Anthraquinone polymer catalysts for alkaline delignification of lignocellulosic matter. Part 1. Syntheses and characterizations

Abstract

Abstract Syntheses of two new styrene monomers are described, which bear a C4 and C3 chain ending with an anthraquinone (AQ) unit, in para and meta positions of the benzene ring. Both monomers were submitted to radical polymerization, and three linear AQ polystyrene (PS) copolymers (CP-A, CP-B, and CP-C) were prepared. The first two differed by the nature of the link between the AQ and the PS network. An ether oxide group in CP-B gave better accessibility of AQ to the lignin polymer in lignocellulosics, and the incorporation of carboxylic acid functions in CP-C increased its hydrophilicity. The copolymers synthesized were characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, ultraviolet, and Fourier Transform Infrared (FTIR) spectroscopies, such as by size exclusion chromatography (SEC) and thermogravimetry (TG). A cross-linked copolymer (CP-3D) bearing AQ units (11.3%) was prepared by emulsion polymerization in the presence of divinylbenzene. Contrary to linear copolymers, the latter was insoluble in aqueous and organic solutions, and displayed remarkable thermal stability.