Decrease In Specific Surface Area Research Articles

Preparation and photocatalytic application of magnetic Fe2O3/SBA-15 nanomaterials

Magnetic Fe2O3/SBA-15 mesoporous nanomaterials were synthesized by means of a facile impregnation and calcination method. As-prepared magnetic nanomaterials were characterized using XRD, N2 adsorption-desorption isotherms, SEM, TEM, VSM and XPS techniques. And the photocatalytic activities of magnetic Fe2O3/SBA-15 on the degradation of rhodamine B were also evaluated. Results indicate that the order structure of as-synthesized nanomaterials still remains, but its specific surface area, pore volume and pore size decrease. The saturation magnetization of the samples increases and its particle size decreases gradually with increasing the calcination temperature. And the existence of SBA-15 mesoporous molecular sieves increases largely the stability of γ-Fe2O3. Moreover, as-synthesized magnetic Fe2O3/SBA-15 shows high photocatalytic activities in the course of the degradation of rhodamine B by photo-Fenton-like reaction at natural pH about 6.3 and visible light irradiation. The structure and amount of catalyst, the concentration of H2O2 and rhodamine B are main influence factors on the degradation of rhodamine B, and these influence results have been depicted quantitatively from dynamics. Rhodamine B in aqueous solution could almost be removed completely after a period of illumination by visible light and overnight in the dark. Meanwhile, as-prepared magnetic Fe2O3/SBA-15 has excellent reusability and stability, which its photocatalytic activity has only a slightly decrease after five consecutive runs. Therefore, as-synthesized magnetic Fe2O3/SBA-15 has a broad prospect of practical application.

Influence of soluble organic matter on mechanical properties of coal and occurrence of coal and gas outburst

Coal is a complex organic rock. A large number of soluble organic matters (SOMs) existing in pores of the coal matrix and even in the macromolecular network structure will inevitably have some impact on the coal seam gas occurrence, migration and outburst risk. From the perspective of structure and composition of coal, a series of experiments were carried out to reveal the mechanism of SOMs on the gas outbursts. The results show that SOMs can improve the coal adsorption ability due to the strongly adsorbent groups. Compared with the raw coal, the SOMs-extracted residual coal undergoes a decrease in specific surface area and an increase in total pore volume, average pore diameter and porosity. Furthermore, compressive strength, tensile strength and elastic modulus of the residual coal are all higher than that of the raw coal, while gas content, gas emission initial velocity, drill cuttings desorption indexes (K1 and Δh2) of the residual coal are all lower than that of the raw coal. In summary, the SOMs in coal can promote coal and gas outbursts. Research results of the project provide a new way of promoting gas extraction and outburst prediction.

Effect of Thermal Treatment on the Structure and Properties of Hydroxyapatite

X-ray diffraction analysis and transmission electron microscopy were used to demonstrate that hydroxyapatite produced by the precipitation method is a powder composed of anisometric particles with longitudinal size of 70–100 nm and transverse size of 7–9 nm. The particles are constituted by crystallites with longitudinal sizes of 22–24 nm and transverse sizes of 8–10 nm. At a temperature of 600°C, the crystallite sizes grow, and the volume porosity and specific surface area decrease. Synthetic hydroxyapatite has a low thermal stability as compared with hydroxyapatite of biological origin.

Investigation of Structure and Photocatalytic Degradation of Organic Pollutants for Protonated Anatase/Titanate Nanosheets during Thermal Treatment

The mesoporous protonated TiO2-derived nanosheets were fabricated through an alkaline hydrothermal method. The samples with a higher specific surface area of 378 m2/g are proven to consist of anatase and titanate phases. The X-ray diffraction studies and Raman spectroscopy techniques are employed for investigating structural transformation of the nanosheets caused by thermal treatment. During the thermal treatment from room temperature to 550 °C, the titanate phase gradually transformed to anatase phase, resulting in the destruction of the nanosheet structure. Particularly, the anatase phase is not observed to grow at the temperatures below 300 °C. The pore volume and specific surface area decrease under thermal treatment, which is ascribed to dehydration. The efficiency of gaseous- and liquid-phase-based photocatalytic activity of the materials is assessed by employing the photodegradation of gaseous benzene and rhodamine B (RhB), respectively. The photocatalytic activities of the samples are strongly influenced by conversion of the phase structure, pore volume, and specific surface area during the thermal treatment. This shows a significant impact on the efficiency of separation and transfer of photogenerated charge carriers.

TiO2 as a catalyst for hydrogen production from hydrogen-iodide in thermo-chemical water-splitting sulfur-iodine cycle

In this work, TiO2 nanoparticles have been prepared by the sol–gel (at different calcination temperatures) and solution-combustion method for hydrogen-iodide decomposition in thermo-chemical water-splitting sulfur-iodine (SI) cycle for hydrogen production. The sol-gel method derived TiO2 (TiO2-SGM-300 and TiO2-SGM-500) provide smaller nanoparticles as compared to the solution-combustion (TiO2-SCM). TEM revealed a particle size of around 4–5 nm of TiO2-SGM-300. XRD and Raman confirmed that TiO2-SGM-300 and TiO2-SGM-500 exhibited pure anatase phase, whereas a small amount of rutile phase was observed in TiO2-SGM-700 and TiO2-SCM samples. It is found that with increase in calcination temperatures during sol-gel method, the average particle size of TiO2 increases and specific surface area decreases. Commercial TiO2 (Degussa P-25) was used for the comparison purpose. As far as the author knows, TiO2 has been used here for the first time for hydrogen-iodide decomposition. The hydrogen-iodide decomposition experiments were carried out in a vertical-fixed bed quartz reactor at a WHSV of 12.9 h−1 under atmospheric pressure. The order of catalytic activity was as follows: TiO2-SGM-300 > TiO2-SCM > TiO2-COMM (commercial). Also, it was observed that the hydrogen-iodide conversion decreases with increase in calcination temperatures of TiO2 during sol–gel method. Their activity was as follows: TiO2-SGM-300 > TiO2-SGM-500 > TiO2-SGM-700. TiO2-SGM-300 catalyst also showed a reasonable time-on-stream stability of 6 h for hydrogen-iodide decomposition. The apparent activation energy of TiO2-SGM-300 is found to be 72.29 kJ mol−1. This shows that the TiO2 has a potential of generating hydrogen from hydrogen iodide in SI cycle. This can further be explored as a catalyst support using some non-precious and precious metal catalysts for hydrogen-iodide decomposition.

Preparation and characterization of Y2O3:Bi3+,Yb3+ nanosheets with wavelength conversion from near-ultraviolet to near-infrared

Y2O3:Bi3+,Yb3+ nanophosphors, which exhibit near-infrared (NIR) emission under near-ultraviolet (near-UV) excitation, are promising candidates for spectral converters in crystalline silicon solar devices. Herein, Y2O3:Bi3+,Yb3+ nanosheets were prepared by calcination of hydrothermally-synthesized precursors. The effects of the calcination temperature on their properties were investigated. The nanosheets calcined at ≤ 800 °C had sheet-like, square morphologies with average lateral sizes of 210–240 nm, which were smaller than precursor nanosheet with 257 nm attributed to shrinkage through the calcination. The thickness of the nanosheet before and after calcination at 800 °C was ~20 nm. Moreover, the nanosheet had a single-crystal nature. However, at calcination temperatures ≥ 900 °C, the nanosheets lost their morphologies, and transformed into irregular particles. The Y2O3:Bi3+,Yb3+ nanosheets showed visible emission from Bi3+ and NIR emission from Yb3+ under near-UV excitation. The PL intensity and PL decay time of the NIR emission monotonically increased with increasing calcination temperature. Both increases can be explained by the following effects: (i) removal of H2O molecules adsorbed on the nanosheet surface, (ii) improvement of crystallinity and decrease of specific surface area, (iii) increase in probability of energy transfer from Bi3+ to Yb3+, and (iv) oxidation of reduced bismuth during calcination. Furthermore, the photostability of the nanosheets under near-UV excitation was improved by increasing calcination temperature.

Synthesis of Cr/Al<sub>2</sub>O<sub>3</sub>- Bentonite Nanocomposite as the Hydrocracking Catalyst of Castor Oil

Synthesis and characterization of Cr/Al2O3-bentonite nanocomposite as a hydrocracking catalyst of castor oil have been conducted. The catalyst was prepared according to the following method. At the first step, bentonite was activated using H2SO4 to obtain H-bentonite, after that the activated clay was pillarized by Al2O3, Next, a salt solution of Cr (NO3)3·9H2O was impregnated in the pillared bentonite sample, followed by calcination and reduction to obtain the final catalyst, i.e. Cr/Al2O3-bentonite. The catalysts including unpillared bentonite were characterized using infrared spectrometer (FT-IR), X-Ray diffractometer (XRD), X-ray Fluorescence spectrometer (XRF), Transmission Electron Microscope (TEM) and gas sorption analyzer. GC-MS analysis was conducted to characterize the hydrocracking product. The research results showed that pillarization of bentonite caused an increasing of the basal spacing of bentonite in an amount of 1.01 nm. Although Chrom was unevenly dispersed on the bentonite and it probably blocked the bentonite framework resulted in the decrease of catalyst specific surface area, Cr/Al2O3-bentonite catalyst gave the best conversion of 64.03%. The GC-MS analysis data showed that the hydrocracking products contained various kinds of organic compounds such as acetone, acetic acid, methyl benzene, octane, heptanal, 2-octene, 1-undecanoic acid, 9-octadecenal and 10-undecenoic acid.

Synthesis and characterization of graphitic magnetic mesoporous nanocomposite and its application in dye adsorption

A simple synthesis route has been developed to prepare pitch resin, which has been as carbon precursor to fabricate graphitic mesoporous carbon by a nanocasting process, and directly incorporating iron metal nitrates species as the magnetic particle precursors infiltrated into the mesoporous framework via two different approaches. The results of nitrogen adsorption-desorption showed a decrease in specific surface area and total volume with magnetic treatment. Comparison between the AB1 dye elimination with two magnetic nanocomposites was investigated. Experimental results showed that the adsorption capacities of the graphitic mesoporous carbons under the impregnation treatment (GMC-I) and the thermal treatment (GMC-II) modification nanoparticles for AB 1 dye were calculated to be 361.7 mg g−1 and 304.5 mg g−1, respectively. The results exhibited that the obtained magnetic mesoporous graphitic carbon nanocomposites can be used as efficient and recycled adsorbents for the removal of bulky dyes from any real sample. In additions, the data of kinetic was well fitted by pseudo second-order model, and the equilibrium adsorption isotherm data of dye onto the two magnetic GMC fitted by Langmuir isotherm model. The calculated thermodynamic parameters (ΔG, ΔH and ΔS) showed that the AB 1 dye adsorption onto the two nanocomposites was feasible, spontaneous and endothermic.

Synthesis of Ni/H-Zr-MCM-48 and their isomerization activity of n-heptane

H-Zr-MCM-48 was synthesized by ion exchange from Zr-MCM-48 which was synthesized by hydrothermal method and Ni/H-Zr-MCM-48 was synthesized by impregnation method. MCM-48, Zr-MCM-48 and Ni/H-Zr-MCM-48 were characterized by various physicochemical methods including X-ray diffraction (XRD), N2 adsorption–desorption, Fourier transform infrared spectroscopy techniques and NH3 temperature programmed desorption (NH3-TPD), etc for comparison. XRD, TEM and N2 adsorption–desorption results suggest that Zr-MCM-48 samples still maintained typical cubic mesoporous framework of MCM-48, with slight decrease of specific surface areas and mesopore orders. MCM-48, Zr-MCM-48 and Ni/H-Zr-MCM-48 were also investigated by n-heptane isomerization as a probe reaction. Compared with MCM-48, Zr-MCM-48 and H-Zr-MCM-18, Ni/H-Zr-MCM-48 catalyst exhibited significantly higher selectivity for the formation of isoparaffin, with lower coke deposition and excellent catalyst stability.

Enhanced catalytic methane combustion over Co3O4 nanowire arrays by cation substitution

By using a simple hydrothermal method, large scale Co3O4 nanowire catalysts have been grown onto stainless steel mesh substrates to increase the catalyst utilization efficiency. To further enhance the catalytic activity, Mn species are doped into Co3O4 for the substitution of Co cations in the lattice to modify the activity of reactive sites. Detailed microstructure characterizations and catalytic performance evaluation have been carried out, and we found that this cation substitution strategy can significantly improve the catalytic properties of Co3O4 nanowires towards methane combustion at low temperature with appropriate amount of Mn species. On the other hand, further increase Mn concentration would result in drastically decrease of specific surface area of synthesized nanostructures and adverse effect on their catalytic activities. This study provides a feasible approach for scalable synthesis and rational optimization of nanotructured metal oxide catalysts applicable for various catalytic applications.

Comparison of different methods to retrieve optical-equivalent snow grain size in central Antarctica

Abstract. The optical-equivalent snow grain size affects the reflectivity of snow surfaces and, thus, the local surface energy budget in particular in polar regions. Therefore, the specific surface area (SSA), from which the optical snow grain size is derived, was observed for a 2-month period in central Antarctica (Kohnen research station) during austral summer 2013/14. The data were retrieved on the basis of ground-based spectral surface albedo measurements collected by the COmpact RAdiation measurement System (CORAS) and airborne observations with the Spectral Modular Airborne Radiation measurement sysTem (SMART). The snow grain size and pollution amount (SGSP) algorithm, originally developed to analyze spaceborne reflectance measurements by the MODerate Resolution Imaging Spectroradiometer (MODIS), was modified in order to reduce the impact of the solar zenith angle on the retrieval results and to cover measurements in overcast conditions. Spectral ratios of surface albedo at 1280 and 1100 nm wavelength were used to reduce the retrieval uncertainty. The retrieval was applied to the ground-based and airborne observations and validated against optical in situ observations of SSA utilizing an IceCube device. The SSA retrieved from CORAS observations varied between 27 and 89 m2 kg−1. Snowfall events caused distinct relative maxima of the SSA which were followed by a gradual decrease in SSA due to snow metamorphism and wind-induced transport of freshly fallen ice crystals. The ability of the modified algorithm to include measurements in overcast conditions improved the data coverage, in particular at times when precipitation events occurred and the SSA changed quickly. SSA retrieved from measurements with CORAS and MODIS agree with the in situ observations within the ranges given by the measurement uncertainties. However, SSA retrieved from the airborne SMART data slightly underestimated the ground-based results.

Development of alkaline electrochemical characteristics demonstrates soil formation in bauxite residue undergoing natural rehabilitation

AbstractMining and mineral processing industries have generated a large amount of polymineral wastes, causing the destruction and degradation of huge areas of landscapes at extensive geographical locations. Rehabilitation of these mine waste landscapes is critical to social and economic sustainability of mining and metallurgy operations, such as alumina refineries. The Bayer process to refine alumina generates large amounts of highly alkaline bauxite residues that are hazardous to plant growth. Innovative methodologies are urgently needed to address this economic and environmental challenges, one of which is soil formation from bauxite residues. Mineral weathering appears the prerequisite to the initiation of soil formation and development of functional soil properties in bauxite residue disposal areas. The present study investigated natural changes of mineralogy, zeta potential, isoelectric point, surface protonation, active alkaline groups, and associated implications for rehabilitation of the bauxite residue disposal area. Alkaline calcite, hydrogarnet, and sodalite minerals were slowly transformed or dissolved with declining levels over weathering time. Amorphous and semiamorphous minerals also decreased with a corresponding decrease in specific surface area and sorption sites. Zeta potential curve of fresh residue had steeper slope than those of aged residues. The isoelectric point of fresh residue was significantly higher, but those of aged residues were significantly lower, with a significant decrease of isoelectric point with increasing time. These attributes in mineralogy and electrochemical characteristics such as transformation of alkaline minerals, and decreases of surface protonation and active alkaline groups, may be used to help the assessment of soil formation status in the bauxite residues of different age and associated rehabilitation requirements.

A green organic-solvent-free route to prepare nanostructured zinc oxide carriers of clotrimazole for pharmaceutical applications

In the context of proposing cleaner production strategies for the pharmaceutical industry, an organic-solvent-free route to prepare nanostructured zinc oxide (NsZnO) reservoirs of clotrimazole (CTZ) was studied.Two different NsZnO materials were synthesized, selecting wet chemical approaches without any organic solvents: chemical bath deposition and a soft-template sol-gel method. Both materials showed a pure crystalline wurzite structure with two different morphologies: aggregates of nanosheets or interconnected nanoparticles. For the former material the specific surface area and the pore volume reached the values of 66 m2/g and 0,230 cm3/g, respectively, which were higher than those of the latter (19 m2/g and 0,050 cm3/g).For the first time, the loading of CTZ in a ZnO carrier was performed using supercritical CO2 as a solvent. The NsZnO materials were characterized, before and after the drug loading, by FESEM, EDS, XRD, nitrogen adsorption isotherms, TGA, DSC. CTZ was dispersed in the NsZnO carrier in amorphous form, with a maximum loading of 17% w/w. The decrease of specific surface area and pore volume upon drug loading for both samples is ascribed to the adsorption of CTZ molecules on the surface of the NsZnO materials. This confirms the feasibility of using the NsZnO as a CTZ carrier. In vitro drug-release was investigated and revealed that the NsZnO carrier can deliver CTZ with a faster release of a larger drug amount when compared to the solid crystalline drug.The novel clean preparation route of a ZnO carrier for CTZ delivery herein presented is easily adabtable to batch small-scale pharmaceutical industrial process.

A simple model of snow albedo decay using observations from the Community Collaborative Rain, Hail, and Snow-Albedo (CoCoRaHS-Albedo) Network

ABSTRACTThe albedo of seasonal snow cover plays an important role in the global climate system due to its influence on Earth's radiation budget and energy balance. Volunteer Community Collaborative Rain, Hail, and Snow-Albedo (CoCoRaHS-Albedo) observers collected 3249 individual daily albedo, snow depth and density measurements using standardized techniques at dozens of sites across New Hampshire, USA over four winter seasons. The data show that albedo increases rapidly with snow depth up to ~0.14 m. Multiple linear regression models using snowpack age, snow depth or density, and air temperature provide reasonable approximations of surface snow albedo during times of albedo decay. However, the linear models also reveal systematic biases that highlight an important non-linearity in snow albedo decay. Modeled albedo values are reasonably accurate within the range of 0.6–0.9, but exhibit a tendency to overestimate lower albedo values and underestimate higher albedo values. We hypothesize that rapid reduction in high albedo fresh snow results from a decrease in snow specific surface area, while during melt-events the presence of liquid water in the snowpack accelerates metamorphism and grain growth. We conclude that the CoCoRaHS-Albedo volunteer observer network provides useful snow albedo, depth and density measurements and serves as an effective model for future measurement campaigns.

Pore structure characterization of low volatile bituminous coals with different particle size and tectonic deformation using low pressure gas adsorption

Low pressure N2 and CO2 adsorption experiments were performed on two low volatile bituminous coals to gain insights into mesopore and micropore characteristics and the effects of particle size, composition (mineral matter and maceral) and tectonic deformation on them. Original coal and tectonized coal were sieved into five particle size fractions, i.e., 18–35 mesh (0.50–1.00mm), 35–60 mesh (0.25–0.50mm), 60–120 mesh (0.125–0.250mm), 120–230 mesh (0.063–0.125mm) and 230–450 mesh (0.032–0.063mm). Low pressure gas adsorption analysis, proximate analysis and maceral analysis were conducted on each particle size fraction. Specific surface area of mesopore varies from 0.22m2/g to 3.06m2/g and from 1.00m2/g to 2.07m2/g in original coal and tectonized coal, and that of micropore is from 123.7m2/g to 164.6m2/g and from 100.7m2/g to 106.7m2/g, respectively. The vast majority of total specific surface area is within micropores. Mesopore specific surface area and volume are dependent on particle size. Decreasing particle size makes some inaccessible mesopores become accessible to N2 molecules, increasing mesopore specific surface area and volume. In contrast to mesopore characteristics, micropore characteristics are independent of particle size. Mineral matter contributes minimally to micropore specific surface area and volume. There is no consistent relationship between mineral matter and mesopore characteristics. Maceral composition, which is represented by the ratio of vitrinite to inertinite, has a uniformly negative correlation with mesopore characteristics, but plays a different role in micropore characteristics. The heterogeneity in composition resulting from sieving is reduced, so the effect of particle size on pore characteristics is weakened in the tectonized coal. Tectonic deformation enhances mesopore specific surface area and volume by removing constricted pore openings and increasing accessible mesopores. Moreover, tectonic deformation is likely to cause micropores collapse, which results in a significant decrease in micropore specific surface area and volume.

Investigation on gasification performance of sewage sludge using chemical looping gasification with iron ore oxygen carrier

Chemical looping gasification (CLG), with inherent characteristic of low pollutant emissions can realize the treatment and disposal principle of sewage sludge of harmlessness, reduction, stabilization and reutilization. This work attempted to investigate the feasibility of CLG of sewage sludge with hematite oxygen carrier. The role of hematite in CLG was firstly determined and it was used as gasification agent to provide the required oxygen for sludge conversion. Subsequently, the effect of various operating parameters on sludge CLG was discussed. An optimal mass ratio of sludge to hematite oxygen carrier was determined at 0.33 to achieve the high-efficient conversion of sludge. The reaction temperature of sludge gasification was set at 900 °C to avoid the excessive reduction of hematite. Suitable steam content was assigned to at 19.52%, where the sludge conversion attained the maximum. Ash deposited caused the decrease of specific surface area of hematite, but the accumulated mineral elements in sludge ash can improve the reactivity of oxygen carrier. Additionally, the ash accumulation also can prolong the gas mean residence time. Hence, the sludge conversion showed a slight uptrend with the cycle numbers. The phosphorus element of sludge was formed of CaH2P2O7 and CaHPO4 during the CLG. Although some sludge ash deposited on the surface of hematite particles, the new compounds were not observed in the reacted oxygen carrier. Additionally, sludge ash has a relatively high resistance trend for bed agglomeration and deposit formation due to the high content of Ca/Al elements. Consequently, the accumulation of sludge ash only reveals physical effects rather than chemical effects on the hematite particles. Thus, it is easy to separate the sludge ash from hematite particles according to the differences in density and size.

Preparation of Nickel Nanoparticles Doped with Activated Carbon and Their Hydrogen Uptake at Room Temperature

This study investigates the hydrogen adsorption properties of activated carbon (AC) doped with nickel nanoparticles, and the effects of surface oxygen functional groups in AC on hydrogen uptake at room temperature. The oxidized AC (AC_OX) sample was prepared by mixing AC in a mixture of H2SO4, deionized water and HNO3 solution. By using an electroless plating process, nickel was deposited into oxidized AC (AC_OX) and denoted as Ni/ AC_OX. The oxidized activated carbon was characterized by Fourier transform infrared spectroscopy (FTIR) and Raman spectra to obtain the functional groups and structural information, respectively. After acid oxidation treatment, the integrated intensity ID/IG for the AC_OX sample is higher than that for the AC sample, indicating that the presence of defects on the former is more obvious than that on the latter. The defects facilitate the adsorption of gases and serve as reactive sites for chemical reactions, and thus surface defects are a key to the nucleation, growth, and stability of metal clusters on the support. The particle size distribution and morphology of nickel were also characterized by SEM and TEM. The SEM image of Ni/AC_OX is apparent that the deposited Ni catalyst has a narrow distribution of particle sizes between 10-20 nm in diameter, nickel content of approximately 8~10 wt. %. The specific surface area (SSA) of samples was determined at 77 K with an analyzer Quantachrome Autosorb-1 using N2 as the adsorbent. The BET surface areas of the AC, AC_OX and Ni/AC_OX samples were determined to be 1100, 870 and 340 m2/g, respectively. In addition, the total pore volumes for samples AC, AC_OX and Ni/AC_OX were 0.7, 0.55 and 0.22cc/g. The acidic oxidation treatment has very little impact on the texture of pristine AC. The decrease in SSA and pore volume in the Ni/AC_OX sample was attributed to the filling and blockage of pores of Ni by an electroless plating process. The pore size distribution patterns of AC, AC_OX and Ni/AC_OX are concentrated below 2 nm, with clear peaks at 0.7 and 1.4 nm. Hydrogen uptake measurements of AC, AC_OX and Ni/ AC_OX were performed using a commercial Sievert’s apparatus. The Raman and FTIR spectra demonstrated that the oxidized AC exhibited a slightly defective surface and oxygen functional groups. The hydrogen uptake of AC, AC_OX and Ni/AC_OX is 0.35, 0.21 and 0.58 wt.%, respectively. The RT hydrogen uptake of catalyst-free AC supports is proportional to the specific surface area and micro-pore volume The acidic oxidation treatment of AC sometimes causes a reduced pore volume and specific surface area, resulting in decreased hydrogen adsorption. It has been reported that oxygen functional groups on carbon can help hydrogen adsorption through the increased hydrogen binding energies. We thus speculated that Ni catalysts supported on oxidized AC could compensate for the low specific surface area, and thus achieve a hydrogen uptake comparable with that of pristine AC. Compared to the RT hydrogen uptake for the pristine AC sample of 0.35 wt%, the amount of hydrogen uptake for Ni/AC_OX is enhanced via spillover by a factor of 1.66. The findings further suggest that surface functionalization is essential for effective doping of Ni catalysts onto AC supports for the spillover process. Figure 1

Regulation of isobutane/1-butene adsorption behaviors on the acidic ionic liquids-functionalized MCM-22 zeolite

Abstract The adsorption ratio of isobutane/1-butene on the catalyst surface is one of the most important factors for the C4 alkylation process. Regulation of isobutane/1-butene adsorption ratio on the zeolite-supported acid catalyst is a big challenge for catalyst preparation. To regulate the isobutane/1-butene adsorption ratio, four types of ionic liquid (i.e., IL) with different alkyl chain lengths and different acid group numbers were synthesized and were subsequently immobilized onto the MCM-22 zeolite. The as-synthesized IL-immobilized MCM-22 (i.e., MCM-22-IL) was characterized by FTIR, TGA, BET, XPS and XRD, and their adsorption capacities and adsorption molar ratios of isobutane to 1-butene (I/O) were investigated to correlate with surface features of MCM-22-IL. Results showed that the immobilization of ILs led to a decrease of specific surface area and pore volume. But the surface density of acid groups was increased and the adsorption molar ratio of isobutane/1-butene (I/O) was significantly improved by the immobilization of ionic liquids. The adsorption molar ratio of I/O is substantially improved from 0.75 to above 0.9 at 300 kPa upon immobilizing ILs. Although the alkyl chain length of ILs was found to have little effect on the adsorption molar ratio of I/O, the increase of acid group numbers led to a dramatic decrease in the adsorption I/O ratio. The results illustrated that immobilizing ionic liquids is an effective way to modify the textural, chemical and morphological properties of MCM-22. Accordingly, the immobilization of ionic liquids provides a novel and a feasible way to regulate the adsorption I/O ratio on an adsorbent or a solid catalyst.

Catalyst Shelf Life: Its Effect on Nitrogen-Doped Carbon Nanotubes

In this work is presented a study of the shelf life of an iron-impregnated MgO (Fe/MgO) sample and an explanation of the effect of its aging on morphology and electroactivity of nitrogen-doped carbon nanostructures prepared by using this catalyst at different ages. Characterizations of Fe/MgO by thermogravimetric analysis (TGA), temperature-programmed desorption mass spectroscopy (TPD-MS), high-resolution X-ray powder diffraction (HR-XRPD), and X-ray photoelectron spectroscopy (XPS) have been performed at different aging times. The catalyst is formed by crystalline MgO, Mg(OH)2, and FeO phases. During aging, CO2 adsorption induces the formation of amorphous carbonate, resulting in a decrease of specific surface area, a redistribution of porosity, a reduction of the iron percentage at the surface, and an increase of iron oxide particle size. Different surface and bulk properties are used to explain different morphologies and electroactivities of the nitrogen-doped carbon nanotubes synthesized at different ...

Pore structure of transitional shales in the Ordos Basin, NW China: Effects of composition on gas storage capacity

The recoverable resource of shale gas is 25 trillion cubic meter, 33% of which is stored in transitional shales in China. This work investigates the effects of organic and inorganic compositions on the development of Upper Paleozoic transitional shale pore structures through a combination of petrophysical and geochemical measurements. 42 shale samples were collected from marsh-lagoon and coastal delta settings in the Ordos Basin, NW China. The samples include the Upper Permian Shanxi shale (average total organic carbon (TOC) of 1.58wt%, Type III kerogen, average vitrinite reflectance (Ro) 2.6%), and the Upper Carboniferous Benxi shale (average TOC of 1.91wt%, Type III kerogen, average Ro 2.74%) at the over-mature stage or dry gas window. An important characteristic of these shales is the large proportion of clay minerals (∼69% in Benxi shale and 54% in Shanxi shale). The quartz content is ∼17% and 40% for Benxi and Shanxi shales, respectively. The pore structure of three samples and one isolated kerogen sample is analyzed via both low-pressure nitrogen and carbon dioxide adsorption methods. Low pressure nitrogen adsorption experiments show that Benxi and Shanxi shales characterized by ultra-low porosity and permeability develop mainly silt-shaped pores and potentially ink-bottle-shaped pores. We find that increasing fractions of organic matter (OM) result in a decrease in both total pore volume and specific surface area (SSA). Low pressure carbon dioxide adsorption experiments show that micropore volumes nonlinearly increase with increasing OM, although the contribution of organic micropore volume is limited. The mesopore and macropore volumes of inorganic compositions contribute mostly to the total pore volume. The OM in transitional shales in Yanchang mainly develop mesopores (with <5nm diameters), which significantly contribute to the SSA, while micropores are the main contributor to SSA in the inorganic matter. For thermally over-mature transitional shales, clay minerals contribute the most to SSA and pore volume as well as the storage capacity of absorbed and free gas.