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With the depletion of fossil resources and environmental issues becoming increasingly serious, the search for renewable raw materials for the design and preparation of high-performance and environmentally-friendly polymer materials has become an urgent task. Biomass polymer is transformed from plants through photosynthesis and is an important renewable resource on the earth. The annual output is about 1.5×1012 tons. This kind of resource is used as a raw material in the field of polymer materials technology, and can achieve “zero emission†of CO2 during the entire life cycle of material production, use, and disposal, which plays a very good role in alleviating the greenhouse effect, and is the best choice for green raw materials. Is of great significance. Cellulose is the most basic, most important and most important component of biomass. According to its structural characteristics, it can be converted to glucose by hydrolysis, and used as a base point for bio-based platform compounds and bio-based polymer materials. The design, preparation and synthesis will provide a feasible technical approach for the effective use of renewable biomass polymers in the field of materials.
Focusing on the research and development of practical cellulose conversion sugar technology, the bio-based polymer materials team of the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences under the leadership of researcher Zhu Jinhe and associate researcher Na Haining, designed and constructed the “decrystallization and rehydrolysisâ€. The two-step cellulose hydrolysis strategy, and through the incorporation of microwaves in this strategy, successfully achieved rapid and highly efficient hydrolysis of cellulose to sugar under relatively mild conditions. The cellulose hydrolysis conversion rate is over 90%, and the glucose yield is up to 76.5%. Compared to traditional one-step homogenous technology, glucose conversion efficiency has been significantly improved (as shown in Figure 1).
Based on the technological capabilities and effectiveness demonstrated by the "two-step" hydrolyzed cellulose technology strategy, the bio-based polymer materials technology team began to establish and pilot small-scale engineering technology in the field of cellulose hydrolysis technology. In the course of technology implementation, the in-depth study of the hydrolytic response of the molecular structure of cellulose has further clearly confirmed the great role of effectively breaking down the highly ordered crystalline structure of cellulose to promote its rapid and efficient hydrolysis. Not only that, it was also found that although the degree of crystallinity of cellulose was significantly reduced in the “decrystallization†step, when the resulting low crystallinity regenerated cellulose was further hydrolyzed, the amorphous part thereof was easily recrystallized during the hydrolysis process. This phenomenon will greatly hinder the continuation of hydrolysis (see Figures 2 & 3).
In response to this problem, the bio-based polymer materials technical team has recently worked to utilize the synergistic effect of microwave and co-catalyst sulfolane to successfully control the recrystallisation of recrystallized cellulose with low crystallinity in the hydrolysis process. Rapid and efficient hydrolysis of regenerated cellulose. Detailed studies have shown that the recrystallization of regenerated cellulose is fully regulated in the hydrolysis process, and the cellulose I-type crystal structure is significantly inhibited. With the increase of sulfolane content in the microwave-assisted hydrolysis system, the proportion of type I structural cellulose gradually decreased, and the degree of inhibition of recrystallization of regenerated cellulose and the hydrolysis efficiency of cellulose also gradually increased. When the amount of sulfolane reached 80wt%, the formation of cellulose type I crystal structure was completely inhibited, the hydrolysis conversion rate of regenerated cellulose reached 98.0%, and the yield of reducing sugar was as high as 71.9%. The in-depth development of this research not only confirmed the key role of regulating the recrystallization of regenerated cellulose to promote its hydrolysis, but also provided a feasible technical idea and technical method for the rapid and effective hydrolysis of regenerated cellulose.
The gradual advancement of this research has not only enriched the key scientific theories and techniques for the rapid hydrolysis of sugar to cellulose, but also laid an important foundation for the comprehensive construction of an effective cellulose hydrolysis and sugar-reducing engineering technology.
This work was supported by the National Natural Science Foundation of China (21274160 and 21304104), the Ningbo Natural Science Foundation (2015A610054), the Ningbo Key Laboratory of Polymer Materials (2010A22001), and the Ningbo Innovation Team (2015B11003). The relevant research results were published in American Chemistry. CIS Sustainable Chemistry & Engineering, 2016, 4(3): 1507-1511 and Bioresource Technology, 2015, 19: 229-233 & 2014, 167: 69-73 & 2013, 137: 106-110.
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