Support effect on selectivity of nitrite reduction in water

Porous ceramic mesoreactors: A new approach for gas–liquid contacting in multiphase microreaction technology

“…The turn-over-frequency (TOF), representing the amount of NO 2 − ions converted per surface-Pd-atom, was calculated for the SePHOB reactor (Pd loading = 0.073 wt%, initial NO 2 − concentration = ∼11 mg/l) to be ∼0.5 × 10 −3 s −1 . This value is relatively small compared to the TOF obtained in previous work (∼3.4 × 10 −3 s −1 ) for ␥-Al 2 O 3 supported Pd catalyst [20]. However, this is not a surprise when considering the high level of conversion as reported in Table 3, as compared to differential experiments [20].…”

“…Due to the low reaction rates of the biologic processes, the catalytic hydrogenation process is mentioned to be more promising for the nitrite removal. Via the catalytic route the nitrite ions are converted to nitrogen (N 2 ) or the undesired product ammonia (NH 4 + ) [17][18][19][20][21].…”

Nitrite reduction over Pd supported CNFs: Metal particle size effect on selectivity

“…This relation must be due to intrinsic differences in catalytic properties of the metal particles, because mass transfer limitations have been excluded [9] and experiments were performed at differential conditions. In our previous work, [9,13] ammonia selectivities above 85% were reported for hairy-foam supported Pd catalysts with different metal loading and Pd dispersion lower than 10%. The highest ammonia selectivity in the current study (82%) is close to that, but for much smaller particles (2.6 nm).…”

“…Calculation of TOF based on the CO chemisorption data, despite the limited accuracy, results in very similar numbers (0.15 ± 0.05 s -1 ) for 2.6 nm and 30 nm particles which also suggests that the actual TOF remains constant with changing particle size. In our previous work [9,13] TOFs of 0.021s -1 (based on CO chemisorption) were reported for hairy foam supported Pd particles of varying dispersion from 5 to 10 %. These catalysts were prepared without PVA, thus having much a much broader size distribution, and no PVA coordinating to the palladium surface.…”

“…It is known that nitrite ions are converted to ammonium and nitrogen exclusively under the conditions used in this study [9,13] the yield of nitrogen was therefore calculated from the difference between the nitrite conversion and the ammonium yield.…”