Selective Oxidation of Glyoxal to Glyoxalic Acid by Air over Mesoporous Silica Supported Pd Catalysts

• Published in: Catalysis letters Vol. 149; no. 7; pp. 1894 - 1902
• Main Authors: Liu, Junchi, Qin, Feng, Huang, Zhen, Huang, Liang, Liao, Zhenan, Xu, Hualong, Shen, Wei
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-07-2019; Springer; Springer Nature B.V
• Subjects: Catalysis; Catalysts; Chemical synthesis; Chemistry; Chemistry and Materials Science; Conversion; Glyoxylic acid; Industrial Chemistry/Chemical Engineering; Mass transfer; Organometallic Chemistry; Oxidation; Oxidation-reduction reaction; Palladium; Palladium catalysts; Physical Chemistry; Selectivity; Silica; Silicon dioxide; Selective catalytic oxidation; Glyoxalic acid; Glyoxal; Mesoporous silica supported Pd
• ISSN: 1011-372X; 1572-879X
• DOI: 10.1007/s10562-019-02799-3

A series of mesoporous silica (KIT-6, MCM-41 and SBA-15) supported Pd catalysts were successfully synthesized and applied for selective oxidation of glyoxal. All of these catalysts exhibited significantly higher activity than commercial Pd/C. Among them, Pd/KIT-6 exhibited the best activity and selectivity with 41.3% glyoxal conversion and 57.0% selectivity to glyoxalic acid. The better performance of Pd/KIT-6 was attributed to its three-dimensional mesoporous structure. The three-dimensional mesoporous structure of KIT-6 could enhance Pd dispersion, providing sufficient accessible active sites which improved the conversion of glyoxal. Meanwhile, the better mass transfer capability of Pd/KIT-6 allowed glyoxalic acid to leave the catalyst easily, reducing the probability of over-oxidation. The ratio of
k
I
(rate constant of initial oxidation reaction) to
k
II
(rate constant of over-oxidation) was compared among three catalysts. The
k
I
/
k
II
of Pd/KIT-6 (0.50) was higher than that of Pd/MCM-41 (0.39) and Pd/SBA-15 (0.34), which reflected its best selectivity from kinetic aspect.
Graphical Abstract