Research Of Gas Chromatograph Applied To Exhaust Analysis

Particular Matter(PM), nitrogen oxides(NOx),total hydrocarbons(THC)and carbon monoxide(CO)et al dramatically decrease when alcohol fuels substitute for gasoline or diesel, but unregulated emissions including methanol, ethanol, formaldehyde and acetaldehyde et al increase comparatively. Because the accumulations of unregulated emissions and their photochemical productions will be seriously harmful to human health and environment, it is necessary to establish the analytic methods that can be provided with higher sensitivity. Direct injection, instant adding pressure, derivative reaction for aldehydes and carbon nanotube adsorption-thermal desorption et al were investigated on the capillary gas chromatograph (GC) to improve the sensitivity of unregulated emissions.Firstly unregulated emissions from methanol-engine (fuels with different volume concentrations of 15%, 85% and 100% methanol, marked as M15, M85 and M100) were analyzed by GC with direct injection, and results showed that this technology basically settled for detection of methanol and formaldehyde unregulated emissions for methanol-fuels.To get higher sensitivity, instant adding pressure was introduced into GC to analyze unregulated emissions, experiment result showed that the detective sensitivities could enhance 8~10 times to direct injection. And evaporation emissions from ethanol-fuel (with 10% volume concentration ethanol, marked as E10) were tried out using this method, experiment result tallied with the former. But there is a disadvantage, it can't analyze the compounds which reserve times are very close (eg: superposition hydrocarbons or aldehydes).Besides to exactly analyze aldehydes in unregulated emissions, GC with derivative reaction was specially tried out, there volatile aldehydes were transformed into unvolatile derivations which could obtain higher sensitivity on flame ionization detector (FID) and avoid internal standard and avoid disturbing of alkyl compounds. It is considered as an effective method to exactly detect aldehydes in unregulated emissions.At last to improve holistic sensitivity of all unregulated emissions, carbon nanotube absorption-thermal desorption /GC was developed, in which multicarbon nanotube was chosen as adsorbent and capillary was chosen as adsorbent tube. It could actualize absorption and thermal desorption online avoiding sample losing during beforehand treatment. The analysis experiments for methanol, ethanol, benzene, 1,3-butadiene et al and practical emission sample proved it to be feasible, reliable and veracious.Above all four methods are very helpful to investigate unregulated emissions from alcohol-engine.