Preparation of a Cellulase-imitated Solid Acid Catalyst With High Acid Density and Its Evaluation for Hydrolysis of Cellulose

Abstract

In this paper, tannic acid, a polyphenolic substance rich in plants, is modified by the glutamic acid and cross-linked with formaldehyde to prepare a high acid density tannin-glutamate acid resin-based imitation enzyme solid acid catalyst (T-Glu-R), which is completely different from traditionally carbon-based solid acid synthesized by concentrated sulfuric acid and carbonized matter. The solid acid catalyst was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetry, and X-ray photoelectron spectroscopy. The catalytic activity and cycle performance of T-Glu-R in the cellulose hydrolysis reaction were evaluated. The results show that the acid density of T-Glu-R reached 7.28 mmol/g, which is much higher than that of the highest acid density of carbon-based solid acid. Microcrystalline cellulose was hydrolyzed in distilled water at 180 °C for 2 h, the yield of total reducing sugars reached 72.15%. After four cycles of hydrolysis, the yield was only reduced by 4.32%, showing excellent cycle performance and stability. The study provides a new strategy with the synthesis of solid acid catalyst for hydrolysis of cellulose converted into platform compounds without concentrated sulfuric acid.