Mesoporous Silica Support Research Articles

Promoted nickel-based catalysts on modified mesoporous silica support: The role of yttria and magnesia on CO2 methanation

In this research, a group of xY 2 O 3 -Ni/MgO-MCM-41catalysts were synthesized by using direct synthesis method for CO 2 hydrogenation and were characterized by employing BET, XRD, HRTEM, XPS, TPD, FE-SEM and TPO to understand the mechanism of CO 2 hydrogenation over yttria-Ni/MgO-MCM-41. Compared to Ni/MgO-MCM-41, all catalysts which contained Yttria showed improved catalytic activity. The one with 2 wt% yttria had the highest catalytic performance, with carbon dioxide conversion and methane selectivity of 65.55% and 84.44% at 673 K, respectively, and high stability after 30 h. The impact of adding yttria, as a promoter, on nickel dispersion and that of enhancing carbon dioxide adsorption sites on basicity sites attracted more attention as effective factors regarding conversion, selectivity, and stability. Mechanism of effect of adding Yttria on Ni/MgO-MCM-41 in CO 2 methanation process. • Incorporation of Magnesia and Yttria promoters are beneficial for CO 2 hydrogenation. • 2Y 2 O 3 -Ni/MgO-MCM-41 showed the highest CO 2 conversion and CH 4 selectivity. • Adding Yttria increased nickel dispersion, reducibility and oxygen vacancy. • With the increase in the Ni active sites, the dissociation of H 2 to atomic hydrogen increased.

SBA-15-Supported Imidazolium Ionic Liquid through Different Linkers as a Sustainable Catalyst for the Synthesis of Cyclic Carbonates: A Kinetic Study and Theoretical DFT Calculations

Various cyclic carbonates were prepared by cycloaddition of carbon dioxide with different epoxides using imidazolium-based catalysts grafted on a mesoporous silica support through 3-aminopropyltrim...

Propylene Epoxidation to Propylene Oxide Over RuO₂, CuO, TeO₂, and TiO₂ Supported on Modified Mesoporous Silicas.

Direct gas phase epoxidation of propylene to propylene oxide (PO) using O₂ is a challenging problem in catalysis research. Silica-supported ruthenium-copper-based catalysts have been recently reported to be promising for propylene epoxidation. In this work, mesoporous silica supports modified with RuO₂, CuO, and TeO₂ with and without TiO₂ were investigated for propylene epoxidation to PO. The prepared catalysts were divided into two groups. The first group consisted of mesoporous silica supports modified with RuO₂, CuO, and TeO₂, and the second group consisted of the same components as the first group but adding TiO₂. The prepared supports and catalysts were characterized using BET surface area analysis and other advanced instrument techniques. It was found that the catalyst made with RuO₂ and TeO₂ impregnated onto porous silica modified with CuO and TiO₂ (denoted as RuTe/CuTiSi) exhibited an excellent PO formation of 344 gPO h-1 kg-1cat, which was superior to that of the other prepared catalysts. Moreover, the addition of TiO₂ into the catalyst greatly improved the PO formation rate and the arrangement of active components in the catalyst and strongly influenced catalytic performance.

REMOVAL OF NORFLOXACIN BY TiO2-SBA-15 PHOTOCATALYST

Ordered SBA-15 mesoporous silica support was synthesized by a sol-gel method using triblock copolymer Pluronic P123 and immobilized with different amounts of photocatalyst TiO2. The synthesized composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 adsorption-desorption isotherms. The synthesized materials possessed specific surface areas SBET of 768 m2/g, 544 m2/g, 421 m2/g and 333 m2/g at the TiO2:SiO2 ratio of 0, 0.25, 1.0 and 5.0, respectively. The adsorption capacities and photocatalytic activities under UV light irradiation of these materials were evaluated for Norfloxacin degradation. Experimental results indicate that the highest activity was observed on the sample with TiO2:SiO2 ratio of 1.

Thia-crown ether functionalized mesoporous silica (SBA-15) adsorbent for selective recovery of gold (Au3+) ions from electronic waste leachate

Abstract The rapid production rate of electrical and electronic devices demands for gold (Au) recovery and recycling from their generated wastes. However, achieving adsorbents with high selectivity for Au remains a challenge. Herein, an Au3+-selective composite adsorbent (15TCE@SBA-15) was successfully fabricated through covalent attachment of thia-crown ether (15TCE) as ligand on mesoporous silica support SBA-15. The physicochemical properties of 15TCE@SBA-15 were extensively examined using FT-IR, SAXRD, TGA, FE-SEM, EDS mapping, surface area (BET), and pore size distribution (BJH, NLDFT) analysis. To evaluate its ability to selectively capture Au3+, adsorption experiments were conducted. The results revealed that 15TCE@SBA-15 was able to capture 126 mg of Au3+ per gram of sample. More importantly, it was highly selective towards Au3+ with distribution coefficient of KD ~2439 L g−1 vs. other cations (i.e. Pd2+, Pt4+, Ni2+, Pb2+, Cu2+, Zn2+) present in spent mobile phones with KD values

Synthesis, Characterization and Catalytic Evaluation of Chromium Oxide Deposited on Titania–Silica Mesoporous Nanocomposite for the Ethane Dehydrogenation with CO2

Ti modification of mesoporous silica support has been reported as an effective way to enhance Cr–Ti–Si interactions that, in turn, impact the catalytic dehydrogenation of ethane with CO2. However, such modification necessitates a repeated, time-consuming and tedious process. In this work, a simple, fast and facile approach has been utilized to synthesize chromium-oxide-loaded titania–silica mesoporous nanocomposites. A series of Cr(y)/Ti(x)–Si mesoporous nanocomposite catalysts with varying Ti and Cr contents were prepared and tested in the dehydrogenation of ethane with carbon dioxide. The as-synthesized catalysts were characterized by XRD, TEM, SEM, BET, UV–Vis–DR, XPS and H2–TPR techniques. The effect of titanium content, as well as chromium loading on the performance of the prepared Cr(y)/Ti(x)–Si catalysts, was investigated. It was found that 2.2 and 8 wt % are the optimum titanium and chromium contents in the synthesized catalysts for obtaining the highest catalytic activity. The superior catalytic performance of the Cr(8)/Ti(2.2)–Si catalyst can be attributed to a higher dispersion of the Cr species, as well as a higher content of the redox Cr species on the surface of the Cr/Ti–Si catalyst. The results showed that the Cr(8)/Ti(2.2)–Si catalyst efficiently dehydrogenated C2H6 in the presence of CO2 giving a 52.3% ethane conversion and 48.0% ethylene yield at 700 °C reaction temperature.

Advances in Designing Au Nanoparticles for Catalytic Epoxidation of Propylene with H2 and O2

Au nanoparticles, which can be used in various industrial and environmental applications, have drawn substantial research interest. In this review, a comprehensive background and some insights are provided regarding recent studies concerning the use of Au nanoparticles for catalytic propylene epoxidation with H2 and O2. Over the last two decades, substantial progress has been made toward the efficient production of propylene oxide (PO); this includes the design of highly dispersed Au catalysts on Ti-modified mesoporous silica supports, the optimization of catalytic epoxidation, and the determination of the mechanisms and reaction pathways of epoxidation. Particularly, the critical roles of catalyst synthesis, the types of material support, Au nanoparticle sizes, and the dispersion amounts of Au nanoparticles are emphasized in this review. In future studies, novel, practical, robust, and highly PO-selective Au nanoparticle catalyst systems are expected to be continually designed for the enhanced catalytic epoxidation of propylene.

Oxidative dehydrogenation of n-butane to butadiene catalyzed by new mesoporous mixed oxides NiO-(beta-Bi2O3)-Bi2SiO5/SBA-15 system

NiO-beta-Bi2O3-Bi2SiO5/SBA-15 catalysts, containing 10−20 wt% Ni and 10−30 wt% Bi loaded as metal weight on mesoporous SiO2 support (SBA-15), were utilized for the oxidative dehydrogenation of n-butane to butadiene, comparing from the viewpoint of Bi oxide phase and combination balance with Ni oxide and the support. Bi2SiO5 and beta-Bi2O3 phases change depending on Ni/Bi ratio. “Reverse core-shell” structure with uniform mesoporosity catalytically active for the oxidative dehydrogenation of n-butane to butadiene was successfully synthesized with semi-dry conversion method. The shell was formed as Bi2SiO5/SBA-15 by partially dissolving an array of silanol inside SBA-15 mesopores with impregnated bismuth nitrate. The Bi2SiO5 of the shell was increased by co-impregnated nickel nitrate. The layered core faced to mesopore was formed as catalytically active NiO/beta-Bi2O3 on the shell. The degrees of formation Bi2SiO5 and beta-Bi2O3 reflected in the butadiene selectivity through changing the reducibility and dispersion properties. The catalyst with moderate loading of 20 wt% Ni and 10 wt% Bi exhibited a high advantage in the n-butane conversion: 30 % and butadiene selectivity: 49 % at 450 °C compared to the less and excess loaded catalysts. The catalytic performance of other mesoporous silica support catalysts also changed differently depending on Bi2SiO5 and beta-Bi2O3 phases.

Supported silver catalysts prepared via melt infiltration: Synthesis, characterization and performance in selective hydrogenation

Heterogeneous supported catalysts are often synthesized by impregnation or precipitation methods. Recently, melt infiltration has emerged as an alternative method that allows high metal loadings and eliminates the need for a solvent, but challenges arise regarding control over the particle size and distribution. In this work, melt infiltration for the synthesis of supported silver catalysts is explored. The narrow pore size distribution of the chosen ordered mesoporous silica support, SBA-15, allowed in depth in-situ and ex-situ characterization of the infiltration of the precursor, molten silver nitrate, into the support and its subsequent decomposition to form metallic silver nanowires or nanoparticles. The heat treatment parameters during decomposition played a key role in determining whether nanowires or nanoparticles were formed. The supported silver catalysts containing high silver weight loadings were investigated in the selective hydrogenation of cinnamaldehyde, where the silver nanowires showed superior activity and selectivity over the nanoparticles. Hence, melt infiltration shows great promise for the synthesis of supported silver catalysts containing high silver weight loadings, which are applicable in, e.g., selective oxidation or hydrogenation reactions.

Highly dispersed Cu supported on mesoporous Al‐KIT‐6 for oxidative carbonylation of methanol to dimethyl carbonate

Microporous NaY zeolite is a common support of Cu catalysts for oxidative carbonylation of methanol, but the dispersion of Cu species on NaY is usually subjected to its micropore size. Here, ordered mesoporous KIT‐6 was employed as the support for Cu catalyst and Al was incorporated into its framework to increase the surface acidity, which eventually improves the surface exchange capacity and Cu dispersion. The evolution of the state of Cu species on KIT‐6 was analyzed combined with control of Cu loading. The physicochemical properties of the supports and corresponding catalysts were characterized by N2 adsorption–desorption, X‐ray diffraction, ammonia temperature programmed desorption, Fourier transform infrared spectra, transmission electron microscopy, hydrogen temperature programmed reduction, and X‐ray photoelectron spectroscopy. It was found that mesoporous KIT‐6 showed better Cu dispersion than microporous NaY zeolite. Agglomerated CuO, dispersed CuO, and Cu2+ are the major Cu species observed on the catalyst surface. The increased surface acidic sites of KIT‐6 by Al incorporation promoted the formation of Cu2+ and dispersion of CuO. With the increase in Cu loading, the Cu2+ content in the catalyst was decreased gradually along with increase in the bulk CuO. It was speculated that some exchanged Cu2+ could be transformed into highly dispersed CuO and even bulk CuO after calcination at a high Cu loading. Combined with the catalyst evaluation results, it was deduced that highly dispersed Cu2+ and CuO particles play significant roles in catalytic activity. The catalyst Cu/Al‐K‐10 achieved the highest space time yield of dimethyl carbonate of 135.4 mg/(g·h), which is 2.7 times the Cu/K‐10 owing to its more dispersed Cu species. This laid the basis for preparing highly dispersed Cu species on mesoporous silica supports.

Ni-Based Nanoparticles on Mesoporous Silica Supports for Single-Stage Arsenic and Chlorine Removal during Diesel Fraction Hydrotreating.

As- and Cl-containing impurities are highly detrimental to sulfided catalysts in hydrotreating processes. To prevent the irreversible loss of activity of the main sulfide catalysts by As and Cl contaminants, a protective double-layered guard bed catalyst is applied. Two types of mesoporous silica supports (SBA-15 and MCF) were used to obtain sorption-catalytic materials. The high specific surface area of the supports allowed for a significant increase in access to the active catalyst centers. The NiMo/SBA-15/Al2O3 and NiMg/MCF/Al2O3 sorption-catalytic materials demonstrated high activity and stability over 48 h for the simultaneous removal of As and Cl. The catalytic materials allowed for reducing the concentrations of As and Cl to less than 0.1 ppm in the diesel fraction under the following conditions: 5.0 MPa pressure, 2.0 h–1 LHSV, 300 L/L H2-to-substrate volume ratio, and 360 °C.

Enhancement of CO2/N2 selectivity and CO2 uptake by tuning concentration and chemical structure of imidazolium-based ILs immobilized in mesoporous silica

Imidazolium-based ionic liquids (ILs) with different cation alkyl chain ([i-C5mim] or [C4mim]) and inorganic anions ([Cl−], [Tf2N−], [PF6−] and [DCA−]) were synthesized and immobilized in commercial mesoporous silica. The synthesized supported ILs (SILs) were characterized using NMR, FTIR, TGA, BET, SEM and TEM. CO2 sorption capacity, reusability and CO2/N2 selectivity were assessed by the pressure-decay technique. The effects of IL concentration, cation and anion chemical structure in CO2 sorption capacity and CO2/N2 separation performance were evaluated. Tests evidenced that the presence of branching on the cation alkyl side chain increases CO2/N2 selectivity. The immobilization of the IL [i-C5TPIm][Cl] on mesoporous silica in different concentrations (50, 20, 10 and 5 %) revealed that lower IL concentration results in higher CO2 sorption capacity. Immobilization of ILs containing fluorinated anions at low concentrations in the mesoporous silica support may promote the improvement of the CO2/N2 selectivity without interfering on CO2 sorption capacity of the original support. CO2 sorption capacity value shown by sample SIL-5 % - [i-C5TPIm][Tf2N] (79.50 ± 0.70 mg CO2 g-1) was close to the value obtained for the pristine mesoporous silica (81.70 ± 2.20 mg CO2 g-1) and the selectivity (4.30 ± 0.70) was more than twice of the one obtained for the support alone (2.32 ± 0.4). Recycle tests demonstrated that the ILs immobilized in mesoporous silica samples are stable, providing a new option to be used in CO2 capture processes.

Ni-Rhodanine Complex Supported on FSM-16 as Mesoporous Silica Support: Synthesis, Characterization and Application in Synthesis of Tri and Tetrasubstituted Imidazoles and 3,4-Dihydropyrimidine-2-(1H)-Ones

A new, efficient and recoverable heterogeneous catalyst was successfully synthesized by functionalization of mesoporous silica FSM-16. The FSM-16/CPTMS-Rh-Ni(II) characterization with several techniques such as, XRD, TGA, FT-IR, SEM, EDX, BET and ICP. As a result, it was found that this synthesized compound acted as catalyst for many multi component reactions. These reactions included the synthesis of 2,4,5-triaryl-1H-imidazoles, 1,2,4,5-tetrasubstituted imidazoles and 3,4-dihydropyrimidine-2-(1H)-ones derivatives.

Photo-induced generation of size controlled Au nanoparticles on pure siliceous ordered mesoporous silica for catalytic applications

Abstract A versatile in situ photochemical reduction approach was used to generate a composite of gold nanoparticles and pure siliceous SBA-15 silica support with regular mesopores. The mesoporous silica support was first synthesized and, after calcination, was suspended in a solution of gold bromide (EtOH or H2O) containing a free radical generator activated by UV irradiation and used for the photochemical reduction of gold precursor. The influence of gold precursor concentration, light intensity and nature of the solvents on the formation and properties of gold nanoparticles (size, dispersion, stability) on the mesoporous SBA-15 support have been studied with the aim of optimizing the dispersion of the gold nanoparticles in the mesoporous network and their chemical stability. The catalytic activity of the resulting AuNPs@SBA-15 nanocomposite was successfully evaluated for the oxidation of benzyl alcohol reaction in liquid-phase.

Imidazolium based ionic liquids confined into mesoporous silica MCM-41 and SBA-15 for carbon dioxide capture

Abstract Ordered mesoporous silica MCM-41 and SBA-15 were impregnated by two imidazolium-based ionic liquids 1-Butyl-3-methylimidazolium Acetate [bmim][Ac] and 1-propyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide [pmim][Tf2N] using a facile impregnation-evaporation approach. The immobilization of ILs into the mesoporous silica supports was found to reduce the derivative decomposition temperatures (Tonset) by about 30 °C compared to the bulk ILs, however the decomposition process was found to occur over a wider temperature range for the IL-immobilized samples. These observations are indicative of interionic interactions between the ILs and the surface of the mesoporous silica supports, which was further corroborated by the shifts in the FTIR bands. The X-ray diffraction patterns (XRD) of the pristine MCM-41, SBA-15 and the IL-modified samples have shown that no textural or morphological changes were observed for the IL-impregnated samples and that the crystal structure of the mesoporous silica supports remained intact. The BET surface area and pore volumes of the composite sorbents have remarkably decreased after the incorporation of the ILs due to the occupation of the pore surface. All the composite sorbents modified with [bmim][Ac] ILs have shown a substantial increase in CO2 sorption capacity especially in the low pressure region up to 6 times higher CO2 uptake at 0.2 bar and 30 °C. On the other hand, the immobilization of [pmim][Tf2N] did not show any improvements in the sorption capacity for all impregnation amounts used. Furthermore, unlike the slow adsorption kinetics in the bulk ILs, the supported ILs exhibited significantly rapid sorption rates, with a stable cyclic adsorption-regeneration performance.

Kinetics of Fischer–Tropsch Synthesis in a 3-D Printed Stainless Steel Microreactor Using Different Mesoporous Silica Supported Co-Ru Catalysts

Fischer–Tropsch (FT) synthesis was carried out in a 3D printed stainless steel (SS) microchannel microreactor using bimetallic Co-Ru catalysts on three different mesoporous silica supports. CoRu-MCM-41, CoRu-SBA-15, and CoRu-KIT-6 were synthesized using a one-pot hydrothermal method and characterized by Brunner–Emmett–Teller (BET), temperature programmed reduction (TPR), SEM-EDX, TEM, and X-ray photoelectron spectroscopy (XPS) techniques. The mesoporous catalysts show the long-range ordered structure as supported by BET and low-angle XRD studies. The TPR profiles of metal oxides with H2 varied significantly depending on the support. These catalysts were coated inside the microchannels using polyvinyl alcohol and kinetic performance was evaluated at three different temperatures, in the low-temperature FT regime (210–270 °C), at different Weight Hourly Space Velocity (WHSV) in the range of 3.15–25.2 kgcat.h/kmol using a syngas ratio of H2/CO = 2. The mesoporous supports have a significant effect on the FT kinetics and stability of the catalyst. The kinetic models (FT-3, FT-6), based on the Langmuir–Hinshelwood mechanism, were found to be statistically and physically relevant for FT synthesis using CoRu-MCM-41 and CoRu-KIT-6. The kinetic model equation (FT-2), derived using Eley–Rideal mechanism, is found to be relevant for CoRu-SBA-15 in the SS microchannel microreactor. CoRu-KIT-6 was found to be 2.5 times more active than Co-Ru-MCM-41 and slightly more active than CoRu-SBA-15, based on activation energy calculations. CoRu-KIT-6 was ~3 and ~1.5 times more stable than CoRu-SBA-15 and CoRu-MCM-41, respectively, based on CO conversion in the deactivation studies.

MCM-41-supported Fe(Mn)/Cu bimetallic heterogeneous catalysis for enhanced and recyclable photo-Fenton degradation of methylene blue

Highly efficient bimetallic heterogeneous photo-Fenton catalysts (Fe2O3/CuO@MCM-41, FCM and MnOx/CuO@MCM-41, MCM) have been successfully prepared via wet impregnation over a mesoporous MCM-41 silica support. FESEM images demonstrate that the metal oxides are highly dispersed on the surface of the MCM-41 matrix consisting of the ordered 2D hexagonal mesostructure. XPS results indicate that the bimetallic oxides species in FCM and MCM are Fe2O3, CuO and MnOx, CuO, respectively. The as-prepared dual-heterojunctions have a significant enhancement of catalytic activities under visible light, compared with the material containing monometal, and prevents the leaching of metal ions species. The degradation efficiencies of MB can be up to 99.65% and 98.22% within 45 min irradiation for FCM1:2 and MCM1:0.5, respectively. And the degradation efficiencies still can reach up to 92% after 10 cycles. Moreover, the synthesized bimetallic dual-heterojunctions catalysts can be employed in very mild condition, and little difference in catalytic effect was observed under different pH value (3.0–9.0). The improved photocatalytic activity can be ascribed to the sufficient interfacial contact between different components for photo energy transfer and e−/h+ pairs separation, which greatly enhance cycle reaction of Fe3+/Fe2+ or Mn4+/Mn3+/Mn2+ after introducing CuO. This research provides a new approach for the development of an effective heterogeneous photo-induced Fenton (Fenton like) catalyst with vast potential for organic pollutant removal.

CO2 Adsorption and Oxidative Degradation of Silica-Supported Branched and Linear Aminosilanes

An array of aminosilanes is synthesized and grafted onto a mesoporous silica support to evaluate the effect of aminosilane structure on CO2 adsorption and oxidative stability. Both linear (NH2(CH2)...

Mesoporous silica/protein biocomposites: Surface, topography, thermal properties

The biocomposite systems based on mesoporous MCF silica support and protein molecules are characterized with regard to their surface, topographic, thermal properties. Mesoporous silica materials (MCF) covered by the adsorbed protein molecules (BSA and OVA) were examined and characterized by using various techniques including X-ray diffraction, the Fourier transform infrared spectroscopy with attenuated total reflectance, X-ray photoelectron spectroscopy and scanning electron microscopy with microanalysis. The results of study focused on a detailed analysis of microstructure (topography, texture), and chemistry (chemical bonds, functional groups, elemental composition) of protein/mesoporous silica biocomposite. Moreover, the thermal properties of prepared biomaterials were investigated by means of TG/DSC-FTIR-MS-coupled technique. These powerful methods provided detailed information for understanding protein adsorption on MCF. Significant differentiation in surface chemistry and topography of MCF material was observed after protein adsorption. Basing on the results of thermal analysis stronger changes of the surface properties and more stable interactions of biomolecules with MCF-d16 support were observed for larger BSA molecules compared to smaller ovalbumin ones.

Performance and Kinetic Evaluation of Synthesized CuO/SBA‐15 Oxygen Carrier for Chemical Looping with Oxygen Uncoupling

Chemical looping oxygen uncoupling (CLOU), a variant of chemical looping combustion (CLC), is one of the most promising combustion technologies for inherent separation and feasible capture of carbon dioxide. Herein, synthesized SBA‐15, a highly ordered mesoporous silica support, is used to host CuO for developing a new variant of an oxygen‐carrier material. Based on thermoanalytical evaluations, a typical CuO/SBA‐15 composition with 36 mass% CuO loading is identified as highly suitable with an average oxygen transport capacity of 3.61%. In addition, extensive studies along with model‐dependent kinetic evaluations are carried out using isothermal thermogravimetric data for the reduction–reoxidation of CuO/SBA‐15. It is observed that the Avrami‐Erofeev random nucleation and subsequence growth model (A2) fitted well for the reduction reaction, while the 3D diffusion model (D3) described suitably the reoxidation reaction in the temperature range of 800–950 °C. Reduction–reoxidation rate data and kinetic information derived from corresponding isothermal conversion curves can contribute immensely to design and establish operational strategies for interconnected CLOU reactors.