Immobilization of nanosilver onto glycine modified lignin hydrogel composites for highly efficient p-nitrophenol hydrogenation

A new type of nanosilver immobilized catalyst based on glycine modified lignin hydrogels with excellent catalytic performance towards p-nitrophenol reduction have been prepared. Glycine was used to provide amino and carboxy groups for complexing silver ions, simultaneously which was also beneficial for in-situ reduction and suppression of silver nanoparticles. As-prepared composites were characterized by X-ray diffraction, scanning electron microscope with EDS, high-resolution transmission electron microscope, X-ray photoelectron spectroscopy, Fourier Transform Infrared Spectrometer and Thermal Gravimetric Analyzer. The developed network with enriched anchoring sites could provide the stability during the catalytic process and enough traction to disperse and stabilize the silver nanoparticles. Batch experiments of 4-NP hydrogenation were carried out to correlate the catalytic performance. The concentration of 4-NP of 5 mmol/L could be finished with only 101 s and the rate of k was 0.0151 s(-1). Moreover, fixed-bed experiments were creatively applied for the tests and the catalyst can maintain high efficiency about 300 min with the flowing rate of 3 mL/min. After being reused ten cycles, the catalyst retained the conversion rate beyond 98%; and the structure has no obvious deterioration and the leaching of nanosilver was neglectful, which could be attributed to the crucial role of introduced glycine component.