화학공학소재연구정보센터
Chemical Engineering and Processing, Vol.47, No.12, 2402-2407, 2008
Additives assisted catalytic cyclo-dehydration of diethylene glycol in near-critical water
The additives assisted the cyclo-dehydration of diethylene glycol (DEG) reaction was studied in near-critical water (NCW). Zinc chloride (ZnCl2,) and sodium carbonate (Na2CO3) were selected to investigate their effects on the cyclo-dehydration of diol. The influences of reaction temperature, time, pressure, reactant/water ratio (r/w) and the concentration of additives oil the product yield of the cyclo-dehydration of DEG were examined. The results showed that the final obtained product was primarily 1,4-dioxane, resulting from the cyclo-dehydration of DEG in NCW. The yield of 1,4-dioxane was only 9.84 wt.% in pure water by reacting at 340 degrees C for 240 min, but the maximum yield of 1,4-dioxane could reach as high as 50.89 wt.% in the solution of 0.50 wt.% ZnCl2 at 340 degrees C for 120 min, and the conversion of DEG was 91.94 wt.%. The complete conversion of DEG was obtained in 1.00 wt.% ZnCl2 at 340 degrees C for 120 min, but the yield of 1,4-dioxane was only 10.18 wt.%. In the case of Na2CO3, it did not have significant promotion effect on the cyclo-dehydration of DEG reaction. All these experimental results demonstrated that ZnCl2 had the positive effects on the dehydration of DEG while Na2CO3 depressed the reaction. Based on these results, a possible reaction mechanism and pathway was proposed in NCW. (C) 2007 Elsevier B.V. All rights reserved.