Preparation method of nanocellulose fibrils

Abstract

The invention relates to a green, economical and sustainable method for preparing nanocellulose fibrils. The preparation method comprises the following steps that 1, a cellulose raw material is added to a citric acid solution to be heated, stirred and hydrolyzed; 2, treated cellulose and hydrolysate are separated through methods of centrifugal sedimentation and the like, and precipitated cellulose is centrifugally washed with water multiple times and diluted into a cellulose suspension; 3, the separated hydrolysate can be directly recycled at least once, citric acid is recovered from the recycled hydrolysate, and the citric acid obtained through recovery can be recycled continuously; 4, the natural structure of the cellulose suspension obtained in the second step is further destroyed through a high pressure homogenizer or ultrasonication or physical mechanical treatment of a disc mill, and the colloidal nanocellulose fibrils are obtained. According to the method for preparing the nanocellulose fibrils, a catalyst is not adopted, the reaction condition is relatively mild, the reaction is easy to control, operation is easy, and the method is friendly to environment.

Description

technical field [0001] The invention relates to the field of preparation of natural polymer materials, in particular to a new method for preparing nano-cellulose fibrils by hydrolyzing natural cellulose raw materials with citric acid combined with physical and mechanical action. Background technique [0002] Nanocellulose fibrils not only have the advantages of cellulose itself such as wide source, non-toxic, water insoluble, and degradable. Nanocellulose fibrils also have various characteristics of nanoparticles, such as nanoscale, high specific surface area, high aspect ratio, low density, etc., and also have high Young's modulus, high tensile strength and high cleanliness. Therefore, nanocellulose fibrils have broad application prospects in the fields of reinforcing materials, catalyst carriers, and drug carriers. Akira reported in JWoodSci, 2013, 59, 449-459 that nanocellulose fibrils can be widely used in nanomaterials, such as aerogels, food packaging materials, nanop...

AI Technical Summary

Problems solved by technology

These treatment methods all have problems of one kind or another. For example, enzyme preparations are relatively expensive and react harshly, with low reaction efficiency and long reaction time; inorganic strong acids and strong alkalis are highly corrosive to equipment and difficult to recycle, polluting the environment; ionic liquids are expensive , and the residual deposition of impurities in the ionic liquid affects its recycling; although many literatures report that TEMPO catalytic oxidation pretreatment can greatly reduce the energy consumption of the homogenization process, but as Delgado-Aguilar in Bioresources, 2015, 10, 5345-5355 et al. reported that TEMPO catalysts are expensive, and there is no way to recycle TEMPO catalysts in industry so far. The cost of preparing nanocellulose fibrils through TEMPO catalytic oxidation pretreatment is about 200 Euros / kg, so TEMPO catalytic oxidation pretreatment is realized. Industrial production is more difficult

[0005] In summary, the existing pretreatment methods mainly have problems such as difficult recovery of catalysts, expensive chemicals, long reaction time, environmental pollution, or poor product quality.

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