Methacrylic acid (MAA) is a specialty monomer for poly methyl methacrylate (PMMA). Partial oxidation of 2-methyl-1,3-propanediol (2MDPO) to MAA is an alternative to commercial technology with fewer process steps, less cost and toxic feedstocks, and longer catalyst lifetime. Here, we evaluated the effect of 2MPDO and oxygen concentrations, reaction temperature, and contact time on product selectivity and 2MPDO conversion over VOCu_0.5/Cs(NH₄)₂PMo₁₂O₄₀. Higher temperature increases selectivity and conversion; MAA selectivity reached 46% at 69% 2MPDO conversion. Higher 2MPDO to O₂ ratio favours higher MAA selectivity due to methacrolein (intermediate) oxidation to MAA (a higher ratio favours consecutive oxidation) or lower combustion of MAA to CO_x. Shorter contact times decrease MAA selectivity. The Mars van Krevelen model characterizes the experimental data better than both the Langmuir-Hinshelwood or Eley-Rideal models; The reaction sequence involves both direct and indirect reactions in which 2MPDO reacts to methacrolein (MAC) as an intermediate and then it oxidizes to MAA (indirect) and/or 2MPDO directly oxidizes to MAA but the indirect reaction rate to MAA is 50 times faster than the direct reaction rate. The reaction is first order with respect 2MPDO and oxygen, and the rate-limiting step is 2MPDO activation on oxidized sites.

中文翻译：

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2-甲基-1,3-丙二醇在流化床反应器中氧化为甲基丙烯酸的动力学

甲基丙烯酸 (MAA) 是聚甲基丙烯酸甲酯 (PMMA) 的特种单体。将 2-甲基-1,3-丙二醇 (2MDPO) 部分氧化为 MAA 是商业技术的替代方案，具有更少的工艺步骤、更低的成本和有毒原料以及更长的催化剂寿命。在这里，我们评估了 2MPDO 和氧气浓度、反应温度和接触时间对 VOCu _0.5 /Cs(NH ₄ ) ₂ PMo ₁₂ O ₄₀上的产物选择性和 2MPDO 转化率的影响。较高的温度会增加选择性和转化率；MAA 选择性在 69% 2MPDO 转化率下达到 46%。更高的 2MPDO 到 O ₂由于异丁烯醛（中间）氧化为 MAA（较高的比率有利于连续氧化）或 MAA 到 CO _{x 的}较低燃烧，比率有利于较高的 MAA 选择性。较短的接触时间会降低 MAA 的选择性。Mars van Krevelen 模型比 Langmuir-Hinshelwood 或 Eley-Rideal 模型更能表征实验数据；反应顺序包括直接和间接反应，其中 2MPDO 作为中间体与甲基丙烯醛 (MAC) 反应，然后氧化为 MAA（间接）和/或 2MPDO 直接氧化为 MAA，但生成 MAA 的间接反应速率比生成 MAA 快 50 倍。直接反应速率。该反应是关于 2MPDO 和氧气的一级反应，限速步骤是氧化位点上的 2MPDO 活化。