A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane ...A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.展开更多
Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effe...Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1～0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃.展开更多
A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron micro...A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.展开更多
In this work, the addition of praseodymium（Pr） into ceria as a mixed oxide support in a form of Ce（1-x）PrxO2（x = 0.01,0.025, 0.050, 0.075 and 0.10） was prepared using a co-precipitation method. The structural an...In this work, the addition of praseodymium（Pr） into ceria as a mixed oxide support in a form of Ce（1-x）PrxO2（x = 0.01,0.025, 0.050, 0.075 and 0.10） was prepared using a co-precipitation method. The structural and textural properties of the synthesized supports were characterized by X-ray diffraction（XRD）, N2 adsorption-desorption, Raman spectroscopy, H2-temperature programmed reduction（H2-TPR） and H2-chemisorption. Upon addition of Pr, XRD patterns and Raman spectra indicated an enlargement of ceria unit cell and the characteristics Raman broad peak at 570 cm^（-1） which was attributed to the existence of oxygen vacancies in the ceria lattice. This indicated that some Ce^（4＋） ions in ceria were replaced by larger Pr^（3＋） cations. To evidence the incorporation of Pr^（3＋） cations into ceria lattice,X-ray absorption near edge structure（XANES） was employed. The results showed that the oxidation states of Ce in mixed oxide supports were slightly lower than 4＋ while those of Pr were still the same as a precursor salt. Therefore, the incorporation of Pr^（3＋） into ceria lattice would lead to strain and unbalanced charge and result in oxygen vacancies. The reducibility of Ce（1-x）PrxO2 mixed oxide supports was investigated by H2-TPR and temperature-resolved X-ray absorption spectroscopy experiment under reduction conditions. XANES spectra of Ce L3 edges showed a lower surface reduction temperature（Ce^（4＋）to Ce^（3＋）） of Ce（0.925）Pr（0.075）O2 than that of CeO2 which agreed with H2-TPR results. H2-chemisorption indicated that Pr promoted the dispersion of the metal catalyst on the mixed oxide support and increased the adsorption site for CO. For WGS reaction, 1% Pd/mixed oxide support had higher WGS activity than 1%Pd/ceria. The increase of WGS activity was due to the increase of Pd dispersion on the support and the existence of oxygen vacancies produced from incorporation of Pr into the ceria lattice.展开更多
Seven kinds of Schiff base metal complexes(C1-C7)were synthesized by the reaction of substituted salicylaldehyde Schiff base with cobalt nitrate,nickel nitrate,and copper nitrate,respectively.The oxygen carrying perfo...Seven kinds of Schiff base metal complexes(C1-C7)were synthesized by the reaction of substituted salicylaldehyde Schiff base with cobalt nitrate,nickel nitrate,and copper nitrate,respectively.The oxygen carrying performance,and the catalytic property of complexes for the oxidation of model sulfides 1-hexanethiol,dibutyl sulfide,and 2-methylthiophene along with their influencing factors were explored,while the oxidized products of the model sulfides were also analyzed and characterized.The results show that the catalytic oxidation property of the complexes is determined by their oxygen carrying performance and solubility in n-octane.The oxygen carrying performance of the complexes is mainly affected by the central ion species,the electronic effects,and the spatial effects of the substituents as well as the degree of conjugation.More specifically,the oxygen carrying performance can be improved by enhancing the oxygenation capacity of the central metal ions,increasing the electron donating ability of the ligand substituent,and diminishing the steric hindrance as well as extending the conjugated chain.Complexes C7 were found to be with high oxygen carrying capacity and high solubility in n-octane,which shows the best catalytic oxidation property,and the oxidation conversion rates for 1-hexylthiol,dibutyl sulfide,and 2-methylthiophene are 74.2%,65.1%,and 22.7%,respectively.Upon using the oxidation catalyst of Schiff base metal complexes,three sulfides can be oxidized by oxygen to form sulfones and sulfoxides.1-Hexanethiol and dibutyl sulfide will continue to be oxidized to form sulfates and sulfites.展开更多
Mononuclear Cu(II)bipyridine(1)and phenantroline complexes(2)were synthesized and immobilized by different procedures on H3PW12O40 polyoxometalate(POM).Characterization by XRD and SEM-EDX were performed to assess the ...Mononuclear Cu(II)bipyridine(1)and phenantroline complexes(2)were synthesized and immobilized by different procedures on H3PW12O40 polyoxometalate(POM).Characterization by XRD and SEM-EDX were performed to assess the preservation of the Keggin structure and stoichiometry of the complex.The immobilized complexes were tested as heterogeneous catalysts for the partial oxidation of tetralin(1,2,3,4-tetrahydronaphthalene)using hydrogen peroxide as oxidant in acetonitrile/water as solvent.[Cu(2,2'-bpy)Cl][H2PW12O40] and[Cu(1,10-phen)Cl][H2PW12O40]oxidized tetralin at room temperature,with 16%conversion with(2),to 1-tetralone and 2-tetralone with 83%selectivity.However,the selectivity for 1-tetralone was only 56%.Different preparation methods for the heterogenization of these complexes on the POM Keggin unit were compared and used to enhance the selectivity to 1-tetralone to 75%.展开更多
The optimum reaction conditions of the oxidative polycondensation of 2-(thien-2-yl-methylene)aminophenol (2-TMAP) has been accomplished by using air O_2,H_2O_2 and NaOCl oxidants in an aqueous alkaline medium between...The optimum reaction conditions of the oxidative polycondensation of 2-(thien-2-yl-methylene)aminophenol (2-TMAP) has been accomplished by using air O_2,H_2O_2 and NaOCl oxidants in an aqueous alkaline medium between 20℃and 90℃.The structures of the monomer and oligomer were confirmed by FT-IR,UV-Vis,~1H-NMR and ^(13)C-NMR and elemental analysis.TGA-DTA,size exclusion chromatography(SEC) techniques and solubility tests were applied for characterization.The ~1H-NMR and ^(13)C-NMR data show that the polymeriz...展开更多
It was studied by spectroscopy that PSII reaction center complex consisting of three polypeptides, D1, D2 and Cytb559, were purified from PSII particle of CeCl3 treated spinach. The results of the experiment show that...It was studied by spectroscopy that PSII reaction center complex consisting of three polypeptides, D1, D2 and Cytb559, were purified from PSII particle of CeCl3 treated spinach. The results of the experiment show that Ce3+ could improve the growth of spinach, and accelerate electron transport of PSII particles. Of chl-a of UV-Vis spectrum of D1/D2/Cytb559 complex, Soret band was blue-shifted by 3 nm and Q band by 2 nm, respectively, and the fluorescence emission peak was blue-shifted by 5 nm in CeCl3-treated spinach compared with the one in control. By the extended X-ray absorption fine structure (EXAFS) spectroscopy methods, it has been found that Ce3+ is coordinated with 8 nitrogen atoms in the first coordination shell with Ce-N bond length of 0.253 nm, and Ce3+ with 6 oxygen atoms in the second coordination shell with Ce-O bond length of 0.32 nm. However, the secondary structure of D1/D2/Cytb559 complex by circular dichroism (CD) spectroscopy has no significant change after CeCl3 treated. It might be that Ce3+ binds to porphyrin rings of chlorophyll and oxygen of amino acid residue of polypeptide in D1/D2/Cytb559 complex, and then accelerates the primary reaction of PSII, intensifies function of P680+ primary electron donor of D1/D2/Cytb559, but there is little change in conformation of PSII reaction center complex.展开更多
基金the National Natural Science Foundation of China (50574046)National Natural Science Foundation of Major Research Projects (90610035)+1 种基金Natural Science Foundation of Yunnan Province (2004E0058Q)High School Doctoral Subject Special Science and Re- search Foundation of Ministry of Education (20040674005)
文摘A series of Ce1-xFexO2 （x=0, 0.2, 0.4, 0.6, 0.8, 1） complex oxide catalysts were prepared using the coprecipitation method. The catalysts were characterized by means of XRD and H2-TPR. The reactions between methane and lattice oxygen from the complex oxides were investigated. The characteristic results revealed that the combination of Ce and Fe oxide in the catalysts could lower the temperature necessary to reduce the cerium oxide. The catalytic activity for selective CH4 oxidation was strongly influenced by dropped Fe species. Adding the appropriate amount of Fe2O3 to CeO2 could promote the action between CH4 and CeO2. Dispersed Fe2O3 first returned to the original state and would then virtually form the Fe species on the catalyst, which could be considered as the active site for selective CH4 oxidation. The appearance of carbon formation was significant and the oxidation of carbon appeared to be the rate-determining step; the amounts of surface reducible oxygen species in CeO2 were also relevant to the activity. Among all the catalysts, Ce0.6Fe0.402 exhibited the best activity, which converted 94.52% of CH4 at 900 ℃.
文摘Ce x Ti 1- x O 2 mixed oxides of different mole ratios ( x =0, 0.1, 0.2～0.9, 1.0) were prepared by co precipitation of TiCl 4 with Ce(NO 3) 3 and then loaded with different amounts of CuO. The effects of CuO on NO+CO reaction were investigated, and the structure and reductive properties of various CuO/Ce x Ti 1- x O 2 were characterized by the methodologies of BET, TPR and XRD. The results show that different Ce/Ti mole ratios and calcination temperatures induce changes of structure and reductive properties of the Ce x Ti 1- x O 2 mixed oxides. When x =0.1～0.5, amorphous CeTi 2O 6 phase mainly forms at 650 ℃ compared to the formation of CeTi 2O 6 which crystallizes at 800 ℃. When x >0.6, some TiO 2 enters the CeO 2 lattice and a CeO 2 TiO 2 solid solution is formed. The activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 650 ℃ is largely affected by the x values, which is the highest when x =0.3, 0.4 and 0.9. The NO conversion reaches 70% at a reaction temperature of 150 ℃. By comparison, the x values have little effect on the activity of 6%CuO/Ce x Ti 1- x O 2 calcined at 800 ℃ . There are strong interactions between CuO and CeTi 2O 6, i.e., formation of the CeTi 2O 6 phase shifts the CuO reduction peak temperature from 380 to 200 ℃, and CuO, in turn, shifts the CeTi 2O 6 reduction peak temperature from 600 to 300 ℃.
基金financially supported by the National Natural Science Foundation of China (Nos. 51004060, 51104074, and 51174105)the Natural Science Foundation of Yunnan Province (No. 2010ZC018)
文摘A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.
基金Project supported by Center of Excellence for Innovation in Chemistry(PERCH-CIC)Commission on Higher Education,Ministry of Education and the Center of Alternative Energy Research and Development,Khon Kaen University
文摘In this work, the addition of praseodymium（Pr） into ceria as a mixed oxide support in a form of Ce（1-x）PrxO2（x = 0.01,0.025, 0.050, 0.075 and 0.10） was prepared using a co-precipitation method. The structural and textural properties of the synthesized supports were characterized by X-ray diffraction（XRD）, N2 adsorption-desorption, Raman spectroscopy, H2-temperature programmed reduction（H2-TPR） and H2-chemisorption. Upon addition of Pr, XRD patterns and Raman spectra indicated an enlargement of ceria unit cell and the characteristics Raman broad peak at 570 cm^（-1） which was attributed to the existence of oxygen vacancies in the ceria lattice. This indicated that some Ce^（4＋） ions in ceria were replaced by larger Pr^（3＋） cations. To evidence the incorporation of Pr^（3＋） cations into ceria lattice,X-ray absorption near edge structure（XANES） was employed. The results showed that the oxidation states of Ce in mixed oxide supports were slightly lower than 4＋ while those of Pr were still the same as a precursor salt. Therefore, the incorporation of Pr^（3＋） into ceria lattice would lead to strain and unbalanced charge and result in oxygen vacancies. The reducibility of Ce（1-x）PrxO2 mixed oxide supports was investigated by H2-TPR and temperature-resolved X-ray absorption spectroscopy experiment under reduction conditions. XANES spectra of Ce L3 edges showed a lower surface reduction temperature（Ce^（4＋）to Ce^（3＋）） of Ce（0.925）Pr（0.075）O2 than that of CeO2 which agreed with H2-TPR results. H2-chemisorption indicated that Pr promoted the dispersion of the metal catalyst on the mixed oxide support and increased the adsorption site for CO. For WGS reaction, 1% Pd/mixed oxide support had higher WGS activity than 1%Pd/ceria. The increase of WGS activity was due to the increase of Pd dispersion on the support and the existence of oxygen vacancies produced from incorporation of Pr into the ceria lattice.
基金This work was supported by the National Natural Science Foundation of China(No.21576292).
文摘Seven kinds of Schiff base metal complexes(C1-C7)were synthesized by the reaction of substituted salicylaldehyde Schiff base with cobalt nitrate,nickel nitrate,and copper nitrate,respectively.The oxygen carrying performance,and the catalytic property of complexes for the oxidation of model sulfides 1-hexanethiol,dibutyl sulfide,and 2-methylthiophene along with their influencing factors were explored,while the oxidized products of the model sulfides were also analyzed and characterized.The results show that the catalytic oxidation property of the complexes is determined by their oxygen carrying performance and solubility in n-octane.The oxygen carrying performance of the complexes is mainly affected by the central ion species,the electronic effects,and the spatial effects of the substituents as well as the degree of conjugation.More specifically,the oxygen carrying performance can be improved by enhancing the oxygenation capacity of the central metal ions,increasing the electron donating ability of the ligand substituent,and diminishing the steric hindrance as well as extending the conjugated chain.Complexes C7 were found to be with high oxygen carrying capacity and high solubility in n-octane,which shows the best catalytic oxidation property,and the oxidation conversion rates for 1-hexylthiol,dibutyl sulfide,and 2-methylthiophene are 74.2%,65.1%,and 22.7%,respectively.Upon using the oxidation catalyst of Schiff base metal complexes,three sulfides can be oxidized by oxygen to form sulfones and sulfoxides.1-Hexanethiol and dibutyl sulfide will continue to be oxidized to form sulfates and sulfites.
文摘Mononuclear Cu(II)bipyridine(1)and phenantroline complexes(2)were synthesized and immobilized by different procedures on H3PW12O40 polyoxometalate(POM).Characterization by XRD and SEM-EDX were performed to assess the preservation of the Keggin structure and stoichiometry of the complex.The immobilized complexes were tested as heterogeneous catalysts for the partial oxidation of tetralin(1,2,3,4-tetrahydronaphthalene)using hydrogen peroxide as oxidant in acetonitrile/water as solvent.[Cu(2,2'-bpy)Cl][H2PW12O40] and[Cu(1,10-phen)Cl][H2PW12O40]oxidized tetralin at room temperature,with 16%conversion with(2),to 1-tetralone and 2-tetralone with 83%selectivity.However,the selectivity for 1-tetralone was only 56%.Different preparation methods for the heterogenization of these complexes on the POM Keggin unit were compared and used to enhance the selectivity to 1-tetralone to 75%.
基金supported by the Government Planning Organization(GPO2002K120170-7)TUBITAK GrantsCommission for a research grant(No.TBAG-105T428).
文摘The optimum reaction conditions of the oxidative polycondensation of 2-(thien-2-yl-methylene)aminophenol (2-TMAP) has been accomplished by using air O_2,H_2O_2 and NaOCl oxidants in an aqueous alkaline medium between 20℃and 90℃.The structures of the monomer and oligomer were confirmed by FT-IR,UV-Vis,~1H-NMR and ^(13)C-NMR and elemental analysis.TGA-DTA,size exclusion chromatography(SEC) techniques and solubility tests were applied for characterization.The ~1H-NMR and ^(13)C-NMR data show that the polymeriz...
基金This work was supported by the National Natural Science Foundation of China (Grant No. 29805003) Person of Ability Recommended Foundation of Suzhou University (Grant No. XQ316011).
文摘It was studied by spectroscopy that PSII reaction center complex consisting of three polypeptides, D1, D2 and Cytb559, were purified from PSII particle of CeCl3 treated spinach. The results of the experiment show that Ce3+ could improve the growth of spinach, and accelerate electron transport of PSII particles. Of chl-a of UV-Vis spectrum of D1/D2/Cytb559 complex, Soret band was blue-shifted by 3 nm and Q band by 2 nm, respectively, and the fluorescence emission peak was blue-shifted by 5 nm in CeCl3-treated spinach compared with the one in control. By the extended X-ray absorption fine structure (EXAFS) spectroscopy methods, it has been found that Ce3+ is coordinated with 8 nitrogen atoms in the first coordination shell with Ce-N bond length of 0.253 nm, and Ce3+ with 6 oxygen atoms in the second coordination shell with Ce-O bond length of 0.32 nm. However, the secondary structure of D1/D2/Cytb559 complex by circular dichroism (CD) spectroscopy has no significant change after CeCl3 treated. It might be that Ce3+ binds to porphyrin rings of chlorophyll and oxygen of amino acid residue of polypeptide in D1/D2/Cytb559 complex, and then accelerates the primary reaction of PSII, intensifies function of P680+ primary electron donor of D1/D2/Cytb559, but there is little change in conformation of PSII reaction center complex.
