The adsorption properties of surface modified activated carbon fibers for hydrogen storages

In this study, activated carbon fibers (ACFs) with high surface area and pore volume have been modified by Ni doping and fluorination. The surface modified ACFs were characterized by BET surface area, SEM/EDS, XRD, and Raman spectroscopy. The changes in pore structure and surface properties of these modified ACFs were correlated with hydrogen storage capabilities. After fluorination treatment, although the micropore volume of ACF was decreased, amounts of hydrogen storage were found to increase. Additionally, micropore volume on ACFs was found to be unchanged with Ni doping, hydrogen storage capacities were considerably increased due to the effect of catalytic activation of nickel. Though fluorination of ACFs increases hydrogen affinity, the effect of catalytic activation of nickel is more prominent, and thus led to better hydrogen storage. Hence, it was concluded that hydrogen storage capacity was related to micropore volumes, Pore size distribution (PSD) and surface properties of ACFs as well as specific surface areas.     

水蒸气活化法制备椰壳活性炭的孔结构特征

以农林废弃物椰壳在600℃炭化2h后的炭化料为原料,以水蒸气为活化剂,研究了活化温度、活化时间、水蒸气用量对活性炭的比表面积、微孔容积和收率等的影响。结果表明：椰壳炭化料的比表面积仅为185m^2／g,且以中孔为主。在活化过程中,通过提高活化温度和水蒸气用量缩短了活化时间,扩宽了孔径;当水蒸气用量和活化温度较为适宜时,延长活化时间,有利于微孔的形成。活性炭的比表面积、总孔容积、微孔容积可达：1465m^2／g,0．9703cm^3/g,0．7519cm^2／g。并通过非定域密度函数理论（NLDFT）对活性炭的孔径分布进行了表征。     

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

A 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     

A novel N-alkylation of amines by alkyl halides on mixed oxides at room temperature

Selective liquid phase N-alkylation of amines by alkyl halides using Al₂O₃–OK as a catalyst in the presence of acetonitrile at room temperature (30 °C) is described. The Al₂O₃–OK catalyst was characterized by XRD, SEM–EDXS, elemental analysis, particle size analysis, BET surface area, pore size and average pore diameter. The catalyst used for this synthetically useful transformation showed a considerable level of reusability as well as good activity.     

Influence of Catalyst (Citric Acid) Concentration on the Physical Properties of TEOS Silica Aerogels

In the present paper, the experimental results on the influence of catalyst (citric acid) concentration on the physical properties of TEOS silica aerogels, are reported. The aerogels have been prepared by hydrolysis and polycondensation of tetraethoxysilane (TEOS) using citric acid (CTA) as a new catalyst followed by supercritical drying in an autoclave. In order to obtain the best quality silica aerogels in terms of monolithy, high transparency, low density, large surface area and high porosity with uniform pore size distribution, the catalyst concentrations were varied from 0.0005 M to 0.1 M by keeping the molar ratio of TEOS : EtOH : H₂O constant at 1 : 5 : 7, respectively. It has been found that the lower (<0.001) CTA concentration resulted in low density, smaller surface area but opaque aerogels whereas higher (>0.005 M) CTA concentration resulted in high density, large surface area, highly transparent but cracked aerogels. On the other hand, medium (between 0.001 and 0.005 M) CTA concentration resulted in monolithic, low density, large surface area and highly transparent silica aerogels. The pore size distribution (PSD) for higher (0.1 M) and lower (0.0005) CTA concentrations shifted towards smaller and larger pore radii respectively, whereas for medium (0.001 M) CTA concentration, the PSD is narrow and uniform, which reduces the differential pressure during supercritical solvent extraction leading to monolithic silica aerogels. These results have been supported and discussed by considering the particle and pore sizes observed by Scanning Electron Microscopy (SEM). The surface area was measured by BET analysis.     

The production of porous carbon nanofibers from cross-linked polyphosphazene nanofibers

Uniform porous carbon nanofibers with an average diameter of 90 nm were fabricated by forming polyphosphazene nanofibers and carbonizing them, without the need for any activation step. The structure and morphology of the carbon nanofibers were characterized by SEM, TEM, EDX, XRD, Raman spectrum and N₂ adsorption. Results showed that the carbon nanofibers have a BET surface area of about 540 m² g⁻¹, a total pore volume of about 0.37 m³ g⁻¹, and a narrow pore size distribution in the micropore range.     

改性HZSM-5上焦化苯与乙醇烷基化制乙苯

通过离子交换法制备硼改性的分子筛,并在连续固定床反应器上对其进行焦化苯与乙醇烷基化反应催化性能和脱硫性能的考察。通过XRD和BET方法对催化剂进行表征,结果表明,改性后催化剂的比表面积、微孔孔容和孔径均减少。反应评价结果显示,改性后乙苯选择性略有降低,苯转化率增加。最佳反应条件：温度（350～400） ℃,n(苯)∶n(乙醇)=(3∶1)～(5∶1),空速（4～6） h^-1。     

A novel method for production of activated carbon from waste tea by chemical activation with microwave energy

This study presents the production of activated carbon from waste tea. Activated carbons were prepared by phosphoric acid activation with and without microwave treatment and carbonisation of the waste tea under nitrogen atmosphere at various temperatures and different phosphoric acid/precursor impregnation ratios. The surface properties of the activated carbons were investigated by elemental analysis, BET surface area, SEM, FTIR. Prior to heat treatment conducted in a furnace, the mixture of the waste tea and H₃PO₄ was treated with microwave heating. The maximum BET surface area was 1157 m²/g for the sample treated with microwave energy and then carbonised at 350 °C. In case of application of conventional method, the BET surface area of the resultant material was 928.8 m²/g using the same precursor and conditions. According to the Dubinin–Radushkevich (DR) method the micropore surface area for the sample treated with microwave energy was higher than the sample obtained from the conventional method. Results show that microwave heating reasonably influenced the micropore surface area of the samples as well as the BET surface area.The samples activated were also characterised in terms of the cumulative pore and micropore volumes according to the BJH, DR and t-methods, respectively.     

固体超强酸催化剂S2O2-8/Fe2O3-Al2O3的制备及其酯化性能

以硝酸铁为铁源、硝酸铝为铝源,通过共沉淀法制备固体超强酸催化剂S₂O^2-₈/Fe₂O₃-Al₂O₃。通过催化剂样品的FT-IR谱图、不同焙烧温度催化剂样品的XRD谱图、不同陈化温度的N2吸附-脱附曲线以及催化剂样品的SEM照片,研究了其晶体的形成过程。催化剂样品红外谱图表明,催化剂中的S=O有较强的共价双键特征,诱导催化剂形成超强酸性;在XRD谱图中既无Al₂O₃的晶相峰,也无Fe₂(SO₄)₃晶相峰,说明Al₂O₃与Fe₂O₃ 在催化剂样品的表面形成了Al₂O₃-Fe₂O₃ 共价键的复杂结构。采用BET方程和BJH模型计算催化剂样品的比表面积和孔径分布,经冰水陈化的催化剂样品平均孔径为9.1 nm,最可几孔径为7.5 nm,比表面积为78.9 m²·g^-1,孔容0.149 cm³·g^-1。研究了催化剂的铁与铝物质的量比、(NH₄)₂S₂O₈浸渍浓度和不同焙烧温度对硬脂酸正丁酯酯化率的影响。在反应温度85 ℃、催化剂用量0.2 g (为反应物总质量的2%)和回流反应150 min的条件下,酯化率可达84.5%。     

A synthesis of copper based metal-organic framework for O-acetylation of alcohols

A novel metal-organic framework, Cu–BDC was synthesized by static hydrothermal method using innocuous solvents and characterized by several techniques such as powder XRD, ESR, TG–DTA, elemental analysis, ICP-AES, SEM, EDXS, FT-IR, BET surface area, pore volume and pore size. The catalytic performance of Cu–BDC was explored for O-acetylation of alcohols under solvent-free conditions at room temperature. The catalyst exhibited remarkable activity and reusability affording the desired products in excellent yields.     

Catalytic filamentous carbon: Structural and textural properties

Catalytic filamentous carbon (CFC) synthesized by the decomposition of methane over iron subgroup metal catalysts (Ni, Co, Fe or their alloys) is a new family of mesoporous carbon materials possessing the unique structural and textural properties. Microstructural properties of CFC (arrangement of the graphite planes in filaments) are shown to depend on the nature of catalyst for methane decomposition. These properties widely vary for different catalysts: the angle between graphite planes and the filament axis can be 0° (Fe-Co-Al₂O₃), 15° (Co-Al₂O₃), 45° (Ni-Al₂O₃), 90° (Ni-Cu-Al₂O₃). The textural properties of CFC depend both on the catalyst nature and the conditions of methane decomposition (T, °C). The micropore volume in CFC is very low, 0.001-0.022 cm³ g⁻¹ at the total pore volume of 0.26-0.59 cm³ g⁻¹. Nevertheless, the BET surface area may reach 318 m² g⁻¹. Results of the TEM (HRTEM), XRD, Raman spectroscopic, SEM and adsorption studies of the structural and textural properties of CFC are discussed.     

Comparisons of pore properties and adsorption performance of KOH-activated and steam-activated carbons

Carbonaceous adsorbents with controllable pore sizes derived from carbonized pistachio shells (i.e., char) were prepared by the KOH activation and steam activation methods in this work. The pore properties including the BET surface area, pore volume, pore size distribution, and pore diameter of these activated carbons were characterized by the t-plot method based on N₂ adsorption isotherms. Through varying the KOH/char ratios from 0.5 to 3, the KOH-activated carbons exhibited BET surface areas ranging from 731 to 1687 m²/g with a similar micropore content (80–92%). The carbons activated by steam at 830 °C for 2 h had a BET surface area of 821 m²/g with the micropore content of 42%. The micropore/total pore volume ratio (V_micro/V_pore) and average pore size (D_pore) were independent of the KOH/char ratio, revealing that KOH activation is a powerful method in developing and controlling the number of micropores with a very similar pore size distribution. The adsorption equilibria and kinetics of methylene blue, basic brown 1, acid blue 74, 2,4-dichlorophenol, 4-chlorophenol, and phenol from water on all activated carbons at 30 °C were investigated to demonstrate the fact that adsorption of organics is not only dependent upon the BET surface area but is also determined by the relative size between pores and molecules. The adsorption isotherms were subjected to the model fitting according to Langmuir and Freudlich equations. By comparing the projected area of adsorbates, the surface coverage of phenols is about 3.6 times of that of dyes (based on unit gram of activated carbon). The Elovich equation was found to suitably describe the adsorption process of all KOH-activated carbons while the adsorption behavior on the steam-activated carbon was reasonably fitted with the intraparticle diffusion model.     

Preparation and Phosphine Adsorption of Activated Carbon Prepared from Walnut Shells by KOH Chemical Activation

Walnut-shell activated carbons (WSACs) with high surface area and predominant micropore development were prepared by KOH chemical activation. The effects of carbonization temperature, activation temperature, and ratio of KOH to chars on the pore development of WSACs and PH₃ adsorption performance of the modified walnut-shell activated carbons (MWSACs) were studied. Criteria for determining the optimum preparation conditions were pore development of WSACs and PH₃ breakthrough adsorption capacity of MWSAC adsorbents. The result shows that the optimum preparation conditions are a carbonization temperature of 700°C, an activation temperature of 700°C, and a mass ratio of 3. The BET surface area and the micropore volume of the optimal WASC are 1636m²/g and 0.641cm³/g, respectively. The micropore volume percentage of WSAC plays an important role in PH₃ adsorption when there is a slight difference in BET surface areas. High-surface-area WSACs with predominant micropores are suitable for PH₃ adsorption removal. The MWSAC adsorbent owns the biggest PH₃ breakthrough adsorption capacity (284.12mg/g) due to the biggest specific surface area, total pore volume, and micropore volume percentage. The MWSAC adsorbent will be a potential adsorbent for PH₃ adsorption removal from yellow phosphorus tail gas.     

纳米ZSM-5分子筛的合成及其催化转化甲醇性能

通过在常规的分子筛合成水热体系中加入适量NaCl,合成了纳米ZSM-5分子筛,采用XRD、SEM、N₂吸附和NH₃-TPD等方法对其结构进行表征,并评价在甲醇制丙烯反应中的催化性能。结果表明,合成的ZSM-5分子筛分散性良好,粒度分布均一,晶粒大小约为100 nm,与微米级ZSM-5分子筛相比,纳米ZSM-5分子筛催化剂具有更大的比表面积（402.0 m²·g^-1）和孔容（0.41 cm³·g^-1）,在甲醇制丙烯催化反应中表现出更好的催化性能,丙烯选择性远高于微米级ZSM-5分子筛,且表现出很高的活性和稳定性,运行140 h,甲醇转化率仍大于90%。     

油茶壳微孔活性炭的制备及表征

以油茶壳为原料,经炭化、KOH活化,制备微孔活性炭。考查了活化温度、活化时间和碱炭比对微孔活性炭碘吸附值和产率的影响,并采用正交试验优化了制备条件。研究结果表明：活化温度800℃、活化时间180 min、碱炭质量比3.5：1时,活性炭的碘吸附值达3 221 mg/g,产率51.2%。采用比表面积孔隙分析仪测定了氮气吸附/脱附等温线,计算得BET比表面积为1 755.72 m²/g,平均孔径为2.15 nm,总孔容为0.328 cm³/g,微孔孔容占总孔容的55.8%;SEM分析可见活性炭表面具有大量孔隙结构;FT-IR分析表明活化促进了—CH₃、—OH热解,活性炭中仍保存含氧官能团。     

Synthesis of activated carbons by chemical activation of new anthracene oil-based pitches and their optimization by response surface methodology

This paper deals with the synthesis of new anthracene oil-based activated carbons by chemical activation with KOH. It focuses on the optimization of the processing conditions involved by means of surface response methodology. A factorial design (2³+3) in one block with four degrees of freedom was used to optimize the process, based on the responses BET surface area, total pore volume, mesopore volume, micropore volume and mol ratio CO:CO₂. The variables measured include KOH to pitch ratio (1:1, 3:1 and 5:1), activation temperature (700 up to 1000 °C) and pitch characteristics. The activation of anthracene oil-based pitch led to activated carbons with BET surface area values of 2880 m² g⁻¹. The factorial design expresses every response factor as a mathematical equation using the experimental variables. The most critical factor for each experiment design response has been identified from the analysis of variance (ANOVA). These mathematical models were also used to obtain the optimum processing conditions for the production of activated carbon with controlled properties. The experimental processing of the optimized activated carbons gave rise to a sample with BET, total pore volume, mesopore volume, micropore volume values which were in good agreement with those predicted by statistical analysis.     

Determination of porosity in pillared clays by N2 adsorption isotherms

N₂ adsorption isotherms of various pillared montmorillonites (PILCs) were analyzed for evaluation of their porosities. The quantitative data of the total and micropore volumes were calculated using the B.J.H. method and the t-plot, respectively. The volume of mesopores is the difference between the total volume and the micropore volume. The linear branch above the P/P ₀ of 0.5 should be used for the calculations of the micropore volume and external surface area.The evaluation of the specific surface area (SA) of the PILCs and influences of the porosity on the calculations were discussed in detail. An upper limit of the monolayer capacity of a porous solid is proposed, based on the adsorption on a nonporous solid. Due to the space restriction in the fine slit-like pores of the PILCs, the specific surface areas calculated with the B.E.T. equation using the adsorption data in a relative pressure region ranging from 0.01 to 0.1 are more accurate.The mean micropore widths of the PILCs, derived from the data of the multi-point B.E.T. SA and micropore volume consist reasonably with the pore widths obtained by XRD diffraction.The step-like curves of the t-plot in low-pressure region and of the logarithmic plot reveal presence of pores of various sizes in the pillared clays. The micropore size distribution can be derived by a new method using the N₂ adsorption data.     

Textural property tuning of ordered mesoporous carbon obtained by glycerol conversion using SBA-15 silica as template

“Wet” and “dry” template methods were used to simultaneously control the pore size, morphology, and graphitization in structurally well-ordered mesoporous carbons. A novel structure has been prepared using glycerol as the carbon source. Depending on the loading amount of the glycerol, the structural characteristics of the mesoporous carbon materials can be controlled. The structurally well-ordered carbon materials have been characterized by various techniques such as nitrogen sorption, XRD, Raman spectroscopy, TGA measurements and SEM. They have graphitic character, high BET surface area (ca 1440 m²/g) and a tunable pore size. They are likely to be useful in a variety of applications including gas storage, electrode materials or catalyst supports.     

Preparation of mesoporous activated carbon fibers by catalytic gasification

A commercial activated carbon fiber with micropores, CH700-20 (Kuraray), was reformed to a mesoporous one by catalytic gasification. The catalytic gasification was composed of two steps: CO₂ pretreatment and air oxidation. Cobalt was used as the catalyst and gasification was performed in the temperature range of 500–700 °C. BET surface area and pore volume of catalytically modified carbon fiber were analyzed by N₂ adsorption. BET surface area of the original CH700-20 was 1,711 m²/g, and the mesopore volume percentage was 11.9%. After catalytic gasification, BET surface area was similar to the original CH700-20, while mesopore volume percentage increased up to 56%. The average pore size of mesopores was 3–4 nm in diameter. The average size of mesopores could be controlled with nanometer resolution by varying the temperature and time of activation.     

Adsorption properties and microporous structure of adsorbents produced from phenolic resin and biomass

Mixtures of novolac resin and olive stone biomass in proportions 20 : 80 (w : w) are cured, pyrolyzed up to 1000°C (material C20a), and activated with steam (material C20a). The adsorption properties of these materials and a commercial activated carbon (CC) are investigated based on the adsorption of nitrogen and pentane. The adsorption capacity, the surface area determined by the BET and DRK equation, and the pore volume determined as micropore volume by the DR equation, and as cumpulative pore volume related to the Kelvin equation, for the materials follow the order C20a > CC > C20. The DR equation can be applied for the adsorption of nitrogen on the materials examined in the region of P/P_o = 0.005 up to 0.3 that exceeds in both sides the common range for the applicability of the DR equation. The activated materials C20a and CC are mainly microporous and reveal the type I isotherms of the Brunauer classification for nitrogen adsorption. The only pyrolyzed material, C20, contains both micropores and mesopores and reveals characteristics of both types I and II. The number of layers for C20a and CC is lower than 2 and for C20 is more than 2. © 1995 John Wiley & Sons, Inc.