Brønsted sites and structural stabilization effect of acidic low-silica zeolite A prepared by partial ammonium exchange

Dyballa, Michael; Obenaus, Utz; Lang, Swen; Gehring, Barbara; Traa, Yvonne; Koller, Hubert; Hunger, Michael

doi:10.1016/j.micromeso.2015.03.030

Cited by 32 publications

(44 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The broadening and overlapping of these peaks can be attributed to severely distorted six coordinated and four coordinated aluminium environments. The presence of six coordinated extraframework Al species in NH 4 -exchanged zeolite A has been previously reported by Klinowski et al [22,24], Sartbaeva et al [15] and M. Dyballa et al [39]. It is evident that some dealumination of the zeolite A framework occurs upon exchange with NH 4 + ions.…”

Section: Nh 4 -Asupporting

confidence: 67%

Local and Average Structural Changes in Zeolite A upon Ion Exchange

2017

View full text Add to dashboard Cite

The infamous 'structure-property relationship' is a long-standing problem for the design, study and development of novel functional materials. Most conventional characterization methods, including diffraction and crystallography, give us a good description of long-range order within crystalline materials. In recent decades, methods such as Solid State NMR (SS NMR) are more widely used for characterization of crystalline solids, in order to reveal local structure, which could be different from long-range order and sometimes hidden from long-range order probes. In particular for zeolites, this opens a great avenue for characterization through studies of the local environments around Si and Al units within their crystalline frameworks. In this paper, we show that some structural modifications occur after partially exchanging the extraframework Na + ions with monovalent, Li + , K + , Rb + and NH 4 + and divalent, Ca 2+ cations. Solid state NMR is deployed to study the local structure of exchanged materials, while average stricture changes can be observed by powder diffraction (PXRD). To corroborate our findings, we also employ Fourier Transform Infrared spectroscopy (FT-IR), and further characterization of some samples was done using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray spectroscopy (EDX).

show abstract

Section: Nh 4 -Asupporting

confidence: 67%

Local and Average Structural Changes in Zeolite A upon Ion Exchange

2017

View full text Add to dashboard Cite

show abstract

“…S4 in the SI and shows no peak at 0 ppm in a fully hydrated state. We furthermore proved the absence of EFAl by calculating the framework nSi/nAl-ratio of the catalyst from deconvolution of the 29 Si MAS NMR spectra (also in Fig. S4).…”

Section: The Chemical Composition Of the Framework -Edx And 27 Al Masmentioning

confidence: 89%

“…transported out of the pores. Comparable observation have been made after dealumination of other 8-MR pore zeolites like Ferrierite and A[14,29], because pore ring sizes below 12-MR restrict the removal of EFAl species[19]. Thus, a diffusion limitation in the 10-and 8-MR pores of the SZR topology results in EFAl species observed by27 Al MAS NMR at 0 ppm.…”

mentioning

confidence: 90%

Tuning the material and catalytic properties of SUZ-4 zeolites for the conversion of methanol or methane

Dyballa

Pappas

Borfecchia

et al. 2018

Microporous and Mesoporous Materials

Self Cite

View full text Add to dashboard Cite

This work describes the synthesis and investigation of improved SUZ-4 catalysts (SZR framework) and their application in methanol-to-olefins and methane-to-methanol conversion. We report boron containing, dealuminated and desilicated SUZ-4 catalysts. Ammonia and pyridine probe molecules enabled the assignment of acid site densities to the 10-MR and 8-MR pores, respectively. The difference in between the theoretically expected and the for the probes accessible acid site density is a good descriptor for the accessibility of pores and acid sites. The access to the 8-MR SUZ-4 pores is sterically hindered by counter ions as well as extra framework aluminum (EFAl) species that account for up to 15% of the aluminum. Dealumination and desilication were successfully applied to optimize the diffusion properties and resulted in outstandingly high BET surface area, nSi/nAl-ratios and potassium exchange degrees. The improved accessibility led to an up to 2-fold increased MTO conversion capacity of the catalysts. Cu-exchanged SUZ-4 was applied in the selective oxidation of methane to methanol. By operando X-Ray absorption spectroscopy (XAS) we showed that Cu II ions are mainly coordinated in 2Al sites of 6-MR motifs and inhibited for redox-reactions.

show abstract

“…The isotherm showed a very strong adsorption in the initial region and a plateau at high relative pressure (>0.9). This pattern indicates that ZSM-5 is a microporous material [44]. 0.3HZSM-5 displayed a combination of type I and IV isotherms with a low slope region at the middle which indicates the presence of few multilayers and a hysteresis loop at relative pressures above 0.4 that could be attributed to capillary condensation in a mesoporous material [45,46].…”

Section: Catalyst Characteristicsmentioning

confidence: 92%

Catalytic Intermediate Pyrolysis of Napier Grass in a Fixed Bed Reactor with ZSM-5, HZSM-5 and Zinc-Exchanged Zeolite-A as the Catalyst

et al. 2016

View full text Add to dashboard Cite

The environmental impact from the use of fossil fuel cum depletion of the known fossil oil reserves has led to increasing interest in liquid biofuels made from renewable biomass. This study presents the first experimental report on the catalytic pyrolysis of Napier grass, an underutilized biomass source, using ZSM-5, 0.3HZSM-5 and zinc exchanged zeolite-A catalyst. Pyrolysis was conducted in fixed bed reactor at 600˝C, 30˝C/min and 7 L/min nitrogen flow rate. The effect of catalyst-biomass ratio was evaluated with respect to pyrolysis oil yield and composition. Increasing the catalyst loading from 0.5 to 1.0 wt % showed no significant decrease in the bio-oil yield, particularly, the organic phase and thereafter decreased at catalyst loadings of 2.0 and 3.0 wt %. Standard analytical methods were used to establish the composition of the pyrolysis oil, which was made up of various aliphatic hydrocarbons, aromatics and other valuable chemicals and varied greatly with the surface acidity and pore characteristics of the individual catalysts. This study has demonstrated that pyrolysis oil with high fuel quality and value added chemicals can be produced from pyrolysis of Napier grass over acidic zeolite based catalysts.

show abstract

Brønsted sites and structural stabilization effect of acidic low-silica zeolite A prepared by partial ammonium exchange

Cited by 32 publications

References 23 publications

Local and Average Structural Changes in Zeolite A upon Ion Exchange

Local and Average Structural Changes in Zeolite A upon Ion Exchange

Tuning the material and catalytic properties of SUZ-4 zeolites for the conversion of methanol or methane

Catalytic Intermediate Pyrolysis of Napier Grass in a Fixed Bed Reactor with ZSM-5, HZSM-5 and Zinc-Exchanged Zeolite-A as the Catalyst

Contact Info

Product

Resources

About