Cloth catalysts in water denitrification

Abstract

Fiber catalysts are easy to handle and free of mass-transfer resistance. This report is the first application of cloth catalysts to water denitrification. In this work, cloths woven from glass fibers (GF) of 7-10 m in diameter, impregnated with Pd, were tested in a semi-batch reactor to evaluate their effectiveness in the catalytic liquid phase hydrogenation of nitrites and nitrates. The catalytic properties of Pd-GF cloths were evaluated as a function of Pd loading as well of chemical composition of the glass, specific surface area and weaving mode of the fibrous support. Investigated catalysts showed the same level of specific activity (per g Pd) as conventional powdered catalysts for liquid-phase hydrogenation of nitrites but their activity for nitrates was about one order of magnitude lower. The nitrite and nitrate removal activities were independent of the catalyst structure; the formation of ammonium ions was highly sensitive to reactant concentration. The stability of Pd-GF cloths is discussed.

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

“…Pd-supported on new composite fibrous (glass fibers covered by ␥-Al 2 O 3 ) showed the highest activity and selectivity towards nitrogen. The activity was more than seven times higher compared to Pd-supported on silica fibrous glass reported in the literature [15].…”

“…The reaction rates r were calculated based on the kinetic parameters determined. At a concentration of nitrite c Nitrite = 10 mg l −1 over the 1%-Pd/AGF a seven-fold higher reaction rate (r = 80 mg min −1 g Pd −1 ) was found, if compared to the rate reported for Pd(0.1%)/SGF (r = 11.5 mg min −1 g Pd −1 ) [15]. So, alumina/silica composite was shown as the most suitable fibrous support in respect to the activity/selectivity of Pd-based catalyst and was chosen for the further kinetics study.…”

“…In order to elucidate the influence of the fibrous support on the Pd activity, the reaction rate of the Pd-supported on AGF was compared with the activity observed over Pd-supported on pure silica glass fibers (SGF) reported by Matatov-Meytal et al [15]. The reaction rates r were calculated based on the kinetic parameters determined.…”

“…Pd-and Pd/Cu-supported on woven glass fibrous materials have been already tested for the catalytic nitrite-nitrate reduction and demonstrated an appreciable activity [15,16]. The main problems for their technical application are a too important ammonia formation and a low resistance to mechanical stress during passage of liquid-phase.…”

Electrospinning of silica sub-microtubes mats with platinum nanoparticles for NO catalytic reduction

“…Therefore, novel forms of catalyst supports, as sub-microtubes catalysts, which are easy to handle, can be packed or constructed in the best form to fit the particular use and show very low resistance to diffusion [5], represent a key research issue for many catalytic industrial processes.…”