Nitrous oxide ammonia + propane

Studiengesselschaft Kohle m.b.H. (2) reported the effect of temperature on solubility level in supercritical gas. The solubility is highest within 20 K of the critical temperature and decreases as temperature is raised to 100 K above the critical temperature. At temperatures near the critical temperature, a sharp rise in solubility occurs as the pressure is increased to the vicinity of the critical pressure and increases further as the pressure is further increased. Less volatile materials are taken up to a lesser extent than more volatile materials, so the vapor phase has a different solute composition than the residual material. There does not seem to be substantial heating or cooling effects upon loading of the supercritical gas. It is claimed that the chemical nature of the supercritical gas is of minor importance to the phenomenon of volatility amplification. Ethylene, ethane, carbon dioxide, nitrous oxide, propylene, propane, and ammonia were used to volatilize hydrocarbons found in heavy petroleum fractions. 

Applications of IR analyzers include the measurement of ammonia, CO, C02, ethylene, hexane, methane, moisture, nitrous oxide, propane, and sulfur dioxide. NIR analyzers can detect the concentrations of benzene, caustic, cetane, gasoline boiling point, heating value, molecular weight, octanes, protein, and p-xylene. The measurement errors of these analyzers are IR—2% FS, NIR—1% FS. 

Carbon dioxide, water, ethane, ethylene, propane, ammonia, xenon, nitrous oxide, and fluoroform have been considered useful solvents for SEE. Carbon dioxide has so far been the most widely used as a supercritical solvent because of its convenient critical temperature, 304°K, low cost, chemical stability, nonflammability, and nontoxicity. Its polar character as a solvent is intermediate between a truly nonpolar solvent such as hexane and a weakly polar solvent. Moreover, COj also has a large molecular quadrupole. Therefore, it has some limited affinity with polar solutes. To improve its affinity, additional species are often introduced into the solvent as modifiers. For instance, methanol increases C02 s polarity, aliphatic hydrocarbons decrease it, toluene imparts aromaticity, R-2-butanol adds chirality, and tributyl phosphate enhances the solvation of metal complexes. 

Supercritical or near-critical fluids can be used both for extraction and chromatography. Many chemicals, primarily organic species, can be separated and analyzed using this approach [6], which is particularly useful in the food industry. Substances that are useful as supercritical fluids include carbon dioxide, water, ethane, ethene, propane, xenon, ammonia, nitrous oxide, and a fluoroform. Carbon dioxide is most commonly used, typically at a pressure near 100 bar. The required operating pressure ranges from about 43 bar for propane to 221 bar for water. Sometimes a solvent modifier is added (also called an entrainer or cosolvent), particularly when carbon dioxide is used. 

Liquefied Gases—liquids at ambient temperature under pressures of about 25 to 2500 psig. Examples are ammonia, carbon dioxide, chlorine, nitrous oxide, propane, and sulfur dioxide. 

Examples of liquefied compressed gases include carbon dioxide, nitrous oxide, anhydrous ammonia, butadiene, chlorine, methyl chloride, methyl mercaptan, sulfur dioxide, vinyl chloride, a number of refrigerant gases including the fluorocarbon gases, and the liquefied petroleum gases (LP-gases) such as butane, isobutane, propane, and propylene. 

Supercritical fluid chromatography employing carbon dioxide as an eluent is frequently operated in a temperature range up to 100°C (110-115, 316). Pressures that conform to an eluent density of 200 to 500 times greater than that of the gas are usually employed. Other eluents frequently utilized besides carbon dioxide include ammonia (T = 132.4 °C), nitrous oxide (Tc = 36.5°C), ethane (Tc = 32.2 °C), ethylene (T = 9.21 °C), propane (T = 96.7 °C), pentane (Tc= 196.5 °C), and chlorotrifluoromethane (Tc = 28.9°C) (129). Low concentrations of a moderator, usually a low molecular-weight alcohol such as methanol, ethanol, or isopropanol can be added to enhance resolution (314). 

---