蒽醌法合成过氧化氢催化剂的研究进展

过氧化氢（H₂O₂, 俗称双氧水）, 由于其强氧化性常用作漂白剂、消毒剂, 同时也作化工原料。目前工业上生产过氧化氢的主要方法为蒽醌法, 全球近99%的产品均通过蒽醌法制得。研究具有高活性、高选择性及经济性的催化剂是合成过氧化氢所面对的最具挑战性的课题, 同时也是工业催化领域的研究热点之一。主要针对蒽醌法制过氧化氢催化剂, 综述了各种活性组分、载体及助剂在蒽醌加氢催化剂中的研究进展, 并简单探讨了各种活性组分的优缺点, 概括了各种载体、助剂的作用, 以期对过氧化氢催化剂的合成制备提供一些有益的启示。     

失效双氧水催化剂中钯的浸出-沉淀富集效率研究

研究了从失效双氧水催化剂中富集钯的工艺，采用“焙烧浸出-硫化沉钯”的工艺实现了钯的高效富集。重点考察在浸出中硫酸浓度、浸出温度、浸出时间、盐酸浓度、NaClO3用量对富集倍数的影响。研究了富集钯的最佳工艺条件，结果表明，钯平均富集12.09倍，钯的平均回收率为99.55%。     

Controllable electrodeposition synthesis of Pd/TMxOy-rGO/CFP composite electrode for highly efficient methanol electro-oxidation

A novel and high-efficiency Pd/TM_xO_y-rGO/CFP (TM_xO_y = Co₃O₄, Mn₃O₄, Ni(OH)₂) electrocatalyst for directly integrated membrane electrode was synthesized by controllable cyclic voltammetry electrodeposition combined with hydrothermal process. The results showed excellent performance towards methanol oxidation reduction. The Pd/Co₃O₄-rGO/CFP as-prepared catalyst has the best electrocatalytic activity, and mass activity is 5181 mA·mg⁻¹_Pd, which is about 40 times and 4.3 times that of the commercial Pd/C and Pt/C catalyst (JM). It can be attributed that the small size of Pd nanoparticle, uniformity of distribution, and the synergistic interaction between transition metal oxide on the support surface and Pd nanoparticles. The prepared Pd/TM_xO_y-rGO/CFP composite electrode is a promising catalyst for integrated membrane electrode assembly of proton exchange membrane fuel cells in the future.     

Direct conversion of syngas to DME as a green fuel in a high pressure microreactor: Influence of slurry solid content on characteristics and reactivity of washcoated CuO–ZnO–Al2O3/HZSM-5 nanocatalyst

Microchannels of a stainless steel microreactor were successfully washcoated with slurry of Cu–ZnO–Al₂O₃/HZSM-5 (CZAZ) nanocatalyst with different concentrations (10, 20 and 30 wt.%). The properties of nanocatalyst and the washcoated microchannels were investigated by XRD, FESEM, N₂ physisorption, FTIR, EDX-Dot mapping and EDX-Line mapping analysis. The best adherence was observed for 20 wt.% catalyst which has a uniform coating, almost no cracks and homogenous dispersion of copper and zinc. Trend of weight gain during 10 soaks in catalyst slurry was very slow for 10 wt.% but faster for 20 and 30 wt.%. Low amount of weight gain was observed for the last soaks of catalyst slurry in the case of 30 wt.% washcoating. The performance of microreactor with different slurry concentrations were evaluated in direct synthesis of DME at 200–300 °C, 60–150 cm³/min and 40 bar. Regardless of slurry concentration, the microreactor exhibited a better reactivity in comparison to fixed-bed reactor performance. Among three different slurry concentrations, 20 wt.% catalyst slurry revealed the best reactivity in direct DME synthesis. The reduction in reactor performance at higher flow rates was significant in the fixed-bed reactor while microreactor, particularly 20 wt.% washcoated channels, revealed less drastic reduction.     

Diffuse characteristics and piezoelectric properties of Tb-doped BCZT ceramics with CaCl2 as sintering aid

Lead-free ceramics 47(Ba_0.7Ca_0.3)TiO₃–0.53Ba(Zr_0.2Ti_0.8)O₃ (BCZT) + 0.2 mol% Tb and xCaCl₂ (x = 0.1,0.2 and 0.3 wt%) were prepared at different temperatures (1300, 1350 and 1410 ℃) by solid-state reaction method. The experimental results reveal that dopants can effectively promote the growth of grain at relatively low sintering temperature and CaCl₂ as the well sintering aid can produce a pronounced liquid phase to fill the gap between grains sintered at 1410 ℃ with 0.2 wt%. Relative densities and piezoelectric properties of samples can be improved by the introduction of Tb and CaCl₂. Comparing with pure BCZT, the residual polarization (P_r) and piezoelectric coefficient (d₃₃^*) of ceramics increase from 8.2 to 11.4 μC/cm² and 568–720 pm/V with 0.2 mol% Tb and 0.2 wt% CaCl₂ doped. The enhanced properties of samples may be related to the appearance of liquid phase which can increase relative densities of ceramics to 96% and the form of defect dipole in ceramics. Moreover, introduction of CaCl₂ makes dielectric peaks (T_c) move to the high-temperature zone about 13 ℃ and become more and more diffuse (γ = 1.71–1.86), which may have the potential electro-caloric effect application in ferroelectrics.     

湿法冶金结合喷雾干燥-热解工艺纯化和控制钨颗粒

钨因其独特的物理化学性能而被广泛的应用于半导体和高温材料。本文依次采用离子交换、溶剂萃取、重结晶、喷雾干燥和煅烧还原的方法对钨酸铵进行处理,成功制备出高纯、分散性好的微米级球形钨粉。其中,利用湿法冶金去除原料中的杂质金属,喷雾干燥和煅烧还原过程控制最终钨粉形貌结构和粒径分布。本文研究了喷雾干燥过程中溶液浓度对雾化粉末形貌的影响规律,并揭示了雾化粉末分解还原过程中的机理。该方法制备出的钨粉纯度高于99.995wt%,平均尺寸约为1.5um。本研究中的湿法冶金和粉末技术可用于合成其他具有高性能要求的金属粉末。     

电镀软金用硫基无氰金配合物电解质研究进展

电镀金工艺中金氰化物([Au(CN)_2]~-)溶液在过程中会释放出剧毒的游离氰化物离子,严重危害到生产人员和自然环境的健康;此外,它们还会对光刻胶造成一定的破坏。近年来无氰电解质得到了发展。基于对50余篇文献的分析,本文比较了亚硫酸金([Au(SO_3)_2]_3~-)、硫代硫酸金([Au(S_2O_3)_2]_3~-)和二者混合电解液,以及其他硫基体系的组成、操作条件、电沉积机理和优缺点,并展望了基于无氰配体电解液的软金电镀技术的研究趋势和发展方向。     

低温电化学合成氨催化剂研究进展

传统的高温高压Haber-Bosch法合成氨工艺消耗大量化石能源,并排放大量的温室气体。在常温常压下通过电化学方法将氮还原成氨是一种潜在策略。电化学固氮领域的主要研究方向之一是通过开发有效的氮还原催化剂来提高电流效率和氨产率。基于对50多篇文献的分析,本文综述了近20年来电化学合成氨催化剂的研究进展,通过对低温下电化学合成氨的金属基和非金属基不同催化剂以及催化效率进行总结和比较,关注具有高法拉第效率和高氨产率的几种金基催化剂,以及电解质性质、掺杂改性对于开发高效的过渡金属基、非金属基催化剂的重要性,对比分析了这3类催化剂的优缺点以及发展潜力。     

高强高导电Cu-Cr-Zr合金时效过程中组织和性能的演化

为阐明Cu-Cr-Zr合金时效过程中的组织性演化规律,本文对经过连续铸造、固溶和冷拉拔的Cu-1.5Cr-0.2Zr合金进行时效处理,研究了时效温度和时效时间对该合金组织和性能的影响,并对该合金在不同温度下的时效行为进行了分析。结果表明:对Cu-Cr-Zr合金施以450℃/3 h时效可获得最佳的性能组合,其显微硬度和导电率分别为241 HV和72.5%IACS。时效时合金化元素的脱溶使合金基体的过饱和度降低,发生了合金化元素再分配过程。时效态Cu-Cr-Zr合金的断裂机制为微孔聚集型延性断裂。     

ICP-AES法测定三苯基膦氯化铑中的微量杂质

将三苯基膦氯化铑用硝酸、高氯酸消解,以混合酸溶解样品,用ICP-AES法测定三苯基膦氯化铑中的微量Al、Cu、Fe、Mg、Pd、Ni、Pb、Pt、Zn杂质元素含量。选择合适波长消除光谱干扰,用背景点扣除的方式消除铑对Fe、Ni、Pb、Pt、Zn的基体干扰。各杂质元素的检测范围为0.001%~0.1%,加标回收率为93.25%~117.0%,精密度(RSD)为0.18%~15.41%。与直流电弧发射光谱分析方法相比,准确度和精密度均得到提高,高纯铑基体消耗减少,操作简化。