ABSTRACT

The results of experimental study on effectiveness of gas-phase total oxidation of toluene towards carbon dioxide and water with the aid of ozone over Co(II)/SiO₂ catalyst are presented in this work. The main objective of the work was to determine ozone demand necessary for total mineralization of toluene at the temperature range of 40–100°C chosen to minimize catalyst poisoning by water. Complete mineralization of toluene was possible if sufficient ozone/toluene ratio was maintained in the gas supplied to the reactor. For ozone/toluene molar ratios less than 20 the extent of toluene mineralization increased with temperature up to a plateau starting at approximately 60°C, which was caused by ozone shortage. Stoichiometry of the total oxidation of toluene with ozone indicates that only one oxygen atom in the ozone molecule is used for the oxidation of toluene, to achieve complete mineralization. Experimentally determined ozone/toluene ratio (20–25) necessary for the total oxidation of toluene was larger than the theoretical one mostly due to ozone losses resulting from its ‘unproductive’ decomposition. At the range of lower values of mineralization rate, the toluene oxidation proceeds according to a more efficient mechanism, indicating less ozone demand being between 6 and 18 moles of ozone per mole of toluene. A possible mechanism of toluene oxidation was suggested. The mechanism involves the formation of •OH radicals, which may explain the effectiveness of Co(II)/SiO₂ catalyst in combination with ozone for the oxidation of toluene and other aromatic VOCs in a low-temperature process.

摘要

Co(II)/SiO ₂臭氧辅助甲苯气相​​全氧化生成二氧化碳和水的实验研究结果催化剂在这项工作中提出。这项工作的主要目标是确定在 40-100°C 的温度范围内甲苯完全矿化所需的臭氧需求，以最大程度地减少水对催化剂的中毒。如果在供应到反应器的气体中保持足够的臭氧/甲苯比率，则甲苯的完全矿化是可能的。对于小于 20 的臭氧/甲苯摩尔比，甲苯矿化的程度随着温度的升高而增加，直到从大约 60°C 开始达到稳定状态，这是由臭氧短缺引起的。用臭氧对甲苯进行总氧化的化学计量表明，臭氧分子中只有一个氧原子用于甲苯的氧化，以实现完全矿化。实验确定的甲苯总氧化所需的臭氧/甲苯比 (20-25) 大于理论值，这主要是由于其“非生产性”分解造成的臭氧损失。在矿化速率的较低值范围内，甲苯氧化根据更有效的机制进行，表明每摩尔甲苯需要较少的臭氧，在 6 至 18 摩尔臭氧之间。提出了甲苯氧化的可能机制。该机制涉及 •OH 自由基的形成，这可以解释 Co(II)/SiO 的有效性 每摩尔甲苯需要 6 到 18 摩尔臭氧，这表明臭氧需求较少。提出了甲苯氧化的可能机制。该机制涉及 •OH 自由基的形成，这可以解释 Co(II)/SiO 的有效性 每摩尔甲苯需要 6 到 18 摩尔臭氧，这表明臭氧需求较少。提出了甲苯氧化的可能机制。该机制涉及 •OH 自由基的形成，这可以解释 Co(II)/SiO 的有效性₂催化剂与臭氧结合用于在低温过程中氧化甲苯和其他芳香族 VOC。