New Technology: Insoluble Pretreatment Of Cellulose By Molten Salt Hydrate

The metabonomics research group, led by Cui Qiu, a researcher at Qingdao Institute of bioenergy and process, Chinese Academy of Sciences, and Professor Tang Yanjun of Zhejiang University of science and technology, innovatively established a low energy consumption, green and efficient insoluble cellulose pretreatment technology with molten salt hydrate. This technology can be used for high-efficiency fibrillation at room temperature, which lays a foundation for further saccharification and functional utilization of cellulose.

Cellulose produced by photosynthesis of green plants can be converted into biofuels, bio based materials or bio based chemicals. As a natural and renewable carbon negative resource, cellulose has broad application prospects. However, natural cellulose has a high crystalline supramolecular structure, and its high proportion of ordered and dense cellulose type I crystal structure makes its hydrolysis and functional modification efficiency low, which limits the effective utilization of cellulose.

Therefore, it is necessary to develop clean and efficient pretreatment technology with low energy consumption to break the dense structure of cellulose and increase its conversion and utilization efficiency. Compared with physical pretreatment with high energy consumption and biological pretreatment with relatively low timeliness, chemical pretreatment is more efficient, especially the use of recyclable green solvent system.

Cellulose (MSH) and cellulose (MSH) have been used to catalyze the conversion of cellulose and cellulose. Among them, the higher the temperature (> 100 OC) is needed to dissolve cellulose by lithium bromide trihydrate (lbth), and the higher the temperature, the easier the degradation of cellulose will be. This will increase the cost of recovery and purification of lbth and increase the complexity of the process. If cellulose can be effectively deconstructed without degradation and dissolution of cellulose, it will be more conducive to solid-liquid separation and solvent recovery and reuse. However, it has not been reported whether lbth can dissociate the crystalline structure of cellulose under mild conditions and to what extent.

It was found that the compact I-type crystalline structure of microcrystalline cellulose was transformed into a loose and disordered amorphous structure after being treated with lbth for 5 minutes at room temperature, and the crystallinity was reduced to 1 / 4 of the original. The BET specific surface area of microcrystalline cellulose increased by 60 times.

The accessibility of cellulose after lbth pretreatment was evaluated in detail by enzymatic hydrolysis kinetics. It was found that under the condition of enzyme dosage of only 2.5 mg protein / g cellulose and enzymatic hydrolysis for 24 hours, the conversion rate of cellulase hydrolysis after 30 minutes of lbth treatment was close to 100%, while that without pretreatment was only 16.7%.

In addition, the system characterization confirmed that lbth could rapidly and efficiently dissociate the microcrystalline cellulose structure at room temperature without dissolving cellulose, which was conducive to solid-liquid separation after pretreatment and solvent recovery and reuse. The study also confirmed that lbth could be recovered almost completely, and because there was no degradation of cellulose, the solvent reuse did not need complex purification, and the reuse effect was not affected by the reuse times. The overall process was clean and efficient.

The related research results were published in carbohydrates polymers. The research work has been supported by the National Natural Science Foundation of China, the strategic leading science and technology project of Chinese Academy of Sciences, Shandong natural science outstanding youth fund and Qingdao Energy Institute Independent deployment fund.