Narrow Mesoporous Distribution Research Articles

ZnO-PANI nanocomposite: Enhanced electrochemical performance towards energy storage

In the present investigation a novel nanocomposite composed of Polyaniline (PANI) and Zinc Oxide (ZnO) has been evaluated for its structural, morphological, and electrochemical properties for its application as high-performance Li-ion battery electrode. The X-ray diffraction (XRD) and Furrier transform infrared (FTIR) spectral analysis confirmed the synthesis of ZnO-PANI nanocomposite. The Field emission- scanning electron microscopy (FE-SEM) images confirmed the uniform distribution of ZnO nanoparticle in PANI matrix, while BET surface area analysis revealed a narrow mesoporous pore distribution with high surface area, enhancing its potential for energy storage. The electrochemical assessment using CR2032 coin cells showcased the remarkable performance of the ZnO-PANI nanocomposite as an electrode material for energy storage. Cyclic voltammetry (CV) analysis revealed distinct reduction and reformation peaks related to ZnO and Li+ insertion into the PANI matrix. The nanocomposite displayed a high specific capacity, with an initial discharge capacity of 1052 mA h g−1, followed by stable performance in subsequent cycles. Notably, Coulombic efficiency consistently exceeded 98 % from the 10th cycle, demonstrating excellent performance. The rate capability was equally impressive, delivering discharge capacities from 1052 mA h g−1 at 0.1C to 771 mA h g−1 at 2C. Long-term cycling tests illustrated exceptional capacity retention, with 92.99 % capacity retained after 500 cycles and outstanding Coulombic efficiency consistently above 99 %. In conclusion, the ZnO-PANI nanocomposite exhibits desirable structural and morphological attributes, exceptional electrochemical performance, and potential for advanced energy applications, particularly in Li-ion batteries.

Development of Mesopore Structure of Mixed Metal Oxide through Albumin-Templated Coprecipitation and Reconstruction of Layered Double Hydroxide.

Mixed metal oxide (MMO) with relatively homogeneous mesopores was successfully obtained by calcination and reconstruction of albumin-templated layered double hydroxide (LDH). The aggregation degree of albumin-template was controlled by adjusting two different synthesis routes, coprecipitation and reconstruction. X-ray diffraction patterns and scanning electron microscopic images indicated that crystal growth of LDH was fairly limited during albumin-templated coprecipitation due to the aggregation. On the hand, crystal growth along the lateral direction was facilitated in albumin-templated reconstruction due to the homogeneous distribution of proteins moiety. Different state of albumin during LDH synthesis influenced the local disorder and porous structure of calcination product, MMO. The N2 adsorption-desorption isotherms demonstrated that calcination on reconstructed LDH produced MMO with large specific surface area and narrow distribution of mesopores compared with calcination of coprecipitated LDH.

Accumulation of Natural Gas with a Prospective Material Based on Graphene Aerogel

The assessment of the possibility of effective use of graphene aerogels for the adsorption storage and transportation of methane is given. For the study, an aerogel based on reduced graphene oxide was synthesized using supercritical methods for processing a hydrogel in an isopropyl alcohol medium. A narrow distribution of micropores with a maximum at 0.8 nm, a narrow distribution of mesopores with a maximum at about 4.5 and 6.5 nm were revealed. The obtained graphene aerogel (GA) was used to study the adsorption of methane at pressures up to 10 MPa and temperatures of 298, 303, 313 K. The maximum gravimetric absorption of methane reaches 0.86 g/g (37 cm3 (STP)/cm3) and 2.6 g/g (109 m3 (STP)/m3) at corresponding pressures of 35 and 100 bar and a temperature of 298 K, which is the highest recorded value for porous carbon previously reported.

Synthesis of mesoporous silica with ordered nanostructural morphology from natural quartz sand

Silica with ordered nanostructured morphology characteristic of mesoporous molecular sieves with cubic packing of cylindrical pores and a three-dimensional porous structure is obtained from natural quartz sand. It was shown by X-ray diffraction, scanning electron microscopy, and low-temperature nitrogen adsorption-desorption that the obtained silica material is thermally stable, amorphous, consists of submicron grains, has a high specific surface area of 1396 m2/g, a pore volume of 0.780 cm3/g and an average diameter of 2.2 nm with a narrow size distribution of mesopores.

Mesoporous composite Ni-C-N/SA for selective adsorption of methylene blue from water

A mesoporous Ni-C-N/Silica aerogel (Ni-C-N/SA) was prepared by impregnation of the cationic [Ni(tepa)]2+ complex onto a negatively charged silica aerogel support followed by suitable thermal treatment. And Ni-C-N/SA was applied as an adsorbent for selective adsorption of methylene blue (MB). When [Ni(tepa)]2+ loading is 20% and thermal treatment temperature is 400 °C (denoted “NiT20-400/SA”), the adsorption of MB by NiT20-400/SA is 54 mg/g, which is three times that of raw silica aerogel (RSA). However, little adsorption was observed for the anionic dye methyl orange (MO) and large sized cationic dye rhodamine B (RhB), demonstrating that NiT20-400/SA showed selective adsorption for MB. The nitrogen adsorption/desorption results demonstrate that the total pore volume of NiT20-400/SA is about 1.27 cm3/g, which is 25.7% higher than that of the RSA. The pore size distribution also changed from a wide range pore size distribution (13–126 nm) in the RSA to a narrow range mesoporous distribution (mainly 5–15 nm) in NiT20-400/SA. All of these results are due to the “binder” effect of [Ni(tepa)]2+ on the RSA surface. XPS shows that multiple-doping with nickel, carbon and nitrogen (Ni-C-N) were successfully added to the RSA surface via the followed pyrolysis of [Ni(tepa)]2+. As temperature increases in the range 200–600 °C, Ni, C and N species undergo [Ni(tepa)]2+ → Ni-C-N → NiO changes process. The larger total pore volume, suitable pore size distribution, and the unique subject-object interaction between cationic dye and Ni-C-N components results in the increased adsorption capacity and selective adsorption of MB.

Carbon aerogels activation by CO2 using an induction heated fluidized bed reactor

Resorcinol–formaldehyde (RF) aerogels were synthesized by polymerization and, then, were carbonized using a novel induction heated fluidized bed reactor (IHFBR). The obtained carbon aerogels were activated using CO2 while the effects of activation time ξ and CO2 concentration γ on the structural properties of carbon aerogels were examined. It is shown that activation by CO2 can be easily achieved using IHFBR while ξ and γ can affect the final structural properties of carbon aerogels. Large ξ or γ results in the loss of narrow and homogeneous distribution of mesopores while low γ solely changes the micropores superficially. Accordingly, possible mechanisms for changes in the structural properties of carbon aerogels were proposed. Using IHFBR can markedly reduce the activation time (from hours to minutes) by furnishing enhanced heat and mass transfer while facilitating the scale up process.

Synthesis of Ni/γ-Al2O3SiO2 catalysts with different silicon precursors for the steam toluene reforming

Abstract This work investigated the intrinsic properties and performances of Ni/γ-Al2O3 SiO2 modified with different silicon precursors for the steam reforming of toluene in biomass gasifier exit conditions (8000 ppmv of toluene, 650 °C). Samples were synthesized by an aqueous sol-gel process in presence of aluminum nitrate, nickel nitrate and the use of either tetramethoxysilane (TMOS, Si-(OCH3)4) or tetraethoxysilane (TEOS, Si-(OC2H5)4) in order to understand the influence of the reactivity of the silicon precursor. Furthermore, the use of N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS, (OCH3)3 Si (CH2)3 NH (CH2)2 NH2) is also investigated in order to understand the influence of a silicon precursor containing an ethylenediamine group, able to complex Ni2+ ions. By the chelation of Ni2+ ions by ethylenediamine groups during the synthesis, Ni/γ-Al2O3 SiO2 samples modified with EDAS showed higher dispersion of the metallic Ni nanoparticles and the higher resistance against the sintering of Ni particles. This was also attributed to the high microporous volume and the narrow mesoporous distribution of the support, which could also prevent the migration of the metallic Ni nanoparticles. The catalytic tests revealed that the reactivity of the silicon precursor played a major role on the conversion of toluene. For alumina supports modified with a silicon precursor with a low reactivity such as TEOS, the low integration of the Si atoms inside the bulk alumina lead to a slightly higher catalytic activity, but also to a high formation of structured carbon. The opposite effect was observed for the samples modified with a highly reactive silicon precursor, such as TMOS or EDAS, which showed a slightly lower catalytic activity, but a higher resistance against coking compared to pure Ni/γ-Al2O3 catalysts.

Preparation and characterization of silicagel from silicate solution obtained by autoclave treatment of copper slag

The formation of silicagel from sodium silicate solution obtained by alkaline autoclave treatment of copper slag was investigated. The influence of the parameters of the gelation process (type of acid used, the pH of the medium, and drying conditions) on the structure and properties of the resulting silicagel, were studied. Silicagels obtained under different conditions were characterized by XRD, low-temperature nitrogen adsorption, FTIR, SEM, and TEM analyses. All silicagels are amorphous with a different degree of crosslinking. The physicochemical characterizations show that the type of acid, the mode of drying and pH influence the dispersity and the morphology of the silicagels prepared. Silicagels obtained at low-pH medium have a higher specific surface area and porosity than silicagels obtained at high-pH medium. Silicagels obtained at low-pH medium have no micropores and their porosity is only expressed by a narrow mesopore distribution. Freeze-drying improves the porosity of the silicagels obtained at high-pH medium. It is confirmed that the dilution of the sodium silicate solution affects the initial pH and the time of gelation.The moisture absorption capacity of the prepared silicagels increases in the following order: silicagel obtained at high-pH medium, dried in air < silicagel obtained at high-pH medium, freeze-dried < silicagel obtained at low-pH medium, dried in air.

Direct synthesis of hierarchically structured MFI zeolite nanosheet assemblies with tailored activity in benzylation reaction

The MFI zeolites with nanosheet assemblies morphology were prepared by a seed-assisted strategy using specially designed bolaform surfactant [C6H13-N+(CH3)2-C6H12-N+(CH3)2-(CH2)12-O-(p-C6H4)2-O-(CH2)12-N+(CH3)2-C6H12-N+(CH3)2-C6H13] [Br−]4 (C6-12-diphe) as a structure-directing agent. The MFI zeolite nanosheet assemblies were composed of MFI nanosheets with randomly organized structure, exhibiting a narrow mesopore distribution. By tuning the Si/Al ratios of MFI zeolite nanosheet assemblies from 60 to 10, the morphology of resultant zeolites changed from nanosheet stacks to house-of-cards-like structures, and to nanosponges. In addition, the porosity and Brønsted acid/Lewis acid ratio exhibited a parabola-type dependence on the Si/Al ratios of obtained zeolites, indicating that meso-/microporosity and acidity of MFI nanosheet assemblies can be systematically tailored by changing the constituents of zeolites. Catalytic performance of MFI zeolite nanosheet assemblies was investigated in the benzylation of benzyl alcohol with mesitylene. The results revealed that MFI zeolite nanosheet assemblies exhibited extraordinary catalytic activity compared to conventional ZSM-5 zeolite. The conversion of benzyl alcohol and selectivity (1,3,5-trimethyl-2-benzylbenzene vs dibenzyl ether) of zeolite catalysts were linearly dependent on the Brønsted acid/Lewis acid ratio, and they exhibited a parabola-type dependence on the Sext/SBET, indicating that a balance between acidity and porosity of zeolites can be realized to modulate the catalytic properties of MFI zeolite nanosheet assemblies guided by C6-12-diphe.

The Influence of TPOACl on the Post‐Synthesis of Hierarchical Zeolite Y and the Catalytic Cracking Application

AbstractA hierarchical zeolite Y was prepared through a facile SiCl4‐dealumination plus alkaline treatment process with the addition of surfactant TPOACl. It was investigated in detail by XRD, BET, MAS NMR, NH3‐TPD and Py‐IR. Compared with single alkaline treatment, the alkaline treatment in the presence of TPOACl could protect the microporosity of zeolite and led to hierarchical pore structures with increased mesoporosity and narrow distribution of mesopores. Accordingly, the mechanism for the desilication and the formation of mesopores in the presence of TPOACl was proposed based on the measurement results of NMR and Py‐IR. The EFAl species could be assembled to poly‐aluminum species in the presence of TPOACl and leads to low content of Lewis acid sites. The hierarchical zeolite Y with high ratio of B/L and high percent of mesopores possesses excellent catalytic performance in the conversion of 1,3,5‐TIPB.

Controllable synthesis of chainlike hierarchical ZSM-5 templated by sucrose and its catalytic performance

Hierarchical ZSM-5 with controllable chainlike structure was hydrothermally synthesized with sucrose as template, characterized by XRD, FT-IR, N2 adsorption, SEM and TEM, and used for methylation of 2-methylnaphthalene. Hierarchical ZSM-5 can be rapidly synthesized, and chainlike morphology is stacked with several submicron crystals. With increasing sucrose amount in the precursor, the chain structure became more obvious, and the surface area and pore volume of mesopores increased. Narrow mesoporous distribution was centered at about 7nm. It is thought that the formation of mesopores is related to the template role of sucrose. Chainlike hierarchical ZSM-5 exhibited high 2-methylnaphthalene conversion and 2,6-dimethylnaphthalene yield.

Microwave-assisted synthesis of 3D flowerlike α-Ni(OH)2 nanostructures for supercapacitor application

Three-dimensional flowerlike a-Ni(OH)2 nanostructures were successfully synthesized by the microwave-assisted reflux as short as 30 min. The crystalline structure and morphology of the products were characterized by X-ray diffraction, N2 adsorption-desorption isotherms, field emission scanning electron microscopy, and transmission electron microscopy. The a-Ni(OH)2 nanostructure shows a large surface area of 173 m2 g-1 and narrow mesopore distribution. The electrochemical properties of the as-prepared a-Ni(OH)2 as an electrode material for supercapacitor were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements in 6 mol/L KOH electrolyte. The a-Ni(OH)2 nanostructure shows a maximum specific capacitance of 2030 F g-1 at a current density of 1 A g-1 and exhibits excellent rate capability. These results suggest that it is a promising electrode material for supercapacitor application.

Hydroconversion of n-hexadecane over bifunctional microporous and mesoporous model catalysts. Influence of pore architecture on selectivity

A model hydrocracking catalyst with a narrow and homogeneous distribution of mesopores of 3.2nm of diameter has been prepared by alumination of the surface of a siliceous MCM-48 material, loaded with platinum and evaluated in the hydroconversion of n-hexadecane. Compared to zeolite catalysts featuring a similar acidity but containing both micropores and mesopores, the Pt/Al-MCM-48 catalyst leads to the same overall activity but with higher hexadecane isomer yields and a symmetrical repartition of the cracked products, typical for primary central cracking, even at very high conversion levels. It is suggested that the unique behavior of the model Pt/Al-MCM-48 mesoporous hydroconversion catalyst is due to optimal sorption energetics of the primary reaction products in the network of uniformly distributed mesopores.

Enhanced performance in NOx reduction by NH3 over a mesoporous Ce–Ti–MoOx catalyst stabilized by a carbon template

The mesopore Ce–Ti–MoOx catalyst stabilized by an in situ formed carbon template showed more than 90% NOx conversion at 175–425 °C for SCR of NOx with NH3. Increasing temperature in the presence of carbon template contributed to the narrow mesoporous distribution and excellent low-temperature SCR activity.

Indene epoxidation over titanium modified MCM-41 mesoporous materials

The current research is focused on the testing of titanium modified MCM-41 in indene epoxidation. Two preparation methods of Ti catalysts with mesoporous structure were tested, namely grafting of titanium on prepared MCM-41 (Ti/MCM-41/gr) and incorporation of titanium into the structure of MCM-41 by co-gelification method (Ti-MCM-41/cg). The tested catalysts exhibited high surface area, well-defined regular structure and narrow pore size distribution of mesopores and therefore represent potential good quality catalytic systems. The successful preparation of catalysts was confirmed by wide range of characterization methods (XRF, XRD, physical adsorption of N2, SEM, UV–Vis and FTIR). The catalytic activity of the prepared Ti catalysts was evaluated in indene epoxidation. The optimization of reaction conditions was performed using two types of oxidizing agents—aqueous solution of tert-butyl hydroperoxide and solution of tert-butyl hydroperoxide in decane. The prepared catalytic systems were successfully used for preparation of 1,2-epoxyindane with high yield (83 %) and the possibility of catalyst regeneration was proved.

Indene epoxidation over immobilized methyltrioxorhenium on MCM-41 silica, fumed silica and aluminosilicate materials

The presented report focuses on the testing of heterogenized methyltrioxorhenium (MTO) in indene epoxidation. A range of mesoporous materials with different SiO2/Al2O3 ratios, namely aluminosilicates type Siral and MCM-41 silica and fumed silica, were used as supports for immobilization of MTO. The tested support materials and prepared catalytic systems exhibited high surface area, well-defined regular structure and narrow pore size distribution of mesopores and therefore represent good quality catalysts for various reactions. The immobilized MTO on various supports was tested for the preparation of 1,2-epoxyindane using two forms of hydrogen peroxide as oxidation agents, namely aqueous solution of hydrogen peroxide and its anhydrous form, urea-hydrogen peroxide. The prepared catalysts were successfully used for the preparation of 1,2-epoxyindane with achieved 100 % selectivities to the desired product at high conversions of indene.

Preparation and evaluation of activated carbon with different polycondensed phosphorus oxyacids (H3PO4, H4P2O7, H6P4O13 and C6H18O24P6) activation employing mushroom roots as precursor

Orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7), polyphosphoric acid (H6P4O13) and phytic acid (C6H18O24P6) were specially employed as activating agents to produce activated carbons from mushroom roots (MR). Thermogravimetric studies of MR after these phosphorus oxyacids (POA) impregnation indicated the thermal degradation of MR was greatly influenced by different polycondensed POA. The prepared activated carbons were characterized by N2 adsorption/desorption isotherms, Fourier-transform infrared spectroscopy (FTIR) and Boehm's titration. The surface area of the carbons was similar but the characteristics of pore volume were different. MRAC-C6H16O24P6 owned the largest surface area and micropore volume. MRAC-H3PO4, MRAC-H4P2O7 and MRAC-H6P4O13 presented a similar micropore volume. MRAC-H6P4O13 exhibited a comparatively narrow mesopore distribution around 4nm. Boehm's titration results indicated that MRAC-C6H16O24P6, MRAC-H6P4O13 and MRAC-H4P2O7 had much more acidic functionalities than MRAC-H3PO4. MRAC-C6H18O24P6 had the highest amount of total acidic surface groups (4.02mmol/g). Batched sorption studies were also performed to compare adsorptive properties of the carbons toward methylene blue (MB). The sorption capacity of MB follows an order of MRAC-C6H16O24P6≈MRAC-H6P4O13>MRAC-H4P2O7>MRAC-H3PO4, which may be assigned to the different pore structures and chemical properties.

Immobilization of Methyltrioxorhenium on Mesoporous Aluminosilicate Materials.

The presented report focuses on an in-depth detailed characterization of immobilized methyltrioxorhenium (MTO), giving catalysts with a wide spectra of utilization. The range of mesoporous materials with different SiO2/Al2O3 ratios, namely mesoporous alumina (MA), aluminosilicates type Siral (with Al content 60%–90%) and MCM-41, were used as supports for immobilization of MTO. The tested support materials (aluminous/siliceous) exhibited high surface area, well-defined regular structure and narrow pore size distribution of mesopores, and therefore represent excellent supports for the active components. Some of the supports were modified by zinc chloride in order to obtain catalysts with higher activities for instance in metathesis reactions. The immobilization of MTO was optimized using these supports and it was successful using all supports. The success of the immobilization of MTO and the properties of the prepared heterogeneous catalysts were characterized using X-ray Fluorescence (XRF), atomic absorption spectroscopy (AAS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), physical adsorption of N2, ultraviolet-visible spectroscopy (UV-Vis), infrared spectroscopy (FTIR), Fourier Transform Infrared Spectroscopy (FTIR) using pyridine as a probe molecule and X-ray photoelectron spectroscopy (XPS). Furthermore, the catalytic activity of the immobilized MTO on the tested supports was demonstrated on metathesis reactions of various substrates.

Synthesis of Porous, Nitrogen‐Doped Adsorption/Diffusion Carbonaceous Membranes for Efficient CO2 Separation

A porous, nitrogen-doped carbonaceous free-standing membrane (TFMT-550) is prepared by a facile template-free method using letrozole as an intermediate to a triazole-functionalized-triazine framework, followed by carbonization. Such adsorption/diffusion membranes exhibit good separation performance of CO2 over N2 and surpassing the most recent Robeson upper bound. An exceptional ideal CO2 /N2 permselectivity of 47.5 was achieved with a good CO2 permeability of 2.40 × 10(-13) mol m m(-2) s(-1) Pa(-1) . The latter results arise from the presence of micropores, narrow distribution of small mesopores and from the strong dipole-quadrupole interactions between the large quadrupole moment of CO2 molecules and the polar sites associated with N groups (e.g., triazine units) within the framework.

Facile Preparation of SiO2/TiO2 Composite Monolithic Capillary Column and Its Application in Enrichment of Phosphopeptides

A novel SiO(2)/TiO(2) composite monolithic capillary column was prepared by sol-gel technology and successfully applied to enrich phosphopeptides as a metal oxide affinity chromatography (MOAC) material. For the monolith preparation, tetramethoxysilane (TMOS) and tetrabutoxytitanium (TBOT) were used as silica and titania source, respectively, and glycerol was introduced to attenuate the activity of titanium precursor, which provided a mild synthetic condition. The prepared monolith was characterized by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results revealed an approximate 1/2 molar ratio of titanium to silica as well as an atom-scale homogeneity in the framework. The scanning electron microscopy (SEM) results demonstrated an excellent anchorage between the column and the inner capillary wall, and nitrogen adsorption-desorption experiments showed a bimodal porosity with a narrow mesopore distribution around 3.6 nm. The prepared monolith was then applied for selective enrichment of phosphopeptides from the digestion mixture of phosphoproteins and bovine serum albumin (BSA) as well as human blood serum, nonfat milk, and egg white using an in-tube solid phase microextraction (SPME) system. Our results showed that SiO(2)/TiO(2) composite monolithic capillary column could efficiently enrich the phosphopeptides from complex matrixes. To the best of our knowledge, this is the first attempt for preparing the silica-metal composite monolithic capillary column, which offers the promising application of the monolith on phosphoproteomics study.