Desulfurization of fuels by means of a nanoporous carbon adsorbent

Mesoporous carbon, CMK-3, was prepared using hexagonal Al-SBA-15 mesoporous silica, instead of SBA-15, as a template. The synthesized materials were examined via X-ray diffraction and N₂-adsorption. The mesoporous carbon was studied for its adsorption of dibenzothiophene (DBT) from petroleum fuels. The performance of this adsorbent was compared with SBA-15 and Al-SBA-15, through which CMK-3 showed higher sulfur adsorption capabilities due to a larger mesopore volume and a higher specific surface area. The uptake capacity for DBT followed the order CMK-3 > Al-SBA-15 > SBA-15. The results confirmed the importance of the adsorbent pore size and its surface chemistry for the adsorption of DBT from liquid phase.Langmuir and Freundlich isotherm models were used to fit equilibrium data for CMK-3. The equilibrium data were best represented by the Langmuir isotherm. Kinetic studies were carried out and showed the sorption kinetics of dibenzothiophene was best described by a pseudo-second-order kinetic model.     

A simple method to synthesize graphitic mesoporous carbon materials with different structures

Graphitic mesoporous carbon materials with different structure were synthesized by reversed replication method. SBA-15 was used as hard template and the synthesized aromatic polymers with different polymerization degree as the carbon sources. Adopting the impregnation method, the carbon source was assembled into the pore of the SBA-15. The silica/aromatic polymers system was carbonized under N₂ atmosphere (high polymerization degree aromatic polymers) and vacuum (low polymerization degree aromatic polymers) to produce the graphitic mesoporous carbon materials with structure of CMK-3 and CMK-5, respectively. It is a easy way to synthesize the graphitic mesoporous carbon materials, especial for the CMK-5 structure. The porous structure and composition of these carbon materials were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrometry, and N₂ adsorption–desorption measurements.     

Improving the electrocapacitive properties of mesoporous CMK-5 carbon with carbon nanotubes and nitrogen doping

Nitrogen-containing carbon composite materials composed of mesoporous carbon CMK-5 and carbon nanotubes (CNTs) were prepared by the chemical vapor deposition method with Fe(NO₃)₃-impregnated SBA-15 as template and pyridine as the carbon precursor. The Fe nanoparticles confined in the channels of SBA-15 induced the formation of mesoporous carbon characteristic of CMK-5, whereas Fe particles homogeneously dispersed on the external surface of SBA-15 served as catalysts for CNTs growth. The contents of CNTs, the N doping level and the microstruture of the carbon composite were closely related to the initial Fe/Si atomic ratio in SBA-15 template. Incorporation of CNTs in the composite was found to substantially reduce the electric resistance, leading to the composite materials exhibiting excellent rate-performance. A maximum specific capacitance of 208 F/g and a power density of 10 kW/kg were achieved in 6.0 mol/L KOH aqueous electrolyte when these carbon composites were applied as supercapacitor electrodes. Moreover, the composite electrode also exhibited good electrochemical stability with no capacitance loss after 1000 cycles of galvanostatic charge-discharge process.     

Indoor formaldehyde removal over CMK-3

The removal of formaldehyde at low concentrations is important in indoor air pollution research. In this study, mesoporous carbon with a large specific surface area was used for the adsorption of low-concentration indoor formaldehyde. A mesoporous carbon material, CMK-3, was synthesized using the nano-replication method. SBA-15 was used as a mesoporous template. The surface of CMK-3 was activated using a 2N H₂SO₄ solution and NH₃ gas to prepare CMK-3-H₂SO₄ and CMK-3-NH₃, respectively. The activated samples were characterized by N₂ adsorption-desorption, X-ray diffraction, and X-ray photoelectron spectroscopy. The formaldehyde adsorption performance of the mesoporous carbons was in the order of CMK-3-NH₃ > CMK-3-H₂SO₄ > CMK-3. The difference in the adsorption performance was explained by oxygen and nitrogen functional groups formed during the activation process and by the specific surface area and pore structure of mesoporous carbon.     

Pd/CMK-3的合成及其在Suzuki-Miyaura碳-碳偶联反应中的应用

利用介孔二氧化硅（SBA-15）为模板、蔗糖为碳源,制备了有序介孔碳材料CMK-3,然后以CMK-3为载体,利用浸渍还原法得到介孔碳负载Pd纳米粒子的复合催化剂（Pd/CMK-3）,通过XRD、TEM以及氮气吸附-脱附等手段对催化剂的微结构和组分进行分析,结果表明CMK-3为有序介孔结构,孔径约为5nm,Pd/CMK-3保留了介孔结构,且孔道中负载有不同尺寸的Pd粒子。应用于无配体催化的Suzuki-Miyaura相似文献   

Adsorption of l-histidine over mesoporous carbon molecular sieves

Mesoporous carbon, CMK-3, was prepared by large pore hexagonal mesoporous silica SBA-15. The structural order and textural properties of all the materials were studied by XRD, HRTEM, and nitrogen adsorption. Adsorption of l-histidine (His) over various porous adsorbents such as CMK-3, SBA-15, and activated carbon was studied from solutions with different pH. His adsorption was observed to be pH dependent with maximum adsorption near the isoelectric point of the amino acid. CMK-3 showed a larger amount of His adsorption as compared to SBA-15 and the conventional adsorbent, namely activated carbon. CMK-3 registers the total adsorption capacity of ca. 1350 μmol g⁻¹ which is ca. 12 times higher than the adsorption capacity of SBA-15. This large difference could be mainly due to the stronger hydrophobic interaction between the non-polar side chains of amino acids and the hydrophobic surface of the mesoporous carbon as compared to mesoporous silica. The influence of ionic strengths on the adsorption of His was also studied and the results are discussed. Nitrogen adsorption of CMK-3 after His adsorption confirmed that His molecules are tightly packed inside the mesopores.     

Characterization and catalytic performance of poly(4-vinylpyridine) supported on mesoporous carbon: comparison with poly(4-vinylpyridine) supported on mesoporous silica

In this study, the synthesis of poly(4-vinylpyridine) (P4VP) supported on mesoporous carbon (CMK-3) by in situ polymerization of 4-vinylpyridine in the presence of CMK-3 has been investigated. The structural properties of the P4VP/CMK-3 were investigated by FT-IR, XRD, BET, TGA, SEM and TEM techniques. The catalytic activity of this new heterogeneous basic catalyst was tested for Knoevenagel reaction. Excellent yields at room temperature in aqueous media and solvent-free conditions were obtained. The catalytic activity of this purely organic hybrid catalyst was compared with P4VP/SBA-15 to clarify the advantages of mesoporous carbon on mesoporous silica as support. The results showed that the stability of P4VP/CMK-3 was excellent and could be reused 10 times without much loss of activity in Knoevenagel reaction. Surprisingly, the composite prepared by mesoporous carbon showed much higher activity than that of P4VP/SBA-15. This unique result opens new perspectives for application of mesoporous carbons as structurally defined hydrophobic catalyst support in catalytic reactions.     

Easy synthesis of an ordered mesoporous carbon with a hexagonally packed tubular structure

Ordered mesoporous carbon with hexagonal arrays of tubes (CMK-5) was successfully synthesized via a nanocasting process by directly using SBA-15, instead of AlSBA-15, as a template, furfuryl alcohol as a carbon source and oxalic acid as the catalyst. The time consuming impregnation of SBA-15 with aluminum could be saved. The as-synthesized CMK-5 exhibits a tubular structure with double pore system. The loading amount of carbon precursor on the pore walls of SBA-15 is the key factor for the formation of the CMK-5 structure with two-dimensional hexagonal arrays of tubes, and the pore diameter can be adjusted by varying the loading amount of the carbon precursor. The CMK-5 carbon exhibits high apparent surface area up to ∼2500 m²/g and high pore volume reaching ∼2 cm³/g, which is due to the unique structure of CMK-5. The characterization results confirmed that carbonization under argon atmosphere instead of vacuum is sufficient for the structural formation of CMK-5 carbons, and can be used as an alternative pathway to prepare tubular-type carbons.     

Calculation of XRD patterns of simulated FDU-15, CMK-5, and CMK-3 carbon structures

XRD patterns of model structures of the ordered mesoporous carbon materials FDU-15, CMK-5, and CMK-3 have been calculated. The structure models had been derived by filling tubular (CMK-5), rod-like (CMK-3), or channel wall (FDU-15) spaces in a given unit cell with carbon atoms. The generated carbon sites then have been used for the calculation of the XRD patterns. It could be shown that XRD patterns of CMK-5 materials vary substantially with variation of the tube diameter and carbon wall thickness. For a certain range of tube diameters, the XRD patterns do not resemble those of CMK-3 or FDU-15. The carbon material FDU-15 is isostructural to the silica SBA-15, CMK-3 is the negative replica of SBA-15. XRD patterns of CMK-3 and FDU-15 models also vary with varying rod or pore diameter but the changes are not as significant as for different CMK-5 models. As expected, the XRD patterns of FDU-15 and CMK-3 resemble each other very much for a given lattice parameter if the rods of CMK-3 are of the same size as the pore diameters of FDU-15.     

用于PEMFC的介孔碳担载铂氧化钨电催化剂的制备与表征

利用介孔碳作为载体,制备介孔碳担载Pt-WO3复合催化剂应用于质子交换膜燃料电池（PEMFC）电极.以苯为碳源,采用气相沉积法复制介孔SiO2Al-SBA-15模板结构合成石墨化介孔碳Cg,采用浸渍法制备无定形介孔碳CMK-3.通过分步沉积,将Pt和WO3担载到介孔碳载体上,采用比表面分析（BET）、X线衍射（XRD）、透射电子显微镜（TEM）、循环伏安法以及单电池极化性能测试对介孔碳担载的复合催化剂进行表征.结果表明：介孔碳作为催化剂载体,其孔道结构有助于催化剂的均匀分散,从而提高催化剂的电催化剂活性.由于石墨化介孔碳的导电性能高于无定形介孔碳,因此Pt-WO3/Cg比Pt-WO3/CMK-3具有更好的电极催化活性.     

Synthesis of polyaniline/mesoporous carbon nanocomposites and their application for CO<Subscript>2</Subscript> sorption

Ordered mesoporous carbons (OMC), were synthesized by nanocasting using ordered mesoporous silica as hard templates. Ordered mesoporous carbons CMK-1 and CMK-3 were prepared from MCM-48 and SBA-15 materials with pore diameters of 3.4 nm and 4.2 nm, respectively. Mesoporous carbons can be effectively modified for CO₂ adsorption with amine functional groups due to their high affinity for CO₂. Polyaniline (PANI)/mesoporous carbon nanocomposites were synthesized from in-situ polymerization by dissolving OMC in aniline monomer. The polymerization of aniline molecules inside the mesochannels of mesoporous carbons has been performed by ammonium persulfate. The nanocomposition, morphology, and structure of the nanocomposite were investigated by nitrogen adsorption-desorption isotherms, Fourier Transform Infrared (FT–IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and thermo gravimetric analysis (TGA). CO₂ uptake capacity of the mesoporous carbon materials was obtained by a gravimetric adsorption apparatus for the pressure range from 1 to 5 bar and in the temperature range of 298 to 348 K. CMK-3/PANI exhibited higher CO₂ capture capacity than CMK-1/PANI owing to its larger pore size that accommodates more amine groups inside the pore structure, and the mesoporosity also can facilitate dispersion of PANI molecules inside the pore channels. Moreover, the mechanism of CO₂ adsorption involving amine groups is investigated. The results show that at elevated temperature, PANI/mesoporous carbon nanocomposites have a negligible CO₂ adsorption capacity due to weak chemical interactions with the carbon nanocomposite surface.     

A simplified route to the synthesis of CMK-3 replica based on precipitation polycondensation of furfuryl alcohol in SBA-15 pore system

A novel method of synthesis of mesoporous, polymer-derived CMK-3 carbon replica was proposed. Instead of a multi-stage, time-consuming and toxic solvent involving procedure, the direct, acid-catalyzed precipitation polycondensation of furfuryl alcohol to poly(furfuryl alcohol) (PFA), as the carbon precursor, in the pore system of SBA-15 silica was used. The optimal PFA/SBA-15 mass ratio resulting in the complete pore filling was found. The final carbon material was obtained by carbonization of the formed composite and subsequent removal of silica by treatment with HF. Low-temperature sorption of nitrogen, powder X-ray diffraction and transmission electron microscopy confirmed the formation of well-ordered, hexagonal carbon mesostructure. The produced CMK-3 exhibited the presence of oxygen-containing surface groups, recognized as mainly carbonyl and carboxyl species by X-ray photoelectron spectroscopy and temperature-programmed desorption. The presence ofthese groups caused the mesoporous carbon to be catalytically active in the oxidative dehydrogenation of ethylbenzene to styrene.     

Preparation of ordered mesoporous SiCN ceramics with large surface area and high thermal stability

For the first time, highly ordered two-dimensional (2-D) and three-dimensional (3-D) mesoporous SiCN ceramics with high surface area and high thermal stability were prepared by nanocasting a preceramic polymer solution into mesoporous carbon templates, CMK-3 and CMK-8, respectively. As a negative replica of CMK-3 carbon, the obtained mesoporous SiCN ceramic possessed an ordered 2-D hexagonal mesostructure, which is similar to the structure of SBA-15 silica except for the reduced dimensions. An ordered 3-D cubic mesoporous SiCN ceramic was also fabricated using CMK-8 as a template. The wall of the mesoporous SiCN replicas consisted of an amorphous SiCN ceramic phase, which possessed high thermal stability at high temperature up to 1000 °C. N₂-sorption isotherms revealed that these ordered mesoporous SiCN ceramics have high BET surface areas (up to 472 m² g⁻¹) and narrow pore-size distributions, which was preserved even after a re-treatment at 1000 °C in air. The use of carbon template played an important role in the preparation of mesoporous SiCN replicas and enhanced the thermal stability of the SiCN products. It is expected that many other types of ordered mesoporous ceramics can be prepared from nanoporous carbon by nanocasting method.     

Remarkable effect of ordered mesoporous carbon support in tantalum oxide-catalyzed selective epoxidation of cyclooctene

The olefin epoxidation is one of the most important reactions in chemical industry. Metal oxide supports often cause drawbacks in catalytic activity and selectivity, which has been overcome by introducing hydrophobic organic groups onto the oxide supports. The present study utilizes ordered mesoporous carbon (CMK-3 and CMK-1) as structurally defined hydrophobic catalyst support. Well-dispersed tantalum oxides supported on the ordered mesoporous carbon were prepared. Their application in catalytic epoxidation of cyclooctene demonstrates that the tantalum oxide catalysts on the ordered mesoporous carbon supports show higher performances than those of the catalysts supported on activated carbon and ordered mesoporous silica SBA-15.     

Detailed structure of the hexagonally packed mesostructured carbon material CMK-3

Detailed investigation of the ordered mesoporous CMK-3 carbon using XRD structural modeling based on the continuous electron density representation and the Rietveld technique allowed deriving comprehensive and consistent information on the material anatomy. The electron density distribution map agrees with carbon ‘bridges’, which seem to be attributed to the material interconnecting carbon nanorods in the CMK-3 mesostructure. These carbon ‘bridges’ are supposed to be derived from former complementary mesopores of the SBA-15 template used.     

Synthesis of mesoporous silica from bottom ash and its application for CO<Subscript>2</Subscript> sorption

A supernatant solution of silicate species extracted from bottom ash in a power plant was used to prepare a mesoporous silica by the synthesis protocol of SBA-15. XRD, N₂ adsorption-desorption, and TEM confirmed a disordered mesopore structure. The pore volume and average pore size of the product were significantly larger than SBA-15 prepared using pure chemicals, and complementary textural mesoporosity was detected. When the mesoporous silica was tested for carbon dioxide sorption after polyethyleneimine (PEI) impregnation, substantially higher CO₂ sorption capacity (169 mg CO₂/g-sorbent) was achieved than that of PEI-impregnated pure SBA-15 under the same test conditions. High CO₂ sorption capacity was maintained when the gas composition was changed to 15% CO₂, and the hybrid material exhibited satisfactory performances during the 10 recycle runs.     

Influence of carbon precursor on porosity,surface composition and catalytic behaviour of CMK-3 in oxidative dehydrogenation of propane to propene

Ordered mesoporous CMK-3 carbon replicas were synthesized by infiltration of mesopores present in a SBA-15 silica template with two different carbon precursors, i.e. sucrose and poly(furfuryl alcohol). The obtained composites were carbonized under an inert gas atmosphere at 550, 650, 750 and 850?°C, and the template was etched with a HF solution. The final carbon replicas were analyzed by various physicochemical techniques, including low-temperature N₂ adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and tested as catalysts in the oxidative dehydrogenation of propane (ODP) at 450?°C. Both series of materials differed strongly with respect to their porosity, but showed very similar surface composition determined by XPS. Higher porosity of CMK-3 prepared using the sucrose precursor influenced propane conversion and selectivity to propene. Furthermore, oxygen containing groups (e.g. carbonyl-type) were found to be less sensitive to the type of carbon precursor than to the ODP reaction conditions.     

Ordered mesoporous tin oxide and tin phosphate synthesized by nanocasting strategy

Ordered mesoporous tin oxide and tin phosphate were successfully synthesized via two-step nanocasting route. The SBA-15 silica and CMK-3 carbon were used as hard templates. Powder X-ray diffraction, nitrogen adsorption and transmission electron microscopy confirmed hexagonal mesoporous structure of resulted products. Mesoporous tin oxide indicated crystalline walls (cassiterite). The mesoporous products showed considerable catalytic activity in propan-2-ol decomposition. The tin oxide led the dehydrogenation towards acetone, while mesoporous tin phosphate exhibited activity of acid sites resulting in dehydration to propene.     

Preparation of nitrogen-doped mesoporous carbon nanopipes for the electrochemical double layer capacitor

The direct functionalization of ordered mesoporous carbon nanopipes was achieved by using nitrogen-containing carbon precursor and SBA-15 as a removable template. The prepared carbon material has uniform pore structure as CMK-5 type and retained a relatively large amount of nitrogen species after pyrolysis and removal of the silica template. The results of cyclic voltammetric measurement showed the prepared nitrogen-functionalized carbon materials was more stable and desirable than CMK-5 for the electrochemical capacitor.     

Porosity and surface properties of mesoporous silicas and their carbon replicas investigated with quasi-equlibrated thermodesorption of <Emphasis Type="Italic">n</Emphasis>-hexane and <Emphasis Type="Italic">n</Emphasis>-nonane

Adsorption of n-hexane and n-nonane on mesoporous micelle-templated silicas (SBA-15 and MLV—multilayer vesicle) and on their carbon replicas (CMK-3 and OCM—onion-like carbonaceous material) was studied by means of quasi-equilibrated thermodesorption technique, utilising a standard TPD setup with a chromatographic detector. Analysis of n-hexane adsorption isobars, determined from the thermodesorption profiles, revealed substantial heterogeneity of the adsorption sites present in the carbonaceous materials. The pore size distributions calculated from the thermodesorption profiles of n-nonane for both siliceous and carbonaceous materials were in agreement with those obtained from the low-temperature nitrogen adsorption isotherms. They confirm an uniform structure of mesopores in SBA-15, CMK-3 and OCM as well as a more complex structure of mesopores in the MLV materials.