Papers by Keyword: Catalytic Activity

Abstract: Recoverable and stable nanocatalysts are essential for peroxymonosulfate - based advanced oxidation processes (AOPs) in wastewater purification treatment. In this paper, Fe₃C nanorods @ nitrogen-doped carbon composites (N-Fe₃C@C) with core-shell architecture were fabricated by the co-precipitation and calcination methods, and characterized and analyzed in terms of their crystal structure, microscopic morphology, and surface chemical elements. In addition, N-Fe₃C@C-4 degraded 85.36% of tetracycline in 10 min under PMS, which was much higher than the catalytic ability of Fe₃O₄ (42.03% in 10 min). Both the active radical trapping and EPR experiments verified that ¹O₂ played a key role for degradation of organic dyes in PMS system. The investigation on the degradation mechanism revealed that the presence of the carbon layer facilitated to adsorb TC, accelerate free radical generation and promote the redox cycle of Fe²⁺/Fe³⁺ in the nanocatalyst. This study offers novel ideas for multifunctional catalysts for advanced wastewater purification treatment.

Abstract: The article deals with the pulse electrolysis energy parameters effect on the current efficiency, phase composition and morphology of the cobalt with refractory metals – tungsten and molybdenum galvanic alloys surface. Synthesized coatings corrosion resistance and synthesized coatings catalytic activity testing results in various acidity media are presented. The obtained experimental data for the various composition alloy Co-Mo-W are compared with respective indicators for individual metals. The synergy effect presence due to the alloying elements mutual influence is experimentally established.

Abstract: The most promising direction in alternative energy is hydrogen energy, using hydrogen as a secondary energy carrier. A key component in hydrogen energy is a fuel cell, especially on solid polymer membranes. Increasing the efficiency, reducing the cost and increasing the service life of such elements is the primary task of this direction. These tasks need to be solved from two sides: by improving the parameters of platinum catalysts in electrochemical reactions of energy sources, as well as by improving the qualities of the membrane. The aim of the work is to synthesize and study composites with palladium and platinum nanoparticles in hydrogen-oxygen fuel cells.

Abstract: The ecological situation in the world requires the solution of environmental problems associated with the processes of wastewater treatment, hydrogen sulfide pollution of various industrial facilities in order to remove such harmful impurities. The unpleasant odor that appears in industrial and adjacent waste processing areas is a constant concern for the protection of the environment. To solve these problems, it is advisable to use selective sorbents - complex. The introduction of metal ions into complex fibers due to the formation of a coordinated bond between the groups of the metal and the polymer ligand gives high molecular weight complex compounds. The operational and selective properties of the materials based on high-molecular-weight complex compounds can be determined by the type of metal ion introduced into macromolecules, the nature of the polymer chain, and thermodynamic stability. By changing the action of the above factors, complexites can be synthesized for use as highly selective catalysts for various chemical processes. The paper presents data on the catalytic activity of fibers with Cu²⁺, Co²⁺, Ni²⁺ ions with complexing fibers containing carboxyl, amidoxime, hydroxamic groups, using the example of the decomposition of hydrogen peroxide and oxidation of H₂S, Na₂S. An inhibitory effect on the oxidation of fiber functional groups in the pH range 5.5 - 12.5 was revealed. The operational and selective properties of materials based on complexites can be determined by the type of metal ion introduced into the macromolecules, by the nature of the polymer chain. By changing the action of the above factors, complexites can be synthesized to be used as highly selective catalysts for various chemical processes. It was found that the catalytic activity of the complex depends on pH, the stereochemistry of the coordination centers in the fiber matrix and significantly exceeds the activity of model low-molecular-weight complex compounds.

Abstract: In this study different pathways for obtaining activated carbon with catalytical activity were analysed. Industrially fast pyrolysis is an efficient way of lignocellulosic biomass processing, since in this process various important high value chemicals are obtained. Biochar is obtained as the by-product in fast pyrolysis process from which activated carbon can be acquired with further chemical activation. Different methods for chemical activation of biochar were tested with the obtained activated charcoals being used as a catalyst in esterification reactions to evaluate their potential use as a heterogenic catalyst. Highest catalytical activity was observed when biochar was pre-treated with sulfuric acid at 80 °C for 24 hours. The obtained activated charcoal could be used as a catalyst for up to five times with no noticeable decrease in catalytic activity.

Abstract: Ni/Cu/Fe mixed metal oxides (Ni/Cu/Fe-MMOs) were prepared by calcination of Ni/Cu/Fe layered double hydroxides (Ni/Cu/Fe-LDHs) precursors. Their composition, structure and morphology were characterized by ICP, XRD, FT-IR, BET and SEM. Ni/Cu/Fe-MMOs were used for catalytic removal of NOx by hydrocarbon. Their catalytic activities were studied by NOx analyzer. The results show that Ni/Cu/Fe-MMOs have homogeneous distribution of hexagon with particles size around 30~50nm and specific surface areas of 10~35 m²∙g^–1. Ni/Cu/Fe-MMOs sample with molar ration of Ni/Cu/Fe = 5:1:3 exhibits the highest NOx conversion of 15.3%. Ni/Co/Cu/Fe-MMOs have better catalytic activities than both Ni/Cu/Fe-MMOs and Cu/Co/Fe-MMOs. For Ni/Cu/Fe-MMOs, propene is the better reductant than octane.

Abstract: ZnO nanoparticles (ZnO NPs) were synthesized through surfactant free non-hydrolytic organic phase method in which zinc acetate and zinc acetylacetonate were selected as precursors. Structural and size analysis of the as-prepared nanoparticles performed on X-ray diffractometer, transmission electron microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy showed that the obtained nanoparticles were crystalline particles with all reflections matching to wurtzite. TEM images revealed that ZnO NPs from synthesis in which zinc acetate involved as precursor had a shape of sphere while zinc acetylacetonate resulted in rod-shaped nanoparticles. Reaction rates from catalytic activity test performed on Methylene Blue dye (MB) were found to be 2.99×10^-2 min^-1 and 1.98×10^-2 min^-1 for spherical and rod-shaped ZnO NPs, respectively. Antibacterial activity experiments shows rod-shaped ZnO NPs almost completely (99.75%) inhibited the growth of Escherichia Coli while only around 6.5% was survived after treatment of spherical ZnO NPs under same conditions.

Abstract: A novel supported catalyst is prepared through immobilization of water soluble phthalocyanine, which is synthesized by modifying tetraminophthalocyanine with cyanuric chloride, onto the supporting material Mg-Al hydrotalcite via co-precipitation method. The structure of the catalyst is characterized by infrared spectroscopy instrument (FT-IR) and X-ray diffractometer. Catalytic activity is examined through comparative experiments. The results show that it exhibits high catalytic activity for degradation of methylene blue (MB) in the presence of H₂O₂, the remaining rate of MB is 12.02% after 6 h. The reaction process conforms to the equation of pseudo-first-order kinetics, and the correlation coefficient R²> 0.99. The recycling tests for five times are also carried out and prove its reusability in catalytic application.

Abstract: This paper discusses the catalytic activity of ZnO/CuO/nanographene platelets composites under visible light and ultrasound irradiation separately. The ZnO/CuO/nanographene platelets composites were synthesized using a sol-gel method. X-ray diffraction and nitrogen adsorption spectroscopy were employed to investigate the structural and surface area of the catalyst. The catalytic activity results showed that the presence of nanographene platelets in ZnO/CuO nanocomposites improved its efficiency in degrading methylene blue. A scavenger method was also used to understand the role of charged carriers and the active radical involved in the catalytic activity.

Abstract: Recent applications of transition metal nanoferrites as catalyst in thermal decomposition of ammonium perchlorate (AP) and combustion of composite solid propellant (CSP), have been reviewed. Catalytic applications include the use of mainly cobalt, nickel, copper, zinc, manganese, cadmium nanoferrites, as well as their mixed-metal combinations. The nanoferrites are obtained mainly by wet-chemical, sol-gel, solvo-thermal, auto-combustion and co-precipitation methods. Addition of nanoferrites to AP led to shifting of the high temperature decomposition peak toward lower temperatures which shows their catalytic activity. The burning rates of CSPs have also been enhanced by these nanoferrites. Contents of Paper