Acrylic acid, an important starting compound for a wide variety of consumer products, is generally produced through selective oxidation of propene. A more sustainable approach would be its synthesis from lactic acid, since this compound is generally produced by fermentation of renewable sugar streams. Up to now, most research on this reaction has involved gas phase reactions, which require high temperatures, often above 300 °C. Building on our previous work, which demonstrated the ionic liquid tetrabutylphosphonium bromide, combined with an acid cocatalyst, as an interesting catalyst for dehydration and dehydrohalogenation reactions, we here report the use of this catalytic system in the conversion of lactide to acrylic acid. Initial experiments showed the formation of the volatile side products ethylene, bromoethane and acetaldehyde, which could explain mass loss that was not well understood heretofore. A combination of liquid phase GC analysis and gas phase FTIR spectroscopy allowed us to close the mass balance. As a result, a reaction network was proposed and supported by experimental studies. Finally, the insights in the reaction network were applied to achieve a very good acrylic acid yield of 70%.

中文翻译：

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phospho离子液体和酸助催化剂将丙交酯转化为丙烯酸†

丙烯酸是多种消费产品的重要起始化合物，通常是通过丙烯的选择性氧化来生产的。一种更可持续的方法是由乳酸合成，因为这种化合物通常是通过可再生糖料流的发酵生产的。到目前为止，对该反应的大多数研究都涉及气相反应，这需要高温，通常要高于300°C。基于我们先前的工作，该工作证明了离子液体溴化四丁基phosph与酸助催化剂的结合，作为脱水和脱卤化氢反应的有趣催化剂，我们在此报告了该催化体系在丙交酯向丙烯酸转化中的应用。初步实验表明，会形成挥发性副产物乙烯，溴乙烷和乙醛，这可以解释迄今为止尚不十分了解的质量损失。液相气相色谱分析和气相FTIR光谱相结合，使我们能够平衡质量平衡。结果，提出了反应网络并得到了实验研究的支持。最后，将反应网络中的见解应用于获得非常高的丙烯酸收率70％。