Oxidation of 1,4-dioxane over Ti-MWW in the presence of H2O2
Oxidation of 1,4-dioxane over Ti-MWW in the presence of H2O2
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DOI：
10.1002/cssc.200700003
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发表时间：
2008-01-01
期刊：
影响因子：
8.4
通讯作者：
Tatsumi, Takashi
中科院分区：
文献类型：
--
作者：
Fan, Weibin;Kubota, Yoshihiro;Tatsumi, Takashi
1，4-二氧六环是一种重要的化学品，用于合成染料、油、油漆、农药和塑料。[1，2]它也是一些化学过程的常见副产品。1，4-二氧六环在水中显示出无限的溶解度;然而，它可能是一种致癌物质，因此被归类为危险化合物和优先污染物。[1-5]如果不从工业废水中去除，它会污染地下水和饮用水。事实上，它已在美国和日本的地表水和地下水中被检测到。[6]虽然水的生物净化通常被使用并且相当有效，但1，4-二氧六环的生物降解几乎是不可能的。它在活性炭上的吸附也很差。空气汽提是不可行的，要么，由于其相当低的蒸汽压（与亨利的法律常数为9.5 10 × 10 - 6大气压m3摩尔/升，在298 K）。然而，通过氧化还原反应改变化学结构可以显著提高其生物降解性。虽然某些金属离子如Fe ~（2+）、Co ~（2+）等对H_2O_2甚至分子氧氧化醚类有催化作用，但均相催化体系会导致催化剂难以回收，并可能造成环境污染。在这种情况下，我们试图在钛硅酸盐上氧化这种材料，因为它们是用于氧化各种有机底物的高活性多相催化剂。[7-10]本文表明，相对于钛硅酸盐TS-1和Ti-Beta，Ti-MWW在H2 O2水溶液中对1，4-二氧六环的氧化表现出高活性。X射线衍射测量证实，所合成的钛硅酸盐均为结晶度高的纯晶相。漫反射UV/维斯光谱揭示了Ti-MWW和TS-1催化剂在约210 nm处的唯一谱带，证实了所有Ti物质具有四面体配位状态。对于Ti-β，除了215 nm处的谱带之外，还存在240 nm附近的肩峰，证实存在一些四面体至八面体Ti物种以及四面体配位物种。这与报告的结果一致。[7-9]通过IR光谱进一步证实了Ti在骨架中的掺入，对于所有样品观察到约960 cm-1的强峰。注意，在Ti-MWW中还存在以930 cm-1为中心的附加峰
1, 4-Dioxane is an important chemical used for the synthesis of dyes, oils, paints, pesticides, and plastics.[1, 2] It is also a common by-product of some chemical processes. 1, 4-Dioxane displays infinite solubility in water; however, it is probably a carcinogen and hence classified as a hazardous compound and a priority pollutant.[1–5] If not removed from industrial waste water, it would contaminate groundwater and drinking water. Indeed, it has been detected in the surface and groundwater in the USA and Japan.[6] While biopurification of water is generally used and quite effective, biodegradation of 1, 4-dioxane is almost impossible. It is also poorly adsorbed onto active carbon. Air stripping is not feasible, either, as a result of its considerably low vapor pressure (with a Henry’s law constant of 9.5 10À6 atm m3 molÀ1 at 298 K). Nevertheless, modification of the chemical structure by means of redox reactions could significantly enhance its biodegradability. Although some metal cations such as Fe2+ and Co2+ could catalyze the oxidation of ethers by H2O2, and even molecular oxygen, a homogeneous catalytic system would lead to the difficult recovery of the catalyst and possibly pollution of the environment. In this context, we attempted to oxidize this material over titanosilicates as they are highly active heterogeneous catalysts for the oxidation of a variety of organic substrates.[7–10] Herein, it is shown that relative to the titanosilicates TS-1 and Ti-Beta, Ti-MWW exhibits high activity for the oxidation of 1, 4-dioxane in aqueous H2O2 solution.X-ray diffraction measurements confirmed that all the as-synthesized titanosilicates are pure crystalline phases with high crystallinity. Diffuse reflectance UV/Vis spectroscopy revealed a sole band at about 210 nm for the Ti-MWW and TS-1 catalysts, confirming that all Ti species have a tetrahedral coordination state. For Ti-Beta, a shoulder band around 240 nm was also present besides a band at 215 nm, confirming that there are some tetrahedral-to-octahedral Ti species as well as tetrahedrally coordinated species. This is in agreement with reported results.[7–9] The incorporation of Ti in the framework was further corroborated by IR spectroscopy, with an intense peak around 960 cmÀ1 observed for all the samples. Note that an additional peak centered at 930 cmÀ1 was also present in the Ti-MWW