美拉德反应与酱香型白酒

本文阐述了美拉德反应机理、反应产物及其香味情况;介绍了美拉德反应产物与酱香型白酒香味成份间的联系。作者以高温大曲为含菌样品,分离到一株嗜热芽孢杆菌——地衣芽孢杆菌,该菌在发酵过程中,不仅具有较高的分解蛋白质能力,且能促进美拉德反应发生,产生浓郁酱香物质——2.3—二氢—3.5—二羟—6甲基—4H—吡喃—4—酮。(又称5—羟基麦芽酚)。在生产过程中加入地衣芽孢杆菌强化发酵,对酱香型白酒质量的提高起到了一定的作用

On the Origin of the Errors of ik as Estimated from K-L Equation in Rotating Disk Electrode System

旋转圆盘电极（RDE）体系主要用于低溶解度反应物的电极过程动力学研究. 在利用RDE技术研究不可逆电极反应动力学时，人们常利用Koutecky-Levich方程排除传质的影响，从总电流估算反应的动力学电流. 由于K-L方程是建立在系统满足稳态扩散模型的基础上，实际运用时如果体系偏离稳态扩散，就有可能对估算的动力学参数造成很大误差. 本文以氧气在多晶铂电极上的还原反应为例系统地估算了不同氧气浓度与电极转速下的误差，结果表明低氧气浓度与低圆盘转速的情况不满足稳态扩散条件，若此时仍根据K-L方程利用外推法进行分析，误差可达30%. 因此作者建议，在RDE体系中利用K-L方程估算动力学参数时，最好忽略低浓度与低转速下的数据，直接使用较高浓度与较高转速下的数据进行计算与分析.Rotating disk electrode system is mainly used to study the kinetics of reactions whose reactants have very low solubility in the electrolyte. For an irreversible reaction, Koutecky-Levich equation (K-L Eq.) is frequently used to deduce the kinetic current ik). Since K-L Eq. is derived based on the assumption that a system should conform the steady-state diffusion conditions, the data recoded from the actual system which deviates from such a condition, great error may be induced for the ik estimated. In this work, polarization curves for oxygen reduction reaction at polycrystalline Pt electrode recorded in solutions with various O2 concentrations and under various electrode rotation speeds have been analyzed systematically. Our analysis reveals that an error of 30% may be introduced by extrapolation to infinite rotation speed in solution with low O2 concentration or by including the data recorded under very slow electrode rotation speeds. The origins of the error and the ways to avoid such error are discussed.国家自然科学基金项目（No. 21073176）及科技部973计划项目（No. 2010CB923302）资助作者联系地址：中国科技大学 化学物理系，合肥微尺度物质科学国家实验室（筹），安徽 合肥 230026Author's Address: Department of Chemical Physics, Hefei National Laboratory for Physical Sciences at Microscale; University of Science and Technology of China, Hefei 230026, China通讯作者E-mail：[email protected]

Recent Progress in the Mechanistic Understanding of Formic Acid Oxidation on Pt Electrode

本文综述了甲酸在铂电极上电催化氧化机理的实验和理论研究进展. 铂电极甲酸的电化学氧化主要有两种途径：1）间接途径，甲酸经由CO中间物氧化为最终产物CO2，室温下该途径对总电流贡献不超过1%；2）直接途径，甲酸直接氧化生成CO2. 作者课题组对文献中桥式吸附甲酸根是否是甲酸氧化反应直接途径的反应中间物的争论进行了详细的分析和探讨，认为桥式吸附的甲酸根不是间接途径中生成CO的前驱体，也不是甲酸直接氧化途径的中间物. 作者课题组还指出了支持甲酸根是甲酸直接氧化途径的反应中间物的推论的问题所在.This article reviews the recent progress in understanding of the mechanisms for formic acid oxidation on Pt electrode. There are two pathways for formic acid oxidation on Pt electrode: (1) Indirect Pathway through which HCOOH is oxidized to CO2 through COad intermediate. This pathway contributes only 1% of the total current; (2) Direct Pathway where HCOOH is oxidized directly to CO2. The results from IR Spectroscopy, single-crystal electrochemistry and DFT calculation all support that the bridge-bonded formate is neither the intermediate of direct pathway nor the precursor for COad formation in indirect pathway. Possible mechanism in the direct pathway for formic acid oxidation is discussed.国家自然基金面上项目（No. 21273215）资助作者联系地址：中国科技大学 化学物理系，合肥微尺度物质科学国家实验室（筹），安徽 合肥 230026Author's Address: Hefei National Laboratory for Physical Science at Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei, 230026, China通讯作者E-mail：[email protected]