摘要
Cr_(2)O_(3)是廉价、无腐蚀性和环境友好的固体金属氧化物,可以在较为温和的反应条件下高效地催化碳酸乙烯酯(EC)酯交换为碳酸二甲酯(DMC)。对比传统催化剂氧化钙,Cr_(2)O_(3)结构稳定,一定程度上解决了成本方面的限制和催化剂与产物分离以及浸出相关的问题。最佳反应条件为:Cr_(2)O_(3)的质量分数为1%(m_(Cr_(2)O_(3))∶m_(EC)),甲醇与EC物质的量之比为10∶1,反应温度为150℃,反应时间为5h,DMC收率为73.4%。并且在进行了连续3次循环回收实验后,依然有68.5%的DMC收率,具有实际应用意义。研究设计了两类实验以及X-射线衍射仪(X-ray Powder,XRD)的表征结果,均证明Cr_(2)O_(3)催化酯交换反应为非均相催化反应,且为真正的催化活性物质。通过对连续使用3次催化剂的XRD、元素分析以及X-射线光电子能谱(X-ray,XPS)的对比表征,发现催化剂的失活机理。即随着反应次数的增加,Cr^(3+)会逐渐被氧化为Cr^(6+)并伴随着碳酸盐的生成,引发Cr_(2)O_(3)的酸碱活性位点发生改变,进而逐渐失活且DMC收率降低。
Cr_(2)O_(3) is a cheap,non-corrosive and environmentally friendly solid metal oxide that can efficiently catalyze the transesterification of vinyl carbonate(EC)to dimethyl carbonate(DMC)under relatively mild reaction conditions.Compared with traditional catalyst calcium oxide,Cr_(2)O_(3) has structural stability,which solves the cost limitation and the problems related to catalyst and product separation and leaching to a certain extent.The optimum reaction conditions are as follows:the mass fraction of Cr_(2)O_(3) is 1%(m_(Cr_(2)O_(3))∶m_(EC)),the molar ratio of methanol to EC is 10∶1,the reaction temperature is 150℃,the reaction time is 5 h,and the DMC yield is 73.4%.After three consecutive cycles of recovery experiment,the DMC yield is still 68.5%,which has practical significance.Two kinds of experiments were designed and the results of X-ray powder(XRD)characterization proved that the transesterification reaction catalyzed by Cr_(2)O_(3) is heterogeneous catalytic reaction and is a real catalytic active substance.The deactivation mechanism of the catalyst was found by XRD,elemental analysis and X-ray photoelectron spectroscopy(XPS).That is,with the increase of reaction times,Cr^(3+)will be gradually oxidized to Cr^(6+)and accompanied by the formation of carbonate,which will lead to the change of acid-base active site of Cr_(2)O_(3),and then gradually inactivated and the DMC yield will decrease.
作者
付文波
段亚文
丛振
薛憬
刘昆
FU Wenbo;DUAN Yawen;CONG Zhen;XUE Jing;LIU Kun(School of Chemistry and Chemical Engineering,Hefei University of Technology,Hefei 230009,China)
出处
《合成化学》
2025年第9期652-659,共8页
Chinese Journal of Synthetic Chemistry
关键词
三氧化二铬
酯交换
碳酸二甲酯
失活机理
非均相催化
Cr_(2)O_(3)
transesterification
dimethyl carbonate
inactivation mechanism
heterogeneous catalysis
