Mechanistic clarification of the elementary reaction steps involved in the metalloporphyrins-catalyzed oxidation of hydrogen sulfide under aerobic aqueous conditions

好氧水条件下金属卟啉催化硫化氢氧化所涉及的基本反应步骤的机理阐明

• 批准号: 261818077
• 负责人: Professorin Dr. Ivana Ivanovic-Burmazovic
• 金额: --
• 依托单位: Lehrstuhl für Anorganische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/261818077?language=en
• 关键词: Mechanistic; clarification; elementary; reaction; steps

H2S is a highly toxic and corrosive environmental pollutant, which removal is necessary for pollution control and processing requirements in industry. In our recently filed patent (WO2012175630 A1 20121227) we describe an invention demonstrating that specially modified water soluble Fe, Mn, Co and Ni porphyrins (in particularly, highly positively charged ones) can be used for very efficient catalytic oxidation of H2S by O2 in pH neutral media. There is no need for separate catalyst re-oxidation, because catalysts are automatically regenerated by O2 present in the surrounding medium at ambient conditions. The catalytic reaction transforms H2S into either solid (elemental sulfur) or soluble products (sulfite/thiosulfate), the choice of which can be tuned by choosing appropriate pH conditions. But, elementary reaction steps behind the catalytic activity of certain metalloporphyrins, as well as the character of the intermediate species and the rate-determining steps are completely unknown. Elucidation of these points will provide the understanding of the factors that are responsible for the catalytic vs. stoichiometric reactivity of different types of metalloporphyrins. As scientists we are not just satisfied with a potential application of our findings and therefore we seek for mechanistic explanations on molecular level to rationally design catalytically active metal complexes based on understanding of their kinetic, thermodynamic, solution and redox behavior. Thus, the proposed studies involve careful examination and kinetic/thermodynamic analysis of each reaction step occurring in the course of the oxidation of the H2S/HS¿ mixtures at different pH by O2, with the application of selected series of water-soluble metalloporphyrins as catalysts. Moreover, the intended investigations will be associated with the identification and characterization of the chemical nature of the reactive intermediates responsible for the oxidation events, as well as with the examination of the catalytic ability of the active species as a function of various factors originating both from the chemical identity of the applied porphyrin catalyst (effects of the porphyrin ring, metal center, its spin-state and axial ligands) and from the selected reaction conditions (temperature, pH or polarity of the reaction medium, concentration of dioxygen and catalyst, etc). Special attention will be paid to the redox properties of the investigated highly charged metalloporphyrins as a function of pH and axial ligands, in order to address the question of inner- vs. outer-sphere electron transfer mechanism. Such systematic mechanistic studies of the catalytic H2S oxidation by metalloporphyrins at the molecular level have not yet been addressed in the literature. Besides the relevance in terms of environmentally and economically acceptable technologies, proposed research will also lead to advances in our understanding of biological effects of H2S.

H2S是一种剧毒、腐蚀性强的环境污染物，其去除是工业污染控制和处理要求所必需的。在我们最近提交的专利（WO2012175630 A1 20121227）中，我们描述了一项发明，该发明证明了特殊改性的水溶性Fe， Mn， Co和Ni卟啉（特别是高正电荷的卟啉）可用于pH中性介质中O2对H2S的高效催化氧化。不需要单独的催化剂再氧化，因为催化剂在环境条件下由周围介质中存在的O2自动再生。催化反应将H2S转化为固体（单质硫）或可溶性产物（亚硫酸盐/硫代硫酸盐），可通过选择适当的pH条件来调整其选择。但是，某些金属卟啉的催化活性背后的基本反应步骤、中间物质的性质和速率决定步骤是完全未知的。阐明这些观点将提供对不同类型的金属卟啉的催化与化学计量反应性的因素的理解。作为科学家，我们不仅满足于我们的发现的潜在应用，因此我们寻求分子水平上的机制解释，以合理地设计催化活性金属配合物，基于对其动力学，热力学，溶液和氧化还原行为的理解。因此，所提出的研究涉及到在不同pH下H2S/HS¿混合物被O2氧化过程中每个反应步骤的仔细检查和动力学/热力学分析，并选择了一系列水溶性金属卟啉作为催化剂。此外，预期的研究将与鉴定和表征导致氧化事件的活性中间体的化学性质有关，以及检查活性物质的催化能力作为各种因素的功能，这些因素来自所应用的卟啉催化剂的化学特性(卟啉环的作用，金属中心，其自旋态和轴向配体)以及所选择的反应条件（反应介质的温度、pH或极性、双氧和催化剂的浓度等）。将特别关注所研究的高电荷金属卟啉的氧化还原特性作为pH和轴向配体的函数，以解决内外球电子转移机制的问题。这种金属卟啉在分子水平上催化H2S氧化的系统机理研究尚未在文献中得到解决。除了在环境和经济上可接受的技术方面的相关性外，拟议的研究还将使我们对H2S的生物效应的理解取得进展。