Lithium-doped sulfated-zirconia catalysts for oxidative coupling of methane to give ethylene and ethane

Li-doped sulfated-zirconia catalysts were found to be effective for oxidative coupling of methane (OCM). The catalyst performances depend on the sulfate content and calcination temperature. A maximum C₂ yield is attained over the catalysts, which contain 6 wt.% sulfate and calcined at 923–973 K, being closely related to the preparation conditions of sulfated-ZrO₂ as solid super-acids. When the performances of the Li-doped sulfated-ZrO₂ (Li/SZ) catalysts were tested at 1023 K as a function of reaction time, both the C₂ and CO_x selectivities remained constant over the range of 8 h, but the CH₄ conversion decreased from 17.5% to 11.9%. The nature of Li/SZ catalysts for the OCM was investigated by X-ray diffraction, XPS, and NH₃ and CO₂ TPD measurements. It could be postulated that the sulfated-ZrO₂ surface could play an important role in the formation of a catalytically active structure by Li-doping.     

Multiphase reacting flow studies of bubble column ozonation reactor for water remediation

A multiphase Volume‐of‐fluid (VOF) model was developed to gain further insights into the reactive flow parameters and electrical capacitance tomography (ECT) measurements on the remediation of hazardous organic pollutants. Low ozone bubble frequencies were obtained for high surface tension fluids, and the liquid viscosity affected the ozone bubbling frequency. The VOF model indicated that the increase of inlet gas velocity enriched the ozone bubble detachment and concomitantly generated larger ozone bubbles, decreasing the detoxification rates. VOF mappings and ECT visualizations of gas‐liquid unveiled preferential routes and highlighted the attenuation of the axisymmetric behavior of the ozonation bubble column under high‐interaction regimes.     

典型乙氧基化装置中环氧乙烷安全操作分析

介绍环氧乙烷操作风险以及导致环氧乙烷在典型乙氧基化反应器中没有有效的气相循环或没有气相循环操作条件下分解的主要原因。环氧乙烷在密闭乙氧基化反应器中达到爆炸极限时，是可以通过控制反应器中氮气浓度避免事故发生。     

Facile synthesis of ultrathin magnetic iron oxide nanoplates by Schikorr reaction

In this work, a very facile one-pot hydrothermal synthesis approach has been developed for the preparation of ultrathin magnetite nanoplates. The hydrothermal procedure was performed by aging ferrous hydroxide under anaerobic conditions, which is known as Schikorr reaction. Ethylene glycol (EG), which was introduced to the reaction as another solvent, played a critical role in the formation process of these nanoplates. Typically, hexagonal Fe₃O₄ nanoplates with a thickness of 10 to 15 nm and a side length of 150 to 200 nm have been synthesized with EG/H₂O = 1:1 in experiments. Our data suggest that the thickness of Fe₃O₄ nanoplates decreases, and the shape of the nanoplate becomes more irregular when the concentration of EG increases. The as-prepared Fe₃O₄ nanoplates were highly crystallized single crystals and exhibited large coercivity and specific absorption rate coefficient.     

Support-induced promotional effects on the activity of automotive exhaust catalysts 1. The case of oxidation of light hydrocarbons (C2H4)

The kinetics of oxidation of a light hydrocarbon (C₂H₄) were studied on catalysts comprising of combinations of one of three metals, Pt, Pd or Rh supported on five different supports, that is, SiO₂, γ-Al₂O₃, ZrO₂ (8% Y₂O₃), TiO₂ or TiO₂ (W⁶⁺). Significant variation of turnover frequency with the carrier was observed, which cannot be explained by structure sensitivity considerations and is attributed to interactions between the metal crystallites and the carrier. The catalytic activity of these metal-support combinations was investigated over a wide range of partial pressures of ethylene and oxygen. In a separate set of experiments, the kinetics of C₂H₄ oxidation were also investigated on polycrystalline Rh films interfaced with ZrO₂ (8 mol% Y₂O₃) solid electrolyte in a galvanic cell of the type: C₂H₄, O₂, Rh/YSZ/Pt, air, during regular open-circuit conditions as well as under Non-Faradic Electrochemical Modification of Catalytic Activity (NEMCA), that is, closed-circuit conditions. Up to 100-fold increase in catalytic activity was observed by supplying O²⁻ ions to the catalyst surface via positive potential application to the catalyst. The observed kinetic behavior upon increasing catalyst potential parallels qualitatively the observed alteration of turnover frequency with variation of the support of the Rh crystallites.     

Cause of catty odour formation in packaged food

In two different ‘cook-in-the-bag’ ham products packed in polyamide-ethylene ionomer laminate pouches, the same obtrusive catty off-odour was complained about. In this paper the analytical resolution of a complex off-odour problem is described. Identification of the catty odour as the mesityf oxide-hydrogen sulphide adduct 4-methyl-4-mercaptopentan-2-one is followed by investigating the formation of the off-odour with the aid of different model experiments. It is pointed out that the ethylene ionomer material that is used for the sealing layer of the multilayer packaging film has some dehydration property for diacetone alcohol, which was found as a residual solvent in the film material in question. Probably this pathway seems most likely to be responsible for the off-odour.     

Rheological properties of ethylene ionomer neutralized with binary metal cation

The roles of ionic bonding in molten ethylene ionomers without ionic aggregates were rheologically characterized in linear regions under shear. We have measured melt viscosities of ethylene-methacrylic acid (EMAA) ionomers by means of dynamic shear experiment. The samples used in this study were binary mixtures selected from Na, Mg and Zn salts of EMAA (MAA=5.4 mol%). The dynamic shear properties revealed that the time-material superposition is applicable to these ionomer blends in a temperature range from 140 to 200 °C. It was also found that these binary mixtures unexpectedly give decreases of zero shear viscosities obtained from a time-material superposition, if the cations were selected from different metal groups such as alkali, alkaline earth and transition metals. This behavior can be explained by the acid-cation exchange mechanism.     

Synthesis, structural characterization and ethylene polymerization behavior of complex [Ph4P][CrCl3{HB(pz)3}] [HB(pz)3 = hydrotris(1-pyrazolyl)borate]

Reaction of CrCl₃(THF)₃ with K[HB(pz)₃] in THF leads to the formation of the complex K[CrCl₃{HB(pz)₃}] (1). The salt metathesis of complex 1 with [Ph₄P]Br in CH₂Cl₂ yields the complex [Ph₄P][CrCl₃{HB(pz)₃}](2). The structure of complex 2 · CHCl₃ has been determined by single crystal X-ray diffraction. In the anion the metal centre shows a distorted octahedral geometry with the hydrotris(1-pyrazolyl)borate bonded as N,N′,N″-donor tripod ligand and three chloride atoms completing the co-ordination sphere. Complex 2 in the presence of MAO leads to the formation of an active catalyst for the polymerization of ethylene.     

无水硅酸钠催化酯交换合成碳酸二甲酯

以廉价的Na2Si O3·9H2O为原料,通过简单的焙烧处理,制备了系列无水硅酸钠,并将其作为固体碱催化剂应用于碳酸乙烯酯(EC)与CH3OH酯交换合成碳酸二甲酯(DMC)的反应。采用TG-DTA、XRD和Hammett指示剂法对无水Na2Si O3进行表征。结果表明,焙烧温度对无水Na2Si O3的碱强度、总碱量及催化活性没有显著影响。当焙烧温度为200℃时,样品(Na2Si O3-200)的碱强度(Ho)为15.0~18.4,总碱量为10.9 mmol/g。以Na2Si O3-200为催化剂,考察了原料配比、温度和时间对酯交换合成DMC反应的影响。当CH3OH与EC的摩尔比为10∶1,在65℃反应2 h后,EC转化率与DMC收率可分别达到89%和88%。即使在室温条件下,Na2Si O3-200也能有效地催化EC与甲醇酯交换反应的进行。此外,经过4次使用后,Na2Si O3-200的催化活性没有出现明显下降的趋势。     

乙烯焦油制备石油树脂的研究

以馏程在210℃以下的乙烯焦油C9馏份为原料,对以Lewis酸和以A1C13为催化剂的两段催化聚合法制备合成石油树脂提出了新的两段聚合的工艺条件。探讨了催化剂添加量、反应温度、反应时间等因素对聚合反应的影响。实验结果显示在总催化剂用量为3%(w),其中AlCl3为1.0%,BF3·Et2O为2%,聚合温度60℃,聚合时间6h的条件下,得到了满足其主要工业指标的石油树脂。