Abstract

Cu(Fe)-containing zeolites are promising catalysts for biomimetic functionalization of light hydrocarbons. Catalysts with various copper states have been elaborated and studied in the peroxide oxidation of methane to methanol and formic acid. ICP-AES, UV–vis DR, EPR, NH₃-TPD, H₂-TPR, and N₂ adsorption techniques were used for the characterization of the Cu(II) states, the textural, acidic and redox properties of the catalysts. The prepared zeolites contained the following Cu species: (1) isolated Cu²⁺ ions, (2) square planar binuclear oxo/hydroxo complexes ([Cu₂(OH)₂]²⁺) in the zeolite channels, (3) CuO- and/or Cu(OH)₂-like clusters and nanoparticles on the zeolite external surface. UV–vis DR spectroscopy also was used for studying the ability of different Cu-ZSM-5 to form Cu peroxocomplexes with H₂O₂. Three types of peroxocomplexes were detected. These were terminal Cu–OOH originated from the isolated Cu²⁺ ions, binuclear Cu(II) with a terminal OOH group and the binuclear Cu(II) with a bridging OO-group formed from the Cu-species with extra lattice oxygen. ¹H and ¹³C NMR analysis revealed the formation of methylhydroperoxide, formaldehyde, and CO₂ as side products during peroxide oxidation of methane. Two pathways of methane oxidation with hydrogen peroxide involving both binuclear Cu-species with extra-lattice oxygen and isolated Fe-sites and/or oligomer oxo-clusters of Fe(III) ions were supposed.

中文翻译：

---

H 2 O 2在Cu-ZSM-5催化剂的不同Cu物种上甲烷氧化

摘要

含铜（Fe）沸石是轻烃仿生功能化的有前途的催化剂。在甲烷过氧化物氧化为甲醇和甲酸的过程中，已经详细研究了具有各种铜态的催化剂。ICP-AES，UV-vis DR，EPR，NH ₃ -TPD，H ₂ -TPR和N ₂吸附技术用于表征Cu（II）态，催化剂的质构，酸性和氧化还原特性。制备的沸石包含以下Cu物种：（1）分离的Cu ²⁺离子，（2）沸石通道中的方形平面双核氧/氢氧配合物（[Cu ₂（OH）₂ ] ₂ ⁺），（3）CuO-和/或Cu（OH）₂类分子簇和沸石外表面上的纳米颗粒。紫外可见DR光谱学还用于研究不同的Cu-ZSM-5与H ₂ O ₂形成Cu过氧配合物的能力。检测到三种类型的过氧配合物。这些是末端Cu-OOH，其起源于分离的Cu ²⁺离子，具有末端OOH基团的双核Cu（II）和具有桥接OO-基团的双核Cu（II），其由具有额外晶格氧的Cu物种形成。¹ H和¹³ C NMR分析表明形成了甲基氢过氧化物，甲醛和CO ₂作为甲烷过氧化物氧化过程中的副产物。假定了过氧化氢甲烷氧化的两种途径，包括双晶铜物种和晶格外氧以及离析的Fe位和/或Fe（III）离子的低聚物氧簇。