Unraveling Structure-Functionality Relationships of Shape-Defined Cu2O Nanocrystal Model Catalysts for Methanol Decomposition
Kaan Karaca
M.Sc. in Chemistry
Advisor: Prof. Dr. Emrah Özensoy
Date: 29.08.2024
Time: 10:30
Place: Chemistry Meeting Room (1st floor – SB Building)
Abstract
Methanol is one of the centerpieces of the chemical industry as a C1 building block and an intermediate producing high-value chemicals such as formaldehyde, methyl methacrylate, methyl tertiary-butyl ether/ tertiary-amylmethylether, and acetic acid. This thesis focuses on the structure-functionality relationships of shape-defined Cu2O model catalysts for methanol decomposition. Cubic and octahedral Cu2O nanocrystal catalysts were synthesized and characterized by various ex-situ methods such as Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), X-Ray Absorption Near Edge (XANES), Extended X-Ray Absorption Fine Structure (EXAFS), Attenuated Total Reflectance Infrared Spectroscopy (ATR-IR), X-Ray Photoelectron Spectroscopy (XPS) and H2-Temperature Programmed Reduction (H2-TPR). The nature of the surface-active sites were characterized by CO adsorption via in-situ Fourier Transform Infrared Spectroscopy (in-situ FTIR) and the morphology-dependent methanol and formaldehyde decomposition properties were studied via in-situ FTIR and Temperature Programmed Desorption (TPD). The results showed that c-Cu2O and o-Cu2O have distinct structure-functionality relationships for methanol decomposition. While o-Cu2O showed higher activity and selectivity towards dioxymethylene production, it lacked activity in producing formate species by further oxidization. On the other hand, c-Cu2O showed superior activity in formate production. Increased formate production over c-Cu2O resulted in significant CO2 production while the selectivity was shifted towards CO for o-Cu2O during methanol TPD. Furthermore, the methanol TPD results demonstrated that c-Cu2O produces syngas suitable for the Fischer-Tropsch process while o-Cu2O showed higher suitability for steam reforming of methanol thus, unraveling the structure-functionality relationships of shape-defined Cu2O nanocrystal model catalysts for methanol decomposition.
Keywords: Cu2O, Methanol Decomposition, Model Catalysts, Structure-Functionality Relationships