Alcohol transport

In Sect. 6.1 we defined the alcohol selectivity coefficient, / , of a membrane Eq. 6.2, which accounts for the ratio between the proton and alcohol transport through it, and the relative selectivity, / r, Eq. 6.3 which compare the alcohol selectivity of the membrane to Nafion under the same experimental conditions. Here we will analyze the abundant data on the methanol selectivity in inorganic and organic Nafion composites in comparison with the selectivity of pure Nation membranes. In order to perform this analysis we will resort to the general selectivity plot described in Fig. 6.2. 

The COTiductivity reported for the A-201 membrane from Tokuyama is 29 mS. cm , which is a modest cmiductivity compared with that of a Nafion proton conducting membrane. The low thickness of this membrane (28 pm) partially compensates this fact, while the alcohol transport is not probably exacerbated. Typical methanol permeabhities of quaternized membranes are lower than 10 cm. s and values as low as 10 cm. s have been reported [214], which imphes that the only concern regarding the apphcabOity in DAFC is imiic COTiductivity. 

Although many problems still remain to be overcome to make the process practical (not the least of which is the question of the corrosive nature of aqueous HBr and the minimization of formation of any higher brominated methanes), the selective conversion of methane to methyl alcohol without going through syn-gas has promise. Furthermore, the process could be operated in relatively low-capital-demand-ing plants (in contrast to syn-gas production) and in practically any location, making transportation of natural gas from less accessible locations in the form of convenient liquid methyl alcohol possible. 

About half of the wodd production comes from methanol carbonylation and about one-third from acetaldehyde oxidation. Another tenth of the wodd capacity can be attributed to butane—naphtha Hquid-phase oxidation. Appreciable quantities of acetic acid are recovered from reactions involving peracetic acid. Precise statistics on acetic acid production are compHcated by recycling of acid from cellulose acetate and poly(vinyl alcohol) production. Acetic acid that is by-product from peracetic acid [79-21-0] is normally designated as virgin acid, yet acid from hydrolysis of cellulose acetate or poly(vinyl acetate) is designated recycle acid. Indeterrninate quantities of acetic acid are coproduced with acetic anhydride from coal-based carbon monoxide and unknown amounts are bartered or exchanged between corporations as a device to lessen transport costs. 

The benefits of alcohol fuels include increased energy diversification in the transportation sector, accompanied by some energy security and balance of payments benefits, and potential air quaUty improvements as a result of the reduced emissions of photochemically reactive products (see Air POLLUTION). The Clean Air Act of 1990 and emission standards set out by the State of California may serve to encourage the substantial use of alcohol fuels, unless gasoline and diesel technologies can be developed that offer comparable advantages. 

Dedicated Vehicles. Only Brazil and California have continued implementing alcohols in the transportation sector. The BraziUan program, the largest alternative fuel program in the world, used about 7.5% of oil equivalent of ethanol in 1987 (equivalent to 150,000 bbl of cmde oil per day). In 1987 about 4 million vehicles operated on 100% ethanol and 94% of all new vehicles purchased that year were ethanol-fueled. About 25% of Brazil s light-duty vehicle fleet (10) operate on alcohol. The leading BraziUan OEMs are Autolatina (a joint venture of Volkswagen and Ford), GM, and Fiat. Vehicles are manufactured and marketed in Brazil. 

It has been found that the flavor of fmit can be increased by a process called precursor atmosphere (PA) (77). When apples were stored in a controlled atmosphere containing butyl alcohol [71-36-3] the butyl alcohol levels increase by a factor of two, and the polar products, butyl ester, and some sesquiterpene products increase significantly. The process offers the possibiUty of compensating for loss of flavor in fmit handling and processing due to improper transportation conditions or excessive heat. 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

The U.S. domestic shipping name of isopropyl alcohol is UN No. 1219 Isopropanol. Anhydrous as well as water solutions to 91 vol % alcohol are considered flammable Hquid materials by the DOT. Both have flash poiats below 37.8°C by the Tag closed-cup method. Acceptable modes of transportation include air, rail, road, and water (124). For international air and water shipments, the International Maritime Organization (IMO) class is 3.2, the packaging group is II, and the primary hazard label required is "Flammable Liquid."... 

Evaporation and Distillation. Steam is used to supply heat to most evaporation (qv) and distillation (qv) processes, such as ia sugar-juice processiag and alcohol distillation. In evaporation, pure solvent is removed and a low volatiUty solute is concentrated. Distillation transfers lower boiling components from the Hquid to the vapor phase. The vapors are then condensed to recover the desired components. In steam distillation, the steam is admitted iato direct coatact with the solutioa to be evaporated and the flow of steam to the condenser is used to transport distillates of low volatiHty. In evaporation of concentrated solutions, there may be substantial boiling poiat elevation. For example, the boiling poiat of an 80% NaOH solution at atmospheric pressure is 226°C. 

In this process the addition of water vapor to the sweep stream can be controlled so that the water activity of the gas phase equals that of the beverage. When this occurs, there is no transport of water across the membrane. The water content of both the beverage feed and the sweep stream is kept constant. These conditions must be maintained for optimum alcohol reduction. The pervaporation system controls the feed, membrane, airstream moisture level, and ethanol recovery functions. An operational system has been developed (13). 

Mobil Oil Corporation has developed a process on a pilot scale that can successfully convert methanol into 96 octane gasoline. Although methanol can be used directiy as a transportation fuel, conversion to gasoline would eliminate the need to modify engines and would also eliminate some of the problems encountered using gasoline—methanol blends (see Alcohol fuels Gasoline and other motor fuels). 

Development of SASOL. Over 70% of South Africa s needs for transportation fuels are being suppHed by iadirect Hquefaction of coal. The medium pressure Fischer-Tropsch process was put iato operation at Sasolburgh, South Africa ia 1955 (47). An overall flow schematic for SASOL I is shown ia Figure 12. The product slate from this faciUty is amazingly complex. Materials ranging from hydrocarbons through oxygenates, alcohols, and acids are all produced. 

Transportation end uses are expected to become a significant outlet. Products under development include an engine valve cover, as are various housings such as those for od pumps, water pumps, starter motors, and certain transmission parts. These end uses employ PPS because it resists high temperatures and is also chemically resistant. Fuel system parts can employ the excellent chemical resistance of PPS, replacing nylon, if alcohol-based fuels are adopted to reduce emissions. 

Some alcohols, eg, propylene glycol, not only lower water activity but also have an additional preservative effect caused by the way they interfere with the ceU membrane transport system of the contaminating microorganisms. Surfactants (qv) may show a similar effect. 

Commercial ethyl alcohol is shipped in railroad tank cars, tank tmcks, 208-L (55-gal) and 19-L (5-gal) dmms, and in smaller glass or metal containers having capacities of 0.473 L (one pint), 0.946 L (one quart), 3.785 L (one U.S. gal), or 4.545 L (one Imperial gal). The 208-L dmms may be of the unlined iron type. If a guarantee of more meticulous quaUty is desired, the dmms may be lined with phenoHc resin. AH containers, of course, must comply with the specifications of the U.S. Department of Transportation. Both 190 proof and 200 proof ethyl alcohol are considered red label (flammable) materials by the DOT, as both have flash points below 37.8°C by the Tag closed-cup method. 

Under the National Energy PoHcy Act of 1992 nonpetroleum-based transportation fuels are to be introduced in the United States. Such fuels include natural gas (see Gas, natural), Hquefied petroleum gas (qv) (LPG), methanol (qv), ethanol (qv), and hydrogen (qv), although hydrogen fuels are not expected to be a factor until after the year 2000 (see also Alcohol fuels Hydrogen energy). 

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