Montmorillonite/Poly(Pyrrole) for Low-Cost Supercapacitor Electrode Hybrid Materials

Conductive polymers such as polypyrrole have been widely used as pseudo-capacitive electrodes for supercapacitors. This work demonstrates a simple method to improve the performance of conductive polymer electrodes by adding montmorillonite in order to perform capacitive behavior. Conductive composite polymers (CCPs) based on montmorillonite/polypyrrole (MMT/PPy(Cl)) have been synthesized by polymerization using FeCl3 as an oxidizing agent. During the preparation of CCP, the effect of MMT/pyrrole mass ratio and the influence of the amount of added H+ and temperature of the synthesis medium on the electrochemical performance of the composite have been investigated. The investigation associated with conductivity measurement allowed us to determine the best conditions to reach a high specific capacitance of 465 F gr-1 measured by cyclic voltammetry with respect to the CCP synthesized at ambient temperature (220 F gr-1) and a 35% increase in capacity compared to its homologue synthesized in neutral conditions at a low temperature. These performances have been advantageously correlated both to the edge acidity of the host material and to the evolution of its conductivity according to the preparation conditions. The galvanostatic charge/discharge tests also confirm the stability of the obtained composite, and a capacitance of 325 F g-1 for the best CCP is recorded with a regime of 1 A g-1. In addition, the durability of the device shows that the proposed material has a relatively good stability during cycling.

Magnetically separable and reusable rGO/Fe3O4 nanocomposites for the selective liquid phase oxidation of cyclohexene to 1,2-cyclohexane diol

A series of magnetically separable rGO/Fe₃O₄ nanocomposites with various amounts of graphene oxide were successfully prepared by a simple ultrasonication assisted precipitation combined with a solvothermal method and their catalytic activity was evaluated for the selective liquid phase oxidation of cyclohexene using hydrogen peroxide as a green oxidant. The prepared materials were characterized using XRD, FTIR, FESEM, TEM, HRTEM, BET/BJH, XPS and VSM analysis. The presence of well crystallized Fe₃O₄ as the active iron species was seen in the crystal studies of the nanocomposites. The electron microscopy analysis indicated the fine surface dispersion of spherical Fe₃O₄ nanoparticles on the thin surface layers of partially-reduced graphene oxide (rGO) nanosheets. The decoration of Fe₃O₄ nanospheres on thin rGO layers was clearly observable in all of the nanocomposites. The XPS analysis was performed to evaluate the chemical states of the elements present in the samples. The surface area of the nanocomposites was increased significantly by increasing the amount of GO and the pore structures were effectively tuned by the amount of rGO in the nanocomposites. The magnetic saturation values of the nanocomposites were found to be sufficient for their efficient magnetic separation. The catalytic activity results show that the cyclohexene conversion reached 75.3% with a highest 1,2-cyclohexane diol selectivity of 81% over 5% rGO incorporated nanocomposite using H₂O₂ as the oxidant and acetonitrile as the solvent at 70 °C for 6 h. The reaction conditions were further optimized by changing the variables and a possible reaction mechanism was proposed. The enhanced catalytic activity of the nanocomposites for cyclohexene oxidation could be attributed to the fast accomplishment of the Fe²⁺/Fe³⁺ redox cycle in the composites due the sacrificial role of rGO and its synergistic effect with Fe₃O₄, originating from the conjugated network of π-electrons in its surface structure. The rapid and easy separation of the magnetic nanocomposites from the reaction mixture using an external magnet makes the present catalysts highly efficient for the reaction. Moreover, the catalyst retained its activity for five repeated runs without any drastic drop in the reactant conversion and product selectivity.

A series of magnetically-separable and reusable rGO/Fe₃O₄ nanocomposites were successfully synthesized for the selective liquid-phase oxidation of cyclohexene to 1,2-cyclohexane-diol.

Synthesis, characterization and optimization of heterogeneous catalytic cyclohexene oxidation by tungstophospho(aqua)ruthenate via the fractional factorial design methodology

Keggin-type tungstophospho(aqua)ruthenate (PRuW) was synthesized and supported on acid activated montmorillonite under mild conditions.

Investigation of the effect of VOx/ZrO2 structure on the catalytic activity in cyclohexene epoxidation

The coexistence of a solid solution with polymeric vanadium species in the case of 5VZr-2 and with the formation of ZrV₂O₇ in the case of 5VZr-3, resulted in good catalytic performance, with up to 80% epoxide selectivity and 32% cyclohexene conversion.

Green synthesis of bisphenol F over 12-phosphotungstic acid supported on acid-activated palygorskite

Hydroxyalkylation of phenol to bisphenol F under mild conditions over various solid acid catalysts.

Allylic oxidation of cyclohexene over ruthenium-doped titanium-pillared clay

Ruthenium-doped H-Montmorillonite (H-Mont) and Ti-pillared clay (Ti-PILC) were prepared then studied for oxidation of cyclohexene, with tert-butylhydroperoxide (TBHP) as the oxygen source.

The effect of redox properties of ceria-supported vanadium oxides in liquid phase cyclohexene oxidation

In the presence of redox catalysts, cyclohexene oxidation leads to an epoxidation product, while in the presence of acidic features; the allylic oxidation is predominant and leads to cyclohexenol and cyclohexenone.