HY Zeolite Research Articles

Catalytic benzylation of arenes using metal-ion modified HY zeolites for sustainable synthesis

Microporous zeolites are commonly employed as catalysts for the benzylation of arenes and benzyl alcohol. However, their catalytic efficiency is often compromised by diffusion limitations, particularly in reactions involving larger arenes. In this study, we developed metal-ion modified HY zeolites using Zn, Mg, and Ni as dopants and investigated their catalytic performance in the benzylation of a range of arenes, including toluene, benzene, mesitylene, p-xylene and with benzyl alcohol (BzOH). The structural and acidic properties of the modified HY zeolites were characterized using a combination of techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, Fourier-transform infrared (FTIR) spectroscopy, ammonia temperature-programmed desorption (NH₃-TPD), and proton magic angle spinning nuclear magnetic resonance (1H MAS NMR) spectroscopy. The presence of catalytically active Brønsted acid sites (BAS) was detected by 1H MAS NMR spectroscopy and it was demonstrated that the HY zeolite's acidity is considerably modulated by the addition of metal ions. The catalytic evaluations indicated that the metal-ion modified HY zeolites exhibited superior activity compared to unmodified HY zeolite, with the catalytic performance following the order Zn/HY > Ni/HY > Mg/HY > HY for the benzylation of benzyl alcohol with mesitylene. Further investigation into the mechanism revealed that the synergistic effect of metal ions and acidity plays a crucial role in enhancing the accessibility of arenes to the surface catalytic sites and thereby improving catalytic performance. These findings underscore the importance of the metal-acidity synergy in optimizing the catalytic efficacy of modified HY zeolites for selective benzylation reactions.

Enhancement of ethylene selectivity in chemical looping oxidative dehydrogenation of ethane using manganese-based redox catalysts supported on HY zeolite

As the crucial role of zeolite catalysts becomes increasingly prominent in refining and petrochemical industries, this study introduces a novel application of xMn / HY catalysts in ethane catalytic dehydrogenation via Chemical Looping Oxidative Dehydrogenation (CL-ODH). The synergistic effect of manganese oxides on the HY framework and a moderate amount of acidic sites within the catalyst facilitates the cleavage of C-H bonds and the desorption of olefins, which are vital for advancing ethane CL-ODH. We identified the reasons for maintaining high ethylene selectivity using advanced characterization techniques such as XRD, SEM, TEM, BET, H2-TPR, NH3-TPD, and Py-IR. Notably, under optimized conditions at 700 °C with a gas time-space velocity (GHSV) of 1800 mL·h−1·g−1, the 3Mn/HY catalyst achieved approximately 97.1 % selectivity for ethylene and a 22.7 % conversion of ethane. These findings present a scalable route for ethylene production, showcasing significant industrial relevance by potentially reducing energy costs and improving yield.

Catalytic conversion of biomass pyrolysis volatiles over composite catalysts of activated carbon and HY zeolite

Bio-oil has complex compositions and high oxygen content, which restricts its high-value utilization. Commercial activated carbon (AC) and HY zeolite were used as composite catalysts to study their effect on pyrolysis volatiles from rice straw and poplar sawdust by changing the mixing modes of two catalysts. The results showed that the loading modes of AC and HY zeolite obviously affected the products distribution and bio-oil components. The lowest yield of bio-oil was obtained when HY zeolite and AC were mechanically mixed at a mass ratio of 1:1 (YACM). But the loading mode of YACM was beneficial to the deoxidation and aromatic hydrocarbon generation. Under the mode of YACM, the aromatics content in rice straw and poplar sawdust bio-oil can be increased from 13.8% and 8.0% without catalyst to 56.4% and 53.1%, respectively. However, the layered loading with upper HY zeolite and lower AC (YTACL) was favorable for formation of phenolic compounds. The selectivity to monocyclic and bicyclic aromatic hydrocarbons followed the order of YTACL > ACTYL > YACM, and YACM > ACTYL > YTACL, respectively. Compared with HY zeolite, AC catalyst possessed smaller pore size and fewer acidity, and the active sites of AC were conducive to rearrangement of furan compounds to generate cyclopentanone, 2-cyclopentenone and methyl-cyclopentenone, and further rearrangement to form phenol. Therefore, the loading mode of YTACL exhibited a promotion effect on the formation of phenol, cresol, toluene, ethylbenzene and p-xylene. The strong acidic sites of HY zeolite were favorable for the aromatization, so the loading mode of ACTYL had good selectivity to the formation of naphthalene, methylnaphthalene, anthracene and pyrene. This work will provide a guide for products regulation from biomass pyrolysis and enrich aromatics and phenols in bio-oil.

Promoting metal oxides–zeolite electron interaction on MnCeOx/HY catalyst for boosting nitrogen oxides reduction

The MnOx-CeO2 metal oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx due to its excellent low temperature performance. However, their strong oxidative ability can lead to NH3 over-oxidation, narrowing the active temperature range and reducing N2 selectivity. Moreover, their weak surface acidity hampers medium to high-temperature activity and alkali metal resistance. Hence, in this study, MnCeOx metal oxides were coupled with HY zeolite to create MnCeOx/HY, demonstrating excellent NH3-SCR performance. The high dispersion of metal oxides on the zeolite surface and their close integration promoted strong electron interaction, effectively reducing oxygen vacancies and surface adsorbed oxygen concentrations. Consequently, the oxidative ability of active metal oxides was appropriately weakened, suppressing undesirable side reactions. MnCeOx/HY also notably suppressed NO adsorption and nitrate formation, promoting the catalytic reaction solely through the E-R mechanism and enhancing N2 selectivity. The abundant strong acid sites on the zeolite surface facilitates NH3 adsorption at moderate to high temperatures, notably expanding the active temperature window. Furthermore, the acid sites of HY zeolite serve as sacrificial sites, preferentially reacting with alkali metals, thus exhibiting excellent resistance to alkali metal poisoning on MnCeOx/HY. Combining with the DFT results, the structure-activity relationships in this study also reveal the importance of the effective synergy between acid sites and redox sites for optimal catalytic performance, offering valuable insights into the development of highly active and alkali-resistant denitrification catalysts.

Effect of pyrolysis operating conditions on the catalytic co‐pyrolysis of low‐density polyethylene and polyethylene terephthalate with zeolite catalysts

AbstractIn this study, the catalytic (co‐)pyrolysis of low‐density polyethylene (LDPE) and polyethylene terephthalate (PET) with HZSM‐5 and HY zeolite catalysts was conducted in a micro‐pyrolysis reactor coupled to a two‐dimensional gas chromatography system. Pyrolysis operating conditions, such as the pyrolysis temperature, the catalyst to feedstock (CF) ratio, and the LDPE:PET ratio, were varied. It was found that for the co‐pyrolysis of LDPE and PET, HZSM‐5 led to higher yields of C2‐C4 olefins and monoaromatic products. Lower CF ratios increased the yield of C2‐C4 olefins for LDPE pyrolysis, but decreased benzene yield for PET pyrolysis, concomitant with an increased yield in benzoic acid. A lower temperature of 400°C which was sufficient for the pyrolysis of LDPE, led to incomplete conversion of PET. Surface response diagrams were used to visualize the impact of the various pyrolysis operating conditions on the yield of C2‐C4 olefins and BTEX, which serve as target products for the circular economy.

Improvement of the Oxidative Desulfurization Performance Using MoO3/CuO‐Modified Hierarchical HY Zeolite

AbstractThe presence of sulfur compounds in the chemical industry poses significant environmental and economic problems, including endangering human and animal lives and damaging equipment. For this purpose, hierarchical HY zeolite (Hie‐Y) with a SiO2/Al2O3 molar ratio 10 was successfully synthesized through sequential desilication‐dealumination using NH4OH treatment. A weak alkaline media with surfactant cetyltrimethylammonium bromide (CTAB) facilitates mesoporosity formation and preserves the zeolite structure. Metal oxide (CuO, MoO3) ‐ hierarchical HY zeolite nanocomposites have been prepared by one or a combination of 3 methods: 1) ion exchange, 2) precipitation, and 3) calcination. The obtained catalysts were characterized using XRD, FT‐IR, FESEM, UV‐Vis, EDS, and BET techniques. The formation of a hierarchical structure is associated with structure preservation, but partial destruction occurs based on the entering Cu in the zeolite pores. These catalysts have been studied in the oxidative desulfurization (ODS) reaction. Several parameters, including temperature, catalyst amount, DBT concentration, and reaction time, were evaluated in ODS using the Taguchi Design of Experiments. Catalytic activity order was obtained as Y<Hie‐Y<Hie‐Y/CuO<Hie‐Y/MoO3<Hie‐Y/MoO3/CuO. Results indicate an activity increase for the Hie‐Y/MoO3/CuO hierarchical structure owing to synergistic effects of secondary mesoporosity and metal oxides. The catalyst was recoverable and reused for five consecutive runs with preservation of catalytic activity.

Mono Lacunary Phosphotungstate Loaded Zeolite HY For the Esterification of Levulinic and Succinic Acid Into Fuel Additives

Mono Lacunary Phosphotungstate Loaded Zeolite HY For the Esterification of Levulinic and Succinic Acid Into Fuel Additives

Disproportionation and Transalkylation of Phenol and Dimethylphenol on Zeolite Catalysts

AbstractSubstantial amounts of phenolic compounds are present in medium‐low temperature coal tar (MLCT), of which dimethylphenol (DMP) is not as valuable to be utilized as the more abundant cresol due to its complex composition and difficulty in isolation. In this study, the disproportionation and transalkylation reactions of MLCT‐related model compound, i.e., 2,6‐DMP, in phenol over zeolite catalysts are investigated using a fixed‐bed reactor for sustainable new option to utilize MLCT‐derived phenolic mixtures. Reactivity is promoted at high temperatures and associated with zeolite acidity and pore structure. Since disproportionation and transalkylation reactions have certain spatial requirements, the micropores of MFI‐type zeolite may cause spatial barriers that make it difficult to carry out the reactions. MCM‐22, characterized by MWW‐type zeolite, maximized the conversion of 2,6‐DMP due to its strong Bronsted acidity and large mesopore volume. FAU‐type zeolite HY with a 3D large 12‐ring through‐channel shows relatively small spatial confinement and certain molecular sieving ability, which enables bimolecular reactions while allowing cresols to flow out of the pores efficiently to obtain the highest cresol selectivity. The addition of phenol significantly inhibits the spontaneous disproportionation of 2,6‐DMP to tricresol. Besides, o‐cresol dominate the cresol products, suggesting that the selectivity of o‐cresol is kinetically controlled.

Mechanistic Understanding of Anthracene Hydrocracking over HY Zeolite Encapsulated Single-Atom Pt Catalysts

Mechanistic Understanding of Anthracene Hydrocracking over HY Zeolite Encapsulated Single-Atom Pt Catalysts

Revealing the two distinctive roles of HY zeolite in enhancing the activity and durability of manganese oxide-zeolite hybrid catalysts for low-temperature NH3-SCR

Recently, metal oxide-zeolite hybrid systems have shown promise in enhancing catalytic performance in low-temperature selective catalytic reduction (SCR), but not much is known as to mechanistic details. The purpose of this study is to examine fluctuations in low-temperature activity contingent upon the presence or absence of zeolite and to elucidate a dual functional mechanism of mixed zeolite in improving the catalytic performance of MnOx, which is closely related to inter-particle diffusion of nitrite and nitrate species from MnOx to zeolite. Firstly, strong Brønsted acid sites on zeolite demonstrate a significantly faster reduction of diffused nitrite species compared to Brønsted/Lewis acid sites on MnOx. More importantly, we discovered that zeolite prevents ammonium nitrate deposition by absorbing and decomposing diffused nitrate species from MnOx. Such distinct interaction between zeolite and both nitrite and nitrate species clarified here will be of great promise in designing future hybrid catalytic materials for low-temperature NH3-SCR reactions.

Hierarchical fluoride-containing zeolite Y supported Ru for catalytic conversion of xylose to xylitol

Hierarchical fluoride-containing zeolite HY (Hie-HY(F)) is an interesting material because it tunes both a high mesoporosity and a moderate acid property, which could benefit the transformation of xylose to xylitol. Herein, we synthesized a new Hie-HY(F) by etching NH4Y with ammonium fluoride (NH4F) under ultrasonication at 60 °C for 20, 40, and 60 min. After etching with NH4F solution, the Hie-HY(F)s contained fluoride in the zeolite frameworks with high mesoporosity and moderate acid properties. The sonication time longer than 20 min caused the structure to collapse rather than the creation of mesoporosity. The Hie-HY(F)s were further used as supports for the Ru catalyst. When loaded with Ru precursor and calcined in air, RuO2 phase was formed in all catalysts. The RuO2 supported on Hie-HY(F)s had a lower reduction temperature than that on HY. Ru supported on Hie-HY(F)-20 gave the reactivity of xylose conversion to xylitol, the highest yield of 80.1 %, providing the reusability up to four cycles.

Microstructure, adsorption site energetics, and formation enthalpy control for FAU-Zeolite Cs+ exchange

Cs-137 is a radionuclide fission product that poses a significant risk to life, making it crucial to develop effective methods for its separation and sequestration from nuclear waste streams. Zeolitic structures have emerged as promising materials. This work examines the influence of structure, exchange site energetics, and formation enthalpies of nascent and cation-exchanged Faujasite-X, -Y, and -HY zeolites in terms of their Cs-exchange selectivity. Their interplay was quantified with the application of high-temperature calorimetry, adsorption isotherms, X-ray diffraction and density functional theory (DFT) calculations. Greater efficacy of Cs+ exchange was demonstrated for the Na+-substituted Fau-Y (NaY) zeolite than that of the Fau-X (NaX) and Fau-HY (Na-HY) zeolites. This is explained by a higher amount of Na+ in un-exchangeable sites in the case of NaX and a lower stability in NaY that favors the ionic exchange with Cs+. Moreover, Cs+ incorporation in the structure increases the stability of each kind of zeolite. Correspondingly, structure and DFT analyses demonstrated site-exchange thermodynamic favorability as well as the contribution from cage cell, which resulted in an energy landscape far more conducive to Cs+ incorporation for NaY than either NaX or Na-HY.

The synthesis for adamantane derivatives of high energy density fuel catalyzed by HY zeolite based on the DFT

The adamantane derivatives are promising high-energy-density fuel due to preferable fuel properties, the activity of HY zeolite is key for synthesis adamantane derivatives on account of easy separation from liquid fuels. The effect of acid strength and type of zeolite on activity from DMTCD to 2c,2t-dimethyladamantane is investigated by the DFT method. The activity on HAlY zeolite with stronger Brønsted acid strength is superior compared to HGaY, HFeY, HInY and HBY. Thus, AlO+/HAlY zeolite is investigated obtaining that smaller gap between LUMO and HOMO leads to the better activity than HAlY. And oxoaluminum cations as Lewis acid improves Brønsted acid strength, in which the activity of AlO+/HAlY with stronger Brønsted/weaker Lewis acid strength is preferable than other HAlY with Lewis acid. Therefore, this work provides guidance for screening of HY zeolite with preferable activity of hydro-isomerization.

In-situ approach to porous nitrogen-doped carbon nanosheets functionalized by Brønsted acidic ionic liquids for microwave-assisted upgrading fructose to 5-hydroxymethylfurfural

In the search for robust and recoverable supported Brønsted acidic ionic liquids (BAILs) catalysts for efficient upgrading bio-sugars to value-added chemicals, an in-situ strategy of supramolecular preorganization-thermal polycondensation is designed to fabricate porous ultrathin nitrogen-doped carbon nanosheets (NCNSs), and then BAILs-functionalized NCNSs catalysts are prepared via successive quaternary ammonization by sultones and anion exchange with Brønsted acids. By adjusting the molar composition of the starting monomers, the textural properties of NCNSs supports are tuned; and by functionalization with different sultones (1,3-propanesultone and 1,4-butanesultone) and organic (trifluoromethanesulfonic acid and p-toluenesulfonic acid) or inorganic (H2SO4 and H3PO4) acids, the surface hydrophobicity and Brønsted acid strength of the catalysts are regulated. The catalysts are applied in microwave-assisted upgrading fructose to 5-hydroxymethylfurfural, and influences of Brønsted acid nature, surface hydrophobicity and textural properties on the catalytic performance are explored. For the most active [C4SO3HN][OTf]-NCNSs-MA-3 catalyst with the advantages of superstrong Brønsted acidity, higher surface hydrophobicity and perfect porous ultrathin sheet-like nanostructure, the conversion of fructose and the yield of 5-hydroxymethylfurfural of 100% and 87.7% are achieved after microwave irradiation for 15 min, outperforming Amberlyst-15 resin and HY zeolite. The catalysts also demonstrate the robust catalytic reusability, and after five consecutive catalytic runs, the obvious activity loss hardly occurs, along with little acid sites leaching.

Engineered Ru on HY zeolite catalyst for continuous and selective hydrodeoxygenation of lignin phenolics to cycloalkanes under moderate conditions

We report a continuous selective hydrodeoxygenation (HDO) process of guaiacol conversion to cycloalkanes under 180 °C/1 MPa, which results in improved HDO chemistry for lignin-based jet fuel production. The incipient wetness impregnation method was modified to prepare an HY zeolite-supported Ru catalyst with better metal dispersion and acid site uniformity, which overcomes the low conversion and selectivity of previous literature. The modified catalyst (Ru-HY-60-MI) was tested in a continuous fixed bed reactor, resulting in increased HDO conversion of guaiacol to cycloalkanes compared to the unmodified catalyst. Pressure, temperature, and weight hourly space velocity-dependent tests validate guaiacol HDO over Ru-HY-60-MI catalyzed ring hydrogenation of guaiacol to 2-methoxycyclohexanol, acid-catalyzed demethoxylation and dehydration to cyclohexene, and further hydrogenation of cyclohexene to cyclohexane. These experiments enable exploring a continuous HDO process, demonstrate effectiveness for other β-β and α-O-4 lignin representatives and real lignin bio-oil, and pave the way towards commercialization of lignin-based jet fuel.

Impact of Metal Impregnation of Commercial Zeolites in the Catalytic Pyrolysis of Real Mixture of Post-Consumer Plastic Waste

This work reports the study of the catalytic pyrolysis of rejected plastic fractions collected from municipal solid waste whose mechanical recovery is not plausible due to technical or poor conservation issues. The chemical recycling using catalytic pyrolysis was carried out over commercial zeolites formulas, i.e., HY and HZSM-5, in which Ni or Co metals were deposited at two different loadings (1 and 5%, wt.). The presence of these transition metals on the zeolitic supports impacted the total production of compounds existing in the liquid oil. The samples were characterized in terms of structural, chemical, and morphologic properties, and the production of different fuel fractions (gasoline, light cycle oil, and heavy cycle oil) was correlated with a combined parameter defined as a ratio of Acidity/BET area.

Catalytic fractionation of Palm Kernel shell with Co and Cu over zeolite HY catalysts

Lignocellulosic biomass has the potential to be transformed valuable chemicals. This study extracted lignin from palm kernel shell with liquid phased oxidative fractionation in the presence of Co and Cu loaded over Zeolite HY catalysts. The oxidative fractionation was conducted at temperatures ranging from 140 °C to 180 °C, with various reaction times of 2–4 h. The GCMS analysis identified various products from the oxidative conversion including phenol derivatives (Butylated hydroxytoluene, 1,2-Benzenediol, etc.), phenolic aldehydes (Vanillin, Syringaldehyde, p-hydroxybenzaldehyde, etc.), and carboxylic acids (p-hydroxybenzoic acid, vanillic acid etc.). At a reaction temperature of 180 °C with a 2 h reaction time, Co/Zeolite HY catalyst yielded 9.81% and Cu/Zeolite HY catalyst yielded 13.53% for phenol derivatives. The optimal yield of lignin-derived compounds was achieved with a 5 wt% catalyst loading in the context of biomass weight, particularly with a 10% metal loading of Co and Cu over Zeolite HY support. Additionally, the total yield of lignin-derived compounds obtained was 32.85% for 10%Co/Zeolite HY and 23.89% for 10%Cu/Zeolite HY, catalysts respectively. This research displays incorporating metals into zeolite support subsequently boosts their catalytic efficiency in lignin oxidation.

Low Palladium‐Loading HY Zeolite Catalyzed Hydrolysis of Hydrosilanes to Silanols and Alkoxysilanes

AbstractA low palladium‐loading heterogeneous catalyst has been developed for the hydrolysis of hydrosilanes to silanols and alkoxysilanes under mild and neutral reaction conditions with broad substrate scope. After five recycling runs, this low palladium‐loading catalyst keeps good activity for this transformation.

A Temperature Perturbation Infrared Spectroscopy Comparison of HY and NaY Zeolite Dehydration/Rehydration

Temperature step infrared spectroscopy is used to monitor vibrations associated with water molecules and zeolite framework during thermal dehydration and rehydration of HY and NaY. Temperature-dependent HY and NaY infrared spectrum intensity and wavenumber trends for O-H stretching vibrations, H-O-H bending vibrations, and zeolite framework vibrations are compared. Changes in hydroxyl stretching and water bending vibration bands confirm that HY has a stronger hydrogen bonding network. The intensity of a band at 3700 cm−1 in NaY spectra varies with temperature and can be correlated with Na+ migration and zeolite water content. Spectral subtractions reveal complex intensity variations in the framework vibration band wavenumber region. Spectrum differences indicate the presence of at least four overlapping contributions in this wavenumber region. The intensities and wavenumbers of these constituents vary with temperature differently for HY and NaY. For both zeolites, infrared spectrum changes detected during thermal dehydration were mostly reversed when water re-adsorbed to the sample after cooling.

Investigation on the adsorption of cationic dyes and heavy metal ions on zeolite HY from aqueous solution

Every living creature on the earth needs access to clean water. Water is being contaminated by humans in numerous ways. Heavy metals and textile dyes are two of the major contaminants in wastewater. Dyes and heavy metals are harmful to human health and have negative effects on the environment as well. Zeolites are excellent adsorbent materials for various types of pollutants including organic and inorganic such as dyes, heavy metals, ammonium ions, etc. In this study, we have presented the synthesis, characterizations, and application of zeolite HY for the extraction of cationic dyes and heavy metal ions. Zeolite Y was synthesized by hydrothermal approach and converted to its H-form. Different characterization techniques such as Fourier Transform Infra-Red (FTIR), Field-Emissions Scanning Electron Microscope (FE-SEM), and X-ray diffraction (XRD) were utilized for the characterization of zeolite HY. The synthesized material zeolite HY (ZHY) was then employed for the adsorption of two cationic dyes i.e., MB and CV, heavy metal ions i.e., cadmium (Cd+2) and chromium (Cr+6) and ammonium (NH4+) ions from its aqueous solution. The adsorption data showed 97.2 % removal of MB 49 % removal of CV, 0 % removal of both Cd+2 and Cr+6 heavy metal ions and 5 % removal of NH4+ ions.