六铝酸钙材料的合成及其显微结构研究

分别采用轻质碳酸钙和活性氧化铝 ,或纯铝酸钙水泥和活性氧化铝为初始原料 ,反应烧结合成了六铝酸钙 (CA6)材料 ,研究了原料和成型压力对合成材料的烧结性能和显微结构的影响 ,同时借助于XRD、TG -DSC、SEM和EDAX等测试手段对其反应过程、物相变化和显微结构进行了分析和观察。研究结果表明 :(1) 130 0℃时 ,合成材料的主晶相为刚玉相和CA2 ,并开始有CA6形成 ;温度升至14 0 0℃ ,CA6大量生成 ;15 0 0℃时反应完成 ,产物全部为CA6相。 130 0～ 15 0 0℃时 ,上述反应表现为体积膨胀过程 ,试样的体积密度和径向线收缩率随温度的变化不大 ;而高于 15 0 0℃时 ,试样明显趋向烧结 ,体积密度升高 ,线收缩率加大。采用纯铝酸钙水泥和活性氧化铝合成的试样的体积密度均高于采用轻质CaCO3 和活性氧化铝的 ,尤其在烧成温度高于 15 0 0℃时。坯体的成型压力对这两种合成试样的烧结性能均没有显著影响。 (2 )合成六铝酸钙材料的晶粒形貌与合成工艺有关 ,制备片状晶粒的六铝酸钙材料需满足两个条件 :一是晶核有足够的发育空间 ,二是从晶核生长形成片状结构需足够的物质扩散。采用纯铝酸钙水泥和活性氧化铝为原料的试样 ,其CA6晶核很容易发育成片状晶形 ,且随着坯体成型压力的增加 ,片状CA6有向等轴状发展的趋势 ;采用     

我国化肥催化剂工业现状

全国48家化肥催化剂制造厂总能力为57Kt/a,产量近30kt/a,设备利用率不到50%。平均万吨氨耗催化剂10.36t,高于国外5.60t水平。现生产31个品种203个型号的催化剂中有103种经部级鉴定,但经常使用的约50种。目前化肥催化剂工业水平与国外相比还存在四方面差距。     

Reforming of methane with carbon dioxide over supported bimetallic catalysts containing Ni and noble metal: I. Characterization and activity of SiO2 supported Ni–Rh catalysts

Cobalt catalysts supported on silica aerogel have been prepared using sol–gel chemistry followed by drying under supercritical ethanol conditions. Three different loadings of cobalt were synthesized: 2, 6, and 10% by weight. Transmission electron micrographs indicate that the metallic cobalt exists as discrete particles 50–70 nm in diameter for the 2 and 6% loadings. The 10% catalyst shows long needles of cobalt. BET and BJH measurements indicate that the catalysts retain the silica aerogel properties of high surface area (∼800 m²/g), large pore volume (∼5 cm³/g), and an average pore diameter in the mesoporous regime (∼25 nm). The catalysts were evaluated for Fischer–Tropsch activity in a laboratory-scale packed bed reactor. All three catalysts were active with the 10% Co catalyst achieving more than 20% CO conversion which corresponds to a rate of 1.53 g CO per g-cat per hour. The catalysts were selective for the C₁₀₊ hydrocarbons with more than 50% of the carbon contained within this fraction. A significant portion of the C₉–C₁₅ hydrocarbon product was observed as 1-olefins which reflects the enhanced mass transport within the very porous aerogel support.     

Oxygen reduction on platinum electrodes in base: Theoretical study

Electrode-potential-dependent activation energies for electron transfer have been calculated using a local reaction center model and constrained variation theory for the oxygen reduction reaction on platinum in base. Results for four one-electron transfer steps are presented. For the first, O₂(ads) is predicted to be reduced to adsorbed superoxide, O₂⁻(ads), which dissociates with a low activation barrier to O(ads) + O⁻(ads). Then a proton transfer form H₂O(ads) to O⁻(ads) takes place, forming OH(ads) + OH⁻(aq). The second electron transfer reacts O(ads) with H₂O(aq) to form a second OH(ads) + OH⁻(aq). The third and fourth electron transfers react the two OH(ads) with two H₂O(aq) to form two H₂O(ads) + two OH⁻(aq). All three different surface reduction reactions are predicted to have reversible potentials in the −0.24 V(SHE) to −0.29 V(SHE) range for 0.1 M base and activation energies for the superoxide formation step are close to the experimentally observed range in 0.1 M base for the overall four-electron to water over the three low index (1 1 0) (1 0 0) and (1 1 1) surfaces: 0.38-0.49 eV at 0.35 eV respectively at 0.88 V(RHE). Predicted reversible potentials for forming O₂⁻(ads) are compared with estimates from the experimental literature. The difference between the acid mechanism, where the peroxyl radical, OOH(ads) is the first reduction intermediate, and the base mechanism, where superoxide, O₂⁻(ads) is the first reduction intermediate, is discussed.     

On the robust control of stable minimum phase plants with large uncertainty in a time constant. A fractional-order control approach

This paper addresses the problem of designing controllers that are robust to a great uncertainty in a time constant of the plant. Plants must be represented by minimum phase rational transfer functions of an arbitrary order. The design specifications are: (1) a phase margin for the nominal plant, (2) a gain crossover frequency for the nominal plant, (3) zero steady state error to step commands, and (4) a constant phase margin for all the possible values of the time constant (T$T$): 0<T<∞$0<T<\infty$. We propose a theorem that defines the structure of the set of controllers that fulfil these specifications and show that it is necessary for these robust controllers to include a fractional-order PI$PI$ term. Examples are developed for both stable and unstable plants, and the results are compared with a standard PI$PI$ controller and a robust controller designed using the QFT$QFT$ methodology.     

Decane reforming reaction over Pt,Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on Y-zeolite

Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on NaY- and HY-zeolite were examined as a catalyst for producing gasoline from n-decane via simultaneous reforming and cracking. The catalysts were prepared by calcining and reducing metal-ion-exchanged Y-zeolite with O₂ and H₂ at 300°C., respectively. Thus prepared catalysts were characterized by hydrogen chemisorption and temperature programmed desorption of ammonia. Pt-Ni/NaY and Pt-Ir/NaY bimetallic catalysts offered the improved activity maintenance compared to Pt/NaY monometallic catalyst. The catalysts supported on HY-zeolite showed higher selectivity toward C₅–C₇ and skeletal isomers of C₅–C₇- and C₈–C₁₀ than those of the catalysts supported on NaY-zeolite, which is a desired characteristic for increasing octane value of gasoline these days. However, deactivation with reaction time was much more pronounced on HY-zeolite-supported catalyst. When the catalyst was prcsulfided with H,S, the stability with time on stream was enhanced and the selectivity was quite different from that of the catalyst before presulfiding. The acidity of Y-zeolite and presulfiding of catalyst greatly influenced the activny, selectivity and stability of Pt, Ir, Pt-Ir and Pt-Ni bimetallic catalysts supported on Y-zeolite in n-decane reforming reaction.     

硫硒化镉大红釉的研究

综述了硫硒化镉大红釉的研究状况，分析了各种充硒化镉釉制备方法的优缺点。提出了独特的硫硒化镉系列色釉的制备工艺－－多熔块反应法。     

伴有平衡反应的分离过程的数学模拟——(Ⅱ)催化精馏塔的模拟计算

提出了平衡反应的非均相催化反应精馏过程的微分数学模型。应用多目标打靶法和 Newtor-Raphson 迭代对模型方程进行了求解。本算法应用于非理想系统,反应动力学未知的快速可逆反应过程。可求得沿塔最大转化率和平衡浓度分布。应用本算法对 MTBE 的催化反应过程进行了模拟计算,能快速稳定收敛。计算结果与文献数据进行比较,表现出良好的一致性。     

Reaction kinetics study of asymmetric polymer-polymer interface

In this study, the reaction kinetics of asymmetric polymer-polymer interface was experimentally and theoretically studied. A new rheological method correlating the change of rheological property of reactive system with the conversion of the in situ formed copolymers was applied to study the reaction kinetics of PBT/epoxy reactive system. Then, the new method was proved to be useful by comparing its results with that obtained from the conventional endgroup determination method. Moreover, the conversion of PBT/epoxy reactive system from rheological method could be well fitted by the numerical analysis, from which the kinetic constant and the diffusion constant of epoxy in PBT could be determined simultaneously.