Thermal Stability of Potassium-Promoted Cobalt Molybdenum Nitride Catalysts for Ammonia Synthesis

The application of cobalt molybdenum nitrides as ammonia synthesis catalysts requires further development of the optimal promoter system, which enhances not only the activity but also the stability of the catalysts. To do so, elucidating the influence of the addition of alkali metals on the structural properties of the catalysts is essential. In this study, potassium-promoted cobalt molybdenum nitrides were synthesized by impregnation of the precursor CoMoO4·3/4H2O with aqueous KNO3 solution followed by ammonolysis. The catalysts were characterized with the use of XRD and BET methods, under two conditions: as obtained and after the thermal stability test. The catalytic activity in the synthesis of ammonia was examined at 450 °C, under 10 MPa. The thermal stability test was carried out by heating at 650 °C in the same apparatus. As a result of ammonolysis, mixtures of two phases: Co3Mo3N and Co2Mo3N were obtained. The phase concentrations were affected by potassium admixture. The catalytical activity increased for the most active catalyst by approximately 50% compared to non-promoted cobalt molybdenum nitrides. The thermal stability test resulted in a loss of activity, on average, of 30%. Deactivation was caused by the collapse of the porous structure, which is attributed to the conversion of the Co2Mo3N phase to the Co3Mo3N phase.

Triethylamine–Water as a Switchable Solvent for the Synthesis of Cu/ZnO Catalysts for Carbon Dioxide Hydrogenation to Methanol

Cu/ZnO catalyst precursors for industrial methanol synthesis catalysts are traditionally synthesised by coprecipitation. In this study, a new precipitation route has been investigated based on anti-solvent precipitation using a switchable solvent system of triethylamine and water. This system forms a biphasic system under a nitrogen atmosphere and can be switched to an ionic liquid single phase under a carbon dioxide atmosphere. When metal nitrate solutions were precipitated from water using triethylamine–water as the anti-solvent a hydroxynitrate phase, gerhardite, was formed, rather than the hydroxycarbonate, malachite, formed by coprecipitation. When calcined and reduced, the gerhardite precursors formed Cu/ZnO catalysts which showed better productivity for methanol synthesis from CO2 hydrogenation than a traditional malachite precursor, despite their larger CuO crystallite size determined by X-ray diffraction. The solvents could be recovered by switching to the biphasic system after precipitation, to allow solvent recycling in the process, reducing waste associated with the catalyst synthesis.

In vitro biofabrication of silver nanoparticles: Optimization, characterization, and activity against beta-lactamases-resistant Enterococcus faecalis

The rate at which nosocomial infections have spread throughout the globe has been alarming. Therefore, the data presented here sheds light on some aspects of AgNPs as promising anti-infective therapy. However, knowledge on the safe usage of AgNPs in the field of medicine is necessary to investigate. AgNPs synthesis, optimization, characterization, and mode of action against Enterococcus faecalis have been studied in this paper. We propose a combination of cell-free supernatant (C-FS) of the intimate organisms; Fusarium solani and Comamonas aquatica as synthesis catalysts. The optimization findings were at pH 9.0 for 72 h in 1 mM AgNO3 using 1:2 v/v (C-FS : AgNO3). UV-vis absorption peak appeared at 425 nm and the crystalline nature of synthesized particles was verified by XRD. FTIR analysis confirmed the presence of protein molecules that acted as reducing and stabilizing agents. Energy-dispersive X-ray analysis exhibited an intense peak at 3 KeV, confirming the formation of AgNPs. Further, FE-SEM images prove AgNPs synthesis. TEM and AFM analysis demonstrated that fabricated AgNPs were relatively monodispersed, approximately spherical, and of size 2-7.5 nm. The growth and biofilm of nosocomial E. faecalis were significantly decreased by the action of AgNPs. Furthermore, antibiotic resistance genes, blaTEM, and blaCTX, were detected in E. faecalis; both genes were degraded enormously via 9 % AgNPs. This is the first study proposing alternative sources to form AgNPs via synergistic metabolites of F. solani and C. aquatica. The results here offer a foundation for developing an effective therapy using AgNPs against nosocomial pathogens.

Combination of Cu/ZnO Methanol Synthesis Catalysts and ZSM-5 Zeolites to Produce Oxygenates from CO2 and H2

Cu/ZnO methanol catalysts were deposited over several ZSM-5 acid zeolites to directly synthesise oxygenates (methanol and dimethyl ether) from a CO2/H2 feed. Catalysts were prepared by two different preparation methodologies: chemical vapour impregnation (CZZ-CVI) and oxalate gel precipitation (CZZ-OG). Chemical vapour impregnation led to Cu/ZnO being deposited on the zeolite surface, whilst oxalate gel precipitation led to the formation of Cu/ZnO agglomerates. For both sets of catalysts a higher concentration of mild and strong acid sites were produced, compared to the parent ZSM-5 zeolites, and CZZ-CVI had a higher concentration of acid sites compared to CZZ-OG. Nevertheless, CZZ-OG shows considerably higher oxygenate productivity, 1322 mmol Kgcat−1 h−1, compared to 192 mmol Kgcat−1 h−1 over CZZ-CVI (ZSM-5(50), 250 ℃, 20 bar, CO2/H2 = 1/3, 30 ml min−1), which could be assigned to a combination of smaller particle size and enhanced methanol mass transfer within the zeolites.

Isomorphic titanium-substituted mesoporous SBA-16 as support for cobalt Fischer–Tropsch synthesis catalysts: Balance between dispersion and reduction

The delicate balance between dispersion and reduction of the Co-based Fischer–Tropsch synthesis catalyst is the golden key to enhancing catalytic performance, which highly depends on an optimized metal–support interaction. In...

Short-channel mesoporous SBA-15 silica modified by aluminum grafting as support for CoRu Fischer-Tropsch synthesis catalysts

Highly ordered short-channel mesoporous silica SBA-15 with large pores (11.2 nm) has been synthesized by using tetramethyl orthosilicate (TMOS) as silica source, the amphiphilic block copolymer Pluronic PE-10400 as structure-directing...