Research On Preparation Of Nano-Crystalline Cellulose From Non-Wood Fiber Materials

Energy such as fossil was gradually decreasing.Disafforestation and fossil exploration led the ecosystem disrupted.Non-wood resources were annually huge and renewable in our country although the wood resources were lacking.Therefore,the development and utilization of non-wood fiber sources had gradually become the important measures to solve problems of resource,energy and environment.Cellulose,as a kind of linear polymer compounds could be isolated from plant fiber raw materials.For the further application of cellulose to prepare nano-crystalline cellulose and its modification application have become a hotspot of research for domestic and foreign relevant scientific researchers.In this paper,non-wood fiber raw materials,such as corn stover,wheat straw and bamboo,were all taken for materials.Combined with the traditional technology of pulping and papermaking,and gradually extracted high purity cellulose from the fiber raw materials.Then chemical method combined with ultrasonic technique had been adopted to prepare nano-crystalline cellulose.However,there were some differences in properties among the non-wood fibrous materials.Therefore,for different sources cellulose,conditions of nano-crystalline cellulose preparation and subsequent related performance characterizations were different.In addition,there are some of lignin,hemicellulose,cellulose and other components in non-wood fibrous materials.Since all of these components could be degraded by acid regents,which might influence the efficiency of NCC preparation.Therefore,pretreatment methods were very important for nano-crystalline cellulose preparation with acid hydrolysis method of chemical methods.Pretreatment processes could be consisted by pulping,bleaching and cellulose purification.Pulping stages were consisted of traditional sulfate process and ethanol technology to remove partial hemicellulose and lignin,and then after more than green TCF bleaching technology and chlorine bleaching further to remove lignin and hemicelluloses.Cellulose purification was the last stage to obtain high purity cellulose.The optimum conditions of acid hydrolysis to prepare NCC from corn stalk were as follows: the optimum conditions for NCC preparation were: Acid A concentration 65%,time,2.5h,temperature,55℃,liquid ratio,1:60;mixed acid: time,2h,temperature,45℃,liquid ratio,1:20;the morphology of NCC was close to spherical nanoparticles whose particle size ranged from 1nm to 100 nm.The crystallinity index was 69.32%.And it remained cellulose I.The optimum conditions for NCC from wheat straw cellulose were as follows: Acid A condition was: Acid A concentration 65%,time,3.5h,temperature,55℃,liquid ratio,1:30;the optimum condition of Acid B hydrolysis was: Acid B concentration,64%,time,3.5h,temperature,45℃,liquid ratio,1:20;the optimum condition of mixed acid was: time,2h,temperature,45℃,liquid ratio,1:20.And its crystallinity had increased about 28% than wheat straw material from XRD.However,as to bamboo material,the optimum conditions for mixed acid to prepare NCC was: acid hydrolysis time,3h,temperature,45℃,liquid ratio,1:20;And the optimum condition of Acid A to prepare NCC was: Acid A concentration,65%,time,3h,temperature,55℃,liquid ratio,1:30;Morphologies from SEM were close to films which were consisted of a large number of tiny NCC paticles.The thermostability of NCC prepared from bamboo cellulose increased about 130℃ than bamboo material.And its crystallinity has increased about 10% than bamboo cellulose derived from pretreatment.