Method for preparing lactide by catalytic method under reduced pressure
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A lactide and catalyst technology, which is applied in the field of lactide preparation by decompression catalytic method, can solve the problems of increased cost, high distillation temperature, waste of raw materials, etc.
Inactive Publication Date: 2012-09-19
NANYANG INST OF TECH
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However, the reaction process is still due to the high distillation temperature, and the final waste residue is 7.6%-20%.
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Embodiment 1
[0021] L-lactic acid is used as raw material to prepare lactide by vacuum catalytic distillation. First, put 200ml of lactic acid into a three-necked flask, and remove the free water in the lactic acid at 75°C and 0.085MPa vacuum for 1 hour;
[0023] Then keep warm at 0.085MPa vacuum degree and 125°C, and decompose water for 5 hours;
[0024] Stir and heat up to 168°C, lactide is distilled out, and the temperature is gradually raised to collect lactide, the highest temperature is 200°C, distillation is 8h, and the crude yield reaches 86%.
Embodiment 2
[0026] L-lactic acid is used as raw material to prepare lactide by vacuum catalytic distillation. First, put 300ml of lactic acid into a three-necked flask, and remove the free water in the lactic acid at 90°C and 0.090MPa vacuum for 2 hours;
[0027] Add catalyzer namely the zinc oxide of reactant mass percent 1%, the stannous octoate of reactant mass percent 1% and the sodium dodecylsulfonate of reactant mass percent 1%;
[0028] Then keep warm at 0.090MPa vacuum degree and 135°C for dehydration reaction for 5h;
[0029] Stir and heat up to 165°C, lactide is distilled out, and the temperature is gradually raised to collect lactide, the highest temperature is 190°C, distillation is 8h, and the crude yield reaches 91%.
[0030] Such as figure 1 As shown, the measurement data of lactide prepared by adding zinc oxide, stannous octoate and sodium dodecylsulfonate after dehydration: infrared spectrum, melting point: 125.4-126.5 ° C, can reduce the lactide production process The...
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Abstract
The invention discloses a method for preparing lactide by a catalytic method under reduced pressure, which is characterized by comprising the following steps: firstly, removing free water in lactic acid at a temperature is 75-90 DEG C and at a vacuum degree of 0.080-0.090 MPa for 1-2 hours; secondly, adding a catalyst and a surfactant, wherein the catalyst consists of zinc oxide with a reactant mass percentage of 0.5-1 percent and stannous octoate with a reactant volume ratio of 0.5-1 percent, the surfactant is Tween 80 with a reactant volume ratio of 0.5-1 percent or sodium dodecyl sulfate with a reactant mass percentage of 0.5-1 percent ; thirdly, at a vacuum degree of 0.080-0.090 MPa and a temperature of 125-135 DEG C, removing combined water and reacting for 5 hours; and fourthly, agitating and raising the temperature to 165-200 DEG C, distilling and collecting the lactide with a crude production rate of 83-91 percent. The method has the beneficial effects that the distillation temperature of the lactide in the lactide preparation process can be reduced, the energy consumption is reduced, the by-product quantity generated at high temperature is reduced, the preparation production rate of the lactide is further improved, and the production cost is reduced.
Description
technical field [0001] The invention belongs to the technical field of preparation of chemical raw materials for biodegradable material intermediates, and in particular relates to a method for preparing lactide by a decompression catalytic method. Background technique [0002] Lactide is an important intermediate in the synthesis of polylactic acid, and its preparation is a key factor affecting the ring-opening polymerization of high molecular weight PLA. At present, most of the synthesis of lactide has a high cracking temperature, so that the energy consumption is very high, and the high-temperature oxidation causes the increase of by-products, and the final yield of lactide is very low, so the price of the prepared lactide is higher than that of the raw material lactic acid. hundred times. In the prior art, such as "Synthesis of High-yielding Lactide", Journal of Chongqing University. 2003, 26 (1): 41-47, using analytically pure zinc oxide as a catalyst, its yield is 68.6...
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