Cellulose depolymerization using zinc chloride hydrate and solid acid catalysts

Increasing the efficiency of cellulose hydrolysis is a crucial milestone to enable its use as a platform for the production of renewable chemicals. Consequently, exploring alternative techniques for cellulose dissolution and subsequent depolymerization and hydrolysis remains a pivotal area of research. This study delves into the performance of diverse solid acid catalysts (ion-exchange resins, metal oxides, and zeolites) for cellulose depolymerization when combined with a concentrated solution of zinc chloride (ZnCl₂) as the reaction medium and extractant. The influence of this molten salt hydrate on cellulose dissolution and the stability of the tested catalysts was thoroughly investigated. Optimal mild operating conditions (90 °C and 2 h) that facilitate enhanced conversion and selective glucose production were identified. The highest glucose yields (exceeding 40%) were obtained with Amberlyst-15 and HZSM-5 (SiO₂/Al₂O₃ = 23), effectively mitigating product degradation and equaling or surpassing the traditional homogeneous system using H₂SO₄. Furthermore, insights into the deactivation mechanisms affecting the best catalysts are provided.