A Comparison of Diesel and Biodiesel Emissions Using Dimethyl Carbonate as an Oxygenated Additive

Abstract

Diesel vehicles account for the majority of new vehicles sales in Europe. This is due to inherent fuel efficiency and high reliability. Global warming concerns have seen demand for renewable alternatives to fossil diesel with low carbon dioxide (CO 2 ) producing emissions. Oxygenated biodiesel fuels such as rapeseed methyl ester (RME) can be utilized in an unmodified conventional diesel engine. RME combustion produces low emissions of unburnt total hydrocarbons (THCs), carbon monoxide (CO), and particulate matter (PM). This is due in part to fuel-born oxygen content (10.8% wt). This study examines the effect of adding fuel-born oxygen in the form of dimethyl carbonate (DMC) (a nontoxic potentially bioderived 53.3% wt oxygenated additive) to conventional pump diesel. It was found that nitrogen oxides (NO x ) increased and that THCs, CO, and PM were reduced by up to 50% with a 96% diesel, 4% DMC blend. Interestingly 2% DMC in diesel can generate comparable particulate, THCs and CO emissions to RME combustion, at just 1.1% wt oxygen. A DMC blend may also have potential in the reduction of as yet unregulated carcinogenic emissions such as benzene and 1,3-butadiene.

Sooting propensity of dimethyl carbonate, soot reactivity and characterization

“…Dimethyl carbonate (DMC, CH 3 OCOOCH 3 ), a carbonate ester, is an attractive oxygenate compound for using as diesel fuel component for reducing soot emissions due to its good characteristics, such as: (1) 100% miscibility in diesel; (2) 53 wt% in oxygen content; (3) no carbon-carbon atomic bonds; and (4) relatively high H/C ratio [1,2].…”

Application of an enhanced Taguchi method for simultaneous reduction of smoke and NOx emissions using oxygenated additives and retarded injection timing in a stationary diesel engine

“…The oxygenates were chosen based on their cetane number and inherent oxygen content. While the former affects ignition delay, combustion duration and eventually NOx emissions [15], the latter influences smoke emissions [9]. Thus three oxygenates with a good range of oxygen content and cetane number, namely DMC, DGM and DEE, were chosen as three levels for the 'oxygenate-type' parameter.…”

“…Earlier researches have preferred blend proportions of oxygenates varying from 5 to 20 % in diesel [9,10,[14][15][16]. Blend proportions greater than 20 % have been reported to cause engine instability, fluctuations in engine speed and losses in power output [11] [15] [27].…”

“…It was suggested that adding oxygenates is a promising approach to solve the problem of simultaneously reducing NOx and smoke emissions due to the inherent trade-off relationship between them in a traditional diesel engine [8]. However, many studies have found that increasing the proportion of oxygenates in diesel can either result in increasing the levels of NOx emissions [9][10][11][12][13] or do not affect their levels at all [14][15][16]. Burnt gas temperature and the duration spent by the gas at that temperature inside the combustion chamber are the two factors that affect NOx levels.…”

REDUCTION OF NOx AND OPACITY FROM DIESEL ENGINE WITH DIMETHYL CARBONATE AND ISOPROPYL ALCOHOL

“…3 The effect of adding fuel-borne oxygen in the form of dimethyl carbonate (DMC) has been reported in (a non-toxic potentially bioderived 53.3% wt oxygenated additive) conventional pump diesel. 4 It was found that nitrogen oxides (NOx) increased and that THCs, CO, and PM were reduced by up to 50% with a 96% diesel, 4% DMC blend. Interestingly 2% DMC in diesel can generate comparable particulate, THCs and CO emissions to RME combustion, at just 1.1% wt oxygen.…”