Adsorption Chemistry of Sulfur Dioxide in Hydrated Na–Y Zeolite

Abstract

Na-Y is one of the oldest known synthetic zeolite materials. Like zeolite X, it has the faujasite framework topology. The framework structure of zeolites Na-X and Na-Y extensively was studied by diffraction methods [1a,b] and the positions of exchangeable cations in dehydrated faujasites are well documented.[1c]Positions and occupation numbers of sodium cations in Na-Y dehydrated by evacuation [2a,b] and drying in gas streams [2c] were derived by solid-state NMR spectroscopy. Neutron-and X-ray-diffraction techniques revealed the presence of guest molecules interacting with the sodium ions, which results in a reorganization of the cation distribution. [1a, 3a,3b] The presence of water molecules in the structure has a strong impact on position and occupation numbers of sodium atoms. [5, 4a,b,c] Exposure of Na-Y zeolite to a gas mixture containing 5-10 % water at 250 8C results in a water content of 50-60 water molecules per unit cell.[5] These water molecules interact with the sodium ions of the host to form a complex water-cation structure. The water-sodium arrangement consists of chains of alternating SV and SIII cations, bridged by water molecules. Additional water molecules associated with cations on SII positions stabilize this structure. When nitrogen oxides are present, these can reversibly be inserted into the water-cation net as N 2 O 3

Reversible NOx storage over Ru/Na–Y zeolite

“…S10 and Table S6 †). The sulfur tolerance previously observed with Na-Y [29][30][31] was now also observed with Ru/Na-Y.…”

“…The presence of SO x does not have an influence on the NO x storage capacity owing to a different location of adsorbed SO x and NO x molecules in Na-Y cages. 30,31 Nevertheless, Na-Y zeolite would fall short in practical application due to the slow NO x desorption kinetics and the requirement of an equimolar mixture of NO and NO 2 in the exhaust, which is difficult to achieve. [29][30][31][32] Since NO is the main NO x compound of engine exhaust gas, NO x adsorption on Na-Y is critically dependent on NO into NO 2 oxidation.…”

“…30,31 Nevertheless, Na-Y zeolite would fall short in practical application due to the slow NO x desorption kinetics and the requirement of an equimolar mixture of NO and NO 2 in the exhaust, which is difficult to achieve. [29][30][31][32] Since NO is the main NO x compound of engine exhaust gas, NO x adsorption on Na-Y is critically dependent on NO into NO 2 oxidation. Practically, the oxidation could be achieved using an upfront catalyst.…”

Reaction Kinetic Study of Solketal Production from Glycerol Ketalization with Acetone

“…Approximately 100 mL of crude glycerin can be generated for each liter of biodiesel produced, i.e., 10%. , Although there is a range of manufactured products using glycerin in its formulation, the used amount is not sufficient to employ the all glycerin produced by the biodiesel industry. Therefore, new technological improvements in converting the excess glycerin into value-added products must be made. , …”

Forty Years of Designing Catalytic and Adsorptive Sites in FAU Type Zeolites at K.U. Leuven

“…However, addition of a controlled amount of water forces the radicals to depart into the alkane liquid surrounding the zeolite crystal, and this allows to start alkane autoxidation at clearly lower temperatures than in an uncatalyzed process [36]. Another unexpected observation was that Na-Y zeolite is an excellent adsorbent for NO x [37,38]. NO x can be trapped as an N 2 O 3 molecule in the faujasite cages, at a specific location in the network of sodium ions and water molecules (Fig.…”