Direct synthesis of hydrogen peroxide from hydrogen and oxygen over Pd/HZSM-5 catalysts: Effect of Brönsted acidity

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2012-11, Vol.363-364, p.230-236
• Main Authors: Park, Sunyoung, Lee, Joongwon, Song, Ji Hwan, Kim, Tae Jin, Chung, Young-Min, Oh, Seung-Hoon, Song, In Kyu
• Format: Article
• Language: English
• Subjects: Brönsted acidity; Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; Hydrogen peroxide; HZSM-5; Ion-exchange; Palladium; Si/Al molar ratio; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Zeolites: preparations and properties
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2012.06.014

In the direct synthesis of hydrogen peroxide from hydrogen and oxygen over Pd/HZSM-5 catalysts, yield for hydrogen peroxide increased with increasing B/L ratio of the catalysts. [Display omitted] ► Direct synthesis of hydrogen peroxide from hydrogen and oxygen was conducted. ► Pd/HZSM-5-X catalysts with different Si/Al molar ratio (X) were used. ► Yield for hydrogen peroxide increased with increasing B/L ratio of the catalyst. ► Yield for hydrogen peroxide increased with increasing Brönsted acidity of the catalyst. Palladium catalysts supported on HZSM-5 (Pd/HZSM-5-X (X=15, 30, 75, 100, and 150)) were prepared with a variation of Si/Al molar ratio (X), and they were applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Conversion of hydrogen over Pd/HZSM-5-X catalysts showed no great difference, while selectivity for hydrogen peroxide over the catalysts exhibited a volcano-shaped curve with respect to Si/Al molar ratio. As a consequence, yield for hydrogen peroxide over the catalysts showed a volcano-shaped curve with respect to Si/Al molar ratio. Yield for hydrogen peroxide over Pd/HZSM-5-X catalysts was closely related to the Brönsted acidity/Lewis acidity (B/L) ratio of the catalysts. Yield for hydrogen peroxide increased with increasing B/L ratio of Pd/HZSM-5-X catalysts. This indicates that Brönsted acid sites of Pd/HZSM-5-X catalysts played an important role for enhancing the catalytic performance in the direct synthesis of hydrogen peroxide. Furthermore, yield for hydrogen peroxide increased with increasing Brönsted acidity of Pd/HZSM-5-X catalysts. Among the catalysts tested, Pd/HZSM-5-30 catalyst with the largest Brönsted acidity showed the highest yield for hydrogen peroxide. Therefore, it is concluded that Brönsted acidity of Pd/HZSM-5-X catalysts served as an important factor determining the catalytic performance in the direct synthesis of hydrogen peroxide.