Ultrahigh Loading Copper Single Atom Catalyst for Palladium-free Wacker Oxidation

Wacker oxidation is an industry-adopted process to transform olefins into value-added epoxides and carbonyls. However, traditional Wacker oxidation involves the use of homogeneous palladium and copper catalysts for the olefin addition and reductive elimination. Here, we demonstrated an ultrahigh loading Cu single atom catalyst(14% Cu, mass fraction) for the palladium-free Wacker oxidation of 4-vinylanisole into the corresponding ketone with N-methylhydroxylamine hydrochloride as an additive under mild conditions. Mechanistic studies by ¹⁸O and deuterium isotope labelling revealed a hydrogen shift mechanism in this palladium-free process using N-methylhydroxylamine hydrochloride as the oxygen source. The reaction scope can be further extended to Kucherov oxidation. Our study paves the way to replace noble metal catalysts in the traditional homogeneous processes with single atom catalysts.     

Highly Efficient Oxygen Reduction Reaction Fe-N-C Cathode in Long-durable Direct Glycol Fuel Cells

The oxygen reduction reaction in direct glycol fuel cells heavily relies on noble metal-based electrocatalysts. In this work, novel Pt group metal-free catalysts based on porous Fe-N-C materials are successfully synthesized as catalysts with high activity and durability for the cathode oxygen reduction reaction (ORR). Through the encapsulation of NH₄SCN salt, the surface elements and pore structure of the catalyst are effectively changed, and the active sites of Fe effectively are increased. The half-wave potential of the best Fe-N-C catalyst was –0.02 V vs. Hg/HgO in an alkaline environment. The porous Fe-N-C catalyst possesses a large specific surface area(1158 m²/g) and shows good activity and tolerance to glycol. The direct glycol fuel cell with the Fe-N-C cathode achieved a maximum power density of 62.2 mW/cm² with 4 mol/L KOH and 4 mol/L glycol solution at 25 °C and maintained discharge for more than 250 h at a 50 A/cm² current density.     

Electrodeposited molybdenum-doped Co3O4 nanosheet arrays for high-performance and stable hybrid supercapacitors

Journal of Solid State Electrochemistry - Long-cycle stability and high-energy density are big challenges for developing high-performance hybrid supercapacitor (HSC) electrode materials. In this...     

Establishment and validation of an SIL-IS LC–MS/MS method for the determination of ibuprofen in human plasma and its pharmacokinetic study

In this work, we developed and validated a highly sensitive, rapid and stable LC–MS/MS method for the determination of ibuprofen in human plasma with ibuprofen-d3 as a stable isotopically labeled internal standard (SIL-IS). Human plasma samples were prepared by one-step protein precipitation. The chromatographic separation was achieved on a Poroshell 120 EC-C₁₈ (2.1 × 50 mm, 2.7 μm). Aqueous solution (containing 0.05% acetic acid and 5 mm NH₄Ac) and methanol were selected as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in negative ion mode. Multiple reaction monitoring mode was used for quantification using target fragment ions m/z 205.0 → 161.1 for ibuprofen and m/z 208.0 → 164.0 for SIL-IS, respectively. This method exhibited a linear range of 0.05–36 μg/ml for ibuprofen with correlation coefficient >0.99. Mean recoveries of ibuprofen in human plasma ranged from 78.4 to 80.9%. The RSD of intra- and inter-day precision were both < 5%. The accuracy was between 88.2 and 103.67%. The matrix effect was negligible in human plasma, including lipidemia and hemolytic plasma. A simple, efficient and accurate LC–MS/MS method was successfully established and applied to a pharmacokinetic study in healthy Chinese volunteers after a single oral administration of ibuprofen granules.     

2,3,3,3-四氟丙烯的合成研究

本文综述了目前2,3,3,3-四氟丙烯（HFO-1234yf）的合成路线,包括氟-氯交换、脱卤化氢、脱卤、脱卤醇、脱次氯酸乙酰酯、脱水、加氢脱卤、脱氢、高温热解、SF₄参与的氟化反应、脱羧等。其中,以2-氯-3,3,3-三氟丙烯（HCFO-1233xf）为原料的氟-氯交换路线、以1,1,1,2,3-五氟丙烷（HFC-245eb）为原料的脱氟化氢路线和2-氯-1,1,1,2-四氟丙烷（HCFC-244bb）为原料的脱氯化氢路线均具有原料容易合成得到、容易实现气相连续化大规模生产的优势,具有工业化价值。另外,分析对这些路线拥有独立知识产权的氟化工企业现状,提出今后HFO-1234yf领域的研究重点。     

泡沫塑料富集-火焰原子吸收光谱法测定金矿石中金

采用聚氨酯泡塑富集硫脲洗脱-火焰原子吸收光谱法测定金矿石中金。对样品称样量、硫脲洗脱时间、磷酸三丁酯的吸附效果和铁元素的干扰等工作条件进行了优化,解决了泡沫塑料吸附效率低和铁元素的干扰等技术性难题,提高了分析结果的精密度和准确度,弥补了传统的泡沫塑料富集-火焰原子吸收光谱法测定金矿石中金量的不足,方法检出限为0.06 μg/g,测定范围为 0.2 μg/g～100 μg/g,测定结果与标准值符合性较好,无显著性差异,精密度(RSD, n = 9) 小于2%。方法具有快速、简便、实用等优点,分析误差满足常规化学分析法的要求,能满足金矿石中金量的快速、准确测定。     

电化学免疫传感器检测TET1蛋白

基于Ten-eleven translocation 1(TET1)蛋白催化5-甲基胞嘧啶(5-Methylcytosine,5mC)生成5-羟甲基胞嘧啶(5-Hydroxymethylcytosine,5hmC),结合5hmC抗体的免疫识别反应,建立了一种电化学分析方法用于TET1蛋白的特异性检测.以金纳米颗粒(Au...     

Ni基乙烷脱氢催化剂的性能及其改进

过渡金属Ni是地球上储量丰富的金属元素, 在加氢脱硫、重整制氢等催化领域应用非常广泛, 但是关于Ni基催化剂在烷烃脱氢方面的研究较少; 因此, 本工作采用不同的方法, 制备了三种结构的Ni基负载催化剂, 即尖晶石分解型、浸渍型和钙钛矿析出型, 并在700 ℃、C₂H₆-N₂气氛中和50 mL•min^-1气体流速下, 探索了它们的乙烷脱氢性能. 结果表明: 尖晶石分解型催化剂Ni_1-xCu_xCr₂O₄还原后在Cr₂O₃表面形成Ni-Cu合金颗粒, 能有效钝化Ni的C—C键断裂活性, 提高乙烯的选择性. Ni含量过高时, Ni不能有效地分散而形成大的金属团簇, 造成乙烷过度裂解, 乙烯选择性较低. 浸渍负载型催化剂Ni_xM_y/Al₂O₃ (M为Cu或Ag) 比表面积大, 表面活性位点分散, 但活性金属与载体结合力弱, 在高温下不稳定; Cu或Ag与Ni形成合金, 可有效提高乙烯选择性, Ag较Cu的效果更佳. 钙钛矿析出型催化剂LaCr_1-xNi_xO₃(LCNi-100x)在还原气氛中析出均匀细小的Ni颗粒, 其与基体结合力强, 抗积碳性能和稳定性较高; 含15% Ni的LCNi-15还原后(R-LCNi-15)表现出最好的催化性能, 乙烯产率最高(24%), 同时具有较好的抗积碳性能和稳定性以及氧化再生性.     

Rapid qualitative profiling and quantitative analysis of Juglandis Mandshuricae Cortex and seven flavonoids by ultra-high performance liquid chromatography–quadrupole/orbitrap high-resolution mass spectrometry

Juglandis Mandshuricae Cortex is the bark of Juglans mandshurica Maxim., which has been used as a folk medicine plant in China and India. In this study, an ultra-high performance liquid chromatography–quadrupole/orbitrap high-resolution mass spectrometry method was developed to clarify and quantify the chemical profiling of Juglandis Mandshuricae Cortex rapidly. A total of 113 compounds were characterized. Among them, seven flavonoids were simultaneously quantified in 15 min, including myricetin, myricetrin, taxifolin, kaempferol, quercetin, quercitrin, and naringenin. The method was validated for accuracy, precision, and the limits of detection and quantification. All calibration curves showed a good linear relationship (r > 0.9990) within test ranges. The intra- and inter-day relative standard deviations were less than 2.16%. Accuracy validation showed that the recovery was between 95.6 and 101.3% with relative standard deviation values below 2.85%. The validated method was successfully applied to determine the contents of seven flavones in Juglandis Mandshuricae Cortex from seven sources and the contents of these places were calculated respectively. This method provides a theoretical basis for further developing the medicinal value of Juglandis Mandshuricae Cortex.     

Isolation of three glucaric acids from Leonurus japonicus Houtt. by using high-speed countercurrent chromatography combined with semi-preparative high-performance liquid chromatography

The isomerism of glucaric acids and the complexity of the composition of Leonurus japonicus Houtt. increased the difficulty of the separation of glucaric acids from the herb. In the present study, three glucaric acids were isolated from Leonurus japonicus Houtt. by using high-speed countercurrent chromatography combined with semi-preparative high-performance liquid chromatography. Cation exchange resin chromatography was applied to remove the alkaloids and enrich the glucaric acid fractions. Preliminary separation of the glucaric acid extract by high-speed countercurrent chromatography was carried out at 45℃ by using an optimized solvent system of ethyl acetate/n-butanol/formic acid/water (1:1:0.01:2, v/v/v/v) with satisfied stationary phase retention and separation factor. The semi-preparative high-performance liquid chromatography was used for further separation and purification of the target fractions, and three monomeric compounds were obtained with purities of 90.0, 91.0, and 95.3%. UV spectroscopy, NMR spectroscopy, and mass spectrometry were employed to identify their structures, which were assigned as 2-syringyl glucaric acid, 2,4-disyringyl glucaric acid, and 3,4-disyringyl glucaric acid, respectively, and 2,4-disyringyl glucaric acid was reported for the first time.