Fuels oxygenates

Isobutyl alcohol [78-83-1] forms a substantial fraction of the butanols produced by higher alcohol synthesis over modified copper—zinc oxide-based catalysts. Conceivably, separation of this alcohol and dehydration affords an alternative route to isobutjiene [115-11 -7] for methyl /-butyl ether [1624-04-4] (MTBE) production. MTBE is a rapidly growing constituent of reformulated gasoline, but its growth is likely to be limited by available suppHes of isobutylene. Thus higher alcohol synthesis provides a process capable of supplying all of the raw materials required for manufacture of this key fuel oxygenate (24) (see Ethers). 

High temperature steam reforming of natural gas accounts for 97% of the hydrogen used for ammonia synthesis in the United States. Hydrogen requirement for ammonia synthesis is about 336 m /t of ammonia produced for a typical 1000 t/d ammonia plant. The near-term demand for ammonia remains stagnant. Methanol production requires 560 m of hydrogen for each ton produced, based on a 2500-t/d methanol plant. Methanol demand is expected to increase in response to an increased use of the fuel—oxygenate methyl /-butyl ether (MTBE). 

The 1990 Clean Air Act mandates for blended oxygenates ia gasoline created a potentially large new use for DIPE as a fuel oxygenate. Isopropyl alcohol can react with propylene over acidic ion-exchange (qv) catalysts at low temperatures, which favor high equiUbrium conversions per pass to produce DIPE (34). 

Flammability Limits There are both upper (or rich) and lower (or lean) limits of flammability of fuel-air or fuel-oxygen mixtures. Outside these hmits, a self-sustaining flame cannot form. Flammability limits for common fuels are listea in Table 27-18. 

Experimental data are available for detonation limits for a limited number of fuel-air and fuel-oxygen mixtures at atmospheric pressure in both confined and nnconfined situations. These are presented in Table 4-4 (Nettleton 1987). 

Matsui, H., and J. H. S. Lee. 1979. On the measure of relative detonation hazards of gaseous fuel-oxygen and air mixtures. Seventeenth Symposium (International) on Combustion, pp. 1269-1280. Pittsburgh, PA The Combustion Institute. 

Shih C-C, ME Davey, J Zhou, JM Tiedje, CS Criddle (1996) Effects of phenol feeding pattern on microbial community structure and cometabolism of trichloroethylene. Appl Environ Microbiol 62 2953-2960. Somsamak P, HH Richnow, MM Haggblom (2005) Carbon isotope fractionation during anaerobic biotransformation of methyl ferf-butyl ether and ferf-amyl methyl ether. Environ Sci Technol 39 103-109. Somsamak P, RM Cowan, MM Haggblom (2001) Anaerobic biotransformation of fuel oxygenates under sulfate-reducing conditions. EEMS Microbiol Ecol 37 259-264. 

Chemical combustion is initiated by the oxidation or thermal decomposition of a fuel molecule, thereby producing reactive radical species by a chain-initiating mechanism. Radical initiation for a particular fuel/oxygen mixture can result from high-energy collisions with other molecules (M) in the system or from hydrogen-atom abstraction by 02or other radicals, as expressed in reactions 6.1-6.3 ... 

Remediation from MTBE and Other Fuel Oxygenates... 

The United States Environmental Protection Agency (U.S. EPA) has identified several hundred MTBE-contaminated sites that have performed treatment of soil and groundwater to remove or destroy MTBE.1 Many of these sites have also treated other fuel components, primarily benzene, toluene, ethylbenzene, and xylene (BTEX), and some have treated fuel oxygenates other than MTBE. Although others have reported about treatment technologies for MTBE cleanup,2 only limited information has been published about cleanup of other oxygenates. These oxygenates include ether compounds, such as ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), diisopropyl ether (DIPE), and tert-amyl ethyl ether (TAEE), as well as alcohol compounds, such as tert-butyl alcohol (TBA), tert-amyl alcohol (TAA), ethanol, and methanol. 

Preliminary information about treatment of fuel oxygenates other than MTBE. 

Lessons learned about the application of these technologies to clean up media contaminated with MTBE and other fuel oxygenates. 

In 1998, approximately 30% of all gasoline in the United States contained oxygenates. At that time, MTBE was the most common fuel oxygenate, present in more than 80% of oxygenated fuels. However, due to increasing restrictions on the use of MTBE, this percentage has decreased over the past several years. In 1998, ethanol was the second most common fuel oxygenate, present in about... 

FIGURE 24.1 Molecular structures of common fuel oxygenates. (Adapted from U.S. EPA, Technologies for Treating MTBE and Other Fuel Oxygenates, EPA 542-R-04-009, United States Environmental Protection Agency, Washington, DC, May 2004.)... 

Only limited information is available about the health risks of oxygenates other than MTBE. Fewer states have established standards and cleanup levels for these contaminants than for MTBE. Currently, there are no federal drinking water advisory or cleanup levels for these other fuel oxygenates. Several states have established, and some states have plans to establish, cleanup levels for other oxygenates.21 Table 24.1 summarizes the number of states that have cleanup levels for fuel oxygenates along with the range of cleanup levels established for each. 

Other researchers have provided additional information related to the methods used for the analysis of fuel oxygenates. The following references provide more detailed information about this... 

State Cleanup Levels for Fuel Oxygenates in Groundwater... 

Fuel Oxygenate States with Cleanup Level 2004 Lowest Cleanup Level (pg/L) Highest Cleanup Level (pg/L)... 

Fuel oxygenates generally exhibit the following physical properties relative to benzene ... 

Properties of Fuel Oxygenates and Other Fuel Constituents... 

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