4-甲氧基环己酮的绿色合成

Green Synthesis of 4-Methoxycyclohexanone

摘要:

为了实现4-甲氧基环己酮的绿色合成，本文首先在负载型镍基纳米催化剂的作用下进行了4-甲氧基苯酚催化加氢反应，然后使用双氧水对加氢反应液进行催化氧化，提高了目标产物4-甲氧基环己酮的总选择性。在催化加氢反应中，考查了沉积-沉淀法和浸渍法这两种制备方法及反应条件对催化剂活性和稳定性的影响。通过XRD、H2-程序升温还原(H2-TPR)及TEM等对催化剂进行了表征，结果发现，沉积-沉淀法制备的Ni/Al2O3-DP催化剂中活性粒子分散度高、粒径较小，并且活性粒子与载体之间有较强的作用力，具有比浸渍法制备的Ni/Al2O3-IMP催化剂更好的活性和稳定性。在4-甲氧基苯酚的加氢反应中，以Ni/Al2O3-DP为催化剂，最佳的反应条件为：反应温度423 K、反应压力4.0 MPa、反应时间1 h、m(4-甲氧基苯酚):m(Ni/Al2O3-DP)=6:1。在氧化反应中，探究了氧化条件对反应活性的影响，结果表明：当n(4-甲氧基环己醇) : n(钨酸钠) : n(草酸) : n(双氧水) = 100:1:1:250时，353 K反应20 h，目标产物4-甲氧基环己酮的选择性可达95.3%。

Abstract:

A green method for the synthesis of 4-methoxycyclohexanone was established in this paper. Catalytic hydrogenation of 4-methoxyphenol was first carried out over supported nickel-based catalysts. Subsequently, the hydrogenation solution was oxidized by hydrogen peroxide to further improve the selectivity for the target product. The influence of two kinds of preparation methods, including deposition-precipitation and impregnation method, as well as reaction conditions on the activity and stability of the catalysts for hydrogenation was investigated. As demonstrated by X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR) and Transmission electron microscopy (TEM) characterizations, the Ni/Al2O3-DP catalyst, prepared by a deposition-precipitation method, exhibited higher dispersion, smaller particle, and stronger interaction between the active particles and the support, compared with the Ni/Al2O3-IMP catalyst, prepared by an impregnation method. These structural characters account for its superior catalytic activity and stability in 4-methoxyphenol hydrogenation. In the hydrogenation of 4-methoxyphenol, Ni/Al2O3-DP was used as catalyst. The optimum reaction conditions were as follows: reaction temperature 423 K, reaction pressure 4.0 MPa, reaction time 1 h, m(4-methoxyphenol): m(Ni/Al2O3-DP) = 6:1.The effect of the oxidation conditions was also investigated to achieve better results. It was found that the total selectivity for 4-methoxycyclohexanone can reach 95.3%, while the reaction temperature is 353 K, the reaction time is 20 h, and the ratio of n(4-methoxycyclohexanol): n(sodium tungstate): n(oxalic acid) : n(hydrogen peroxide) is 100: 1: 1: 250.