五氧化二钒催化环己烯烯丙位氧化

Allylic Oxidation of Cyclohexene Catalyzed by Vanadium Pentoxide

研究了以五氧化二钒为催化剂,以过氧化氢水溶液为氧源氧化环己烯.考察了溶剂种类、溶剂用量、催化剂用量和反应温度等因素对催化剂性能的影响.结果表明,常温下环己烯在此催化体系中主要发生烯丙位氧化反应生成环己烯酮.溶剂的种类对催化活性和烯丙位酮式氧化的选择性具有较大的影响,丙酮是该反应的合适溶剂.在丙酮与环己烯的体积比为4,五氧化二钒与环己烯的质量比为1∶40,过氧化氢与环己烯的摩尔比为3和反应温度为20℃的条件下,反应24h后的环己烯转化率可达60%以上,环己烯酮选择性可达85%.催化反应过程中丙酮可能与过氧化氢作用生成过氧化酮,从而进行氧转移,催化剂则经过V5+/V4+物种的循环使环己烯氧化成为环己烯酮等产物.

Oxidation of cyclohexene catalyzed by vanadium pentoxide was carried out under mild conditions with aqueous hydrogen peroxide as the oxidant. The effects of the solvent type, solvent amount, catalyst amount, and reaction temperature on the reaction were investigated. The allylic oxidation of cyclohexene was the dominate reaction, and cyclohexene-2-one was obtained as the major product. The solvent type significantly affects the catalyst activity and the selectivity for cyclohexene-2-one. Particularly acetone is an optimal choice for improving the conversion of cyclohexene. Under the conditions of V（acetone） ： V（cyclohexene） = 4, m （V2O5） ： rn（cyclohexene） = 1：40, n（H202） ： n（cyclohexcne） = 3, 20 ℃, and 24 h, the conversion of cyclohexene reached up to 60 % and the selectivity for cyclohexene-2-one was 85 %. It is proposed that the oxidation of cyclohexene catalyzed by vanadium pentoxide involves a reversible V ^5＋/V^4 ＋ species redox cycle using acetone as the oxygen transfer agent.