Investigation On Acidic Functional Groups And Structure Stability Of Char-Based Solid Acids

Char-based solid acids prepared from biomass resources have become a hot spot in catalysts research field since 2004. Catalytic stabilities of these catalysts mainly depends on stabilities of their sketch and active acid centers. Therefore, that improving their mechanical performances and analyzing reasons why their catalytic stabilities decreasing can provide a new method for further improving the catalysts’ catalytic stabilities. It also provides basic data for research of the catalysts’ industrialization.The role of acidic groups of camphor char-based sulfonic acid in reaction of epoxy cyclohexane with methanol was investigated by shielding sulfonic acid functional groups and carboxylic acid functional groups or phenolic hydroxyl groups. Sulfonic acid groups were the active sites in the catalyst, carboxylic acid functional groups show weak catalytic activity, while phenolic hydroxyl groups show no activity. However, the presence of phenolic hydroxyl groups in camphor char-based sulfonic acid help to improve its catalytic performance. Results of kinetics study show that the promoting effect of the weak acid functional groups on this reaction is realized by promoting the absorption and desorption of the reaction substrate on the catalyst surface.Bamboo char-based sulfonic acid was prepared from bamboo dusk, and its catalytic stability had been detected in water-contained system--the synthesis of cyclohexanone ethylene ketal and anhydrous system--alcoholysis of epoxy cyclohexane. Catalytic activity of this solid catalyst decreased because of losing of sulfonic acid functional groups. In water-contained system, the reasons for decrease of sulfonic acid density were hydrolysis of sulfonic acid functional groups and synthesis of sulfonic acid ester, while in anhydrous system the main reason was synthesis of sulfonic acid ester. However, catalytic activity of bamboo char-based sulfonic acid can be recovered by H+ exchange and resulfonation.Char-based sulfonic acid with high wear resistance was prepared through vacuum carbonization of bamboo pieces, char formaldehyde treatment and sulfonation. Test method of wear resistance of char-based sulfonic acid was established, and formaldehyde treatment conditions were optimized. Wear resistance of char-based sulfonic acid was greatly improved by treating the char precursor with formaldehyde. Wear rate of the formaldehyde treated catalyst decreased to 4.03%, compared to that of the untreated sample 25.28%. The optimal treated conditions were mchar:V formaldehyde:Vsulfuric acid =4:20:1, temperature 40 ℃, time 8 h.