Hydrogenation of residual oil

The primary purpose of residual oil hydrogenation is to break down long-chain hydrocarbons and increase the yield of light oil, whilst simultaneously removing sulphur, nitrogen, metals and other impurities from the oil. The process is carried out under relatively severe high-temperature and high-pressure conditions.

Its main product, hydrogenated heavy oil, is used as feedstock for catalytic cracking. Other light fractions serve as feedstock for pre-hydrogenation in reforming and for diesel hydrogenation. The primary purpose of diesel hydrogenation is to remove impurities such as sulphur and nitrogen from the diesel fraction, whilst converting the unsaturated hydrocarbons in the diesel into saturated hydrocarbons. This increases the calorific value of the diesel whilst also improving its storage stability.

Residue is the heaviest fraction of crude oil; it is rich in high-density hydrocarbons and exhibits significant variations in composition. It is therefore necessary to study it in order to clarify these differences in chemical composition, thereby providing a reference basis and essential fundamental data for the selection of residue lightening processes.

During the hydrogenation of residual oil, the main reactions that occur include metal removal, desulphurisation, denitrification, deasphalting and decarbonisation. Residual oil hydrogenation units have short operating cycles and the catalysts cannot be regenerated. Residual oil processing is divided into two processes: hydrotreating and hydrocracking, with reactors of three types: fixed-bed, moving-bed and fluidised-bed.

Mass spectrometry has now been successfully applied to the group composition analysis of petrol, coal oil, diesel and heavy oil fractions; these methods have long been included in the American Society for Testing and Materials (ASTM) standard methods and have also been widely adopted in China.

As these methods are designed for fractions with low or no gum content, they only address the group composition of saturated and aromatic components, without considering gum.

To meet the growing demand for light petroleum products, and in light of the continuous emergence of new catalytic cracking processes and technologies, as well as the urgent need for deep processing of residual oil, the blending and full refining of atmospheric or vacuum residual oil have begun. Consequently, it is essential to understand the changes in the composition of residual oil during the catalytic hydrocracking process.

An online mass spectrometer was utilised to study the changes in the compositional fractions of residual oil during the hydrogenation process. The gasification conditions and the reproducibility of the methods for the saturated, aromatic and asphaltene fractions of the residual oil were investigated. Asphaltenes were precipitated from the residual oil using n-heptane, and the asphaltene-free fraction was separated into saturated, aromatic and asphaltene fractions using a series of adsorption columns comprising aluminium oxide and silica gel.

Advantages of the ProC-TOF online mass spectrometer in the coal chemical industry

① The instrument features a high degree of integration and automation, enabling dynamic, continuous sampling and online gas analysis; it offers rapid response times and powerful data analysis capabilities.

② The instrument offers high stability; it utilises solenoid valves or multi-port rotary valves for switching between multiple gas pathways during the process, enabling automatic multi-point and multi-component monitoring. Its compact design ensures convenience and efficiency.

③ The sampling and pre-treatment units are tailor-made to meet specific requirements, facilitating functions such as pressure regulation, filtration, dehumidification and heating. Temperature-controlled inlet lines effectively prevent the condensation of process gases during sampling. The instrument is also equipped with a filament protection device to maximise the service life of the filament. The unit comes with a two-stage vacuum pump, enabling a range of applications from high vacuum to ultra-high vacuum to meet the diverse configuration requirements of the coal chemical industry.

④ It features user-friendly task management functions and rapid automatic calibration, including background calibration, fragment calibration and ionisation sensitivity calibration. It is fully compatible with other software systems and is equipped with a network interface to enable remote control.