Processes
·
2022
·Vol. 10
·期 7
·1302
·
IF 3.352
Hailun Ren,Weihong Li
3-hydroxybutyraldehyde (3-HBA) is mainly employed to synthesize 1,3-BDO (1,3-butanediol), which is one of the most important components in cosmetics moisturizers. In this study, a series of composite oxide catalysts were prepared by bringing alkaline earth metal Ca and rare earth metal La to the composite oxide MgO/Al2O3, which were made through the co-precipitation method. These catalysts were applied in the synthesis of 3-HBA through acetaldehyde (AcH) condensation. The structure, texture, and acidic properties of these catalysts were characterized using various characterization methods, and the effects of catalyst composition, reaction temperature, reaction pressure, and residence time on the conversion of AcH were investigated as well. The results showed that the introduction of Ca and La weakened the acidic property and enhanced the basic property, which favored the AcH condensation to synthesize 3-HBA. At a temperature of 20 °C, pressure of 200 kPa, and residence time of 70 min, 0.5%La-2.3%Ca-2MgO/Al2O3exhibited a better catalytic activity, and the conversion of AcH reached 95.89%. The selectivity and yield of 3-HBA were 92.08% and 88.30%, respectively. The stability test indicated that the high AcH conversion could be maintained for 5 h.Keywords:composite oxides;acetaldehyde;condensation catalyst;3-hydroxybutyraldehyde
✓ 已验证
产品关联
DOI
高影响因子
Molecular Catalysis
·
2022
·
IF 5.089
Junji Chen,Heshan Cai,Tianxiang Zhao
Aluminium oxide (Al 2 O 3 ) is a promising catalyst support due to its excellent stability, high specific surface area, low price, and wide applicability. At present, most of the synthesis methods of Al 2 O 3 are wet chemical process, and the solid-state synthesis of catalysts is underdeveloped under solvent-free conditions. In this study, we proposed a novel strategy for solvent-free synthesis of Rh/Al 2 O 3 catalysts via mechanochemistry. The pore properties of the catalysts can be tuned by simply adjusting the amount of template CTAB and calcination temperatures. As a proof of concept, as-prepared catalysts are used to catalyze hydrolytic dehydrogenation of ammonia borane. The best catalyst Rh/Al 2 O 3 -CTAB(0.4)-500 achieves a total turnover frequency of 186.0 mol H2 ·mol Rh −1 ·min −1 at 298 K and the activation energy is 44.8 kJ·mol −1 . It also exhibits good cycling properties for catalyzing the hydrolysis of ammonia borane completely even after five runs. The catalysts were also characterized by various methods, including SEM, TEM, XPS, XRD, etc., to study the relationship between their structure and catalytic performance. The results show that the high activity of the catalyst is closely related to its large BET specific surface area and appropriate average pore size.
✓ 已验证
产品关联
DOI
高影响因子
TRIBOLOGY INTERNATIONAL
·
2022
·
IF 5.62
Shuna Chen,Yunfeng Su,Qiuan Sun,Hengzhong Fan,Junjie Song,Litian Hu,Yongsheng Zhang
A fibrous monolithic ceramic was constructed with Al 2 O 3 fiber cells surrounded by Cr 2 O 3 phase-two kinds of brittle ceramics, to achieve an excellent combination of high strength and toughness, which is usually mutually exclusive in engineering materials . The material was demonstrated to fail in a non-brittle fracture manner and showed a typical rising R-curve behavior with the maximum crack growth toughness of 9.05 MPa m 1/2 . Meanwhile, the composite ceramic exhibited excellent tribological performance at high temperatures, with the lowest friction coefficient of 0.29 and wear rate of 1.07 × 10 −5 mm 3 /Nm at 600 °C. It was also demonstrated that the thermal stability of Cr 2 O 3 has a great influence on the wear mechanism when the temperature was above 800 °C.
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2022
·
IF 8.035
Junwei Wu,Guofeng Zhao,Min Song,Huimin Wang,Yan Wei,Xuejiao Chen,Guanying Wang,Zifeng Yan
Catalytic ethane dehydrogenation (CEDH) to ethylene is an important alternative to oil-based cracking processes due to the shale gas revolution, but the dominant Pt-based catalysts still suffer from fast deactivation, caused by coke formation and Pt sintering. Herein, we report a catalyst of nanosheets-stacked Al 2 O 3 -flower anchoring Pt species onto pentacoordinated Al (Al V ) sites with a low Pt loading of only 0.07 wt%. This catalyst was prepared by a simple wet impregnation method without introducing any promoter, exhibiting a stable ethane conversion of 25–27 % (close to thermodynamic equilibrium conversion) with ethylene selectivity of 95–97 % within a single running of 300 h (590 °C, 33 vol% C 2 H 6 /N 2 , GHSV C2H6 of 2100 mL h −1 g −1 ), and moreover, a high TOF value of 6084 h −1 could be achieved. This work offers a promising CEDH catalyst, with both very high Pt dispersion (from appropriate amount of Al V sites) and intensified mass transfer (from nanosheet feature).
✓ 已验证
产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2022
·
IF 7.392
Xing Xie,Dan Yang
The poor interfacial compatibility between inorganic thermally conductive nanoparticles and organic polymeric matrix largely limits the improvement of thermal conductivity (λ) of composites. In this study, poly(catechol-polyamine) (PCPA) and bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si69) were used to multi-functionalize alumina (Al 2 O 3 ) nanoparticles (denoted as Al 2 O 3 -PCPA-Si69) to improve the interfacial compatibility and prepare effective thermally conductive epoxy natural rubber (ENR) composites. The non-covalent PCPA modification protected the inner thermal characteristics of Al 2 O 3 nanoparticles and the Si69 with vulcanization accelerator structure provided strong covalent bond between Al 2 O 3 filler and rubber chains during vulcanization. Owing to the constructed thermally conductive pathways and decreased interfacial resistance, the λ of ENR composite reached 0.3773 W (mK) −1 at Al 2 O 3 -PCPA-Si69 nanoparticles content of 30 vol%, which is 270 % of the pure ENR (0.1400 W (mK) −1 ). The multi-functionalization of Al 2 O 3 nanoparticles is highly efficient and cost effective, which can be expanded in other thermally conductive fillers to make them attractive candidate for insulating electronic field.
✓ 已验证
产品关联
DOI
高影响因子
Journal of Manufacturing Processes
·
2022
·
IF 5.684
Yong Zeng,Xingfu Chen,Lijun Sun,Haihua Yao,Jimin Chen
The mechanical properties of 3D printed alumina ceramics are degraded due to the micro anisotropy, interlayer interface defects and microporous characteristics. In order to improve its mechanical properties, solid phase sintered, liquid phase sintered and solid-liquid phase sintered alumina (Al 2 O 3 ) ceramics were prepared by Vat photopolymerization 3D printing technology, respectively. In the experiment, Al 2 O 3 was used as the main material to study the effects of TiO 2 solid phase additive, MgO-SiO 2 liquid phase additives and TiO 2 -MgO-SiO 2 solid-liquid phase additives on Al 2 O 3 ceramics sintering behavior and mechanical properties, so as to improve the sintering density and mechanical properties of alumina ceramics. The best composition ratio and sintering temperature were determined by shrinkage, relative density, Raman, XRD and SEM characterization. Under optimal sintering conditions , The comprehensive properties of Al 2 O 3 ceramics prepared by liquid phase sintering are more balanced. And has excellent mechanical properties. The flexural strength reached 317 ± 34 MPa and the Vickers hardness up to 1250 ± 102 HV 30 . Thus, nine types of truss structures are prepared to study their mechanical properties. By changing the structure types, the order of compressive strength is FCC > BCC > DLS. By changing the number of units, the order of compressive strength is 3 × 3 × 3 units >2 × 2 × 2 units >1 × 1 × 1 units. The Al 2 O 3 ceramics prepared by the liquid phase sintering exhibit excellent mechanical compression properties and energy absorption capacity . The FCC structure of 3 × 3 × 3 units can reach 23.2 ± 1.7 MPa compressive strength.
✓ 已验证
产品关联
DOI
高影响因子
Processes
·
2022
·Vol. 10
·期 8
·1542
·
IF 3.352
Feng Cheng,Xiuwei Li
The reduction of metal oxides by biochar is an important reaction for many biomass utilization technologies. This work investigated the temperature–programmed reduction (TPR) of NiO/Al2O3by in situ generated biochar from citric acid pyrolysis. Firstly, NiO/Al2O3was loaded with citric acid by impregnation and then heated from ambient temperature to 900 °C in a N2flow. The process was on–line analyzed by the TGA–FTIR technique. Secondly, a series of intermediates was obtained and characterized by XRD, CHNO elemental analysis, and temperature programmed oxidation (TPO). Lastly, a control experiment of unsupported NiO was conducted to show the influence of Al2O3support on the NiO reduction. Results showed that the whole heating process could be resolved into two parts that is citric acid pyrolysis and NiO reduction at a heating rate of 5 °C/min. The NiO reduction occurred above 400 °C with the biochar from citric acid pyrolysis as reductant. In the temperature–programmed reduction process, the Al2O3–supported NiO exhibited three reduction phases in contrast with only one reduction phase for the unsupported NiO. A hypothesis was proposed to explain this. The presence of Al2O3support may result in different deposition sites of biochar (on NiO or on Al2O3), and consequently different reduction mechanisms.Keywords:metal oxide reduction;biomass pyrolysis;solid–state reaction;biochar gasification
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2021
·Vol. 223
·期 8
·2100234
·
IF 2.527
Xun Zhang,Yiming Sun,Xiuping Yin,Yue Ma,Lianqi Zhang,Defa Wang
Gel polymer electrolyte (GPE) has attracted extensive interest due to superior interfacial compatibility, excellent plasticity, and improved electrochemical stability. Polymer matrix is of great importance to the performance of lithium metal battery, especially for Ni-rich cathode system with high working potential. Herein, a rigid-flexible composite polymer matrix comprising methylcellulose (MC), polymethyl methacrylate (PMMA), and Al 2 O 3 is prepared. After saturated with the liquid electrolyte of 1 M LiDFOB in EC/DMC (1:1, v:v), the obtained GPE exhibits a high ionic conductivity of 0.20 × 10 −3 S cm −1 and a wide electrochemical stable window up to 5.6 V. The synergistic effect of inorganic fillers and the ester groups on polymer matrix are conducive to the uniform deposition of Li-ion and advantageous to the formation of smooth and robust interfacial passivation layer. After assembled with Ni-rich cathode LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA), a capacity of 158.1 mAh g −1 is maintained after 200 cycles at 0.1 C, while a high value of 133.1 mAh g −1 is delivered at 2 C. These results indicate that the as-prepared MC-PMMA-Al 2 O 3 GPE (abbreviated as MPAA) is favorable for the interfacial compatibility of lithium metal batteries and shows superior electrochemical stability at high working voltage.
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2021
·
IF 4.527
Xin Xu,Junyi Zhang,Pan Jiang,Desheng Liu,Xin Jia,Xiaolong Wang,Feng Zhou
Three-dimensional (3D) printing of ceramics has attracted increasing attention in various fields. However, the pyrolysis of organic components used for binding or polymerization in 3D printing commonly causes a large shrinkage (up to 30 %–40 %), high porosity, and cracking or deformation, severely limiting practical applications. In this study, 3D printing of Al 2 O 3 ceramic architectures with ultra-low shrinkage is realized by introducing inorganic binder aluminum dihydrogen phosphate (Al(H 2 PO 4 ) 3 , AP) as a ceramic precursor. Compared to organic binders, the inorganic AP binder can undergo crystallization conversion, which reduces mass loss during sintering at high temperatures, resulting in low shrinkage. Moreover, AP can be used as a rheological modifier to regulate the printability of the ceramic ink for direct ink writing of Al 2 O 3 ceramic architectures, such as wood-piled scaffolds, honeycomb structures , and tubes with high fidelity. The resultant Al 2 O 3 structural ceramics sintered at 1250 °C exhibit good mechanical performance and structural integrity. Most importantly, the linear shrinkage of the printed ceramics is less than 5 %, which is several times lower than that of ceramics with organic binders. This study provides a viable strategy for fabricating high-performance ceramic architectures with good dimensional fidelity for practical applications.
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2021
·
IF 4.527
Yu He,Yunxiang Cai,Ling Zhang,Kaige Liu,Gang Liu,Bingxi Xiang,Jianpang Zhai,Ling Bing Kong,Tianshu Zhang,Yin Liu
Al 2 O 3 transparent ceramics have important applications in electronics, solid-state lighting, military and 5G industries. At present, thin and large-size Al 2 O 3 ceramics are urgently required by enterprises. Tape casting method has emerged as a powerful tool in producing transparent ceramics, but the preparation of the slurries is generally very time consuming. In this study, a one-step ball milling process was proposed to fabricate Al 2 O 3 transparent ceramics through non-aqueous tape casting, in which green tapes were obtained with uniform texture and no distortion. Thickness of the Al 2 O 3 transparent ceramics approached 0.1 mm. The effects of dry pressing on single and double-layer tapes were also compared. It was found that dry pressing has essentially no effect on monolayer samples, but contributed to improve the densification and promoted grain growth of the bilayer samples. Our results could be used as reference for the preparation of extremely thin Al 2 O 3 transparent ceramic wafers.
✓ 已验证
产品关联
DOI
高影响因子
ADVANCED ENGINEERING MATERIALS
·
2021
·Vol. 23
·期 6
·2001490
·
IF 3.862
Xu Guo,Xiaohong Chen,Ping Liu,Honglei Zhou,Shaoli Fu,Wei Li,Xinkuan Liu,Fengcang Ma,Zhengpeng Wu
CNTs/Cu-Al 2 O 3 composites are successfully prepared by internal oxidation, chemical vapor deposition and spark plasma sintering (SPS) method. The influence of Al content (0.12 and 0.6 wt%) on the morphology of grown carbon nanotubes and the mechanical properties of composites are systematically studied. The results show that under the same growth process, more carbon nanotubes are obtained on the surface of the powders with 0.6 wt% Al content. The CNTs/Cu-Al 2 O 3 composites with 0.12 wt% Al content displays higher mechanical properties, the tensile strength is 280 MPa, and the micro-hardness is 123.3 HV, which is increased by 40.7 and 78.2% in contrast with that of pure copper, respectively. Moreover, the electrical conductivity of CNTs/Cu-Al 2 O 3 (Al content is 0.12 wt%) composites is still at the high level of 83.2% IACS. This work uses chemical vapor deposition to improve the dispersion and interfacial bonding of CNTs in the matrix and increase the properties of the composites, which provides a new idea for the preparation of high strength metal matrix composites.
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2021
·
IF 5.316
Pengfei Wang,Qing Xia,Yuncheng Zhou,Xueqian Ji,Hailan Feng,Yuxing Xu,Jun Yang,Qiangqiang Tan
The nickel-rich cathode materials (LiNi 0.8 Co 0.15 Al 0.05 O 2 , NCAs) in Lithium ion batteries often suffer from oxygen loss problems under partially overcharged conditions (>4.3 V), leading to capacity fading and safety problem. Herein, we utilize a facile ball-milling method to coat the NCAs with a shell of cerium aluminum composite oxide (CeO 2 -Al 2 O 3 ), which is commonly used as oxygen storage material. Proved by in situ X-ray diffraction results, the coating CeO 2 -Al 2 O 3 layer is capable to suppress the lattice volume change and irreversible phase transition of NCAs. The CeO 2 -Al 2 O 3 coating layer can adsorb released oxygen under overcharged conditions and replenish lattice oxygen of NCAs under oxygen-leaned conditions. The protective layer can also prevent dissolution of the transition metals caused by HF attack in electrolytes. As a result, the as prepared electrode presents high specific capacity of 186.4 mA h g −1 and excellent cycle stability with capacity retention of 94.1% after 300 cycles at a rate of 0.5 C under overcharged conditions (3.0–4.5 V). Coating CeO 2 -Al 2 O 3 is an efficient strategy to solve capacity fading problem and safety problem caused by partially overcharge, and such strategy shows significant promise for practical applications.
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）