Direct oxidation of H2 to H2O2 and decomposition of H2O2 over oxidized and reduced Pd-containing zeolite catalysts in acidic medium

被引:68
作者
Choudhary, VR [1 ]
Sansare, SD [1 ]
Gaikwad, AG [1 ]
机构
[1] Natl Chem Lab, Div Chem Engn, Pune 411008, Maharashtra, India
关键词
oxidation of H-2 to H2O2; decomposition of H2O2; zeolite supported Pd catalysts; Pd/H-ZSM-5; Pd/H-GaAlMFI; Pd/H-beta;
D O I
10.1023/A:1021032819400
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Both the conversion and H2O2 selectivity (or yield) in direct oxidation of H-2-to-H2O2 (using 1.7 mol% H-2 in O-2 as a feed) and also the H2O2 decomposition over zeolite (viz. H-ZSM-5, H-GaAlMFI and H-beta) supported palladium catalysts (at 22 degreesC and atmospheric pressure) are strongly influenced by the zeolite support and its fluorination, the reaction medium (viz. pure water, 0.016 M or 1.0 M NaCl solution or 0.016 M H2SO4, HCl, HNO3, H3PO4 and HClO4), and also by the form of palladium (Pd-0 or PdO). The oxidized (PdO-containing) catalysts are active for the H-2-to-H2O2 conversion and show very poor activity for the H2O2 decomposition. However, the reduced (Pd-0-containing) catalysts show higher H-2 conversion activity but with no selectivity for H2O2, and also show much higher H2O2 decomposition activity. No direct correlation is observed between the H-2-to-H2O2 conversion activity (or H2O2 selectivity) and the Pd dispersion or surface acidity of the catalysts. Higher H2O2 yield and lower H2O2 decomposition activity are, however, obtained when the non-acidic reaction medium (water with or without NaCl) is replaced by the acidic one.
引用
收藏
页码:81 / 87
页数:7
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