Styrene epoxidation with Mn catalysts at low temperature
Date Issued
2014
Date
2014
Author(s)
Hung, Jui-Wen
Abstract
The research is epoxidation of styrene to styrene oxide with H2O2 oxidant in liquid phase. Because of safety and environment consideration, styrene epoxidation must be carried out at low temperature (i.e., below 25℃). Therefore active catalysts, such as Mn-zeolite, have been used in this research. The following experimental results were obtained: (1) Phase separation problem was found in reaction system with Mn-zeolite catalysts for epoxidation of styrene published in literature, which caused mole in-balance and data-error problems. By using Aspen Plus decanter model simulation, the right composition in reaction system with a homogeneous phase was determined and applied in this research. (2) Mn+2 has been ion-exchanged into three types zeolites (A, Y and Beta). Mn-Beta possesses the best catalytic activity for styrene epoxidation. (3) NaHCO3 plays important role in the reaction. No reaction occurred if no NaHCO3 was added into the reaction system. When 0.32 wt% of NaHCO3 was in reaction solution, styrene oxide yield of about 64% was obtained. (4) The reaction activity decreased with the increase of reaction temperature, which againsts the common sense of reaction kinetics. The reason was from that at higherer reaction temperature, more Mn+2 of active catalytic sites were exchanged out of zeolite support by Na+ in the solution, to form inactive MnCO3 precipates. (5) The concentration of H2O2 affected the reaction results. At -5 ℃ reaction temperature and mole ratio of Styrene and H2O2. at 0.25:1, the highest conversion of styrene of 90% was obtained. (6) Mn-Beta had much higher activity than MnO of heterogeneous catalysts and slightly higher than MnSO4 of homogeneous catalysts. Moreover, Mn-Beta can be recycled and reused. Finally, yield of styrene oxide can reach to 71.3%.
Subjects
環氧化反應
苯乙烯
氧化苯乙烯
低溫
錳-沸石
Type
thesis
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