油页岩固定床热解反应器中内构件强化作用

在内构件(传热板和中心集气管)外热式固定床反应器中研究了油页岩热解产物生成特性,并与无内构件的相同常规固定床反应器内的油页岩热解行为对比,考察了两反应器中油页岩升温特性、热解产物分布、页岩油品质以及气体产物组成的变化规律.结果表明,内置传热板和中心集气管显著强化了反应器内的传热,相对于无内构件常规固定床反应器,料层升温速率提高了约2倍.对于依兰油页岩,其热解页岩油产率明显提高,最高达11.1 wt%(干燥基),明显高于无构件常规固定床反应器获得的页岩油产率.随着外加热炉温度的升高,内构件固定床反应器的页岩油产率逐渐增加,而无内构件常规固定床反应器的页岩油产率则明显降低.当外加热炉温度为1000℃时,前者页岩油产率是后者的2.3倍,并且内构件固定床反应器的热解水产率较低.两反应器中热解气产物组成相近,其H2与CH4之和占气体总量的70 vol%左右,热值为4406~5400 kcal/Nm3.     

基于混酸回流制备碳点的中和过程

Carbon dots (C dots) are relatively novel carbon nanomaterials that have attracted significant interest due to their unique photoluminescence, good biocompatibility, and stability. The preparation methods of C dots was usually summarized into "top-down" and "bottom-up", and mixed acid reflux is a top-down strategy that can be used to synthesize C dots, during which neutralization is a necessary step that can significantly influence the properties and potential applications of the final product. Previously, this research area mainly focused on tuning the properties of C dots by changing the starting materials and/or varying the reaction conditions; the influence of the reagents used during neutralization has been largely ignored. As the previously reported C dots prepared by mixed acid reflux were obtained from different starting materials under varied conditions, a meaningful comparison is difficult. Herein, yellow-emitting C dots were prepared by mixed acid-refluxing a carbon-rich material derived from fullerene carbon soot. For the same batch of as-prepared C dots, the influences of four reagents, i.e., NaOH, Na₂CO₃, K₂CO₃, and NH₃·H₂O, during neutralization on the structures and photoluminescence of the resulting C dots were investigated in detail. The results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy clearly showed that the reagent used during neutralization can affect the degree of dissociation of the acidic functional groups on the C dots. This is further supported by examination of the C dot/surfactant mixtures where subtle changes in the phase behavior were observed. Structural changes of the C dots cause variations in their surface states, ultimately altering the optical characteristics, including UV-vis absorption and fluorescence. Among the treated C dots, the sample prepared with Na₂CO₃ showed the strongest emission under the same excitation wavelength, while that prepared with NH₃·H₂O exhibited a distinct red shift (~8 nm) in the emission curve. The results presented herein provide clear evidence that neutralization reagent selection is important for optimizing the properties of the resulting C dots obtained by mixed acid reflux. In addition, the photoluminescence of the C dots can be influenced by their counterions, providing a novel method for tuning the properties of C dots while explaining their behavior in saline solutions. In short, the basicity of the neutralizing reagent and the type of counterions affect the structure of the C dots surface, which brings different performances. This work reminds researchers that it is necessary to use the type of neutralizing reagent as an experimental condition when preparing C dots in the future.     

Adsorption of cationic methylene blue dye using microwave-assisted activated carbon derived from acacia wood: Optimization and batch studies

This study assesses the performance of optimized acacia wood-based activated carbon (AWAC) as an adsorbent for methylene blue (MB) dye removal in aqueous solution. AWAC was prepared via a physicochemical activation process that consists of potassium hydroxide (KOH) treatment, followed by carbon dioxide (CO₂) gasification under microwave heating. By using response surface methodology (RSM), the optimum preparation conditions of radiation power, radiation time, and KOH-impregnation ratio (IR) were determined to be 360 W, 4.50 min, and 0.90 g/g respectively, which resulted in 81.20 mg/g of MB dye removal and 27.96% of AWAC’s yield. Radiation power and IR had a major effect on MB dye removal while radiation power and radiation time caused the greatest impact on AWAC’s yield. BET surface area, mesopore surface area, and pore volume of optimized AWAC were found to be 1045.56 m²/g, 689.77 m²/g, and 0.54 cm³/g, respectively. Adsorption of MB onto AWAC followed Langmuir and pseudo-second order for isotherm and kinetic studies respectively, with a Langmuir monolayer adsorption capacity of 338.29 mg/g. Mechanism studies revealed that the adsorption process was controlled by film diffusion mechanism and indicated to be thermodynamically exothermic in nature.     

Experimental Investigation on the Mass Diffusion Behaviors of Calcium Oxide and Carbon in the Solid-State Synthesis of Calcium Carbide by Microwave Heating

Microwave (MW) heating was proven to efficiently solid-synthesize calcium carbide at 1750 °C, which was about 400 °C lower than electric heating. This study focused on the investigation of the diffusion behaviors of graphite and calcium oxide during the solid-state synthesis of calcium carbide by microwave heating and compared them with these heated by the conventional method. The phase compositions and morphologies of CaO and C pellets before and after heating were carefully characterized by inductively coupled plasma spectrograph (ICP), thermo gravimetric (TG) analyses, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The experimental results showed that in both thermal fields, Ca and C inter-diffused at a lower temperature, but at a higher temperature, the formed calcium carbide crystals would have a negative effect on Ca diffusion to carbon. The significant enhancement of MW heating on carbon diffusion, thus on the more efficient synthesis of calcium carbide, manifested that MW heating would be a promising way for calcium carbide production, and that a sufficient enough carbon material, instead of CaO, was beneficial for calcium carbide formation in MW reactors.     

甚高频激发容性耦合氩等离子体的电子能量分布函数的演变

甚高频激发的容性耦合等离子体由于离子通量和能量的相对独立可控而受到人们的关注. 本文采用朗缪尔探针诊断技术测量了40.68 MHz激发的容性耦合Ar等离子体的特性(如电子能量概率分布、电子温度和密度等)随宏观参量的演变情况. 实验结果表明, 电子能量概率分布随着气压的增加从双麦克斯韦分布逐步转变为单麦克斯韦分布并最终演变为Druyvesteyn分布, 而射频激发功率的增加促进了低能电子布居数的增强; 在从等离子体放电中心移向边界的过程中, 低能电子的布居数显著下降, 而高能电子的布居则有所上升; 放电极板间距的变化直接导致了等离子体中电子加热模式的转变. 另外, 我们也对等离子体中的高低能电子密度和温度的分配情况进行了讨论.     

Measurements of the spatially resolved electron temperature and plasma potential in ferrite-core side type Ar/He inductively-coupled plasmas

Spatial distributions of the effective electron temperature (T_eff) and plasma potential were studied from the measurement of an electron energy probability function in a side type ferrite-core inductively coupled plasma with an argon–helium mixture. As the helium gas was diluted at the fixed total gas pressure of 5 mTorr in an argon discharge, the distribution of the plasma density and plasma potential changed from a concave to a flat profile, and finally became a convex profile, while all spatial profiles of T_eff were hollow shapes with helium dilution in the argon discharge. This evolution of the plasma potential with helium gas could be explained by the increased energy relaxation length (λ_ε), indicating the transition of electron kinetics from local to non-local kinetics.     

水浴加热密闭溶样石墨炉原子吸收光谱法测定化探样品中的痕量金

以王水、氟化钾、Fe3+溶液为溶剂,对化探样品进行水浴加热分解1.5 h,经泡沫塑料吸附后,于90℃以上硫脲溶液中解吸20 min,然后采用石墨炉原子吸收光谱仪测定其中的金含量。对仪器分析条件进行了优化。金的质量分数在0.1~100.0 ng/g范围内与吸光度呈良好的线性,线性相关系数r2=0.999 3,检出限为0.100 ng/g。该方法对金标准物质测定结果的相对标准偏差为5.96%~9.25%(n=12),对国家一级标准物质进行分析,测定结果与标准值相符合。该方法满足1∶50 000化探样品中痕量金的分析要求。     

叶丝在增温增湿与滚筒烘丝工序中香味组分变化分析

该文研究了制丝线增温增湿和滚筒烘丝工序加工对叶丝香味组分的影响,采用溶剂超声萃取前处理结合GC-MS法测定叶丝的香味组分,并对SIROX增温增湿工序和滚筒烘丝工序前后叶丝香味组分的相对含量进行了分析,比较了工序前后、工序间香味组分的变化趋势。结果显示:①经SIROX增温增湿工序加工后,乙酸、苯甲醇等18种组分相对含量减少,糠醇、2,4-二羟基-2,5-二甲基-3(2H)-呋喃-3-酮等6种组分相对含量增加;②经滚筒烘丝工序加工后,乙酸、麦芽酚等14种组分相对含量减少,糠醇、糠醛等6种组分相对含量增加;③经增温增湿及滚筒烘丝两工序后,乙酸、2,3-丁二醇等23种组分相对含量减少,糠醇、2,4-二羟基-2,5-二甲基-3(2H)-呋喃-3-酮等4种组分相对含量增加;④两工序间的温度、湿度剧烈变化,使叶丝内部组分发生了美拉德反应、降解反应、挥发等,香味组分经两个工序后发生了一系列显著变化。该研究对提升卷烟产品质量、优化工艺参数、开发高质量产品具有重要意义。     

Ultrafast,Low‐Cost,and Mass Production of High‐Quality Graphene

Fast, mass, and low‐cost production of high‐quality graphene, which is alluring, remains a great challenge, even though some approaches have shown potential for mass synthesis of graphene. Very recently a great breakthrough was made by Tour and co‐workers (Nature 2020, 577, 647–651): in just a second, easily exfoliated and highly crystalline graphene was produced from abundant carbon‐containing species by cost‐effective flash Joule heating with a low energy input of 7.2 kJ per gram graphene. Such an ultrafast, economic, and scalable process for high‐quality graphene production can be considered as a milestone in the graphene field and is highlighted in this article.