Surfactant effects on hydrate formation in an unstirred gas/liquid system: An experimental study using HFC-32 and sodium dodecyl sulfate

This paper deals with the effects of a surfactant additive on the formation of a clathrate hydrate in a quiescent guest-gas/liquid-water system. The paper first presents our strong suspicion against the existing hypothesis that the surfactant-micelle formation in the liquid-water phase promotes the hydrate formation. It is pointed out that the Krafft point for sodium dodecyl sulfate (SDS), a popular anionic surfactant often used in previous hydrate-forming experiments, is presumably higher than the system temperatures set in these experiments and hence that no micelles may have formed in these experiments. The paper then describes our experimental observations of the hydrate formation from a hydrofluorocarbon gas, HFC-32 (CH₂F₂), to show how the hydrate formation behavior is affected by the addition of SDS to the water when brought into contact with HFC-32. In each experiment, HFC-32 gas was continuously supplied to a rectangular chamber partially filled with a quiescent pool of water (pure water or an aqueous SDS solution) to compensate for the gas consumption due to the hydrate formation, thereby maintaining a constant pressure inside the chamber. The present experiments featured the following characteristics: (a) detailed visual observations along horizontal axes through large side windows in the test chamber, and (b) surface tension measurements of the aqueous SDS solutions with the aid of a pendant-drop device inserted in the same chamber to determine the SDS-in-water solubility, which seems to have been misunderstood as the critical micelle concentration (CMC) in some previous studies, under the hydrate-forming conditions. The former revealed that the addition of SDS to the pool-forming water results in the formation of thick, highly porous hydrate layers not only on the liquid-pool surface but also on the chamber walls above the level of the pool surface, leaving the bulk of the liquid pool free from hydrate crystals. The latter led to an important finding that the SDS concentration at which the rate of the hydrate formation peaks is slightly lower than the solubility (the false CMC). An excessive addition of SDS beyond the solubility was found to cause a decrease in the rate of hydrate formation but an increase in the final level of the water-to-hydrate conversion.     

Interactions between Polymeric Dispersants and Calcium Silicate Hydrates

To better understand the mechanism of interaction between hydrating silicate-based cements and polymeric dispersants of the type used as superplasticizers in modern construction concretes, two different types of polymeric dispersant were added (at concentrations of 1 and 10 g/L) during the synthesis of calcium silicate hydrate (C-S-H) via the pozzolanic reaction in dilute slurries of lime and reactive silica, at Ca/Si ratios in the range of 0.66–1.50. Although both polymers gave degrees of adsorption of >79% in all cases studied, no significant structural modifications of the resulting C-S-H products were observed via X-ray diffraction or ²⁹Si magic angle spinning–nuclear magnetic resonance. These results differ from recent work in which it was shown that similar types of polymer could intercalate into the interlayers of C-S-H that was made using an alternative process. It is suggested that the process by which the C-S-H is formed may have a strong influence on whether C-S-H can intercalate polymers. This observation is relevant to understanding the fate of such polymers in concrete.     

水合氯醛结晶工艺的研究

研究了水合氯醛结晶工艺 ,当等摩尔的三氯乙醛和水混合 ,萃取剂氯仿加入量2 5%～ 35% ,加入的温度 4 0～ 50℃ ,在结晶前期加入结晶改良剂HS时 ,产品结晶时间和烘干时间缩短一半 ,产率 84 %、纯度 99 5%。     

2-氨基芴的合成研究

以2-硝基芴为原料,在95%乙醇溶液中以Fe3 -C为催化剂,以水合肼为还原剂,合成了2-氨基芴。通过实验确定的优化工艺条件是:水合肼与2-硝基芴的摩尔比为3.5:1;反应时间为4小时,反应温度为85℃;催化剂1g活性碳 0.2gFeCl3·6H2O;溶剂比8ml/g。产品的熔点:127℃-127.5℃,还原反应收率达92%。     

巴柳氮的合成改进

以对-硝基苯甲酰氯为起始原料,经缩合、还原、重氮化、偶合4步反应制得巴柳氮,总收率73. 9%。利用TLC ,IR ,1HNMR对产品进行了表征。     

2,2′-双[4-(3-氨基苯氧基)苯基]丙烷的合成

提出了以间二硝基苯和双酚A为原料经缩合和水合肼催化还原合成聚酰亚胺的单体2,2′-双[4-(3-氨基苯氧基)苯基]丙烷的新工艺,考察了各类工艺条件对目标产物收率的影响,得到最适宜反应条件,在优化条件下,总收率为85.5%。HPLC面积归一法测定目标产物纯度为99.97%,并用元素分析和红外光谱对目标产物进行了表征。     

加热灼烧法分析消石灰中Ca(OH)2和CaO的含量

介绍了在漂白粉生产中利用加热灼烧法分析消石灰中Ca(OH)2和CaO含量的方法和步骤.采用该方法可提高分析的准确性,有利于指导消石灰的生产过程和陈化时间,从而提高漂白粉的质量.     

Evaluation of embeddable potential sensor for corrosion monitoring in concrete structures

Embeddable potential sensor based on MnO₂ was assembled and characterised in concrete. The stability, reversibility, polarisability and impedance characteristics have been studied with respect to known reference. The corrosion performance of reinforced steel with respect to MnO₂ sensor was monitored by different electrochemical techniques. Reversibility of MnO₂ sensor indicated that difference of ±5 mV between the forward and reverse scan indicates the better reversibility characteristics in concrete. The rebar potentials (E_R) of steel with respect to MnO₂ are −315 and −525 mV for passive and active conditions of rebar in concrete. The corrosion current from potentiodynamic polarisation and R_ct from a.c. impedance technique clearly differentiated the behaviour of steel embedded in chloride contaminated concrete (active condition) from uncontaminated concrete (passive condition) with respect to MnO₂ sensor. All these studies revealed that corrosion monitoring of steel in concrete using embedded MnO₂ as a better potential sensor for steel in concrete. In addition it is easy to fabricate for amenable miniaturisation, varied configuration as demanded for corrosion monitoring in concrete structures.     

对氨基苄醇的合成研究

以4-硝基苄醇为原料,分别采用Pd/C,Fe(Ⅲ)-MgO或Fe(Ⅲ)-水合肼为催化剂合成了对氨基苄醇。通过对比三种催化剂所得产物的收率和气相色谱检测的含量可知:以4-硝基苄醇合成对氨基苄醇时应选用Fe(Ⅲ)-水合肼为催化剂,其收率可达79.8%,气谱检测含量为98.7%。     

广西及周边地区水合肼市场分析

介绍了水合肼产品及其应用领域,概述了水合肼的国内市场状况,分析了广西及周边地区水合肼的消费情况。市场分析结果表明水合肼作为一种液体产品,本公司虽有生产的原料优势,但市场销售优势并不明显,建设水合肼项目具有较大的市场风险。