低阶煤热萃取物与瘦煤共炭化焦炭的微观结构及显微强度研究

以众唯瘦煤作为主炼焦煤,大同长焰煤萃取物作为添加剂,进行共炭化处理制备坩埚焦。利用偏光显微镜法定量研究焦炭光学显微组分,获得焦炭的各向异性指数(DRAS);采用XRD及分峰拟合的方法研究了焦炭的微晶粒径(L_c)、芳香缩合度(I_a)、石墨化度(g);利用Raman光谱结合分峰拟合的方法研究了焦炭中理想石墨微晶含量(I_g)。对所得焦炭的光学显微组分进行定量分析发现:大同长焰煤热解萃取产物的添加对共炭化焦炭的光学显微组分有显著的影响,利用偏光显微镜法计算出焦炭的DRAS与XRD和Raman计算的焦炭微晶参数呈现很好一致性。并且,焦炭的显微强度与其微观结构关联性极大。     

Pt/ZnO 在室温水相无碱条件下绿色催化苯甲醇选择性氧化

醇类化合物选择性氧化是有机合成中一个非常重要的反应, 在精细化工领域具有重要应用. 而以水为绿色溶剂, 分子氧为绿色氧化剂实现醇类化合物选择性氧化是绿色化学领域的一大挑战. Pt 催化剂由于其优异的活化氧气和 C-H 键的能力在该反应中得到了广泛应用. 但是, 常规的 Pt 催化剂通常需要在较高温度和较高氧气压力以及加碱的条件下才能发挥作用, 从而引起了催化剂腐蚀等一系列问题. 从绿色化学角度出发, 进一步优化 Pt 催化剂, 让其能够在室温无碱条件下以空气为氧化剂选择性氧化醇类合成羰基化合物具有重要的研究价值和应用前景.本文通过化学还原法制备了 Pt/ZnO 催化剂, 系统研究了该催化剂在水相无碱条件下选择性氧化苯甲醇生成苯甲醛反应中的催化性能. X 射线电子衍射和透射电镜等结果表明, Pt 颗粒较小(3.2 ± 0.3 nm), 均匀分散在 ZnO 载体上; X 射线光电子能谱表明 ZnO 载体能够稳定 Pt 纳米颗粒表面的 Pt0物种. 上述催化剂在水相苯甲醇选择性氧化反应中, 在室温下即可催化空气高选择性氧化苯甲醇到苯甲醛 (选择性>99%), 并表现出比 Pt/SiO2, Pt/Al2O3, Pt/TiO2, Pt/Ca(Mg)-ZSM-5 等催化剂更为优异的催化活性. 这可归结于 Pt 和 ZnO 之间的协同作用. 该协同作用通过动力学实验和密度泛函理论计算 (DFT)得到了证实. 氧分压实验表明, 在以空气为氧化剂时, O2的活化并不是限制 Pt/ZnO 催化活性的关键因素, 而动力学同位素效应实验则证实了苯甲醇的 C-H 键活化是整个反应的决速步骤. 通过构建不同的理论模型, 分别计算了 Pt/ZnO 界面处以及纯 Pt 位点上苯甲醇选择性氧化的反应过程. 结果表明, 苯甲醇和氧气分子倾向于分别在 ZnO 和 Pt 上进行吸附, 随后由吸附的氧气分子来活化苯甲醇中的 C-H 键, 进而生成苯甲醛和水. 而当 ZnO 不参与苯甲醇的吸附活化时, 整个反应的活化能会大大提高, 表明 ZnO 和 Pt 之间的协同作用对于整个反应至关重要. 此外, Pt/ZnO 表现出非常优异的稳定性, 循环使用 4 次后, 催化剂结构以及催化活性没有显著变化.进一步向 Pt/ZnO 催化剂中引入少量 Bi 元素对 Pt 的电子结构进行修饰, 可以将 Pt/ZnO 的催化活性提高 3 倍. 所制备的 Pt/Bi-ZnO 复合物是目前报道的相同条件下催化苯甲醇选择性氧化反应转化频率 (45.1 h-1)最高的催化剂.     

Ruthenium(II)‐Catalyzed Synthesis of Spirobenzofuranones by a Decarbonylative Annulation Reaction

The first decarbonylative insertion of an alkyne through C?H/C?C activation of six‐membered compounds is reported. The Ru‐catalyzed reaction of 3‐hydroxy‐2‐phenyl‐chromones with alkynes works most efficiently in the presence of the ligand PPh₃ to provide spiro‐indenebenzofuranones. Unlike previously reported metal‐catalyzed decarbonylative annulation reactions, in the present decarbonylative annulation reaction, the annulation occurs before extrusion of carbon monoxide.     

Near‐Infrared Fluorescent Molecular Probe for Sensitive Imaging of Keloid

Early detection of skin diseases is imperative for their effective treatment. However, fluorescence molecular probes that allow this are rare. The first activatable near‐infrared (NIR) fluorescent molecular probe is reported for sensitive imaging of keloid cells, skin cells from abnormal scar fibrous lesions. As keloid cells have high expression levels of fibroblast activation protein‐alpha (FAPα), the probe (FNP1) is designed to have a caged NIR dye and a FAPα‐cleavable peptide substrate linked by a self‐immolative segment. FNP1 can quickly and specifically turn on its fluorescence at 710 nm by 45‐fold in the presence of FAPα, allowing it to effectively recognize keloid cells from normal skin cells. Integration of FNP1 with a simple microneedle‐assisted topical application enables sensitive detection of keloid cells in metabolically‐active human skin tissue with a theoretical limit of detection down to 20 000 cells.     

Selective C−H Halogenation with a Highly Fluorinated Manganese Porphyrin

The selective C?H functionalization of aliphatic molecules remains a challenge in organic synthesis. While radical chain halogenation reactions provide efficient access to many halogenated molecules, the use of typical protocols for the selective halogenation of electron‐deficient and strained aliphatic molecules is rare. Herein, we report selective C?H chlorination and fluorination reactions promoted by an electron‐deficient manganese pentafluorophenyl porphyrin catalyst, Mn(TPFPP)Cl. This catalyst displays superior properties for the aliphatic halogenation of recalcitrant, electron‐deficient, and strained substrates with unique regio‐ and stereoselectivity. UV/Vis analysis during the course of the reaction indicated that an oxo‐Mn^V species is responsible for hydrogen‐atom abstraction. The observed stereoselectivity results from steric interactions between the bulky porphyrin ligand and the intermediate substrate radical in the halogen rebound step.     

Thioketone‐Directed Palladium(II)‐Catalyzed C−H Arylation of Ferrocenes with Aryl Boronic Acids

A palladium(II)‐catalyzed thioketone‐chelation‐assisted direct C?H arylation of ferrocenes is described. With thioketone as an efficient directing group, various monoaryl‐ and diaryl‐substituted thiocarbonylferrocenes were obtained by palladium‐catalyzed direct C?H functionalization in high yields under mild and base‐free reaction conditions. Furthermore, the arylated thiocarbonylferrocene could undergo diverse transformations.     

Electric conductivity of concentrated aqueous solutions of propionic acid, sodium propionate and their mixtures

Specific electric conductivity (EC) of concentrated aqueous solutions of propionic acid (PA), sodium propionate (SP), and water/PA/SP mixtures is measured in the temperature range of 15–90°C. Specific EC passes a maximum at the increase in the electrolyte concentration in the mixtures of water/PA, water/SP, and water/PA/SP containing a similar PA concentration. The maximum EC value of the aqueous PA solution at the given temperature is used as the generalizing term. It is shown that the values of reduced EC (ratio of EC and its maximum value at the given temperature) fall on a single curve in the whole studied range of temperatures and concentrations of the water/PA mixture. The EC activation energy is calculated for all the studied solutions. It is found that the EC activation energy of these solutions decreases at the temperature increase and grows at the increase of the concentration of electrolyte.     

Using the rotating disk electrode for evaluating film porosity of conductive polymers

Conductive polymer (poly-o-phenylenediamine and poly-3-methylthiophene) films were synthesized on a rotating disk electrode. Dependences of the limiting penetration currents on the nature of the polymer and film thickness were obtained in solutions containing electroactive substances (hydroquinone, quinone) reducing or oxidiring at redox potentials beyond the range of polymer electroactivity (selected by adjusting the pH value). The transport of hydroquinone and quinone test species through the pores in polymer films was examined based on the results of these studies, and the degree of film porosity was evaluated.     

Thermal degradation of copolymers from vinyl acetate and vinyl alcohol

The thermal degradation of poly(vinyl acetate) (PVA), poly(vinyl alcohol) (PVAL), vinyl acetate-vinyl alcohol (VAVAL), vinyl acetate-vinyl-3,5-dinitrobenzoate (VAVDNB) and vinyl alcohol-3,5-dinitrobenzoate (VALVDNB) copolymers have been studied using differential thermal analysis (DTA) and thermogravimetry (TG) under isothermal and dynamic conditions in nitrogen. Thermal analysis indicates that PVA and PVAL are thermally more stable than VAVAL copolymers, being PVAL the most stable polymer. The presence of small amounts of vinyl-3,5-dinitrobenzoate (VDNB) in PVA or PVAL produces a marked decrease in the thermal stability of both homopolymers, being VALVDNB copolymers the less stable materials. The apparent activation energy of the degradative process was determined by the Kissinger and Flynn-Wall methods which agree well.     

Isothermal kinetics of dehydration of equilibrium swollen poly(acrylic acid) hydrogel

An isothermal dehydration of equilibrium swollen poly(acrylic acid) hydrogel in the temperature range from 306 to 361 K was investigated. The specific parameters connected with shape of the conversion curves were defined. The activation parameters (E, lnA) of the isothermal dehydration of equilibrium swollen poly(acrylic acid) hydrogel were calculated, using Johnson-Mehl-Avrami (JMA), ‘initial rate’ and ’stationary point’ methods. The reaction models for the investigated dehydration are determined using the ‘model-fitting’ method. It was established that both, the reaction model and activation parameters of the hydrogel dehydration were completely different for the isothermal process than for the non-isothermal one. It was found that the increase in dehydration temperature lead to the changes in isothermal kinetic model for the investigated hydrogel dehydration. It was established that the apparent activation energy (E) of hydrogel dehydration is similar to the value of the molar enthalpy of water evaporation.