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Chinese Journal of Catalysis
2007, Vol. 28, No. 4
Online: 25 April 2007

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Coupling of Epoxides with Carbon Dioxide Catalyzed by Ruthenium Porphyrin JIN Lili;CHANG Tao;JING Huanwang* 2007, 28 (4):  287-289.  Abstract ( 2325 )   [Full Text(HTML)] () PDF (162KB) ( 1080 )   The coupling reaction of epoxides with carbon dioxide catalyzed by ruthenium porphyrin was studied. Reaction conditions were optimized. The new catalyst system of Ru(TPP)(PPh3)2/phenyltrimethylammonium tribromide (PTAT) promoted by ethyl diazoacetate (EDA) is very efficient to catalyze the coupling reaction of rious epoxides and CO2 at 323 K and the molar ratio of substrate∶catalyst∶EDA∶PTAT=200∶1∶1∶2.

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Oxidation of Alcohols over Vanadium Catalysts Wimonrat TRAKARNPRUK;Piyanoot HOONSART 2007, 28 (4):  290-292.  Abstract ( 1630 )   [Full Text(HTML)] () PDF (162KB) ( 748 )   Oxidation of various alcohols (benzyl alcohol, 1-phenylethanol, and cyclohexanol) was studied over vanadium catalysts using tert-butyl hydroperoxide as an oxidant. Vanadium complexes with catecholate or pyrazine 2-carboxylate ligands were prepared and characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, ultraviolet-visible spectroscopy, and elemental analysis. The effect of solvent was investigated. It was found that when the oxidation reaction was performed in toluene solvent, benzyl alcohol was oxidized to benzaldehyde without any overoxidation to benzoic acid; on the contrary, in acetonitrile solvent, both benzaldehyde and benzoic acid were formed. The catalytic activity of some vanadium phosphorus oxides was also compared, and the results showed that higher product yields were obtained when using acetonitrile as the solvent than using toluene.

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The Effect of Supports on the Activity of Methane Dissociation over Rh Catalysts WANG Rui;XU Hengyong*;CHEN Yanxin;LI Wenzhao 2007, 28 (4):  293-295.  Abstract ( 1915 )   [Full Text(HTML)] () PDF (227KB) ( 691 )   The Rh-CeO2 interaction and the activity of CH4 dissociation were investigated on Al2O3- and SiO2-supported Rh catalysts by using the pulse reaction technique, infrared spectroscopy of CO adsorbed , and infrared spectroscopy of pyridine adsorbed. The Rh-CeO2 interaction was strongly influenced by the acidity of support. Addition of CeO2 to Rh/Al2O3 increased the number of Lewis acid sites on Al2O3, which in turn enhanced the ability of Al2O3 to accept electrons. This decreased the electron density of Rh and consequently facilitated the activation and dissociation of CH4 on Rh. On the contrary, the addition of CeO2 to Rh/SiO2 decreased both the number and the strength of Lewis acid sites on SiO2, which weakened the electron-accepting ability of SiO2. As a result, it brought out an increase in the electron density of Rh and inhibited CH4 dissociation on Rh.

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Efficient Synthesis of N-Propyl Aniline from Aniline and 1-Propanol over Cu/SiO2 Catalyst MIAO Zhili;LI Chunmei;DONG Xue;LIU Jing;SHI Lei*;SUN Qi 2007, 28 (4):  296-298.  Abstract ( 1699 )   [Full Text(HTML)] () PDF (186KB) ( 778 )   N-propyl aniline was efficiently synthesized in vapor phase from aniline and 1-propanol at atmospheric pressure over the Cu/SiO2 catalyst that was prepared by the incipient wetness method and temperature-programmed calcinations. The catalyst exhibited very high activity and selectivity. At the reaction temperature of 260 ℃, 1-propanol conversion reached 100%, and the selectivity for N-propyl aniline exceeded 92%. The results of X-ray diffraction showed that the Cu/SiO2 catalyst with high catalytic activity and selectivity had good crystallinity of copper.

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Influence of Pretreatment of Titanium Substrate on Long-Term Stability of TiO2 Film ZHANG Li;ZHANG Pengyi*;CHEN Songzhe 2007, 28 (4):  299-306.  Abstract ( 1918 )   [Full Text(HTML)] () PDF (770KB) ( 869 )   TiO2 films coated on titanium substrates pretreated using different methods were prepared and characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, and electrochemical impedance spectroscopy. The results indicated that the TiO2 film coated on the substrate pretreated with oxalic acid (TiO2/Ti-OC) was tightly, whereas the film coated on the substrate pretreated with sodium carbonate solution (TiO2/Ti-SC) was loose. The catalytic activity of the TiO2/Ti-OC film for the degradation of benzamide remained up to 70% even after dipping in deionized water for 280 d, whereas the TiO2/Ti-SC film lost its photoactivity after dipping in water for 60 d. The deactivation of the catalyst was attributed to the flaking of the coated TiO2, which was caused by the continuous growth of the passive film between the substrate and coated catalyst. Oxalic acid pretreatment could largely prevent the passive film from growing on the substrate and therefore greatly increased the stability of the catalyst during a long-term running. In a 35 day test of continuous declorization of aqueous reactive brilliant red X-3B solution, TiO2/Ti-SC exhibited very high photocatalytic activity and stability.

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Hydrogen Evolution Reaction on Foam Ni-Supported WC Electrocatalyst WU Mei;WEI Zidong;SHEN Peikang* 2007, 28 (4):  307-311.  Abstract ( 2440 )   [Full Text(HTML)] () PDF (472KB) ( 1107 )   Foam Ni-supported Ni-WC electrocatalysts were prepared using direct chemical reduction and intermittent microwave heating methods. The electrocatalysts were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show that the onset potential for the hydrogen evolution reaction on the foam Ni-WC electrocatalyst is 60 mV more positive than that on the pure foam Ni electrocatalyst. The concentration of the electrolyte and the temperature are critical for the catalytic performance of the foam Ni-WC electrocatalyst.

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Liquid-Phase Selective Hydrogenation of Phenol to Cyclohexanone over Pd-Ce-B/Hydrotalcite Catalyst LIU Jianliang;LI Hui;LI Hexing* 2007, 28 (4):  312-316.  Abstract ( 2207 )   [Full Text(HTML)] () PDF (383KB) ( 1019 )   Supported Pd-Ce-B catalysts were prepared by chemical reduction of Pd and Ce ions deposited on hydrotalcite (HT) with an Al3+/(Al3++Mg2+) molar ratio of 0.2. In the reaction of liquid-phase selective hydrogenation of phenol, the as-prepared Pd-Ce-B/HT catalyst exhibited much higher activity and selectivity for cyclohexanone than Pd-Ce-B/Al2O3, Pd-Ce-B/MgO, and Pd-Ce-B/SiO2. The maximum phenol conversion and selectivity for cyclohexanone over 5.8%Pd-Ce-B/HT reached 82.0% and 80.3%, respectively. Based on the results of various characterizations, the catalyst structure-activity correlation and the promoting effects of the Ce dopant and acidic-basic properties of the support on the catalyst behavior were discussed.

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Cr(Ⅲ)-Based Catalyst System for Oligomerization of Ethylene to 1-Octene with High Selectivity ZHANG Baojun;WANG Gang;WANG Sihan;ZHANG Deshun;WANG Yanji* 2007, 28 (4):  317-320.  Abstract ( 1879 )   [Full Text(HTML)] () PDF (231KB) ( 780 )   A four-membered catalyst system (chromium acetyl acetonate (Cr(acac)3)-diphosphinoamine-methylaluminoxane-hexachloroethane) was used in ethylene oligomerization. The effects of promoters, cocatalysts, and reaction conditions such as Al/Cr molar ratio, reaction temperature, and reaction pressure on its catalytic activity and selectivity for 1-octene were studied. The results showed that the four-membered catalyst system for ethylene oligomerization improved the selectivity for 1-octene evidently. Besides the target product 1-octene, main side-products such as 1-hexene, methylcyclopentane, and methylenecyclopentane were also valuable. Methylaluminoxane was an indispensable cocatalyst for producing 1-octene with high selectivity. Hexachloroethane showed a significant promotion effect on improving selectivity towards 1-octene over chromium centers.

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Methanol Steam Reforming over CuZnAl Catalysts Derived from Hydrotalcite PrecursorsⅢ. Effect of Metal Salts Adopted for Hydrotalcite Synthesis TANG Ying;LIU Ye;LU Yong*;ZHU Ping;HE Mingyuan 2007, 28 (4):  321-326.  Abstract ( 2242 )   [Full Text(HTML)] () PDF (411KB) ( 812 )   A series of CuZnAl catalysts for methanol steam reforming have been prepared via pyrogenation of hydrotalcite-like precursors at 600 ℃, which were synthesized by the traditional Na2CO3/NaOH coprecipitation method using nitrates, acetates, sulfates, and chlorides of copper and zinc as Cu(Ⅱ) and Zn(Ⅱ) sources. The use of acetates and nitrates facilitated the crystallization of CuZnAl hydrotalcites, and the derived catalysts had large specific surface area, high Cu dispersion, and good reducibility of CuO. The use of sulfates and chlorides inhibited hydrotalcite crystallization, leading to the reduction of the specific surface area and the reducibility of CuO in the corresponding catalysts. The catalysts prepared from acetates and nitrates were highly active and stable for methanol steam reforming, but those prepared from sulfates and chlorides were inactive due to the poisoning of SO2-4 and Cl- residues. The catalyst prepared from acetates provided much lower CO concentration (0.03%-0.04%) in the dry product gas compared to the catalyst prepared from nitrates (0.2%) with >95% methanol conversion at 250 ℃ and WHSV of 3.28 h-1. Furthermore, CO concentration was reduced to 0.005% over the catalyst prepared from acetates with >95% methanol conversion when the reaction temperature was decreased to 210 ℃ and WHSV to 0.5 h-1. N2O titration and CO2 temperature-programmed desorption measurements indicated that both of the catalysts from acetates and nitrates possessed close values (～50 m2/g) of Cu surface area and very similar basic properties. Temperature-programmed reduction results showed that the peak temperature of CuO for the catalyst from acetates was 70 ℃ lower than that for the catalyst from nitrates, which was attributed to the strong interaction between CuO and ZnO. It might be the intrinsic reason for the significant reduction of the CO concentration on the catalyst from acetates.

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Atomic Force Microscopy Study of Nanostructure of Pt Loaded on TiO2 Fiber ZHOU Xuefeng;LI Wei;ZHENG Zhong;HE Ming;YANG Zhuhong;FENG Xin;LU Xiaohua* 2007, 28 (4):  327-332.  Abstract ( 2023 )   [Full Text(HTML)] () PDF (471KB) ( 1042 )   The surface topography and structure of platinum loaded on TiO2 fiber were investigated by atomic force microscopy. The micron-sized platinum domains were rectangle-like on the TiO2 fiber with low content of Pt but were hexagon-like on the TiO2 fiber with high content of Pt. The topography of Pt domains on TiO2 fiber was similar to Pt nanocluster on TiO2 (110), but the size of Pt domains was obviously larger. The specific topography of Pt domains and the ordered distribution of nano-crystals of TiO2 fiber implied that there was a strong metal-support interaction between Pt and TiO2 fiber. There were many terraces on the Pt domains, and the height of terraces mainly ranged from two to four times the interplanar distance of Pt (111). Moreover, the specific surface area of Pt/TiO2 fiber was almost unchanged before and after the loading of Pt. The strong metal-support interaction and the terrace structure of Pt might be the reasons that the photocatalytic activity of Pt/TiO2 fiber was high although the Pt was micron-sized domains.

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Immobilization of Lipase from Penicillium expansum and Its Application to Transesterification of Corn Oil LI Nanwei;WU Hong;ZONG Minhua*;LOU Wenyong 2007, 28 (4):  333-338.  Abstract ( 2331 )   [Full Text(HTML)] () PDF (340KB) ( 1044 )   Lipase from Penicillium expansum was immobilized by physical adsorption. An inexpensive resin D4020 was selected as the support after screening 20 kinds of supports from different sources for the better immobilization performance. The effects of immobilization conditions on the immobilization efficiency and transesterification activity of the immobilized lipase were systematically studied. The results showed that the optimal enzyme amount, pH, and adsorption time were 0.7 g/g, 9.4, and 4 h, respectively. The transesterification activity of the immobilized lipase could be improved by using 0.5% galactose as a lyoprotectant. Under optimal conditions, the transesterification activity of the immobilized enzyme was 404.4 U/g, whereas the free enzyme did not exhibit transesterification activity. Subsequently, transesterification of corn oil to biodiesel catalyzed by the immobilized lipase was explored. Tert-amyl alcohol was found to be the most suitable reaction medium with a favorable amount of 0.5 ml/g. The optimum enzyme amount, water added, and reaction temperature were 60.6 U/g, 1.2%, and 35 ℃, respectively. A three-step methanolysis protocol was used and one molar equivalent of methanol was added at a reaction time of 0, 2, and 6 h, respectively, by which a methyl ester yield of 85.0% was obtained after reaction for 24 h. Good operational stability was achieved after the enzyme was immobilized, and 62.8% of its original activity was retained after repeated use for 10 batches. The transesterification activity and operational stability of the Penicillium expansum lipase were enhanced remarkably by immobilization.

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Effects of Molecular Mass and Acyl Donors on Enzymatic Acylation of Konjac Glucomannan CHEN Zhigang;ZONG Minhua 2007, 28 (4):  339-344.  Abstract ( 2213 )   [Full Text(HTML)] () PDF (420KB) ( 1020 )   The effects of weight-average molecular mass (Mw) of konjac glucomannan (KGM) and acyl donors on its acylation catalyzed by an immobilized lipase Novozym 435 in t-BuOH were investigated. The results demonstrated that the Mw of KGM had a significant effect on the acylation. The initial reaction rate and degree of substitution of the product decreased with the increase in Mw of KGM. These could be related to the difference in solubility of KGM, viscosity of the reaction system, steric hindrance, and granule structure of KGM with different Mw values. When fatty acid vinyl esters were used as acyl donors for the Novozym 435-catalyzed acylation of KGM in t-BuOH, the initial reaction rate and substitution degree of the product decreased with increasing carbon-chain length of fatty acid vinyl esters. Novozym 435-catalyzed acylation of KGM with various acyl donors in t-BuOH was highly regioselective and occurred predominantly at the C6-OH group of KGM.

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Hydration of Ethylene Oxide to Ethylene Glycol over SnO2-Nb2O5/MgAl2O4/α-Al2O3 Catalyst LI Yingcheng;*;YAN Shirun;YANG Weimin;XIE Zaiku;CHEN Qingling;YUE Bin;HE Heyong 2007, 28 (4):  345-350.  Abstract ( 2221 )   [Full Text(HTML)] () PDF (440KB) ( 699 )   The SnO2-Nb2O5/MgAl2O4/α-Al2O3 catalyst was prepared by modification of α-Al2O3 with MgAl2O4 along with the doping of SnO2 in Nb2O5 and used for hydration of ethylene oxide (EO) to monoethylene glycol (MEG). The effects of Sn/Nb molar ratios on the structure, the acidity and the catalytic performance of the catalyst were investigated by using X-ray diffraction, infrared spectroscopy, temperature-programmed desorption of NH3 and of EO. The phase composition of niobium species, the catalyst acidity, and the adsorption states and strength of EO were markedly influenced by the Sn/Nb molar ratios, leading to different EO conversion and MEG selectivity. MEG selectivity of 95.2% was achieved at n(Sn)/n(Nb)=0.8. The characterization of the used catalyst revealed that no obvious change was recorded, indicating the good hydrothermal stability of the catalyst.

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Preparation of Chitosan-Mediated Expanded Graphite-Supported Amorphous Ni-B Alloy Catalysts and Their Catalytic Hydrogenation Performance WU Meixia;LI Wei*;ZHANG Minghui;TAO Keyi 2007, 28 (4):  351-356.  Abstract ( 2096 )   [Full Text(HTML)] () PDF (435KB) ( 945 )   A series of chitosan-mediated expanded graphite-supported amorphous Ni-B alloy catalysts were successfully prepared by a silver-catalyzed electroless plating method in an aqueous solution. The effects of chitosan on the structure, composition, surface texture, and dispersion of Ni-B particles on expanded graphite were characterized by X-ray powder diffraction, inductively coupled plasma analysis, transmission electron microscopy, selected area electron diffraction, and scanning electron microscopy. The characterization results show that the amorphous structure of Ni-B particles is not influenced by chitosan. The activity of as-prepared catalysts was tested by the hydrogenation of sulfolene to sulfolane and the selective hydrogenation of p-chloronitrobenzene to p-chloroaniline. In comparison with the catalyst without chitosan, the presence of a proper amount of chitosan in the catalyst leads to homogeneous dispersion of Ni-B particles, small size of Ni-B particles, and high catalytic activity.

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Synthesis and Characterization of Mesoporous Aluminum Silicate as a Remarkable Solid Acid Catalyst for Alkylation of Phenol with 1-Octene Zahra MEHRABAN;Faezeh FARZANEH;Mehdi GHANDI;Alireza ABBASI 2007, 28 (4):  357-363.  Abstract ( 2121 )   [Full Text(HTML)] () PDF (459KB) ( 901 )   Mesoporous aluminum silicate molecular sieves with Si/Al molar ratios of 25, 50, 100, and 150 were synthesized from aluminum isopropoxide, tetraethylorthosilicate, and cetyltrimethylammonium bromide by the sol-gel method using acetylacetone as the chelating agent. The results of X-ray diffraction, N2 adsorption, high-resolution transmission electron microscopy, and 27Al nuclear magnetic resonance showed that a mesoporous molecular sieve with a wormhole framework structure was formed. The synthesized molecular sieve with a Si/Al molar ratio of 25 successfully catalyzed the alkylation of phenol with 1-octene at 160 ℃ in liquid phase to the monoalkyl-substituted product quantitatively.

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Highly Dispersed W/Al2O3 Hydrodesulfurization Catalyst Prepared by Hydrothermal Deposition Method WANG Hao;FAN Yu;SHI Gang;LIU Haiyan;BAO Xiaojun* 2007, 28 (4):  364-370.  Abstract ( 2185 )   [Full Text(HTML)] () PDF (445KB) ( 973 )   A novel hydrothermal deposition method for preparing the highly dispersed W/Al2O3 hydrodesulfurization catalyst was developed and compared with the conventional impregnation method. By the hydrothermal deposition method, WO3 was deposited on the γ-Al2O3 support via the precipitation reaction of sodium tungstate and hydrochloric acid under hydrothermal conditions. A cation surfactant hexadecyltrimethylammoni-um bromide (CTABr) was used in the hydrothermal deposition process to prevent the aggregation of WO3 particles. The catalyst was characterized by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, N2 adsorption, and temperature-programmed reduction. The catalyst activity was tested using hydrodesulfurization of dibenzothiophene. The results showed that compared with the catalyst prepared by the impregnation method, the catalyst with the same metal content prepared by the hydrothermal deposition method had higher dispersion of tungsten species, larger specific surface area and pore volume, weaker metal-support interaction, and shorter length and higher stacking of WS2 slabs. As a result, the activity of the catalyst prepared by hydrothermal deposition was 15%-18% higher than that of the catalyst prepared by the impregnation method. The high dispersion of tungsten species and the weak interaction between tungsten species and alumina in the catalyst prepared by hydrothermal deposition should be attributed to the low diffusion resistance of the hydrothermal solution and the structural stabilization effect of the surfactant CTABr.

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Methane Dehydroaromatization over Mo/HZSM-5 Catalyst:Effect of Dealumination of HZSM-5 Zeolite SONG Yibing;SUN Changyong;WU Yanqing;SHEN Wenjie*;LIN Liwu* 2007, 28 (4):  371-376.  Abstract ( 2422 )   [Full Text(HTML)] () PDF (345KB) ( 744 )   Two dealumination methods were used to modify the framework composition of the HZSM-5 zeolite. The structure and acidity of dealuminated zeolite samples were investigated by MAS NMR and FT-IR. It was found that the catalytic performance of the Mo/HZSM-5 catalyst for methane dehydroaromatization was closely related to the acidity of the HZSM-5 zeolite. On the parent zeolite with n(Si)/n(Al)≈27, the presence of superfluous strong Brnsted acid sites caused severe coke deposition during the reaction. Hydrothermal treatment of the parent zeolite extracted tetrahedral Al from the framework and thus led to a significant reduction in the number of Brnsted acid sites. The formation of aromatics over this hydrothermally treated zeolite was suppressed owing to the deficiency of acid sites available for the aromatization of C2 intermediates. High-temperature N2 treatment induced mild dealumination of HZSM-5, destroyed the origin strong Brnsted acid sites, but retained sufficient weak acid sites. This treatment effectively restrained coke deposition and satisfied the requirement of the aromatization of C2 intermediates during the reaction. Therefore, a remarkable improvement in the catalyst durability and selectivity for aromatics was observed.

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Preparation of LiF-Doped TiO2 and Its Photocatalytic Performance for Degradation of Methylene Blue JIANG Hongfu;ZHOU Zuoxing;LIU Xingqin;MENG Guangyao* 2007, 28 (4):  377-382.  Abstract ( 2136 )   [Full Text(HTML)] () PDF (458KB) ( 814 )   LiF-doped TiO2 catalysts were prepared by the sol-gel method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and photoluminescence. The photocatalyst activity for the degradation of methylene blue was evaluated, and the effects of the LiF doping amount, annealing temperature, and pH value of the reaction liquid were investigated. LiF doping favored the formation of the rutile phase, introduced a large amount of hydroxyl, and increased the oxygen vacancy concentration on the surface of TiO2, which led to the high photocatalytic activity of LiF-doped TiO2. Under the conditions of 8% LiF doping, annealing temperature of 500 ℃, and reaction liquid pH value of 6.6, the photocatalytic activity of LiF-doped TiO2 was 5 times higher than that of undoped TiO2.

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Kinetic Study on p-Nitrophenyl Picolinate Hydrolysis Catalyzed by Metallomicelle WANG Min;LI Jun;SANG Xuemei;XIE Jiaqing* 2007, 28 (4):  383-388.  Abstract ( 2170 )   [Full Text(HTML)] () PDF (413KB) ( 869 )   Two transition metal ion macrocyclic complexes, NiR and CuR (R: 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane perchloric acid), were synthesized and characterized. Metallomicelles made up of nickel(Ⅱ) and copper(Ⅱ) complexes with surfactant n-lauroyl sarcosinate (LSS) were used as a mimetic hydrolytic metalloenzyme for catalytic hydrolysis of p-nitrophenyl picolinate (PNPP). The specific absorption spectra of the hydrolytic reaction systems indicated that the key intermediates made up of PNPP and Ni(Ⅱ) or Cu(Ⅱ) complexe were formed during the reaction process. Based on the specific absorption spectra, the mechanism of PNPP catalytic hydrolysis was proposed, and a kinetic mathematical mode was established. The results showed that the two metallomicelles exhibit high catalytic activity for the hydrolysis of PNPP. The catalytic hydrolysis of PNPP is an intramolecular nucleophilic substitution reaction, so the rate of the catalytic reaction is higher than that of spontaneous hydrolysis. The catalytic mechanism proposed is supported by the results of spectral analysis and the kinetic calculation. The structure of NiR and CuR is similar so that the difference of catalytic activity between the two metallomicelles is less.