Impregnation Protocol Research Articles

Convergent Active Site Evolution in Platinum Single Atom Catalysts for Acetylene Hydrochlorination and Implications for Toxicity Minimization.

Platinum single atoms anchored onto activated carbon enable highly stable Hg-free synthesis of vinyl chloride (VCM) via acetylene hydrochlorination. Compared to gold-based alternatives, platinum catalysts are in initial phases of development. Most synthetic approaches rely on chloroplatinic acid, presenting opportunities to explore other precursors and their impact on catalyst structure, reactivity, and toxicity aspects. Here, we synthesize platinum single atom catalysts (Pt SACs, 0.2-0.8 wt % Pt) employing diverse Pt2+ and Pt4+ complexes with ammine, hydroxyl, nitrate, and chloride ligands, following a scalable impregnation protocol on activated carbon extrudates. X-ray absorption spectroscopy (XAS) reveals that Pt4+ species reduce to Pt2+ upon deposition onto the support. Despite similar oxidation states, the initial activity is precursor dependent, with tetraammine-derived Pt SACs displaying 2-fold higher VCM yield than chlorinated counterparts, linked to superior hydrogen chloride binding abilities by density functional theory (DFT) simulations. Their activity gradually converges due to dynamic active site restructuring, delivering remarkable precursor-independent stability over 150 h. Operando XAS and DFT studies uncover reaction-induced ligand exchange, generating common active and stable Pt-Cl x (x = 2-3) species. Convergent active site evolution enables flexibility in metal precursor selection and thus toxicity minimization through multiparameter assessment. This study advances safe-by-design catalysts for VCM synthesis, highlighting the importance of toxicity analyses in early-stage catalyst development programs.

A facile, environmentally-benign, green and a novel synthesis of tert-butyl-quinolines by using Fe3O4-MWCNT@CeO2 as recyclable catalyst

The aim of the present work is to examine the catalytic activity of ceria (CeO2) supported on a nano-composite of iron oxide and multi-walled carbon nanotubes (Fe3O4-MWCNT). A simple impregnation protocol was used to synthesize Fe3O4-MWCNT@CeO2 nano-composite, and a diversity of analytical techniques (including XRD, BET, TGA, SEM, TEM, and EDS) were used to thoroughly describe the catalyst material. The CeO2 supported on Fe3O4-MWCNT were found to be uniformly distributed throughout the nano-composite, irregular spherical in shape, and ranged in size from 5 to 15 nm, according to high-resolution TEM image. Afterwards, the synthesis of novel tert-butyl-quinoline analogues via a multi-component condensation comprising substituted aldehydes, dimedone, 3°-butylacetoacetate, and NH4OAc was used to evaluate the catalytic performance of the Fe3O4-MWCNT@CeO2 nano-composite. Their large specific surface area, porosity, unique exposed surfaces, and stability all contribute to their effectiveness. The catalyst's extremely active surfaces are highlighted by the notably high turn-over frequency. Thus, using ethanol as the green solvent, we suggest an effective and reusable catalytic approach that works at mild reaction condition with excellent product yields (90–97 %). This makes that nano-composite inexpensive, safe for the environment, and very atom-efficient. When compared to existing commercial approaches, our protocol is found to be more sustainable and efficient.

Vapor-phase dehydrogenation of 3-methyl-2-butanol over silica-supported Cu-catalyst prepared by mannitol-assisted impregnation

Abstract Silica-supported Cu (Cu/SiO2) prepared by using an organic additive-assisted impregnation method was employed as a catalyst for the dehydrogenation of 3-methyl-2-butanol (3M2BO) to 3-methyl-2-butanone (methyl isopropyl ketone, MIPK). The utilization of organic additives, especially mannitol, during the impregnation protocol has led to the generation of a Cu/SiO2 catalyst containing highly dispersed Cu nanoparticles, i.e. high Cu surface area (SACu). These properties contributed to the high activity of the mannitol-assisted Cu/SiO2 catalyst, in which the activity was limited only by the equilibrium nature of the reaction. The proportional relationship between the formation rate of the MIPK with the SACu confirmed the benefits of the utilization of organic additives. In addition, the improvement in the SACu of Cu/SiO2 prepared using mannitol only gave a negligible side product originating from the dehydration of 3M2BO; thus, the equilibrium MIPK yield of 99.5% was achieved even at 300 °C.

Improving HCC Prognostic Models after Liver Resection by AI-Extracted Tissue Fiber Framework Analytics.

Despite advances in diagnostic and treatment technologies, predicting outcomes of patients with hepatocellular carcinoma (HCC) remains a challenge. Prognostic models are further obscured by the variable impact of the tumor properties and the remaining liver parenchyma, often affected by cirrhosis or non-alcoholic fatty liver disease that tend to precede HCC. This study investigated the prognostic value of reticulin and collagen microarchitecture in liver resection samples. We analyzed 105 scanned tissue sections that were stained using a Gordon and Sweet's silver impregnation protocol combined with Picric Acid-Sirius Red. A convolutional neural network was utilized to segment the red-staining collagen and black linear reticulin strands, generating a detailed map of the fiber structure within the HCC and adjacent liver tissue. Subsequent hexagonal grid subsampling coupled with automated epithelial edge detection and computational fiber morphometry provided the foundation for region-specific tissue analysis. Two penalized Cox regression models using LASSO achieved a concordance index (C-index) greater than 0.7. These models incorporated variables such as patient age, tumor multifocality, and fiber-derived features from the epithelial edge in both the tumor and liver compartments. The prognostic value at the tumor edge was derived from the reticulin structure, while collagen characteristics were significant at the epithelial edge of peritumoral liver. The prognostic performance of these models was superior to models solely reliant on conventional clinicopathologic parameters, highlighting the utility of AI-extracted microarchitectural features for the management of HCC.

Chemoselective vapor-phase hydrogenation of 6-methyl-5-hepten-2-one over Cu/SiO2 catalyst prepared by organic additive-assisted impregnation

Abstract Silica-supported Cu (Cu/SiO2) catalyst prepared by using organic additive-assisted impregnation was employed for the chemoselective hydrogenation of a C=O bond in 6-methyl-5-hepten-2-one (1) to produce 6-methyl-5-hepten-2-ol (2) in a vapor phase at a temperature between 140 and 200 °C and an ambient pressure of H2 flow. The Cu was responsible for the selectivity to 2, and the organic additive increased the Cu surface area (SACu), which consecutively enhanced the performance of the Cu/SiO2 catalyst. The proportional correlation between the SACu and the formation rate of 2 further confirmed the benefits of the utilization of organic additives during the impregnation protocol.

Direct Valorization of Recycled Palladium as Heterogeneous Catalysts for Total Oxidation of Methane

Electronic waste as an alternative source of palladium is used for the preparation of heterogeneous catalysts for methane oxidation. The strategy developed in this paper involves two steps: optimization of the leaching protocol to recover the Pd from the waste, and development of a suitable impregnation protocol directly from the leachate, which is a strongly acidic solution. The precipitation-deposition technique is particularly suitable for the preparation of catalysts from acidic media. The impact of Ba, Bi, and Ag impurities on the catalytic performance is studied on model catalysts. The presence of these elements and their impact on the catalytic properties are analyzed and discussed using X-ray diffraction, nitrogen physisorption, scanning and transmission electron microscopy. Through variation of the pH, the impurities co-deposited with Pd can be limited and the catalytic performance of catalysts derived from real waste can be greatly enhanced.

Conversion of glucose to fructose over Sn and Ga-doped zeolite Y in methanol and water media

In this study, we use zeolite Y as a support for the synthesis of Sn and Ga doped zeolites aimed at the isomerization of glucose to fructose. Though these materials are inactive in water, they are active in methanol and we could ascertain a reaction pathway involving a hydride shift for the interconversion of glucose to fructose and mannose, and a Brønsted acid pathway with the formation of a methyl fructoside intermediate and its hydrolysis to fructose if water was added afterwards. By using characterizations comprising: chemisorption, XPS, XRD, HAADF-STEM and EXAFS; it was possible to demonstrate that a straightforward impregnation protocol for the preparation of our catalysts, led to Sn/Y mainly consisting of small SnO2 clusters on the external surface of the zeolite, whereas Ga/Y consisting of highly dispersed Ga species mostly inside the zeolite pores; and a catalytic activity that appears to be dominated by Brønsted acid sites.

Contrast-enhanced micro-CT to assess dental pulp tissue debridement in root canals of extracted teeth: a series of cascading experiments towards method validation.

To validate a new method for the evaluation of pulp tissue debridement in the root canals of extracted teeth using an impregnation protocol involving potassium triiodide, a radiocontrast solution known as Lugol's, combined with micro-computed tomographic (micro-CT) imaging. The impact of NaOCl on the radiopacity of Lugol's solution was assessed using a two-fold dilution series of Lugol in distilled water and 5.25% NaOCl, which were then pipetted into transparent dishes and radiographed. To verify the influence of Lugol on the proteolytic effect of NaOCl, a dissolution test was performed using fresh bovine meat. Ten slices did not undergo any tissue processing, whilst twenty slices were fixed in formaldehyde for 24h. After that, 10 of them were immersed in Lugol for another 24h. Then, all specimens were placed in NaOCl and the time required for a complete tissue dissolution was recorded. For the last experiments (histological validation and micro-CT assessment), 8 extracted mandibular premolars with formerly vital pulps were immersed in buffered formalin, scanned in a micro-CT device, accessed, immersed in Lugol for 7days and scanned again. Then, the root canals of 5 teeth were prepared and scanned, and the volume of remaining pulp tissue identified and quantified, whilst 3 teeth were histologically processed. The same specimens were subjected to histological assessment, and the images of the histologic sections were registered with the corresponding micro-CT images to verify whether the pulp tissue in the histological sections matched its counterpart in the Lugol-impregnated tissues identified in the micro-CT slices. There was no discernible effect on radiopacity when NaOCl was mixed with Lugol's solution. Tissue processing did not affect the time required for the complete dissolution of fresh bovine meat. Histological evaluation revealed a correlation between micro-CT and histological images confirming the identification of Lugol-impregnated pulp tissue in micro-CT images. The radiocontrast Lugol's solution was unaffected by NaOCl and did not interfere with its soft tissue dissolution capability. The impregnation protocol using Lugol's solution allowed the visualization of pulp tissue on the micro-CT images and the identification of pulp remnants after chemical-mechanical canal procedures.

Adsorption of direct yellow brown D3G from aqueous solution using loaded modified low-cost lignite: Performance and mechanism

ABSTRACT Low-cost lignite-based, copper-containing adsorbents (Cu-raw) were developed through a simple ultrasonic impregnation protocol for enhanced adsorption of direct yellow brown D3G (DYB) from aqueous solutions while treating copper-containing wastewater. The adsorbent was characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersion spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption isotherms and kinetics were studied, and the factors that affect the adsorption, such as adsorbent dosage and solution pH, were investigated. The results showed that DYB adsorption was highly pH dependent and the isotherm of adsorption could be well described by the Langmuir-Freundlich model and the maximum DYB adsorption capacity was estimated to be 369 mg/g at 25°C. The electrostatic and chelating interactions were the main interfacial interaction mechanism, and the synergetic removal performance of lignite toward cationic metal ions and anionic dye was shown. The kinetic data were well fitted to the pseudo-second-order equation, indicating that chemical sorption was the rate-limiting step. The findings reported in this work highlight the potential of using lignite as an effective low-cost adsorbent for the removal of organic pollutants from wastewater.

Size-Dependent Vulnerability of Lumbar Motor Neuron Dendritic Degeneration in SOD1G93A Mice.

The motor neuron (MN) soma surface area is correlated with motor unit type. Larger MNs innervate fast fatigue-intermediate (FInt) or fast-fatiguable (FF) muscle fibers in type FInt and FF motor units, respectively. Smaller MNs innervate slow-twitch fatigue-resistant (S) or fast fatigue-resistant (FR) muscle fibers in type S and FR motor units, respectively. In amyotrophic lateral sclerosis (ALS), FInt and FF motor units are more vulnerable, with denervation and MN death occurring for these units before the more resilient S and FR units. Abnormal MN dendritic arbors have been observed in ALS in humans and rodent models. We used a Golgi-Cox impregnation protocol to examine soma size-dependent changes in the dendritic morphology of lumbar MNs in SOD1G93A mice, a model of ALS, at pre-symptomatic, onset and mid-disease stages. In wildtype control mice, the relationship between MN soma surface area and dendritic length or dendritic spine number was highly linear (i.e., increased MN soma size correlated with increased dendritic length and spines). By contrast, in SOD1G93A mice, this linear relationship was lost and dendritic length reduction and spine loss were observed in larger MNs, from pre-symptomatic stages onward. These changes correlated with the neuromotor symptoms of ALS in rodent models. At presymptomatic ages, changes were restricted to the larger MNs, likely to comprise vulnerable FInt and FF motor units. Our results suggest morphological changes of MN dendrites and dendritic spines are likely to contribute ALS pathogenesis, not compensate for it. Anat Rec, 303:1455-1471, 2020. © 2019 American Association for Anatomy.

Novel rhodium on carbon catalysts for the oxidation of benzyl alcohol to benzaldehyde: A study of the modification of metal/support interactions by acid pre-treatments

Rhodium nanoparticles or rhodium organometallic complexes are mainly used in catalysis for reduction or hydroformylation reactions. In this work instead, we explored the capabilities of Rh nanoparticles as an oxidation catalyst, applied to the oxidation of benzyl alcohol to benzaldehyde under very mild conditions (100 °C, and atmospheric pressure) as a model reaction. Here we report the preparation of novel Rh/C catalysts by using an impregnation protocol, with particular emphasis on the pre-treatment of the carbon supports by using HNO3 and HCl, as well as the characterization of these materials by using an array of methods involving TEM, XPS and XRPD. Our preparation method led to a wide Rh particle size distribution ranging from 20 to 100 nm, and we estimate an upper limit diameter of Rh nanoparticles for their activity towards benzyl alcohol oxidation to be ca. 30 nm. Furthermore, a HNO3 pre-treatment of the activated carbon support was able to induce a smaller and narrower particle size distribution of Rh nanoparticles, whereas a HCl pre-treatment had no effect or sintered the Rh nanoparticles. We rationalise these results by HNO3 as an acid able to create new nucleation sites for Rh on the carbon surface, with the final effect of smaller nanoparticles, whereas for HCl the effect of sintering was most likely due to site blocking of the nucleation sites over the carbon surface. The roles of acid centres on the carbon surfaces for the oxidation reaction was also investigated, and the larger their amounts the larger the amounts of by-products. However, by treatment with HNO3 we were able to convert neutral or basic carbons into supports capable to enhance the catalytic activity of Rh, and yet minimised detrimental effects on the selectivity of the oxidation to benzaldehyde.

High-resolution synchrotron-based X-ray microtomography as a tool to unveil the three-dimensional neuronal architecture of the brain

The assessment of neuronal number, spatial organization and connectivity is fundamental for a complete understanding of brain function. However, the evaluation of the three-dimensional (3D) brain cytoarchitecture at cellular resolution persists as a great challenge in the field of neuroscience. In this context, X-ray microtomography has shown to be a valuable non-destructive tool for imaging a broad range of samples, from dense materials to soft biological specimens, arisen as a new method for deciphering the cytoarchitecture and connectivity of the brain. In this work we present a method for imaging whole neurons in the brain, combining synchrotron-based X-ray microtomography with the Golgi-Cox mercury-based impregnation protocol. In contrast to optical 3D techniques, the approach shown here does neither require tissue slicing or clearing, and allows the investigation of several cells within a 3D region of the brain.

Enhanced Nano-Catalyst Infiltration of Anode-Supported SOFCs through Surface Modification of Electrodes By Catechol Surfactants

The wet impregnation/infiltration method has been a well-utilized route to incorporate nanoparticles inside the electrode architecture by co-firing the metal salt solutions that are wicked to the internal pore structure. Impregnation/infiltration of catalytically active nanoparticles brings an extension of the phase boundaries in the active area which reduces the polarization resistance. There are three main infiltration parameters that impact on reducing the electrode polarization resistance and over potential: a) nano-catalyst concentration, b) nano-catalyst location after infiltration, and c) nano-catalyst decoration. It should be noted that those factors are all interrelated and can fail or be achieved altogether. The nanocatalyst concentration is usually controlled by performing repetitive infiltration steps. In these experiments, co-firing is needed after each infiltration step, to open up free network path inside the electrode, then the process is repeated until the desired amount is achieved. One major potential risk of repetitive infiltration is the clogging of the porosity. This labor-intensive protocol also suffers from inhomogeneous deposition and gas starvation issues during the cell operation due to the inefficient decoration of the infiltrates at the active area where the deepest region of the electrode is located. Otherwise, the metal nitrate solution dries at the top or middle region of the electrode and the nano-catalysts sits far away from the active layer, hence the impact in polarization resistance reduction can be seen less. Due to these issues, there is a need to control the deposition rate and achieve a homogenous nano-catalyst distribution and reduce the number of infiltration steps. One solution is adding wetting agents to the precursor mixture to enhance the penetrability. Pressure or vacuum assisted infiltration can also help to wick the solution through the electrode. In this study, catechol-based molecules which are a specific type of bio-monomers found in the nature of multi-functional end-groups, such as dopamine, poly-norepinephrine (pNE), and derivatives are used as electrode surface modifiers. Apart from the neurotransmitter functions, these end-groups are naturally capable of strong adhesive properties when bio-monomers are linked and polymerized. The polymerized surfactant can bind with the metal cation by chelation. Within the past decades, catechol based molecules are used as bio-derived surfactants in various coating studies. Mostly, studies have been focused on planar, dense and single-phase substrates. However, SOFC electrodes of percolated porous architecture vary tens to hundreds of microns in thickness. The porosity level depends on the SOFC type and manufacturing method, but can vary between 10-50%. In addition, the electrodes consist of multi-constituents. For example, conventional anode electrode comprises nickel oxide (NiO) and yttria stabilized zirconia (YSZ) mixture and the conventional cathode is composed of lanthanum strontium manganite (La1−xSrxMnO3 , LSM) and yttria stabilized zirconia (YSZ). The motivation of this work is to monitor the long-term stability of the polymerized norepinephrine assisted CeO2, ceria nano-catalyst infiltrated commercial button SOFCs by single step infiltraton. Investigating the optimum nano-catalyst concentration for that particular off-the-shelf SOFC architecture is also a focus area for this work. The initial part of the study investigated the deposition and polymerization kinetics of the catechol-surfactant film on NiO, YSZ and LSM surfaces. Deposition parameters such as immersion time, solid loading and polymerization technique were all studied. The study aim was to pinpoint the acceptable polymerization degree and adhered film/particle layer thickness range to enhance homogeneous coating of porous SOFC electrode walls by preventing pore clogging. The experiments showed that the pNE coating layer can be tuned from 25 nm to 150 nm. In the second part of the study, these coated substrates were immersed into the cerium nitrate solution to form CeO2, ceria, nanoparticles to observe the ceria layer coarsening as a function of the pNE layer thickness and cerium precursor immersion time. The study assisted in understanding the optimal ceria decoration after the annealing process at the SOFC operating temperature (750oC). Experiments showed that tuning the immersion time and solid loading induced nano-catalyst decoration from discrete particles to film formation onto the planar substrates. The optimal protocols were applied to impregnate anode-supported SOFC button cells. The electrochemical performance and the stability of the infiltrated anode-supported SOFCs were measured over 300 hours and the performance was correlated to the decoration of the nano-catalyst impregnated electrodes. The developed impregnation protocol resulted in >20% increase in power density at 750° when the same protocol was applied to a commercial anode-supported SOFC. Acknowledgements: The authors would like to thank James Poston at NETL-Morgantown for his assistance in SEM/EDS characterization. The WVU Shared Research Facilities are also acknowledged for their assistance in materials characterization.

Cytological staining of protozoa: a case study on the impregnation of hypotrichs (Ciliophora: spirotrichea) using laboratory-synthesized protargol

ABSTRACTProtargol (silver proteinate) impregnation is a common method used to identify and characterize ciliated protozoa. Unfortunately, chemical companies have stopped producing the ‘strong’ protargol powder used in this method. Based on an in-house protocol for its synthesis published in 2013, more than 10 batches of protargol powder were produced and subsequently applied in taxonomic studies. During these studies, the protocol for protargol powder synthesis was slightly modified and employed a peptone not originally listed in the 2013 protocol. This modification improved the results of the impregnation protocol. Protargol preparations of hypotrichs were optimized by adjusting the pH during staining rather than during the synthesis. The pH was adjusted to 7.5–7.6, and an acetone developer was used. While the conditions used in this study are not completely comparable to those using the commercially produced protargol, access to this information could help researchers investigate the diversity of ciliates, particularly hypotrichs.

Bio-Surfactant Assisted Infiltration of SOFC Electrodes

Wet nano-catalyst impregnation of porous Solid Oxide Fuel Cell (SOFC) electrodes is a recognized process to enhance electrochemical performance. This impregnation method typically includes multiple pipet deposition steps of aqueous salt solutions onto the SOFC electrodes in order to achieve a desired catalyst loading level. In the current work, it was found that this labor-intensive and time-consuming process could be simplified through the use of a bio-adhesive (or bio-derived surfactant). The surfactant-assisted impregnation protocol allowed for the homogenous incorporation of a nano-catalyst within the electrode in a single salt solution deposition step. The process results in a lower electrode overpotential with enhanced long-term stability. In the current study, bio-inspired catechol-based surfactants were used to act as a wetting and local chelating agent which adhered within the 3-D electrode architectures. The work initially assessed the use of polymerized dopamine (PDA) and/or nor-epinephrine (PNE) neurotransmitters as the bio-template layer for metal oxide or hydroxide deposition. The adhered bio-template on the pore walls was shown to provide higher nano-catalyst loading by avoiding segregation of the precipitate within the porous structure, which typically results in the migration and distribution of the solute near the surface during the drying process. Another advantage of using the protocol developed in this work was that both electrodes could be infiltrated simultaneously by utilizing a simple dip-coating method within a single thermal step. Additional studies in this work focussed on the deposition and aggregate (and/or film) formation kinetics of the dopamine and epinephrine surfactants in order to better understand the nano-catalyst deposition morphology. The work investigated the deposition of these layers on YSZ substrates, which would act as an ideal surface to characterize (over the 3-D electrode layers). This work then led to the investigation of other catechol molecules, such as caffeic acid, cinnamic acid, and gallic acid onto YSZ planar substrates. In order to complete this study, commercial YSZ single crystals were submersed into surfactant solutions for 1 to 24 hours. The surface was dried and gently inscribed by a fine needle tip to measure the surfactant thickness by Atomic Force Microscopy (AFM). The result showed that the polymerization method and surfactant type had a significant effect on the adhered layer thickness, which varied from 30 to 500 nm within 24 hours of immersion time. In addition, the effect of these surfactants on the chelation and precipitation of metal oxide nano-catalyst from precursor solutions were also studied The optimal conditions were resolved from the surfactant coating studies which were used to impregnate nano-ceria (CeO2) based nano-catalyst into the electrodes of anode-supported SOFC button cells. The final studies of this work investigated the effect of the critical nano-catalyst infiltrant concentration on the fuel cell performance. Commercial button cells were infiltrated with norepinephrine (PNE) and then impregnated with different molarities of cerium salt solution for both electrodes by dip-coating method. After deposition, the samples were only exposed to a singular drying/firing step. The process achieved loadings ranging between 0.4 to 8.3 mg of nano-ceria after the firing (calcination) step at 750oC. Infiltrated cells were operated at 750oC using humidified hydrogen fuel for ~300 hours. The SOFC performance was evaluated by electrochemical impedance spectroscopy (EIS) in the 48th, 150th and 300th hours. EIS analysis showed that the infiltrated cells did not show a significantly lower resistance than the baseline cell in the first 48th hour. However, in the 150th to 300th hour, the resistance of the infiltrated cells reduced in both the high-frequency and mid-frequency regimes (associated with the anode and cathode, respectively). Furthermore, the resistance of the low-frequency regime (associate with mass diffusion) decreased between the 48th to 300th hour. The resistance relaxation in this region was probably due to increased gas diffusion related to nano-ceria sintering (and opening of the microstructure porosity). In the study, a gradual decrease in the total electrode overpotential was observed up to the 5 mg nano-ceria loading level. The cell displayed a 35% reduction in polarization over the baseline cell after 300 hours of testing. The overpotential of 8.5 mg nano-ceria infiltrated cell displayed a similar electrode overpotential value as the baseline cell after 300 h of testing (i.e., with no nano-catalyst loading). The correlation between the cell performance (as a function of loading time) to the nano-catalyst distribution/morphology is currently being investigated. In addition, methods for controlling the grain boundary migration rate using various solid-solution or secondary-phase stabilization strategies are also being investigated in order to achieve long-term stability of the infiltrated cells.

Facile synthesis of CuSO4/TiO2 catalysts with superior activity and SO2 tolerance for NH3-SCR: physicochemical properties and reaction mechanism

A series of CuSO4/TiO2 binary oxide catalysts with different CuSO4 loadings (0–20 wt%) were prepared by a facile solid state impregnation protocol.

X-ray microtomography provides new insights into vacuum impregnation of spinach leaves

Vacuum impregnation is used in the food industry to facilitate the impregnation of porous products with, e.g. firming, antioxidant, antimicrobial or cryoprotective agents. X-ray micro-tomography (μCT) was used to study the process of vacuum impregnation in spinach leaves. Low (300 mbar absolute pressure) and mild vacuum (150 mbar absolute pressure) impregnation protocols were used to impregnate an isotonic solution of trehalose in the leaves and μCT was used to make observations of the cross section of the impregnated samples and quantify their porosity. Results revealed that the free volume in the spongy mesophyll is easier to impregnate than the spaces around the palisade mesophyll. The low vacuum impregnation protocol provoked less impregnation close to the edge of the leaf than in its centre, probably accounting for an influence of the tissue structure on impregnation. The vacuum impregnation protocols tested in this investigation drastically decreased the proportion of large pores (>100 μm) and increased the proportion of small pores (<50 μm). The mild vacuum impregnation protocol, which was designed on the basis of measured apparent porosity, did not achieve full impregnation of the tissue.

Magnetite and Metal‐Impregnated Magnetite Catalysts in Organic Synthesis: A Very Old Concept with New Promising Perspectives

AbstractMagnetite is a well‐known material, with the impregnation of transition metals onto its surface being a very old protocol for preparing catalysts. However, only recently, the combination of both, magnetite and impregnation protocols, have been recognized as a powerful methodology to prepare catalysts. The impregnation protocol, of nearly all transition metals in the magnetite surface, has rendered the first generation of catalysts. These simple catalysts have been used in a very broad range of organic transformations. Thus, simple imine derivative formation or unknown reactions such as the direct cross β‐alkylation of primary alcohols, through dehydrogenation, oxidation, addition, hydrogen autotransfer, and multicomponent reactions has been accomplished using these catalysts. In most cases, these catalysts could be just isolated by magnetic decantation and reused several times without a detrimental effect on the initial results. In some cases, the study of the surface of the catalyst by means of several surface characterization techniques has permitted to determine the real species involved in the process and their structural changes within the reaction cycles. Furthermore, the post‐modification of the catalysts by reduction or oxidation of the immobilized metal, or by the addition of ligands, has enlarged the applicability of this type of catalysts.

Highly efficient mesoporous Pd/CeO2 catalyst for low temperature CO oxidation especially under moisture condition

The Pd/CeO2 catalyst was successfully prepared by an improved impregnation protocol. The resulting materials possessed relatively high specific surface area and highly dispersed Pd nanoparticles. For low temperature CO oxidation reaction, 2.5wt% Pd loaded catalyst showed the much higher reaction activity. The total conversion temperature was as low as 40°C under dry condition, much lower than that synthesized by other method. More importantly, the material also showed excellent catalytic activity and stability under moisture condition. When 2.5vol% H2O was introduced into the feed gas, the catalytic activity showed significantly enhancement, the CO total conversion temperature decreased from 40°C to 30°C. The catalytic mechanism and reaction kinetic study were also discussed in detail.

Effect of impregnation protocol in the metallic sites of Pt–Ag/activated carbon catalysts for water denitration

The influence of the Pt precursor and the impregnation protocol in the catalytic behavior of 3%Pt–1.5%Ag supported on activated carbon for water denitration in a continuous reactor was studied. Pt(NH3)4(NO3)2 and H2PtCl6 were selected as Pt precursors. Five protocols were investigated: sequential impregnations (both sequences), co-impregnation, physical mixture of monometallic catalysts, and physical mixture of a bimetallic catalyst with a Pt monometallic catalyst. The samples were characterized by XRD, XPS, TPR, HRTEM and physisorption. It was found that the catalytic activity strongly depends on the synthesis protocol and the Pt precursor, which modify the particle size. Higher nitrate rates are achieved using H2PtCl6 than Pt(NH3)4(NO3)2; this is mainly related to the smaller metal particle size of the former, evidenced by HRTEM. Nitrate consumption rate is directly related with the mean particle size. The physical mixture of monometallic catalysts resulted in the highest nitrogen rate.