Study On The Key Technology Of Straw Based Dissolving Pulp

Dissolving pulp is a kind of chemical refining pulp with high cellulose content,which is obtained from natural crops after a series of chemical and physical treatment.It has a wide application field and a huge market.China is rich in crop resources,but straw and other biomass resources are not fully utilized at present,and the high-value utilization degree is low.In this paper,corn straw was used as raw material to produce dissolving pulp,and lignin was used to prepare syringaldehyde.Firstly,the lignin was extracted from corn straw.The NaOH amount,the 1,4-butanediol content and the reaction time were optimized.The optimal reaction conditions were:50g corn straw powder/8g NaOH,60%1,4-butanediol,1h reaction time,the highest extraction rate of lignin was 33.69±0.56%.Then syringaldehyde was prepared from the extracted straw lignin.The effects of catalyst type,catalyst dosage and reaction time on the syringaldehyde yield and lignin conversion were investigated.The results showed that when the reaction time was 2 h,the amount of Cu doping was 0.8,and LaFe0.2Cu0.8O3/lignin(g/g)was 1:20,the highest the syringaldehyde yield was 5.11%,and the highest lignin conversion was 74.12%.Then,the hemicellulose was removed by cold alkali method with the holocellulose as raw material.The samples with different hemicellulose content were prepared,and then the reaction performance and cellulose structure of the dissolving pulp were analyzed.The results show that the crystallinity and polymerization degree of cellulose increase,the cross-sectional area of microcrystalline and the aggregation size of basic fibril increase during the process of hemicellulose removal by cold subtraction.Although the content of hemicellulose decreased from 29.55%to 9.57%,the reaction performance of dissolving pulp still showed a downward trend.The results show that the change of cellulose structure parameter is the main factor that causes the change of dissolving pulp reaction performance.Finally,acid deep eutectic solvent(DES)was used to improve the performance of dissolving pulp.The types of DES,reaction time,reaction temperature and the conditions of the HBA/HBD ratio were discussed.The optimal reaction conditions were:DES,1:2 molar ratio of HBA/HBD,3 hours reaction time and 130℃ reaction temperature.After the improvement,the reaction performance of the dissolving pulp was 72.04±3.41%,the water retention value was 292.24%,and the polymerization degree was 713.56.All the parameters were greatly improved.