Determination of aromatics in hydrocarbons by near infrared spectroscopy and calibration therefor
AssigneeAshland Oil, Inc.
InventorsSteven M. Maggard, William T. Welch
Life of this patent
Estimating the term…
Abstract
Mid-distillate hydrocarbon fuels, preferably having initial boiling points above 350.degree. F., are separated e.g. by prep-HPLC into non-aromatic and aromatic fractions which are used to set 0% aromatics (the non-aromatics) and 100% aromatics (the aromatics) on an NIR spectrophotometer. From NIR aromatic band absorbances of unknown samples, their percent aromatics is determined using this two-point calibration and the Beer-Lambert equation. Preferred NIR bands of 1650-1700 and 2120-2256 exhibit excellent correlation with aromatics content.
Claims17
A process for measuring the aromatics content of hydrocarbons using a near infrared spectrophotometer comprising in combination the steps of:
- a. selecting a sample generally representative of said hydrocarbons;
- b. separating out a non-aromatic hydrocarbon portion from an aromatics portion of said sample;
- c. measuring the absorbance of said aromatics portion and said non-aromatics portion or a portion containing known mixed proportions of aromatics, and/or saturates, and/or olefins, in the range of 1650-1700 or 2120-2256 nm;
- d. by Beer-Lambert's Law or other methods of data resolution, calibrating said near infrared spectrophotometer or a related computer receiving a signal from the spectrophotometer to provide a signal indicative of the concentration of aromatics, or non-aromatics, in at least one additional hydrocarbon sample;
- e. thereafter measuring the absorbance of the same or a different hydrocarbon sample with said calibrated spectrophotometer in at least one of said ranges;
- and
- f. determining the aromatics content of said same or different sample from its absorbance.
A process of calibrating or recalibrating a near infrared spectrophotometer for measurement of aromatics content of hydrocarbons comprising in combination the steps of:
- a. selecting a first sample generally representative of said hydrocarbons;
- b. separating out the non-aromatic hydrocarbon portion from the aromatic portion of said first sample;
- c. measuring in a first spectrophotometer the absorbance of said aromatics portion and said non-aromatics portion or a portion containing known mixed proportions of aromatics, and/or saturates, and/or olefins, in the range of 1650-1700 or 2120-2256 nm;
- d. by Beer-Lambert's Law or other methods of data resolution, calibrating said first near infrared spectrophotometer or related computer receiving a signal from the spectrophotometer;
- e. calibrating a second spectrophotometer or related computer or re-calibrating said first spectrophotometer or related computer, referencing such instrument to a sample measured in steps c. and d., and adjusting said instrument to provide a value equal to the value obtained in steps c. and d.
Dependencies are inferred from the claim text.