单组分聚氨酯乳液制备及其结构与性能研究

采用预聚合法,以聚酯二元醇(PEA)、甲苯二异氰酸酯(TDI)、二羟甲基丙酸(DMPA)为基本原料合成了分子链上带有亲水基团(-COOH)的聚氯酯预聚体。以特殊的水化方式制得聚酯型水性聚氨酯乳液。讨论了温度、-NCO-与-OH的物质的量之比(R)、亲水基团含量、合成工艺分别对材料力学性能、耐水性、玻璃化转变温度(Tg)等的影响。研究发现,采用前中和工艺、在高速搅拦下将预聚物加入到水中的水化方式,当R值为1．2,羧基含量为1．6％时,合成的聚酯型水性聚氨酯乳液具有较好的贮存稳定性,且涂膜的耐水性和力学性能良好。     

Methane activation without using oxidants over Mo/HZSM-5 zeolite catalysts

The effect of Mo loading, calcination temperature, reaction temperature and space velocity on the catalytic performance of methane dehydrogenation and aromatization without using oxidants over Mo/HZSM-5 has been studied. The XRD and BET measurements show that Mo species are highly dispersed in the channels of the HZSM-5 zeolite, resulting from the interaction between the Mo species and the zeolite, which also leads to a decrease in its crystallinity. The Brønsted acidity, the channel structure and the state and location of Mo species in the zeolite seem to be crucial factors for its catalytic performance. It was found that 2% Mo/HZSM-5 calcined at 773 K showed the best aromatization activity among the tested catalysts, the methane conversion being 9% at 1013 K with the selectivity to aromatics higher than 90%. The experimental results obtained from the variation of space velocity gave evidence that ethylene is an initial product. On the basis of these results a possible mechanism for methane dehydrogenation and aromatization has been proposed in which both the heterolytic splitting of methane in a solid acid environment and a molybdenum carbene-like complex as an intermediate are of significance.     

Effective Coke Removal in Methane to Benzene (MTB) Reaction on Mo/HZSM-5 Catalyst by H2 and H2O Co-addition to Methane

The catalytic dehydro-aromatization reaction over Mo/HZSM-5 catalyst was drastically stabilized by the co-addition of 5.4% H₂ and 1.8% H₂O to methane feed at 750 °C, 0.3 MPa and methane space velocity of 3000 mL g⁻¹ h⁻¹, suppressing the coke formation effectively, compared with single hydrogen or steam addition.     

Pulse study of methane partial oxidation to syngas over SiO2-supported nickel catalysts

Methane was pulsed over pure CuO and NiO as well as Cu/La₂O₃ and Ni/La₂O₃ catalysts at 600° C. Results indicate that the mechanisms for methane activation over copper and nickel are quite different. Over CuO, methane is converted to CO₂ and H₂O, most likely via the combustion mechanism; whereas metallic copper does not activate methane. Over NiO in the presence of metallic nickel sites, methane activation follows the pyrolysis mechanism to give CO, CO₂, H₂ and H₂O. Similar results were obtained over the Cu/La₂O₃ and Ni/La₂O₃ catalysts. XRD investigations indicate that copper and nickel existed as CuLa₂O₄ and LaNiO₃ respectively in the La₂O₃-supported catalysts. The effect of La₂O₃ on the activation of methane is discussed.     

Decomposition of nitric oxide over perovskite oxide catalysts: effect of CO2, H2O and CH4

Direct nitric oxide decomposition over perovskites is fairly slow and complex, its mechanism changing dramatically with temperature. Previous kinetic study for three representative compositions (La_0.87Sr_0.13Mn_0.2Ni_0.8O_3−δ, La_0.66Sr_0.34Ni_0.3Co_0.7O_3−δ and La_0.8Sr_0.2Cu_0.15Fe_0.85O_3−δ) has shown that depending on the temperature range, the inhibition effect of oxygen either increases or decreases with temperature. This paper deals with the effect of CO₂, H₂O and CH₄ on the nitric oxide decomposition over the same perovskites studied at a steady-state in a plug-flow reactor with 1 g catalyst and total flowrates of 50 or 100 ml/min of 2 or 5% NO. The effect of carbon dioxide (0.5–10%) was evaluated between 873 and 923 K, whereas that of H₂O vapor (1.6 or 2.5%) from 723 to 923 K. Both CO₂ and H₂O inhibit the NO decomposition, but inhibition by CO₂ is considerably stronger. For all three catalysts, these effects increase with temperature. Kinetic parameters for the inhibiting effects of CO₂ and H₂O over the three perovskites were determined. Addition of methane to the feed (NO/CH₄=4) increases conversion of NO to N₂ about two to four times, depending on the initial NO concentration and on temperature. This, however, is still much too low for practical applications. Furthermore, the rates of methane oxidation by nitric oxide over perovskites are substantially slower than those of methane oxidation by oxygen. Thus, perovskites do not seem to be suitable for catalytic selective NO reduction with methane.     

二氧化碳催化加氢研究进展

介绍了近年来由 CO2 催化加氢制取甲醇、烃类、醛类、甲酸和二甲醚等反应的研究进展     

Reactive pozzolana from Indian clays—their use in cement mortars

Studies were undertaken to produce reactive pozzolana i.e. metakaolin from four kaolinitic clays collected from different sources in India. The metakaolin produced from these clays at 700-800 °C show lime reactivity in between 10.5 to 11.5 N/mm² which is equivalent to commercially available calcined clay Metacem-85. The microstructure of the metakaolin has been reported. The effect of addition of metakaolin up to 25% in the Portland cement mortars was investigated. An increase in compressive strength and decrease of porosity and pore diameter of cement mortars containing metakaolin (10%) was noted over the cement mortars without metakaolin. The hydration of metakaolin blended cement mortars was investigated by differential thermal analysis (DTA) and scanning electron microscopy (SEM). The major hydraulic products like C-S-H and C₄AH₁₃ have been identified. Durability of the cement mortars with and without metakaolin was examined in different sulphate solutions. Data show better strength achievement in cement mortars containing 10% MK than the OPC mortars alone.     

Complete Oxidation of Methane at Low Temperature over Pt Catalysts Supported on High Surface Area SnO2

The catalytic activity of Pt catalysts supported on high surface area tin(IV) oxide in the complete oxidation of CH₄ traces under lean conditions at low temperature was studied in the absence and in the presence of water (10 vol.%) or H₂S (100 vol.ppm). Their catalytic properties were compared to those of Pd/Al₂O₃ and Pt/Al₂O₃. In the absence of H₂S in the feed, Pt/SnO₂appears as a very promising catalyst for CH₄ oxidation, being even significantly more active under wet conditions than the best reference catalyst, Pd/Al₂O₃. Catalysts steamed-aged at 873 K were also studied in order to simulate long term ageing in real lean-burn NGV exhaust conditions. To this respect, Pt/SnO₂ is slightly less resistant than Pd/Al₂O₃. In the presence of H₂S, Pt/SnO₂catalysts are rapidly and almost completely poisoned, comparably to Pd/Al₂O₃and the catalytic activity is hardly restored upon oxidising treatment below 773 K. A synergetic effect between Pt and specific surface SnO₂sites active in CH₄oxidation is proposed to explain the superior catalytic behaviour of Pt/SnO₂.     

钻井泥浆抑制剂JFT的实验研究

针对钻井过程中泥页岩的水化膨胀导致井壁不稳定和泥浆性能恶化这一严重问题 ,通过室内试验研制了一种阳离子型聚合物抑制剂———JFT ,并进行了性能评价。结果表明 ,该抑制剂具有好的水溶性、时间稳定性和热稳定性 ,其适应温度范围广 (在 30～ 95℃下不生成絮状沉淀 ) ,有效浓度为 1 %的JFT比 5 %KCl的抑制性好。     

Catalytic partial oxidation of methane to synthesis gas in a ceramic membrane reactor

Methane has been selectively converted to synthesis gas using a two-zone fixed bed of a Ni/Al₂O₃ catalyst inside a modified ceramic membrane. The first zone of the reactor was surrounded by an impervious wall, and therefore behaved as a conventional fixed bed reactor. In the second zone, some of the reaction products could preferentially diffuse out of the reactor, which yielded higher than equilibrium methane conversions. The influence of the different operating conditions has been studied, and the performance of the membrane reactor has been compared to that of a fixed bed reactor. The membrane reactor has also been used at pressures above atmospheric (2 bar), with good conversions and selectivities.