USY Zeolite Research Articles

Structural, textural and toluene adsorption properties of NH4HF2 and alkali modified USY zeolite

Abstract The non-framework aluminum is inevitably formed in the process of preparing the ultra-stable Y zeolite (USY), which severely blocks the mesopores of USY zeolite. It is necessary to treat the USY with the appropriate acid and/or alkali. In this paper, the USY zeolite is firstly dealuminated with NH4HF2 solution and then desiliconized with NaOH or NH4OH solution. The effect and mechanism of NH4HF2 and different alkali treatments on the structural and textural property of USY zeolite are elaborately demonstrated. It is found that the non-framework Al remaining in the mesopores of USY is significantly removed by the NH4HF2 solution. The desiliconization reaction is more likely to start near the mesoporous wall because the Al concentration in here is low and the repulsive force against OH− is weak. The OH− ions from NaOH solution not only etch the framework Si near the inner wall of the mesopores, but also remove the Si on the surface of NH4HF2-etched USY zeolite. However, the concentration of OH− ions is too low when NH4OH is used as the desiliconization agent, the OH− ions just react with silicon around the mesopores. Therefore, the NaOH/NH4HF2-etched USY contains both some micropores and macropores, and the NH4OH/NH4HF2-etched USY only possesses more mesopores with pore sizes of ～10 nm. In addition, NaOH/NH4HF2-etched USY exhibits excellent toluene adsorption performance at low pressure stage, while NH4OH/NH4HF2-etched USY has the highest adsorption capacity on toluene at high pressure stage.

Deep insight into CO adsorption on Ni-USY zeolite catalyst by FTIR spectroscopy. Evidence for isotopic isomerism

FTIR spectra of CO adsorbed on reduced Ni-containing USY zeolites with Si/Al = 30 besides weak H-bond with bridged hydroxyls and silanol groups and bonding to Ni2+ cations reveal formation of mono-, di- and tricarbonyls with Ni+ sites. The bands of adsorbed CO species are very narrow, with FWMH˜1–1.5 cm−1. The spectra of isotopically mixed nickel dicarbonyl species reveal the splitting, which shows that two CO molecules occupy non-equivalent positions, so that the species exist in two isomeric forms, despite the similarity of sites, following from the spectra of monocarbonyls. Possible explanations of this phenomenon are discussed.

Cover Feature: Thermochemistry of Surfactant‐Templating of USY Zeolite (Chem. Eur. J. 43/2019)

High temperature oxide melt solution calorimetry has been used to determine that the slight destabilization caused by the additional surface generated by the mesoporosity introduced in USY zeolite through surfactant-templating (ca. 2 kJ mol−1 SiO2) is significantly lower than the energetic stabilization resulting from surfactant–silica interactions (in the range of −6.0 to −12 kJ mol−1 SiO2), which drives the rearrangement of the zeolite structure to produce the new hierarchical architecture. More information can be found in the Communication by A. Navrotsky, J. García-Martínez, et al. on page 10045.

Thermochemistry of Surfactant-Templating of USY Zeolite.

With the aim of understanding the thermochemistry of the introduction of mesoporosity in zeolites by using surfactants, high temperature oxide melt solution calorimetry was used to determine the change in the enthalpy of formation of USY zeolite before and after the introduction of mesoporosity. Our results confirm that this process only slightly destabilizes the zeolite by the additional surface area. However, this can be overcome by the stabilizing effect of the interactions between the surfactant and the zeolite framework.

Isoprene Synthesis Using MIL-101(Cr) Encapsulated Silicotungstic Acid Catalyst

A single-stage synthesis of isoprene from methyl tert-butyl ether (MTBE) and formalin in an organic-aqueous two-phase system was studied by using solid acid catalysts, i.e., USY zeolite, silicotungstic acid (STA) 25 wt% encapsulated in MIL-101(Cr) (STA25@MIL-101), and STA 25 wt% encapsulated in SBA-15 (STA25@SBA-15). From preliminary experiments, the catalytic activity decreased in the order: STA25@MIL-101 > SBA25@SBA-15 > USY zeolite. This suggested that isoprene formation was favored with high surface area and high acid strength of catalyst. Then, the porous hybrid material of a MIL-101 metal organic framework and STA was studied in more detail. MIL-101 was not efficient for isoprene synthesis at mild reaction condition. On increasing STA loading, which was well correlated with the Brӧnsted acid property, the catalyst activity increased in the order: MIL-101 < STA30@MIL-101 < STA60@MIL-101. The high acidity catalyst gave high isoprene yield at optimum low temperature and low side reaction products. For the STA30@MIL-101 and STA60@MIL-101 catalysts, the isoprene yield could be sustained at 18.5% (0.4% SD) and 30.0% (1.5% SD), respectively over three recycling runs. It is apparent that no STA leaching from the low STA loading catalyst occurred.

Influence of desilication conditions on the shynthesis of herarchical zeolite Y

Hierarchical zeolites were synthesized by two methodologies, following desilication procedures of commercial zeolites. Starting from USY zeolite (Zeolyst CBV720,Si/Al=15), the effect of the amount of CTAB in the desilication media and the hydrothermal treatment time on the synthesized materials were analyzed.The results showed that the surfactant amount has a higher influence on relative crystallinity (%RC) and textural properties of the materials than synthesis time. All the samples showed a lower BET surface area compared with the starting zeolite, although mesopore surface area increased from 210.33 to 467.30 m2/g in the case of Z720-75sample. In the case of USY zeolite withSi/Al=2.6 (ZeolystCBV500),a previous dealumination with H4EDTA and anacid washingwith Na2H2EDTAsteps were included.It was found that the micropore and the mesopore surface areasincreased 13.96% and 11.23%, respectively, compared with the parent zeolite; furthermore, the %RC was 99% after treatmentprocedures.

A flexible Cu-based catalyst system for the transformation of fructose to furanyl ethers as potential bio-fuels

Biomass-derived furanyl ethers, such as 5-alkoxymethylfurfurals (AMFs) and 2,5-bis(alkoxymethyl)furans (BAMFs), can be employed as promising biofuels or additives. The development of multifunctional catalysts for the efficient production of furanyl ethers from sugars through 5-hydroxymethylfurfural (HMF) as an intermediate is highly desirable but challenging, because multiple reactions including dehydration, etherification and hydrogenation get involved and the side reaction of sugars and HMF to form humins is inevitable. In this contribution, we found that the introduction of CuO resulted in the generation of Lewis acid sites at the cost of Bronsted acid sites over CuO-USY catalysts through the formation of Al-O-Cu(II) species. The dispersity of CuO particles and the amount of Lewis acid sites could be manipulated by adjusting the loading of CuO. If 5 wt% CuO was supported on USY zeolite to give a CuO(5)-USY catalyst, CuO particles with a high dispersity (36.4%) afforded abundant Lewis acid sites (457.1 μmol/g). Lewis acid over CuO(5)-USY greatly promoted the acid-catalyzed dehydration of fructose to HMF and HMF etherification to AMFs, resulting in a HMF yield up to 86.2% from fructose and AMFs yields greater than 90% from HMF. Interestingly, a combination of CuO(5)-USY and a small amount of metallic Cu powder was able to offer desirable BAMFs yields by the reductive etherification of HMF under hydrogen atmosphere. As a result, 5-methoxymethylfurfural (MMF) of 79.6% and 2,5-bis(methoxymethyl)furan (BMMF) yield of 74.5% were achieved from fructose through HMF as an intermediate in the presence of CuO(5)-USY alone or with metallic Cu as a co-catalyst. Therefore, the above Cu-based catalyst system holds the promise to flexibly produce a family of AMFs or BAMFs from fructose via a facile two-step approach.

Hydroconversion of Waste Cooking Oil into Bio-Jet Fuel over NiMo/SBUY-MCM-41

A hierarchical SBUY-MCM-41 catalyst was prepared by sacrificing USY (a microporous molecular sieve) to synthesize the MCM-41 zeolite via a hydrothermal method. The hydroconversion of waste cooking oil into hydrocarbon fuel over a NiMo/SBUY-MCM-41 catalyst was investigated. The micropores of the Y building units were inherited by the SBUY-MCM-41 zeolite, in which a special hierarchical structure was formed and the accessibility of reactants to the micropore active sites was improved. The hierarchical SBUY-MCM-41 showed high acidity and hydrothermal stability. Compared with mesoporous Al-MCM-41 and microporous USY zeolites, the SBUY-MCM-41-supported NiMo catalyst significantly enhanced the selective cracking of waste cooking oil for the production of jet-fuel-range hydrocarbons (37.3%), with the highest selectivity for the formation of C10–C14 hydrocarbons and a satisfactory selectivity for the formation of jet-fuel-range aromatics (7.6%), as well as a few cyclic compounds. The improved selectivity is the result of the special hierarchical structure and acid distribution of SBUY-MCM-41. This work provides a new strategy to synthesize a hierarchical catalyst for producing alternative jet fuel from waste cooking oil and vegetable oils.

Glycerol conversion into biofuel additives by acetalization with pentanal over heteropolyacids immobilized on zeolites

Abstract Dodecamolydbophosphoric acid (HPMo) immobilized on USY zeolite was used as a catalyst for the acetalization of glycerol with pentanal at 70 °C. Catalysts were prepared with different amounts of heteropolyacid, and the most active sample was the HPMo2@Y catalyst (1.1 wt.%). The products of glycerol acetalization with pentanal were (2-butyl-1,3-dioxolan-4-yl)methanol, a five-member ring compound, and 2-butyl-1,3-dioxan-5-ol, a six-member ring compound. Good values of selectivity for the five-member ring compound (80–85%) were obtained with all materials. The reaction conditions were optimized using HPMo2@Y as a catalyst. The optimal conditions were determined to be 70 °C reaction temperature with 0.3 g catalyst and a 1:2.5 M ratio of glycerol to pentanal. The catalytic stability of HPMo2@Y was studied. The acetalization of glycerol with pentanal was performed using the same sample. High catalytic activity for HPMo2@Y was observed.

Time-Resolved Dynamics of Intracrystalline Mesoporosity Generation in USY Zeolite

The treatment of zeolites with surfactants in alkaline media is an effective and versatile technique to impart intracrystalline well-defined mesoporosity in these materials. In this study, the dynamics of surface reconstruction that occurs during the treatment of USY zeolite by surfactant-templating was monitored in situ by atomic force microscopy. The development of surfactant-templated mesoporosity and the concurrent healing of defects that are characteristic of steamed zeolites occur in less than 1 h at room temperature, which emphasizes the low energy barriers needed to reorganize the crystalline structure of this zeolite. This transformation was also followed by X-ray diffraction, N2 adsorption, and transmission electron microscopy analysis of ultramicrotomed samples to confirm that the rapid formation of surfactant-templated mesoporosity and the reconstruction of the zeolite crystals occur not only on the surface of the zeolite but also homogeneously throughout the whole zeolite. This process involv...

Ultra-deep hydrodesulfurization of cracked and atmospheric gasoil blend: Direct and interactive impacts of support composition, chelating agent, metal and promoter loadings

The effects of active phase and composite support compositions on activity of the HDS catalyst were investigated. Direct and interactive effects of USY/γ-Al2O3 support composition, total metal (Ni + Mo) loading, molar ratios of Ni/(Ni + Mo) and EDTA/Ni on activated catalysts sulfur content and hydrodesulfurization activity were investigated using response surface methodology (RSM). 27 catalysts with surface area, pore volume and BJH adsorption (desorption) average pore sizes in the range of 199 to 277 m2/g, 0.50 to 0.63 cm3/g and 88 (75) to 107 (90) Å were prepared. The concentration of sulfur remained in the hydrocarbon product, treated with different catalysts, was measured and results were in the range of 10 to 37 ppm. Based on the developed models, the most active catalyst was determined to be the one with composite support containing 10 wt% USY zeolite, loaded with 18 wt% metal oxides with Ni/(Ni + Mo) and EDTA/Ni molar ratios of 0.417, and 2, respectively. The lowest sulfur content of the hydrotreated gasoil blend was predicted to be 2.3 ppm, which was experimentally validated to be 3.1 ppm.

Degradation of Polypropylene and Polyethylene Wastes Over HZSM-5 and USY Zeolites

This work provides evidence that ultra-stable Y zeolite (USY) and HZSM-5 zeolites were active as catalysts for the pyrolysis of urban plastic wastes, decreasing its degradation temperature. When HZSM-5 was used as the catalyst, at 450 °C and 30 min, an increase in the solid fraction and a reduction in the liquid fraction were observed. On the other hand, the best catalytic cracking performance was observed for the reaction catalyzed by USY zeolite, and a higher amount of liquid fraction was obtained. Moreover, the increase of reaction time and temperature was favorable to obtain better results in thermal pyrolysis. As to the liquid fraction composition, its components were alkylbenzenes, olefins, and naphthalenes in the thermal pyrolysis whereas alkylbenzenes were the main component in the HZSM-5-catalysed pyrolysis and that catalyzed by USY provides higher amounts of olefins.

Vanadium contamination on the stability of zeolite USY and efficient passivation by La2O3 for cracking of residue oil

It is of great significance to identify the destructive role of high deposited vanadium on the USY-based cracking catalysts and find a facile approach to vanadium passivation for processing residue oil. Herein, the destruction degree of the steam-treated vanadium-contaminated USY zeolites, which also contained a certain amount of Na ions, was investigated by N2 physical adsorption, NH3-TPD, HRTEM, 27Al MAS NMR and catalytic cracking evaluation. The results reveal that high deposited vanadium causes severe damage to the structure of USY, resulting in a sharp deterioration in cracking performance. Furthermore, CeO2 and La2O3 were studied as vanadium passivating agents. The introduction of La2O3 using physical mixing could preserve the zeolite structure to a large extent without altering the properties of USY. The superior passivation performance might be mainly attributed to the fact that La2O3 introduced by simple physical mixing prefers to interact with vanadium species, rather than migrate into the channels and cavities of zeolites USY.

Influence of USY zeolite recrystallization on physicochemical properties and catalytic performance of NiMo/USY-Al2O3 hydrocracking catalysts

The effect of ultrastable zeolite Y recrystallization on the properties of NiMo/USY-Al2O3 hydrocracking catalyst has been studied. The mesoporosity, being introduced as the result of zeolite Y recrystallization, is mainly preserved at the subsequent steps of NiMo catalysts preparation. The total concentration of Brønsted acid sites in the catalysts varies proportionally to that for the corresponding zeolites used for preparation. It is observed that the higher the recrystallization degree the lower the concentration of strong Brønsted acid sites in the catalysts. UV–vis DRS, HRTEM and XPS data suggest that the state of supported Ni and Mo is similar for the catalysts prepared with parent and recrystallized zeolites. The catalysts based on recrystallized zeolites have significantly higher activity in hexadecane hydrocracking as compared to the catalyst obtained using parent zeolite. This effect is rationalized in terms of the improved accessibility of zeolite acid sites after recrystallization. Moreover, the mesoporosity introduced by zeolite Y recrystallization has a positive effect on the selectivity of NiMo/USY-Al2O3 hydrocracking catalyst.

Surfactant-templated zeolites for the production of active pharmaceutical intermediates.

A hierarchical USY zeolite has been produced using the surfactant-templating method and used as a catalyst for the production of two important active pharmaceutical ingredients. The presence of intracrystalline mesoporosity in the zeolite results in a significant increase in both the activity (up to 30 fold increase in TOF) and reusability for Friedel-Crafts alkylation and aldol condensation steps.

Improved Catalytic Technology for Waste Plastic Processing: Toward Novel Remediation and Emission Control Measures

A mesoporous zeolite USY to process waste plastic, illustrated on low-density polyethylene, is presented. The technology is mobile and can be used as a remediation and control measure to the emissions in the open environment. The core of this approach lays on the catalytic material employed. It is a zeolite USY that possesses both micropores (up to 2 nm) and mesopores (between 2 and 50 nm) that was prepared by desilication using a mixture of mesopore inducing agents, tetra-butyl ammonium hydroxide and sodium hydroxide. This gives rise to a well-defined zeolite USY with double intracrystalline mesoporosity and higher intrinsic acidity. Those improvements had a positive impact on the cracking of low-density polyethylene, with a lowering of the cracking temperature, ascribed to the enhanced mass transfer of the reactant into the acid sites. The lowering of the reaction temperature reduces the energy requirements with operational savings of 0.50 MW with respect to the thermal process and 80 kW with respect to the untreated zeolite for a plant of 50 kt per year, though the scale of operation can be adjusted to the local requirements. The lower operation temperature triggered by the catalyst has also benefits in terms of lower capital investment since low-cost construction materials would be required. The zeolite preparation is industrially scalable. All these features make the deployment of this technology a realistic option.

Efficient conversion of corn stover into 5-ethoxymethylfurfural catalyzed by zeolite USY in ethanol/THF medium

An efficient and green conversion process of producing 5-ethoxymethylfurfural (EMF) from corn stover was developed. The solid zeolite USY provided the good catalytic performance in ethanol medium with tetrahydrofuran (THF) as co-solvent, which can promote the formation of EMF, reducing the formation of ethyl levulinate and 5-hydroxymethylfurfural. The reaction conditions were optimized via response surface methodology leading to a maximum EMF yield of 21.8% in ethanol/THF (volume ratio 1:1) under the conditions of 168 °C, 1 wt% USY loading and 2.9 h. Meanwhile, USY can be reused in five consecutive reaction runs with high activity, upholding the same initial activity and structural integrity. A plausible reaction pathway for the conversion of corn stover to EMF in ethanol/THF medium was further proposed. This study showed that the improved catalytic system presents an efficient method for direct production of EMF from lignocellulosic biomass.

Mechanistic insights on catalytic conversion fructose to furfural on beta zeolite via selective carbon-carbon bond cleavage

The mechanism for the formation of furfural by dehydration of d-fructose via selective carbon-carbon (CC) bond cleavage was investigated over beta zeolite (Hβ). Several different pore size zeolites were employed to determine the shape selectivity of fructose isomers. Zeolitic pore sizes that smaller than the kinetic diameter of cyclic fructose also produced yield furfural (∼22.5%), while the high yield (66.0%) of hydroxymethylfurfural (HMF) can be achieved over large pore zeolite (USY zeolite), which could accommodate the cyclic fructose. These results indicated that the furfural formation likely began with acyclic fructose. In situ13C NMR and GCMS studies, using labeled 13C-1-fructose as substrate, suggested that the conversion of fructose to furfural involved with splitting of the C5-C6 bond. Furthermore, the C1 compound from the cleavage of CC bond was identified as formaldehyde, inferring that the selective scission of CC bond was ascribe to the retro-aldol reaction. Interestingly, in situ NMR studies implied that the acyclic fructose mainly derived from pyranose forms. In addition, compared with glucose, fructose directly converted to furfural at the higher yield and reaction rate.

Different binders in FCC catalyst preparation: impact on catalytic performance in VGO cracking

In the present study, four different binders including two synthesized alumina-silica sol and two commercially available binders comprising LUDOX AS-30 colloidal silica and LUDOX AS-40 colloidal silica have been applied for preparation of FCC catalyst. Other catalyst components were included such as USY zeolite, kaolin, alumina, ZSM-5 zeolite and cerium nitrate. Four catalysts have been synthesized through spray drying of aqueous slurries of the components. The influence of different binders on the cracking performance and product distribution of FCC catalysts as well as their morphology has been investigated. Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray powder diffraction, ammonia temperature-programmed desorption, inductive coupled plasma, Brunauer–Emmett–Teller and Barrett–Joyner–Halenda analysis have been operated to characterize the prepared catalysts. The reasonable spherical shaped particles of 40–50 μm size were obtained applying the synthesized alumina-silica sol and LUDOX-AS-40 colloidal silica as binder. The cracking activity of the prepared FCC catalysts was investigated in catalytic cracking of vacuum gas oil in a microactivity test unit and compared with the commercially available FCC catalyst. The results indicated that the synthesized catalysts have excellent activity with respect to the commercial one in terms of maximizing gasoline yields along with less alkanes production. The reusability of the catalysts was examined in four repeated cycles.

Study of the effects of regeneration of USY zeolite on the catalytic cracking of polyethylene

In this work, a study of the deactivation and reuse of USY zeolite for the pyrolysis of polyethylene has been carried out in a batch reactor at 500 °C. From the different tested zeolite/plastic ratios, 1/10 is the optimal ratio which allows giving rise to a liquid product free of wax. Regeneration was established by heating at 500 °C for 3 h coked zeolite in presence of air. The liquid yield begins to increase from the 11th cycle of regeneration until reaching a maximum at the 14th cycle showing a lost in the zeolite activity producing a viscous product.The liquid fraction derived from the first eight cycles was a mixture of C4-C27 compounds with a maximum C5-C7 fraction. In the 14th cycle of regeneration, compounds having higher carbon number were obtained and the yield of linear compounds increases up to 29%. To explain the relative activity of the regenerated zeolite, the textural properties and the XRD patterns results of the zeolite recovered after the 1st and 14th cycles have been compared with those obtained with fresh catalyst. The study showed that after 14 cycles of regeneration, the zeolite is still active but its activity level has decreased.