Catalytic Composition Research Articles

In English

Among the studied (Pd), Co-, Ce-, Zr-oxide catalysts including catalysts deposited on structured cordierite support, the catalyst prepared by co-deposition of ceria and cobalt oxide is characterized by higher activity in reaction of reduction of nitrogen (I), (II) oxides (CO + NO, N 2 O + NO + CO) compared with samples prepared by successive deposition. This may be caused by an increase in both mobility of surface oxygen and dispersity of components in the catalytic composition.

Hydrotreatment of petroluem on Ni6-PMo n W(12–n)(S)/Al2O3 catalysts

The dependence of the catalytic activity of nickel–molybdenum–tungsten sulfide catalysts on the Mo/W molar ratio is studied in order to develop an effective catalytic composition for the hydrorefining of petroleum. Threemetallic catalysts of Ni6-PMonW12–n/Al2O3 composition, where n = 0–12 (Ni6-PMonW12–n(S)/Al2O3 after sulfurizing), are synthesized. The morphology of the active-phase particles of sulfide samples is investigated using high-resolution transmission electron microscopy. The average length of NiMo(W)S phase layers, the average number of layers in a crystallite, the number of Mo(W) atoms in a layer, and the fraction of Mo(W) atoms in the rib and angular positions are calculated. The effect of the Mo/W molar ratio on the catalytic activity of the prepared samples is studied during the dibenzothiophene hydrogenolysis, hydrodesulfurization (HDS), and hydrogenation of olephins and aromatic compounds when hydrotreating diesel fractions and vacuum gas oil. A sample with molar ratio Mo: W = 1: 1 was found to be the one most active in the reactions of HDS and hydrogenation.

Tracing dissolved organic matter (DOM) from land-based aquaculture systems in North Patagonian streams

Chile is the second largest producer of salmonids worldwide. The first step in the production of salmonids takes place in land-based aquacultures. However, the effects of the discharge from these aquacultures on stream dissolved organic matter (DOM) content, molecular composition and degradability are unknown. The aim of this study was thus to investigate the inputs of anthropogenic DOM from land-based aquaculture to the predominantly pristine river systems of North Patagonia. We hypothesized, that i) DOM exported from land-based aquaculture mainly consists of protein-like fluorescence (tyrosine and tryptophan) released from fish feces and food remains, and that ii) this DOM is highly degradable and therefore rapidly turned-over within the receiving streams. In the North Patagonian region we conducted a screening of ten land-based aquacultures and an intensive sampling campaign for one aquaculture. This was combined with longitudinal transects and a degradation experiment in order to couple the composition of DOM exported from land-based aquacultures to its degradability in streams. We measured dissolved organic carbon (DOC) concentration by high-temperature catalytic oxidation and DOM composition by fluorescence spectroscopy and parallel factor analysis. In the effluent of the ten screened aquacultures and in the repeated sampling of one aquaculture, we consistently found an increase of DOC concentrations and a dominance of protein-like fluorescence. The protein-like fluorescence rapidly disappeared downstream of the aquacultures, and in the degradation experiment. 21% of the DOC export from the repeatedly sampled aquaculture resulted from food addition and 76% from fish production. We conclude that large amounts of degradable DOM are exported from land-based aquacultures. This probably has strong effects on the ecological structure and function of North Patagonian streams, and similarly affected streams worldwide.

Mixed Oxides FeVOx for Selective Oxidation of Octanol to Octanal under Solvent‐free Condition

AbstractThe two‐component mixed oxides FeVOx with various molar ratio of Fe to V were prepared and their phase composition, structure and morphology were determined by XRD and SEM. This prepared material was employed for liquid‐phase oxidation of octanol using H2O2 as oxidant. The mixed oxide FeVOx with 2.5 : 1 of Fe to V molar ratio was found to be an effective catalyst with high selectivity to octanal under solvent‐free condition. The relationship between the catalytic performance and phase compositions of the mixed oxides was investigated by the test of its activity and XRD characterization. The catalytic action of the active sites including redox and acidic sites formed by interaction between VOx and FeOx on the surface of the catalyst was discussed. The catalyst was easily recovered and reused.

Formation and Study of Porous Alumina and Catalytic Coatings by the Use of Cold Gas Dynamic Spraying Method

Cold gas dynamic spraying was used to obtain coatings based on γ-Al2O3 and Pd-CeO2/γ-Al2O3 catalyst on a stainless steel foil. The coatings were studied by thermal cycling, BET, SEM, TEM, and XPS methods. The textural and adhesion characteristics of the coatings were found to depend on the composition of initial alumina powders with metallic aluminum (weight ratios of the components were varied from 2:8 to 8:2). It was shown that a mixture containing 25% γ-Al2O3 and 75% Al provides the optimal properties of the coatings. The effect produced by a method of the active component introduction into the coating on the catalytic properties of samples was examined. A considerable advantage of Pd introduction by impregnation in the preliminarily sprayed γ-Al2O3 layer over the direct spraying of the finished catalytic composition on the foil was demonstrated.

Iron-based catalytic systems in atom-transfer controlled-radical-polymerization processes

The literature data about the use of catalytic systems and compositions based on iron and its complexes for the controlled synthesis of polymers via the atom-transfer mechanism are generalized and analyzed. The effects of the oxidation number of a metal atom, the ligand environment, the structure of a radical initiator, the activating additives, and other factors on the molecular-weight characteristics of the polymers and the kinetics of vinyl polymerization are considered.

Cu-Zn-Al-O catalysts for the oxidative desulfurization of dibenzothiophene, a typical sulfur-containing compound of the diesel fraction

The possibility of oxidative desulfurization of dibenzothiophene dissolved in toluene as a model organosulfur compound of diesel fuel in the presence of catalytic CuZnAl compositions was studied. It was shown that the CuZnAl catalysts at 350–450°C ensure sulfur removal from the model fuel to the extent of up to 40–45%. Part of the sulfur is removed as SO2, and some sulfur is absorbed on the catalyst surface.

CuII(Sal-Ala)/CuAlLDH Hybrid as Novel Efficient Catalyst for Artificial Superoxide Dismutase (SOD) and Cyclohexene Oxidation by H2O2

This work presents Cu II (Sal-Ala) complex immobilized on the CuAlLDH as a novel efficient catalyst for artificial superoxide dismutase (SOD) enzyme activity and cyclohexene oxidation. The physico-chemical prop- erties of Cu II (SalAla)/CuAlLDH were investigated by XRD, XPS, FTIR, DRUV and TGA techniques. The correlation between the catalytic performances, structure and composition of the hybrid catalyst is also discussed.

Probing the catalytic activity of bimetallic versus trimetallic nanoshells

The synthesis of trimetallic nanoparticles represents an emerging strategy to maximize catalytic performances in noble metal-based catalysts. However, the controllable synthesis of trimetallic nanomaterials as well as the exact role played by the addition of a third metal in their composition over catalytic performances remains unclear. In this paper, we describe the synthesis of trimetallic nanoshells having AgAuPd, AgAuPt, and AgPdPt compositions by a sequential galvanic replacement reaction approach between Ag nanospheres as sacrificial templates and the corresponding metal precursors, i.e., AuCl4 − (aq), PdCl4 2− (aq), and/or PtCl6 2− (aq). In each of these systems, the composition could be systematically tuned by varying the molar ratios between Ag and each metal precursor. Nanoshells having Ag56Au28Pd16, Ag78Au9Pt13, and Ag71Pd16Pt13 compositions were employed as model systems to investigate the effect of the addition of the third metal in their composition over the catalytic activities toward the 4-nitrophenol reduction. Our data demonstrate a significant enhancement in conversion percentages and thus the catalytic activities relative to the sum of their bimetallic counterparts, and this increase was dependent on the nature of the metals, corresponding to 826, 135, and 56 % for Ag56Au28Pd16, Ag78Au9Pt13, and Ag71Pd16Pt13 nanoshells relative to their bimetallic analogs. The results presented herein demonstrate the strong correlation between catalytic activity and composition in multimetallic nanoshells, and that the incorporation of a third metal may represent a promising approach to boost catalytic activities for a variety of transformations.

ChemInform Abstract: 2‐(1‐Hydroxypropyn‐2‐yl)‐1‐vinylpyrroles: The First Successful Favorsky Ethynylation of Pyrrolecarbaldehydes.

AbstractThe reaction is achieved by the super basic catalytic composition NaOH/EtOH/DMSO.

Elucidating the catalytic subunit composition of distinct proteasome subtypes: a crosslinking approach employing bifunctional activity-based probes.

In addition to two well-recognized proteasome subtypes-constitutive proteasomes and immunoproteasomes-mounting evidence also suggests the existence of intermediate proteasome subtypes containing unconventional mixtures of catalytic subunits. Although they appear to play unique biological roles, the lack of practical methods for detecting distinct proteasome subtypes has limited functional investigations. Here, we report the development of activity-based probes that crosslink two catalytic subunits within intact proteasome complexes. Identification of the crosslinked subunit pairs provides direct evidence of the catalytic subunit composition of proteasomes. Using these probes, we found that U266 multiple myeloma cells contain intermediate proteasomes comprising both β1i and β2, but not β1 and β2i, consistent with previous findings with other cell types. Our bifunctional probes can be utilized in functional investigations of distinct proteasome subtypes in various biological settings.

Abstract 3236: Development of a novel cross-linking strategy to identify distinct proteasome subtypes

Abstract Introduction: This research was conducted to develop a practical method to identify distinct proteasome subtypes. Approval of the proteasome inhibitors bortezomib and carfilzomib for clinical use has validated the proteasome as an anticancer target. These inhibitors target two well-recognized proteasome subtypes, the constitutive proteasome and the immunoproteasome, which comprise distinct sets of catalytic subunits. Additional proteasome subtypes containing mixtures of constitutive and immunoproteasome catalytic subunits have more recently been identified. These intermediate proteasome subtypes display unique proteolytic activity profiles and play important roles in the production of certain tumor antigens. However, much regarding their regulation, functions, and relevance as drug targets remains unknown, largely due to limitations in current experimental methods used to differentiate between proteasome subtypes. We have therefore developed bifunctional activity-based probes capable of cross-linking different catalytic subunit pairs within individual proteasome complexes. These probes allow a straightforward readout of proteasome catalytic subunit composition and facilitate functional studies of distinct proteasome subtypes. Experimental Procedures: Bifunctional proteasome probes were synthesized by coupling pairs of proteasome inhibitors via linkers of varying lengths and compositions. Positions for inhibitor derivatization were selected based on computational modeling, and linkers were chosen based on distances between the active sites of each targeted subunit pair. The ability of these compounds to cross-link distinct catalytic subunit pairs in both purified proteasomes and in cancer cell lysates was visualized by western blotting analysis. Competition assays with subunit-selective proteasome inhibitors were employed to confirm the identities of the cross-linked subunit pairs. Data Summary: The structures of the bifunctional proteasome probes were confirmed by mass spectrometry and nuclear magnetic resonance spectroscopy. Western blotting results demonstrated the ability of these compounds to cross-link multiple pairs of proteasome catalytic subunits, allowing the composition of distinct proteasome subtypes present within cancer cells to be evaluated. Conclusions: We have successfully developed a set of bifunctional proteasome probes for analysis of proteasome catalytic subunit composition. These probes will be used to elucidate the unique functions of distinct proteasome subtypes present within cancer cells. Citation Format: Kimberly C. Carmony, Do-Min Lee, Lalit Kumar Sharma, Jieun Park, Kyung-Bo Kim, Wooin Lee. Development of a novel cross-linking strategy to identify distinct proteasome subtypes. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3236. doi:10.1158/1538-7445.AM2014-3236

Enhancement of Electrochemical Oxidation of Ammonia and Ammonium Carbonate over Pt Black Catalysts through Interaction with Manganese Dioxide Nanoparticles

In this study, the potential of ammonia (NH3) and ammonium carbonate ((NH4)2CO3) was investigated as alternative fuels of the fuel cell platform. Considering that the anodic oxidation activity of the ammonia compounds is the key for the overall cell performance, this study focused on its improvement by way of including a catalytic additive, which aided in decreasing the use of a precious metal catalyst. Manganese dioxide (MnO2) was chosen for that purpose. Four different types, specifically alpha (α), beta (β), gamma (γ), and delta (δ), were prepared and tested via an electrochemical analysis. A cyclic voltammetry (CV) test was performed with physically mixed catalytic compositions as nanocomposites, such as 20:80, 50:50, 80:20, 90:10, and 95:5. Among these, only 95 wt % Pt and 5 wt % γ-MnO2 exhibited an intended activity increase. Although the replaced amount of Pt was not very substantial, the increase in power density at least doubled in a single cell test. This study supported the notion that ammonia ...

Determination of organogenic elements in the composition of functional compounds and materials

The presented analysis methods (automatic and gravimetric) are used to determine the main composition of various organic functional materials such as paramagnetic chelating agents for the synthesis of molecular magnetics, polyfluoroaromatic compounds for the preparation of special latices, new antivirus and analgesic agents, photoinitiator compounds for cationic polymerization, fluorophores for organic light emitting diodes, and so on. Conditions for the quantitative formation of final products of the complete decomposition of the compound (CO2, H2O, N2, SO2) are shown: the application of special oxide catalytic compositions and also the use of selectively adsorbing reagents for the removal of compounds hindering the determination of organogenic elements. Their determination error does not exceed ±0.3 % abs.

Preparation of biodiesel from soybean oil catalyzed by Al-Ca hydrotalcite loaded with K2CO3 as heterogeneous solid base catalyst

A novel heterogeneous solid base catalyst was prepared with the support of Al-Ca hydrotalcite, the load of K2CO3 and successfully applied to the transesterification of soybean oil with methanol to biodiesel (fatty acid methyl esters). The prepared catalysts were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer, transmission electron microscopy, thermogravimetry analysis, differential scanning calorimetry and the Hammett indicator methods. The results indicated that K2CO3 loaded to Al-Ca hydrotalcite was decomposed into catalytic active compositions of K2O and Al–O–K. The effect of various parameters such as reaction temperature, amount of catalyst, reaction time and the amount of methanol on the catalytic active was investigated. The optimal reaction conditions were obtained by this experiment: a methanol/oil mole ratio of 13:1, a reaction temperature of 65°C, a catalyst amount of 2.0wt.% and a reaction time of 2.0h. The catalyst has longer lifetime and biodiesel yield could be still over 87.4% after being used for four cycles.

Synthesis of poly(norbornene-co-styrene) copolymers containing high styrene incorporation using bis(β-ketoamino) copper catalysts

Poly(norbornene-co-styrene) copolymers were synthesized by copolymerizations of norbornene (NB) and styrene (St) with bis(β-ketoamino) copper complexes [ArNC(R)CHC(R)O]2Cu (1, Ar = 2,6-dimethylphenyl, R = CH3; 2, Ar = 2,6-diisopropylphenyl, R = CH3; 3, Ar = 2,6-diisopropylphenyl, R = CF3) in the presence of methylaluminoxane (MAO). The influences of catalyst structure, comonomer feeding ratio, n(Al)/n(Cu) molar ratio, and copolymerization temperature on catalytic activity and compositions of the copolymers were typically investigated. Determination of the reactivity ratios shows a much high reactivity for norbornene (r(NB) = 19.52, r(St) = 0.48), which supports a coordination mechanism. The structural characterizations of the obtained poly(NB-co-St) copolymers show that styrene units are successfully incorporated into norbornene sequences, and isolated styrene or very short styrene sequences are randomly distributed on the copolymer chain. A high incorporation of styrene up to 35.6 mol% in the poly(NB-co-St) copolymer can be achieved by bis(β-ketoamino) copper catalyst 1.

A FRET-based approach for identification of proteasome catalytic subunit composition.

Mammalian cells have two main types of proteasomes, the constitutive proteasome and the immunoproteasome, each containing a distinct set of three catalytic subunits. Recently, additional proteasome subtypes containing a non-standard mixture of catalytic subunits have gained increasing attention, especially due to their presence in cancer settings. However, practical methods for identifying proteasome subtypes have been lacking. Here, we report the development of the first fluorescence resonance energy transfer (FRET)-based strategy that can be utilized to identify different proteasome subtypes present within cells. We have developed FRET donor- and acceptor-probes that are based on previously reported peptide epoxyketones and selectively target individual proteasome catalytic subunits. Using the purified proteasome and cancer cell lysates, we demonstrate the feasibility of a FRET-based approach for determining the catalytic subunit composition of individual 20S proteasome subtypes. Ultimately, this approach may be utilized to study the functions of individual proteasome subtypes in cells.

Correlations between the catalytic layer composition, the relative humidity and the performance for PEMFC carbon aerogel based membrane electrode assemblies

The parameters influencing the water management or the gas diffusion have a large impact on the performances of the PEMFC. In this work, we focused on the influence of the composition of the cathode catalytic layer on the performance of the MEA in relation to the relative humidity. A carbon aerogel was synthesized as catalyst support with a texture minimizing diffusive losses. We studied the influence of the Nafion content by preparing various cathode catalytic layers whose hydric properties were modified by adding PTFE as a hydrophobic agent. We evaluated the impact of the cathodic relative humidity by testing MEAs on a single cell test bench. We showed that modifying the composition of the catalytic layers playing on the content of both Nafion and PTFE, enables to improve the performance due to a better water management. The best performance was obtained with a Nafion/Carbon mass ratio (N/C) of 0.5 and a PTFE/Carbon (PTFE/C) mass ratio of 0.35 allowing 40% more power at 0.4 V and 75%RH. A first positive evaluation of the impact of PTFE is also done with TEC10E40E.

Modulated crystalline Ag-Ci oxygen-evolving catalysts for electrocatalytic water oxidation

In this paper we synthesized a crystalline Ag-Ci oxygen-evolution catalyst with an entirely new composition and structure in situ in a carbonate solution (pH = 8.3) with Ag+ at 70 °C. We studied the factors that influenced the synthesis of the oxygen-evolution catalyst (electrolyte environment temperature, silver ion concentration, concentration of carbonates) under mild conditions. The structure, morphology, composition, and catalytic activity of Ag-Ci catalyst were analyzed using techniques such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical measurements. Our results showed that the diffraction peaks of the Ag-Ci catalysts synthesized at 70 °C were consistent with the AgO phase and that the catalytic composition of the Ag-Ci catalyst was the AgⅠO/AgⅡO redox couple. The oxygen-evolution rate of the catalyst synthesized in a carbonate solution (pH = 8.3) at 70 °C was 50 times higher than that synthesized at 5 °C (18.3 μmol h−1); additionally, its oxygen evolution overpotential decreased to 246.7 mV. The electrolyte solution and Ag+ ion concentration greatly impacted the catalytic activity of the Ag-Ci catalyst for water splitting.

Technology of catalytic processing of chark chemical tar

The effective technology of catalytic cracking of high-boiling fractions of tar in the presence of the suspension catalytic compositions is developed. The technology differs from applied technologies in industryby that the process is carried out directly in the reactor at a temperature of 4200C. It is shown at use of the catalyst Ba -AI-Si the yield of liquid products reaches 84,0 % including an yield of petrol fractions with boiling temperature to 1800C 34,0% that is approximately higher in 2 times, than at process implementation without the catalyst. Optimality of the catalyst was confirmed by increase of petrol fraction of isoparaffin up to 59,3 mas. %.