CO2 Reforming of CH4 over Ni／CeO2-ZrO2-Al203 Prepared by Hydrothermal Synthesis Method

The Ni/CeO2-ZrO2-A12O3 catalyst with different A12O3 and NiO contents were prepared by hydrothermal synthesis method. The catalytic performance for CO2 reforming of CH4 reaction, the interaction among components and the relation between Ni content and catalyst surface basicity were investigated. Results show that the interaction between NiO and A12O3 is stronger than that between NiO and CeO2-ZrO2. The addition of A12O3 can prevent the formation of large metallic Ni ensembles, increase the dispersion of Ni, and improve catalytic activity, but excess A12O3 causes the catalyst to deactivate easily. The interaction between NiO and CeO2 results in more facile reduction of surface CeO2. The existence of a small amount of metallic Ni can increase the number of basic sites. As metallic Ni may preferentially reside on the strong basic sites, increasing Ni content can weaken the catalyst basicity.     

Zeolite Catalyzed Alkylation of Biphenyl. Where Does Shape-Selective Catalysis Occur?

Liquid-phase alkylation of biphenyl (BP) was studied over large-pore zeolites. Selective formation of the least bulky products, 4,4-diisopropylbiphenyl (4,4-DIPB) occurred only in the isopropylation of BP over one- or two-dimensional zeolites, H-mordenite (HM), ZSM-12, SSZ-24, SAPO-5, SSZ-31, and CIT-5. These shape-selective catalyses are ascribed to steric restriction of transition state and to easiness of the substrates to enter into the pores. HM gave the highest selectivity among them. The dealumination of HM enhanced catalytic activity and the selectivity for 4,4-DIPB because of the decrease of coke deposition. Non-regioselective catalysis occurs on external acid sites over HM with the low SiO₂/Al₂O₃ ratio because severe coke deposition deactivates the acid sites inside the pores by blocking pore openings. The selectivity of DIPB isomers was changed with propylene pressure and/or with reaction temperature. Selective formation of 4,4-DIPB was observed at moderate temperatures such as 250°C, whereas the decrease of the selectivity of 4,4-DIPB occurred at higher temperatures as 300°C. 4,4-DIPB yielded selectively under high propylene pressure (<0.3 MPa) at 250°C, while the selectivity of 4,4-DIPB decreased under low propylene pressure as 0.2 MPa. However, 4,4-DIPB was almost exclusive isomer in the encapsulated DIPB isomers inside the pores under every temperature and pressure. The decrease of the selectivity of 4,4-DIPB is due to the isomerization of 4,4-DIPB on the external acid sites. The deactivation of external acid sites of HM was examined by the modification with cerium and other rare earth metal oxide on HM. Selectivities of 4,4-DIPB were improved over modified HM even at high temperatures because of the suppression of non-regioselective alkylation and isomerization at the external acid sites. The ethylation of BP to ethylbiphenyls (EBPs) and diethylbiphenyls (DEBPs) was non-regioselective. The ethylation of BP to EBPs was controlled kinetically. However, there was difference in reactivities of EBPs and DEBPs for their further ethylation. 4-EBP was ethylated preferentially among the isomers, although the formation of 4,4-DEBP was less selective. 4-EBP and 4,4-DEBP have the highest reactivities among EBPs and DEBPs for the ethylation to polyethylbiphenyls (PEBPs). These results show that the environments of HM pores are too loose for shape-selective formation of the least bulky isomers, 4-EBP and 4,4-DEBP, in the ethylation of BP, and that HM pores have enough space for the further ethylation of 4,4-DEBP.     

磁性纳米固体酸SO4^2ˉ-TiO2-Fe3O4催化剂的合成、表征及催化性能的研究

首先研究制备了Fe3O4和SO4^2ˉ-TiO2固体酸催化剂，在此基础上采用共沉淀和浸渍的方法制备了磁性和超细SO4^2ˉ-TiO2-Fe3O4固体酸催化剂。利用XRD，TEM和FT—IR等分析测试手段对催化剂的结构和性能进行了表征。测定结果证实该催化剂具有较小的粒度，较高的磁性表现。在乙酸丁酯合成反应中SO4^2ˉ-TiO2-Fe3O4展示了很高的催化活性（酯化率可达82．7％），而且利用Fe3O4的磁性可对催化剂进行分离和回收．     

Infrared spectroscopic study on the reaction mechanism of CO hydrogenation over Pd/CeO2

In situ infrared spectroscopy was applied to elucidate the reaction mechanism of CO hydrogenation over Pd/CeO₂. Instead of direct dissociation of CO, a new reaction pathway is proposed for methane formation, involving geminal dicarbonyl intermediates and (HCO)₂(a) intermediates, which may be located on the surface of Pd covered with thin layers of reduced ceria (SMST effect). Transformation of methane formation sites into methanol formation ones by the oxidation with water vapor formed during the CO-H₂ reaction is proposed, which may be located on the Pd (111) planes adjacent to ceria support.     

Characterization of Ru/CeO2-Al2O3 catalysts and their Performance in CO2 Methanation

Ru/Al₂O₃ and Ru/CeO₂-Al₂O₃ samples were used as catalysts in CO₂ methanation. The catalysts were characterized by temperature-programmed reduction (TPR) and X-ray diffraction. The promoting effect of ceria on the cataytic activity of the catalysts under study in CO₂ methanation was observed.     

正向化学沉淀法制备纳米ZrO2及其表征

以ZrOCl2·8H2O和NH3·H2O为原料,采用正向化学沉淀法制得了纳米ZrO2,并系统地研究了不同反应条件如:反应物初始浓度、反应温度、沉淀剂加入方式、溶液pH值、煅烧温度和时间等对粒径大小、均匀度的影响,采用Malvem粒度分布仪、扫描电子显微镜、红外光谱仪和X射线衍射仪等对产品进行了表征,并得出结论:正向化学沉淀法制备纳米氧化锆,所得粒子粒度较小、均匀性好,而且反应速度较快、操作简便.     

Improvement of Electrical Conductivity in Fluorite Related Y2O3 and Fluorite CeO2 Systems Based on A Unique Effective Index

Y₂O₃ has a crystal structure of c-type rare-earth oxide. Y₂O₃ does not show an oxide ionic conductivity. On the other hand, CeO₂ based oxide is one of the most interesting of the fluorite oxides since the ionic conductivity of it is higher than that of yttria-stabilized zirconia. However, CeO₂ based oxides are partially reduced and develop electronic conductivity under reduced atmosphere.In this study, the effective index for the improvement of ionic conductivity in Y₂O₃ and CeO₂ systems was defined using ionic radii from the viewpoint of crystallography. The utility of this effective index on some electrical properties was investigated.This revised version was published online in November 2005 with corrections to the Cover Date.     

杂化材料的制备、性能及应用

较详细地介绍了杂化材料的概念及其制备方法、性能和应用。重点是有机高分子－无机杂化材料的制备、性能及应用。     

天然气中温SOFC阳极材料铒掺杂的氧化铈的制备与性能研究

采用溶胶-凝胶法合成了新型中温固体氧化物燃料电池(IT-SOFC)阳极材料Ce_1-xEr_xO_y(x=0.00,0.10,0.15,0.20,0.25,0.30)(EDC),并采用共压-共烧结法制备了以NiO-EDC复合阳极为支撑、以Ce_0.8Gd_0.2O_2-δ(GDC)为电解质、以La_0.8Sr_0.2Co_0.8Fe_0.2O_3-δ(LSCF)-GDC为复合阴极的单电池。利用XRD和SEM等方法对阳极材料EDC进行了晶相结构、微观形貌和化学相容性等分析。在400~700 ℃范围内,以加湿天然气(3% H₂O)为燃料气,氧气为氧化气测试了电池的电化学性能。结果表明：EDC阳极材料具有良好的孔道结构;11种不同阳极组成的单电池中50%(质量分数)NiO-50%(质量分数)Ce_0.85Er_0.15O_y(E15C85)阳极支撑的单电池具有最佳的电化学性能,在650 ℃时其最大电流密度为117.84 mA·cm^-2和最大比功率为24.37 mW·cm^-2。     

掺杂MoO_3对Ce_(0.8)Nd_(0.2)O_(1.9)固体电解质结构与电性能的影响

采用溶胶凝胶方法将过渡金属氧化物MoO3加入到Ce0.8Nd0.2O1.9体系中,讨论MoO3的掺杂对微观结构及电性能的影响。通过X-射线衍射(XRD)、场发射扫描电镜(FE-SEM)等手段对氧化物进行结构表征,交流阻抗谱测试电性能。结果表明:烧结过程中MoO3在晶粒边缘形成液相,增加了晶粒间浸润性,晶粒间位置重排并接触,晶界滑移加快,促使材料致密化,晶界体积分数降低;总电导率和晶界电导率因晶界电阻减少而提高。600℃时,NDC的σt和σgb分别为6.42×10-3和2.03×10-2S·cm-1,加入MoO3后材料的σt提高约1.5倍,σgb提高约4倍。MoO3是NDC体系理想的烧结助剂。