Relationship between the reducibility and selectivity of CeMoxV1-xO4 catalysts by kinetic parameters of TPR

CeVO4, CeMo0.01V0.99O4 and CeMo0.03V0.97O4 were prepared by co-precipitation method. The addition of molybdenum as promoter shows a positive effect on the catalytic behavior of CeVO4 in oxidative dehydrogenation of propane to propylene. The reduction behaviors of the catalysts were characterized by temperature-programmed reduction. The activation energies of reduction process for the catalysts were obtained at different reduction rates by Kissinger method. The addition of Mo to CeVO4 enhances the selectivity to propylene.     

142-164Dy核的低能谱和电磁跃迁的相互作用玻色子模型

采用IBM模型研究了^142-164Dy核的低能正宇称态的能谱和电磁跃迁。应用U(5)→SU(3)的简化哈密顿量较好地描述了它们的能谱和电磁跃迁。研究结果表明，该核基本属于U(5)→SU(3)的过渡核Spectra and E2 transition rates for the even even 142-164Dy isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian capable of describing their spectra and transition is used. It is found that the even even 142-164Dy isotopes are in the transition from U(5)to SU(3) dynamical symmetry.     

荧光分析法测定荜茇有效成分荜茇宁

根据荜茇有效成分荜茇宁的荧光被表面活性剂OP-10显著增敏的特征,提出了胶束增敏荧光法测定蒙药荜茇中荜茇宁的荧光分析新方法.荜茇宁的含量在2.0～16.0μg/mL范围内,与其荧光强度呈良好的线性关系,相关系数为0.9992,方法的回收率为96.9%～104.5%.此方法适合蒙药荜茇中荜茇宁的测定.     

Er,Yb:KGd(WO4)2激光晶体的生长

采用顶部籽晶熔盐法,以K2WO4为助熔剂生长出铒、镱共掺钨酸钆钾[Er,Yb：KGd（WO4）2简称Er,Yb：KGW]激光晶体。XRD分析结果表明晶体为低温相Er,Yb：KGW晶体,即β-Er,Yb：KGW晶体。通过差热分析测量,确定其相变温度和熔点分别为1020℃和1080℃。测量了晶体190-2000nm的室温透过光谱,结果表明除980nm的吸收谱带是Er^3＋离子和Yb^3＋离子的共同谱带之外,其余均属于Er^3＋离子。     

纳米ZnO的制备及光催化活性的研究

纳米ZnO由于它的电子结构的特性和潜在的应用受到广泛的关注[1].ZnO既是一个典型的催化材料,又是一类非常有代表性的电化学,光化学半导体材料[2].ZnO的制备国内外有不少报道,如溶胶凝胶法[3]、喷雾干燥法[4]、超声辐射沉淀法[5]等.……     

Inhibitory effects of silk protein, sericin on UVB-induced acute damage and tumor promotion by reducing oxidative stress in the skin of hairless mouse

This study was conducted to assess protective effect of an antioxidant protein, sericin, on UVB-induced acute damage and tumor promotion in mouse skin. In experiment 1, HR-1 hairless mice were treated with 180 mJ/cm2 of ultraviolet B light (UVB) once daily for 1 and 7 days. The treatment for 7 days caused red sunburn lesions of the skin. The intensity of red color and area of these lesions were inhibited by the topical application of sericin at the dose of 5 mg after UVB treatment. Immunohistochemical analyses showed that the application of sericin significantly suppressed UVB-induced elevations in 4-hydroxynonenal (4-HNE), expression of cyclooxygenase-2 (COX-2) protein, and proliferating cell nuclear antigen (PCNA)-labeling index in the UVB-exposed epidermis. In experiment 2, HR-1 hairless mice were treated with 200 nmol of 7,12-dimethylbenz [alpha] anthracene (DMBA) followed 1 week later by irradiation with 180 mJ/ cm2 of UVB twice weekly for 22 weeks. The protective effect of sericin was evident in terms of significant reduction in tumor incidence and tumor multiplicity at the dose of 5 mg. The results suggest that sericin possesses photoprotective effect against UVB-induced acute damage and tumor promotion by reducing oxidative stress, COX-2 and cell proliferation in mouse skin.     

Preparation and characterization of nanocrystalline ZnO by direct precipitation method

Nanocrystalline ZnO was prepared with ZnCl₂·2H₂O and (NH₄)₂CO₃ as raw materials by direct precipitation method. The precursor was proved to be [Zn₅(OH)₆(CO₃)₂] by TG-DTG-DTA and IR analysis. This precursor was calcined at 300°C for 1, 2 and 3 hours respectively, and then the nanocrystalline ZnO of different grain size were obtained. The nanocrystalline ZnO was characterized using X-ray diffraction (XRD), TEM and Brunner-Emmett-Teller method (BET). Experimental results for nanocrystalline ZnO showed that the minimum size was about 8nm, the maximum was about 15 nm and the mean grain size was 12 nm, the surface area was 80.56 m²/g and the purity was 99.9% when the precursor was calcined at 300°C for 2 h. __________ Translated from Journal of Inner Mongolia Normal University (Natural Science Edition), 2006, 35(1) (in Chinese)     

Synergetic effect between NiO and Ni3V2O8 in propane oxidative dehydrogenation

The oxidative dehydrogenation (ODH) of propane was investigated on Ni-V-O catalysts in a wide range of vanadium contents (5-40%). The addition of a small amount of vanadium significantly increased the catalytic activity of NiO for oxidative dehydrogenation of propane to propene. The formation of propene has a good correlation with the coexistence of NiO and Ni₃V₂O₈. This result strongly suggests that a synergetic effect exists between them in Ni_XV_1-XO_Y (X = 0.95 to 0.6). The best results were obtained with a high Ni/V ratio (e.g. X = 0.95 to 0.85). The active sites and selective oxygen species are discussed. The influence of the catalyst preparation technique and the redox properties of the catalyst were also examined.     

Studies on the oxidative dehydrogenation of propane to propene over Co-V-O catalysts

A series of Co-V-O catalysts were prepared and their catalytic performances for the oxidative dehydrogenation of propane to propene were investigated. It was found that the p-type catalysts showed higher catalytic behavior than the n-type catalyst.     

Cu-Mn-O催化剂的结构对丙烷还原NO反应的性能影响

以尿素为沉淀剂, 分别用水热法和均相沉淀法制备了一系列Cu-Mn-O氧化物催化剂, 并对催化剂进行了BET, XRD, XPS和FT-IR等表征, 考察了Cu-Mn-O催化剂在无氧条件下对丙烷还原去除NO的催化反应性能. 结果表明, Cu-Mn-O体系的物相组成与制备方法和焙烧温度有关, 并影响丙烷还原NO反应的催化性能. 当焙烧温度在500～600 ℃时, 水热法制备的样品中的主要物相是Cu_1.5Mn_1.5O₄和CuMn₂O₄|而尿素均相沉淀法样品中的主要物相为类尖晶石Cu_1.5Mn_1.5O₄|当焙烧温度在700～900 ℃时, 水热法样品中的主相为尖晶石CuMn₂O₄, 而均相沉淀法中仍是Cu_1.5Mn_1.5O₄相. 因此, 对水热法而言, 当焙烧温度由600 ℃增加到700 ℃时, 发生了Cu_1.5Mn_1.5O₄到CuMn₂O₄的相变, 这一相变不仅影响晶粒度和比表面积, 并提高了丙烷还原NO反应的催化活性. 根据XRD, XPS的实验结果和尖晶石结构的特征, 得到了详细的Cu_1.5Mn_1.5O₄和CuMn₂O₄的结构式, 并根据得到的结构式在一定深度上解释了二者催化性能的差别. XRD结果显示在无氧条件下进行丙烷还原NO反应后, 反应温度为600 ℃时, 催化剂中的主相尖晶石结构遭到破坏, 分解为MnO, CuO和Cu的混合物. 这些由尖晶石分解而成的混合物在无氧条件下仍对催化反应有优异的催化活性(NO转化率达到40%). 在本工作中, 用FT-IR表征了反应后的催化剂表面, 发现了大量的NO₂吸附物种和少量的NO₃吸附物种. 这是C₃H₈还原NO反应的中间产物, 从而进一步为“协同反应机理”提供了依据.