Jafar Mohsin, Kumar Adarsh, Gupta Vinita G, Tyagi Avesh K, Bhattacharyya Kaustava
Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.
Homi Bhabha National Institute, Mumbai 400 094, India.
ACS Omega. 2025 Mar 25;10(13):13080-13104. doi: 10.1021/acsomega.4c10501. eCollection 2025 Apr 8.
Toluene, a highly stable aromatic hydrocarbon, is utilized as a benchmark molecule for thermal mineralization by the catalytic community. Mostly, the catalysts used for toluene mineralization either use platinum group metals (PGM) as catalysts or are regulated by a plasma incinerator. Though these catalysts/processes promise better efficiency and lower reaction temperature, they are neither cost-effective nor do they produce thermally stable byproducts. However, most of the metal-oxide catalysts used for toluene degradation are less efficient owing to incomplete mineralization and formation of stable intermediates, which results in higher mineralization temperature. The present work showcases tungsten- and molybdenum-based Scheelites [BaXO (X = W, Mo, and MoW)], which have been utilized for toluene mineralization at ∼200 °C. The intermediates formed during adsorption and thermal reaction are deciphered as a function of temperature using in situ FT-IR studies including their kinetic behavior. These surface intermediates formed over the Scheelite catalysts under an oxidative/inert atmosphere elucidate the toluene mineralization mechanism as a function of temperature/time. The surface active sites for these oxide catalysts for both adsorption and formation of reaction intermediates are deciphered using detailed X-ray photoelectron spectroscopy (XPS) studies. It shows the effective role of the oxidation states of constituent oxides M-O (M = Mo/ W) in the reaction mechanism. Mineralization of in a nonoxidative atmosphere shows a Mars and Van Krevelen (MVK) type of mechanism, suggesting participation of lattice oxygen for the catalytic reaction. To the best of our knowledge, this work represents one of the lowest temperatures achieved for toluene mineralization using oxide catalysts. The identification of reaction intermediates can guide further optimization efforts to minimize the mineralization temperature.
甲苯是一种高度稳定的芳烃，被催化领域用作热矿化的基准分子。大多数用于甲苯矿化的催化剂要么使用铂族金属（PGM）作为催化剂，要么由等离子体焚烧炉调控。尽管这些催化剂/工艺有望实现更高的效率和更低的反应温度，但它们既不具有成本效益，也不会产生热稳定的副产物。然而，大多数用于甲苯降解的金属氧化物催化剂由于矿化不完全和形成稳定中间体而效率较低，这导致矿化温度较高。目前的工作展示了基于钨和钼的白钨矿[BaXO（X = W、Mo和MoW）]，它们已被用于在约200°C下进行甲苯矿化。使用原位傅里叶变换红外光谱（FT-IR）研究，包括其动力学行为，将吸附和热反应过程中形成的中间体作为温度的函数进行解析。在氧化/惰性气氛下，这些在白钨矿催化剂上形成的表面中间体阐明了甲苯矿化机理与温度/时间的关系。使用详细的X射线光电子能谱（XPS）研究解析了这些氧化物催化剂用于吸附和反应中间体形成的表面活性位点。结果表明，组成氧化物M-O（M = Mo/W）的氧化态在反应机理中发挥了有效作用。在非氧化气氛中甲苯的矿化显示出Mars和Van Krevelen（MVK）类型的机理，表明晶格氧参与了催化反应。据我们所知，这项工作代表了使用氧化物催化剂实现甲苯矿化的最低温度之一。反应中间体的鉴定可以指导进一步的优化工作，以尽量降低矿化温度。
