Liu Qingjing, Wang Ruisheng, Li Ranjia, Wang Xiaosheng, Zhao Suoqi, Yu Changchun
State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing, 102249, P. R. China.
College of New Energy and Materials, China University of Petroleum, Beijing, 102249, P. R. China.
ACS Omega. 2024 Aug 17;9(34):36751-36760. doi: 10.1021/acsomega.4c05565. eCollection 2024 Aug 27.
Mn-NaWO-based catalysts with different supports were prepared using the incipient wetness impregnation method and evaluated for their oxidative coupling of methane (OCM) reaction performance. The results demonstrated that the SiO- supported catalyst exhibited the best catalytic performance, and the introduction of HO further enhanced its activity. Under the conditions of a feed gas mixture of CH/O/HO = 6:1:24 at 800 °C and atmospheric pressure, the CH conversion and C selectivity over the Mn-NaWO/SiO catalyst increased from 28.4% and 77.4% (without HO) to 33.2% and 84.9%, respectively. In contrast, the catalytic activity using TiO and MgO supports drastically declined. Characterizations using X-ray diffraction (XRD), infrared spectroscopy ( IR), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H-TPR), and oxygen temperature-programmed desorption (O-TPD) revealed that the introduction of steam not only served as a diluent to decrease the partial pressures of the reactants CH and O, thereby reducing deep oxidation reactions in the gas phase, but also interacted with surface oxygen species (O ) and silica to form adjacent surface-bonded disilanol free radicals Si-OH. This interaction facilitated the dehydrogenation and coupling of two methane molecules on the catalyst surface, resulting in the generation of C products, significantly enhancing the catalytic activity and selectivity of OCM.
采用初湿浸渍法制备了具有不同载体的锰-钨酸钠基催化剂，并对其甲烷氧化偶联（OCM）反应性能进行了评价。结果表明，SiO₂负载的催化剂表现出最佳的催化性能，引入H₂O进一步提高了其活性。在800℃和常压下，CH₄/O₂/H₂O = 6:1:24的原料气混合物条件下，Mn-NaWO₄/SiO₂催化剂上的CH₄转化率和C₂选择性分别从28.4%和77.4%（无H₂O时）提高到33.2%和84.9%。相比之下，使用TiO₂和MgO载体时催化活性急剧下降。利用X射线衍射（XRD）、红外光谱（IR）、X射线光电子能谱（XPS）、氢气程序升温还原（H₂-TPR）和氧气程序升温脱附（O₂-TPD）进行表征发现，引入蒸汽不仅作为稀释剂降低了反应物CH₄和O₂的分压，从而减少了气相中的深度氧化反应，还与表面氧物种（O*）和二氧化硅相互作用形成相邻的表面键合二硅醇自由基Si-OH。这种相互作用促进了两个甲烷分子在催化剂表面的脱氢和偶联，导致C₂产物的生成，显著提高了OCM的催化活性和选择性。
