Gas–phase oxidation of methacrolein to methacrylic acid was carried out over an acid-modified Cr₂O₃/SiO₂ catalyst. While only total oxidation occurred over bare Cr₂O₃/SiO₂, the acid-modified Cr₂O₃/SiO₂ showed catalytic activity for the formation of methacrylic acid. In particular, H₃PW₁₂O₄₀ strong Brønsted acid was the most effective modifier for improving both activity and selectivity. The interface between Cr₂O₃ and H₃PW₁₂O₄₀ particles on SiO₂ appears to be responsible for the formation of active sites for the selective formation of methacrylic acid. The strong Brønsted acid would help the activation of methacrolein through rendering it more electrophilic, which is a key step for the formation of methacrylic acid over the present catalyst.

在酸改性的Cr ₂ O ₃ / SiO ₂催化剂上将甲基丙烯醛气相氧化为甲基丙烯酸。尽管仅在裸露的Cr ₂ O ₃ / SiO _2上发生了完全氧化，但酸改性的Cr ₂ O ₃ / SiO ₂表现出了催化活性，从而形成了甲基丙烯酸。特别地，H ₃ PW ₁₂ O ₄₀强布朗斯台德酸是同时提高活性和选择性的最有效的改性剂。Cr ₂ O ₃和H ₃ PW ₁₂ O之间的界面SiO ₂上的_40个颗粒似乎负责形成活性位点，以选择性地形成甲基丙烯酸。强布朗斯台德酸通过使其更具亲电性而有助于活化甲基丙烯醛，这是在本催化剂上形成甲基丙烯酸的关键步骤。