Mesopore Content Research Articles

High Proton-Conducting Sulfonated Poly (Ether Ether Ketone)/ Functionalized Mesoporous Silica Composite Membranes

A novel organic–inorganic mesoporous silica functionalized with perfluoroalkylsulfonic acid groups analogous to that of Nafion® has been prepared. A condensation reaction between surface silanol groups of the mesoporous silicas and 1,2,2-trifluoro-2-hydroxy-1-trifluoromethylethane sulfonic acid Beta-sultone was conducted. High proton conducting sulfonated poly(ether ether ketone) (sPEEK)/ functionalized mesoporous silica composite membranes were prepared through homogeneous dispersive mixing and solvent casting method. In the study, proton conductivity (σ) of composite membrane is increased from 0.01 to 0.038 (S/cm) as the modified mesoporous silica content is increased from 0 to 5 wt. %. It is found that the ion exchange capacity (IEC) is increased from 1.54 to 1.70 (meq/g) as the modified mesoporous silica content is increased from 0 to 5 wt. %. From morphology investigation, it is found that incorporation of modified mesoporous silica by rotary vacuum evaporation enables the preparation of homogeneous membranes. The membranes present a good adhesion between inorganic domains which could be used for fuel cell applications.

Mesoporous Silica Supported Sulfated Zirconia Prepared by a Sol?Gel Process

Mesoporous silica-supported sulfated zirconia aerogels with different Zr/Si and S/Zr molar ratios were prepared using a one-step preparation. The characterization of these solids was conducted using N2 physisorption at 77 K, X-ray diffraction, mass spectrometry, and sulfur chemical analysis. The isomerization of n-Hexane was used as a catalytic test. Highly improved textural properties were obtained for these solids, and two types of mesopores were observed. Depending on the zirconium content, the size and amount of mesopores are highly affected. The importance of sulfates effectively bonded to Zr(IV) is elucidated, both for achieving high catalytic activity and for a good sulfur thermal stability. The catalytic activity (for a sample prepared with a particular S/Zr ratio) expressed per gram of Zr(IV) is comparable to that of pure sulfated zirconia.

Comparisons of porous and adsorption properties of carbons activated by steam and KOH

In this work, fir woods and pistachio shells were used as source materials to prepare porous carbons, which were activated by physical (steam) and chemical (KOH) methods. Pore properties of these activated carbons including the BET surface area, pore volume, pore size distribution, and pore diameter were first characterized by a t-plot method based on N 2 adsorption isotherms. Highly porous activated carbons with BET surface area up to 1009–1096 m 2/g were obtained. The steam and KOH activation methods produced carbons with mesopore content in the range 9–15 and 33–49%, respectively. The adsorption equilibria and kinetics of tannic acid, methylene blue, 4-chlorophenol, and phenol from water on such carbons at 30 °C were then investigated to check their chemical characteristics. The Freundlich equation gave a better fit to all adsorption isotherms than the Langmuir equation. On the other hand, the intraparticle diffusion model could best follow all adsorption processes. In comparison with KOH-activated carbons, it was shown that the rate of external surface adsorption with steam-activated carbons was significantly higher but the rate of intraparticle diffusion was much lower.

Effect of pore size distribution of coal-based activated carbons on double layer capacitance

A series of coal-based activated carbons representing a wide range of mesopore content, from 16.7 to 86.9%, were investigated as an electrode in electric double layer capacitors (EDLCs) in 1 mol l −1 H 2SO 4 and 6 mol l −1 KOH electrolytic solutions. The activated carbons (ACs) used in this study were produced from chemically modified lignite, subbituminous and bituminous coals by carbonization and subsequent activation with steam. The BET surface area of ACs studied ranged from 340 to 1270 m 2 g −1. The performance of ACs as EDLC electrodes was characterized using voltammetry, galvanostatic charge/discharge and impedance spectroscopy measurements. For the carbons with surface area up to 1000 m 2 g −1, the higher BET surface area the higher specific capacitance (F g −1) for both electrolytes. The surface capacitance (μF cm −2) increases also with the mesopore content. The optimum range of mesopore content in terms of the use of ACs studied for EDLCs was found to be between 20 and 50%. A maximum capacitance exceeding 160 F g −1 and a relatively high surface capacitance about 16 μF cm −2 measured in H 2SO 4 solution were achieved for the AC prepared from a sulfonated subbituminous coal. This study shows that the ACs produced from coals exhibit a better performance as an electrode material of EDLC in H 2SO 4 than in KOH electrolytic solutions. For KOH, the capacitance per unit mesopore surface is slightly lower than that referred to unit micropore surface (9.1 versus 10.1 μF cm −2). However, in the case of H 2SO 4 the former capacitance is double and even higher compared with the latter (23.1 versus 9.8 μF cm −2). On the other hand, the capacitance per micropore surface area is the same in both electrolytes used, about 10.0 μF cm −2.

Preparation of mesoporous activated carbon fiber by steam activation in the presence of cerium oxide and its adsorption of Congo red and Vitamin B12 from solution

Activated carbons are widely used in separation and purification processing, and as catalysis supports [1, 2]. Activated carbon fibers (ACFs) as a new type of activated carbon have an excellent adsorptive property due to large specific surface area, pore volume, and uniform microporosity. Generally, the micropore in ACF cannot meet some special demands, such as adsorption of bulky molecules from solution and catalyst supports for macromolecule reaction [3]. So, it is desired to increase the mesopore and macropore content in ACF and exploit its new applications. Polymer additives or catalyst was added to the carbon source and carbonized to obtain mesoporous carbon fiber; but it was difficult to eliminate the catalyst from the mesoporous carbon fiber matrix [4–6]. The transition metal and rare earth metal compounds can promote the development of mesopores in activated carbon [7–9]. The activation reaction takes place in the immediate vicinity of metal/oxide particles, leading to the formation of mesopores and macrospores by pitting holes into the carbon matrix [10]. Potassium hydrate can promote the mesopore development, but it needs higher loading amount if the post-treatment is complex. Yttrium acetylacetonate [Y(acac)3] was added to the precursor of carbon and used as catalyst to increase the mesopore content of ACF, but the cost was high [11]. Cerium oxide showed certain activity due to its role in the oxidization–reduction cycle [12] and it could promote the mesopore development in activated carbon with scatter pore size distribution due to the original property of activated carbon [13]. In the current work, cerium nitrate was selected to investigate its catalytic effect on the mesopore development of commercial ACF with steam activation. The commercial ACF was first impregnated with the aqueous solution of cerium nitrate. The loadings of cerium nitrate on the basis of activated carbon were 2.0 wt%. The samples were then dried at 110 ◦C for

04/00192 Treatment of fly ash-based additive to increase compressive strength of cement binder: Lakshmanan, V. et al. U.S. Pat. Appl. Publ. US 2003 79,656 (Cl 106–705; C04B18/06), 1 May 2003, US Appl. PV299,644

In this study, activated mesocarbon microbeads (AMCMBs) with high mesopore content were prepared from the chemical activation of mesocarbon microbeads (MCMBs) with KOH. The resulting activated mesocarbon microbeads possess well-developed pore structure. The maximum value of the total pore volume is 2.45 cm3/g, and BET surface area can reach 3182 m2/g. Especially, the resulting mesoporous activated microbeads also have mesopore content ranging from 56.1% to 65.7%. It can be seen from the isotherms of N2 at −196 °C that the resulting activated mesocarbon microbeads have high adsorption capacity.

The Preparation and Characterization of Activated Carbon from Coffee Residue

Coffee residues from instant coffee plants were used to produce mesoporous activated carbon. A series of carbonization and activation conditions were examined to elucidate the effect of each condition. The specific surface area, mesopore and total pore volumes were evaluated by nitrogen adsorption at 77 K, and the surface chemistry was characterized by FTIR. The activated carbon derived in the conditions of a ZnCl2/coffee weight ratio of 3, an activation temperature of 600°C and a CO2 activation time of 4 h (R30T600H4) yielded a surface area of 900 m2/g, a total pore volume of 1.01 cm3/g with a mesopore content of 92%. The FTIR results demonstrated that the C–H group was the main functional group on the surface of coffee-derived activated carbon. The adsorptive capacities of R30T600H4 compared with a commercial activated carbon CAL for phenol, methylene blue and erythrosine red. We found that for small molecules such as phenol and methylene blue the adsorption capacity of R30T600H4 was lower than that of CAL, whereas, for larger molecules such as erythrosine red R30T600H4 was higher. The mesoporous structure and the surface chemistry of coffee-derived activated carbon associated in the adsorption were discussed.

04/00184 Preparation of activated mesocarbon microbeads with high mesopore content: Shen, Z. and Xue, R. Fuel Processing Technology, 2003, 84, (1–3), 95–103

04/00184 Preparation of activated mesocarbon microbeads with high mesopore content: Shen, Z. and Xue, R. Fuel Processing Technology, 2003, 84, (1–3), 95–103

03/02209 Activated carbons produced from unburned carbon in fly ash and their application for mercury capture: Zhang, Y. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 32–33

Introduction Following the current demand to develop technologies to utilize high carbon content fly ash from coal-fired utility combustors or gasifiers, a one-step activation protocol has been developed by the authors to produce activated carbons from unburned carbon in fly ash. Compared to the conventional two-step process that includes a devolatilization of the raw materials, followed by an activation step, unburned carbon only requires a one-step activation process, since it has already gone through a devolatilization process while in the combustor or gasifier. The produced activated carbons with a fine particle size are not only rich in micropores, but they also present a high content of mesopores, which leads to good mass transfer properties during the adsorption process. Mercury has been identified as a hazardous air pollutant of greatest potential public health concern by the Environmental Protection Agency (EPA), with coal-fired utility boilers being the largest source of anthropogenic mercury emissions. Based upon the EPA report, in 1997 it was estimated that 48 tons of mercury were emitted into atmosphere from coal-fired utilities, including 26 tons of elemental mercury and 20.5 tons of oxidized mercury, and where the state of Pennsylvania emitted around 5 tons. The injection of carbon adsorbent upstream of the electrostatic precipitator (ESP) or baghouse particulate collection devices is a promising technology to control mercury emissions from coal-fired combustion systems. A large excess of carbon adsorbent is normally required for injection upstream of the ESP or baghouse in order to obtain a high level of mercury capture. This is because the concentration of mercury in the flue gas is extremely low, (on the order of 1 ppb by volume), as well as the complexity of the flue gas composition and the poor selectivity of the carbon sorbent towards mercury. The typical carbon-tomercury mass ratios used in recent pilot-scale studies of mercury capture in power plant systems were between 1000:1 to 100,000:1. Therefore, the cost of the carbon sorbent plays an important role in the feasibility of the proposed technologies. Based on the low cost of fly ash carbon, its inherent porosity together with its fine particle size, the unburned carbon has been tested as a potential mercury sorbent candidate. However, its mercury capacity is lower than that of commercial carbons, probably due to its high ash content and low surface area. Accordingly, the present paper focuses on the activation of the unburned carbon after conventional demineralization process in order to increase the porosity of the unburned carbon. In addition, the prepared activated unburned carbon samples were tested for mercury adsorption using a fixed-bed with a simulated flue gas at 280F.

Preparation of activated mesocarbon microbeads with high mesopore content

In this study, activated mesocarbon microbeads (AMCMBs) with high mesopore content were prepared from the chemical activation of mesocarbon microbeads (MCMBs) with KOH. The resulting activated mesocarbon microbeads possess well-developed pore structure. The maximum value of the total pore volume is 2.45 cm 3/g, and BET surface area can reach 3182 m 2/g. Especially, the resulting mesoporous activated microbeads also have mesopore content ranging from 56.1% to 65.7%. It can be seen from the isotherms of N 2 at −196 °C that the resulting activated mesocarbon microbeads have high adsorption capacity.

A simple method for developing mesoporosity in activated carbon

A simple process was proposed based on a combination of chemical and physical activation for the production of activated carbon. The process was expected to improve the mesoporosity in activated carbons. The KOH- or ZnCl2-chemical activation coupled with CO2-physical activation of lignocellulosic materials, such as coconut shells and palm stones, were used as a simultaneously chem-physical activation for increasing the mesoporosity. The porosity of the resultant activated carbons was characterized by nitrogen adsorption isotherms at 77 K. Both chemicals and CO2 had effects on the formation of mesopores. Intensified activation conditions, such as high chemical ratio to the precursors, long soaking time, elevated temperature, increased the mesoporosity in activated carbons. The surface area and the nature of the porosity can be controlled by means of the experimental parameters. By changing the ratio of activating agent to carbon precursor, it is possible to control the pore size from supermicropore (1.5–2.0 nm) to mesopore (2–3.49 nm). The BET-surface area of the carbons can be over 2100 m2/g; the mesopore content (ratio of mesopore volume to total pore volume) is 71%. Furthermore, the activated carbon from palm stones possesses mesopore content as high as 94%.

Nanopore Formation and Adsorption Property of Carbonized Phenol Resin

Porous carbons were prepared by carbonization of phenol resins of different novolac/resol ratio. By mixing 20wt % of resol with novolac (Carbon samples Ph-C2 and Ph-C3), BET and mesopore surface areas remarkably increased. The addition of more than 50wt% of resol (Carbon samples Ph-C4 and Ph C-5) deceased BET specific surface area and scarcely accelerated the formation of mesopore. The adsorption of acid dye (Acid Blue 9), basic dye (Basic Brown 1), direct dye (Direct Yellow 11) and metal ions, Cr (VI), Pb (II), and Zn (II) were investigated. The adsorbed amounts of Basic Brown 1 and Cr (VI) on Ph-C2 are higher than those on Ph-C4 and Ph-C5. Direct Yellow 11 of large molecule in size highly adsorbed on Ph-C2 and Ph-C3 of high mesopore content.

Mesoporous high-surface-area activated carbon

Coconut shells and palm seeds have been used as raw materials to obtain activated carbons with high surface area by simultaneous treatment with zinc chloride and carbon dioxide as the physical and chemical agents, respectively. Both the surface area and the mesopore content could be tuned by controlling the experimental parameters, viz., ZnCl 2-to-raw material ratio, duration of exposure to the carbon dioxide atmosphere and temperature of activation. In particular, ZnCl 2-to-shell ratios above 1 yielded high surface areas, and ratios above 2 resulted in high mesopore content. The adsorption capacity and nature of the porosity were investigated by adsorption experiments using adsorbates with different molecular sizes (viz., phenol, methylene blue and erythrosine red). The capacities of the mesoporous activated carbons were much higher than those of microporous carbons for larger adsorbates, confirming the presence of large amounts of mesopores in the former. The measured adsorption capacities for the prepared samples conformed to the expectations based on micropore and mesopore area and volume estimations.

Novel activation process for preparing highly microporous and mesoporous activated carbons

An improved ZnCl 2-chemical activation method is proposed to produce highly porous activated carbons. The novel process can produce either microporous carbons or mesoporous carbons from lignocellulosic materials, such as coconut shells and palm seeds. The porosity of the resultant activated carbons was characterized by nitrogen adsorption isotherms at 77 K. The BET-surface area of the carbons can be over 2400 m 2/g; the mesopore content (ratio of mesopore volume to total pore volume) is 71%. Furthermore, the activated carbon from palm seeds possesses mesopore content as high as 94%. Thermogravimetric analysis (TGA) was used to monitor the course of pyrolysis of coconut shell and ZnCl 2-impregnated coconut shell. The adsorptive properties for phenol and dyes were tested.

Pore structure of vermiculite that has been activated by two-stage acid etching

Acid treatment of vermiculite from the Kovdor deposit in two stages offers a means for performing a controlled etching and obtaining a sorbent with a predominant content of uniform mesopores.