ZrO2 Surface Research Articles

Improved activity and coking-resistance of Fe2O3/ZrO2 catalysts by hydrothermal synthesis in propane dehydrogenation with CO2: Experimental, DFT calculations, and deactivation modeling

In this work, two ZrO2-supported Fe2O3 catalysts were synthesized through the impregnation (Fe2O3/t-ZrO2) and the hydrothermal (Fe2O3/c-ZrO2) methods. The hydrothermal preparation improved the catalyst activity and propylene yield; propane conversion: 45.8 % vs. 31.2 %, propylene yield: 31.1 % vs. 23.2 %. This higher activity was attributed to the high specific surface area and thereby higher Fe dispersion that led to more formation of active Fe3 + sites. According to results, the t-ZrO2 surfaces were known to be more favorable for coke reaction compared to c-ZrO2. Adsorption energy of propane and propylene onto the most stable surfaces of ZrO2 was measured as a criterion for side reactions and coke deposits by DFT calculations. The results showed that propane and propylene are more adsorbed onto t-ZrO2 than onto c-ZrO2, which indicates more cracking of propane and propylene onto t-ZrO2. Finally, the experimental data were successfully fitted with the Deactivation Model with Residual Activity (DMRA). It was found that the Fe2O3/c-ZrO2 catalyst has a higher resistance against the deactivation by coke deposits compared to the Fe2O3/t-ZrO2 catalyst; activation energy of deactivation function: 83.64 vs. 70.09 kJ/mole.

CO induces the reduction of Mo in the glass liquid to molybdenum carbide to form glass defects in the hybrid furnace

In this work, a ceramic platinum continuous melting optical glass furnace containing oxygen combustion was taken as an example to analyze the causes of a unique glass defect. It was finally determined that the defect in the glass was composed of the top condensate, the brick skeleton, and the Mo2C generated in the glass liquid. It was determined that the monoclinic Al2O3 and ZrO2 phase in the brick desorbed the surface hydroxyl and water molecules under the high temperature environment inside the furnace, forming Lewis acid sites with the ability to adsorb electrons. CO was adsorbed on the surface of Al2O3 and ZrO2 by Lewis acid sites and fell into the glass liquid with the top condensate and the brick skeleton.CO then reduced Mo ions in the glass melt to form Mo2C, causing the formation of the defects in the glass.

Neutrophils Respond Selectively to Physical Cues: Roughness Modulates Its Granule Release, and NETosis.

Our study examined how different titanium alloy Ti6Al4V (Ti64) and zirconia (ZrO2) surfaces, ranging from rough to very smooth, affect the expression of elastase (NE), matrix metalloproteinase (MMP)-8, MMP-9, and extracellular traps (NETs) by neutrophils. Discs of Ti64 and ZrO2, 10 mm in diameter and 1.5 mm thick, were created using diamond-impregnated polishing burs and paste to produce rough (Ra > 3 µm), smooth (Ra ≥ 1 to 1.5 µm), and very smooth (Ra < 0.1 µm) surfaces. Neutrophils from Wistar rats were cultured on these surfaces, and the culture supernatants were then examined for NE, MMP-8, and MMP-9 using ELISA. At the same time, NET formation was demonstrated immunohistochemically by staining neutrophils with CD16b and DNA with DAPI. Overall, the expressions of NE and MMP-8 were significantly higher from neutrophil culture on Ti64 and ZrO2 rough surfaces compared to the very smooth surface (R > S > VS) after 2 h and 4 h of culture. The expression of MMP-9 also increased with culture time; however, no significant surface effects on expression were observed. Similarly, rough Ti64 and ZrO2 surfaces (R & S) also showed significantly larger NET formation compared to the very smooth surface (VS) after 4 h and 8 h cultures. Our findings suggest that increasing surface roughness on Ti64 and ZrO2 triggers higher NE, MMP-8, and NET formation secretion.

Boosting the Formation of Brønsted Acids on Flame-made WOx/ZrO2 for Glucose Conversion.

WOx/ZrO2with ahigher concentrationof Brønsted acid sites (BAS) and a bigger ratio of Brønsted to Lewis acid sites (B/L) than achievable by conventional impregnation (IM)were synthesized usingflame spray pyrolysis (FSP). The rapid quenching and short residence time inherent to FSP prevent the accumulation of W atoms on the ZrO2 support and thus provide an excellent surface dispersion of WOx species. As a result, FSP-made WOx/ZrO2 (FSP-WOx/ZrO2) has a much higher surface concentration of three-dimensional Zr-WOx clusters than corresponding materials prepared by conventional impregnation (IM-WOx/ZrO2). The coordination of W-OH to the unsaturated Zr4+ sites in these clusters results in a remarkable decrease of the concentration of Lewis acid sites (LAS) on the surface of ZrO2 and promotes the formation of bridging W-O(H)-Zr hydroxyl groups acting as BAS. FSP-WOx/ZrO2 possesses ~80% of BAS and a B/L ratio of around 4, while IM-WOx/ZrO2 exhibits ~50% BAS and a B/L ratio of around 1. These catalysts were evaluated in the dehydration of glucose to HMF. The catalytic study demonstrated that B/L ratio plays a crucial role in glucose conversion. The best catalyst, FSP-WOx/ZrO2 with a W/Zr ratio of 1/10 affords nearly 100% glucose conversion and an HMF selectivity of 56-69%.

Ni–CaZrO3 with perovskite phase loaded on ZrO2 for CO2 methanation

CO2 methanation has emerged as a promising strategy for the greenhouse gas CO2 utilization and storage of hydrogen. However, achieving low temperature activity and high temperature stability remains challenging due to the sintering of Ni-based catalysts. To address these limitations, this study introduces a Ni–CaZrO3 catalyst featuring a perovskite phase supported on ZrO2, prepared via citrate complexation and impregnation methods. In this approach, a perovskite-type oxide (PTO) of CaZrO3 forms through a solid reaction on the surface of ZrO2 with impregnated CaO. The formation of CaZrO3 on Ni/ZrO2 restrains the ZrO2 support aggregation and reduces the particle size of Ni nanoparticles (NPs), thereby enhancing the activity for CO2 methanation. The interaction between Ni–CaZrO3, and ZrO2 effectively confines the Ni NPs and CaZrO3, enhancing the sintering resistance of Ni–CaZrO3. This leads to excellent stability of the resulting catalyst for CO2 methanation. The Ni–CaZrO3/ZrO2 catalyst achieves 85% CO2 conversion and maintains 100% methane selectivity at 300 °C, demonstrating the prolonged stability over 100 h at 550 °C. Notably, the loading of CaZrO3 in a perovskite phase on ZrO2 via solid surface reaction represents an interesting and valuable route, which could be extended to loading other PTOs for industrial applications.

Stable Zinc Metal Battery Development: Using Fibrous Zirconia for Rapid Surface Conduction of Zinc Ions With Modified Water Solvation Structure.

The two most critical technical issues in Zn-based batteries, dendrite formation, and hydrogen evolution reaction, can be simultaneously addressed by introducing negatively charged fibrous ZrO2 as a separator. Electron redistribution between ZrO2 and Zn2+ ions renders the ZrO2 surface a preferred adsorption site for Zn2+ ions, making surface conduction the primary ion-transport mode. Surface conduction enables fibrous ZrO2 to exhibit a 6.54 times higher single-Zn-ion conductivity than that of conventional glass fiber, minimizing the concentration gradient of Zn2+ and suppressing dendrite formation. Additionally, strong Zr─O─Zn bonding stabilizes the Zn2+ ions with fewer solvated H2O molecules (≈2), preventing water molecules from approaching the electrode surface, as evidenced by a 58.8% decrease in the hydrogen evolution rate. Consequently, the cycling stability of a fibrous-ZrO2-based Zn/Zn symmetric cell (3000h at 1mAhcm-2 and 5mAcm-2) is approximately ten times greater than that of the conventional variant. Furthermore, a fibrous-ZrO2-based Zn-I2 full cell exhibits a notably high energy density (271.4Whkg-1) as well as a long lifespan (≈5000 cycles) at an ultrahigh current density (4Ag-1).

Effects of ZrO2 Nano-Particles' Incorporation into SnAgCu Solder Alloys: An Experimental and Theoretical Study.

This study investigates the mechanism and effects of incorporating different ZrO2 nano-particles into SAC0307 solder alloys. ZrO2 nano-powder and nano-fibers in 0.25-0.5 wt% were added to the SAC0307 alloy to prepare composite solder joints by surface mount technology. The solder joints were shear tested before and after a 4000 h long 85 °C/85% RH corrosive reliability test. The incorporation of ZrO2 nano-particles enhanced the initial shear force of the solder joint, but they decreased the corrosion resistance in the case of 0.5 wt%. SEM, EDS, and FIB analysis revealed intensive growth of SnO2 on the solder joint surfaces, leading to the formation of Sn whiskers. Density functional theory (DFT) simulations showed that, despite Sn being able to bond to the surface of ZrO2, the binding energy was weak, and the whole system was therefore unstable. It was also found that ZrO2 nano-particles refined the microstructure of the solder joints. Decreased β-Sn grain size and more dispersed intermetallic compounds were observed. The microstructural refinement caused mechanical improvement of the ZrO2 composite solder joints by dispersion strengthening but could also decrease their corrosion resistance. While ZrO2 nano-particles improved the solder joint mechanical properties, their use is recommended only in non-corrosive environments, such as microelectronics for space applications.

Superhydrophobicity induced antibacterial adhesion and durability of laser bidirectionally-textured zirconia surfaces with different inclination angles

Femtosecond laser bidirectional texturing with different laser energy densities and inclination angles was performed on zirconia (ZrO2) surfaces. The laser bidirectional texturing models under different inclination angles were constructed to predict the water contact angles (WCAs), and the superhydrophobicity induced antibacterial adhesion mechanism was analyzed. The results revealed that under the combined effect of the optimal laser energy density (7.0 J/cm2) and inclination angle (90°), the laser-textured ZrO2 surface could obtain a micro-nano dual-scale structure composed of periodic regular micro-cones and nanoparticles. This structure not only promoted the adsorption of carbon-containing hydrophobic groups from the stearic acid and the air to form a superhydrophobic surface with excellent chemical/mechanical durability and anti-fouling/self-cleaning abilities, but also minimized the contact area with the bacterial suspension (solid/liquid contact area ratio of 6 %) to enhance antibacterial ability. The optimal stearic acid-modified laser-textured ZrO2 surface exhibited an extremely low adhesive force (Fadhesive=6.69 μN) to the bacterial suspension, and thus achieved the highest antibacterial ratio of 85.3 %. This study is expected to enrich the application of ZrO2 ceramics in the medical field.

Effect of The Amount of 3-(trimethoxysilyl) propyl methacrylate on Improving Surface’s Adhesive Properties of Zirconia

Abstract The objective of this research was silanize zirconium oxide (ZrO2) nanoparticles with 3-(trimethoxysilyl) propyl methacrylate (γ -MPS). Silanization is a surface treatment process of a material using silane compounds to improve the surface adhesive and compatibility of ZrO2 with other materials or coatings and to modify its surface. The surface modification of ZrO2 by 3-(trimethoxysilyl) propyl methacrylate as coupling agents under the influence of ultrasonic waves. The silanized ZrO2 was characterized Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA). The FTIR analysis indicated the interaction of the silane compound on the ZrO2 surface, showing characteristic peaks corresponding to Zr-OH, C-H stretching, carbonyl groups, and Zr-O-Si bonds, indicating successful grafting. The FTIR spectra for the ZrO2 nanoparticles, showing peaks at 1088 cm−1 showed the formation of Zr-O-Si covalent bonds. ZrO2 nanoparticles also exhibited a characteristic peak at 400 cm−1, indicating the deformation of Zr-O-Zr bonds. C=C, and C=O peaks are observed in the range of 1632-1714 cm−1. Thermogravimetric analysis (TGA) measures showed a higher weight loss of the silanized ZrO2 when higher amounts of silane were added.

Exchange of CO2 with CO as Reactant Switches Selectivity in Photoreduction on Co-ZrO2 from C1-3 Paraffin to Small Olefins.

Photocatalytic reduction of CO2 into C2,3 hydrocarbons completes a C-neutral cycle. The reaction pathways of photocatalytic generation of C2,3 paraffin and C2H4 from CO2 are mostly unclear. Herein, a Co0-ZrO2 photocatalyst converted CO2 into C1-3 paraffin, while selectively converting CO into C2H4 and C3H6 (6.0±0.6 μmol h-1 gcat -1, 70 mol %) only under UV/Visible light. The photocatalytic cycle was conducted under 13CO and H2, with subsequent evacuation and flushing with CO. This iterative process led to an increase in the population of C2H4 and C3H6 up to 61-87 mol %, attributed to the accumulation of CH2 species at the interface between Co0 nanoparticles and the ZrO2 surface. CO2 adsorbed onto the O vacancies of the ZrO2 surface, with resulting COH species undergoing hydrogenation on the Co0 surface to yield C1-3 paraffin using either H2 or H2O (g, l) as the reductant. In contrast, CO adsorbed on the Co0 surface, converted to HCOH species, and then split into CH and OH species at the Co and O vacancy sites on ZrO2, respectively. This comprehensive study elucidates intricate photocatalytic pathways governing the transformation of CO2 into paraffin and CO to olefins.

Micro-arc driven porous ZrO2 coating for tailoring surface properties of titanium for dental implants application

Titanium (Ti) is an ideal material for dental implants due to its excellent properties. However, corrosion and mechanical wear lead to Ti ions and particles release, triggering inflammatory responses and bone resorption. To overcome these challenges, surface modification techniques are used, including micro-arc oxidation (MAO). MAO creates adherent, porous coatings on Ti implants with diverse chemical compositions. In this context, zirconia element stands out in its wear and corrosion properties associated with low friction and chemical stability. Therefore, we investigated the impact of adding zirconium oxide (ZrO2) to Ti surfaces through MAO, aiming for improved electrochemical and mechanical properties. Additionally, the antimicrobial and modulatory potentials, cytocompatibility, and proteomic profile of surfaces were investigated. Ti discs were divided into four groups: machined – control (cpTi), treated by MAO with 0.04 M KOH – control (KOH), and two experimental groups incorporating ZrO2 at concentrations of 0.04 M and 0.08 M, composing the KOH@Zr4 and KOH@Zr8 groups. KOH@Zr8 showed higher surface porosity and roughness, even distribution of zirconia, formation of crystalline phases like ZrTiO4, and hydrophilicity. ZrO2 groups showed better mechanical performance including higher hardness values, lower wear area and mass loss, and higher friction coefficient under tribological conditions. The formation of a more compact oxide layer was observed, which favors the electrochemical stability of ZrO2 surfaces. Besides not inducing greater biofilm formation, ZrO2 surfaces reduced the load of pathogenic bacteria evidenced by the DNA-DNA checkerboard analysis. ZrO2 surfaces were cytocompatible with pre-osteoblastic cells. The saliva proteomic profile, evaluated by liquid chromatography coupled with tandem mass spectrometry, was slightly changed by zirconia, with more proteins adsorbed. KOH@Zr8 group notably absorbed proteins crucial for implant biological responses, like albumin and fibronectin. Incorporating ZrO2 improved the mechanical and electrochemical behavior of Ti surfaces, as well as modulated biofilm composition and provided suitable biological responses.

Revealing the surface structure and morphology evolution of Co nanoparticle supported on ZrO2 surfaces

The optimization of structure-dependent activity of supported metal catalysts has driven the dynamic determination of the morphology of Co nanoparticles on ZrO2 using atomic-level simulations. Density functional theory (DFT) calculations combined with ab initio molecular dynamics (AIMD) simulations were used to investigate the surface structure, nucleation mechanism and morphology evolution of Con clusters supported on different ZrO2 facets. As the size of the Con (n = 1–5) cluster increases, the competition between Co-Co bonding and the interaction of Con clusters with the ZrO2 surface further promotes the nucleation of larger clusters. Co atoms prefer to nucleate into large clusters on both c-ZrO2(111) and t-ZrO2(101) surfaces, but this behavior is unfavorable on the m-ZrO2(-111) surface. The analysis of electric properties suggests that the types of hybrid orbitals and the number of electron transfer accounts for the difference in energies of Con clusters on ZrO2 surfaces. Further, the AIMD simulations verified the stable structure of small Co5 cluster obtained by DFT, and predicted the morphology of large Co13 clusters on ZrO2 surfaces under realistic reaction conditions, consistent with the experimental SAM images. Our work provides an intuitive understanding of structure and morphology evolution of catalysts for the targeted design of catalysts to achieve the desired activity and explore more reaction possibilities.

Zirconia and Crofer Joint Made by Reactive Air Brazing Using the Silver Base Paste and Cu-Ti Coating Layer.

This study proposes a method to enhance the airtightness of the joint between the ZrO2 and Crofer alloy using coating technology. With the aid of vacuum sputtering technology, a titanium-copper alloy layer with a thickness between 1.5 μm and 6 μm was first deposited on the surface of ZrO2 and Crofer, respectively. The chemical composition of the deposited reaction layer was 70.2 Cu and 29.8 Ti in at%. Then, using silver as the base material in the reactive air brazing (RAB) process, we explore the use of this material design to improve the microstructure and reaction mechanism of the joint surface between ceramics and metal, compare the effects of different pretreatment thicknesses on the microstructure, and evaluate its effectiveness through air tightness tests. The results show that a coating of Cu-Ti alloy on the ZrO2 substrate can significantly improve bonding between the Ag filler and ZrO2. The Cu-Ti metallization layer on the ZrO2 substrate is beneficial to the RAB. After the brazing process, the coated Cu-Ti layers form suitable reaction interfaces between the filler, the metal, the filler, and the ceramic. In terms of coating layer thickness, the optimized 3 μm coated Cu-Ti alloy layer is achieved from the experiment. Melting and dissolving the Cu-Ti coated layer into the ZrO2 substrate results in a defect-free interface between the Ag-rich braze and the ZrO2. The air tightness test result shows no leakage under 2 psig at room temperature for 28 h. The pressure condition can still be maintained even under high-temperature conditions of 600 °C for 24 h.

The promotional effects of ZrO2 modification on the activity and selectivity of Co/SiC catalysts for Fischer-Tropsch synthesis

Co/SiC catalysts have exhibited excellent performance in Fischer-Tropsch synthesis reaction. However, few research focuses on investigating the effect of SiC supports surface properties of on catalyst performance. In this study, ZrO2 was utilized to modify the SiC surface, leading to the preparation of a series of Co-ZrO2/SiC catalysts. The physicochemical properties of the catalyst were comprehensively analyzed by using N2 adsorption, XRD, H2-TPR, XPS analyses. Catalytic performance was evaluated using a fixed bed reactor, shedding light on the effect of ZrO2 modified SiC support on cobalt-based Fischer-Tropsch synthesis catalysts. The results indicated that ZrO2 surface modification on SiC resulted in an enhanced reduction degree of Co/SiC catalysts. Additionally, ZrO2 exhibited strong interaction with the amorphous phase on the SiC surface, thereby weakening the interaction between Co and the amorphous phase. This led to an increase in the electron density of cobalt species, consequently improving the selectivity of Co/SiC catalysts towards long-chain hydrocarbons.

Interfacial adsorption and catalysis of single-atom Pt-loaded ZrO2 surfaces for enhancing formaldehyde oxidation

The emerging transition metal single-atom catalysts (SACs) are expected to have high activity for converting detrimental formaldehyde (HCHO) under mild conditions. Currently, the exploitation of novel SACs with designed or modified support surfaces remains largely imperative. Herein, we used density functional theory to explore the catalytic performance for HCHO oxidation on various single-atom Pt-loaded ZrO2 surfaces, in which oxygen vacancy and lattice hydroxyl group were included on the surfaces. The surface modifications could enhance the co-adsorption of HCHO and O2 molecules and provide more active sites due to interfacial electron redistribution. The transition state search approach was applied to investigate the oxidation pathways on various ZrO2-supported SAC surfaces, wherein distinct dehydrogenation mechanisms and intermediates were clarified. The oxygen vacancy defects and hydroxyl groups can enhance the catalytic activity for HCHO oxidation by providing active receptor sites for the H-transfer and facilitating the CH bond breakage. Microkinetic modeling was further used to characterize the reaction rates and kinetics behavior of HCHO oxidation on the SAC surfaces. Our simulation demonstrates the excellent catalytic performance of the modified ZrO2-supported SAC in the HCHO oxidation. Meanwhile, the mechanism is also an important implication for the synthesis and design of novel SACs.

Superhydrophobic synergistic antibacterial ZrO2-based surfaces with tertiary hierarchical structures fabricated by femtosecond laser texturing and surface modification

Zirconia (ZrO2) is a hard and brittle dental implant material without anti-infective property. This work reports the preparation of a tertiary micro-nano hierarchical structure on a ZrO2 surface via femtosecond laser texturing combined with magnetron sputtering deposition of an Ag layer (Ag/ZrO2), aiming to achieve a superhydrophobic synergistic antibacterial effect. Laser-scanning pitch and Ag layer thickness were systematically optimized for obtaining the tertiary hierarchical structure. The wettabilities, antibacterial properties and durabilities of various ZrO2 and stearic acid modified Ag/ZrO2 (S-Ag/ZrO2) surfaces were further tested and comparatively analyzed. The results revealed that the optimal process parameters were a laser-scanning pitch of 30 μm and an Ag layer thickness of 100 nm. The as-obtained S-Ag/ZrO2 sample displayed a tertiary micro-nano hierarchical structure, which was featured by a periodic regular conical micro-convex structure covered with ZrO2 nano-protrusions and Ag nanoparticles. This structure could not only greatly reduce the solid-liquid contact area to achieve outstanding superhydrophobicity and durability, it could also sustainably release bacteria-killing Ag+ to obtain an antibacterial ratio of 95.1 % and ensure a long-term antibacterial effect. In addition, the optimal S-Ag/ZrO2 sample having this structure showed a PC12 cell survival rate of up to 81.75 %, demonstrating its good biocompatibility. This work may be of great inspiration and reference for the expansion of the use of ZrO2 in dentistry.

New insights and reaction mechanisms on ZrO2 (110) surface enhanced catalytic hydrolysis of CFC-12: a density functional theory study.

Freon, a greenhouse gas that contributes to the depletion of the ozone layer, has been the subject of investigation in this study. The catalytic hydrolysis enhancement of CFC-12 by ZrO2 was examined using a density functional theory approach. A detailed reaction mechanism and a new reaction pathway were proposed. The study found that CFC-12 is more likely to be adsorbed on the ZrO2 surface in the CFC-12-TO(F) configuration, while H2O is more likely to be adsorbed on the ZrO2 surface in the H2O-TO(H) configuration. Additionally, H2O replaces CFC-12 on the surface of ZrO2. The hydrolysis of CFC-12 is primarily determined by the first dechlorination process, while the defluorination process is comparatively easier. ZrO2 has a catalytic effect on both dechlorination and defluorination processes, with a more pronounced effect on the former. The production of C-OH bonds is inhibited, which facilitates the dechlorination and defluoridation processes. This work was carried out in the Dmol3 program in the Material Studio 2017, including the geometric structure optimization and energy calculations. The GGA/PBE method was used in this work, along with the DNP basis, spin-polarized set, and DFT-D correction. The possible TSs were guessed based on the linear synchronous transit/quadratic synchronous transit/conjugate gradient (LST/QST/CG) method, and they were further confirmed and reoptimized to ensure that the only one imaginary frequency exists in the TSs.

Structure and Chemical Reactivity of Y-Stabilized ZrO2 Surfaces: Importance for the Water-Gas Shift Reaction.

The surface structure and chemical properties of Y-stabilized zirconia (YSZ) have been subjects of intense debate over the past three decades. However, a thorough understanding of chemical processes occurring at YSZ powders faces significant challenges due to the absence of reliable reference data acquired for well-controlled model systems. Here, we present results from polarization-resolved infrared reflection absorption spectroscopy (IRRAS) obtained for differently oriented, Y-doped ZrO2 single-crystal surfaces after exposure to CO and D2O. The IRRAS data reveal that the polar YSZ(100) surface undergoes reconstruction, characterized by an unusual, red-shifted CO band at 2132 cm-1. Density functional theory calculations allowed to relate this unexpected observation to under-coordinated Zr4+ cations in the vicinity of doping-induced O vacancies. This reconstruction leads to a strongly increased chemical reactivity and water spontaneously dissociates on YSZ(100). The latter, which is an important requirement for catalysing the water-gas-shift (WGS) reaction, is absent for YSZ(111), where only associative adsorption was observed. Together with a novel analysis Scheme these reference data allowed for an operando characterisation of YSZ powders using DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy). These findings facilitate rational design and tuning of YSZ-based powder materials for catalytic applications, in particular CO oxidation and the WGS reaction.

Glucose Isomerization to Fructose Catalyzed by MgZr Mixed Oxides in Aqueous Solution

The catalytic isomerization of glucose to fructose plays a pivotal role in the application of biomass as a feedstock for chemicals. Herein, we propose a facile solid-state-grinding strategy to construct ZrO2/MgO mixed oxides, which offered an excellent fructose yield of over 34.55% and a high selectivity of 80.52% (80 °C, 2 h). The co-mingling of amphiphilic ZrO2 with MgO improved the unfavorable moderate/strongly basic site distribution on MgO, which can prohibit the side reactions during the reaction and enhance the fructose selectivity. Based on the catalyst characterizations, MgO was deposited on the ZrO2 surface by plugging the pores, and the addition of ZrO2 lessened the quantity of strongly basic sites of MgO. Additionally, the presence of ZrO2 largely enhanced the catalyst stability in comparison with pure MgO by recycling experiments.

Chemisorption of tetrakis(dimethylamino)zirconium on zirconium oxide: Density functional theory study

We investigated the chemisorption mechanism of tetrakis(dimethylamino)zirconium, Zr(NMe2)4, on zirconium oxide (ZrO2) to understand the first half-reaction of the atomic layer deposition (ALD) process of ZrO2 films. A hydroxylated monoclinic ZrO2 (-111) 2×2 slab model was constructed, and the surface hydroxyl group density was optimized. The obtained density through the optimization procedure was 4.5 nm−2, which closely matches the value reported in the literature. Then, the sequential ligand exchange reactions involving a Zr(NMe2)4 molecule and the –OH terminated ZrO2 surface were simulated. The first two reactions had low activation energies of 0.19 and 0.24 eV and were exothermic. Conversely, the third reaction was endothermic. Therefore, the resulting surface species after chemisorption was expected to be O2Zr(NMe2)2*, which is consistent with in situ analyses in the literature.