| Grapefruit peel is a natural and multifunctional biosorbent.Due to the excellent adsorption properties exhibited by its micropores,aerogels made from grapefruit peel have become a novel material with properties such as light weight,high specific surface and high porosity,which have potential applications in the fields of adsorption,oil-water separation and catalysis.In addition,palladium-catalyzed coupling reactions are a powerful means of constructing C-C bonds in organic synthesis,and the Suzuki coupling reaction for the production of linked aryl groups has been one of the most popular coupling reactions in recent years.Traditional coupling reactions for the construction of C-C bonds are cumbersome to prepare,use toxic solvents and ligands,and post-treatment of ligands and residues of palladium complexes in the reaction medium not only affect the quality of the product,but also pollute the environment,which is not in line with the development of green chemistry.The use of economical and sustainable methods as well as the reuse of palladium catalysts is necessary.In this paper,cellulose aerogels(grapefruit peel aerogels and non-woven aerogels)were prepared and modified.The modified grapefruit peel aerogels were used as palladium catalyst carriers for the Suzuki coupling reaction and the catalytic activity and recycling ability of the catalysts were investigated.This paper is divided into three parts,the first part prepares grapefruit peel aerogel;the second part designs and synthesizes a reusable cellulose aerogel-loaded palladium catalyst carrier for Suzuki cross-coupling reaction;the third part prepares non-woven aerogel to broaden the source of aerogel.The microscopic morphology and crystal structure of the samples before and after modification were also studied with the help of characterisation methods such as scanning electron microscopy,X-ray diffraction and transmission electron microscopy.The details are as follows.1.Study on the preparation modification and adsorption properties of grapefruit peel aerogels.In this study,freeze-drying process was used to prepare grapefruit peel aerogel,and the modification scheme of methyltrimethoxysilane,sodium sulfide,potassium hydroxide and dipotassium hydrogen phosphate was determined.The adsorption performance of the naringen peel aerogel on water and corn oil before and after modification was investigated,as well as the oil absorption performance and recycling capacity at different temperatures.The results showed that the adsorption capacities of naringen peel aerogels before and after modification were 3.12 g/g,8.08 g/g,7.73 g/g and6.39 g/g for water and 3.39 g/g,6.84 g/g,4.13 g/g,4.95 g/g and 5.00 g/g for corn oil,respectively,and the water and oil absorption capacities were higher than those before modification.The hydrophobic angles of the modified teff peel aerogels were 109.5°,0°,0° and 22.6°,indicating that the teff peel aerogels modified with methyltrimethoxysilane had excellent hydrophobicity.In addition,the high adsorption capacity was maintained after 5 recycling,making it a promising recyclable adsorbent.2.Pd/M-GPA-1 nanocatalysts were designed and synthesised on methyltrimethoxysilane modified grapefruit peel aerogels.The catalytic activity of the catalysts was investigated in a Suzuki coupling reaction with reflux under ambient atmosphere.The optimum reaction conditions were determined by screening the conditions: potassium carbonate as the base,p-xylene as the reaction solvent,reaction time of 30 min and reaction temperature of140℃.The substrate was also extended under the optimum conditions to explore the tolerance of the functional groups.The results showed that the Suzuki coupling reaction was influenced by the electron effect of the substrate and that the presence of electron-absorbing groups favoured the coupling reaction.The catalysts provided coupling products in 54-97% yields after five cycles.3.The non-woven aerogel was prepared from non-woven fabric in a system of sodium hydroxide/urea/water(6.5/12/81.5 wt%)in combination with a freeze-drying process and modified with methyltrimethoxysilane for hydrophobicity with a hydrophobic angle of102.5° and relatively good thermal stability at a thermal decomposition temperature of150℃.The modified nonwoven aerogel reached adsorption equilibrium at an adsorption time of 35 min,and the adsorption amount of oil at equilibrium was 10.83 g/g.Due to its good hydrophobic and lipophilic properties,it can be used for oil-water separation.The non-woven aerogel broadens the source of cellulose aerogel and extends the use of non-woven fabrics. |
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