New Mexico uses high-octane testing method
Octane testing has traditionally been a slow, cumbersome, expensive process for states. New Mexico, for example, is required to analyze 10,000-12,000 samples per year, but the testing is so costly the state is unable to meet these requirements.
Looking for a cheaper, quicker atternative, the New Mexico Department of Agriculture (DOA) has begun using a near-infrared screening (NIR) system that cuts testing costs from $50 a sample to $1 per sample and turnover from one hour to minutes.
According to Floyd Highfill, state chemist for the DOA’s Standards and Consumer Services Division Petroleum Standards Laboratory, the division now can cover the state’s 110,000 square miles — which incorporates 2,200 gasoline outlets and 20 major distributors with a testing frequency of three times per year because of NIR’s reduced turnaround time.
“Octane monitoring with CFR engines can take up to an hour for the test and verification and involves actually running a test engine with all the attendant emission controls and maintenance problems,” Highfill says. “By contrast, it only takes 60 seconds for test and verification with NIR, and the method is clean and non-destructive.”
Like other forms of spectroscopy, NIR measures light energy of known intensity and frequency range as it illuminates a sample. In most cases, the wavelength range is between 800 and 2,400 nanometers, depending on the component. Energy passing through the sample is reflected back and compared with the incident light level to measure absorbance,
Virtually all hydrocarbon molecular entities selectively absorb light energy at particular frequencies in the NIR range, and any molecule that contains a hydroxyl, carboxyl, amine or carbon-hydrogen bond will absorb NIR energy.
For octane monitoring, the instrument is tuned to measure absorbance features that correspond to octane content. The absorbance vs. wavelength plot gives a pattern that allows quantification. However, determination of octane levels involves more than a single wavelength measurement, and resident software is used to convert the spectrum to an octane number.
Currently, the laboratory runs the NIR quantum analyzer for production testing and runs suspect specimens through two CFR engines to verify the accuracy of the NIR results.
By screening the samples for octane by NIR first and running only suspect samples on the CFR engines, corrective action can be taken at the pump or distribution point much more quickly, Highfill says.
In addition, the NIR screening cuts response time to consumer complaints from days to hours. “With CFR testing, when we finally got verification that a sample was octane-deficient, it was often too late to take effective corrective measures because the violate gasoline was already in consumers’ gas tanks,” Highfill says.
Eventually, with changes in ASTM regulations, Highfill believes the state may be able to switch exclusively to NIR for octane monitoring.
In addition to quick turnaround and high throughput, there are a number of safety and environmental benefits that come with NIR analysis of octane, Highfill says. “Compared to CFR octane engine testing, we are storing, handling and disposing of much less gasoline,” he says. “CFR testing requires 1-quart samples, but NIR testing requires only a fraction of that.”
Highfill also sees an expanded role for NIR in the division’s Petroleum Standards Laboratory. “We want to develop models for monitoring other constituents of fuel oils. These would include flash point, viscosity distillation range, ravity and cetane, which corresponds to octane in gasoline. For gasoline, we also want to include vapor pressure and oxygenates, as well as distillation range.”
“In doing this, we can eliminate 95 percent of the expensive and labor-intensive wet chemistry methods currently needed for detection of violations,” Highfill says.