Temperature-Responsive HCl-Releasing Catalysts for Cellulose Hydrolysis into Glucose
Abstract Conversion of cellulose into glucose is one of the important approaches to biomass utilization, but the insolubility of cellulose in water makes it difficult to hydrolyze particularly in the case of heterogeneous catalysis due to the mass transfer obstacle between solid catalyst particles and cellulose particles. Temperature-responsive HCl-releasing catalysts have unique characteristic as they allow to catalyze the hydrolysis reaction of cellulose under homogeneous catalysts while the released HCl can be recovered and reused via simple cooling after reaction. In this paper, three mesoporous N-doped carbon materials (CNs) with temperature-responsive HCl-releasing ability were synthesized by carbonization of aminoguanidine hydrochloride at 400, 500 and 600 °C respectively. The basicity and the temperature-responsive HCl-releasing behavior of the as-prepared CNs are examined by means of acid–base titration and high temperature releasing experiment. The experimental results show that, of the three samples, CN-400 possesses the maximum HCl intake of 1.28 mmol HCl/g and can release about 1.15 mmol HCl/g when being heated to 220 °C. Employing CN-400· n HCl as the catalyst, a total reducing sugars (TRS) yield of 81.1% and 61.1% glucose yield can be obtained after reaction under 220 °C for 60 min. The considerable basic sites are derived from the pyridine nitrogen and indispensable for HCl-releasing to catalyze cellulose hydrolysis. Furthermore, CN-400· n HCl possesses excellent catalytic stability. Graphic Abstract Temperature-responsive acid-releasing catalysts provide a novel and green solid-liquid phase cellulose conversion reaction system.
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