The absorption of oxygen and styrene in water-silicone oil emulsions was independently studied in laboratory-scale bubble reactors at a constant gas flow rate for the whole range of emulsion compositions (0-10% v/v). The volumetric mass transfer coefficients to the emulsions were experimentally measured using a dynamic absorption method. It was assumed that the gas phase contacts preferentially the water phase. In the case of oxygen absorption, it was found that the addition of silicone oil hinders oxygen mass transfer compared to an air-water system. Decreases in kLaoxygen of up to 25% were noted. Such decreases in the oxygen mass transfer coefficient, which imply longer aeration times to transfer oxygen, could represent a limiting step in biotechnological processes strongly dependent on oxygen concentration. Nevertheless, as the large affinity of silicone oil for oxygen enables greater amounts of oxygen to be transferred from the gas phase, it appears that the addition of more than 5% silicone oil should be beneficial to increase the oxygen transfer rate. In the case of styrene absorption, it was established that the volumetric mass transfer coefficient based on the emulsion volume is roughly constant with the increase in the emulsion composition. In spite of the relatively high cost of silicone oil, water-silicone oil emulsions remain relevant to treat low-solubility volatile organic compounds, such as styrene, in low-concentration gas streams. 相似文献
Summary: The effect of impurities on the coordination polymerization has generally been classified and discussed in different ways and has been investigated in detail in the syndiospecific homo‐ and copolymerization of styrene. With regard to impurities of styrene, phenylacetylene as an unpolar impurity containing separate multiple bonds, 1‐phenyl‐1,2‐ethanediol and ω‐hydroxyacetophenone as examples of polar impurities, and ethylbenzene as an other unpolar impurity have been investigated regarding the effect on the polymerization rate and the influence on the molecular properties of the syndiotactic polystyrenes. In the syndiospecific copolymerization with p‐methylstyrene, indene shows a different behavior regarding the decrease of the polymerization conversion depending on the comonomer concentrations present in the monomer mixture. Additionally, the effect of impurities of the catalyst system on the syndiospecific styrene polymerization has been demonstrated, particularly of octahydrofluorene as a component of the transition metal compound and of trimethylaluminium as a component of the cocatalyst methylaluminoxane. All results have been discussed with respect to the mechanisms of the effects on polymerization behavior and on polymer properties.
Dependence of the relative polymerization conversion on the amount of indene added to the monomer mixture in styrene (ST)/p‐methylstyrene (PMS) copolymerization (catalyst n‐ratio: 0.5; molar ratio MAO:Ti = 110:1; polymerization temperature: 60 °C; polymerization time: 45 min). 相似文献