固氮酶活性中心结构模型的EHMO研究

应用群分解EHMO程序,研究了基于MoFe-蛋白X射线衍射结果的固氮酶活性中心结构模型.对比和分析了该模型中尚未确定的配体Y分别为S、O、N、C、H和H…H时的总能量和电荷分布等.结果表明Y=O量为有利.本文进一步提出了Y=O的模型在底物活化过程中Y(O)的邻位加氢后作为活性中心吞吐底物与产物窗口的可能作用方式.     

OXIDATIVE COUPLING OF METHANE OVER Na_2CO_3 DOPED ZIRCONIUM DIORIDE

Na_2CO_3/ZrO_2 catalyst shows a high activity of oxidative coupling of methane. It possesses stronger electron donor ability than that of ZrO_2 catalyst. The activation of methane is supposed to relate to the O_2~- or O_2~(2-) and O~- species.     

甲烷氧化偶联CaF2／Sm2O3催化剂的研究

甲烷氧化偶联ＣａＦ_２／Ｓｍ_２Ｏ_３催化剂的研究周水琴，龙瑞强，黄亚萍，万惠霖，蔡启瑞（厦门大学化学系，固体表面物理化学国家重点实验室，厦门，３６１００５）关键词甲烷氧化偶联，氟化钙，三氧化二钐，离子交换，氧物种甲烷氧化偶联制乙烯是催化领域中最活跃的?..     

钒促铑基催化剂上合成气反应中的H2／D2同位素效应

铑基催化剂可催化合成气生成甲烷、乙醇等,CO中C—O键断裂是该反应的关键步骤。Ⅴ助剂可显著提高Rh的催化活性,其作用本质被认为是促进了CO的直接解离。本文考察了Ⅴ助剂对Rh催化性能的影响及Rh/SiO_2、Rh-V(1:1)/SiO_2上合成气反应的H_2/D_2同位素效应,根据实验结果及键级守恒-Morse势法的计算结果初步探讨了Ⅴ助剂的作用本质。     

THE VORTICITY STRUCTURE OF HOMOGENEOUS ISOTROPIC TURBULENCE IN IT5 FINAL PERIOD OF DECAY

流体力学工作者很早就认识到,湍流运动是由许许多多微小的涡旋廷动所组成.本论文的目的,在于从粘性不可压缩流体的线性性化以后的运动方程的漪旋运动解,来说明均匀各向同性湍流在后期衰变时期的运动现象.确定在这时期作为湍流元随机运动着的涡旋的物理条件是:首先,涡旋的涡量分布必须集中在涡旋的几何中心附近,其次,每一个涡旋的总角动量是一常数.我们运用辛和林家翘的方法来计算湍流中的二元速度关联函数,从而导致米里洪西科夫解.这个解的速度关联和湍能耗拍定律都和白却勒尔与爆生德的实验相符合.最后,我仍指出了湍流的湍性结构是和作为湍流元的涡旋的涡性结构有密切联系以及依据现有涡旋运动解来计算出高元速度关联和其他种类关联函数的可能性.     

FINITE DIFFERENCE SIMULATION OF A STRATIFIED TWO-PHASE SYSTEM

SUMMARY

We have analyzed several different approaches for simulating the fluid motion of a stratified two-phase system. The flow regime is transformed to a regular domain for numerical integration and the standard finite difference formulas are applied to discretize the governing and mapping equations. Five different interface iteration schemes that are based on the kinematic condition and the normal stress balance have been derived to update the position of the liquid-liquid interface. We have found that the iterative scheme based on the normal stress balance is more stable and is applicable to a wide range of capillary numbers, and that these appear to be the only sensitive parameter in the stratified two-phase system under consideration.     

苹果酸钼外消旋体的合成、光谱性质和结构表征

钼酸铵和外消旋苹果酸溶液反应得到外消旋苹果酸钼 ( )配合物 ,( NH4) 4[Mo∧ O2 ( S,S-Hmal) 2 ]·[MoΔO2 ( R,R-Hmal) 2 ],对该配合物进行了元素分析、电导测定、旋光和红外光谱表征 ,并测定了晶体结构 .该化合物晶体属单斜晶系 ,P2 1 / a空间群 ,晶胞参数 :a=0 .80 61 ( 2 ) nm,b=1 .32 86( 2 ) nm,c=1 .32 32 ( 2 ) nm,β=91 .80 ( 2 )°,V=1 .4 1 64( 9) nm3,Z=2 ,Dc=2 .0 0 8g· cm- 3 ,F( 0 0 0 ) =864,μ=9.70cm- 1 ,一致性因子 R=0 .0 5 1 ,Rw=0 .0 5 8.在该单核配合物阴离子中 ,钼上的两个苹果酸配体具有相同手性 ,它以α-烷氧基和α-羧基双齿配位形成畸变的八面体构型 ,而另一个β-羧酸则保持自由状态     

高稳定度CH4/CO2重整Ni/MgO催化剂的研究

用TPR,TPD,TPO,TPMC(程序升温CH₄解离积炭)和活性评价等手段研究了普通浸渍法与载体盐助分散浸渍法制得的CH₄/CO₂重整制合成气Ni基催化剂的性能.结果表明,用载体盐助分散浸渍制备的催化剂Ni-O-Mg间作用较强,吸附CO₂能力较大,CH₄解离积炭量少,因此其稳定性及寿命较好.     

Synthesis of Small Crystal-sized Zeolite NaY

Comparing with their larger crystal-sized counterparts, small crystal-sized zeolites possess many advantages^[1], which have been attracting extensive interests of scientific and industrial community. In this paper, we present a novel method of synthesizing small crystal-sized zeolite NaY via optimizing the mixing sequence of source materials.     

Synthesis,Structure and Mechanism of a Series of Novel Nanocrystalline Rare Earth Orthovanadate Catalysts for Oxidative Dehydrogenation of Light Alkanes at Low Temperatures

The oxidative dehydrogenation of light alkanes to light alkenes is one of the potentially important catalytic processes for the effective utilization of light alkanes. However, high temperatures were required to initiate the reactions on heterogeneous catalysts reported by other authors in the literature^[1,2]. In recent years we reported a series of novel nanocrystalline rare earth orthovanadates synthesized by the peroxyl and nitrate methods for oxidative dehydrogenation of propane at low temperatures^[3,4]. In this paper the synthesis of a series of novel nanocrystalline rare earth orthovanadates (LnVO₄, Ln=Y, La, Ce, Pr, Nd, Sm Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) by the citrate method is reported, together with the structural characterization and excellent performances of the catalysts for oxidative dehydrogenation of light alkanes.