导叶式旋风管整流罩减阻的实验研究

研究开发了一种新型减阻结构——整流罩,安装在排气管的入口处。此减阻元件可以减弱旋风管内旋流的旋转强度,而对外旋流基本没有影响,从而可以在保证总效率基本不变的情况下,较大程度地降低旋风管的压降,达到减阻的目的。     

Preparation of Titanium Oxide Supported MCM-48 by the Designed Dispersion of Titanylacetylacetonate

Titaniumoxide supported MCM-48 was prepared by a novel synthesis method, utilizing titanylacetyl-acetonate as the Ti source. The process consists of an adsorption and subsequent thermolysis of the Ti-complex. The interaction of the complex with the surface was studied by FTIR, TGA and chemical analysis. Further characterization was done by XRD, Raman, UV-DR and N₂ adsorption measurements. The Ti-complex is irreversibly adsorbed on the MCM-48 surface by a hydrogen bonding mechanism independent of the Ti loading. During calcination, the supported TiO(acac)₂ complex is converted towards supported titaniumoxide, whereby the Ti atoms are partly incorporated into the pore walls of MCM-48. The adsorption of TiO(acac)₂ is an efficient way to create supported titaniumoxides with a high surface area.     

Ni-PMo_(12)/MCM-48催化剂的制备与催化性能研究

通过水热合成法制备了中孔分子筛MCM-48,并采用等体积浸溃法负载活性组分镍(Ni)和磷钼酸(PMo12).采用XRD、BET吸附、红外吡啶吸附等方法对催化剂进行表征.考察了反应温度、还原温度和还原时间对异构化催化性能的影响及催化性能随反应时间的变化.结果表明,w(Ni)=3%-w(PMo12)=30%/MCM-48对正庚烷异构化反应具有较好的异构化性能,当还原温度400℃、反应温度300℃时,催化剂催化性能最好,转化率为14.2%时,异构化选择性能够达到65.6%.     

The Reduction and Oxidation of Co Species in CoZSM-5 Zeolites Studied by IR Spectroscopy

The process of reducing Co ions in zeolite CoZSM-5 by NO, H₂ and CO, as well as of oxidizing them by O₂ was studied by IR spectroscopy with CO as the probe molecule for Co²⁺ and NO as the probe for Co³⁺. Two zeolites of different Co status were used: in the first, Co²⁺ ions were localized mostly in cation exchange positions, and in the second most of the Co²⁺ occurred in the form of CoO and oxide-like clusters. IR studies evidenced that NO reduced some Co³⁺ to Co²⁺ already at room temperature, and also reduced some Co²⁺ to lower oxidation states (probably Co⁺) at 670 and 1070 K. Only Co²⁺ in exchange positions could be reduced with NO. The treatment of zeolite CoZSM-5 with H₂ or with CO at 670 and 1070 K made the reduction of Co³⁺ to Co²⁺ (the contribution of Co³⁺ decreased and the contribution of Co²⁺ increased). IR studies illustrated that the most electron-acceptor Co³⁺ (characterized by a high frequency Co³⁺–NO band) were transformed, by reduction, into the most electron-acceptor Co²⁺ (characterized by a high frequency Co²⁺–CO band). The treatment of zeolite CoZSM-5 with oxygen at 670–1070 K resulted in the oxidation of Co²⁺ to Co³⁺ (the contribution of Co²⁺ decreased while the contribution of Co³⁺ increased).     

分子筛MCM-48负载杂多酸催化合成乳酸丁酯性能研究

通过浸渍法分别将磷钨酸、磷钼酸负载于MCM-48分子筛内,制备负载型杂多酸催化剂,并采用傅里叶变换红外光谱(FT-IR)、N_2吸附-脱附、X射线衍射(XRD)等方法对负载型催化剂进行表征。将负载型杂多酸催化剂应用于乳酸丁酯合成反应,在催化剂用量及反应温度确定的条件下,考察了正丁醇和乳酸物质的量比、杂多酸负载量、反应时间对酯化率的影响。结果表明,MCM-48分子筛分别负载磷钨酸和磷钼酸是合成乳酸丁酯较为理想的催化剂,在最佳条件下,催化合成乳酸丁酯酯化率在94%以上,且负载型催化剂回收容易,可重复使用。     

晶粒细化对Co-5Y合金高温氧化性能的影响

采用机械合金化（MA）和热压烧结技术制备了细晶Co-5Y合金（用MACo-5Y表示），研究了其在900℃空气中的氧化行为。并与熔炼Co-5Y合金（用CACo-5Y表示）的氧化行为作了比较，讨论了晶粒细化对氧化行为的影响。晶粒细化后生成的大量晶界和相界，成为C0离子和氧离子的快速扩散通道，使得MACo-5Y合金的氧化速率要高于CACo-5Y合金。但由于晶粒细化后改变了合金基体的组织结构，合金的内氧化受到抑制。     

Investigation of the Reduction/Oxidation Behavior of Cobalt Supported on Nano-ceria

The oxidation and reduction behavior of cobalt catalysts supported on nano-ceria (5–8 nm) was investigated under hydrogen, oxygen and water atmospheres. A novel quantitative isothermal reduction (QIR) technique was introduced to analyze the kinetics and activation barrier of Co reduction. CoO to Co reduction was found to be of first order in the 250–350 °C temperature range. Temperature programmed reduction and oxidation experiments were conducted and the Kissinger method was used to obtain apparent activation energies for reduction and oxidation with O₂. The apparent activation energy for CoO reduction was found to agree with that obtained from the QIR technique. Re-oxidation of Co metal was found to have a slightly lower activation energy barrier than the reduction. The reduction and oxidation behavior was further investigated with in situ XANES where the reaction order for reduction was observed to change at 450 °C. The pre-reduced samples were seen to re-oxidize under a water atmosphere, where the oxidation followed first order kinetics. Re-oxidation by water yielded a higher activation energy when compared to re-oxidation under oxygen.     

Mechanical Stability of Mesoporous Materials, MCM-48 and MCM-41

The structural collapse of mesoporous molecular sieves, MCM-48 and MCM-41 materials by mechanical compression was found to occur mechanochemically through hydrolysis of Si–O–Si bonds. Their ordered structures were retained by compressing the well-dried samples under dry N2. Trimethylsilylation of mesoporous materials proved effective in eliminating their instability to compression through enhancing hydrophobicity.     

介孔分子筛MCM-48对果胶酶吸附研究

利用水热合成法制备得到纳米介孔分子筛MCM-48,并研究了其对果胶酶的吸附固载性能和吸附条件及过程特点,测定了固载果胶酶的活性。动力学研究表明,MCM-48与果胶酶间的吸附符合准二阶动力学方程。热力学计算表明,该吸附过程ΔH=-68.94kJ/mol,ΔS=-197.90J·mol~(-1)·K~(-1),说明MCM-48对于果胶酶的吸附是一个放热的、熵减的吸附过程。通过对比游离酶(酶活力14 569U)和固定化果胶酶(酶活力13 345U)的酶活力,说明固载在MCM-48中的果胶酶依然具有良好的活性,这对于保持果胶酶的天然结构以及生物活性非常有益。     

Ruthenium Supported on Nitrogen‐Doped Carbon Nanotubes for the Oxygen Reduction Reaction in Alkaline Media

Nitrogen‐doped carbon nanotubes (N‐CNTs) prepared via thermal chemical vapor deposition (CVD), were used to support ruthenium (Ru) nanoparticles made using a microwave assisted reduction technique. The amount of Ru deposited on N‐CNTs was varied between 0 and 10 wt.%. The activity of the prepared nanocatalysts toward the oxygen reduction reaction (ORR) was characterized using the rotating disk electrode and voltammetry techniques. The ORR activity was higher at lower concentrations of Ru on N‐CNTs. The four electron pathway of ORR is more favorable on 2Ru/N‐CNTs and 5Ru/N‐CNTs than 10Ru/N‐CNTs.     

Electrochemical Reduction of Oxygen on Carbon Supported Pt and Pt/Ru Fuel Cell Electrodes in Alkaline Solutions

A study of O₂ reduction in 1 M NaOH solution at gas diffusion electrodes made from carbon supported Pt and Pt/Ru catalysts is reported. Two Tafel regions were observed for both the Pt and Pt/Ru electrodes. Although the same mechanism was suggested for oxygen reduction on both Pt and Pt/Ru catalysts, the O₂ reduction activity was lower on Ru. Electrochemical Impedance Spectroscopy (EIS) analysis was carried out at different potentials and showed the significant contribution of diffusion on the reaction process and kinetics. The effect of methanol on O₂ reduction was investigated in solutions containing various concentrations of methanol. The electrode performance deteriorated with increasing methanol concentration because of a mixed cathode potential. The methanol tolerance, i. e., the methanol concentration which polarises the O₂ reduction reaction for O₂ reduction, at the Pt/C electrode with a Pt loading of 1.2 mg cm^–2 is 0.2 M methanol in 1 M NaOH.     

Electrochemical Characteristics and Performance of Platinum Nanoparticles Supported by Vulcan/Polyaniline for Oxygen Reduction in PEMFC

We report a Pt/Vulcan carbon–polyaniline (VC–PANI) catalyst for the oxygen reduction reaction (ORR). This electrocatalyst was prepared from Pt nanoparticles supported by a VC–PANI composite substrate. Electrochemical performance was measured using potentiostat/galvanostats technique and a proton exchange membrane fuel cell (PEMFC) test station. The electrochemical properties of the electrodes were characterized using linear sweep voltammetry, AC impedance spectroscopy and chronoamperometry. Electrochemical characterization by hydrogen adsorption/desorption cyclic voltammetry and CO stripping voltammetry indicates that the electrochemical active surface areas of the Pt/VC–PANI are comparable to the commercial catalyst. The performance of the Pt/VC–PANI and Pt/C(E‐TEK) + PANI electrocatalysts were found to be 1.82 and 1.33 times higher than of the Pt/C(E‐TEK) electrode. The surface morphologies of the electrodes were characterized by using scanning electron microscopy (SEM). PANI has a fibrous structure and the improved performance was attributed to the PANI effect and synergistic effects between the carbon Vulcan and the PANI fiber. These results indicate that Pt/VC–PANI is a promising catalyst for the ORR in PEMFCs using an H₂/O₂ feed.     

A Facile Diethylene Glycol Reduction Method for the Synthesis of Ultrafine Pd/C Electrocatalyst with High Electrocatalytic Activity for Methanol Oxidation

The high‐quality carbon supported Pd nanoparticles (Pd/C) composites have wide applications in catalysis. In this work, we demonstrate an efficient diethylene glycol (DEG) reduction method for the synthesis of a Pd/C catalyst with high dispersion and small particle size. During the synthesis, no surfactants and halogen ions are introduced in the reaction system, and DEG efficiently acts as solvent and reducing agent, which results in a “clean” Pd surface. Meanwhile, compared to the classic ethylene glycol (EG) reduction method, the present DEG reduction method can produce the high‐quality Pd/C composites. As a result, the as‐prepared Pd/C electrocatalyst exhibits a large electrochemical active surface area and good electrocatalytic performance for the methanol oxidation reaction in an alkaline media, due to the high dispersion and small particle size. This result indicates the as‐prepared Pd/C electrocatalyst has potential applications in alkaline direct methanol fuel cells.     

聚苯乙烯载体负载茂金属催化剂的合成及表征

合成了聚苯乙烯负载的茂金属催化剂,考察了硅胶用量、二乙烯基苯与苯乙烯体积比、洗涤温度和洗涤次数对催化剂的影响,并对其进行了表征.确定硅胶加入量为1 g,二乙烯基苯与苯乙烯体积比为0.08,洗涤温度60℃,洗涤次数为4次;XPS表征证明合成了聚苯乙烯载体茂金属催化剂.     

Pt-SDB疏水催化剂的还原工艺研究

以水-氢同位素催化交换性能为衡量指标,对粒径为2.0 mm的Pt-SDB疏水催化剂的还原工艺进行了研究。首先确定了最优还原温度为280℃,并结合XRD、TG和TPR分析了还原温度变化对催化剂性能的影响;进一步优化确定了还原的时间与气速:24h和0.5 L/min,对Pt-SDB催化剂的制备和应用具有重要的指导意义。     

锆掺杂MCM-48氧化硅的合成及其表征

以正硅酸乙酯为硅源,丙醇锆为锆源,十六烷基三甲基溴化铵为模板剂,通过水热合成法制备Zr-MCM-48介孔材料,提高材料的耐碱性能.利用XRD、N2吸附-脱附、XPS等手段对产物进行了结构和性能的分析.XRD检测显示当Zr/Si物质的量比小于0.1时,可以获得长程有序的MCM-48结构.N2吸附-脱附实验、XPS测试等证实Zr已经掺入MCM-48骨架中.稳定性实验结果表明Zr/Si物质的量比为0.03时,Zr-MCM-48材料的耐碱性能明显增强,进一步表明Zr掺入了MCM-48材料的骨架中.     

氧化铌负载型催化剂的制备及催化性能研究

以乙酸和正丁醇催化酯化合成乙酸丁酯为探针反应 ,对氧化铌负载型催化剂的制备与催化活性进行了一系列研究 ,得出了优惠工艺条件。正丁醇的转化率达 95% ,乙酸丁酯选择性 1 0 0 %。     

MCM-48介孔分子筛合成和改性研究进展

MCM-48介孔分子筛因具备高度有序的孔道,较大的比表面积,可控的形貌,良好的催化性能及优异的传质与扩散效率等优势成为化学工业、信息技术和环境能源等领域的研究热点.整理了MCM-48介孔分子筛的合成方法,主要包括水热合成法、微波合成法、室温合成法、相转变合成法,概述了不同的合成原料(如硅源、模板剂)和合成条件(如pH值...     

生物质还原磁化褐铁矿的实验研究

研究了广西崇左褐铁矿磁性转化和还原机理. 通过生物质与褐煤焙烧还原褐铁矿的对比实验,考察了焙烧温度、焙烧时间、原料配比等工艺条件对矿物磁性的影响. 结果表明,生物质还原的最佳焙烧温度为650℃左右,焙烧时间30 min,生物质用量为15%~20%. 结合XRD分析结果,确定以褐煤及生物质还原铁矿主要得到磁性Fe3O4及g-Fe2O3,温度高时易转化成硅酸铁,影响后续磁选回收铁.