Monolith Surface Research Articles

L-Cysteine-Bonded Polymeric Monolithic Stationary Phase for Enantioseparation of Dansyl Amino Acids in Capillary Liquid Chromatography.

A chiral monolith stationary phase was fabricated by modifying the monolith surface using L-cysteine through a thiol-epoxy click reaction. L-cysteine-bonded polymer monolith was characterized by scanning electron microscopy/energy-dispersive X-ray and attenuated total reflectance Fourier-transformed infrared. The monomer content and modification temperature were carefully optimized to create a polymer monolith with excellent mechanical stability and permeability. Our findings revealed that the column morphology depended significantly on the porogen concentration and modification temperature for its morphology and efficiency. Adequate pores and binding sites were formed with the optimal porogen content, while a higher modification temperature improved the modification yield, enhancing peak shapes and increasing separation efficiency. The column demonstrated its capability for enantioseparation of dansyl glutamic acid, dansyl aspartic acid, dansyl methionine, and dansyl phenylalanine using a 60mM ammonium acetate buffer solution and acetonitrile in a 20:80 v/v ratio. It maintained good mechanical stability and repeatability with no relative standard deviation exceeding 7%. These results indicated that the L-cysteine-bonded polymer monolith has excellent potential as a chiral stationary phase.

Chromoionophores decorated silica-polymer hybrid monolith as the solid-state optical sensor for the simultaneous detection of Pb2+, Hg2+, and Cd2+ in aqueous and cigarette samples

This work reports on fabricating a flexible and reliable three-in-one solid-phase ocular sensor to perceive and confiscate the trace Pb2+, Hg2+, and Cd2+ using a structurally customized probe-anchored porous hybrid monolithic sensor. The dual combination of silica/polymer hybrid monolith was achieved from the bulk polymerization of 3-(trimethoxysilyl) propyl methacrylate (TSPM) and pentaerythritol trimethacrylate (PETMA), i.e., poly(TSPM-co-PETMA). The monolithic template delivered a well-ordered porous structure and greater surface area that enabled the regular impregnation of chromophoric probe (TAN), i.e., (E)-1-(thiazol-2-yldiazenyl) naphthalene-2-ol onto monolith surface for sensing target analytes under lower ppb levels. FE-SEM, HR-TEM, EDAX, SAED, p-XRD, FT-IR, TGA and N2 isotherm were deployed to characterize the structural and exterior topographies of the hybrid sensor. The geometrically frozen TAN molecules onto the hybrid monolith form a charge transfer complex with the target ions, thereby rendering a consecutive color shift from light orange to brown for Pb2+, reddish maroon for Hg2+, and purplish pink for Cd2+. The sensor offered a linear response with metal ion concentrations ranging from 0.2 to 100 ppb with lower detection limit values of 0.42, 0.50, and 0.48 ppb for Pb2+, Hg2+, and Cd2+, respectively. The hybrid sensor affords distinct ion sensitivity and selectivity towards Pb2+, Hg2+, and Cd2+ with a quick response time of ≤ 80 s of contact. Furthermore, the sensor was tested with natural samples like environmental water and cigarette samples to validate the method’s real-time monitoring ability. The resultant statistical data demonstrated that the proposed colorimetric sensor was renewable and more feasible for practical application.

Bifunctionalised acid-base hierarchically structured monolithic microreactor for continuous-flow tandem catalytic process of cyanocinnamate synthesis

The results on zirconia-amine bifunctional modification of hierarchically porous silica monoliths for continuous-flow processes ar presented. The study reports the synthesis and properties of the modified porous monoliths and their performance in the tandem process of deacetalization-Knoevenagel condensation reaction. The properties of the materials were studied by thermal analysis, FTIR spectroscopy, XRF and nitrogen adsorption. It was found that both active centres were uniformly distributed along the monolithic cores, and the antagonistic interaction of the acid and base centres was not observed. It was shown that hydrophobicity of the monolith surface has opposite effects on the efficiency of the studied reactions. The overall rate of the tandem process depends on the rate of the condensation reaction. The performance of the bifunctional microreactors was checked and compared with those of cascade-connected monofunctional microreactors and batch reactor. The yield of cyanocinnamate product obtained in both flow systems was ca. 78%; however, pressure drop in the bimodified reactor was only half of that in the cascade. An effective way of water supply to the reaction system has been proposed. The research demonstrates the benefits of using flow-through structured micro-/mesoreactors in tandem reaction processes.

N-doped nano-casted carbon monolith for Pb (II) removal and photocatalytic degradation of thiamethoxam from aqueous solution.

Single rock-like N-doped carbon monolith (ND-PFCM) was successfully constructed via nanocasting method. Phenol formaldehyde resin was taken as carbon source and nitrogen was incorporated in monoliths through NaNH2 activation. The synthesized monoliths were used for the removal of Pb (II) from aqueous solution. Various characterization techniques, namely Brunauer-Emmett-Teller (BET), Raman spectroscopy, UV-visible diffuse reflectance spectra (DRS) UV-DRS, zeta potential, scanning electron microscopy (SEM), TEM (transmission electron microscopy), TGA (thermogravimetric analysis), and XPS (X-ray photoelectron spectroscopy), were utilized to characterize synthesized monolithic samples. The different parameters such as pH, adsorbent dosage, and time were enquired on the removal efficiency of monoliths toward Pb(II). ND-PFCM exhibited the highest adsorption capacity of 330.03mgg-1 in 180min at pH 6. This is attributed to the fact that the better texture properties and presence of nitrogen functional groups enhance the uptake of Pb (II) ions on the monolith surface. In the kinetic studies, pseudo-second-order model fitted best with the experimental data. Furthermore, the removal of thiamethoxam (TM) from aqueous solution was done by using different weight ratios of ND-PFCM under the visible light. The maximum removal efficiency of 97.35% with rate constant of 0.02085min-1was obtained in 160min. Moreover, monoliths exhibited good reusability for five consecutive cycles. The findings suggest that the synthesized monoliths exhibit characteristics suitable and eco-friendly for sustainable use in water treatment applications.

Preparation of chiral monoliths with new modulation of the monolith surface chemistry for the enantioseparation of chiral drugs by nano-liquid chromatography

Here, we report the preparation and application of two new chiral monoliths for the enantioseparation of chiral drugs in nano-LC. Using 3‑chloro-2-hydroxypropylmethacrylate (HPMA-Cl, 2) as a precursor monomer, two different chiral monomers namely, Nα-Boc-Lys-HPMA (3A) and Nα-Fmoc-Lys-HPMA (3B) were synthesized and used for the preparation of chiral polymer monoliths. The first monolithic column (referred to as monolith I) was prepared by an in-situ polymerization of Nα-Boc-Lys-HPMA as the chiral monomer and ethylene dimethacrylate while the second monolithic column (referred to as monolith II) was prepared by an in-situ polymerization of Nα-Fmoc-Lys-HPMA as the chiral monomer and ethylene dimethacrylate as the crosslinker. Methanol and 1-propanol were used as the porogenic solvents. The prepared chiral monoliths were investigated for the enantioseparation of chiral drugs, including β-blockers (e.g., atenolol, propranolol, metoprolol) and anti-inflammatory drugs (e.g., ketoprofen, ibuprofen, flurbiprofen, naproxen, etodolac). The enantioseparation could be achieved via the formation of π-π interactions on the aromate-rich and aromate-poor chiral molecules while enantioseparation mechanism of chiral drugs included mostly π-π interactions and hydrogen bonding. Monolith II showed better enantioselectivity than Monolith I and the resolution values up to 2.12 were successfully achieved.

Effect of hydrophilic/lipophilic balance on the porogenic properties of non-ionic surfactants for monolith preparation and chromatographic separation

The effect of hydrophilic/lipophilic balance (HLB) of polyoxyethylene ethers of different chain lengths on the microporogenic properties of the Brij surfactants has been studied. The objective of this work is to help better understand the role of each porogen and to set criteria for selecting the proper non-ionic surfactant, based on the HLB value. Seven recipes of different porogen compositions were first prepared and the highest efficiency was achieved using decane/decanol/dodecanol mixture with Brij® 30. Then, four other Brij surfactants covering the entire HLB scale were tested, and the prepared monoliths were characterized by SEM, BET, FT-IR and chromatography. The results showed that increasing the HLB from 9.72 to 18.84 was accompanied by an increase in monolith density and surface areas. The optimum HLB range was found to be 10 to 15. Surfactants of lower HLB formed either nonporous or less efficient columns, while those of higher HLB formed non-permeable columns. Adjusting the HLB was possible by mixing surfactants of different HLB. The prepared monoliths could be used in the isocratic mode with a mobile phase consisting of a mixture of ACN and water (20:80, v/v) at a flow rate of 1.5 μL min−1 to separate five sulfa drugs. The separation results showed that the elution order of the compounds correlated with their lipophilicity, with sulfamerazine (logp = 0.52) being the first to elute, and sulfaquinoxoline (logp=1.70) being the most retained. The asymmetry factors of the separated compounds ranged between 1.18 and 1.25, and the resolution was found to be in the range 2.92−7.80. The prepared monoliths could be also successfully separate a mixture of four different nonsteroidal anti-inflammatory drugs and a mixture of four benzoic acid derivatives. This work assists in optimizing the surfactant-based porogenic mixture to meet the desired porosity, surface area, morphology and chromatographic separation requirements.

Magnetically derived fabrication of aligned porous poly(sulfonated polystyrene-co.-chitosan) monolith as a high efficient adsorbent for metal ions separation

Designing and tuning towards the porous structure of adsorbents is of great importance for promoting the adsorptive performance. Herein, a magnetic-induced copolymerization method is applied to generate an aligned porous structure in the aligned porous poly(SPS-co.-CTS) monolith. Typically, the aligned macropores primarily derives from the equilibrium of the magnetic dipolar force to the thermodynamic Brown force by tuning the applied magnetostatic field intensity to 25 mT. Due to the aligned macroporous structure, the monolith features with low back pressure, low mass transfer resistance and high adsorptive capacity. The hydrophilicity of the monolith surface is further improved by capping chitosan activated by amino onto its porous surface via the Hinsber reaction. Detail analyses are performed by a series of physical characterizations, by which exhibit the aligned macropores centering at 5.18 μm, specific surface reaching 54 m2 g−1 and large porosity. Finally, batch adsorption experiments confirm that the adorptive behaviors to Cu2+ ions and Co2+ ions submit to the Langmuir model and Pseudo-second order adsorption kinetics. Most intriguing, the film mass transfer ([kLa]f) has been stabilized due to the aligned macropores, thus facilitating the porous diffusion ([kLa]d) and improving the chromatographic performance of the monolith. All results demonstrate that the aligned porous poly(SPS-co.-CTS) monolith promises broad applications in the field of wastewater remediation.

3D-printed PEGDA monolith with robust silane-grafted chitosan for enhanced textile wastewater treatment

A novel and newly developed 3D-printed poly (ethylene glycol) monolith grafted with chitosan was fabricated by adopting a robust approach, combining 3D printing technology and surface grafting to improve the adsorption capacity. In present work, response surface methodology (RSM) approach was used to investigate the controlling factors of dipping time, chitosan concentration, pH and temperature. All factors have significant effect on adsorption performance, except for dipping time. The removal efficiency (R %) of methyl orange (MO) dye ranged from 20.8 % to 90.4 % and the equilibrium uptake capacity (K) ranged from 1 to 12.7 (mg/g) after 2 h. Six isotherm models, adsorption kinetics, followed by thermodynamic studies were performed. BOD and COD tests were analyzed to investigate the feasibility of its use in wastewater treatment. The recyclability of the grafted - chitosan PEGDA monolith was verified by evaluating its adsorption for four cycles and retained at 78 %, indicating it is stable and reusable. It also has good mechanical properties and stability, which is practical to be applied in real application. The synergistic effect of 3D-printed monolith and tuneable chemical properties of the monolith surface enhances the adsorptionftable performance, while implementing a statistical tool to determine the optimal conditions and influenceable process parameters with good predictability.

Особенности каталитической трансформации метанола в углеводороды в условиях микроструктурированных потоков

The methanol into hydrocarbons transformation is a complex catalytic reaction accompanied by the formation of a wide range of hydrocarbons and proceeding on the surface of acid sites of various zeolites. Zeolite H-ZSM-5 considered to be most often used catalyst for this process. H-ZSM-5 is a highly dispersed material with a crystal diameter of 1–20 microns, which complicates its direct use in reactors with a fixed catalyst bed due to the high hydraulic pressure drop of the catalytic bed. Traditionally in industry, this issue is solved by using complex reactor systems with a fluidized bed, which is justified for large-scale production. In small and medium-size plants, the use of fluidized bed systems is not economically feasible. One of the possible solutions to this problem is the use of a monolithic catalyst with a supported layer of H-ZSM-5 zeolite. This article presents a study of the catalytic activity of a zeolite-containing microstructured monolith in methanol into hydrocarbons transformation. The monolith was synthesized by pressing a zeolite-containing mass followed by drying, calcining, and secondary growth of the zeolite on the monolith surface. A sample of a monolith with an average channel diameter of 0.5, 1.0, 1.5, 2.0 mm were synthesized this way. Samples of the microstructured catalyst were tested at varying temperatures from 250 to 450 °C and at varying the specific methanol feed rate from 0.65 to 2.3 kg (MeOH)/(kg (Cat) h). For this purpose, the monolithic catalyst was placed in a reactor for testing microstructured catalysts, which consisted of a pump, a temperature controller, a catalytic reactor, a condenser, a separating funnel, and a chromatograph. Varying the conditions showed that for the preferential production of gaseous C1–C4 hydrocarbons, it is advisable to carry out the reaction under the following conditions: the average diameter of the catalyst channels is 2 mm, the reaction temperature is 350 °C, the methanol feed rate is 1.65 kg (MeOH)/(kg (Cat) h). For the predominant formation of liquid hydrocarbons of the C5–C8 fraction, it is advisable to carry out the transformation of methanol into hydrocarbons under the following conditions: the average diameter of the catalyst channels is 1 mm, the reaction temperature is 350 °C, the methanol feed rate is 0.65 kg (MeOH) / (kg (Cat) h). For the predominant formation of liquid hydrocarbons of the C9–C12 fraction, it is advisable to carry out the transformation of methanol into hydrocarbons under the following conditions: the average diameter of the catalyst channels is 0.5 mm, the reaction temperature is 350 °C, and the methanol feed rate is 0.65 kg (MeOH) / (kg (Cat) h).

Styrene-based polymerised high internal phase emulsions using monomers in the internal phase as co-surfactants for improved liquid chromatography.

Poly(styrene-co-divinylbenzene)-based monoliths were prepared from the polymerisation of water-in-monomer high internal phase emulsions, where the water-soluble monomers acrylamide (AAm) or poly(ethylene glycol) diacrylate (PEGDA) (Mw 258) were also included in the 90 vol% internal phase. Both AAm and PEGDA were found to act as co-surfactants, resulting in the obtainment of monoliths with greater homogeneity in some cases. As a result these materials demonstrated significantly improved chromatographic performance for the separation of a standard mixture of proteins using reversed-phase liquid chromatography, in comparison to monoliths prepared with no internal phase monomer. In particular, the columns grafted with PEGDA were capable of separating a more complex mixture consisting of seven components. The inclusion of monomers in the internal phase also allowed for the functionalisation of the monolith's surface where the degree of polymerisation that occurred in the internal phase, which was governed by the monomer content in the internal phase and initiation location, determined whether polymeric chains or a hydrogel were grafted to the surface. A monolith grafted with AAm was also found to be capable of retaining polar analytes as a result of the increase in surface hydrophilicity.

Porous Single-Crystalline Monolith to Enhance Catalytic Activity and Stability.

Engineering the catalytic activity and stability of materials would require the identification of the structural features that can tailor active sites at surfaces. Porous single crystals combine the ordered lattice structures and disordered interconnected pores, and they would therefore provide the advantages of precise structure features to identify and engineer the active sites at surfaces. Herein, we fabricate porous single-crystalline vanadium nitride (VN) at centimeter scale and further dope Fe (Fe0.1V0.9N) and Co (Co0.1V0.9N) in lattice to engineer the active sites at surface. We demonstrate that the active surface is composed of unsaturated coordination of V-N, Fe-N, and Co-N structures which lead to the generation of high-density active sites at the porous single-crystalline monolith surface. The interconnected pores aid the pore-enhanced fluxion to facilitate species diffusion in the porous architectures. In the nonoxidative dehydrogenation of ethane to ethylene, we demonstrate the outstanding performance with ethane conversion of 36% and ethylene selectivity of 99% at 660°C. Remarkably stability as a result of their single-crystalline structure, the monoliths achieve the outstanding performance without degradation being observed even after 200 hours of a continuous operation in a monolithic reactor. This work not only demonstrates the effective structural engineering to simultaneously enhance the stability and overall performance for practically useful catalytic materials but also provide a new route for the element doping of porous single crystals at large scale for the potential application in other fields.

Selective adsorption of cationic dye utilizing poly(methacrylic acid-co-ethylene dimethacrylate) monolith from wastewater

In this study, poly(methacrylic acid-co-ethylene dimethacrylate (poly(MAA-co-EDMA)) monolith was prepared for the selective adsorption of acidic dye, namely methylene blue (MB), from wastewater. The fabrication of the monolith was carried out by photoinitiation polymerization by irradiating a mixture of methacrylic acid (MAA), ethylene dimethacrylate (EDMA), porogenic solvents and an initiator. Batch adsorption assays were performed to examine the impact of monolith dosage and initial dye concentration on the adsorption capacity and efficiency of the monolith towards MB dye molecules. This adsorption kinetic study revealed that MB adsorption on the monolith followed pseudo-second-order model and equilibrium adsorption behavior was best modeled by Langmuir adsorption isotherm indicating a monolayer adsorption with a maximum adsorption capacity of 50.00 mg g-1. Owing to the presence of negative binding sites on the monolith surface, cationic MB molecules are selectively adsorbed from MB/methyl orange (MO) mixture with an adsorption efficiency of 99.54% at equilibrium time. Moreover, the MB adsorbed monolith was regenerated up to four cycles and the percentage removal efficiency of MB on the monolith dropped to 67.64 % after the fourth cycle. Finally, the monolith effectively adsorbed MB from the tap water in presence of competing ions and the maximum adsorptive capacity obtained was 47.62 mg g-1 with 84.5% adsorption efficiency. Hence, poly(MAA-co- EDMA) monolith is an adequate sorbent for the treatment of cationic dyes in the presence of other dyes and competing ions from wastewater.

Effect of the crystalline layer on the electrical behaviour of 17.7Li2O·5.2ZrO2·68.1SiO2·9.0Al2O3 glass ceramic monoliths

Li2O–ZrO2–SiO2–Al2O3 (LZSA) glass ceramic systems are usually obtained from powder technology to obtain materials with a low thermal expansion coefficient (CTE). However, in these cases, there is a high residual porosity. An alternative to reduce the porosity involves the production of monoliths. Nevertheless, there is still a lack of crystallisation kinetics and the final properties of glass ceramic monoliths are affected such as electrical properties. This study aims to evaluate the electrical behaviour as function of the crystalline layer thickness formed on the monolith surface of a 17.7Li2O·5.2ZrO2·68.1SiO2·9.0Al2O3 (molar basis) glass ceramic LZSA composition. Monoliths thermally treated at 750, 800, and 850 °C were chosen to evaluate based on the range of the crystalline layer growth. Electrochemical impedance spectroscopy was used for the electrical characterisation of LZSA glass and the glass ceramics. The resistivity increased with increasing thermal treatment temperature due to the formation of lithium-based crystalline phases. The electrical conductivity at 25 °C of the glass ceramic thermally treated at 850 °C decreased to 1.4 × 10−13 S cm−1 from 8.7 × 10−11 S cm−1 for LZSA glass. Based on the electrical behaviour, monoliths thermally treated at 850 °C can be considered potential for dielectric industrial applications.

Preparation of monolithic polymer-magnetite nanoparticle composites into poly(ethylene-co-tetrafluoroethylene) tubes for uses in micro-bore HPLC separation and extraction of phosphorylated compounds

This paper describes the fabrication of a novel microbore monolithic column modified with magnetite nanoparticles (MNPs) prepared in a poly(ethylene-co-tetrafluoroethylene) (EFTE) tubing, and its application as stationary phase for the chromatographic separation of phosphorylated compounds. In order to obtain the composite column, a two-step procedure was performed. The formation of a glycidyl methacrylate-based monolith inside the activated ETFE tube was firstly carried out. Then, two incorporation approaches of MNPs in monoliths were investigated. The generic polymer was modified with 3-aminopropyltrimethoxysilane (APTMS) to be subsequently attached to MNP surfaces. Alternatively, APTMS-coated MNPs were firstly prepared and subsequently used for attachment onto the monolith surface through reaction of epoxy groups present in the generic monolith. This last strategy gave a reproducible layer of MNPs coated onto the polymer monolith as well as robust and permeable chromatographic columns. The retention behaviour of this MNP-based composite monolithic column was studied by using small phosphorylated compounds (adenosine phosphates). It was found that the retention of model analytes was ruled by partitioning and adsorption HILIC mechanisms. The columns also exhibited satisfactory performance in the separation of these target compounds, showing good chromatographic behaviour after two months of continued use. These composite monolithic columns were also successfully applied to the extraction of a tryptic digest of β-casein.

3D-printed HZSM-5 and 3D-HZM5@SAPO-34 structured monoliths with controlled acidity and porosity for conversion of methanol to dimethyl either

The ability to control the morphology and porosity of zeolite-structured monolith is an important step in the design of zeolite-based catalysts. Herein, additive manufacturing method was used for the rapid synthesis of H-ZSM-5 structured monoliths (3D-HZSM5) with hierarchical porosity (macro-meso-micro) and controlled type and density of acid sites. After 3D-HZSM5 monolith formation, the silicoaluminophosphate (SAPO-34) was grown on the 3D-HZSM5 structured monolith surface via secondary growth method for formation of 3D-HZSM5@SAPO-34 structured monolith. The samples were characterized before and after SAPO-34 growth by XRD, N2 physorption, NH3-TPD, Py-IR and SEM. The characterization results revealed formation of SAPO-34 layer on 3D-HZSM5 structured monolith and also modification also imply that formulation of H-ZSM-5 powder into monolith resulted in slightly less Brønsted acid sites while the density of Lewis acid sites increased. The performance of the 3D-HZSM5 and 3D-HZSM5@SAPO-34 structured monoliths were investigated in catalytic conversion of methanol to dimethyl ether (DME) over a temperature range of 180 to 320 °C for 10 h time on stream. The selectivity to DME was significantly increased as a result of modification in acidity and porosity of the 3D-printed HZSM-5 structured monolith as compared to its powder counterpart and also 3D-HZSM5@SAPO-34 structured monolith. SAPO-34 growth enhanced the density of strong acid sites which caused further conversion of DME to higher hydrocarbons. The highest DME selectivity reached 96% on 3D-HZSM5 structured monolith at 180 °C, which also achieved ~70% conversion of methanol.

Eco-friendly production of metal nanoparticles immobilised on organic monolith for pepsin extraction

Abstract Polymer monoliths modified by using nanoparticles (NPs) integrate high NP specific surface area with different monolith surface chemistry and high porosity. As a result, they have extensive applications within different fields, whereas nanomaterial-functionalised porous polymer monoliths have elicited considerable interest from investigators. This study is aimed at fabricating organic polymer-based monoliths from polybutyl methacrylate-co-ethylenedimethacrylate (BuMA-co-EDMA) monoliths prior to immobilization of gold or silver metal on the pore surface of the monoliths using reducing reagent (extracts of lemon peels). This was intended to denote a sustainable technique of immobilizing nanoparticles that are advantageous over physical and chemical techniques because it is safe in terms of handling, readily available, environmentally friendly, and cheap. Two different methods were used in the study to effectively immobilize nanoparticles on monolithic components. The outcomes showed that soaking the monolith rod in the prepared nano solution directly and placing it within ovens at temperatures of 80°C constituted the most effective method. Characterisation of the fabricated monolith was undertaken using SEM/EDX analysis, UV-vis. spectra analysis, and visual observation. The SEM analysis showed that nanoparticles were extensively immobilised on the surface polymers. Another peak was attained through EDX analysis, thus confirming the Au atom existence at 2.83% alongside another peak that proved the Ag atom existence at 1.92%. The fabricated components were used as sorbents for purifying protein. The ideal performance was achieved using gold nanoparticles (GNPs) immobilised organic monolith that attained a greater pepsin extraction recovery compared to silver nanoparticles (SNPs) immobilised organic monoliths alongside bare organic-based monolith.

New age monolithic design-based visible light responsive and reusable photocatalyst material using iron oxide-modified mesoporous titania framework

In this work, we report a facile route for the synthesis of worm-like mesoporous $$\hbox {Fe}_{2}\hbox {O}_{3}$$-doped $$\hbox {TiO}_{2}$$ monolithic composites through a direct template sol–gel method, for the photocatalytic degradation of textile dye (acid blue 113) pollutants. The monolith surface morphology and structural properties have been characterized using p-XRD, HR-SEM–EDAX, HR-TEM–SAED, TGA, UV–Vis–DRS, PLS, FTIR, XPS and BET analyses. The stoichiometric doping of $$\hbox {Fe}_{2}\hbox {O}_{3}$$ unleashes visible light photocatalytic activity through a red shift in the light absorption character of $$\hbox {TiO}_{2}$$, thereby narrowing the energy band gap, and an eventual increase in $$\hbox {e}^{-}/\hbox {h}^{+}$$ separation centres. The monolithic photocatalyst exhibits better properties in terms of surface area, pore volume and diameter. The physico-chemical parameters, such as solution pH, dopant stoichiometry, catalyst quantity, dye concentration, photo-sensitizers and light intensity have been optimized to enhance the photocatalysis efficiency. The photocatalyst exhibits complete dye mineralization within 0.5 h, and also reusable for five continuous cycles.

Au sensitized La–CeO2 catalyst coated ceramics monoliths for toluene catalysis application

Coating procedure for ceramic monoliths was optimized by wash coating with ϒ-alumina for the deposition of Au sensitized La–CeO2 catalyst. Effect of four different catalyst coating methods on ceramics monolith surface for toluene catalytic activity was investigated. Au sensitized La–CeO2 catalyst was prepared via wetness impregnation and co-precipitation chemical methods. The catalyst was characterized using XRD, FESEM, EDS, TEM, XPS, Raman, BET and Elemental mapping techniques. Nanoparticles composed flakes morphology of catalyst was confirmed by electron microscopy. Average nanocrystalline size of 6.7 nm and surface area 33 m2/g of catalyst was estimated using Scherrer's formula and BET analysis respectively. Adherence tests were carried out by applying ultrasonic vibrations and hot air blower to optimize ϒ-alumina coating on ceramics monolith. Toluene catalytic activity studied at different operating temperatures and concentrations. Stability and reuse of catalyst coated ceramics monoliths for toluene activity were confirmed. A mechanism of toluene degradation was briefed.

Incorporating Pb2+ Templates into the Crystalline Structure of MnO2 Catalyst Supported on Monolith: Applications in H2O2 Decomposition.

Several MnO2 catalysts, promoted with Pb2+ ions and supported on a wash-coated monolith (WMon), briefly, xPbyMn-WMon (x = 0, 0.5, 1.0, 1.5, 2, and 2.5 and y = 8 wt %), were prepared. The presence of Pb2+ affects the manganese oxidation state, crystalline phase, thermal resistance, metal dispersion, and catalytic performance. According to XPS spectra, XRD patterns and HRTEM images, manganese was dispersed on the monolith surface as Mn3+ and Mn4+ species in both α and β crystalline phases. The ratios of Mn4+/Mn3+ states and α/β phases were highly enhanced, and the desired PbxMn8O16 phase (coronadite) was formed. Concentrations of the defect oxygen (Mn–O–H) and oxygen vacancies, which improve the catalyst reducibility and the MnO2 reduction temperature, were also increased. Further, based on the H2 chemisorption analysis, the Pb2+ template would increase the manganese dispersion and the reaction sites. Meanwhile, the average MnO2 crystallite size was decreased from 13.26 to 8.15 nm. The optimum catalyst 1.5Pb8Mn-WMon exhibited an activity 149% more than the manganese-only catalyst in decomposition of H2O2. Evaluation of catalyst stability in the presence of Pb2+ after 10 recycles showed only a 6.8% decrease. The catalytic reaction was evaluated based on different criteria.

Structured Monolithic Catalysts vs. Fixed Bed for the Oxidative Dehydrogenation of Propane.

The deposition of V-based catalysts for the oxidative dehydrogenation of propane to propene on cordierite honeycomb monoliths was optimised as a strategy to decrease the contact time in a structured reactor with respect to a conventional fixed bed one. 10 wt% VOx supported over SiO2 or Al2O3 were used as catalysts, deposed over the monolith using silica or alumina as primer, respectively. Both the alumina supported catalyst and the bohemite primer precursor were effectively deposed by dip-coating from stable powder suspensions, whereas insufficient adhesion was obtained when loading pre-synthesised SiO2 over the cordierite. A new method based on sol-gel production of SiO2 from tetraethylortosilicate (TEOS) over the monolith surface was set up. A correlation was derived for the prevision of the amount of silica deposed depending on the amount of TEOS. Both primer and catalyst loading were optimised as for uniformity and stability of the coating and resulted 0.5–1 wt % primer and 0.15 wt % of catalyst. Activity testing confirmed the strong improvement of propene productivity by increasing the time factor (i.e. Ncm3 of flowing reactant/min gcat), which ended in a one order of magnitude increase of productivity for the honeycomb-supported samples with respect to the fixed bed configuration.