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US 6,841,779 B1Granted
Measurement of wax precipitation temperature and precipitated solid weight percent versus temperature by infrared spectroscopy
AssigneeUniversity of Utah Research Foundation
InventorsRichard Roehner, Francis V. Henson
Life of this patent
Estimating the term…
Abstract
Disclosed is a FT-IR spectroscopy method for the determination of the wax precipitation temperature, and the estimation of the amount of precipitated solid wax material (both crystalline and amorphous) present in a liquid hydrocarbon, such as a petroleum crude oil.
Claims8
A method of determining wax precipitation temperature (WPT) for a liquid hydrocarbon sample, the method comprising:
- Measuring infra-red light absorbance of the sample,
- The measuring made at a plurality of temperatures at a same wave number to obtain a plurality of data points of total absorbance (ATOTAL) vs. temperature (T),
- the wave number corresponding to a wavelength at which the infrared light is absorbed by long chain methylene on a molecule,
- calculating by a linear regression a slope (SS) of ATOTAL vs. T from the data points in which a solid phase is apparent and are data points below the WPT,
- calculating by a linear regression a slope (SL) of ATOTAL vs. T from the data points in which the sample is essentially free of a solid phase and are data points above the WPT,
- calculating the temperature which is at the intersection of lines ATOTAL=T*SS and ATOTAL=T*SL, which temperature is the determined wax precipitation temperature.
3 more elements
A method of determining wax precipitation temperature (WPT) and percent solid for a liquid hydrocarbon sample, the method comprising:
- measuring infrared light absorbance of the sample,
- the measuring made at a plurality of temperatures at a same wave number to obtain a plurality of data points of total absorbance (ATOTAL) vs. temperature (T),
- the wave number corresponding to a wavelength at which the infrared light is absorbed by long chain methylene on a molecule,
- calculating by a linear regression a slope (SS) of ATOTAL vs. T from the data points in which a solid phase is apparent,
- calculating by a linear regression a slope (SL) of ATOTAL vs. T from the data points in which the sample is essentially free of a solid phase,
- calculating the temperature which is at the intersection of lines ATOTAL=T*SS and ATOTAL=T*SL, which temperature is the determined wax precipitation temperature;
- calculating the weight percent of solids of the liquid hydrocarbon sample at a selected temperature (TS)below the WPT from the data points of ATOTAL vs. T by the equation;
- wt. % S=[(ATOTAL−AL)/ATOTAL]×100
- where wt. % S is the weight percent of solids, where AL is the liquid absorbance at the selected temperature determined by linear extrapolation of the line ATOTAL=T*SL, derived from data points in the liquid phase of total absorbance vs. temperature to the selected temperature below the WPT, such that AL is derived from the equation;
- AL=TS*SL.
7 more elements
A method for determining solid/liquid properties of a petroleum sample, the method comprising;
- measuring integrated absorbance of the sample at a wave number near 720 cm−1 that corresponds to the CH2 rocking vibration of long chain methylene (LCM), the measuring made at a plurality of temperatures at the same wave number to obtain a plurality of data points of total absorbance (ATOTAL) vs. temperature,
- determining the wax precipitation temperature (WPT) from the data points by calculating the temperature at which the linear slope of total absorbance vs. temperature changes as the data points change from the those below the WPT to those above the WPT.
An apparatus for determining wax precipitation temperature and percent solids for a liquid hydrocarbon sample, the apparatus comprising:
- an absorbance detector for measuring the infra-red light absorbance of the sample,
- the measuring made at a plurality of temperatures at a same wave number to obtain a plurality of data points of total absorbance (ATOTAL) vs. temperature (T),
- the wave number corresponding to a wavelength at which the infrared light is absorbed by long chain methylene on a molecule;
- a calculator for
- calculating by a linear regression a slope (SS) of ATOTAL vs. T from the data points in which a solid phase is apparent,
- calculating by a linear regression a slope (SL) of ATOTAL vs. T from the data points in which the sample is essentially free of a solid phase,
- calculating the temperature which is at the intersection of lines ATOTAL=T*SS and ATOTAL=T*SL, which temperature is the determined wax precipitation temperature;
- calculating the weight percent of solids of the liquid hydrocarbon sample at a selected temperature (TS)below the WPT from the data points of ATOTAL vs. T by the equation;
- wt. % S=[(ATOTAL−AL)/ATOTAL]×100
- where wt. % S is the weight percent of solids, where AL is the liquid absorbance at the selected temperature determined by linear extrapolation of the line ATOTAL=T*SL, derived from data points in the liquid phase of total absorbance vs. temperature to the selected temperature below the WPT, such that AL is derived from the equation;
- AL=TS*SL.
8 more elements
An apparatus for determining solid/liquid properties of a petroleum sample, the apparatus comprising;
- means for measuring integrated absorbance of the sample at a wave number near 720 cm−1 that corresponds to the CH2 rocking vibration of long chain methylene (LCM), the measuring made at a plurality of temperatures at the same wave number to obtain a plurality of data points of total absorbance (ATOTAL) VS. temperature,
- means for determining the wax precipitation temperature (WPT) from the data points by calculating the temperature at which the linear slope of total absorbance vs. temperature changes as the data points change from the those below the WPT to those above the WPT.
Dependencies are inferred from the claim text.