Oxidative cracking of harmful aromatic compounds and the recycling

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K19089
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 34:Inorganic/coordination chemistry, analytical chemistry, and related fields
• Research Institution: University of Tsukuba
• Principal Investigator: Kojima Takahiko 筑波大学, 数理物質系, 教授 (20264012)
• Project Period (FY): 2018-06-29 – 2020-03-31
• Keywords: ルテニウム錯体 / パラジウム錯体 / 水溶液 / 芳香族化合物の酸化分解 / 水素発生

Outline of Final Research Achievements

We have established a catalytic system for cracking of aromatic compounds in acidic water to produce formic acid as well as carboxylic acids having substituents of aromatic rings, using a Ru(II)-aqua complex having a N-heterocyclic carbene (NHC) as a part of a ligand and (NH4)2[Ce(NO3)6] as an oxidant. On the basis of quantitative product analysis, kinetic analysis of the catalytic reactions and detection of intermediate products, we have clarified the reaction mechanism. In addition, by adjusting the pH value of a reaction solution and adding a Rh(III) catalyst, we have succeeded in evolving H2 from formic acid generated by the oxidative cracking reactions. On the other hand, we have developed a catalytic system for cracking polyhalogenated aromatics in water using a Pd(II)-NHC complex as a catalyst and Oxone as an oxidant. It was also revealed that both of oxygen atoms of formic acid is derived from Oxone.

Free Research Field

化学

Academic Significance and Societal Importance of the Research Achievements

芳香族化合物の触媒的酸化反応は、水酸化が盛んに研究されているのに対し、本研究では、新規な酸化活性種であるRu(III)-オキシル錯体の反応性として、芳香環の酸化的分解による水素源となるギ酸が生成することを見いだした。これは、電子的に等価なRu(IV)-オキソ錯体とは全く異なるユニークな反応性として特筆に値する。また、環境汚染物質である芳香族化合物を、水溶液中で効率よくギ酸及びカルボン酸に分解し、ギ酸をワンポットでエネルギー源としての水素に変換する手法を確立したことは、環境・エネルギー問題の解決への一助となる。