Quality Control In The Petrochemical And Refinery Industry Using Nir Spectroscopy

INTRODUCTION

Oil and gas and one of the popular fuels in the world. Chemicals derived from petroleum or natural gas, also known as "petrochemicals", are an essential part of the modern chemical industry. The petrochemical sector became increasingly popular around the early 1940s during World War II.

Oil refining aims to provide a defined range of products according to agreed specifications. Simple refineries use distillation columns to separate crude oil into different fractions based on their chemical properties, and the relative quantity depends directly on the type of crude oil used. Therefore, it is necessary to obtain a variety of crude oils that can be mixed into suitable raw materials to produce the required quantity and quality of the final product.

Therefore, quality control in this industry is extremely necessary and important to operate effectively and comply with industry standards. NIR near-infrared spectroscopy is a technique particularly suited to making the quality control of these end products more efficient and cost-effective for manufacturers. Furthermore, NIRS is recognized and accepted by ASTM as an alternative to other techniques.

EXPERIMENTAL METHODS

The interaction between light and samples is collected and fully visualized by the NIR spectrometer. NIR spectroscopy operates in the near-infrared region of the electromagnetic spectrum, typically from 780 nm to 2500 nm. It measures the absorption of NIR light by a sample, which induces overtones and combination bands of molecular vibrations, primarily of C-H, O-H, N-H, and S-H bonds. The resulting spectra provide detailed information about the sample's chemical composition and physical properties. The NIR spectrum of an oil sample is similar to the figure below.

And since most petroleum products are composed predominantly of hydrocarbons, it is worthwhile to investigate the spectral features of some pure hydrocarbons. In the NIR region (10,000 cm^-1 to 4000 cm^-1 or 1000 nm to 2500 nm), four major hydrocarbon absorption bands are generally observed, as shown in Figure 2 (n-hexane). These bands are centered at (A) 9200 cm^-1 to 7800 cm^-1 , (B) 7500 cm^-1 to 6400 cm^-1 , (C) 6300 cm^-1 to 5200 cm^-1 , and (D) 4700 cm^-1 to 4000 cm^-1 , which correspond, respectively, to the second overtone, the combination, the first overtone, and the combination bands of –CH vibrations.

Combined with highly intelligent statistical algorithms to help develop powerful calibration models. From there, it helps improve the accuracy and performance of the method.

Advantages of NIR technique

• Fast technique
• No sample preparation required
• Does not destroy the sample
• Measure directly on the line
• Easy to operate
• Lower cost than other techniques

APPLICATIONS

The refining process can be divided into three different segments: Upstream, Midstream, Downstream. So at what steps can NIR spectroscopy be applied?

Reality shows that NIR spectroscopy can be applied at all three stages.

Upstream converts crude oil into explosive intermediates and stage products, so the application of inline measurements is a perfect choice. The midstream is inter-axially inspected for quality upon receipt and supply. This stage requires rapid testing, so NIR spectroscopy is also used effectively. Downstream at fuel depots and filling stations, regulators require many of the same quality parameters to be measured during gasoline and diesel production, and this can also be done using NIRS. There is a significant advantage if analysis can be performed on-site using fresh samples and without the hassle of having to transport them to a testing laboratory.

RECOMMENDED EQUIPMENT

For applications using Near-infrared spectroscopy (NIRS), INTINS offers the Ocean Optics NIRQuest+ spectrometer product line with high sensitivity and good resolution from 2.8 nm to 6.48 nm. NIRQuest+ is available in three versions covering different wavelengths from 900-2450 nm.

NIRQuest+ can measure very small changes in absorbed signal, which are typical of harmonic overtones in the NIR. Its higher sensitivity enables better measurement accuracy, particularly in low-light conditions. Also, at longer wavelengths, NIRQuest+ measures diffuse reflection at low noise levels, resulting in cleaner spectra at wavelengths where distinct spectral features can be difficult to capture.

Figure 2: NIRQuest+ Spectrometer

At the same time, we can provide other accompanying optical devices such as fiber, light sources... suitable depending on the customer's application needs.

CONCLUSIONS

Near-infrared (NIR) spectroscopy offers significant benefits for quality control in the petrochemical and refinery industry, enabling rapid and non-destructive analysis of raw materials, process monitoring, product quality assurance, and environmental compliance. By leveraging the capabilities of NIR spectroscopy, industry stakeholders can enhance operational efficiency, ensure product integrity, and meet regulatory requirements effectively.