METHOD FOR PRODUCING GLYCERIC ACID CARBONATE

Abstract

The present invention relates to a method for preparing a compound of the formula (I) with a specific definition of the substituent R.sub.3

##STR00001##

a mixture and also a corresponding application/use.

Claims

1. A method for preparing a compound of the formula (I) ##STR00023## where R.sub.3 is selected from H and straight-chain, branched or cyclic C.sub.1-12-alkyl groups, the method comprising: providing or preparing a compound of the formula (II) ##STR00024## where R.sub.3 has the definition selected for formula (I) and carrying out platinum-catalysed oxidation of the compound of the formula (II) with gaseous oxygen to give the compound of the formula (I).

2. The method according to claim 1, wherein a catalyst is used for the platinum-catalysed oxidation comprising platinum as a solid, optionally comprising platinum as a solid on a support material, further optionally comprising platinum as a solid on carbon.

3. The method according to claim 1, where R.sub.3 is hydrogen.

4. The method according to claim 1, wherein the platinum-catalysed oxidation is carried out in an aqueous medium.

5. The method according to claim 4, wherein at the start of the platinum-catalysed oxidation step in the aqueous medium the pH is 7 or <7.

6. The method according to claim 4, wherein the platinum-catalysed oxidation is carried out such that, on formation of the compound of the formula (I), the pH in the aqueous medium decreases, optionally by at least 2 pH units.

7. The method according to claim 4, wherein the platinum-catalysed oxidation is carried out without addition of base or buffer.

8. The method according to claim 4, wherein the platinum-catalysed oxidation is carried out at least until the pH falls below 2, wherein at the start of the platinum-catalysed oxidation in the aqueous medium the pH is 7 or less than 7.

9. The method according to claim 1, wherein at the start of the platinum-catalysed oxidation the molar ratio of the platinum used to the compound of the formula (II) is greater than 2:100.

10. The method according to claim 1, wherein the platinum-catalysed oxidation is carried out at least intermittently, optionally for most of the time, at a temperature in the range of 50 to 90° C.

11. The method according to claim 4, wherein the platinum-catalysed oxidation is carried out in such a way that the gaseous oxygen is introduced into the aqueous medium.

12. A process comprising carrying out Heyns oxidation (a) for oxidizing a compound of the formula (II) ##STR00025## where R.sub.3 is selected from H and straight-chain, branched or cyclic C.sub.1-12-alkyl groups, wherein the Heyns oxidation is carried out without addition of base or buffer.

13. A mixture comprising a catalyst comprising platinum as a solid, optionally comprising platinum as a solid on a support material, further optionally comprising platinum as a solid on carbon, and also one or more compounds selected from the group consisting of (a) compounds of the formula (II) ##STR00026## where R.sub.3 is selected from H and straight-chain, branched or cyclic C.sub.1-12-alkyl groups, and optionally one or more compounds selected from the group consisting of (b) compounds of the formula (III) ##STR00027## where R.sub.3 is selected from H and straight-chain, branched or cyclic C.sub.1-12-alkyl groups.

Description

EXAMPLES

1. General Experimental Setup

[0121] In a first step, a “platinum on carbon” catalyst was added to an aqueous glycerol carbonate solution (compound of the formula (II), where R.sub.3 is H, in water) (the details for the catalyst below are molar based on glycerol carbonate).

[0122] In a second step, the solution with added heterogeneous catalyst (hereinafter referred to as suspension) was heated to the desired temperature and oxygen (99.995%, Air Liquide) was introduced into the suspension via a frit at the desired pressure or the desired flow rate (cf. Table 1) for the period of the experimental procedure.

[0123] In a third step, (a) the ratio of compound of the formula (I) to compound of the formula (II) and (b) the ratio of compound of the formula (I) to compound of the formula (IV) was determined by .sup.1H- and .sup.13C-NMR at various time points. For further details and descriptions of the experimental parameters see section 2 and Table 1 below.

2. Specific Experimental Parameters and Results

[0124] Details and experimental parameters are summarized in Table 1 below, with the following meanings: [0125] “#” example number [0126] “O.sub.2 [l/h]” oxygen flow rate (in the open reaction procedure; relates to examples 1 to 12) [0127] “Pressure [bar]” oxygen pressure in the reactor (in the closed reaction procedure; relates to examples 13 to 15) [0128] “GC [w/w %]” glycerol carbonate concentration in water [0129] “Pt [mol %]” amount of supported platinum used based on the total amount of glycerol carbonate in the suspension [0130] “Pt/C [w/w %]” platinum loading of the heterogeneous catalyst [0131] “Output [%]” crude yield based on 100% conversion, wherein crude yield refers to the suspension residue after removal of the catalyst by filtration and evaporation of the readily volatile components [0132] “(I):(II)” quantitative ratio of glyceric acid carbonate to glycerol carbonate (degree of conversion and selectivity) [0133] “(I):(IV)” quantitative ratio of glyceric acid carbonate to glyceric acid (degree of selectivity and extent of decomposition reaction).

[0134] Platinum on carbon catalysts from Sigma Aldrich with the following product numbers were used as catalysts:

[0135] Pt/C [w/w %] 10: product number: 80980−PVC [w/w %] 5: product number: 80982

TABLE-US-00001 TABLE 1 O.sub.2 Pressure T t GC Pt Pt/C Output # [l/h] [bar] [° C.] [h] [w/w %] [mol %] [w/w %] [%] (I):(II) (I):(IV) 1 22.5 — 70 12 8.3 5 10  0 — — 2 22.5 — 70 2 8.3 5 10 — 81 95 3 22.5 — 70 3 8.3 5 10 — 88 92 4 22.5 — 70 4 8.3 5 10 93 92 92 5 22.5 — 80 4 8.3 5 10 70 99 92 6 22.5 — 90 4 8.3 5 10 60 99 92 7 22.5 — 90 2 8.3 5 10 — 96 96 8 22.5 — 90 2 12 5 10 — 60 90 9 22.5 — 90 2 15.3 5 10 — 16 89 10 65.0 — 70 2 8.3 5 10 — 74 94 11 65.0 — 70 4 8.3 5 10 — 87 93 12 22.5 — 70 2 8.3 5 10 — 81 95 13 — 2 70 2 8.3 5 5 55 91 89 14 — 2 70 2 8.3 5 10 80 90 92 15 — 2 70 2 8.3 2.5 10 78 69 91

[0136] In examples 2, 3 and 7 to 12, the “output” was not determined.

[0137] Example 1 shows that after a reaction time of 12 hours all reactants were completely decomposed to CO.sub.2. Particular preference is given to a reaction time of 2 to 4 hours.

[0138] Example 5 shows (compared to examples 4 and 6) that a selectivity optimum with moderate output losses was achieved at a particularly preferred reaction temperature of 80° C. and a preferred reaction time of 4 hours.

[0139] Example 7 shows (compared to examples 8 and 9) that a glycerol carbonate concentration of 8.3 w/w % results in very high “(I):(II)” and “(I):(IV)” ratios compared to concentrations of 12 and 15.3 w/w % in examples 8 and 9 respectively, at otherwise identical reaction time.

[0140] Examples 2, 10 and 11 show that an increase of the oxygen flow rate results in no notable increase in the “(I):(II)” and “(I):(IV)” ratios (neither at a reaction time of 2 nor of 4 hours).

[0141] In contrast, examples 12 and 14 show that an increase in pressure in the reactor (i.e. in the closed reaction procedure) leads to an increase in the “(I):(II)” ratio.

[0142] The results of the examples conducted shown above show that the platinum loading of the heterogeneous catalyst influences the reaction parameters reaction time and reaction temperature (“t” and “T”) but not the quality of the reaction (read off by the “(I):(II)” and “(I):(IV)” ratios). For instance, examples 13 and 14 show that the reaction using a catalyst with reduced loading (example 13) results in very similar “(I):(II)” and “(I):(IV)” ratios but leads to a distinctly lower output (at identical reaction time).

[0143] Examples 14 and 15 show that a reduction in the absolute amount of platinum (cf. column Pt[mol %]) negatively affects the “(I):(II)” ratio.

[0144] According to Table 1, examples 4, 5 and 14 represent particularly preferred method procedures.

[0145] In all oxidation reactions carried out it was observed that the pH of the respective aqueous medium after 120 minutes was <0.5, starting from an initial pH in the range of 4 to 5 (at “t”=0 hours and the respective temperatures stated in each case in Table 1). The pH therefore fell in each of the examples by at least 3 pH units. A base or a buffer was not added to any of the respective suspensions.

[0146] The course of the pH is shown in more detail in Table 2 below for three selected example reactions. The example reaction shown in Table 2 conducted at a temperature of 70° C. corresponds to examples 10 and 11 in Table 1. The example reaction shown in Table 2 conducted at a temperature of 80° C. corresponds to example 5 and the example reaction conducted at 90° C. corresponds to example 6 in Table 1.

TABLE-US-00002 TABLE 2 70° C. 80° C. 90° C. Time Time Time [min] (I):(II) (I):(IV) pH [min] (I):(II) (I):(IV) pH [min] (I):(II) (I):(IV) pH 0 0 0 5.9 0 0 0 4.3 0 0 0 4.8 60 59 100 0.5 30 33 100 0.8 30 21 100 0.9 120 74 94 0.6 60 68 94 0.6 60 55 89 0.4 180 82 93 0.4 90 84 93 0.2 90 61 88 0.4 240 87 93 0.4 120 91 95 0.2 120 85 90 0.4 300 92 92 0.4 150 94 93 0.2 150 95 94 0.4 360 94 89 0.3 180 98 93 0.2 180 99 94 0.4 420 96 89 0.2 210 99 93 0.1 210 99 92 0.4 480 100 87 0.2 240 99 92 0.1 240 99 92 0.4

[0147] In addition, the influence of stabilizing the pH was investigated. In example 16 the pH was buffered to pH=5.5 during the reaction while in example 17 the pH was not stabilized. Further details and experimental parameters are summarized in Table 3 below.

TABLE-US-00003 TABLE 3 O.sub.2 Pressure T t GC Pt Pt/C Buffering # [l/h] [bar] [° C.] [h] [w/w %] [mol %] [w/w %] [pH] (I):(II) (I):(IV) 16 22.5 — 90 5 2.5 2.5 10 5.5 41 34 17 22.5 — 90 5 2.5 2.5 10 — 98 94

[0148] Comparison of examples 16 and 17 shows that much higher conversions and selectivities can be achieved without buffering.