Synthesis of n-Butyl Lactate by Transition-Metal-Substituted Phosphotungstic Acid Salt

Fatty acid ester perfume occupied an important position in food industry. The characteristics of them were variety, easy synthesis and low price. They were widely used in daily flavor, edible flavor and industrial flavor. POMs were a kind of stong acid bifunctional mild environment-friendly catalysts, their drawback was excellent solubility and could not be reused. Here, series of transition-metal-substituted phosphotungstate K6 [PW11O39MⅡ (H2O)] (M = Cu, Co, Ni) Lewis acid heterogeneous phase catalysts based on mono-lacunary-Keggin type K7 [PW11O39] were prepared by stereoselect-eve method, K6 [PW11O39MⅡ (H2O)] (M = Cu, Co, Ni) were abbreviated as PW11MⅡ (H2O) (M = Cu, Co, Ni). They were characterized by FT-IR, PXRD and element analysis. The coordinating water of transition metal was Lewis acid catalytic sites after activated. When mole ratio of butanol and lactic acid was 2: 1, amount of PW11MⅡ (H2O) (M = Cu, Co, Ni) was 0.125 g, volume of cyclohexane was 15 mL, the reaction temperature was 105°C, reaction time was 2 h, conversion rate of n-butyl lactate were in order: 85.9%, 79.6%, 66.3%. Activity of PW11X (X = Cu, Co, Ni) had no obvious changes after three times recycling. In addition, magnetic studies indicate that antiferromagnetic interactions exist in the three compounds