Heteropoly acids are among the best catalysts to produce carboxylic acids from light hydrocarbons. The Keggin structure maintains metals at a high oxidation particularly in the presence of cesium, vanadium, and copper. They effectively catalyze the partial oxidation of 2-methyl-1,3-propanediol (2MPDO)—a co-product in the hydroformylation of allyl alcohol to 1–4 butanediol. Converting 2MPDO to methacrylic acid would improve the economics of this route to 1–4 butanediol. Here, we establish the relationship between heteropoly acid performance and calcination temperature at 300 °C and 350 °C. The molybdenum oxidation state was higher after the high temperature treatment but it reduced to a greater extent during reaction (from Mo⁶⁺ to Mo⁵⁺). The higher extent of reduction confirms the higher O²⁻ → Mo⁶⁺ charge-transfer in the Keggin anion. Maximum MAA and MAC selectivities were 61% and 28%, respectively, at 250 °C after 480 min over cycling oxidation–reduction and 2MPDO/O₂/Ar = 13/10/77 as the best reaction condition and feed composition. Though, the route of direct dehydration of 2MPDO (C–OH bond cleavage) followed by oxidation to MAC is the most direct path to the products detected, we propose a mechanism that passes through the homolytic dissociation of the tertiary C–H bond,considering that bonding energies energies are very similar.

杂多酸是从轻烃生产羧酸的最佳催化剂之一。Keggin结构使金属保持高氧化度，特别是在铯，钒和铜的存在下。它们有效催化2-甲基-1,3-丙二醇（2MPDO）的部分氧化，这是烯丙醇加氢甲酰化成1-4丁二醇的副产物。将2MPDO转化为甲基丙烯酸将提高该路线至1-4丁二醇的经济性。在这里，我们建立了杂多酸性能与300°C和350°C煅烧温度之间的关系。高温处理后，钼的氧化态较高，但在反应过程中还原程度更大（从Mo ⁶⁺到Mo ⁵⁺）。还原程度越高，则证实Keggin阴离子中的O ²⁻  →Mo ⁶⁺电荷转移越高。经过最佳的反应条件和进料组成，经过循环氧化还原和2MPDO / O ₂ / Ar = 13/10/77循环480分钟后，在250°C时，最大MAA和MAC选择性分别为61％和28％。尽管将2MPDO直接脱水（C–OH键断裂）然后氧化为MAC的途径是检测到的产物的最直接途径，但我们提出了一种通过叔C–H键的均质解离的机制，考虑到结合能的能量非常相似。