Zirconium Species Research Articles

Investigation of metal-H2O systems at elevated temperatures: Part III. solubility data and new Zr Pourbaix diagrams at 298.15 K and 373.15 K.

Abstract The fuel bundles in coolant systems of CANDUTM reactors operate between 533 to 583 K (260 to 310°C). Given these extreme conditions and because of its neutronic properties, zirconium and Zircaloy-4 are used in these applications which require corrosion resistance at elevated temperatures. However, thermodynamic and hydrolysis properties of aqueous zirconium species have not been measured above standard conditions, making prediction using standard thermodynamic tools, such as the Pourbaix (E-pH) diagram difficult. This lack of information is addressed through solubility measurements and the development of elevated temperature Pourbaix diagrams for zirconium and Zircaloy-4. These Pourbaix diagrams of zirconium and a multi-element diagram (Sn, Zr, Cr) of Zircaloy-4 were developed at 373.15 K (100°C) and are presented in this work. Solubility measurements were made using a batch-style pressure vessel and concentration measurements were made using ICP-OES and ICP-MS, for zirconium and Zircaloy-4, respectively. For Zr(OH)6(2-); Zr(OH)4 (aq); Zr(OH)3+; and Zr(OH)2(2+) the Gibbs energy of formation (ΔG(°f,373.15 K)°) were found to be: -2177.4±8.5 kJ/mol, -1704.9±1.5 kJ/mol, -1808.8±8.9 kJ/mol, and -1095.1±2.7 kJ/mol, respectively.

Harnessing Zirconocene (III) for Photoinduced Carbon Radical Generation

Abstract With recent advances in photoredox chemistry, a variety of methods for generating carbon radicals have emerged. This review highlights recent approaches for radical generation utilizing zirconocene(III), a species infrequently employed in organic syntheses. Of particular interest are methods employing visible light irradiation, which induce C–Zr bond homolysis of alkyl zirconium species or activate a photoredox catalyst to reduce zirconocene(IV).

Enhancement Properties of Zr Modified Porous Clay Heterostructures for Adsorption of Basic-Blue 41 Dye: Equilibrium, Regeneration, and Single Batch Design Adsorber.

Zirconium porous clay heterostructures (Zr-PCH) were synthesized using intercalated clay minerals by zirconium species with different contents of zirconium. The presence of zirconium and silica species was confirmed by X-ray diffraction, X-ray fluorescence, and magic-angle spinning nuclear magnetic resonance. The insertion of zirconium improved the thermal stability, the specific surface area with a maximum of 950 m2/g, and the acidity concentration of 0.993 mol of protons per g of solid. These materials were used to adsorb the basic blue-41 from aqueous solution. The adsorption efficiency was examined at different conditions, with a maximum adsorbed amount of 346 mg/g as estimated from Langmuir model. This value was dependent on zirconium content in the PCHs. The adsorption process was found to be favorable and spontaneous. The efficiency of the spent materials was maintained after five reuse cycles with a decrease by 15% of the original value for a particular Zr-PCH material with a Zr content of 6.82%. Single stage batch adsorber was suggested using the mass balance equation and Langmuir isotherm model. The amount of PCH materials required depended on the target percentage of adsorption at specific volume and initial concentration of the basic-blue-41 dye solution.

Insights into the decomposition of zirconium acetylacetonate using synchrotron radiation: Routes to the formation of volatile Zr-intermediates

AbstractThe thermal decomposition of Zr(acac)4 is studied in a SiC-microreactor on the micro-second time scale. By utilizing synchrotron radiation and photoelectron photoion coincidence spectroscopy, six important zirconium intermediates, as for instance Zr(C5H7O2)2(C5H6O2), and Zr(C5H6O2)2, are identified in the gas phase for the first time. The adiabatic ionization thresholds of intermediately formed zirconium species are estimated and the main products of their thermal decomposition, acetylacetone, acetylallene and acetone are characterized unambiguously and isomer-selectively. Based on all detected intermediates, we deduce the predominant pyrolysis pathways of the precursor in the temperature range from 400 to 900 K. Our findings are complemented by numerical simulations of the flow field in the microreactor, which show that the choice of dilution gas significantly influences the temperature profile and residence times in the microreactor, such that helium provides a more uniform flow field than argon and should preferentially be used. Graphical abstract Using a soft ionization method coupled to velocity map imaging (VMI), leads to valuable insights in the thermal decomposition of Zr(C5H7O2)4, used in the synthesis of functional nanomaterials and ceramic coatings. Thanks to the use of a microreactor, important gas

Water- and reduction-free preparation of oxygen vacancy rich Cu-ZnO-ZrO2 catalysts for promoted methanol synthesis from CO2

Methanol synthesis via CO2 hydrogenation has been documented as a promising route for CO2 catalytic utilization and clean energy supply, yet conventional catalysts should be further improved to facilitate methanol generation. Herein, oxygen vacancy rich Cu-ZnO-ZrO2 catalysts were prepared via a facile solid-state method. As-obtained CZZ catalysts perform dramatically in CO2 hydrogenation reactions with high methanol selectivity up to 93.5% at 240 °C and 3.0 MPa. They consist of metallic copper, zinc oxide and amorphous zirconium species, and present considerable surface areas. Benefited from the facile preparation process, no wastewater is produced, and no reduction is required. The samples also contain high proportions of oxygen vacancies (up to 60.4%) compared with the conventional catalyst (only 47.6%). Accordingly, these oxygen vacancies benefit adsorption of CO2 and migration of intermediates, and therefore benefit the methanol formation and elevate the methanol selectivity. Remarkable catalytic properties are therefore achieved using these catalysts.

Ordered mesoporous zirconium silicates as a catalyst for biofuel precursors synthesis

Zirconium incorporated three-dimensional ordered mesoporous silica (FDU-5) catalysts with different Si/Zr (100, 50 and 25) ratios were synthesized using an Evaporation Induced Self Assembly (EISA) method to maximize the incorporation of zirconium sites in the silica framework. The physicochemical properties of the synthesized materials were characterized by several techniques such as XRD, N2 sorption, diffuse reflectance UV–Vis, TEM, ammonia TPD, ICP-OES and pyridine adsorbed FT-IR. The catalytic activity was evaluated in acid-catalyzed esterification of glycerol with acetic acid. The effects of different reaction parameters were studied to optimize the maximum yields, such as reaction temperature, catalyst loading, acid/alcohol molar ratio, and reaction time. Esterification of glycerol with levulinic acid and levulinic acid with ethanol was also performed to synthesize fuel precursors. Reaction results showed that the prepared Zr-FDU-5(25) material was a very high catalytic activity, which depended mostly on the zirconium species' availability on the surfaces and framework. This zirconium containing FDU-5 material was very active in the esterification reaction and selective product formation at certain reaction conditions. The selected catalyst was recycled five times without significant loss in its activity.

Visualizing Element Migration over Bifunctional Metal-Zeolite Catalysts and its Impact on Catalysis.

The catalytic performance of composite catalysts is not only affected by the physicochemical properties of each component, but also the proximity and interaction between them. Herein, we employ four representative oxides (In2 O3 , ZnO, Cr2 O3 , and ZrO2 ) to combine with H-ZSM-5 for the hydrogenation of CO2 to hydrocarbons directed by methanol intermediate and clarify the correlation between metal migration and the catalytic performance. The migration of metals to zeolite driven by the harsh reaction conditions can be visualized by electron microscopy, meanwhile, the change of zeolite acidity is also carefully characterized. The protonic sites of H-ZSM-5 are neutralized by mobile indium and zinc species via a solid ion-exchange mechanism, resulting in a drastic decrease of C2+ hydrocarbon products over In2 O3 /H-ZSM-5 and ZnO/H-ZSM-5. While, the thermomigration ability of chromium and zirconium species is not significant, endowing Cr2 O3 /H-ZSM-5 and ZrO2 /H-ZSM-5 catalysts with high selectivity of C2+ hydrocarbons.

Visualizing Element Migration over Bifunctional Metal‐Zeolite Catalysts and its Impact on Catalysis

AbstractThe catalytic performance of composite catalysts is not only affected by the physicochemical properties of each component, but also the proximity and interaction between them. Herein, we employ four representative oxides (In2O3, ZnO, Cr2O3, and ZrO2) to combine with H‐ZSM‐5 for the hydrogenation of CO2to hydrocarbons directed by methanol intermediate and clarify the correlation between metal migration and the catalytic performance. The migration of metals to zeolite driven by the harsh reaction conditions can be visualized by electron microscopy, meanwhile, the change of zeolite acidity is also carefully characterized. The protonic sites of H‐ZSM‐5 are neutralized by mobile indium and zinc species via a solid ion‐exchange mechanism, resulting in a drastic decrease of C2+hydrocarbon products over In2O3/H‐ZSM‐5 and ZnO/H‐ZSM‐5. While, the thermomigration ability of chromium and zirconium species is not significant, endowing Cr2O3/H‐ZSM‐5 and ZrO2/H‐ZSM‐5 catalysts with high selectivity of C2+hydrocarbons.

Al and Zr Porous Clay Heterostructures as Removal Agents of Basic Blue-41 Dye from an Artificially Polluted Solution: Regeneration Properties and Batch Design.

The removal of Basic Blue-41 dye molecules was carried out by using two doped porous clay heterostructures by aluminum (Al) or zirconium (Zr) species. The proposed method of synthesis showed its efficiency, starting from Al or Zr intercalated hydrolyzed species, prior to its reaction with dodecylamine (C12 amine) and tetraethyl orthosilicate (TEOS) as a silica source. The intercalated precursors and their porous clay heterostructures (PCH) derivatives were characterized by different techniques. Solid NMR technique proved the presence of Al species into the intercalated silica between the clay sheets, and in addition to Si in different environments within the PCH materials. The Zr-PCH material exhibited a higher surface area and pore volume compared to its Al-PCH counterpart, with a mesoporous character for both materials. A maximum removed amount of 279 and 332 mg/g was achieved and deduced from the Langmuir equation. The regeneration tests revealed that the removal efficiency of Zr-PCH was retained after five regeneration runs, with a loss of 15% of the original value; meanwhile, the Al-PCH lost 45% of its efficiency after only three cycles. A single-stage batch design was proposed based on the Langmuir isotherm parameters. The increase of the removal capacity of Zr-PCH led to the reduction of the required amounts for the target removal of BB-41 dye compared to Al-PCH.

In-situ construction and catalytic property of highly exposed Lewis acidity on hierarchical Zr-zeolite assisted by K+ cation

Herein, highly exposed Lewis acidity on hierarchical Zr-HSZ zeolite (Hollownest-Structured Zr-zeolite) have been firstly constructed by one-step rotating hydrothermal synthesis with the assistance of K+, which are characterized by various techniques. The addition of small amount of K+ ions (K/Si molar ratio of 0.07) into the synthetic reaction gel is found to be highly efficient for the crystallization of Zr-doping HSZ zeolite, in which K+ ions play important roles for the charge balance of reaction gel, promoting the formation of Zr-O-Si bonds and accelerating the crystallization process consequently. Thus-prepared materials own distinct weak acid property and contain purely Lewis acid sites, which are proven by ammonia-TPD and pyridine-FT-IR. Two types of zirconium species are detected by UV–vis and XPS characterizations, one of which is the isolated >Zr=Ospecies (Zr4+open) in high dispersion on the surface of zeolite, the other is the tetrahedral species in the zeolite framework (Zr4+closed). The unique hollownest morphology of HSZ material with hierarchically porous structure constructed by intergrown MWW nanosheet crystals has no hindrance on the mass transfer and diffusion of substrate molecules, and provides enough reaction spaces for reactant molecules. Also, the high dispersion of Zr4+open species on the surface of HSZ material has endowed it with highly exposed Lewis acid sites, beneficial to the acid-catalyzed transformation. As expected, Zr-HSZ-K catalyst shows highly catalytic performance for the acid-catalyzed Prins condensation to nopol from β-pinene and paraformaldehyde, which achieved high conversion (93.2%) and selectivity (96.0%) with TON of 163.6, and exhibited highly recyclable stability. This work has highlighted one-step rota-construction of metal-doping HSZ zeolite with highly exposed catalytic active sites for the catalytic conversion of bulky organic molecules.

Illuminating anti-hydrozirconation: controlled geometric isomerization of an organometallic species.

A general strategy to enable the formal anti-hydrozirconation of arylacetylenes is reported that merges cis-hydrometallation using the Schwartz Reagent (Cp2ZrHCl) with a subsequent light-mediated geometric isomerization at λ = 400 nm. Mechanistic delineation of the contra-thermodynamic isomerization step indicates that a minor reaction product functions as an efficient in situ generated photocatalyst. Coupling of the E-vinyl zirconium species with an alkyne unit generates a conjugated diene: this has been leveraged as a selective energy transfer catalyst to enable E → Z isomerization of an organometallic species. Through an Umpolung metal–halogen exchange process (Cl, Br, I), synthetically useful vinyl halides can be generated (up to Z : E = 90 : 10). This enabling platform provides a strategy to access nucleophilic and electrophilic alkene fragments in both geometric forms from simple arylacetylenes.

Extraction of Zirconium From Iraqi Bauxite Ore

This research is devoted to the study of the extraction of zirconium from Iraqi Bauxite Ore by using hydrometallurgical method. The chemical analysis was done to the bauxite ore by using X-ray florescence, X-ray diffraction and atomic absorption spectroscopy. Zirconium Extraction was performed via three stages; the first stage is leaching of bauxite with sodium hydroxide for alumina leaching. The second stage is leaching of zirconium species from the remained powder produced from stage one after washing with deionized water and, nitric acid (HNO3 solutions). The results of the first stage has reflected the recovery of 42.27 % of Al2O3 which has been leached 100°C temperature, 7.5 molar of NaOH, liquid to solid ratio of 20/1, and stirring rate 450 rpm. The highest leaching percent of zirconium (Zr%) from the red mud approached 98.48 % at 100°C temperature, 7 molar acid concentration, 120 min. contact time, solid to liquid ratio (S/L) of 16/1, and stirring rate of 450 rpm. 99.47% recovery of zirconium was accomplished from nitric acid solutions by use of 3molar tri-n-butylephosphate (TBP)in kerosene at ,contact time for 6 min, and organic to aqueous phase (O/A) of 4/1.

Facile and reversible digestion and regeneration of zirconium-based metal-organic frameworks

The digestion/regeneration of metal-organic frameworks (MOFs) has important applications for catalysis, drug delivery, environmental decontamination, and energy storage, among other applications. However, research in this direction is limited and very challenging. Here, we develop a facile method to digest and regenerate a series of zirconium-based metal-organic frameworks (Zr-MOFs) by bicarbonate or carbonate salts. As an example, UiO-66 demonstrates well the mechanism of reversible digestion/regeneration processes. By analyzing the digested zirconium species via X-ray diffraction, Fourier transform infrared spectroscopy and Raman scattering spectroscopy, a digestion mechanism based on the formation of dissoluble complexes [Zr2(OH)2(CO3)4]2− is proposed. Impressively, ultrafine Pd nanoparticles can be extracted from Pd@PCN-224 via this strategy. This work, thus, may provide new insight for the development of renewable MOFs and their practical applications.

Physicochemical surface-structure studies of highly active zirconocene polymerisation catalysts on solid polymethylaluminoxane activating supports

Static 91Zr ssNMR, SEM-EDX, and DRIFT spectroscopy indicate that a common zirconium species, [CpR2ZrMe]+, is present in all sMAO supported catalyst systems.

Sulfated Zirconia with Different Crystal Phases for the Production of Ethyl Levulinate and 5‐Hydroxymethylfurfural

Distinct crystal phases of an oxide affect the configuration of surface atoms, which might further affect coordination with sulfate during sulfonation for the preparation of SO42−/MxOy type of acid catalyst. Herein, such an effect is investigated with zirconia of the tetragonal or monoclinic phase as the model catalysts. The results show that sulfonation inhibits the transformation of zirconia from the tetragonal phase to the monoclinic phase, whereas the varied phase of zirconia also affects the bonding patterns of sulfate species with zirconia in sulfonation. The sulfated zirconia of monoclinic phase contains more abundant acidic sites and more Brønsted acid sites than that of sulfated zirconia of tetragonal phase. Consequently, the sulfated zirconia of monoclinic phase is more active than the sulfated zirconia of tetragonal phase for the conversion of furfuryl alcohol in ethanol and conversion of fructose in dimethyl sulfoxide, achieving the yield of ethyl levulinate of 96.4% and a high yield of 5‐hydroxymethylfurfural. The sulfated zirconia is not stable in protic solvent due to the leaching of sulfur species and the change in configurations of the sulfate species and the zirconium species, but in the aprotic solvent, they show good stability and recyclability.

In situ synthesis of B4C–SiC, B4C–TiB2, and B4C–ZrB2 composites from organic–inorganic hybrid precursor via a simple bottom-up approach

Boron carbide (B4C) and its in situ composites were synthesized via a simple bottom-up process using low-cost boric acid and a sucrose-based precursor solution with silicon (Si), titanium (Ti), or zirconium (Zr) species. The precursor solution was first dried at 250 °C and then heat-treated at 1650 °C for 90 min under argon and hydrogen gas flow. Free boron oxide phases appeared in the boric acid-rich precursor compositions, whereas free carbon appeared in the sucrose-rich compositions. The B4C particles exhibited a coarser and elongated morphology with boron-rich stoichiometric compositions (B/C:4/1), whereas the particles had a finer equiaxed morphology in carbon-rich compositions (B/C:2/1). As the carbon concentration increased in the precursor solution, the hexagonal lattice parameters of B4C and its corresponding lattice volume decreased. On the other hand, the addition of Si, Ti, or Zr species into the precursor solution resulted in the formation of a silicon carbide (SiC), a titanium diboride (TiB2), or a zirconium diboride (ZrB2) phase along with the B4C phase and was associated with an overall reduction in the average particle size and a more uniform size distribution. Moreover, the addition of these species increased the B4C lattice parameter with a corresponding increase in the lattice volume; this was most likely due to an elemental substitution into the B4C lattice. In addition, the data provide evidence that the formation of an ideal B4C lattice is possible when synthesized from carbon-rich precursors using this method, despite the potential presence of free carbon.

Stirring-ageing technique to develop zirconium-pillared bentonite clay along with its surface profiling using various spectroscopic techniques

The pillared clays are getting wide attention due to the easiness in tailoring their surface for customized applications. In our laboratory, we have adopted a novel synthetic route to pillar zirconium species within intercalation spaces of bentonite clay through stirring-ageing technique and prepared the zirconium-pillared bentonite clay (ZPBC). A series of experiments conducted to optimize the stirring-ageing time span revealed that 2–4 h span is sufficient for getting a good yield of ZPBC. The synthesized ZPBC was characterized using certain well-developed sophisticated techniques to obtain their physical, structural and morphological properties. The high surface area 109 m2 g−1 noticed for ZPBC is suitable in retaining the chemical moieties of special interest during pollutant removal processes. X-ray fluorescence studies revealed that there is an increase in wt% of Zr (4.76%) in pillared clay compared to Na-bentonite which indicates that Zr has been successfully loaded on the surface of parent clay during pillarization. The mineralogical composition and the gradual changes in the interlayer spacing of parent and pillared clay are well established using X-ray diffraction technique. The Raman spectrum identifies changes in the lattice vibration modes of ZPBC as pillaring takes place. The surface topographical changes that occurred in clay after modification were revealed from the scanning electron microscopy images. The prepared ZPBC were tested successfully for the removal of phosphate from aqueous solution and obtained a maximum adsorption capacity 58.83 mg g−1 at 30 °C.

Tuning the Performance of Conversion Coatings with Various Additives

Traditionally, conversion coatings based on metal phosphates and chromium based species were extensively used in industrial coating processes to provide anti-corrosion properties to metal substrates (e.g. AA6111, steel). Due to increasing environmental constraints, new solutions based on titanium and zirconium species are currently being commercialized around the world. The growth of conversion coatings on metal alloys exhibits oxidation reactions at the alloy surface (e.g. M → Mn+ + ne‒). These electrons are consumed in the reduction of solution species (e.g. H+ + e‒ → ½ H2) leading to gaseous evolution and deposition of solid species at the alloy surface. At this step, a higher pH in the vicinity of alloy surface causes decomposition of the passivating ion, which in turn leads to initiation and growth of the coating layer. Interfacial properties, such as adhesion and anti-corrosion behavior, are dependent on the chemical bonding, thermodynamic stability, uniformity, and continuity of this coating layer along the metal surface. This presentation will show our recent studies on the effect of various additives in the conversion coating solutions using electrochemical tools, thermodynamic stability measurements, and electron microscopic analysis.

Selective oxidation of H2S over Fe supported on Zr-intercalated Laponite clay mesoporous composite catalysts at low temperature

A series of iron supported on Zr-intercalated clay composite catalysts with mesoporous structure, a high specific surface area, and high thermal stability were successfully synthesized (named Fe/Zr-Lap catalysts) and tested for H2S selective oxidation. The structural characteristics and physicochemical properties of the catalysts were investigated using various methods. The iron species existed mainly as isolated Fe3+ and polymeric (FeO)n species in an octahedral coordination. All of the Fe/Zr-Lap catalysts exhibited excellent catalytic activity at relatively low temperatures (120–200 °C). The 8% Fe/Zr-Lap catalyst presented the best catalytic performance at 180 °C. It is likely that highly dispersed iron species, abundant chemically adsorbed oxygen vacancies, synergistic effect of iron and zirconium species, and improved reducibility played important roles in the reaction. Besides, the reaction and deactivation mechanisms were also proposed.

Facile fabrication of fluorine free zirconium zinc stearate based superhydrophobic and superoleophilic coating on cotton fabric with superior antibacterial property

A simple solution technique has been adopted to fabricate in situ generated zirconium zinc stearate based superhydrophobic and superoleophilic fluorine-free coating on cotton fabric with superior antibacterial and excellent photocatalytic properties. The materials properties of the specimen such as crystallinity/crystal phase, chemical bonding, surface morphology, and surface roughness have been characterized systematically. The coated cotton derived from an optimized precursor composition shows the retention of superhydrophobicity with static water contact angle ~163° after several cycles of machine laundering and mechanical abrasion. It is seen that zirconium species may have caused an enhancement in laundering durability and mechanical robustness while hierarchical morphology of zinc stearate is responsible for acquiring superior antibacterial property along with self cleaning ability of the coating to make the coated fabric promising for real life application such as military uniform, biomedical clothing/devices. In addition, the coated cotton is found to be suitable for separation of oil from oil-water mixtures with high efficiency (~99%) even after 10 cycles of repeated use. Thus, the material can be used for separation of oil from oil-contaminated industrial wastewater/marine water. Moreover, AgBr modified superhydrophobic cotton fabric shows excellent photocatalytic activity towards degradation of organic dye. This facile process can be up-scaled for commercial use.