A natural polymer catalyst, silica-supported chitosan palladium complex (abbr. as SiO2-CS-Pd) was found to catalyze the hydrogenation of phenol and cresols to corresponding cyclohexanones in high yield and 100% select...A natural polymer catalyst, silica-supported chitosan palladium complex (abbr. as SiO2-CS-Pd) was found to catalyze the hydrogenation of phenol and cresols to corresponding cyclohexanones in high yield and 100% selectivity at 70 degrees C and 1.01325 x 10(5) Pa mild conditions. N/Pd molar ratio in the complex, temperature and solvents have much influence on the reaction. The reactivity order of reactants was found to be: phenol >m->p->o- The catalyst is stable during the reaction and could be repeatedly used for several times without much decrease in its catalytic activity.展开更多
A new chitosan-supported borohydride reducing reagent (CBER) was prepared by treatment of KBH4 with the resin of chitosan derivative, which was first synthesized from: the reaction of cross-linked chitosan microsphere...A new chitosan-supported borohydride reducing reagent (CBER) was prepared by treatment of KBH4 with the resin of chitosan derivative, which was first synthesized from: the reaction of cross-linked chitosan microsphere with glycidyl trimethylammonium chloride. CBER could reduce aromatic carbonyl compound to corresponding alcohol.展开更多
Laccase was immobilized on the ceramic-chitosan composite support by using glutaraldehyde as the cross-linking reagent. The immobilization conditions and characterization of the immobilized enzyme were investigated. T...Laccase was immobilized on the ceramic-chitosan composite support by using glutaraldehyde as the cross-linking reagent. The immobilization conditions and characterization of the immobilized enzyme were investigated. The immobilization of laccase was successfully realized when 3.0 mL of 1.25 mg/mL of laccase at a pH value of 4.0 reacted with 0.15 g of ceramic-chitosan composite support(CCCS) at 4 ℃ for 24 h. The immobilized enzyme exhibited a maximum activity at pH 3.0. The optimal temperatures for immobilized enzyme were 25 ℃ and 50 ℃. The K_m value of immobilized laccase for ABTS was 66.64 μmol/L at a pH value of 3.0 at 25 ℃. Compared with free laccase, the thermal, operating and storage stability of immobilized laccase was improved after the immobilization.展开更多
文摘A natural polymer catalyst, silica-supported chitosan palladium complex (abbr. as SiO2-CS-Pd) was found to catalyze the hydrogenation of phenol and cresols to corresponding cyclohexanones in high yield and 100% selectivity at 70 degrees C and 1.01325 x 10(5) Pa mild conditions. N/Pd molar ratio in the complex, temperature and solvents have much influence on the reaction. The reactivity order of reactants was found to be: phenol >m->p->o- The catalyst is stable during the reaction and could be repeatedly used for several times without much decrease in its catalytic activity.
基金the National Natural Science Foundation of China (No.29977014).
文摘A new chitosan-supported borohydride reducing reagent (CBER) was prepared by treatment of KBH4 with the resin of chitosan derivative, which was first synthesized from: the reaction of cross-linked chitosan microsphere with glycidyl trimethylammonium chloride. CBER could reduce aromatic carbonyl compound to corresponding alcohol.
文摘Laccase was immobilized on the ceramic-chitosan composite support by using glutaraldehyde as the cross-linking reagent. The immobilization conditions and characterization of the immobilized enzyme were investigated. The immobilization of laccase was successfully realized when 3.0 mL of 1.25 mg/mL of laccase at a pH value of 4.0 reacted with 0.15 g of ceramic-chitosan composite support(CCCS) at 4 ℃ for 24 h. The immobilized enzyme exhibited a maximum activity at pH 3.0. The optimal temperatures for immobilized enzyme were 25 ℃ and 50 ℃. The K_m value of immobilized laccase for ABTS was 66.64 μmol/L at a pH value of 3.0 at 25 ℃. Compared with free laccase, the thermal, operating and storage stability of immobilized laccase was improved after the immobilization.