The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of ty...The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produced...展开更多
Ti-containing phosphate（ Ti-P-O ） catalysts with different molar ratios of P to Ti （0--2. 0 ） were synthesized and characterized by XRD, N2-adsorption/desorption, IR and temperature-programmed desorption （TPD） m...Ti-containing phosphate（ Ti-P-O ） catalysts with different molar ratios of P to Ti （0--2. 0 ） were synthesized and characterized by XRD, N2-adsorption/desorption, IR and temperature-programmed desorption （TPD） methods. The catalytic properties of Ti-P-O samples in the vapor-phase O-methylation of catechol with methanol were also studied. The catechol conversion increases with the increase of the molar ratio of P to Ti in a range of 0-0. 33, while a further increase in the P content leads to a decrease of the catalytic activity. Meanwhile, the selectivities of the catalysts to the main product（guaiacol） increase gradually with the increase of the molar ratio of P to Ti. The presence of relatively strong Lewis acidic and/or basic sites in the P-free catalyst should be responsible for the formation of C-alkylation products. The weak acid-base characteristics of the catalysts are favourable for the mono-O-methylation of catechol. In comparison with the Lewis acidic sites, the Bronsted acidic sites on the catalysts are more active for the title reaction.展开更多
Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at ro...Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at room temperature(APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N 2 temperature, XRD, UV-Vis, NH 3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Brnsted acid sites were more effective for the reaction.展开更多
The selective H2O2 oxidation reaction of phenol to catechol on Ln-ZrO2 catalyst has improved the selectivity to 85%, to compare with the conventional titania catalyst. With addition of rare earth such as lanthanum, ne...The selective H2O2 oxidation reaction of phenol to catechol on Ln-ZrO2 catalyst has improved the selectivity to 85%, to compare with the conventional titania catalyst. With addition of rare earth such as lanthanum, neodymium, to zirconia as catalyst, the selectivity is increased by 72% and 60% respectively in comparison with the bare titania catalyst.展开更多
The liquid phase alkylation of catechol with tert-butyl alcohol to produce 4-tert-butyl catechol (4-TBC) was carried out over MCM-41, HZSM-5, H-exchanged montmorillonite and novel acidic porous montmorillonite heteros...The liquid phase alkylation of catechol with tert-butyl alcohol to produce 4-tert-butyl catechol (4-TBC) was carried out over MCM-41, HZSM-5, H-exchanged montmorillonite and novel acidic porous montmorillonite heterostructures (PMHs). Upon all catalysts tested, 4-TBC is the main product and 3-tert-butyl catechol (3-TBC) and 3,5-di-tert-butyl catechol are the side products. The synthetic PMHs showed higher conversion of catechol and better selectivity to 4-TBC compared to other solid acid catalysts tested. Over the PMHs derived from H-exchanged montmorillonite through template extraction processes, the suitable reaction temperature is ca 410 K, the ratio of catechol to tert-butyl alcohol is 1:2. Increasing the amount of catalyst (lower weight hourly space velocity) can improve the conversion of catechol and influence the selectivity slightly. The reasonable reaction time is ca 8 h.The type and strength of acidity of H-montmorillonite and PMH were determined by pyridine adsorption FT-IR and ammonia temperature-programmed desorption techniques. The medium and strong acid sites are conducive to producing 4-TBC and the weak acid sites to facilitating the 3-TBC formation. The differences between the PMHs from calcination and those fi'om extraction are attributed to proton migration and acidity change in the gallery surface.展开更多
Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly bas...Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.展开更多
Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted cate...Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted catechols and their radicals generated after H-abstraction. It was found that although the charge difference between hydrogen-bonded H and O played a role in determining HIHB, HIHB was mainly governed by the hydrogen bond length. As the oxygen-centered radical has great tendency to form a chemical bond with the H atom, hydrogen bond lengths in catecholic radicals are systematically shorter than those in catechols. Hence, the HIHB for the former are higher than those for the latter.展开更多
In a quest for better chelating therapy drugs for the treatment of intoxication by Fe, Al, oractinides, two new series of mixed catechol-bisphosphonate through amide linkage were synthesized.Benzyl group was used as p...In a quest for better chelating therapy drugs for the treatment of intoxication by Fe, Al, oractinides, two new series of mixed catechol-bisphosphonate through amide linkage were synthesized.Benzyl group was used as protecting group to avoid the breakage of amide by acid hydrolysis orimcomplete reaction in silylation-dealkylation using bromotrimethylsilane.展开更多
基金supported by the National Natural Science Foundation of China(No.20875059)
文摘The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produced...
基金Supported by the Development Project of Science and Technology of Jilin Province(Nos. 20050309-1 and 20040563), the Spe-cialized Research Fund for the Doctoral Program of Higher Education(No.20040183003), CNPC(No.JTGS 20040010), and the Na-tional Natural Science Foundation of China(No.20403006)
文摘Ti-containing phosphate（ Ti-P-O ） catalysts with different molar ratios of P to Ti （0--2. 0 ） were synthesized and characterized by XRD, N2-adsorption/desorption, IR and temperature-programmed desorption （TPD） methods. The catalytic properties of Ti-P-O samples in the vapor-phase O-methylation of catechol with methanol were also studied. The catechol conversion increases with the increase of the molar ratio of P to Ti in a range of 0-0. 33, while a further increase in the P content leads to a decrease of the catalytic activity. Meanwhile, the selectivities of the catalysts to the main product（guaiacol） increase gradually with the increase of the molar ratio of P to Ti. The presence of relatively strong Lewis acidic and/or basic sites in the P-free catalyst should be responsible for the formation of C-alkylation products. The weak acid-base characteristics of the catalysts are favourable for the mono-O-methylation of catechol. In comparison with the Lewis acidic sites, the Bronsted acidic sites on the catalysts are more active for the title reaction.
基金Supported by the Foundation of Science of Jilin Province Science and Technique Com mittee( No.990 5 4 6 )
文摘Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at room temperature(APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N 2 temperature, XRD, UV-Vis, NH 3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Brnsted acid sites were more effective for the reaction.
文摘The selective H2O2 oxidation reaction of phenol to catechol on Ln-ZrO2 catalyst has improved the selectivity to 85%, to compare with the conventional titania catalyst. With addition of rare earth such as lanthanum, neodymium, to zirconia as catalyst, the selectivity is increased by 72% and 60% respectively in comparison with the bare titania catalyst.
基金Supported by the National Natural Science Foundation of China (No. 20376075) the Natural Science Foundation of Zhejiang Province (No. 201057).
文摘The liquid phase alkylation of catechol with tert-butyl alcohol to produce 4-tert-butyl catechol (4-TBC) was carried out over MCM-41, HZSM-5, H-exchanged montmorillonite and novel acidic porous montmorillonite heterostructures (PMHs). Upon all catalysts tested, 4-TBC is the main product and 3-tert-butyl catechol (3-TBC) and 3,5-di-tert-butyl catechol are the side products. The synthetic PMHs showed higher conversion of catechol and better selectivity to 4-TBC compared to other solid acid catalysts tested. Over the PMHs derived from H-exchanged montmorillonite through template extraction processes, the suitable reaction temperature is ca 410 K, the ratio of catechol to tert-butyl alcohol is 1:2. Increasing the amount of catalyst (lower weight hourly space velocity) can improve the conversion of catechol and influence the selectivity slightly. The reasonable reaction time is ca 8 h.The type and strength of acidity of H-montmorillonite and PMH were determined by pyridine adsorption FT-IR and ammonia temperature-programmed desorption techniques. The medium and strong acid sites are conducive to producing 4-TBC and the weak acid sites to facilitating the 3-TBC formation. The differences between the PMHs from calcination and those fi'om extraction are attributed to proton migration and acidity change in the gallery surface.
文摘Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.
基金supported by the National Natural Science Foundation of China (Grant No. 30100035).
文摘Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted catechols and their radicals generated after H-abstraction. It was found that although the charge difference between hydrogen-bonded H and O played a role in determining HIHB, HIHB was mainly governed by the hydrogen bond length. As the oxygen-centered radical has great tendency to form a chemical bond with the H atom, hydrogen bond lengths in catecholic radicals are systematically shorter than those in catechols. Hence, the HIHB for the former are higher than those for the latter.
文摘In a quest for better chelating therapy drugs for the treatment of intoxication by Fe, Al, oractinides, two new series of mixed catechol-bisphosphonate through amide linkage were synthesized.Benzyl group was used as protecting group to avoid the breakage of amide by acid hydrolysis orimcomplete reaction in silylation-dealkylation using bromotrimethylsilane.
