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RSC Adv ; 12(43): 27793-27808, 2022 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-36320253


Thiosemicarbazone-linked 3-acetylpyridine (T3AP), was synthesized and tested on copper strips in hydrochloric acid. Gravimetric measurements and electrochemical impedance spectroscopy were used to investigate the optimized inhibitory behavior of T3AP using the response surface methodology (RSM), with the optimized result obtained using a temperature of 42.90 °C, acid concentration of 2.38 M, inhibitor concentration of 3.80 mM, and time of 18.97 h, with inhibition efficiency up to approximately 93%. Validation of the experimental and predicted RSM showed that no significant difference in the inhibition efficiency with the confidence level value up to 97% was obtained. The isotherm study shows that T3AP obeys the Langmuir isotherm adsorption model, with physisorption and chemisorption adsorption mechanisms. The effectiveness of inhibitor performance of T3AP can be visually observed using scanning electron microscopy and X-ray photoelectron spectroscopy. The characterization revealed that the reactive S and N atoms in the T3AP inhibitor form strong chemical adsorption through N-Cu and Cu-S bonds on the copper surface. Computational analysis was also carried out, and we found that the stable energy gap between the occupied and unoccupied molecular orbitals (4.6891 eV) and high binding energy (540.962 kJ mol-1) adsorption from molecular dynamics were in agreement with the experimental findings.

RSC Adv ; 9(66): 38760-38771, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-35540239


This study investigated the physicochemical and catalytic properties of mesoporous magnesium silicate catalysts prepared at various Mg/CTAB ratios (0.25, 0.50, 0.75 and 1.00). The XPS analysis detected a mixture of enstatite and magnesium carbonate species when the Mg/CTAB ratio was 0.25, and 0.50. A mixture of forsterite and magnesium carbonate species were detected when the Mg/CTAB ratio was 0.75 whereas for the Mg/CTAB ratio of 1.00, enstatite and magnesium metasilicate species were detected. A catalyst with the Mg/CTAB ratio of 1.00 demonstrated the highest catalytic activity in the oxidation of styrene. The styrene conversion rate was 59.0%, with 69.2% styrene oxide (StO) selectivity. The H2O2 molecules were activated regio-specifically by the magnesium species to prevent rapid self-decomposition while promoting selective interaction with styrene. All the parameters that influence the styrene conversion and product selectivity were evaluated using analysis of variance (ANOVA) with Tukey's test. The ANOVA analysis showed that the reaction time (h), Mg/CTAB ratio, styrene/H2O2 ratio, catalyst loading (mg) and temperature (°C) affect styrene conversion and product selectivity (StO) significantly (p < 0.05). The oxidation of styrene was well fitted to the pseudo-first-order model. The activation energy, E a of the catalysed styrene epoxidation reaction was calculated to be 27.7 kJmol-1. The catalyst can be reused several times without any significant loss in its activity and selectivity. The results from this study will be useful in designing and developing low cost, high activity catalysts from alkaline earth metals.