Enhancement of NO adsorption performance on zeolite via a facile modification strategy.

Adsorption is a promising technology for simultaneously capturing nitrogen oxides (NO) from flue gases and recycling NO as a profitable chemical, for which a robust and efficient adsorbent provides the key step for success in practical applications. This work reports the enhancement of NO adsorption performances with less cost of desorption energy on Cu-ZSM-5 zeolites prepared by a facile and rapid (690 s) modification method, the incipient-wetness impregnation coupled with microwave drying (IM). In comparisons to H-ZSM-5, Na-ZSM-5 and conventionally liquid-phase ion-exchanged counterparts under sub-1000 ppm NO feed concentrations and room temperature, the IM sample renders a record NO adsorption capacity (q) of 0.

Condensation Separation of NO with Dimerization Reaction in the Presence of Noncondensable Gas: Critical Assessment and Model Development.

Pure nitrogen dioxide (NO) has significant economic value and is widely used in many fields, for which condensation technology plays an important role in separation and purification. However, developing cost-effective NO condensers remains challenging due to the lack of precise theoretical guidelines and comprehensive understanding of NO condensation process. In this work, NO condensation at various inlet surface subcoolings, mole fractions of noncondensable gas (NCG), and numbers was studied with a visualization experimental system.

Separation of SO and NO with the Zeolite Membrane: Molecular Simulation Insights into the Advantageous NO Dimerization Effect.

NO and SO, as valuable chemical feedstock, are worth being recycled from flue gases. The separation of NO and SO is a key process step to enable practical deployment. This work proposes SO separation from NO using chabazite zeolite (SSZ-13) membranes and provides insights into the feasibility and advantages of this process using molecular simulation.

NO removal with efficient recycling of NO from iron-ore sintering flue gas: A novel cyclic adsorption process.

Conventional flue gas nitrogen oxides (NO) abatement technologies commonly convert NO into harmless compounds, while less effort has been made to recycle NO as a profitable chemical in many industries. Towards this end, adsorption is a promising technology for which an advanced technique for NO desorption and efficient sorbent regeneration provides the key step for success in practical applications. This work reports a novel cyclic adsorption process for NO removal with recycling of NO from iron-ore sintering flue gas of a steel plant.

Getting insight into the influence of coexisting airborne nanoparticles on gas adsorption performance over porous materials.

Adsorption as one of the most important air cleaning methods has been extensively applied during which the coexisting airborne nanoparticles (NPs) with sizes close to adsorbent pore sizes could inevitably influence gas adsorption processes. In this work, the influence of sub-20 nm NPs on toluene adsorption on ZSM-5 zeolites exchanged with different cations (Li, Na and K) were studied based on gas-and-particle coexisting adsorption/filtration tests. Affinities for both toluene and NPs on adsorbents follow Li-ZSM-5 > Na-ZSM-5 > K-ZSM-5 regarding the orders of charge density, pore size, and internal and external specific surface areas.

Molecular Simulation of Naphthalene, Phenanthrene, and Pyrene Adsorption on MCM-41.

The adsorption of three typical polycyclic aromatic hydrocarbons (PAHs), naphthalene, phenanthrene, and pyrene with different ring numbers, on a common mesoporous material (MCM-41) was simulated based on a well-validated model. The adsorption equilibriums (isotherms), states (angle distributions and density profiles), and interactions (radial distribution functions) of three PAHs within the mesopores were studied in detail. The results show that the simulated isotherms agreed with previous experimental results.

Glow discharge plasma-assisted template removal of SBA-15 at ambient temperature for high surface area, high silanol density, and enhanced CO₂ adsorption capacity.

Glow discharge plasma was successfully applied for effective removal of the organic template P-123 from SBA-15 ordered mesoporous silica at near-room-temperature (below 50 °C) and in a short operation time (2 h). The as-made SBA-15 treated with glow discharge exhibited a larger surface area of 1025 m(2) g(-1) with larger pores and microspore volume as compared with that of conventional calcination (550 °C and 5 h, 827 m(2) g(-1)). In addition to less structural shrinkage, the plasma-prepared SBA-15 showed significantly increased silanol density from 5.

CO2 capture from the atmosphere and simultaneous concentration using zeolites and amine-grafted SBA-15.

CO(2) capture from the atmosphere and concentration by cyclic adsorption-desorption processes are studied for the first time. New high microporosity materials, zeolite types Li-LSX and K-LSX, are compared to zeolite NaX and amine-grafted SBA-15 with low amine content. Breakthrough performance showed low silica type X (LSX) to have the most promise for application in dry conditions and capable of high space velocities of at least 63,000 h(-1), with minimal spreading of the CO(2) breakthrough curve.

Characteristics of hydrogen storage by spillover on Pt-doped carbon and catalyst-bridged metal organic framework.

Metal dispersion is a crucially important factor for hydrogen spillover storage on metal/carbon materials. For Pt on carbon (Pt/C), dispersion into nearly 2 nm clusters or nanoparticles is necessary to facilitate spillover. On an effective Pt/C spillover sorbent, temperature-programmed desorption (TPD) results reveal the highest hydrogen signal is from the high-energy Pt edges, steps or (110) surfaces, even though the (111) faces are more abundant.

Catalytic effects of TiF3 on hydrogen spillover on Pt/carbon for hydrogen storage.

Recent studies have shown that using the hydrogen spillover phenomena is a promising approach for developing new materials for hydrogen storage at ambient temperature. However, the rates need to be improved. Significant catalytic effects on both spillover (i.

Mechanism of propene poisoning on Fe-ZSM-5 for selective catalytic reduction of NO(x) with ammonia.

Application of Fe-zeolites for urea-SCR of NO(x) in diesel engine is limited by catalyst deactivation with hydrocarbons. In this work, we investigated the effect of propene on the activity of Fe-ZSM-5 for selective catalytic reduction of NO(x) with ammonia (NH(3)-SCR), and proposed a deactivation mechanism of Fe(3+) active site blockage by propene residue. The NO conversion decreased in the presence of propene at various temperatures, while the effect was not significant when NO was replaced by NO(2) in the feed, especially at low temperatures (<300 degrees C).

Catalyzed hydrogen spillover for hydrogen storage.

A crucial bottleneck in developing a hydrogen economy is hydrogen storage. This is particularly true for transportation using hydrogen as the fuel for fuel cells. The U.

A robust volumetric apparatus and method for measuring high pressure hydrogen storage properties of nanostructured materials.

A volumetric apparatus to measure hydrogen adsorption and desorption at room temperature and up to 100 atm has been constructed and studied for accuracy, reproducibility, and stability. The design principles are presented and considerable attention to detail is given to examine the effects of diurnal temperature changes in the manifold and helium adsorption by carbon-based adsorbents during free volume measurement. A heuristic for helium correction is derived from a model with a basis in literature and verified through calculation of adsorbent density.

Isotope tracer study of hydrogen spillover on carbon-based adsorbents for hydrogen storage.

A composite material comprising platinum nanoparticles supported on molecular sieve templated carbon was synthesized and found to adsorb 1.35 wt % hydrogen at 298 K and 100 atm. The isosteric heat of adsorption for the material at low coverage was approximately 14 kJ/mol, and it approached a value of 10.

Gas adsorption and storage in metal-organic framework MOF-177.

Gas adsorption experiments have been carried out on a zinc benzenetribenzoate metal-organic framework material, MOF-177. Hydrogen adsorption on MOF-177 at 298 K and 10 MPa gives an adsorption capacity of approximately 0.62 wt %, which is among the highest hydrogen storage capacities reported in porous materials at ambient temperatures.

Desulfurization of liquid fuels by adsorption on carbon-based sorbents and ultrasound-assisted sorbent regeneration.

Several carbon-based adsorbents, CuCl/AC, PdCl2/AC, and Pd/AC (where AC denotes activated carbon), were studied for desulfurization of a model jet fuel by selective adsorption of thiophenic molecules. Comparisons with gamma-Al2O3 support and desulfurization of a commercial jet fuel were also studied. The results showed that the selective sulfur adsorption capacity of PdCl2 was higher than that of CuCl and Pd(0), in agreement with molecular orbital results.

Hydrogen storage in low silica type X zeolites.

Low silica type X zeolites (LSX, Si/Al = 1) fully exchanged by alkali-metal cations (Li(+), Na(+), and K(+)) were studied for their hydrogen storage capacities. Hydrogen adsorption isotherms were measured separately at 77 K and <1 atm, and at 298 K and <10 MPa. It was found that the hydrogen adsorption capacity of LSX zeolite depended strongly on the cationic radius and the density of the cations that are located on the exposed sites.

Hydrogen storage in metal-organic frameworks by bridged hydrogen spillover.

The possible utilization of hydrogen as the energy source for fuel-cell vehicles is limited by the lack of a viable hydrogen storage system. Metal-organic frameworks (MOFs) belong to a new class of microporous materials that have recently been shown to be potential candidates for hydrogen storage; however, no significant hydrogen storage capacity has been achieved in MOFs at ambient temperature. Here we report substantially increased hydrogen storage capacities of modified MOFs by using a simple technique that causes and facilitates hydrogen spillover.

Adsorption of spillover hydrogen atoms on single-wall carbon nanotubes.

Spillover of hydrogen on nanostructured carbons is a phenomenon that is critical to understand in order to produce efficient hydrogen storage adsorbents for fuel cell applications. The spillover and interaction of atomic hydrogen with single-walled carbon nanotubes (SWNTs) is the focus of this combined theoretical and experimental work. To understand the spillover mechanism, very low occupancies (i.

Significantly enhanced hydrogen storage in metal-organic frameworks via spillover.

The utilization of hydrogen in fuel-cell powered vehicles is limited by the lack of a safe and effective system for hydrogen storage. At the present time, there is no viable storage technology capable of meeting the DOE targets. Porous metal-organic frameworks (MOFs) are novel and potential candidates for hydrogen storage.

Heterogeneous extended langmuir model with multiregion surfaces for adsorption of mixtures.

The multiregion or multisite adsorption theory is applied to the heterogeneous extended Langmuir (HEL) model for predicting adsorption from mixtures. A new model, multiregion HEL (MR-HEL), is derived. MR-HEL is thermodynamically consistent.

Hydrogen storage in nanostructured carbons by spillover: bridge-building enhancement.

The hydrogen storage capacity in nanostructured carbon materials can be increased by atomic hydrogen spillover from a supported catalyst. A simple and effective technique was developed to build carbon bridges that serve to improve contact between a spillover source and a secondary receptor. In this work, a supported catalyst (Pd-C) served as the source of hydrogen atoms via dissociation and primary spillover and AX-21 or single-walled carbon nanotubes (SWNTs) were secondary spillover receptors.

A modification of the Doong-Yang model for gas mixture adsorption using the lewis relationship.

The Doong-Yang model, which is used for predicting gas mixture adsorption equilibrium from pure-component isotherms of the Dubinin type, is modified by incorporating the Lewis relationship. The modified model is tested against experimental data for four binary systems, including a like-component (or nearly ideal) mixture, CH(4) + C(2)H(6), a moderately nonideal mixture, CO(2) + C(2)H(4), and two highly nonideal mixtures, CO(2) + C(3)H(8) and CO(2) + H(2)O. Comparisons are made with the ideal adsorbed solution (IAS) theory and the Bering model.

Predicting adsorption isotherms of low-volatile compounds by temperature programmed desorption: iodine on carbon.

Equilibrium adsorption isotherms for low-volatile compounds are extremely difficult to measure. A simple technique using temperature programmed desorption (TPD) is proposed. It is demonstrated that the two parameters needed for constructing the Langmuir isotherm can be derived with data from the TPD technique alone.

Hydrogen storage in graphite nanofibers: effect of synthesis catalyst and pretreatment conditions.

A series of graphite nanofibers (GNFs) that were subjected to various pretreatments were used to determine how modifications in the carbon structure formed during either synthesis or pretreatment steps results in active or inactive materials for hydrogen storage. The nanofibers possessing a herringbone structure and a high degree of defects were found to exhibit the best performance for hydrogen storage. These materials were exposed to several pretreatment procedures, including oxidative, reductive, and inert environments.