聚合物热解法制备碳纳米管/铝复合粉末及其反应动力学研究

采用聚合物热解化学气相沉积(PP-CVD)法, 通过聚乙二醇(PEG)的原位热解提供碳源、柠檬酸(CA)和硝酸钴反应产生催化剂纳米粒子, 在微纳米级的片状铝粉基底上原位生长碳纳米管(CNTs)。通过实验和反应动力学建模研究了PP-CVD反应机理, 揭示了PEG热解气相成分和催化剂纳米粒子表面气-固反应对CNTs生长速率的影响规律。CO初始分压和反应温度提高, CNTs生长速率提高; H₂初始分压和催化剂密度提高, CNTs生长速率降低。模型预测的CNTs平均长度随反应温度和反应时间的变化趋势符合实验结果。因此, 本研究为进一步优化CNTs/铝复合粉末制备工艺提供了新的理论依据。     

关于CO变换技术优化的一种设计实施方法

CO变换反应是放热反应,进行反应的温度越低越有利于反应进行。因此,如何降低催化剂的反应温度成为衡量CO变换系统优劣的潜在标准。阐述了解决CO变换工序在正常运行期间产生的变换炉出口的CO气体超标、催化剂反应温度过高、分离器压差过大等诸多问题的原因,对于CO变换工序所遇到的诸多问题,有针对性的展开了分析,制定了多种改进方案,优化了CO变换工艺,解决了其中一部分难题,提高了生产装置的负荷,缩短了CO变换工序触媒升温时间,增加了触媒运行周期,确保了后续装置的稳定运行。     

热丝化学气相生长金刚石温度场流场模拟计算和反应器设计原理研究

在对于现有金刚石气相生长工艺特点综合分析的基础上，通过对于热丝化学气相生长金刚石工艺过程状态参数的空间场模拟及相应的实验研究，揭示了热阻塞、热绕流等背离反应基本条件的现象，以及状态参数高度不均匀性的场分布，导致偏离金刚石生长所需合理条件。这些正是当前热丝化学气相生长金刚石速率低、成本高、质量不稳定的重要原因。空间模拟及生长实验结果证明，通过选择合理的反应器结构和反应条件，可以控制反应状态参数空间场，使其符合气相生长金刚石要求，达到在保证质量稳定南时，实现大面积高速生长。这些结果为大面积高速度高质量气相生长金刚石明确了新的发展前景和具体实现途径。     

铜(Ⅰ)催化、无配体条件下的脂肪族二元醇和芳香卤代烃的C-O偶联反应研究

以环己烷二甲醇和卤代芳烃为原料,CuBr作为催化剂,在无配体条件下,通过C-O交叉偶联反应合成了脂肪-芳香二醚类化合物。对活性较低的脂肪族二元醇和卤代烃的交叉偶联反应进行了初步的探索,考察了偶联反应的影响因素,对产物的结构进行了结构确认和荧光性能的研究。     

热丝化学气相生长金刚石温度场流场模拟计算和反应器设计原理研究

在对于现有金刚石气相生长工艺特点综合分析的基础上,通过对于热丝化学气相生长金刚石工艺过程状态参数的空间场模拟及相应的实验研究,揭示了热阻塞,热绕流等背离反应基本条件的现象,以及状态参数高度不均匀性的场分布,导致偏离金刚石生长所需合理条件。这些正是当前热丝化学气相生长金刚石速率低,成本高,质量不稳定的重要原因。     

甲烷氧化偶联反应的进展

叙述了在甲烷氧化偶联法制取乙烯的反应中，性能不同的催化剂对反应产物的影响，不同反应条件对反应产物的影响，以及甲烷罐头化偶联反应催化剂的催化机理。     

CO_2与环氧化物反应选择性的研究现状

CO2与环氧化合物制备生物降解材料一直是实现CO2资源化利用的有效途径。近年来越来越多的科技工作者致力于开发高效的均相、非均相催化剂以及调控反应条件以控制反应的选择性,从而获得性能优异的目标产物,目前相关方面的综述较少。文中综述了国内外关于CO2与环氧化物在产物选择性、区域选择性、光学选择性3个方面的研究现状、进展及发展动向。并重点指出CO2与环氧化物在反应过程中催化剂配体、反应温度、压力以及助催化剂的使用对反应在选择性方面的影响规律。     

气相法纳米合成装置的工艺研究

文章主要介绍了气相法制备纳米材料的原理,以及气相法纳米合成装置的设计与组装。在气相法制备纳米材料原理基础上,以反应原理简单、可调可控为原则,设计组装了气相纳米合成装置,并研究了其工艺。     

碳基固体酸催化大豆油酯交换制备生物柴油

通过一步碳化-磺化法制备了碳基固体酸催化剂,采用IR、XRD以及TG对催化剂进行了表征;并将催化剂用于催化大豆油与甲醇的酯交换反应制备生物柴油中,考察了相关因素对反应的影响,用气相色谱分析生物柴油的产率。实验结果表明,碳基固体酸催化大豆油与甲醇的酯交换反应效果显著,最佳反应条件为:醇油摩尔比36∶1、反应温度130℃、反应时间4h、催化剂用量为大豆油质量的10%时,生物柴油的收率可达95.5%。催化剂重复利用6次,活性下降较小。     

威斯康星大学研发新型燃料电池用氢制备工艺

美国威斯康星大学正在研发一种制氢工艺,以山梨糖醇或乙二醇为原料,所得氢气中CO体积分数低于6 0×10 - 6 。预期此工艺比传统的天然气蒸气转化制氢便宜得多,因为它使用镍基催化剂代替铂,可在温和的反应温度下(2 2 5℃,以前为6 0 0～10 0 0℃)生产贫CO的氢气。原料可依据情况采用二氧化碳副产品的再生资源。新工艺采用液相管式反应器,变换反应在压力2 5MPa和温度2 2 5℃下进行。碳水化合物的水溶液连续加入反应器,在雷尼镍锡催化剂上生成H2和CO ,后者在溶液里形成气泡。当气泡上升进入反应器第二区域时,该区域的温度比前面高约10℃,气…     

环境友好的固定床烃类晶格氧选择氧化技术

以正丁烷选择氧化制顺丁烯二酸酐为例，说明按照氧化还原进行的烃类选择氧化反应，采用将催化循环的不同步骤在空间或时间上分离的强制周期操作方法，可大幅度提高反应的选择性，改进环境工效，实现环境友好。重点介绍了强制周期操作的固定床反应技术在烃类选择氧化反应中的应用。     

Mesoporous titanium dioxide nanocatalyst: a recyclable approach for one‐pot synthesis of 5‐hydroxymethylfurfural

The present study deals with the production of 5‐hydroxymethyl furfural (HMF) from fructose by chemo‐conversion method using chemical catalyst, conventionally achieved by microwave‐assisted dehydration process. Five different chemical catalysts, namely oxalic acid, phosphotungstic acid and mesoporous titanium dioxide nanoparticles (TNPs) were compared at constant conditions of which TNPs yielded a maxima of 33.95%. The optimum temperature and catalyst loading were found to be 200°C and 20%, respectively, at a 5% optimum substrate concentration during 15 min optimum reaction time to yield 61.53% HMF. The efficiency of synthesised TNPs was investigated further through reusability studies. TNPs were properly recycled and the catalytic activity recovery was good even after a 14 batch reactions. The specific surface area of the TNP obtained is about 105.46 m² /g and its pore‐volume is about 0.42 cm³ /g according to single point adsorption. A large accessible surface area combined with a minimal pore size (15.92 nm) obtained with mesoporous TNPs is desirable for better catalyst loading, high‐yield HMF, retention and reduced diffusion constraints.Inspec keywords: mesoporous materials, recycling, production management, dissociation, nanoparticles, nanotechnologyOther keywords: mesoporous titanium dioxide nanocatalyst, recyclable approach, one‐pot synthesis, 5‐hydroxymethyl furfural production, HMF, chemo‐conversion method, chemical catalyst, microwave‐assisted dehydration process, oxalic acid, phosphotungstic acid, mesoporous titanium dioxide nanoparticles, TNP     

A Bifunctional Highly Efficient FeNx/C Electrocatalyst

Herein, a type of Fe, N‐codoped carbon electrocatalyst (FeN_x/C, Fe‐N‐BCNT#BP) containing bamboo carbon nanotubes and displaying bifunctional high catalytic efficiency for both oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR) is reported. It shows high electrocatalytic activity and stability for both the ORR process with onset potential of 1.03 V_RHE in alkaline and the CO2RR to CO with high faradic efficiency up to 90% and selectivity of about 100% at low overpotential of 0.49 V. For CO2RR to CO, it is revealed that Fe₃C is active but the activity of FeN_x centers is lower than that of C–N‐based centers, contrary with that observed for ORR. Due to its low cost and high electrocatalytic performance for these two reduction reactions, the obtained catalyst is very promising for extensive application in future. The revealed huge activity difference of the same types of active sites for different reactions can efficiently guide the synthesis of advanced materials with multifunction.     

Modeling of the HiPco process for carbon nanotube production. I. Chemical kinetics

A chemical kinetic model is developed to help understand and optimize the production of single-walled carbon nanotubes via the high-pressure carbon monoxide (HiPco) process, which employs iron pentacarbonyl as the catalyst precursor and carbon monoxide as the carbon feedstock. The model separates the HiPco process into three steps, precursor decomposition, catalyst growth and evaporation, and carbon nanotube production resulting from the catalyst-enhanced disproportionation of carbon monoxide, known as the Boudouard reaction: 2 CO(g)-->C(s) + CO2(g). The resulting detailed model contains 971 species and 1948 chemical reactions. A second model with a reduced reaction set containing 14 species and 22 chemical reactions is developed on the basis of the detailed model and reproduces the chemistry of the major species. Results showing the parametric dependence of temperature, total pressure, and initial precursor partial pressures are presented, with comparison between the two models. The reduced model is more amenable to coupled reacting flow-field simulations, presented in the following article.     

Photocatalytic decomposition of perfluorooctanoic acid (PFOA) by TiO2 in the presence of oxalic acid

Heterogeneous photocatalytic decomposition of perfluoroocatanoic acid (PFOA) by TiO(2) under 254 nm UV light was investigated. Adding oxalic acid as a hole-scavenger significantly accelerated PFOA decomposition under nitrogen atmosphere. Fluoride ion, formic acid and six shorter-chain perfluorinated carboxylic acids (PFCAs) bearing C(2)-C(7) were identified as intermediates. When using perchloric acid (HClO(4)) as a replacement of oxalic acid to maintain the same pH of the reaction solution, PFOA did not decomposition efficiently. Compared with oxalic acid, potassium iodide (KI, another hole-scavenger) also led to a slower PFOA decomposition, while the addition of an electron acceptor (potassium persulfate, K(2)S(2)O(8)) obviously inhibited PFOA decomposition. This suggested that oxalic acid played more than one role in PFOA decomposition rather than simply providing acidity and acting as a hole-scavenger. The electron paramagnetic resonance (EPR) measurements confirmed the existence of carboxyl anion radicals (CO(2)(-)) in the photocatalytic process, which was a result of the reaction between oxalic acid and photogenerated hole. These findings indicated that PFOA decomposition was primarily induced by CO(2)(-) radicals, although photogenerated electron was also conducive to PFOA decomposition. A possible mechanism for PFOA decomposition was proposed.     

Advances in carbon nanotubes as efficacious supports for palladium-catalysed carbon–carbon cross-coupling reactions

Since the 1970s, palladium-catalysed carbon–carbon (C–C) bond formation has made a critical impact in organic synthesis. In early studies, homogeneous palladium catalysts were extensively used for this reaction with limitations such as difficulty in separation and recycling ability. Lately, heterogeneous palladium-based catalysts have shown promise as surrogates for conventional homogeneous catalysts in C–C coupling reactions, since the product is easy to isolate, while the catalyst is reusable and hence sustainable. Recently, a better part of these heterogeneous palladium catalysts are supported on carbon nanotubes (Pd/CNTs), that have shown superior catalytic performance and better recyclability since the CNT support imparts stability to the palladium catalyst. This review discusses the wide variety of surface functionalization techniques for CNTs that improve their properties as catalyst supports, as well as the methods available for loading the catalyst nanoparticles onto the CNTs. It will survey the literature where Pd/CNTs catalysts have been utilized for C–C coupling reactions, with particular emphasis on Suzuki–Miyaura and Mizoroki–Heck coupling reactions. It will also highlight some of the important parameters that affect these reactions.     

Kinetics of Mo, Ni, V and Al leaching from a spent hydrodesulphurization catalyst in a solution containing oxalic acid and hydrogen peroxide

The kinetics of molybdenum, nickel, vanadium and aluminium leaching from a spent hydrodesulphurization catalyst in a solution containing oxalic acid and hydrogen peroxide was investigated. The effects of temperature and particle size were examined. In addition, the reaction mechanism for the dissolution of the spent catalyst was discussed. The results of the kinetic analysis for various experimental conditions indicated that the reaction rate of leaching process is controlled by chemical reaction at the particle surface. The values of the activation energies of 31±2, 36±4, 30±4 and 57±3 kJ mol(-1) for Mo, Ni, V and Al, respectively, are characteristic for mechanism controlled by chemical reaction.     

固体超强酸SO42-/TiO2-Al2O3的制备及其催化合成冰片

采用溶胶-凝胶法和浸渍法制备了系列SO_4~(2-)/TiO_2-Al_2O_3固体超强酸催化剂,运用XRD、NH_3-TPD、FT-IR、PyFTIR、XPS、SEM等技术手段,研究了复合催化剂材料的结构与性质,初步探讨了固体超强酸SO_4~(2-)/TiO_2-Al_2O_3催化剂的构效关系,得到适宜的催化剂制备条件为:n(TiO_2)/n(Al_2O_3)=1∶2、硫酸浸渍浓度1mol/L、催化剂焙烧温度500℃。考察了物料物质的量比、催化剂用量、反应时间等对催化合成冰片的影响。结果表明,在物料物质的量比为1∶0.4,催化剂用量为α-蒎烯质量的7%,采用程序升温方式(65℃-1h,75℃-4h,90℃-1h)加热的条件下,固体超强酸SO_4~(2-)/TiO_2-Al_2O_3催化剂的催化活性最高,α-蒎烯的转化率高达100%,龙脑的收率高达59.74%,SO_4~(2-)/TiO_2-Al_2O_3固体超强酸催化剂在重复使用6次的条件下,α-蒎烯的转化率均不变,龙脑的收率下降2.99%,催化剂的重复使用性良好。     

Hydrogenation of CO to methane over mesoporous nickel-iron-alumina xerogel nano-catalysts

Mesoporous nickel-iron-alumina xerogel ((40-x)Ni(x)FeAX) nano-catalysts with different iron content (x = 0, 2.5, 5, 7.5, and 10) were prepared by a single-step sol-gel method for use in the methane production from carbon monoxide and hydrogen. The effect of iron content on the catalytic performance of (40-x)Ni(x)FeAX catalysts was investigated. In the methanation reaction, yield for CH4 decreased in the order of 35Ni5FeAX > 32.5Ni7.5FeAX > 30Ni10FeAX > 37.5Ni2.5FeAX > 40Ni0FeAX. This indicated that optimal iron content of mesoporous nickel-iron-alumina xerogel nano-catalyst was required for maximum production of CH4 in the methanation reaction. Experimental results revealed that optimal CO dissociation energy and large H2 adsorption ability of the catalyst were favorable for methane production. Among the catalysts tested, 35Ni5FeAX catalyst, which retained the most optimal CO dissociation energy and the largest H2 adsorption ability, exhibited the best catalytic performance in terms of conversion of CO and yield for CH4 in the methanation reaction. CO dissociation energy and H2 adsorption ability of the catalyst played a key role in determining the catalytic performance of (40-x)Ni(x)FeAX in the methanation reaction.     

Environmentally friendly efficient one-pot esterification of cyclohexane with CuO-promoted sulfated zirconia

The production of dibutyl phthalate directly from oxidation and esterification of cyclohexane, catalyzed by CuO-modified sulfated zirconia (SZCu) by one-pot under mild condition, was studied. The esterification reaction process was monitored by UV-vis spectra and the distribution of the products was analyzed by gas chromatograph-mass spectrometry (GC-MS). The result revealed that the SZCu catalyst was efficient in the direct oxidation and esterification of cyclohexane to ester. The selectivity for ester (dibutyl phthalate) can reach up to 72.2 wt.%, and the yield of ester was 29.5 wt.%. The esterification reaction, that offers several advantages such as usage of environmental friendly oxidant, simple work-up procedure, no-solvent conditions, short reaction times, easy recovery and reusability of the catalyst, is necessary for chemosynthesis industry from the environment standpoint. The regeneration property of SZCu was also tested in this work.