AP-109 FTIR ANALYSIS OF OXYGENATES FOR MOTORGASOLINE

By Hue Phan A method to measure oxygenates in motor gasoline by Fourier Transform Infrared spectroscopy wasstudied. A set of gasoline samples with oxygenate concentrations ranging from 1 to 10 percent by weight were prepared by adding MTBE and/or ethanol to the super gasoline. The results show that these compounds exhibit a linear Beer's law response over the specified concentration range. This suggests that the described method is a possible alternative to the existing standard method for measuringgasoline oxygenates. Potential applications include on-line or field monitoring of gasolines. Introduction Instrumentation Motor vehicles are significant contributors of carbon monoxide emissions. By adding oxygenates togasoline, the combustion process in the engine becomes more efficient, and thus the exhaust emissions of carbon monoxide are reduced. The Clean Air Act requires a minimum oxygen content for all gasoline sold or dispensed within any control area. The current methods for the measurement of gasoline oxygenates are usually time-consuming and require large sample volumes. Recently, there has been interest in the use of infrared spectroscopy for the measurement ofoxygenates in gasolines. In this study, we examined a set of gasoline samples with MTBE and/or ethanol added at a concentration ranging from 1 to 10 percent by weight. This paper presents the infrared analysis for oxygenates in gasoline and illustrates the agreement with Beer's law. The Midac M2000 Ftir spectrometer was equipped with an Axiom tunnel flow through ATR cell. Thesensing element was a Zinc Selenide cylindrical reflectance industrial crystal. The optical bench was configured with a room temperature DTGS detector. All spectra were recorded at 4cm
-1 resolutionand thirty-two scans were averaged for each sample. The spectrometer scanning rate using the DTGS detector was 1scan/second. Experiment Two stock solutions of 10% MTBE and 10% ethanol in gasoline were prepared separately. A set ofgasoline samples with MTBE and ethanol added from 1 to 10% concentration were prepared using the stock solutions. The list of the sample compositions of the prepared gasolines are shown on Table 1. For example, line 4 shows the (MTBE,Ethanol) compositions as follows: (3,0), (3,1), ... and (3,10).
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