Anionic Clays as Potential Slow-Release Fertilizers: Nitrate Ion Exchange

Several nitrate containing anionic clays were synthesized at different temperatures and the kinetics of NO₃ ^– release were determined to test their suitability as slow-release N fertilizers. A sample (Mg:Al = 2:1) synthesized at 60°C with smaller particle size released 75, 86 and 100% of its NO₃ ^– in 1, 3 and 7 days, respectively when equilibrated with a simulated soil solution. On the other hand, the 175°C/2 hrs sample with larger particle size released 65, 77 and 84% of its nitrate in 1, 3 and 7 days, respectively. Another anionic clay (synthesized at 175°C/24 hrs) of higher charge density (Mg:Al = 2:1) containing NO₃ ^– was equilibrated with a 0.012 N NaCl or Na₂CO₃ to test the role of different anions in releasing the NO₃ ^– anion from the interlayers. The results showed that Cl^– released more NO₃ ^– than did CO₃ ^2– from this anionic clay after all the treatment times probably as a result of the CO₃ ^2– anion blocking the release of NO₃ ^– from the interior of the crystals. When a lower charge density (Mg:Al = 3:1) sample (synthesized at 175°C/48 hrs) was equilibrated with 0.02N solution of anions the release of nitrate was as follows: Cl^– < F^– < SO₄ ⁼ CO₃ ^2–. These results suggest that the divalent SO₄ ⁼ and CO₃ ^2– anions are more effective in the release of NO₃ ^– from this lower charge density anionic clay. Time-resolved structural analysis of NO₃ ^– exchange with CO₃ ^2– in the above anionic clay using synchrotron x-ray diffraction showed that ion exchange is rapid because of small crystal size and lower charge density. Thus the release of NO₃ ^– from anionic clays is an interplay among the type of anions present in soil solution, their concentration, pH of soil solution, the charge density and crystal size of anionic clay etc.     

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.     

化学法处理铜合金屑工艺的热力学和动力学分析

本文对化学法处理普通黄铜屑，直接制备纯铜粉末进行了热力学和动力学分析研究及试验表明：Zn，Fe等元素的酸浸反应容易进行，氧化及还原速度快．酸浸过程受扩散控制，其动力学方程为进一步的热力学分析指出，本工艺适合于处理各种铜合金尾料，尤其适合于黄铜类铜合金尾料。     

超细粉体微胶囊红磷阻燃剂的研制

红磷经湿法研磨预处理，在一定pH值（9．0－9．5），表面活性剂用量为0．8％－1．0％，2200Hz超声波振荡15min后，采用蜜胺树脂预聚体原位法包覆，制得了微胶囊红磷阻燃剂的超细粉体，其平均粒径为2．186um，并探讨了预处理，PH值，表面活性剂及超声波对粒度的影响。     

The preparation of coupled WO3/TiO2 photocatalyst by ball milling

The coupled photocatalyst WO₃/TiO₂ is prepared by ball milling by doping WO₃ into TiO₂ and using H₂O solution as disperser. The coupled photocatalyst WO₃/TiO₂ is characterized by UV–VIS diffuse reflection spectrum, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Transmission electron microscopy (TEM). The results show that the optimum percentage of WO₃ doped is 3% and that the photocatalytic activity of the coupled WO₃/TiO₂ photocatalyst is much higher than that of TiO₂ and WO₃–TiO₂ with no ball milling. Compared with TiO₂, the photoexcited wavelength range of the WO₃/TiO₂ photocatalyst red-shifts about 50 nm, and the light absorption intensity is also improved. The crystal phase of TiO₂ is not changed and new crystal phases are not found during the process of ball milling. WO₃ and TiO₂ coupled highly, forming the WO₃/TiO₂ photocatalyst. The increased photocatalytic activity of the coupled photocatalyst may be attributed to the enhance charge separation efficiency and the extend wavelength range of photoexcitation.     

Oxidative coupling of methane over LaCoO3−δ-based mixed oxides

The catalytic activity of LaCoO_3–-based mixed oxides for the oxidative coupling of methane has been tested by TPR and cyclic reaction. Characterization has been done by XRD, TGA and Mössbauer spectrometry. It is likely that the perovskite-crystal structure containing hypervalent metal ions has an important role and that unique structural oxygen species in the perovskite contribute to the partial oxidation of methane.     

反应过程中升华型催化剂的物性变化(Ⅱ) X—射线衍射结果

对衰化程度不同的升华型催化剂进行了 X—射线衍射测定。发现在使用过程中催化剂比表面迅速减小,但氯化汞-活性炭催化剂的新旧样品中,氯化汞均保持单层分散。但即将废弃的醋酸锌-活性炭催化剂上,醋酸锌的单层分散情况受到破坏,出现了醋酸锌晶相峰。晶相峰的出现可能与后期使用温度偏高引起烧结有关。晶相峰的出现会降低催化活性,使之不得不被废弃。     

抗静电粉末涂料的制备

简述了抗静电粉末涂料的制备机理及铝粉、氧化镁、二氧化钛和抗静电助剂添加量对涂料性能的影响，并简述其应用。     

Selectivities in methanol oxidation over silica supported molybdena

Selectivities in methanol oxidation over silica supported molybdenum oxide catalysts were investigated in relation with the phase distribution. The supported catalysts were prepared by impregnation with ammonium heptamolybdate. In addition to crystalline MoO₃, Mo containing cluster species of 1–2 nm size were observed by STEM even from a used catalyst with 13% catalyst loading. The percentage of Mo present as crystalline MoO₃ increases with the catalyst loading. An ESCA study indicates that part of surface Mo in the supported catalysts is reduced to Mo⁵⁺. The dimethyl ether selectivity increases with the catalyst loading and its formation occurs over the crystalline MoO₃ phase. The Selectivities to CO and methyl formate are greatly enhanced because of the presence of support, and are relatively independent of the catalyst loading and phase distribution. The dependence and independence of the Selectivities of different byproducts on the loading make the silica supported catalysts with high catalyst loadings less selective for the partial oxidation of methanol to formaldehyde.     

Preparation of nano-sized silicon carbide powder using thermal plasma

Nano-sized silicon carbide (SiC) powder was prepared by thermal plasma process using silicon tetrachloride (SiCl₄) and methane (CH₄). The synthesized powder was characterized by X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and particle size analyzer. The powder was dominated by β-SiC including some of α-SiC and free carbon species. The quality of the powder was varied with process conditions such as the molar ratio of H/Si and C/Si, and collecting positions. It was known that the conversion to SiC was mainly affected by the addition of hydrogen gas because it promoted the decomposition and reduction of SiCL. CH₄ was easily decomposed to carbon species for the formation of SiC as well as removal of impure oxygen, but excessive carbon suppressed the formation of crystalline SiC and resulted in the solid carbon contamination. The optimum ratio of H/Si was approx. 26 and that of C/Si was 1.1. For collecting positions, the powder collected at the vessel and filter was preferable to that at the reaction tube. The average size of the powder synthesized was estimated to be below 100 nm and uniform in distribution.