Pt/Al2O3 coated with N-doped carbon as a highly selective and stable catalyst for catalytic hydrogenation of p-chloronitrobenzene to p-chloroaniline

Selective catalytic hydrogenation of p-chloronitrobenzene on Pt-based catalysts is a green and high-efficient way for p-chloroaniline production. However, supported monometallic Pt catalysts often exhibit undesirable p-chloroaniline selectivity. We herein reported supported Pt catalysts with N-doped carbon (NC) as an overcoating (Pt/Al₂O₃@NC) to overcome the disadvantage. Three Pt/Al₂O₃@NC catalysts with different NC coating amounts were prepared by in situ carbonization of an ionic liquid. For comparison, Al₂O₃ coated by NC and Pt/Al₂O₃ coated by SiO₂ were also prepared. A combination characterization confirmed that the NC overcoating was successfully formed on Pt/Al₂O₃ surface and Pt particles were completely coated by NC layers when ion liquid amount increased to 25 μl per g catalyst. Due to the intimate contact of NC layers and Pt particles Pt-NC heterojunctions were effectively formed on the catalyst surface. For the catalytic hydrogenation of p-chloronitrobenzene, Pt/Al₂O₃@NC with 25 μl ionic liquid as the NC precursor exhibited 100% selectivity to p-chloroaniline at 100% conversion of p-chloronitrobenzene. A lower ionic liquid amount led to decreased selectivity to p-chloroaniline. Furthermore, no deactivation was observed on Pt/Al₂O₃@NC during 5 catalytic cycles. The findings in the study demonstrate that coating noble metal catalysts by N-doped carbon is a promising method to enhance the selectivity and stability for catalytic hydrogenation of p-chloronitrobenzene.

Pt/Al₂O₃ with N-doped carbon overcoating exhibited 100% selectivity to p-chloroaniline for catalytic hydrogenation of p-chloronitrobenzene.     

Promotion of Pt/CeO2 catalyst by hydrogen treatment for low-temperature CO oxidation

Low temperature CO oxidation reaction is known to be facilitated over platinum supported on a reducible cerium oxide. Pt species act as binding sites for reactant CO molecules, and oxygen vacancies on surface of cerium oxide atomically activate the reactant O₂ molecules. However, the impacts of size of Pt species and concentration of oxygen vacancy at the surface of cerium oxide on the CO oxidation reaction have not been clearly distinguished, thereby various diverse approaches have been suggested to date. Here using the co-precipitation method we have prepared pure ceria support and infiltrated it with Pt solution to obtain 0.5 atomic% Pt supported on cerium oxide catalyst, and then systematically varied the size of Pt from single atom to ∼1.7 nm sized nanoparticles and oxygen vacancy concentration at surface of cerium oxide by controlling the heat-treatment conditions, which are temperature and oxygen partial pressure. It is found that Pt nanoparticles in range of 1–1.7 nm achieve 100% of CO oxidation reaction at ∼100 °C lower temperature compared to Pt single atom owing to the facile adsorption of CO but weaker binding strength between Pt and CO molecules, and the oxygen vacancy in the vicinity of Pt accelerates CO oxidation below 150 °C. Based on this understanding, we show that a simple hydrogen reduction at 550 °C for the single atom Pt supported on CeO₂ catalyst induces the formation of highly dispersed Pt nanoparticles with size of 1.7 ± 0.2 nm and the higher concentration of surface oxygen vacancies simultaneously, enabling 100% conversion from CO to CO₂ at 200 °C as well as 16% conversion even at 150 °C owing to the synergistic effects of Pt nanoparticles and oxygen vacancies.

Understanding on effects of Pt size and oxygen vacancy at CeO₂ surface in Pt/CeO₂ catalyst for CO oxidation reaction enables to boost catalytic activity.     

Cu assisted loading of Pt on CeO2 as a carbon-free catalyst for methanol and oxygen reduction reaction

The widely studied Pt/C catalyst for direct methanol fuel cells (DMFCs) suffers severe carbon corrosion under operation, which undermines the catalytic activity and durability. It is of great importance to develop a carbon-free support with co-catalytic functionality for improving both the activity and durability of Pt-based catalysts. The direct loading of Pt on the smooth surface of oxides may be difficult. Herein, the Cu assisted loading of Pt on CeO₂ is developed. Cu pre-coated CeO₂ was facilely synthesized and Pt was electrochemically deposited to fabricate the carbon-free PtCu/CeO₂ catalyst. The PtCu/CeO₂ catalyst has a mass activity up to 1.84 and 1.57 times higher than Pt/C towards methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), respectively. Better durability is also confirmed by chronoamperometry and accelerated degradation tests. The strategy in this work would be greatly helpful for developing an efficient carbon-free support of Pt-based catalysts for applications in DMFCs.

TEM images of the PtCu/CeO₂-21 catalyst. The scale bar in image (B) is 5 nm. Image (C) shows the area chosen for elemental mapping; image (D, E, and F) show the mapping of Ce, Cu, and Pt, respectively.     

CuO and CeO2 assisted Fe2O3/attapulgite catalyst for heterogeneous Fenton-like oxidation of methylene blue

In this paper, CuO and CeO₂ were screened as co-catalyst components for Fe₂O₃/attapulgite (ATP) catalyst, and three new catalysts (CuO–Fe₂O₃/ATP, CeO₂–Fe₂O₃/ATP and CuO–CeO₂–Fe₂O₃/ATP) were prepared for degradation of methylene blue (MB). The three catalysts'' characteristics were determined by BET, XRD, FT-IR, SEM and XPS. MB degradation in different systems and at different pH values was also studied. Under the conditions of H₂O₂ concentration of 4.9 mmol L⁻¹, catalyst dosage of 5 g L⁻¹, pH of 5, reaction temperature of 60 °C and MB initial concentration of 100 mg L⁻¹, the as-synthesized catalysts showed much greater reaction rate and degradation efficiency of MB than Fe₂O₃/ATP catalyst. In addition, the reusability of the as-prepared composites was evaluated. The intermediate products of MB degradation were identified by LC-MS and the possible degradation process of MB was put forward.

A novel heterogeneous catalyst CuO–CeO₂–Fe₂O₃/ATP was synthesized for MB degradation and the catalytic mechanism was put forward.     

Preparation of Ni based mesoporous Al2O3 catalyst with enhanced CO2 methanation performance

A Ni based mesoporous γ-Al₂O₃ (MA) catalyst was prepared via partial hydrolysis without organic surfactants and employed in the carbon dioxide methanation reaction. The obtained catalysts were characterized by N₂ adsorption–desorption, H₂-TPR, XRD, XPS, TG, SEM and TEM-EDS techniques. CO₂ methanation was performed in a fixed-bed reactor. A high surface area of MA with excellent hydrothermal stability was obtained, which promoted the dispersion of nickel species, producing a better catalytic performance. Incorporation of more NiO species into the Ni/MA catalyst increased the amount of active metallic Ni sties, further improving the catalytic activity and CH₄ selectivity. Moreover, the monolithic skeleton of MA with fabric-like walls suppressed the aggregation of active metallic Ni sites and carbon deposition, enhancing the catalyst''s stability, which provides a new insight for potential industrial applications.

A Ni based mesoporous γ-Al₂O₃ (MA) catalyst was prepared via partial hydrolysis without organic surfactants and employed in the carbon dioxide methanation reaction.     

Fe2O3 enhanced high-temperature arsenic resistance of CeO2–La2O3/TiO2 catalyst for selective catalytic reduction of NOx with NH3

High-temperature arsenic resistance catalysts of CeLa_0.5Fe_x/Ti (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) series were prepared and measured under a simulation condition of arsenic poisoning. The as-prepared catalysts were characterized by XRD, SEM, TEM, and XPS. The specific surface area and pore size of the catalysts were measured. At x = 0.2, the catalyst shows the best arsenic resistance and catalytic performance. The active temperature range of the CeLa_0.5Fe_0.2/Ti catalyst is 345–520 °C when the gas hourly space velocity is up to 225 000 mL g⁻¹ h⁻¹. Compared with commercial vanadium-based catalysts, CeLa_0.5Fe_0.2/Ti shows much better catalytic performance. The introduction of Fe will improve the dispersion of CeO₂ and increase the concentration of Ce³⁺ and unsaturated active oxygen on the surface. The NH₃-TPD and H₂-TPR results show that the CeLa_0.5Fe_0.2/Ti catalyst has more acidic sites and more excellent redox performance than CeLa_0.5Fe₀/Ti. The CeLa_0.5Fe_0.2/Ti catalyst might have application prospects in the field of selective catalytic reduction of NO_x with NH₃.

The NO conversion of the CeLa_0.5Fe_0.2/Ti is obviously better than that of the commercial vanadium-based catalyst with regard to arsenic resistance and it has good N₂ selectivity, and good SO₂ resistance.     

Catalytic conversion of carbohydrates into 5-ethoxymethylfurfural using γ-AlOOH and CeO2@B2O3 catalyst synergistic effect

Selective catalytic conversion of carbohydrates to 5-ethoxymethylfurfural (EMF) is a critical approach to the biorefinery. In this work, solid acid catalysts of γ-AlOOH and CeO₂@B₂O₃ were used to convert carbohydrates to EMF in a one-pot process, performed in an ethanol/DMSO solvent system. The synergistic effect of γ-AlOOH and CeO₂@B₂O₃ was studied. Furthermore, the morpho-structural properties of the catalysts were characterized, and the effects of reaction time, reaction temperature, catalyst load, and the amount of cosolvent on the conversion of glucose to EMF were examined and optimized. Under the reaction conditions of 170 °C for 20 h, glucose, sucrose, cellobiose, inulin and starch were used as raw materials, and the EMF yield range was 9.2–27.7%. The results showed that the synergistic effect of γ-AlOOH and CeO₂@B₂O₃ further causes the combination of multiple acid sites with different types and strength distributions. Particularly, the collaboration between weak, medium-strong, and strong acid, as well as between Lewis and Brønsted acidity, is of great significance for EMF generation. The reusability experiments showed that the combined catalytic system was easily separated and maintained catalytic activity for five successive reactions without further intermediate regeneration steps. This work provides a promising route for the catalytic conversion of biomass-derived carbohydrates into EMF.

γ-AlOOH and CeO₂@B₂O₃ solid acid catalysts were synthesized for the one-pot selective conversion of carbohydrates into 5-ethoxymethylfurfural under their synergistic catalysis.     

Ni nanocatalysts supported on mesoporous Al2O3–CeO2 for CO2 methanation at low temperature

The selectivity and activity of a nickel catalyst for the hydrogenation of carbon dioxide to form methane at low temperatures could be enhanced by mesoporous Al₂O₃–CeO₂ synthesized through a one-pot sol–gel method. The performances of the as-prepared Ni/Al₂O₃–CeO₂ catalysts exceeded those of their single Al₂O₃ counterpart giving a conversion of 78% carbon dioxide with 100% selectivity for methane during 100 h testing, without any deactivation, at the low temperature of 320 °C. The influence of CeO₂ doping on the structure of the catalysts, the interactions between the mesoporous support and nickel species, and the reduction behaviors of Ni²⁺ ions were investigated in detail. In this work, the addition of CeO₂ to the composites increased the oxygen vacancies and active metallic nickel sites, and also decreased the size of the nickel particles, thus improving the low temperature catalytic activity and selectivity significantly.

The addition of CeO₂ to form Ni composite catalysts increased the oxygen vacancies and active metallic nickel sites thus improving the low temperature CO₂ methanation performance.     

Dehydrocyclization–cracking of methyl oleate by Pt catalysts supported on a ZnZSM-5–Al2O3 hierarchical composite

The dehydrocyclization–cracking of methyl oleate was performed by ZnZSM-5–Al₂O₃ hierarchical composite-supported Pt catalysts in the range of 450–550 °C under 0.5 MPa hydrogen pressure. Most catalysts converted methyl oleate completely and produced aromatics with more than 10 wt% yield as well as valuable fuels even at 450 °C. The reactivity of catalysts changed remarkably depending on the addition method of Pt, while supporting Pt of 0–0.16 wt% did not affect the pore structure of each catalyst. When Pt was introduced into the composite support by the conventional impregnation method, remarkable hydrocracking proceeded through the decarboxylation and decarbonylation of methyl oleate and the successive conversion of C17 fragments and gave the significant amounts of gaseous products. Nevertheless, the selectivity for the aromatics of the gasoline fraction was relatively high and the yields of aromatics reached maximum 19% at 500 °C under 0.5 MPa, suggesting that gaseous olefins would be cyclized through the Diels–Alder reaction on ZnZSM-5 in the composite support. In contrast, when Pt was introduced into catalysts by ion-exchange with ZnZSM-5, the significant conversion of methyl oleate was inhibited and produced liquid fuels in a wide range.

The ideal reaction route in the dehydrocyclization–cracking of methyl oleate catalyzed by Pt/ZnZSM-5–Al₂O₃ is to produce xylene, toluene, and hydrogen through decarboxylation.     

Novel blended catalysts consisting of a TiO2 photocatalyst and an Al2O3 supported Pd–Au bimetallic catalyst for direct dehydrogenative cross-coupling between arenes and tetrahydrofuran

Dehydrogenative cross-coupling (DCC) is a clean methodology to make C–C bonds by using abundant C–H bonds. The blended catalyst, developed in this study, consists of a TiO₂ photocatalyst and an Al₂O₃ supported Pd–Au bimetallic catalyst and shows superior activity to the conventional TiO₂ photocatalyst loaded with the corresponding metal co-catalyst for the direct DCC between various arenes and tetrahydrofuran, with concomitant evolution of hydrogen gas. The reactions were done under mild conditions without consuming any oxidising agent or other additional chemicals. This new approach of separating the photocatalyst and the metal catalyst parts allows their independent modification to improve the overall catalytic performance.

A TiO₂ photocatalyst physically mixed with a supported Pd–Au bimetallic catalyst is more efficient than Pd loaded TiO₂ sample for the photocatalytic DCC between arene and THF.     

Continuous selective deoxygenation of palm oil for renewable diesel production over Ni catalysts supported on Al2O3 and La2O3–Al2O3

The present study provides, for the first time in the literature, a comparative assessment of the catalytic performance of Ni catalysts supported on γ-Al₂O₃ and γ-Al₂O₃ modified with La₂O₃, in a continuous flow trickle bed reactor, for the selective deoxygenation of palm oil. The catalysts were prepared via the wet impregnation method and were characterized, after calcination and/or reduction, by N₂ adsorption/desorption, XRD, NH₃-TPD, CO₂-TPD, H₂-TPR, H₂-TPD, XPS and TEM, and after the time-on-stream tests, by TGA, TPO, Raman and TEM. Catalytic experiments were performed between 300–400 °C, at a constant pressure (30 bar) and different LHSV (1.2–3.6 h⁻¹). The results show that the incorporation of La₂O₃ in the Al₂O₃ support increased the Ni surface atomic concentration (XPS), affected the nature and abundance of surface basicity (CO₂-TPD), and despite leading to a drop in surface acidity (NH₃-TPD), the Ni/LaAl catalyst presented a larger population of medium-strength acid sites. These characteristics helped promote the SDO process and prevented extended cracking and the formation of coke. Thus, higher triglyceride conversions and n-C₁₅ to n-C₁₈ hydrocarbon yields were achieved with the Ni/LaAl at lower reaction temperatures. Moreover, the Ni/LaAl catalyst was considerably more stable during 20 h of time-on-stream. Examination of the spent catalysts revealed that both carbon deposition and degree of graphitization of the surface coke, as well as, the extent of sintering were lower on the Ni/LaAl catalyst, explaining its excellent performance during time-on-stream.

Highly selective and stable Ni supported on La₂O₃–Al₂O₃ catalyst on the deCO/deCO₂ reaction paths for the production of renewable diesel.     

Microstructure of interface regions and mechanical properties of Ti/Al 2O 3 and Ti-alloy/Al 2O 3 joints for dental implants

Titanium and alumina are very well suited as constituents of dental metal/ceramic implants because of their excellent biocompatibility and their special chemical and mechanical properties which can be exploited to tailor composite implant structures. However, prior attempts to join pure titanium without any intermediate layer to alumina ceramic led to unsatisfactory results mainly due to thermal expansion mismatch between both materials. Therefore we used recently developed Ti alloys containing 30%wt Ta or 40%wt Nb for manufacturing dental implants. Moreover, we studied two alternative methods to join pure titanium with alumina using intermediate layers to reduce internal stresses within the joint caused by thermal expansion mismatch. We examined the interface region of these joints by metallographic, mechanical, analytical, and electron microscopy methods. Additionally, a comparison of the properties of the hitherto investigated types of joints with a view of their applicability in dental implants is given. Promising results were obtained for Ti/alumina joints with Nb interlayers. The studies are continuing.     

Deactivation by HCl of CeO2–MoO3/TiO2 catalyst for selective catalytic reduction of NO with NH3

The effect of HCl on a CeO₂–MoO₃/TiO₂ catalyst for the selective catalytic reduction of NO with NH₃ was investigated with BET, XRD, NH₃-TPD, H₂-TPR, XPS and catalytic activity measurements. The results showed that HCl had an inhibiting effect on the activity of the CeO₂–MoO₃/TiO₂ catalyst. The deactivation by HCl of the CeO₂–MoO₃/TiO₂ catalyst could be attributed to pore blockage, weakened interaction among ceria, molybdenum and titania, reduction in surface acidity and degradation of redox ability. The Ce³⁺/Ce⁴⁺ redox cycle was damaged because unreactive Ce³⁺ in the form of CeCl₃ lost the ability to be converted to active Ce⁴⁺ in the SCR reaction. In addition, a decrease in the amount of chemisorbed oxygen and the concentrations of surface Ce and Mo was also responsible for the deactivation by HCl of the CeO₂–MoO₃/TiO₂ catalyst.

The effect of HCl on a CeO₂–MoO₃/TiO₂ catalyst for the selective catalytic reduction of NO with NH₃.     

Incorporation of Al2O3, GO,and Al2O3@GO nanoparticles into water-borne epoxy coatings: abrasion and corrosion resistance

Nano-Al₂O₃ particles and graphene oxide (GO) nanosheets were modified by 3-aminopropyltriethoxysilane (KH550), and then dispersed in epoxy resin, and finally modified-Al₂O₃/epoxy, modified-GO/epoxy and modified-Al₂O₃@GO/epoxy composite coatings were prepared on steel sheets by the scraping stick method. The microstructure, phase identification, surface bonding and composition of the nanoparticles were characterized by SEM, XRD, FT-IR, and Raman spectroscopy, respectively. The hardness of the coating was assessed by the pencil hardness method. The abrasion resistance of the coating was tested by a sand washing machine. The corrosion resistance of the coating was assessed using salt spray, a long-period immersion test, potentiodynamic polarization curves and electrochemical impedance spectra. With the addition of a small amount of nanoparticles, the dispersion of nanoparticles in the epoxy resin was good. When the content of nano-Al₂O₃ particles was equal to 1.5 wt%, the particles in the epoxy exhibited the best dispersion and stability. However, the GO and Al₂O₃@GO nanofillers in the epoxy resin exhibited poor dispersion and stability. The hardness, abrasion and corrosion resistance of the composite coatings were improved with the addition of a small amount of nanoparticles, but the performance began to decline after exceeding a certain content range of the nanoparticles. A relatively good abrasion resistance for the coatings was obtained when the content of Al₂O₃, GO and Al₂O₃@GO after modification was 1.5 wt%, 0.2 wt% and 0.4 wt%, respectively. The corrosion resistance of the coatings doped with nano-Al₂O₃ particles was better than that of the coatings incorporating GO nanosheets and Al₂O₃@GO hybrids. The corrosion mechanism of the composite coatings in 3.5 wt% NaCl solution was addressed and studied.

Nano-Al₂O₃ particles and graphene oxide (GO) nanosheets were modified by 3-aminopropyltriethoxysilane (KH550), and then dispersed in epoxy resin, and finally modified-Al₂O₃/epoxy, modified-GO/epoxy and modified-Al₂O₃@GO/epoxy composite coatings were prepared on steel sheets by the scraping stick method.     

Recycling the CoMo/Al2O3 catalyst for effectively hydro-upgrading shale oil with high sulfur content and viscosity

Hydrotreatment is an effective upgrading technology for removing contaminants and saturating double bonds. Still, few studies have reported the hydro-upgrading of shale oil, with unusually high sulfur (13200 ppm) content, using the CoMo/Al₂O₃ catalyst. Here we report an extensive study on the upgrading of shale oil by hydrotreatment in a stirred batch autoclave reactor (500 ml) for sulfur removal and viscosity reduction. From a preliminary optimization of the reaction factors, the best-operating conditions were 400 °C, an initial H₂-pressure of 5 MPa, and an agitation rate of 800 rpm, a catalyst-to-oil ratio of 0.1, and a reaction time of 1 h. We could achieve a sulfur removal efficiency of 87.1% and 88.2% viscosity reduction under the optimal conditions. After that, the spent CoMo/Al₂O₃ was repeatedly used for subsequent upgrading tests without any form of pre-treatment. The results showed an increase in the sulfur removal efficiency with an increase in the number of catalyst runs. Ultimately, 99.5–99.9% sulfur removal from the shale oil was achieved by recycling the spent material. Both the fresh and the spent CoMo/Al₂O₃ were characterized and analyzed to ascertain their transformation levels by XRD, TEM, TG, XPS, TPD and N₂ adsorption analysis. The increasing HDS efficiency is attributed to the continuing rise in the sulfidation degree of the catalyst in the sulfur-rich shale oil. The light fraction component in the liquid products (IBP–180 °C) was 30–37 vol% higher than in the fresh shale oil. The product oil can meet the sulfur content requirement of the national standard marine fuel (GB17411-2015/XG1-2018) of China.

The CoMo/Al₂O₃ catalyst was used to upgrade shale oil. Sulfur removal was increased on the spent catalyst. The transition of oxidic Mo-species into active phase MoS₂ was observed with recycling. The high sulfidation degree of the CoMo/Al₂O₃ suppressed deactivation by coking.     

2-Nitrophenol sensor-based wet-chemically prepared binary doped Co3O4/Al2O3 nanosheets by an electrochemical approach

Herein, the wet-chemical process (co-precipitation) was used to prepare nanosheets (NSs) of Co₃O₄/Al₂O₃ in an alkaline medium (pH ∼ 10.5). The synthesized NSs were totally characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV/vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). The synthesized NSs were deposited onto a glassy carbon electrode (GCE) to prepare a very thin layer with a conducting binder for detecting 2-nitrophenol (2-NP) selectively by a reliable electrochemical method. The proposed chemical sensor exhibits good sensitivity (54.9842 μA μM⁻¹ cm⁻²), long-term stability, and enhanced chemical response by electrochemical approaches. The resultant current is found to be linear over the concentration range (LDR) from 0.01 nM to 0.01 mM. The estimated detection limit (DL) is equal to 1.73 ± 0.02 pM. This study introduces a potential route for future sensitive sensor development with Co₃O₄/Al₂O₃ NSs by an electrochemical approach for the selective detection of hazardous and carcinogenic chemicals in environmental and health care fields.

This potential research work introduces a route of future sensitive sensor development with Co₃O₄/Al₂O₃ NSs by electrochemical approach to selective detection of hazardous and carcinogenic chemicals in environmental and health care fields.     

Nb-doped and Al2O3 + B2O3-coated granular secondary LiMn2O4 particles as cathode materials for lithium-ion batteries

In this work, to improve the cyclability and high-temperature performance of cubic spinel LiMn₂O₄ (LMO) as cathode materials, Nb⁵⁺-doped LiMn₂O₄ powders coated and uncoated with Al₂O₃ and/or B₂O₃ were synthesized via the modified solid-state reaction method. It was found that Nb⁵⁺-doped and B₂O₃ + Al₂O₃-coated LMO powders comprising 5 μm granular agglomerated fine primary particles smaller than 350 nm in diameter exhibited superior electrochemical properties with initial discharge capacity of 101.68 mA h g⁻¹; we also observed capacity retention of 96.31% after 300 cycles at room temperature (RT) and that of 98% after 50 cycles at 55 °C and 1C rate.

Nb-doped and Al₂O₃ + B₂O₃-coated granular secondary LMO particles enabling superior cycling performance at 25 and 55 °C.     

Synthesis,electronic structures,and photoluminescence properties of an efficient and thermally stable red-emitting phosphor Ca3ZrSi2O9:Eu3+,Bi3+ for deep UV-LEDs

A series of red-emitting Ca₃ZrSi₂O₉:Eu³⁺,xBi³⁺ phosphors was synthesized using a conventional high temperature solid-state reaction method, for the purpose of promoting the emission efficiency of Eu³⁺ in a Ca₃ZrSi₂O₉ host. The site preference of Bi³⁺ and Eu³⁺ in the Ca₃ZrSi₂O₉ host was evaluated by formation energy. The effects of Bi³⁺ on electronic structure, luminescent properties, and related mechanisms were investigated. The inner quantum yield of the optimized sample increased to 72.9% (x = 0.08) from 34.6% (x = 0) at 300 nm ultraviolet light excitation. The optimized sample (x = 0.08) also showed excellent thermal stability, and typically, 84.2% of the initial emission intensity was maintained when the temperature increased to 150 °C from 25 °C, which is much higher than that without Bi³⁺ doping (70.1%). The mechanisms of emission properties and thermal stability enhancement, as well as the redshift of the charge transfer band (CTB) induced by Bi³⁺ doping in the Ca₃ZrSi₂O₉:Eu³⁺ phosphor, were discussed. This study elucidates the photoluminescence properties of Bi³⁺-doped Ca₃ZrSi₂O₉:Eu³⁺ phosphor, and indicates that it is a promising luminescent material that can be used in ultraviolet light-emitting diodes.

A red-emitting phosphor Ca₃ZrSi₂O₉:Eu³⁺,Bi³⁺ with high quantum yield and thermal stability was developed by introducing Bi³⁺ as an efficient sensitizer.     

Conversion of levulinic acid to γ-valerolactone over Ru/Al2O3–TiO2 catalyst under mild conditions

Novel catalytic material with high catalytic activity and hydrothermal stability plays a key role in the efficient conversion of levulinic acid (LA) to γ-valerolactone (GVL) in water. In this study, mixed oxides Al₂O₃–TiO₂, Al₂O₃–MoO₃ and Al₂O₃–Co₃O₄ were synthesized by co-precipitation using aqueous solution of NaOH as precipitant. Ru catalysts supported on mixed oxides were prepared by impregnation method and their catalytic performances were tested in the hydrogenation of LA to GVL on a fixed bed reactor. The physicochemical properties of the catalysts were characterized by XRD, H₂-TPR, NH₃-TPD, and BET techniques. The TiO₂ component significantly affected the acidity of the catalyst, and thus its catalytic activity for the GVL yield was affected. The desired product GVL with a yield of about 97% was obtained over the Ru/Al₂O₃–TiO₂ catalyst under mild conditions (WHSV = 1.8 h⁻¹, T = 80 °C). Moreover, the catalyst Ru/Al₂O₃–TiO₂ exhibited excellent thermal stability in the test period of time.

Novel catalytic material with high catalytic activity and hydrothermal stability plays a key role in the efficient conversion of levulinic acid (LA) to γ-valerolactone (GVL) in water.     

Fabrication of a ceramic/metal (Al2O3/Al) composite by 3D printing as an advanced refractory with enhanced electrical conductivity

Fused deposition modelling (3D) printing is used extensively in modern fabrication processes. Although the technique was designed for polymer printing, it can now be applied in advanced ceramic research. An alumina/aluminum (Al₂O₃/Al) composite refractory can be fabricated by mixing metallic aluminum in a polymer to form an Al/polymer composite filament. The filament can be printed via a regular thermoplastic material extrusion printer with no machine modification. In this study, Al/polymer composite samples were printed in a crucible shape and sintered at different temperatures to form Al₂O₃/Al composite refractory specimens. The sintered samples were examined via several analytical techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, compressive testing, hardness testing, XPS, and Hall measurement. Unlike other ceramic printing techniques that require expensive 3D printing machines and a very high temperature furnace (above 1500 °C) for post processing, this study demonstrates the viability of fabricating refractory items using a cost-effective fused deposition modelling 3D printer and a low temperature furnace (900 °C). The samples did not disintegrate at 1400 °C and were still sufficiently electrically conductive for advanced refractory applications.

An Al₂O₃/Al composite is fabricated by the 3D printing, sintering, and calcination processes that can be used in refractory applications.