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【答案】应助回帖
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可乐易拉罐: 金币+20, 翻译EPI+1, ★★★很有帮助 2012-03-30 18:21:06
可乐易拉罐: 金币+30 2012-04-12 21:44:12
Dimethyl carbonate (DMC) is widely used in high performance resin, solvents, etc as a kind of important synthetic organic intermediates. Compared with phosgene method and oxidation hydroformylation method, the ester exchange method has the advantages of mild reaction conditions, low toxicity and high selectivity . It has become a hot spot for DMC synthesis process research. But there are also some shortcomings for the reaction system about the separation and repetition of the catalyst ,therefore, searching for the right catalyst and carrier and improving the activity and selectivity of the catalyst are the key to break through the bottleneck for DMC synthesis process research.
This paper uses ester exchange reaction to synthesize DMC by active methanol and carbonated vinyl acetate (EC) . Alkaline metal Mg of salt in Mg (NO3) 2 · 6 H2O is used as the precursor, MgO active components is loaded through the volumetric immersion method , , the different load of MgO/gamma-irradiation Al2O3 and MgO/NaY catalyst are prepared respectively . the catalysts prepared are used in ester exchange reaction under constant temperature of heating oil bath in the circle of the flask . the X-ray diffraction, CO2 temperature programming desorption and warming scanning electron microscopy means are used for characterization of the catalyst.
After examining the different catalytic performance of the catalysts ,we find MgO/gamma-irradiation Al2O3 showed a higher DMC seletivity in the ester exchange reaction . high load of MgO gamma-irradiation Al2O3 in the surface of is reuinted and resulted in the decline of dispersion , so activity decreases . compared with gamma-irradiation Al2O3 carrier , the catalyst using NaY as the carrier showed higher selectivity and activity . NaY zeolite
has clear distribution of holes and high specific area ,as well as the excellent thermal stability .besides , MgO/NaY catalyst can be in repeated use , so it is a good catalyst for ester exchange reaction . Investigation of catalytic process condition showed that under the condition of 12% MgO/NaY as catalyst, reaction temperature 140 ℃, reaction time 3 h, n (EC) : n (methanol) for the 1:8, catalyst for 5%, it has the best catalytic performance , the EC conversion and selectivity DMC are 94.3%, and the DMC yield reached 89%. |
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