Inhibition of acrylic acid polymerization by phenothiazine and p-methoxyphenol. II. Catalytic inhibition by phenothiazine
Inhibition of acrylic acid polymerization by phenothiazine and p-methoxyphenol. II. Catalytic inhibition by phenothiazine
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吩噻嗪和对甲氧基苯酚抑制丙烯酸聚合。
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
Leon B. Levy
中科院分区：
文献类型：
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作者：
Leon B. Levy
对甲氧基苯酚对丙烯酸的抑制符合传统的化学计量机制，但吩噻嗪通过完全不同的催化循环抑制丙烯酸，该循环不依赖于氧的存在。我们认为这一机制可能涉及自由基、吩噻嗪n -基化和吩噻嗪本身之间的一对单电子转移反应，后者是循环再生的。推导了用吩噻嗪、对甲氧基酚和吩噻嗪在无氧条件下稳定的丙烯酸中抑制剂和氧的消失率的Arrhenius方程。高氧对对甲氧基酚消耗比的实际意义是相当重要的：如果商业丙烯酸（通常用对甲氧基酚稳定）在储存过程中被无意中加热，决定聚合开始的限制物质将是溶解氧而不是对甲氧基酚，除非氧气（空气）被供应并以足以克服其消耗速度的速度溶解在液体中。
Inhibition of acrylic acid by p-methoxyphenol fits a conventional stoichiometric mechanism but phenothiazine inhibits acrylic acid via a completely different, catalytic cycle which does not depend on the presence of oxygen. We propose that this mechanism may involve a pair of single electron transfer reactions between free radicals, phenothiazine N-radicalcation, and phenothiazine itself, the latter being cyclically regenerated. Arrhenius equations were derived for the rates of disappearance of inhibitor and oxygen in acrylic acid stabilized with phenothiazine and with p-methoxyphenol and also with phenothiazine in the absence of oxygen. The practical implication of high oxygen to p-methoxyphenol consumption ratios is quite important: if commercial acrylic acid (usually stabilized with p-methoxyphenol) is inadvertently heated during storage, the limiting substance determining the onset of polymerization will be the dissolved oxygen and not p-methoxyphenol unless oxygen (air) is being supplied to and dissolved in the liquid at a rate sufficient to overcome the rate of its consumption.