Variations in surface functional groups, carbon chemical state and graphitization degree during thermal deactivation of diesel soot particles

The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters(DPFs).This work focused on the changes in the surface functional groups,carbon chemical state,and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600℃,800℃,and 1000℃ and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer(TGA-GC/MS).The surface functional groups and carbon chemical statewere characterized using Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS).The graphitization degree was evaluated by means of Raman spectroscopy(RS).The concentrations of aliphatic C–H,C–OH,C=O,and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature,while the sp^(2)/sp^(3) hybridized ratio and graphitization degree enhance.These results provide comprehensive evidence of the decreased reactivity of soot samples.Among oxygenated functional groups,the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability.TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000℃ thermal treatment of diesel soot.

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

Low-temperature-pyrolysis preparation of nanostructured graphite towards rapid potassium storage with high initial Coulombic efficiency

Industrially prepared artificial graphite(AG)is attractive for potassium-ion batteries(PIBs),but its rate performance is poor and the production process is energy intensive,so developing an efficient strategy to produce novel graphite with low energy consumption and high performance is economically important.Herein,a nanostructured graphite composed of multi-walled carbon nanotubes(MWCNTs)and graphite shells was prepared by one-pot method through low-temperature pyrolysis of iron-based metal-organic framework(MOF)and carbon source.The high graphitization degree of nanostructured graphite makes the initial Coulombic efficiency(ICE)exceed 80%,and the three-dimensional(3D)conductive network ensures a specific capacity of 234 mAh·g^(−1)after 1000 cycles at a high current density of 500 mA·g^(−1).In addition,the typical graphite potassium storage mechanism is also demonstrated by in situ X-ray diffraction(XRD)and in situ Raman spectroscopy,and its practicality is also proved by the voltage of the full cells.This work provides a feasible way to optimize the practical production process of AG and expand its application in energy storage.

Influence of order degree of coaly graphite on its structure change during preparation of graphene oxide

Coaly graphite is an important natural graphite resource that derived from coal under a natural process that associated with igneous intrusion.Flake graphite is usually used for the chemical synthesis of graphene oxide(GO),the main precursor for preparation of graphene,but few papers pay attention to preparing GO using coaly graphite.In this paper,four kinds of natural coaly graphite with different graphitization degrees were exposed to a modified Hummer’s oxidation method to prepare GO.The flake graphite sample was also used for comparison.The results showed that the structural change process from graphite to GO were significantly affected by the graphitization degree of the original coaly graphite.The relationship between yields of GO and graphitization degrees of the coaly graphite was explored.The mechanism of why the graphite with low graphitization degrees cannot be totally oxidized was proposed.Coaly graphite with a graphitization degree of higher than 80% was easier to be oxidized and yielded the same amount of GO as the flake graphite did,suggesting it is the potential substitute for the flake graphite to produce GO in bulk quantities.

Effect of process conditions on the synthesis of carbon nanotubes by catalytic decomposition of methane

A new dual-composition catalyst based on Ni-Mo/MgO with high efficiency of producing carbon nanotubes （CNTs） from methane was reported recently. In the present article, with this type of catalyst, the impact of such experimental parameters as reaction temperature, reaction time, concentration of H2, flow rate ratio of CH4 to H2 on yield and graphitization were investigated, leading to the following optimal growth conditions： reaction time 60min, reaction temperature 900℃, CH4：H2 about 100：20mL/min, under which high-yield multi-walled CNTs bundles were synthesized. Raman measurement indicated that the as-synthesized product was well-graphitized, and the purity was estimated over 95% by TG-DSC analysis. In terms of the above results, an explanation of high-efficiency formation of CNTs bundles and the co-catalysis mechanism of Ni-Mo/MgO were suggested. 2007 Chinese Societv of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.

Experimental research on semi-coke for blast furnace injection

The combustion properties and grindability of Shenmu low-rank coal(SM)and its four different semi-cokes were studied by the self-designed equipment and Hardgrove method.The four semi-cokes were obtained under the pyrolysis temperature of 400,500,600 and 700℃,named as SM-400,SM-500,SM-600 and SM-700,respectively.The analyses of nitrogen adsorp-tion,Fourier-transform infrared spectroscopy(FTIR)spectra and Raman spectra were carried out to explain the change in combustion ratio and grindability.The result showed that the specific surface area of samples had an essential effect on the combustion ratio of SM-400 and SM-500.Meanwhile,the grindability depended on the strength of coal matrix,and the augment of pore amounts would increase the grindability.The functional groups and graphitization degree of the same sam-ple were identical with the combustion ratio.With the pyrolysis upgrading temperature increasing,the combustion ratio of sample decreased,corresponding to the decrease in the benzene ring and the increase in graphitization degree.In addition,the thermogravimetric analysis was carried out,and the result was compared against what was shown in the data of com-bustion ratio.For pulverized coal injection,the combustion ratio was more intuitive and more accurate than combustibility.