Haiyang Zhu

Influence of magnesia modification on the properties of copper oxide supported on γ-alumina

XRD, BET, TPR, UV-vis DRS and in situ FT-IR were employed to investigate the dispersion, reduction and CO(2)-adsorption behaviors of copper oxide supported on magnesia modified gamma-Al(2)O(3) (Mg-Al) samples. The results indicate that magnesia could be highly dispersed on the surface of gamma-Al(2)O(3) to form a monolayer and the dispersion capacity is about 1.55 mmol/(100 m(2)gamma-Al(2)O(3)). For copper oxide supported on Mg-Al samples, both the dispersion capacity and the reduction temperature of surface CuO decrease with the MgO loading. CO(2)-adsorption IR results show that the surface strong basic amount for the catalysts increases with the dispersed MgO loading. In addition, the activity of CO oxidation suggests that the main active species in this system should be small CuO cluster and the existence of dispersed MgO enhances the activity of CO oxidation. The catalysts might be applied in pollution control devices for vehicle exhaust, CO gas sensors, catalytic combustion and gas purification of CO(2) lasers. All the results have been discussed by the consideration of the variation of gamma-Al(2)O(3) surface structure before and after magnesia modification.

Effect of titania structure on the properties of its supported copper oxide catalysts.

Anatase and rutile have the same chemical composition as TiO(2) but different crystalline structures (space group of D(4h)(19)-I4(1) for anatase and D(4h)(14)-P4(2) for rutile, respectively), which result in different surface structures and can be used ideally to investigate the effects of support and surface structure on the properties of their supported catalysts. In this work, anatase- or rutile-supported copper oxide catalysts (signed as Cu-A and Cu-R, thereafter) prepared by the impregnation method were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), and H(2) temperature-programmed reduction (H(2)-TPR) to study the support effect of titania on the physicochemical properties and catalytic properties for the NO reduction by CO of these supported copper oxide catalysts. The results indicated that (1) copper oxide presented different dispersion capacities on anatase or rutile; (2) dispersed copper oxide species on anatase and rutile also showed different reduction behaviors; i.e., one-step reduction for dispersed copper oxide species in Cu-A and stepwise reduction for that in Cu-R; (3) the NO+CO activity test suggested dispersed copper oxide and small CuO particles on rutile are the main active species under the current reaction conditions and copper oxide supported on rutile is more active than that on anatase, which might result from Cu(+) species in Cu-R sample formed during the reaction due to its stepwise reduction behavior.

Effect of MnOx modification on the activity and adsorption of CuO/Ce0.67Zr0.33O2 catalyst for NO reduction

The present work explored the effect of MnO(x) modification on the activity and adsorption of CuO/Ce(0.67)Zr(0.33)O(2) catalyst for NO reduction by CO. XRD, Raman, UV, XPS, H(2)-TPR, and in situ FT-IR were used to characterize these catalysts. Results suggested that the incorporation of copper and manganese species resulted in the lattice expansion and the decease of microstrain of ceria-zirconia, thus inducing the formation of oxygen vacancies. There was a strong interaction between surface copper, manganese, and the support via charge transfer. The addition of manganese species could promote the reduction of the resultant catalysts and assist copper oxide in changing the valence and the support in supplying oxygen. These reduction behaviors were dependent on the loading amounts of MnO(x) and the impregnation procedure. In addition, the introduction of MnO(x) cannot change the adsorption type of NO, but readily helped to activate the adsorbed NO species. As a result, these factors were responsible for the enhancement of activity and selectivity through MnO(x) modification.

Influence of ferric oxide modification on the properties of copper oxide supported on γ-alumina

X-ray diffraction (XRD), Mössbauer spectroscopy, and temperature-programmed reduction (TPR) were employed to investigate the dispersion and reduction behaviors of the Fe(2)O(3)/CuO/gamma-Al(2)O(3) system. The results indicated that: (1) the crystalline CuO particle in the CuO/gamma-Al(2)O(3) samples was redispersed during impregnating CuO/gamma-Al(2)O(3) samples with Fe(NO(3))(3) solutions; (2) two different dispersion states of surface iron species could be observed, i.e., State I corresponding to the iron(III) species located in the D layer on the surface of gamma-Al(2)O(3) and State II corresponding to those in the C layer. The dispersed states of surface iron(III) species were closely related to the iron loading amount; (3) the copper species located in the D layer of alumina surface was easily reduced and the copper species located in the C layer were more stable, which could be due to the influence of the iron(III) species in the different layers; (4) in the NO+CO reaction, the catalytic performances were enhanced due to the Cu-Fe synergism and the main active species in this system should be the surface-dispersed copper oxide species.

A comparative study on the dispersion behaviors and surface acid properties of molybdena on CeO2 and ZrO2 (Tet).

Dispersion of molybdena on CeO(2), ZrO(2) (Tet), and a mixture of CeO(2) and ZrO(2) (Tet), was investigated by using laser Raman spectroscopy (LRS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and temperature programmed reduction (TPR). The results indicate that molybdena is dispersed on both individual oxide support and mixed oxide support at the adopted molybdena loadings (0.2 and 0.8 mmol Mo(6+)/100 m(2)) and the structure of the supported molybdena species is intimate association with its loading amount. Two molybdena species are identified by Raman results, i.e. isolated MoO(4)(2-) species at 0.2 mmol Mo(6+)/100 m(2) and polymolybdate species at 0.8 mmol Mo(6+)/100 m(2). IR spectra of ammonia adsorption prove that isolated MoO(4)(2-) species are Lewis acid sites on the Mo/Ce and/or Zr samples, and the polymolybdate species are Brönsted acid sites on the Mo/Ce and/or Zr samples. Moreover, a combination of the Raman, IR and TPR results confirms that at 0.2 mmol Mo(6+)/100 m(2) Ce+Zr, molybdena is preferentially dispersed on the surface of CeO(2) when a mixed oxide support (CeO(2) and ZrO(2)) is present, which was explained in term of the difference of the surface basicity between CeO(2) and ZrO(2) (Tet). Surface structures of the oxide supports were also taken into consideration.

Tacrolimus population pharmacokinetics according to CYP3A5 genotype and clinical factors in Chinese adult kidney transplant recipients

Tacrolimus is characterized by a narrow therapeutic index and a considerable inter‐ and intraindividual pharmacokinetic variability. The aim of our study was to develop a population pharmacokinetic model of tacrolimus in adult kidney transplant of Chinese patients, identify factors especially CYP3A5*3 genetic polymorphism that explain variability, and determine dosage regimens.

A study of thoria on the surface of γ-Al2O3

Abstract The dispersion of thoria on the surface of γ-Al2O3 and the surface properties of ThO2/γ-Al2O3 samples, as well as the influence of the loading amount of thoria on the reduction behavior of copper oxide species, have been studied using XRD, XPS, FTIR, and TPR. The results indicate that the dispersion capacity of thoria, like that of ceria, is much lower than for two other tetravalent metal oxides, zirconia and titania, and the surface adsorption amount of the carbonyl compound and H2O slightly increases with increasing thoria loading. The different thoria loadings can influence the reduction behavior of the dispersed copper oxide by comparing the TPR results of CuO/ThO2/γ-Al2O3 samples. In addition, the lower dispersion capacities of thoria and ceria on γ-Al2O3 are tentatively discussed by considering the structural stability of the two oxides.