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Crystallite aluminosilicates are inorganic microporous materials with well-defined pore-size and pore-structures, and have important industrial applications, including gas adsorption and separation, catalysis, etc. Crystallite aluminosilicates are commonly synthesized via hydrothermal processes, where the oligomerization of silicic acids is crucial. The mechanisms for the oligomerization of poly-silicic acids in neutral aqueous solution were systematically investigated by extensive first-principles-based calculations. We showed that oligomerization of poly-silicic acid molecules proceeds through the lateral attacking and simultaneously proton transfer from the approaching molecule for the formation of a 5-coordinated Si species as the transition state, resulting in the ejection of a water molecule from the formed poly-silicic acid. The barriers for this mechanism are in general more plausible than the conventional direct attacking of poly-silicic acid with reaction barriers in the range of 150-160 kJ/mol. The formation of linear or branched poly-silicic acids by intermolecular oligomerization is only slightly more plausible than the formation of cyclic poly-silicic acids via intramolecular oligomerization according to the reaction barriers (124.2-133.0 vs. 130.6-144.9 kJ/mol). The potential contributions of oligomer structures, such as the length of the linear oligomers, ring distortions and neighboring linear branches, etc., to the oligomerization were also investigated but found negligible. According to the small differences among the reaction barriers, we proposed that kinetic selectivity of the poly-silicic acids condensation would be weak in neutral aqueous solution and the formation of zeolite-like structures would be thermodynamics driven.

D‐Glucose‐to‐L‐sorbose isomerization on Lewis acidic zeolite is a highly attractive avenue for sorbose production. But the L‐sorbose yield is limited by the competing D‐glucose‐to‐D‐fructose isomerization and reaction equilibrium. In this work, it is suggested that ethanol directs the glucose conformation for selective D‐glucose‐to‐L‐sorbose isomerization. It also reacts with the produced L‐sorbose to form ethyl‐sorboside, which allows the D‐glucose‐to‐L‐sorbose isomerization to proceed beyond the thermodynamic equilibrium limit. It is shown that a bifunctional zeolite Beta containing framework titanium (Ti) and boron (B) is a selective catalyst for this tandem reaction: Lewis acidic framework Ti catalyzes the D‐glucose‐to‐L‐sorbose isomerization via an intramolecular 5,1‐hydride shift process as confirmed by isotopic tracing experiments followed by 13C‐NMR, while weak Brønsted acid framework B selectively promotes the sorbose ketalization with ethanol. A remarkably high yield of L‐sorbose with a high fraction of sugar (>95 %: 27 % unreacted glucose, 11.4 % fructose, 57 % sorbose) was obtained after the mixture produced in ethanol was hydrolyzed. [ABSTRACT FROM AUTHOR]

A kind of cadmium sulfide (CdS) nanocomposite with different crystalline phases was grown on the surface of H-mordenite zeolite (HMOR) by a chemical liquid-phase co-precipitation method. In this work, 2 wt% CdS@HMOR photocatalytic material with the coexistence phase (hexagonal phase and cubic phase) of cadmium sulfide was grown on the surface of HMOR by controlling the reaction temperature and ammonia concentration. Photocatalytic degradation of methylene blue (MB) was used as an index to detect the photocatalytic performance of materials. The results indicated that the photocatalytic degradation efficiency of the system with HMOR was significantly improved in comparison to that without HMOR (CdS, 40.34%, 0.2578 h−1). It was found that 2 wt% CdS@HMOR had the best photocatalytic activity. The degradation rate of MB was 84.15% in 2 h, and the degradation rate constant was 0.8884 h−1. When 1.5 ml H2O2 was introduced into the system, the degradation rate of MB was increased to 98.98%, and the degradation rate constant was 1.9976 h−1. SEM, HRTEM, PL, EIS and photocurrent showed that the cubic and hexagonal phases of CdS were in contact with each other on the HMOR surface, forming a good electron transport. By XRD, XPS and SEM tests, the results of materials after four cycles of reactions showed that the structure of the 2 wt% CdS@HMOR was still stable. Therefore, HMOR may provide a good support for CdS, and the synergistic effect between them is beneficial for the occurrence of photocatalytic reactions. HMOR can act as an electron receptor to inhibit the recombination of carriers. The homo-junction between different phases of CdS on the surface of HMOR is beneficial to the separation of photo-induced carriers. These results indicate that the construction of phase heterojunctions on zeolites and the synergism among them are a method for improving the photocatalytic activity. [ABSTRACT FROM AUTHOR]

BACKGROUND Sodalite has been commonly employed as a photochromic material, and low Si/Al ratio sodalite is theoretically suitable for hydrogen storage. Consequently, a green and energy-saving synthetic route towards sodalite from inexpensive sources is highly desirable. Oil shale ash is a fly ash by-product produced from oil shale and has been used to synthesize NaA and zeolite X. In this paper, oil shale ash was selected as raw material to synthesize hydroxysodalite. RESULTS The highly crystallized hydroxysodalite was synthesized by hydrothermal reaction without any pretreatment. The binary crystallization phase diagram was obtained. The optimum reactant molar ratio, hydrothermal reaction temperature, and time are as follows: 10Na2O: 2SiO2: 75H2O, 180 °C, 24 h. The synthesized hydroxysodalite was further characterized by scanning electron microscopy. CONCLUSION High purity and well-crystallized hydroxysodalite was successfully synthesized from oil shale ash without pretreatment. Relatively high molar ratios of Na2O/ SiO2 as well as low molar ratios of H2O/ Na2O favour the formation of hydroxysodalite. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Zeolite omega is used as a catalyst in various fields. Expensive tetramethylammonium cations are the conventional structure-directing agents for the synthesis of zeolite omega. In this work, glycerol was used as both solvent and structure-directing agent instead of expensive quaternary ammonium compounds. Zeolite omega has been obtained through conversion of magadiite in this glycerol-water system. The effects of various parameters such as reaction time, temperature, alkalinity and glycerol content were discussed. RESULTS Pure zeolite omega could be obtained at 120°C for 10 days with the reactants molar composition of 14 SiO2: Al2O3: 10 Na2O: 169 H2O: 200 glycerol. Water content plays an important role in the solvothermal conversion of magadiite to zeolite omega. CONCLUSION The zeolite omega obtained from this system is a rather pure phase free from impurities. A preferential location of the Al atoms in the six-membered rings of the gmelinites in zeolite omega was observed. A method including extraction and calcination was introduced to remove organic species by which highly ordered pore structure of zeolite was well retained. The present work develops a novel synthesis method for zeolite omega. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

[Display omitted] • Potential propane dehydrogenation (PDH) pathways over Ga hydride species trapped by Al-pairs in Ga/ZSM-5 were investigated. • These in-situ formed undercoordinated Ga hydride species are preferred for PDH. Undercoordinated b[GaH]2+ would exhibit PDH activity superior to other Ga species. • The most plausible PDH pathway over undercoordinated b[GaH]2+ is the carbenium pathway. • Ga hydride species evolves as the PDH proceeds. Ga/ZSM-5 is widely used to catalyze propane dehydrogenation (PDH). For the harsh operation conditions, the detailed active species, and the plausible reaction pathways that are responsible for the observed superior PDH performance remain unresolved for Ga/ZSM-5. Reduced extraframework Ga hydride species trapped at zeolite framework Al-pairs, including b[GaH]2+, [Ga]+-BAS, [GaH 2 ]+-BAS, etc. are an important kind of Ga species known as active species for PDH. In this work, the PDH pathways these over these Ga species were investigated theoretically at temperatures and pressures relevant to experiments. We showed that dynamically generated undercoordinated b[GaH]2+ would exhibit significantly higher catalytic activity at PDH conditions as compared with other Ga hydride species. The most plausible PDH pathway over b[GaH]2+ is the carbenium pathway. The Ga species and BAS act in concert in promoting the H 2 elimination and β-H transfer, and in turning PDH efficient. Ga hydride species may also form as intermediates along the PDH pathways as active sites for subsequent activation and conversion of propane, suggesting the evolution of Ga hydride species trapped by Al-pairs in Ga/ZSM-5 at operation conditions. The findings are expected to pave the way for better understanding of the experimentally observed operation condition dependent PDH performance of Ga/ZSM-5. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermodynamics calculations at conditions relevant to experiments show that [Ga]+(I) is plausible at high temperature and low P H2O , and [Ga(OH) 2 ]+(III) is plausible at low temperature and high P H2O. • The calculated energy and free energy barriers for H 2 formation, dissociation and H 2 O formation are among the highest, suggesting stability of corresponding Ga species. • The coordination of framework O to Ga center are rather flexible, making dynamic formation of undercoordinated Ga species feasible at operation conditions. • [GaH]2+(III) is not as plausible as [Ga]+(I). Less reactive [GaH 2 ]+(III) can be avoid by control the distribution of Al. Ga/ZSM-5 has been studied for a long time for its efficiency in catalytic dehydrogenation and conversion of light alkanes. Atomically dispersed extra-framework Ga species, such as [Ga]+(I), [GaH 2 ]+(III), [GaO]+(III), [GaHOH]+(III), [Ga(OH) 2 ]+(III) and [GaH]2+(III), etc. were proposed as reaction centers for such processes. To rationale the observed catalytic performances of Ga/ZSM-5, we investigated the electronic structures of these Ga species and pathways for their interconversion in zeolite channels by first-principles based calculations. Results from thermodynamics calculations at conditions relevant to experiments show that [Ga]+(I) is plausible at high temperature and low P H2O , and [Ga(OH) 2 ]+(III) is plausible at low temperature and high P H2O. On pathways for interconversion of proposed Ga species, the calculated energy and free energy barriers for H 2 dissociation and H 2 O formation are among the highest and correlate with involvement of Ga centers and their coordination with H and O-containing ligands. The coordination of framework O to Ga center are rather flexible, making dynamic formation of undercoordinated Ga species feasible at operation conditions and these species may attend subsequent chemical processes. We expect the findings would help to understand the formation and evolution of atomically dispersed reaction centers in zeolite channels under operation conditions. [ABSTRACT FROM AUTHOR]

Mordenite and ZSM-5 (with MOR and MFI topology, respectively) have been synthesized using cyclohexylamine (CHA) as structure directing agent. The zeolite crystals obtained were characterized by X-ray diffraction (XRD), infrared spectra (IR), Raman spectra, thermal analysis (TG/DTA), elemental analysis (EA) and 13 C MAS NMR spectroscopy. It was found that CHA was trapped in the two zeolites in its protonated state together with some other organic species. Furthermore, the oxidation of CHA restricted in zeolites by H 2 O 2 has been studied. The oxidation products of restricted CHA were nitro compound and saturated hydrocarbons in mordenite, whereas nitro compound, cyclanes and amines in ZSM-5. The adsorption tests illustrated that the as-synthesized samples and their oxidized products have high adsorption capacity for Ni (II). This work opens new opportunities for further research of molecular reactions on the inorganic hybrids, and provides a new idea for the application of SDAs present in molecular sieves. [ABSTRACT FROM AUTHOR]

Two kinds of zeolites (mordenite and AlPO 4 -5, with MOR and AFI topology, respectively) have been synthesized using hexamethyleneimine (HMI) as structure directing agent. It is found that HMI is incorporated intact in its protonated form in MOR and AFI. Furthermore, the oxidation of HMI restricted in the two zeolites by H 2 O 2 has been studied. Analysis of FT-IR, Raman spectra, TG/DTA, EA and 13 C MAS NMR show that the restricted HMI molecules are changed into saturated hydrocarbons and some other amines in AFI, whereas unchanged in MOR. The adsorption tests illustrated that the as-synthesized samples and their oxidized products have high adsorption capacity for Ni(II). This work opens new opportunities for further research of molecular reactions on the inorganic hybrids, and provides a new idea for the application of SDAs present in molecular sieves. [ABSTRACT FROM AUTHOR]

Sodalite materials with different Si/Al ratios and ferrierite have been successfully crystallized using ethylene glycol (EG) as structure directing agent. The zeolite crystals obtained were characterized by X-ray diffraction (XRD), infrared spectra (IR), Raman spectra, thermal analysis (TG), elemental analysis (EA), inductively coupled plasma Mass Spectrometer (ICP) and multinuclear MAS NMR spectroscopy. It is found that EG is occluded in the ferrierite and sodalites in the same state. Furthermore, the oxidation by H 2 O 2 and HIO 4 of EG restricted within these zeolites has been studied. Based on the IR, Raman spectra, TG, EA and 13 C NMR spectra data, it has been found that the restricted EG molecules in the two sodalites remained unchanged during the oxidation process because they are occluded in the β-cage. In ferrierite, the oxidation products were alkanes and other alcohols by H 2 O 2 , whereas alkynes, acetals and ketals produced by HIO 4 . These oxidation products are different from the bulk reaction. This work not only promotes the study of SDAs in the synthesis of zeolites, but also provides a new idea for further research of molecular reactions on the inorganic hybrids. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Zeolite X (ZX) was synthesized by diatomite in a template-free system. • The synthetic ZX was modified by thiourea (TU). • TU molecules were loaded onto both exterior and interior surfaces of ZX. • The adsorption capacity for Cd(II) of ZX-TU is much higher than raw ZX. Abstract Zeolite X (ZX) was synthesized by diatomite in a water system, and then the synthetic zeolite was modified by thiourea (TU). The synthetic and modified ZX were characterized by XRD, FT-IR, TG/DTA, elemental analysis (CHNS), FE-SEM, EDX, elemental mapping and N 2 adsorption/desorption isotherms, respectively. All the results confirmed that the TU molecules were loaded onto both the exterior and interior surfaces of ZX during the modification process. Compared to the raw ZX, the modified ZX has a higher removal capacity in the Cd(II) removal experiments. In ZX-TU sample, removal of Cd(II) takes place via ion exchange and complexation processes. The maximum adsorption capacity is 92.47 mg/g at 25 °C. This cost-effective zeolite can be a functional material for heavy metal removal. [ABSTRACT FROM AUTHOR]

Zeolite L has been synthesized by magadiite conversion method. The crystallization behavior and changes of medium-range structure during the crystallization were investigated by X-ray diffraction, scanning electron micrograph, vibrational spectroscopy and 27 Al magic angle spinning nuclear magnetic resonance. It is indicated that parts of 6 member-rings in magadiite still exist as secondary building units although the long-range order of magadiite was collapsed in the initial stage. The 4 member-rings and 8 member-rings were formed after the sample was heated for 3 h and 4 h, respectively. The influence of various parameters such as reaction temperature, time and substrate composition was examined. Highly crystallized and pure zeolite L could be prepared from the substrates with molar composition: 0.56M 2 O–xAl 2 O 3 SiO 2 49H 2 O (M 2 O = K 2 O + Na 2 O, x = 0.0033–0.04) by heating at 140 °C for 18 h, 160 °C for 12 h or 180 °C for 8 h. [ABSTRACT FROM AUTHOR]

Herein, a bifunctional self-pillared MFI nanosheets zeolite (Sn-B-SPP) is designed to achieve the highly selective conversion of sucrose to fructose, which is significant for utilization of the nature abundant sucrose. This Sn- and B-containing SPP zeolite was prepared through a facile solid-state ion exchange approach based on a B-SPP, which overcomes the difficulty of direct nucleation. Sn-B-SPP possesses the structural advantages of ultra-thin intergrown nanosheets materials such as high external surface area, extremely short diffusion length and highly exposed active sites, which are conducive for the conversion of bulky substrates. Meanwhile, the concerted Lewis acidity and weak Brønsted acidity are essential for the sucrose conversion in alcohol, achieving a 77.0% fructose yield in 4 h after hydrolysis, far surpassing the performance of its microporous analogue and conventional hierarchical Sn–B-MFI. Bifunctional Sn-B-SPP zeolite with orthogonal rotation intergrown structure was successfully prepared and utilized for highly selective conversion of sucrose to fructose. [Display omitted] • A bifunctional Sn-B-SPP zeolite is designed via a simple, robust and environmental-friendly solid ion exchange approach. • Sn-B-SPP zeolites with ultra-thin intergrown nanosheets structure are conducive for the conversion of bulky substrates. • Highly selective conversion of sucrose to fructose is achieved over the Sn-B-SPP while maintaining high sugar balance. • The better catalytic activity is due to the nanosheets intergrown structure and the concerted Lewis and Brønsted acid sites. [ABSTRACT FROM AUTHOR]

ZSM-22 zeolite has been synthesized using diethylamine (DEA) as structure directing agent. The crystal obtained was characterized by XRD, IR, TG/DTA, elemental analysis, ICP and 13 C MAS NMR spectroscopy. It is found that DEA is incorporated intact in its protonated form in TON. Furthermore, the oxidation of DEA restricted in the TON by H 2 O 2 and HIO 4 has been studied. Based on the IR, TG/DTA, EA and 13 C NMR spectra data, it has been found that the oxidation products were saturated hydrocarbons and some other amines by H 2 O 2 , whereas saturated hydrocarbons, other amines and ethyleneimine produced by HIO 4 . These oxidation products are different from the bulk reaction. This work opens new opportunities for further research of molecular reactions on the inorganic hybrids. [ABSTRACT FROM AUTHOR]

Changes of medium-range structure during the crystallization of zeolite omega from magadiite were characterized. It is found that although the long-range order of magadiite is collapsed in the initial stage, parts of 5-member rings and 6-member rings are still preserved as secondary building units. The fraction of 5-member rings and 6-member rings increases as the crystallization progresses. The 4-member ring chains are formed at a stage later than that of 5-member rings and 6-member rings. [ABSTRACT FROM AUTHOR]

A novel copper phthalocyanine/mordenite zeolite (CuPcs/MOR) photocatalyst was synthesized and tested to be a good photocatalyst for NO x removal. With CuPcs 0.85 /MOR 2 composite as catalyst, the degradation rate of NO 2 can reach 71.4% under irradiation for 2 h than that of pure CuPcs, attributing to the synergistic effect between them. The process of NO x photocatalytic degradation was discussed, indicating that the MOR with adsorption property not only increased the active sites of CuPcs but also accelerated the charge transfer. A small amounts of copper oxide species are produced during the synthesis, forming co-catalyst with copper phthalocyanine in the system to eliminate nitrogen oxides. Copper phthalocyanine/mordenite zeolite was synthesized and shown an excellent photocatalytic catalyst for the degradation of nitrogen oxides (NO x). Specifically, the degradation rate of NO 2 can reach 71.4% under visible light irradiation for 2 h. The synergistic effect of adsorption and photocatalytic oxidation between zeolite and semiconductor plays an important role in the removal of NO x. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Small crystal zeolites beta with molar Si/Al ratios of 21, 30 and 40.5 were successfully obtained by treating parent beta (Si/Al=14.5) with different oxalic acid concentrations. The influence of Si/Al ratio of zeolite beta on effective mesopore formation via NaOH treatment was studied by investigating the changes in crystallinity, morphology, chemical composition, acidity and textural property of zeolite beta before and after alkaline treatment. The catalytic performance was evaluated in terms of α-pinene isomerization and benzoylation of naphthalene with benzoyl chloride. Substantial mesoporosity could be developed for zeolites beta with molar Si/Al ratios of 14.5–30, coupled with better preserved microporosity. Though the largest mesopore surface area (488m2 g−1) was achieved when Si/Al=30, the crystallinity of zeolite beta was partly destroyed. The substantially improved catalytic activity of alkaline treated samples in α-pinene isomerization is mainly attributed to the developed mesoporosity, but the volcano curve change in catalytic activities of alkaline treated samples in benzoylation of naphthalene manifested that both mesoporosity and acid property play important role in a medium strong acid catalyzed reaction. [Copyright &y& Elsevier]

Abstract: A study on magadiite recrystallization is undertaken to relate the influence of short-chain tetraalkylammonium (TAA+) cations to the zeolite obtained. Using different types of short-chain TAA+ cations under various reactant conditions, OFF, MOR and MFI zeolites are obtained respectively. The infrared spectroscopy (IR), N2 adsorption analysis, thermogravimetry and differential thermal analysis (TG/DTA) of MOR zeolite in the presence or absence of tetraethylammonium (TEA+) cations are carried out for comparison purpose; these results elucidate that TEA+ cations exist in the micropore of MOR zeolite. The roles of TAA+ cations in the recrystallization of magadiite into zeolites are systematically investigated. It is possible that OFF zeolite could be prepared easily when a small quantity of tetramethylammonium (TMA+) cations are used and TEA+ cations interact strongly with MOR zeolite framework. The influence of tetrapropylammonium (TPA+) cations and tetrabutylammonium (TBA+) cations is structure directing on the magadiite recrystallization. [ABSTRACT FROM AUTHOR]

Abstract: ZSM-5 crystals, of which granule size is about 120 µm along c axis, are employed as a good host material for TiO2 loading. Optical microscopy photographs, X-ray powder diffraction spectra and surface area calculated from nitrogen adsorption data at −196 °C have been carried out and show that the titanium dioxide clusters are infiltrating into the pores of ZSM-5. TiO2/ZSM-5 host-guest material, regardless of whether being prepared by microwave and water bath heating, shows similar features except for the TiO2 contents. The materials have a photoluminescence emission peak at 2.85 eV, which is ascribed to the band edge emission. A red shift was observed on the photoluminescence emission spectra when NH3 adsorbed into the pores of TiO2/ZSM-5 material. [Copyright &y& Elsevier]

Abstract: The cobalt (II)-exchanged zeolite A (NaCoA) was prepared by cation exchange process with zeolite A (NaA) and Co(NO3)2 in aqueous solution. A static volumetric system was employed to evaluate the N2 and O2 adsorption properties of NaCoA at 298K. It was found that the N2 adsorption capacity of NaCoA increased rapidly with the rising pressure, and the adsorption isotherm of N2 became nonlinear in low pressure region. The O2 adsorption capacity of NaCoA increased slightly with pressure. The introduction of Co2+ into the NaA enhanced the N2 adsorption capacity and N2/O2 selectivity, which could be contributed to the π-complexation between N2 and Co2+. This strong interaction brought about a series of high value for Henry''s constant, Langmuir constant, adsorption selectivity and adsorption capacity of N2 in NaCoA. Infrared spectra were also carried out to illustrate that the N2 were bonding with Co2+. [Copyright &y& Elsevier]

Zeolite beta with high crystallinity has been successfully synthesized by using kenyaite conversion method with seed crystals under hydrothermal treatment at 125 °C for 36 h. The OSDA-free synthesis of zeolite beta could be obtained from the mixture composition of 0.96 NaOH: SiO 2 : 0.0167 Al 2 O 3 : 180 H 2 O by adding 25 wt % seeds. To study the crystallization behaviours and the medium-range structure changes during the conversion process, the prepared zeolite beta was characterized by powder X-ray diffraction, field-emission scanning electron microscope, Fourier transform infrared spectroscopy, energy dispersive spectroscopy, solid-state 27Al MAS and 29Si MAS NMR spectroscopy. The growth of zeolite beta happened on the surface of kenyaite. The five-membered rings and six-membered rings in kenyaite were partly preserved and the four-membered rings were formed by the connection of five-membered rings during the crystallization process. Meanwhile, the effects of reaction time, the initial mixture composition, the quantity of beta seed crystals and temperature in the synthesis were investigated. The as-synthesized zeolite beta, with relatively high thermal stability, exhibits good catalytic performance in the cyclohexanol dehydration reaction system. Image 1 • High crystalline and pure zeolite beta could be obtained through the conversion of kenyaite by a seed-directed OSDA-free rount in 36 h. • Changes of medium-range structure during the crystallization were investigated. • The various parameters as reaction temperature, time, the quantity of beta seeds and gel composition all have very important influence on zeolite beta synthesis. • The synthesized zeolite beta, with relatively high thermal stability, exhibits certain catalytic performance in the cyclohexanol dehydration reaction system. [ABSTRACT FROM AUTHOR]

Abstract: The thermal diffusion method is employed for ZnO loading into ZSM-5 crystals (ca. 120μm along c axis) which is regarded as a good host material for guest encapsulation. Optical microscopy photographs and X-ray powder diffraction spectra are obtained and show that the ZnO clusters are infiltrated into ZSM-5 crystals, instead of locating on the surface of the crystals. An intense porosity analysis based on density functional theory is used to illustrate the pore texture of the ZnO-loaded samples. The sample prepared at 650°C has ZnO clusters existing mainly in the external surface of ZSM-5. As for the sample prepared at 750°C, the micropores of ZSM-5 have been occupied. [Copyright &y& Elsevier]

Abstract: The magnesium (II)-exchanged zeolite A (MgA) was prepared by cation exchange process using sodium form zeolite A (NaA) and MgCl2 in aqueous solution. The prepared MgA was characterized by infrared spectroscopy and X-ray powder diffraction analysis. The results showed that the LTA structure remains after cation exchange. A static volumetric system was employed to evaluate the N2 and O2 adsorption properties of all the samples at 298K. It was found that the N2 adsorption capacity of MgA increased rapidly with pressure rise, and the adsorption isotherm of N2 became nonlinear in low pressure region. The O2 adsorption capacity of MgA increased slightly with pressure. The introducing Mg2+ into the sodium type zeolite A greatly enhanced the N2 adsorption capacity. The highest N2 adsorption capacity and N2/O2 selectivity appeared in the sample with 64.3% of Mg2+ replaced. [Copyright &y& Elsevier]