Pt/C,Pd/C,Pd-Bi/C催化剂的应用研究

采用浸渍法制备 Pt/C,Pd/C和 Pd- Bi/C催化剂。将三种催化剂对葡萄糖的脱氢和加氧氧化两种反应的催化效果作对比研究 ,发现三种催化剂对这两个反应有着完全相反的催化顺序 :催化脱氢时 Pt/C效率最高 ,而加氧反应中 Pd- Bi/C却具有绝对优势。为解释此结果 ,结合催化剂的表征 [2 ] ,尝试提出了催化加氧和脱氢的机理 ,并确定了 Pd- Bi/C催化剂中的最佳 Bi/Pd比和两种催化反应的最佳工艺条件。实验结论 :Pt/C用于葡萄糖催化脱氢为可行的工业化途径 ,而 Pd- Bi/C对葡萄糖的催化加氧则具有挑战酶催化过程的能力 ,有一定的市场应用前景     

Universal Brønsted-Evans-Polanyi Relations for C–C,C–O,C–N,N–O,N–N,and O–O Dissociation Reactions

Abstract  

It is shown that for all the essential bond forming and bond breaking reactions on metal surfaces, the reactivity of the metal surface correlates linearly with the reaction energy in a single universal relation. Such correlations provide an easy way of establishing trends in reactivity among the different transition metals.     

C60／C70分离,提纯技术

评述了近几年来Ｃ６０／Ｃ７０分离提纯技术的发展。指出这一领域的研究意义和发展趋势。     

New Trends and Future Opportunities in the Enzymatic Formation of C−C,C−N,and C−O bonds

Organic chemistry provides society with fundamental products we use daily. Concerns about the impact that the chemical industry has over the environment is propelling major changes in the way we manufacture chemicals. Biocatalysis offers an alternative to other synthetic approaches as it employs enzymes, Nature's catalysts, to carry out chemical transformations. Enzymes are biodegradable, come from renewable sources, operate under mild reaction conditions, and display high selectivities in the processes they catalyse. As a highly multidisciplinary field, biocatalysis benefits from advances in different areas, and developments in the fields of molecular biology, bioinformatics, and chemical engineering have accelerated the extension of the range of available transformations (E. L. Bell et al., Nat. Rev. Meth. Prim. 2021 , 1, 1–21). Recently, we surveyed advances in the expansion of the scope of biocatalysis via enzyme discovery and protein engineering (J. R. Marshall et al., Tetrahedron 2021 , 82, 131926). Herein, we focus on novel enzymes currently available to the broad synthetic community for the construction of new C−C, C−N and C−O bonds, with the purpose of providing the non-specialist with new and alternative tools for chiral and sustainable chemical synthesis.     

Recent Advances in Electrochemical,Ni-Catalyzed C−C Bond Formation

Nickel-catalyzed cross-electrophile coupling (XEC) is an efficient method to form carbon-carbon bonds and has become an important tool for building complex molecules. While XEC has most often used stoichiometric metal reductants, these transformations can also be driven electrochemically. Electrochemical XEC (eXEC) is attractive because it can increase the greenness of XEC and this potential has resulted in numerous advances in recent years. The focus of this review is on electrochemical, Ni-catalyzed carbon-carbon bond forming reactions reported since 2010 and is categorized by the type of anodic half reaction: sacrificial anode, sacrificial reductant, and convergent paired electrolysis. The key developments are highlighted and the need for more scalable options is discussed.     

乙烯联产混合C4,C5烃的利用

本文主要介绍了国内外对乙烯联产混合Ｃ４、Ｃ５烃的利用。并由此转化为高值化产品，降低乙烯生产成本，提高经济效益     

High-strength medium-entropy (Ti,Zr,Hf)C ceramics up to 1800°C

Medium-entropy (Ti,Zr,Hf)C ceramics were prepared by hot pressing a dual-phase medium-entropy carbide powder with low oxygen content (0.45 wt%). The results demonstrate that the medium-entropy (Ti,Zr,Hf)C ceramics sintered at 2100°C had a relative density of 99.2% and an average grain size of 1.9 ± 0.6 μm. The flexural strength of (Ti,Zr,Hf)C carbide ceramics at room temperature was 579 ± 62 MPa. With an increase in temperature to 1600°C, the flexural strength showed an increase up to 619 ± 57 MPa, and had no significant degradation even up to 1800°C. The high-temperature flexural strengths of (Ti,Zr,Hf)C were obviously higher than those of the monocarbide ceramics (TiC, ZrC, and HfC). The primary strengthening mechanism in (Ti,Zr,Hf)C could be attributed to the high lattice parameter mismatch effects between TiC and ZrC, which not only inhibited the fast grain coarsening of (Ti,Zr,Hf)C ceramics, but also increased the grain-boundary strength of the obtained ceramics.     

ZN—A,B,C智能多路流量仪

本文介绍ZN系列智能多路气体、液体流量仪。剖析其基本原理,叙述基本功能,表明了这种仪表的优越性。一、引官气体、液体流量的测量广泛存在于化工、轻工等各行各业,流量测量仪表已成为企业能源管理与控制的重要组成部份,它直接影响着企业的升级.     

自烧结C,TiC／C和SiC—B4C／C材料的热处理行为

本文研究了自烧结Ｃ，ＴｉＣ／Ｃ和ＳｉＣ－Ｂ４Ｃ／Ｃ材料高处理后的行为变化，实验发现随着处理温度的升高，各类材料的收缩率和重量损失随之增加，自烧结Ｃ和ＴｉＣ／Ｃ材料的弯曲强度逐渐下降，而ＳｉＣ－Ｂ４Ｃ／Ｃ复合材料的弯曲强度在２２７３Ｋ时达到一个最高值。     

BippyPhos: A Highly Versatile Ligand for Pd-Catalyzed C−N,C−O and C−C Couplings

Numerous ligands have been designed for the Buchwald-Hartwig Amination (BHA). Among the ligands developed is BippyPhos. This ligand was originally designed to enable a coupling of primary amines with aryl halides. Further studies showed that the ligand has fairly broad utility for Pd-catalyzed C−N, C−O and C−C couplings. This review describes the various Pd-catalyzed applications involving BippyPhos as a supporting ligand. While BippyPhos may not often be the most optimal ligand for various Pd-catalyzed couplings, it typically will provide adequate results as a starting point prior to screening for optimization.     

高效液相色谱同时测定维生素C,苯甲酸,山梨酸,糖精钠

用反相高效液相色谱同时测定维生素Ｃ、苯甲酸、山梨酸、糖精钠,方法简便,快速,准确度和精密度都很谪,回收率高,重现性好,变异系数为４．７％。     

Microstructure,Thermophysical, and Ablative Performances of a 3D Needled C/C–SiC Composite

The microstructure, thermophysical, and ablative properties of a 3D needled C/C–SiC composite fabricated by chemical vapor infiltration combined with the liquid silicon infiltration process were investigated. The composite was composed of 64 wt% C, 20 wt% SiC, and 16 wt% Si. The thermal diffusivity in the plane direction was much higher than that in the through-the-thickness direction, while it was reversed for the coefficients of thermal expansion, and the differences reduced with increasing temperature. The linear and mass ablation rates in the oxyacetylene flame were 0.0039 mm/s and 0.0016 g/s on average, respectively. Various ablation processes including sublimation, thermochemical denudation, and oxidations occurred in different sections.     

快速,大量提纯C60的方法

介绍两种速，大量提纯Ｃ６０的方法：（１）采用复结晶及活性炭吸附、吸滤相结合的方法，得到纯Ｃ６０及Ｃ７０富集物；（２）采用中性氧化铝－活性炭／硅胶层吸滤法制备纯Ｃ６０。     

Surface Activities, Foam Properties, HLB, and Krafft Point of Some n-Alkanesulfonates (C14–C18) with Different Isomeric Distributions

A homologue series of sodium secondary n-alkanesulfonates (C₁₄, C₁₆ and C₁₈) were obtained by photosulfochlorination process with two different reaction conditions. Different length chains with different isomeric distributions of n-alkanesulfonates are expected to present variations in physicochemical properties. In this investigation, the relationships between their isomeric distribution and their chain length and micellar behaviors were thoroughly explored. Their CMC at different temperatures were determined using specific conductivity and surface tension measurements. Through surface tension isotherms, the surface activities (??_CMC) were obtained. The surface absorption amounts (??_max) and the molecular areas (A _min) were calculated using Gibb??s equation. As expected, these surfactants exhibit good surface properties. It was shown that the CMC values increase with increasing the percentage of secondary isomers, with a surface tension decrease. It was also shown that the CMC values decrease with increasing chain length. The HLB values were calculated for each surfactant and the results obtained suggest that they are O/W emulsifiers. The foam properties of synthesized surfactants were evaluated and compared to those obtained for commercial samples. It was shown that the foamability is influenced both by the length of the hydrophobic moiety and the percentage of secondary isomers. It can be easily concluded that the C₁₄ sulfonates show the best foaming properties independently of their isomeric distribution. The Krafft point values obtained indicate that the micellization and the surfactant solubility mainly depend on the proportion of secondary isomers and the length of hydrophobic moiety.     

广州乙烯工程副产C5,C9馏份的利用探讨

本文介绍了石脑油和轻柴油裂解生产乙烯装置副产的C_5、C_9馏份的多种用途,特别作为发展技术密集、附加产值高的精细化工的原料。并探讨了广州乙烯工程副产C_5、C_9馏份的综合利用方案,对C_5馏份提出了近期、中期及远期的利用对策,C_9馏份则建议为混合馏份的利用。     

B4C(W,Ti)C陶瓷复合材料的制备及其性能

采用热压烧结工艺制备了B4C/(W,Ti)C陶瓷复合材料.研究表明:B4C/(W,Ti)C陶瓷材料烧结时将产生化学反应,反应产物为TiB2和W2B5.B4C/(W,Ti)C陶瓷材料的性能与(W,Ti)C的含量密切相关,随(W,Ti)C含量的增加,材料的致密度、抗弯强度和断裂韧性逐渐增加,硬度逐渐减小;当保温时间低于50min时,材料的致密度、抗弯强度和硬度显著降低;B4C/(W,Ti)C陶瓷复合材料的最佳性能参数为:抗弯强度693MPa,维氏硬度23.5GPa,断裂韧性3.9MPa·m1/2.磨损实验表明,B4C/(W,Ti)C陶瓷材料在低速小载荷的实验条件下,耐磨性能优异,在高速大载荷的实验条件下,磨损过程中局部点的高温导致试样表面发生氧化,加剧了材料的磨损.