Egg-shell membrane reactors for nitrite hydrogenation: Manipulating kinetics and selectivity

Proton Shuttling Flattens the Energy Landscape of Nitrite Catalytic Reduction

“…The resulting kinetic isotope effect (k N14 /k N15 ) was 1.04 ± 0.02 (Table 4), which is in line with previous reports on reduction of nitrite containing aromatic molecules. 45 Considering that the maximum ratio of specific rate constants for 14 N to 15 N is 1.14 at 25 °C, [65] it is clear that the small values obtained here suggest that there is no significant primary KIE. This further supports the idea that the rate determining step is not related to N-N bond formation nor N-O cleavage as previously suggested.…”

Formic acid generating in situ H2 and CO2 for nitrite reduction in the aqueous phase

“…In addition, it is well known that the selectivity to nitrogen can be improved by decreasing the pH [39][40][41][42], e.g. by co-feeding CO 2 in many lab studies.…”

“…Formic acid, nitrite, nitrate and ammonium concentrations in the reactants and products were measured with an ion-chromatograph (DIONEX, ICS 3000) equipped with an UltiMate autosampler. It is well known that exclusively ammonia and nitrogen form during the reduction of nitrite, 13,40,46,54,55 including nitrite reduction with formic acid, 45 and nitrogen was calculated based on the mass balance. All the experiments on the reduction of nitrite with formic acid were performed while flowing He through the reactor as described, resulting in concentrations of gas products below the detection limit of the GC.…”

“…Therefore, in this paper nitrite reduction is studied as a model reaction.Using hydrogen as the reducing agent has disadvantages in terms of hydrogen transportation and storage at high pressure. In addition, it is well known that the selectivity to nitrogen can be improved by decreasing the pH, 39–42 e.g. by co-feeding CO 2 in many lab studies.…”

Scalable Reactor Design for Electrocatalytic Nitrite Reduction with Minimal Mass Transfer Limitations

“…Catalytic nitrate and nitrite reduction experiments in batch reactors typically measure fast intrinsic reaction rates provided an excess hydrogen supply, rapid mixing to minimize boundary layer mass transfer limitations near catalyst surfaces, and fast intraparticle mass transfer with small particle sizes (e.g., <26.1 μm). However, slow H 2 mass transfer can limit reaction rates in practically useful flow-through reactors like fixed bed flow-through reactors. − One of the most efficient was a trickle bed reactor whose overall reaction rates were at the highest 18% of reaction rates in batch mode due to H 2 mass transfer limitations. , More recent alternative membrane reactors with embedded catalyst particles were developed to enhance hydrogen mass transfer to catalyst particles. ,− While mass transfer was shown to be improved, optimization in operational parameters like flow rate and catalyst metal deposition is needed to further improve overall reaction rates in those reactors.…”