Liquid-phase oxidation of benzene to phenol by molecular oxygen over transition metal substituted polyoxometalate compounds
Liquid-phase oxidation of benzene to phenol by molecular oxygen over transition metal substituted polyoxometalate compounds
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DOI：
10.1016/j.catcom.2005.06.015
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发表时间：
2005-10-01
影响因子：
3.7
通讯作者：
Inaba, M
中科院分区：
文献类型：
--
作者：
Liu, YY;Murata, K;Inaba, M
在丙酮/环丁砜/水混合溶剂中，以过渡金属取代聚氧乙烯酸盐（TMSP）为催化剂，抗坏血酸为还原剂，分子氧液相氧化苯合成苯酚。[（C_4H_9）（4）N]（5）[PW_（11）CuO_（39）（H_2O）]是本研究中最好的催化剂。在323 K下反应12 h，苯的转化率为9.2%（TON = 25.8），苯酚的选择性为91.8%。TMSP化合物中取代过渡金属对苯转化率的影响顺序为：Cu > V > Fe > Mn > Ti > Cr > Co > Ni > Zn。TMSP化合物中中心原子对苯转化率的影响顺序为：P近似于Si > Ge > B。[SiW_（11）O_（39）]（8-）与[PW_（11）O_（39）]（7-）对苯的氧化反应类似，是一种很好的过渡金属多氧杂多酸配体。加入环丁砜溶剂后，苯酚的选择性显著提高，但在混合溶剂中加入大量环丁砜会降低苯的转化率。抗坏血酸是TMSP化合物上O-2氧化苯生成苯酚所必需的。催化体系中较高的氧分压保证了更多的氧分子溶解在溶剂中，促进了苯的转化。(c)2005 Elsevier B. V.保留所有权利。
Transition metal substituted polyoxometalate (TMSP) compounds were used as catalysts for the liquid-phase oxidation of benzene to phenol by molecular oxygen with ascorbic acid as a reducing agent in an acetone/sulfolane/water mixed solvent. [(C4H9)(4)N](5)[PW11CuO39(H2O)] is the best catalyst tested in this study. It showed 9.2% benzene conversion (TON = 25.8) and 91.8% selectivity to phenol for the oxidation of benzene at 323 K for 12 h. The effect of the substituted transition metal in the TMSP compounds on the benzene conversion is in the order: Cu > V > Fe >> Mn > Ti > Cr > Co > Ni > Zn. The effect of the central atom in the TMSP compounds on the benzene conversion is in the order: P approximate to Si > Ge > B. [SiW11O39](8-) is a good polyoxometalate ligand for transition metal ions as [PW11O39](7-) for the oxidation of benzene. The selectivity to phenol was dramatically improved by adding the sulfolane solvent, but the benzene conversion decreased when a large amount of sulfolane was used in the mixed solvent. Ascorbic acid is indispensable for forming phenol from benzene oxidation by O-2 over TMSP compounds. Higher O-2 pressure in the catalytic system ensured more oxygen molecules solving in the solvent, and promoted the benzene conversion. (c) 2005 Elsevier B.V. All rights reserved.