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High value-added utilization of plastic waste has historically been a problem, which has driven researchers to make long-term and unremitting efforts to tackle it. High-performance carbon based solid acid (CSA) was prepared from polyvinyl chloride (PVC) and polyethylene (PE) in different proportions. The small amount of chlorine is still residual on the edge of graphitic carbon sheets after co-carbonization and sulfonation. Strong electronegative –Cl group and the high-density phenolic –OH group, double-adsorption group, are covalently bonded to the edges of the graphitic carbon sheets, contributing to the decrystallization of cellulose to a large extent. Meanwhile, PVC and PE-derived CSAs have significantly higher –SO3H group density than PVC-derived CSA and cellulose-derived CSA. These are obviously beneficial to the improvement of hydrolysis activity, which can be attributed to structural optimization caused by co-carbonization PVC and PE. The CSA with a mixture of 80% proportions has great catalytic activity and repeatability.

A carbon-based solid acid (CSA) was prepared from phenolic residue which is the solid waste generated from the refining of crude phenol. Influence of various reaction conditions on hydrolysis of cellulose over phenolic residue-derived solid acid (PRCSA) is discussed. The results indicate that both cellulose hydrolysis and the effectiveness of PRCSA need a suitable temperature range. The glucose can be adsorbed on the surface of PRCSA due to the hydroxyl-rich structure of PRCSA. The behavior of generated glucose in competitive adsorption with unreacted cellulose on PRCSA suppresses the continuing hydrolysis of cellulose to some extent. For PRCSA, the number of effective active sites increases with the decrease of catalyst particle size. In heterogeneous hydrolysis of cellulose assisted by inorganic salts, the promotion of KCl and NaCl is remarkable, which is attributed to the decrystallization of chloride ions on cellulose and the ion exchange between cations and H + in –SO 3 H bonded to PRCSA.

Carbon-based solid acid (CSA) was successfully prepared using phenolic residue as starting material. The characterization results indicate that such solid acid catalyst mainly consists of four building blocks: the condensed aromatic carbon sheets, the active groups (including SO3H, COOH and phenolic OH), the side chains (including CH3 and OCH3) and the bridge linkages (including O , CH2 , CH2 CH2 , and OCH2 ) acting as the intermediates between aromatic clusters. Most of these building blocks, except for the SO3H, could be derived from the corresponding part of the phenolic residue. Aliphatic side chains have been demonstrated to greatly improve the sulfonation activity of carbon precursor and promote the catalytic performance in cellulose hydrolysis, and the carbon-based catalyst sulfonated for just 1 h could exhibit almost similar catalytic activity compared with the catalyst sulfonated for a longer time. However, their hydrophobicity and steric hindrance reduced the utilization efficiency of the sulfonic acid groups to a certain extent.