Mesoporous Zirconia Research Articles

Allylic and Benzylic Oxidation over CrIII‐Incorporated Mesoporous Zirconium Phosphate with 100 % Selectivity

Elite selection: The selective oxidation of allylic and benzylic compounds to the corresponding carbonyl compounds (enones), using H2O2 as oxidant and methanol as solvent over chromiumincorporated mesoporous zirconium phosphate, is evaluated.

Transition metals supported on mesoporous ZrO 2 for the catalytic control of indoor CO and PM emissions

Mesoporous ZrO 2 support has been prepared by using a low cost natural biopolymer chitosan as template, and different transition metals from the first row (Fe, Co, Ni, Cu and Mn) were impregnated on the synthesized support. The synthesized catalysts have been characterized by XRD, BET-SA, SEM, TEM, O 2-TPD and TG analysis to study the material details as well as to understand the catalytic mechanism. The activity of these catalysts has been investigated for CO and PM oxidation. Incorporation of transition metals improved the activity for both CO and PM oxidation. It has been observed that Co–ZrO 2 is the most active catalyst for studied reactions while, Ni based catalysts show the lowest activity for both the reactions. The transition metal supported catalysts follow the activity sequence Co–ZrO 2 > Mn–ZrO 2 > Cu–ZrO 2 > Fe–ZrO 2 > Ni–ZrO 2. The effect of CO 2, SO 2 and H 2O on CO oxidation activity was also investigated, and despite partial deactivation, the catalysts show good CO oxidation activity. The characterization of the materials by O 2-TPD studies explains the better catalytic performance for the Co–ZrO 2, Mn–ZrO 2 and Cu–ZrO 2 catalysts, as compared to Fe–ZrO 2 and Ni–ZrO 2. Such mesoporous zirconia with reasonably good surface area and without ordered structure could be useful for both CO and PM oxidation reactions.

The influence of preparation conditions on ZrO 2 nanoparticles with different PEG–PPG–PEG surfactants by statistical experimental design

In this study mesoporous Zirconia powder with high surface area was prepared by using PEG–PPG–PEG new block copolymer as the non-ionic surfactant. The preparation conditions were optimized by Taguchi method of experimental design and Minitab Software to synthesize high surface area tetragonal-ZrO 2 nanoparticles. The BET surface area of powders was 114–175 m 2/gr and the particles size calculated by Deby–Sherrer equation was 5–9 nm. pH = 11, aging time 38 h, Zr molarity 0.03, Surfactant/Zr mole ratio 0.04 and molecular weight 8400 were the best conditions to manufacture ZrO 2 with higher surface area. The sample prepared under optimized conditions was compared to that synthesized by PEG surfactant. XRD patterns of two ZrO 2 samples, hysteresis loop, pore size distribution, BET surface area and SEM results are similar.

Highly Efficient and Regioselective Halogenation over Well Dispersed Rhenium-Promoted Mesoporous Zirconia

Highly dispersed rhenium oxide supported on mesoporous zirconia (Re/m-ZrO2) catalysts were prepared by a simple impregnation method, and excellent catalytic performances were obtained in liquid phase halogenation of aromatic substrates by using hydrogen peroxide and ammonium halide under mild and near neutral conditions. The para-directed selectivity in cases of bromination of aromatic substrates resulted from the stereo effect of the substrates.

Exploring in Situ Functionalization Strategy in a Hard Template Process: Preparation of Sodium-Modified Mesoporous Tetragonal Zirconia with Superbasicity

An in situ functionalization strategy was developed in a hard template process to fabricate mesoporous solid superbases, and sodium-modified mesoporous zirconia (NaMZ) was successfully prepared. The obtained materials were characterized by various methods including XRD, TEM, N2 adsorption, IR spectroscopy, XRF, and CO2 TPD. The results show that the NaMZ materials exhibit well-defined mesostructure, tetragonal crystalline frameworks, and superbasicity with a high strength of 27.0. The NaOH solution plays a double role by removing the silica template SBA-15 and functioning as the guest. The sodium species is thus coated onto the mesoporous zirconia formed in situ. Hence, the fabrication and functionalization of mesoporous zirconia can be realized in one step, which avoids the possible structural damage of nonsiliceous mesoporous oxides in post-treatment. The stability of metastable tetragonal zirconia was found to be due to the confined space provided by the mesoporous silica template and the formation of Si–O–Zr linkages. It was also demonstrated that the NaMZ materials exhibited excellent basic catalytic performance. The turnover frequency (TOF) value on the material NaMZ-2 can reach 95.0 h–1 with 100% selectivity to the target product dimethyl carbonate, which is much higher than the value for the extensively used homogeneous catalyst CH3ONa (45.8 h–1).

Fabrication of Mesoporous ZrO<sub>2</sub> by Using Rosin-Based Quaternary Ammonium Salt

Mesoporous zirconias were prepared by precipitation method using rosin-based quaternary ammonium salt as a directing agent. The samples were characterized by means of XRD, FT-IR and N2-adsorption and desorption measurements. The phase of precursors was amorphous, and well crystallized tetragonal zirconias were obtained after the calcination at 450 °C. The synthesized mesoporous zirconias possessed high surface areas ranging from 183.56 to 203.87 m2g-1 and big pore diameters varying from 6.27 to 7.58 nm. The content of the rosin-based quaternary ammonium salt had significant influence on the textural properties of the mesoporous zirconias. Surface areas, pore volumes and pore diameters of the mesoporous zirconias decreased when increasing the surfactant dosage.

ChemInform Abstract: Mesoporous Solid Acid Catalysts

AbstractReview: 174 refs.

Adsorption of Carbon Dioxide on Mesoporous Zirconia: Microcalorimetric Measurements, Adsorption Isotherm Modeling, and Density Functional Theory Calculations

Mesoporous zirconia was prepared using the sol–gel process and the EISA method. It presents a specific surface area of 90 m2·g–1 and an interparticular porosity associated with a pore diameter of around 4–5 nm, and it crystallizes in the tetragonal symmetry. The determination of the CO2 adsorption properties (both the isotherm and adsorption enthalpies) coupled with isotherm modeling using a multi-Langmuir model and density functional theory (DFT) calculations on different representative clusters evidenced that the surface of zirconia is heterogeneous from an energetic point of view. It emerges from both the experimental and the theoretical results that (i) the adsorption sites associated with the lowest enthalpies of adsorption (between −24 and −34 kJ·mol–1) represent nearly 65–70% of the total number of the adsorption sites present on the zirconia surface. They correspond to the interactions (physisorption) between carbon dioxide and oxygen atoms or hydroxyl groups of the surface. (ii) The adsorption sites associated with higher enthalpies of adsorption (around −65 kJ·mol–1) correspond to the interactions between carbon dioxide and Zr atoms; they represent around 5% of the total amount of adsorption sites. (iii) The adsorption sites associated with high enthalpies of adsorption (below −70 kJ·mol–1) represent only a small fraction of the adsorption sites (around 10%) and correspond probably to the interaction of CO2 with structural surface defects or charged sites.

Effect of sol-age on the surface and optical properties of sol-gel derived mesoporous zirconia thin films

Mesoporous ZrO2 thin films have been deposited by a modified sol-gel dip coating technique using HCl as catalyst. Effects of sol-age on the surface and on the optical properties are studied. Transmission electron micrographs of the films reveal the pore dimensions in mesoporous regime. A strong correlation in surface topography with sol-age has been observed where increase in sol-age induces a systematic enhancement in the value of root mean square roughness of the films. Optical study shows that deposited films have high transmittance and an enhancement of 5.6 times in porosity in films prepared with sol-age of 10 days with respect to that of 1 day. Band gap estimation by Tauc's plots of films is observed to 5.74 eV, which shows invariance with the sol-age.

Synthesis, Characterization, and Biofuel Application of Mesoporous Zirconium Oxophosphates

Mesoporous zirconium oxophosphates have been synthesized through the evaporation-induced self-assembly (EISA) method in the presence of an amphiphilic block copolymer, pluronic F127 as template under strongly acidic conditions. The mesophases of the materials were analyzed by using small-angle powder X-ray diffractions and transmission electron microscopic (TEM) image analysis. N2 adsorption−desorption studies showed high surface area (260−312 m2 g−1) and narrow pore size distribution (4.5−5.5 nm) for the materials. NH3-TPD and pyridine-IR analyses suggested the presence of strong Lewis and Brönsted acid sites. These mesoporous materials showed excellent catalytic activity in biodiesel reaction for the effective conversion of the long chain fatty acids to their respective methyl esters. The maximum biodiesel yield was about 91% under optimal reaction conditions. High catalytic activity could be attributed to the large surface area and the presence of large number of acidic sites located at the surface of the materials. The catalysts showed negligible loss of activity after five repetitive cycles.

Mesoporous zirconia nanobelts: Preparation, characterization and applications in catalytical methane combustion

Mesoporous ZrO 2 nanobelts (MZNs) have been prepared by a calcination route of ZrS 3 nanobelts in air. The nanobelts prepared at 400–600 °C are the mixtures of tetragonal and monoclinic phases, and have well-distributed mesopores (pore diameter of about 3.4–3.6 nm). As the calcination temperature increased from 400 to 1200 °C, the structures changed from tetragonal to monoclinic phase, while the morphologies turned from regular nanobelts to bead-like nanowires, and the mesopores disappeared bit by bit. Fe-doped and Fe 2O 3-loaded MZNs have been prepared to compare the catalytic activities of Fe-doped, Fe 2O 3-loaded, and pure MZNs for methane combustion. The results showed that Fe 2O 3-loaded MZNs have rather high catalytic activity, suggesting its potential application in practice. Methane combustion data over the catalysts are well fitted by a first-order kinetic expression.

Surfactant assisted synthesis of high surface area ceria modified mesoporous tetragonal zirconia powder and its chromium adsorption study

Mesoporous zirconia modified by ceria has been synthesized through a surfactant-assisted route by using zirconyl oxychloride and ceric ammonium nitrate as precursors and dodecylamine as a template. The as-synthesized inorganic-template hybrid possesses high surface area (275 m 2 g −1) and large pore volume (0.52 cm 3 g −1). A template-free mesoporous zirconia–ceria with a decreased surface area of 80 m 2 g −1 and pore volume of 0.07 cm 3 g −1 was formed by heat treatment of the as-synthesized matrix at 500 °C for 2 h. The introduction of as small as 2 mol% ceria into the zirconia lattice has helped in stabilizing the technologically important tetragonal (t-) phase of zirconia up to 800 °C. The sample obtained even after calcination at 500 °C exhibits high adsorption capacities, ∼85% for chromium(VI) ions from aqueous solutions without any adjustment of pH, at room temperature, and within a period as short as 1 h. These present studies show that the mesoporous zirconia modified by ceria could be considered as a potential adsorbent for removing toxic Cr(VI) ions from aqueous solutions.

Microwave assisted synthesis of fine chemicals in solvent-free conditions over mesoporous zirconium phosphate

Synthesis of various industrially important fine chemicals under microwave irradiation (MWI) in solvent-free conditions over mesoporous zirconium phosphate (m-ZrP) is reported. m-ZrP is synthesized by MWI in basic medium using a precursor solution of zirconium carbonate complex as zirconium source and CTAB as a pore-directing agent. MWI time and MWI power were found to have significant influence on the textural properties of synthesized m-ZrP. Microscopic analyses of the synthesized m-ZrP indicate the presence of worm like pores with spherical morphology. DRIFT analysis of pyridine adsorbed m-ZrP and NH3-TPD measurements indicate the presence of appreciable amount of Brönsted acid sites. Synthesized m-ZrP exhibits high catalytic activity towards Claisen–Schmidt condensation reaction in solvent-free conditions under microwave irradiation. The m-ZrP showed high activity towards other acid catalyzed reactions such as Friedel–Craft benzylation, Pechmann condensation and carbonyl group protection reaction, and also for the synthesis of benzo-xanthenes in solvent-free conditions under MWI. The catalytic activity of m-ZrP is substantially higher than that of conventional layered ZrP. The synthesized catalysts are re-usable for at least five times after regeneration, without losing their catalytic activity significantly.

Facile Method for Synthesis of Polyamine-Functionalized Mesoporous Zirconia and Its Catalytic Evaluation toward Henry Reaction

Different amine-functionalized mesoporous zirconia were prepared by a co-condensation method using silane [aminopropyltrimethoxysilane (APTES), N-(2 amino ethyl)-3-amino propyl trimethoxy silane (AAPTMS), and 3-[2-(2-amino ethyl amino) ethyl amino] propyl trimethoxy silane (AEPTMS)] and zirconium butoxide. The materials were characterized by X-ray diffraction, BET surface area analysis, 13C magic angle spinning-nuclear magnetic resonance (NMR), Fourier transfer infrared spectroscopy (FTIR), scanning electron micrography (SEM), and thermogravimetric analysis (TGA)−differential thermal analysis (DTA). FTIR and NMR results revealed the successful grafting of organic amines onto the surface of zirconia. The catalytic activities were investigated for liquid phase Henry reaction of aromatic aldehydes with nitro methane.

Mesoporous zirconium phosphate: An efficient catalyst for the synthesis of coumarin derivatives through Pechmann condensation reaction

Mesoporous zirconium phosphate (m-ZrP) is used as a solid acid catalyst for the synthesis of coumarins via Pechmann condensation reaction and gave high catalytic activity for the condensation of phenols and ethyl acetoacetate in both conventional heating as well as microwave assisted method. The condensation reaction is studied in detail by varying the reaction parameters like effect of solvent, molar ratio of the reactants, temperature, and catalyst loading. Among the substituted phenols, m-amino phenol is more reactive and 100% yield is obtained in very short time at low temperature due to the presence of ring activating amine group in meta position. The m-ZrP is also active even for simple phenol and 57% yield of 4-methyl coumarin is obtained in conventional heating method. Microwave assisted synthetic method is found to be advantageous over conventional heating for the synthesis of coumarins, as it provides improved yield in very less time.

Synthesis and characterization of zirconia-grafted SBA-15 nanocomposites

The preparation of highly ordered mesoporous zirconia is of special interest when targeting applications in catalysis. Nevertheless, most of the previously reported attempts led to materials with a low hydrothermal stability. Herein, we accordingly report about the benefit of using mesoporous silica as a host support in which accessible zirconia crystallites are stabilized on the surface. The zirconia surface coverage could be tuned and optimized by playing on the most sensitive synthesis parameters, namely the quantity of zirconia, the calcination temperature and the pore diameter of the host support. The acid properties of the so-obtained materials were determined, showing a remarkable linear relationship between the amount of introduced zirconia and the number of acid sites, which evidenced a high accessibility of the acid sites in the nano-composite, due to a homogeneous dispersion of the zirconia phase in the pores of the silica host support.

A facile method for the synthesis of copper modified amine-functionalized mesoporous zirconia and its catalytic evaluation in C–S coupling reaction

A new copper modified amine functionalized zirconia has been synthesized by a co-condensation method using zirconium butoxide and aminopropyltriethoxy-silane (APTES) in the presence of a cationic surfactant CTAB followed by impregnation of copper. Nitrogen adsorption-desorption, X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), (13)C nuclear magnetic resonance (NMR), scanning electron micrography (SEM), transmittance electron micrography (TEM), thermo gravimetric analysis-differential thermal analysis (TGA-DTA), X-ray photoelectron spectroscopy (XPS) and UV-vis DRS spectroscopic tools are used to characterize the materials. FT-IR and DRS results indicated the incorporation of Cu and amino groups on the surface of zirconia. This Cu-anchored mesoporous material acts as an efficient, reusable catalyst in the aryl-sulfur coupling reaction between aryl iodide and thiophenol for the synthesis of value added diarylsulfides.

Gold catalysts supported on ceria-modified mesoporous zirconia for low-temperature water–gas shift reaction

New gold catalytic system prepared on ceria-modified mesoporous zirconia used as water–gas shift (WGS) catalyst is reported. Mesoporous zirconia was synthesized using surfactant templating method through a neutral [C13(EO)6-Zr(OC3H7)4] assembly pathway. Ceria modifying additive was deposited on mesoporous zirconia by deposition–precipitation method. Gold-based catalysts with different gold content (1–3 wt. %) were synthesized by deposition–precipitation of gold hydroxide on mixed metal oxide support. The supports and the catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N2 adsorption analysis and temperature programmed reduction. The catalytic behavior of the gold-based catalysts was evaluated in WGS reaction in a wide temperature range (140–300 °C) and at different space velocities and H2O/CO ratios. The influence of gold content and particle size on the catalytic performance was investigated. The WGS activity of the new Au/ceria-modified mesoporous zirconia catalysts was compared with that of gold catalysts supported on simple oxides CeO2 and mesoporous ZrO2, revealing significantly higher catalytic activity of Au/ceria-modified mesoporous zirconia. A high degree of synergistic interaction between ceria and mesoporous zirconia and a positive modification of structural and catalytic properties by ceria have been achieved. It is clearly revealed that the ceria-modified mesoporous zirconia is of much interest as potential support for gold-based catalyst. The Au/ceria-modified mesoporous zirconia catalytic system is found to be effective catalyst for WGS reaction.

Hybrid Inorganic−Organic Adsorbents Part 1: Synthesis and Characterization of Mesoporous Zirconium Titanate Frameworks Containing Coordinating Organic Functionalities

A series of functional hybrid inorganic-organic adsorbent materials have been prepared through postsynthetic grafting of mesoporous zirconium titanate xerogel powders using a range of synthesized and commercial mono-, bis-, and tris-phosphonic acids, many of which have never before been investigated for the preparation of hybrid phases. The hybrid materials have been characterized using thermogravimetric analysis, diffuse reflectance infrared (DRIFT) and 31P MAS NMR spectroscopic techniques and their adsorption properties studied using a 153Gd radiotracer. The highest level of surface functionalization (molecules/nm2) was observed for methylphosphonic acid (∼3 molecules/nm2). The level of functionalization decreased with an increase in the number of potential surface coordinating groups of the phosphonic acids. Spectral decomposition of the DRIFT and 31P MAS NMR spectra showed that each of the phosphonic acid molecules coordinated strongly to the metal oxide surface but that for the 1,1-bis-phosphonic acids and tris-phosphonic acids the coordination was highly variable resulting in a proportion of free or loosely coordinated phosphonic acid groups. Functionalization of a porous mixed metal oxide framework with the tris-methylenephosphonic acid (ATMP-ZrTi-0.33) resulted in a hybrid with the highest affinity for 153Gd3+ in nitric acid solutions across a wide range of acid concentrations. The ATMP-ZrTi-0.33 hybrid material extracted 153Gd3+ with a Kd value of 1×10(4) in 0.01 M HNO3 far exceeding that of the other hybrid phases. The unfunctionalized mesoporous mixed metal oxide had negligible affinity for Gd3+ (Kd<100) under identical experimental conditions. It has been shown that the presence of free or loosely coordinated phosphonic acid groups does not necessarily translate to affinity for 153Gd3+. The theoretical cation exchange capacity of the ATMP-ZrTi-0.33 hybrid phase for Gd3+ has been determined to be about 0.005 mmol/g in 0.01 M HNO3. This behavior and that of the other hybrid phases suggests that the surface-bound ATMP ligand functions as a chelating ligand toward 153Gd3+ under these acidic conditions.

Synthesis, characterization and electrochemical properties of mesoporous zirconia nanomaterials prepared by self-assembling sol–gel method with Tween 20 as a template

Zirconium dioxide nanomaterials, including nanoparticles and their derived films, were synthesized using a new surfactant self-assembling sol–gel route, which involves complexation of zirconium alkoxide precursor with acetylacetone as a chelating agent and Tween 20 as a structural directing agent. The properties of the synthesized material were studied using XRD, SEM, SAXS, HRTEM and N 2 adsorption and desorption analysis. It was found that Tween 20 can greatly increase the BET surface area and pore volume, inhibit crack formation in the derived film and retard particle growth at some extent. There exists tetragonal crystalline network with narrow pore size distribution in the ZrO 2 nano-materials prepared with Tween 20 in the sol. Furthermore, a mechanism on the formation of mesopore ZrO 2 structure via the Tween 20 self-assembling sol–gel process is presented. With the selection of the sono-gel carbon electrode modified by the mesoporous ZrO 2 film (M-ZrO 2 film) prepared with 1.10 g Tween 20/ml zirconia sol, enhanced electrochemical responses (i.e., enhanced peak currents) to catechol and ascorbic acid were confirmed using cyclic voltammetry (CV). Moreover, the modified electrode demonstrated additional improved electrochemical properties, such as good reversibility ( i pc/ i pa ≈ 1) and high selectivity (exceptionally resolved oxidation peaks between catechol and ascorbic acid), good stability and repeatability.