沸腾状态下十二烷基甲基二羟乙基溴化铵微波合成的动力学研究

Study on the Kinetics of the Synthesis of Dodecylmethyldihydroxyethyl Ammonium Bromide

通常,人们利用微波进行化学合成,如果反应温度控制在低于溶剂的沸点温度,反应体系一旦达到所设定温度,自动控温系统就会自动切断加热电源,停止加热。对于微波反应来说,也就停止了微波的连续作用,而系统仅仅是保持在恒温状态。如果系统的保温效果很好的话,微波的作用可能就比较少,而仅仅是热效应对化学反应作用,没有体现出微波的持续作用。该研究选择特定的溶剂体系,采用在溶剂沸点温度下进行微波有机合成反应,以保证微波始终持续作用。结合题示表面活性剂的合成,探讨了微波合成反应的动力学参数,分析了微波作用原理。分别在微波作用以及传统加热两种方式下,考察了十二烷基甲基二羟乙基溴化铵合成动力学,获得了两种方式下的反应动力学参数,结果表明,微波的作用没有改变反应级数,两种情况下都是一级反应。微波作用下的活化能为ΔH=33.59 kJ/mol;而传统加热的活化能为ΔH=55.83 kJ/mol。该文提出以单位时间单位容积内、微波作用下反应物的变化量减去相同温度条件下传统加热时的变化量,作为微波对反应速率的贡献量Δ(-rA)的概念。实验结果表明,在同一温度条件下,反应时间越短,即反应物浓度越高,微波对反应速率的贡献量Δ(-rA)就越大;在其他条件相同时,反应温度越低,微波对反应速率的贡献量Δ(-rA)就越大。

In general microwave reaction synthesis process, if the setting reaction temperature was lower than the boiling point of the solvent, when the system temperature attains the set point, the temperature automatic control system will cut the microwave heating power source, so that, the microwave cannot effect on the reaction system continuously. The system was thermal insulation state. Actual, the reaction was not effected by the temperature by the microwave. In this paper, the reaction temperature were the boiling point of the solvents, the synthesis of dodeeylmet hyldihydroxyethyl ammonium bromide and its kinetics were studied under microwave irradiation and conventional heating. The kinetic parameters were obtained. The activation energy is 33.59 kJ/mol under microwave irradiation, while the activation energy is 55.83 kJ/mol under normal heating. The new concept of microwave devotion △（-rA） for chemical reaction was proposed in this paper. It is the increment of the reaction rate of microwave reaction and traditional reaction. The experimental result indicated that in the same temperature, the lower reactant concentration, the higher of the microwave devotion △（-rA）. And the lower of temperature, the higher of the the microwave devotion △（-rA）.