The sustainable synthesis of two important intermediates relevant for the production of bio-based polymers, 2,5-furandicarboxylic acid (FDCA) and 5-hydroxymethyl-2-furancarboxylic acid (HFCA), via oxidation of 5-(hydroxymethyl)furfural (HMF) was investigated using supported gold- and silver-based catalysts in water with air as the oxidant. High yields and selectivities for the production of FDCA (89%) and HFCA (≥98%) were achieved under the optimized reaction conditions with Au/ZrO₂ and Ag/ZrO₂ catalysts, respectively. While FDCA was mainly formed in the presence of gold catalysts at a maximum productivity of 67 mol_FDCA h⁻¹ mol_Au⁻¹, silver catalysts showed a remarkably high activity in aldehyde oxidation producing HFCA in almost quantitative yields with a maximum productivity of 400 mol_HFCA h⁻¹ mol_Ag⁻¹. By variation of the reaction parameters, the Au/ZrO₂ catalyst could be tuned to produce also HFCA, whereas the Ag/ZrO₂ catalyst exclusively produced HFCA in a wide range of reaction parameters. The observed differences in catalyst selectivities can be taken as a starting point for further mechanistic investigation on the oxidation of HMF, contributing to a fundamental understanding of this reaction which is particularly important for establishing the production of bio-based polymers.

中文翻译：

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负载型金和银基催化剂，用于将5-（羟甲基）糠醛选择性好氧氧化为2,5-呋喃二甲酸和5-羟甲基-2-呋喃甲酸

通过氧化5-（羟甲基）糠醛（HMF）可持续合成与生物基聚合物生产相关的两种重要中间体2,5,5-呋喃二甲酸（FDCA）和5-羟甲基-2-呋喃甲酸（HFCA））是在水中以空气为氧化剂，使用负载型金和银基催化剂研究的。在优化的反应条件下，分别用Au / ZrO ₂和Ag / ZrO ₂催化剂可实现高产量和选择性的生产FDCA（89％）和HFCA（≥98％）。FDCA主要在金催化剂存在下形成，最大生产率为67 mol _FDCA h ^-1 mol _Au ^-1，银催化剂在醛氧化反应中显示出很高的活性，以几乎定量的产率产生HFCA，最大生产率为400 mol _HFCA h ^-1 mol _Ag ^-1。通过改变反应参数，可以调节Au / ZrO ₂催化剂以产生HFCA，而Ag / ZrO ₂催化剂在很宽的反应参数范围内只产生HFCA。观察到的催化剂选择性差异可以作为进一步研究HMF氧化机理的起点，有助于对该反应的基本了解，这对于建立生物基聚合物的生产特别重要。