Volume 6, Issue 6

Cobalt supported on alumina (10 wt% Co/Al 2 O 3 ) was synthesized by three different methods; sol-gel (SG), microemulsion (ME) and impregnation (IMP). The materials were characterized by the Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), X-ray fluorescence, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Their catalytic activity was investigated toward the formation of Biginelli reaction products, 3,4-dihydropyrimidin(1 H )-ones (DHPMs). The catalysts were found to be efficient for this reaction with yields between 50% and 71% and can be reused without great loss of efficiency. Among the catalytic systems, that prepared by the SG method is the most active with 71% of DHPMs yield under solvent free conditions at 100°C for 1 h of reaction time.

A comparison activity of phenol and its derivatives in carboxylation reaction with sodium ethyl carbonate was carried out (the ratio between substrate and sodium ethyl carbonate was 2:1, T=185°С, Pco 2 =10 atm, τ=7 h). p-Cresol, p-chlorophenol, phenol, m-cresol, p-fluorophenol, p-bromophenol, and m-chlorophenol showed the highest activity in this reaction. o-Cresol and o-chlorophenol showed moderate activity but 2,4-dichlorophenol did not enter into the reaction. The optimum conditions for the carboxylation reaction of phenol with sodium ethyl carbonate under microwave irradiation was determined (microwave irradiation power 450 W, duration 9 min; the ratio of the initial reagents, phenol, and sodium ethylcarbonate was 1.5:1). A comparison activity of phenol and its methyl- and halogen substituted derivatives in the carboxylation reaction with sodium ethyl carbonate under microwave irradiation was conducted. The reaction proceeded in accordance with the rule of electrophilic substitution reaction of aromatic compounds and, in all cases, went selectively into the o-position to form corresponding phenol carbonic acid derivatives with yields ranging from 6.8%–39.5%.

The present work describes a facile, convenient, and green pathway for MnO 2 nanoparticles (MnNPs) synthesis using manganese acetate salt as a precursor and methanolic extract of Phyllanthus amarus as a reducing agent. Curcumin extracted from turmeric was used as a stabilizing agent. The characterization of MnNPs was performed using ultraviolet-visible (absorption and emission), Fourier transformed-infrared (FT-IR), thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and selected area electron diffraction pattern (SAED) techniques. The vibrational mode of O–Mn–O observed at around 580 cm −1 in the FT-IR spectra confirms their occurrence. The morphology of MnO nanorods was investigated from Scanning electron microscopy (SEM) and TEM studies. The diffraction patterns revealed the crystalline nature of MnO 2 . The solid-state fluorescence investigations of MnNPs exhibited an emission intensity at 518 nm revealing the crystallinity of the sample. The results emphasized the potent application of Phyllanthus amarus extract for the synthesis of MnNPs with economic viability and ease in scaling up for mass production.

The kinetics of isothermal green microwave-assisted extraction of caffeine from guarana seed powder with water at a temperature range from 40°C to 60°C was investigated. The caffeine concentration in the water extract was determined by UV-Vis spectrophotometry. By applying the isoconversional method, it was established that the kinetics of the caffeine extraction from the guarana seed powder with microwave heating is an elementary kinetic process. The model fitting method was used to determine the kinetic model of the caffeine extraction under microwave heating. It was found that the kinetics of the caffeine extraction can, under microwave heating, be modeled by the Jander’s model of three dimensional diffusion. The kinetic parameters, activation energy and pre-exponential factor of the caffeine extraction were determined.

This study investigated the adsorption capacities of various contaminants on glucose-derived hydrochar (GH) and glucose-activated carbon (GAC) functionalized with triethylenetetramine (TETA). The two-stage synthesis process consisted of (1) hydrothermal carbonization using various TETA concentrations (1%–5%) to create TETA-functionalized GHs, and (2) chemical activation with NaOH to produce TETA-GACs. The basic properties of the adsorbents were examined using Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. The adsorption characteristics of the GH and GAC samples toward two heavy metal ions (Pb 2+ and Cu 2+ ), phenol, methylene green (MG5), and acid red 1 (AR1) were also examined. The results indicated that GAC 1% and GH 1% exhibited excellent adsorption capacities. Specifically, the maximum adsorption capacities of GAC 1% and GH 1% reached 370 mg/g and 128 mg/g for Pb 2+ , 208 mg/g and 84 mg/g for Cu 2+ , 196 mg/g and 137 mg/g for phenol, 175 mg/g and 67 mg/g for MG5, and 156 mg/g and 21 mg/g for AR1, respectively. In conclusion, amine functionalization on the surface of GHs and GACs efficiently enhances the removal capacities of various contaminants in water.

With the goal of adding the appropriate amount of SrCO 3 to coal, the synergistic effects of SrCO 3 and desulfurization agents were studied by using a sulfur determination device and a carbon–sulfur spectrometer. Mineral constituents were investigated with an XRD diffraction analyzer. Results show that, at a given temperature, desulfurization efficiency increased in varying degrees based on the proportion of added SrCO 3 . An increasing amount of calcium sulphoaluminates also appeared in the ash residue. Meanwhile, SrCO 3 , sulfur capture capacity improved when the temperature reached 1200°C because of the large amount of generated calcium sulphoaluminates (3CaO·3Al 2 O 3 ·CaSO 4 ) and the controlled decomposition of CaSO 4 . At temperatures of 1200°C–1300°C, the ascending rate of the sulfur-fixing ratio decreased due to the sharp decomposition of CaSO 4 and the pyrolysis of a small amount of calcium sulphoaluminate. From 1300°C, the decomposition of increasing amounts of calcium sulphoaluminate gradually worsened the desulfurization. The diffraction peak of calcium sulphoaluminate was the strongest at 1300°C and the sulfur-fixing ratio was also the largest. Therefore, calcium sulphoaluminate reached the highest level at this temperature.