NIR spectroscopy in the petrochemical and refinery industry: The ASTM compliant tool for QC and product screening – Part 1
Introduction to the petrochemical and refining industry
Oil and gas for fuel are produced in nearly every corner of the globe, from small private wells generating around 100 barrels a day, to the large bore wells producing upwards of 40 times that volume. Despite this great variation in size, many parts of the refining process are quite similar.
Oil refining aims to provide a defined range of products according to agreed specifications. Simple refineries use a distillation column (Figure 1) to separate crude oil into different fractions based on their chemical properties, and the relative quantities are directly dependent on the crude oil used. Therefore, it is necessary to obtain a range of crudes that can be blended into a suitable feedstock to produce the required quantity and quality of end products.
Figure 1. Illustration of a fractionating distillation column used for the purposes of refining crude oil into several desirable end products.
Read on for a short overview on NIR spectroscopy followed by application examples for the petrochemical and refinery industry to learn how petrochemical producers and refineries alike can benefit from NIRS.
NIR technology: a brief overview
The interaction between light and matter is a well-known process. Light used in spectroscopic methods is typically not described by the applied energy, but in many cases by the wavelength or in wavenumbers.
A NIR spectrometer such as the Metrohm NIRS DS2500 Petro Analyzer measures this light-matter interaction to generate spectra such as those displayed in Figure 2. NIRS is especially sensitive to the presence of certain functional groups like -CH, -NH, -OH, and -SH. Therefore, NIR spectroscopy is an ideal method to quantify different QC parameters like water content (moisture), cetane index, RON/MON (research and motor octane numbers), flash point, and cold filter plugging point (CFPP), just to name a few. Furthermore, the interaction is also dependent upon the matrix of the sample itself, which also allows the detection of physical and rheological parameters like density and viscosity.
Figure 2. Diesel spectra resulting from the interaction of NIR light with the respective samples.
Figure 3. Liquid sample placement for NIR spectra measurement on the smart vial holder from Metrohm.
Figure 4. A. Measurements of liquids are typically done with disposable vials. B. The NIRS measurement mode is known as transmission, where light travels through the sample while being absorbed (from left to right in the illustration).
- Fast technique with results in less than a minute.
- No sample preparation required – measure samples as-is.
- Low cost per sample – no chemicals or solvents needed.
- Environmentally friendly technique – no waste generated.
- Non-destructive – precious samples can be reused after analysis.
- Easy to operate – inexperienced users are immediately successful.
Read our previous blog posts to learn more about NIRS as a secondary technique.
Where can NIRS be used in the refining process?
The refining process can be divided into three different segments:
Upstream describes the process of converting crude oil into intermediate products. Refineries are usually very large complexes with several hazardous explosive areas. Therefore, operators are reluctant to transport samples from the different processes to the laboratory. Even the process of obtaining samples for analysis at external QC laboratories is laborious and can require significant paperwork and certified transport services. For obvious reasons, in most cases inline measurements are preferred. These types of measurements are typically done by process NIRS analyzers.
Figure 5. Flowchart of how crude oil becomes gasoline at the local gas station, and where NIRS can perform quality checks during the process.
Downstream at fuel depots and gas stations, the regulatory agencies require measurement of many of the same quality parameters as in the production of gasoline and diesel, and this can also be accomplished with NIRS. There is a significant advantage if the analysis can be done on-site using fresh samples and without the hassle of needing to transport them to testing laboratories.
Figure 6. Examples of mobile fuel testing with the Metrohm DS2500 Petro Analyzer.
NIRS as an ASTM compliant tool for QC
«These practices cover a guide for the multivariate calibration of infrared spectrometers used in determining the physical or chemical characteristics of materials. These practices are applicable to analyses conducted in the near infrared (NIR) spectral region (roughly 780 to 2500 nm) through the mid infrared (MIR) spectral region (roughly 4000 to 400 cm-1).»
Multivariate analysis of petroleum products
«This practice covers a guide for the multivariate calibration of infrared (IR) spectrophotometers and Raman spectrometers used in determining the physical, chemical, and performance properties of petroleum products, liquid fuels including biofuels, and lubricants. This practice is applicable to analyses conducted in the near infrared (NIR) spectral region (roughly 780 nm to 2500 nm) through the mid infrared (MIR) spectral region (roughly 4000 cm-1 to 40 cm-1).»
«This practice covers requirements for the validation of measurements made by laboratory, field, or process (online or at-line) infrared (near- or mid-infrared analyzers, or both), and Raman analyzers, used in the calculation of physical, chemical, or quality parameters (that is, properties) of liquid petroleum products and fuels.»
«This practice covers requirements for establishing performance-based qualification of vibrational spectroscopic analyzer systems intended to be used to predict the test result of a material that would be produced by a Primary Test Method (PTM) if the same material is tested by the PTM.»
Typical NIRS applications and parameters for the petrochemical and refinery industry
Petrochemicals are subject to standardized test methods to determine their chemical, physical, and tribological properties. Laboratory testing is an indispensable part of both research and development and quality control in the production of petrochemicals. The following test parameters are typically important to measure in the petrochemical and refinery industry (Table 1).
Table 1. Examples for use of NIRS for selected petrochemical QC parameters.
|Specific Gravity (API)||Gravity meter||ASTM D298||
|Boiling Point||Distillation||ASTM D2887|
|Cold Filter Plugging Point (CFPP)||Standardized filter device||ASTM D6371|
|Pour Point||Pour Point analyzer||ASTM D97|
|Cloud Point||Cloud Point analyzer||ASTM D2500|
|Flash Point||Flash Point tester||ASTM D93|
|Fatty Acid Methyl Ester (FAME)||FTIR||ASTM D7806|
|Reid Vapor Pressure||RVP analyzer||ASTM D323|
|PIANO (Paraffins, Isoparaffins, Aromatics, Naphthenes, Olefins)||Gas chromatograph||ASTM D6729|
|Octane Number (RON/MON)||CFR Engine||ASTM D2699
|Cetane Number||CFR Engine||ASTM D613|
|Diene value / MAV index||Titration||UOP 327-17|
|Parameter||Conventional method||ASTM method||Relevant NIRS Application Notes|
Future installments in this series
This article is a general overview of the use of NIR spectroscopy as the ideal QC tool for the petrochemical / refinery industry. Future installments will be dedicated to the most important applications and will include much more detailed information. Don’t miss our next blogs on the topics of:
- Gasoline / Diesel / Jet fuel
- Pyrolysis gasoline (Pygas)
- ASTM Norms
For more information
We offer NIRS for lab, NIRS for process, as well as Raman solutions