Palladium nanoparticles supported on amine-functionalized alginate foams for hydrogenation of 3-nitrophenol

Abstract

A new material, consisting of alginate-polyethyleneimine (AP) foam, with high percolating properties has been designed for palladium recovery in fixed-bed reactor. The foam, having high affinity for Pd(II), can be also used for manu-facturing heterogeneous hydrogenation catalyst. SEM-EDX and TEM analyses were performed to determine the structure of the foams and the distribution of Pd nanoparticles (after metal reduction). Metal-sorbent interactions and oxida-tion state of Pd are characterized by XPS. Pd(0)-bearing foams are investigated for the hydrogenation of 3-nitrophenol (3-NP) using HCOOH as the hydrogen donor. The maximum sorption capacity of Pd(II) by AP foams reaches up to 224 mg g -1 . The water flux (under water-depth pressure of 6 mbar) reaches 24.8 mL cm -2 min -1 (superficial flow velocity: 14.9 m h -1 ). The foams are remarkably stable: The mass loss under strong shaking for 2 days does not exceed 3%. For catalytic application, Pd loading conditions were optimized (flow rate, metal concentration) to reach 101 mg Pd g -1 (97% metal removal). Under these conditions, Pd overloading and nanoparticles aggregation can be minimized. The catalytic hydrogenation of 3-nitrophenol (using formic acid as the hydrogen donor) was optimum for a HCOOH/3-NP molar ratio close to 160 (pH between 3 and 4). High flow rates minimize diffusion effects; the apparent rate constant (for pseudo-first-order rate equation) reaches 9.7 9 10 -3 s -1 . The reuse of the foams over 30 cycles shows the long-term stability of catalytic activity. The test on continuous (one-pass) mode shows a progressive poisoning of the catalyst. However, a simple washing with water is sufficient for recov-ering catalytic activity.

Batch sorption and fixed-bed elution for Pd recovery using stable amine-functionalized melamine sponge

“…element appears as the bond between N and Pd (Wang et al, 2020c), further demonstrating the reaction between amine groups and chloro-anionic Pd species. It is noteworthy that a new band at 289.1 eV for C 1s appears.…”

Classification, synthesis, characterization, and applications of metal nanoparticle-containing hybrid microgels: a comprehensive review

“…However, at low pH (pK a # pH), the neutral amino groups are protonated into ammonium (cationic (-NH 3 + )) ions, leading to electrostatic repulsion between the ammonium ions and causing the hybrid microgels to swell. 98,132,[199][200][201][202][203] Hydrogen bonding is present between the ammonium ions and water molecules, but electrostatic repulsion occurs between the ammonium ions themselves due to their like charges. Consequently, more water molecules can enter into the pores of the microgels in the cationic structure (protonated form, swelling state) compared to the neutral structure (deprotonated form, deswelling state).…”

A Critical Review of Palladium Nanoparticles Decorated in Smart Microgels

“…In this way, the catalytic performance as well as the adsorption capacity of microgels and hybrid microgels can be controlled by swelling and deswelling behavior. Wang et al [67] have reported the synthesis of palladium nanoparticles loaded in an alginate-polyethyleneimine A-P(EtI) crosslinked organic polymer system. The loading of palladium (II) ions is controlled by adjusting the pH of the medium.…”

“…They monitored this adsorption process with a UV-visible spectrophotometer. Wang et al [67] have synthesized microgel, which is then used for the sorption of palladium ions and simultaneously for the catalytic reduction of 3NiP. The sorption of palladium ions occurs due to ion-dipole interactions.…”