Mesoporous System Research Articles

Nanotherapeutics for regeneration of degenerated tissue infected by bacteria through the multiple delivery of bioactive ions and growth factor with antibacterial/angiogenic and osteogenic/odontogenic capacity

Therapeutic options are quite limited in clinics for the successful repair of infected/degenerated tissues. Although the prevalent treatment is the complete removal of the whole infected tissue, this leads to a loss of tissue function and serious complications. Herein the dental pulp infection, as one of the most common dental problems, was selected as a clinically relevant case to regenerate using a multifunctional nanotherapeutic approach. For this, a mesoporous bioactive glass nano-delivery system incorporating silicate, calcium, and copper as well as loading epidermal growth factor (EGF) was designed to provide antibacterial/pro-angiogenic and osteo/odontogenic multiple therapeutic effects. Amine-functionalized Cu-doped bioactive glass nanospheres (Cu-BGn) were prepared to be 50–60 nm in size, mesoporous, positive-charged and bone-bioactive. The Cu-BGn could release bioactive ions (copper, calcium and silicate ions) with therapeutically-effective doses. The Cu-BGn treatment to human umbilical vein endothelial cells (HUVEC) led to significant enhancement of the migration, tubule formation and expression of angiogenic gene (e.g. vascular endothelial growth factor, VEGF). Furthermore, the EGF-loaded Cu-BGn (EGF@Cu-BGn) showed pro-angiogenic effects with antibacterial activity against E. faecalis, a pathogen commonly involved in the pulp infection. Of note, under the co-culture condition of HUVEC with E. faecalis, the secretion of VEGF was up-regulated. In addition, the osteo/odontogenic stimulation of the EGF@Cu-BGn was evidenced with human dental pulp stem cells. The local administration of the EGF@Cu-BGn in a rat molar tooth defect infected with E. faecalis revealed significant in vivo regenerative capacity, highlighting the nanotherapeutic uses of the multifunctional nanoparticles for regenerating infected/damaged hard tissues.

Single subconjunctival injection formulation using sol-gel mesoporous silica as a controlled release system for drop-free post-cataract surgery care.

To develop a mesoporous silica drug delivery system and target drop-free care after cataract surgery with a single subconjunctival injection. Laboratory. Experimental animal study. Ketorolac was infiltration-loaded into sol-gel mesoporous silica particles encapsulated with poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) using a layer-by-layer adsorption technique (SG-Ket-LBL). The formulation was subjected to an in vitro and in vivo drug release study in addition to ocular toxicology evaluation. Thermogravimetric analysis revealed that the drug loading efficiency was 4.4% for the SG-Ket-LBL particles. The in vivo safety study demonstrated that the formulation was well tolerated after subconjunctival injection and aqueous humor pharmacokinetics showed sustained therapeutic drug release for the targeted time window of 6 to 8 weeks. Findings indicated that sol-gel mesoporous silica could be used as a drug carrier for subconjunctival administration. The tested formulation, SG-Ket-LBL, provided therapeutic ketorolac for 6 to 8 weeks, which might be used for a single subconjunctival injection to replace nonsteroidal anti-inflammatory drug eyedrops after cataract surgery.

Nanopore effects on the combustion temperature of resorcinol-formaldehyde xerogels

Abstract The rationalization of thermal analysis data of porous substances is often complicated by the fact that it is not always possible to synthesise non-porous reference samples. Therefore, it is difficult to quantify the effect that the porosity has on the thermal behaviour. Here, we present detailed investigations about the thermal behaviour of a mesoporous model system consisting of a resorcinol-formaldehyde xerogel, synthesised via an acid-catalysed route. Samples were prepared with different pore sizes varied over the entire nanoscale range (from Thermogravimetric analysis of this model system revealed a pronounced increase in combustion temperature and decrease in combustion rate for samples with mean pore diameters smaller than 20 nm. Interestingly, this finding can be correlated with the Knudsen regime of the diffusion of oxygen.

Synthesis and characterization of MCM-41–SBA-15 mixed-phase silica with trimodal mesoporous system and thick pore wall

The ability to design the porosity of silicas, both their pore size and their wall surface, is a concern of industrial interest. Pore structure is an important parameter that determines the performance of several processes, where the surface and accessibility are vital. In this work, a MCM-41–SBA-15 mixed-phase silica (MPS) with trimodal mesoporous system and thick pore wall was synthesized by a two-step template route. For this purpose, the gel solution of a bimodal MCM-41 silica was modified by the addition of a SBA-15 template before aging stage. Low-angle XRD results confirmed that the mixed-phase silica contained a combination of both MCM-41 and SBA-15 pore structures. TEM images showed that SBA-15 structure seemed to be located on the outside of MPS particles, while MCM-41 channels were located inside. Through this synthesis route not only the wall thickness of the starting silicas was increased, but also their pores sizes were preserved in the mixed-phase silica. MPS silica was further evaluated as support for the co-catalyzed ethylene polymerization under slurry phase. The trimodal pore system and thick pore wall provided a higher catalytic activity than the individual SBA-15 and MCM-41, demonstrating the advantage of the two-step synthesis strategy conducted herein.

Mesoporous Silica-Based Nanoparticles in Pharmaceutical Sciences: A Mini-Review

The sustained and comprehensive need in the field of materials having immense thermal, chemical, and mechanical stability lead to the evolution of mesoporous silica nanoparticles (MSNs). Due to higher surface area and ridged tuneable particular size, silica-based mesoporous (2-50nm) drug delivery system recently becomes a prime orb for loading different guest molecules such as peptides, proteins, anticancer drugs. The most common type of mesoporous nanoparticles is MCM-41 and SBA-15. MSMs has a wide range of applications in drug delivery, imaging, and catalysis. It was in the 1970’s, when the first patent was field related to MSMs, however during 1990, the full-fledged research started for MSMs. During that era, Mobil Corporation Laboratories, Japan started synthesizing of MSMs. Yet, the University of California also pioneered in MSMs synthesis, as they claimed to prepare 4.6-30 nm MSMs with a hexagonal array of pores; they further named it as SBA-15. MSMs has huge application in drug delivery system. Because of its larger surface area of the pores, the cytotoxin or drug can be filed within the pores like a Trojan Horse. Within the intercellular environment, by the endocytosis process, the small particles will be engulfed by biological cell membranes depending on what ligands attached within MSMs i.e., loaded RNA, loaded DNA, surface protein, PEG, and monoclonal antibody. Surprisingly, advanced research on MSMs concluded that cancerous cells have the tendencies to take MCM-41 than the healthy cells of the host; giving scientists a new hope that MCM-41 will one day be used commercially to treat a certain type of cancers. Modern research also shows that for the poorly water-soluble drug, SBA-15, TUD-1, HMM-33 and FSM-16 of MSMs has tremendous potential to improve in-vitro dissolution profiling i.e., upon loading of itraconazole (a poorly water-soluble drug) within SBA-15, it can able to stimulate GI fluid and facilitate transepithelial intestinal transport which ultimately results in higher drug absorption. In this mini-review, we attempted to discuss MSNs synthesis methods, morphology, preparations, mechanisms and recent research in the MSNs Drug delivery system. Thus, we concluded that more in vivo biocompatibility studies, biodistribution studies, toxicity studies, and clinical research is the fundamental prerequisite for further advancement in mesoporous silica-based nanoparticles (MSNs).

Comparison of Drug Release and Adsorption under Supersaturating Conditions for Ordered Mesoporous Silica with Indomethacin or Indomethacin Methyl Ester.

Incomplete drug release from mesoporous silica systems has been observed in several studies. This work aims to increase the understanding of this phenomenon by investigating the mechanism of drug-silica interactions and adsorption behavior from supersaturated aqueous solutions of two similar drug molecules with different hydrogen bonding capabilities. Drug-silica interactions between indomethacin or its methyl ester and SBA-15 were investigated using spectroscopic techniques (infrared, fluorescence and X-ray photoelectron) and adsorption experiments. The results demonstrate that the predominant mechanism of interaction of both drugs with silica is hydrogen bonding between drug acceptor carbonyl groups with donor groups on the silica surface. The presence of a drug hydrogen bond donor group did not enhance drug adsorption. No evidence was obtained for drug adsorption through nonspecific hydrophobic interactions. Drug adsorption onto the silica surface was investigated under supersaturating conditions through the generation of adsorption isotherms. Similar adsorption isotherms were observed for each compound when the concentration scale was normalized to the drug amorphous solubility. In other words, the equilibrium between the drug adsorbed on the silica surface and free drug in solution was related to the drug activity in solution. The high tendency of the drug to adsorb when the solution is supersaturated was, in turn, found to limit the extent of drug release during dissolution under nonsink conditions. Thus, adsorption provides an explanation for incomplete drug release.

Convenient and fast synthesis of various chromene pharmaceuticals assisted by highly porous volcanic micro-powder with nanoscale diameter porosity

Herein, a volcanic-based mesoporous catalytic system is precisely characterized by various analytical methods and suitably used for facilitating the organic synthesis reactions. Briefly, high reaction yield (99%) has been obtained in short reaction times (4 min) in the synthesis reactions of chromene pharmaceutical derivatives, through applying this highly efficient organometallic catalyst. From mechanistic aspect, effective electronic interactions between heteroatoms like oxygen with the surface of pumice microparticles provide a suitable condition for covalent bindings. As the main advantages of the volcanic pumice, high catalytic performance after activation of the chemical functional groups via acid treatment, magnetic property, and completely natural basis (biocompatibility and biodegradability) could be referred. Highly porous structure leads reactants to be entrapped in the tiny pores and activated for covalent binding. Moreover, significant convenience in the separation of the particles and great reusability could be mentioned as additional excellences for this catalyst.

Molecular aspects, electrochemical properties and water oxidation catalysis on a nanoporous TiO2 electrode anchoring a mononuclear ruthenium(II) aquo complex

A mononuclear Ru aquo complex, [Ru(C8Otpy)(H2dcbpy)(OH2)]2+ (C8Otpy = 4′-octyloxy-2,2′:6′,2′′-terpyridine, H2dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) was stably adsorbed on a nanoporous TiO2 surface to afford a TiO2 electrode anchoring the complex. The adsorption isothermal of the complex on the TiO2 surface was analyzed by the Langmuir adsorption model to provide a maximum coverage of Гmax = 4.4 × 10−8 mol cm−2 and an adsorption equilibrium constant of Kads = 1.1 × 104 M−1, suggesting that the monolayer of the complex is formed on the TiO2 surface. The cyclic voltammetry measurement of the complex on the TiO2 surface suggested the diffusion-controlled charge transport via electron hopping between the complexes through the TiO2 layer. Pourbaix diagram showed that the complex undergoes a non-H+-coupled 1e- redox reaction of a RuIIOH/RuIIIOH pair of the complex on the TiO2 electrode due to pH buffering ability of the TiO2 surface in a range of pH 5−11. Bulk electrolysis at 1.7 V vs Ag/AgCl using the complex-anchoring TiO2 electrode provided a high and steady catalytic current density of 0.39 mA cm−2 with 83 % Faradaic efficiency for O2 evolution during 1 h electrolysis. However, we presume that the complex is transformed to RuOx nanoparticles on the TiO2 electrode during the electrocatalysis, on the basis of our earlier report on the complex / mesoporous ITO electrode system (Dalton Trans., 2020, 49, 1416−1423.). The RuOH/TiO2 electrode is the efficient anode for water oxidation under the acidic conditions, irrespective of the molecular catalyst of RuOH and the alternative catalysts formed via its oxidative transformation.

Role of Folic Acid in the Therapeutic Action of Nanostructured Porous Silica Functionalized with Organotin(IV) Compounds Against Different Cancer Cell Lines.

The synthesis, characterization and cytotoxic activity against different cancer cell lines of various mesoporous silica-based materials containing folate targeting moieties and a cytotoxic fragment based on a triphenyltin(IV) derivative have been studied. Two different mesoporous nanostructured silica systems have been used: firstly, micronic silica particles of the MSU-2 type and, secondly, mesoporous silica nanoparticles (MSNs) of about 80 nm. Both series of materials have been characterized by different methods, such as powder X-ray diffraction, X-ray fluorescence, absorption spectroscopy and microscopy. In addition, these systems have been tested against four different cancer cell lines, namely, OVCAR-3, DLD-1, A2780 and A431, in order to observe if the size of the silica-based systems and the quantity of incorporated folic acid influence their cytotoxic action. The results show that the materials are more active when the quantity of folic acid is higher, especially in those cells that overexpress folate receptors such as OVCAR-3 and DLD-1. In addition, the study of the potential modulation of the soluble folate receptor alpha (FOLR1) by treatment with the synthesized materials has been carried out using OVCAR-3, DLD-1, A2780 and A431 tumour cell lines. The results show that a relatively high concentration of folic acid functionalization of the nanostructured silica together with the incorporation of the cytotoxic tin fragment leads to an increase in the quantity of the soluble FOLR1 secreted by the tumour cells. In addition, the studies reported here show that this increase of the soluble FOLR1 occurs presumably by cutting the glycosyl-phosphatidylinositol anchor of membrane FR-α and by the release of intracellular FR-α. This study validates the potential use of a combination of mesoporous silica materials co-functionalized with folate targeting molecules and an organotin(IV) drug as a strategy for the therapeutic treatment of several cancer cells overexpressing folate receptors.

Ionically Generated Built‐In Equilibrium Space Charge Zones—a Paradigm Change for Lead Halide Perovskite Interfaces

AbstractMethylammonium lead iodide (MAPI) is the archetype of the intensively researched class of perovskites for photovoltaics. Nonetheless, even equilibrium aspects are far from being fully understood. Equilibrium space charge effects at the MAPI/TiO2 and MAPI/Al2O3 interfaces are discussed, which are of paramount significance for solar cells. Different from the photovoltaic literature in which such built‐in potentials are considered as being generated solely by electronic charge carriers, a generalized picture that considers the equilibrium distribution of both ionic and electronic carriers is applied. Experimental evidence is given that shows it is the ions that are responsible for the equilibrium space charge potential, the reason being a pronounced ion adsorption at the contacts. The electronic redistribution is a sheer consequence of the so‐established electric field. Experiments with mesoporous oxide as well as experiments with MAPbBr3 (MAPBr) indicate photovoltaic relevance and material generality in terms of the choice of the lead‐based perovskite. The occurrence of space charge effects at heterojunctions generated by ionic redistribution is not only a novel concept in photovoltaics, it also provides a new path to modifying charge‐selective interfaces, as well as a better understanding of the behavior in mesoporous systems.

Effect of the type of siliceous template and carbon precursor on physicochemical and catalytic properties of mesoporous nanostructured carbon-palladium systems

Two series of nanostructured carbon replicas were synthesized through a hard-templating method using ordered SBA-15 or disordered mesoporous spherical silica gel as the templates and furfuryl alcohol or sucrose as the carbon source. They were explored to synthesize the Pd catalysts (ca. 1.5 wt% Pd loading) by the colloid-based microemulsion procedure which allowed preparing the catalysts of monodispersed Pd particles of similar size (4–5 nm). The palladium phase in the catalysts (e.g. the Pd particles distribution and extent of agglomeration) varied depending on the textural and surface characteristics of the carbon replicas. In the furfural hydrogenation studied as a probe reaction (2-propanol, 35 °C, 6 bar H2), furfuryl alcohol and tetrahydrofurfuryl alcohol were the major products formed. The catalytic reactivity has been related to the properties of the Pd phase including the surface Pd concentration and the extent of the Pd particles aggregation accompanied by the nearest palladium environment expressed by the surface O/Pd atomic ratio. At high O/Pd ratio the reaction slowed down because of a facilitated furfuryl alcohol adsorption resulting most probably in a blockage of the active sites. The SiO2 sucrose system provided the catalyst which was characterized by relatively low O/Pd ratio with well-dispersed Pd particles and the highest and stable activity for the furfural hydrogenation. The SBA-series catalysts, with lower O/Pd and more aggregated Pd particles, exhibited lower activity but somewhat higher tendency to the tetrahydrofurfuryl alcohol formation.

Construction of Biocompatible Dual-Drug Loaded Complicated Nanoparticles for in vivo Improvement of Synergistic Chemotherapy in Esophageal Cancer

Combination chemotherapy is a routine treatment for esophageal cancer, but some shortcomings, such as drug toxicity and side effects, greatly limit the clinical application of combination therapy. To overcome these shortcomings, we have developed a mesoporous silica nanoparticle system that was used to load doxorubicin and β-elemene. β-elemene was encapsulated in the pore of mesoporous silica nanoparticle and doxorubicin was electrostatically adsorbed on the surface of mesoporous silica nanoparticle by hyaluronic acid to construct dual drugs synergistic nanoparticles (bMED NPs, ~77.15 nm). In vitro studies demonstrated that bMED NPs had a good treatment effect in esophageal cancer cell lines. In vivo fluorescence imaging results demonstrated that bMED NPs could accumulate in tumor sites and achieve in vivo long-term circulation and continuous drug release. In addition, bMED NPs exhibited significant antitumor effects in the esophageal cancer mouse model, which may provide a great platform for esophageal cancer chemotherapy.

Enhancement of the dispersion and catalytic performances of copper in the hydrogenation of cinnamaldehyde by incorporation of aluminium into mesoporous SBA-15 silica

Copper is active in hydrogenation reactions, but it is a base metal difficult to disperse inside mesostructured supports, with adverse consequences on the catalytic properties. Incorporating aluminium into mesoporous SBA-15 silicas allows solving both problems of Cu dispersion and activity. The incorporation of 20 wt.% Al2O3 in the SBA-15 host structure leads to an increase of the copper metallic surface area by a factor 6 compared to the pure siliceous SBA-15-supported catalyst. The support also proves to be stable upon exposure to the impregnation aqueous solution used for copper introduction. The incorporation of Al provides Lewis acidic sites that favour the transformation of cinnamaldehyde into cinnamyl alcohol, a feature usually assigned to larger metal particles. As a consequence, the catalytic activity of Cu catalysts is enhanced compared to silica-supported Cu catalysts, while the chemoselectivity towards the unsaturated alcohol appears to be similar to that of a mesoporous alumina-supported system.

Antioxidant activity and modified release profiles of morin and hesperetin flavonoids loaded in Mg- or Ag-modified SBA-16 carriers

The problems related with low solubility and instability in physiological environment of flavonoids are currently a challenge for their potential application for prevention and therapy of major chronic diseases, including cardiovascular and neurodegenerative diseases, cancer etc. Promising approach to overcome these drawbacks is incorporation of these compounds into mesoporous silica carriers. In this study we develop SBA-16 silica nanoparticles modified by a post-synthesis method with Mg (4 wt.%) or Ag (4 wt.%) as a carriers for simultaneous delivery of poorly soluble biological active compounds and essential micronutrients or antimicrobial agents. Hesperetin, a natural flavonone, and morin, a natural flavonol, belong to the big family of flavonoids were loaded by incipient wetness impregnation on the parent and Ag- or Mg-modified mesoporous supports. The initial, modified and drug loaded SBA-16 materials were characterized by powder XRD, N2 physisorption, thermogravimetric analysis and SEM measurements. The interactions between metals, silica surface and flavonoids were studied by ATR-FTIR and UV–Vis spectroscopies. Improved release profiles are observed for flavonoids loaded in mesoporous materials in comparison with pure flavonoids. Loading of flavonoids in parent and modified mesoporous carriers made the sustained delivery of the bioactive compound possible. A comparative study on anti-proliferative effect of the tested flavonoids loaded into modified silica carriers vs. free drug was investigated on a panel of three human cell lines. The evaluation of the antioxidant capacity shows that loading of the flavonoids into parent and modified silica supports can improve their activity against free radicals, which could be explained by the improved solubility of the loaded flavonoids in comparison with the pure ones. The obtained mesoporous delivery systems are promising as oral formulations for delivery of flavonoids, essential microelements and antimicrobial agents.

Transitional MOFs: Exposing Metal Sites with Porosity for Enhancing Catalytic Reaction Performance.

The exploration of transitional metal-organic frameworks (MOFs) is important because of their unique properties and promising applications. Hence, finding a suitable strategy to design transitional MOFs with different states has become a key issue. Herein, we develop a modulator-induced strategy for fabricating transitional MOFs with carboxylic ligands by building esterification reaction. The exposed metal sites, mesoporous systems, morphologies, crystallinities, and components of transitional MOFs can be finely controlled when different modulators are employed. Notably, the Pt/solid-transitional MOF catalyst with more mesopores enhances conversion in the hydrogenation reaction of n-hexene, and the flower-like-transitional MOF catalyst with more Lewis acid sites exhibits better performance in the cycloaddition reaction. Therefore, the modulator-induced strategy may provide significant inspiration for preparing various transitional MOFs by building suitable chemical reactions.

PH-responsive mesoporous silica drug delivery system for targeted cancer chemotherapy

ABSTRACT In this paper, a kind of pH-responsive mesoporous silica targeted drug delivery system (DOX-loaded N-CQDs/HA gated pSiO2/MPEG-Glu) was designed and synthesised. In this system, active mesoporous silica (pSiO2) worked as a carrier material, methoxy polyethene glycol amine (MPEG) and L-glutamic acid (Glu) can be coupled and grafted to the surface of the pSiO2 drug carrier to improve the stability of the drug delivery system, nitrogen-doped carbon quantum dots (N-CQDs) and hyaluronic acid (HA) can inhibit the rapid release of drug. Ultraviolet (UV-Vis) spectrum showed that the drug-loading rate of DOX is 8.9%, the drug release in vitro study suggested that the prepared silica drug delivery system had significant pH-responsive and targeted DOX release, the drug release rate is 55.7% at pH = 5.0, which was much higher than the release of pH = 7.4; CLSM and MTT showed that the drug delivery system can enter into cancer cells through endocytosis and the DOX can act on cell nucleus, exhibiting a targeted therapy on cancer cells.

Pistachio Shell-Derived Carbon Activated with Phosphoric Acid: A More Efficient Procedure to Improve the Performance of Li-S Batteries.

A sustainable and low-cost lithium–sulfur (Li–S) battery was produced by reusing abundant waste from biomass as a raw material. Pistachio shell was the by-product from the agri-food industry chosen to obtain activated carbon with excellent textural properties, which acts as a conductive matrix for sulfur. Pistachio shell-derived carbon activated with phosphoric acid exhibits a high surface area (1345 m2·g−1) and pore volume (0.67 cm3·g−1), together with an interconnected system of micropores and mesopores that is capable of accommodating significant amounts of S and enhancing the charge carrier mobility of the electrochemical reaction. Moreover, preparation of the S composite was carried out by simple wet grinding of the components, eliminating the usual stage of S melting. The cell performance was very satisfactory, both in long-term cycling measurements and in rate capability tests. After the initial cycles required for cell stabilization, it maintained good capacity retention for the 300 cycles measured (the capacity loss was barely 0.85 mAh·g−1 per cycle). In the rate capability test, the capacity released was around 650 mAh·g−1 at 1C, a higher value than that supplied by other activated carbons from nut wastes.

Mesoporous polymer systems based on divinylbenzene copolymers modified with linear rubbers

Porous polymer systems based on divinylbenzene copolymers modified with co-monomers (ethylvinylbenzene, methyl acrylate, methacrylic acid) and linear rubber macromolecules (polybutadiene, polyisoprene, polyisobutylene, polystyrene-butadiene, polyacrylonitrile-butadiene) were investigated. The copolymers in the form of spherical beads were synthesized by radical suspension polymerization of monomer compositions with appropriate porogenic organic solvents. It was found that modification of the divinylbenzene copolymers by linear rubbers enables the synthesis of sorbents with a controlled fractional composition of micro- and mesopores. A universal method is suggested for a quantitative estimation of fractional pore size distribution in the range of micro and mesopores from the data of low-temperature nitrogen sorption. Calculations of integral and differential distributions are based on using methods of quenched solid density functional theory (QSDFT), non-local density functional theory and the Barrett-Joyner-Halenda method based on capillary condensation theory. According to QSDFT calculations, the porous system of sorbents contains three groups of pores of certain sizes: 1.7–3.3, 3.3–6.6 and 8.4–40 nm. Upon introduction of polyisoprene into the polymer system the sorbent containing primarily 8–24 nm mesopores is obtained; upon the introduction of polyisobutylene, the sorbent with pore sizes of 4–6 nm is synthesized. The volume and surface area of micropores in the copolymers with polyisoprene and polyisobutylene may be increased by extracting a part of the rubber phase with toluene. Specific surface area of the copolymers varies in the range of 230–570 m2 g−1. Scanning electron microscopy studies of the porous structure of the polymer systems showed that in the copolymers with polybutadiene the porous structure is formed by the aggregates of globules 20–60 nm. The copolymer with polyisobutylene has a 3D skeletal structure with 100–200 nm voids.

Tuning combined steam and dry reforming of methane for “metgas” production: A thermodynamic approach and state-of-the-art catalysts

Nowadays, combined steam and dry reforming of methane (CSDRM) is viewed as a new alternative for the production of high-quality syngas (termed as “metgas”, H2:CO of 2.0) suitable for subsequent synthesis of methanol, considered as a promising renewable energy vector to substitute fossil fuel resources. Adequate operation conditions (molar feed composition, temperature and pressure) are required for the sole production of “metgas” while achieving high CH4, CO2 and H2O conversion levels. In this work, thermodynamic equilibrium analysis of CSDRM has been performed using Gibbs free energy minimization where; (i) the effect of temperature (range: 200–1000 °C), (ii) feed composition (stoichiometric ratio as compared to a feed under excess steam or excess carbon dioxide), (iii) pressure (range: 1–20 bar) and, (iv) the presence of a gaseous diluent on coke yields, reactivity levels and selectivity towards “metgas” were investigated. Running CSDRM at a temperature of at least 800 °C, a pressure of 1 bar and under a feed composition where CO2+H2O/CH4 is around 1.0, are optimum conditions for the theoretical production of “metgas” while minimizing C(s) formation for longer experimental catalytic runs. A second part of this work presents a review of the recent progresses in the design of (principally) Ni-based catalysts along with some mechanistic and kinetic modeling aspects for the targeted CSDRM reaction. As compared to noble metals, their high availability, low cost and good intrinsic activity levels are main reasons for increasing research dedications in understanding deactivation potentials and providing amelioration strategies for further development. Deactivation causes and main orientations towards designing deactivation-resistant supported Ni nanoparticles are clearly addressed and analyzed. Reported procedures based on salient catalytic features (i.e., acidity/basicity character, redox properties, oxygen mobility, metal-support interaction) and recently employed innovative tactics (such as confinement within mesoporous systems, stabilization through core shell structures or on carbide surfaces) are highlighted and their impact on Ni0 reactivity and stability are discussed. The final aspect of this review encloses the major directions and trends for improving synthesis/preparation designs of Ni-based catalysts for the sake of upgrading their usage into industrially oriented combined reforming operations.

A mesoporous non-precious metal boride system: synthesis of mesoporous cobalt boride by strictly controlled chemical reduction.

Generating high surface area mesoporous transition metal boride is interesting because the incorporation of boron atoms generates lattice distortions that lead to the formation of amorphous metal boride with unique properties in catalysis. Here we report the first synthesis of mesoporous cobalt boron amorphous alloy colloidal particles using a soft template-directed assembly approach. Dual reducing agents are used to precisely control the chemical reduction process of mesoporous cobalt boron nanospheres. The Earth-abundance of cobalt boride combined with the high surface area and mesoporous nanoarchitecture enables solar-energy efficient photothermal conversion of CO2 into CO compared to non-porous cobalt boron alloys and commercial cobalt catalysts.