Zeolite Erionite Research Articles

Synthesis and Structural Analysis of High-Silica ERI Zeolite with Spatially-Biased Al Distribution as a Promising NH3-SCR Catalyst.

Erionite (ERI) zeolite has recently attracted considerable attention for its application prospect in the selective catalytic reduction of NOx with NH3 (NH3-SCR), provided that the high-silica (Si/Al > 5.5) analog with improved hydrothermal stability can be facilely synthesized. In this work, ERI zeolites with different Si/Al ratios (4.6, 6.4, and 9.1) are synthesized through an ultrafast route, and in particular, a high-silica ERI zeolite with a Si/Al ratio of 9.1 is obtained by using faujasite (FAU) as a starting material. The solid-state 29Si MAS NMR spectroscopic study in combination with a computational simulation allows for figuring out the atomic configurations of the Al species in the three ERI zeolites. It is revealed that the ERI zeolite with the highest Si/Al ratio (ERI-9.1, where the number indicates the Si/Al ratio) exhibits a biased Al occupancy at T1 site, which is possibly due to the presence of a higher fraction of the residual potassium cations in the can cages. In contrast, the Al siting in ERI-4.6 and ERI-6.4 proves to be relatively random.

Catalytic efficiency of various ion-exchanged forms of Erionite zeolite for the synthesis of 2-methylquinoxaline

Erionite zeolite was successfully converted into various ion-exchanged forms to be used as catalysts. These catalysts were characterized by various techniques like Fourier transform infrared spectroscopy (FTIR), Electron dispersive spectroscopy (EDS), Brunauer Emmet Teller (BET) surface area measurement, X-ray diffraction (XRD) and Temperature programmed desorption (TPD). Their activity was tested by quite simple and selective method for the synthesis of 2-methylquinoxaline that showed excellent results at shorter reaction time for all catalysts with maximum yield of 88.0% for H+-Erionite at room temperature in 1h. Reaction was found to increase with catalytic dose and reaction temperature and at 100 °C the yield of 2-methylquinoxaline was found to be 99.4%. BET surface area, NH3-TPD values and activity of catalysts was found to decrease in the order of increasing size of exchanged ion (Cs+< K+< Li+<H+). All catalysts were recycled many times with negligible loss in activity showing their stability.

Degradation of dye containing in textile wastewater by sequential process: photocatalytic and biological treatment.

In this research, a combined photocatalytic and biological treatment is proposed for the elimination of pollutants present in textile wastewater using a natural erionite zeolite (PE) and aluminum oxide (PA) synthesized by the sol-gel method as photocatalysts, and solar radiation. Both catalysts were characterized by XRD, SEM, and EDS. For biological treatment two bacterial consortium were used: BC1 (Escherichia coli N16, Serratia k120, Pseudomonas putida B03 and Enterobacter hormaechei), and consortium BC2 (Escherichia coli N16, Serratia Mc107, Enterobacter N9, Enterobacter hormaechei Mc9). The photocatalytic and microbiological treatments were carried out initially separately and subsequently in a sequential manner, first the photocatalytic followed by the microbiological to determine if a synergistic effect was achieved. Comparing the photocatalytic performance, erionite showed higher performance of dyes degradation (54.75%) than alumina (28.62%). While in the biological process, BC1 decreased the dye concentration to 56.93% and BC2 to 53.56%. Finally, the best combined process was PA+BC1 reaching pollutants degradation 64.62%, showing that the application of both processes promotes a decolorization in textile wastewater. The water resulting from the combined photocatalysis-microbiological degradation processes was tested for toxicity using Daphnia magna, obtaining that none of the effluents shows toxicity.

Increasing the catalytic performance of erionite by hierarchization

Abstract The texture and acidity of a parent synthetic erionite zeolite (ERI structure) are modified by a two-step top-down treatment involving acid (HNO3) and base (NaOH) biased leaching as well as an unbiased HF/NH4F leaching. These zeolites are compared to a bottom-up prepared nanosized ERI, UZM-12. The structural (XRD, 29Si MAS NMR), textural (N2 adsorption-desorption, STEM) and acidic (FT-IR spectroscopy of adsorbed probe molecules) properties of the parent and hierarchical ERI are also carefully monitored. Among all top-down hierarchization strategies applied for 8-ring ERI structure, the sequential leaching in acid (HNO3) and caustic (NaOH) solutions is the most efficient to add mesoporosity to the native microporosity. The catalytic performances of the hierarchical materials and their parent are assessed in the dealkylation of 1,3,5-triisopropylbenzene (TiPBz); they are in line with the mesoporous external surface area and the external surface acid site density for all samples. The best top-down hierarchical ERI has similar catalytic properties as the nanosized ERI, UZM-12.

Cu-Erionite Zeolite Achieves High Yield in Direct Oxidation of Methane to Methanol by Isothermal Chemical Looping

We herein report that a copper-ion-exchanged erionite zeolite (Cu-ERI) exhibited a methanol yield as high as 147 μmol/g-zeolite, equaling 0.224 μmol/μmol-Cu, in the direct oxidation of methane to m...

Facile synthesis of low-silica zeolite erionite by ultrasonic-assisted method

Low-silica zeolite erionite (ERI) with a high purity/crystallinity was synthesized via ultrasonic-assisted aging for only 2 h with an initial dilute sol in the presence of offretite (OFF) seeds. Compared to the conventional approaches, ultrasound in the synthesis can enhance the crystallization rate and the ERI content because the ultrasonic aging facilitates the formation of ERI precursors. The resultant sample has hierarchical column-like aggregates with a great specific surface area (i.e., 415.7 m2/g), and abundant intracrystalline mesopores (i.e., 0.25 cm3/g), which are determined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy and N2 adsorption-desorption. The aggregates exhibit a high CO2 adsorption capacity probably since a rich aluminum content in the framework preferentially adsorbs CO2.

Theoretical study of the effect of isomorphous substitution by $$\hbox {Al}^{3+}$$ and/or $$\hbox {Fe}^{3+}$$ cations to tetrahedral positions in the framework of a zeolite with erionite topology

The isomorphous substitution of $$\hbox {Al}^{3+}$$ and/or $$\hbox {Fe}^{3+}$$ cations into the erionite zeolite framework were studied through periodic density functional theory computations. Taking as reference the Mulliken charges for siliceous framework computed in previous work (Antunez-Garcia et al. in J Mol Struct 1059:232–238, 2014), the present results show that the basicity of ERI zeolite increases when those cations are introduced into the framework. It was also observed that when at least two $$\hbox {Si}^{4+}$$ cations are isomorphically substituted by $$\hbox {Fe}^{3+}$$ in the unit cell of the erionite zeolite, it acquires magnetic properties. The results show that a specific net-spin polarization (up or down) could be correlated with particular configurations of erionite zeolite, containing ferric iron.

Critical Admission Temperature of H₂ and CH₄ in Nanopores of Exchanged ERI Zeolites.

Due to the nanoporous nature of zeolitic materials, they can be used as gas adsorbents. This paper describes the effect of critical admission temperature through narrow pores of natural ERI zeolites at low levels of coverage. This phenomenon occurs by adsorption of CH4 and H2 on pores in natural erionite. The zeolite was exchanged with aqueous solutions of Na+, Mg2+, and Ca2+ salts at different concentrations, times, and temperatures of treatment. Experimental data of CH4 and H2 adsorption were treated by the Langmuir equation. Complementarily, the degree of interaction of these gases with these zeolites was evaluated by the evolution of isosteric heats of adsorption. The Ca2+ and Mg2+ cations favor the adsorption phenomena of H2 and CH4. These cations occupy sites in strategic positions Ca1, Ca2, and Ca3, which are located in the nanocavities of erionite zeolites and K2 in the center of 8MR. Following the conditions of temperature and the exchange treatment, ERICa2 and ERINa3 samples showed the best behavior for CH4 and H2 adsorption.

An efficient route for synthesis of ERI zeolite through conversion of FAU zeolite in the presence of N,N-dimethylpiperidinium hydroxide

Abstract In this study, an efficient route was developed to prepare high quality erionite (ERI) zeolite by hydrothermal conversion of faujasite (FAU) zeolite as an aluminosilicate source in the presence of N,N-dimethylpiperidinium hydroxide (DMPOH). Pure ERI zeolite was successfully synthesized within only 8 h by carefully controlling the alkalinity (OH−/SiO2) of the initial gel and the proportion of DMP+ and K+. Compared with the conventional ERI zeolite synthesized via a Charge Density Mismatch method, the FAU-derived ERI zeolites show superior properties such as higher crystallinity, smaller crystal size, larger micropore volume and better hydrothermal stability. In addition, catalytic test in the ethanol dehydration reaction shows that the ERI zeolites obtained from FAU exhibit extraordinary performances to those of the conventional one. Finally, crystallization process from FAU to ERI was investigated in detail by UV Raman and XRD. The results show that the framework of ERI zeolite is formed by rearrangement of 4-rings generated from the initial FAU zeolite.

Ultrafast synthesis of high-silica erionite zeolites with improved hydrothermal stability.

High-silica erionite (ERI) zeolites are conventionally synthesised via a so-called charge density mismatch (CDM) approach, and a typical synthesis takes several days to complete. We herein demonstrate an ultrafast route to synthesise high-silica erionite zeolites in as short as 2 h at 210 °C. The fast-synthesised ERI has been proved to show higher hydrothermal stability compared with the conventionally synthesised product.

A DFT study of hydrogen adsorption on Be, Mg and Ca frameworks in erionite zeolite

The molecular hydrogen adsorption was investigated on additional frameworks with earth alkaline metal atoms (Be, Mg and Ca) in 24T ERI zeolite cluster model by means of Density Functional Theory study. HOMO and LUMO energy values, chemical potential, chemical hardness, electronegativity, adsorption energy and adsorption enthalpy values have been calculated in this study. Mg-ERI and Ca-ERI clusters have much lower chemical potentials with much lower adsorption energy values when compared to the value of Be-ERI cluster. Additionally, they are softer than Be-ERI cluster with respect to their lower chemical hardness values. Hydrogen adsorption enthalpy values were computed as −3.6 and −3.9kJ/mol on Mg-ERI and Ca-ERI clusters, respectively. These adsorption enthalpy values are significantly larger than the enthalpy value of liquefaction for hydrogen molecule. This consequently specifies that Mg-ERI and Ca-ERI zeolite structures which have higher chemical reactivity appear to be a promising candidate cryoadsorbent for hydrogen storage.

Fabrication of polyaniline/zeolite composites and their response towards nitrogen dioxide

A composite of Polyaniline with zeolite erionite was synthesized by chemical oxidative polymerization method. The effect of cation type, cyclic interval, NO2 concentration over time, zeolite content on the response of polyanline and polyaniline/zeolite erionite composites towards NO2 was studied. Na-form shows largest response towards NO2 because of small electronegativity. The effect of cyclic interval on the response of the composite was studied and it was found that with increasing no. of cyclic intervals the response decreases. The response of the nanocomposite on exposing to NO2 first increases and then attains a constant value after some time.With increase in zeolite content; the response goes on increasing and attains a steady state beyond 50% zeolite content. The composites were characterized by FTIR, SEM and XRD techniques.

Creating nanoporosity in Na, Ca and Mg exchanged erionite zeolite

This paper deals with the emergence of pores in natural erionite zeolite during ion-exchange treatment with aqueous Na+, Mg2+ and Ca2+ solutions of different concentrations. The exchange took place at variable time and temperature of exposure. The effect of this cationic exchange upon the zeolite micropores is analysed by scanning electron microscopy, energy dispersive X-ray spectroscopy and N2 adsorption at 76 K. The characterisation results suggest the presence of Na+ at the pores' mouth that causes an increased adsorption inside nanocavities as well as on the external area of the exchanged zeolites. The generation of pores emerging in erionite zeolites after ion exchange was evaluated through Dubinin-Astakhov and classical Barrett-Joyner-Halenda methods. Depending on the exchanging conditions, Na+ was found to be well distributed and accessible for N2 adsorption. The results indicate that the tested exchange treatments with Na+ favour creation of emerging pores, as an increase of the adsorption capacity occurs.

A theoretical study of Cu clusters in siliceous erionite

In terms of periodic density functional theory method, we present a theoretical study of the structure and electronic properties of different composites, obtained by the inclusion of distinct Cux (x=2,4,6,8) clusters within the C1 cage of siliceous erionite–zeolite. Results shows that for a periodic distribution of Cux clusters on zeolite, the hosting of those is trough electrostatic confinement which is governed by framework oxygen atoms located at particular equivalent sites. However, when the permanency of a cluster in a C1 cage is compromised, the cluster–cluster long range Coulomb interactions could rise to keep it inside. In addition, results also show that the electronic properties of free Cux clusters are largely transferred to the formed composite.

Synthesis and Characterization of ERI-Type UZM-12 Zeolites and Their Methanol-to-Olefin Performance

A wide variety of different linear, diquaternary alkylammonium ions have been used as supplementary crystallization structure-directing agents (SDAs) in the synthesis of UZM-12, a high-silica version of zeolite erionite, via a charge density mismatch (CDM) approach. When tetraethylammonium is used as a CDM SDA, the crystallization of UZM-12 was found to be critically dependent not only on the type of alkali metal cations added as another crystallization SDA to the synthesis mixture, but also on the size of the groups on the diquaternary ammonium ion employed and the length of its central polymethylene chain that are closely related to the dimensions of cylindrical 23-hedral [4(12)6(5)8(6)] eri cages in this small-pore zeolite. (27)Al MQ MAS NMR measurements reveal a preferential location of Al on the high-multiplicity site over the lower-multiplicity site of the UZM-12 framework. The catalytic results from the methanol-to-olefin reaction over a series of H-UZM-12 zeolites with similar acidic properties but different crystallite sizes (100-2500 nm in length) demonstrate that the nanocrystallinity (probably the ≤100 nm range) may have a detrimental effect on the activity and stability for this reaction, probably due to the fast buildup of large coke molecules on the external surface of zeolite crystallites that inhibits the methanol diffusion to intrazeolitic acid sites, rendering them ultimately inaccessible for catalysis.

Estudo e caracterização da zeólita OFF Tipo T empregando diferentes fontes de silício

Offretite T zeolite was synthesized using different source of Si (Ludox AS-30, Ludox LS-30 and Aerosil 200 Degussa). The obtained materials were characterized by different complementary techniques: XRD, textural analysis by N2 adsorption, IV, SEM and chemistry analysis. This zeolite has an intermediary structure between offretite and erionite zeolites. In all experiments offretite T phase was obtained. Offretite phase presenting better crystalility are obtained in synthesis with stirring and employing aerosil as silicon source. This zeolite presents a potencial application as catalyst for hydroisodewaxing process.

Recent Developments in the Therapy of Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is most often caused by environmental and occupational exposure to durable mineral fibres including asbestos and the zeolite erionite. In Turkey, MPM due to environmental exposure to erionite is a serious public health problem in rural parts of Anatolia where there is also some evidence of genetic predisposition in some families.Although much is already known of MPM aetiology, therapeutic efforts remain poor and neither chemotherapy nor surgery have been shown to prolong survival significantly. Radiation therapy assists in reducing tumour growth and temporarily relieving pain, but does not extend the overall survival time. Single agent chemotherapy has shown a response rate of 10–33% not improved by combination chemotherapy. New agents including the anti-metabolites gemcitabine and specifically antifolates such as pemetrexed and raltitrexed seem more promising with response rates up to 48%, when combined with platinum compounds. The best characterised new agent is pemetrexed (LY 231514, ALIMTA) which inhibits the multiple folate-dependent enzymes thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotideformyltransferase (GARFT). A phase I combination study showed a response in 45% of patients and a large randomised single blind Phase III study was initiated in 1999. The pemetrexed/cisplatin combination significantly improved median survival when compared with cisplatin alone (12.1 months vs. 9.3 months) and was also significantly better in other efficacy parameters such as response rate, time to progressive disease, lung function and subjective indicators of quality of life. This combination should now be considered standard front-line therapy for patients with MPM.

Sources and Types of Mineral Dust in Regions of Turkey with Endemic Malignant Mesothelioma

It has been proposed that the observed high incidence of fibre-related diseases, particularly malignant pleural mesothelioma (MPM), in Turkey can serve as a surrogate indicator of exposure to natural mineral fibres. Environmental exposure to the amphibole tremolite and the zeolite erionite are almost certainly the cause of this disease in the areas of Turkey where these minerals are found. In this study, field reconnaissance and mineralogical investigations were conducted to provide information to evaluate the environmental impacts of minerals in these endemic MPM regions. Some published data has also been re-evaluated and correlated with the current study.The results help to confirm that prolonged out-door and in-door exposure to these various mineral fibres may be the cause of MPM. Mixed fibres of tremoliteactinolite, anthophyllite, crocidolite, chrysotile and silica have been found in the asbestos-rich-regions where the disease is endemic. Fibre dimension is known to be a critical factor in the development of MPM and other mineral fibre-related diseases and so in addition to other studies the type and form of these minerals was examined. In the locations where nonfibrous tremolite and chrysotile-like minerals were present instead of endemic MPM, a high incidence of calcified pleural plaques (CPP) and pleural thickening (PT) was observed. Although examples of the zeolite group of minerals have been found in various locations throughout Turkey, only in Central Anatolia is erionite found in a fine fibrous form. This is the only area of Turkey where MPM is considered to be endemic through exposure to that form of the mineral. The studies also indicate that beside erionite, other fibres such as actinolite, tremolite, crocidolite, chrysotile, crystalline silica (cristobalite) and volcanic glass shards are present in the environment, and are found in human and sheep lung tissue samples.

Crystal structure-crystal chemistry relationships in the zeolites erionite and offretite

The new mineral tschortnerite, ideally Ca 4 (K,Ca,Sr,Ba) 3 Cu 3 (0H) 8 [Si 12 Al 12 0 4S ]·ϰH 2 0, ϰ &gt; 20, occurs as well-formed cubes up to a maximum size of 0.15 mm in a Ca-rich xenolith at the Bellberg volcano near Mayen, Eifel, Germany. The light blue, transparent crystals are optically isotropic, n = 1.504(2). Microprobe analysis (in weight percent) gave CaO 13.10, CuO 9.64, SrO 4.49, BaO 1.93, K 2 O 1.37, Fe 2 O 3 0.30, Al 2 O 3 25.21, SiO 2 30.25, H 2 O (calc, by difference) 13.71. The empirical formula based on 48 O atoms within the tetrahedral net is Ca 5.60 Sr 1.04 K 0.70 Ba 0.30 Cu 2.90 Fe 0.09 Al 11.85 Si 12.06 O 48 (OH) 8.44· 14.01H 2 O. Tschörtnerite is cubic, space group Fm3̅m [a = 31.62(1) Å, V = 31614 Å 3 , Z = 16]. The density is -D meas = 2.1 g/cm 3 , D calc = 2.10 g/cm 3 . Single-crystal X-ray investigations showed that tschortnerite is a zeolite; the structure contains interconnection of double six-rings, double eight-rings, sodalite cages, truncated cubo-octahedra, and previously unknown 96-membered cages (tschörtnerite cage). A new structural unit is the [Cu 12 (OH) 2 JCa 8 O 24 (H 2 O) 8 cluster centered within the truncated cubo-octahedron. The cluster is formed by a rhomb- dodecahedron-like arrangement of comer connected CuO 4 squares, the eight CaO 7 poly- hedra are branched. The sodalite cage houses Ca 4 (OH) 4 O 12 clusters of edge-sharing CaO 6 octahedra. Half-occupied (K,Ca,Sr,Ba) positions were located in the basal and top face of the double eight-rings, i.e., the border to the tschortnerite cage. Within the large tschort­nerite cage only H 2 O molecules were localized.

Crystal chemistry of the zeolites erionite and offretite

This study clarifies the crystal structure variations and relationships in the zeolites erionite and offretite. The crystal structure analyses used Rietveld analysis of X-ray powder diffraction data, obtained both by synchrotron radiation and conventional X-ray sources, and on diffraction patterns obtained by transmission electron microscopy. The framework Al atoms in erionite are preferentially located in the single six-membered ring of tetrahedra (T2 site), whereas the Si-Al distribution is essentially disordered on the tetrahedral framework sites in offretite. In both zeolites, the center of the cancrinite cage is always occupied by K cations in similar amounts in both minerals. The erionite cage in erionite is occupied by Ca and Na atoms distributed on four distinct cation sites. Mg ions can be present up to 0.8 atoms per cell and are located between the Ca1 and Ca3 sites and very close to the Ca2 site on the symmetry axis. In offretite, the Mg site is located on the trigonal axis of the gmelinite cage and the Mg atoms are bonded to a variable number (five or six) of H 2 O molecules, depending on the site population. The structural data and TEM analysis clearly show that the crystal chemistry of the extraframework cations, Mg in particular, is a major factor controlling whether erionite or offretite crystallizes, the Si-Al distribution in the framework, and the possible stacking intergrowths of the two minerals.