Methanol emission

Fig. 2. CEC methanol-fueled veliide exhaust profile for (a) HC, hydrocarbons (b) NO and (c) CO. Solid line represents State of California standard maximum emissions. Methanol HC emissions are calculated as CH g5 and not corrected for flame-ionization detector response.

Methanol is the typical fuel with one carbon (Cl) atom for fuel cells. Methanol was one of the first small molecules chosen to study the oxidation on platinum group metals in the very early beginning of electrocatalysis. In that time, the oxidation of other Cl molecules such as formic acid and formaldehyde (interest in CO oxidation came latter with the oxidation of reformatted gases) were investigated as a model oxidation because their elementary steps were supposedly present in the mechanism of methanol oxidation. From the point of view of CO2 emission, methanol has, among the other small molecules, the highest energy production per unit of produced... 

Of course, FFV drivers do not have to use methanol. Emissions benefits are not obtained if methanol is not used, and fuel economy is not optimized for methanol nor are emissions. However the State of California has concluded that advantages offered by the flexibiUty of the FFV far outweigh the disadvantages (37). 

Fig. 5. Emissions from a GM Corsica VFV for gasoline and gasoline—methanol mixtures where represents total organic material, including hydrocarbons, methanol, and formaldehyde U represents NO formaldehyde and Hcarbon monoxide.

Additional research for both ethanol and methanol showed that the amount of ignition improver could be reduced by systems increa sing engine compression (63). Going from 17 1 to 21 1 reduced the amount of TEGDN requited for methanol from 5% by volume to 3%. Ignition-improved methanol exhibited very low exhaust emissions compared to diesels particulate emissions were eliminated except for small amounts associated with engine oil, NO was even lower with increased compression, and CO and hydrocarbons were also below diesel levels. 

Benefits depend upon location. There is reason to beheve that the ratio of hydrocarbon emissions to NO has an influence on the degree of benefit from methanol substitution in reducing the formation of photochemical smog (69). Additionally, continued testing on methanol vehicles, particularly on vehicles which have accumulated a considerable number of miles, may show that some of the assumptions made in the Carnegie Mellon assessment are not vahd. Air quaUty benefits of methanol also depend on good catalyst performance, especially in controlling formaldehyde, over the entire useful life of the vehicle. 

Methanol substitution strategies do not appear to cause an increase in exposure to ambient formaldehyde even though the direct emissions of formaldehyde have been somewhat higher than those of comparable gasoline cars. Most ambient formaldehyde is in fact secondary formaldehyde formed by photochemical reactions of hydrocarbons emitted from gasoline vehicles and other sources. The effects of slightly higher direct formaldehyde emissions from methanol cars are offset by reduced hydrocarbon emissions (68). 

In the late 1980s attempts were made in California to shift fuel use to methanol in order to capture the air quaHty benefits of the reduced photochemical reactivity of the emissions from methanol-fueled vehicles. Proposed legislation would mandate that some fraction of the sales of each vehicle manufacturer be capable of using methanol, and that fuel suppHers ensure that methanol was used in these vehicles. The legislation became a study of the California Advisory Board on Air QuaHty and Fuels. The report of the study recommended a broader approach to fuel quaHty and fuel choice that would define environmental objectives and allow the marketplace to determine which vehicle and fuel technologies were adequate to meet environmental objectives at lowest cost and maximum value to consumers. The report directed the California ARB to develop a regulatory approach that would preserve environmental objectives by using emissions standards that reflected the best potential of the cleanest fuels. 

M. D. Jackson, S. Uimasch, and D. D. Lowell, "Heavy-Duty Methanol Engines Wear and Emissions," 8th Int. Sjmp. onylkoholFuels (Tokyo, Japan, Nov. 13-16,1988). 

R. Baranescu and co-workers, "Prototype Development of a Methanol Engine for Heavy-Duty AppHcation-Performance and Emissions," Sy4E Paper 891655, SyPE Future Transportation Technology Conf. (Aug. 7—20,1989), Society of Automotive Engineers, Warrendale, Pa. 

C. M. Urban, T. J. Timbario, and R. L. Bechtold, "Performance and Emissions of a DDC 8V-71 Engine Pueled with Cetane Improved Methanol," SyPE Paper 892064, SyPE Int. Fuels and Eubricants Meeting and Expo. (Baltimore, Md., Sept. 25—28,1989) Society of Automotive Engineers, Warrendale, Pa. 

M. A. DeLuchi, "Emissions of Greenhouse Gases from the Use of Gasoline, Methanol, and Other Alternative Transportation Puels," ia W. Kohl, ed.. Methanol as an yiltemativeFuel Choice yin yissessment, ]oim. Hopkias Poreiga PoHcy lastitute, Washiagtoa, D.C., 1990, pp. 167—199. 

In the United States, the Clean Air Act of 1970 imposed limitations on composition of new fuels, and as such methanol-containing fuels were required to obtain Environmental Protection Agency (EPA) waivers. Upon enactment of the Clean Air Act Amendments of 1977, EPA set for waiver unleaded fuels containing 2 wt % maximum oxygenates excluding methanol (0.3 vol % maximum). Questions regarding methanol s influence on emissions, water separation, and fuel system components were raised (80). 

Methanol, a clean burning fuel relative to conventional industrial fuels other than natural gas, can be used advantageously in stationary turbines and boilers because of its low flame luminosity and combustion temperature. Low NO emissions and virtually no sulfur or particulate emissions have been observed (83). Methanol is also considered for dual fuel (methanol plus oil or natural gas) combustion power boilers (84) as well as to fuel gas turbines in combined methanol / electric power production plants using coal gasification (85) (see Power generation). 

Emissions from methanol vehicles are expected to produce lower HC and CO emissions than equivalent gasoline engines. However, methanol combustion produces significant amounts of formaldehyde (qv), a partial oxidation product of methanol. Eormaldehyde is classified as an air toxic and its emissions should be minimized. Eormaldehyde is also very reactive in the atmosphere and contributes to the formation of ozone. Emissions of NO may also pose a problem, especiaHy if the engine mns lean, a regime in which the standard three-way catalyst is not effective for NO reduction. 

Heavy-duty diesel engines can also be modified to operate on neat methanol. Emissions of NO and particulates are generaHy lower than the original engine. These types of engines have typicaHy been used in urban buses to help reduce ambient poHution levels. 

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