Improved sulfur-resistant ability on CO oxidation of Pd/Ce0.75Zr0.25O2 over Pd/CeO2-TiO2 and Pd/CeO2

The influence of sulfation on Pd/Ce0.75Zr0.25O2, Pd/Ce O2-Ti O2 and Pd/Ce O2 was investigated. Physical structure and chemical properties of different catalysts were characterized by N2 adsorption, X-ray diffraction(XRD), CO chemisorption, X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FT-IR) and X-ray fluorescence(XRF). After 10 h SO2 sulfation, it was found that the decrement on CO oxidation catalytic activity was limited on Pd/Ce0.75Zr0.25O2 compared to Pd/Ce O2-Ti O2 and Pd/Ce O2. It demonstrated that Pd/Ce0.75Zr0.25O2 was more sulfur resistant compared to the other two catalysts. After sulfur exposure, catalyst texture was not much influenced as shown by N2 adsorption and XRD, and surface Pd atoms were poisoned indicated by CO chemisorption results. Pd/Ce0.75Zr0.25O2 and Pd/Ce O2-Ti O2 exhibited less sulfur accumulation compared to Pd/Ce O2 in the sulfation process. Furthermore, XPS results clarified that surface sulfur amount, especially surface sulfates amount on the sulfated catalysts was more crucial for the deactivation in sulfur containing environment.     

纳米TiO2负载钯催化剂的性能研究

采用浸渍法制备了纳米TiO2负载钯催化剂,以乙炔选择催化加氢制备乙烯为反应模型考察了稀土元素La、空速对纳米Pd／TiO2催化剂性能的影响,并与纳米SiO2为载体的Pd—La／SiO2催化剂的性能做了比较。实验结果表明,纳米Pd／TiO2催化剂具有良好的催化活性和性能稳定性,La的加入显著提高了乙烯的选择性、增幅达加％左右。与Pd—La／SiO2催化剂相比,Pd—La／TiO2催化剂具有更高的选择性。     

Performance of Pd/CeO2-ZrO2-Al2O3 catalyst for motorcycle

The Pd-only catalysts for motorcycle were prepared by impregnating CeO2-ZrO2-Al2O3 and CeO2-ZrO2+Al2O3 with PdCl2 aque-ous solution and characterized by X-ray diffraction (XRD), oxygen storage capacity (OSC) and H2-temperature-programmed reduction (H2-TPR) methods. The XRD result indicated that the CeO2-ZrO2-Al2O3 compound prepared by co-precipitation formed a single solid solu-tion and had good thermal stability, and Pd phase was not observed in all catalysts. The TPR results showed that the reduction temperature of Pd/CeO2-ZrO2-Al2O3 catalyst was lower than that of Pd/CeO2-ZrO2+Al2O3 catalyst whether they were fresh or aged catalysts. The Pd/CeO2-ZrO2-Al2O3 exhibited high three-way catalytic activity at low temperature, high thermal stability, and wide working window, sug-gesting a great potential for applications.     

从失效活性Pd/C中回收钯

介绍了失效活性Pd／C催化剂经制粒焙烧、浓盐酸浸出、二氯二氨络亚钯沉淀精炼法提纯、水合联胺还原制取海绵Pd粉的工艺。钯回收率≥95％，纯度≥99．95％。     

Catalytic Behavior of CO Oxidization over Pd/ZrO2 - CeO2 Catalyst

The effects of Pd loading, cerium content, the special surface area of the support and calcination temperature on the catalytic properties of Pd-loaded zirconia-ceria mixed oxide were studied.The results show that loading Pd and increasing cerium content in the mixed oxides can enhance the catalytic activity.There is a little effect of calcination temperature on catalytic activities, implying that these catalysts are effective with good thermal stability.     

A potential role for U2AF-SAP 155 interactions in recruiting U2 snRNP to the branch site

Base pairing between U2 snRNA and the branchpoint sequence (BPS) is essential for pre-mRNA splicing. Because the metazoan BPS is short and highly degenerate, this interaction alone is insufficient for specific binding of U2 snRNP. The splicing factor U2AF binds to the pyrimidine tract at the 3' splice site in the earliest spliceosomal complex, E, and is essential for U2 snRNP binding in the spliceosomal complex A. We show that the U2 snRNP protein SAP 155 UV cross-links to pre-mRNA on both sides of the BPS in the A complex. SAP 155's downstream cross-linking site is immediately adjacent to the U2AF binding site, and the two proteins interact directly in protein-protein interaction assays. Using UV cross-linking, together with functional analyses of pre-mRNAs containing duplicated BPSs, we show a direct correlation between BPS selection and UV cross-linking of SAP 155 on both sides of the BPS. Together, our data are consistent with a model in which U2AF binds to the pyrimidine tract in the E complex and then interacts with SAP 155 to recruit U2 snRNP to the BPS.