In situ discovery on the formation of supported silver catalysts for ethylene epoxidation

• Published in: Advanced powder technology : the international journal of the Society of Powder Technology, Japan Vol. 33; no. 9; p. 103732
• Main Authors: Sun, Like, Huang, Haoyang, Che, Ping, Lin, Qiang, Lian, Kuo, Li, Jinbing, Zhang, Yu, Han, Yongsheng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2022
• Subjects: Ethylene epoxidation; Selectivity; Silver catalysts; Size effect; Thermal decomposition; Selectivity; Thermal decomposition; Ethylene epoxidation; Size effect; Silver catalysts
• ISSN: 0921-8831; 1568-5527
• DOI: 10.1016/j.apt.2022.103732

[Display omitted] •Thermal decomposition of silver precursor was investigated by an in-situ microscope.•Two separate processes, namely crystallization and decomposition, were identified.•The crystallization occurred firstly followed by the decomposition to generate silver particles.•Sizes and properties of silver particles were influenced by thermal atmospheres. Silver particles supported on alumina are the main industrial catalysts for ethylene epoxidation. Silver catalysts are usually produced by an impregnation method followed by thermal decomposition. Although the decomposition process determines the structures and properties of silver catalysts, we are short of information on this high temperature process. Herein we employed a confocal laser scanning microscope (CLSM) equipped with a heating stage to disclose the thermal decomposition process of silver precursor towards the preparation of high selective silver catalysts. It is found that the formation of silver catalysts experiences two steps: crystallization and decomposition. The crystallization occurs at the temperature below 80℃, resulting in the formation of silver complex. Further heating the sample to 140℃, leads to the formation of silver particles at alumina wafers. The atmosphere has a significant effect on the formation and performance of catalysts. When the samples are heated in the nitrogen, small silver particles with similar size are formed, which leads to a high selectivity of ethylene epoxidation. The role of thermal atmospheres on the size and property of silver catalysts is discussed in this paper.