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New Insights on the Dynamic Role of the Protecting Agent on the Reactivity of Supported Gold Nanoparticles
ChemCatChem ( IF 3.8 ) Pub Date : 2020-01-16 , DOI: 10.1002/cctc.201902061 Giorgio Grillo 1 , Federica Menegazzo 2 , Silvia Tabasso 3 , Michela Signoretto 2 , Maela Manzoli 1 , Giancarlo Cravotto 1
ChemCatChem ( IF 3.8 ) Pub Date : 2020-01-16 , DOI: 10.1002/cctc.201902061 Giorgio Grillo 1 , Federica Menegazzo 2 , Silvia Tabasso 3 , Michela Signoretto 2 , Maela Manzoli 1 , Giancarlo Cravotto 1
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A very efficient catalyst (AuCePVA) was prepared by depositing gold colloids on CeO2 and using polyvinyl alcohol (PVA) as protective agent. Complete conversion and selectivity in furfural (2‐FA) oxidative esterification to methyl‐2‐furoate (Me‐2‐F) was obtained without base under conventional heating at 120 °C. AuCePVA was compared with Au/CeO2 obtained by deposition‐precipitation method, pointing out that along with the size of the Au nanoparticles and the surface sites of the ceria support, also PVA chains played a role during reaction. In situ FTIR spectroscopy measurements of adsorbed molecules at controlled temperature and pressure demonstrated that PVA acted not merely as gold stabilizer, but also as mediator during the 2‐FA oxidative esterification, leaving both Au and ceria sites available for catalysis at the reaction temperature. In a perspective of process intensification, the microwave‐assisted (MW‐assisted) 2‐FA oxidative esterification was carried out. Depending on the reaction time and temperature, AuCePVA favoured the oxidation of the hemiacetal into the ester rather than the re‐oxidation of the acetal into the ester, due to the formation of Ce3+ sites under MW irradiation.
中文翻译：
保护剂对负载型金纳米粒子反应性动态作用的新见解
通过在CeO 2上沉积金胶体并使用聚乙烯醇（PVA）作为保护剂来制备非常高效的催化剂（AuCePVA）。在120°C的常规加热条件下，无需碱就可实现糠醛（2-FA）氧化酯化为2-糠酸甲酯（Me-2-F）的完全转化和选择性。将AuCePVA与通过沉积沉淀法获得的Au / CeO 2进行了比较，指出除了Au纳米颗粒的尺寸和二氧化铈载体的表面位点外，PVA链在反应过程中也发挥了作用。原位FTIR光谱在受控的温度和压力下对吸附分子的测量表明，PVA不仅充当金稳定剂，而且在2-FA氧化酯化过程中还充当介体，使Au和二氧化铈位点都可在反应温度下催化。从过程强化的角度出发，进行了微波辅助（MW辅助）2-FA氧化酯化反应。根据反应时间和温度，AuCePVA倾向于将半缩醛氧化成酯，而不是缩醛再氧化成酯，因为在MW辐射下会形成Ce 3+位点。
更新日期：2020-01-17
中文翻译：
保护剂对负载型金纳米粒子反应性动态作用的新见解
通过在CeO 2上沉积金胶体并使用聚乙烯醇（PVA）作为保护剂来制备非常高效的催化剂（AuCePVA）。在120°C的常规加热条件下，无需碱就可实现糠醛（2-FA）氧化酯化为2-糠酸甲酯（Me-2-F）的完全转化和选择性。将AuCePVA与通过沉积沉淀法获得的Au / CeO 2进行了比较，指出除了Au纳米颗粒的尺寸和二氧化铈载体的表面位点外，PVA链在反应过程中也发挥了作用。原位FTIR光谱在受控的温度和压力下对吸附分子的测量表明，PVA不仅充当金稳定剂，而且在2-FA氧化酯化过程中还充当介体，使Au和二氧化铈位点都可在反应温度下催化。从过程强化的角度出发，进行了微波辅助（MW辅助）2-FA氧化酯化反应。根据反应时间和温度，AuCePVA倾向于将半缩醛氧化成酯，而不是缩醛再氧化成酯，因为在MW辐射下会形成Ce 3+位点。
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