Zr OH Research Articles

What factors determine activity of UiO-66 in H2O2-based oxidation of thioethers? The role of basic sites

Zr-based metal–organic frameworks (Zr-MOFs) have attracted significant attention as selective oxidation catalysts due to their stability in aqueous and oxidative media and high activity in H2O2 activation. Oxidation of thioethers with aqueous H2O2 over Zr-MOFs reveals extremely high selectivity toward the formation of sulfones even at low conversions. Herein, the main factors determining activity of Zr-MOF in the thioether oxidation have been investigated using zirconium terephthalate UiO-66 as a model catalyst and methyl phenyl sulfide (MPS) as a model substrate. Samples of UiO-66 differing in the particle size, number of defects, and composition have been synthesized. The particle size was evaluated based on high resolution transmission electron microscopy images. Thermogravimetric analysis (TGA), proton nuclear magnetic resonance spectroscopy (1H NMR), and inductively coupled plasma atomic emission spectroscopy (ICP-OES) were employed for quantification of defects and determination of the composition of the UiO-66 samples. The number of basic sites was determined by liquid-phase adsorption of isobutyric acid. It was demonstrated that this characteristic depends on both the number of defects and specific composition of UiO-66 and can be affected by dehydration/hydration procedures. The number of basic sites turned out close to the number of terminal Zr–OH2/OH groups in the Zr-MOF defects determined by combinations of 1H NMR/TGA and 1H NMR/ICP-OES, suggesting that the basic sites are represented by Zr-OH groups at open Zr sites. Kinetic studies implicated that catalytic activity of UiO–66 in MPS oxidation is proportional to the number of basic sites provided that the particle size of the Zr-MOF does not exceed 10–20 nm. Acid additives suppress both the thioether oxidation and H2O2 dismutation, pointing to the key role of basic Zr–OH groups in these two catalytic reactions.

Structural evolution, synthesis mechanism and thermal conductivity of (La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 high-entropy ceramic prepared by concurrent chemical coprecipitation method

(La0.2Nd0.2Sm0.2Gd0.2Yb0.2)2Zr2O7 (Ln2Zr2O7) ceramic powders with nanoscale were synthesized by concurrent chemical coprecipitation method. The thermal behaviors and structural evolution of Ln2Zr2O7 precursor were investigated. The synthesis mechanism and thermal conductivity of Ln2Zr2O7 ceramic were also discussed in detail. Results show that a kind of complex polymeric compound containing -[Zr–OH–Zr]- and -[Zr–OH-Ln]- network structure was formed in the as-synthesized Ln2Zr2O7 precursor, which directly transformed to Ln2Zr2O7 crystals through dehydroxylation and structural ordering during the calcination process. The bulk Ln2Zr2O7 ceramics have a lower thermal conductivity of 1.20–1.47 W/(m·K), which can be attributed to the high-entropy effect resulting from the introduction of multiple rare earth elements.

The FTIR image comparison of zirconium sulfate synthesis products from the pathways of Na2ZrO3 and zirconium oxychloride compounds

PSTA BATAN has synthesized zirconium sulfate (ZS) through two methods. Synthesis pathway (I) from Na2ZrO3 (CDZ) and (II) through zirconium oxychloride (ZOC). This research aimed to compare both pathways by utilizing FTIR. Path (I) was done using concentrations of H2SO4 65%, contact time of 30, 60, 90, and 150 min, and temperatures of 125, 150, 175, and 225 °C. While path II has been carried out in previous studies [1]. The FTIR image comparison was finished by tracing sulfate derivative functional groups from a wavenumber of 4000–400 cm−1. The O–H stretching at 3441.01 cm−1 as the Zr(OH)Zr group and OH vibration in 3425.68 cm−1 were found at each pathway. However, at pathway (II), we observed another vibration at 3132.40 cm−1 as the NH3 compound group. Furthermore, the track records of S–O and SO stretching on both pathways were checked at 1635.64, 1095.57, and 956.69 cm−1, respectively, as H3O+, SO42−, and SO32− species. The real difference in pathway (I) was revealed by the presence of H2SO4 residue at 802.39 cm−1. At the same time, the Zr–O–Zr and O–Zr–O stretching could be detected in both pathways at the wavenumber of 594.09 and 470.63 cm−1 consecutively. The form of synthesis pathway (I) product was predicted as Zr(SO4)2, while the product of path (II) forecasted as Zr(NH3)(SO4)2 compound.

Solvent-dependent strategy to construct mesoporous Zr-based metal-organic frameworks for high-efficient adsorption of tetracycline

The accumulated antibiotics in the aquatic environment pose great threat to human and ecological health, boosting the development of porous materials for antibiotic removal. Mesoporous metal-organic frameworks (MOFs) have shown great promise in adsorption, which, however, usually need supramolecular design or cooperative template strategy for synthesis. Here we report the successful construction of mesoporous zirconium based metal-organic frameworks (Zr-MOFs) via a simple solvent-dependent strategy. Regulation of the ratio of water to N, N-dimethylacetamide during synthesis determined the porous structure of the synthesized MOFs. Systematic characterizations including SEM, FTIR, XRD and nitrogen sorption isotherm were carried out for structure analysis of the MOFs. With water fraction of 20% (v/v), the obtained Zr-MOF exhibited the highest adsorption capacity (Qmax of 337.0 mg⋅g−1) towards tetracycline (TC). The adsorption kinetics fitted the pseudo-second-order kinetics, and the adsorption isotherms fitted the Freundlich model well. Adsorption mechanism investigation revealed that the abundant Zr–OH groups stemming from coordination defects mainly accounted for TC adsorption. The hydrogen bonding interaction between TC and Zr-MOF and the generated mesopores contributed to the satisfactory adsorption capacity. This work is anticipated to provide insights on facile synthesis of mesoporous MOFs and application in environmental remediation.

The Aqueous Chemistry of Zirconium as a Basis for Better Understanding the Formation of Zirconium Conversion Coatings: Updated Thermodynamic Data

This work tackles the aqueous chemistry of Zr, aiming to contribute to a better understanding of Zr conversion coatings as one of the important contemporary means of corrosion protection. Equilibrium predominance diagrams based on experimentally confirmed Zr–OH and Zr–F aqueous species concerning Zr amorphous solid phase, along with an updated Zr E−pH (Pourbaix) diagram, are constructed. Since ZrO2+ existence had been conclusively disproven in both the aqueous and solid states, we chose to depict mononuclear species with ZrOH3+ and polynuclear with Zr4(OH)8 8+. The formation of the Zr solid phase is assumed to include Zr tetrameric species, Zr4(OH)8 8+, as a fundamental building block thereof. The role of F– and ZrF6 2– ions in Zr conversion baths and subsequently formed coatings is described. The introduction of ZrF6 2– anions keeps Zr solvated in the form of a complex, thus preventing the early onset of hydrolysis. The conversion of Zr species and the coating formation mechanism are further discussed from electrochemical and sol-gel perspectives, aiming to give a foundation for future predictions and rationalisation of Zr conversion coating formation, with the possibility of extensions to various bath additives.

Constructing solubility-diffusion domain in pebax by hybrid-phase MOFs for efficient separation of carbon dioxide and methane

A MIL-88B-on-UIO-66 (Abbreviation for UIO@MIL) hybrid-phase MOFs with rod-to-octahedral structure was obtained by the epitaxial growth method, and was added to Pebax matrix to develop a series of Pebax/UIO@MIL MMMs for CO2/CH4 separation. In UIO@MIL hybrid-phase MOF, CO2 solubility domain is formed in the core of UIO@MIL due to the abundant Zr–OH on the surface of UIO-66. MIL-88B has large pores and special rod-like structure that can entangled with the Pebax chain and adjust the spacing of the Pebax chain to form CO2 diffusion domains in MMMs. The results show that Pebax/UIO@MIL-4 membrane has the best CO2 separation performance, the CO2 permeability is 379.07 ± 10.00Barrer, and the CO2/CH4 selectivity is 38.1 ± 1.33. Therefore, hybrid-phase MOFs fillers provide a novel idea for the design of excellent MMMs.

Probing adsorption of water and DMF in UiO-66(Zr) using solid-state NMR

• 1 H and 13 C NMR study of the role of water and DMF in UiO-66. • Hydrogen bonds are probed by solid-state NMR. • Selective deuteration of the Zr–OH groups to remove the 1 H– 1 H dipolar interaction. • Selective deuteration of the aromatic hydrogen atoms to remove the 1 H– 1 H dipolar interaction.

Hydrogen dissociation sites on indium-based ZrO2-supported catalysts for hydrogenation of CO2 to methanol

The formation and nature of surface indium species in zirconia-supported catalysts for the hydrogenation of CO2 to methanol has been investigated by infrared (IR) spectroscopy. We studied the dissociation of hydrogen on In2O3/m-ZrO2, In2O3/t-ZrO2, In2O3/am-ZrO2 and m-ZrO2:In catalysts (m-, t- and am- refers to monoclinic, tetragonal and amorphous, respectively and m-ZrO2:In is a solid solution material), with and without a redox pretreatment. Indium hydride species and hydroxyl groups form at room temperature on the surface of all redox-treated catalysts upon their exposure to hydrogen. The activity and concentration of surface indium sites capable of heterolytic activation of H2 is the highest in In2O3/m-ZrO2(redox). The sites for the dissociation of hydrogen also exist, although in lower concentration, on the surface of calcined In2O3/m-ZrO2 and m-ZrO2:In catalysts (evacuated at 400 °C), i.e. the catalysts featuring the highest activity in the hydrogenation of CO2 to methanol. Noteworthy, the room temperature reaction between CO2 and InH species of redox-treated catalysts gave surface formate species, i.e. intermediates of the methanol synthesis pathway, only for In2O3/m-ZrO2(redox) and m-ZrO2:In(redox), highlighting more favourable reactivity of InH species and carbonates on the m-ZrO2 support. In situ X-ray absorption spectroscopy (XAS) at the In K-edge demonstrates the transformation of In2O3/m-ZrO2, during reduction in H2 at 400 °C, into highly dispersed In sites with an average oxidation state between In2+ and In0. Subsequent oxidation recovers the In3+ oxidation state (in the in situ XAS experiment) and forms a m-ZrO2:In solid solution. Thus, H2 dissociation in the most active m-ZrO2:In catalyst proceeds on In3+–O–Zr4+ sites dispersed in m-ZrO2, forming In–H and Zr–OH sites.

Manipulation of Lewis acid–base complexation in the Zr-centered quaternary system for monodisperse spherical zircons

Zircon (ZrSiO4) is a distinctive material widely investigated and applied for its superb physicochemical advantages. To date, great challenges remain in the synthesis of high-quality zircon powders for their stringent crystallization requirements at elevated temperature and inherent preferential growth along the [200] direction. Herein we, for the first time, present monodisperse spherical zircon (MSZ) powders synthesized via a facile one-step hydrothermolysis at 200 °C by rationally manipulating the Lewis acid–base complexation of zirconium with competitive ions (Lewis basic R ligands) in a Zr–OH–R–F quaternary system. Systematical investigations were revealed encircling the complexation of Zr4+ with the R ligands from various sources, which involve the adjusting acids (HR), Zr/Si reactants and halogen-containing mineralizers. Sufficient acidity from the adjusting acid and weak enough Zr–R affinity are confirmed as two paramount factors modulating the crystallization and growth of high-quality MSZ crystals, which undergo a unique metamorphic morphological transition from monolayered, to multilayered, to donut-shaped and ultimately to micrometer-sized spherical particles. The hydrothermal zircons are first confirmed as Zr-deficient (Zr/Si ratios <1.0) zirconium silicates as (ZrO4)1–xSi[(OH)1–y·Ry]4x, rather than the Si-deficient Zr(SiO4)1–x[(OH)·R]4x as initially proposed and hitherto generally accepted. The MSZ powders exhibit fair thermal stability and terrific monodispersity even after calcination at 1100 °C, superior photoreflectance and much lower thermal conductivity (0.18–0.48 W m−1 K−1) over non-spherical zircons. The novel MSZ powders provide arresting prospects to extend the applications of zircon in many traditional and emerging fields.

E. coli@UiO-67 composites as a recyclable adsorbent for bisphenol A removal

E. coli@UiO-67 composites were obtained using an effective and simple self-assembly method. The composites showed unique properties as a remarkable and recyclable adsorbent for the efficient removal of bisphenol A (BPA) from water with a high adsorption capacity (402.930 mg g−1). The increase in pore size is a key factor why E. coli@UiO-67 composites maintained high capacity. The reason might be due to that the composites with large pore sizes and defects could effectively improve mass transport and active molecular metal sites. The adsorption of BPA is a chemisorption process due to the Zr–OH groups in UiO-67 exhibit affinity toward BPA molecules, π–π interaction, and electrostatic attraction. The adsorption efficiency remained at 82.5% after 15 cycles without any remarkable changes in the PXRD patterns of E. coli@UiO-67. Moreover, the use of microorganism-loading MOFs could reduce the cost to at least 50% and minimize secondary pollution through nanoscale MOFs usage reduction. The developed composites have advantages, including low-cost, high adsorption capacity, easy to be separated and regenerated from aqueous solution, a large number of cycles, short adsorption equilibrium time, and stability, showing excellent application prospects. The presented strategy would be a potentially promising way to produce novel MOFs-based adsorbents with high-performance to control environmental pollution from wastewater.

The effective adsorption of tetracycline onto zirconia nanoparticles synthesized by novel microbial green technology

Pseudomonas aeruginosa bacteria have been used in this study for zirconia nanoparticles synthesis through green technology for adsorption driven bioremediation of tetracycline from wastewater. The characterization of synthesized nano zirconia has been performed by employing dynamic light scattering, field emission-transmission electron microscopy, energy dispersive X-ray, X-ray diffraction, fourier transform infrared spectroscopy, and point of zero charge analysis. The zirconia nanoparticles have shown average particle size ~15 nm, monoclinic and tetragonal crystal structure with 6.41 nm of crystallite size, the presence of elemental zirconium and oxygen, and the occurrence of functional groups like O–Zr–OH, Zr–O–Zr and Zr–O bonds. The zirconia nanoparticles mediated adsorption of tetracycline has been found to be effective at solution pH 6.0 and in a very less contact time 15 min. Strong electrostatic interaction between zwitterionic form of tetracycline and protonated surface of zirconia nanoparticles is the governing adsorption mechanism in this study. The kinetic study has been performed on the basis of the tetracycline adsorption process revealing that the adsorption phenomenon follows pseudo-second order kinetic, further suggesting chemisorption of tetracycline over zirconia nanoparticles. The Langmuir isotherm model has been found to be the best fitted model among the all isotherm models indicating the involvement of monolayer uptake of tetracycline on the surface of zirconia nanoparticles. Moreover, the maximum tetracycline adsorption capacity of zirconia nanoparticles calculated by the Langmuir isotherm model is close to 526.32 mg/g. This finding is quite reasonable to accept that zirconia nanoparticle may be used as an alternative adsorbent to mitigate the tetracycline contamination in wastewater.

Oxidative desulfurization catalyzed by a novel ZrP/MCM-41 catalyst with high performance

The excellent catalytic performance of the ZrP/MCM-41 catalyst in oxidative desulfurization was attributed to the Zr–OH sites.

Preparation, characterization and growth mechanism of ZrO2 nanosheets

High quality single-crystal zirconia nanosheets were successfully prepared via molten salt method, using solvothermally synthesized product as precursor. The effects of heat treatment temperature and soaking time on the phase composition and morphology of samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, Thermal analyzer, Raman spectrometer, Field-emission scanning electron microscope and Transmission electron microscope. The results show that zirconia nanosheets with a thickness of 60–80 nm and a width-thickness ratio up to 13 could be obtained by using NaCl and Na3PO4 as composite salts at 900 °C for 5 h. The precursors containing Zr–OH and Zr–O bonds have relatively high activity, which is beneficial to crystal growth. In addition, the as-prepared nanosheets with exposed (001) plane are monoclinic-structured and show no distinct defect. The growth behavior of particles during dissolution-recrystallization process is analogous to self-focusing mechanism. The preparation method can be extended to wet-chemical synthesis of other nanomaterials.

A Thermodynamic Model for ZrO2(am) Solubility at 25 °C in the Ca2+–Na+–H+–Cl−–OH−–H2O System: A Critical Review

Zirconium is an important element in the nuclear fuel cycle. Thermodynamic data and models to reliably predict Zr–OH system behavior in various conditions including high ionic strengths are required and currently are unavailable. Most available experimental data are rather old, obtained using inadequate methodologies, and provide equilibrium constant values that differ by many orders of magnitude. Previous reviews have recommended values based on available data. These reviews used all of the available data, including poor quality data, in a global fit to determine these values. This has resulted in recommended thermodynamic models with a large number of polynuclear species and a number of mononuclear species with values of thermodynamic constants for the solubility product of ZrO2(am) and Zr–OH hydrolysis constants that are many orders of magnitude different from those for the reliable analogous Hf reactions. In this critical review, we have evaluated the quality of the available data, selected only those data that are of high quality, and reinterpreted all of the high quality data using SIT and Pitzer models for applications to high ionic strength solutions. Herein for 25 °C we (1) present formation constant values for ZrOH3+, $$ {\text{Zr}}\left( {\text{OH}} \right)_{2}^{2 + } $$ , Zr(OH)4(aq), $$ {\text{Zr}}\left( {\text{OH}} \right)_{5}^{ - } $$ , and $$ {\text{Zr}}\left( {\text{OH}} \right)_{6}^{2 - } $$ , and the solubility product for ZrO2(am) which are consistent with the Hf system, (2) report a revised value for the formation constant of $$ {\text{Ca}}_{3} {\text{Zr}}\left( {\text{OH}} \right)_{6}^{4 + } $$ , (3) show that several hypothetical polynuclear species ( $$ {\text{Zr}}_{3} \left( {\text{OH}} \right)_{9}^{3 + } $$ , Zr4(OH) 15 + , and Zr4(OH)16(aq)) proposed in previous reviews are not needed, and (4) show that polynuclear species ( $$ {\text{Zr}}_{3} \left( {\text{OH}} \right)_{4}^{8 + } $$ and $$ {\text{Zr}}_{4} \left( {\text{OH}} \right)_{8}^{8 + } $$ ) are not important in a very extensive H+ concentration range (0.1–10−15.4 mol·kg−1). Our review has also resulted in SIT and Pitzer ion-interaction parameters applicable to as high ionic strength solutions as 5.6 mol·kg−1 in NaCl, 2.11 mol·kg−1 in CaCl2, and 23.5 mol·kg−1 in NaOH.

NMR Spectroscopy Reveals Adsorbate Binding Sites in the Metal–Organic Framework UiO-66(Zr)

We assign 1H and 13C NMR resonances emanating from acetone, methanol, and cyclohexane adsorbed inside the pores of UiO-66(Zr). These results are informed by density functional theory (DFT) calculations, which probe the role of two competing effects inside of the pore environment: (i) nucleus independent chemical shifts (NICSs) generated by ring currents in conjugated linkers and (ii) small molecule coordination to the metal-oxyhydroxy cluster. These interactions are found to perturb the chemical shift of in-pore adsorbate relative to ex-pore adsorbate (which resides in spaces between the MOF particles). Changes in self-solvation upon adsorption may also perturb the chemical shift. Our results indicate that cyclohexane preferentially adsorbs in the tetrahedral pores of UiO-66(Zr), while acetone and methanol adsorb at the Zr–OH moieties on the metal-oxyhydroxy clusters in a more complex fashion. This method may be used to probe molecular adsorption sites and material void saturation with selected adsorbates...

Synthesis, thermal behavior and physicochemical characterization of ZrO2/PEG inorganic/organic hybrid materials via sol–gel technique

Six zirconia–polyethylene glycol (ZrO2/PEG) inorganic/organic hybrid materials were synthesized by the sol–gel technique with different amount of polyethylene glycol (PEG) (corresponding to 6, 12, 24, 50, 60 and 70 mass%). Scanning electron microscopy and Fourier transform infrared spectroscopic (FT-IR) techniques were used in a recent study to characterize the materials with PEG content up to 50 mass%, while in the present one this characterization was extended to the more promising materials with higher PEG content (60 and 70 mass%). All the six materials confirmed their nanocomposite hybrid nature and the formation of hydrogen bonds between the inorganic zirconia matrix and the water-soluble organic component, which involve the Zr–OH groups and both the terminal OH groups and oxygen atoms in the ethereal units of the polymer chains. Moreover, the occurrence of interactions between PEG and acetylacetone, an inhibitor used during the sol–gel synthesis, was observed in the samples with high polymer content. The thermal behavior of all six hybrid materials was studied for the first time by thermogravimetry and differential thermal analysis from room temperature to 1023 K, aiming at identifying all physical and chemical processes occurring in these interesting materials, with particular reference to the decomposition of PEG to establish their thermal stabilities and the most suitable temperature condition for a further thermal treatment. The results revealed that PEG degradation occurs in the range temperature 473–873 K, and the degradation temperature decreases with increasing the PEG content. A probable explanation for PEG-rich materials is due to free PEG (not involved in the formation of H bonds) not affected by the stabilizing effect of the linkage with the inorganic matrix that causes a shift of degradation temperature toward lower values.

Effects of CO2 adsorption on proton migration on a hydrated ZrO2 surface: an ab initio molecular dynamics study

Hydration reactions on a carbonate-terminated cubic ZrO2(110) surface were analyzed using ab initio molecular dynamics (AIMD) simulations. After hydration reactions, carbonates were still present on the surface at 500 K. However, these carbonates are very weak conjugate bases and only act as steric hindrance in proton hopping processes between acidic chemisorbed H2O molecules (Zr-OH2) and monodentate hydroxyl groups (Zr-OH-). Similar to a carbonate-free hydrated surface, Zr-OH2, Zr-OH-, and polydentate hydroxyl groups ([double bond splayed left]OH+) were observed, while the ratio of acidic Zr-OH2 was significantly larger than that on the carbonate-free hydrated surface. A thermodynamic discussion and bond property analysis reveal that CO2 adsorption significantly decreases the basicity of surface oxide ions ([double bond splayed left]O), whereas the acidity of Zr-OH2 is not affected. As a result, protons released from [double bond splayed left]OH+ react with Zr-OH- to form Zr-OH2, leading to a deficiency of proton acceptor sites, which decreases the proton conductivity by the hopping mechanism.

Reaction Mechanism of Nerve-Agent Decomposition with Zr-Based Metal Organic Frameworks

We present a detailed study of the decomposition of Sarin on the Zr-based UiO-66 and MOF-808 metal organic frameworks (MOFs) using electronic structure calculations. The central step of the mechanism involves nucleophilic addition of OH to the nerve agent coordinated to a Zr atom of the MOF. This addition process generates a phosphorus pentacoordinated intermediate from which phosphonic acid products are formed through an elimination step, which also produces HF or isopropanol. Two major mechanisms have been probed. In the lowest-energy mechanism, a hydroxide ligand coordinated to a MOF Zr atom acts as the nucleophile in the addition step. In the second mechanism, which exhibits a slightly larger barrier, this Zr–OH group acts as a base to deprotonate a water molecule and generate a hydroxide moiety that concertedly adds to the nerve agent. In both mechanisms, the phosphonic acid products of the nerve-agent decomposition are strongly bound to the MOFs, suggesting that regeneration of the catalyst at the g...

Insight into Oxide-Bridged Heterobimetallic Al/Zr Olefin Polymerization Catalysts.

Reaction of (TBBP)AlMe⋅THF with [Cp*2 Zr(Me)OH] gave [(TBBP)Al(THF)-O-Zr(Me)Cp*2 ] (TBBP=3,3',5,5'-tetra-tBu-2,2'-biphenolato). Reaction of [DIPPnacnacAl(Me)-O-Zr(Me)Cp2 ] with [PhMe2 NH]+ [B(C6 F5 )4 ]- gave a cationic Al/Zr complex that could be structurally characterized as its THF adduct [(DIPPnacnac)Al(Me)-O-Zr(THF)Cp2 ]+ [B(C6 F5 )4 ]- (DIPPnacnac=HC[(Me)C=N(2,6-iPr2 -C6 H3 )]2 ). The first complex polymerizes ethene in the presence of an alkylaluminum scavenger but in the absence of methylalumoxane (MAO). The adduct cation is inactive under these conditions. Theoretical calculations show very high energy barriers (ΔG=40-47 kcal mol-1 ) for ethene insertion with a bridged AlOZr catalyst. This is due to an unfavorable six-membered-ring transition state, in which the methyl group bridges the metal and ethene with an obtuse metal-Me-C angle that prevents synchronized bond-breaking and making. A more-likely pathway is dissociation of the Al-O-Zr complex into an aluminate and the active polymerization catalyst [Cp*2 ZrMe]+ .

Effect of Introduction of B3+ OR Al3+ Ions in the Structure of Ti-, Sn-, AND Zr-Containing Heirarchical Zeolites on the Concentration of Lewis and Brønsted Acid Centers

It was established that Ti-, Sn-, and Zr-containing hierarchical zeolites of the BEA and MTW structural types contain two types of Lewis acid centers, the strength of which increases in the order Ti-MTW < Zr-MTW ≤ Sn-MTW, and also weak Bronsted acid centers formed by defect Sn—OH and Zr—OH terminal groups. The introduction of boron or aluminum ions into the structure of Ti-, Sn-, and Zr-silicate BEA and MTW zeolites leads to the appearance of additional Lewis and Bronsted acid centers.