Talk about the application of near-infrared spectroscopy technology in the petrochemical field

Spectrum of nature.

Principles of near-infrared spectroscopy technology

Near-infrared spectrum (NIR) is an electromagnetic wave between the visible (VIS) and mid-infrared (MIR) regions. According to the American Society for Experimentation and Materials, its wavelength range is 800~2500nm. Near-infrared spectrum is the frequency doubling and combined spectrum band of molecular vibration spectrum. It mainly refers to the absorption of hydrogen-containing groups C-H, O-H, N-H, and S-H, including rich information on the composition and molecular structure of most types of organic matter.

The Lambert-Beer absorption law is the theoretical basis of near-infrared spectroscopy analysis: the spectral characteristics of the sample change with its composition and intrinsic structural transformation. Since different groups or the same group have obvious differences in absorption wavelengths in different chemical environments, they can be used as an effective carrier to obtain information on the composition or properties of organic compounds. For some substances without near-infrared spectrum absorption (such as some inorganic ionic compounds), their information can also be reflected indirectly through the spectral changes caused by their influence on coexisting bulk substances.

The main application fields of near-infrared spectroscopy include: petroleum and petrochemicals, basic organic chemicals, fine chemicals, metallurgy, life sciences, pharmaceuticals, clinical medicine, agriculture, food, beverages, tobacco, textiles, papermaking, cosmetics, quality supervision, environment protection, universities and research institutes, etc. Expected future applications also include: medical detection of skin, health conditions, etc.; online analysis, quality analysis and process control; big data applications (non-model prediction) and near-infrared entering community homes.

These industries have the characteristics of on-site analysis, so portable near-infrared spectrometers with compact structure, small size and light weight are more often needed. Near-infrared analysis technology is a modern analysis technology that integrates chemometrics, spectroscopy, computer applications and other disciplines.

Characteristics of near-infrared spectroscopy technology

Fast analysis

Since the spectrum measurement process can generally be completed within 1 minute (multi-channel instruments can be completed within 1 sec), the composition or properties of the sample can be quickly determined through the established calibration model.

High analysis efficiency

Through one spectrum measurement and the established corresponding calibration model, multiple components or properties of the sample can be measured simultaneously. In industrial analysis, a leap from single-project operation to workshop-based multi-index simultaneous analysis can be achieved. This is very important for production process analysis of multi-index monitoring. It can ensure the frequency and quality of analysis without increasing the number of analysts. This ensures the smooth operation of the production equipment.

Low cost of analysis

Near-infrared spectroscopy does not consume samples during the analysis process, and consumes almost no other power except a little electricity. Compared with commonly used standard or reference methods, testing costs can be significantly reduced.

Good test reproducibility

Due to the stability of spectral measurements, test results are rarely affected by artifacts, and near-infrared spectroscopy generally shows better reproducibility compared to standard or reference methods.

No sample pretreatment is required, and spectral measurement is convenient

Due to the strong penetrating ability and scattering effect of near-infrared light, transmission or diffuse reflection spectroscopy can be used depending on the physical state of the sample and the strength of its light transmission ability. Samples in different physical states such as liquid, solid, semi-solid and colloidal can be directly measured through corresponding sample measuring devices.

Facilitates online analysis

Due to the good transmission characteristics of near-infrared light in optical fiber, the instrument can be moved away from the sampling site through the optical fiber, and the measured spectral signal can be transmitted to the instrument in real time. After calling the established calibration model for calculation, the composition or property results of the samples in the production device can be directly displayed. In addition, samples in harsh environments can also be measured through optical fibers.

Typical non-destructive analysis techniques

No sample is consumed during the spectral measurement process, and there is no impact on the sample from its appearance to its interior. In view of this characteristic, this technology is increasingly being used in in vivo analysis and medical clinical fields.

Application cases of near-infrared spectroscopy rapid inspection technology

Quick review of crude oil quality

The properties of crude oil vary greatly. From mining, trade, circulation to final processing, each link needs to evaluate the relevant properties of crude oil. However, the existing crude oil evaluation methods require a long analysis time and a large workload. In many cases, the timeliness of analysis cannot be met, crude oil rapid evaluation technology emerged as the times require, and near-infrared spectroscopy technology has become the first choice due to its advantages such as convenient measurement, low cost, and can be used for on-site or online analysis.

Crude oil evaluation based on near-infrared spectroscopy analysis technology has the characteristics of easy operation, small sample consumption, non-destructive testing, short analysis time, accurate properties, etc., and can achieve rapid routine evaluation of crude oil; according to the expert database including the raw materials, intermediate products and final product indicators of each unit of the refinery, combined with the global historical database, can achieve a comprehensive evaluation of crude oil. The entire crude oil quick evaluation process from obtaining the sample to completing the comprehensive evaluation does not take more than 30 minutes.

The crude oil quick evaluation system mainly includes pre-treatment, near-infrared analyzer, metrology software and model, crude oil management software and crude oil historical database. The main process is to collect near-infrared oil samples in a high-pressure sample cell after impurities are removed through pre-treatment at constant temperature and pressure. Chemometrics software and models predict the spectrum to obtain a routine evaluation report, and combine it with the customized corporate crude oil historical database and expert database to obtain the final comprehensive evaluation report of crude oil.

Quick screening at gas stations

When undertaking the supervision and spot inspection of refined oil products by the market supervision department using the rapid inspection screening method, after the rapid inspection vehicle arrives at the gas station to be inspected, the inspection technicians turn on the near-infrared spectroscopy and other inspection equipment to keep the inspection equipment in a stable and balanced state; after the technician extracts the vehicle gasoline, remove the sample and place it in the sample pool. The sample injection volume should meet the needs of the sample pool and ensure that the luminosity passes through the sample pool effectively and there are no bubbles; open the vehicle gasoline spectrum acquisition instrument to collect the spectrum; after collect spectroscopy, retrieve the automotive gasoline analysis method for data analysis, and obtain the numerical value of the research method octane number. If the data is unqualified and the retest is still unqualified, the rapid screening result of the sample can be considered unqualified. Immediately inform the person in charge of the gas station and report to the local market supervision and law enforcement personnel to initiate law enforcement procedures to temporarily seal the oil-filled product. At the same time, testing technicians re-sample 2L samples and bring them back to the laboratory to test the research octane number according to the methods specified in national standards, the results will be reported to the market supervision department after 24 hours, and the final results will be subject to the laboratory test results.

Development Trends of Near-Infrared Spectrometers

Internationally, miniaturization of near-infrared spectroscopic analysis instruments is an important development direction, and a variety of micro-miniaturized near-infrared spectrometers have appeared on the market. The rise of IoT technology in many fields such as smart agriculture, smart factories, smart healthcare, and smart cities has become the main force driving the development of near-infrared spectrum sensors in the direction of miniaturization.

With the development of new principles, new materials and new processing and manufacturing technologies, the specific performance of portable near-infrared spectrometers regardless of the spectroscopic method for specific application scenarios will be further improved and optimized, and the overall performance of various types of instruments will also become better and better. For example, the size of the instruments will become smaller and lighter, the consistency between instruments will become better and better, the wavelength range of the instruments will become wider and wider, and the measurement accessories will become more and more highly efficient, the optical performance indicators of the instrument will also be comprehensively improved.

Miniature near-infrared spectrometers will also play an increasingly important role in multi-band and multi-spectral data fusion, such as the fusion of near-infrared spectroscopy with laser-induced breakdown spectroscopy, fusion with Raman spectroscopy, and fusion with other spectral imaging . In addition to improvements in spectrometer hardware, improvements in chemometrics algorithms cannot be ignored.

For example, how to transplant the calibration model established based on a large spectral database on a laboratory desktop instrument to a portable instrument, and how to update the model on the application side, are issues worthy of in-depth study. In addition, in order to ensure that the performance of micro-scale spectrometers is guaranteed during the application process, it is also very important to establish instrument installation and operation qualification procedures.

In terms of application, with the continuous improvement of people's living standards and the growing demand for a better life, the demand for high-quality consumer goods has increased significantly. The quality and quality of consumer goods have attracted more and more attention from consumers. There is also an increasing focus on the authenticity identification and quality traceability of consumer goods. As one of the core sensing components of IoT nodes, micro near-infrared spectrometers will be increasingly used in daily necessities such as food and medicine. In the future, the close integration of micro-sized near-infrared spectroscopy instruments with smartphones and cloud platforms will make data transmission and storage more flexible and convenient, and will also lay the foundation for big data analysis and applications. Therefore, it can be expected that in the future, the main users of miniature near-infrared spectroscopy instruments will not be spectroscopic analysis workers, but ordinary consumers, that is, consumer-level applications will account for the majority.