Gas—Liquid Mass Transfer Coefficient in Stirred Tank Reactors

Volumetric gas—liquid mass transfer coefficient (k_La) data available in the literature for larger tanks (T = 0.39 m to 2.7 m) have been analyzed on the basis of relative dispersion parameter, N/N_cd. It was observed that at a given superficial gas velocity (V_G), k_La values were approximately the same irrespective of geometric configuration (size of the tank, type and size of the impellers, type of the sparger, etc.) at a particular N/N_cd. A single correlation based on N/N_cd is presented which shows satisfactory agreement with the k_La data of different workers.     

What do we mean by “catalytic activity”?

The relative reactivities of the lower alkanes in hydrogenolysis on a Pt/Al₂O₃ catalyst depend on the H₂ pressure used, as do those of a Ru/Al₂O₃ catalyst, pretreated in various ways, for propane hydrogenolysis. Apparent activation energies also vary with H₂ pressure. No single rate measurement adequately represents catalytic activity, which is properly defined as the rateconstant for the slow step.     

Intelligent cooling structure design of "Z-pins like" silicon rods to enhance the ablation resistance of C/C-ZrC-SiC composites above 2500 °C

In order to improve the ablation resistance of C/C-ZrC-SiC composites by reducing the damage of the protective oxide layer, novel "Z-pins like" silicon rods, which were designed and fabricated by liquid phase sintering, were utilised as a dissipative agent. The microstructure evolution and thermal dissipation behaviour were investigated after ablating above 2500 °C for 300 s. After the "Z-pins like" silicon rods were implanted, the anti-ablative property of the C/C-ZrC-SiC composites was drastically improved by the dissipative thermal protection mechanism. The linear ablation rate of the "Z-pins like" silicon rod-reinforced C/C-ZrC-SiC composite was -0.28 μm/s, which is 112.72% lower than the unmodified composite. Additionally, the actual ablative temperature dropped approximately 357 °C, which enabled abundant SiO₂ to remain in the ablation centre. Furthermore, a dense SiO₂-rich oxide layer with a low oxygen diffusion coefficient is formed that covers the entire ablative surface.     

N-甲酰吗啉芳烃抽提塔试验研究

用小型碳钢筛板萃取塔进行了宽馏分重整脱庚烷油的N 甲酰吗啉抽提试验 ,考察了抽提温度、溶剂比、溶剂含水率对总芳烃收率及选择性的影响。结果表明 ,在抽提温度为 60℃、溶剂含水为 3 % (m )和溶剂比S/F =4(V)的抽提操作条件下 ,溶剂选择性较高 ,并可获得高的芳烃回收率     

Electrochemical behaviour of Mn3+/Mn2+, Co3+/Co2+ and Ce4+/Ce4+ redox mediators in methanesulfonic acid

The redox behaviour of Mn³⁺/Mn²⁺, Co³⁺/Co²⁺ and Ce⁴⁺/Ce³⁺ mediators commonly used in indirect oxidation of organic compounds were evaluated in methane sulfonic acid on a glassy carbon working electrode employing cyclic voltammetry. Manganic methanesulfonate exhibits higher instability in dilute methanesulfonic acid. The solid MnO₂ formed during disproportionation on the glassy carbon electrode further affects the reproducibility. Cobaltic methanesulfonate formation occurs only at oxygen evolution region rendering the overall oxidation process less efficient. Ceric methane sulfonate formation is highly efficient over a wide acid concentration range. Ceric methanesulfonate can also be employed over a wide temperature range to oxidize different aromatic compounds.     

B113－2型低汽／气比CO高温变换催化剂的研制

介绍了Ｂ１１３－２Ｍ低汽／气比ＣＯ高温变换催化剂的研制方法及其特点．实验室测试表明，Ｂ１１３－２型催化剂具有堆密度低、运行强度高、选择性好、抗沸水性能优、本体含硫低及低温活性好等优点．     

硅丙涂料的现状及发展趋势

介绍了硅丙涂料在国内外市场的生产及需求现状,指出了硅丙涂料产品的发展方向。     

Surface Chemical Modification of Poly(Methylphenylphosphazene)

Summary The surface reactivity of poly(methylphenylphosphazene), PMPP, and its derivatives containing silane, PMPP-SiH, and alcohol, PMPP-OH, substituents was investigated. These polymers were fabricated into films by casting from THF solutions and reactions were carried out at the interface between solid film samples and solutions. The surface of PMPP was successfully modified by deprotonation under dilute conditions followed by reactions with RMe₂SiCl [where R = CH=CH₂, and H]. While surfaces of PMPP-OH were not readily modified, those containing Si-H groups reacted with oxygen when heated and with carbon tetrachloride. The polymer surfaces were examined by contact angle measurements, attenuated total reflectance infrared spectroscopy (ATR-IR), and scanning electron microscopy (SEM). We dedicate the paper to Christopher W. Allen in recognition of his outstanding contributions to inorganic ring and polymer chemistry.     

STUDY ON PERMEATION OF ACETONE/NITROGEN MIXED GAS THROUGH AL2O3 MICROPOROUS MEMBRANES: MOLECULAR DYNAMICS

In this work, by applying Materials Studio 2.2 software package, molecular dynamics (MD) was performed to investigate the dynamic processes of 1:4 acetone/nitrogen mixed gas permeating through different Al₂O₃ microporous membranes. Three systems were modeled by considering different box lengths, microporous sizes, and textures of Al₂O₃ membranes to compare different permeation behaviors. In each system, initial mixed gas contained 20 acetone molecules and 80 nitrogen molecules, and its density was set to 0.1 g/cm³. Analysis on the concentration profiles of nitrogen molecules (N2) and acetone molecules (Ace) in each system at different sampling times was implemented to discuss the permeation behaviors of smaller N2 and larger Ace. The results showed that adsorption and diffusion occurred synchronously but adsorption was dominant for acetone molecules and that the adsorption on the floor surface of the feed gas region more easily reached equilibrium (local equilibrium) than the diffusion and the adsorption on the ceiling of the initially vacuum region. Furthermore, for nitrogen, adsorption followed diffusion. Higher temperature is in favor of the enrichment of acetone on the floor surface of the feed gas region but against the adsorption of nitrogen. The adsorptive layer was found to be a double-layer with COMPASS force field and to be a monolayer with PCFF force field.     

Enhancement by SO2 of initial activity for selective catalytic reduction of NO with CH3OH over \gamma-alumina

The effect of SO₂ on catalytic activity for NO reduction to N₂ by methanol in excess oxygen over $\gamma$ -alumina has been investigated. SCR activity increased initially upon exposure of a fresh $\gamma$ -alumina catalyst to SO₂ which is attributed to formation of Brønsted acid sites. Longer exposure to SO₂ leads to a decline in catalytic activity to a lower steady-state NO_x reduction activity which is independent of the SO₂ content in the feed gas.