Comparative Example)

(3) 200 g of pulverulent catalyst having 5% by weight of platinum on activated carbon, corresponding to 10 g or 0.0513 mol of Pt (source: Sigma-Aldrich), were charged into a 4 liter glass reactor and stirred together with 957 g of water at 1000 rpm. Subsequently, 410 g of oxydiol (I) with the distribution shown in table 1a and an average molar mass of 200 g/mol were added, the mixture was equilibrated to 60 C., and 50 L/h of oxygen were passed through the reaction mixture with further stirring. The molar ratio of Pt to oxydiol (I) was thus 0.025, and the concentration of water in the liquid phase was 70% by weight. Since no base had been added, the initial pH was 6.9. After 27 hours, full conversion had been attained. The feed of oxygen was ended, and the reaction mixture was cooled down and discharged from the glass reactor. The reaction mixture had a pH of 1.5. It was filtered through a D4 glass freight and the filtercake was washed three times with 200 mL each time of warm water. The filtrate was then concentrated on a rotary evaporator at 45 C. at a pressure down to 10 mbar. 280 g of product mixture with the composition shown in table 1b were obtained. The analyses of the organic components were each effected by gas chromatography. The water content was determined by Karl Fischer titration.

(4) TABLE-US-00001 TABLE 1a (reactant) Oxydiol (I) x = 0 x = 1 x = 2 x = 3 x = 4 x = 5 x = 6 x = 7 GC 4.9 23.9 31.0 22.1 11.2 4.5 1.4 0.3 area %

(5) TABLE-US-00002 TABLE 1b (product) y = 0 y = 1 y = 2 y = 3 y = 4 Oxydicarboxylic acid 26.6 31.1 24.7 11.2 1.9 (II) [GC area %] Glycolic acid 4.5 [GC area %] Water [% by wt.] 7

(6) Taking account of the water content of 7% by weight and with the approximate estimate that the 4.5 GC area % of glycolic acid corresponds to about 4.5% by weight of glycolic acid based on the anhydrous product mixture, a yield of about 249 g of oxydicarboxylic acid (II) was thus found.

Example 2 (Inventive)

(7) 78 g of pulverulent catalyst of the same type as in example 1, having 5% by weight of platinum on activated carbon, corresponding to 3.9 g or 0.020 mol of Pt (source: SigmaAldrich), were charged into a 4 liter glass reactor and stirred together with 957 g of water at 1000 rpm. Subsequently, analogously to example 1, 410 g of oxydiol (I) with the distribution shown in table 1a and an average molar mass of 200 g/mol were added, the mixture was equilibrated to 60 C., and 50 L/h of oxygen were passed through the reaction mixture with further stirring. The molar ratio of Pt to oxydiol (I) was thus 0.0098, and the concentration of water in the liquid phase was 70% by weight. Since no base had been added, the initial pH was 6.9. After 67 hours, full conversion had been attained. The feed of oxygen was ended, and the reaction mixture was cooled down and discharged from the glass reactor. The reaction mixture likewise had a pH of 1.5. It was filtered through a D4 glass freight and the filtercake was washed three times with 200 mL each time of warm water. The filtrate was then concentrated on a rotary evaporator at 45 C. at a pressure down to 10 mbar. 436 g of product mixture with the composition shown in table 2b were obtained. The analyses of the organic components were each effected by gas chromatography. The water content was determined by Karl Fischer titration.

(8) TABLE-US-00003 TABLE 2b (product) y = 0 y = 1 y = 2 y = 3 y = 4 Oxydicarboxylic acid 12.3 29.2 32.5 19.6 5.8 (II) [GC area %] Glycolic acid 0.3 [GC area %] Water [% by wt.] 4.9

(9) Taking account of the water content of 4.9% by weight and with the approximate estimate that the 0.3 GC area % of glycolic acid corresponds to about 0.3% by weight of glycolic acid based on the anhydrous product mixture, a yield of about 413 g of oxydicarboxylic acid (II) was thus found.

(10) The two examples show that, in the case of an inventive molar ratio of Pt to oxydiol (I) of 0.0098 (example 2), about a 65% higher yield of oxydicarboxylic acid (II) is obtained than in the case of a molar ratio of 0.025 (example 1). Moreover, at the inventive molar ratio of example 2, only an extremely small amount of 0.3 GC area % of troublesome glycolic acid was formed, whereas, at the higher ratio in example 1, the amount of glycolic acid obtained was 15 times higher at 4.5 GC area %.

Example 3

(11) The catalyst removed in example 2 was used again under the experimental conditions described in example 2. 464 g of product mixture with the composition shown in table 3b were obtained.

(12) TABLE-US-00004 TABLE 3b (product) y = 0 y = 1 y=2 y = 3 y = 4 Oxydicarboxylic acid 11.0 29.0 33.0 20.0 6.0 (II) [GC area %] Glycolic acid 0.8 [GC area %] Water [% by wt.] 6.8

(13) Taking account of the water content of 6.8% by weight and with the approximate estimate that the 0.8 GC area % of glycolic acid corresponds to about 0.8% by weight of glycolic acid based on the anhydrous product mixture, a yield of about 429 g of oxydicarboxylic acid (II) was thus found.

Example 4

(14) The catalyst removed in example 3 was used again under the experimental conditions described in example 2. 467 g of product mixture with the composition shown in table 4b were obtained.

(15) TABLE-US-00005 TABLE 4b (product) y = 0 y = 1 y = 2 y = 3 y = 4 Oxydicarboxylic acid 11.1 28.5 33.0 20.5 6.3 (II) [GC area %] Glycolic acid 0.7 [GC area %] Water [% by wt.] 7.3

(16) Taking account of the water content of 7.3% by weight and with the approximate estimate that the 0.7 GC area % of glycolic acid corresponds to about 0.7% by weight of glycolic acid based on the anhydrous product mixture, a yield of about 428 g of oxydicarboxylic acid (II) was thus found.

(17) Examples 3 and 4 show that the catalyst used can be reused repeatedly.