Reduction of nitrite-ions in water over Pd-supported on structured fibrous materials

Abstract

The catalytic hydrogenation of nitrite in water to nitrogen over Pd-supported on different woven fibrous materials is studied.Low porosity carbon fibers, low porosity D-type glass fibers and composite (glass covered by ␥-aluminia) fibers are used.The dispersion of Pd is compared for different supports at various Pd-loadings and correlated with the catalytic activity. The ammonia as an undesired by-product was also observed and the main parameters suppressing its formation are discussed. A reactor concept based on woven fibrous catalysts is suggested and the main design parameters for the technical application are estimated.

Structured multiphase reactors based on fibrous catalysts: nitrite hydrogenation as a case study

“…This value is considered as the intrinsic reaction rate, controlled by chemical reaction (k eff → k R for u g0 > 25 cm/s). This is confirmed by a comparison of the experimental results with the intrinsic rate constant determined in a batchwise operated stirred tank reactor [13]. The difference between the values, K R,bubble column = k R V liquid m pd −1 = 3.8 l min −1 g pd −1 in this study compared to K R,stirred tank = 3.2 l min −1 g pd −1 , may be explained by the difference in the pH values.…”

“…The Pd loading was kept constant at 1 wt.% for all experiments. Before starting the reaction, the catalysts were reduced in a sodium formate (HCOONa) aqueous solution (10 wt.%) at 80 • C. The 1%Pd/AGF catalyst obtained by this preparation method shows a high activity and a high selectivity towards nitrogen [13]. …”

“…To overcome this problem, Hähnlein et al [10] suggested incorporating the fine catalyst particles into hollow fibers of an inner diameter of 200 m, whereas Daub et al [11] proposed to use catalytic membranes for the reduction [12] used porous egg shell catalysts with a diameter of 1.7 mm and a thickness of the reaction zone of 120 m in conventional fixed bed reactors and found a strong influence of the mass transport processes on the effective kinetics. Recently, we studied the kinetics of the reduction of nitrite ions in water over Pd supported on structured fibrous materials [13]. The studies were concentrated on the investigation of the intrinsic kinetics of the catalytic nitrite reduction, since this process appears to be the limiting step in the reduction of nitrate to nitrogen [5].…”

Loop reactor staged with structured fibrous catalytic layers for liquid-phase hydrogenations

“…These types of catalysts should be classified as arranged catalysts (Cybulski and Moulijn, 1998). They were tested for intrinsic activity/selectivity in liquid-phase hydrogenation of benzaldehyde to toluene (Kiwi-Minsker et al, 1999), nitrobenzene to aniline (Perez et al, 1997;Höller et al, 2000a,b) and nitrite ions in water to nitrogen (Höller et al, 2001c). The palladium-based catalysts demonstrated high efficiency in these model reactions.…”

Srat Chemistry and Acid Consumption During Simulated DWPF Melter Feed Preparation

“…Palladium is also a room temperature hydrogenation catalyst for destruction of nitrite ion. 13,14 Reaction products include N 2 , NH 3 , NO, and hydroxide ions. It is possible that hydrogen production due to Pd is consumed by nitrite ion hydrogenation until the nitrite ion concentration is driven below a concentration that permits some of it to escape into the off-gas system.…”