纳米Pd/Fe催化甲醇/水中2,2',4,4'-四溴联苯醚(BDE-47)还原脱溴

Catalytic debromination of 2,2′,4,4′-Tetrabromodiphenylether (BDE- 47) by Pd/Fe nanoparticles in methanol/water

构建了纳米Pd/Fe催化还原甲醇/水中2,2',4,4'-四溴联苯醚(BDE-47)反应体系,常压下采用单因素实验系统考察了纳米Pd/Fe催化还原甲醇/水中2,2',4,4'-四溴联苯醚(BDE-47)的主要影响因素,并分析了BDE-47还原反应的中间产物及终产物.结果表明,纳米Pd/Fe的反应活性随Pd负载率的提高而先升后降;甲醇-水体积比高于50∶50后,BDE-47去除率随甲醇-水体积比升高而降低;在25～40℃内,BDE-47去除率随反应温度的升高而升高,随BDE-47初始浓度的增加而降低,增加纳米Pd/Fe量可提高反应速率;酸性及弱碱性条件有利于BDE-47还原.BDE-47还原主要为脱溴反应,是一个从n溴到(n-1)溴联苯醚的逐步脱溴过程,反应进行90min后,BDE-47分子中溴原子完全被脱除,反应终产物为二苯醚.

In this study, a reaction system on catalytic reduction of 2,2′,4,4′-Tetrabromodiphenylether （BDE- 47） by Pd/Fe nanoparticles in methanol/water was conducted to investigate factors affecting the system and the reductive intermediates as well as products by single factor experiments under atmospheric pressure. The results demonstrated that the reaction activity of Pd/Fe nanoparticles initially improved and then impaired with the increasing loading of Pd. The ratio of methanol-water must be higher than 50 ∶50 to ensure the complete dissolution of 10 mg · L-1 of BDE- 47, and the removal rate decreased with the increasing methanol-to-water ratio. In addition, BDE- 47 removal rate was increased with the increasing reaction temperature and the decreasing initial concentration of BDE- 47 over the range of 25~40 ℃. Moreover, increasing the dosage of Pd/Fe nanoparticles could accelerate the reduction rate. Acid or alkalescence （pH） was more favorable for BDE- 47 reduction. The reduction of BDE- 47 was a stepwise debromination reaction process which was dominated by the pathway from n-bromo- to （n-1）-bromodiphenyl ethers. The bromine atoms in BDE-47 were completely removed after 90min, generating diphenyl oxide as the final product.