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Context: Freon, a greenhouse gas that contributes to the depletion of the ozone layer, has been the subject of investigation in this study. The catalytic hydrolysis enhancement of CFC-12 by ZrO2 was examined using a density functional theory approach. A detailed reaction mechanism and a new reaction pathway were proposed. The study found that CFC-12 is more likely to be adsorbed on the ZrO2 surface in the CFC-12-TO(F) configuration, while H2O is more likely to be adsorbed on the ZrO2 surface in the H2O-TO(H) configuration. Additionally, H2O replaces CFC-12 on the surface of ZrO2. The hydrolysis of CFC-12 is primarily determined by the first dechlorination process, while the defluorination process is comparatively easier. ZrO2 has a catalytic effect on both dechlorination and defluorination processes, with a more pronounced effect on the former. The production of C–OH bonds is inhibited, which facilitates the dechlorination and defluoridation processes. Methods: This work was carried out in the Dmol3 program in the Material Studio 2017, including the geometric structure optimization and energy calculations. The GGA/PBE method was used in this work, along with the DNP basis, spin-polarized set, and DFT-D correction. The possible TSs were guessed based on the linear synchronous transit/quadratic synchronous transit/conjugate gradient (LST/QST/CG) method, and they were further confirmed and reoptimized to ensure that the only one imaginary frequency exists in the TSs. [ABSTRACT FROM AUTHOR]

Sulfur-resistant Mo-based catalysts have become promising for the one-step synthesis of methanethiol (CH3SH) from CO/H2/H2S, but the low reactant conversion and poor product selectivity have constrained its development. Herein, we synthesized K-MoS2/Al2O3 and K-Mo2C/Al2O3 catalysts via the sulfurization and carbonization of K-Mo-based catalysts in the oxidized state, respectively. During the synthesis of CH3SH, both K-Mo2C/Al2O3 and K-MoS2/Al2O3 showed excellent catalytic performance, and the activity of the former is superior to that of the latter. The effect of different treatments on the catalytic performance of Mo-based catalysts was investigated by XRD, BET, Raman spectroscopy, H2-TPR, and reactants-TPD characterization. The results showed that the sulfide-treated sample showed stronger metal-support interactions and contributed to the formation of K2S, which exposed more active sites and stabilized the formation of C-S bonds. Carbonized samples enhanced the activation of H2, which promoted the hydrogenation of the intermediate species of carbonyl sulfide (COS) and thus improved the selectivity of CH3SH. [ABSTRACT FROM AUTHOR]

In this work, we propose a rapid and facile method (oxalic acid leaching under microwave-assisted conditions) to study the simultaneous recovery of vanadium (V) and nickel (Ni) from spent fluid catalytic cracking (SFCC) catalysts. The central issue in all of these studies is to test the modeling and experimental results of excellent fitting effects of leaching parameters. In order to maximize the recovery of V and Ni, leaching parameters were investigated. Furthermore, response surface methodology (RSM) was applied to optimize the leaching parameters. The optimum conditions obtained were as follows: oxalic acid concentration of 1.8 mol/L; leaching time of 91 min; microwave-assisted power of 500 W; H2O2 concentration of 1.1 mol/L. The maximum leaching rates of V and Ni reached the values of 91.36% and 46.35%, respectively. The results showed that microwave energy was very helpful in improving the efficiency of the leaching process and shortening the leaching time by 75%. According to the shrinking core model, test results showed that a surface chemical reaction was the controlling step of the overall reaction kinetics. The activation energy of V and Ni during the leaching reaction was calculated to be 3.28 and 34.41 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG), which is a solid waste in phosphate fertilizer industry, is harmful to the environment. The pyrogenetic decomposition is mainly used in the utilization of PG, and PG decomposition residue is produced in the decomposition process. In this paper, the migration and conversion rules of elements (Al, Si, P, K, Ca, and Fe) in the purification procedure of CaO in PG decomposition residue was investigated. The acid–base method was used to purify CaO. Content and chemical forms of elements in the purification procedure were analyzed by many characterization methods such as SEM and EDS. And moreover, changes on chemical forms of elements were supported theoretically by some ternary phase diagrams, which were made by the FactSage thermodynamics software. The result showed that, the soluble silicon dioxide and the acid‐insoluble material in PG decomposition residue were effectively removed by using the acid–base method. Meanwhile, impurities separated from CaO and the CaO sample were produced in the experiment, the former can be used to produce the building materials, refractories, insulating materials in various industrial fields, and CaO sample could be used as the filler, building materials, decolorant, etc. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1020–1030, 2018 [ABSTRACT FROM AUTHOR]