| Solid acid catalysis is one of the important transformation technologies of modern green chemical industry.Among them,biomass carbon sulfonic acids(BCSAs),a kind of environmentally friendly catalysts have attracted much attention because of their low cost,easy availability,high acidity and high activity.However,traditional BCSAs have shortcomings such as less stable structure,low thermal stability and accessibility of acid sites,which restricts their wide application in industry.In order to improve these shortcomings of BCSAs,the dissertation is focused to study the preparation of new structural recombination(SR)BCSAs by intercalation and chemical cross-linking method and their characterization and acid catalytic performance.The main research contents and results are as follows:1.Bamboo carbon(HTBC)prepared by hydrothermal catalytic carbonization was used as a raw material,sodium hydroxide(Na OH),cetyltrimethylammonium bromide(CTMAB)and formaldehyde(FA)aqueous solution were used as a pretreatment agent,an intercalation agent,and a cross-linking agent,respectively,the FA cross-linked SR biomass carbon sulfonic acids(HTBCSAs-FA)were prepared successfully by preswelling,intercalation,chemical crosslinking,heat curing and sulfonation of HTBC,The effect of chemical cross-linking treatment conditions on FA cross-linking effect was investigated and its processing conditions were optimized.The structure,surface functional groups,thermal stability and particle morphology of the catalysts were characterized by small angle X-ray diffraction(SAXRD),FT infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA)and transmission electron microscopy(TEM).Microwave-promoted cellulose hydrolysis reaction was used to examine their acid catalytic properties.The results showed that the structural stability of HTBCSA-FA is better than that of traditional HTBCSA.In the cellulose hydrolysis reaction,the acid catalytic efficiency(conversion number TON,5.19)of the former is significantly higher than that of the latter(3.02),and its reusability has also been greatly improved.2.Using glutaraldehyde(GA)instead of formaldehyde as a crosslinking agent,the GA-crosslinked SR biomass carbon sulfonic acids(HTBCSAsGA)were also prepared by the above treatment processes.The effects of crosslinking conditions,curing temperature on the structural stability and acidity of HTBCSAs-GA catalysts were investigated and the acid catalytic properties were evaluated using the alcoholysis of furan methanol with n-butanol for the synthesis of N-butyl levulinate and the reaction conditions were optimized.The results showed that the GA cross-linking method could improve the structural stability of HTBCSA,and it was superior to the above FA cross-linking method in improving the acidity stability of acid sites(increased by 17℃).HTBCSA-GA under optimized conditions(reaction time 10 h,reaction temperature 90℃,furan methanol: n-butanol = 1 mmol: 60 mmol),the yield of N-butyl levulinate obtained by this alcoholysis was 64.02%,significantly higher than55.97% of HTBCSA,and after three repeated reactions,the decrease in the yield of N-butyl levulinate and the density of sulfonic acid groups on HTBCSA-GA were significantly less than those on HTBCSA.3.Using ethylenediamine(EDA)as a crosslinking agent and the above treatment processes,the preparation and characterization of EDA-cross linked SR biomass carbon sulfonic acids(HTBCSAs-EDA)were carried out and their acid catalysis performance was examined using microwavepromoted cellulose hydrolysis.The preparation conditons of HTBCSAsEDA and their acid catalysis reaction conditions were optimized.The results showed that the EDA cross-linking method can also significantly improve the structural stability of HTBCSA,especially the thermal stability of its acid sites(the thermal decomposition temperature of its sulfonic acid group is increased by 26℃),which leads to a significant improvement in catalytic efficiency(TON increased by 2.91)and reusability for cellulose hydrolysis reaction. |
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