Gravimetric and Spectroscopic Studies of Reversible Hydrogen Sorption on Nanoporous Clinoptilolite

Abstract Large surface aluminosilicate compounds such as zeolites are not the best option for hydrogen storage due to their low hydrogen sorption capacity above cryogenic temperatures. However, the known crystal structure and easy ion exchange allows considering zeolites as easily tuneable media that with a little effort can be changed to suitable porous media for hydrogen sorption. Metal (Li, Mg) and ammonia ion exchange is performed in natural clinoptilolite samples with the aim to increase the amount of adsorbed hydrogen. The Fourier transform infrared spectroscopy of the prepared samples is used to study sorption of hydrogen molecules in the vicinity of light metal ions. An original thermogravimetric method is applied to characterise the amount of sorbed hydrogen. Our experiments show that the highest hydrogen uptake (~ 6.2 wt%) is for a clinoptilolite sample treated in acid. The cation exchange did not provide the expected hydrogen sorption capability; however, the amount of sorbed hydrogen exceeded that for the initial material.

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Molecular Simulation Study on Catenation Effects on Hydrogen Uptake Capacity of MOFs

MRS Proceedings ◽

10.1557/proc-0971-z06-03 ◽

2006 ◽

Vol 971 ◽

Author(s):

Dong Hyun Jung ◽

Tae Bum Lee ◽

Daejin Kim ◽

Kangsung Park ◽

Jaheon Kim ◽

...

Keyword(s):

Molecular Dynamics ◽

Force Field ◽

Molecular Dynamics Simulations ◽

Hydrogen Adsorption ◽

Hydrogen Uptake ◽

Adsorbed Hydrogen ◽

Hydrogen Molecules ◽

Metal Organic ◽

Dynamics Simulations ◽

Gcmc Simulations

ABSTRACTIn order to investigate the reason for the higher capacity of the interpenetrating isoreticular metal-organic frameworks (IRMOFs) at lower temperatures, we performed grand canonical Monte Carlo (GCMC) simulations and molecular dynamics simulations at 77 K for a set of the interpenetrating IRMOF-11 and the non-interpenetrating counterpart IRMOF-12. From the GCMC simulations, we found universal force field (UFF) is better for describing the hydrogen adsorption behavior than DREIDING force field. The results from the molecular dynamics simulations showed the density of adsorbed hydrogen molecules was increased in the various pores created by the catenation of IRMOF comparing to that of the pores in IRMOF-12. Moreover, the adsorbed hydrogen molecules in IRMOF-11 have the smaller diffusion coefficients. It means that their dynamic behavior is more restricted because of the complexity of the interpenetrating network of IRMOF-11. These results of molecular simulations show the small pores created by the catenation are important for the increase of hydrogen adsorption on IRMOF-11 at lower temperatures.

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Experimental and Theoretical Studies of Sonically Prepared Cu–Y, Cu–USY and Cu–ZSM-5 Catalysts for SCR deNOx

Catalysts ◽

10.3390/catal11070824 ◽

2021 ◽

Vol 11 (7) ◽

pp. 824

Author(s):

Przemysław J. Jodłowski ◽

Izabela Czekaj ◽

Patrycja Stachurska ◽

Łukasz Kuterasiński ◽

Lucjan Chmielarz ◽

...

Keyword(s):

Ion Exchange ◽

Ultrasonic Irradiation ◽

Active Phase ◽

Spectroscopic Studies ◽

In Situ Drifts ◽

Ft Ir ◽

Diffuse Reflectance Infrared ◽

Experimental And Theoretical Studies

The objective of our study was to prepare Y-, USY- and ZSM-5-based catalysts by hydrothermal synthesis, followed by copper active-phase deposition by either conventional ion-exchange or ultrasonic irradiation. The resulting materials were characterized by XRD, BET, SEM, TEM, Raman, UV-Vis, monitoring ammonia and nitrogen oxide sorption by FT-IR and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). XRD data confirmed the purity and structure of the Y/USY or ZSM-5 zeolites. The nitrogen and ammonia sorption results indicated that the materials were highly porous and acidic. The metallic active phase was found in the form of cations in ion-exchanged zeolites and in the form of nanoparticle metal oxides in sonochemically prepared catalysts. The latter showed full activity and high stability in the SCR deNOx reaction. The faujasite-based catalysts were fully active at 200–400 °C, whereas the ZSM-5-based catalysts reached 100% activity at 400–500 °C. Our in situ DRIFTS experiments revealed that Cu–O(NO) and Cu–NH3 were intermediates, also indicating the role of Brønsted sites in the formation of NH4NO3. Furthermore, the results from our experimental in situ spectroscopic studies were compared with DFT models. Overall, our findings suggest two possible mechanisms for the deNOx reaction, depending on the method of catalyst preparation (i.e., conventional ion-exchange vs. ultrasonic irradiation).

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Removal of Mg from spring water using natural clinoptilolite

Clay Minerals ◽

10.1180/claymin.2012.047.1.81 ◽

2012 ◽

Vol 47 (1) ◽

pp. 81-92 ◽

Cited By ~ 1

Author(s):

S. Tomić ◽

N. Rajić ◽

J. Hrenović ◽

D. Povrenović

Keyword(s):

Ion Exchange ◽

Kinetic Studies ◽

Spring Water ◽

Zeolite A ◽

Zeolitic Tuff ◽

Rate Limiting Step ◽

Intra Particle Diffusion ◽

Pseudo Second Order ◽

Natural Clinoptilolite ◽

Rate Limiting

AbstractNatural zeolitic tuff from Brus (Serbia) consisting mostly of clinoptilolite (about 90%) has been investigated for the reduction of the Mg concentration in spring water. The sorption capacity of the zeolite is relatively low (about 2.5 mg Mg g-1for the initial concentration of 100 mg Mg dm-3). The zeolitic tuff removes Mg from water solutions by ion exchange, which has been demonstrated by energy dispersive X-ray analysis (EDS). The extent of ion exchange was influenced by the pH and the initial Mg concentration. Kinetic studies revealed that Lagergen's pseudo-second order model was followed. Intra-particle diffusion of Mg2+influenced the ion exchange, but it is not the rate-limiting step. Rather than having to dispose of the Mg-loaded (waste) zeolite, a possible application was tested. Addition to a wastewater with a low concentration of Mg showed that it could successfully make up for the lack of Mg micronutrient and, accordingly, enabled the growth of phosphate-accumulating bacteriaA. Junii, increasing the amount of phosphate removed from the wastewater.

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