Effect Of Activation Temperature Research Articles

Influence of Sintering Temperature on Photoluminescence of Gd2O3:Eu3+ Phosphors Prepared by Liquid Phase Reaction Method

Nanostructured materials with diameters less than 100 nm have been studied vigorously in recent years. Many studies have been devoted on exceptional optical properties induced by quantum confinement for fundamental research and applications. For excellent luminescence characteristics, phosphor particles have to acquire fine size, narrow size distribution, non-aggregation, good crystalline, and spherical morphology. A liquid-phase reaction method was chosen in this study due to the low reaction temperature. Gd2O3:Eu3+ phosphors were synthesized by the liquid-phase reaction method and the effect of activation temperature on optical properties of the phosphors was investigated.

BET, TG–DTG, FT-IR, SEM, iodine number analysis and preparation of activated carbon from acorn shell by chemical activation with ZnCl2

Activated carbons were produced from acorn shell by chemical activation with zinc chloride (ZnCl2) at 600°C in N2 atmosphere and their characteristics were investigated. The effects of activation temperature, duration time, impregnation concentration of agent and impregnation time were examined. Adsorption capacity was demonstrated with BET and iodine number. The obtained activated carbons were characterized by measuring their porosities and pore size distributions. BET surface area of the best produced activated carbon was 1289m2/g. The surface chemical characteristics of activated carbons were determined by FT-IR spectroscopic method. The microstructure of the produced activated carbons was examined by scanning electron microscopy (SEM). Thermal gravimetry (TG) and derivative thermal gravimetry (DTG) analysis of produced activated carbon was carried out.

Potential application of activated carbon from maize tassel for the removal of heavy metals in water

Water-pollution problems worldwide have led to an acute shortage of clean and pure water for both domestic and human consumption. Various technologies and techniques are available for water treatment which includes the use of activated carbon. In this study activated carbons used for the removal of lead (II) ions from water samples were prepared from maize tassels (an agricultural waste residue) which were modified using physical and chemical activation. In the physical activation CO2 was used as the activating agent, while in chemical activation H3PO4 with an impregnation ratio ranging from 1 to 4 was employed. The maize tassel was pyrolysed at different temperatures ranging from 300°C to 700°C in an inert atmosphere for a period of 60min and activated at 700°C for 30min. The effects of activation temperature, impregnation ratio and duration were examined. The resultant modified tassels were characterised by measuring their particle-size distribution, porosities, pore volume, and pore-size distribution using scanning electron microscopy (SEM). The activated carbon produced by chemical activation had the highest BET surface area ranging from 623m2g−1 to 1262m2g−1. The surface chemistry characteristics of the modified tassels were determined by FT–IR spectroscopy and Boehm’s titration method. The experimental data proved that properties of activated carbon depend on final temperature of the process, impregnation ratio and duration of the treatment at final temperature. The adsorption studies showed that chemically prepared activated carbon performed better than physically prepared activated carbon.

Preparation and characterization of activated carbons for SO2 adsorption from Taixi anthracite by physical activation with steam

Taixi anthracite was used as a precursor to prepare activated carbons (AC) for SO2 adsorption from flue gas. In this work the activated carbons were prepared by physical activation with steam. Specifically, the effects of activation temperature and burn-off degree on the physico-chemical properties of the resulting AC samples were comparatively studied. The different types of pore volumes, pore size distributions and surface chemistries of the activated carbons on the SO2 adsorption were also analyzed. The results show that the increasing burn-off leads to samples with continuous evolution of all types of pores except ultramicropore. The ultramicropore volume increases to a maximum of 0.169 cm3/g at around 50% burn-off and then decreases for 850 °C activation. At higher activation temperature, the micropore volume decreases and the mesopore structure develops to a certain extent. For all the resulting AC samples, the quantities of the basic surface sites always appear much higher than the amount of the acidic sites. The activated carbon prepared with higher micropore volume, smaller median pore diameter and higher quantities of the basic surface sites represents better SO2 sorption property.

Preparation of activated carbons for SO 2 adsorption by CO 2 and steam activation

Taixi anthracite was used as a precursor to prepare microporous activated carbons for SO 2 adsorption from flue gas. In this work the activated carbons were prepared by physical activation with carbon dioxide and steam, respectively. Specifically, the effects of activation temperature and burn-off degree on the physico-chemical properties of two series were comparatively studied. The physical properties of the AC samples on the SO 2 adsorption were also investigated. The surface area and porosity of sample was studied by N 2 adsorption at 77 K. The surface chemistry was evaluated by FTIR. The BET surface areas and micropore volumes of steam-activated carbons are always larger than those by CO 2 activation except the samples with burn-off above 70%. The CO 2 activation leads to samples with continuous evolution of ultramicropore volumes. At higher activation temperature, the decrease of micropore volume is attributed to an external burn-off for both series. All the activated carbons show basic properties, which makes these samples suitable for SO 2 adsorption. It is observed that a large micropore volume does not necessarily assure an optimal adsorption of SO 2; rather, the pore size and pore size distribution should be considered as important parameters.

Preparation and characterization of activated carbon from cotton stalks in a two-stage process

Activated carbons are prepared from cotton stalks by chemical activation with ZnCl 2, H 2SO 4 and physical activation using CO 2 and steam–CO 2 mixture for temperatures of 750, 850 and 900 °C. The effects of activation temperature and duration time, impregnation concentration of agent, impregnation times, and physical activating agent are examined. These materials are characterized by adsorption/desorption of N 2 to determine the BET areas, thermogravimetric analysis (TG, DTA), FTIR and scanning electron microscopy (SEM). ZnCl 2 under CO 2 atmosphere was found more effective than H 2SO 4 as a chemical reagent under identical conditions in terms of porosity development. The maximum BET surface area is found to be 2053 m 2/g for active carbons produced with ZnCl 2 activation under CO 2 atmosphere.

Effect of activation temperature on the surface copper particles and catalytic properties of Cu–Ni–Mg–Al oxides from hydrotalcite-like precursors

Abstract The Cu–Ni–Mg–Al oxides catalysts for furfural hydrogenation were prepared from the hydrotalcite-like precursors, and the effect of activation temperature on the Cu0 particles and catalytic properties of the catalyst was thoroughly investigated. The catalyst activated by H2 at 300 °C was found to exhibit the best catalytic activity, due to the presence of the smallest Cu0 particles with a high dispersion. Moreover, the bigger Cu0 particles were active for furfuralcohol hydrogenolysis to 2-methylfuran in the liquid-phase (ethanolic solution), and the hydrogenation of the furan ring of furfuralcohol and 2-methylfuran on Cu0 particles was easily achieved in the vapour-phase.

Experimental Design To Optimize the Preparation of Activated Carbons from Herb Residues by Vacuum and Traditional ZnCl2 Chemical Activation

Doehlert matrix was used to optimize the experimental conditions for the preparation of activated carbons from herb residues by vacuum chemical activation and traditional chemical activation using ZnCl2 as activation agent. The effects of activation temperature and impregnation ratio, the most influential factors of ZnCl2 chemical activation, were studied. The obtained activated carbons were characterized by total yield and methylene blue and iodine adsorption value. Each response has been described by a second-order model, and the predicted model presented a good agreement with experimental data. The results showed that activated carbons prepared by vacuum chemical activation have higher yield and better adsorption capacity. The removal percentages of methylene blue for the two optimal activated carbons and a commercial activated carbon were determined. The activated carbon prepared by vacuum chemical activation exhibited the highest methylene blue removal efficiency.

リンゴ剪定枝から調製した活性炭の特性に及ぼす賦活温度の影響

本研究では，リンゴ剪定枝から空気賦活で調製した活性炭の収率や灰分，比表面積，吸湿率に及ぼす賦活温度の影響を明らかにし，それらの物性に関してスギを原料とした活性炭と比較検討を行った。その結果，リンゴ剪定枝を原料とした活性炭の賦活収率は，900℃が最も低く，スギを原料としたものよりも低い値を示した。また，灰分はリンゴ剪定枝の方が高かった。比表面積は，900℃が最も高く，灰分を除いて換算した比表面積はスギよりも高い値を示した。吸湿率は，相対湿度および賦活温度が高くなるに従って高くなり，灰分を除いて換算した吸湿率はスギよりも高い値を示した。

Pig bone derived hierarchical porous carbon and its enhanced cycling performance of lithium–sulfur batteries

Pig bone derived carbon with a unique hierarchical porous structure was prepared by potassium hydroxide (KOH) activation. The effects of activation temperature on the textural properties of the pig bone based carbons were investigated. The hierarchical porous carbons exhibit the largest BET specific surface areas and pore volume when the activation temperature reaches 850 °C, and the carbon still maintains a highly hierarchical structure even when the temperature is up to 950 °C. The pig bone derived hierarchical porous carbon/sulfur composites have been tested as a novel cathode for lithium–sulfur batteries. The result shows that the cycle stability and the utilization of sulfur in the lithium–sulfur batteries have been largely improved. The hierarchical porous carbon/sulfur cathode has a high initial capacity of 1265 mAh g−1 and 643 mAh g−1 after 50 cycles, which is higher than that of the normal cathodes with compact structures.

Low temperature CO oxidation on Cu–Cu2O/TiO2 catalyst prepared by photodeposition

A series of Me/TiO2 samples (Me = V, Cr, Mn, Fe, Co, Ni, Cu and Zn) with designed Me : TiO2 ratio of 1 : 10 were prepared by a photodeposition method and studied for the oxidation of CO. The Cu/TiO2 catalyst exhibited remarkably high activity and an overall CO oxidation could be achieved at <100 °C. The effects of activation temperatures, GHSV and initial CO concentration on CO oxidation over Cu/TiO2 were further investigated. XRD, TEM, XPS-AES, H2-TPR and FTIR of CO adsorption were employed to characterize Cu/TiO2 samples and the exact composition of Cu/TiO2 prepared by photo-deposition was determined to be Cu–Cu2O/TiO2. Based on the catalytic and characterization results, the possible mechanism for CO oxidation over Cu–Cu2O/TiO2 was discussed. Finally, the durability and deactivation of Cu–Cu2O/TiO2 during CO oxidation was investigated in time-on-stream reaction.

Production of activated carbon from olive bagasse by physical activation

Activated carbons were produced from olive bagasse and their characteristics were investigated. Olive bagasse was first carbonized at 500 °C in N 2 atmosphere. Then, the obtained chars were activated with steam. The effects of activation temperature and duration were examined. The resultant activated carbons were characterized by measuring their porosities and pore size distributions. The activated carbons produced had the BET surface areas ranging from 523 to 1106 m 2/g. The total pore volume was increased from 0.2981 to 0.6067 cm 3/g. Adsorption capacity was demonstrated by the iodine numbers. The surface chemical characteristics of activated carbons were determined by FTIR spectroscopic method and Boehm's titration method. The microstructure of the activated carbons prepared was examined by scanning electron microscopy (SEM). The experimental data was proved that the properties of activated carbons depend on the final temperature of the process and duration of treatment at the final temperature.

A comparison of physical activation of carbon xerogels with carbon dioxide with chemical activation using hydroxides

Carbon xerogels synthesized with a fixed resorcinol/sodium carbonate molar ratio (R/C) were physically activated using CO 2. The effect of activation temperature and activation time on the final properties of the activated carbon xerogels was evaluated. The specific surface area increases from ∼600 m 2 g −1 to 2000 m 2 g −1 and more by increasing the temperature and duration of the activation step. A comparison between physical activation with CO 2 and chemical activation with hydroxides was also performed: it was found that both processes produce an increase of the micropore volume and specific surface area without altering the mesoporosity developed during the synthesis. However, chemical activation can lead to the development of the narrow microporosity mainly whereas, in physical activation, the widening of the narrow micropores takes place whatever the process conditions.

Cu2(pyrazine-2,3-dicarboxylate)2(4,4′-bipyridine) Porous Coordination Sorbents: Activation Temperature, Textural Properties, and CO2 Adsorption at Low Pressure Range

The effect of activation temperature on the textural properties and low-pressure adsorption performance of the porous coordination polymer Cu2(pzdc)2(bpy) [pzdc = pyrazine-2,3-dicarboxylate, bpy = 4,4′-bipyridine], better known as CPL-2, was considered to elucidate the material potential for separations. The effective activation temperature range was estimated via coupled thermal gravimetric and Fourier transforms infrared spectroscopy analysis. A textural property analysis via the αs-plot, Dubinin−Radushkevich and Horvath−Kawazoe methods show that a significant reduction in effective surface area and micropore volume occurs when the activation temperature is increased from 373 to 423 K. Cooling of the sample in a moisture-free environment revealed that such reduction is nonreversible, as evidenced by single-component CO2 equilibrium adsorption tests. Although CO2 equilibrium adsorption isotherms exhibit a linear behavior in the ambient pressure range, an increase in activation temperature eventually decr...

Effect of activation at elevated temperature on Li-ion batteries with flame-retarded electrolytes

The effect of activation temperature on Li-ion batteries with flame-retarded electrolytes containing 5 wt.% dimethyl methyl phosphonate (DMMP) and trimethyl phosphate (TMP) is investigated respectively. It is found that activation at elevated temperature promotes the formation of a stable solid electrolyte interface layer on the graphite electrode, which may significantly suppress the reductive decomposition of DMMP and TMP and avoid graphite exfoliation. But fierce oxidation of the electrolytes on the LiCoO 2 electrode at elevated temperature is harmful to the cell performance. A procedure of so-called altered temperature activation (ATA) is adopted for LiCoO 2/graphite full-cells. It can compromise the contradictive effects on the separate electrodes at the elevated temperature. High capacity and good rate capability are obtained for the cells with the flame-retarded electrolytes, especially for the TMP-containing electrolyte.

Effects of CO 2 activation on porous structures of coconut shell-based activated carbons

In this paper, textural characterization of an activated carbon derived from carbonized coconut shell char obtained at carbonization temperature of 600 °C for 2 h by CO 2 activation was investigated. The effects of activation temperature, activation time and flow rate of CO 2 on the BET surface area, total volume, micropore volume and yield of activated carbons prepared were evaluated systematically. The results showed that: (i) enhancing activation temperature was favorable to the formation of pores, widening of pores and an increase in mesopores; (ii) increasing activation time was favorable to the formation of micropores and mesopores, and longer activation time would result in collapsing of pores; (iii) increasing flow rate of CO 2 was favorable to the reactions of all active sites and formation of pores, further increasing flow rate of CO 2 would lead carbon to burn out and was unfavorable to the formation of pores. The degree of surface roughness of activated carbon prepared was measured by the fractal dimension which was calculated by FHH (Frenkel–Halsey–Hill) theory. The fractal dimensions of activated carbons prepared were greater than 2.6, indicating the activated carbon samples prepared had very irregular structures, and agreed well with those of average micropore size.

Pilot Preparation of Activated Carbon for Natural Gas Storage

Pilot preparation was carried out for activated carbon from petroleum coke/KOH chemical activation, to improve the methane storage capacity. The effects of activation temperature in the range from 973 to 1073 K and particle size from 0.10 to 0.45 mm were studied by nitrogen adsorption isotherms and scan electronic microscopy. It was found the activation temperature significantly influenced the porous structure of activated carbon, with the operation range from 1003 to 1043 K. Also the surface area and pore volume of activated carbon could be enhanced by the smaller particle size of petroleum coke, because of the relatively larger particle surface. Through the methane storage analysis, it was observed that higher surface area and pore volume were beneficial to higher adsorption capacity, while the lower methane delivery was attributed to more developed porosity, implying that desorption capacity was also closely related to the porous morphology.

Preparation of a carbon monolith with hierarchical porous structure by ultrasonic irradiation followed by carbonization, physical and chemical activation

A two-step direct and simple method for the preparation of a hierarchical porous carbon monolith with micropores, mesopores and macropores is described. The two stages give more flexibility in the preparation of a porous carbon monolith. In step I a macroporous interconnected carbon monolith is prepared by ultrasonic irradiation during sol–gel polycondensation. The effects of sol–gel temperature, catalyst concentration and ultrasonic power on the structure of the monolith are investigated. In step II, mesopores are induced in the monolith by Ca(NO 3) 2 impregnation followed by CO 2 activation. The effect of activation temperature is also studied. A hierarchical interconnected carbon monolith with mean pore size diameter of 1.2 μm, BET surface area of 624 m 2/g, mesopore volume of 0.38 cm 3/g and micropore volume of 0.22 cm 3/g has been obtained from Ca(NO 3) 2 impregnation of the macroporous carbon monolith followed by CO 2 activation at 850 °C.

Preparation and characterization of polymer‐based spherical activated carbons with tailored pore structure

AbstractA series of spherical activated carbons (SACs) with different pore structure were prepared from divinylbenzene‐based polymer through CO2 activation. The effect of activation temperature and retention time on the yield and textural properties of the resulting SACs were studied. The SACs were characterized by N2 adsorption, X‐ray diffraction, scanning electron microscopy, and aqueous adsorption assays. Either increasing activation temperature or extending retention time decreases the yield of SACs. The BET surface area and pore volume increase with activation temperature and reach a maximum at 1000°C and then decrease at higher activation temperatures. At 1000°C, BET surface area, total pore volume, and mesopore pore volume increase with retention time from 0.5 to 2 h, and meanwhile micropore volume decreases. The micropores are gradually widened into mesopores with increasing activation temperature or extending retention time. SEM and XRD analyses of SAC10 verify the presence of developed porous structure composed of disordered micrographite stacking. Aqueous adsorption assays indicate that SACs have good adsorption capacity for phenol. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

PREPARATION AND CHARACTERIZATION OF POLYMER-BASED SPHERICAL ACTIVATED CARBONS

A series of spherical activated carbons (SACs) with different pore structures were prepared from chloromethylated polydivinylbenzene by ZnCl2 activation. The effects of activation temperature and retention time on the yield and textural properties of the resulting SACs were studied. All the SACs are generated with high yield of above 65% and exhibit relatively high mesopore fraction (me%) of 35.7%−43.6% compared with conventional activated carbons. The sample zlc28 prepared at 800°C for 2 h has the largest BET surface area of 891 m 2 g −1 and pore volume of 0.489 cm 3 g −1 . SEM and XRD analyses of zlc28 verify the presence of developed porous structure composed of disordered micrographite stacking with large amounts of interspaces in the order of nanometers.