Effect of manganese on the catalytic performance of an iron-manganese bimetallic catalyst for light olefin synthesis

A systematic study was carried out to investigate the promotion effect of manganese on the performance of a coprecipitated iron-manganese bimetallic catalyst for the light olefins synthesis from syngas. The catalyst samples were characterized by N2 physisorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), Mo¨ssbauer spectroscopy, H2-differential thermogravimetric analysis (H2-DTG), CO temperature-programmed reduction (CO-TPR) and CO2 temperature-programmed desorption (CO2-TPD). The Fischer-Tropsch synthesis (FTS) performance of the catalyst was measured at 1.5 MPa, 250 C and syngas with H2 /CO ratio of 2.0. The characterization results indicated that the addition of manganese decreases the catalyst crystallite size, and improves the catalyst BET surface area and pore volume. The presence of manganese suppresses the catalyst reduction and carburization in H2 , CO and syngas, respectively. The addition of manganese improves the catalytic activity of water-gas shift reaction and suppresses the oxidation of iron carbides in the FTS reaction. The incorporation of manganese improves the catalyst surface basicity and results in a significant improvement in the selectivities to light olefins and heavy hydrocarbons (C5+ ), and furthermore an inhibition of methane formation in FTS. The pure iron catalyst (Mn-00) has the highest initial FTS catalytic activity (65%) and the lowest selectivity (17.35 wt%) to light olefins (C=2-C=4 ). The addition of an appropriate amount of manganese can improve the catalyst FTS activity.     

AunY(n＝1—9)掺杂团簇的结构和电子性质研究

采用相对论有效原子实势(RECP)近似和密度泛函(B3LYP)方法，选择LANL2DZ基组，优化得到了Au_nY(n＝1—9)二元掺杂团簇稳定的基态结构和电子性质.研究结果表明，掺杂Y原子的Au_nY(n＝1—9)团簇随n的变化，其电离势、电子亲合能和费米能级与Au_n(n＝2—9)一样具有“奇-偶”振荡效应；团簇离子的稳定性具有“幻数”现象，Au₂Y⁺和Au₆Y⁺比其他团簇离子更稳定，与质谱实验结果一致；同一团簇中，团簇最稳定的异构体(基态)是趋于Y原子有最大的邻近的Au原子数. 关键词： Au-Y团簇 密度泛函 平衡几何结构 电子性质     

Pure quantitative characterization of linear groups over the binary field

The purpose of this paper is to discuss the pure scalar characterization of the automorphism group Aut (L ₅(2)) and the linear group L ₆(2). It is proved that Aut(L ₅(2)) and L ₆(2) can be characterized quantitatively by the set of element orders. The main results are obtained by using William’s work on prime graph components of finite groups and Brauer characters in trivializing the possible 2-subgroups. __________ Translated from Chinese Annals of Mathematics, 2003, 24A(6): 675–682. This work was supported by the National Natural Science Foundation of China under grant number 10171074     

Cr~(4 )∶YAG固体激光器效率的理论分析

对Cr~(4 )∶YAG固体激光器的吸收效率、量子效率、储存效率和提取效率等本征效率进行了分析.Cr~(4 )∶YAG晶体的吸收截面、发射截面、上能级寿命和激活离子浓度等对激光器的本征效率有很大的影响.提高Cr~(4 )∶YAG晶体的光学品质和激活离子的掺杂浓度,优化泵浦源的运转波长和激光腔的设计都能显著改善Cr~(4 )∶YAG固体激光器的本征效率.     

最高阶元素个数为4pm的有限群

本文研究了最高阶元素个数对群结构的影响．运用群阶的素因子，k阶循环子群共轭类的长，以及K3-单群和K4-单群的相关结论，证明了最高阶元素个数为4p^m（p为素数，p〉17,2p＋1≠2^a3^b，且2^a3^b-1是素数，m是正整数）的有限群是可解群．     

论有限群元素共轭类的平均长度

本文研究有限群元素共轭类的平均长度问题.利用初等群论方法和有限群特征标理论,在共轭类平均长度为某一定数时,获得了对有限群结构的刻划,且对有限群数量性质的研究是有意义的.     

Estimations for ultimate boundary of a new hyperchaotic system and its simulation

This paper has investigated the boundedness of a new hyperchaotic Rabinovich system. We have obtained the global exponential attractive set and the ultimate bound Ω _λ for this system. Furthermore, we can conclude that the rate of the trajectories of the system going from the exterior of the set Ω _λ,2 to the interior of the set Ω _λ,2 is an exponential rate. The estimate of the trajectories rate is also obtained. Numerical simulations are presented to show the effectiveness of the proposed scheme.     

6-苄氨基腺嘌呤-Cu(Ⅱ) -三苯甲烷类染料体系的吸收和共振瑞利散射光谱及其分析应用

在pH值为5.37～5.58的HAc-NaAc缓冲溶液中,6-苄氨基嘌呤(6-BA)能与Cu(Ⅱ)反应生成螯合物[6-BA·Cu]2+,可再与三苯甲烷类染料形成三元离子缔合物,其摩尔比分别为2∶1(里斯沙明绿)、3∶1(固绿)和2.5∶1(水溶性苯胺蓝).反应体系的吸收光谱发生变化,其共振瑞利散射光谱(RRS)和倍频散射(FDS)显著增强,3个体系的最大RRS峰均位于372 nm附近,6-BA浓度在一定范围内的增加与相应的RRS强度( △IRRs)、FDS( △IFDS)强度和吸光度(△A)均呈线性关系.其RRS检出限分别为5.48 μg/L(里斯沙明绿)、18.43 μg/L(固绿)和9.34 μg/L(水溶性苯胺蓝).据此建立6-BA-Cu(Ⅱ)-里斯沙明绿染料体系测定痕量6-BA的RRS法,并用于豆芽中6-BA的快速测定,结果令人满意.此外,还应用计算化学软件Gaussview3.07和Gaussian03W,采用密度泛函法,在B3 LYP/6 -31G基组水平上计算6-BA的电荷分布,并对里斯沙明绿体系的反应机理及RRS增强的主要原因进行了初步探讨.     

Global dissipativity of a class of BAM neural networks with time-varying and unbound delays

In this paper, we study the global dissipativity of a class of BAM neural networks with both time-varying and unbound delays. Based on Lyapunov functions and inequality techniques, several algebraic criteria for the global dissipativity are obtained. And the linear matrix inequality (LMI) approach is exploited to establish sufficient easy-to-test conditions which are related to the derivative of delay for the global dissipativity. Meanwhile, the estimations of the positive invariant set, globally attractive set and globally exponential attractive set are given out. Finally, two examples are presented and analyzed to demonstrate our results.