Effects of potassium concentration and osmotic pressure of sea water on the cell-turgor pressure of Chaetomorpha linum

The unicellular littoral alga Chaetomorpha linum is especially capable of maintaining its cell-turgor constant by regulation of the internal osmotic pressure, when the salinity of the sea water is altered. The decrease or increase of the external potassium concentration is seen to be an important cause of this turgor regulation, as well as the alteration of the external osmotic pressure, which was already known to be an important factor. This has been shown by experiments in artificial sea water with reduced osmolality and variable potassium concentration (1 to 50 mMol/l).     

A short-cut method for assessing absorbents for post-combustion carbon dioxide capture

A short-cut method for the estimation of the minimum regeneration energy and optimum solvent flow rate in post-combustion carbon dioxide capture by absorption is presented. It is developed for comparing solvents of which only little thermo-physical data is known. The closed absorber–desorber cycle is described by an equilibrium stage model (modified Kremser equation with discretized equilibrium curves). The method can be implemented in any mathematical toolbox or as stand-alone solution. The only required input is the solubility data at absorber and desorber conditions, the heat of absorption and heat capacities. The caloric data may be estimated. The method was applied to monoethanolamine (MEA) and two solvents from the EU-project CASTOR. Comparisons with experimental results from pilot-plant studies with MEA show that the method, despite its simplicity, gives reasonable results. The method should also be useful in other applications where absorbents, of which only little data is available, need to be screened.     

Nativ-basierte Grundöle für die Produktion von Kühlschmierstoffen

Aims and Scope

Compared to mineral oil products, cooling lubricants based on fatty acid esters have technological advantages. Moreover, they are more environmentally compatible and make a contribution to a sustainable economy. Nevertheless, they are rarely applied in practice, because of their comparably high price, that is based on raw-material and synthesis costs. Alternatives concerning raw-materials and synthesis pathways are considered and properties of resulting ester products are compared.

Methods

The investigations aimed at three fatty acid-2-ethyl-hexylesters that were synthesized in an enzymatic-catalytic routine based on peanut oil, suet, and waste edible fat and at esters that were conventionally produced from animal and plant fats and 2-ethyl-1-hexanol. Physical properties, fatty acid patterns, contents of free fatty acids, as well as oxidative and hydrolytic stabilities were determined. Thermolysis experiments were performed.

Results

The physical properties of the seven esters, density, viscosity, pourpoint, and flash point, were comparable and gave reason for the assumption, that the products could be used as basis oils in lubricant formulations. Hydrolysis stabilities of the esters were high and thermal stress did not point at high potential of hazardous compounds formation. Especially the enzymatic-catalytically produced esters showed deficits concerning oxidation stabilities and free fatty acid contents.

Outlook

For practice it will be necessary to define minimum qualities for raw-materials and resulting ester oils to be used as lubricant basis oils. Moreover, processes have to be developed, that yield high quality ester products from waste edible and animal fats without loosing the advantage of low-cost raw-materials by high production and refinement costs. Surely, one contribution is the further development of the energy-saving enzymtic alcoholysis for ester production.