A facile versatile green one-step procedure to fabricating functionalized cellulose nanocrystals (CNCs) with high yields and thermostability was put forward via molten oxalic acid hydrolysis by aid of simultaneous microwave and sonication. The synchronized hydrolysis and esterification of cellulose took place in the one-pot solvent-free reaction, and thus we developed an environmentally benign and scalable concurrent acid hydrolysis/Fischer esterification method to produce acid-functionalized CNCs using microwave and sonication in 85.5% yield. Compared to classical methods for the functionalization of CNCs, the presented study avoided the extensive consumption of water and solvent and achieved zero waste liquid discharge. Moreover, the used solid acid could easily be recycled to make it possible for the large-scale and cleaner production of CNCs. The resultant CNCs with high thermal stability and excellent dispersion stability are excellent for nano-biocomposite applications.
Tungsten-containing WHZSM-5 was synthesized in acid solution by using inorganic ways and using water glass as silicon source and tungstic acid as tungsten source and aluminum sulfate as aluminum source. The influences of the different tungsten content on the catalytic performance of WHZSM-5 were studied. The sample of highest catalytic activity was characterized by XRD、FT-IR、TG-DTA、N2 adsorption -desorption.The results suggested that the synthesized molecular sieve is Microporous molecular sieve of typical ZSM-5 structure with W incorporated into the framework of the molecular sieve.The performance of catalytic performance for Friedel-Crafts of toluene was studied.The result showed that in optimum conditions,the conversion rate of toluene is up to 99% and selectivity up to 90%.After regeneration, the catalytic could be reused for five times, and the reaction activity will be basically unchanged.
An environmentally benign approach for the manufacture of maleic anhydride functionalized cellulose nanocrystals (MA-CNCs) via one-pot tandem reactions with H2SO4 as a catalyst under organic solvent-free conditions was put forward. The effects of ball milling time, ultrasonication temperature and time on the yield and degree of substitution (DS) have been explored.
In temperature sensitive hydrogels, the swelling degree or light transmittance of the gel itself changes with variations in ambient temperature, prompting its wide application in controlled drug release, tissue engineering, and material separation. Considering the amphiphilic structure of β-cyclodextrin (β-CD), a cellulose-based supramolecular hydrogel with superior temperature sensitivity was synthesized based on a combination of cellulose and β-CD as well as the host-guest interaction between β-CD and polypropylene glycol (PPG). In the one-pot tandem reaction process, chemical grafting of β-CD on cellulose and the inclusion complexation of β-CD with PPG were performed simultaneously in a NaOH/urea/water system. The obtained supramolecular hydrogel had a lower critical solution temperature (LCST) of 34 °C. There existed covalent bonding between the cellulose and β-CD, host-guest complexation between the β-CD and PPG, and hydrogen bonding and hydrophobic interactions between the components in the network structure of the supramolecular hydrogel. The combination of various covalent and non-covalent bonds endowed the resulting supramolecular hydrogel with good internal network structure stability and thermal stability, as well as sensitive temperature responsiveness within a certain range-implying its potential as a smart material in the fields of medicine, biology, and textiles. This work is expected to bring new strategies for the fabrication of cellulose-based thermosensitive materials, benefitting the high-value utilization of cellulose.
Carboxylated cellulose nanocrystals (CCN) were prepared from bamboo pulp by ammonium persulfate (APS) with an ultrasonication-assisted technique. The effects of ultrasonication time, APS concentration, and reaction temperature on the yield of CCN were investigated. The morphology, structure, crystallinity, and thermal properties of prepared samples were analyzed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The CCN presented rod-like shapes with diameter ranging from 10 to 30 nm and length of 50 to 200 nm. FTIR showed that CCN still kept with the basic chemical structure of cellulose, and at the 1735 cm-1 appearing the peak of C=O. The XRD pattern indicated that CCN was characteristic of the cellulose I crystal form, and the crystallinity of CCN was 63%. TGA revealed that CCN had a lower thermal stability than bamboo pulp. This research explored a low-cost and eco-friendly way to prepare CCN.
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