Synthesis, characterization and evaluations of the Ag/ZSM-5 for ethylene oxidation at room temperature: Investigating the effect of water and deactivation
Synthesis, characterization and evaluations of the Ag/ZSM-5 for ethylene oxidation at room temperature: Investigating the effect of water and deactivation
复制标题
用于室温乙烯氧化的 Ag/ZSM-5 的合成、表征和评估：研究水和失活的影响
DOI：
10.1016/j.cej.2018.04.095
复制
发表时间：
2018-09-01
影响因子：
15.1
通讯作者：
Hao, Zhengping
中科院分区：
文献类型：
--
作者：
Yang, Hongling;Ma, Chunyan;Hao, Zhengping
制备了不同SiO_2/Al_2O_3比的Ag/ZSM-5催化剂，并对其在25℃下的乙烯氧化反应进行了评价。结果表明，在25℃时，所有的Ag/ZSM-5催化剂都能将乙烯完全氧化为CO_2。与其他Ag/ZSM-5催化剂相比，SiO_2/Al_2O_3比为38的Ag/ZSM-5催化剂具有更好的催化稳定性。在25℃下，Ag/ZSM-5(SiO_2/Al_2O_3=38)催化剂的乙烯转化率在405min内保持在100%左右，然后在接下来的450min内乙烯转化率逐渐降至零。结果表明，Bronsted酸中心是C_2H_4的吸附中心，而水蒸汽对C_2H_4吸附中心的抑制是乙烯氧化活性丧失的重要原因之一。H2O吸附-脱附动力学结果表明，在SiO_2/Al_2O_3比为38的Ag/ZSM-5催化剂上，H2O的缓慢吸附和快速脱附特性使其对乙烯氧化具有良好的催化稳定性。考虑到Bronsted酸中心上H2O吸附对Ag/ZSM-5催化剂上乙烯氧化催化稳定性的负面影响，本工作将为设计高性能的室温乙烯消除催化剂提供新的思路。
Ag/ZSM-5 catalysts with different SiO2/Al2O3 ratios were prepared and evaluated for ethylene oxidation at 25 degrees C. Ethylene can be completely oxidized into CO2 by all the Ag/ZSM-5 catalysts at 25 degrees C. It is found that SiO2/Al2O3 ratio of ZSM-5 has a significant effect on catalytic stability. Ag/ZSM-5 with SiO2/Al2O3 ratio of 38 exhibits enhanced catalytic stability compared with other Ag/ZSM-5 catalysts. The conversion of ethylene with Ag/ZSM-5 (SiO2/Al2O3 = 38) remained approximately 100% for 405 min at 25 degrees C, and then the ethylene conversion gradually decreased to zero in the following 450 min. It is revealed that Bronsted acid sites are the C2H4 adsorption sites and the inhibition of C2H4 adsorption sites by H2O vapor is one of the crucial reasons of the activity loss for ethylene oxidation. H2O adsorption-desorption kinetics results demonstrate that slow adsorption and fast desorption characters of H2O on Ag/ ZSM-5 with SiO2/Al2O3 ratio of 38 contribute to its good catalytic stability for ethylene oxidation. Taking into account the elucidation of the negative effect of H2O adsorption on Bronsted acid sites on the catalytic stability of Ag/ ZSM-5 catalysts for ethylene oxidation, this work will provide new insights into designing high-performance catalysts for ethylene elimination at room temperature.