Hydrocarbons aerosolization

Data on dispersion and combustion of aerosol-air clouds are scarce, although Burgoyne (1963) showed that the lower flannmability limits on a weight basis of hydrocarbon aerosol-air mixtures are in the same range as those of gas- or vapor-air mixtures, namely, about 50 g/m. ... 

Perrone H, Passero MA. 1983. Hydrocarbon aerosol pneumonitis in an adult. Arch Intern Med 143(8) 1607-1608. 

Presumably, as with Callisto and Ganymede, the crust and mantle are primarily water ice. Models of the atmospheric chemistry however suggest that the surface should receive a continual rain of hydrocarbon aerosols, some of which may be liquid under Titan surface conditions (Lunine, 1993 Lunine et ai, 1983). 

Although hydrocarbon aerosol propellants are relatively inexpensive, nontoxic, and environmentally friendly (since they are not damaging to the ozone layer and are not greenhouse gases), their use is limited by their flammability. While hydrocarbon propellants are primarily used in topical aerosol formulations, it is possible that butane may also be useful in metered-dose inhalers as a replacement for chloro-fluorocarbons. 

In 1997, Eastoe et al. launched a study of fluorinated anionic sulfosuccinate surfactants, which are analogous to the hydrocarbon Aerosol-OT (sodium bis-2-ethylhexyl sulfosuccinate, AOT) (13,24-26, 27 a). Example molecular structures are shown on Figure 1. Furthermore, fluoroalkylphosphates have been assessed for C02-activity (27 b, c). A detailed presentation of these systems is given in section 2 below. In 2001, Erkey and co-workers also showed interest in these very promising sulfosuccinate surfactants (28, 29). Small-angle X-ray scattering (SAXS) was used to characterize di-HCF4 at 0.1 M in CO2 at 27 °C and 345 bar for w between 0 and 20 (29). 

Hydrocarbon aerosol hair sprays contain an alcohol-hydrocarbon solvent-propellant system, a synthetic polymeric resin, a base to neutralize the resin if it is a carboxylic acid-containing resin, plasticizer(s), fragrance, and, in some cases, surfactant(s) to improve the spreading characteristics of the polymer. Most of the new low-VOC aerosol hairsprays contain alcohol-water as the solvent system and dimethyl ether as the propellant. Together the alcohol-dimethyl ether content must be below 55% (54.5%). For cost considerations, dimethyl ether is the propellant of choice, although Hydrofluorocarbon 152-A is exempt as a VOC and provides acceptable, but expensive formulations with previously used resins [54]. In Europe and other parts of the world, there are no VOC limits, and hydrocarbon-alcohol systems with virtually no water are widely used. 

The solvents in pump sprays are limited to alcohol-water mixtures and are, therefore, not as complex as the solvent-propellant mixtures of aerosols. Generally, ethyl alcohol is the primary solvent, and water the secondary solvent. In some cases, small quantities of propanols or even glycols are also used. The solvent and, of course, the pump spray system largely determine the spray characteristics of a given product, and spray characteristics are very important to the functional character of the product [54]. The solvent-propellant systems of today s hydrocarbon aerosol hairsprays used outside the United States generally consist of alcohol combined with hydrocarbons such as isobutene, butane, or propane and virtually no water. For low-VOC systems, dimethyl ether is the propellant of choice. For additional details on aerosol propellants for hairsprays, see the previous discussion on VOC propellants and the article by Root [53].The solvent-propellant in both aerosol and pump sprays contains the VOC and presents the apparent environmental problem. As stated, the CARB regulations for 1999 of 55% VOC present the target that has stimulated research and development in this area. 

Liang M-C, Seager S, Parkinson C, Lee AY-L, Yung YL (2004) On the insignificance of photochemictil hydrocarbon aerosols in the atmospheres of close-in extrasolar giant planets. Astrophys J Lett 605 L61-L64... 

Carbon contamination of the produced sulfur can result from liquid hydrocarbon droplets in the feed gas or by condensation of feed gas hydrocarbons. This problem is besr avoided by operating the process about 10°F above the feed gas hydrocarbon dew point and by removing any hydrocarbon aerosol in the feed gas (compressor lube oil, etc.) with a coalescing filter (Allen, 1995). Yet another potential form of sulfur contamination can occur when the feed gas contains a significant amount of mcrcaptans. Any disulfides formed will lend to coat the surface of the sulfur particles. If the sulfur is to be recovered as a salable product, special attention needs to be paid to the design of the overall system to avoid production of low-quality, disulfide-contaminated sulfur. Elimination of mercaptans and heavy hydrocar-... 

Uses O/w emulsifier for cosmetics, topical pharmaceuticals opacifier, thickener for llq. cream shampoos aux. emulsifier In hydrocarbon aerosol systems such as shave creams... 

Solutions. To dehver a spray, the formulated aerosol product should be as homogeneous as possible. That is, the active ingredients, the solvent, and the propellant should form a solution. Because the widely used halocarbon and hydrocarbon propellants do not always have the desired solubiUty characteristics for all the components in the product concentrate, special formulating techniques using solvents such as alcohols (qv), acetone (qv), and glycols (qv), are employed. 

Sprays. Aerosol spray emulsions are of the water-in-oil type. The preferred propellant is a hydrocarbon or mixed hydrocarbon—hydrofluorocarbon. About 25 to 30% propellent, miscible with the oil, remains in the external phase of the emulsion. When this system is dispensed, the propellant vaporizes, leaving behind droplets of the w/o emulsion (Fig. 2b). A vapor tap valve, which tends to produce finely dispersed particles, is employed. Because the propellant and the product concentrate tend to separate on standing, products formulated using this system, such as pesticides and room deodorants, must be shaken before use. 

Propellants. The propellant, said to be the heart of an aerosol system, maintains a suitable pressure within the container and expels the product once the valve is opened. Propellants may be either a Hquefied halocarbon, hydrocarbon, or halocarbon—hydrocarbon blend, or a compressed gas such as carbon dioxide (qv), nitrogen (qv), or nitrous oxide. 

Hydroca.rbons. Hydrocarbonsn such as propane, butane, and isobutane, which find use as propellants, are assigned numbers based upon their vapor pressure in psia at 21°C. For example, as shown in Table 2, aerosol-grade propane is known as A-108, / -butane as A-17. Blends of hydrocarbons, eg, A-46, and blends of hydrocarbons and hydrochlorocarbons orHCFCs are also used. The chief problem associated with hydrocarbon propellants is their flammabihty. 

Hydrocarbons have, for the most part, replaced CFCs as propellants. Most personal products such as hair sprays, deodorants, and antiperspirants, as well as household aerosols, are formulated using hydrocarbons or some form of hydro-carbon—halocarbon blend. Blends provide customized vapor pressures and, if halocarbons are utilized, a decrease in flammabiUty. Some blends form azeotropes which have a constant vapor pressure and do not fractionate as the contents of the container are used. 

In 1987 nonmotor fuel uses of butanes represented ca 16% of the total consumption. Liquid petroleum gas (LPG) is a mixture of butane and propane, typically in a ratio of 60 40 butane—propane however, the butane content can vary from 100 to 50% and less (see Liquefied petroleum gas). LPG is consumed as fuel in engines and in home, commercial, and industrial appHcations. Increasing amounts of LPG and butanes are used as feedstocks for substitute natural gas (SNG) plants (see Fuels, synthetic). / -Butane, propane, and isobutane are used alone or in mixture as hydrocarbon propellents in aerosols (qv). 

Total Hydrocarbon Gontent. The THC includes the methane combined in air, plus traces of other light hydrocarbons that are present in the atmosphere and escape removal during the production process. In the typical oxygen sample, methane usually constitutes more than 90% of total hydrocarbons. The rest may be ethane, ethylene, acetylene, propane, propylene, and butanes. Any oil aerosol produced in lubricated piston compressor plants is also included here. 

The popularity of aerosols has been declining. A widely used group of propellants, the fluorinated hydrocarbons, have been restricted in use since it was found that they can harm the environment by reducing the o2one layer of the upper atmosphere (see AiRPOLLUTlON ATMOSPHERIC MODELING Ozone). 

The different types of furniture pohshes include hquid or paste solvent waxes, clear oil pohshes, emulsion oil pohshes, emulsion wax pohshes, and aerosol or spray pohshes (3). Nonwoven wipes impregnated with pohsh ingredients have been targeted at consumers who do not wish to expend the time to dust before polishing (11). Compilations of representative formulas are given in References 3, 4, 12, and 13. Paste waxes contain ca 25 wt % wax, the remainder being solvent. Clear oil pohshes contain 10—15 wt % oil and a small amount of wax, the rest being solvent. Aerosol or spray products may contain 2—5 wt % of a sihcone polymer, 1—3 wt % wax, 0—30 wt % hydrocarbon solvent, and ca 1 wt % emulsifier. The remainder is water. 

GASFLOW models geometrically complex containments, buildings, and ventilation systems with multiple compartments and internal structures. It calculates gas and aerosol behavior of low-speed buoyancy driven flows, diffusion-dominated flows, and turbulent flows dunng deflagrations. It models condensation in the bulk fluid regions heat transfer to wall and internal stmetures by convection, radiation, and condensation chemical kinetics of combustion of hydrogen or hydrocarbon.s fluid turbulence and the transport, deposition, and entrainment of discrete particles. 

Wall Loss of Oxidation Products. It is known that some classes of hydrocarbons (the higher terpenes, for instance) are prolific aerosol formers when subjected to atmospheric oxidation. Other classes, aromatic hydrocarbons for instance, although they do not form large amounts of suspended aerosol, have been shown to lose (at least under some conditions) large amounts of oxidation products to the reaction vessel walls. The fate of these oxidation products in the open atmosphere remains open to question, as does the extent to which they continue to participate in gas-phase chemistry (187). 

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