XRD evaluation of KOH activation process and influence of coal rank

Three Japanese coals with different rank (Ohmine, Miike and Taiheiyo coals) were activated with KOH from 300 to 850 °C. Higher rank coal with lower oxygen content showed a high yield and also a large specific surface area determined by N₂ adsorption isotherms. X-ray diffraction (XRD) patterns of the activated carbons were measured to characterize stacking structure of aromatic layers by standardized analysis of coal by XRD method, considering the presence of slit-shaped micropores among the stacking structure. Structural parameters obtained by this method were related to the yield and the surface area in order to discuss the feature of micropores developed during the activation.     

神府煤KOH催化水蒸气活化制备活性炭和H2

以神府3^-1煤为原料,研究了KOH催化水蒸气活化法制备活性炭,并联产H2的主要影响因素,分析了浸溃比、活化温度、活化时间对活性炭吸附性能和H2产量的影响规律,归纳总结了耦合活化机理。结果表明,当KOH与煤浸渍比为0．5,活化温度为700℃,单元活化时间为10min时,制得的活性炭性能较好,碘值达到851mg／g,亚甲基蓝吸附值达到431mg／g,此时H2产量约33．1mmoL／g。     

Properties of adsorbents prepared by the alkali activation of Aleksandriisk brown coal

Highly microporous adsorbents (micropore fraction of ～70%) were prepared by the alkali activation-thermolysis (800°C, 1 h) of brown coal (C ^daf = 70.4%) in the presence of potassium hydroxide at the KOH/coal weight ratio R _KOH ≤ 2.0 g/g. The dependences of the specific surface areas and adsorption capacities of the adsorbents for methylene blue (A_MB, mg/g), iodine (A_I, mg/g), and hydrogen (\(A_{H_2 } \), wt %) on R _KOH were determined. The adsorbents obtained at R _KOH ≥ 1.0 g/g exhibited developed specific surface areas and good adsorption characteristics (A_I = 1000–1200 mg/g, A_MB = 200–250 mg/g, and \(A_{H_2 } \) ≤ 3.16 wt % at 0.33 MPa). The high capacity for hydrogen allowed us to consider brown coal adsorbents as promising materials for use as hydrogen accumulators.     

Liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit

The liquid products of the alkaline activation of brown coal from the Aleksandriiskoe deposit (800°C; 1 h; activator, KOH) were studied by thermal analysis, IR spectroscopy, and ¹H and ¹³C NMR spectroscopy. They were formed in ∼30% yield; they consisted of pyrogenic water (∼50%) and a resinous mixture of organic substances with increased hydrogen and oxygen contents and decreased carbon and sulfur contents. On heating, potassium hydroxide completely decomposed the quinoid structures of coal, decreased the concentration of aromatic components in resin, and increased the concentrations of CH₃-, -CH₂-, and OH-groups. This is consistent with the well-known thermally initiated reactions of alkaline degradation and dehydrogenation at high temperatures (400–800°C). The thermal lability of resinous products was evaluated, and the heats of combustion (32.4–32.7 MJ/kg) were determined; the latter values indicate that these products can be used as fuel.     

Nanoporous brown coal adsorbents prepared by alkaline activation with thermal shock

The properties of nanoporous adsorbents prepared from brown coal by alkaline activation with thermal shock (800°C) were studied. The dependences of the value of S _BET and the volumes of macropores, mesopores, micropores, and pores to 1 nm in diameter in the nanoporous adsorbents on isothermal exposure time (to 90 min) and the nature of alkali (LiOH, NaOH, and KOH) were determined. The comparison of changes in pore volumes and pore size distributions indicated that the adsorbent with the most developed subnanopore structure was formed at the initial stage (to 10 min) of activation. In this material, about a half of the total pore volume consisted of pores with diameters to 1 nm.     

Effects of brown coal quality and process parameters on the hydroliquefaction of brown coal

During the development of the HVB process the influence of different parameters on the process have been investigated. In this Paper the influence of the properties of the brown coal on the process is reported. It is shown that: (1) the petrographical composition of Rhenish brown coal has virtually no effect on the HVB process; (2) the problems of sedimentation caused by the ash composition of the brown coal can be overcome by a particular thermal pretreatment of the coal; and (3) the moisture content of the brown coal is of minor importance for the technical realization of the HVB process.     

KOH activation of mesoporous carbons obtained by soft-templating

Mesoporous phenolic resin-based carbons were prepared by soft-templating synthesis and activated by KOH. It is shown that the KOH activation of these mesoporous carbons results in a substantial increase of microporosity with simultaneous preservation of mesoporous structure. The resulting micro- and mesoporous carbons possess high surface area and large volume of mesopores.     

Hydrogenation of brown coal: 10. Multi-element promoters for the liquefaction of wet Victorian brown coal in synthesis gas

A series of multi-element promoters based on copper, nickel or cobalt in association with sodium aluminate, sodium silicate, or magnesium acetate have been shown to be excellent promoters of the reaction of only partially dried (40 wt% moisture) Victorian brown coal with synthesis gas in the presence of tetralin. The best of these promoters, based on copper (0.30 mole kg⁻¹ dry coal) and sodium aluminate (1.10 mole kg⁻¹ dry coal) features a high conversion (94 wt%) for liquefaction at 405 °C with a high yield of useful liquid products (46 wt%) soluble in light petroleum. The process also yields a net production of hydrogen through in-situ promotion of the water gas shift reaction.     

褐煤综合利用中原料煤干燥特性研究

研究了褐煤资源高效综合利用中干燥时间、干燥温度、干燥方式等因素对原料煤性质,特别是粗褐煤蜡和腐植酸产率的影响。结果表明:原料煤的干燥需要在适宜的温度下和时间内进行,水分不是越低越好,否则不仅浪费能源和时间,还会影响主要产品的产率及品质。褐煤蜡产率与含水量之间存在重要的内在联系,即不同干燥条件下,水质量分数在10%—20%之间时,褐煤蜡产率均较高。同时,原煤在开采后允许进行一定时间的放置,除水质量分数降低外不会对原煤产生其他影响。建议在褐煤综合利用中,原料煤的干燥最好在100—150℃之间进行,调节干燥时间(需30—60 min),使水质量分数控制在10%—20%之间。     

Synthesis of mesoporous carbons for supercapacitors from coal tar pitch by coupling microwave-assisted KOH activation with a MgO template

Mesoporous carbons (MCs) for supercapacitors were prepared from coal tar pitch by a microwave-assisted one-step process coupling the potassium hydroxide (KOH) activation and magnesium oxide (MgO) template. MCs were characterized by scanning electron microscope and X-ray diffraction. The results show that the specific surface area (S_BET), micropore volume and specific capacitance of MCs made by microwave heating as well as the energy density of MC capacitors pass through a maximum with increasing mass of MgO and the relative mass ratio of KOH/pitch. The S_BET of MCs varies from 1003 to 1394 m²/g. The S_BET and total pore volume of MC and microporous carbon made by microwave heating are bigger than that made by conventional heating. Under optimum conditions with the masses of coal tar pitch, MgO, KOH at 9 g, 12 g, 6 g, and the microwave power at 600 W, MC (MC_9-12-6) made at 30 min heating time shows a high specific capacitance of 224 F/g in 6 M KOH aqueous electrolyte after 1000 cycles. The results have shown that microwave-assisted rapid KOH activation coupled with the MgO template is an efficient one-step approach to the preparation of low cost yet high performance MCs for supercapacitors.     

煤与KOH共热解制备富氢合成气的研究

以制备富氢合成气为目的,进行了煤与KOH共热解试验。试验在升温速率6％／min,120mL／minN2气氛下进行,采用GC—TCD测定合成气的组成,考察了碱煤比对释氢特性、合成气组成与转化率的影响。结果表明,在不同的碱煤比下,合成气中H2始终占据优势,碱煤比为2：1时,氢气产量与转化效率达到最优。     

Evidence for the presence of cyanide during carbon activation by KOH

The observation that carbon activation by KOH gives rise to a significant formation of cyanide moieties is confirmed. However, contrary to what has been reported, our results show that the N₂ used as an atmosphere during the activation process has little to do with the formation of such cyanide moieties. The main source of cyanides is ascribed to structural nitrogen already present in the precursors. Reducing species (H₂ and metallic K) formed during the KOH carbon activation process might promote the transformation of that structural nitrogen to cyanides. In order to minimise cyanide formation (and related environmental concerns), materials with low nitrogen content should be selected as precursors for the preparation of KOH-activated carbons.     

Rheological behaviour of Victorian brown coal

As part of an investigation into the use of extrusion as a feed mechanism for processing very wet, soft, brown coals, a parallel plate plastometer was used to obtain absolute rheological data for Loy Yang coal which had been previously work-softened by shearing for various lengths of time. A Bingham model was found to describe the flow behaviour of the material adequately. Most of the resistance to deformation was found to be produced by viscous and not plastic stresses, from which it was concluded that the work-softening effect is a result of a decrease in Bingham viscosity. The fine structure of the coal is broken down by shearing and the water released as a consequence acts as a lubricant between the particles. The ruptured bonds do not remake on standing. It is concluded that any investigation of coal rheology, or the design of any industrial handling or processing operation in which coal rheology might be important, should take account of not only the total water content of the coal but also the disposition of that water. For example, coals with low water contents which would not be thought suitable for extrusion because of their apparent stiffness may be suitable if water can be liberated from the structure by shearing.     

Low-temperature oxidation of Victorian brown coal

A study has been made of low-temperature oxidation of Victorian brown coal at 35 °C and oxygen pressure of 0.1 M Pa and regression analysis of the experimental results shows that the reaction can best be described by the continuous reaction model. The reaction is subject to reaction product inhibition, apparently caused by product adsorption. Progressive conversion is obtained through a series of cycles consisting of a reaction step followed by evacuation of the coal. The rate equation developed from the continuous reaction model describes satisfactorily the progress of the reaction in each of these cycles. A study of earlier findings on the nature of Victorian brown coal oxidation products indicates that the product water may be significant in this reaction inhibition.     

KOH活化对超级电容器用氮掺杂石墨烯的影响

为了制备高比表面积、适宜孔径的石墨烯基材料,从而使其具备良好的电化学性能,化学活化法已经被广泛地研究。本文以氧化石墨烯(GO)为基体,密胺树脂预聚体为氮掺杂剂,采用KOH活化法制备超级电容器用氮掺杂石墨烯材料。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、比表面积和孔隙度分析(BET)、循环伏安法(CV)及恒电流充放电法(GCD)等对其微观形貌和电化学性质进行分析。结果表明:在活化温度800℃,活化倍率3.0时,样品的比表面积为554.32 m2/g,比电容达到312 F/g,具有更好的电化学特性。     

Molecular structure of a brown coal

A model for the structural unit of a typical Rheinische Braunkohle has been developed from the results of elemental analyses, pyrolysis experiments and titration studies and from extrapolation of literature data for similar coals. The model presented here has been successfully applied to explain the pyrolysis and hydropyrolysis behaviour of Rheinische Braunkohle.     

Improving the thermal-shock resistance of corundum ceramic

Conclusions We have studied the effect of coarse-grained additives of electrocorundum, sintered mullite, SiC, and electrosmelted ZrO₂ on the thermal-shock resistance of a corundum ceramic obtained from a mixture of technical alumina and glass-forming oxides. New ceramic materials have been obtained with a higher thermal-shock resistance, a lower open porosity, and adequate strength. The materials can be used in the manufacture of articles to be operated under conditions of stringent thermal loading.Translated from Ogneupory, No. 2, pp. 44–48, February, 1982.