A time‐dependent multiphysics,multiphase modeling framework for carbon nanotube synthesis using chemical vapor deposition

A time‐dependent multiphysics, multiphase model is proposed and fully developed here to describe carbon nanotubes (CNTs) fabrication using chemical vapor deposition (CVD). The fully integrated model accounts for chemical reaction as well as fluid, heat, and mass transport phenomena. The feed components for the CVD process are methane (CH₄), as the primary carbon source, and hydrogen (H₂). Numerous simulations are performed for a wide range of fabrication temperatures (973.15–1273.15 K) as well as different CH₄ (500–1000 sccm) and H₂ (250–750 sccm) flow rates. The effect of temperature, total flow rate, and feed mixture ratio on CNTs growth rate as well as the effect of amorphous carbon formation on the final product are calculated and compared with experimental results. The outcomes from this study provide a fundamental understanding and basis for the design of an efficient CNT fabrication process that is capable of producing a high yield of CNTs, with a minimum amount of amorphous carbon. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

羰基化反应多相催化剂的研究进展

综述了国内外羰基化反应中多相催化剂的研究现状、技术特点及最新进展,指出了羰基化反应多相催化剂的研究方向。     

活性炭表面模拟烟气与元素汞间均/异相氧化反应特性

通过固定床吸附实验,在130℃温度下模拟研究燃煤烟气组分在椰壳活性炭(CS-AC)表面吸附气态元素汞(Hg⁰)过程中的作用与影响,揭示模拟烟气组分、Hg⁰以及活性炭表面三者间的均相、异相氧化反应特性。实验研究了CS-AC在N₂和模拟烟气气氛下对Hg⁰的吸附,模拟烟气组分与Hg⁰间的均相氧化反应,以及吸附模拟烟气组分后CS-AC在N₂气氛下对Hg⁰的吸附。研究表明在N₂气氛下CS-AC对Hg⁰不具备物理吸附的能力,而在模拟烟气组分下CS-AC对Hg⁰具有较强的吸附能力,初始吸附效率达80%。仅在模拟烟气均相反应作用下,大约只有14%的Hg⁰被氧化为Hg²⁺。经过预先跟常规模拟烟气吸附反应,CS-AC表面具备一定氧化性化学元素基团（如NO_x）后,能够在N₂气氛下对Hg⁰进行化学吸附,初始吸附效率达67%左右。可以认为模拟烟气和Hg⁰两者间的均相作用不是促进CS-AC在模拟烟气组分下对Hg⁰具有较强的吸附能力的主因。活性炭吸附Hg⁰的过程中,活性炭表面在烟气组分氧化Hg⁰的过程中起到了积极的促进作用。无论在N₂气氛下,还是在模拟烟气下,CS-AC吸附Hg⁰是气氛中氧化性组分、Hg⁰和活性炭表面三者间的异相化学氧化吸附反应过程。     

渗透蒸发和化学反应的耦合

渗透蒸发是分离液相混合物的膜分离方法，常用于有机物脱水及有机物－－有机物的分离。借助于渗透蒸发把化学反应产物部分或全部从反应体系中脱去，可使产物收率不受化学平衡的限制。     

Understanding and optimization of chemical reactor performance for bimodal reaction sequences

The relative contributions of heterogeneously catalyzed and homogeneous bulk phase reactions in bimodal reaction sequences have been assessed via 1D reactor simulations. Starting from a reaction network only comprising two parallel, irreversible heterogeneously catalyzed and homogeneous bulk phase steps, complementary consecutive steps were included with the option of being reversible. The final product formed after a minimum number of homogeneous bulk phase reactions is obtained with high yields in continuous flow fixed bed reactors. The products obtained after a higher number of homogeneous bulk phase reactions generally dominate in slurry reactors. Yields of the latter may exhibit an optimum as a function of the catalyst amount in the reactor. The adsorption enthalpies of the intermediates in the reaction network critically determine the position and shape of this maximum. The reversibility of the homogeneous bulk phase steps provides specific opportunities to tune the product yields in bimodal reaction sequences. © 2016 American Institute of Chemical Engineers AIChE J, 63: 111–119, 2017     

Conjugate mathematical model of ignition of magnesium samples

A distributed mathematical model of ignition of a magnesium particle with allowance for the heterogeneous chemical reaction and the region of the thermal influence of the particle on the gas is developed. A solution of the problem in a steady formulation is found, which allows expanding the classification of the thermal history of the particle-gas system. A numerical model for solving the considered class of boundary-value problems of magnesium-particle ignition is proposed, and the mathematical model is verified in terms of the ignition delay as a function of the Nusselt number. A limiting size of the gas layer near the particle, which determines the ignition mode, is identified. Stability of some heating regimes to finite and infinitesimal disturbances is demonstrated. It is shown that the ignition process can be controlled by a high-frequency thermal action on unstable states of the particle-gas system. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 3, pp. 57–63, May–June, 2006.     

碳纳米管阵列在电化学中的应用

高定向的碳纳米管阵列由于有优越的电导率、高比表面积、发达的多孔结构而具有良好的电化学性能如大容量、优异的速率性能和较长的循环寿命,这些独特的性质使其在电化学领域显现出巨大的应用潜力。本文简要介绍了碳纳米管阵列的制备,并从电化学储能、电化学催化和电化学传感器等领域综述近年来碳纳米管阵列在电化学应用中的最新研究进展,分析了其所面临的问题,并提出了未来碳纳米管阵列在电化学应用中的发展方向。关键词：碳纳米管阵列;电化学性能;储能;催化;传感器中图分类号：     

MnO_2动态催化氧还原的研究

为了提高MnO2催化氧还原效率,采用B i改性MnO2经350℃高温处理后作为氧还原的催化剂,草酸铵造孔剂及MWNTs为复合电催化剂,氧电极可获得50 mA/cm2的工作电流密度(-200 mV)。B i改性MnO2的微观形貌分析表明,其晶体颗粒尺度约100 nm,且粒径分布较均匀,呈自然团聚外貌,团聚物直径在2~8μm。B i改性MnO2催化氧还原机理为:在放电过程中,由于B i改性的MnO2具有良好的可逆性能,因此O2在MnO2上发生的电子得失过程是瞬间过程,而不是MnO2的晶格转变,仅仅是质子-电子的传递。当缺氧时,MnO2发生还原反应,才会发生晶格转变。     

催化法合成喹啉及其衍生物的研究进展

总结并综述了催化法合成喹啉及其衍生物的研究进展,分析了不同种类催化剂（无机酸、金属络合物、固体酸和金属氧化物等）作用下,喹啉及其衍生物的合成路线（Skraup法、Doebner-Von Miller法和Friedlander法等）及其反应机理,并从绿色合成工艺和新型催化剂开发等方面提出了今后的研究方向。     

碳材料在多相催化过程中的应用

碳是自然界中存在最为广泛的元素,具有丰富的结构和形态。碳材料不仅可以作为理想的催化剂载体,其本身也表现出对多种催化过程的优异性能。综述了碳材料在化学品制造、环境催化与能源催化等领域的最近研究进展,并总结了碳材料在这些过程中的催化作用机理。     

碳纳米管修饰电极的研究进展

化学修饰电极如今在电化学和电分析化学中应用极为广泛。综述了碳纳米管的结构和性能,介绍了碳纳米管修饰电极的制备及应用。     

Variable‐temperature IR spectroscopic studies of CO adsorbed on Na‐ZSM‐5 and Na‐Y zeolites

CO interacts with extraframework alkali metal cations (M⁺=) of zeolites to form both M⁺CO and M⁺OC species. By using variabletemperature FTIR spectroscopy, these Cbonded and Obonded species were found to be in a temperaturedependent equilibrium. For the same cation, the difference in interaction energy depends upon the zeolite framework. Thus, for the equilibrium process ZNa⁺=CO ZNa⁺OC, where Z represents the zeolite framework, H ⁰ was found to take the values 3.8 and 2.4 kJ mol^– for CO/NaZSM5 and CO/NaY, respectively. The Cbonded species show always the highest cation–CO interaction energy.     

Heterogeneous or Homogeneous? A Case Study Involving Palladium‐Containing Perovskites in the Suzuki Reaction

The utility of a series of palladium‐containing perovskite catalysts in the Suzuki reaction is described; turnover numbers of up to 400,000 are reported. A detailed investigation into the mode of action of these catalysts encompassing kinetic studies, catalyst poisoning, microscopy and three‐phase tests demonstrate that these heterogeneous materials are pre‐catalysts that operate by a solution‐phase mechanism