NaY Zeolite Research Articles

Ultra-deep removal of thiophene in coke oven gas over Y zeolite: Effect of acid modification on adsorption desulfurization

The ultra-deep removal of thiophene to 0.1 ppmv level is necessary for coke oven gas to methane process. NaY zeolite was reported to have this potential, and acid sites in NaY play an important role on its desulfurization performance. Based on this situation, sorbents with different types and strengths of acids were prepared by modifying NaY in ammonium nitrate and citric acid solutions. Their desulfurization behaviors in simulated coke oven gas were evaluated by fixed bed. The results show that both ammonium nitrate and citric acid modification on NaY are beneficial to the breakthrough adsorption capacity of thiophene (Qb-thiophene). The NaY after modified in 0.10 mol/L citric acid solution has the highest Qb-thiophene at 100 °C. Ammonium nitrate modification could significantly increase medium-strong Bronsted acid in NaY, whereas citric acid modification mainly increases weak Lewis acid. On medium-strong Bronsted acid sites, thiophene polymerization reaction would occur easily, which would result in the obvious decrease of Qb-thiophene from 71.31 to 35.3 mg/g due to the acid sites covering and micropores blocking by thiophene oligomer. The increase of Lewis acid is conducive to desulfurization. Moreover, on Lewis acid site, the temperature region for thiophene removal is wider than that on Bronsted acid.

Synthesis of Pure Phase NaP2 Zeolite from the Gel of NaY by Conventional and Microwave-Assisted Hydrothermal Methods

The gel of zeolite NaY has potential as a precursor of other zeolites. The particular interest in this work is to convert the gel of NaY to NaP2. We found that the pure phase NaP2 can be produced simply by the conventional hydrothermal (CH) method at 150 °C for 24 h. This NaP2 sample, named CH150, has an average particle size of 10.3 µm and an Si/Al ratio of 1.82. In the case of single crystallization via microwave-assisted hydrothermal (MH) method, various parameters were studied, including the crystallization temperature (90, 150, 175 °C) and time (15, 30, 45, 60 min). The samples were analyzed by X-ray diffraction and scanning electron microscopy. However, mixed phases of P1 and P2 or ANA were obtained from all samples. Another attempt was made by a double crystallization via MH method as followed: at 90 °C for 1 h, quickly cooled down to room temperature in the microwave chamber and aged for 23 h, and finally at 150 °C for 1 h. The sample, named MH90A150, has an average crystal size of 16.45 µm and an Si/Al ratio of 1.85. The high Al content of NaP2 in both samples (CH150 and MH90A150) could lead to interesting applications.

Observation of La-exchanged NaY zeolite using aberration-corrected scanning transmission electron microscopy

The determination of metal location in zeolite and an estimation of site occupancy by using spherical aberration-corrected scanning transmission electron microscopy ( Cs -corrected STEM) were attempted through the observation of La-exchanged NaY zeolite (LaNaY). LaNaY was prepared by the ion exchange of NaY zeolite and observed using high-angle annular dark-field (HAADF)-STEM. Simultaneous imaging of both the zeolite framework and La atomic columns revealed the La positions to be in sites I and I’. From the averaged HAADF intensity of each La site, the La occupancy was estimated to be about a fourth for both sites I and I’. The estimated La occupancy of site I was much larger than that measured by XRD, suggesting that the STEM data reflects the highly dehydrated state of LaNaY. In addition, methods for observation of individual La atoms are described. • La atoms and T-sites in La-exchanged NaY zeolite were simultaneously visualized. • The locations of La atoms were determined, and the La site occupancy was estimated. • Methods for observing individual La atoms were described.

Synthesis Procedure and Industrial Applications of NaY Zeolite for Various Processes: A Review

Faujasite Y zeolites, due to their outstanding properties, have numerous applications in the chemical industries like petroleum refining, adsorption, FCC, petrochemical, aromatic alkylation, natural gas dehydration, separation, and environmental protection. The astonishing properties include high surface area, high porosity, high thermal stability and large ion-exchange capacity. In this review study, a summary of different synthesis techniques of this type of zeolite has been addressed. Different kinds of techniques like seeding, free template, organic template, increasing the alkali treatment and temperature control methods are described. Subsequently, because of its important role as a catalyst for different processes, the application of this zeolite was reviewed for different chemical processes.

Synthesis of Zeolite Nay From Dealuminated Metakaolin as Ni Support for Co2 Hydrogenation to Methane

AbstractThe conversion of CO2 into carbon feedstock via CO2 hydrogenation to methane requires a stable catalyst for reaction at high temperatures. Zeolite NaY (abbreviated hereafter as NaY) synthesized from naturally occurring kaolin provides a stable support for Ni nanoparticles. Kaolin can be further dealuminated using sulfuric acid to reduce the Si/Al ratio, but the presence of the remaining sulfur is detrimental to the formation of NaY. The objective of the present study was to synthesize NaY from dealuminated metakaolin, using a method that minimizes the detrimental effects of sulfur, and to investigate the effect of its activity on CO2 methanation. Kaolin from Bangka Belitung, Indonesia, was calcined at 720°C for 4 h to form metakaolin (M) and subsequently treated with sulfuric acid to form dealuminated metakaolin (DM). Excess sulfur was removed by washing with deionized water at 80°C. Zeolite NaY was then synthesized from the M and DM via a hydrothermal method; the relationship between morphology, structural properties, and the catalytic activity of NaY was determined for CO2 methanation at 200–500°C. The presence of excess sulfur following dealumination of metakaolin produced NaY with small surface area and porosity. After Ni impregnation, the synthesized NaY exhibited significant catalytic activity and stability for the reaction at 250–500°C. Analysis by scanning electron microscopy and high-resolution transmission electron microscopy showed the formation of well-defined octahedral structures and large surface areas of ~500 m2/g when NaY was synthesized using DM. Catalytic activity indicated significant conversion of CO2 (67%) and CH4 selectivity (94%) of Ni/NaY from DM in contrast to only 47% of CO2 conversion with 77% of CH4 selectivity for Ni/NaY synthesized from M. Dealuminated metakaolin also produced robust NaY, which indicated no deactivation at 500°C. The combination of well-defined crystallite structures, large surface area, and small Al contents in NaY synthesized from DM helped in CO2 conversion and CH4 selectivity for the reaction at 200–500°C.

Aqueous-Phase Cellulose Hydrolysis over Zeolite HY Nanocrystals Grafted on Anatase Titania Nanofibers

Acid-catalyzed aqueous-phase hydrolysis of cellulose was investigated over zeolite HY nanocrystals grafted on anantase titania nanofibres (HY-TiO2). H-exchanged NaY zeolite nanocrystals of controlled size (40–60 nm) were synthesized and deposited over TiO2 nanofibres prepared by hydrothermal treatment of anatase nanoparticles. The resulting materials were characterized by XRD, SEM, TEM, NH3-TPD and FT-IR, and evidenced a homogeneous distribution of HY nanocrystals across the TiO2 nanofibres. HY-TiO2 catalysts exhibited higher turnover numbers and selectivity to glucose than large (500 nm to 2 μm) unsupported HY nanoparticles; this performance enhancement is attributed to the greater accessibility of Bronsted acid sites in HY nanocrystals to cellulose particles. The importance of active site accessibility to β-1,4-glycosidic bond cleavage was highlighted by a significant increase in the rates of glucose and cellobiose hydrolysis (versus cellulose) over HY-TiO2-100. Engineering of zeolite particle size is a critical design parameter for the valorization of sterically-challenging cellulosic feedstocks.

Growth process and short chain alcohol separation performance of fluoride-containing NaY zeolite membrane

Growth process of the NaY zeolite membranes was investigated by fluoride-containing precursor synthesis gel. Compared with the fluoride-free precursor synthesis gel, the irregular NaY zeolite crystals were dissolved into amorphous by the fluoride-containing precursor synthesis gel initially, the amorphous contained the Y-type zeolite characteristic bands by the IR characterization. The fine square NaY zeolite crystals arose from the amorphous, which were accumulated and gradually grew into a dense NaY zeolite layer on the support surface after 6.5 h. Because the excessive NaY zeolites were dissolved by the strong alkaline and fluoride-containing precursor synthesis gel, there was plenty of amorphous on NaY zeolites layer for prolonging the crystallization time. The as-synthesized NaY zeolite membranes had a good separation performance and repeatability for separation of 10 wt% methanol (MeOH)/methyl methacrylate (MMA) mixture by pervaporation, the flux and separation factor were (1.27 ± 0.07) kg ∙ m−2 ∙ h−1 and (4900 ± 1500) at 323 K, respectively. Besides, the NaY zeolite membranes were applied to separate the other short chain alcohol from the various alcohol/organic ester and alcohol/organic ether mixtures, the NaY zeolite membranes showed high short chain alcohol perm-selectivity.

A New Type of Composite Membrane PVA-NaY/PA-6 for Separation of Industrially Valuable Mixture Ethanol/Ethyl Tert-Butyl Ether by Pervaporation.

Pervaporation is a membrane technique used to separate azeotropic and close boiling solvents. Heterogenous PVA composite membranes with NaY zeolite supported on polyamide-6 were fabricated and utilized in organic–organic pervaporation. The efficiency of prepared membranes was evaluated in the separation of ethanol/ethyl tert-butyl ether (EtOH/ETBE) using separation factor (β) and the thickness normalized pervaporation separation index (PSIN). Implementation of the fringe projection phase-shifting method allowed to the determined contact angle corrected by roughness. The influence of the presence of water traces in the feed on the overall separation efficiency was also discussed using the enrichment factor for water (EFwater). The incorporation of NaY into PVA matrix increases surface roughness and hydrophilicity of the composite membrane. It was found that membranes selectively transport ethanol from the binary EtOH/ETBE mixture. The values of β (2.3) and PSIN (288 μm g m−2 h−1) for PVA-NaY/PA6 membrane were improved by 143% and 160% in comparison to the values for the pristine PVA/PA6 membrane. It was found that membranes showed EFwater > 1, thus revealing the preferential transport of water molecules across membranes. These results are also significant for the design of membranes for the removal of water excess from the mixtures of organic solvents.

Highly efficient selective oxidation of 2-methylnaphthalene to vitamin K3 over mesoporous Al/Ti-SBA-15 catalysts: The effect of acid sites and textural property

Catalytic oxidation of 2-methylnaphthalene to 2-methyl-1,4-naphthoquinone (vitamin K3) is a significant pathway to produce vitamin groups K. High pollution and low-productivity of the traditional method require a greener catalyst and process. In this work, Al/Ti-SBA-15 with different nSi/nAl and nSi/nTi ratios were hydrothermally prepared in mild acidic condition and tested in partial oxidation of 2-methylnaphthalene. Commercial zeolites NaY, β and ZSM-5 were applied to investigate the influence of mass transfer resistance and acidity on catalytic performance. Catalysts were characterized by XRD, N2 adsorption-desorption, TEM, NH3-TPD, FTIR and Py-FTIR. We have found that the 2-methylnaphthalene conversion and vitamin K3 selectivity depend strongly on the mesoporous structure as well as Brönsted acid concentration and strength. Irregular micropores and strong acidity will accelerate the cleavage of C = C in aromatic rings, leading to the production of phthalic anhydride. DFT calculation reveals that incorporation of aluminum in SBA-15 can reduce the energy gap, facilitating the electron transfer. And as a consequence of the substitution of Al in tetrahedral positions in SBA-15, Al-SBA-15 (10) gives the best result with 72% yield to vitamin K3. This catalyst markedly reduces the activation energy due to the modified activated center. Repeated experiments recommend that Al-SBA-15 is a steady and high-efficiency catalyst for the production of vitamin K3.

Monte Carlo Simulations of Adsorption of Thiophene/Benzene in NaX and NaY Zeolites from Model Fuel

The process of adsorptive desulfurization requires sorbents to have high adsorption capacity and selectivity for thiophene in contrast to aromatics or alkanes. We investigated the adsorption of thiophene, benzene, and their mixtures in the presence of n-octane by the sodium-exchanged FAU zeolite using the grand canonical Monte Carlo simulations. The adsorption isotherms were computed and compared with available experimental data. The simulation results show that the change in the Si/Al ratio of zeolite may cause significant differences in adsorption selectivity, which was also observed by experiments. The NaX zeolite shows a higher adsorption selectivity than the NaY zeolite. The location of cations in the zeolites results in a change of pore size and creates an additional type of adsorption site, which subsequently results in different adsorption selectivities between thiophene and benzene in model fuel.

Effect of Manganese and zeolite composition on zeolite-supported Ni-catalysts for dry reforming of methane

This study examines the effects of manganese (Mn) on zeolite-supported Ni catalysts for dry reforming of methane (DRM). Three commercially-available zeolites (NH4-ZSM5, NH4-Y, Na-Y) were used as catalyst supports for the Ni (10 wt%) catalysts, and 4 different loadings of Mn (0-15 wt%) were used. The activities of the catalysts were screened, and selected catalysts were investigated for 24 hours in the DRM reaction. It was found that the effects of Mn on catalyst activity depends upon the type of zeolite support. Generally, however, Mn decreased the activity of the zeolite-supported Ni-based catalyst, but reactivity was more stable over a 24 -h reaction period. The beneficial effects of Mn as a promoter on NH4-ZSM5 and NH4-Y zeolites are to reduce carbon deposition, to decrease the crystal size of Ni, and to increase Ni dispersion on the zeolite. However, as Mn loading increases, the crystallinity of the zeolite structure and its micropore surface area generally decrease. Mn loading at 10 wt% and 15 wt% on Na-Y is detrimental to catalyst activity and to crystal structure, as it facilitates the destruction of the crystal structure of the Na-Y zeolite and significantly enhances sintering in a high temperature reducing atmosphere.

An efficient strategy to improve the catalytic activity of CuY for oxidative carbonylation of methanol: Modification of NaY by H4EDTA-NaOH sequential treatment

Abstract The micropore of the pristine NaY zeolite limits the number of active center Cu+ as well as the diffusion of reactant and product molecules, meanwhile, owing to its small size of hexagonal prisms and sodalite cages as compared to the kinetic diameter of the reactants leads to the low Cu+ utilization, which is not conductive to the oxidative carbonylation of methanol over CuY zeolite. In this work, the NaY zeolite with abundant mesopore was obtained without evident sacrifice of framework Al by sequential H4EDTA-NaOH treatment. The hexagonal prisms and sodalite cages were broken during the H4EDTA-NaOH sequential treatment process resulting in the formation of mesopores, which facilitated the exchange of Cu(NH3)42+ with Na+ and improved the accessibility of Cu+ to reactant molecules. Moreover, the extracted Al species from the framework of NaY by H4EDTA treatment gradually reinserted back into the framework of NaY zeolite during the subsequent alkali treatment with the increased NaOH concentration, which improved the number of available exchanged sites with Cu(NH3)42+. Hence, the number of accessible active center Cu+ was significantly improved. Besides, the formation of mesopores promoted the diffusion of reactants and product molecule. The obtained results indicate that modification of NaY by sequential H4EDTA-NaOH treatment is an effective strategy to enhance the catalytic performance of CuY for oxidative carbonylation reaction.

Adsorption Properties of SF6 on Zeolite NaY, 13X, Activated Carbon, and Silica Gel

The SF6 adsorption isotherms on zeolite 13X, zeolite NaY, activated carbon, and silica gel were investigated over a temperature range of 298–358 K and at pressure from 0 to 1000 kPa. Experimental r...

Deposition of NiO Nanoparticles on Nanosized Zeolite NaY for Production of Biofuel via Hydrogen-Free Deoxygenation.

Nickel-based catalysts play an important role in the hydrogen-free deoxygenation for the production of biofuel. The yield and quality of the biofuel are critically affected by the physicochemical properties of NiO supported on nanosized zeolite Y (Y65, crystal size of 65 nm). Therefore, 10 wt% NiO supported on Y65 synthesized by using impregnation (IM) and deposition–precipitation (DP) methods were investigated. It was found that preparation methods have a significant effect on the deoxygenation of triolein. The initial rate of the DP method (14.8 goil·h−1) was 1.5 times higher than that of the IM method (9.6 goil·h−1). The DP-Y65 showed the best deoxygenation performance with a 80.0% conversion and a diesel selectivity of 93.7% at 380 °C within 1 h. The outstanding performance from the DP method was due to the smaller NiO particle size (3.57 ± 0.40 nm), high accessibility (H.F value of 0.084), and a higher Brönsted to Lewis acidity (B/L) ratio (0.29), which has improved the accessibility and deoxygenation ability of the catalyst. The NH4+ released from the decomposition of the urea during the DP process increased the B/L ratio of zeolite NaY. As a result, the pretreatment to convert Na-zeolite to H-zeolite in a conventional zeolite synthesis can be avoided. In this regard, the DP method offers a one-pot synthesis to produce smaller NiO-supported nanosized zeolite NaY with a high B/L ratio, and it managed to produce a higher yield with selectivity towards green diesel via deoxygenation under a hydrogen-free condition.

Hydrogenolysis of glycerol to 1,2-propanediol without external H2 addition in alkaline medium using Ni-Cu catalysts supported on Y zeolite

Ni, Cu and Ni-Cu catalysts supported on NaY-zeolite (NaY) were prepared with 20 wt% of each metal by using wet impregnation method. They were characterized by X-ray fluorescence, X-ray diffraction, N2 adsorption-desorption, temperature-programmed reduction, temperature-programmed desorption of ammonia and temperature-programmed oxidation. The catalytic tests of glycerol hydrogenolysis were performed in alkaline medium (NaOH/glycerol molar ratios of 0, 0.25 and 0.5) employing continuous flow reaction system using a space velocity of 2 h−1 at 260 °C, and pressure of 46 bar for 30 h. The catalytic tests showed that the concomitant use of Ni and Cu proved to be more effective for the process of glycerol hydrogenolysis to 1,2-propanediol without the external H2 addition, since each metal plays a distinct role. The catalytic tests showed a significant increase in the yield to 1,2-propanediol with the addition of NaOH to the reaction medium; the highest conversion of glycerol (96.4%) and yield to 1,2-propanediol (31.8%) were obtained employing NaOH/glycerol molar ratio = 0.5 and Ni-Cu catalyst. No catalytic deactivation was observed for 30 h, showing that the catalysts exhibit good catalytic stability and good resistance to coke deposition.

Natural Aluminosilicate-based Y Zeolite for Catalytic Cracking of n-Hexadecane

Natural zeolite and kaolin are abundant in Indonesia especially in Java and Belitung islands. These materials generally contain high aluminosilicate minerals that can be used as silica and alumina sources for the formation of NaY zeolite. This research aimed to identify the modification of NaY zeolite structure using Bayat natural zeolite as alumina source and Belitung kaolin as silica source and its catalytic activity for n-hexadecane cracking. Pretreatment of materials were performed in several steps: activation, purification, fragmentation for Bayat–Klaten natural zeolite, and silica extraction for Belitung kaolin. The synthesis of NaY was performed hydrothermally using seed-assisted method with crystallization times of 24 and 48 h. The surface area analysis showed a typical surface area of microporous zeolite (i.e., a pore diameter of 1.897 nm) and surface area of 309.4 cm2/g. Meanwhile, powder X-ray diffraction characterization showed that the as-synthesized materials have the structure of NaY zeolite. The optimum crystallization time was 24 h with Si/Al ratio of 4.10. Furthermore, both synthetic and natural sourced NaY zeolites were converted into HY zeolites and employed as cracking catalyst of n-hexadecane in a fixed-bed reactor at 500 °C for 75 s. The natural sourced HY resulted in 59.80% conversion and 59.80% yield of gasoline product (C9–C12). These values were lower than the results given by synthetic HY (80%).

Facile synthesis of hierarchical structure of NaY zeolite using silica from cogon grass for acid blue 185 removal from water

Abstract Facile preparation of hierarchical structure NaY zeolite from cogon grass silica is synthesized by microwave-assisted hydrothermal method and subsequently desilicated in ultrasonic-assisted alkaline treatment. This work aims to improve the removal efficiency of acid blue-185 (AB-185) by using hierarchical NaY zeolite. When treated the parent NaY in NaOH solution with various concentrations (0.1, 0.5 and 1.0 M), the Si/Al ratios and micropore surface area decrease but increase a maximum pore size distribution of mesopore with the NaOH concentration due to the desilication effect. Moreover, the mesopore surface area and volume significantly increase and reach to the maximum value with a concentration of 0.5 M (132 m2 g−1 and 0.12 cm3 g−1). Consequently, the NaY (0.5 M) gives the highest percentage of AB-185 removal (80 ± 1.2 %) at a pH of 5 owing to the abundant adsorption sites and the eased accessibility of dye molecules. The adsorption data fit well with the Langmuir isotherm rather than Freundlich isotherm models with a correlation coefficient of 0.99. Maximum adsorption capacity of AB-185 on NaY (0.5 M) is larger than that on the parent NaY (84.5 mg/g vs 19.4 mg/g). In addition, the adsorption process of AB-185 on NaY (0.5 M) is more favorable by the pseudo-second-order kinetic model indicating the main rate-control is chemisorption. The existence of interactions between AB-185 and the NaY (0.5 M) is confirmed by FTIR and XPS. The reusability of the NaY (0.5 M) preserves original adsorption capacity, up to five cycles indicating a promising adsorbent for water treatment.

Exploiting the π-bonding for the separation of benzene and cyclohexane in zeolites

Separation of benzene and cyclohexane is one of the greatest challenges in industry. Their close boiling points and similar properties make them difficult compounds to separate. In this context, adsorption-based separation using zeolites or aluminosilicates is a promising technology. In the present work, we combine experimental measurements, density functional theory, and classical simulations to study the targeted separation. We analyse the effect of the sodium content in the adsorption of benzene and cyclohexane in three zeolites with FAU topology; high silica FAU, NaY and NaX. Quasi-equilibrated temperature adsorption and desorption measurements, first principles calculations, and classical simulations reveal the strong interaction between benzene molecules and sodium cations present in aluminosilicates and identify this fact as the key factor for the separation. We have developed a set of parameters to study the targeted separation by fitting to the experimental values and have run Monte Carlo simulations in the Grand-Canonical ensemble to obtain the adsorption isotherms and isobars. In addition, we have performed density functional theory calculations to analyse the specific interaction between benzene or cyclohexane and extra-framework sodium cations. Our results show that NaY and NaX zeolites are able to separate these compounds with extremely high efficiency.

Prepared hydrophobic Y zeolite for adsorbing toluene in humid environment

Abstract Decontamination of air or other gas streams loaded with low-concentration volatile organic compounds (VOCs) and high humidity is a prevalent task for adsorption using zeolites. Hydrophobic adsorbents were prepared with NaY zeolites as raw materials by the high-temperature hydrothermal treatment, and the degree of ion-exchange was considered as a key factor. Adsorbents were characterized by XRD, FTIR spectra, N2 adsorption-desorption isotherm, SEM, water contact angle, TG/DTG, and the adsorption capacities of water and toluene were evaluated by static adsorption test and dynamic adsorption breakthrough study. The results showed that high degree of ion-exchange was beneficial to dealumination from zeolite skeleton and crystal of zeolite remains intact in the high-temperature hydrothermal treatment. The framework silicon-aluminum ratio (SiO2/Al2O3) of modified zeolite obtained by high-temperature hydrothermal treatment reached 12.41 while the degree of ion-exchange was three (SY-3). Moreover, the hydrophobic index (HI) of SY-3 increased from 0.047 of initial NaY zeolite to 10.059. In addition, regeneration of SY-3 was easier than that of initial NaY zeolite. Our work also has further studied the mass transfer in the zeolite and mechanism of high-temperature hydrothermal treatment under the effect of different ion-exchange degree.

Immobilized ionic liquid on the zeolite: its characterization and catalytic activity in the synthesis of coumarins via Pechmann reaction

In this work, in the first step, the 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride ([MTMSPIm]Cl) is immobilized on HY and NaY zeolites as an acidic catalyst. The synthesized catalysts were well characterized by different methods such as FTIR, TGA, XRD, BET, SEM, EDX and ICP. The characterizations of catalysts indeed show the ionic liquid supported on amine-functionalized zeolites. Also, the result shows the micro-/mesoporous structure for catalysts which have been emerged as an important class of catalytic materials. The micro-/mesocatalyst ([MTMSPIm]Cl@zeolite) was used as an acidic catalyst to synthesize coumarins via Pechmann reaction in solvent-free condition. The effect of different factors such as catalyst amount, solvent and time was investigated. Finally, catalyst can be easily separated and reused for the next reactions at least for five runs without any significant changes in yield and structure of the catalyst. Comparison of modified zeolite with [MTMSPIm]Cl shows higher yield and selectivity and mild condition related to other works.