Non-porous Supports Research Articles

Kinetic and thermodynamic studies on the thermal inactivation of lipase immobilized on glutaraldehyde-activated rice husk silica.

The objective of this study was to obtain sufficient information on the thermal stabilization of a food-grade lipase from Thermomyces lanuginosus (TLL) using the immobilization technique. To do this, a new non-porous support was prepared via the sequential extraction of SiO2 from rice husks, followed by functionalization with (3-aminopropyl) triethoxysilane - 3-APTES (Amino-SiO2), and activation with glutaraldehyde - GA (GA-Amino-SiO2). We evaluated the influence of GA concentration, which varied from 0.25% v v-1 to 4% v v-1, on the immobilization parameters and enzyme thermal stabilization. The thermal inactivation parameters for both biocatalyst forms (soluble or immobilized TLL) were calculated by fitting a non-first-order enzyme inactivation kinetic model to the experimental data. According to the results, TLL was fully immobilized on the external support surface activated with different GA concentrations using an initial protein load of 5mgg-1. A sharp decrease of hydrolytic activity was observed from 216.6 ± 12.4 U g-1 to 28.6 ± 0.9 U g-1 of after increasing the GA concentration from 0.25% v v-1 to 4.0% v v-1. The support that was prepared using a GA concentration at 0.5% v v-1 provided the highest stabilization of TLL - 31.6-times more stable than its soluble form at 60°C. The estimations of the thermodynamic parameters, e.g., inactivation energy (Ed), enthalpy (ΔH#), entropy (ΔS#), and the Gibbs energy (ΔG#) values, confirmed the enzyme stabilization on the external support surface at temperatures ranging from 50 to 65°C. These results show promising applications for this new heterogeneous biocatalyst in industrial processes given the high catalytic activity and thermal stability.

Ultrafast inactivation of SARS-CoV-2 by 254-nm UV-C irradiation on porous and non-porous media of medical interest using an omnidirectional chamber

Covid-19 has spurred a renewed interest in decontamination techniques for air, objects and surfaces. Beginning in 2020, urgent effort was done to permit the reuse of UV-C for inactivating SARS-CoV-2. However, those studies diverged widely on the dose necessary to reach this goal; until today, the real value of the sensitivity of the virus to a 254-nm illumination is not known precisely. In this study, decontamination was performed in an original UV-C large decontamination chamber (UVCab, ON-LIGHT, France) delivering an omnidirectional irradiation with an average dose of 50 mJ/cm2 in 60 s. Viral inactivation was checked by both cell culture and PCR test. SARS-CoV-2 was inactivated by UV-C light within 3 s on both porous (disposable gown) and non-porous (stainless steel and apron) surfaces. For the porous surface, an irradiation of 5 min was needed to achieve a completely negative PCR signal. The Z value estimating the sensitivity of SARS-CoV-2 to UV-C in the experimental conditions of our cabinet was shown to be > 0.5820 m2/J. These results illustrate the ability of this apparatus to inactivate rapidly and definitively high loads of SARS-CoV-2 deposited on porous or non-porous supports and opens new perspectives on material decontamination using UV-C.

Freestanding μm-thin nanomesh electrodes exceeding 100x current density enhancement for high-throughput electrochemical applications

Nanomeshes (NMs), regularly interconnected 3D nanowire-networks, obtained from electroplating in rationally designed alumina templates, are attractive for numerous fields due to their extremely high surface area and porosity. Until now, non-porous support substrates were required to provide sufficient mechanical robustness to the highly porous NM. However, to exploit these compelling nano-architectures as freestanding electrodes in electrochemical flow cells, e.g. water electrolysis, it is essential that the nanowire-network is accessible from all sides requiring a porous support structure. To demonstrate the advantage of the high volumetric NM surface area of 26 m2/cm3 for water electrolysis up to 1 A/cm2, we monolithically integrated a nickel NM with an open support grid in a facile and up-scalable fabrication flow. The freestanding NM electrodes show beyond state-of-the-art performance for the alkaline hydrogen- and oxygen evolution reaction (HER and OER), with over 100x enhanced current densities in respect to planar nickel. Interestingly, the regular nano-architecture of the electrodes causes an intrinsic catalytic effect for the HER. The high potential of these novel 4 μm thin electrodes toward high-throughput electrochemical applications is shown by the significant 400 mV lower overpotential compared to commercial 1.6 mm thick nickel foams (<0.01 m2/cm3) in the alkaline anion-exchange membrane water electrolysis.

Dry reforming of methane over calcium-deficient hydroxyapatite supported cobalt and nickel catalysts

Calcium-deficient hydroxyapatite (HAP) non-porous supports were synthesized from Ca(NO3)2 and NH4H2PO4 (conventional synthesis route, HAP_N support) and from CaCO3 and H3PO4 (new synthesis route, HAP_C support) by wet chemical precipitation method. Monometallic and bimetallic supported catalysts were prepared by incipient wetness impregnation using Co(NO3)2 and Ni(NO3)2 salts. The size of Co- and Ni-based particles varied from some nm to dozens nm. Dry reforming of methane (DRM) tests at 700 °C, and 1.6 bar shows that HAP-supported cobalt catalysts were systematically more active than HAP-supported nickel catalysts, which is a new finding in DRM. Increasing the molar ratio of Ca/P from 1.43 (HAP_N) to 1.60 (HAP_C) support led to a slight decrease of the catalytic activity but an improvement of the catalytic stability. Thus, HAP_C support synthesized from CaCO3 and H3PO4 is a good candidate for designing an efficient catalyst for the DRM reaction.

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes.

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 °C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

Effects of Mesopore Internal Surfaces on the Structure of Immobilized Pd-Bisphosphine Complexes Analyzed by Variable-Temperature XAFS and Their Catalytic Performances

In this study, mesoporous and nonporous silica-supported Pd complexes were synthesized and characterized. Variable-temperature XAFS measurements and a curve-fitting analysis showed a slightly larger contribution of σ2static when the Pd complexes were on a nonporous support in comparison to a mesoporous support. In contrast, the catalytic performance of the attached Pd complex in the Suzuki-Miyaura cross-coupling reaction was not affected by such small differences in the static disorder of the Pd complex.

Pervaporation multilayer membranes based on a polyelectrolyte complex of λ-carrageenan and chitosan

A polyelectrolyte complex (PEC) was prepared from chitosan (CS) and λ-carrageenan (λ-CAR) using a layer-by-layer deposition of polyion solutions on a plated nonporous support. This material was then used as a multilayer membrane for the pervaporation separation of aqueous ethanol solutions. The fabricated complex film (25–30μm thick) was a multilayer system (λ-CAR-PEC-CS) containing a polycation CS (MW 3.1×105, DDА 0.93), a polyanion λ-CAR (MW 3.5×105, extracted from the alga Chondrus armatus), and a PEC layer formed between the two polyion layers. X-ray diffraction indicated a significant structuring of the film in the region of the composite PEC-CS bilayer. The structural and morphological characteristics of the CS surface in the multilayer membrane, as revealed by atomic force microscopy, were close to the characteristics of the dense CS film. However, this structure changed following pervaporation (i.e., the distinct spherical structures on the surface disappeared). Similarly, the initially loose surface of λ-CAR in the composite changed to an ordered domain after pervaporation. The transport properties of the pervaporation membranes were tested by examining the separation of ethanol-water mixtures of different compositions. The flux increased with an increase in the weight percentage of water in the feed mixture, but the separation capacity of the membrane was unchanged. In a range of feed concentrations of 50–94wt%, the membrane mainly releases water with a corresponding concentration in the permeate of 99.9–99.8wt% and substantial fluxes of 0.003–1.130kgm−2h−1 at 40°C. The obtained results indicate significant prospects for the use of non-gelling type CARs for the formation of highly effective pervaporation membranes.

To the nature of the support effect in palladium-catalyzed aqueous-phase hydrogenation of maleic acid

Influence of the support nature on catalytic properties of the supported Pd nanoparticles in liquid-phase (water, ethanol) hydrogenation of maleic acid (MA) to succinic one was extensively studied. Different oxides (SiO2, diatomites, WO3, Ta2O5, Nb2O5, V2O5, TiO2, CeO2, ZrO2, Ga2O3, In2O3, Cr2O3, Fe2O3, Al2O3), salts (CaF2, BaSO4) and carbon supports either with extremely low or high porosity were employed as the catalyst supports. XPS studies of the catalysts revealed no significant support-induced changes of the electronic state of the active component. For palladium on non-porous supports, its TOF values in MA hydrogenation turned to be constant in ethanol medium but varied with the support nature in water. In the case of porous supports, the TOFs diminished in both media and were governed by mean pore size and surface acidity of the supports. The dependence of TOF values on mean distance between adjacent Pd nanoparticles is also revealed. The catalytic results are explained by the presence of the electric double layer at the catalyst-solution interface, which affect its catalytic performance.

Preparation of kaolin-based low-cost porous ceramic supports using different amounts of carbonates

Flat ceramic membrane supports were prepared using kaolin as the major constituent with varying amounts of carbonates and sintered at 900°C. The prepared supports were subjected to SEM, XRD, and porosity tests. The supports prepared without using carbonates had the largest mean pore size with the lowest porosity. The porosity of membranes increased by increasing the amount of calcium carbonate. The supports prepared using calcium carbonate had wider pore size distribution on the surface than those prepared using sodium carbonate. Small amount (10%) of sodium carbonate acts as a pore modifier resulting in smaller mean pore size, while large amount (>20%) of sodium carbonate blocks the pores by forming a sodium silicate layer and results in nonporous support. Therefore, calcium carbonate should be preferred over sodium carbonate for preparing highly porous ceramic membranes.

Vanadium oxide catalysts on structured microfiber supports for the selective oxidation of hydrogen sulfide

Vanadium(V) oxide catalysts for the selective oxidation of hydrogen sulfide to sulfur on a nonporous glass-fiber support with a surface layer of a porous secondary support (SiO2) are studied. The catalysts are obtained by means of pulsed surface thermosynthesis. Such catalysts are shown to have high activity and acceptable selectivity in the industrially important region of temperatures below 200°C. A glass-fiber catalyst containing vanadium oxide (10.3 wt % of vanadium) in particular ensures the complete conversion of H2S at a temperature of 175°C and a reaction mixture hourly space velocity (RMHSV) of 1 cm3/(gcat s) with a sulfur yield of 67%; this is at least 1.35 times higher than for the traditional iron oxide catalyst. Using a structured glass-fiber woven support effectively minimizes diffusion resistance and greatly simplifies the scaleup of processes based on such catalysts. Such catalysts can be used for the cleansing of tail gases from Claus units and in other processes based on the selective oxidation of H2S.

Synthesis of new composite polymer membrane from tapioca grains—polysulfone for desalination

Nowadays, membrane technology has gained significant attention from scientific community throughout the world due to their attractive features such as low costs, low energy costs, and high efficiency in water purification. Different types of membranes and its performance study have been widely applied in the desalination processes. One of the drawbacks in membrane preparation was usage of hazardous chemicals causing serious environmental pollution. Here, we attempted to prepare partial green composite membranes using tapioca grains. The same membranes were subjected to various characterizations and the results were fairly encouraging showing salt rejection as high as 71%. This study aimed to synthesize polysulfone and tapioca membranes over nonporous support of K.C. 27.0 using diffusion-induced phase separation technique method. Newly synthesized polymer membranes were subjected to Infra-red spectral study and water uptake. Their surface morphology is visualized by SEM.

Pore Structure and Bifunctional Catalyst Activity of Overlayers Applied by Atomic Layer Deposition on Copper Nanoparticles

We present a model system, based on spherical nonporous supports, to facilitate the characterization of supported metal catalysts stabilized by atomic layer deposition (ALD) against sintering and leaching under liquid-phase conditions. Calcination at high temperatures (973 K) produces pores in the ALD overcoat, and we image these pores using scanning transmission electron microscopy and electron energy loss spectroscopy (STEM/EELS). We determine the size of these pores to be ∼1 nm using small-angle X-ray scattering (SAXS). Finally, we demonstrate the use of ALD to synthesize novel bifunctional catalysts by the addition of an acidic oxide layer to the stabilizing overcoat.

LPS inmobilization on porous and non-porous supports as an approach for the isolation of anti-LPS host-defense peptides

Lipopolysaccharides (LPSs) are the major molecular component of the outer membrane of Gram-negative bacteria. This molecule is recognized as a sign of bacterial infection, responsible for the development of local inflammatory response and, in extreme cases, septic shock. Unfortunately, despite substantial advances in the pathophysiology of sepsis, there is no efficacious therapy against this syndrome yet. As a consequence, septic shock syndrome continues to increase, reaching mortality rates over 50% in some cases. Even though many preclinical studies and clinical trials have been conducted, there is no Food and Drug Administration-approved drug yet that interacts directly against LPS. Cationic host-defense peptides (HDPs) could be an alternative solution since they possess both antimicrobial and antiseptic properties. HDPs are small, positively charged peptides which are evolutionarily conserved components of the innate immune response. In fact, binding to diverse chemotypes of LPS and inhibition of LPS-induced pro-inflammatory cytokines from macrophages have been demonstrated for different HDPs. Curiously, none of them have been isolated by their affinity to LPS. A diversity of supports could be useful for such biological interaction and suitable for isolating HDPs that recognize LPS. This approach could expand the rational search for anti-LPS HDPs.

Selective hydrogenation of acetophenone over nickel supported on titania

The catalytic activity of Ni impregnated on various phases of titania, viz. rutile, anatase and high surface area, has been investigated for the hydrogenation of acetophenone. The TPR profile of Ni/rutile suggests a strong metal–support interaction. The observed catalytic activity order is Ni/rutile > Ni/anatase > Ni/TiO2. The greater activity of Ni/rutile is attributed to higher concentration of Ni on the surface and SMSI. The catalyst samples showed sintering of Ni when calcined at 900 °C, which resulted in a drop in their catalytic activity. The catalyst stability studies showed that activity is lost only marginally in rutile and anatase. The electronic interaction between Ni and rutile promotes the formation of electron enriched Ni–H species which interact with the carbonyl group of acetophenone. The hydrogenation proceeds with atom economy to form phenylethanol irrespective of the reaction conditions suggesting that these catalysts are of significant importance in green chemistry. The results obtained in this investigation clearly establish that Ni/rutile, a non-porous support, is better for this class of reaction.

Oxidative Hydrolysis of Cellobiose to Glucose

Cellobiose hydrolysis into glucose was chosen as a model system for cellulose breakdown to investigate glycosidic bond cleavage. The hydrolysis was enhanced by increased acidity in an inert gas medium, while air-assisted hydrolysis with a neutral solution achieved over 70% glucose yield. Hydrogen peroxide, as a stronger oxidant than air, converted cellobiose to carboxyl compounds, which lowered the glucose selectivity. At 150 °C, the selectivity from cellobiose to glucose was very low on porous γ-Al2O3 supported catalysts, even lower than without a catalyst. When the active metals were prepared on non-porous supports such as spherical alumina (α phase), the overall yield of glucose was dramatically improved at 120 °C. Similar improvements were obtained for another disaccharide model, sucrose, which achieved greater than 90% sucrose conversion with selectivity in excess of 90% at 80 °C.

A copper catalyst on nonporous supports based on copper oxalate as a precursor

A method for obtaining copper catalysts on nonporous supports by the thermal decomposition of copper oxalate in the absence of oxygen was suggested. The catalytic properties of the catalyst were studied in the model reaction of the conversion of propanol-2 into acetone and propylene. The influence of the content of copper in the catalyst, reaction temperature, and conditions of oxalate decomposition on the degree of alcohol conversion and ratio between reaction channels was studied. Electron photomicrographs were obtained, specific surface areas were measured, and X-ray powder patterns of the catalyst were recorded.

Atrazine biodegradation by a bacterial community immobilized in two types of packed-bed biofilm reactors

Through selective enrichment of atrazine-metabolizing microorganisms, a microbial community was selected from agricultural soil. Bacterial isolates, identified by their closest similarity with 16S rDNA sequences stored in NCBI GeneBank, belonged to the genera: Massilia, Stenotrophomonas, Klebsiella, Sphingomonas, Ochrobactrum, Arthrobacter, Microbacterium, Xanthomonas and Ornithinimicrobium. From these strains, only the first six used atrazine as nitrogen and carbon source. The microbial community attached to a non-porous support was evaluated for its atrazine biodegradation rate and removal efficiency under aerobic conditions in two types of packed-bed biofilm reactors fed with a mineral salt medium containing glucose plus atrazine, or atrazine as the sole carbon and nitrogen source. Removal efficiencies near 100% were obtained at loading rates up to 10 mg l−1 h−1. After long periods of continuous operation, the richness of microbial species in biofilm reactors diminished to only three bacterial strains; Stenotrophomonas sp., Ochrobactrum sp. and Arthrobacter sp. By PCR analysis of their DNA, the presence of atzABC genes codifying for the enzymes of the upper catabolic pathway of atrazine, was confirmed in the three strains. The gene atzD that encodes for the cyanuric acid amidohydrolase enzyme was detected only in Stenotrophomonas sp.

Synthesis and Characterization of Pure-Silicazeolite- Beta Membrane

The semiconductor industry needs low dielectric constant (low k-value) materials to more advance microprocessor and chips by reducing the size of the device features. In fabricate this context, a new material with lower k value than conventional silica ( k = 3.9 - 4.2 ) is needed in order to improve the circuit performance. As per the recent International Semiconductor Technology plan, a low-k material with a k = 1.6 will be needed by 2010. The choice of the inorganic zeolite membrane is an attractive option for low k material and suitable for microprocess application. In the present study, a pure silica zeolite beta membrane coated on the non-porous stainless steel support was synthesized using in situ crystallization of a gel with the composition of SiO 2 : 0.6 TEAOH : 0.6 HF : 10.1 H 2 O. The crystallization was carried in the presence of tetraethylammonium hydroxide TEA(OH) as structure directing agent, fumed silica, HF and deionized water at pH value of 9. The crystallization under hydrothermal conditions at 130°C was carried out for the time period of 14 days. The membrane was characterized by X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Nitrogen Adsorption and Scanning Electron Microscope (SEM). SEM micrographs show highly crystalline, truncated square bipyramidal morphology of pure silica zeolite beta was coated on the non-porous stainless steel support. The membrane dielectric constant, k-value was measured as 2.64 which makes it suitable for the microprocessor applications. Keywords: Zeolite membrane, zeolite BETA and microprocessor AJSTD Vol. 23 Issue 4 pp. 285-293 (2006)

A Light for the Cure

Zeolites are mesoporous minerals used as ion-exchange beds in water purification and softening, and as chemical reaction platforms. Pure silica zeolites have been grown as polycrystalline films on nonporous supports, but the potential utility of these materials depends on their hydrophobicity and porosity, which in turn depends on the presence of grain boundaries. Post-deposition treatments have been used to remove the hydrophilic silanols that form, but typically these approaches either fail to penetrate the pore structure or fail to stand up to the heating required to remove the organic template used during zeolite growth.

Feasibility of gas/solid carboligation: Conversion of benzaldehyde to benzoin using thiamine diphosphate-dependent enzymes

A carboligation was investigated for the first time as an enzymatic gas phase reaction, where benzaldehyde was converted to benzoin using thiamine diphosphate (ThDP)-dependent enzymes, namely benzaldehyde lyase (BAL) and benzoylformate decarboxylase (BFD). The biocatalyst was immobilized per deposition on non-porous support. Some limitations of the gas/solid biocatalysis are discussed based on this carboligation and it is also demonstrated that the solid/gas system is an interesting tool for more volatile products.