Preparation and characterization of activated carbon from date stones by physical activation with steam

Activated carbons are produced from wastes of Algerian date stones by pyrolysis and physical activation in the presence of water vapor into a heated fixed-bed reactor. The effect of pyrolysis temperature and activation hold time on textural and chemical surface properties of raw date stones and carbon materials produced are studied. As expected, the percentage yield decreases with increase of activation temperature and hold time. The characterization of carbon materials is performed by scanning electron microscopy (SEM). X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption (BET). Results show the presence of cellulose and hemicellulose in the raw material, and the predominance of carbon and graphite after pyrolysis. Different oxygen-containing functional groups are found in the raw material while aromatic structures are developed after pyrolysis and activation. The best specific surface area (635 m² g⁻¹) and microporous volume (0.716 cm³ g⁻¹) are obtained when the date stones are grinded, pyrolysed at 700 °C under a 100 cm³ min⁻¹ nitrogen flow and then activated under water vapor at 700 °C for 6 h.     

Preparation of activated carbon from sawdust by zinc chloride activation

A series of activated carbons were prepared from sawdust by zinc chloride activation in different operation conditions. The effects of operation parameters such as impregnation ratio, activation temperature and time on the adsorption properties of activated carbons were measured and analyzed in order to optimize these operation conditions. The experimental results show that under the experimental circumstances studied, both the yield and the adsorption for iodine and methylene blue of activated carbon can reach a relatively higher value in the chemical activation process with the impregnation ratio of 100% ZnCl₂/sawdust in the activation temperature of 500 °C carbonized for 60–90 minutes which are the optimum activation conditions in making wood activated carbon. The most important operation parameter in chemical activation with zinc chloride was found to be the impregnation ratio.     

Synthesis of thermally stable mesoporous cerium oxide with nanocrystalline frameworks using mesoporous silica templates

Highly ordered mesoporous cerium oxides, composed of nanocrystalline pore walls and exhibiting high thermal stability even at 973 K, were synthesized using mesoporous silica templates with hexagonal p6mm and cubic Ia3d symmetries.     

Preparation of activated carbon from polyaniline by zinc chloride activation as supercapacitor electrodes

Activated carbon for supercapacitor electrode was prepared from polyaniline using chemical activation with ZnCl₂. The morphology, surface chemical composition, and surface area of the as-prepared carbon materials were investigated by scanning electron microscope, atomic force microscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller measurement, respectively. Electrochemical characteristics were evaluated by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy tests in 6.0 mol L⁻¹ KOH aqueous solution. The electrochemical measurements showed that ZnCl₂ activation led to better capacitive performances. The activated carbon presented a high-specific gravimetric capacitance of 174 F g⁻¹, with rectangular cyclic voltammetry curves at a scan rate of 2 mV s⁻¹, and it remained 93% even at a high scan rate of 50 mV s⁻¹. These demonstrated that activated carbon would be a promising electrode material for supercapacitors.

     

Preparation of activated carbon from polyaniline by zinc chloride activation as supercapacitor electrodes

Activated carbon for supercapacitor electrode was prepared from polyaniline using chemical activation with ZnCl₂. The morphology, surface chemical composition, and surface area of the as-prepared carbon materials were investigated by scanning electron microscope, atomic force microscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller measurement, respectively. Electrochemical characteristics were evaluated by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy tests in 6.0?mol?L^?? KOH aqueous solution. The electrochemical measurements showed that ZnCl₂ activation led to better capacitive performances. The activated carbon presented a high-specific gravimetric capacitance of 174?F?g^??, with rectangular cyclic voltammetry curves at a scan rate of 2?mV?s^??, and it remained 93% even at a high scan rate of 50?mV?s^??. These demonstrated that activated carbon would be a promising electrode material for supercapacitors.     

Preparation and characterization of highly mesoporous spherical activated carbons from divinylbenzene-derived polymer by ZnCl(2) activation

Highly mesoporous spherical activated carbons (SACs) were prepared from divinylbenzene-derived polymers by ZnCl(2) activation; the effects of activation temperature and retention time on the yield and textural properties of the resulting SACs were studied. SACs thus prepared were characterized by N(2) adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and aqueous adsorption assays. All the SACs were generated with high yield (>54%) and high mesopore fraction (around 80%). SEM and XRD analyses of SAC28 verified the presence of the disordered micrographite stacking with developed mesoporosity. Compared with conventional activated carbons, SAC28 prepared in our study exhibited a comparable adsorption capacity of 190 mg g(-1) for bisphenol A and even more excellent capacity of 330 mg g(-1) for phenol. Bisphenol A preloading significantly reduced the adsorption capacity of SAC28 for phenol due to both reduction of adsorption sites and pore blockage.     

Preparation of activated ordered mesoporous carbons with a channel structure

Activated ordered mesoporous carbons with a channel structure (AOMCs-CS) were successfully prepared by imposing CO(2) activation on ordered mesopore carbon C-FDU-15. It is found that the continuous carbon framework of the precursor C-FDU-15 plays an important role in keeping the order structure of the resulting AOMCs-CS. The mild activation (e.g., 31 wt % burnoff) does not impair the order degree. After that, the order degree gradually decreases with further increasing burnoff. However, the basic hexagonal mesostructure of C-FDU-15 can still be found in the AOMCs-CS when the burnoff is up to 73 wt %, although many carbon walls are punched and thus many larger mesopores and marcropores are generated. With increasing burnoff, the surface area and volume of micropores increase first and then decrease, and the surface area and volume of mesopores continuously increase. The highest measured Brunaruer-Emmett-Teller (BET) surface area, micropore volume, and total pore volume of the AOMCs-CS reach 2004 m(2)/g, 0.50 cm(3)/g, and 1.22 cm(3)/g, respectively.     

Preparation of activated carbon from date pits: Effect of the activation agent and liquid phase oxidation

Two series of activated carbons have been prepared from date pits; series C, using carbon dioxide as activating agent, and series S, prepared by activation with steam under the same experimental conditions. The obtained samples were oxidized with nitric acid in order to introduce more oxygen surface groups. The surface area and porosity of the parent and oxidized activated carbons were studied by N₂ adsorption at 77 K and CO₂ adsorption at 273 K. The oxygen surface complexes were characterized by temperature-programmed decomposition (TPD). The results show that carbon dioxide and steam activations produce microporous carbons with an increasing amount of CO evolving groups when increasing the burn-off. On the other hand, oxidation with nitric acid increases the amount of CO and CO₂ evolved by the decomposition of surface oxygen groups, this increase being related to the development of porosity in the carbon with the degree of activation and to the activating agent used (CO₂ versus steam).     

Preparation of mesoporous activated carbons from coal liquefaction residue for methane decomposition

Mesoporous activated carbons were prepared from direct coal liquefaction residue(CLR)by KOH activation method,and the experiments were carried out to investigate the effects of KOH/CLR ratio,solvent for mixing the CLR and KOH,and carbonization procedure on the resultant carbon texture and catalytic activity for catalytic methane decomposition(CMD).The results showed that optimal KOH/CLR ratio of 2:1; solvent with higher solubility to KOH or the CLR,and an appropriate carbonization procedure are conductive to improving the carbon pore structure and catalytic activity for CMD.The resultant mesoporous carbons show higher and more stable activity than microporous carbons. Additionally,the relationship between the carbon textural properties and the catalytic activity for CMD was also discussed.     

Benzylic oxygenation of alkylarenes with molecular oxygen in the presence of activated carbon

A variety of alkylarenes such as fluorenes, xanthenes, and anthrone were effectively oxygenated to the corresponding carbonyl compounds with molecular oxygen as oxidant in the presence of activated carbon.     

高热稳定性有序介孔TiO_2/活性炭制备及其孔-孔协同光催化性能

以十六烷基三甲基溴化铵(CTAB)表面活性剂和钛酸四丁酯分别为造孔模板和钛源,通过超声辅助溶剂挥发自组装技术制备有序介孔氧化钛(ordered mesoporous Ti O2,OMPT)及其活性炭负载体(ordered mesoporous Ti O2/AC,OMPTA).为探讨OMPTA结构与性能之间的关系,采用超声辅助溶胶-凝胶技术合成了无孔氧化钛/活性炭(nonporous Ti O2/AC,NPTA)负载体,利用热重-差热(TG-DTA)、X射线衍射(XRD)、氮气吸附-解吸、透射电子显微镜(TEM)和紫外漫反射(DRS)等手段对制备材料结构进行表征.以酸性红B(acid red B,ARB)的光催化降解为探针实验,评价OMPTA的光催化性能和使用寿命,提出了孔-孔协同光催化扩增机制,并探讨了催化条件(染料浓度、催化剂浓度和溶液p H)对协同扩增效果的影响.结果表明:相对于纯OMPT,OMPTA具有晶粒生长的高活化能、较小的粒径尺寸和对有序介孔结构的高热稳定性,这归功于活性炭的吸附力和非晶相层对晶粒生长的阻碍作用.由于孔-孔协同光催化扩增效应,导致OMPTA在NPTA、OMPT-AC、OMPT、P25和NPT中具有更高的催化活性.热处理温度强烈影响OMPTA的光催化活性,其中OMPTA-500具有最高的光催化活性,这归功于其具备完善的结晶性、相对高浓度的羟基和Ti3+离子.同时,OMPTA-500在重复使用过程中也具有很高的光催化性能.当使用OMPTA-500为催化剂对ARB降解时,最佳的催化条件为催化剂浓度1 g/L,ARB浓度15 mg/L,p H 5.     

Preparation of activated carbon from cherry stones by physical activation in air. Influence of the chemical carbonisation with H2SO4

In the preparation of activated carbon (AC) by the method of physical activation, the carbonisation stage is usually carried out by heat treatment of a precursor at a given temperature in an inert atmosphere, whereas the activation stage is performed in air, carbon dioxide or steam atmosphere. Here, the use of a chemical carbonisation-based method with H₂SO₄ in aqueous solution as an alternative to the physical carbonisation method is studied. Using cherry stones (CS), AC was prepared by physical activation in air, as usual, and by carbonising with H₂SO₄ prior to activating in air. CS was carbonised at 600 °C in nitrogen atmosphere or with H₂SO₄ solutions of various concentrations and the resulting products were activated at 350–550 °C in air. Characterisation was undertaken by proximate analysis, TG–DTG analysis, N₂ adsorption at −196 °C, mercury porosimetry, density measurements and FT-IR spectroscopy. By the H₂SO₄-chemical carbonisation, AC with a lower inorganic matter content, wider pore size distribution in the meso- and macropore ranges, higher mesopore volume and carboxylic acid groups are prepared. The development of microporosity is similar regardless of the carbonisation method provided that the activation of the chemically carbonised product is effected at higher temperature. Physical carbonisation results in AC with an homogeneous macroporosity and with quinone type functional groups. Yield is also slightly higher by this carbonisation method.     

Preparation and characterization of activated carbon from bagasse fly ash

Activated carbons from bagasse fly ash (BFA) were prepared by one step chemical activation using ZnCl₂ as activating agent, or combination method of chemical with CO₂ physical activation (physicochemical activation). The development of porosity was studied in correlation with the method of activation, activation temperature, and also the chemical weight ratio. A typical sample by the combination method at 600 °C and weight ratio of ZnCl₂:BFA = 2 exhibited micropore volume of 0.528 cc/g, mesopore volume of 0.106 cc/g and surface area of 1200 m²/g. For determining the adsorption capacity of the carbon samples in solutions, phenol and methylene blue equilibrium adsorption experiments were conducted. The properties and adsorption capacity of the synthesized activated carbons has been compared to commercial activated carbon (Norit^® SX Plus).     

Preparation and characterization of activated carbon fibers from liquefied wood

Wooden activated carbon fibers (WACFs) were prepared from phenolated Chinese fir (Cunninghamia lanceolata) using CO₂ activation; microstructure characterization, the adsorption capacity, BET-specific surface area, and pore distribution of WACFs were investigated by SEM and X-ray analysis. Results showed that WACFs have a smooth surface and round or elliptical cross-section. The (002) crystal plane diffraction peak of the WACFs was obviously heightened, also showing an apparent (100) diffraction peak. With increased activation temperature, the value of d ₍₀₀₂₎ gradually decreased, whereas the values of the crystallite sizes L _a and L _c initially decreased and then increased. The L _c/d ₍₀₀₂₎ and g values corresponding to the degree of change in the graphitization structure increased. WACFs mainly have micropores as well as a few macro- and mesopores. The micropore diameter of WACFs has a narrow range (0.3–0.5 nm). With increased activation temperature, the single-point surface area, Brunauer-Emmett-Teller surface area, micropore area, single-point total pore volume, and micropore volume of WACFs increased, while the pore diameter decreased. At 900 °C, the iodine adsorption and yield rate of WACFs were 779.22 mg/g and 51.48 %, respectively.     

氯化锂活化制备活性炭及吸附锂离子性能研究

采用化学活化法,用猪血粉为前驱体和新型活化剂氯化锂活化制备锂离子活性炭（LB-AC）并进行吸附锂离子研究。用氯化锂对猪血粉进行活化后我们得到比表面积为695 m2?g-1,总孔体积为0.3 cm3?g-1的LB-AC。通过扫描电子显微镜、元素分析、X 射线衍射分析和红外光谱分析等分析手段对LB-AC表面形貌和表面基团进行表征。吸附?解吸实验结果表明,随着温度升高,锂离子的吸附容量随之增加,表明LB-AC对锂离子的吸附是一种吸热反应。当温度增加至35 ℃和45 ℃时,其吸附容量分别增加至1.41 mg?g-1和1.52 mg?g-1。锂离子的初始浓度增加,吸附容量也增加。锂的脱附随着盐酸浓度的升高而增加。LB-AC对锂离子的选择性很高,且吸附剂在碱性环境下吸附容量更高,在酸性环境下基本不吸附。     

Dehydrogenation of ethylbenzene with nitrous oxide in the presence of mesoporous silica materials modified with transition metal oxides

The novel mesoporous templated silicas (MCM-48, SBA-15, MCF, and MSU) were used as supports for transition metal (Cu, Cr, or Fe) oxides. The catalysts were synthesized using the incipient wetness impregnation, and characterized by low-temperature N2 sorption, DRIFT, photoacoustic IR spectroscopy, UV-vis diffuse reflectance spectroscopy, and temperature-programmed desorption of ammonia. It was shown that the preparation method used results in different distributions and dimensions of the transition metal oxide clusters on the inert support surface. The prepared catalysts were tested in the reaction of oxidative dehydrogenation of ethylbenzene in the presence of nitrous oxide. The iron-containing catalysts showed the highest catalytic activity. The presence of isolated Fe3+ was found to be the most important factor influencing the ethylbenzene conversion. The undesirable effect of the increase in selectivity toward CO2 was observed for the samples with the highest concentrations of acidic surface sites.     

Production of molded activated carbon from carbon black and petroleum pitch by alkaline activation

Method for obtaining molded activated carbon on the basis of carbon black, petroleum pitch, and potassium hydroxide is suggested. The method consists in mixing of these components in the presence of a solvent, molding, and subsequent carbonization at temperatures of 600–1000°C, followed by washing. The resulting samples have a specific surface area of up to 700 m² g^–1, total pore volume of 0.6–1.5 cm³ g^–1, and crushing strength of 1–4 MPa. This material can find industrial use in purification of technological gases and fluids in fixed-bed adsorbers.     

Preparation of mesoporous aluminum hydroxide and oxide in ionic liquids

Mesoporous aluminum hydroxides and oxides were synthesized using ionic liquids (ILs) as templates. The influence of various factors (the nature of the IL, pH, ultrasonication, surfactants, reagent ratio, and the nature of the aluminum precursor) on the specific surface area and pore volume was analyzed.     

High activity mesoporous copper doped cerium oxide catalysts for the total oxidation of polyaromatic hydrocarbon pollutants

The doping of mesoporous ceria with copper significantly enhances activity for naphthalene total oxidation, the enhanced performance is controlled by the increased concentration of surface oxygen defects.