The modification of SiO2 by various organic groups and its influence on the properties of cobalt-based catalysts for Fischer-Tropsch synthesis

SiO₂ was modified by various organic groups before the impregnation of cobalt precursor. These modified supports and the corresponding catalysts were characterized by BET, ²⁹Si CP MAS NMR, XRD, Raman, XPS and H₂-TPR. These characterizations clearly show the changes of morphology as well as reducibility of the catalysts. The organic modification of SiO₂ remarkably influences the reducibility and catalytic properties of Co catalysts. Co catalyst supported on (CH₃)₃-modified SiO₂ exhibits high activity and C₅⁺ hydrocarbon selectivity. However, COOH-, NH₂-, and NH₂(CH₂)₂NH-modified SiO₂ distinctly suppress the catalytic activity of Co catalysts.     

Single‐Crystalline Dodecahedral and Octodecahedralα‐Fe2O3 Particles Synthesized by a Fluoride Anion–Assisted Hydrothermal Method

Despite significant advances in iron oxide nanoparticles, it is still a challenge to synthesize regular polyhedral single‐crystalline α‐Fe₂O₃ particles because the surface energies of several low‐index planes are fairly similar. In the work presented here, well‐dispersed and single‐crystalline dodecahedral and octodecahedral α‐Fe₂O₃ particles are synthesized by a facile hydrothermal method with the aid of F^? anions. The crystalline structure of the polyhedral particles is disclosed by various characterization techniques. The dodecahedral particles are of hexagonal bipyramidal shape and enclosed by twelve equivalent (101) planes. The octodecahedral particles are formed by adding six equivalent (111) planes on the two tips of a dodecahedral particle, that is, they are enclosed by twelve (101) planes and six (111) planes. The existence of F^? anions plays a crucial role in the control of polyhedral particle shape. The function of F^? anions in the shape formation of the polyhedral particles is proposed as follows: 1) A high concentration of exposed Fe³⁺ cations induces preferential adsorption of F^? anions on the (100) plane and leads to the slowest growth along the [100] direction. When the concentration of F^? anions is higher than 24 mM , a stable speed ratio of growth along the [001] and [100] directions results in the exposure of (101) planes. 2) With a lower concentration of F^? anions, six symmetrical (111) planes with low concentration of exposed Fe³⁺ cations are present at the tops of a dodecahedral particle to form an octodecahedron. Furthermore, the dodecahedral and octodecahedral α‐Fe₂O₃ particles show much stronger magnetism than the previously reported α‐Fe₂O₃ nanostructures, having coercivities of 4986 Oe and 6512 Oe, respectively. Such high coercivities are attributed to a large local magnetic anisotropy, which might be induced by the polyhedron with equivalent crystallographic planes and/or the presence of F^? anions.     

沙市中山路历史建筑改造与再利用初探

近年来,随着城市化和振兴老城区的步伐加快,历史性街区的开发要么粗暴地采取"剃头式"的大面积拆除方式,要么保守地采取成片保护的模式。该文以沙市中山路改造和再利用为例,从城市发展与历史文化之间关系的角度,提出了基于城市文化发展脉络的可持续性改造与再利用的原则和经营策略,希望能起到抛砖引玉的作用。     

Adsorption thermodynamics of CO2 on nitrogen-doped biochar synthesized with moderate temperature ionic liquid

The purpose of this work was to investigate the thermodynamic characteristics of carbon dioxide (CO₂) adsorption on a promising nitrogen-doped biochar at constant temperature and isopiestic pressure. The biochar was prepared as a CO₂ adsorbent based on catalytic pyrolysis of pristine coconut shells using urea as the nitrogen source and moderate temperature ionic liquid as a catalyst. The results showed that CO₂ adsorption on the biochar was a spontaneous, dominantly physical, exothermic, and entropy decrement process that could be well described by the slip model and the dual-site Langmuir model. Those thermodynamic parameters, including interface potential, exhibited a series of interesting tendencies with the changes in adsorption temperature and pressure. Under the conditions of 273 K and 100 kPa, the adsorption capacity and the interface potential were 4.6 mmol/g and −16.7 J/g, respectively. And the site energy ranged from 2.57 to 5.13 kJ/mol in the test conditions, which became narrow with increasing temperature. The temperature exhibited positive effects on interface potential, enthalpy change, entropy change, enthalpy change, internal energy change but negative effects on adsorption capacity, Gibbs free energy change, and Helmholtz free energy change. Interestingly, the pressure exhibited the opposite effect trends. The peak pressure with maximum temperature effect at a given temperature and the peak temperature with maximum pressure effect at a given pressure were found to exist for some thermodynamic parameters. These exhibited a different but significantly beneficial perspective to understand the mass and energy transfer during CO₂ adsorption on the biochar at constant temperature and isopiestic pressure, which have rarely been reported before.     

全麦粉的添加对油馕面团品质的影响

考察添加不同比例的全麦粉,对油馕面团粉质特性、拉伸性、糊化特性、混合粉溶剂保留特性、面团水分分布和面团面筋蛋白二级结构的影响。结果表明,随着全麦粉含量的增加面团加工性质变差,面团吸水率由65.18%增加至最大值80.30%,面团形成时间从4.13 min增加到最大值5.34 min;面团的峰值黏度、谷值黏度、回生值和衰减值呈下降趋势,而糊化温度则不断提高;拉伸能量由87 cm2降低至30 cm2,延展度由156 mm降低至92 mm,拉伸阻力由302 EU降低至242 EU。当全麦粉完全取代精粉时与精粉组相比（全麦粉取代率为0%）,混合粉的碳酸钠、蔗糖和水溶剂保留率分别增加了20.56%、18.69%和34.94%,而乳酸溶剂保留率则降低23.47%;核磁结果显示,面团中水分分布变化情况为A21/A2升高,A22/A2和A23/A2下降;傅里叶变换红外光谱仪测定结果显示,面筋蛋白结构中α-螺旋和β-折叠的总相对含量由68.57%下降为50.89%,无规卷曲相对含量增加了31.5%,稳定的二级结构下降、不稳定的二级结构相对含量上升,导致面筋蛋白结构变差。     

变电站接地网参数的计算与分析

接地网参数计算的方法主要包括两类:经验公式和数值计算。但常规的计算方法只能计算出接地网的工频接地电阻,而要准确的评估接地网的安全与否,接地网的电位分布、电位梯度分布、接触电压、跨步电压等也是必不可少的参数。在此,本文根据恒定电流场理论,应用表面电荷法和边界元法编写的接地网通用计算程序,该程序不仅可以计算出接地网的电阻,还能算出地表电位分布等参数。同时借助数据处理软件绘制得到了电位分布和电位梯度分布的三维表面图、色阶图、灰度图和等高线图。通过220k V变电站接地网为例,验证了该方法的准确性、可行性,能为变电站接地网的安全性评估提供依据。     

北方农村复合颗粒燃料取暖全生命周期评价研究

以秸秆和煤为原料制备复合颗粒燃料,利用全生命周期评价方法,研究颗粒燃烧取暖全生命周期过程中的能源消耗和环境影响。结果表明：颗粒燃料取暖全生命周期过程中能量投入为908 MJ/t,燃烧释放热量15490 MJ/t,能量产出投入比为17.1,能源转化效率较高。颗粒燃料的能量投入主要来自玉米种植,种植过程中的氮肥使用消耗较多能量。对气候变化（GWP）和酸化（AP）贡献较大的清单数据为颗粒燃料的燃烧,其中燃烧污染物排放的直接贡献最大,贡献率分别为53.22%和46.08%;对水资源消耗（WU）贡献较大的清单数据为颗粒燃料的压制,贡献率为71.56%;对富营养化潜值（EP）贡献较大的清单数据为颗粒燃料燃烧后的废渣排放,贡献率为43.40%。     

Exploring the patterns of international technology diffusion in AI from the perspective of patent citations

Scientometrics - This paper presents the findings from a thorough analysis of international technology diffusion (ITD) in artificial intelligence (AI) technologies. We construct a novel framework...     

Causes and Effects of a Water Spill from the Underground Pit of the Dashu Pyrite Mine,Southern Sichuan Basin,Southwest China

Mine Water and the Environment - In March 2019, a well was drilled in the north of the Dashu pyrite mining area in southwest China to extract shale gas from below the pyritic layer. This well...     

芳纶固载BiOBr复合材料的制备及其光催化降解染色废水

为解决粉体光催化剂在降解纺织印染废水过程中易团聚、难以回收利用的问题,采用溶剂热法制备芳纶固载BiOBr(BiOBr/AF)复合材料,对材料的微观形貌和结构进行表征与分析,研究了BiOBr/AF在可见光照射下对模拟染色废水的光催化深度降解性能.结果表明:以乙二醇为溶剂,柠檬酸为螯合剂,芳纶为固载基体,于160℃下反应1...