Tailoring the aluminum nanocrystal surface oxide for all-aluminum-based antenna-reactor plasmonic photocatalysts.

Aluminum nanocrystals (AlNCs) are of increasing interest as sustainable, earth-abundant nanoparticles for visible wavelength plasmonics and as versatile nanoantennas for energy-efficient plasmonic photocatalysis. Here, we show that annealing AlNCs under various gases and thermal conditions induces substantial, systematic changes in their surface oxide, modifying crystalline phase, surface morphology, density, and defect type and concentration. Tailoring the surface oxide properties enables AlNCs to function as all-aluminum-based antenna-reactor plasmonic photocatalysts, with the modified surface oxides providing varying reactivities and selectivities for several chemical reactions.

Ultrahigh toughness zirconia ceramics.

The attainment of both high strength and toughness is the ultimate goal for most structural materials. Although ceramic material has been considered for use as a structural material due to its high strength and good chemical stability, it suffers from the limitation of low toughness. For instance, although Y2O3-stabilized tetragonal ZrO2 polycrystals (Y-TZPs) exhibit remarkable toughness among ceramics due to their phase transformation toughening mechanism, this toughness is still much weaker than that of metals. Here, we report Y-TZP-based ceramic materials with toughnesses exceeding 20 MPa m1/2, which is comparable to those of metals, while maintaining strengths over 1,200 MPa. The superior mechanical properties are realized by reducing the phase stability of tetragonal zirconia by tailoring the microstructure and chemistry of the Y-TZP. The proposed ceramic materials can further advance the design and application of ceramic-based structural materials.

Fabrication and Magnetic Behavior of Jellyfish-Like Ni Nanowires Synthesized Using Bilayered Nanoporous Anodic Alumina Templates.

The potential to produce nanostructures with intricate shapes in large quantities holds promise for a range of applications in the fields of nanoelectronics and biomedicine. Here a method for fabricating jellyfish-like Ni nanowires (JFNWs) using bilayered nanoporous anodic alumina templates with through pores of varying diameters in each layer is presented. To assess the capabilities of this method, samples are created with different voltages during the second step of anodization, resulting in distinct geometrical characteristics of the second layer of the template, and subsequently synthesize Ni JFNWs. By employing magnetometry and first-order reversal curve (FORC) method, the magnetic properties are examined and a significant alteration in their magnetic behavior, attributed to the differing shapes of the JFNWs and the magnetostatic interactions within the array, is observed. The study utilizes magnetic force microscopy to evaluate the stray magnetic fields generated by the individual JFNWs and unveils their unusual and asymmetric distribution. Through simulations based on the experimental data, the study analyzes the field- and current-induced domain wall movement in a single JFNW and their array. The findings reveal non-trivial micromagnetic configurations in these structures, including a remarkable 'corkscrew' state, and allow for an examination of the process of magnetization switching.

Heat-Localized and Salt-Resistant 3D Hierarchical Porous Ceramic Platform for Efficient Solar-Driven Interfacial Evaporation.

Solar-driven interfacial evaporation (SDIE) is a highly promising approach to achieve sustainable desalination and tackle the global freshwater crisis. Despite advancements in this field, achieving balanced thermal localization and salt resistance remains a challenge. Herein, the study presents a 3D hierarchical porous ceramic platform for SDIE applications. The utilized alumina foam ceramics (AFCs) exhibit remarkable corrosion resistance and chemical stability, ensuring a prolonged operational lifespan in seawater or brines. The millimeter-scale air-filled pores in AFCs prevent thermal losses through conduction with bulk water, resulting in heat-localized interfaces. The hydrophilic nature of macroporous AFC skeletons facilitates rapid water replenishment on the evaporating surface for effective salt-resistant desalination. Benefiting from its self-radiation adsorption and side-assisted evaporation capabilities, the AFC-based evaporators exhibit high indoor evaporation rates of 2.99 and 3.54 kg m-2 h-1 under one-sided and three-sided illumination under 1.0 sun, respectively. The AFC-based evaporator maintains a high evaporation rate of ≈2.77 kg m-2 h-1 throughout the 21-day long-term test. Furthermore, it achieves a daily water productivity of ≈10.44 kg m-2 in outdoor operations. This work demonstrates the potential of 3D hierarchical porous ceramics in addressing the trade-off between heat localization and salt resistance, and contributes to the development of durable solar steam generators.

Synergistic Enhancement of Mechanical and Electrochemical Properties in Grafted Polymer/Oxide Hybrid Electrolytes.

Lithium metal batteries operated with high voltage cathodes are predestined for the realization of high energy storage systems, where solid polymer electrolytes offer a possibility to improve battery safety. Al2O3_PCL is introduced as promising hybrid electrolyte made from polycaprolactone (PCL) and Al2O3 nanoparticles that can be prepared in a one-pot synthesis as a random mixture of linear PCL and PCL-grafted Al2O3. Upon grafting, synergistic effects of mechanical stability and ionic conductivity are achieved. Due to the mechanical stability, manufacture of PCL-based membranes with a thickness of 50 µm is feasible, yielding an ionic conductivity of 5·10-5 S cm-1 at 60 °C. The membrane exhibits an impressive performance of Li deposition in symmetric Li||Li cells, operating for 1200 h at a constant and low overvoltage of 54 mV and a current density of 0.2 mA cm-2. NMC622 | Al2O3_PCL | Li cells are cycled at rates of up to 1 C, achieving 140 cycles at >80% state of health. The straightforward synthesis and opportunity of upscaling as well as solvent-free polymerization render the Al2O3_PCL hybrid material as rather safe, potentially sustainable and affordable alternative to conventional polymer-based electrolytes.

The downregulation of TREM2 exacerbates toxicity of development and neurobehavior induced by aluminum chloride and nano-alumina in adult zebrafish.

To investigate the difference in the development and neurobehavior between aluminum chloride (AlCl3) and nano-alumina (AlNPs) in adult zebrafish and the role of triggering receptor expressed on myeloid cells (TREM2) in this process. Zebrafish embryos were randomly administered with control, negative control, TREM2 knockdown, AlCl3, TREM2 knockdown + AlCl3, AlNPs, and TREM2 knockdown + AlNPs, wherein AlCl3 and AlNPs were 50 mg/L and TREM2 knockdown was achieved by microinjecting lentiviral-containing TREM2 inhibitors into the yolk sac. We assessed development, neurobehavior, histopathology, ultrastructural structure, neurotransmitters (AChE, DA), SOD, genes of TREM2 and neurodevelopment (α1-tubulin, syn2a, mbp), and AD-related proteins and genes. AlCl3 significantly lowered the malformation rate than AlNPs, and further increased rates of malformation and mortality following TREM2 knockdown. The locomotor ability, learning and memory were similar between AlCl3 and AlNPs. TREM2 deficiency further exacerbated their impairment in panic reflex, microglia decrease, and nerve fibers thickening and tangling. AlCl3, rather than AlNPs, significantly elevated AChE activity and p-tau content while decreasing TREM2 and syn2a levels than the control. TREM2 loss further aggravated impairment in the AChE and SOD activity, and psen1 and p-tau levels. Therefore, AlCl3 induces greater developmental toxicity but equivalent neurobehavior toxicity than AlNPs, while their toxicity was intensified by TREM2 deficiency.

Alumina inorganic molecularly imprinted polymer modified multi-walled carbon nanotubes for uric acid detection in sweat.

Alumina inorganic molecularly imprinted polymer (MIP) modified multi-walled carbon nanotubes (MWCNTs) on a glassy carbon electrode (MWCNTs-Al2O3-MIP/GCE) was firstly designed and fabricated by one-step electro deposition technique for the detection of uric acid (UA) in sweat. The UA templates were embedded within the inorganic MIP by co-deposition with Al2O3. Through the evaluation of morphology and structure by Field Emission Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM), it was verified that the specific recognition sites can be fabricated in the electrodeposited Al2O3 molecular imprinted layer. Due to the high selectivity of molecular imprinting holes, the MWCNTs-Al2O3-MIP/GCE electrode demonstrated an impressive imprinting factor of approximately 2.338 compared to the non-molecularly imprinted glassy carbon electrode (MWCNTs-Al2O3-NIP/GCE) toward uric acid detection. Moreover, it exhibited a remarkable limit of detection (LOD) of 50 nM for UA with wide detection range from 50 nM to 600 µM. The MWCNTs-Al2O3-MIP/GCE electrode also showed strong interference resistance against common substances found in sweat. These results highlight the excellent interference resistance and selectivity of MWCNTs-Al2O3-MIP/GCE sensor, positioning it as a novel sensing platform for non-invasive uric acid detection in human sweat.

Quarter Century Outcomes of Alumina Ceramic-on-Ceramic Total Hip Arthroplasty.

BACKGROUND: Alumina ceramic-on-ceramic (CoC) bearings were widely used in total hip arthroplasty (THA) due to their superior wear resistance and inert properties, making them ideal for young, active patients who require long-lasting implants. This study aimed to synthesize findings from previous reports, providing a comprehensive follow-up of at least 25 years on the clinical and radiologic outcomes, the prevalence of osteolysis, and implant survivorship in patients undergoing primary cementless CoC THA. METHODS: We have previously reported 5- to 10-year outcomes following the implementation of third-generation alumina-on-alumina bearings in a consecutive series of 100 primary cementless THAs. This report updates those results with a minimum follow-up of 25 years. Of the original cohort, 58 patients who had 67 hips were available for the latest follow-up. Clinical assessments were performed using the Harris Hip Score and pain questionnaires. Radiographic evaluations were employed to assess implant fixation and osteolysis. RESULTS: At the final follow-up, the implant survival rate was an impressive 96.3%, with revision of the implant as the end point. The mean Harris Hip Score improved significantly from preoperative values to 90.1, indicating excellent functional outcomes. The incidence of ceramic-related noise increased over time, with three cases of ceramic head fractures requiring a change of bearings. Notably, the extent of stem notching observed in earlier reports did not show further progression. Radiologically, all implants demonstrated bony ingrowth with no signs of aseptic loosening or major osteolysis. CONCLUSIONS: The long-term (minimum 25-year) follow-up of alumina-on-alumina bearings in primary cementless THA demonstrates outstanding implant survivorship, excellent functional outcomes, and minimal adverse effects over 25 years. Despite some issues like ceramic-related noise and component fractures, the overall performance of CoC bearings remains highly encouraging, particularly suitable for young, active patients. Surgeons should provide appropriate education to both potential THA candidates and patients who already have THAs with CoC bearings. LEVEL OF EVIDENCE: Therapeutic Level IV.

Ceramic-on-Ceramic Total Hip Arthroplasty Using a Double Tapered, Proximally Coated Stem: 15 to 24-year Clinical and Radiologic Follow-Up.

BACKGROUND: Total hip arthroplasty implant choice profoundly affects survivorship, complications, and failure modes. This study evaluates the long-term (average 18 year) outcomes of ceramic-on-ceramic hip arthroplasty using uncemented shells and stems. Despite an impressive 20-year cumulative percent revision of 5.9%, the hydroxyapatite proximally coated femoral components evaluated in this study have seen declining use since 2003. METHODS: A review of 349 consecutive total hip arthroplasties from 1999 to 2007 was matched to 272 cases with registry data. A survivorship analysis included 274 hips (Group A) after excluding patients lost to follow-up and navigated cases. Group B comprised 135 patients who had complete datasets spanning a minimum of 15 years. RESULTS: Kaplan-Meier analysis identified a 95.6% survivorship plateau at 16 to 24 years, with no significant impact from age, sex, component size, or original pathology. In Group B, EuroQol-5 Dimensions-5 Levels (EQ5D5L) scores indicated favorable outcomes in mobility, self-care, activities, pain/discomfort, and anxiety/depression, with an EQ5D visual analog score mean of 79.24. Functional scores, including the Harris Hip Score, Oxford Hip Score, and Forgotten Joint Score, showed positive outcomes. Radiologic assessments revealed no osteolysis or loose components, with a mean Engh score of 21.69. Dorr classification identified bone quality variations. Better Engh scores corresponded to higher levels of patient satisfaction. Age at surgery was correlated with better functional scores, while sex influenced various outcomes. CONCLUSIONS: This comprehensive study, spanning an average of 18.23 years, combined multiple patient-reported outcome measures with extensive clinical and radiologic follow-up. It reported a notably high survivorship rate for this implant combination but highlighted the declining use of the hydroxyapatite proximally coated femoral stem used in this study, potentially facing withdrawal risks in Australia. LEVEL OF EVIDENCE: Therapeutic Level IV.

Trends in research on characterization, treatment and valorization of hazardous red mud: A systematic review.

Meta-analysis of red mud-related literature in English published from 1976 to 2022 and in Chinese from 1990 to 2022 was performed to support critical analysis and evaluation of the available literature based on the following aspects of red mud research: (a) characterization, (b) treatment for harmfulness minimization, (c) recovery of valuable metals, (d) environmental applications, and (e) uses as construction materials. It was found that (a) sinter red mud tended to contain more silica and calcium, and less iron, sodium and aluminium compared to Bayer red mud; (b) gypsum was the most frequently used agent for harmfulness reduction treatment of red mud, followed by flue gas/CO2; (c) the mean optimal pH for adsorption of major anionic pollutants was 8.42 ± 1.13 (arsenite), 3.73 ± 0.68 (arsenate), 3.50 ± 2.38 (phosphate), 4.43 ± 1.04 (fluoride) and 3.80 ± 1.54 (chromate); (d) wastewater treatment has attracted more attention compared to contaminated soils and waste gases; (e) recovery of iron and scandium has attracted more attention compared to other metals; (f) cement making has been the focus in construction uses. Most of the research findings were based on laboratory-scale experiments that focused on efficacy rather than efficiency. There was a lack of integrated approaches for research in red mud valorization.

Mechanochemical recycling of cellulose multilayer carton packages to produce micro and nanocellulose from the perspective of techno-economic and environmental analysis.

Despite being composed of recyclable materials, the main technological challenge of multilayer carton packs involves the efficient decompatibilization of the cellulosic, polymeric, and metallic phases. Here, a simple two-step mechanochemical process is described that uses only aqueous media and mechanical force to promote phase separation in order to fully recycle multi-layer carton packaging. The first step produces value-added micro- and nanocellulose, while in the second step, aluminum is extracted, forming precipitated aluminum and aluminum oxyhydroxides. Solid polyethylene (PE) remains with a degree of purity defined by the process efficiency. The results show that cellulose is efficiently extracted and converted into micro- and nanocellulose after 15 min of milling. In the second stage, approximately 90% of the aluminum is extracted from the PE after 15 min of milling. Due to the separation and drying medium conditions, the finely divided particles of extracted aluminum also have oxyhydroxides in their composition. It is believed that a passivation layer forms on the metallic aluminum particle. The techno-economic analysis revealed a positive net present value (NPV) of $17.5 million, with a minimum selling price of 1.62 USD/kg of cellulose. The environmental analysis concluded that most of the environmental impact of the process is associated with the entry of carton packages into the system, incorporating a small environmental load related to the industrial process. The results indicate a promising option toward a circular economy and carbon neutrality.

Field-tested innovation: Sustainable utilization of secondary alumina dross for flash setting admixtures production.

Secondary alumina dross (SAD) has emerged as an alternative to bauxite in the production of flash setting admixtures (FSA), a critical admixture in shotcrete. However, the presence of hazardous components has hampered its large-scale adoption. This study conducted field tests at an FSA factory, utilizing SAD as the primary raw material, to evaluate the feasibility and environmental risks. The results confirmed that SAD can effectively replace bauxite in FSA production without compromising quality, as it closely resembled the chemical properties of bauxite. Emissions of fluorides, heavy metals, dioxins in flue gases during production met the relevant Chinese standards. The analysis of hazardous component distribution revealed that more than 50% of volatile components, such as Cl, Cd, Pb, and Zn, were directed into fly ash, exhibiting a significant internal accumulation pattern. In contrast, more than 95% of low-volatility components, including Cu, Cr, Mn, and F, were transferred to the FSA, and the introduction of CaCO3 was confirmed to effectively immobilize F. Moreover, the leaching risk of heavy metals and fluorides in FSA applications slightly increased but remained minimal and within acceptable limits. This technology provides an environmentally sound solution for the disposal of SAD.

Basic Sites on Alumina with Preadsorbed Ethanol and Ammonia-An IR Study.

The adsorption of ethanol and ammonia changes the basic properties of alumina, and new basic sites are created. Ethanol reacts with surface Al-OH groups, forming ethoxy group Al-O-C2H5. The substitution of Al-OH by Al-O-C2H5 increases the negative charge of neighbouring oxygen atoms, and they became sufficiently basic to react with adsorbed CO2 forming carbonate species CO32-. These carbonates were found to be monodentate and bidentate species. Preadsorption of ammonia also increases the basicity of alumina, but the mechanism is different than for ethanol adsorption. Adsorbed ammonia interacts with surface Lewis acid sites being three-coordinated aluminium atoms. This interaction is accompanied by an electron transfer from ammonia molecules to surface sites, and increases the basicity of the neighbouring oxygens, which can react with the absorbed CO2. The carbonate species formed are polydentate ones.

A Comparative Study of Ni-Based Catalysts Prepared by Various Sol-Gel Routes.

The use of heterogeneous catalysts to increase the development of green chemistry is a rapidly growing area of research to save industry money. In this paper, mesoporous SiO2-Al2O3 mixed oxide supports with various Si/Al ratios were prepared using two different sol-gel routes: hydrolytic sol-gel (HSG) and non-hydrolytic sol-gel (NHSG). The HSG route was investigated in both acidic and basic media, while the NHSG was explored in the presence of ethanol and diisopropyl ether as oxygen donors. The resulting SiO2-Al2O3 mixed oxide supports were characterized using EDX, N2 physisorption, powder XRD, 29Si, 27Al MAS-NMR and NH3-TPD. The mesoporous SiO2-Al2O3 supports prepared by NHSG seemed to be more regularly distributed and also more acidic. Consequently, a simple one-step NHSG (ether and alcohol routes) was selected to prepare mesoporous and acidic SiO2-Al2O3-NiO mixed oxide catalysts, which were then evaluated in ethylene oligomerization. The samples prepared by the NHSG ether route showed better activity than those prepared by the NHSG alcohol route in the oligomerization of ethylene at 150 °C.

Fracture strength of anterior cantilever resin-bonded fixed partial dentures fabricated from high translucency zirconia with different intaglio surface treatments.

PURPOSE: To compare the fracture resistance and failure modes of anterior cantilever resin-bonded fixed partial dentures (RBFPDs) fabricated from high translucency zirconia with different intaglio surface treatments. MATERIALS AND METHODS: Sound-extracted canines (N = 50) were randomly divided into five groups (n = 10) to be restored with high translucency zirconia RBFBDs of different intaglio surface treatments. The RBFPD was designed using exocad software and fabricated using a CAM milling machine. The RBFPDs were treated differently: abrasion with 50 µm alumina particles (Group 1); abrasion with 30 µm silica-coated alumina particles (Group 2); abrasion with silica-coated alumina particles (30 µm) and silane application (Group 3); abrasion with silica-coated alumina particles (30 µm) and 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) primer application (Group 4); abrasion with silica-coated alumina particles (30 µm) and silane, and 10-MDP primer application. All RBFPDs were cemented using dual-cured resin cement. The RBFPDs underwent 6000 thermal cycles with distilled water at 5/55°C for 2 min per cycle and then mechanical cyclic loading with 1200,000 cycles of 50 N at a 1.7 Hz frequency at an angle of 135° to the abutment's long axis. Then, RBFPDs were loaded to fracture using a universal testing machine at 1 mm/min. Maximum fracture forces and failure modes were recorded. Fractured specimens and uncemented specimens were examined using a scanning electron microscope. Data was analyzed using ANOVA and Games-Howell post hoc tests at p < 0.05. RESULTS: Mean fracture load results showed a statistically significant difference between the research groups (p < 0.0001) and it ranged from 69.78 to 584 N. Group 4 exhibited the highest fracture load mean (p < 0.0001) which was significantly different from all other groups. Group 2 recorded a significantly higher fracture load mean than Group 3 (p = 0.029). Three modes of failure were observed: prosthesis debonding, prosthesis fracture, and abutment fracture. CONCLUSIONS: Abrasion of zirconia surface with 30 µm silica-coated alumina particles and application of 10-MDP primer yielded the highest mean fracture loads of monolithic high translucency zirconia RBFPD. The mode of fracture of the RBFPDs was influenced by the type of surface treatments.

Controlling the Phase Transformation of Alumina for Enhanced Stability and Catalytic Properties.

Current transition alumina catalysts require the presence of significant amounts of toxic, environmentally deleterious dopants for their stabilization. Herein, we report a simple and novel strategy to engineer transition aluminas to withstand aging temperatures up to 1200 °C without inducing the transformation to low-surface-area α-Al2O3 and without requiring dopants. By judiciously optimizing the abundance of dominant facets and the interparticle distance, we can control the temperature of the phase transformation from θ-Al2O3 to α-Al2O3 and the specific surface sites on the latter. These specific surface sites provide favorable interactions with supported metal catalysts, leading to improved metal dispersion and greatly enhanced catalytic activity for hydrocarbon oxidation. The results presented herein not only provide molecular-level insights into the critical factors causing deactivation and phase transformation of aluminas but also pave the way for the development of catalysts with improved activity for catalytic hydrocarbon oxidation.

Vapor/Vapor-Solid Interfacial Growth of Covalent Organic Framework Membranes on Alumina Hollow Fiber for Advanced Molecular Separation.

Covalent organic frameworks (COFs), known for their chemical stability and porous crystalline structure, hold promises as advanced separation membranes. However, fabricating high-quality COF membranes, particularly on industrial-preferred hollow fiber substrates, remains challenging. This study introduces a novel vapor/vapor-solid (V/V-S) method for growing ultrathin crystalline TpPa-1 COF membranes on the inner lumen surface of alumina hollow fibers (TpPa-1/Alumina). Through vapor-phase monomer introduction onto polydopamine-modified alumina at 170 °C and 1 atm, efficient polymerization and crystallization occur at the confined V-S interface. This enables one-step growth within 8 h, producing 100 nm thick COF membranes with strong substrate adhesion. TpPa-1/Alumina exhibits exceptional stability and performance over 80 h in continuous cross-flow organic solvent nanofiltration (OSN), with methanol permeance of about 200 L m-2 h-1 bar-1 and dye rejection with molecular weight cutoff (MWCO) of approximately 700 Da. Moreover, the versatile V/V-S method synthesizes two additional COF membranes (TpPa2Cl/Alumina and TpHz/Alumina) with different pore sizes and chemical environments. Adjusting the COF membrane thickness between 100-500 nm is achievable easily by varying the growth cycle numbers. Notably, TpPa2Cl/Alumina demonstrates excellent OSN performance in separating the model active pharmaceutical ingredient glycyrrhizic acid (GA) from dimethyl sulfoxide (DMSO), highlighting the method's potential for large-scale industrial applications.

Construction of Medusa-Like Adhesive Carbon Nanotube Array Induced by Deformation of Alumina Sheets.

To change the binary structure of nanotube and nanotube array in vertically aligned carbon nanotube arrays, this work deposits regularly arranged amorphous alumina sheets on the classical array growth catalyst (10 nm-thick alumina and 2 nm-thick iron) and obtains an array similar to the Medusa head. Subsequent experiments revealed that these alumina sheets show both unstable and stable qualities during growth: unstable in that they thermally deform and change their newly discovered characteristics of blocking carbon source diffusion, which regulates the nanotube growth order in specific areas; stable in that they withstand the deformation caused by heat and sequential growth of nanotubes, serving as a substrate and buffer layer for Medusa's hair, i.e., nanotube bundles on the array surface. Their combination splits this binary structure into a tertiary architecture consisting of nanotubes, nanotube bundles, and the array spanning nano-, micro-, and milli-meter. Benefiting from this structure, this array exhibits a unique near-isotropic adhesion characteristic compared to existing reports and outperforms classical and patterned arrays with the same classical catalyst and growth conditions.

Insight into the Evolution Track for the Metathesis of Alkenes within Hierarchical Zeolite-Based Catalysts.

The usage of hierarchical MFI zeolite enables a boost of the catalytic performance of Mo-based catalysts for the olefin-metathesis reaction. The harvest of active catalysts roots in a segmental evolution track between hierarchical zeolite and Al2 O3 slices for the fabrication of active sites. The working evolution track requires the indispensable engagements from intracrystalline mesoporous surface, Al2 O3 slices, and zeolitic Brønsted acid sites. The infilling of disaggregated Al2 O3 slices into the intracrystalline mesopores triggers the creation of localized intrazeolite-Al2 O3 interfaces, which enables the subsequent migration and trapping of surface molybdates into the micropores. The insulation of intrazeolite-Al2 O3 interface or shielding of zeolitic Brønsted acid sites leads to the break of the evolution track. Our findings disclose the hidden functionality of mesoporosity as intrazeolite interface boundary for the fabrication of active sites and supply a new strategy for the rational design of zeolite catalysts.

The Role of Lewis Acid Sites in γ-Al2 O3 Oligomerization.

Olefin oligomerization by γ-Al2 O3 has recently been reported, and it was suggested that Lewis acid sites are catalytic. The goal of this study is to determine the number of active sites per gram of alumina to confirm that Lewis acid sites are indeed catalytic. Addition of an inorganic Sr oxide base resulted in a linear decrease in the propylene oligomerization conversion at loadings up to 0.3 wt %; while, there is a >95 % loss in conversion above 1 wt % Sr. Additionally, there was a linear decrease in the intensity of the Lewis acid peaks of absorbed pyridine in the IR spectra with an increase in Sr loading, which correlates with the loss in propylene conversion, suggesting that Lewis acid sites are catalytic. Characterization of the Sr structure by XAS and STEM indicates that single Sr2+ ions are bound to the γ-Al2 O3 surface and poison one catalytic site per Sr ion. The maximum loading needed to poison all catalytic sites, assuming uniform surface coverage, was ∼0.4 wt % Sr, giving an acid site density of ∼0.2 sites per nm2 of γ-Al2 O3 , or approximately 3 % of the alumina surface.