Synthesis and Characterization of Palladium Nanoparticles Immobilized on Modified Cellulose Nanocrystals as Heterogeneous Catalyst for Reduction of Nitroaromatic Compounds

Properties of APTES-Modified CNC Films

Sulfated cellulose nanocrystals' (CNCs') facile aqueous dispersibility enables producing films, fibers, and other materials using only water as a solvent but prevents using sulfated CNCs in applications that require water immersion. We report that modifying CNCs with 3-aminopropyl-triethoxysilane (APTES) via a simple, single-pot reaction scheme dramatically improves the hydrolytic stability of CNC films. The effects of APTES modification on CNCs' properties were studied using attenuated total reflectance Fourier transform infrared spectroscopy, atomic force and optical microscopy, thermogravimetric analysis, dynamic light scattering, and ultimate analysis. Substituting a mere 12.6% of the CNCs' available hydroxyl groups with APTES dramatically increased the hydrolytic stability of shear cast films while only having minor impacts on their mechanical properties. In addition, quartz crystal microbalance with dissipation monitoring (QCMD) and multiparametric surface plasmon resonance (MP-SPR) studies showed that the CNC-APTES films also had a greater irreversible binding with carbofuran, a pesticide and emerging contaminant. These results highlight that APTES modification is a promising method for increasing the utility of sulfated CNCs in sensors, adsorbents, and other applications requiring water immersion.

PdCu alloy prepared by ultrasonic method catalyzes the degradation of p-nitrophenol

PdCu alloy nanocatalysts supported on NiFe layered double hydroxide (PdCu-LDHs) were prepared by a green ultrasound-assisted reduction method. The cavitation effect of ultrasound made part of CO₃^2- decompose to CO₂, and NO₃^- and Cl^- replace intercalation, which anchor the PdCu between layers. The action of ultrasound dissociated hydroxyl groups (-OH) on surface of LDHs to H· to reduce Cu²⁺ and Pd²⁺ to Cu⁰ and Pd⁰ and Cu promote the synergy between Pd alloy and LDHs. The electronic effects between Cu and Pd improved the catalytic performance for the reduction reaction of 4-NP and the stability of PdCu-LDHs. The PdCu-LDHs prepared at 400 W, 25 kHz, 1 h, can completely degrade p-nitrophenol (4-NP) within 5 min with n(4-NP)/n(Pd) = 50 and n(4-NP)/n(NaBH₄) = 0.15. The TOF value is 988.20 h^-1, which is 27.7 times that of Pd/C catalyst (commercial).

Wood-Sourced Polymers as Support for Catalysis by Group 10 Transition Metals

Despite providing interesting solutions to reduce the number of synthetic steps, to decrease energy consumption or to generate less waste, therefore contributing to a more sustainable way of producing important chemicals, the expansion of the use of homogeneous catalysis in industrial processes is hampered by several drawbacks. One of the most important is the difficulty to recycle the noble metals generating potential high costs and pollution of the synthesized products by metal traces detrimental to their applications. Supporting the metals on abundant and cheap biosourced polymers has recently appeared as an almost ideal solution: They are much easier to recover from the reaction medium and usually maintain high catalytic activity. The present bibliographical review focuses on the development of catalysts based on group 10 transition metals (nickel, palladium, platinum) supported on biopolymers obtained from wood, such as cellulose, hemicellulose, lignin, and their derivatives. The applications of these catalysts in organic synthesis or depollution are also addressed in this review with examples of C-C couplings, oxidation, or hydrogenation reactions.