超/近临界区含水量对乙酸丁酯酯交换反应的影响

为了阐明超/近临界区有机合成反应中水的作用机制,以乙酸丁酯与甲醇的酯交换反应作为模型体系,测定了240～320 ℃下不同水体积分数对乙酸丁酯酯交换反应的影响.以260 ℃的典型结果为例,实验结果可以分成3个区域：当水体积分数<3.2％时,乙酸丁酯的转化率随水体积分数增加而显著降低；水体积分数在3.2%～11.8％区域,乙酸丁酯转化率变化较少；当水体积分数超过11.8％后,乙酸丁酯转化率随着水体积分数增加快速上升.结果表明：水在该体系中同时起到了溶剂、反应物和催化剂的作用,同时水在超临界区和近临界区起的主要作用是不同的.

Effects of water content on transesterification of butyl acetate in super/near critical region

In order to elucidate the functions of water on the super/near critical organic reactions, transesterification of butyl acetate with methanol was selected as model reaction. Effects of volume fraction of water on transesterification of butyl acetate from 240 to 320 ℃ were studied and regular results were obtained. Taking typical results at 260 ℃ as example, the influence of water can be divided into three areas. For volume fraction of water less than 3.2%, the conversion of butyl acetate decreases sharply as water content increases while in the region of 3.2% 11.8% volume fraction of water has litter influence on the butyl acetate conversion. For volume fraction of water more than 11.8%, the conversion of butyl acetate increases as volume fraction of water increases. It is concluded that water can act as solvent, reactant and catalyst at the same reaction system and it has different functions at near critical and supercritical region.