Establishing a productive heterogeneous catalyst based on silver nanoparticles supported on a crosslinked vinyl polymer for the reduction of nitrophenol

The treatment of toxic nitrophenols in industrial wastewater is urgently needed from environmental, health, and economic points of view. The current study addresses the synthesis of the crosslinked vinyl polymer poly(acrylonitrile-co-2-acrylamido-2-methylpropane sulfonic acid) (poly(AN-co-AMPS)) through free radical copolymerization techniques using acrylonitrile (AN) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) monomers with different ratios and potassium persulfate (KPS) as an initiator in an aqueous medium. The prepared copolymer was utilized as a supporting matrix for silver nanoparticles (AgNPs) via the chemical reduction of silver nitrate within the copolymer framework. Different techniques were employed to characterize the prepared poly(AN-co-AMPS) and Ag/poly(AN-co-AMPS) composites, such as Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis. The results exhibit that silver metal was excellently dispersed across the surface of poly(AN-co-AMPS) without any agglomeration, presenting as nanocrystals with an average particle size equal to 6.21 nm. Also, BET analysis confirmed that the Ag/poly(AN-co-AMPS) composite exhibits mesoporous characteristics with a surface area of 59.615 m2 g-1. Moreover, the Ag/poly(AN-co-AMPS) composite was effectively applied as a heterogeneous catalyst for the catalytic reduction of hazardous 4-nitrophenols (4-NP) with a rate constant equal to 0.28 min-1 and half-life time equal to 2.47 min to a less toxic compound in the presence of NaBH4 as a reductant. Furthermore, the reusability experiment confirmed the excellent stability of Ag/poly(AN-co-AMPS). The catalyst can be easily separated from the reaction mixture using a simple centrifuge and directly reused for up to four successive cycles without a remarkable decrease in its catalytic activity. The conversion percentage of 4-NP after the four cycles was found to be 93%.

Oxyfunctionalization of Benzylic C-H Bonds of Toluene Mediated by Covalently Anchored Co-Schiff Bases

Oxyfunctionalization of toluene to value-added benzaldehyde, benzyl alcohol and benzoic acid is of great significance. In this work, Co-Schiff bases were immobilized on commercial silica gel by covalent anchoring, and resulting catalysts were used to catalyze the oxidation of toluene in the presence of the cocatalyst N-hydroxyphthalimide (NHPI). The catalysts exhibited excellent textural and structural properties, reliable bonding and a predomination of the cobaltous ions. The catalyst synthesized by diethylamino salicylaldehyde (EASA) possessed a grafting density of 0.14 mmol/g and exhibited a toluene conversion of 37.5%, with predominant selectivities to benzaldehyde, benzyl alcohol and benzoic acid under solvent-free conditions. It is concluded that the effect of ligands on their catalytic performance might be related to their electron-donating or -withdrawing properties.

Dielectric Permittivity, AC Electrical Conductivity and Conduction Mechanism of High Crosslinked-Vinyl Polymers and Their Pd(OAc)2 Composites

Semiconductor materials based on metal high crosslinked-vinyl polymer composites were prepared through loading of Pd(OAc)₂ on both Poly(ethylene-1,2-diyl dimethacrylate) (poly(EDMA)) and poly(ethylene-1,2-diyl dimethacrylate-co-methyl methacrylate) (Poly(EDMA-co-MMA)). The thermochemical properties for both poly(EDMA) and poly(EDMA-co-MMA) were investigated by thermal gravimetric analysis TGA technique. The dielectric permittivity, AC electrical conductivity and conduction mechanism for all the prepared polymers and their Pd(OAc)₂ composites were studied. The results showed that the loading of polymers with Pd(OAc)₂ led to an increase in the magnitudes of both the dielectric permittivity and AC electrical conductivity (σ_ac). The value of σ_ac increased from 1.38 × 10⁻⁵ to 5.84 × 10⁻⁵ S m⁻¹ and from 6.40 × 10⁻⁶ to 2.48 × 10⁻⁵ S m⁻¹ for poly(EDMA) and poly(EDMA-co-MMA), respectively, at 1 MHz and 340 K after loading with Pd(OAc)₂. Additionally, all the prepared polymers and composites were considered as semiconductors at all the test frequencies and in the temperature range of 300–340 K. Furthermore, it seems that a conduction mechanism for all the samples could be Quantum Mechanical Tunneling (QMT).