Kinetic and autocatalytic effects during the hydrogen production by methane decomposition over carbonaceous catalysts

The reaction kinetics of methane decomposition to yield hydrogen and carbon has been investigated comparing different types of carbonaceous catalysts: two ordered mesoporous carbons (CMK-3 and CMK-5) and two commercial carbon blacks (CB-bp and CB-v). The evolution of the reaction rate along the time has been analyzed concluding that it is governed by different and opposite events: reduction of active sites by carbon deposition, autocatalytic effects of the carbon deposits and pore blockage and diffusional constraints. A relatively simple kinetic model has been developed that fits quite well the experimental reaction rate curves in spite of the complexity of the involved phenomena.     

The Uses of Deuterium in the Study of Heterogeneous Catalysis

The discovery and isolation of deuterium in 1932 was followed almost immediately by applications to the study of heterogeneous catalysis which appeared in the classical papers of A. and L. Farkas, of Taylor and Morikawa, and of Horiuti and Polanyi. These were primarily studies of isotopic exchange between various hydrides and deuterium, e.g., between methane and deuterium, and between water and deuterium.

These investigations provided, for the first time, secure information about the ease of bond cleavage and formation in hydrides: that the bond in H, was cleaved a t a detectable rate on many metals and on chromium oxide at the temperature of liquid air; that on metals the bonds in ammonia and water were readily cleaved although less easily than the H-H bond; that on nickel, for example, C-H bonds were usually more readily cleaved than C-C bonds; and that the rate of cleavage of C-H was in the order methane < ethane < pro-pane.     

Sustainable approach toward synthesis of green functional carbonaceous 3-D micro/nanostructures from biomass

This study proposes a novel technique to synthesize functional carbonaceous three-dimensional (3-D) micro/nanocompounds from agricultural by-products using femtosecond laser irradiation. Biowastes of rice husk and wheat straw are value-engineered to carbonaceous structures in a single-step process under ambient conditions. Our results demonstrate that by controlling the laser fluence, structures with a variety of different morphologies from nanostructures to microstructures can be achieved. Also, the results indicate that altering the laser processing parameters influences the chemical composition of the synthesized structures. This sustainable approach presents an important step towards synthesizing 3-D micro/nanofibrous compounds from biowaste materials. These structures, as-synthesized or as nanocomposite fillers, can have practical uses in electronic, sensing, biological, and environmental applications.     

The carbonization of thin polyaniline films

Polyaniline films on silicon and ceramic supports were prepared in situ during the oxidative polymerization of aniline. The films were heated up to 500 °C in an inert nitrogen atmosphere. The changes in molecular structure during the carbonization have been studied by infrared spectroscopy and Raman scattering using 514, 633 and 785 nm laser excitation lines. The transformation from polyaniline salt to the base form has been detected above 100 °C. The conversion to nitrogen-containing carbon-like material followed above 200 °C. The molecular structure of the films produced during heating to 500 °C contains crosslinked phenazine-like and oxidized quinonoid units. The aniline oligomers deposited on the support in the early stages of aniline oxidation are stable during heating as it has been observed by resonance Raman scattering using 785 nm laser excitation line. The water contact angles changed after carbonization, and the films became more hydrophilic as carbonization progressed.     

The effect of non-sulphide gangue minerals on the flotation of sulphide minerals from Carlin-type gold ores

Flotation pre-concentration of sulphide and gold values from certain Carlin-type deposits characterised as double-refractory gold ores is quite challenging. Numerous studies conducted on these ores in many laboratories globally (including the present study) under a variety of chemical and physical conditions have merely confirmed low recovery (and poor concentrate grades) for sulphide minerals and gold, and poor separation between sulphide minerals and carbonaceous matter, even when the valuable minerals are adequately liberated. None of the traditional reasons based on liberation or the choice of chemical and physical conditions and separation strategies could provide satisfactory explanation for the observed poor separation.In this study, the focus was on the role of non-sulphide gangue (NSG) minerals. It was hypothesised that specific NSG minerals have a detrimental effect on flotation recovery of gold bearing minerals and their separation selectivity. In order to test this hypothesis and delineate the effect of the various gangue minerals, a new approach was taken. This involved first isolating the various mineral components of a double-refractory gold ore from one of the Carlin-type deposits using a gravity separation technique. Then flotation experiments were performed using a mixture design on various mixtures of these isolated components under controlled conditions. The results of these mixture experiments supported the hypothesis and demonstrated, for the first time for these types of ores, that even small amounts of NSG minerals, especially carbonaceous matter and clays, had a large adverse effect on the flotation of sulphides and selectivity of separation. While it is tempting to attribute the observed effects solely to slime coating, there is no basis to do so at this stage; it is more reasonable to propose that multiple contributions exist. The results of this study provide the much-needed context and direction for further fundamental studies and for developing processing strategies.     

锂离子电池用碳负极材料

本文比较了锂离子电池中所应用的各类碳材料的结构.综述了碳材料贮锂机理的几个主要观点。指出利用聚合物及其纳米复合材料作前驱体,适当条件下进行结构预控,是获得高产量、低成本、强贮锂能力碳材料的有效手段.     

碳质中间相形成机理研究

碳质中间相是制备高性能炭材料制品的优质前驱体，其产品已在高性能复合材料、超高功率石墨电极和二次锂离子电池用负极材料等方面得到了成功应用。碳质中间相产品的结构复杂、形态各异，造成了生产这些产品涉及的原料和处理过程的多样化。为了分析和预测一定条件下获得的碳质中间相产品的性能，进而确定其具体的用途，需要弄清碳质中间相的形成机理。通过系统地探讨碳质中间相的形成过程，对以往文献中的解释给予了归纳和分析。分析认为传统解释中存在许多不合理的地方，不能对一些现象给予合理的解释；“微域构筑”理论在传统解释的基础上有了很大进步，但由于该理论中引入了实际上并不存在的片层微晶单元而使其存在缺陷；“颗粒基本单元构筑”理论摒弃了以上两种理论中的不合理成分，能够对碳质中间相的形成过程进行很好的解释。此外，对“颗粒基本单元构筑”理论的一些应用也进行了讨论。     

炭质吸附剂吸附储存天然气浅谈

介绍了近年来利用炭质吸附剂吸附储存天然气的研究。结果表明：炭质吸附剂对于甲烷的理论吸附量与２０ＭＰａ下压缩天然气的量基本相当,但自前所生产的活性炭尚不能达到如此高的吸附量：炭质吸附剂的孔结构是影响甲烷吸附储存量的主要因素,此外吸脱附热效应以及天然气中其他杂质的存在对甲烷的吸附储存也有一定的影响。     

Review on the interface engineering in the carbonaceous titania for the improved photocatalytic hydrogen production

Hydrogen is the prime source of energy with enormous attention in the current research development process as it is safe, clean, eco-friendly, and can be produced from renewable resources through simple catalytic reactions. Scalable production of hydrogen through photocatalysis has been achieved using carbon-modified semiconductors since 2009. In this direction, this review delivers comprehensive understandings into the interface and structural interactions between TiO₂ and carbonaceous materials such as carbon, carbon nanotubes, graphene, activated carbon, graphitic carbon nitride, carbon quantum dots, etc., and their influences toward improving the hydrogen generation activity of these systems. Besides, recently developed carbonaceous materials such as 3-D graphene, carbon nanohorns, and carbon nanocones have also been discussed on their character in the photocatalytic water splitting procedure. In general, the observed improvements in this carbon-modified TiO₂ attributed to the synergetic effects, which offer the active migration of charge carriers and reduced recombination rates in the photocatalyst. Finally, highlighting the future perspectives of the carbonaceous materials in photocatalytic applications are concluded.     

由沥青制备炭基凝胶的研究

以煤焦油沥青为原料,经过氧化、碱溶制备出水性中间相沥青,着重考察了制备条件对水性中间相沥青在水相中凝胶化的影响。结果表明：氧化温度、浓度和溶胶的pH值对水性中间相沥青的凝胶化有影响;水性中间相沥青（AMP）可以在较宽的pH值范围内形成凝胶。在碱性条件下,氧化温度降低、pH值升高和AMP浓度提高均可缩短炭基凝胶的凝胶时间;以强酸为絮凝剂在酸性条件下水性中间相沥青絮凝为炭基凝胶;在中性条件下,给溶胶中加入乙醇可形成炭基凝胶。