Au-Pd bimetallic catalyst, application of Au-Pd bimetallic catalyst in selective preparation of lactic acid by catalytic oxidation of 1,2-propylene glycol and preparation method
A bimetallic catalyst and catalytic oxidation technology, which is applied in the direction of metal/metal oxide/metal hydroxide catalyst, organic compound preparation, carboxylate preparation, etc., can solve the problem of harsh reaction conditions and achieve less catalyst consumption , good catalytic life, and mild reaction conditions
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Embodiment example 1
[0034] (1) Preparation of supported Au-Pd bimetallic catalyst: Au-Pd catalyst was prepared by immobilized sol method. First configure a certain concentration of PdCl 2 and HAuCl 4 solution, adding polyvinyl alcohol (PVA) (1 wt%, PVA / metal = 1.2 (wt / wt)) as a gelling agent. Cool in an ice-water bath, slowly add 0.1 M NaBH 4 (NaBH 4 / metal=5 mol / mol) to form a dark brown sol. Continue to stir for 30 min, add carrier to the suspension under vigorous stirring, stir for 2 h, centrifuge 3 times at 8000 r / min, wash with deionized water at 70 °C to remove excess PVA and Cl - , dried overnight at 110 ℃ to prepare the Au-Pd bimetallic catalyst.
[0035] figure 1 for Au-Pd / CeO 2 Catalyst XRD pattern, only the corresponding CeO appears on the catalyst diffraction pattern 2 The diffraction peaks of Au and Pd crystals did not appear, so it can be considered that the Au-Pd / CeO prepared by the immobilized sol method 2 The Au and Pd particles on the catalyst are well dispersed without...
Embodiment example 2
[0042] The Au-Pd catalyst was prepared by the same method as in Example 1, and the process of catalytic oxidation of 1,2-propanediol to lactic acid was the same as in Example 1, but the stirring speed of the reactor was 200 r / min, 400 r / min, and 600 r / min, 800 r / min, 1000 r / min and 1200 r / min, the effect of stirring rate on the reaction performance of 1,2-propanediol can be obtained.
[0043] It can be seen from the above that when the stirring rate is lower than 800 r / min, the conversion rate of 1,2-propanediol and the selectivity of lactic acid gradually increase with the increase of the stirring rate. The conversion rate increases slowly, but the selectivity of lactic acid decreases gradually, therefore, the more suitable stirring speed is 800 r / min.
Embodiment example 3
[0045] The Au-Pd catalyst was prepared by the same method as in Example 1, and the process of catalytic oxidation of 1,2-propanediol to lactic acid was the same as in Example 1, but the reaction temperatures were 50 °C, 60 °C, 70 °C, 80 °C and 90 °C , the effect of reaction temperature on the reactivity of 1,2-propanediol can be obtained.
[0046] It can be seen from the above that, as the reaction temperature rises, the conversion rate of 1,2-propanediol continues to increase, and high temperature is beneficial to the conversion of 1,2-propanediol. However, when the reaction temperature exceeds 80 °C, the selectivity of lactic acid drops sharply, which may be caused by the deep oxidation reaction of the formed lactic acid due to the high temperature. Therefore, the suitable reaction temperature is 80 °C.
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